Suppression Of Endogenous Glucose Production Research Articles

The effect of small increases in blood glucose on insulin secretion and endogenous glucose production in humans.

Small glycemic increments (≤0.5 mmol/L) can exert suppressive actions on endogenous glucose production (EGP) however it is unclear if this is an insulin dependent or independent process. Here, we performed a low-rate glucose infusion in control participants without diabetes and in people with type 1 diabetes (T1D) to better understand this phenomenon. Glucose kinetics, hormones and metabolites were measured during a 1 mg/kg/min glucose infusion (90 min) which rapidly increased glucose by ∼0.3 mmol/L in control participants. Insulin concentrations and secretion quickly increased by ∼20%, resulting in a ∼40% suppression of EGP, while glucose disposal remained unchanged. Free fatty acids (FFA) and glucagon were gradually suppressed to ∼30% below baseline at 60 min. When repeated under constant basal insulin concentrations in participants with T1D, glucose infusion caused only partial and transient EGP suppression, hence glucose increased in a near-linear manner, reaching levels ∼2 mmol/L above baseline at 90 min. FFAs and glucagon remained unchanged, while glucose disposal modestly increased. This demonstrates that small glycemic increments exert subtle stimulatory effects on insulin secretion that have potent metabolic actions on the liver and adipose tissue. It is conceivable that subtle increases in glucose could potentially serve as a signal for β-cell adaptation.

In vivo mapping of postprandial hepatic glucose metabolism using dynamic magnetic resonance spectroscopy combined with stable isotope flux analysis in Roux-en-Y gastric bypass adults and non-operated controls: A case-control study.

Roux-en-Y gastric bypass (RYGB) surgery alters postprandial glucose profiles, causing post-bariatric hypoglycaemia (PBH) in some individuals. Due to the liver's central role in glucose homeostasis, hepatic glucose handling might differ in RYGB-operated patients with PBH compared to non-operated healthy controls (HC). We enrolled RYGB-operated adults with PBH and HCs (n = 10 each). Participants ingested 60 g of [6,6'-2H2]-glucose (d-glucose) after an overnight fast. Deuterium metabolic imaging (DMI) with interleaved 13C magnetic resonance spectroscopy was performed before and until 150 min post-d-glucose intake, with frequent blood sampling to quantify glucose enrichment and gluco-regulatory hormones until 180 min. Glucose fluxes were assessed by mathematical modelling. Outcome trajectories were described using generalized additive models. In RYGB subjects, the hepatic d-glucose signal increased early, followed by a decrease, whereas HCs exhibited a gradual increase and consecutive stabilization. Postprandial hepatic glycogen accumulation and the suppression of endogenous glucose production were lower in RYGB patients than in HCs, despite higher insulin exposure, indicating lower hepatic insulin sensitivity. The systemic rate of ingested d-glucose was faster in RYGB, leading to a higher, earlier plasma glucose peak and increased insulin secretion. Postprandial glucose disposal increased in RYGB patients, without between-group differences in peripheral insulin sensitivity. Exploiting DMI with stable isotope flux analysis, we observed distinct postprandial hepatic glucose trajectories and parameters of glucose-insulin homeostasis in RYGB patients with PBH versus HCs. Despite altered postprandial glucose kinetics and higher insulin exposure, there was no evidence of impaired hepatic glucose uptake or output predisposing to PBH in RYGB patients.

The deuterated glucose insulin tolerance test: a new tool to delineate insulin-stimulated glucose uptake from suppression of endogenous glucose production

The deuterated glucose insulin tolerance test: a new tool to delineate insulin-stimulated glucose uptake from suppression of endogenous glucose production

A 3-Week Ketogenic Diet Increases Skeletal Muscle Insulin Sensitivity in Individuals With Obesity: A Randomized Controlled Crossover Trial.

