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Kajani S, Laker RC, Ratkova E, Will S, Rhodes CJ. Hepatic glucagon action: beyond glucose mobilization. Physiol Rev 2024; 104:1021-1060. [PMID: 38300523 DOI: 10.1152/physrev.00028.2023] [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: 07/11/2023] [Revised: 01/10/2024] [Accepted: 01/11/2024] [Indexed: 02/02/2024] Open
Abstract
Glucagon's ability to promote hepatic glucose production has been known for over a century, with initial observations touting this hormone as a diabetogenic agent. However, glucagon receptor agonism [when balanced with an incretin, including glucagon-like peptide 1 (GLP-1) to dampen glucose excursions] is now being developed as a promising therapeutic target in the treatment of metabolic diseases, like metabolic dysfunction-associated steatotic disease/metabolic dysfunction-associated steatohepatitis (MASLD/MASH), and may also have benefit for obesity and chronic kidney disease. Conventionally regarded as the opposing tag-team partner of the anabolic mediator insulin, glucagon is gradually emerging as more than just a "catabolic hormone." Glucagon action on glucose homeostasis within the liver has been well characterized. However, growing evidence, in part thanks to new and sensitive "omics" technologies, has implicated glucagon as more than just a "glucose liberator." Elucidation of glucagon's capacity to increase fatty acid oxidation while attenuating endogenous lipid synthesis speaks to the dichotomous nature of the hormone. Furthermore, glucagon action is not limited to just glucose homeostasis and lipid metabolism, as traditionally reported. Glucagon plays key regulatory roles in hepatic amino acid and ketone body metabolism, as well as mitochondrial turnover and function, indicating broader glucagon signaling consequences for metabolic homeostasis mediated by the liver. Here we examine the broadening role of glucagon signaling within the hepatocyte and question the current dogma, to appreciate glucagon as more than just that "catabolic hormone."
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Affiliation(s)
- Sarina Kajani
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
| | - Rhianna C Laker
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
| | - Ekaterina Ratkova
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Mölndal, Sweden
| | - Sarah Will
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
| | - Christopher J Rhodes
- Early Cardiovascular, Renal and Metabolism, Biopharmaceuticals R&D, AstraZeneca, Gaithersburg, Maryland, United States
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Nelson AB, Queathem ED, Puchalska P, Crawford PA. Metabolic Messengers: ketone bodies. Nat Metab 2023; 5:2062-2074. [PMID: 38092961 DOI: 10.1038/s42255-023-00935-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 10/20/2023] [Indexed: 12/21/2023]
Abstract
Prospective molecular targets and therapeutic applications for ketone body metabolism have increased exponentially in the past decade. Initially considered to be restricted in scope as liver-derived alternative fuel sources during periods of carbohydrate restriction or as toxic mediators during diabetic ketotic states, ketogenesis and ketone bodies modulate cellular homeostasis in multiple physiological states through a diversity of mechanisms. Selective signalling functions also complement the metabolic fates of the ketone bodies acetoacetate and D-β-hydroxybutyrate. Here we discuss recent discoveries revealing the pleiotropic roles of ketone bodies, their endogenous sourcing, signalling mechanisms and impact on target organs, and considerations for when they are either stimulated for endogenous production by diets or pharmacological agents or administered as exogenous wellness-promoting agents.
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Affiliation(s)
- Alisa B Nelson
- Division of Molecular Medicine, Department of Medicine, University of Minnesota, Minneapolis, MN, USA
| | - Eric D Queathem
- Division of Molecular Medicine, Department of Medicine, University of Minnesota, Minneapolis, MN, USA
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Patrycja Puchalska
- Division of Molecular Medicine, Department of Medicine, University of Minnesota, Minneapolis, MN, USA.
| | - Peter A Crawford
- Division of Molecular Medicine, Department of Medicine, University of Minnesota, Minneapolis, MN, USA.
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA.
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Current Evidence Surrounding the Use of Sodium Bicarbonate in the Critically Ill Patient. CURRENT EMERGENCY AND HOSPITAL MEDICINE REPORTS 2023. [DOI: 10.1007/s40138-023-00260-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
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Pan A, Sun XM, Huang FQ, Liu JF, Cai YY, Wu X, Alolga RN, Li P, Liu BL, Liu Q, Qi LW. The mitochondrial β-oxidation enzyme HADHA restrains hepatic glucagon response by promoting β-hydroxybutyrate production. Nat Commun 2022; 13:386. [PMID: 35046401 PMCID: PMC8770464 DOI: 10.1038/s41467-022-28044-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 01/06/2022] [Indexed: 11/09/2022] Open
Abstract
Disordered hepatic glucagon response contributes to hyperglycemia in diabetes. The regulators involved in glucagon response are less understood. This work aims to investigate the roles of mitochondrial β-oxidation enzyme HADHA and its downstream ketone bodies in hepatic glucagon response. Here we show that glucagon challenge impairs expression of HADHA. Liver-specific HADHA overexpression reversed hepatic gluconeogenesis in mice, while HADHA knockdown augmented glucagon response. Stable isotope tracing shows that HADHA promotes ketone body production via β-oxidation. The ketone body β-hydroxybutyrate (BHB) but not acetoacetate suppresses gluconeogenesis by selectively inhibiting HDAC7 activity via interaction with Glu543 site to facilitate FOXO1 nuclear exclusion. In HFD-fed mice, HADHA overexpression improved metabolic disorders, and these effects are abrogated by knockdown of BHB-producing enzyme. In conclusion, BHB is responsible for the inhibitory effect of HADHA on hepatic glucagon response, suggesting that HADHA activation or BHB elevation by pharmacological intervention hold promise in treating diabetes.
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Affiliation(s)
- An Pan
- State Key Laboratory of Natural Medicines, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Xiao-Meng Sun
- State Key Laboratory of Natural Medicines, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Feng-Qing Huang
- State Key Laboratory of Natural Medicines, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Jin-Feng Liu
- Clinical Metabolomics Center, China Pharmaceutical University, Nanjing, 211198, China
| | - Yuan-Yuan Cai
- State Key Laboratory of Natural Medicines, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Xin Wu
- State Key Laboratory of Natural Medicines, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Raphael N Alolga
- Clinical Metabolomics Center, China Pharmaceutical University, Nanjing, 211198, China
| | - Ping Li
- State Key Laboratory of Natural Medicines, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Bao-Lin Liu
- State Key Laboratory of Natural Medicines, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Qun Liu
- State Key Laboratory of Natural Medicines, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China.
- Clinical Metabolomics Center, China Pharmaceutical University, Nanjing, 211198, China.
| | - Lian-Wen Qi
- State Key Laboratory of Natural Medicines, School of Traditional Chinese Pharmacy, China Pharmaceutical University, Nanjing, 210009, China.
- Clinical Metabolomics Center, China Pharmaceutical University, Nanjing, 211198, China.
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Daniele G, Solis-Herrera C, Dardano A, Mari A, Tura A, Giusti L, Kurumthodathu JJ, Campi B, Saba A, Bianchi AM, Tregnaghi C, Egidi MF, Abdul-Ghani M, DeFronzo R, Del Prato S. Increase in endogenous glucose production with SGLT2 inhibition is attenuated in individuals who underwent kidney transplantation and bilateral native nephrectomy. Diabetologia 2020; 63:2423-2433. [PMID: 32827269 PMCID: PMC7527374 DOI: 10.1007/s00125-020-05254-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 05/30/2020] [Indexed: 12/02/2022]
Abstract
AIMS/HYPOTHESIS The glucosuria induced by sodium-glucose cotransporter 2 (SGLT2) inhibition stimulates endogenous (hepatic) glucose production (EGP), blunting the decline in HbA1c. We hypothesised that, in response to glucosuria, a renal signal is generated and stimulates EGP. To examine the effect of acute administration of SGLT2 inhibitors on EGP, we studied non-diabetic individuals who had undergone renal transplant with and without removal of native kidneys. METHODS This was a parallel, randomised, double-blind, placebo-controlled, single-centre study, designed to evaluate the effect of a single dose of dapagliflozin or placebo on EGP determined by stable-tracer technique. We recruited non-diabetic individuals who were 30-65 years old, with a BMI of 25-35 kg/m2 and stable body weight (±2 kg) over the preceding 3 months, and HbA1c <42 mmol/mol (6.0%). Participants had undergone renal transplant with and without removal of native kidneys and were on a stable dose of immunosuppressive medications. Participants received a single dose of dapagliflozin 10 mg or placebo on two separate days, at a 5- to 14-day interval, according to randomisation performed by our hospital pharmacy, which provided dapagliflozin and matching placebo, packaged in bulk bottles that were sequentially numbered. Both participants and investigators were blinded to group assignment. RESULTS Twenty non-diabetic renal transplant patients (ten with residual native kidneys, ten with bilateral nephrectomy) participated in the study. Dapagliflozin induced greater glucosuria in individuals with residual native kidneys vs nephrectomised individuals (8.6 ± 1.1 vs 5.5 ± 0.5 g/6 h; p = 0.02; data not shown). During the 6 h study period, plasma glucose decreased only slightly and similarly in both groups, with no difference compared with placebo (data not shown). Following administration of placebo, there was a progressive time-related decline in EGP that was similar in both nephrectomised individuals and individuals with residual native kidneys. Following dapagliflozin administration, EGP declined in both groups, but the differences between the decrement in EGP with dapagliflozin and placebo in the group with bilateral nephrectomy (Δ = 1.11 ± 0.72 μmol min-1 kg-1) was significantly lower (p = 0.03) than in the residual native kidney group (Δ = 2.56 ± 0.33 μmol min-1 kg-1). In the population treated with dapagliflozin, urinary glucose excretion was correlated with EGP (r = 0.34, p < 0.05). Plasma insulin, C-peptide, glucagon, prehepatic insulin:glucagon ratio, lactate, alanine and pyruvate concentrations were similar following placebo and dapagliflozin treatment. β-Hydroxybutyrate increased with dapagliflozin treatment in the residual native kidney group, while a small increase was observed only at 360 min in the nephrectomy group. Plasma adrenaline (epinephrine) did not change after dapagliflozin and placebo treatment in either group. Following dapagliflozin administration, plasma noradrenaline (norepinephrine) increased slightly in the residual native kidney group and decreased in the nephrectomy group. CONCLUSIONS/INTERPRETATION In nephrectomised individuals, the hepatic compensatory response to acute SGLT2 inhibitor-induced glucosuria was attenuated, as compared with individuals with residual native kidneys, suggesting that SGLT2 inhibitor-mediated stimulation of hepatic glucose production via efferent renal nerves occurs in an attempt to compensate for the urinary glucose loss (i.e. a renal-hepatic axis). TRIAL REGISTRATION ClinicalTrials.gov NCT03168295 FUNDING: This protocol was supported by Qatar National Research Fund (QNRF) Award No. NPRP 8-311-3-062 and NIH grant DK024092-38. Graphical abstract.
