Rate Of Hepatic Glucose Production Research Articles

The impact of short-term eucaloric low- and high-carbohydrate diets on liver triacylglycerol content in males with overweight and obesity: a randomized crossover study

BackgroundIntrahepatic triacylglycerol (liver TG) content is associated with hepatic insulin resistance and dyslipidemia. Liver TG content can be modulated within days under hypocaloric conditions. ObjectivesWe hypothesized that 4 d of eucaloric low-carbohydrate/high-fat (LC) intake would decrease liver TG content, whereas a high-carbohydrate/low-fat (HC) intake would increase liver TG content, and further that alterations in liver TG would be linked to dynamic changes in hepatic glucose and lipid metabolism. MethodsA randomized crossover trial in males with 4 d + 4 d of LC and HC, respectively, with ≥2 wk of washout. 1H-magnetic resonance spectroscopy (1H-MRS) was used to measure liver TG content, with metabolic testing before and after intake of an LC diet (11E% carbohydrate corresponding to 102 ± 12 {mean ± standard deviation [SD]) g/d, 70E% fat} and an HC diet (65E% carbohydrate corresponding to 537 ± 56 g/d, 16E% fat). Stable [6,6-2H2]-glucose and [1,1,2,3,3-D5]-glycerol tracer infusions combined with hyperinsulinemic-euglycemic clamps and indirect calorimetry were used to measure rates of hepatic glucose production and lipolysis, whole-body insulin sensitivity and substrate oxidation. ResultsEleven normoglycemic males with overweight or obesity (BMI 31.6 ± 3.7 kg/m2) completed both diets. The LC diet reduced liver TG content by 35.3% (95% confidence interval: −46.6, −24.1) from 4.9% [2.4–11.0] (median interquartile range) to 2.9% [1.4–6.9], whereas there was no change after the HC diet. After the LC diet, fasting whole-body fat oxidation and plasma beta-hydroxybutyrate concentration increased, whereas markers of de novo lipogenesis (DNL) diminished. Fasting plasma TG and insulin concentrations were lowered and the hepatic insulin sensitivity index increased after LC. Peripheral glucose disposal was unchanged. ConclusionsReduced carbohydrate and increased fat intake for 4 d induced a marked reduction in liver TG content and increased hepatic insulin sensitivity. Increased rates of fat oxidation and ketogenesis combined with lower rates of DNL are suggested to be responsible for lowering liver TG. This trial was registered at clinicaltrials.gov as NCT04581421.

Endurance training and essential amino acid intervention synergize to ameliorate fructose-induced metabolic dysfunction in mice

Purpose: Excessive fructose (FRU) consumption can rapidly produce multiple features of metabolic syndrome, including dysregulation of systemic metabolism, insulin resistance, and diabetes. Essential amino acids (EAAs) and endurance exercise training (ET) improve abnormal metabolism in various disease conditions, yet their combined effect and metabolic mechanism remain unclear. Thus, the current study aimed to investigate metabolic kinetic mechanism and the combined effect of EAA and ET on fructose-induced metabolic dysfunction. Materials and methods: Mice were randomly divided into 5 groups with an 8-week intervention: normal chow (CON), FRU, FRU+ET, FRU+EAA or FRU+ET+ EAA, followed by stable isotope tracer infusions ([U-13C16]palmitate, [D2]glucose, and [D5]glycerol) or D2O administration to determine substrate metabolic flux rates and their contribution to TCA cycle flux and protein synthesis rates of various organs, respectively. Summary of results: FRU-induced adverse changes in body weight and physical function were reversed by ET, EAA, or ET+EAA. In stable isotope tracing analysis, ET and ET+EAA alleviated hyperglycemia by suppressing hepatic glucose production rate, while EAA and ET+EAA normalized palmitate turnover and contribution to TCA cycle in various organs. Additionally, the altered protein synthesis measured using a D2O labeling method was normalized by ET and ET+EAA. Conclusion:These findings suggest that the combined treatment of dietary EAAs and ET more effectively mitigates fructose-induced metabolic dysfunction by normalizing hepatic glucose production rate, protein synthesis rates, and fatty acid metabolism. This research was supported by a grant of the Korea Health Technology R&D Project through the Korea Health industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (HI22C2208), and the National Research Foundation of Korea (NRF), funded by the Korea government (MSIT) (No. 2021R1A2C3005801), and partially funded by MYOCARE INC. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Intraduodenal nutrient infusion differentially alters intestinal nutrient sensing, appetite, and satiety responses in lean and obese subjects

