201
|
Glucagon receptor antibody completely suppresses type 1 diabetes phenotype without insulin by disrupting a novel diabetogenic pathway. Proc Natl Acad Sci U S A 2015; 112:2503-8. [PMID: 25675519 DOI: 10.1073/pnas.1424934112] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Insulin monotherapy can neither maintain normoglycemia in type 1 diabetes (T1D) nor prevent the long-term damage indicated by elevated glycation products in blood, such as glycated hemoglobin (HbA1c). Here we find that hyperglycemia, when unaccompanied by an acute increase in insulin, enhances itself by paradoxically stimulating hyperglucagonemia. Raising glucose from 5 to 25 mM without insulin enhanced glucagon secretion ∼two- to fivefold in InR1-G9 α cells and ∼18-fold in perfused pancreata from insulin-deficient rats with T1D. Mice with T1D receiving insulin treatment paradoxically exhibited threefold higher plasma glucagon during hyperglycemic surges than during normoglycemic intervals. Blockade of glucagon action with mAb Ac, a glucagon receptor (GCGR) antagonizing antibody, maintained glucose below 100 mg/dL and HbA1c levels below 4% in insulin-deficient mice with T1D. In rodents with T1D, hyperglycemia stimulates glucagon secretion, up-regulating phosphoenolpyruvate carboxykinase and enhancing hyperglycemia. GCGR antagonism in mice with T1D normalizes glucose and HbA1c, even without insulin.
Collapse
|
202
|
Obrochta KM, Krois CR, Campos B, Napoli JL. Insulin regulates retinol dehydrogenase expression and all-trans-retinoic acid biosynthesis through FoxO1. J Biol Chem 2015; 290:7259-68. [PMID: 25627686 DOI: 10.1074/jbc.m114.609313] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
All-trans-retinoic acid (atRA), an autacoid derived from retinol (vitamin A), regulates energy balance and reduces adiposity. We show that energy status regulates atRA biosynthesis at the rate-limiting step, catalyzed by retinol dehydrogenases (RDH). Six h after re-feeding, Rdh1 expression decreased 80-90% in liver and brown adipose tissue and Rdh10 expression was decreased 45-63% in liver, pancreas, and kidney, all relative to mice fasted 16 h. atRA in the liver was decreased 44% 3 h after reduced Rdh expression. Oral gavage with glucose or injection with insulin decreased Rdh1 and Rdh10 mRNA 50% or greater in mouse liver. Removing serum from the medium of the human hepatoma cell line HepG2 increased Rdh10 and Rdh16 (human Rdh1 ortholog) mRNA expression 2-3-fold by 4 h, by increasing transcription and stabilizing mRNA. Insulin decreased Rdh10 and Rdh16 mRNA in HepG2 cells incubated in serum-free medium by inhibiting transcription and destabilizing mRNA. Insulin action required PI3K and Akt, which suppress FoxO1. Serum removal increased atRA biosynthesis 4-fold from retinol in HepG2 cells, whereas dominant-negative FoxO1 prevented the increase. Thus, energy status via insulin and FoxO1 regulate Rdh expression and atRA biosynthesis. These results reveal mechanisms for regulating atRA biosynthesis and the opposing effects of atRA and insulin on gluconeogenesis, and also suggest an interaction between atRA and insulin signaling related diseases, such as type II diabetes and cancer.
Collapse
Affiliation(s)
- Kristin M Obrochta
- From the Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, California 94720
| | - Charles R Krois
- From the Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, California 94720
| | - Benito Campos
- From the Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, California 94720
| | - Joseph L Napoli
- From the Department of Nutritional Sciences and Toxicology, Graduate Program in Metabolic Biology, University of California, Berkeley, California 94720
| |
Collapse
|
203
|
Dhumpa R, Truong TM, Wang X, Bertram R, Roper MG. Negative feedback synchronizes islets of Langerhans. Biophys J 2014; 106:2275-82. [PMID: 24853756 DOI: 10.1016/j.bpj.2014.04.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 04/01/2014] [Accepted: 04/11/2014] [Indexed: 01/19/2023] Open
Abstract
Insulin is released from the pancreas in pulses with a period of ~ 5 min. These oscillatory insulin levels are essential for proper liver utilization and perturbed pulsatility is observed in type 2 diabetes. What coordinates the many islets of Langerhans throughout the pancreas to produce unified oscillations of insulin secretion? One hypothesis is that coordination is achieved through an insulin-dependent negative feedback action of the liver onto the glucose level. This hypothesis was tested in an in vitro setting using a microfluidic system where the population response from a group of islets was input to a model of hepatic glucose uptake, which provided a negative feedback to the glucose level. This modified glucose level was then delivered back to the islet chamber where the population response was again monitored and used to update the glucose concentration delivered to the islets. We found that, with appropriate parameters for the model, oscillations in islet activity were synchronized. This approach demonstrates that rhythmic activity of a population of physically uncoupled islets can be coordinated by a downstream system that senses islet activity and supplies negative feedback. In the intact animal, the liver can play this role of the coordinator of islet activity.
Collapse
Affiliation(s)
- Raghuram Dhumpa
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306
| | - Tuan M Truong
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306
| | - Xue Wang
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306
| | - Richard Bertram
- Department of Mathematics and Program in Neuroscience, Florida State University, Tallahassee, FL 32306; Program in Molecular Biophysics, Florida State University, Tallahassee, FL 32306.
| | - Michael G Roper
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306; Program in Molecular Biophysics, Florida State University, Tallahassee, FL 32306.