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Affiliation(s)
- Giuseppe Daniele
- Department of Clinical and Experimental Medicine, Section of Metabolic Diseases and Diabetes, University of Pisa, Via Paradisa 2, 56124, Pisa, Italy
| | - Carolina Solis-Herrera
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Angela Dardano
- Department of Clinical and Experimental Medicine, Section of Metabolic Diseases and Diabetes, University of Pisa, Via Paradisa 2, 56124, Pisa, Italy
| | - Andrea Mari
- Metabolic Unit, CNR Institute of Neuroscience, Padova, Italy
| | - Andrea Tura
- Metabolic Unit, CNR Institute of Neuroscience, Padova, Italy
| | - Laura Giusti
- Department of Clinical and Experimental Medicine, Section of Metabolic Diseases and Diabetes, University of Pisa, Via Paradisa 2, 56124, Pisa, Italy
| | - Jancy J Kurumthodathu
- Department of Clinical and Experimental Medicine, Section of Metabolic Diseases and Diabetes, University of Pisa, Via Paradisa 2, 56124, Pisa, Italy
| | - Beatrice Campi
- Department of Clinical and Experimental Medicine, Section of Metabolic Diseases and Diabetes, University of Pisa, Via Paradisa 2, 56124, Pisa, Italy
| | - Alessandro Saba
- Department of Clinical and Experimental Medicine, Section of Metabolic Diseases and Diabetes, University of Pisa, Via Paradisa 2, 56124, Pisa, Italy
| | - Anna Maria Bianchi
- Department of Clinical and Experimental Medicine, Section of Metabolic Diseases and Diabetes, University of Pisa, Via Paradisa 2, 56124, Pisa, Italy
| | - Carla Tregnaghi
- Department of Clinical and Experimental Medicine, Section of Metabolic Diseases and Diabetes, University of Pisa, Via Paradisa 2, 56124, Pisa, Italy
| | - Maria Francesca Egidi
- Department of Clinical and Experimental Medicine, Section of Metabolic Diseases and Diabetes, University of Pisa, Via Paradisa 2, 56124, Pisa, Italy
| | - Muhammad Abdul-Ghani
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Ralph DeFronzo
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Stefano Del Prato
- Department of Clinical and Experimental Medicine, Section of Metabolic Diseases and Diabetes, University of Pisa, Via Paradisa 2, 56124, Pisa, Italy.
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Capozzi ME, Coch RW, Koech J, Astapova II, Wait JB, Encisco SE, Douros JD, El K, Finan B, Sloop KW, Herman MA, D'Alessio DA, Campbell JE. The Limited Role of Glucagon for Ketogenesis During Fasting or in Response to SGLT2 Inhibition. Diabetes 2020; 69:882-892. [PMID: 32005706 PMCID: PMC7171961 DOI: 10.2337/db19-1216] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 01/27/2020] [Indexed: 12/18/2022]
Abstract
Glucagon is classically described as a counterregulatory hormone that plays an essential role in the protection against hypoglycemia. In addition to its role in the regulation of glucose metabolism, glucagon has been described to promote ketosis in the fasted state. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are a new class of glucose-lowering drugs that act primarily in the kidney, but some reports have described direct effects of SGLT2i on α-cells to stimulate glucagon secretion. Interestingly, SGLT2 inhibition also results in increased endogenous glucose production and ketone production, features common to glucagon action. Here, we directly test the ketogenic role of glucagon in mice, demonstrating that neither fasting- nor SGLT2i-induced ketosis is altered by interruption of glucagon signaling. Moreover, any effect of glucagon to stimulate ketogenesis is severely limited by its insulinotropic actions. Collectively, our data suggest that fasting-associated ketosis and the ketogenic effects of SGLT2 inhibitors occur almost entirely independent of glucagon.
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Affiliation(s)
- Megan E Capozzi
- Duke Molecular Physiology Institute, Duke University, Durham, NC
| | - Reilly W Coch
- Duke Molecular Physiology Institute, Duke University, Durham, NC
- Division of Endocrinology, Department of Medicine, Duke University, Durham, NC
| | - Jepchumba Koech
- Duke Molecular Physiology Institute, Duke University, Durham, NC
| | - Inna I Astapova
- Duke Molecular Physiology Institute, Duke University, Durham, NC
- Division of Endocrinology, Department of Medicine, Duke University, Durham, NC
| | - Jacob B Wait
- Duke Molecular Physiology Institute, Duke University, Durham, NC
| | - Sara E Encisco
- Duke Molecular Physiology Institute, Duke University, Durham, NC
| | | | - Kimberly El
- Duke Molecular Physiology Institute, Duke University, Durham, NC
| | - Brian Finan
- Novo Nordisk Research Center, Indianapolis, IN
| | - Kyle W Sloop
- Diabetes and Complications, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN
| | - Mark A Herman
- Duke Molecular Physiology Institute, Duke University, Durham, NC
- Division of Endocrinology, Department of Medicine, Duke University, Durham, NC
- Department of Pharmacology and Cancer Biology, Duke University, Durham, NC
| | - David A D'Alessio
- Duke Molecular Physiology Institute, Duke University, Durham, NC
- Division of Endocrinology, Department of Medicine, Duke University, Durham, NC
| | - Jonathan E Campbell
- Duke Molecular Physiology Institute, Duke University, Durham, NC
- Division of Endocrinology, Department of Medicine, Duke University, Durham, NC
- Department of Pharmacology and Cancer Biology, Duke University, Durham, NC
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Sato Y, Nunoi K, Kaku K, Yoshida A, Suganami H. Basal insulin secretion capacity predicts the initial response and maximum levels of beta-hydroxybutyrate during therapy with the sodium-glucose co-transporter-2 inhibitor tofogliflozin, in relation to weight loss. Diabetes Obes Metab 2020; 22:222-230. [PMID: 31608549 PMCID: PMC6973158 DOI: 10.1111/dom.13890] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 09/11/2019] [Accepted: 09/27/2019] [Indexed: 01/14/2023]
Abstract
AIMS To investigate predictors of the initial response of beta-hydroxybutyrate (BHB) and maximum BHB (max-BHB) values during long-term therapy with the sodium-glucose co-transporter-2 inhibitor tofogliflozin (TOFO), and to explore the association of the initial elevation of BHB with subsequent clinical effects in people with type 2 diabetes mellitus. METHODS We analysed 774 people receiving TOFO in phase 3 trials in two groups based on measurable BHB change at week 4 (initial response): the top quartile [n = 194] and the three lower quartiles [n = 579]. Multivariate analysis was used to determine baseline predictors of inclusion in the top quartile and the max-BHB values. To investigate the association of the initial response with subsequent clinical effects, adjusted changes in variables in the two groups were compared using an analysis of covariance model. RESULTS Of the participants, 66% were men, and the mean age, glycated haemoglobin, body mass index and estimated glomerular filtration rate were 58.5 years, 8.1%, 25.6 kg/m2 and 83.9 mL/min/1.73 m2 , respectively. Median changes in BHB at week 4 in the top quartile and lower three quartiles were +246.4* and +30.8* μmol/L, respectively (*P < .001 vs baseline). Lower baseline insulin secretion capacity predicted the inclusion in the top quartile and greater max-BHB levels. The top quartile was associated with greater weight loss following greater increases in free fatty acids and greater reductions in fasting C-peptide levels compared with the lower three quartiles. CONCLUSIONS Lower basal insulin secretion capacity might predict greater initial BHB elevations and max-BHB levels during long-term TOFO therapy. Greater weight loss through lipid use might be related to high initial BHB elevations.
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Affiliation(s)
- Yuichi Sato
- Department of Diabetes and EndocrinologySt Mary's HospitalFukuokaJapan
| | - Kiyohide Nunoi
- Department of Diabetes and EndocrinologySt Mary's HospitalFukuokaJapan
| | - Kohei Kaku
- Department of Internal MedicineKawasaki Medical SchoolOkayamaJapan
| | - Akihiro Yoshida
- Cardiovascular and Diabetes Product Marketing DepartmentKowa Company, LtdTokyoJapan
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Friend MA, Bhanugopan MS, McGrath SR, Edwards JH, Hancock S, Loudon K, Miller D, McGilchrist P, Refshauge G, Robertson SM, Thompson AN, Masters DG. Do calcium and magnesium deficiencies in reproducing ewes contribute to high lamb mortality? ANIMAL PRODUCTION SCIENCE 2020. [DOI: 10.1071/an17588] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
High lamb mortality continues to be a significant economic and welfare problem within the Australian sheep industry, with 20–30% of lambs born in commercial flocks dying mostly within 3 days of birth. Clinical hypocalcaemia and hypomagnesaemia cause ewe mortality, and, subsequently, either fetal or lamb death, but it is not known whether subclinical deficiencies of calcium (Ca) and magnesium (Mg) compromise lamb survival. This review considers the potential mechanisms through which Ca and Mg deficiencies may influence lamb survival, and factors influencing the risk of deficiency. Pastures grazed by lambing ewes may be marginal in calcium (Ca; <4 g/kg DM) and magnesium (Mg; <0.9 g/kg DM) but also have a high dietary cation–anion difference (>12 meq/100 g DM) and high concentrations of potassium (K; >30 g/kg DM) and nitrogen. In young cereal crops, sodium concentrations are also often low (<0.9 g/kg DM). This combination of minerals and other nutrients creates an imbalance in supply and increases susceptibility to acute Ca (hypocalcaemia) and Mg (hypomagnesaemia) deficiency. Calcium is required for smooth muscle function and has a direct role in uterine contraction, so may influence the duration of parturition. Low Ca and Mg intake both influence insulin release and sensitivity, low Mg results in poor glycaemic control and insulin resistance by impairing both insulin secretion and its action on peripheral tissues, also potentially altering the duration of parturition as well as risk of metabolic disease. Magnesium is also a neuroprotectant that slows the neuronal damage during hypoxia and has been linked with thermogenesis in offspring and increased immunoglobulins in colostrum. These functions indicate potential importance in improving the ease of parturition and improved ability of the newborn lamb to thermoregulate and survive after birth. Subclinical Ca and Mg deficiencies commonly occur in 20% of lambing ewes grazing temperate pastures, so further studies are warranted to investigate whether correction of these deficiencies can improve lamb survival.
