Rate Of Gluconeogenesis Research Articles

Metformin : as First-Line Treatment for Type 2 Diabetes Prevention

Objectives: To assess the effect of Metformin, this has multiple pharmacodynamic effects and preventionin type 2 diabetes (T2DM).Design: Case - control study.Setting: Outpatient clinics of Diabetic Endocrine Research Lab and patients reporting to medicine departmentof Sheth Vadilal Sarabhai General Hospital ( Smt. NHL Municipal Medical College ) , Ahmedabad, Gujarat .Participants: A total of 240 patients, 100 control group healthy normal and nondiabetic 140 study group withType 2 Diabetes treated with Metformin and not known with a contraindication for the use of Metforminwere approached, given informed consent, and entered the study.e .Intervention : Addition of Metformin to Insulin Therapy three times a day.Primary Outcomes: Vitamin B12, Folic acid , Serum Homocysteine.Results : Metformin Treatment compare with control, was associated with a mean difference in VitaminB12 -340.26 and confidence 6.71 ( 95 % confidence interval 27.53 to 40.95: P= < 0.0001) , and in Folateconcentration of -6.24 and confidence 0.18 ( 95% confidence interval 0.74 to 1.1:P=0.026 ) , and an increasein Homocysteine concentration of 18.97 and confidence 0.93 ( 95% confidence interval 3.83 to 5.69 : P=<0.0001 ) . In addition, decrease Vitamin B12 and Folate could be explained by the increase in Homocysteine.The average person with type 2 DM has 3 times the normal rate of gluconeogenesis, Metformin treatmentreduces this by over one – third.Conclusion : Metformin use for long term has been associated with increased homocysteine level andmalabsorption of Vitamin B12 which is preventable and some researchers and our findings suggests ,recommend screening or prevention strategies .Metformin’s efficacy, security, profile, benefic CardioVascular & metabolic effects, and its capacity to be associated with other antidiabetic agents makes thisdrug the first glucose lowering agent of choice when treating patients with T2DM.

Metformin improves blood glucose by increasing incretins independent of changes in gluconeogenesis in youth with type 2 diabetes.

Metformin is the only approved oral agent for youth with type 2 diabetes but its mechanism of action remains controversial. Recent data in adults suggest a primary role for the enteroinsular pathway, but there are no data in youth, in whom metformin efficacy is only ~50%. Our objectives were to compare incretin concentrations and rates of glucose production and gluconeogenesis in youth with type 2 diabetes before and after short-term metformin therapy compared with peers with normal glucose tolerance (NGT). This is a case-control observational study in youth with type 2 diabetes who were not on metformin (n = 18) compared with youth with NGT (n = 10) who were evaluated with a 2day protocol. A 75g OGTT was administered to measure intact glucagon-like 1 peptide (iGLP-1), gastric inhibitory polypeptide (GIP) and peptide YY (PYY). Insulinogenic index (IGI) and whole-body insulin sensitivity were calculated using glucose and insulin levels from the OGTT. Basal rates of gluconeogenesis (2H2O), glucose production ([6,6-2H2]glucose) and whole-body lipolysis ([2H5]glycerol) were measured after an overnight fast on study day 2. Youth with type 2 diabetes (n = 9) were subsequently evaluated with an identical 2day protocol after 3months on the metformin study. Compared with individuals with NGT, those with type 2 diabetes had higher fasting (7.8 ± 2.5 vs 5.1 ± 0.3mmol/l, mean ± SD p = 0.002) and 2h glucose concentrations (13.8 ± 4.5 vs 5.9 ± 0.9mmol/l, p = 0.001), higher rates of absolute gluconeogenesis (10.0 ± 1.7 vs 7.2 ± 1.1μmol [kg fat-free mass (FFM)]-1min-1, p < 0.001) and whole-body lipolysis (5.2 ± 0.9 vs 4.0 ± 1.4μmol kgFFM-1min-1, p < 0.01), but lower fasting iGLP-1 concentrations (0.5 ± 0.5 vs 1.3 ± 0.7pmol/l, p < 0.01). Metformin decreased 2h glucose (pre metformin 11.4 ± 2.8 vs post metformin 9.9 ± 1.9mmol/l, p = 0.04) and was associated with ~20-50% increase in IGI (median [25th-75th percentile] pre 1.39 [0.89-1.47] vs post 1.43 [0.88-2.70], p = 0.04), fasting iGLP-1 (pre 0.3 ± 0.2 vs post 1.0 ± 0.7pmol/l, p = 0.02), 2h iGLP (pre 0.4 ± 0.2 vs post 1.2 ± 0.9pmol/l, p = 0.06), fasting PYY (pre 6.3 ± 2.2 vs post 10.5 ± 4.3pmol/l, p < 0.01) and 2h PYY (pre 6.6 ± 2.9 vs post 9.0 ± 4.0pmol/l, p < 0.01). There was no change in BMI, insulin sensitivity or GIP concentrations pre vs post metformin. There were no differences pre vs post metformin in rates of glucose production (15.0 ± 3.9 vs 14.9 ± 2.2μmol kgFFM-1min-1, p = 0.84), absolute gluconeogenesis (9.9 ± 1.8 vs 9.7 ± 1.7μmol kgFFM-1min-1, p = 0.76) or whole-body lipolysis (5.0 ± 0.7 vs 5.3 ± 1.3μmol kgFFM-1min-1, p = 0.20). Post metformin iGLP-1 and PYY concentrations in youth with type 2 diabetes were comparable to levels in youth with NGT. Overall, the improved postprandial blood glucose levels and increase in incretins observed in the absence of changes in insulin sensitivity and gluconeogenesis, support an enteroinsular mechanistic pathway in youth with type 2 diabetes treated with short-term metformin.