| |
Collapse
|
204
|
Silencing of ANGPTL 3 (angiopoietin-like protein 3) in human hepatocytes results in decreased expression of gluconeogenic genes and reduced triacylglycerol-rich VLDL secretion upon insulin stimulation. Biosci Rep 2014; 34:e00160. [PMID: 25495645 PMCID: PMC4266921 DOI: 10.1042/bsr20140115] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Homozygosity of loss-of-function mutations in ANGPTL3 (angiopoietin-like protein 3)-gene results in FHBL2 (familial combined hypolipidaemia, OMIM #605019) characterized by the reduction of all major plasma lipoprotein classes, which includes VLDL (very-low-density lipoprotein), LDL (low-density lipoprotein), HDL (high-density lipoprotein) and low circulating NEFAs (non-esterified fatty acids), glucose and insulin levels. Thus complete lack of ANGPTL3 in humans not only affects lipid metabolism, but also affects whole-body insulin and glucose balance. We used wild-type and ANGPTL3-silenced IHHs (human immortalized hepatocytes) to investigate the effect of ANGPTL3 silencing on hepatocyte-specific VLDL secretion and glucose uptake. We demonstrate that both insulin and PPARγ (peroxisome-proliferator-activated receptor γ) agonist rosiglitazone down-regulate the secretion of ANGPTL3 and TAG (triacylglycerol)-enriched VLDL1-type particles in a dose-dependent manner. Silencing of ANGPTL3 improved glucose uptake in hepatocytes by 20–50% and influenced down-regulation of gluconeogenic genes, suggesting that silencing of ANGPTL3 improves insulin sensitivity. We further show that ANGPTL3-silenced cells display a more pronounced shift from the secretion of TAG-enriched VLDL1-type particles to secretion of lipid poor VLDL2-type particles during insulin stimulation. These data suggest liver-specific mechanisms involved in the reported insulin-sensitive phenotype of ANGPTL3-deficient humans, featuring lower plasma insulin and glucose levels. We show that silencing of ANGPTL3 in human hepatocytes in addition to reducing secretion of TAG-enriched VLDL upon insulin stimulation enhances glucose uptake and improves insulin response. Thus, our data provide insight into the lower insulin and glucose levels observed in humans with ANGPTL3 loss-of-function mutation.
Collapse
|
205
|
Welcome M, Pereverzev V. Glycemic Allostasis during Mental Activities on Fasting in Non-alcohol Users and Alcohol Users with Different Durations of Abstinence. Ann Med Health Sci Res 2014; 4:S199-207. [PMID: 25364589 PMCID: PMC4212377 DOI: 10.4103/2141-9248.141959] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Glycemic allostasis is the process by which blood glucose stabilization is achieved through the balancing of glucose consumption rate and release into the blood stream under a variety of stressors. This paper reviews findings on the dynamics of glycemic levels during mental activities on fasting in non-alcohol users and alcohol users with different periods of abstinence. Referred articles for this review were searched in the databases of PubMed, Scopus, DOAJ and AJOL. The search was conducted in 2013 between January 20 and July 31. The following keywords were used in the search: alcohol action on glycemia OR brain glucose OR cognitive functions; dynamics of glycemia, dynamics of glycemia during mental activities; dynamics of glycemia on fasting; dynamics of glycemia in non-alcohol users OR alcohol users; glycemic regulation during sobriety. Analysis of the selected articles showed that glycemic allostasis during mental activities on fasting is poorly regulated in alcohol users even after a long duration of sobriety (1-4 weeks after alcohol consumption), compared to non-alcohol users. The major contributor to the maintenance of euglycemia during mental activities after the night's rest (during continuing fast) is gluconeogenesis.
Collapse
Affiliation(s)
- Mo Welcome
- Department of Normal Physiology, Belarusian State Medical University, Minsk, Belarus
| | - Va Pereverzev
- Department of Normal Physiology, Belarusian State Medical University, Minsk, Belarus
| |
Collapse
|
206
|
Rojas JM, Schwartz MW. Control of hepatic glucose metabolism by islet and brain. Diabetes Obes Metab 2014; 16 Suppl 1:33-40. [PMID: 25200294 PMCID: PMC4191916 DOI: 10.1111/dom.12332] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Accepted: 04/18/2014] [Indexed: 12/19/2022]
Abstract
Dysregulation of hepatic glucose uptake (HGU) and inability of insulin to suppress hepatic glucose production (HGP) contribute to hyperglycaemia in patients with type 2 diabetes (T2D). Growing evidence suggests that insulin can inhibit HGP not only through a direct effect on the liver but also through a mechanism involving the brain. Yet, the notion that insulin action in the brain plays a physiological role in the control of HGP continues to be controversial. Although studies in dogs suggest that the direct hepatic effect of insulin is sufficient to explain day-to-day control of HGP, a surprising outcome has been revealed by recent studies in mice, investigating whether the direct hepatic action of insulin is necessary for normal HGP: when the hepatic insulin signalling pathway was genetically disrupted, HGP was maintained normally even in the absence of direct input from insulin. Here, we present evidence that points to a potentially important role of the brain in the physiological control of both HGU and HGP in response to input from insulin as well as other hormones and nutrients.
Collapse
Affiliation(s)
- Jennifer M. Rojas
- Diabetes and Obesity Center of Excellence, Department of Medicine, University of Washington, Seattle, Washington, USA
| | - Michael W. Schwartz
- Diabetes and Obesity Center of Excellence, Department of Medicine, University of Washington, Seattle, Washington, USA
| |
Collapse
|
207
|
Kleinert M, Sylow L, Fazakerley DJ, Krycer JR, Thomas KC, Oxbøll AJ, Jordy AB, Jensen TE, Yang G, Schjerling P, Kiens B, James DE, Ruegg MA, Richter EA. Acute mTOR inhibition induces insulin resistance and alters substrate utilization in vivo. Mol Metab 2014; 3:630-41. [PMID: 25161886 PMCID: PMC4142396 DOI: 10.1016/j.molmet.2014.06.004] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Revised: 06/20/2014] [Accepted: 06/23/2014] [Indexed: 01/12/2023] Open
Abstract
The effect of acute inhibition of both mTORC1 and mTORC2 on metabolism is unknown. A single injection of the mTOR kinase inhibitor, AZD8055, induced a transient, yet marked increase in fat oxidation and insulin resistance in mice, whereas the mTORC1 inhibitor rapamycin had no effect. AZD8055, but not rapamycin reduced insulin-stimulated glucose uptake into incubated muscles, despite normal GLUT4 translocation in muscle cells. AZD8055 inhibited glycolysis in MEF cells. Abrogation of mTORC2 activity by SIN1 deletion impaired glycolysis and AZD8055 had no effect in SIN1 KO MEFs. Re-expression of wildtype SIN1 rescued glycolysis. Glucose intolerance following AZD8055 administration was absent in mice lacking the mTORC2 subunit Rictor in muscle, and in vivo glucose uptake into Rictor-deficient muscle was reduced despite normal Akt activity. Taken together, acute mTOR inhibition is detrimental to glucose homeostasis in part by blocking muscle mTORC2, indicating its importance in muscle metabolism in vivo.