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Alsalim W, Persson M, Ahrén B. Different glucagon effects during DPP-4 inhibition versus SGLT-2 inhibition in metformin-treated type 2 diabetes patients. Diabetes Obes Metab 2018; 20:1652-1658. [PMID: 29498469 DOI: 10.1111/dom.13276] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 02/26/2018] [Accepted: 02/27/2018] [Indexed: 01/09/2023]
Abstract
AIMS Previous studies have shown that dipeptidyl peptidase (DPP)-4 inhibition lowers glucagon levels whereas sodium-glucose co-transporter 2 (SGLT-2) inhibition increases them. This study evaluated the extent of these opposite effects in a direct comparative head-to-head study. METHODS In a single-centre, randomized study with a cross-over design, 28 metformin-treated patients with type 2 diabetes (T2D) (mean age, 63 years; baseline HbA1c, 6.8%) were treated with vildagliptin (50 mg twice daily) or dapagliflozin (10 mg once daily) for 2 weeks, with a 4-week wash-out period between the two separate treatments. After each treatment period, a meal test was undertaken, with measurements of islet and incretin hormones and 4-hour area under the curve (AUC) levels were estimated. RESULTS Fasting glucagon (35.6 ± 2.5 vs 39.4 ± 3.4 pmoL/L; P = .032) and postprandial glucagon (4-hour AUCglucagon , 32.1 ± 2.3 vs 37.5 ± 2.7 nmoL/L min; P = .001) were ~15% lower after vildagliptin compared to dapagliflozin treatment. This was associated with stronger early (15 minute) C-peptide response and higher 4-hour AUCC-peptide (P < .010), higher 4-hour AUC of the intact form of glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) (P < .001) and lower 4-hour AUC of total GIP and GLP-1 (P < .001). CONCLUSION Treatment with DPP-4 inhibition with vildagliptin results in 15% lower fasting and postprandial glucagon levels compared to SGLT-2 inhibition with dapagliflozin. DPP-4 inhibition also induces more rapid insulin secretion and higher levels of intact incretin hormones, resulting in stronger feedback inhibition of incretin hormone secretion than SGLT-2 inhibition.
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Affiliation(s)
- Wathik Alsalim
- Department of Clinical Sciences Lund, Lund University, Lund, Sweden
| | | | - Bo Ahrén
- Department of Clinical Sciences Lund, Lund University, Lund, Sweden
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The mechanisms mediating the antiepileptic effects of the ketogenic diet, and potential opportunities for improvement with metabolism-altering drugs. Seizure 2017; 52:15-19. [DOI: 10.1016/j.seizure.2017.09.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 09/09/2017] [Accepted: 09/11/2017] [Indexed: 02/06/2023] Open
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Daniele G, Xiong J, Solis-Herrera C, Merovci A, Eldor R, Tripathy D, DeFronzo RA, Norton L, Abdul-Ghani M. Dapagliflozin Enhances Fat Oxidation and Ketone Production in Patients With Type 2 Diabetes. Diabetes Care 2016; 39:2036-2041. [PMID: 27561923 PMCID: PMC5079607 DOI: 10.2337/dc15-2688] [Citation(s) in RCA: 146] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 08/01/2016] [Indexed: 02/03/2023]
Abstract
OBJECTIVE Insulin resistance is associated with mitochondrial dysfunction and decreased ATP synthesis. Treatment of individuals with type 2 diabetes mellitus (T2DM) with sodium-glucose transporter 2 inhibitors (SGLT2i) improves insulin sensitivity. However, recent reports have demonstrated development of ketoacidosis in subjects with T2DM treated with SGLT2i. The current study examined the effect of improved insulin sensitivity with dapagliflozin on 1) mitochondrial ATP synthesis and 2) substrate oxidation rates and ketone production. RESEARCH DESIGN AND METHODS The study randomized 18 individuals with T2DM to dapagliflozin (n = 9) or placebo (n = 9). Before and after 2 weeks, subjects received an insulin clamp with tritiated glucose, indirect calorimetry, and muscle biopsies. RESULTS Dapagliflozin reduced fasting plasma glucose (167 ± 13 to 128 ± 6 mg/dL) and increased insulin-stimulated glucose disposal by 36% (P < 0.01). Glucose oxidation decreased (1.06 to 0.80 mg/kg ⋅ min, P < 0.05), whereas nonoxidative glucose disposal (glycogen synthesis) increased (2.74 to 4.74 mg/kg ⋅ min, P = 0.03). Dapagliflozin decreased basal glucose oxidation and increased lipid oxidation and plasma ketone concentration (0.05 to 0.19 mmol/L, P < 0.01) in association with an increase in fasting plasma glucagon (77 ± 8 to 94 ± 13, P < 0.01). Dapagliflozin reduced the ATP synthesis rate, which correlated with an increase in plasma ketone concentration. CONCLUSIONS Dapagliflozin improved insulin sensitivity and caused a shift from glucose to lipid oxidation, which, together with an increase in glucagon-to-insulin ratio, provide the metabolic basis for increased ketone production.
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Affiliation(s)
- Giuseppe Daniele
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, TX
| | - Juan Xiong
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, TX
| | - Carolina Solis-Herrera
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, TX
| | - Aurora Merovci
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, TX
| | - Roy Eldor
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, TX
| | - Devjit Tripathy
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, TX
| | - Ralph A DeFronzo
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, TX
| | - Luke Norton
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, TX
| | - Muhammad Abdul-Ghani
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, TX
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Aizawa Y, Shirai T, Kobayashi T, Hino O, Tsujii Y, Inoue H, Kazami M, Tadokoro T, Suzuki T, Kobayashi KI, Yamamoto Y. The tuberous sclerosis complex model Eker (TSC2+/-) rat exhibits hyperglycemia and hyperketonemia due to decreased glycolysis in the liver. Arch Biochem Biophys 2015; 590:48-55. [PMID: 26550928 DOI: 10.1016/j.abb.2015.10.019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 10/29/2015] [Accepted: 10/29/2015] [Indexed: 12/17/2022]
Abstract
Tuberous sclerosis complex (TSC) presents as benign tumors that affect the brain, kidneys, lungs and skin. The inactivation of TSC2 gene, through loss of heterozygosity is responsible for tumor development in TSC. Since TSC patients are carriers of heterozygous a TSC2; mutation, to reveal the risk factors which these patients carry prior to tumor development is important. In this experiment, Eker rat which carry a mutation in this TSC2 gene were analyzed for their metabolic changes. Wild-type (TSC2+/+) and heterozygous mutant TSC2 (TSC2+/-) Eker rats were raised for 100 days. As a result, the Eker rats were found to exhibit hyperglycemia and hyperketonemia. However the high ketone body production in the liver was observed without accompanying increased levels of plasma free fatty acids or insulin. Further, production of the ketone body β-hydroxybutyrate was inhibited due to the low NADH/NAD(+) ratio resulting from the restraint on glycolysis, which was followed by inhibition of the malate-aspartate shuttle and TCA cycle. Therefore, we conclude that glycolysis is restrained in the livers of TSC2 heterozygous mutant rats, and these defects lead to abnormal production of acetoacetate.
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Affiliation(s)
- Yumi Aizawa
- Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo 156-8502, Japan
| | - Tomomi Shirai
- Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo 156-8502, Japan
| | - Toshiyuki Kobayashi
- Department of Pathology and Oncology Juntendo University Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan
| | - Okio Hino
- Department of Pathology and Oncology Juntendo University Faculty of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan
| | - Yoshimasa Tsujii
- Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo 156-8502, Japan
| | - Hirofumi Inoue
- Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo 156-8502, Japan
| | - Machiko Kazami
- Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo 156-8502, Japan
| | - Tadahiro Tadokoro
- Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo 156-8502, Japan
| | - Tsukasa Suzuki
- Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo 156-8502, Japan
| | - Ken-Ichi Kobayashi
- Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo 156-8502, Japan
| | - Yuji Yamamoto
- Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya, Tokyo 156-8502, Japan.
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McCarty MF, DiNicolantonio JJ, O’Keefe JH. Ketosis may promote brain macroautophagy by activating Sirt1 and hypoxia-inducible factor-1. Med Hypotheses 2015; 85:631-9. [DOI: 10.1016/j.mehy.2015.08.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 07/06/2015] [Accepted: 08/01/2015] [Indexed: 12/25/2022]
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Abdul-Ghani MA, Norton L, DeFronzo RA. Renal sodium-glucose cotransporter inhibition in the management of type 2 diabetes mellitus. Am J Physiol Renal Physiol 2015; 309:F889-900. [PMID: 26354881 DOI: 10.1152/ajprenal.00267.2015] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 09/02/2015] [Indexed: 12/22/2022] Open
Abstract
Hyperglycemia is the primary factor responsible for the microvascular, and to a lesser extent macrovascular, complications of diabetes. Despite this well-established relationship, approximately half of all type 2 diabetic patients in the US have a hemoglobin A1c (HbA1c) ≥7.0%. This is associated in part with the side effects, i.e., weight gain and hypoglycemia, of currently available antidiabetic agents and in part with the failure to utilize medications that reverse the basic pathophysiological defects present in patients with type 2 diabetes. The kidney has been shown to play a central role in the development of hyperglycemia by excessive production of glucose throughout the sleeping hours and enhanced reabsorption of filtered glucose by the renal tubules secondary to an increase in the threshold at which glucose spills into the urine. Recently, a new class of antidiabetic agents, the sodium-glucose cotransporter 2 (SGLT2) inhibitors, has been developed and approved for the treatment of patients with type 2 diabetes. In this review, we examine their mechanism of action, efficacy, safety, and place in the therapeutic armamentarium. Since the SGLT2 inhibitors have a unique mode of action that differs from all other oral and injectable antidiabetic agents, they can be used at all stages of the disease and in combination with all other antidiabetic medications.
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Affiliation(s)
- Muhammad A Abdul-Ghani
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Luke Norton
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, Texas
| | - Ralph A DeFronzo
- Division of Diabetes, University of Texas Health Science Center at San Antonio, San Antonio, Texas
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15
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Crocker DE, Fowler MA, Champagne CD, Vanderlugt AL, Houser DS. Metabolic response to a glucagon challenge varies with adiposity and life-history stage in fasting northern elephant seals. Gen Comp Endocrinol 2014; 195:99-106. [PMID: 24239794 DOI: 10.1016/j.ygcen.2013.11.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 10/06/2013] [Accepted: 11/04/2013] [Indexed: 10/26/2022]
Abstract
Metabolic adaptations for extended fasting in wildlife prioritize beta-oxidation of lipids and reduced glucose utilization to support energy metabolism. The pancreatic hormone glucagon plays key roles in regulating glycemia and lipid metabolism during fasting in model species but its function in wildlife species adapted for extended fasting is not well understood. Northern elephant seals (NES) undergo natural fasts of 1-3months while under constraints of high nutrient demands including lactation and development. We performed a glucagon challenge on lactating, molting and developing NES, early and late in their natural fasts, to examine the impact of this important regulatory hormone on metabolism. Glucagon caused increases in plasma glucose, insulin, fatty acids, ketones and urea, but the magnitude of these effects varied widely with adiposity and life-history stage. The strong impact of adiposity on glucose and insulin responses suggest a potential role for adipose derived factors in regulating hepatic metabolism and pancreatic sensitivity. Elevations in plasma glucose in response to glucagon were strongly associated with increases in protein catabolism, suggesting negative impacts of elevated glucagon on protein sparing. Glucagon promoted rapid ketone accumulation suggesting that low ketoacid levels in NES reflect low rates of production. These results demonstrate strong metabolic impacts of glucagon and support the idea that glucagon levels are downregulated in the context of metabolic adaptation to extended fasting. These results suggest that the regulation of carbohydrate and lipid metabolism in NES changes with adiposity, fasting duration and under various constraints of nutrient demands.