Rev-erbαheterozygosity produces a dose-dependent phenotypic advantage in mice.

Numerous mutational studies have demonstrated that circadian clock proteins regulate behavior and metabolism. Nr1d1(Rev-erbα) is a key regulator of circadian gene expression and a pleiotropic regulator of skeletal muscle homeostasis and lipid metabolism. Loss of Rev-erbα expression induces muscular atrophy, high adiposity, and metabolic syndrome in mice. Here we show that, unlike knockout mice, Nr1d1 heterozygous mice are not susceptible to muscular atrophy and in fact paradoxically possess larger myofiber diameters and improved neuromuscular function, compared to wildtype mice. Heterozygous mice lacked dyslipidemia, a characteristic of Nr1d1 knockout mice and displayed increased whole-body fatty-acid oxidation during periods of inactivity (light cycle). Heterozygous mice also exhibited higher rates of glucose uptake when fasted, and had elevated basal rates of gluconeogenesis compared to wildtype and knockout littermates. Rev-erbα ablation suppressed glycolysis and fatty acid-oxidation in white-adipose tissue (WAT), whereas partial Rev-erbα loss, curiously stimulated these processes. Our investigations revealed that Rev-erbα dose-dependently regulates glucose metabolism and fatty acid oxidation in WAT and muscle.

Glucose and lipid metabolism screening models of hepatocyte spheroids after culture with injectable fiber fragments.

With the rise of obesity, diabetes, and other metabolic diseases, in vitro hepatic cell and tissue models play an essential role in the identification of active pharmaceutical ingredients. Up to now, three-dimensional (3D) culture models have rarely focused on hepatic glucose and lipid metabolism. In addition, primary human liver cells suffer from limited availability and interdonor difference for establishing reproducible models. Thus, in the current study, the most available human liver cancer cell line (HepG2) and primary hepatocytes from rats (rPH) were proposed to construct 3D spheroids using injectable fiber fragments with galactose grafts (gSF) as the substrate. rPH and HepG2 spheroids show strong cell-cell and cell-fiber fragment interactions to promote the cell viability, albumin, and urea syntheses. Compared with HepG2 spheroids, rPH spheroids indicate stronger glucose metabolism abilities in terms of glucose consumption, intracellular glycogen content, gluconeogenesis rate, and sensitivity to glucose modulator hormones like insulin and glucagon. On the other hand, HepG2 spheroids display strong lipid metabolism abilities in producing significantly higher levels of total cholesterol and triglyceride. Compared with those without fiber fragments, the gSF-supported 3D culture establishes effective models for in vitro glucose (rPH spheroids) and lipid metabolisms (HepG2 spheroids). The screening models are confirmed from the respective enzyme activities and gene expressions and show significantly higher sensitivity and clinically related responses to hypoglycemic and lipid-lowering drugs. Thus, the culture configuration demonstrates a predictable in vitro platform for defining glucose and lipid metabolism profiles and screening therapeutic agents for metabolism disorders like diabetes and obesity.

Effects of stress-induced increases of corticosterone on circulating triglyceride levels, biliverdin concentration, and heme oxygenase expression

When exposed to stressors, animals physiologically respond by secreting glucocorticoid hormones. Most birds, reptiles, and amphibians secrete corticosterone (CORT), which allows them to maximize short-term survival, including by modulating lipid metabolism. However, the factors regulating lipid metabolism, particularly during acute (i.e., short-term) stressors, are not well-characterized. To investigate one putative mechanism, we examined how expression of the enzyme heme oxygenase (HO), which primarily converts heme into biliverdin, changes during an acute stressor. Because HO has links to decreased levels of triglycerides, we tested the hypothesis that an acute stressor increases HO expression, which would concomitantly decrease circulating lipid levels. We compared free-living house sparrow (Passer domesticus) nestlings exposed to a one-hour stressor to control individuals, and quantified HO expression and biliverdin concentration in spleen, liver, or kidney tissue, as well as circulating CORT, triglyceride, and glycerol levels. Nestlings exposed to a stressor had reduced circulating triglycerides consistent with an increased rate of gluconeogenesis during an acute stressor. Concentrations of triglycerides were also negatively correlated with HO expression in the liver, which is consistent with mammalian studies. However, contrary to our predictions, exposure to a stressor did not affect HO expression, or biliverdin concentration in liver, spleen, or kidney. Overall, our results support links between CORT, triglyceride levels, and HO expression, though the molecular pathways connecting these metrics still need to be elucidated.

