1
|
Voigt JH, Lauritsen KM, Pedersen SB, Hansen TK, Møller N, Jessen N, Laurenti MC, Dalla Man C, Vella A, Gormsen LC, Søndergaard E. Four weeks SGLT2 inhibition improves beta cell function and glucose tolerance without affecting muscle free fatty acid or glucose uptake in subjects with type 2 diabetes. Basic Clin Pharmacol Toxicol 2024; 134:643-656. [PMID: 38409617 DOI: 10.1111/bcpt.13991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2023] [Revised: 01/25/2024] [Accepted: 02/06/2024] [Indexed: 02/28/2024]
Abstract
AIMS Sodium glucose co-transporter-2 (SGLT2) inhibition lowers glucose levels independently of insulin, leading to reduced insulin secretion and increased lipolysis, resulting in elevated circulating free fatty acids (FFAs). While SGLT2 inhibition improves tissue insulin sensitivity, the increase in circulating FFAs could reduce insulin sensitivity in skeletal muscle and the liver. We aimed to investigate the effects of SGLT2 inhibition on substrate utilization in skeletal muscle and the liver and to measure beta-cell function and glucose tolerance. METHODS Thirteen metformin-treated individuals with type 2 diabetes were randomized to once-daily empagliflozin 25 mg or placebo for 4 weeks in a crossover design. Skeletal muscle glucose and FFA uptake together with hepatic tissue FFA uptake were measured using [18F]FDG positron emission tomography/computed tomography (PET/CT) and [11C]palmitate PET/CT. Insulin secretion and action were estimated using the oral minimal model. RESULTS Empagliflozin did not affect glucose (0.73 ± 0.30 vs. 1.16 ± 0.64, μmol/g/min p = 0.11) or FFA (0.60 ± 0.30 vs. 0.56 ± 0.3, μmol/g/min p = 0.54) uptake in skeletal muscle. FFA uptake in the liver (21.2 ± 10.1 vs. 19 ± 8.8, μmol/100 ml/min p = 0.32) was unaffected. Empagliflozin increased total beta-cell responsivity (20 ± 8 vs. 14 ± 9, 10-9 min-1, p < 0.01) and glucose effectiveness (2.6 × 10-2 ± 0.3 × 10-2 vs. 2.4 × 10-2 ± 0.3 × 10-2, dL/kg/min, p = 0.02). CONCLUSIONS Despite improved beta-cell function and glucose tolerance, empagliflozin does not appear to affect skeletal muscle FFA or glucose uptake.
Collapse
Affiliation(s)
| | - Katrine M Lauritsen
- Steno Diabetes Center Aarhus, Aarhus, Denmark
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
- Danish Diabetes Academy, Odense University Hospital, Odense, Denmark
| | - Steen Bønløkke Pedersen
- Steno Diabetes Center Aarhus, Aarhus, Denmark
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | | | - Niels Møller
- Steno Diabetes Center Aarhus, Aarhus, Denmark
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Niels Jessen
- Steno Diabetes Center Aarhus, Aarhus, Denmark
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Marcello C Laurenti
- Endocrine Research Unit, Department of Endocrinology, Diabetes and Nutrition, Mayo Clinic, Rochester, Minnesota, USA
| | - Chiara Dalla Man
- Department of Information Engineering, University of Padua, Padua, Italy
| | - Adrian Vella
- Endocrine Research Unit, Department of Endocrinology, Diabetes and Nutrition, Mayo Clinic, Rochester, Minnesota, USA
| | - Lars C Gormsen
- Department of Nuclear Medicine and PET Centre, Aarhus University Hospital, Aarhus, Denmark
| | - Esben Søndergaard
- Steno Diabetes Center Aarhus, Aarhus, Denmark
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
- Danish Diabetes Academy, Odense University Hospital, Odense, Denmark
- Endocrine Research Unit, Department of Endocrinology, Diabetes and Nutrition, Mayo Clinic, Rochester, Minnesota, USA
| |
Collapse
|
2
|
Storoschuk KL, Lesiuk D, Nuttall J, LeBouedec M, Khansari A, Islam H, Gurd BJ. Impact of fasting on the AMPK and PGC-1α axis in rodent and human skeletal muscle: A systematic review. Metabolism 2024; 152:155768. [PMID: 38154612 DOI: 10.1016/j.metabol.2023.155768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2023] [Revised: 12/18/2023] [Accepted: 12/22/2023] [Indexed: 12/30/2023]
Abstract
Based primarily on evidence from rodent models fasting is currently believed to improve metabolic health via activation of the AMPK-PGC-1α axis in skeletal muscle. However, it is unclear whether the skeletal muscle AMPK-PGC-1α axis is activated by fasting in humans. The current systematic review examined the fasting response in skeletal muscle from 34 selected studies (7 human, 21 mouse, and 6 rat). From these studies, we gathered 38 unique data points related to AMPK and 47 related to PGC-1α. In human studies, fasting mediated activation of the AMPK-PGC-1α axis is largely absent. Although evidence does support fasting-induced activation of the AMPK-PGC-1α axis in rodent skeletal muscle, the evidence is less robust than anticipated. Our findings question the ability of fasting to activate the AMPK-PGC-1α axis in human skeletal muscle and suggest that the metabolic benefits of fasting in humans are associated with caloric restriction rather than the induction of mitochondrial biogenesis. Registration: https://doi.org/10.17605/OSF.IO/KWNQY.
Collapse
Affiliation(s)
- K L Storoschuk
- School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - D Lesiuk
- School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - J Nuttall
- School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - M LeBouedec
- School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - A Khansari
- School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - H Islam
- School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, BC, Canada
| | - B J Gurd
- School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada.
| |
Collapse
|
3
|
Solianik R, Židonienė K, Brazaitis M. Short-duration cold exposure decreases fasting-induced glucose intolerance but has no effect on resting energy expenditure. Cryobiology 2023; 113:104564. [PMID: 37541564 DOI: 10.1016/j.cryobiol.2023.104564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 06/19/2023] [Accepted: 08/01/2023] [Indexed: 08/06/2023]
Abstract
The aim of the present study was to investigate whether brief cold exposure can reverse fasting-induced glucose intolerance and insulin resistance, and improve resting energy expenditure (REE). Twelve young non-obese women were randomly assigned to undergo the following conditions: 2 days of fasting with two 10-min whole-body cold-water immersions on separate days (FAST-COLD), 2 days of fasting without cold-water immersions (FAST), 2 days of usual diet with two 10-min whole-body cold-water immersions on separate days (COLD), or 2 days of usual diet without cold-water immersions (CON) in a randomised crossover fashion. Changes in REE and substrate utilisation, and glucose tolerance and insulin sensitivity from the oral glucose tolerance test were examined. The results showed that FAST-COLD and FAST trials increased (P < 0.05) REE and decreased (P < 0.05) respiratory quotient, but these variables did not differ significantly between the FAST-COLD and FAST trials. The glucose and insulin area under the curves (AUCs) were higher (P < 0.05) in the FAST-COLD and FAST trials than in the CON and COLD trials, and these AUCs were lower (P < 0.05) in the FAST-COLD than in the FAST trial. Matsuda index was lower in the FAST trial than in the CON trial (P < 0.05), and tended to be greater after the FAST-COLD trial than after the FAST trial (P = 0.060). In conclusion, cold exposure had no effect on REE but decreased fasting-induced glucose intolerance which was accompanied by a maintained insulin sensitivity.
Collapse
Affiliation(s)
- Rima Solianik
- Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania.
| | - Katerina Židonienė
- Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania
| | - Marius Brazaitis
- Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania
| |
Collapse
|
4
|
Warner SO, Dai Y, Sheanon N, Yao MV, Cason RL, Arbabi S, Patel SB, Lindquist D, Winnick JJ. Short-term fasting lowers glucagon levels under euglycemic and hypoglycemic conditions in healthy humans. JCI Insight 2023; 8:e169789. [PMID: 37166980 PMCID: PMC10371233 DOI: 10.1172/jci.insight.169789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 05/09/2023] [Indexed: 05/12/2023] Open
Abstract
Fasting is associated with increased susceptibility to hypoglycemia in people with type 1 diabetes, thereby making it a significant health risk. To date, the relationship between fasting and insulin-induced hypoglycemia has not been well characterized, so our objective was to determine whether insulin-independent factors, such as counterregulatory hormone responses, are adversely impacted by fasting in healthy control individuals. Counterregulatory responses to insulin-induced hypoglycemia were measured in 12 healthy people during 2 metabolic studies. During one study, participants ate breakfast and lunch, after which they underwent a 2-hour bout of insulin-induced hypoglycemia (FED). During the other study, participants remained fasted prior to hypoglycemia (FAST). As expected, hepatic glycogen concentrations were lower in FAST, and associated with diminished peak glucagon levels and reduced endogenous glucose production (EGP) during hypoglycemia. Accompanying lower EGP in FAST was a reduction in peripheral glucose utilization, and a resultant reduction in the amount of exogenous glucose required to maintain glycemia. These data suggest that whereas a fasting-induced lowering of glucose utilization could potentially delay the onset of insulin-induced hypoglycemia, subsequent reductions in glucagon levels and EGP are likely to encumber recovery from it. As a result of this diminished metabolic flexibility in response to fasting, susceptibility to hypoglycemia could be enhanced in patients with type 1 diabetes under similar conditions.
Collapse
Affiliation(s)
- Shana O. Warner
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Yufei Dai
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Nicole Sheanon
- Department of Pediatrics, Division of Pediatric Endocrinology, Cincinnati Children’s Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Michael V. Yao
- Department of Pediatrics, Division of Endocrinology, University of New Mexico, Albuquerque, New Mexico, USA
| | - Rebecca L. Cason
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Shahriar Arbabi
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Shailendra B. Patel
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Diana Lindquist
- Imaging Research Center, Department of Radiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA
| | - Jason J. Winnick
- Department of Internal Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| |
Collapse
|
5
|
Lee WD, Liang L, AbuSalim J, Jankowski CS, Samarah LZ, Neinast MD, Rabinowitz JD. Impact of acute stress on murine metabolomics and metabolic flux. Proc Natl Acad Sci U S A 2023; 120:e2301215120. [PMID: 37186827 PMCID: PMC10214130 DOI: 10.1073/pnas.2301215120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 04/10/2023] [Indexed: 05/17/2023] Open
Abstract
Plasma metabolite concentrations and labeling enrichments are common measures of organismal metabolism. In mice, blood is often collected by tail snip sampling. Here, we systematically examined the effect of such sampling, relative to gold-standard sampling from an in-dwelling arterial catheter, on plasma metabolomics and stable isotope tracing. We find marked differences between the arterial and tail circulating metabolome, which arise from two major factors: handling stress and sampling site, whose effects were deconvoluted by taking a second arterial sample immediately after tail snip. Pyruvate and lactate were the most stress-sensitive plasma metabolites, rising ~14 and ~5-fold. Both acute handling stress and adrenergic agonists induce extensive, immediate production of lactate, and modest production of many other circulating metabolites, and we provide a reference set of mouse circulatory turnover fluxes with noninvasive arterial sampling to avoid such artifacts. Even in the absence of stress, lactate remains the highest flux circulating metabolite on a molar basis, and most glucose flux into the TCA cycle in fasted mice flows through circulating lactate. Thus, lactate is both a central player in unstressed mammalian metabolism and strongly produced in response to acute stress.
Collapse
Affiliation(s)
- Won Dong Lee
- Department of Chemistry, Princeton University, Princeton, NJ08544
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ08544
- Ludwig Institute for Cancer Research, Princeton University, Princeton, NJ08544
| | - Lingfan Liang
- Department of Chemistry, Princeton University, Princeton, NJ08544
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ08544
- Ludwig Institute for Cancer Research, Princeton University, Princeton, NJ08544
| | - Jenna AbuSalim
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ08544
- Ludwig Institute for Cancer Research, Princeton University, Princeton, NJ08544
- Department of Molecular Biology, Princeton University, Princeton, NJ08544
| | - Connor S.R. Jankowski
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ08544
- Ludwig Institute for Cancer Research, Princeton University, Princeton, NJ08544
- Department of Molecular Biology, Princeton University, Princeton, NJ08544
| | - Laith Z. Samarah
- Department of Chemistry, Princeton University, Princeton, NJ08544
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ08544
- Ludwig Institute for Cancer Research, Princeton University, Princeton, NJ08544
| | - Michael D. Neinast
- Department of Chemistry, Princeton University, Princeton, NJ08544
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ08544
- Ludwig Institute for Cancer Research, Princeton University, Princeton, NJ08544
| | - Joshua D. Rabinowitz
- Department of Chemistry, Princeton University, Princeton, NJ08544
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ08544
- Ludwig Institute for Cancer Research, Princeton University, Princeton, NJ08544
- Department of Molecular Biology, Princeton University, Princeton, NJ08544
| |
Collapse
|
6
|
Ingersen A, Helset HR, Calov M, Chabanova E, Harreskov EG, Jensen C, Hansen CN, Prats C, Helge JW, Larsen S, Dela F. Metabolic effects of alternate-day fasting in males with obesity with or without type 2 diabetes. Front Physiol 2022; 13:1061063. [PMID: 36531168 PMCID: PMC9748572 DOI: 10.3389/fphys.2022.1061063] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 11/21/2022] [Indexed: 10/14/2023] Open
Abstract
Alternate-day fasting induces oscillations in energy stores. We hypothesized that repeated oscillations increases insulin secretion and sensitivity, and improve metabolic health in patients with obesity with or without type 2 diabetes (T2DM). Twenty-three male patients fasted every other day for 30 h for 6 weeks. Experiments included resting energy expenditure, continuous glucose monitoring, intravenous glucose tolerance test, euglycemic hyperinsulinemic clamp, body composition, hepatic triglyceride content, muscle biopsies which were performed at baseline, during 3 weeks without allowed weight loss, and after additional 3 weeks with weight loss. Bodyweight decreased ∼1% and further ∼3% during weeks one to three and four to six, respectively (p < 0.05). Only minor changes in fat mass occurred in weeks 1-3. With weight loss, visceral fat content decreased by 13 ± 3% and 12 ± 2% from baseline in patients with and without T2DM, respectively (p < 0.05). Hepatic triglyceride content decreased by 17 ± 9% and 36 ± 9% (with diabetes) and 27 ± 8% and 40 ± 8% (without diabetes) from baseline to week 3 and week 6, respectively (all p < 0.05). Muscle lipid and glycogen content oscillated with the intervention. Glucose homeostasis, insulin secretion and sensitivity was impaired in patients with T2DM and did not change without weight loss, but improved (p < 0.05) when alternate day fasting was combined with weight loss. In conclusion, alternate-day fasting is feasible in patients with obesity and T2DM, and decreases visceral fat and liver fat deposits. Energy store oscillations by alternate-day fasting do not improve insulin secretion or sensitivity per se. Clinical Trial registration: (ClinicalTrials.gov), (ID NCT02420054).