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Affiliation(s)
| | - Melinda A Fowler
- Sonoma State University, Rohnert Park, CA 94928, USA; Simon Fraser University, Burnaby, BC V5A 1S6, Canada
| | - Cory D Champagne
- Sonoma State University, Rohnert Park, CA 94928, USA; National Marine Mammal Foundation, San Diego, CA 92106, USA
| | | | - Dorian S Houser
- Sonoma State University, Rohnert Park, CA 94928, USA; National Marine Mammal Foundation, San Diego, CA 92106, USA
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Abstract
Ketone bodies are produced in the liver and are utilized in other tissues in the body as an energy source when hypoglycemia occurs in the body. There are three ketone bodies: acetoacetate, beta hydroxy butyrate, and acetone. Ketone bodies are usually present in the blood, and their level increases during fasting and starvation. They are also found in the blood of neonates and pregnant women. In diabetic ketoacidosis, high levels of ketone bodies are produced in response to low insulin levels and high levels of counter-regulatory hormones.
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Affiliation(s)
- Muhammad Akram
- Department of Eastern Medicine and Surgery, Faculty of Medical and Health Sciences, The University of Poonch , Rawalakot, Azad Jammu and Kashmir, Pakistan
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17
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Foster DW. Malonyl-CoA: the regulator of fatty acid synthesis and oxidation. J Clin Invest 2012; 122:1958-9. [PMID: 22833869 DOI: 10.1172/jci63967] [Citation(s) in RCA: 230] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In the catabolic state with no food intake, the liver generates ketones by breaking down fatty acids. During the nocturnal fast or longer starvation periods, this protects the brain, which cannot oxidize fatty acids. In 1977, we published a study in the JCI noting the surprising realization that malonyl-CoA, the substrate of fatty acid synthesis, was also an inhibitor of fatty acid oxidation. Subsequent experiments have borne out this finding and furthered our understanding of molecular metabolism.
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Affiliation(s)
- Daniel W Foster
- Department of Internal Medicine, University Of Texas SW Medical Center, Dallas, Texas 75390-9030, USA.
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18
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Du X, Kosinski JR, Lao J, Shen X, Petrov A, Chicchi GG, Eiermann GJ, Pocai A. Differential effects of oxyntomodulin and GLP-1 on glucose metabolism. Am J Physiol Endocrinol Metab 2012; 303:E265-71. [PMID: 22621866 DOI: 10.1152/ajpendo.00142.2012] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glucagon-like peptide-1 (GLP-1) and oxyntomodulin (OXM) are peptide hormones secreted postprandially from the gut that stimulate insulin secretion in a glucose-dependent manner. OXM activates both the GLP-1 receptor (GLP1R) and the glucagon receptor (GCGR). It has been suggested that OXM acutely modulates glucose metabolism solely through GLP1R agonism. Because OXM activates the GLP1R with lower affinity than GLP-1, we generated a peptide analog (Q→E, OXMQ3E) that does not exhibit glucagon receptor agonist activity but retains the same affinity as OXM for GLP1R. We compared the effects of OXM and OXMQ3E in a glucose tolerance test and, to better characterize the effect on glucose metabolism, we performed controlled infusions of OXM or OXMQ3E during a hyperglycemic clamp performed in wild-type, Glp1r(-/-), and Gcgr(-/-) mice. Our findings show that OXM, but not OXMQ3E, activates the GCGR in vivo. Second, OXM and OXMQ3E improve glucose tolerance following an acute glucose challenge and during a hyperglycemic clamp in mice. Finally, OXM infusion during a glucose clamp reduces the glucose infusion rate (GIR) despite a simultaneous increase in insulin levels in Glp1r(-/-) mice, whereas OXM and OXMQ3E increase GIR to a similar extent in Gcgr(-/-) mice. In conclusion, activation of the GCGR seems to partially attenuate the acute beneficial effects on glucose and contributes to the insulinotropic action of oxyntomodulin.
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Affiliation(s)
- Xiaobing Du
- In Vivo Pharmacology, Merck Sharp & Dohme Corporation, Rahway, NJ 07065, USA
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19
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Ortega FJ, Moreno-Navarrete JM, Sabater M, Ricart W, Frühbeck G, Fernández-Real JM. Circulating glucagon is associated with inflammatory mediators in metabolically compromised subjects. Eur J Endocrinol 2011; 165:639-45. [PMID: 21798957 DOI: 10.1530/eje-11-0384] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Acute phase mediators promote metabolic changes by modifying circulating hormones. However, there is virtually no data about the link between glucagon and inflammatory parameters in obesity-related chronic low-grade inflammation. STUDY DESIGN We performed both cross-sectional and longitudinal (diet-induced weight loss) studies. METHODS Circulating glucagon concentrations (ELISA), parameters of glucose and lipid metabolism, interleukin 6 (IL6), and complement factor B (CFB) were analyzed in 316 subjects (250 men and 66 women). The effects of weight loss were investigated in an independent cohort of 20 subjects. RESULTS Circulating glucagon significantly correlated with glucose (r=0.407, P<0.0001), HbAlc (r=0.426, P<0.0001), fasting triglycerides (r=0.356, P=0.001), and parameters of innate immune response system such as IL6 (r=0.342, P=0.050) and CFB (r=0.404, P=0.002) in obese subjects with altered glucose tolerance, but not in individuals with normal glucose tolerance (NGT). In obese and NGT subjects, glucagon was associated with fasting triglycerides (r=0.475, P=0.003) and CFB (r=0.624, P=0.001). In obese subjects, glucagon (P=0.019) and CFB (P=0.002) independently contributed to 26% of fasting triglyceride variance (P<0.0001) after controlling for the effects of age and fasting serum glucose concentration in multiple lineal regression models. Moreover, concomitant with fat mass, fasting triglycerides, and CFB, weight loss led to significantly decreased circulating glucagon (-23.1%, P=0.004). CONCLUSIONS According to the current results, acute phase reactants such as IL6 and CFB are associated with fasting glucagon in metabolically compromised subjects. This suggests that glucagon may be behind the association between inflammatory and metabolic parameters in obesity-associated chronic low-grade inflammation.
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Affiliation(s)
- Francisco J Ortega
- Service of Diabetes, Endocrinology and Nutrition (UDEN), Institut d'Investigació Biomédica de Girona (IdIBGi), Hospital of Girona Dr Josep Trueta, Girona, Spain
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20
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Chua HR, Schneider A, Bellomo R. Bicarbonate in diabetic ketoacidosis - a systematic review. Ann Intensive Care 2011; 1:23. [PMID: 21906367 PMCID: PMC3224469 DOI: 10.1186/2110-5820-1-23] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2011] [Accepted: 07/06/2011] [Indexed: 01/31/2023] Open
Abstract
Objective This study was designed to examine the efficacy and risk of bicarbonate administration in the emergent treatment of severe acidemia in diabetic ketoacidosis (DKA). Methods PUBMED database was used to identify potentially relevant articles in the pediatric and adult DKA populations. DKA intervention studies on bicarbonate administration versus no bicarbonate in the emergent therapy, acid-base studies, studies on risk association with cerebral edema, and related case reports, were selected for review. Two reviewers independently conducted data extraction and assessed the citation relevance for inclusion. Results From 508 potentially relevant articles, 44 were included in the systematic review, including three adult randomized controlled trials (RCT) on bicarbonate administration versus no bicarbonate in DKA. We observed a marked heterogeneity in pH threshold, concentration, amount, and timing for bicarbonate administration in various studies. Two RCTs demonstrated transient improvement in metabolic acidosis with bicarbonate treatment within the initial 2 hours. There was no evidence of improved glycemic control or clinical efficacy. There was retrospective evidence of increased risk for cerebral edema and prolonged hospitalization in children who received bicarbonate, and weak evidence of transient paradoxical worsening of ketosis, and increased need for potassium supplementation. No studies involved patients with an initial pH < 6.85. Conclusions The evidence to date does not justify the administration of bicarbonate for the emergent treatment of DKA, especially in the pediatric population, in view of possible clinical harm and lack of sustained benefits.
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Affiliation(s)
- Horng Ruey Chua
- Department of Intensive Care, Austin Health, Melbourne, Victoria, Australia.
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21
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Marchesini G, Bianchi GP, Vilstrup H, Capelli M, Zoli M, Pisi E. Elimination of infused branched-chain amino-acids from plasma of patients with non-obese type 2 diabetes mellitus. Clin Nutr 2009; 10:105-13. [PMID: 16839904 DOI: 10.1016/0261-5614(91)90096-u] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/1990] [Accepted: 01/04/1991] [Indexed: 01/27/2023]
Abstract
Increased plasma levels of branched-chain amino-acids (BCAA) have been demonstrated in poorly controlled diabetes mellitus, and related to absolute or relative insulin deficiency. To study the pathogenesis of this alteration, the elimination of BCAA from plasma was measured in 8 patients with non-obese type 2 diabetes mellitus and in 8 age-matched control subjects during steady-state BCAA concentrations induced by a primed-continuous infusion. Fasting BCAA levels were increased by 40-50% in patients with diabetes. The plasma clearances of valine, isoleucine, and leucine, calculated as infusion rate divided by steady-state concentration, were reduced by 20% in diabetics, despite 50% hyperinsulinemia (P < 0.01). Basal BCAA levels and BCAA clearance were negatively correlated (r(2) = 0.46 - 0.56). The endogenous basal appearance rates of BCAA, estimated by the basal concentrations multiplied by the plasma clearances, were normal in diabetics, and there was no difference in the apparent volumes of distribution of BCAA. The increased basal concentration of BCAA in poorly controlled type 2 diabetics (693 [SD 114; n = 8] mumol/l vs 479 [88; n = 8] in controls (P < 0.005) is attributable to changes in plasma clearances, without any change in the efflux of BCAA into plasma. This may be due to insulin resistance.
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Affiliation(s)
- G Marchesini
- Istituto di Clinica Medica Generale e Terapia, Università di Bologna, Via Massarenti 9, I-40138 Bologna, Italy
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22
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Sestoft L, Folke M, Gammeltoft S, Bartels PD, Kristensen LO. Development of diabetic ketoacidosis: some observations on and deductions about the sources of acid. ACTA MEDICA SCANDINAVICA. SUPPLEMENTUM 2009; 639:7-16. [PMID: 6775497 DOI: 10.1111/j.0954-6820.1980.tb12857.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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23
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Leonard JV. Problems in the congenital lactic acidoses. CIBA FOUNDATION SYMPOSIUM 2008; 87:340-56. [PMID: 6280937 DOI: 10.1002/9780470720691.ch19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The congenital lactic acidosis form a heterogeneous group of inborn errors that includes defects of gluconeogenesis, the pyruvate dehydrogenase complex, the Krebs cycle and the respiratory chain. These disorders are not easily classified because of the absence of specific metabolites, difficulties in providing suitable tissue specimens and technical problems with the enzyme assays. The commonest causes of lactic acidosis due to inborn errors are the deficiencies of glucose-6-phosphatase and fructose bisphosphatase, which present with hypoglycaemia, lactic acidosis and hepatomegaly. Pyruvate carboxylase and phosphoenolpyruvate deficiencies vary considerably in both clinical expression and biochemical findings. Neurological symptoms predominate in defects of the pyruvate dehydrogenase complex, and some cases of the spinocerebellar ataxias may be due to partial defects of the pyruvate and 2-oxoglutarate dehydrogenase complexes.