A ketogenic diet (KD) can induce weight loss and improve glycemic regulation, potentially reducing the risk of developing type 2 diabetes. To elucidate the underlying mechanisms behind these beneficial effects of a KD, we investigated the impact of a KD on organ-specific insulin sensitivity (IS) in skeletal muscle, liver, and adipose tissue. We hypothesized that a KD would increase IS in skeletal muscle. The study included 11 individuals with obesity who underwent a randomized, crossover trial with two three-week interventions: 1) KD and 2) standard diet. Skeletal muscle IS was quantified as the increase in glucose disposal during a hyperinsulinemic-euglycemic clamp (HEC). Hepatic IS and adipose tissue IS were quantified as the relative suppression of endogenous glucose production (EGP) and the relative suppression of palmitate flux during the HEC. The KD led to a 2.2 kg weight loss, increased insulin-stimulated glucose disposal, whereas the relative suppression of EGP during the HEC was similar. In addition, the KD decreased insulin-mediated suppression of lipolysis. In conclusion, a KD increased skeletal muscle IS in individuals with obesity.

β-Cell Function, Incretin Effect, and Glucose Kinetics in Response to a Mixed Meal in Patients With Type 2 Diabetes Treated With Dapagliflozin Plus Saxagliptin.

To explore the complementary effects of a combination of dipeptidyl peptidase 4 and sodium-glucose cotransporter 2 inhibitors added to metformin on hormonal and metabolic responses to meal ingestion. Forty-five patients (age 58 ± 8 years; HbA1c 58 ± 6 mmol/mol; BMI 30.7 ± 3.2 kg/m2) with type 2 diabetes uncontrolled with metformin were evaluated at baseline and 3 and 28 days after 5 mg saxagliptin (SAXA), 10 mg dapagliflozin (DAPA), or 5 mg saxagliptin plus 10 mg dapagliflozin (SAXA+DAPA) using a mixed-meal tolerance test (MMTT) spiked with dual-tracer glucose to assess glucose metabolism, insulin secretion, and sensitivity. At day 3, fasting and mean MMTT glucose levels were lower with SAXA+DAPA (-31.1 ± 1.6 and -91.5 ± 12.4 mg/dL) than with SAXA (-7.1 ± 2.1 and -53 ± 10.5 mg/dL) or DAPA (-17.0 ± 1.1 and -42.6 ± 10.0 mg/dL, respectively; P < 0.001). Insulin secretion rate (SAXA+DAPA +75%; SAXA +11%; DAPA +3%) and insulin sensitivity (+2.2 ± 1.7, +0.4 ± 0.7, and +0.4 ± 0.4 mg ⋅ kg-1⋅ min-1, respectively) improved with SAXA+DAPA (P < 0.007). Mean glucagon-like peptide 1 (GLP-1) was higher with SAXA+DAPA than with SAXA or DAPA. Fasting glucagon increased with DAPA and SAXA+DAPA but not with SAXA. Fasting endogenous glucose production (EGP) increased with SAXA+DAPA and DAPA. During MMTT, EGP suppression was greater (48%) with SAXA+DAPA (vs. SAXA 44%; P = 0.02 or DAPA 34%; P = 0.2). Metabolic clearance rate of glucose (MCRglu) increased more with SAXA+DAPA. At week 4, insulin secretion rate, β-cell glucose sensitivity, and insulin sensitivity had further increased in the SAXA+DAPA group (P = 0.02), with no additional changes in GLP-1, glucagon, fasting or MMTT EGP, or MCRglu. SAXA+DAPA provided superior glycemic control compared with DAPA or SAXA, with improved β-cell function, insulin sensitivity, GLP-1 availability, and glucose clearance.

Glucagon-like peptide-1 receptor blockade impairs islet secretion and glucose metabolism in humans.

BACKGROUNDProglucagon can be processed to glucagon-like peptide1 (GLP-1) within the islet, but its contribution to islet function in humans remains unknown. We sought to understand whether pancreatic GLP-1 alters islet function in humans and whether this is affected by type 2 diabetes.METHODSWe therefore studied individuals with and without type 2 diabetes on two occasions in random order. On one occasion, exendin 9-39, a competitive antagonist of the GLP-1 Receptor (GLP1R), was infused, while on the other, saline was infused. The tracer dilution technique ([3-3H] glucose) was used to measure glucose turnover during fasting and during a hyperglycemic clamp.RESULTSExendin 9-39 increased fasting glucose concentrations; fasting islet hormone concentrations were unchanged, but inappropriate for the higher fasting glucose observed. In people with type 2 diabetes, fasting glucagon concentrations were markedly elevated and persisted despite hyperglycemia. This impaired suppression of endogenous glucose production by hyperglycemia.CONCLUSIONThese data show that GLP1R blockade impairs islet function, implying that intra-islet GLP1R activation alters islet responses to glucose and does so to a greater degree in people with type 2 diabetes.TRIAL REGISTRATIONThis study was registered at ClinicalTrials.gov NCT04466618.FUNDINGThe study was primarily funded by NIH NIDDK DK126206. AV is supported by DK78646, DK116231 and DK126206. CDM was supported by MIUR (Italian Minister for Education) under the initiative "Departments of Excellence" (Law 232/2016).