BackgroundIntestinal nutrient sensing regulates food intake and energy metabolism by acting locally and relaying nutritional status to the brain. It is unclear whether these mechanisms are altered in obese humans. ObjectivesWe aimed to investigate differences in duodenal nutrient sensing in humans with or without obesity and the effects of transiently blocking vagal transmission on nutrient sensing, hunger, and appetite. MethodsIn a single-blinded, randomized, cross-over design, subjects with or without obesity (n = 14 and n = 11, respectively) were infused intraduodenally with saline or a combination of glucose and oleic acid for 90 min (glucose load: 22.5 g, 1 kcal/min; oleic acid load: 10 g, 1 kcal/min) in the presence or absence of local anesthetic (benzocaine). Blood was sampled at 10-min intervals (120–240 min) and 15-min intervals until termination of the study for measurements of gut hormones, insulin, leptin, and C-peptide. Hunger and satiety sensations were scored using the visual analog scale, and hepatic glucose production and glucose oxidation rates were measured. ResultsDuodenal nutrient infusion in lean subjects led to a 65% drop in acyl ghrelin release and robustly increased cholecystokinin 8 (CCK-8) release (65%; P = 0.023); benzocaine infusion delayed this response (2-factor repeated-measures analysis of variance, P = 0.0065). In contrast, subjects with obesity had significantly blunted response to nutrient infusion, and no further effects were observed with benzocaine. Additionally, significant delays were observed in peptide YY (3-36), pancreatic polypeptide, glucose inhibitory peptide, and glucagon-like peptide 1 (7-36) response. No significant interactions were found between body mass index (BMI) or baseline hormone levels and areas under the curve for hormones except CCK-8 (BMI, P = 0.018; baseline CCK, P = 0.013). Nutrient-induced hunger and satiety sensations were impeded by benzocaine only in the lean cohort. Hunger and satiety sensations in subjects with obesity were not responsive to nutrient entry into the duodenum, and no additional effects were observed by blocking neural signaling. ConclusionNutrient-induced gut hormone release and response to transient vagal blockade are significantly blunted in subjects with obesity.This trial was registered at clinicaltrials.org as NCT02537314.

Quantifying insulin-mediated and noninsulin-mediated changes in glucose dynamics during resistance exercise in type 1 diabetes.

Exercise can cause dangerous fluctuations in blood glucose in people living with type 1 diabetes (T1D). Aerobic exercise, for example, can cause acute hypoglycemia secondary to increased insulin-mediated and noninsulin-mediated glucose utilization. Less is known about how resistance exercise (RE) impacts glucose dynamics. Twenty-five people with T1D underwent three sessions of either moderate or high-intensity RE at three insulin infusion rates during a glucose tracer clamp. We calculated time-varying rates of endogenous glucose production (EGP) and glucose disposal (Rd) across all sessions and used linear regression and extrapolation to estimate insulin- and noninsulin-mediated components of glucose utilization. Blood glucose did not change on average during exercise. The area under the curve (AUC) for EGP increased by 1.04 mM during RE (95% CI: 0.65-1.43, P < 0.001) and decreased proportionally to insulin infusion rate (0.003 mM per percent above basal rate, 95% CI: 0.001-0.006, P = 0.003). The AUC for Rd rose by 1.26 mM during RE (95% CI: 0.41-2.10, P = 0.004) and increased proportionally with insulin infusion rate (0.04 mM per percent above basal rate, CI: 0.03-0.04, P < 0.001). No differences were observed between the moderate and high resistance groups. Noninsulin-mediated glucose utilization rose significantly during exercise before returning to baseline roughly 30-min postexercise. Insulin-mediated glucose utilization remained unchanged during exercise sessions. Circulating catecholamines and lactate rose during exercise despite relatively small changes observed in Rd. Results provide an explanation of why RE may pose a lower overall risk for hypoglycemia.NEW & NOTEWORTHY Aerobic exercise is known to cause decreases in blood glucose secondary to increased glucose utilization in people living with type 1 diabetes (T1D). However, less is known about how resistance-type exercise impacts glucose dynamics. Twenty-five participants with T1D performed in-clinic weight-bearing exercises under a glucose clamp. Mathematical modeling of infused glucose tracer allowed for quantification of the rate of hepatic glucose production as well as rates of insulin-mediated and noninsulin-mediated glucose uptake experienced during resistance exercise.