Collapse
Affiliation(s)
- Maximilian Kleinert
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, August Krogh Centre, University of Copenhagen, Copenhagen, Denmark
| | - Lykke Sylow
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, August Krogh Centre, University of Copenhagen, Copenhagen, Denmark
| | - Daniel J. Fazakerley
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Darlinghurst, New South Wales 2010, Australia
| | - James R. Krycer
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Darlinghurst, New South Wales 2010, Australia
- School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, Australia
| | - Kristen C. Thomas
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Darlinghurst, New South Wales 2010, Australia
| | - Anne-Julie Oxbøll
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, August Krogh Centre, University of Copenhagen, Copenhagen, Denmark
| | - Andreas B. Jordy
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, August Krogh Centre, University of Copenhagen, Copenhagen, Denmark
| | - Thomas E. Jensen
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, August Krogh Centre, University of Copenhagen, Copenhagen, Denmark
| | - Guang Yang
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Darlinghurst, New South Wales 2010, Australia
| | - Peter Schjerling
- Institute of Sports Medicine, Department of Orthopedic Surgery, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Bente Kiens
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, August Krogh Centre, University of Copenhagen, Copenhagen, Denmark
| | - David E. James
- Diabetes and Obesity Program, Garvan Institute of Medical Research, Darlinghurst, New South Wales 2010, Australia
- Charles Perkins Centre, School of Molecular Bioscience, The University of Sydney, Sydney, Australia
| | | | - Erik A. Richter
- Molecular Physiology Group, Department of Nutrition, Exercise and Sports, August Krogh Centre, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
208
|
Lee YB, Lee JH, Park ES, Kim GY, Leem CH. Personalized metabolic profile estimations using oral glucose tolerance tests. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 116:25-32. [DOI: 10.1016/j.pbiomolbio.2014.08.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 08/13/2014] [Indexed: 10/24/2022]
|
209
|
Wong HS, Chen J, Leong PK, Leung HY, Chan WM, Ko KM. Cistanches Herba reduces the weight gain in high fat diet-induced obese mice possibly through mitochondrial uncoupling. J Funct Foods 2014. [DOI: 10.1016/j.jff.2014.06.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
|
210
|
Khu LY, Storey KB, Rubtsov AM, Goncharova NY. Regulation of glucokinase activity in liver of hibernating ground squirrel Spermophilus undulatus. BIOCHEMISTRY (MOSCOW) 2014; 79:727-32. [PMID: 25108335 DOI: 10.1134/s0006297914070141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The kinetic properties of glucokinase (GLK) from the liver of active and hibernating ground squirrels Spermophilus undulatus have been studied. Entrance of ground squirrels into hibernation from their active state is accompanied by a sharp decrease in blood glucose (Glc) level (from 14 to 2.9 mM) and with a significant (7-fold) decrease of GLK activity in the liver cytoplasm. Preparations of native GLK practically devoid of other molecular forms of hexokinase were obtained from the liver of active and hibernating ground squirrels. The dependence of GLK activity upon Glc concentration for the enzyme from active ground squirrel liver showed a pronounced sigmoid character (Hill coefficient, h=1.70 and S0.5=6.23 mM; the experiments were conducted at 25°C in the presence of enzyme stabilizers, K+ and DTT). The same dependence of enzyme activity on Glc concentration was found for GLK from rat liver. However, on decreasing the temperature to 2°C (simulation of hibernation conditions), this dependency became almost hyperbolic (h=1.16) and GLK affinity for substrate was reduced (S0.5=23 mM). These parameters for hibernating ground squirrels (body temperature 5°C) at 25°C were found to be practically equal to the corresponding values obtained for GLK from the liver of active animals (h=1.60, S0.5=9.0 mM, respectively); at 2°C sigmoid character was less expressed and affinity for Glc was drastically decreased (h=1.20, S0.5=45 mM). The calculations of GLK activity in the liver of hibernating ground squirrels based on enzyme kinetic characteristics and seasonal changes in blood Glc concentrations have shown that GLK activity in the liver of hibernating ground squirrels is decreased about 5500-fold.
Collapse
Affiliation(s)
- L Ya Khu
- Department of Biochemistry, Faculty of Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
| | | | | | | |
Collapse
|
211
|
Free glycogen in vaginal fluids is associated with Lactobacillus colonization and low vaginal pH. PLoS One 2014; 9:e102467. [PMID: 25033265 PMCID: PMC4102502 DOI: 10.1371/journal.pone.0102467] [Citation(s) in RCA: 143] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 06/17/2014] [Indexed: 11/23/2022] Open
Abstract
Objective Lactobacillus dominates the lower genital tract microbiota of many women, producing a low vaginal pH, and is important for healthy pregnancy outcomes and protection against several sexually transmitted pathogens. Yet, factors that promote Lactobacillus remain poorly understood. We hypothesized that the amount of free glycogen in the lumen of the lower genital tract is an important determinant of Lactobacillus colonization and a low vaginal pH. Methods Free glycogen in lavage samples was quantified. Pyrosequencing of the 16S rRNA gene was used to identify microbiota from 21 African American women collected over 8–11 years. Results Free glycogen levels varied greatly between women and even in the same woman. Samples with the highest free glycogen had a corresponding median genital pH that was significantly lower (pH 4.4) than those with low glycogen (pH 5.8; p<0.001). The fraction of the microbiota consisting of Lactobacillus was highest in samples with high glycogen versus those with low glycogen (median = 0.97 vs. 0.05, p<0.001). In multivariable analysis, having 1 vs. 0 male sexual partner in the past 6 months was negatively associated, while BMI ≥30 was positively associated with glycogen. High concentrations of glycogen corresponded to higher levels of L. crispatus and L. jensenii, but not L. iners. Conclusion These findings show that free glycogen in genital fluid is associated with a genital microbiota dominated by Lactobacillus, suggesting glycogen is important for maintaining genital health. Treatments aimed at increasing genital free glycogen might impact Lactobacillus colonization.