GDF15 increases insulin action in the liver and adipose tissue via a β-adrenergic receptor-mediated mechanism

Growth differentiation factor 15 (GDF15) induces weight loss and increases insulin action in obese rodents. Whether and how GDF15 improves insulin action without weight loss is unknown. Obese rats were treated with GDF15 and displayed increased insulin tolerance 5h later. Lean and obese female and male mice were treated with GDF15 on days 1, 3, and 5 without weight loss and displayed increased insulin sensitivity during a euglycemic hyperinsulinemic clamp on day 6 due to enhanced suppression of endogenous glucose production and increased glucose uptake in WAT and BAT. GDF15 also reduced glucagon levels during clamp independently of the GFRAL receptor. The insulin-sensitizing effect of GDF15 was completely abrogated in GFRAL KO mice and also by treatment with the β-adrenergic antagonist propranolol and in β1,β2-adrenergic receptor KO mice. GDF15 activation of the GFRAL receptor increases β-adrenergic signaling, in turn, improving insulin action in the liver and white and brown adipose tissue.

1579-P: Impact of Adipose Tissue Insulin Sensitivity on Hepatic Insulin Sensitivity Preservation in Longitudinal Observation of Patients with NAFLD

Hepatic insulin resistance associated with NAFLD is a major pathogenesis of type 2 diabetes and its complications. In addition to reducing lipids in the liver, identifying the factors that may preserve hepatic insulin sensitivity (H-IS) is crucial. In this study, we investigated the factors that may preserve H-IS in patients with NAFLD in longitudinal observations. Comprehensively, putative biomarkers in blood and urine, body composition, tissue-specific lipid accumulation and insulin sensitivity by 1H-MRS and hyperinsulinemic euglycemic clamp, respectively, and pathological diagnosis using liver biopsy were assessed in patients with NAFLD (n=62) at baseline. After more than one year of general treatment, consented 36 patients (average age 51.3±11.2, men n=21, diabetes n=23) were subjected to the same assessment as baseline. To investigate the indices associated with H-IS, all indices were compared between upper and lower one third patients of Δ% suppression of endogenous glucose production (EGP) (+11.5±4.0 vs. -10.9±5.1%, respectively). As results, body weight, fasting plasma glucose, HbA1c, muscle and adipose tissue insulin sensitivity, visceral fat, and adiponectin levels were significantly improved in improved H-IS group. Interestingly, Δhepatic lipid content or fibrosis index was not different between the improved and worsened H-IS groups. Furthermore, simple regression analysis with Δ% suppression of EGP and all indices revealed that Δ% suppression of free fatty acid, visceral fat area, and adiponectin levels were significantly associated with Δ% suppression of EGP. Multiple regression analysis with Δ% suppression of EGP and these three indices showed that only Δ% suppression of free fatty acid significantly associated with Δ% suppression of EGP. Taken together, not only lipid volume but also the quality of accumulated lipid is important to preserve hepatic insulin sensitivity in patients with NAFLD. Disclosure F.Shigiyama: None. S.Hiruma: None. N.Kumashiro: Research Support; Terumo Corporation, LifeScan Diabetes Institute, Sumitomo Dainippon Pharma Co., Ltd., Speaker's Bureau; Daiichi Sankyo, Novo Nordisk.