POST SURGICAL BYPASS OF DIABETIC KETOACIDOSIS PROTOCOL

SESSION TITLE: Monday Medical Student/Resident Case Report Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/21/2019 02:30 PM - 03:15 PM INTRODUCTION: Serum–glucose cotransporter-2 (SGLT-2) inhibitors are associated with potential euglycemic diabetic ketoacidosis (eDKA) in patients with type 1 and type 2 diabetes mellitus (T2DM). We describe a case of eDKA in a T2DM patient after gastric bypass surgery, treated with empagliflozin monotherapy, which exposed limitations of standardized DKA protocols. CASE PRESENTATION: A 49-year-old male with a history of morbid obesity and T2DM presented with three weeks of lethargy and weakness, in the setting of recent Roux-en-Y gastric bypass surgery. Previously, his T2DM was controlled with dulaglutide, insulin, and metformin. Following his surgery he was switched to empagliflozin only. On admission, the patient had a pH of 7.14, anion gap of 27, betahydroxybutyrate level of 9.98, ketonuria, and a glucose level of 178. In the ICU, he was maintained on IV insulin and D5/NS infusion. He required up to 8ml/hour of IV insulin due to difficulty controlling his ketoacidosis and consequently required high doses of supplemental dextrose, deviating substantially from standard DKA protocol. After 48 hours, his anion gap closed and he was transitioned to a subcutaneous basal-bolus insulin regimen. At discharge, empagliflozin was discontinued and he was prescribed a basal-bolus insulin regimen. DISCUSSION: SGLT-2 inhibitors present an invaluable option in managing diabetes mellitus. While SGLT-2 inhibitors are often used as monotherapy, eDKA can be clinically difficult to differentiate from routine complications of post-gastric bypass surgery. This may delay the diagnosis while increasing the severity of eDKA, health care costs, and length of hospital admission. The proposed mechanism of eDKA and SGLT-2 inhibitors involves increased urinary ketone reabsorption and large amounts of glucose in the urine in the presence of an increased rate of gluconeogenesis and free fatty acid release (1-3). Precipitants include a reduction of co-regimented insulin, alcohol consumption, infection, prolonged exercise, and reduced carbohydrate intake (1). In the post-operative setting, the duration of eDKA in patients with T2DM treated with SGLT-2 inhibitors is poorly defined and often requires several days of intravenous insulin therapy (1). Stopping this medication 24 to 48 hours prior to surgery, due to its half-life of about 12 hours, has not demonstrated significant benefit (1). CONCLUSIONS: SGLT-2 inhibitors present an invaluable option in managing diabetes mellitus. Importance of their risk to cause eDKA has become more relevant to prescribers, considering the increased number of case reports present to date. While SGLT-2 inhibitors are often used as monotherapy, eDKA can be clinically difficult to differentiate from routine complications of post-gastric bypass surgery. This may delay the diagnosis while increasing the severity of eDKA, health care costs, and length of hospital admission. Reference #1: Peters A., Buschur E., Buse J., Cohan P., Diner J., and Hirsch I. Euglycemic Diabetic Ketoacidosis: A Potential Complication of Treatment With Sodium-Glucose Cotransporter 2 Inhibition. Diabetes Care 2015 Sep; 38(9): 1687-1693 Reference #2: Bashir J., Nalla P., Peter R., Bain S., Chudleigh R. A Case Series of DKA Occuring in Patients Receiving Treatment with SGLT-2 Inbitors. Diabetes Obes Metab. 2018; 20:1800-1801 Reference #3: Ireland JT, Thomson WS. Euglycemic diabetic ketoacidosis. BMJ1973;3:107 DISCLOSURES: No relevant relationships by Rahul Chaudhari, source=Web Response No relevant relationships by Stephen Schwartz, source=Web Response No relevant relationships by cyrus vahdatpour, source=Web Response

A comparison of the nutritional physiology and gut microbiome of urban and rural house sparrows (Passer domesticus).

Urbanization influences food quality and availability for many wild species, but our knowledge of the consequences urbanization has on the nutritional physiology of these animals is currently limited. To fill this gap, we captured House Sparrows (Passer domesticus) from rural and urban environments and hypothesized that increased access to human refuse in urban areas may significantly alter the gut microbiome and nutritional physiology of Sparrows. While there were no significant differences in circulating triglycerides or free glycerol concentrations between populations, urban birds had significantly greater blood glucose concentrations, which suggests greater circulating glucagon concentrations, accessibility to carbohydrates, and/or higher rates of gluconeogenesis in an urban setting. Rural birds had significantly more plasma uric acid, suggesting that they may metabolize more proteins or experience lower inflammation than urban birds. Rural birds also had significantly higher liver free glycerol concentrations, indicating that they metabolize more fat than urban birds. There were no significant differences in the relative abundance of gut microbial taxa at the phyla level between the two populations, but linear discriminant analysis effect size (LEfSe) showed that urban House Sparrows were more enriched with class- and order-level microbes from the phylum Proteobacteria, which are implicated in several mammalian intestinal and extra-intestinal diseases. These findings demonstrate that urbanization significantly alters the nutritional physiology and the composition of the gut microbiome of House Sparrows.

Sex Dependent Dysregulation of Hepatic Glucose Production in Lean Type 2 Diabetic Rats.