Bone morphogenetic protein-9 maybe an important factor which improves insulin resistance in PCOS

Background Polycystic ovary syndrome (PCOS) is closely related to insulin resistance (IR). Bone morphogenetic protein-9 (BMP-9) plays an important role in maintaining glucose homeostasis, but an association between BMP-9 and PCOS has not been reported. Here, we report the changes in BMP-9 and the influence of this protein on IR in PCOS. Methods 57 PCOS patients were selected (among them 25 received interventional treatment with exenatide (EX) for 3 months, and 32 received no treatment). 22 normal control individuals and 30 IR patients were also recruited. We evaluated IR with the euglycaemic-hyperinsulinaemic clamp (EHC) technique. IR and the glucose metabolism rate were assessed by EHC and [3-3H]glucose tracer experiments. We determined the protein expression levels of BMP-9, p-AKT (protein kinase B) and androgen receptor in the ovaries and liver by Western blotting. Results We found that circulating BMP-9 levels were significantly decreased in PCOS with IR patients. Circulating BMP-9 levels and p-AKT levels were decreased in HFD and PCOS rats and increased after MF and EX treatment. The glucose infusion rate, glucose disappearance rate and suppression of hepatic glucose production decreased in the HFD and PCOS groups, the opposite results were found for HGP. AR protein expression levels increased in the HFD and PCOS groups and decreased in the MF and EX groups. Conclusions Our study results suggest that BMP-9 is an independent factor that influences IR in PCOS patients. The decrease in BMP-9 levels in the liver and ovaries may be involved in IR through the PI3K/AKT signaling pathway in PCOS rats.

Evaluation of Hepatic Glucose Production in a Polycystic Ovary Syndrome Mouse Model.

Polycystic ovary syndrome (PCOS) is a common disease that results in disorders of glucose metabolism, such as insulin resistance and glucose intolerance. Dysregulated glucose metabolism is an important manifestation of the disease and is the key to its pathogenesis. Therefore, studies involving evaluation of glucose metabolism in PCOS are of utmost importance. Very few studies have quantified hepatic glucose production directly in PCOS models using non-radioactive glucose tracers. In this study, we discuss step-by-step instructions for the quantification of the rate of hepatic glucose production in a PCOS mouse model by measuring M+2 enrichment of [6,6-2H2]glucose, a stable isotopic glucose tracer, via gas chromatography - mass spectrometry (GCMS). This procedure involves creation of stable isotopic glucose tracer solution, use of tail vein catheter placement and infusion of the glucose tracer in both fasting and glucose-rich states in the same mouse in tandem. The enrichment of [6,6-2H2]glucose is measured using pentaacetate derivative in GCMS. This technique can be applied to a wide variety of studies involving direct measurement of the rate of hepatic glucose production.

Analysis of Insulin Resistance in Nonalcoholic Steatohepatitis.