1547-P: The Differential Effect of Glucagon-Like Peptide-1 Receptor Blockade on Glucose Metabolism in People With and Without Type 2 Diabetes

Glucagon-Like Peptide-1 (GLP-1) is present within the islet but the effects of GLP-1 Receptor (GLP1R) blockade on islet function in humans remains unknown. To address this, we studied 12 nondiabetic individuals (54 ± 2 years, 33 ± 1 kg/m2) and 11 people with type 2 diabetes (DM2 - 58 ± 2 years, 34 ± 2 kg/m2) on 2 occasions in random order. On each occasion, after an overnight fast, [3-3H] glucose was used to measure glucose turnover during fasting and a hyperglycemic clamp (~9 mmol/l) using the tracer dilution technique. On one occasion exendin-9,39 (300pmol/kg/min) was infused to block GLP1R, while on the other saline was infused. Exendin-9,39 increased fasting glucose concentrations in those without (4.6 ± 0.4 vs. 5.5 ± 0.1 mmol/l, saline vs. exendin-9,39 respectively, p = 0.04) and in those with DM2 (7.3 ± 0.5 vs. 8.3 ± 0.6 mmol/l, p = 0.03). Fasting islet hormone concentrations were unchanged, but inappropriate for the higher fasting glucose observed during exendin-9,39 infusion. The same pattern was seen in people with DM2 except that fasting glucagon concentrations increased (8.3 ± 0.5 vs. 10.2 ± 0.6 pmol/l, p &amp;lt; 0.01) and remained elevated throughout hyperglycemia (4.7 ± 0.4 vs. 7.7 ± 0.6 pmol/l, p &amp;lt; 0.02). Insulin secretion rate calculated by deconvolution of C-peptide concentrations was also decreased in DM2 (0.54 ± 0.08 vs. 0.51 ± 0.08 nmol/min, p = 0.02). Consequently, suppression of endogenous glucose production by hyperglycemia was impaired in people with DM2 (2.9 ± 0.4 vs. 5.7 ± 0.3 μmol/kg/min, p &amp;lt; 0.01). Intriguingly, 1st phase response to hyperglycemia was decreased in those without DM2 (3.5 ± 0.6 vs. 2.5 ± 0.5 nmol per 10 min, p = 0.04). These data show that in humans, GLP1R blockade impairs fasting α- and β-cell function resulting in fasting hyperglycemia. Subtle effects are also present in response to hyperglycemia. This implies that intra-islet GLP1R activation sustains islet responses to glucose and it does so to a greater degree in people with DM2. Disclosure A.A. Welch: None. R.A. Farahani: None. M. Zeini: None. A.M. Egan: None. M.C. Laurenti: None. C. Cobelli: None. C. Dalla Man: Research Support; Sanofi-Aventis Deutschland GmbH, Becton, Dickinson and Company. A. Vella: Other Relationship; Novo Nordisk. Advisory Panel; Rezolute, Inc. Consultant; Crinetics Pharmaceuticals, Inc., Hanmi Pharm. Co., Ltd., Zealand Pharma A/S. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK126206)

1649-P: Biased GLP-1 Improves Weight Loss with Additional Benefits on Glucose Homeostasis via Biased GIP in Diabetic Rodent Models

GLP-1 and GIP when combined can deliver complementary pharmacology. CT-868 (CT) and CT-859 are biased dual GLP-1 and GIP receptor modulators with no β-arrestin coupling on either receptor. Effect of both compounds on weight loss (WL) and glucose (GLUC) homeostasis were assessed in relevant rodent models. At non-GIPR engaging doses in ob/ob mice, 30 nmol/kg CT achieved greater WL vs 200 nmol/kg Liraglutide (LI), an unbiased GLP-1RA (19.8% vs 11.5%, p=0.002), indicating biased GLP-1 improves WL vs unbiased GLP-1. GLUC tolerance test (GTT) in GIPR-/- mice showed similar reduction in AUCGLUC with LI and CT-859 at 20 nmol/kg 4h after dosing (53% vs 62%, p=NS), but only CT-859 maintained significant reduction after 24h and 48h, indicating biased GLP-1 induces a sustained GLUC lowering effect. After 14d of dosing in Akita mice with non-GIPR engaging doses of CT 20 nmol/kg, blood glucose (BG) decreased 30% vs LI 20 nmol/kg (p=0.01) indicating superior effect of biased GLP-1 on glycemic control. At GIPR engaging doses, CT 200 nmol/kg on background of insulin (INS) significantly lowered BG vs LI 200nmol/kg in Akita (↓35%, p=0.009) and DIO-STZ (↓32%, p&amp;lt;0.0001) mice. Akita mice treated for 14d with CT 300 nmol/kg + low INS normalized BG to same extent as vehicle + high INS, but with 68% lower INS levels (p &amp;lt; 0.0001). In GLP-1R-/- mice, CT 300 nmol/kg lowered AUCGLUC 38% vs vehicle (p&amp;lt;0.0001) without concomitant INS excursion, showing that GIP enhances INS independent GLUC disposal or INS sensitivity. In response to pyruvate challenge, CT 100 nmol/kg suppressed AUCGLUC 36% (p&amp;lt;0.05) and 14% (p=0.006) on a background of INS treatment in Akita and GLP-1R-/- mice, respectively, suggesting GIPR activation may contribute to suppression of endogenous GLUC production. Together, these data demonstrate that CT provides improved WL via biased GLP-1 with enhanced GLUC homeostasis via biased GIP relative to unbiased GLP-1 (LI). These findings have translated to T2D patients treated with CT-868. Disclosure R.Rodriguez: Employee; Carmot Therapeutics, Inc. T.Tracy: Employee; Carmot Therapeutics, Inc. M.Morales: None. A.Hergarden: Employee; Carmot Therapeutics, Inc. D.Lam: Employee; Carmot Therapeutics, Inc. S.Krishnan: Employee; Carmot Therapeutics, Inc. S.K.Hansen: Board Member; Carmot Therapeutics, Inc. M.Chakravarthy: Employee; Carmot Therapeutics, Inc.