We have characterized a lean type 2 diabetic rat model by gestational low protein programming. We aimed to identify if the regulation of hepatic glucose production (HGP) via gluconeogenesis and glycogenolysis is affected and if there are any sex differences. Fasting (6–7 months old) type 2 diabetic rats received 2H2O followed by a primed constant rate infusion of [6,6-2H2] glucose. Blood samples were drawn during steady states after 4 h of fasting and following a euglycemic hyperinsulinemic clamp. HGP and the fraction of glucose derived from gluconeogenesis under fasting and euglycemic states were measured from steady state glucose enrichments after the infusion of [6,6-2H2]glucose and 2H2O tracers. Glycogenolysis was determined by calculating the difference between total HGP and gluconeogenesis rates. Hepatic gene expression of enzymes involved in HGP were quantified using qPCR. HGP rates was similar during fasting in both groups and sexes. However, under simulated fed condition, HGP rate was suppressed in controls but not in type 2 diabetic rats. They also showed inefficient HGP suppression in a simulated fed state. Differential analysis showed that suppression of both gluconeogenesis and glycogenolysis under simulated fed state was affected in these low protein programmed type 2 diabetic rats. These effects were greater in females when compared to males. Further, key genes involved in these processes like G6Pase, Pepck, pyruvate carboxylase, and glycogen phosphorylase in liver were dysregulated. Our data shows impaired suppression of HGP via gluconeogenesis and glycogenolysis in type 2 diabetic rats with greater effects on females.

Protective effects of melatonin on sepsis-induced liver injury and dysregulation of gluconeogenesis in rats through activating SIRT1/STAT3 pathway

Sepsis, a life-threatening disease with high morbidity and mortality in critically ill patients, usually leads to serious complications including liver damage and dysregulated metabolic homoeostasis. The aim of this study was to evaluate the therapeutic potential of melatonin in rats with caecal ligation and puncture (CLP)-induced sepsis, which mimics critical infections in humans and explore the underlying molecular mechanisms. Male Sprague-Dawley rats received CLP surgery under anaesthesia to induce polymicrobial sepsis. Melatonin (20 mg/kg) was intraperitoneally (i.p.) injected every 12 h for 7 days after CLP, with or without intraperitoneal injection of the SIRT1 inhibitor EX527 (5 mg/kg). Markers of glucose metabolism, inflammation, liver function and associated signaling pathway were measured. Septic rats exhibited marked inhibition of the hepatic SIRT1/STAT3 pathway, along with increased blood glucose levels and hepatic gluconeogenesis. Melatonin administration efficiently attenuated liver dysfunction and glucose metabolism disorders by promoting hepatic SIRT1 expression and STAT3 phosphorylation. Furthermore, inhibition of SIRT1 by EX527 significantly diminished the protective effects of melatonin on sepsis induced liver injury, hyperglycaemia and STAT3 inactivation. These results emphasize that melatonin is a potential therapeutic agent for sepsis-associated liver injury and glucose metabolism disorders, possibly acting by targeting SIRT1-mediated STAT3 activation in the liver.

Metabolic Effects of Metformin in Humans.

Both insulin deficiency and insulin resistance due to glucagon secretion cause fasting and postprandial hyperglycemia in patients with diabetes. Metformin enhances insulin sensitivity, being used to prevent and treat diabetes, although its mechanism of action remains elusive. Patients with diabetes fail to store glucose as hepatic glycogen via the direct pathway (glycogen synthesis from dietary glucose during the post-prandial period) and via the indirect pathway (glycogen synthesis from "de novo" synthesized glucose) owing to insulin deficiency and glucagoninduced insulin resistance. Depletion of the hepatic glycogen deposit activates gluconeogenesis to replenish the storage via the indirect pathway. Unlike healthy subjects, patients with diabetes experience glycogen cycling due to enhanced gluconeogenesis and failure to store glucose as glycogen. These defects raise hepatic glucose output causing both fasting and post-prandial hyperglycemia. Metformin reduces post-prandial plasma glucose, suggesting that the drug facilitates glucose storage as hepatic glycogen after meals. Replenishment of glycogen store attenuates the accelerated rate of gluconeogenesis and reduces both glycogen cycling and hepatic glucose output. Metformin also reduces fasting hyperglycemia due to declining hepatic glucose production. In addition, metformin reduces plasma insulin concentration in subjects with impaired glucose tolerance and diabetes and decreases the amount of insulin required for metabolic control in patients with diabetes, reflecting improvement of insulin activity. Accordingly, metformin preserves β-cell function in patients with type 2 diabetes. Several mechanisms have been proposed to explain the metabolic effects of metformin, but evidence is not conclusive and the molecular basis of metformin action remains unknown.

Impaired ketogenesis and increased acetyl-CoA oxidation promote hyperglycemia in human fatty liver.