Insulin resistance is a major phenotype observed in nonalcoholic steatohepatitis (NASH), the advanced stage of nonalcoholic fatty liver disease (NAFLD). Insulin resistance in NASH is characterized by reductions in whole body, hepatic, and adipose tissue insulin sensitivity. The mechanisms underlying hepatic insulin resistance is primarily associated with hepatic glucose production (HGP) rate. Hepatic insulin resistance can also be a consequence or a driving factor of hepatic lipid accumulation by increasing free fatty acid synthesis, delivery, and catabolism. The common method to assess hepatic insulin resistance is to measure hepatic glucose production (HGP) using isotope tracer distribution technique. However, non-radioactive approaches have been developed to assess hepatic insulin resistance in the context of NASH. In this chapter, we describe themethods to evaluate hepatic insulin resistance in animal models of NASH by examining insulin sensitivity and glucose tolerance as well as the key molecules in hepatic insulin signaling pathways.

Exercise-Induced Improvements to Whole Body Glucose Metabolism in Type 2 Diabetes: The Essential Role of the Liver.

Type 2 diabetes (T2D) is a metabolic disease characterized by obesity, insulin resistance, and the dysfunction of several key glucoregulatory organs. Among these organs, impaired liver function is recognized as one of the earliest contributors to impaired whole-body glucose homeostasis, with well-characterized hepatic insulin resistance resulting in elevated rates of hepatic glucose production (HGP) and fasting hyperglycemia. One portion of this review will provide an overview of how HGP is regulated during the fasted state in healthy humans and how this process becomes dysregulated in patients with T2D. Less well-appreciated is the liver's role in post-prandial glucose metabolism, where it takes up and metabolizes one-third of orally ingested glucose. An abundance of literature has shown that the process of hepatic glucose uptake is impaired in patients with T2D, thereby contributing to glucose intolerance. A second portion of this review will outline how hepatic glucose uptake is regulated during the post-prandial state, and how it becomes dysfunctional in patients with T2D. Finally, it is well-known that exercise training has an insulin-sensitizing effect on the liver, which contributes to improved whole-body glucose metabolism in patients with T2D, thereby making it a cornerstone in the management of the disease. To this end, the impact of exercise on hepatic glucose metabolism will be thoroughly discussed, referencing key findings in the literature. At the same time, sources of heterogeneity that contribute to inconsistent findings in the field will be pointed out, as will important topics for future investigation.

Mild sustained physiological hyperglycemia impairs hepatic insulin sensitivity in healthy individuals with normal glucose tolerance

Previous studies have shown that chronic hyperglycemia exacerbates skeletal muscle insulin resistance and worsens β-cell function. However, the effect of sustained physiologic hyperglycemia on hepatic insulin sensitivity stays unclear. This paper is the Chinese translation of Mild physiologic hyperglycemia induces hepatic insulin resistance in healthy normal glucose-tolerant participants , published on Journal of Clinical Endocrinology & Metabolism [Tripathy D, Merovci A, Basu R, et al. J Clin Endocrinol Metab, 2019, 104(7): 2842-2850] after obtaining the copyright of the original journal. This study examined the effect of sustained physiologic hyperglycemia on endogenous glucose production(EGP) in 16 healthy individuals with three-step hyperinsulinemic euglycemic clamp. The results showed that sustained physiologic hyperglycemia for only 48 hours increased the rate of basal hepatic glucose production and induced hepatic insulin resistance in healthy persons with normal glucose tolerance, indicating the role of glucotoxicity in the increase of hepatic glucose production in type 2 diabetes. Key words: Hyperglycemia; Insulin resistance; Normal glucose tolerance

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.