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Abstract
Ketone bodies accumulate in the plasma in conditions of fasting and uncontrolled diabetes. The initiating event is a change in the molar ratio of glucagon:insulin. Insulin deficiency triggers the lipolytic process in adipose tissue with the result that free fatty acids pass into the plasma for uptake by liver and other tissues. Glucagon appears to be the primary hormone involved in the induction of fatty acid oxidation and ketogenesis in the liver. It acts by acutely dropping hepatic malonyl-CoA concentrations as a consequence of inhibitory effects exerted in the glycolytic pathway and on acetyl-CoA carboxylase (EC 6.4.1.2). The fall in malonyl-CoA concentration activates carnitine acyltransferase I (EC 2.3.1.21) such that long-chain fatty acids can be transported through the inner mitochondrial membrane to the enzymes of fatty acid oxidation and ketogenesis. The latter are high-capacity systems assuring that fatty acids entering the mitochondria are rapidly oxidized to ketone bodies. Thus, the rate-controlling step for ketogenesis is carnitine acyltransferase I. Administration of food after a fast, or of insulin to the diabetic subject, reduces plasma free fatty acid concentrations, increases the liver concentration of malonyl-CoA, inhibits carnitine acyltransferase I and reverses the ketogenic process.
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Abstract
Diabetic ketoacidosis is an important complication of diabetes in children and is the most frequent diabetes-related cause of death in childhood. The pathophysiology of this condition can be viewed as an exaggeration of the normal physiologic mechanisms responsible for maintaining an adequate fuel supply to the brain and other tissues during periods of fasting and physiologic stress. The optimal therapy has been a subject of controversy, particularly because the most frequent serious complication of diabetic ketoacidosis-cerebral edema-and the relationship of this complication to treatment are incompletely understood. In this article, the author reviews the pathophysiology of diabetic ketoacidosis and its complications and presents an evidence-based approach to the management of this condition.
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Affiliation(s)
- Nicole Glaser
- Department of Pediatrics, School of Medicine, University of California-Davis, 2516 Stockton Boulevard, Sacramento, CA 95817, USA.
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26
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Abstract
Metabolism cycles daily between the fed and fasted states. The pathways of energy production are reversible and distinct. In the anabolic (fed) state, the liver stores glucose as glycogen, and fatty acid/triglyceride synthesis is active. In the catabolic (fasted) state, the liver becomes a glucose producer, lipogenesis is slowed, and fatty acid oxidation/ketogenesis is activated. The rate-limiting step for the latter is vested in the carnitine/carnitine palmitoyltransferase (CPT) system, and the off/on regulator of this is malonyl CoA. The AMP-induced protein kinase primarily determines the concentration of malonyl CoA. Four other systems have significant influence: two on fatty acid oxidation and two on lipogenesis. Peroxisome proliferator-activated receptor gamma-1 alpha, a master regulator of metabolism, induces hepatic gluconeogenesis and fatty acid oxidation in the catabolic phase. Deficiency of stearoyl CoA desaturase, although having no role in gluconeogenesis, powerfully induces fatty acid oxidation and weight loss despite increased food intake in rodents. Major stimulators of lipogenesis are carbohydrate-responsive element binding protein and the Insig system. The malonyl CoA-regulated CPT system has been firmly established in humans. The other systems have not yet been confirmed in humans, but likely are active there as well. Activation of fatty acid oxidation has considerable clinical promise for the treatment of obesity, type 2 diabetes, steatohepatitis, and lipotoxic damage to the heart.
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Affiliation(s)
- Daniel W Foster
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX 75390-9030, USA.
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27
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Rosival V. Diabetic ketoacidosis. Pediatr Emerg Care 2005; 21:76; author reply 76-7. [PMID: 15643333 DOI: 10.1097/01.pec.0000150993.57346.e0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Ishii-Iwamoto EL, Ferrarese ML, Constantin J, Salgueiro-Pagadigorria C, Bracht A. Effects of norepinephrine on the metabolism of fatty acids with different chain lengths in the perfused rat liver. Mol Cell Biochem 2000; 205:13-23. [PMID: 10821418 DOI: 10.1023/a:1007094310429] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The effects of norepinephrine on ketogenesis in isolated hepatocytes have been reported as ranging from stimulation to inhibition. The present work was planned with the aim of clarifying these discrepancies. The experimental system was the once-through perfused liver from fasted and fed rats. Fatty acids with chain lengths varying from 8-18 were infused. The effects of norepinephrine depended on the metabolic state of the rat and on the nature of the fatty acid. Norepinephrine clearly inhibited ketogenesis from long-chain fatty acids (stearate > palmitate > oleate), but had little effect on ketogenesis from medium-chain fatty acids (octanoate and laureate). With palmitate the decrease in oxygen uptake was restricted to the substrate stimulated portion; with stearate, the decrease exceeded the substrate stimulated portion; with oleate, oxygen uptake was transiently inhibited. Withdrawal of Ca2+ attenuated the inhibitory effects. 14CO2 production from [1-14C]oleate was inhibited. Net uptake of the fatty acids was not affected by norepinephrine. In livers from fed rats, oxygen uptake and ketogenesis from stearate were only transiently inhibited. The conclusions are: (a) in the fasted state norepinephrine reduces ketogenesis and respiration by means of a Ca2+-dependent mechanism; (b) the degree of inhibition varies with the chain length and the degree of saturation of the fatty acids; (c) norepinephrine favours esterification of the activated long-chain fatty acids in detriment to oxidation; (d) in the fed state the stimulatory action of norepinephrine on glycogen catabolism induces conditions which are able to reverse inhibition of ketogenesis and oxygen uptake.
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Madsen L, Berge RK. 3-Thia fatty acid treatment, in contrast to eicosapentaenoic acid and starvation, induces gene expression of carnitine palmitoyltransferase-II in rat liver. Lipids 1999; 34:447-56. [PMID: 10380116 DOI: 10.1007/s11745-999-0384-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The aim of the present study was to investigate the hepatic regulation and beta-oxidation of long-chain fatty acids in peroxisomes and mitochondria, after 3-thia- tetradecylthioacetic acid (C14-S-acetic acid) treatment. When palmitoyl-CoA and palmitoyl-L-carnitine were used as substrates, hepatic formation of acid-soluble products was significantly increased in C14-S-acetic acid treated rats. Administration of C14-S-acetic acid resulted in increased enzyme activity and mRNA levels of hepatic mitochondrial carnitine palmitoyltransferase (CPT)-II. CPT-II activity correlated with both palmitoyl-CoA and palmitoyl-L-carnitine oxidation in rats treated with different chain-length 3-thia fatty acids. CPT-I activity and mRNA levels were, however, marginally affected. The hepatic CPT-II activity was mainly localized in the mitochondrial fraction, whereas the CPT-I activity was enriched in the mitochondrial, peroxisomal, and microsomal fractions. In C14-S-acetic acid-treated rats, the specific activity of peroxisomal and microsomal CPT-I increased, whereas the mitochondrial activity tended to decrease. C14-S-Acetyl-CoA inhibited CPT-I activity in vitro. The sensitivity of CPT-I to malonyl-CoA was unchanged, and the hepatic malonyl-CoA concentration increased after C14-S-acetic acid treatment. The mRNA levels of acetyl-CoA carboxylase increased. In hepatocytes cultured from palmitic acid- and C14-S-acetic acid-treated rats, the CPT-I inhibitor etomoxir inhibited the formation of acid-soluble products 91 and 21%, respectively. In contrast to 3-thia fatty acid treatment, eicosapentaenoic acid treatment and starvation increased the mitochondrial CPT-I activity and reduced its malonyl-CoA sensitivity. Palmitoyl-L-carnitine oxidation and CPT-II activity were, however, unchanged after either EPA treatment or starvation. The results from this study open the possibility that the rate control of mitochondrial beta-oxidation under mitochondrion and peroxisome proliferation is distributed between an enzyme or enzymes of the pathway beyond the CPT-I site after 3-thia fatty acid treatment. It is suggested that fatty acids are partly oxidized in the peroxisomes before entering the mitochondria as acylcarnitines for further oxidation.
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Affiliation(s)
- L Madsen
- Department of Clinical Biochemistry, Haukeland Hospital, University of Bergen, Norway.
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30
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Madsen L, Garras A, Asins G, Serra D, Hegardt FG, Berge RK. Mitochondrial 3-hydroxy-3-methylglutaryl coenzyme A synthase and carnitine palmitoyltransferase II as potential control sites for ketogenesis during mitochondrion and peroxisome proliferation. Biochem Pharmacol 1999; 57:1011-9. [PMID: 10796071 DOI: 10.1016/s0006-2952(99)00004-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
3-Thia fatty acids are potent hypolipidemic fatty acid derivatives and mitochondrion and peroxisome proliferators. Administration of 3-thia fatty acids to rats was followed by significantly increased levels of plasma ketone bodies, whereas the levels of plasma non-esterified fatty acids decreased. The hepatic mRNA levels of fatty acid binding protein and formation of acid-soluble products, using both palmitoyl-CoA and palmitoyl-L-carnitine as substrates, were increased. Hepatic mitochondrial carnitine palmitoyltransferase (CPT) -II and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase activities, immunodetectable proteins, and mRNA levels increased in parallel. In contrast, the mitochondrial CPT-I mRNA levels were unchanged and CPT-I enzyme activity was slightly reduced in the liver. The CoA ester of the monocarboxylic 3-thia fatty acid, tetradecylthioacetic acid, which accumulates in the liver after administration, inhibited the CPT-I activity in vitro, but not that of CPT-II. Acetoacetyl-CoA thiolase and HMG-CoA lyase activities involved in ketogenesis were increased, whereas the citrate synthase activity was decreased. The present data suggest that 3-thia fatty acids increase both the transport of fatty acids into the mitochondria and the capacity of the beta-oxidation process. Under these conditions, the regulation of ketogenesis may be shifted to step(s) beyond CPT-I. This opens the possibility that mitochondrial HMG-CoA synthase and CPT-II retain some control of ketone body formation.
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Affiliation(s)
- L Madsen
- Department of Clinical Biochemistry, Haukeland Hospital, University of Bergen, Norway.