Non-alcoholic fatty liver disease (NAFLD) is a highly prevalent, and potentially morbid, disease that affects one-third of the U.S. population. Normal liver safely accommodates lipid excess during fasting or carbohydrate restriction by increasing their oxidation to acetyl-CoA and ketones, yet lipid excess during NAFLD leads to hyperglycemia and, in some, steatohepatitis. To examine potential mechanisms, flux through pathways of hepatic oxidative metabolism and gluconeogenesis were studied using five simultaneous stable isotope tracers in ketotic (24-hour fast) individuals with a wide range of hepatic triglyceride contents (0-52%). Ketogenesis was progressively impaired as hepatic steatosis and glycemia worsened. Conversely, the alternative pathway for acetyl-CoA metabolism, oxidation in the tricarboxylic (TCA) cycle, was upregulated in NAFLD as ketone production diminished and positively correlated with rates of gluconeogenesis and plasma glucose concentrations. Increased respiration and energy generation that occurred in liver when β-oxidation and TCA cycle activity were coupled may explain these findings, inasmuch as oxygen consumption was higher during fatty liver and highly correlated with gluconeogenesis. These findings demonstrate that increased glucose production and hyperglycemia in NAFLD is not a consequence of acetyl-CoA production per se, but how acetyl-CoA is further metabolized in liver.

Some Musings About Differential Energy Metabolism With Ketogenic Diets.

Ketogenic states are of 3 major types: total starvation and those resulting from the consumption of semistarvation, ketogenic diets, and eucaloric ketogenic diets. All are characterized by little or no dietary carbohydrate, resulting in a fat-based metabolism with sustained ketonemia of varying degrees in each state. The latter 2 diets are clinically useful with important impacts on both aspects of the energy balance equation with increased satiety and less hunger on the intake side and probably increased energy expenditure on the output side; both may have important implications for the successful long-term management of obesity. Consideration of older research regarding the hormonal response to carbohydrate-free dieting and recent findings on hepatic glycogen status that occurs with sustained ketonemia support the likelihood that there are profound differences in 24-hour gluconeogenesis rates between ketogenic diets and balanced diets containing substantial carbohydrate. This metabolic distinction could have a meaningful impact to increase the thermic effect of feeding and daily energy expenditure amounting to 100kcal/d or more with each of the ketogenic diets.

288-LB: Effects of the Hepatic Mitochondrial Calcium Uniporter on Hepatic Gluconeogenesis and Mitochondrial Metabolism in Awake Mice

Increased hepatic glucose production, due to increased rates of gluconeogenesis, is a contributor to both fasting and postprandial hyperglycemia in patients with T2D. Recent evidence implicates a role for hepatic calcium signaling in mediating glucagon's effect to stimulate glucose production and mitochondrial oxidation; however, the cellular and molecular mechanisms by which glucagon promotes these alterations remain poorly understood. We hypothesize that an acute physiological increase in plasma glucagon concentrations will increase cytosolic and mitochondrial calcium concentrations, promoting increases in rates of hepatic mitochondrial oxidation and gluconeogenesis in a transcription-independent manner. To test this hypothesis, we used mice with a liver-specific loss of the mitochondrial calcium uniporter (MCU), which is the main transporter that allows rapid transport of calcium into the mitochondrial matrix. We found that glucagon increased oxygen consumption rate by 80% (p&amp;lt;0.0001) in WT hepatocytes, while this effect was abrogated in MCU KO hepatocytes. We also measured hepatic mitochondrial oxidation (VCS) in vivo using Positional Isotopomer NMR Tracer Analysis (PINTA) and found a 74% decrease in VCS (p=0.05) in MCU KO mice compared to WT mice. This suggests that tightly regulated mitochondrial calcium signaling is necessary for regulating hepatic mitochondrial oxidation. Next, we measured intrahepatic lipolysis and hepatic gluconeogenesis in vitro and in vivo. We found that glucagon increased lipolysis (p=0.05) and glucose production (p=0.024) by ∼1.5 fold in MCU KO compared to WT hepatocytes. Furthermore, in vivo PINTA results showed that glucagon increased pyruvate carboxylase flux (VPC) by 68% (p=0.08) in MCU KO mice. Taken together, these results suggest that mitochondrial calcium signaling through MCU is necessary to regulate the effect of glucagon to modulate hepatic gluconeogenesis and mitochondrial oxidation. Disclosure J. Lee: None. L. Goedeke: None. Y. Zhang: None. R.J. Perry: Research Support; Self; AstraZeneca. R. Goodman: None. V. Mootha: Advisory Panel; Self; Janssen Pharmaceuticals, Inc. Consultant; Self; 5AM Ventures. Other Relationship; Self; Raze Therapeutics. G.I. Shulman: Advisory Panel; Self; AstraZeneca, Janssen Research &amp; Development, Merck &amp; Co., Inc. Advisory Panel; Spouse/Partner; Merck &amp; Co., Inc. Board Member; Self; Novo Nordisk A/S. Consultant; Self; Aegerion Pharmaceuticals, IMetabolic BioPharma Corporation, Longitude Capital, Nimbus Discovery, Inc., Staten Biotechnology B.V. Funding National Institutes of Health

285-LB: Short-Term Effect of Saturated and Monounsaturated Fatty Acids on Hepatic Energy Metabolism