1951-P: Prolonged (12-Hour) Glucagon Infusion Leads to Transient Elevation of Plasma Glucose but Sustained Elevation of Hepatic Glucose Production

Recently, novel non-glycemic effects of glucagon have been described. Although short-term glucagon infusion is well known to elevate plasma glucose levels, long-term effect of increased plasma glucagon on glucose and lipid metabolism is unclear. The aim of the present study was to evaluate the effect of 12-hour glucagon infusion on hepatic glucose production and lipid metabolism in healthy NGT individuals. 8 NGT subjects (5M/3F, age=35± 5 years, BMI = 24 ± 1 kg/m2, HbA1c 5.2± 0.1%) received an 2-hour (75gram) OGTT. On a different day subjects received a 12-hour (6PM to 6 AM) glucagon infusion (3ng/kg/minutes) with the measurement of hepatic glucose production (HGP) with 3-3H-glucose on the following morning from 6-10 AM. HGP in glucagon infused subjects was compared to values in 20 age/gender/weight matched NGT subjects studied after an overnight fast from 6-10 AM. Plasma glucose, insulin, C-peptide, glucagon, and FFA concentrations were obtained every 15 minutes during OGTT. Plasma glucagon concentrations increased from 40 ± 4 to 120 ± 34 pg/ml at 6 AM. Plasma glucose increased 2 hours after the start of infusion from 95 ± 6 to 111 ± 6 mg/dl (p&amp;lt;0.005); after 12 hours of glucagon infusion the plasma glucose concentration declined to the mean baseline levels. After 12-hour glucagon infusion (6 AM), plasma insulin and C-peptide were not significantly changed. Basal hepatic glucose production was significantly higher following prolonged (12-hour) glucagon infusion compared to NGT control subjects following 12-hour overnight fast (3.1 ± 0.1 vs. 2.2 ± 0.2 mg/kg/minutes, p&amp;lt;0.05). Plasma FFA concentrations did not change following 12-hour glucagon infusion (0.629±0.1 vs. 0.670±0.2mml/l, p=ns). Thus 12-hour glucagon infusion led to higher basal rate of HGP, but unchanged plasma FFA levels. These results demonstrate that prolonged physiologic hyperglucagonemia results in a transient elevation of plasma glucose concentration but sustained increase in hepatic glucose production. Disclosure X. Chen: None. A. Merovci: None. E. Case: None. R.A. DeFronzo: Advisory Panel; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Elcelyx Therapeutics, Inc., Intarcia Therapeutics, Inc., Janssen Pharmaceuticals, Inc., Novo Nordisk Inc. Research Support; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Janssen Pharmaceuticals, Inc., Merck &amp; Co., Inc. Speaker's Bureau; Self; AstraZeneca, Novo Nordisk Inc. D. Tripathy: None.

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.

Mild Physiologic Hyperglycemia Induces Hepatic Insulin Resistance in Healthy Normal Glucose-Tolerant Participants.

Chronic hyperglycemia worsens skeletal muscle insulin resistance and β-cell function. However, the effect of sustained physiologic hyperglycemia on hepatic insulin sensitivity is not clear. To examine the effect of sustained physiologic hyperglycemia (similar to that observed in patients with type 2 diabetes) on endogenous (primarily reflecting hepatic) glucose production (EGP) in healthy individuals. Volunteers participated in a three-step hyperinsulinemic (10, 20, 40 mU/m2 per minute) euglycemic clamp before and after a 48-hour glucose infusion to increase plasma glucose concentration by ∼40 mg/dL above baseline. EGP was measured with 3-3H-glucose before and after chronic glucose infusion. Sixteen persons with normal glucose tolerance [eight with and eight without a family history (FH) of diabetes] participated in the study. EGP. Basal EGP increased following 48 hours of glucose infusion (from a mean ± SEM of 2.04 ± 0.08 to 3.06 ± 0.29 mg/kgffm⋅ min; P < 0.005). The hepatic insulin resistance index (basal EGP × fasting plasma insulin) markedly increased following glucose infusion (20.1 ± 1.8 to 51.7 ± 6.6; P < 0.005) in both FH+ and FH- subjects. Sustained physiologic hyperglycemia for as little as 48 hours increased the rate of basal hepatic glucose production and induced hepatic insulin resistance in health persons with normal glucose tolerance, providing evidence for the role of glucotoxicity in the increase in hepatic glucose production in type 2 diabetes.