Collapse
|
212
|
Coate KC, Kraft G, Moore MC, Smith MS, Ramnanan C, Irimia JM, Roach PJ, Farmer B, Neal DW, Williams P, Cherrington AD. Hepatic glucose uptake and disposition during short-term high-fat vs. high-fructose feeding. Am J Physiol Endocrinol Metab 2014; 307:E151-60. [PMID: 24865981 PMCID: PMC4101635 DOI: 10.1152/ajpendo.00083.2014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In dogs consuming a high-fat and -fructose diet (52 and 17% of total energy, respectively) for 4 wk, hepatic glucose uptake (HGU) in response to hyperinsulinemia, hyperglycemia, and portal glucose delivery is markedly blunted with reduction in glucokinase (GK) protein and glycogen synthase (GS) activity. The present study compared the impact of selective increases in dietary fat and fructose on liver glucose metabolism. Dogs consumed weight-maintaining chow (CTR) or hypercaloric high-fat (HFA) or high-fructose (HFR) diets diet for 4 wk before undergoing clamp studies with infusion of somatostatin and intraportal insulin (3-4 times basal) and glucagon (basal). The hepatic glucose load (HGL) was doubled during the clamp using peripheral vein (Pe) glucose infusion in the first 90 min (P1) and portal vein (4 mg·kg(-1)·min(-1)) plus Pe glucose infusion during the final 90 min (P2). During P2, HGU was 2.8 ± 0.2, 1.0 ± 0.2, and 0.8 ± 0.2 mg·kg(-1)·min(-1) in CTR, HFA, and HFR, respectively (P < 0.05 for HFA and HFR vs. CTR). Compared with CTR, hepatic GK protein and catalytic activity were reduced (P < 0.05) 35 and 56%, respectively, in HFA, and 53 and 74%, respectively, in HFR. Liver glycogen concentrations were 20 and 38% lower in HFA and HFR than CTR (P < 0.05). Hepatic Akt phosphorylation was decreased (P < 0.05) in HFA (21%) but not HFR. Thus, HFR impaired hepatic GK and glycogen more than HFA, whereas HFA reduced insulin signaling more than HFR. HFA and HFR effects were not additive, suggesting that they act via the same mechanism or their effects converge at a saturable step.
Collapse
Affiliation(s)
- Katie C Coate
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Guillaume Kraft
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Mary Courtney Moore
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee;
| | - Marta S Smith
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Christopher Ramnanan
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Jose M Irimia
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Peter J Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Ben Farmer
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Doss W Neal
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee; Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee; and
| | - Phil Williams
- Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee; and Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Alan D Cherrington
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| |
Collapse
|
213
|
Abstract
The glucokinase (GK) enzyme (EC 2.7.1.1.) is essential for the use of dietary glucose because it is the first enzyme to phosphorylate glucose in excess in different key tissues such as the pancreas and liver. The objective of the present review is not to fully describe the biochemical characteristics and the genetics of this enzyme but to detail its nutritional regulation in different vertebrates from fish to human. Indeed, the present review will describe the existence of the GK enzyme in different animal species that have naturally different levels of carbohydrate in their diets. Thus, some studies have been performed to analyse the nutritional regulation of the GK enzyme in humans and rodents (having high levels of dietary carbohydrates in their diets), in the chicken (moderate level of carbohydrates in its diet) and rainbow trout (no carbohydrate intake in its diet). All these data illustrate the nutritional importance of the GK enzyme irrespective of feeding habits, even in animals known to poorly use dietary carbohydrates (carnivorous species).
Collapse
|
214
|
Wang Y, Shao J, Zaro JL, Shen WC. Proinsulin-transferrin fusion protein as a novel long-acting insulin analog for the inhibition of hepatic glucose production. Diabetes 2014; 63:1779-88. [PMID: 24353179 PMCID: PMC3994961 DOI: 10.2337/db13-0973] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Proinsulin-transferrin (ProINS-Tf) fusion protein was evaluated for its in vivo pharmacokinetics, efficacy, and mechanism. Our previous studies have shown that ProINS-Tf was converted to active insulin-transferrin (INS-Tf) via the transferrin (Tf)-receptor-mediated pathway in hepatoma cells. We hypothesized that this fusion protein can be administered as a prodrug and be converted to a biologically active protein with specificity for the liver versus other insulin (INS)-sensitive tissues (muscle and adipose). Administration as an inactive prodrug with liver-specific action compared with other INS-sensitive tissues conceivably reduces negative side effects seen with other INS analogs. In this report, the data show that ProINS-Tf exhibited a slow, but sustained, in vivo hypoglycemic efficacy and long plasma half-life. The fusion protein showed activity in the liver, as evidenced by decreased expression of two key hepatic glucose production (HGP) enzymes, PEPCK and glucose-6-phosphatase, and increased glycogen levels under feeding conditions. Furthermore, the INS receptor (IR) phosphorylation (activation) in liver and muscle tissues was compared with postinjection of INS or ProINS-Tf. While INS activated IR in both the liver and muscle, ProINS-Tf only showed activation in the liver. Thus, ProINS-Tf fusion protein can potentially be administered as a prodrug with sustained Tf-mediated activation and selectivity in inhibiting HGP.
Collapse
|
215
|
Bouchard-Mercier A, Rudkowska I, Lemieux S, Couture P, Vohl MC. An interaction effect between glucokinase gene variation and carbohydrate intakes modulates the plasma triglyceride response to a fish oil supplementation. GENES AND NUTRITION 2014; 9:395. [PMID: 24643341 DOI: 10.1007/s12263-014-0395-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Accepted: 02/27/2014] [Indexed: 02/08/2023]
Abstract
A large inter-individual variability in the plasma triglyceride (TG) response to fish oil consumption has been observed. The objective was to investigate the gene-diet interaction effects between single-nucleotide polymorphisms (SNPs) within glucokinase (GCK) gene and dietary carbohydrate intakes (CHO) on the plasma TG response to a fish oil supplementation. Two hundred and eight participants were recruited in the greater Quebec City area. The participants completed a 6-week fish oil supplementation (5 g fish oil/day: 1.9-2.2 g EPA and 1.1 g DHA). Thirteen SNPs within GCK gene were genotyped using TAQMAN methodology. A gene-diet interaction effect on the plasma TG response was observed with rs741038 and CHO adjusted for age, sex and BMI (p = 0.008). In order to compare the plasma TG response between genotypes according to CHO, participants were divided according to median CHO. Homozygotes of the minor C allele of rs741038 with high CHO >48.59 % had a greater decrease in their plasma TG concentrations following the intake of fish oil (p < 0.05) than C/C homozygotes with low CHO and also than the other genotypes either with high or low CHO. The plasma TG response to a fish oil supplementation may be modulated by gene-diet interaction effects involving GCK gene and CHO.