Nonalcoholic fatty liver disease (NAFLD) is the most common form of liver disease affecting about 30% of the U.S. population. The prognosis for simple liver steatosis is relatively benign; however, chronic inflammation and progressive fibrosis may lead to nonalcoholic steatohepatitis (NASH) and later to cirrhosis and hepatocellular carcinoma. There is no established treatment to stop progression from NAFLD to NASH to date. Therefore, we developed a protocol to investigate the acute impact of saturated (SFA) and monounsaturated (MUFA) fatty acids on liver energy metabolism and their potential lipotoxic effects. Conscious, unrestrained, overnight fasted 12 weeks old male C57Bl/6J mice were given continuous, intravenous infusions of either saline, 20% lard oil or 20% olive oil emulsions (as described in Stein DT et al. J Clin Invest. 1997; 100 (2): 398-403) for 5 hrs. Lipid infusion was accompanied by primed, continuous infusion of [6,6-2H2] glucose (16mg/kg/min for 5 min and 0.8 mg/kg/min continuously) and sodium [13C3]lactate (200 μM/kg/min 5 min and 40 μM/kg/min continuously) intravenously for 4 and 2 hrs, respectively. Both plasma and liver free fatty acids were upregulated in SFA and MUFA groups. However, liver triglycerides, alanine aminotransferase (ALT) and aspartate transaminase (AST) were significantly increased, whereas plasma insulin and glucose levels significantly decreased, only in the MUFA group. 13C and 2H-enrichment of plasma glucose and liver alanine, glutamate, lactate and urea obtained at the end of the study were measured by GC-MS and used to regress liver metabolic fluxes using a flexible flux modeling platform (INCA). We observed that both SFA and MUFA increased the absolute rate of dihydroxyacetone phosphate (DHAP) flux from glycerol. Absolute flux of acetyl-CoA production was shifted from synthesis through pyruvate dehydrogenase toward increased contribution from fatty acid oxidation. On the other hand, only MUFA decreased the gluconeogenesis rate. Disclosure T. Bednarski: None. M. Rahim: None. J. Young: Consultant; Self; Pfizer Inc. Stock/Shareholder; Self; Metalytics. Funding National Institutes of Health (R01DK106348)

MON-159 Increased Gluconeogenesis and Lower Glycogenolysis in Patients with Non-Selective Compared Selective Insulin Resistance

Type 2 diabetes is characterized by increased hepatic glucose production and selective insulin resistance that occurs downstream of the insulin receptor. However, the differential pathways and exact molecules implicated in selective insulin signaling are unclear. To elucidate the hepatic mechanistic pathways affected by selective versus non-selective insulin resistance, we compared basal rates of hepatic glucose production and its components, gluconeogenesis and glycogenolysis, in patients with severe non-selective insulin resistance (insulin receptor mutations (INSR)) to patients with selective insulin resistance (lipodystrophy and type 2 diabetes). In 7 patients with INSR, 14 with lipodystrophy and 9 with type 2 diabetes, we measured rates of hepatic glucose production (via [6,6-2H2] glucose) and fractional gluconeogenesis (via 2H2O) after an overnight fast. Absolute rates of gluconeogenesis were calculated as the product of fractional gluconeogenesis and hepatic glucose production, and glycogenolysis were calculated as hepatic glucose production minus gluconeogenesis. In patients with INSR, lipodystrophy and type 2 diabetes, HbA1c (8.2 ± 2.8, 8.4 ± 1.9, 7.4 ± 0.9%) and fasting glucose (120 ± 70, 159 ± 55, 127 ± 32 mg/dl) were comparable (P>0.05). Fasting serum insulin was higher in INSR vs. lipodystrophy and type 2 diabetes (332 ± 355, 48 ± 50, 50 ± 16 μU/ml; P<0.01). Patients with INSR and lipodystrophy had higher hepatic glucose production vs. type 2 diabetes (24.0 ± 4.0, 24.1 ± 6.2, 15.8 ± 4.3 µmol/kgLEAN/min; P<0.01). Fractional gluconeogenesis was higher in INSR vs. lipodystrophy and type 2 diabetes (77.1 ± 9.4, 55.4 ± 11.5, 59.1 ± 5.9%; P<0.01). Absolute gluconeogenesis was highest in INSR, intermediate in lipodystrophy, and lowest in type 2 diabetes (19.1 ± 4.4, 13.5 ± 4.2, 9.5 ± 1.9 µmol/kgLEAN/min; P<0.01). Glycogenolysis was lowest in INSR, highest in lipodystrophy, and intermediate in type 2 diabetes (4.9 ± 2.2 vs. 10.6 ± 4.8, 6.3 ± 2.6 µmol/kgLEAN/min; P<0.01). Higher hepatic glucose production in lipodystrophy vs. type 2 diabetes is consistent with higher hepatic insulin resistance in patients with lipodystrophy, but comparable fractional rates of gluconeogenesis and glycogenolysis confirm similar mechanisms of selective post-receptor insulin resistance. By contrast, the markedly higher contribution of gluconeogenesis to hepatic glucose production in INSR may reflect complete loss of insulin signaling for glycogen accumulation and/or suppression of gluconeogenesis. Further studies should evaluate whether greater substrate and fuel availability for gluconeogenesis, and/or lower hepatic glycogen stores are important determinants of the components of glucose production in patients with non-selective insulin resistance due to INSR mutation.