Collapse
Affiliation(s)
- Arthur Ingersen
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Geriatrics, Bispebjerg-Frederiksberg University Hospital, Copenhagen, Denmark
| | - Hildegunn Rømma Helset
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Monika Calov
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Elizaveta Chabanova
- Department of Diagnostic Radiology, Copenhagen University Hospital, Copenhagen, Denmark
| | - Eva Gjerlevsen Harreskov
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Christina Jensen
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Christina Neigaard Hansen
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Clara Prats
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jørn Wulff Helge
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Steen Larsen
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Clinical Research Centre, Medical University of Bialystok, Bialystok, Poland
| | - Flemming Dela
- Xlab, Center for Healthy Aging, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Geriatrics, Bispebjerg-Frederiksberg University Hospital, Copenhagen, Denmark
| |
Collapse
|
7
|
Kido K, Egawa T, Watanabe S, Kawanaka K, Treebak JT, Hayashi T. Fasting potentiates insulin-mediated glucose uptake in rested and prior-contracted rat skeletal muscle. Am J Physiol Endocrinol Metab 2022; 322:E425-E435. [PMID: 35344394 DOI: 10.1152/ajpendo.00412.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A single bout of exercise can potentiate the effect of insulin on skeletal muscle glucose uptake via activation of the AMPK-TBC1 domain family member 4 (TBC1D4) pathway, which suggests a positive correlation between AMPK activation and insulin sensitization. In addition, prolonged fasting in rodents is known to upregulate and thereby synergistically enhance the effect of exercise on muscle AMPK activation. Therefore, fasting may potentiate the insulin-sensitizing effect of exercise. In the present study, we mimicked exercise by in situ muscle contraction and evaluated the effect of a 36-h fast on muscle contraction-induced insulin sensitization. Male Wistar rats weighing 150-170 g were allocated to either a 36-h fasting or feeding group. The extensor digitorum longus (EDL) muscles were electrically contracted via the common peroneal nerve for 10 min followed by a 3-h recovery period. EDL muscles were dissected and incubated in the presence or absence of submaximal insulin. Our results demonstrated that acute muscle contraction and 36 h of fasting additively upregulated AMPK pathway activation. Insulin-stimulated muscle glucose uptake and site-specific TBC1D4 phosphorylation were enhanced by prior muscle contraction in 36-h-fasted rats, but not in fed rats. Moreover, enhanced insulin-induced muscle glucose uptake and Akt phosphorylation due to 36 h of fasting were associated with a decrease in tribbles homolog 3 (TRB3), a negative regulator of Akt activation. In conclusion, fasting and prior muscle contraction synergistically enhance insulin-stimulated TBC1D4 phosphorylation and glucose uptake, which is associated with augmented AMPK pathway activation in rodents.NEW & NOTEWORTHY In this study, we revealed that 36 h of fasting additively upregulated acute muscle contraction-induced AMPK pathway activation in rats. Besides, fasting and muscle contraction synergistically enhanced insulin-stimulated site-specific TBC1D4 phosphorylation and glucose uptake, which was associated with augmented AMPK pathway activation. These results contribute to understanding the regulation of muscle insulin sensitivity.
Collapse
Affiliation(s)
- Kohei Kido
- Laboratory of Sports and Exercise Medicine, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan
- Faculty of Sports and Health Science, Fukuoka University, Fukuoka, Japan
- Institute for Physical Activity, Fukuoka University, Fukuoka, Japan
| | - Tatsuro Egawa
- Laboratory of Sports and Exercise Medicine, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan
| | - Shinya Watanabe
- Faculty of Sports and Health Science, Fukuoka University, Fukuoka, Japan
| | - Kentaro Kawanaka
- Faculty of Sports and Health Science, Fukuoka University, Fukuoka, Japan
- Institute for Physical Activity, Fukuoka University, Fukuoka, Japan
| | - Jonas T Treebak
- Faculty of Health and Medical Sciences, Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, Copenhagen, Denmark
| | - Tatsuya Hayashi
- Laboratory of Sports and Exercise Medicine, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan
| |
Collapse
|
8
|
Huang K, Liu Y, Perrimon N. Roles of Insect Oenocytes in Physiology and Their Relevance to Human Metabolic Diseases. FRONTIERS IN INSECT SCIENCE 2022; 2:859847. [PMID: 38468774 PMCID: PMC10926422 DOI: 10.3389/finsc.2022.859847] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 02/14/2022] [Indexed: 03/13/2024]
Abstract
Oenocytes are large secretory cells present in the abdomen of insects known to synthesize very-long-chain fatty acids to produce hydrocarbons and pheromones that mediate courtship behavior in adult flies. In recent years, oenocytes have been implicated in the regulation of energy metabolism. These hepatocyte-like cells accumulate lipid droplets under starvation and can non-autonomously regulate tracheal waterproofing and adipocyte lipid composition. Here, we summarize evidence, mostly from Drosophila, establishing that oenocytes perform liver-like functions. We also compare the functional differences in oenocytes and the fat body, another lipid storage tissue which also performs liver-like functions. Lastly, we examine signaling pathways that regulate oenocyte metabolism derived from other metabolic tissues, as well as oenocyte-derived signals that regulate energy homeostasis.
Collapse
Affiliation(s)
- Kerui Huang
- Department of Genetics, Harvard Medical School, Blavatnik Institute, Boston, MA, United States
| | - Ying Liu
- Department of Genetics, Harvard Medical School, Blavatnik Institute, Boston, MA, United States
| | - Norbert Perrimon
- Department of Genetics, Harvard Medical School, Blavatnik Institute, Boston, MA, United States
- Harvard Medical School, Howard Hughes Medical Institute, Boston, MA, United States
| |
Collapse
|
9
|
Stratton MT, Albracht-Schulte K, Harty PS, Siedler MR, Rodriguez C, Tinsley GM. Physiological responses to acute fasting: implications for intermittent fasting programs. Nutr Rev 2022; 80:439-452. [PMID: 35142356 DOI: 10.1093/nutrit/nuab094] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Intermittent fasting (IF) is a dietary strategy that involves alternating periods of abstention from calorie consumption with periods of ad libitum food intake. There is significant interest in the body of literature describing longitudinal adaptations to IF. Less attention has been given to the acute physiological responses that occur during the fasting durations that are commonly employed by IF practitioners. Thus, the purpose of this review was to examine the physiological responses - including alterations in substrate metabolism, systemic hormones, and autophagy - that occur throughout an acute fast. Literature searches were performed to locate relevant research describing physiological responses to acute fasting and short-term starvation. A single fast demonstrated the ability to alter glucose and lipid metabolism within the initial 24 hours, but variations in protein metabolism appeared to be minimal within this time frame. The ability of an acute fast to elicit significant increases in autophagy is still unknown. The information summarized in this review can be used to help contextualize existing research and better inform development of future IF interventions.
Collapse
Affiliation(s)
- Matthew T Stratton
- Energy Balance and Body Composition Laboratory; Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, Texas, USA
| | - Kembra Albracht-Schulte
- Energy Balance and Body Composition Laboratory; Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, Texas, USA
| | - Patrick S Harty
- Energy Balance and Body Composition Laboratory; Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, Texas, USA
| | - Madelin R Siedler
- Energy Balance and Body Composition Laboratory; Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, Texas, USA
| | - Christian Rodriguez
- Energy Balance and Body Composition Laboratory; Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, Texas, USA
| | - Grant M Tinsley
- Energy Balance and Body Composition Laboratory; Department of Kinesiology and Sport Management, Texas Tech University, Lubbock, Texas, USA
| |
Collapse
|
10
|
Increasing whole-body energetic stress does not augment fasting-induced changes in human skeletal muscle. Pflugers Arch 2021; 473:241-252. [PMID: 33420549 DOI: 10.1007/s00424-020-02499-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Revised: 10/29/2020] [Accepted: 11/25/2020] [Indexed: 11/27/2022]
Abstract
Fasting rapidly (≤ 6 h) activates mitochondrial biogenic pathways in rodent muscle, an effect that is absent in human muscle following prolonged (10-72 h) fasting. We tested the hypotheses that fasting-induced changes in human muscle occur shortly after food withdrawal and are modulated by whole-body energetic stress. Vastus lateralis biopsies were obtained from ten healthy males before, during (4 h), and after (8 h) two supervised fasts performed with (FAST+EX) or without (FAST) 2 h of arm ergometer exercise (~ 400 kcal of added energy expenditure). PGC-1α mRNA (primary outcome measure) was non-significantly reduced (p = 0.065 [ηp2 = 0.14]) whereas PGC-1α protein decreased (main effect of time: p < 0.01) during both FAST and FAST+EX. P53 acetylation increased in both conditions (main effect of time: p < 0.01) whereas ACC and SIRT1 phosphorylation were non-significantly decreased (both p < 0.06 [ηp2 = 0.15]). Fasting-induced increases in NFE2L2 and NRF1 protein were observed (main effects of time: p < 0.03), though TFAM and COXIV protein remained unchanged (p > 0.05). Elevating whole-body energetic stress blunted the increase in p53 mRNA, which was apparent during FAST only (condition × time interaction: p = 0.04). Select autophagy/mitophagy regulators (LC3BI, LC3BII, BNIP3) were non-significantly reduced at the protein level (p ≤ 0.09 [ηp2 > 0.13]) but the LC3II:I ratio was unchanged (p > 0.05). PDK4 mRNA (p < 0.01) and intramuscular triglyceride content in type IIA fibers (p = 0.04) increased similarly during both conditions. Taken together, human skeletal muscle signaling, mRNA/protein expression, and substrate storage appear to be unaffected by whole-body energetic stress during the initial hours of fasting.
Collapse
|
11
|
Zhang H, Ma J, Tang K, Huang B. Beyond energy storage: roles of glycogen metabolism in health and disease. FEBS J 2020; 288:3772-3783. [PMID: 33249748 DOI: 10.1111/febs.15648] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 11/19/2020] [Accepted: 11/25/2020] [Indexed: 12/19/2022]
Abstract
Beyond storing and supplying energy in the liver and muscles, glycogen also plays critical roles in cell differentiation, signaling, redox regulation, and stemness under various physiological and pathophysiological conditions. Such versatile functions have been revealed by various forms of glycogen storage diseases. Here, we outline the source of carbon flux in glycogen metabolism and discuss how glycogen metabolism guides CD8+ T-cell memory formation and maintenance. Likewise, we review how this affects macrophage polarization and inflammatory responses. Furthermore, we dissect how glycogen metabolism supports tumor development by promoting tumor-repopulating cell growth in hypoxic tumor microenvironments. This review highlights the essential role of the gluconeogenesis-glycogenesis-glycogenolysis-PPP metabolic chain in redox homeostasis, thus providing insights into potential therapeutic strategies against major chronic diseases including cancer.
Collapse
Affiliation(s)
- Huafeng Zhang
- Department of Pathology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jingwei Ma
- Department of Immunology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Ke Tang
- Department of Biochemistry and Molecular Biology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Bo Huang
- Department of Biochemistry and Molecular Biology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.,Department of Immunology and National Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College, Beijing, China.,Clinical Immunology Center, CAMS, Beijing, China
| |
Collapse
|
12
|
Høgild ML, Gudiksen A, Pilegaard H, Stødkilde-Jørgensen H, Pedersen SB, Møller N, Jørgensen JOL, Jessen N. Redundancy in regulation of lipid accumulation in skeletal muscle during prolonged fasting in obese men. Physiol Rep 2020; 7:e14285. [PMID: 31724339 PMCID: PMC6854099 DOI: 10.14814/phy2.14285] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Fasting in human subjects shifts skeletal muscle metabolism toward lipid utilization and accumulation, including intramyocellular lipid (IMCL) deposition. Growth hormone (GH) secretion amplifies during fasting and promotes lipolysis and lipid oxidation, but it is unknown to which degree lipid deposition and metabolism in skeletal muscle during fasting depends on GH action. To test this, we studied nine obese but otherwise healthy men thrice: (a) in the postabsorptive state (“CTRL”), (b) during 72‐hr fasting (“FAST”), and (c) during 72‐hr fasting and treatment with a GH antagonist (GHA) (“FAST + GHA”). IMCL was assessed by magnetic resonance spectroscopy (MRS) and blood samples were drawn for plasma metabolomics assessment while muscle biopsies were obtained for measurements of regulators of substrate metabolism. Prolonged fasting was associated with elevated GH levels and a pronounced GHA‐independent increase in circulating medium‐ and long‐chain fatty acids, glycerol, and ketone bodies indicating increased supply of lipid intermediates to skeletal muscle. Additionally, fasting was associated with a release of short‐, medium‐, and long‐chain acylcarnitines to the circulation from an increased β‐oxidation. This was consistent with a ≈55%–60% decrease in pyruvate dehydrogenase (PDHa) activity. Opposite, IMCL content increased ≈75% with prolonged fasting without an effect of GHA. We suggest that prolonged fasting increases lipid uptake in skeletal muscle and saturates lipid oxidation, both favoring IMCL deposition. This occurs without a detectable effect of GHA on skeletal muscle lipid metabolism.
Collapse
Affiliation(s)
- Morten L Høgild
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Anders Gudiksen
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | | | - Hans Stødkilde-Jørgensen
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,The MR Research Center, Aarhus University Hospital, Copenhagen, Denmark
| | - Steen Bønløkke Pedersen
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Niels Møller
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Jens O L Jørgensen
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark.,Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Niels Jessen
- Department of Clinical Medicine, Aarhus University, Aarhus, Denmark.,Department of Clinical Pharmacology, Aarhus University Hospital, Aarhus, Denmark.,Department of Biomedicine, Aarhus University, Aarhus, Denmark
| |
Collapse
|
13
|
Hjelholt A, Høgild M, Bak AM, Arlien-Søborg MC, Bæk A, Jessen N, Richelsen B, Pedersen SB, Møller N, Lunde Jørgensen JO. Growth Hormone and Obesity. Endocrinol Metab Clin North Am 2020; 49:239-250. [PMID: 32418587 DOI: 10.1016/j.ecl.2020.02.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Growth hormone (GH) exerts IGF-I dependent protein anabolic and direct lipolytic effects. Obesity reversibly suppresses GH secretion driven by elevated FFA levels, whereas serum IGF-I levels remain normal or elevated due to elevated portal insulin levels. Fasting in lean individuals suppresses hepatic IGF-I production and increases pituitary GH release, but this pattern is less pronounced in obesity. Fasting in obesity is associated with increased sensitivity to the insulin-antagonistic effects of GH. GH treatment in obesity induces a moderate reduction in fat mass and an increase in lean body mass but the therapeutic potential is uncertain.