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31
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Pailla K, Lim SK, De Bandt JP, Aussel C, Giboudeau J, Troupel S, Cynober L, Blonde-Cynober F. TNF-alpha and IL-6 synergistically inhibit ketogenesis from fatty acids and alpha-ketoisocaproate in isolated rat hepatocytes. JPEN J Parenter Enteral Nutr 1998; 22:286-90. [PMID: 9739031 DOI: 10.1177/0148607198022005286] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND During sepsis, lipid metabolism is shunted toward triacylglycerol synthesis and hepatic lipogenesis. A decrease in ketogenesis from free fatty acids also is observed, probably mediated by cytokines involved in host response to infection. Whether such an inhibition of ketogenesis occurs with other ketone body precursors such as ketoacids is not known. The aim of this study was to determine the effects of tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) on hepatic ketone body production from octanoic acid, a medium-chain fatty acid, and from alpha-ketoisocaproate (KIC), the ketoanalogue of leucine. METHODS The experiments were conducted in cultured hepatocytes isolated from 24-hour-fasted Sprague-Dawley rats. Hepatocyte monolayers were incubated for 6 hours, with either KIC or octanoic acid (1 mmol/L), in the presence of glucagon and TNF-alpha (25 micro/L) IL-6 (15 microg/L) and/or IL-6. Acetoacetate, beta-hydroxybutyrate, and free fatty acids were determined in culture medium by enzymatic methods and KIC was measured by high-performance liquid chromatography. RESULTS KIC and octanoic acid uptake by hepatocytes was 79% and 92%, respectively, over 6 hours, and cytokines had no influence. However, TNF-alpha and IL-6 caused inhibition of ketogenesis from alpha-ketoisocaproate (5.6% +/- 2.3% and 4.4% +/- 3.0%, respectively), and from octanoic acid (7.9% +/- 2.9%, 5.7% +/- 3.2%, respectively). In addition, when the two cytokines were present together in the culture medium, the inhibition was enhanced (inhibition of ketogenesis from KIC: 14.0% +/- 4.8%; from octanoic acid: 11.6% +/- 3.4%). CONCLUSIONS In our experimental conditions, cytokines mediate an inhibition of ketogenesis; this process could be explained by a direct effect of cytokines on metabolic pathways of octanoic acid and KIC oran indirect effect by modification of the mitochondrial redox state.
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Affiliation(s)
- K Pailla
- Biochem Laboratory Emile Roux Hospital, Limeil-Brévannes, France
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32
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Itoh N, Koiwa M, Hatsugaya A, Yokota H, Taniyama H, Okada H, Kudo K. Comparative analysis of blood chemical values in primary ketosis and abomasal displacement in cows. ZENTRALBLATT FUR VETERINARMEDIZIN. REIHE A 1998; 45:293-8. [PMID: 9719761 DOI: 10.1111/j.1439-0442.1998.tb00830.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Blood chemical values, including ketone bodies, were measured in 25 cows with abomasal displacement (displacement group), 16 cows with primary ketosis (ketosis group), and nine normal controls to investigate the pathophysiology of abomasal displacement. Increases in aspartate aminotransferase, gamma-glutamyl transpeptidase, non-esterified fatty acid (NEFA), and ketone bodies (3-hydroxybutyric acid and acetoacetic acid) were observed in the displacement and ketosis groups. Total cholesterol increased significantly in the ketosis group but decreased in the displacement group. Glucose was significantly low and reversely correlated to ketone bodies in the ketosis group but was not low and was not correlated with ketone bodies in the displacement group. While NEFA was correlated to ketone bodies in the ketosis group, it was not in the displacement group. A correlation between the values of acetoacetic acid and 3-hydroxybutyric acid was seen in both the ketosis and displacement groups. The fact that blood chemical values in ketosis cows were clearly different from those in displacement cows suggest that the biochemical mechanism of ketogenesis is different between these two groups.
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Affiliation(s)
- N Itoh
- Large Animal Clinical Center, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Japan
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33
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Arias G, Asins G, Hegardt FG, Serra D. The effect of dexamethasone treatment on the expression of the regulatory genes of ketogenesis in intestine and liver of suckling rats. Mol Cell Biochem 1998; 178:325-33. [PMID: 9546617 DOI: 10.1023/a:1006875716407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The influence of the injection of dexamethasone on ketogenesis in 12 day old suckling rats was studied in intestine and liver by determining mRNA levels and enzyme activity of the two genes responsible for regulation of ketogenesis: carnitine palmitoyl transferase I (CPT I) and mitochondrial HMG-CoA synthase. Dexamethasone produced a 2 fold increase in mRNA and activity of CPT I in intestine, but led to a decrease in mit. HMG-CoA synthase. In liver the mRNA levels and activity of both CPT I and mit. HMG-CoA synthase decreased. Comparison of these values with the ketogenic rate of both tissues following dexamethasone treatment suggests that mit. HMG-CoA synthase could be the main gene responsible for the regulation of ketogenesis in suckling rats. The changes produced in serum ketone bodies by dexamethasone, with a profile that is more similar to the ketogenic rate in the liver than that in the intestine, indicate that liver contributes more to ketone body synthesis in suckling rats. Two day treatment with dexamethasone produced no change in mRNA or activity levels for CPT I in liver or intestine. While mRNA levels for mit. HMG-CoA synthase changed little, the enzyme activity is decreased in both tissues.
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Affiliation(s)
- G Arias
- Department of Biochemistry, School of Pharmacy, University of Barcelona, Spain
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34
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Yajnik CS, Sardesai BS, Bhat DS, Naik SS, Raut KN, Shelgikar KM, Orskov H, Alberti KG, Hockaday TD. Ketosis resistance in fibrocalculous pancreatic diabetes: II. Hepatic ketogenesis after oral medium-chain triglycerides. Metabolism 1997; 46:1-4. [PMID: 9005960 DOI: 10.1016/s0026-0495(97)90158-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A majority of patients with fibrocalculous pancreatic diabetes (FCPD) do not become ketotic even in adverse conditions. It is not clear whether this ketosis resistance is due to reduced fatty acid release from adipose tissue or to impaired hepatic ketogenesis. We tested hepatic ketogenesis in FCPD patients using a ketogenic challenge of oral medium-chain triglycerides (MCTs) and compared it with that in matched insulin-dependent diabetes mellitus (IDDM) patients and healthy controls. After oral MCTs, FCPD patients showed only a mild increase in blood 3-hydroxybutyrate (3-HB) concentrations (median: fasting, 0.13 mmol/L; peak, 0.52) compared with IDDM patients (fasting, 0.44; peak, 3.39) and controls (fasting, 0.04; peak, 0.75). Plasma nonesterified fatty acid (NEFA) concentrations were comparable in the two diabetic groups (FCPD: fasting, 0.50 mmol/L; peak, 0.79; IDDM: fasting, 0.91; peak, 1.04). Plasma C-peptide concentrations were low and comparable in the two diabetic groups. Plasma glucagon concentrations were higher in IDDM patients in the fasting state, but declined to levels comparable to those in FCPD patients after oral MCTs. Plasma carnitine concentrations were comparable in the two groups of patients. It is concluded that the failure to stimulate ketogenesis under these conditions could be partly due to inhibition of a step beyond fatty acid entry into the mitochondria.
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Affiliation(s)
- C S Yajnik
- Diabetes Unit, King Edward Memorial Hospital, Pune, India
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35
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Holtenius P, Holtenius K. New aspects of ketone bodies in energy metabolism of dairy cows: a review. ZENTRALBLATT FUR VETERINARMEDIZIN. REIHE A 1996; 43:579-87. [PMID: 9011147 DOI: 10.1111/j.1439-0442.1996.tb00491.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Increased lipolysis, low insulin/glucagon ratios and malonyl-CoA concentrations are prerequisites for ketogenesis. From an aetiological viewpoint, there are two quite different types of metabolic disorders in which ketosis can occur, the hypoglycaemic-hypoinsulinaemic and the hyperglycaemic-hyperinsulinaemic type. The former, Type I, generally occurs 3-6 weeks after calving in cows whose milk secretion is so extensive that the demand for glucose exceeds the capacity for glucose production. To protect the body from hazardous protein degradation by a high rate of gluconeogenesis, this process is inhibited and the increased energy requirements are met by the elevated utilization of ketone bodies. In this strong catabolic metabolic state the plasma levels of glucose and insulin are very low, the levels of ketone bodies are high and there are small risks for fat accumulation in the liver cells. The hyperglycaemic, hyperinsulinaemic form, Type II, generally occurs earlier in lactation. An important aetiologic factor is overfeeding in the dry period, which can lead to disturbances in the hormonal adaptation of metabolism at calving with increased plasma levels of insulin and glucose and often out not always also with hyperketonaemia. If combined with stress, there may be increased lipolysis in adipose tissues, lipid synthesis and accumulation in the liver, i.e. the development of fatty liver. This hyperglycaemic form of disturbance has many similarities with the initial stage of non-insulin-dependent (Type II) diabetes in humans. It has been shown that ketone bodies inhibit protein degradation and thereby gluconeogenesis and also are able to spare glucose by inhibiting glucose utilization. They also can inhibit lipolysis and function as a regulatory safety system, replacing insulin, in situations when the activity of this hormone is low, as in Type I ketosis. Ketone bodies thus have important functions as substrates replacing glucose in many tissues and also as signal substances in the regulation of energy metabolism.
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Affiliation(s)
- P Holtenius
- Department of Cattle and Sheep Diseases, Swedish University of Agricultural Sciences, Uppsala, Sweden
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36
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Ubukata E, Mokuda O, Sakamoto Y, Shimizu N. Effect of various glucagon/insulin molar ratios on blood ketone body levels in rats by use of osmotic minipumps. Diabetes Res Clin Pract 1996; 34:1-6. [PMID: 8968684 DOI: 10.1016/s0168-8227(96)01325-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The bihormonal control by insulin and glucagon of blood ketone body level was studied. Mixed solutions with various molar ratios of glucagon and insulin (G/I) were subcutaneously infused continuously for five days by use of the osmotic minipump in the normal rats. The concentrations of insulin and glucagon solution were set at the high G/I molar ratio, the moderate G/I molar ratio and the low G/I molar ratio. In addition, the moderate G/I molar ratio group was divided into three sub-groups: low glucagon and low insulin, moderate glucagon and moderate insulin, and high glucagon and high insulin. After five days, the rats were decapitated to measure plasma ketone body, free fatty acid (FFA), glucose, insulin and glucagon. The FFA level was not significantly different among three groups. The glucose level was not different between the high and moderate G/I molar ratio groups, and decreased in the low G/I molar ratio group. 3-beta-hydroxybutyrate (3-OHBA) and acetoacetate (AcAc) levels in the high G/I molar ratio group were elevated, and 3-OHBA level in the low G/I molar ratio group was lowered compared to those in the moderate G/I molar ratio group. Among three moderate G/I molar ratio sub-groups, there was no difference in 3-OHBA and AcAc levels. These results demonstrate that plasma ketone body levels are controlled by the plasma G/I molar ratio.