Cafeteria Diet Feeding in Young Rats Leads to Hepatic Steatosis and Increased Gluconeogenesis under Fatty Acids and Glucagon Influence.

Gluconeogenesis overstimulation due to hepatic insulin resistance is the best-known mechanism behind elevated glycemia in obese subjects with hepatic steatosis. This suggests that glucose production in fatty livers may differ from that of healthy livers, also in response to other gluconeogenic determinant factors, such as the type of substrate and modulators. Thus, the aim of this study was to investigate the effects of these factors on hepatic gluconeogenesis in cafeteria diet-induced obese adult rats submitted to a cafeteria diet at a young age. The livers of the cafeteria group exhibited higher gluconeogenesis rates when glycerol was the substrate, but lower rates were found when lactate and pyruvate were the substrates. Stearate or glucagon caused higher stimulations in gluconeogenesis in cafeteria group livers, irrespective of the gluconeogenic substrates. An increased mitochondrial NADH/NAD+ ratio and a reduced rate of 14CO2 production from [14C] fatty acids suggested restriction of the citric acid cycle. The higher glycogen and lipid levels were possibly the cause for the reduced cellular and vascular spaces found in cafeteria group livers, likely contributing to oxygen consumption restriction. In conclusion, specific substrates and gluconeogenic modulators contribute to a higher stimulation of gluconeogenesis in livers from the cafeteria group.

Paradigm Shifts in Nocturnal Glucose Control in Type 2 Diabetes.

A better understanding of nocturnal regulation of glucose homeostasis will provide the framework for designing rational therapeutic strategies to improve the management of overnight glucose in patients with type 2 diabetes (T2D). To establish the nocturnal pattern and regulation of glucose production (EGP) in humans and to determine whether the pattern is dysregulated in people with T2D. Subjects were infused with [3-3H] glucose overnight. Arterial blood samples were drawn for hormones and analytes to estimate EGP throughout the night. Deuterium-labeled water was provided to measure gluconeogenesis (GNG) using the hexamethylenetetramine method of Landau. Mayo Clinic Clinical Research Trials Unit, Rochester, MN, USA. A total of 43 subjects [23 subjects with T2D and 20 nondiabetic (ND) subjects comparable for age and body mass index] were included in this study. Glucose and EGP. Plasma glucose, C-peptide, and glucagon concentrations were higher throughout the night, whereas insulin concentrations were higher in subjects with T2D vs ND subjects at 1:00 and 4:00 am but similar at 7:00 am. EGP was higher in the subjects with T2D than in the ND subjects throughout the night (P < 0.001). Glycogenolysis (GGL) fell and GNG rose, resulting in significantly higher (P < 0.001) rates of GNG at 4:00 and 7:00 am and significantly (P < 0.001) higher rates of GGL at 1:00, 4:00, and 7:00 am in T2D as compared with ND. These data imply that optimal therapies for T2D for nocturnal/fasting glucose control should target not only the absolute rates of EGP but also the contributing pathways of GGL and GNG sequentially.

Increased Gluconeogenesis Is Not an Early Feature of Whole-Body Insulin Resistance in Black Women—The Federal Women Study

In contrast to white women, fasting hyperglycemia is not an early diabetes risk marker in black women. The etiology of this racial difference in risk is unknown but could be related to differences in rates of gluconeogenesis and hepatic fat in black women. Using stable isotope tracers [2H2O], [6,62H2]glucose, and ([2H5]glycerol), we partitioned basal glucose production into its two components (gluconeogenesis and glycogenolysis) and measured basal whole body lipolysis. Whole body (SI), hepatic (HIS) and adipose tissue insulin sensitivity were calculated in two groups of federally employed pre-menopausal women, without diabetes: 24 black and 19 white; age 37±6 (mean±SD), range 25-50y; BMI 33±6, range 24.9-45.2 kg/m2. Hepatic and visceral fat were measured by proton MRS. The prevalence of prediabetes (17% vs. 26%), age and BMI were similar in blacks and whites, all P&amp;gt;0.4). Black women had less fasting hyperglycemia (4% vs. 22%, P=0.1), lower visceral and hepatic fat (P&amp;lt;0.01) but similar SI, adipose tissue insulin sensitivity and whole body lipolysis (all P&amp;gt;0.5). Basal glucose, insulin and FFA concentrations were similar in both groups (P&amp;gt;0.05). Blacks had lower glucose production (2.52±0.34 vs. 2.75±0.28 mg·kglbm-1·min-1, P&amp;lt;0.05), fractional gluconeogenesis (57.6±10.6 vs. 66.3±11.4%, P=0.02), and absolute gluconeogenesis (1.44±0.28 vs. 1.77±0.31 mg·kglbm-1·min-1, P&amp;lt;0.01). HIS correlated with SI and hepatic fat (both r=0.5, P&amp;lt;0.01) and the relationship did not differ by race (P&amp;gt;0.05). However, at the same SI blacks had higher HIS (intercepts P&amp;lt;0.01). In summary, black women had relatively preserved HIS and lower hepatic fat, while white women had higher gluconeogenesis and hepatic fat associated with fasting hyperglycemia. Fasting glucose may be a poor early diabetes marker in black women because gluconeogenesis was low despite whole-body insulin resistance. Disclosure S.T. Chung: None. M.W. Haymond: Advisory Panel; Self; Zealand Pharma A/S. Other Relationship; Self; Xeris Pharmaceuticals, Inc.. A. Onuzuruike: None. L. Mabundo: None. H. Garraffo: None. P.J. Walter: None. A.B. Courville: None. A.M. Gharib: None. S. Chacko: None. A.E. Sumner: None.