Collapse
Affiliation(s)
- Astrid Hjelholt
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark; Medical Research Laboratory, Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark
| | - Morten Høgild
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark; Medical Research Laboratory, Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark
| | - Ann Mosegaard Bak
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark; Medical Research Laboratory, Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark
| | - Mai Christiansen Arlien-Søborg
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark; Medical Research Laboratory, Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark
| | - Amanda Bæk
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark; Medical Research Laboratory, Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark
| | - Niels Jessen
- Steno Diabetes Center Aarhus, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, Aarhus 8200, Denmark; Department of Clinical Pharmacology, Aarhus University Hospital, Aarhus, Denmark; Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Bjørn Richelsen
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark; Medical Research Laboratory, Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark; Steno Diabetes Center Aarhus, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, Aarhus 8200, Denmark
| | - Steen Bønløkke Pedersen
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark; Medical Research Laboratory, Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark
| | - Niels Møller
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark; Medical Research Laboratory, Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark
| | - Jens Otto Lunde Jørgensen
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark; Medical Research Laboratory, Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus N 8200, Denmark.
| |
Collapse
|
14
|
Packer M. Autophagy-dependent and -independent modulation of oxidative and organellar stress in the diabetic heart by glucose-lowering drugs. Cardiovasc Diabetol 2020; 19:62. [PMID: 32404204 PMCID: PMC7222526 DOI: 10.1186/s12933-020-01041-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 05/09/2020] [Indexed: 02/07/2023] Open
Abstract
Autophagy is a lysosome-dependent intracellular degradative pathway, which mediates the cellular adaptation to nutrient and oxygen depletion as well as to oxidative and endoplasmic reticulum stress. The molecular mechanisms that stimulate autophagy include the activation of energy deprivation sensors, sirtuin-1 (SIRT1) and adenosine monophosphate-activated protein kinase (AMPK). These enzymes not only promote organellar integrity directly, but they also enhance autophagic flux, which leads to the removal of dysfunctional mitochondria and peroxisomes. Type 2 diabetes is characterized by suppression of SIRT1 and AMPK signaling as well as an impairment of autophagy; these derangements contribute to an increase in oxidative stress and the development of cardiomyopathy. Antihyperglycemic drugs that signal through insulin may further suppress autophagy and worsen heart failure. In contrast, metformin and SGLT2 inhibitors activate SIRT1 and/or AMPK and promote autophagic flux to varying degrees in cardiomyocytes, which may explain their benefits in experimental cardiomyopathy. However, metformin and SGLT2 inhibitors differ meaningfully in the molecular mechanisms that underlie their effects on the heart. Whereas metformin primarily acts as an agonist of AMPK, SGLT2 inhibitors induce a fasting-like state that is accompanied by ketogenesis, a biomarker of enhanced SIRT1 signaling. Preferential SIRT1 activation may also explain the ability of SGLT2 inhibitors to stimulate erythropoiesis and reduce uric acid (a biomarker of oxidative stress)—effects that are not seen with metformin. Changes in both hematocrit and serum urate are the most important predictors of the ability of SGLT2 inhibitors to reduce the risk of cardiovascular death and hospitalization for heart failure in large-scale trials. Metformin and SGLT2 inhibitors may also differ in their ability to mitigate diabetes-related increases in intracellular sodium concentration and its adverse effects on mitochondrial functional integrity. Differences in the actions of SGLT2 inhibitors and metformin may reflect the distinctive molecular pathways that explain differences in the cardioprotective effects of these drugs.
Collapse
Affiliation(s)
- Milton Packer
- Baylor Heart and Vascular Institute, Baylor University Medical Center, 621 N. Hall Street, Dallas, TX, 75226, USA. .,Imperial College, London, UK.
| |
Collapse
|
15
|
Tobias IS, Lazauskas KK, Siu J, Costa PB, Coburn JW, Galpin AJ. Sex and fiber type independently influence AMPK, TBC1D1, and TBC1D4 at rest and during recovery from high-intensity exercise in humans. J Appl Physiol (1985) 2020; 128:350-361. [PMID: 31895596 DOI: 10.1152/japplphysiol.00704.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Women and men present different metabolic responses to exercise, yet whether this phenomenon results from differences in fiber type (FT) composition or other sex-specific factors remains unclear. Therefore, our aim was to examine the effects of sex and FT independently on AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC), Tre-2/BUB2/CDC1 domain family (TBC1D)1, and TBC1D4 in response to acute exercise. Segregated pools of myosin heavy chain (MHC) I and MHC IIa fibers were prepared from vastus lateralis biopsies of young trained men and women at rest and during recovery (0 min, 45 min, 90 min, or 180 min) from high-intensity interval exercise (6 × 1.5 min at 95% maximum oxygen uptake). In resting MHC I vs. IIa fibers, AMPKα2, AMPKγ3, and TBC1D1 were higher and TBC1D4 expression was lower in both sexes, along with higher phospho (p)-TBC1D1Ser660 and lower p-TBC1D4Thr642. Women expressed higher ACC than men in MHC IIa fibers and higher AMPKβ1, AMPKβ2, TBC1D1, and TBC1D4 in both FTs. Immediately after exercise, p-AMPKαThr172 increased only in MHC IIa fibers, whereas p-ACCSer221 increased in both FTs, with no change in p-TBC1D1Ser660 or p-TBC1D4Thr642. During recovery, delayed responses were observed for p-AMPKαThr172 in MHC I (45 min), p-TBC1D4Thr642 in both FTs (45 min), and p-TBC1D1Ser660 (180 min). FT-specific phosphorylation responses to exercise were similar between men and women. Data indicate that sex and FT independently influence expression of AMPK and its substrates. Thus failing to account for sex or FT may reduce accuracy and precision of metabolic protein measurements and conceal key findings.NEW & NOTEWORTHY This investigation is the first to compare muscle fiber type (FT)-specific analysis of proteins between the sexes, providing comprehensive data on AMP-activated protein kinase (AMPK), acetyl-CoA carboxylase (ACC), Tre-2/BUB2/CDC1 domain family (TBC1D)1, and TBC1D4 before and in the hours following high-intensity interval exercise (HIIT). Expression and phosphorylation of specific AMPK isoforms, ACC, TBC1D1, and TBC1D4 were shown to be FT dependent, sex dependent, or both, and TBC1D1 showed an unexpected delay in FT-dependent phosphorylation in the time period following HIIT.
Collapse
Affiliation(s)
- Irene S Tobias
- Biochemistry and Molecular Exercise Physiology Laboratory, Center for Sport Performance, California State University, Fullerton, California
| | - Kara K Lazauskas
- Biochemistry and Molecular Exercise Physiology Laboratory, Center for Sport Performance, California State University, Fullerton, California
| | - Jeremy Siu
- Biochemistry and Molecular Exercise Physiology Laboratory, Center for Sport Performance, California State University, Fullerton, California
| | - Pablo B Costa
- Biochemistry and Molecular Exercise Physiology Laboratory, Center for Sport Performance, California State University, Fullerton, California
| | - Jared W Coburn
- Biochemistry and Molecular Exercise Physiology Laboratory, Center for Sport Performance, California State University, Fullerton, California
| | - Andrew J Galpin
- Biochemistry and Molecular Exercise Physiology Laboratory, Center for Sport Performance, California State University, Fullerton, California
| |
Collapse
|
16
|
Voss TS, Vendelbo MH, Kampmann U, Pedersen SB, Nielsen TS, Johannsen M, Svart MV, Jessen N, Møller N. Substrate metabolism, hormone and cytokine levels and adipose tissue signalling in individuals with type 1 diabetes after insulin withdrawal and subsequent insulin therapy to model the initiating steps of ketoacidosis. Diabetologia 2019; 62:494-503. [PMID: 30506451 DOI: 10.1007/s00125-018-4785-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 10/18/2018] [Indexed: 12/31/2022]
Abstract
AIMS/HYPOTHESIS Lack of insulin and infection/inflammation are the two most common causes of diabetic ketoacidosis (DKA). We used insulin withdrawal followed by insulin administration as a clinical model to define effects on substrate metabolism and to test whether increased levels of counter-regulatory hormones and cytokines and altered adipose tissue signalling participate in the early phases of DKA. METHODS Nine individuals with type 1 diabetes, without complications, were randomly studied twice, in a crossover design, for 5 h followed by 2.5 h high-dose insulin clamp: (1) insulin-controlled euglycaemia (control) and (2) after 14 h of insulin withdrawal in a university hospital setting. RESULTS Insulin withdrawal increased levels of glucose (6.1 ± 0.5 vs 18.6 ± 0.5 mmol/l), NEFA, 3-OHB (127 ± 18 vs 1837 ± 298 μmol/l), glucagon, cortisol and growth hormone and decreased HCO3- and pH, without affecting catecholamine or cytokine levels. Whole-body energy expenditure, endogenous glucose production (1.55 ± 0.13 vs 2.70 ± 0.31 mg kg-1 min-1), glucose turnover, non-oxidative glucose disposal, lipid oxidation, palmitate flux (73 [range 39-104] vs 239 [151-474] μmol/min), protein oxidation and phenylalanine flux all increased, whereas glucose oxidation decreased. In adipose tissue, Ser473 phosphorylation of Akt and mRNA levels of G0S2 decreased, whereas CGI-58 (also known as ABHD5) mRNA increased. Protein levels of adipose triglyceride lipase (ATGL) and hormone-sensitive lipase phosphorylations were unaltered. Insulin therapy decreased plasma glucose concentrations dramatically after insulin withdrawal, without any detectable effect on net forearm glucose uptake. CONCLUSIONS/INTERPRETATION Release of counter-regulatory hormones and overall increased catabolism, including lipolysis, are prominent features of preacidotic ketosis induced by insulin withdrawal, and dampening of Akt insulin signalling and transcriptional modulation of ATGL activity are involved. The lack of any increase in net forearm glucose uptake during insulin therapy after insulin withdrawal indicates muscle insulin resistance. TRIAL REGISTRATION ClinicalTrials.gov NCT02077348 FUNDING: This study was supported by Aarhus University and the KETO Study Group/Danish Agency for Science Technology and Innovation.
Collapse
Affiliation(s)
- Thomas S Voss
- Medical Research Laboratory, Aarhus University, Nørrebrogade 44, building 3, DK-8000, Aarhus C, Denmark
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Mikkel H Vendelbo
- Department of Nuclear Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Ulla Kampmann
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Steen B Pedersen
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Thomas S Nielsen
- The Novo Nordisk Foundation Center for Basic Metabolic Research, Section on Integrative Physiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Mogens Johannsen
- Section for Forensic Chemistry, Department of Forensic Medicine, Aarhus University, Aarhus, Denmark
| | - Mads V Svart
- Medical Research Laboratory, Aarhus University, Nørrebrogade 44, building 3, DK-8000, Aarhus C, Denmark
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Niels Jessen
- Research Laboratory for Biochemical Pathology and Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Department of Clinical Pharmacology, Aarhus University Hospital, Aarhus, Denmark
| | - Niels Møller
- Medical Research Laboratory, Aarhus University, Nørrebrogade 44, building 3, DK-8000, Aarhus C, Denmark.
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark.
| |
Collapse
|
17
|
Protein synthesis signaling in skeletal muscle is refractory to whey protein ingestion during a severe energy deficit evoked by prolonged exercise and caloric restriction. Int J Obes (Lond) 2018; 43:872-882. [PMID: 30242237 DOI: 10.1038/s41366-018-0174-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 05/24/2018] [Accepted: 06/24/2018] [Indexed: 12/13/2022]
Abstract
BACKGROUND Exercise and protein ingestion preserve muscle mass during moderate energy deficits. OBJECTIVE To determine the molecular mechanisms by which exercise and protein ingestion may spare muscle mass during severe energy deficit (5500 kcal/day). DESIGN Fifteen overweight, but otherwise healthy men, underwent a pre-test (PRE), caloric restriction (3.2 kcals/kg body weight/day) + exercise (45 min one-arm cranking + 8 h walking) for 4 days (CRE), followed by a control diet (CD) for 3 days, with a caloric content similar to pre-intervention while exercise was reduced to less than 10,000 steps per day. During CRE, participants ingested either whey protein (PRO, n = 8) or sucrose (SU, n = 7) (0.8 g/kg body weight/day). Muscle biopsies were obtained from the trained and untrained deltoid, and vastus lateralis. RESULTS Following CRE and CD, serum concentrations of leptin, insulin, and testosterone were reduced, whereas cortisol and the catabolic index (cortisol/total testosterone) increased. The Akt/mTor/p70S6K pathway and total eIF2α were unchanged, while total 4E-BP1 and Thr37/464E-BP1 were higher. After CRE, plasma BCAA and EAA were elevated, with a greater response in PRO group, and total GSK3β, pSer9GSK3β, pSer51eIF2α, and pSer51eIF2α/total eIF2α were reduced, with a greater response of pSer9GSK3β in the PRO group. The changes in signaling were associated with the changes in leptin, insulin, amino acids, cortisol, cortisol/total testosterone, and lean mass. CONCLUSIONS During severe energy deficit, pSer9GSK3β levels are reduced and human skeletal muscle becomes refractory to the anabolic effects of whey protein ingestion, regardless of contractile activity. These effects are associated with the changes in lean mass and serum insulin, testosterone, and cortisol concentrations.
Collapse
|
18
|
Bak AM, Vendelbo MH, Christensen B, Viggers R, Bibby BM, Rungby J, Jørgensen JOL, Møller N, Jessen N. Prolonged fasting-induced metabolic signatures in human skeletal muscle of lean and obese men. PLoS One 2018; 13:e0200817. [PMID: 30183740 PMCID: PMC6124727 DOI: 10.1371/journal.pone.0200817] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 07/03/2018] [Indexed: 11/19/2022] Open
Abstract
Insulin resistance is a well-known physiological adaptation to prolonged fasting in healthy skeletal muscle. Obesity is associated with insulin resistance and metabolic inflexibility in skeletal muscle, and a pronounced increase in the risk of metabolic complications. Under the hypothesis that the metabolic traits of insulin resistance associated with prolonged fasting are different from insulin resistance associated with obesity, we examined nine obese and nine lean participants during 12 and 72h of fasting, respectively. Insulin resistance in obese participants was associated with impaired insulin signaling, and reduced levels of glucose-6-phosphate and TCA-cycle intermediates. 72h of fasting in lean participants reduced insulin-stimulated glucose uptake to levels similar to obese participants fasted for 12h. This was associated with increased lipid oxidation, but not accumulation of diacylglycerol or acylcarnitines and impairment of insulin signaling. Prolonged fasting was associated with pronounced increases in β-hydroxybutyrate and β- hydroxybutyrylcarnitine levels in skeletal muscle suggesting augmented ketone body metabolism. Fasting induced insulin resistance may be a consequence of substrate competition. The underlying mechanism behind insulin resistance in obesity is thus not comparable to the physiological adaptations in skeletal muscle induced by prolonged fasting in lean participants.