Collapse
Affiliation(s)
- Annie Bouchard-Mercier
- Institute of Nutrition and Functional Foods (INAF), Laval University, 2440 Hochelaga Blvd., Quebec, G1V 0A6, Canada
| | | | | | | | | |
Collapse
|
216
|
Salehi M, Gastaldelli A, D'Alessio DA. Blockade of glucagon-like peptide 1 receptor corrects postprandial hypoglycemia after gastric bypass. Gastroenterology 2014; 146:669-680.e2. [PMID: 24315990 PMCID: PMC3943944 DOI: 10.1053/j.gastro.2013.11.044] [Citation(s) in RCA: 182] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 10/30/2013] [Accepted: 11/20/2013] [Indexed: 02/08/2023]
Abstract
BACKGROUND & AIMS Postprandial glycemia excursions increase after gastric bypass surgery; this effect is even greater among patients with recurrent hypoglycemia. These patients also have increased postprandial levels of insulin and glucagon-like peptide 1 (GLP-1). We performed a clinical trial to determine the role of GLP-1 in postprandial glycemia in patients with hyperinsulinemic hypoglycemia syndrome after gastric bypass. METHODS Nine patients with recurrent hypoglycemia after gastric bypass (H-GB), 7 patients who were asymptomatic after gastric bypass (A-GB), and 8 healthy control subjects underwent a mixed-meal tolerance test (350 kcal) using a dual glucose tracer method on 2 separate days. On 1 day they received continuous infusion of the GLP-1 receptor antagonist exendin (9-39) (Ex-9), and on the other day they received a saline control. Glucose kinetics and islet and gut hormone responses were measured before and after the meal. RESULTS Infusion of Ex-9 corrected hypoglycemia in all patients with H-GB. The reduction in postprandial insulin secretion by Ex-9 was greater in the H-GB group than in the other groups (H-GB, 50% ± 8%; A-GB, 13% ± 10%; controls, 14% ± 10%) (P < .05). The meal-derived glucose appearance was significantly greater in subjects who had undergone gastric bypass compared to the controls and in the H-GB group compared to the A-GB group. Ex-9 shortened the time to reach peak meal-derived glucose appearance in all groups without a significant effect on overall glucose flux. Postprandial glucagon levels were higher among patients who had undergone gastric bypass than controls and increased with administration of Ex-9. CONCLUSIONS Hypoglycemia after gastric bypass can be corrected by administration of a GLP-1 receptor antagonist, which might be used to treat this disorder. These findings are consistent with reports that increased GLP-1 activity contributes to hypoglycemia after gastric bypass. ClinicalTrials.gov, Number: NCT01803451.
Collapse
Affiliation(s)
- Marzieh Salehi
- Division of Endocrinology, Diabetes, & Metabolism, Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio.
| | - Amalia Gastaldelli
- Cardiometabolic Risk Unit, CNR Institute of Clinical Physiology, Pisa, Italy
| | - David A D'Alessio
- Division of Endocrinology, Diabetes, & Metabolism, Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, Ohio; Cincinnati VA Medical Center, Cincinnati, Ohio
| |
Collapse
|
217
|
Silvestre M, Viollet B, Caton P, Leclerc J, Sakakibara I, Foretz M, Holness M, Sugden M. The AMPK-SIRT signaling network regulates glucose tolerance under calorie restriction conditions. Life Sci 2014; 100:55-60. [DOI: 10.1016/j.lfs.2014.01.080] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 01/14/2014] [Accepted: 01/27/2014] [Indexed: 01/31/2023]
|
218
|
Sinnett SE, Brenman JE. Past strategies and future directions for identifying AMP-activated protein kinase (AMPK) modulators. Pharmacol Ther 2014; 143:111-8. [PMID: 24583089 DOI: 10.1016/j.pharmthera.2014.02.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 02/13/2014] [Indexed: 12/30/2022]
Abstract
AMP-activated protein kinase (AMPK) is a promising therapeutic target for cancer, type II diabetes, and other illnesses characterized by abnormal energy utilization. During the last decade, numerous labs have published a range of methods for identifying novel AMPK modulators. The current understanding of AMPK structure and regulation, however, has propelled a paradigm shift in which many researchers now consider ADP to be an additional regulatory nucleotide of AMPK. How can the AMPK community apply this new understanding of AMPK signaling to translational research? Recent insights into AMPK structure, regulation, and holoenzyme-sensitive signaling may provide the hindsight needed to clearly evaluate the strengths and weaknesses of past AMPK drug discovery efforts. Improving future strategies for AMPK drug discovery will require pairing the current understanding of AMPK signaling with improved experimental designs.
Collapse
Affiliation(s)
- Sarah E Sinnett
- Neurobiology Curriculum, University of North Carolina at Chapel Hill (UNC), United States
| | - Jay E Brenman
- UNC Neuroscience Center, United States; Department of Cell Biology and Physiology, UNC, United States.
| |
Collapse
|
219
|
Turner N, Cooney GJ, Kraegen EW, Bruce CR. Fatty acid metabolism, energy expenditure and insulin resistance in muscle. J Endocrinol 2014; 220:T61-79. [PMID: 24323910 DOI: 10.1530/joe-13-0397] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Fatty acids (FAs) are essential elements of all cells and have significant roles as energy substrates, components of cellular structure and signalling molecules. The storage of excess energy intake as fat in adipose tissue is an evolutionary advantage aimed at protecting against starvation, but in much of today's world, humans are faced with an unlimited availability of food, and the excessive accumulation of fat is now a major risk for human health, especially the development of type 2 diabetes (T2D). Since the first recognition of the association between fat accumulation, reduced insulin action and increased risk of T2D, several mechanisms have been proposed to link excess FA availability to reduced insulin action, with some of them being competing or contradictory. This review summarises the evidence for these mechanisms in the context of excess dietary FAs generating insulin resistance in muscle, the major tissue involved in insulin-stimulated disposal of blood glucose. It also outlines potential problems with models and measurements that may hinder as well as help improve our understanding of the links between FAs and insulin action.