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Affiliation(s)
- E Ubukata
- Third Department of Internal Medicine, Teikyo University School of Medicine, Chiba, Japan
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37
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Stein DT, Esser V, Stevenson BE, Lane KE, Whiteside JH, Daniels MB, Chen S, McGarry JD. Essentiality of circulating fatty acids for glucose-stimulated insulin secretion in the fasted rat. J Clin Invest 1996; 97:2728-35. [PMID: 8675683 PMCID: PMC507365 DOI: 10.1172/jci118727] [Citation(s) in RCA: 251] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We asked whether the well known starvation-induced impairment of glucose-stimulated insulin secretion (GSIS) seen in isolated rat pancreas preparations also applies in vivo. Accordingly, fed and 18-24-h-fasted rats were subjected to an intravenous glucose challenge followed by a hyperglycemic clamp protocol, during which the plasma-insulin concentration was measured. Surprisingly, the acute (5 min) insulin response was equally robust in the two groups. However, after infusion of the antilipolytic agent, nicotinic acid, to ensure low levels of plasma FFA before the glucose load, GSIS was essentially ablated in fasted rats, but unaffected in fed animals. Maintenance of a high plasma FFA concentration by coadministration of Intralipid plus heparin to nicotinic acid-treated rats (fed or fasted), or further elevation of the endogenous FFA level in nonnicotinic acid-treated fasted animals by infusion of etomoxir (to block hepatic fatty acid oxidation), resulted in supranormal GSIS. The in vivo findings were reproduced in studies with the perfused pancreas from fed and fasted rats in which GSIS was examined in the absence and presence of palmitate. The results establish that in the rat, the high circulating concentration of FFA that accompanies food deprivation is a sine qua non for efficient GSIS when a fast is terminated. They also serve to underscore the powerful interaction between glucose and fatty acids in normal beta cell function and raise the possibility that imbalances between the two fuels in vivo could have pathological consequences.
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Affiliation(s)
- D T Stein
- Department of Internal Medicine, Gifford Laboratories, University of Texas Southwestern Medical Center at Dallas 75235, USA
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38
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Royo T, Pedragosa MJ, Ayté J, Gil-Gómez G, Vilaró S, Hegardt FG. Immunolocalization of mitochondrial 3-hydroxy-3-methylglutaryl CoA synthase in rat liver. J Cell Physiol 1995; 162:103-9. [PMID: 7814442 DOI: 10.1002/jcp.1041620112] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We report the preparation of specific polyclonal antibodies raised against two synthetic peptides deduced from the cDNA sequence for the rat liver mitochondrial 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) synthase gene. Immunoelectron microscopy using these antibodies on hepatic cryoultrathin sections confirms the mitochondrial localization of this protein in hepatocytes. Immunofluorescence microscopy on frozen sections of adult rat liver revealed fluorescence inside all hepatocytes, with no evidence of zonation, indicating that ketogenesis may not be limited to specific regions of rat liver but is extended to all hepatocytes.
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Affiliation(s)
- T Royo
- Unit of Biochemistry, School of Pharmacy, University of Barcelona, Spain
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39
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Holtenius P, Olsson G, Björkman C. Periparturient concentrations of insulin glucagon and ketone bodies in dairy cows fed two different levels of nutrition and varying concentrate/roughage ratios. ZENTRALBLATT FUR VETERINARMEDIZIN. REIHE A 1993; 40:118-27. [PMID: 8480460 DOI: 10.1111/j.1439-0442.1993.tb00608.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
High producing multiparous dairy cows were fed either diets differing in energy content or diets with identical energy and protein content but differing in roughage content at the end of the dry period and beginning of lactation. Basal insulin and ketone bodies were analysed every week from 3 weeks before to 7 weeks after calving. Pancreatic glucagon was estimated 3 weeks before, 1-3 days after, and 3 weeks after calving. Before calving the feeding regimen had a very strong influence on the basal insulin level. High amounts of concentrate increased basal insulin levels until one week before calving and caused an interruption in the physiological decreasing course. After calving the insulin levels were low in all groups of cows. Before calving there were small variations in the glucagon levels, and no influence of feeding was observed. After calving there was a strong increase, especially in the cows fed the highest amounts of concentrate. Feeding high amounts of concentrate resulted in varying and in many cases increased levels of ketone bodies in plasma. Hyperketonemic cows had lower insulin and higher glucagon levels than normal cows. The influence of non-structural carbohydrates in the feed on pancreatic hormones is a cause of ketogenesis is discussed.
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Affiliation(s)
- P Holtenius
- Department of Cattle and Sheep Diseases, Swedish University of Agricultural Sciences, Uppsala
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40
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Avogaro A, Cryer PE, Bier DM. Epinephrine's ketogenic effect in humans is mediated principally by lipolysis. THE AMERICAN JOURNAL OF PHYSIOLOGY 1992; 263:E250-60. [PMID: 1514604 DOI: 10.1152/ajpendo.1992.263.2.e250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
To quantify epinephrine's effects on acetoacetate and beta-hydroxybutyrate kinetics, we infused subjects with 0.3 and 2.5 micrograms/min epinephrine, either alone or with a concomitant somatostatin infusion with insulin, glucagon, and growth hormone replaced at postabsorptive levels (islet clamp). Additional subjects received no epinephrine but sequential infusions of heparin plus 10% Intralipid at rates of 0.5 and 3.0 ml/min. Both epinephrine and Intralipid increased ketone body appearance (unaffected by islet clamp), augmented the interconversion rates between ketone bodies and, during the 2.5 micrograms/min infusion, caused a marked increase in beta-hydroxybutyrate appearance. The fraction of plasma free fatty acid (FFA) flux appearing as plasma ketones increased from 6 to 7% in the basal state to 11% at the high-epinephrine infusion. This fraction was also unaffected by the islet clamp and was not different from values obtained at similar Intralipid plus heparin-induced elevations in plasma FFA levels. We conclude that epinephrine's ketogenic effect in humans is primarily the result of its lipolytic effect, is accompanied by a significantly increased rate of ketone body interconversion, is manifest largely as an increase in plasma beta-hydroxybutyrate appearance at high plasma epinephrine values, and is not limited by portal insulin at post-absorptive levels.
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Affiliation(s)
- A Avogaro
- Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63141
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41
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Yamaguchi T, Shimahara Y, Takada Y, Ino K, Mori K, Kobayashi N, Yamaoka Y, Ozawa K. Evaluation of ketogenesis in seriously reduced hepatic mitochondrial redox state. An analysis of survivors and non-survivors in critically ill hepatectomized patients. Scand J Gastroenterol 1992; 27:472-8. [PMID: 1631493 DOI: 10.3109/00365529209000107] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Ketogenesis was evaluated in 33 critically ill hepatectomized patients in relation to the arterial ketone body ratio (acetoacetate to 3-hydroxybutyrate), which reflects hepatic mitochondrial redox state. In 15 patients whose arterial ketone body ratio decreased to below 0.4, blood ketone body levels were significantly increased concomitant with marked increase of blood lactate and plasma alanine levels. In the 6 survivors of these 15 patients, the arterial ketone body ratio was restored within the next 2 days, and blood ketone body levels were decreased. By contrast, in the nine non-survivors, the arterial ketone body ratio remained below 0.4, and blood ketone body levels were decreased, accompanied by significant increases in blood lactate and plasma alanine levels in the terminal stages. These results suggest that ketogenesis acts as an alternative process for ATP synthesis in the liver in critically ill patients. Death occurs when the liver falls into an energy crisis concomitant with the cessation of ketogenesis.
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Affiliation(s)
- T Yamaguchi
- Second Dept. of Surgery, Faculty of Medicine, Kyoto University, Japan
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42
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Casals N, Roca N, Guerrero M, Gil-Gómez G, Ayté J, Ciudad CJ, Hegardt FG. Regulation of the expression of the mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase gene. Its role in the control of ketogenesis. Biochem J 1992; 283 ( Pt 1):261-4. [PMID: 1348927 PMCID: PMC1131023 DOI: 10.1042/bj2830261] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have explored the role of mitochondrial 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase in regulating ketogenesis. We had previously cloned the cDNA for mitochondrial HMG-CoA synthase and have now studied the regulation in vivo of the expression of this gene in rat liver. The amount of processed mitochondrial HMG-CoA synthase mRNA is rapidly changed in response to cyclic AMP, insulin, dexamethasone and refeeding, and is greatly increased by starvation, fat feeding and diabetes. We conclude that one point of ketogenic control is exercised at the level of genetic expression of mitochondrial HMG-CoA synthase.
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Affiliation(s)
- N Casals
- Unidad de Bioquímica, Facultad de Farmacia, Universidad de Barcelona, Spain
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43
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Zimmermann T, Franke H, Peuker M, Dargel R. Quantitative studies on fatty acid metabolism in isolated parenchymal cells from normal and cirrhotic livers in rats. J Hepatol 1992; 15:10-6. [PMID: 1506625 DOI: 10.1016/0168-8278(92)90005-a] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Parenchymal cells isolated from normal and thioacetamide-induced micronodular cirrhotic rat livers were used to evaluate changes in hepatocellular fatty acid (FA) metabolism in cirrhosis. Exogenous free FA (FFA) are rapidly taken up by hepatocytes obtained either from normal or cirrhotic livers. They are predominantly esterified to triglycerides and accumulate intracytoplasmatically as lipid droplets with increasing cellular FFA uptake. In the parenchymal cells of cirrhotic livers, however, the following changes were observed when compared with controls: (i) decreased cellular output of esterified FA derived both from exogenous sources and from de novo FA synthesis; (ii) increased total ketone body production, mainly as beta-hydroxybutyrate; (iii) decreased cholesterol synthesis; and (iv) enhanced incorporation of newly synthesized FA into phospholipids in spite of an unaffected rate of FA synthesis. In summary, the data provide evidence for intrinsic alterations in the lipid metabolism in the parenchymal cells of cirrhotic livers which are preserved in the isolated hepatocytes under optimum incubation conditions for oxygen and substrate supply.