Collapse
Affiliation(s)
- Ann Mosegaard Bak
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
- Department of Endocrinology and Internal Medicine (MEA), Aarhus University Hospital, Aarhus, Denmark
- * E-mail:
| | - Mikkel Holm Vendelbo
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
- Department of Nuclear Medicine and PET Center, Aarhus University Hospital, Aarhus, Denmark
| | - Britt Christensen
- Department of Endocrinology and Internal Medicine (MEA), Aarhus University Hospital, Aarhus, Denmark
- Research Laboratory for Biochemical Pathology, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Rikke Viggers
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
- Research Laboratory for Biochemical Pathology, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Bo Martin Bibby
- Department of Public Health, Aarhus University, Aarhus, Denmark
| | - Jørgen Rungby
- Department of Biomedicine, Aarhus University, Denmark
| | - Jens Otto Lunde Jørgensen
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
- Department of Endocrinology and Internal Medicine (MEA), Aarhus University Hospital, Aarhus, Denmark
| | - Niels Møller
- Medical Research Laboratory, Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
- Department of Endocrinology and Internal Medicine (MEA), Aarhus University Hospital, Aarhus, Denmark
| | - Niels Jessen
- Department of Endocrinology and Internal Medicine (MEA), Aarhus University Hospital, Aarhus, Denmark
- Department of Biomedicine, Aarhus University, Denmark
- Department of Clinical Pharmacology, Aarhus University Hospital, Denmark
| |
Collapse
|
19
|
Sun Y, Shi H, Yin S, Ji C, Zhang X, Zhang B, Wu P, Shi Y, Mao F, Yan Y, Xu W, Qian H. Human Mesenchymal Stem Cell Derived Exosomes Alleviate Type 2 Diabetes Mellitus by Reversing Peripheral Insulin Resistance and Relieving β-Cell Destruction. ACS NANO 2018; 12:7613-7628. [PMID: 30052036 DOI: 10.1021/acsnano.7b07643] [Citation(s) in RCA: 269] [Impact Index Per Article: 44.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Exosomes are nanosized extracellular vesicles (EVs) that show great promise in tissue regeneration and injury repair as mesenchymal stem cell (MSC). MSC has been shown to alleviate diabetes mellitus (DM) in both animal models and clinical trials. In this study, we aimed to investigate whether exosomes from human umbilical cord MSC (hucMSC-ex) have a therapeutic effect on type 2 DM (T2DM). We established a rat model of T2DM using a high-fat diet and streptozotocin (STZ). We found that the intravenous injection of hucMSC-ex reduced blood glucose levels as a main paracrine approach of MSC. HucMSC-ex partially reversed insulin resistance in T2DM indirectly to accelerate glucose metabolism. HucMSC-ex restored the phosphorylation (tyrosine site) of the insulin receptor substrate 1 and protein kinase B in T2DM, promoted expression and membrane translocation of glucose transporter 4 in muscle, and increased storage of glycogen in the liver to maintain glucose homeostasis. HucMSC-ex inhibited STZ-induced β-cell apoptosis to restore the insulin-secreting function of T2DM. Taken together, exosomes from hucMSC can alleviate T2DM by reversing peripheral insulin resistance and relieving β-cell destruction, providing an alternative approach for T2DM treatment.
Collapse
Affiliation(s)
- Yaoxiang Sun
- Jiangsu Key Laboratory of Medical Science and Laboratory Medicine, Institute of Stem Cell, School of Medicine , Jiangsu University , Zhenjiang , Jiangsu 212013 , China
- Department of Clinical Laboratory , The Affiliated Yixing Hospital of Jiangsu University , Yixing , Jiangsu 214200 , China
| | - Hui Shi
- Jiangsu Key Laboratory of Medical Science and Laboratory Medicine, Institute of Stem Cell, School of Medicine , Jiangsu University , Zhenjiang , Jiangsu 212013 , China
| | - Siqi Yin
- Jiangsu Key Laboratory of Medical Science and Laboratory Medicine, Institute of Stem Cell, School of Medicine , Jiangsu University , Zhenjiang , Jiangsu 212013 , China
| | - Cheng Ji
- Jiangsu Key Laboratory of Medical Science and Laboratory Medicine, Institute of Stem Cell, School of Medicine , Jiangsu University , Zhenjiang , Jiangsu 212013 , China
| | - Xu Zhang
- Jiangsu Key Laboratory of Medical Science and Laboratory Medicine, Institute of Stem Cell, School of Medicine , Jiangsu University , Zhenjiang , Jiangsu 212013 , China
| | - Bin Zhang
- Jiangsu Key Laboratory of Medical Science and Laboratory Medicine, Institute of Stem Cell, School of Medicine , Jiangsu University , Zhenjiang , Jiangsu 212013 , China
| | - Peipei Wu
- Jiangsu Key Laboratory of Medical Science and Laboratory Medicine, Institute of Stem Cell, School of Medicine , Jiangsu University , Zhenjiang , Jiangsu 212013 , China
| | - Yinghong Shi
- Jiangsu Key Laboratory of Medical Science and Laboratory Medicine, Institute of Stem Cell, School of Medicine , Jiangsu University , Zhenjiang , Jiangsu 212013 , China
| | - Fei Mao
- Jiangsu Key Laboratory of Medical Science and Laboratory Medicine, Institute of Stem Cell, School of Medicine , Jiangsu University , Zhenjiang , Jiangsu 212013 , China
| | - Yongmin Yan
- Jiangsu Key Laboratory of Medical Science and Laboratory Medicine, Institute of Stem Cell, School of Medicine , Jiangsu University , Zhenjiang , Jiangsu 212013 , China
| | - Wenrong Xu
- Jiangsu Key Laboratory of Medical Science and Laboratory Medicine, Institute of Stem Cell, School of Medicine , Jiangsu University , Zhenjiang , Jiangsu 212013 , China
| | - Hui Qian
- Jiangsu Key Laboratory of Medical Science and Laboratory Medicine, Institute of Stem Cell, School of Medicine , Jiangsu University , Zhenjiang , Jiangsu 212013 , China
| |
Collapse
|
20
|
Moberg M, Hendo G, Jakobsson M, Mattsson CM, Ekblom-Bak E, Flockhart M, Pontén M, Söderlund K, Ekblom B. Increased autophagy signaling but not proteasome activity in human skeletal muscle after prolonged low-intensity exercise with negative energy balance. Physiol Rep 2018; 5. [PMID: 29208687 PMCID: PMC5727276 DOI: 10.14814/phy2.13518] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 11/02/2017] [Indexed: 01/01/2023] Open
Abstract
Little is known about the molecular regulation of skeletal muscle protein turnover during exercise in field conditions where energy is intake inadequate. Here, 17 male and 7 female soldiers performed an 8 days long field-based military operation. Vastus lateralis muscle biopsies, in which autophagy, the ubiquitin-proteasome system, and the mTORC1 signaling pathway were studied, were collected before and after the operation. The 187 h long operation resulted in a 15% and 29% negative energy balance as well as a 4.1% and 4.6% loss of body mass in women and men, respectively. After the operation protein levels of ULK1 as well as the phosphorylation of ULK1Ser317 and ULK1Ser555 had increased by 11%, 39%, and 13%, respectively, and this was supported by a 17% increased phosphorylation of AMPKThr172 (P < 0.05). The LC3b-I/II ratio was threefold higher after compared to before the operation (P < 0.05), whereas protein levels of p62/SQSTM1 were unchanged. The β1, β2, and β5 activity of the proteasome and protein levels of MAFbx did not change, whereas levels of MuRF-1 were slightly reduced (6%, P < 0.05). Protein levels and phosphorylation status of key components in the mTORC1 signaling pathway remained at basal levels after the operation. Muscle levels of glycogen decreased from 269 ± 12 to 181 ± 9 mmol·kg dry·muscle-1 after the exercise period (P < 0.05). In conclusion, the 8 days of field-based exercise resulted in induction of autophagy without any increase in proteasome activity or protein ubiquitination. Simultaneously, the regulation of protein synthesis through the mTORC1 signaling pathway was maintained.
Collapse
Affiliation(s)
- Marcus Moberg
- Åstrand Laboratory of Work Physiology, the Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Gina Hendo
- Åstrand Laboratory of Work Physiology, the Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Madelene Jakobsson
- Åstrand Laboratory of Work Physiology, the Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - C Mikael Mattsson
- Åstrand Laboratory of Work Physiology, the Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Elin Ekblom-Bak
- Åstrand Laboratory of Work Physiology, the Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Mikael Flockhart
- Åstrand Laboratory of Work Physiology, the Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Marjan Pontén
- Åstrand Laboratory of Work Physiology, the Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Karin Söderlund
- Åstrand Laboratory of Work Physiology, the Swedish School of Sport and Health Sciences, Stockholm, Sweden
| | - Björn Ekblom
- Åstrand Laboratory of Work Physiology, the Swedish School of Sport and Health Sciences, Stockholm, Sweden
| |
Collapse
|
21
|
Breuker C, Amouzou C, Fabre O, Lambert K, Seyer P, Bourret A, Salehzada T, Mercier J, Sultan A, Bisbal C. Decreased RNF41 expression leads to insulin resistance in skeletal muscle of obese women. Metabolism 2018; 83:81-91. [PMID: 29410345 DOI: 10.1016/j.metabol.2018.01.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 12/22/2017] [Accepted: 01/17/2018] [Indexed: 01/30/2023]
Abstract
CONTEXT Toll-like receptor 4 (TLR4) activation contributes to obesity-associated insulin resistance in skeletal muscles (SM). TLR4 signaling involves two pathways: the myeloid differentiation primary response gene 88 (MyD88) leading to inflammatory cytokines production and the toll/interleukin-1 receptor domain-containing adapter-inducing interferon (IFN) I (TRIF)-dependent pathways leading to type 1 interferon (IFNI) and interferon stimulated genes (ISG) expression. The E3 ubiquitin ligase RNF41 allows the preferential activation of the TRIF-IFNI pathway; however, its role in insulin response has not been reported. METHODS We measured RNF41 level and IFNI pathway activation (ISG expression) in SM biopsies of obese insulin sensitive (OIS) and obese insulin resistant (OIR) women. Then we isolated and differentiated in myotubes, primary human SM cell progenitors from OIS and OIR SM biopsies. We modulated RNF41 and ISG expression in these myotubes and investigated their effects on insulin response. RESULTS RNF41 expression is down-regulated in vivo in OIR SM and myotubes compared to OIS SM and myotubes. TLR4 activation with palmitate induces TRIF-IFNI pathway and ISG in OIS myotubes but not in OIR myotubes. Inhibition of RNF41 expression with siRNF41 in OIS myotubes treated with palmitate attenuates insulin response, IFNI pathway activation and ISG induction, mimicking OIR phenotype. Further, overexpression of RNF41 in OIR myotubes increases insulin response and ISG expression. Exposure to IFNI or to its inducer polyinosinic-polycytidylic acid, restores ISG expression and insulin sensitivity in OIR myotubes and OIS myotubes transfected with siRNF41. CONCLUSION Our results identify RNF41 as essential to IFNI pathway activation in order to maintain muscle insulin sensitivity during human obesity.
Collapse
Affiliation(s)
- Cyril Breuker
- PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, 34295 Montpellier cedex 5, France; Centre Hospitalier Universitaire (CHU) Montpellier, 34295 Montpellier, France
| | - Cacylde Amouzou
- PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, 34295 Montpellier cedex 5, France
| | - Odile Fabre
- PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, 34295 Montpellier cedex 5, France
| | - Karen Lambert
- PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, 34295 Montpellier cedex 5, France
| | - Pascal Seyer
- PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, 34295 Montpellier cedex 5, France
| | - Annick Bourret
- PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, 34295 Montpellier cedex 5, France
| | - Tamim Salehzada
- PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, 34295 Montpellier cedex 5, France
| | - Jacques Mercier
- PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, 34295 Montpellier cedex 5, France; Centre Hospitalier Universitaire (CHU) Montpellier, 34295 Montpellier, France
| | - Ariane Sultan
- PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, 34295 Montpellier cedex 5, France; Centre Hospitalier Universitaire (CHU) Montpellier, 34295 Montpellier, France
| | - Catherine Bisbal
- PhyMedExp, University of Montpellier, INSERM U1046, CNRS UMR 9214, 34295 Montpellier cedex 5, France.
| |
Collapse
|
22
|
Lundsgaard AM, Sjøberg KA, Høeg LD, Jeppesen J, Jordy AB, Serup AK, Fritzen AM, Pilegaard H, Myrmel LS, Madsen L, Wojtaszewski JFP, Richter EA, Kiens B. Opposite Regulation of Insulin Sensitivity by Dietary Lipid Versus Carbohydrate Excess. Diabetes 2017; 66:2583-2595. [PMID: 28768703 DOI: 10.2337/db17-0046] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 07/27/2017] [Indexed: 11/13/2022]
Abstract
To understand the mechanisms in lipid-induced insulin resistance, a more physiological approach is to enhance fatty acid (FA) availability through the diet. Nine healthy men ingested two hypercaloric diets (in 75% excess of habitual caloric intake) for 3 days, enriched in unsaturated FA (78 energy % [E%] fat) (UNSAT) or carbohydrates (80 E% carbohydrate) (CHO) as well as a eucaloric control diet (CON). Compared with CON, the UNSAT diet reduced whole-body and leg glucose disposal during a hyperinsulinemic-euglycemic clamp, while decreasing hepatic glucose production. In muscle, diacylglycerol (DAG) and intramyocellular triacylglycerol were increased. The accumulated DAG was sn-1,3 DAG, which is known not to activate PKC, and insulin signaling was intact. UNSAT decreased PDH-E1α protein content and increased inhibitory PDH-E1α Ser300 phosphorylation and FA oxidation. CHO increased whole-body and leg insulin sensitivity, while increasing hepatic glucose production. After CHO, muscle PDH-E1α Ser300 phosphorylation was decreased, and glucose oxidation increased. After UNSAT, but not CHO, muscle glucose-6-phosphate content was 103% higher compared with CON during the clamp. Thus, PDH-E1α expression and covalent regulation, and hence the tricarboxylic acid cycle influx of pyruvate-derived acetyl-CoA relative to β-oxidation-derived acetyl-CoA, are suggested to impact on insulin-stimulated glucose uptake. Taken together, the oxidative metabolic fluxes of glucose and FA are powerful and opposite regulators of insulin action in muscle.