Collapse
Affiliation(s)
- Nigel Turner
- Department of Pharmacology School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia Diabetes and Obesity Division, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, Australia St Vincent's Clinical School, University of New South Wales, Sydney, New South Wales, Australia Department of Physiology, Monash University, Clayton, Victoria 3800, Australia
| | | | | | | |
Collapse
|
220
|
Briand F, Prunet-Marcassus B, Thieblemont Q, Costard C, Muzotte E, Sordello S, Sulpice T. Raising HDL with CETP inhibitor torcetrapib improves glucose homeostasis in dyslipidemic and insulin resistant hamsters. Atherosclerosis 2014; 233:359-362. [PMID: 24530763 DOI: 10.1016/j.atherosclerosis.2014.01.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 01/10/2014] [Accepted: 01/12/2014] [Indexed: 11/19/2022]
Abstract
We investigated whether raising HDL-cholesterol levels with cholesteryl ester transfer protein (CETP) inhibition improves glucose homeostasis in dyslipidemic and insulin resistant hamsters. Compared with vehicle, torcetrapib 30 mg/kg/day (TOR) administered for 10 days significantly increased by ∼40% both HDL-cholesterol levels and 3H-tracer appearance in HDL after 3H-cholesterol labeled macrophages i.p. injection. TOR significantly reduced fasting plasma triglycerides, glycerol and free fatty acids levels by 65%, 31% and 23%, respectively. TOR also reduced blood glucose levels and plasma insulin by 20% and 49% respectively, which led to a 60% reduction in HOMA-IR index (all p<0.01). After 3H-2-deoxyglucose and insulin injection, TOR significantly increased glucose uptake in oxidative soleus muscle, liver and heart by 26, 33 and 70%, respectively. Raising HDL levels with the CETP inhibitor torcetrapib improves glucose homeostasis in dyslipidemic and insulin resistant hamsters. Whether similar effect would be observed with other CETP inhibitors should be investigated.
Collapse
Affiliation(s)
- François Briand
- Physiogenex SAS, Prologue Biotech, 516 Rue Pierre et Marie Curie, 31670 Labège, France.
| | | | - Quentin Thieblemont
- Physiogenex SAS, Prologue Biotech, 516 Rue Pierre et Marie Curie, 31670 Labège, France
| | - Clément Costard
- Physiogenex SAS, Prologue Biotech, 516 Rue Pierre et Marie Curie, 31670 Labège, France
| | - Elodie Muzotte
- Physiogenex SAS, Prologue Biotech, 516 Rue Pierre et Marie Curie, 31670 Labège, France
| | - Sylvie Sordello
- Physiogenex SAS, Prologue Biotech, 516 Rue Pierre et Marie Curie, 31670 Labège, France
| | - Thierry Sulpice
- Physiogenex SAS, Prologue Biotech, 516 Rue Pierre et Marie Curie, 31670 Labège, France
| |
Collapse
|
221
|
Cooperation between brain and islet in glucose homeostasis and diabetes. Nature 2013; 503:59-66. [PMID: 24201279 DOI: 10.1038/nature12709] [Citation(s) in RCA: 213] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 09/19/2013] [Indexed: 12/19/2022]
Abstract
Although a prominent role for the brain in glucose homeostasis was proposed by scientists in the nineteenth century, research throughout most of the twentieth century focused on evidence that the function of pancreatic islets is both necessary and sufficient to explain glucose homeostasis, and that diabetes results from defects of insulin secretion, action or both. However, insulin-independent mechanisms, referred to as 'glucose effectiveness', account for roughly 50% of overall glucose disposal, and reduced glucose effectiveness also contributes importantly to diabetes pathogenesis. Although mechanisms underlying glucose effectiveness are poorly understood, growing evidence suggests that the brain can dynamically regulate this process in ways that improve or even normalize glycaemia in rodent models of diabetes. Here we present evidence of a brain-centred glucoregulatory system (BCGS) that can lower blood glucose levels via both insulin-dependent and -independent mechanisms, and propose a model in which complex and highly coordinated interactions between the BCGS and pancreatic islets promote normal glucose homeostasis. Because activation of either regulatory system can compensate for failure of the other, defects in both may be required for diabetes to develop. Consequently, therapies that target the BCGS in addition to conventional approaches based on enhancing insulin effects may have the potential to induce diabetes remission, whereas targeting just one typically does not.