Dehydration and insulinopenia are necessary and sufficient for\xa0euglycemic ketoacidosis in SGLT2 inhibitor-treated rats

Sodium-glucose transport protein 2 (SGLT2) inhibitors are a class of anti-diabetic agents; however, concerns have been raised about their potential to induce euglycemic ketoacidosis and to increase both glucose production and glucagon secretion. The mechanisms behind these alterations are unknown. Here we show that the SGLT2 inhibitor (SGLT2i) dapagliflozin promotes ketoacidosis in both healthy and type 2 diabetic rats in the setting of insulinopenia through increased plasma catecholamine and corticosterone concentrations secondary to volume depletion. These derangements increase white adipose tissue (WAT) lipolysis and hepatic acetyl-CoA content, rates of hepatic glucose production, and hepatic ketogenesis. Treatment with a loop diuretic, furosemide, under insulinopenic conditions replicates the effect of dapagliflozin and causes ketoacidosis. Furthermore, the effects of SGLT2 inhibition to promote ketoacidosis are independent from hyperglucagonemia. Taken together these data in rats identify the combination of insulinopenia and dehydration as a potential target to prevent euglycemic ketoacidosis associated with SGLT2i.

Mechanism by Which Dapagliflozin Induces Euglycemic Ketoacidosis in Rats

Sodium-glucose transport protein 2 inhibitors (SGLT2i) are the most recent class of antidiabetic agents; however concerns have been raised about their potential to induce euglycemic ketoacidosis by an unknown mechanism. Here we report that dapagliflozin increases rates of hepatic ketogenesis (35±4 vs. 136±8 μmol/[kg-min], p&amp;lt;0.0001) in normal Sprague-Dawley rats by increasing plasma catecholamine (epinephrine 0.5±0.1 vs. 7.3±0.5 nM, p&amp;lt;0.001, norepinephrine 2.5±0.5 vs. 19.8±5.2 nM, p&amp;lt;0.01) and corticosterone (115±15 vs. 233±28 ng/mL, p&amp;lt;0.01) concentrations secondary to volume depletion (weight change -1.9±0.4% vs. -7.1±0.4%), thereby increasing white adipose tissue lipolysis, hepatic acetyl-CoA content, hepatic glucose production and hepatic ketogenesis. Dapagliflozin-induced reductions in plasma insulin concentrations were shown to be necessary but not sufficient to induce these changes since the effects of dapagliflozin to increase hepatic ketogenesis were abrogated when extracellular volume depletion was prevented with saline infusion or free access to water. Furosemide treatment induced similar volume depletion and increases in plasma catecholamine and corticosterone concentrations without any associated changes in WAT lipolysis, hepatic glucose production or hepatic ketogenesis, likely due to its lack of an effect on plasma insulin levels. Furthermore the effects of dapagliflozin to promote increased rates of hepatic ketogenesis and hepatic glucose production were dissociated from changes in plasma glucagon concentrations, which increased (89.5±3.8 vs. 379.2±11.8 ng/mL, p&amp;lt;0.0001) through a central mechanism following ICV injection of dapagliflozin without any alterations in body weight or ketosis, and hepatic malonyl-CoA. Taken together these data identify SGLT2i-induced dehydration as a potential target to prevent SGLT2i-induced euglycemic ketoacidosis. Disclosure R.J. Perry: None.J.D. Song: None.Y. Wang: None. G.I. Shulman: Advisory Panel; Self; AstraZeneca, Janssen Research &amp; Development, Merck &amp; Co., Inc., Novo Nordisk Inc.. Research Support; Self; Gilead Sciences, Inc..

Effect of fibre additions to flatbread flour mixes on glucose kinetics: a randomised controlled trial.