Collapse
Affiliation(s)
- Anne-Marie Lundsgaard
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Kim A Sjøberg
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Louise D Høeg
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Jacob Jeppesen
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Andreas B Jordy
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Annette K Serup
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Andreas M Fritzen
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | | | - Lene S Myrmel
- National Institute of Nutrition and Seafood Research, Bergen, Norway
| | - Lise Madsen
- National Institute of Nutrition and Seafood Research, Bergen, Norway
- Laboratory of Genomics and Molecular Biomedicine, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Jørgen F P Wojtaszewski
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Erik A Richter
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| | - Bente Kiens
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, Faculty of Science, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
23
|
Svart MV, Rittig N, Kampmann U, Voss TS, Møller N, Jessen N. Metabolic effects of insulin in a human model of ketoacidosis combining exposure to lipopolysaccharide and insulin deficiency: a randomised, controlled, crossover study in individuals with type 1 diabetes. Diabetologia 2017; 60:1197-1206. [PMID: 28389705 DOI: 10.1007/s00125-017-4271-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 03/15/2017] [Indexed: 12/25/2022]
Abstract
AIMS/HYPOTHESIS Diabetic ketoacidosis (DKA) is often caused by concomitant systemic inflammation and lack of insulin. Here we used an experimental human model to test whether and how metabolic responses to insulin are impaired in the early phases of DKA with a specific focus on skeletal muscle metabolism. METHODS Nine individuals with type 1 diabetes from a previously published cohort were investigated twice at Aarhus University Hospital using a 120 min infusion of insulin (3.0/1.5 mU kg-1 min-1) after an overnight fast under: (1) euglycaemic conditions (CTR) or (2) hyperglycaemic ketotic conditions (KET) induced by an i.v. bolus of lipopolysaccharide and 85% reduction in insulin dosage. The primary outcome was insulin resistance in skeletal muscle. Participants were randomly assigned to one of the two arms at the time of screening using www.randomizer.org . The study was not blinded. RESULTS All nine volunteers completed the 2 days and are included in the analysis. Circulating concentrations of glucose and 3-hydroxybutyrate increased during KET (mean ± SEM 17.7 ± 0.6 mmol/l and 1.6 ± 0.2 mmol/l, respectively), then decreased after insulin treatment (6.6 ± 0.7 mmol/l and 0.1 ± 0.07 mmol/l, respectively). Prior to insulin infusion (KET vs CTR) isotopically determined endogenous glucose production rates were 17 ± 1.7 μmol kg-1 min-1 vs 8 ± 1.3 μmol kg-1 min-1 (p = 0.003), whole body phenylalanine fluxes were 2.9 ± 0.5 μmol kg-1 min-1 vs 3.1 ± 0.4 μmol kg-1 min-1 (p = 0.77) and urea excretion rates were 16.9 ± 2.4 g/day vs 7.3 ± 1.7 g/day (p = 0.01). Insulin failed to stimulate forearm glucose uptake and glucose oxidation in KET compared with CTR (p < 0.05). Glycogen synthase phosphorylation was impaired in skeletal muscle. CONCLUSIONS/INTERPRETATION In KET, hyperglycaemia is primarily driven by increased endogenous glucose production. Insulin stimulation during early phases of DKA is associated with reduced glucose disposal in skeletal muscle, impaired glycogen synthase function and lower glucose oxidation. This underscores the presence of muscle insulin resistance in the pathogenesis of DKA. Trial registration www.clinicaltrials.gov (ID number: NCT02157155). Funding This work was funded by the Danish Council for Strategic Research (grant no. 0603-00479B).
Collapse
Affiliation(s)
- Mads V Svart
- Department of Internal Medicine and Endocrinology, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Nikolaj Rittig
- Department of Internal Medicine and Endocrinology, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Ulla Kampmann
- Department of Internal Medicine and Endocrinology, Aarhus University Hospital, Aarhus, Denmark
| | - Thomas S Voss
- Department of Internal Medicine and Endocrinology, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Niels Møller
- Department of Internal Medicine and Endocrinology, Aarhus University Hospital, Aarhus, Denmark
- Department of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Niels Jessen
- Department of Clinical Pharmacology, Aarhus University Hospital, Aarhus, Denmark.
- Department of Biomedicine, Aarhus University, Wilhelm Meyers Alle 4, DK-8000, Aarhus C, Denmark.
| |
Collapse
|
24
|
Edinburgh RM, Betts JA, Burns SF, Gonzalez JT. Concordant and divergent strategies to improve postprandial glucose and lipid metabolism. NUTR BULL 2017. [DOI: 10.1111/nbu.12259] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
| | | | - S. F. Burns
- Nanyang Technological University; Singapore Singapore
| | | |
Collapse
|
25
|
TINSLEY GRANTM, MORALES ELISA, FORSSE JEFFREYS, GRANDJEAN PETERW. Impact of Acute Dietary Manipulations on DXA and BIA Body Composition Estimates. Med Sci Sports Exerc 2017; 49:823-832. [DOI: 10.1249/mss.0000000000001148] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
|
26
|
Jensen J, O'Rahilly S. AMPK is required for exercise to enhance insulin sensitivity in skeletal muscles. Mol Metab 2017; 6:315-316. [PMID: 28377870 PMCID: PMC5369262 DOI: 10.1016/j.molmet.2017.01.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Accepted: 01/18/2017] [Indexed: 10/26/2022] Open
Affiliation(s)
- Jørgen Jensen
- Department of Physical Performance, Norwegian School of Sport Sciences, Norway.
| | - Stephen O'Rahilly
- Welcome Trust-MRC Institute of Metabolic Science, University of Cambridge, United Kingdom
| |
Collapse
|
27
|
Lin PJ, Borer KT. Third Exposure to a Reduced Carbohydrate Meal Lowers Evening Postprandial Insulin and GIP Responses and HOMA-IR Estimate of Insulin Resistance. PLoS One 2016; 11:e0165378. [PMID: 27798656 PMCID: PMC5087910 DOI: 10.1371/journal.pone.0165378] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 10/06/2016] [Indexed: 12/28/2022] Open
Abstract
Background Postprandial hyperinsulinemia, hyperglycemia, and insulin resistance increase the risk of type 2 diabetes (T2D) and cardiovascular disease mortality. Postprandial hyperinsulinemia and hyperglycemia also occur in metabolically healthy subjects consuming high-carbohydrate diets particularly after evening meals and when carbohydrate loads follow acute exercise. We hypothesized the involvement of dietary carbohydrate load, especially when timed after exercise, and mediation by the glucose-dependent insulinotropic peptide (GIP) in this phenomenon, as this incretin promotes insulin secretion after carbohydrate intake in insulin-sensitive, but not in insulin-resistant states. Methods Four groups of eight metabolically healthy weight-matched postmenopausal women were provided with three isocaloric meals (a pre-trial meal and two meals during the trial day) containing either 30% or 60% carbohydrate, with and without two-hours of moderate-intensity exercise before the last two meals. Plasma glucose, insulin, glucagon, GIP, glucagon-like peptide 1 (GLP-1), free fatty acids (FFAs), and D-3-hydroxybutyrate concentrations were measured during 4-h postprandial periods and 3-h exercise periods, and their areas under the curve (AUCs) were analyzed by mixed-model ANOVA, and insulin resistance during fasting and meal tolerance tests within each diet was estimated using homeostasis-model assessment (HOMA-IR). Results The third low-carbohydrate meal, but not the high-carbohydrate meal, reduced: (1) evening insulin AUC by 39% without exercise and by 31% after exercise; (2) GIP AUC by 48% without exercise and by 45% after exercise, and (3) evening insulin resistance by 37% without exercise and by 24% after exercise. Pre-meal exercise did not alter insulin-, GIP- and HOMA-IR- lowering effects of low-carbohydrate diet, but exacerbated evening hyperglycemia. Conclusions Evening postprandial insulin and GIP responses and insulin resistance declined by over 30% after three meals that limited daily carbohydrate intake to 30% compared to no such changes after three 60%-carbohydrate meals, an effect that was independent of pre-meal exercise. The parallel timing and magnitude of postprandial insulin and GIP changes suggest their dependence on a delayed intestinal adaptation to a low-carbohydrate diet. Pre-meal exercise exacerbated glucose intolerance with both diets most likely due to impairment of insulin signaling by pre-meal elevation of FFAs.
Collapse
Affiliation(s)
- Po-Ju Lin
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Katarina T. Borer
- School of Kinesiology, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail:
| |
Collapse
|
28
|
Edgett BA, Scribbans TD, Raleigh JP, Matusiak JB, Boonstra K, Simpson CA, Perry CG, Quadrilatero J, Gurd BJ. The impact of a 48-h fast on SIRT1 and GCN5 in human skeletal muscle. Appl Physiol Nutr Metab 2016; 41:953-62. [DOI: 10.1139/apnm-2016-0130] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The present study examined the impact of a 48 h fast on the expression and activation status of SIRT1 and GCN5, the relationship between SIRT1/GCN5 and the gene expression of PGC-1α, and the PGC-1α target PDK4 in the skeletal muscle of 10 lean healthy men (age, 22.0 ± 1.5 years; peak oxygen uptake, 47.2 ± 6.7 mL/(min·kg)). Muscle biopsies and blood samples were collected 1 h postprandial (Fed) and following 48 h of fasting (Fasted). Plasma insulin (Fed, 80.8 ± 47.9 pmol/L; Fasted, not detected) and glucose (Fed, 4.36 ± 0.86; Fasted, 3.74 ± 0.25 mmol/L, p = 0.08) decreased, confirming participant adherence to fasting. Gene expression of PGC-1α decreased (p < 0.05, –24%), while SIRT1 and PDK4 increased (p < 0.05, +11% and +1023%, respectively), and GCN5 remained unchanged. No changes were observed for whole-muscle protein expression of SIRT1, GCN5, PGC-1α, or COX IV. Phosphorylation of SIRT1, AMPKα, ACC, p38 MAPK, and PKA substrates as well as nuclear acetylation status was also unaltered. Additionally, nuclear SIRT1 activity, GCN5, and PGC-1α content remained unchanged. Preliminary findings derived from regression analysis demonstrate that changes in nuclear GCN5 and SIRT1 activity/phosphorylation may contribute to the control of PGC-1α, but not PDK4, messenger RNA expression following fasting. Collectively, and in contrast with previous animal studies, our data are inconsistent with the altered activation status of SIRT1 and GCN5 in response to 48 h of fasting in human skeletal muscle.
Collapse
Affiliation(s)
- Brittany A. Edgett
- School of Kinesiology and Health Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
| | - Trisha D. Scribbans
- School of Kinesiology and Health Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
| | - James P. Raleigh
- School of Kinesiology and Health Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
| | - Jennifer B.L. Matusiak
- School of Kinesiology and Health Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
| | - Kristen Boonstra
- Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Craig A. Simpson
- Department of Emergency Medicine, Queen’s University, Kingston, ON K7L 3N6, Canada
| | | | - Joe Quadrilatero
- Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Brendon J. Gurd
- School of Kinesiology and Health Studies, Queen’s University, Kingston, ON K7L 3N6, Canada
| |
Collapse
|
29
|
Long-term treatment with nicotinamide induces glucose intolerance and skeletal muscle lipotoxicity in normal chow-fed mice: compared to diet-induced obesity. J Nutr Biochem 2016; 36:31-41. [PMID: 27567590 DOI: 10.1016/j.jnutbio.2016.07.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 05/06/2016] [Accepted: 07/05/2016] [Indexed: 12/11/2022]
Abstract
Nicotinamide (NAM), or vitamin B3, is an essential coenzyme for ATP synthesis and an inhibitor of sirtuin 1. Recently, conflicting results were reported regarding the treatment of NAM in type 2 diabetes and obesity. The aim of this study was to determine whether and how long-term treatment with NAM at lower dose would affect insulin sensitivity in mice fed chow diet. We treated mice with NAM (100 mg/kg/day) and normal chow for 8 weeks. Strikingly, NAM induced glucose intolerance and skeletal muscle lipid accumulation in nonobese mice. NAM impaired mitochondrial respiration capacity and energy production in skeletal muscle, in combination with increased expression of the mediators for mitophagy (p62, PINK1, PARK2 and NIX) and autophagy (FOXO3, Bnip3, CTSL, Beclin1 and LC-3b). Next, we treated mice with high-fat diet (HFD) and resveratrol (RSV; 100 mg/kg/day) for 8 weeks. RSV protected against HFD-induced insulin resistance and obesity. HFD increased skeletal muscle lipid content as well as NAM, but this increase was attenuated by RSV. In contrast to NAM, HFD enhanced fatty acid oxidative capacity. Muscle transcript levels of genes for mitophagy and autophagy were largely suppressed by HFD, whereas RSV did not rescue these effects. These differences suggest that skeletal muscle autophagy may represent adaptive response to NAM-induced lipotoxicity, whereas reduced autophagy in skeletal muscle may promote HFD-induced lipotoxicity. Our results demonstrate that chronic NAM supplementation in healthy individuals, although at lower dose than previously reported, is still detrimental to glucose homeostasis and skeletal muscle lipid metabolism.
Collapse
|
30
|
Consitt LA, Saxena G, Saneda A, Houmard JA. Age-related impairments in skeletal muscle PDH phosphorylation and plasma lactate are indicative of metabolic inflexibility and the effects of exercise training. Am J Physiol Endocrinol Metab 2016; 311:E145-56. [PMID: 27221120 PMCID: PMC4967149 DOI: 10.1152/ajpendo.00452.2015] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Accepted: 05/19/2016] [Indexed: 01/12/2023]
Abstract
The purpose of this study was to determine whether plasma lactate and skeletal muscle glucose regulatory pathways, specifically PDH dephosphorylation, are impaired during hyperinsulinemic conditions in middle- to older-aged individuals and determine whether exercise training could improve key variables responsible for skeletal muscle PDH regulation. Eighteen young (19-29 yr; n = 9 males and 9 females) and 20 middle- to older-aged (57-82 yr; n = 10 males and 10 females) individuals underwent a 2-h euglycemic hyperinsulinemic clamp. Plasma samples were obtained at baseline and at 30, 50, 90, and 120 min for analysis of lactate, and skeletal muscle biopsies were performed at 60 min for analysis of protein associated with glucose metabolism. In response to insulin, plasma lactate was elevated in aged individuals when normalized to insulin action. Insulin-stimulated phosphorylation of skeletal muscle PDH on serine sites 232, 293, and 300 decreased in young individuals only. Changes in insulin-stimulated PDH phosphorylation were positively related to changes in plasma lactate. No age-related differences were observed in skeletal muscle phosphorylation of LDH, GSK-3α, or GSK-3β in response to insulin or PDP1, PDP2, PDK2, PDK4, or MPC1 total protein. Twelve weeks of endurance- or strength-oriented exercise training improved insulin-stimulated PDH dephosphorylation, which was related to a reduced lactate response. These findings suggest that impairments in insulin-induced PDH regulation in a sedentary aging population contribute to impaired glucose metabolism and that exercise training is an effective intervention for treating metabolic inflexibility.