Collapse
|
222
|
Campos-Ferraz PL, Bozza T, Nicastro H, Lancha AH. Distinct effects of leucine or a mixture of the branched-chain amino acids (leucine, isoleucine, and valine) supplementation on resistance to fatigue, and muscle and liver-glycogen degradation, in trained rats. Nutrition 2013; 29:1388-94. [DOI: 10.1016/j.nut.2013.05.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 04/08/2013] [Accepted: 05/07/2013] [Indexed: 11/28/2022]
|
223
|
Affiliation(s)
- Marzieh Salehi
- Department of Medicine, Division of Endocrinology, University of Cincinnati, Cincinnati, Ohio
| | - David A. D’Alessio
- Department of Medicine, Division of Endocrinology, University of Cincinnati, Cincinnati, Ohio
- Cincinnati VA Medical Center, Cincinnati, Ohio
- Corresponding author: David A. D’Alessio,
| |
Collapse
|
224
|
Regnault TRH, Gentili S, Sarr O, Toop CR, Sloboda DM. Fructose, pregnancy and later life impacts. Clin Exp Pharmacol Physiol 2013; 40:824-37. [DOI: 10.1111/1440-1681.12162] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 08/08/2013] [Accepted: 08/14/2013] [Indexed: 02/06/2023]
Affiliation(s)
- Timothy RH Regnault
- Department of Obstetrics and Gynaecology; Children's Health Research Institute; Western University; London ON Canada
| | - Sheridan Gentili
- School of Pharmacy and Medical Sciences; Sansom Institute for Health Research; University of South Australia; Adelaide SA Australia
| | - Ousseynou Sarr
- Department of Obstetrics and Gynaecology; Children's Health Research Institute; Western University; London ON Canada
| | - Carla R Toop
- School of Pharmacy and Medical Sciences; Sansom Institute for Health Research; University of South Australia; Adelaide SA Australia
| | - Deborah M Sloboda
- Department of Biochemistry and Biomedical Sciences; Faculty of Health Sciences; McMaster University; Hamilton ON Canada
| |
Collapse
|
225
|
Ghafoory S, Breitkopf-Heinlein K, Li Q, Scholl C, Dooley S, Wölfl S. Zonation of nitrogen and glucose metabolism gene expression upon acute liver damage in mouse. PLoS One 2013; 8:e78262. [PMID: 24147127 PMCID: PMC3798318 DOI: 10.1371/journal.pone.0078262] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 09/10/2013] [Indexed: 11/18/2022] Open
Abstract
Zonation of metabolic activities within specific structures and cell types is a phenomenon of liver organization and ensures complementarity of variant liver functions like protein production, glucose homeostasis and detoxification. To analyze damage and regeneration of liver tissue in response to a toxic agent, expression of liver specific enzymes was analyzed by in situ hybridization in mouse over a 6 days time course following carbon tetrachloride (CCl4) injection. CCl4 mixed with mineral oil was administered to BALB/c mice by intraperitoneal injection, and mice were sacrificed at different time points post injection. Changes in the expression of albumin (Alb), arginase (Arg1), glutaminase 2 (Gls2), Glutamine synthetase (Gs), glucose-6-phosphatase (G6pc), glycogen synthase 2 (Gys2), Glycerinaldehyd-3-phosphat-Dehydrogenase (Gapdh), Cytochrom p450 2E1 (Cyp2e1) and glucagon receptor (Gcgr) genes in the liver were studied by in situ hybridization and qPCR. We observed significant changes in gene expression of enzymes involved in nitrogen and glucose metabolism and their local distribution following CCl4 injury. We also found that Cyp2e1, the primary metabolizing enzyme for CCl4, was strongly expressed in the pericentral zone during recovery. Furthermore, cells in the damaged area displayed distinct gene expression profiles during the analyzed time course and showed complete recovery with strong albumin production 6 days after CCl4 injection. Our results indicate that despite severe damage, liver cells in the damaged area do not simply die but instead display locally adjusted gene expression supporting damage response and recovery.
Collapse
Affiliation(s)
- Shahrouz Ghafoory
- Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg, Germany
| | - Katja Breitkopf-Heinlein
- Department of Medicine II, Section Molecular Hepatology - Alcohol Associated Diseases, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Qi Li
- Department of Medicine II, Section Molecular Hepatology - Alcohol Associated Diseases, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Catharina Scholl
- Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg, Germany
| | - Steven Dooley
- Department of Medicine II, Section Molecular Hepatology - Alcohol Associated Diseases, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Stefan Wölfl
- Institute of Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg, Germany
| |
Collapse
|
226
|
Edgerton DS, An Z, Johnson KMS, Farmer T, Farmer B, Neal D, Cherrington AD. Effects of intraportal exenatide on hepatic glucose metabolism in the conscious dog. Am J Physiol Endocrinol Metab 2013; 305:E132-9. [PMID: 23673158 PMCID: PMC3725568 DOI: 10.1152/ajpendo.00160.2013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Incretins improve glucose metabolism through multiple mechanisms. It remains unclear whether direct hepatic effects are an important part of exenatide's (Ex-4) acute action. Therefore, the objective of this study was to determine the effect of intraportal delivery of Ex-4 on hepatic glucose production and uptake. Fasted conscious dogs were studied during a hyperglycemic clamp in which glucose was infused into the hepatic portal vein. At the same time, portal saline (control; n = 8) or exenatide was infused at low (0.3 pmol·kg⁻¹·min⁻¹, Ex-4-low; n = 5) or high (0.9 pmol·kg⁻¹·min⁻¹, Ex-4-high; n = 8) rates. Arterial plasma glucose levels were maintained at 160 mg/dl during the experimental period. This required a greater rate of glucose infusion in the Ex-4-high group (1.5 ± 0.4, 2.0 ± 0.7, and 3.7 ± 0.7 mg·kg⁻¹·min⁻¹ between 30 and 240 min in the control, Ex-4-low, and Ex-4-high groups, respectively). Plasma insulin levels were elevated by Ex-4 (arterial: 4,745 ± 428, 5,710 ± 355, and 7,262 ± 1,053 μU/ml; hepatic sinusoidal: 14,679 ± 1,700, 15,341 ± 2,208, and 20,445 ± 4,020 μU/ml, 240 min, area under the curve), whereas the suppression of glucagon was nearly maximal in all groups. Although glucose utilization was greater during Ex-4 infusion (5.92 ± 0.53, 6.41 ± 0.57, and 8.12 ± 0.54 mg·kg⁻¹·min⁻¹), when indices of hepatic, muscle, and whole body glucose uptake were expressed relative to circulating insulin concentrations, there was no indication of insulin-independent effects of Ex-4. Thus, this study does not support the notion that Ex-4 generates acute changes in hepatic glucose metabolism through direct effects on the liver.