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Affiliation(s)
- T Zimmermann
- Institute of Pathological Biochemistry, Friedrich-Schiller-University, Jena, Federal Republic of Germany
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44
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Beylot M, Picard S, Chambrier C, Vidal H, Laville M, Cohen R, Cotisson A, Mornex R. Effect of physiological concentrations of insulin and glucagon on the relationship between nonesterified fatty acids availability and ketone body production in humans. Metabolism 1991; 40:1138-46. [PMID: 1943742 DOI: 10.1016/0026-0495(91)90207-d] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
To determine the effect of insulin and glucagon on the transformation of nonesterified fatty acids (NEFA) into ketone bodies (KB), we measured simultaneously in normal subjects NEFA and KB kinetics at different NEFA levels in the presence of basal (control test) or increasing insulin concentrations with glucagopenia (somatostatin + insulin infusion, insulin test) and without glucagopenia (somatostatin + insulin + glucagon infusion, glucagon test). NEFA levels were controlled during these tests by an intravenous (IV) infusion of a triglyceride emulsion. During the control test, a moderate increase of NEFA (464 +/- 30 to 715 +/- 56 mumol/L) increased the percentage of NEFA converted into KB (13.3% +/- 1.4% to 26.4% +/- 2.1%, P less than .05), and there was a linear relationship between this percentage and NEFA levels (r = .788, P less than .01). During the insulin and glucagon tests, the progressive increase in NEFA induced by the triglyceride emulsion infusion was associated, despite the increase of insulinemia, with an increase in KB production rate (P less than .05) and in the proportion of NEFA used for ketogenesis in the presence (8.1% +/- 1.2% to 14.2% +/- 6.3%, P less than .05) and absence (15.7% +/- 2.8% to 25.2% +/- 3.99%, P less than 0.05) of glucagopenia. In both tests, this percentage was always linearly related with NEFA levels (P less than .05) and the slopes of these relationships were comparable to that observed in the control test. However, the fraction of NEFA used for ketogenesis was always higher (P less than .05) during glucagon substitution than in its absence.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- M Beylot
- INSERM U. 197, Faculté de Médecine Alexis Carrel, Lyon, France
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45
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Takada Y, Yamaguchi T, Kiuchi T, Mori K, Shimahara Y, Kobayashi N, Yamaoka Y, Ozawa K. Effect of glucagon on hepatic energy charge and arterial ketone body ratio in normal rabbits. Gastroenterology 1991; 100:1041-5. [PMID: 2001801 DOI: 10.1016/0016-5085(91)90280-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Glucagon has been regarded as a hepatotrophic factor, although it is also known to stimulate energy-consuming reactions in the liver, such as gluconeogenesis and ureogenesis. To clarify the effect of glucagon on the hepatic energy metabolism, the changes in arterial ketone body ratio, which reflects the hepatic mitochondrial redox state [( NAD+]/[NADH]), as well as those in energy charge and mitochondrial oxidative phosphorylation of the liver after IV glucagon injection were studied in normal rabbits. Arterial ketone body ratio decreased significantly from 1.04 +/- 0.08 to 0.61 +/- 0.11 (mean +/- SEM; P less than 0.01) within 30 minutes after glucagon injection. Hepatic energy charge also decreased from 0.883 +/- 0.014 to 0.789 +/- 0.014 (P less than 0.01) at 30 minutes, whereas mitochondrial phosphorylation rate inversely increased from 38.4 +/- 9.5 to 87.3 +/- 9.7 (nanomoles adenosine triphosphate per milligram mitochondrial protein per minute; P less than 0.01) at 30 minutes. Arterial ketone body ratio and energy charge were subsequently restored to the initial values at 60 minutes and 2 hours, respectively. The present study suggests that glucagon causes an increase in energy expenditure in the liver that results in a transient decrease in hepatic energy charge accompanied by a decrease in arterial ketone body ratio.
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Affiliation(s)
- Y Takada
- Second Department of Surgery, Faculty of Medicine, Kyoto University, Japan
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46
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Quant PA, Robin D, Robin P, Ferre P, Brand MD, Girard J. Control of hepatic mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase during the foetal/neonatal transition, suckling and weaning in the rat. EUROPEAN JOURNAL OF BIOCHEMISTRY 1991; 195:449-54. [PMID: 1671765 DOI: 10.1111/j.1432-1033.1991.tb15724.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
(1) We assayed active and total (i.e. active plus succinylated) 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase in mitochondria isolated from foetal, neonatal, suckling or weaned rats. (2) HMG-CoA synthase was substantially succinylated and inactivated in mitochondria isolated from term-foetal, (1-h-old, 6-h-old, 1-day-old) neonatal, suckling and high carbohydrate/low-fat (hc)-weaned rats. Succinylation of HMG-CoA synthase was very low in mitochondria isolated from the livers of foetal, 30-min-old neonatal and high-fat/carbohydrate-free (hf)-weaned rats. (3) There was a negative correlation between active HMG-CoA synthase and succinyl-CoA content in mitochondria isolated from term-foetal, suckling and hc-weaned rats. (4) Differences in active enzyme could not be entirely accounted for by differences in succinylation and inactivation of the synthase. Immunoassay confirmed that the absolute amounts of mitochondrial HMG-CoA synthase increased during the foetal/neonatal transition and decreased with hc weaning. The levels remained elevated with hf weaning. (5) From these data we propose that mitochondrial HMG-CoA synthase is controlled by two different mechanisms in young rats. Regulation by succinylation provides a mechanism for rapid modification of existing enzyme in response to changing metabolic states. Changes in the absolute amounts of HMG-CoA synthase provide a more long-term control in response to nutritional changes.
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Affiliation(s)
- P A Quant
- Centre de Recherches sur la Nutrition du Centre National de la Recherche Scientifique, Meudon-Bellevue, France
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Borrebaek B, Halse K, Tveit B, Dahle HK, Ceh L. Plasma glucose, ketone bodies, insulin, glucagon and enteroglucagon in cows: diurnal variations related to ketone levels before feeding and to the ketogenic effects of feeds. Acta Vet Scand 1990. [PMID: 2205090 DOI: 10.1186/bf03547572] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Ingestions of a moderately ketogenic silage twice daily were followed by transient increments in plasma insulin and ketone bodies and decreases in plasma glucose. Ketone bodies and glucose were negatively correlated throughout the day, but the insulin elevations culminated before the maximal effects on ketone bodies and glucose were established. Cows with varying glucose levels before morning feeding reacted to a highly ketogenic silage by decreasing their glucose level uniformly to about 3 mmol/l, in spite of a widely varying feeding-induced insulin increment. Hay-feeding caused insulin increments of the same magnitude as silage-feeding, but the glucose decrease and the ketone increment was much smaller. The results indicate some direct action of ketone bodies on blood sugar regulation, in addition to effects mediated by insulin. The role of ketone bodies as the insulinotropic factor was not confirmed. The insulin level after feeding seems to be determined by the carbohydrate status of the animal before feeding. No significant changes in plasma glucagon were observed after feeding, and no consistent differences in plasma levels of this hormone were found when non-ketonemic, ketonemic, and clinically ketotic cows were compared. The plasma level of enteroglucagon (GLI) was positively correlated to the relative amount of concentrates consumed, but no relation to plasma glucose was found.
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48
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Quant PA, Tubbs PK, Brand MD. Glucagon activates mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase in vivo by decreasing the extent of succinylation of the enzyme. EUROPEAN JOURNAL OF BIOCHEMISTRY 1990; 187:169-74. [PMID: 1967579 DOI: 10.1111/j.1432-1033.1990.tb15291.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
1. 3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase (EC 4.1.3.5) in extracts of rat liver mitochondria can be inactivated by succinyl-CoA and activated by incubation in a medium designed to cause desuccinylation ('desuccinylation medium'). 2. The enzyme is less active in extracts of whole liver from control rats than from rats treated with glucagon or mannoheptulose. Incubation in desuccinylation medium raises the activity in extracts from control rats to the same value as treated rats, suggesting that the extent of succinylation in vivo is greater in controls than in hormone-treated animals. 3. This result is also obtained in liver homogenates and in isolated mitochondria. 4. Increasing the succinyl-CoA content of mitochondria to the same high level lowers the enzyme activity to the same value in mitochondria isolated from control or treated rats. In each case subsequent incubation of the lysates in desuccinylation medium raises the enzyme activity by the same extent. 5. Measurement of the incorporation of radiolabel from 2-oxo[5-14C]glutarate into protein is consistent with the proposal that all these changes in activity in isolated mitochondria may be explained by changes in the extent of succinylation of the enzyme. 6. From these data and our earlier work we conclude that, in vivo, mitochondrial HMG-CoA synthase in fed rats is normally substantially succinylated (about 40%) and inactivated, and that glucagon increases the activity of HMG-CoA synthase by lowering the concentration of succinyl-CoA and thus decreasing the extent of succinylation of the enzyme (to less than 10%). This may be an important control mechanism in ketogenesis.
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Affiliation(s)
- P A Quant
- Department of Biochemistry, University of Cambridge, England
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Borrebaek B, Halse K, Tveit B, Dahle HK, Ceh L. Plasma glucose, ketone bodies, insulin, glucagon and enteroglucagon in cows: diurnal variations related to ketone levels before feeding and to the ketogenic effects of feeds. Acta Vet Scand 1990; 31:5-15. [PMID: 2205090 PMCID: PMC8133160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Ingestions of a moderately ketogenic silage twice daily were followed by transient increments in plasma insulin and ketone bodies and decreases in plasma glucose. Ketone bodies and glucose were negatively correlated throughout the day, but the insulin elevations culminated before the maximal effects on ketone bodies and glucose were established. Cows with varying glucose levels before morning feeding reacted to a highly ketogenic silage by decreasing their glucose level uniformly to about 3 mmol/l, in spite of a widely varying feeding-induced insulin increment. Hay-feeding caused insulin increments of the same magnitude as silage-feeding, but the glucose decrease and the ketone increment was much smaller. The results indicate some direct action of ketone bodies on blood sugar regulation, in addition to effects mediated by insulin. The role of ketone bodies as the insulinotropic factor was not confirmed. The insulin level after feeding seems to be determined by the carbohydrate status of the animal before feeding. No significant changes in plasma glucagon were observed after feeding, and no consistent differences in plasma levels of this hormone were found when non-ketonemic, ketonemic, and clinically ketotic cows were compared. The plasma level of enteroglucagon (GLI) was positively correlated to the relative amount of concentrates consumed, but no relation to plasma glucose was found.
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Affiliation(s)
- B Borrebaek
- Department of Biochemistry, Veterinary College of Norway, Oslo
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Quant PA, Tubbs PK, Brand MD. Treatment of rats with glucagon or mannoheptulose increases mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase activity and decreases succinyl-CoA content in liver. Biochem J 1989; 262:159-64. [PMID: 2573345 PMCID: PMC1133242 DOI: 10.1042/bj2620159] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
1. The activity of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase (EC 4.1.3.5) in extracts of rapidly frozen rat livers was doubled in animals treated in various ways to increase ketogenic flux. 2. Some 90% of the activity measured was mitochondrial, and changes in mitochondrial activity dominated changes in total enzyme activity. 3. The elevated HMG-CoA synthase activities persisted throughout the isolation of liver mitochondria. 4. Intramitochondrial succinyl-CoA content was lower in whole liver homogenates and in mitochondria isolated from animals treated with glucagon or mannoheptulose. 5. HMG-CoA synthase activity in mitochondria from both ox and rat liver was negatively correlated with intramitochondrial succinyl-CoA levels when these were manipulated artificially. Under these conditions, the differences between mitochondria from control and hormone-treated rats were abolished. 6. These findings show that glucagon can decrease intramitochondrial succinyl-CoA concentration, and that this in turn can regulate mitochondrial HMG-CoA synthase. They support the hypothesis that the formation of ketone bodies from acetyl-CoA may be regulated by the extent of succinylation of mitochondrial HMG-CoA synthase.
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Affiliation(s)
- P A Quant
- Department of Biochemistry, University of Cambridge, U.K
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