Collapse
Affiliation(s)
- Leslie A Consitt
- Department of Biomedical Sciences, Ohio University, Athens, Ohio; Ohio Musculoskeletal and Neurological Institute, Ohio University, Athens, Ohio; Diabetes Institute, Ohio University, Athens, Ohio;
| | - Gunjan Saxena
- Department of Biomedical Sciences, Ohio University, Athens, Ohio
| | - Alicson Saneda
- Department of Biological Sciences, Ohio University, Athens, Ohio
| | - Joseph A Houmard
- Department of Kinesiology, Human Performance Laboratory, East Carolina University, Greenville, North Carolina; and East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina
| |
Collapse
|
31
|
Vendelbo MH, Christensen B, Grønbæk SB, Høgild M, Madsen M, Pedersen SB, Jørgensen JOL, Jessen N, Møller N. GH signaling in human adipose and muscle tissue during 'feast and famine': amplification of exercise stimulation following fasting compared to glucose administration. Eur J Endocrinol 2015; 173:283-90. [PMID: 26034073 DOI: 10.1530/eje-14-1157] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2014] [Accepted: 06/01/2015] [Indexed: 01/16/2023]
Abstract
OBJECTIVE Fasting and exercise stimulates, whereas glucose suppresses GH secretion, but it is uncertain how these conditions impact GH signaling in peripheral tissues. To test the original 'feast and famine hypothesis' by Rabinowitz and Zierler, according to which the metabolic effects of GH are predominant during fasting, we specifically hypothesized that fasting and exercise act in synergy to increase STAT-5b target gene expression. DESIGN AND METHODS Eight healthy men were studied on two occasions in relation to a 1 h exercise bout: i) with a concomitant i.v. glucose infusion ('feast') and ii) after a 36 h fast ('famine'). Muscle and fat biopsy specimens were obtained before, immediately after, and 30 min after exercise. RESULTS GH increased during exercise on both examination days and this effect was amplified by fasting, and free fatty acid (FFA) levels increased after fasting. STAT-5b phosphorylation increased similarly following exercise on both occasions. In adipose tissue, suppressors of cytokine signaling 1 (SOCS1) and SOCS2 were increased after exercise on the fasting day and both fasting and exercise increased cytokine inducible SH2-containing protein (CISH). In muscle, SOCS2 and CISH mRNA were persistently increased after fasting. Muscle SOCS1, SOCS3, and CISH mRNA expression increased, whereas SOCS2 decreased after exercise on both examination days. CONCLUSIONS This study demonstrates that fasting and exercise act in tandem to amplify STAT-5b target gene expression (SOCS and CISH) in adipose and muscle tissue in accordance with the 'feast and famine hypothesis'; the adipose tissue signaling responses, which hitherto have not been scrutinized, may play a particular role in promoting FFA mobilization.
Collapse
Affiliation(s)
- Mikkel H Vendelbo
- Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark
| | - Britt Christensen
- Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark
| | - Solbritt B Grønbæk
- Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark
| | - Morten Høgild
- Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark
| | - Michael Madsen
- Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark
| | - Steen B Pedersen
- Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark
| | - Jens O L Jørgensen
- Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark
| | - Niels Jessen
- Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark
| | - Niels Møller
- Departments of Endocrinology and Internal MedicineNuclear Medicine and PET CenterResearch Laboratory for Biochemical PathologyAarhus University Hospital, Nørrebrogade 44, 8000 Aarhus, Denmark
| |
Collapse
|
32
|
Bengmark S. Obesity, the deadly quartet and the contribution of the neglected daily organ rest - a new dimension of un-health and its prevention. Hepatobiliary Surg Nutr 2015; 4:278-88. [PMID: 26312244 DOI: 10.3978/j.issn.2304-3881.2015.07.02] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Accepted: 02/28/2015] [Indexed: 12/23/2022]
Abstract
The "deadly quartet": excessive weight, hypertension, impaired glucose homeostasis, and atherogenic dyslipidemia constitute a greater threat to health than the added effects of smoking and alcohol abuse. It is strongly associated with unrestricted consumption of processed, refined foods. Recent observations from experience in South East Asia shows that the interval between lifestyle changes and associated change in disease pattern is shorter than earlier believed. Recent experience from obesity studies in Africa demonstrates not only dramatic changes in health but also large social consequences from being overweight. Obesity is not only a result of overeating - dozens of other factors are known to contribute. Our palaeolithic forefathers and those living a similar lifestyle today are reported to rarely have diseases and to live a long life. One such group is the Hunzas, living in Northern Pakistan, are reported to live on a daily 1,800-calorie 99% plant-based diet, consisting in 73% of mostly unrefined/unprocessed carbohydrates, 17% fat and 10% protein. They, and most likely also our forefathers, do/did most likely only eat twice a day, at noon and early evening. Calorie-restriction (CR) and also fasting was early recommended and has been so during thousands of years - early Greek medicine and giants such as Hippocrates, Galenus and later also Paracelsus prescribed restrictions in eating and fasting. So did Middle Age physicians and other nutrition experts such as Louis Cornado. Today it is again practiced around the World. Overeating and heavy postprandial metabolism is a great burden to the body causing elevated levels in blood of endotoxin, increased inflammatory and oxidative stress, release of tumor necrosis factor-α, and other pro-inflammatory cytokines, increases in numbers of and activating of leukocytes, a reaction that is potentiated by the presence of large-chain fatty acids and sugars. Various metabolic, uremic, microbiota-derived and environmental poisons accumulate in large amounts in the adipose tissues. High levels of poisons in the adipose tissues decreases the turnover of fats in order to protect other organs. The content in adipose of POPs - altogether 17 dioxins/furans and 18 polychlorinated biphenyl congeners, has been reported to be 2-3 times higher in obese compared to lean persons. Daily fasting consisting in 16 to 18 hours of avoidance of calorie intake offers an interesting alternative. An attractive policy is to abstain from eating between 18:00 in the evening and 10:00 or 12:00 AM, a plan, which I personally have practiced during many years.
Collapse
Affiliation(s)
- Stig Bengmark
- Division of Surgery & Interventional Science, University College London, London, WC1E 6AU, UK
| |
Collapse
|
33
|
Smith GI, Yoshino J, Stromsdorfer KL, Klein SJ, Magkos F, Reeds DN, Klein S, Mittendorfer B. Protein Ingestion Induces Muscle Insulin Resistance Independent of Leucine-Mediated mTOR Activation. Diabetes 2015; 64:1555-63. [PMID: 25475435 PMCID: PMC4407849 DOI: 10.2337/db14-1279] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 11/24/2014] [Indexed: 12/12/2022]
Abstract
Increased plasma branched-chain amino acid concentrations are associated with insulin resistance, and intravenous amino acid infusion blunts insulin-mediated glucose disposal. We tested the hypothesis that protein ingestion impairs insulin-mediated glucose disposal by leucine-mediated mTOR signaling, which can inhibit AKT. We measured glucose disposal and muscle p-mTOR(Ser2448), p-AKT(Ser473), and p-AKT(Thr308) in 22 women during a hyperinsulinemic-euglycemic clamp procedure with and without concomitant ingestion of whey protein (0.6 g/kg fat-free mass; n = 11) or leucine that matched the amount given with whey protein (n = 11). Both whey protein and leucine ingestion raised plasma leucine concentration by approximately twofold and muscle p-mTOR(Ser2448) by ∼30% above the values observed in the control (no amino acid ingestion) studies; p-AKT(Ser473) and p-AKT(Thr308) were not affected by whey protein or leucine ingestion. Whey protein ingestion decreased insulin-mediated glucose disposal (median 38.8 [quartiles 30.8, 61.8] vs. 51.9 [41.0, 77.3] µmol glucose/µU insulin · mL(-1) · min(-1); P < 0.01), whereas ingestion of leucine did not (52.3 [43.3, 65.4] vs. 52.3 [43.9, 73.2]). These results indicate that 1) protein ingestion causes insulin resistance and could be an important regulator of postprandial glucose homeostasis and 2) the insulin-desensitizing effect of protein ingestion is not due to inhibition of AKT by leucine-mediated mTOR signaling.
Collapse
Affiliation(s)
- Gordon I Smith
- Department of Medicine and Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, St. Louis, MO
| | - Jun Yoshino
- Department of Medicine and Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, St. Louis, MO
| | - Kelly L Stromsdorfer
- Department of Medicine and Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, St. Louis, MO
| | - Seth J Klein
- Department of Radiology, Washington University School of Medicine, St. Louis, MO
| | - Faidon Magkos
- Department of Medicine and Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, St. Louis, MO
| | - Dominic N Reeds
- Department of Medicine and Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, St. Louis, MO
| | - Samuel Klein
- Department of Medicine and Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, St. Louis, MO
| | - Bettina Mittendorfer
- Department of Medicine and Center for Human Nutrition and Atkins Center of Excellence in Obesity Medicine, Washington University School of Medicine, St. Louis, MO
| |
Collapse
|
34
|
Albers PH, Pedersen AJT, Birk JB, Kristensen DE, Vind BF, Baba O, Nøhr J, Højlund K, Wojtaszewski JFP. Human muscle fiber type-specific insulin signaling: impact of obesity and type 2 diabetes. Diabetes 2015; 64:485-97. [PMID: 25187364 DOI: 10.2337/db14-0590] [Citation(s) in RCA: 141] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Skeletal muscle is a heterogeneous tissue composed of different fiber types. Studies suggest that insulin-mediated glucose metabolism is different between muscle fiber types. We hypothesized that differences are due to fiber type-specific expression/regulation of insulin signaling elements and/or metabolic enzymes. Pools of type I and II fibers were prepared from biopsies of the vastus lateralis muscles from lean, obese, and type 2 diabetic subjects before and after a hyperinsulinemic-euglycemic clamp. Type I fibers compared with type II fibers have higher protein levels of the insulin receptor, GLUT4, hexokinase II, glycogen synthase (GS), and pyruvate dehydrogenase-E1α (PDH-E1α) and a lower protein content of Akt2, TBC1 domain family member 4 (TBC1D4), and TBC1D1. In type I fibers compared with type II fibers, the phosphorylation response to insulin was similar (TBC1D4, TBC1D1, and GS) or decreased (Akt and PDH-E1α). Phosphorylation responses to insulin adjusted for protein level were not different between fiber types. Independently of fiber type, insulin signaling was similar (TBC1D1, GS, and PDH-E1α) or decreased (Akt and TBC1D4) in muscle from patients with type 2 diabetes compared with lean and obese subjects. We conclude that human type I muscle fibers compared with type II fibers have a higher glucose-handling capacity but a similar sensitivity for phosphoregulation by insulin.
Collapse
Affiliation(s)
- Peter H Albers
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, August Krogh Centre, University of Copenhagen, Copenhagen, Denmark Diabetes Research Unit, Novo Nordisk A/S, Maaloev, Denmark
| | - Andreas J T Pedersen
- Department of Endocrinology, Diabetes Research Center, Odense University Hospital, Odense, Denmark
| | - Jesper B Birk
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, August Krogh Centre, University of Copenhagen, Copenhagen, Denmark
| | - Dorte E Kristensen
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, August Krogh Centre, University of Copenhagen, Copenhagen, Denmark
| | - Birgitte F Vind
- Department of Endocrinology, Diabetes Research Center, Odense University Hospital, Odense, Denmark
| | - Otto Baba
- Section of Biology, Department of Oral Function and Molecular Biology, School of Dentistry, Ohu University, Koriyama, Japan
| | - Jane Nøhr
- Diabetes Research Unit, Novo Nordisk A/S, Maaloev, Denmark
| | - Kurt Højlund
- Department of Endocrinology, Diabetes Research Center, Odense University Hospital, Odense, Denmark
| | - Jørgen F P Wojtaszewski
- Section of Molecular Physiology, Department of Nutrition, Exercise and Sports, August Krogh Centre, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
35
|
Wijngaarden MA, Bakker LEH, van der Zon GC, 't Hoen PAC, van Dijk KW, Jazet IM, Pijl H, Guigas B. Regulation of skeletal muscle energy/nutrient-sensing pathways during metabolic adaptation to fasting in healthy humans. Am J Physiol Endocrinol Metab 2014; 307:E885-95. [PMID: 25249505 DOI: 10.1152/ajpendo.00215.2014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
During fasting, rapid metabolic adaptations are required to maintain energy homeostasis. This occurs by a coordinated regulation of energy/nutrient-sensing pathways leading to transcriptional activation and repression of specific sets of genes. The aim of the study was to investigate how short-term fasting affects whole body energy homeostasis and skeletal muscle energy/nutrient-sensing pathways and transcriptome in humans. For this purpose, 12 young healthy men were studied during a 24-h fast. Whole body glucose/lipid oxidation rates were determined by indirect calorimetry, and blood and skeletal muscle biopsies were collected and analyzed at baseline and after 10 and 24 h of fasting. As expected, fasting induced a time-dependent decrease in plasma insulin and leptin levels, whereas levels of ketone bodies and free fatty acids increased. This was associated with a metabolic shift from glucose toward lipid oxidation. At the molecular level, activation of the protein kinase B (PKB/Akt) and mammalian target of rapamycin pathways was time-dependently reduced in skeletal muscle during fasting, whereas the AMP-activated protein kinase activity remained unaffected. Furthermore, we report some changes in the phosphorylation and/or content of forkhead protein 1, sirtuin 1, and class IIa histone deacetylase 4, suggesting that these pathways might be involved in the transcriptional adaptation to fasting. Finally, transcriptome profiling identified genes that were significantly regulated by fasting in skeletal muscle at both early and late time points. Collectively, our study provides a comprehensive map of the main energy/nutrient-sensing pathways and transcriptomic changes during short-term adaptation to fasting in human skeletal muscle.