Using Hyperpolarized [2-13C] Dihydroxyacetone to Detect Hepatic Gluconeogenesis

Diabetes afflicts millions of people worldwide and contributes to elevated risk of cardiovascular disease and stroke. Imaging of hepatic metabolic activity using MRI could prove advantageous for diagnosis, treatment monitoring, etc. With the advent of hyperpolarized (HP) carbon-13 based MRI, rapid imaging of metabolic flux is feasible without the use of ionizing radiation. In this work, we have utilized HP [2-13C]dihydroxyacetone (DHA) to observe hepatic metabolism in real time in a perfused mouse (C57BLKS/J) liver model. We have utilized fatty acids and a 1:10 ratio of pyruvate to lactate in the perfusate to mimic physiological conditions. Figure 1 shows the various metabolites observed following the injection of DHA. Ratios of integrals of three-carbon intermediates and hexose sugars (and phosphates) are used to determine the rate of gluconeogenesis. Hepatic gluconeogenic rates are measured in parallel with gold standard tracer methods, confirming the accuracy of HP imaging. Figure 1: Representative 13C NMR spectrum (sum) of hyperpolarized [2-13C] DHA metabolism in perfused liver at 14.1 T. Spectra were measured without 1H decoupling. Phosphoenolpyruvate (PEP) and glycerol-3-phosphate (G3P) are observed. Note that PEP is normally considered a low concentration metabolites, but it is easily detected here. Disclosure M. Merritt: None. M. Ragavan: None. T. Tsarova: None.

Regulation of Hepatic Glucose and Lipid Metabolism by the Acetyl‐CoA Hydrolase Acyl‐CoA Thioesterase 12 (Acot12)

Acetyl‐CoA is a key determinant of gluconeogenesis and lipid biosynthesis in the liver, and the sources of acetyl‐CoA within hepatocytes are well defined. Acot12 is a cytosolic enzyme that catalyzes the hydrolysis of acetyl‐CoA into acetate plus CoASH. In addition to its enzymatic domains, Acot12 also contains a steroidogenic acute regulatory protein‐related lipid transfer (START) domain, which functions as lipid sensor. Although enriched in the liver, the biological functions of Acot12 remain unknown. We hypothesized that Acot12 activity may suppress hepatic glucose production and lipogenesis.MethodsTo overexpress Acot12 in C57BL/6J mice and in primary cultured mouse hepatocytes, we generated Acot12.Ad adenovirus and used null.Ad adenovirus as the control. Expression levels of Acot12 were assessed by real‐time PCR, immunoblot analysis and immunofluorescence. Tolerance tests to glucose (GTTs), pyruvate (PTTs) and insulin (ITTs) were performed after 6, 16 and 4 h fasting periods, respectively. Plasma and hepatic lipid concentrations were measured using enzymatic assays. Rates of basal and cAMP‐stimulated rates of gluconeogenesis from pyruvate plus lactate, as well as de novo lipogenesis from acetate were determined in cultured hepatocytes. Fatty acid oxidation rates in liver tissue and primary hepatocytes were quantified from to the conversion of 14C‐palmitate into 14C‐acid soluble metabolites and 14C‐CO2.ResultsAcot12.Ad increased Acot12 mRNA and elevated protein levels by 10‐fold in mouse livers. Acot12 overexpression improved glucose tolerance, as evidence by decreased values of area‐under‐the curve (AUC) during the course of the GTTs. Decreased AUC values were also observed during PTTs, which reflect rates of gluconeogenesis. No differences were observed for ITTs, which largely reflect peripheral insulin responsiveness. Acot12 overexpression reduced hepatic phospholipids and plasma cholesterol concentrations. In primary hepatocytes, overexpression of Acot12 reduced basal and cAMP‐stimulated rates of glucose production, as well as rates of de novo lipogenesis. In addition, Acot12 overexpression increased fatty acid oxidation rates in both liver tissue and primary hepatocytes. This correlated with higher mRNA expression levels of the plasma membrane fatty acid transporter CD36 and of mitochondrial CPT1a, which promotes fatty acid uptake for oxidation.ConclusionsTaken together, our findings reveal that Acot12 activity in the liver suppresses both glucose production and lipogenesis. Increased rates of hepatocellular fatty acid uptake and oxidation presumably reflect compensatory mechanisms directed towards the repletion of TCA cycle intermediates that support glucose and lipid biosynthesis. We speculate that Acot12 regulates hepatic nutrient metabolism by controlling cytosolic acetyl‐CoA concentrations within the liver.Support or Funding InformationThis work was supported by NIH grants DK048873, DK056626 and DK103046, as well as the American Liver Foundation.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.