We previously found that guar gum (GG) and chickpea flour (CPF) added to flatbread wheat flour lowered postprandial blood glucose (PPG) and insulin responses dose dependently. However, rates of glucose influx cannot be determined from PPG, which integrates rates of influx, tissue disposal and hepatic glucose production. The objective was to quantify rates of glucose influx and related fluxes as contributors to changes in PPG with GG and CPF additions to wheat-based flatbreads. In a randomised cross-over design, twelve healthy males consumed each of three different 13C-enriched meals: control flatbreads (C), or C incorporating 15 % CPF with either 2 % (GG2) or 4 % (GG4) GG. A dual isotope technique was used to determine the time to reach 50 % absorption of exogenous glucose (T 50 %abs, primary objective), rate of appearance of exogenous glucose (RaE), rate of appearance of total glucose (RaT), endogenous glucose production (EGP) and rate of disappearance of total glucose (RdT). Additional exploratory outcomes included PPG, insulin, glucose-dependent insulinotropic peptide and glucagon-like peptide 1, which were additionally measured over 4 h. Compared with C, GG2 and GG4 had no significant effect on T 50 %abs. However, GG4 significantly reduced 4-h AUC values for RaE, RaT, RdT and EGP, by 11, 14, 14 and 64 %, respectively, whereas GG2 showed minor effects. Effect sizes over 2 and 4 h were similar except for significantly greater reduction in EGP for GG4 at 2 h. In conclusion, a soluble fibre mix added to flatbreads only slightly reduced rates of glucose influx, but more substantially affected rates of postprandial disposal and hepatic glucose production.

Deletion of interleukin 1 receptor-associated kinase 1 (Irak1) improves glucose tolerance primarily by increasing insulin sensitivity in skeletal muscle

Chronic inflammation may contribute to insulin resistance via molecular cross-talk between pathways for pro-inflammatory and insulin signaling. Interleukin 1 receptor-associated kinase 1 (IRAK-1) mediates pro-inflammatory signaling via IL-1 receptor/Toll-like receptors, which may contribute to insulin resistance, but this hypothesis is untested. Here, we used male Irak1 null (k/o) mice to investigate the metabolic role of IRAK-1. C57BL/6 wild-type (WT) and k/o mice had comparable body weights on low-fat and high-fat diets (LFD and HFD, respectively). After 12 weeks on LFD (but not HFD), k/o mice (versus WT) had substantially improved glucose tolerance (assessed by the intraperitoneal glucose tolerance test (IPGTT)). As assessed with the hyperinsulinemic euglycemic glucose clamp technique, insulin sensitivity was 30% higher in the Irak1 k/o mice on chow diet, but the Irak1 deletion did not affect IPGTT outcomes in mice on HFD, suggesting that the deletion did not overcome the impact of obesity on glucose tolerance. Moreover, insulin-stimulated glucose-disposal rates were higher in the k/o mice, but we detected no significant difference in hepatic glucose production rates (± insulin infusion). Positron emission/computed tomography scans indicated higher insulin-stimulated glucose uptake in muscle, but not liver, in Irak1 k/o mice in vivo Moreover, insulin-stimulated phosphorylation of Akt was higher in muscle, but not in liver, from Irak1 k/o mice ex vivo In conclusion, Irak1 deletion improved muscle insulin sensitivity, with the effect being most apparent in LFD mice.

Maternal rates of lipolysis and glucose production in late pregnancy are independently related to foetal weight.