Collapse
Affiliation(s)
- Marjolein A Wijngaarden
- Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Leontine E H Bakker
- Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Gerard C van der Zon
- Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
| | - Peter A C 't Hoen
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands; and
| | - Ko Willems van Dijk
- Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, The Netherlands; Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands; and
| | - Ingrid M Jazet
- Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Hanno Pijl
- Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | - Bruno Guigas
- Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands; Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands
| |
Collapse
|
36
|
Vendelbo MH, Møller AB, Christensen B, Nellemann B, Clasen BFF, Nair KS, Jørgensen JOL, Jessen N, Møller N. Fasting increases human skeletal muscle net phenylalanine release and this is associated with decreased mTOR signaling. PLoS One 2014; 9:e102031. [PMID: 25020061 PMCID: PMC4096723 DOI: 10.1371/journal.pone.0102031] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Accepted: 06/13/2014] [Indexed: 12/12/2022] Open
Abstract
Aim Fasting is characterised by profound changes in energy metabolism including progressive loss of body proteins. The underlying mechanisms are however unknown and we therefore determined the effects of a 72-hour-fast on human skeletal muscle protein metabolism and activation of mammalian target of rapamycin (mTOR), a key regulator of cell growth. Methods Eight healthy male volunteers were studied twice: in the postabsorptive state and following 72 hours of fasting. Regional muscle amino acid kinetics was measured in the forearm using amino acid tracers. Signaling to protein synthesis and breakdown were assessed in skeletal muscle biopsies obtained during non-insulin and insulin stimulated conditions on both examination days. Results Fasting significantly increased forearm net phenylalanine release and tended to decrease phenylalanine rate of disappearance. mTOR phosphorylation was decreased by ∼50% following fasting, together with reduced downstream phosphorylation of 4EBP1, ULK1 and rpS6. In addition, the insulin stimulated increase in mTOR and rpS6 phosphorylation was significantly reduced after fasting indicating insulin resistance in this part of the signaling pathway. Autophagy initiation is in part regulated by mTOR through ULK1 and fasting increased expression of the autophagic marker LC3B-II by ∼30%. p62 is degraded during autophagy but was increased by ∼10% during fasting making interpretation of autophagic flux problematic. MAFbx and MURF1 ubiquitin ligases remained unaltered after fasting indicating no change in protesomal protein degradation. Conclusions Our results show that during fasting increased net phenylalanine release in skeletal muscle is associated to reduced mTOR activation and concomitant decreased downstream signaling to cell growth.
Collapse
Affiliation(s)
- Mikkel Holm Vendelbo
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
- * E-mail:
| | - Andreas Buch Møller
- Research Laboratory for Biochemical Pathology, Aarhus University Hospital, Aarhus, Denmark
| | - Britt Christensen
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Birgitte Nellemann
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Berthil Frederik Forrest Clasen
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
- Research Laboratory for Biochemical Pathology, Aarhus University Hospital, Aarhus, Denmark
| | - K. Sreekumaran Nair
- Division of Endocrinology, Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota, United States of America
| | | | - Niels Jessen
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
- Research Laboratory for Biochemical Pathology, Aarhus University Hospital, Aarhus, Denmark
- Department of Molecular Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - Niels Møller
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| |
Collapse
|
37
|
Vendelbo MH, Møller AB, Treebak JT, Gormsen LC, Goodyear LJ, Wojtaszewski JFP, Jørgensen JOL, Møller N, Jessen N. Sustained AS160 and TBC1D1 phosphorylations in human skeletal muscle 30 min after a single bout of exercise. J Appl Physiol (1985) 2014; 117:289-96. [PMID: 24876356 DOI: 10.1152/japplphysiol.00044.2014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND phosphorylation of AS160 and TBC1D1 plays an important role for GLUT4 mobilization to the cell surface. The phosphorylation of AS160 and TBC1D1 in humans in response to acute exercise is not fully characterized. OBJECTIVE to study AS160 and TBC1D1 phosphorylation in human skeletal muscle after aerobic exercise followed by a hyperinsulinemic euglycemic clamp. DESIGN eight healthy men were studied on two occasions: 1) in the resting state and 2) in the hours after a 1-h bout of ergometer cycling. A hyperinsulinemic euglycemic clamp was initiated 240 min after exercise and in a time-matched nonexercised control condition. We obtained muscle biopsies 30 min after exercise and in a time-matched nonexercised control condition (t = 30) and after 30 min of insulin stimulation (t = 270) and investigated site-specific phosphorylation of AS160 and TBC1D1. RESULTS phosphorylation on AS160 and TBC1D1 was increased 30 min after the exercise bout, whereas phosphorylation of the putative upstream kinases, Akt and AMPK, was unchanged compared with resting control condition. Exercise augmented insulin-stimulated phosphorylation on AS160 at Ser(341) and Ser(704) 270 min after exercise. No additional exercise effects were observed on insulin-stimulated phosphorylation of Thr(642) and Ser(588) on AS160 or Ser(237) and Thr(596) on TBC1D1. CONCLUSIONS AS160 and TBC1D1 phosphorylations were evident 30 min after exercise without simultaneously increased Akt and AMPK phosphorylation. Unlike TBC1D1, insulin-stimulated site-specific AS160 phosphorylation is modified by prior exercise, but these sites do not include Thr(642) and Ser(588). Together, these data provide new insights into phosphorylation of key regulators of glucose transport in human skeletal muscle.
Collapse
Affiliation(s)
- M H Vendelbo
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark; Department of Nuclear Medicine and PET center, Aarhus University Hospital, Aarhus, Denmark
| | - A B Møller
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark; Research Laboratory for Biochemical Pathology, Aarhus University Hospital, Aarhus, Denmark
| | - J T Treebak
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section of Integrative Physiology, University of Copenhagen, Copenhagen, Denmark
| | - L C Gormsen
- Department of Nuclear Medicine and PET center, Aarhus University Hospital, Aarhus, Denmark
| | - L J Goodyear
- Joslin Diabetes Center and Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - J F P Wojtaszewski
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, The August Krogh Centre, University of Copenhagen, Copenhagen, Denmark; and
| | - J O L Jørgensen
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - N Møller
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - N Jessen
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark; Research Laboratory for Biochemical Pathology, Aarhus University Hospital, Aarhus, Denmark; Department of Molecular Medicine, Aarhus University Hospital, Aarhus, Denmark
| |
Collapse
|
38
|
Nellemann B, Vendelbo MH, Nielsen TS, Bak AM, Høgild M, Pedersen SB, Biensø RS, Pilegaard H, Møller N, Jessen N, Jørgensen JOL. Growth hormone-induced insulin resistance in human subjects involves reduced pyruvate dehydrogenase activity. Acta Physiol (Oxf) 2014; 210:392-402. [PMID: 24148194 DOI: 10.1111/apha.12183] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 09/09/2013] [Accepted: 10/17/2013] [Indexed: 12/15/2022]
Abstract
AIM Insulin resistance induced by growth hormone (GH) is linked to promotion of lipolysis by unknown mechanisms. We hypothesized that suppression of the activity of pyruvate dehydrogenase in the active form (PDHa) underlies GH-induced insulin resistance similar to what is observed during fasting. METHODS Eight healthy male subjects were studied four times in a randomized, single-blinded parallel design: Control, GH, Fasting (36 h) and GH + Fasting. GH (30 ng × kg(-1) × min(-1)) or saline was infused throughout the metabolic study day. Substrate metabolism and insulin sensitivity were assessed by indirect calorimetry and isotopically determined rates of glucose turnover before and after a hyperinsulinemic euglycemic clamp. PDHa activity, PDH-E1α phosphorylation, PDK4 expression and activation of insulin signalling proteins were assessed in skeletal muscle. RESULTS Both fasting and GH promoted lipolysis, which was associated with ≈50% reduction in insulin sensitivity compared with the control day. PDHa activity was significantly reduced by GH as well as fasting. This was associated with increased inhibitory PDH-E1α phosphorylation on site 1 (Ser(293)) and 2 (Ser(300)) and up-regulation of PDK4 mRNA, while canonical insulin signalling to glucose transport was unaffected. CONCLUSION Competition between intermediates of glucose and fatty acids seems to play a causal role in insulin resistance induced by GH in human subjects.
Collapse
Affiliation(s)
- B. Nellemann
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - M. H. Vendelbo
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - T. S. Nielsen
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - A. M. Bak
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - M. Høgild
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - S. B. Pedersen
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - R. S. Biensø
- Centre of Inflammation and Metabolism & August Krogh Centre; Department of Biology; University of Copenhagen; Copenhagen Denmark
| | - H. Pilegaard
- Centre of Inflammation and Metabolism & August Krogh Centre; Department of Biology; University of Copenhagen; Copenhagen Denmark
| | - N. Møller
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - N. Jessen
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| | - J. O. L. Jørgensen
- Department of Endocrinology and Internal Medicine; Aarhus University Hospital; Aarhus Denmark
| |
Collapse
|
39
|
Treebak JT, Pehmøller C, Kristensen JM, Kjøbsted R, Birk JB, Schjerling P, Richter EA, Goodyear LJ, Wojtaszewski JFP. Acute exercise and physiological insulin induce distinct phosphorylation signatures on TBC1D1 and TBC1D4 proteins in human skeletal muscle. J Physiol 2013; 592:351-75. [PMID: 24247980 DOI: 10.1113/jphysiol.2013.266338] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
We investigated the phosphorylation signatures of two Rab-GTPase activating proteins TBC1D1 and TBC1D4 in human skeletal muscle in response to physical exercise and physiological insulin levels induced by a carbohydrate rich meal using a paired experimental design. Eight healthy male volunteers exercised in the fasted or fed state and muscle biopsies were taken before and immediately after exercise. We identified TBC1D1/4 phospho-sites that (1) did not respond to exercise or postprandial increase in insulin (TBC1D4: S666), (2) responded to insulin only (TBC1D4: S318), (3) responded to exercise only (TBC1D1: S237, S660, S700; TBC1D4: S588, S751), and (4) responded to both insulin and exercise (TBC1D1: T596; TBC1D4: S341, T642, S704). In the insulin-stimulated leg, Akt phosphorylation of both T308 and S473 correlated significantly with multiple sites on both TBC1D1 (T596) and TBC1D4 (S318, S341, S704). Interestingly, in the exercised leg in the fasted state TBC1D1 phosphorylation (S237, T596) correlated significantly with the activity of the α2/β2/γ3 AMPK trimer, whereas TBC1D4 phosphorylation (S341, S704) correlated with the activity of the α2/β2/γ1 AMPK trimer. Our data show differential phosphorylation of TBC1D1 and TBC1D4 in response to physiological stimuli in human skeletal muscle and support the idea that Akt and AMPK are upstream kinases. TBC1D1 phosphorylation signatures were comparable between in vitro contracted mouse skeletal muscle and exercised human muscle, and we show that AMPK regulated phosphorylation of these sites in mouse muscle. Contraction and exercise elicited a different phosphorylation pattern of TBC1D4 in mouse compared with human muscle, and although different circumstances in our experimental setup may contribute to this difference, the observation exemplifies that transferring findings between species is problematic.
Collapse
Affiliation(s)
- Jonas T Treebak
- The August Krogh Centre, Department of Nutrition, Exercise and Sports, Section of Molecular Physiology, University of Copenhagen, Universitetsparken 13 DK-2100, Copenhagen, Denmark.
| | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Keska A, Lutoslawska G, Czajkowska A, Tkaczyk J, Mazurek K. Variability in HOMA-IR, lipoprotein profile and selected hormones in young active men. ScientificWorldJournal 2013; 2013:412764. [PMID: 24348155 PMCID: PMC3848348 DOI: 10.1155/2013/412764] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 09/25/2013] [Indexed: 11/30/2022] Open
Abstract
Resistance to insulin actions is contributing to many metabolic disturbances. Such factors as age, sex, nutrition, body fat, and physical activity determine body insulin resistance. Present study attempted to asses insulin resistance and its metabolic effects with respect to energy intake in young, lean, and active men. A total of 87 men aged 18-23 participated in the study. Plasma levels of glucose, insulin, lipoproteins, cortisol, and TSH were determined. Insulin resistance was expressed as Homeostasis Model Assessment for Insulin Resistance (HOMA-IR) and calculated using homeostatic model. The median value of HOMA-IR (1.344) was used to divide subjects into two groups. Men did not differ in anthropometric parameters, daily physical activity, and plasma TSH and cortisol levels. However, in men with higher HOMA-IR significantly lower daily energy intake was observed concomitantly with higher TG, TC, and HDL-C concentrations in plasma versus their counterparts with lower HOMA-IR. Exclusively in subjects with higher HOMA-IR significant and positive correlation was noted between HOMA-IR and TC and LDL-C. We concluded that despite a normal body weight and physical activity, a subset of young men displayed unfavorable changes in insulin sensitivity and lipid profile, probably due to insufficient energy intake.
Collapse
Affiliation(s)
- Anna Keska
- Department of Biochemistry and Biology, Józef Pilsudski University of Physical Education, P.O. Box 55, 01-968 Warsaw 45, Poland
| | - Grazyna Lutoslawska
- Department of Biochemistry and Biology, Józef Pilsudski University of Physical Education, P.O. Box 55, 01-968 Warsaw 45, Poland
| | - Anna Czajkowska
- Department of Physiology, Józef Pilsudski University of Physical Education, P.O. Box 55, 01-968 Warsaw 45, Poland
| | - Joanna Tkaczyk
- Department of Biochemistry and Biology, Józef Pilsudski University of Physical Education, P.O. Box 55, 01-968 Warsaw 45, Poland
| | - Krzysztof Mazurek
- Department of Sports Medicine, Józef Pilsudski University of Physical Education, P.O. Box 55, 01-968 Warsaw 45, Poland
| |
Collapse
|
41
|
Consitt LA, Van Meter J, Newton CA, Collier DN, Dar MS, Wojtaszewski JF, Treebak JT, Tanner CJ, Houmard JA. Impairments in site-specific AS160 phosphorylation and effects of exercise training. Diabetes 2013; 62:3437-47. [PMID: 23801578 PMCID: PMC3781473 DOI: 10.2337/db13-0229] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The purpose of this study was to determine if site-specific phosphorylation at the level of Akt substrate of 160 kDa (AS160) is altered in skeletal muscle from sedentary humans across a wide range of the adult life span (18-84 years of age) and if endurance- and/or strength-oriented exercise training could rescue decrements in insulin action and skeletal muscle AS160 phosphorylation. A euglycemic-hyperinsulinemic clamp and skeletal muscle biopsies were performed in 73 individuals encompassing a wide age range (18-84 years of age), and insulin-stimulated AS160 phosphorylation was determined. Decrements in whole-body insulin action were associated with impairments in insulin-induced phosphorylation of skeletal muscle AS160 on sites Ser-588, Thr-642, Ser-666, and phospho-Akt substrate, but not Ser-318 or Ser-751. Twelve weeks of endurance- or strength-oriented exercise training increased whole-body insulin action and reversed impairments in AS160 phosphorylation evident in insulin-resistant aged individuals. These findings suggest that a dampening of insulin-induced phosphorylation of AS160 on specific sites in skeletal muscle contributes to the insulin resistance evident in a sedentary aging population and that exercise training is an effective intervention for treating these impairments.