Collapse
Affiliation(s)
- Dale S Edgerton
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
| | | | | | | | | | | | | |
Collapse
|
227
|
Nelson P, Nelson K. Innervation of the placenta and uterus: Competition between cytotrophoblasts and nerves? Placenta 2013; 34:463-6. [DOI: 10.1016/j.placenta.2013.03.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 02/22/2013] [Accepted: 03/13/2013] [Indexed: 01/17/2023]
|
228
|
Coate KC, Smith MS, Shiota M, Irimia JM, Roach PJ, Farmer B, Williams PE, Moore MC. Hepatic glucose metabolism in late pregnancy: normal versus high-fat and -fructose diet. Diabetes 2013; 62:753-61. [PMID: 23223020 PMCID: PMC3581200 DOI: 10.2337/db12-0875] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Net hepatic glucose uptake (NHGU) is an important contributor to postprandial glycemic control. We hypothesized that NHGU is reduced during normal pregnancy and in a pregnant diet-induced model of impaired glucose intolerance/gestational diabetes mellitus (IGT/GDM). Dogs (n = 7 per group) that were nonpregnant (N), normal pregnant (P), or pregnant with IGT/GDM (pregnant dogs fed a high-fat and -fructose diet [P-HFF]) underwent a hyperinsulinemic-hyperglycemic clamp with intraportal glucose infusion. Clamp period insulin, glucagon, and glucose concentrations and hepatic glucose loads did not differ among groups. The N dogs reached near-maximal NHGU rates within 30 min; mean ± SEM NHGU was 105 ± 9 µmol·100 g liver⁻¹·min⁻¹. The P and P-HFF dogs reached maximal NHGU in 90-120 min; their NHGU was blunted (68 ± 9 and 16 ± 17 µmol·100 g liver⁻¹·min⁻¹, respectively). Hepatic glycogen synthesis was reduced 20% in P versus N and 40% in P-HFF versus P dogs. This was associated with a reduction (>70%) in glycogen synthase activity in P-HFF versus P and increased glycogen phosphorylase (GP) activity in both P (1.7-fold greater than N) and P-HFF (1.8-fold greater than P) dogs. Thus, NHGU under conditions mimicking the postprandial state is delayed and suppressed in normal pregnancy, with concomitant reduction in glycogen storage. NHGU is further blunted in IGT/GDM. This likely contributes to postprandial hyperglycemia during pregnancy, with potential adverse outcomes for the fetus and mother.
Collapse
Affiliation(s)
- Katie C. Coate
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Marta S. Smith
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Masakazu Shiota
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Jose M. Irimia
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Peter J. Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Ben Farmer
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Phillip E. Williams
- Department of Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee
- Diabetes Research and Training Center, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Mary Courtney Moore
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
- Corresponding author: Mary Courtney Moore,
| |
Collapse
|
229
|
Coate KC, Kraft G, Irimia JM, Smith MS, Farmer B, Neal DW, Roach PJ, Shiota M, Cherrington AD. Portal vein glucose entry triggers a coordinated cellular response that potentiates hepatic glucose uptake and storage in normal but not high-fat/high-fructose-fed dogs. Diabetes 2013; 62:392-400. [PMID: 23028137 PMCID: PMC3554368 DOI: 10.2337/db12-0417] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The cellular events mediating the pleiotropic actions of portal vein glucose (PoG) delivery on hepatic glucose disposition have not been clearly defined. Likewise, the molecular defects associated with postprandial hyperglycemia and impaired hepatic glucose uptake (HGU) following consumption of a high-fat, high-fructose diet (HFFD) are unknown. Our goal was to identify hepatocellular changes elicited by hyperinsulinemia, hyperglycemia, and PoG signaling in normal chow-fed (CTR) and HFFD-fed dogs. In CTR dogs, we demonstrated that PoG infusion in the presence of hyperinsulinemia and hyperglycemia triggered an increase in the activity of hepatic glucokinase (GK) and glycogen synthase (GS), which occurred in association with further augmentation in HGU and glycogen synthesis (GSYN) in vivo. In contrast, 4 weeks of HFFD feeding markedly reduced GK protein content and impaired the activation of GS in association with diminished HGU and GSYN in vivo. Furthermore, the enzymatic changes associated with PoG sensing in chow-fed animals were abolished in HFFD-fed animals, consistent with loss of the stimulatory effects of PoG delivery. These data reveal new insight into the molecular physiology of the portal glucose signaling mechanism under normal conditions and to the pathophysiology of aberrant postprandial hepatic glucose disposition evident under a diet-induced glucose-intolerant condition.
Collapse
Affiliation(s)
- Katie C. Coate
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Guillaume Kraft
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Jose M. Irimia
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Marta S. Smith
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Ben Farmer
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Doss W. Neal
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Peter J. Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Masakazu Shiota
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Alan D. Cherrington
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee
- Corresponding author: Alan D. Cherrington,
| |
Collapse
|
230
|
Kleinert M, Sylow L, Richter EA. Regulation of glycogen synthase in muscle and its role in Type 2 diabetes. ACTA ACUST UNITED AC 2013. [DOI: 10.2217/dmt.12.54] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
231
|
Cappello G, Franceschelli A, Cappello A, De Luca P. Ketogenic enteral nutrition as a treatment for obesity: short term and long term results from 19,000 patients. Nutr Metab (Lond) 2012; 9:96. [PMID: 23110922 PMCID: PMC3557201 DOI: 10.1186/1743-7075-9-96] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 10/10/2012] [Indexed: 12/25/2022] Open
Abstract
Background Only protein diet has been used successfully to prevent loss of lean body mass first in post-surgical and then in obese patients. We studied overweight and obese patients receiving short treatments of an exclusively protein-based nutritional solution as 24-hour enteral infusion. Methods 19,036 patients (age 44.3 ± 13, M:F = 2:5) with an initial body mass index of 36.5 ± 7.1 underwent 10-day cycles of enteral nutrition through a fine nasogastric tube. The nutritional solution consisted solely of 50–65 g of proteins, plus vitamins and electrolytes. The 24-hour infusion was controlled with a small portable pump. Before and after each 10-day cycle body composition was checked with a Handy 3000 impedance analyzer. At the onset of treatment, average fat mass was 40.9 ± 12.8 kg while body cell mass was 42.7 ± 7.2 kg in males and 27.4 ± 4.6 kg in females. Results After an average of 2.5 cycles the patients lost 10.2 ± 7.0 kg of body weight, 5.8 ± 5.5 kg of fat mass and 2.2 ± 3.3 kg of body cell mass. No significant adverse effects were recorded except asthenia and constipation which were easily controlled with therapy. Long-term results were obtained from 15,444 patients and after an average of 362 ± 296 days we found a mean weight regain of 15.4%. Conclusion Ketogenic Enteral Nutrition treatment of over 19,000 patients induced a rapid 10% weight loss, 57% of which was Fat Mass. No significant adverse effects were found. The treatment is safe, fast, inexpensive and has good one-year results for weight maintenance.
Collapse
Affiliation(s)
- Gianfranco Cappello
- Clinical Nutrition Service of the Department of Surgery Paride Stefanini, University of Rome La Sapienza, Rome, Italy.
| | | | | | | |
Collapse
|