Associations between maternal glucose levels and increased foetal growth are well established, and independent relationships with maternal weight, weight gain and insulin resistance are also observed. The relative roles of lipolysis and glucose production in the determination of these observations remain unclear. We examined, through detailed physiological studies, the relationship between maternal late gestational energy substrate production (glucose and glycerol), maternal weight and weight gain, and estimated foetal size in the third trimester. Twenty-one nulliparous pregnant women, without gestational diabetes (GDM) assessed at 28weeks with oral glucose tolerance test, were recruited. Rates of hepatic glucose production (GPR) and rates of glycerol production (reflecting lipolysis) using [13 C6 ]-glucose and [2 H5 ]-glycerol were measured at 34-36weeks of gestation. Respiratory quotient was assessed by indirect calorimetry and body composition by measurements of total body water (TBW; H218 O) and body density (BODPOD). Foetal weight was estimated from ultrasound measures of biparietal diameter, femoral length and abdominal circumference. At 34-36weeks, bivariate analyses showed that GPR and lipolysis correlated with estimated foetal weight (r=.71 and .72, respectively) as well as with maternal weight, fat mass and fat-free mass, but not maternal weight gain. In multivariate analyses, rates of both glucose production (r=.42) and lipolysis (r=.47) were independently associated with foetal size explaining 63% of the variance. Both maternal rates of lipolysis and hepatic glucose production in late gestation are strongly related to estimated foetal weight.

Decreased basal hepatic glucose uptake in impaired fasting glucose.

This research aimed to define the pathophysiological defects responsible for the elevated fasting plasma glucose (FPG) concentration and excessive rise in post-load plasma glucose observed in individuals with impaired fasting glucose (IFG). We used tracer techniques to quantify basal splanchnic (primarily hepatic) glucose uptake and glucose fluxes following glucose ingestion in individuals with normal glucose tolerance (NGT; n=10) and IFG (n=10). Individuals with IFG had a comparable basal rate of hepatic glucose production to those with NGT (15.2±0.2 vs 18.0±0.8μmolmin-1[kg lean body mass (LBM)]-1; p=0.09). However, they had a significantly reduced glucose clearance rate during the fasting state compared with NGT (2.64±0.11 vs 3.62±0.20ml min-1[kgLBM]-1; p<0.01). The difference between the basal rate of glucose appearance measured with [3-3H]glucose and [1-14C]glucose, which represent basal splanchnic glucose uptake, was significantly reduced in IFG compared with NGT (1.39±0.28 vs 3.16±0.44μmolmin-1[kgLBM]-1; p=0.02). Following glucose ingestion, the total amount of exogenous glucose that appeared in the systemic circulation was not significantly different between groups. However, suppression of endogenous glucose production (EGP) was markedly impaired in individuals with IFG. These results demonstrate that decreased tissue (liver) glucose uptake, not enhanced EGP, is the cause for elevated FPG concentration in individuals with IFG, while the excessive rise in plasma glucose concentration following a glucose load in these individuals is the result of impaired suppression of hepatic glucose production.

Mechanism for leptin's acute insulin-independent effect to reverse diabetic ketoacidosis.

The mechanism by which leptin reverses diabetic ketoacidosis (DKA) is unknown. We examined the acute insulin-independent effects of leptin replacement therapy in a streptozotocin-induced rat model of DKA. Leptin infusion reduced rates of lipolysis, hepatic glucose production (HGP), and hepatic ketogenesis by 50% within 6 hours and were independent of any changes in plasma glucagon concentrations; these effects were abrogated by coinfusion of corticosterone. Treating leptin- and corticosterone-infused rats with an adipose triglyceride lipase inhibitor blocked corticosterone-induced increases in plasma glucose concentrations and rates of HGP and ketogenesis. Similarly, adrenalectomized type 1 diabetic (T1D) rats exhibited decreased rates of lipolysis, HGP, and ketogenesis; these effects were reversed by corticosterone infusion. Leptin-induced decreases in lipolysis, HGP, and ketogenesis in DKA were also nullified by relatively small increases (15 to 70 pM) in plasma insulin concentrations. In contrast, the chronic glucose-lowering effect of leptin in a STZ-induced mouse model of poorly controlled T1D was associated with decreased food intake, reduced plasma glucagon and corticosterone concentrations, and decreased ectopic lipid (triacylglycerol/diacylglycerol) content in liver and muscle. Collectively, these studies demonstrate marked differences in the acute insulin-independent effects by which leptin reverses fasting hyperglycemia and ketoacidosis in a rodent model of DKA versus the chronic pleotropic effects by which leptin reverses hyperglycemia in a non-DKA rodent model of T1D.