Collapse
Affiliation(s)
- Leslie A. Consitt
- Department of Biomedical Sciences, Ohio Musculoskeletal and Neurological Institute, Diabetes Institute, Ohio University, Athens, Ohio
- Corresponding author: Leslie A. Consitt,
| | - Jessica Van Meter
- Department of Kinesiology, Human Performance Laboratory, East Carolina University, Greenville, North Carolina
| | - Christopher A. Newton
- Division of Endocrinology, Metabolism and Lipids, Department of Internal Medicine, Emory University, Atlanta, Georgia
| | - David N. Collier
- Department of Pediatrics, Brody School of Medicine at East Carolina University, Greenville, North Carolina
| | - Moahad S. Dar
- Section of Endocrinology & Metabolism, Department of Internal Medicine, Brody School of Medicine at East Carolina University, Greenville, North Carolina
| | - Jørgen F.P. Wojtaszewski
- Molecular Physiology Group, The August Krogh Centre, Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jonas T. Treebak
- Novo Nordisk Foundation Center for Basic Metabolic Research, Section on Integrative Physiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Charles J. Tanner
- Department of Kinesiology, Human Performance Laboratory, East Carolina University, Greenville, North Carolina
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina
| | - Joseph A. Houmard
- Department of Kinesiology, Human Performance Laboratory, East Carolina University, Greenville, North Carolina
- East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina
| |
Collapse
|
42
|
Swimming exercise training-induced left ventricular hypertrophy involves microRNAs and synergistic regulation of the PI3K/AKT/mTOR signaling pathway. Eur J Appl Physiol 2013; 113:2473-86. [DOI: 10.1007/s00421-013-2685-9] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Accepted: 06/18/2013] [Indexed: 01/16/2023]
|
43
|
Abstract
INTRODUCTION: Individuals with obesity and type 2 diabetes (T2D) are typically insulin resistant, exhibiting impaired skeletal muscle glucose uptake. Animal and cell culture experiments have shown that site-specific phosphorylation of the Rab-GTPase-activating proteins AS160 and TBC1D1 is critical for GLUT4 translocation facilitating glucose uptake, but their regulation in human skeletal muscle is not well understood. METHODS: Here, lean, obese and T2D subjects underwent a euglycemic-hyperinsulinemic clamp, and vastus lateralis muscle biopsies were obtained before, and at 30 and 180 min post insulin infusion. RESULTS: Obese and T2D subjects had higher body mass indexes and fasting insulin concentrations, and T2D subjects showed insulin resistance. Consistent with the clamp findings, T2D subjects had impaired insulin-stimulated phosphorylation of AS160 Thr642, a site previously shown to be important in glucose uptake in rodents. Interestingly, insulin-stimulated phosphorylation of TBC1D1 Thr590, a site shown to be regulated by insulin in rodents, was only increased in T2D subjects, although the functional significance of this difference is unknown. CONCLUSION: These data show that insulin differentially regulates AS160 and TBC1D1 phosphorylation in human skeletal muscle. Impaired insulin-stimulated glucose uptake in T2D subjects is accompanied by dysregulation of AS160 and TBC1D1 phosphorylation in skeletal muscle, suggesting that these proteins may regulate glucose uptake in humans.
Collapse
|
44
|
Aas V, Bakke SS, Feng YZ, Kase ET, Jensen J, Bajpeyi S, Thoresen GH, Rustan AC. Are cultured human myotubes far from home? Cell Tissue Res 2013; 354:671-82. [PMID: 23749200 DOI: 10.1007/s00441-013-1655-1] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 05/03/2013] [Indexed: 12/25/2022]
Abstract
Satellite cells can be isolated from skeletal muscle biopsies, activated to proliferating myoblasts and differentiated into multinuclear myotubes in culture. These cell cultures represent a model system for intact human skeletal muscle and can be modulated ex vivo. The advantages of this system are that the most relevant genetic background is available for the investigation of human disease (as opposed to rodent cell cultures), the extracellular environment can be precisely controlled and the cells are not immortalized, thereby offering the possibility of studying innate characteristics of the donor. Limitations in differentiation status (fiber type) of the cells and energy metabolism can be improved by proper treatment, such as electrical pulse stimulation to mimic exercise. This review focuses on the way that human myotubes can be employed as a tool for studying metabolism in skeletal muscles, with special attention to changes in muscle energy metabolism in obesity and type 2 diabetes.
Collapse
Affiliation(s)
- Vigdis Aas
- Institute of Pharmacy and Biomedical Laboratory Science, Faculty of Health Sciences, Oslo and Akershus University College of Applied Sciences, Oslo, Norway,
| | | | | | | | | | | | | | | |
Collapse
|
45
|
Tsatsoulis A, Mantzaris MD, Bellou S, Andrikoula M. Insulin resistance: an adaptive mechanism becomes maladaptive in the current environment - an evolutionary perspective. Metabolism 2013; 62:622-33. [PMID: 23260798 DOI: 10.1016/j.metabol.2012.11.004] [Citation(s) in RCA: 111] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Revised: 11/08/2012] [Accepted: 11/14/2012] [Indexed: 01/07/2023]
Abstract
Human survival has relied upon the ability to withstand starvation through energy storage, the capacity to fight off infection by a proinflammatory immune response, and the ability to cope with physical stressors by an adaptive stress response. Energy storage, mainly as glycogen in liver and triglycerides in adipose tissue, is regulated by the anabolic actions of insulin. On the other hand, mobilization of stored energy during infection, trauma or stress is served by the temporary inhibition of insulin action (insulin resistance) in target tissues by proinflammatory cytokines and stress hormones. In the current environment, high energy intake, low physical activity, and chronic stress favor the storage of surplus fat in adipose tissue depots that far exceeds their storage capacity and liporegulation. Lipid overload in central fat depots initiates an inflammatory response and adipocyte dysfunction with resultant low-grade systemic inflammation and lipid overflow to peripheral tissues. In turn, proinflammatory cytokines and non-oxidized lipid metabolites, accumulated in liver and muscle cells, activate the mechanism of insulin resistance as would occur in the case of infection or stress. The same factors together with the ensuing insulin resistance further contribute to pancreatic β-cell dysfunction and ultimately to type 2 diabetes and cardiovascular disease. The present review supports the hypothesis that insulin resistance evolved as a physiological adaptive mechanism in human survival and that the same mechanism is inappropriately activated on a chronic basis in the current environment, leading to the manifestations of the metabolic syndrome.
Collapse
Affiliation(s)
- Agathocles Tsatsoulis
- Department of Endocrinology, Medical School, University of Ioannina, 45110 Ioannina, Greece.
| | | | | | | |
Collapse
|
46
|
Wijngaarden MA, van der Zon GC, van Dijk KW, Pijl H, Guigas B. Effects of prolonged fasting on AMPK signaling, gene expression, and mitochondrial respiratory chain content in skeletal muscle from lean and obese individuals. Am J Physiol Endocrinol Metab 2013; 304:E1012-21. [PMID: 23512807 DOI: 10.1152/ajpendo.00008.2013] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Obesity in humans is often associated with metabolic inflexibility, but the underlying molecular mechanisms remain incompletely understood. The aim of the present study was to investigate how adaptation to prolonged fasting affects energy/nutrient-sensing pathways and metabolic gene expression in skeletal muscle from lean and obese individuals. Twelve lean and 14 nondiabetic obese subjects were fasted for 48 h. Whole body glucose/lipid oxidation rates were determined by indirect calorimetry, and blood and skeletal muscle biopsies were collected and analyzed. In response to fasting, body weight loss was similar in both groups, but the decrease in plasma insulin and leptin and the concomitant increase in growth hormone were significantly attenuated in obese subjects. The fasting-induced shift from glucose toward lipid oxidation was also severely blunted. At the molecular level, the expression of insulin receptor-β (IRβ) was lower in skeletal muscle from obese subjects at baseline, whereas the fasting-induced reductions in insulin signaling were similar in both groups. The protein expression of mitochondrial respiratory chain components, although not modified by fasting, was significantly reduced in obese subjects. Some minor differences in metabolic gene expression were observed at baseline and in response to fasting. Surprisingly, fasting reduced AMPK activity in lean but not in obese subjects, whereas the expression of AMPK subunits was not affected. We conclude that whole body metabolic inflexibility in response to prolonged fasting in obese humans is associated with lower skeletal muscle IRβ and mitochondrial respiratory chain content as well as a blunted decline of AMPK activity.
Collapse
Affiliation(s)
- Marjolein A Wijngaarden
- Department of Endocrinology and Metabolic Diseases, Leiden University Medical Center, Leiden, The Netherlands
| | | | | | | | | |
Collapse
|
47
|
Frank P, Katz A, Andersson E, Sahlin K. Acute exercise reverses starvation-mediated insulin resistance in humans. Am J Physiol Endocrinol Metab 2013; 304:E436-43. [PMID: 23269410 DOI: 10.1152/ajpendo.00416.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Within 2-3 days of starvation, pronounced insulin resistance develops, possibly mediated by increased lipid load. Here, we show that one exercise bout increases mitochondrial fatty acid (FA) oxidation and reverses starvation-induced insulin resistance. Nine healthy subjects underwent 75-h starvation on two occasions: with no exercise (NE) or with one exercise session at the end of the starvation period (EX). Muscle biopsies were analyzed for mitochondrial function, contents of glycogen, and phosphorylation of regulatory proteins. Glucose tolerance and insulin sensitivity, measured with an intravenous glucose tolerance test (IVGTT), were impaired after starvation, but in EX the response was attenuated or abolished. Glycogen stores were reduced, and plasma FA was increased in both conditions, with a more pronounced effect in EX. After starvation, mitochondrial respiration decreased with complex I substrate (NE and EX), but in EX there was an increased respiration with complex I + II substrate. EX altered regulatory proteins associated with increases in glucose disposal (decreased phosphorylation of glycogen synthase), glucose transport (increased phosphorylation of Akt substrate of 160 kDa), and FA oxidation (increased phosphorylation of acetyl-CoA carboxylase). In conclusion, exercise reversed starvation-induced insulin resistance and was accompanied by reduced glycogen stores, increased lipid oxidation capacity, and activation of signaling proteins involved in glucose transport and FA metabolism.
Collapse
Affiliation(s)
- Per Frank
- The Swedish School of Sport and Health Sciences, Åstrand Laboratory of Work Physiology, Box 5626, 114 86 Stockholm, Sweden.
| | | | | | | |
Collapse
|
48
|
Soeters MR, Soeters PB, Schooneman MG, Houten SM, Romijn JA. Adaptive reciprocity of lipid and glucose metabolism in human short-term starvation. Am J Physiol Endocrinol Metab 2012; 303:E1397-407. [PMID: 23074240 DOI: 10.1152/ajpendo.00397.2012] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The human organism has tools to cope with metabolic challenges like starvation that are crucial for survival. Lipolysis, lipid oxidation, ketone body synthesis, tailored endogenous glucose production and uptake, and decreased glucose oxidation serve to protect against excessive erosion of protein mass, which is the predominant supplier of carbon chains for synthesis of newly formed glucose. The starvation response shows that the adaptation to energy deficit is very effective and coordinated with different adaptations in different organs. From an evolutionary perspective, this lipid-induced effect on glucose oxidation and uptake is very strong and may therefore help to understand why insulin resistance in obesity and type 2 diabetes mellitus is difficult to treat. The importance of reciprocity in lipid and glucose metabolism during human starvation should be taken into account when studying lipid and glucose metabolism in general and in pathophysiological conditions in particular.
Collapse
Affiliation(s)
- Maarten R Soeters
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.
| | | | | | | | | |
Collapse
|
49
|
Srivastava RAK, Pinkosky SL, Filippov S, Hanselman JC, Cramer CT, Newton RS. AMP-activated protein kinase: an emerging drug target to regulate imbalances in lipid and carbohydrate metabolism to treat cardio-metabolic diseases. J Lipid Res 2012; 53:2490-514. [PMID: 22798688 DOI: 10.1194/jlr.r025882] [Citation(s) in RCA: 205] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The adenosine monophosphate-activated protein kinase (AMPK) is a metabolic sensor of energy metabolism at the cellular as well as whole-body level. It is activated by low energy status that triggers a switch from ATP-consuming anabolic pathways to ATP-producing catabolic pathways. AMPK is involved in a wide range of biological activities that normalizes lipid, glucose, and energy imbalances. These pathways are dysregulated in patients with metabolic syndrome (MetS), which represents a clustering of major cardiovascular risk factors including diabetes, lipid abnormalities, and energy imbalances. Clearly, there is an unmet medical need to find a molecule to treat alarming number of patients with MetS. AMPK, with multifaceted activities in various tissues, has emerged as an attractive drug target to manage lipid and glucose abnormalities and maintain energy homeostasis. A number of AMPK activators have been tested in preclinical models, but many of them have yet to reach to the clinic. This review focuses on the structure-function and role of AMPK in lipid, carbohydrate, and energy metabolism. The mode of action of AMPK activators, mechanism of anti-inflammatory activities, and preclinical and clinical findings as well as future prospects of AMPK as a drug target in treating cardio-metabolic disease are discussed.
Collapse
|
50
|
Soeters MR, Soeters PB. The evolutionary benefit of insulin resistance. Clin Nutr 2012; 31:1002-7. [PMID: 22682085 DOI: 10.1016/j.clnu.2012.05.011] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 04/26/2012] [Accepted: 05/16/2012] [Indexed: 12/13/2022]
Abstract
Insulin resistance is perceived as deleterious, associated with conditions as the metabolic syndrome, type 2 diabetes mellitus and critical illness. However, insulin resistance is evolutionarily well preserved and its persistence suggests that it benefits survival. Insulin resistance is important in various states such as starvation, immune activation, growth and cancer, to spare glucose for different biosynthetic purposes such as the production of NADPH, nucleotides in the pentose phosphate pathway and oxaloacetate for anaplerosis. In these conditions, total glucose oxidation by the tricarboxylic acid cycle is actually low and energy demands are largely met by fatty acid and ketone body oxidation. This beneficial role of insulin resistance has consequences for treatment and research. Insulin resistance should be investigated at the cellular, tissue and whole organism level. The metabolic pathways discussed here, should be integrated in the accepted and valid mechanistic events of insulin resistance before interfering with them to promote insulin sensitivity at any cost.
Collapse
Affiliation(s)
- Maarten R Soeters
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, PO Box 22660, 1100 DD Amsterdam, The Netherlands.
| | | |
Collapse
|