1559-P: Glucagon Receptor–Mediated Improvements in Glycemia Are Dependent on Agonist Pharmacodynamics

Glucagon is considered the main glucose counter-regulatory hormone to insulin. Although, chronic glucagon receptor (GCGR) agonism induces hyperglycemia and glucose intolerance, it also improves insulin secretion and action. Surprisingly, we found chronic treatment with the selective, long-acting GCGR agonist, IUB288, improves ad libitum glycemia and glucose tolerance 4h after treatment. These glycemic improvements were associated with enhanced AKT phosphorylation, despite control-like insulin levels. We next tested if these results could be replicated with a short acting GCGR agonist. IUB94 displays improved aqueous solubility but maintains the short half-life and potency of native glucagon. 4h glucose excursion was monitored in lean mice after injection of IUB288, IUB94, or vehicle. We observed a transient rise in blood glucose (BG) 15min after either IUB288 or IUB94 compared to vehicle. Intriguingly, IUB288-treated mice exhibited improved BG from 120-240min, while BG in IUB94-treated mice was similar to vehicle controls. These data suggest that acute BG regulation is agonist-dependent yet, it remains unclear if pharmacodynamics or some inherent difference in potency is influencing the 4h BG. We next treated lean mice for 4d with vehicle or IUB288, measuring ad libitum glycemia over the final 24h period. IUB288-treated mice displayed improved glycemia 4h after the last injection and hyperglycemia after 12h, compared to vehicle-treated controls, suggesting chronic GCGR agonism is not exclusively hyperglycemic. Surprisingly, 4d IUB288 treatment in diet-induced obese (DIO) mice reduced ad libitum glycemia for a longer duration than observed in chow IUB288-treated mice. IUB288 treatment also increased glucose infusion rate, suppression of endogenous glucose production, and AKT phosphorylation during hyperinsulinemic-euglycemic clamps. These data provide insight into the potential therapeutic use of sustained-acting GCGR agonists against diabetes and obesity. Disclosure S.Nason: None. T.Kim: None. J.Antipenko: None. B.Yang: None. R.Dimarchi: None. K.M.Habegger: Consultant; Glyscend Inc., Research Support; Eli Lilly and Company, Novo Nordisk, Glyscend Inc., Stock/Shareholder; Glyscend Inc. Funding National Institutes of Health

Hyperglycemia, pregnancy outcomes and maternal metabolic disease risk during pregnancy and lactation in a lean gestational diabetes mouse model.

Hyperglycemia in pregnancy (HIP) is a pregnancy complication characterized by mild to moderate hyperglycemia that negatively impacts short- and long-term health of mother and child. However, relationships between severity and timing of pregnancy hyperglycemia and postpartum outcomes have not been systemically investigated. We investigated the impact of hyperglycemia developing during pregnancy (gestational diabetes mellitus, GDM) or already present pre-mating (pre-gestational diabetes mellitus, PDM) on maternal health and pregnancy outcomes. GDM and PDM were induced in C57BL/6NTac mice by combined 60% high fat diet (HF) and low dose streptozotocin (STZ). Animals were screened for PDM prior to mating, all underwent an OGTT on gestational day (GD)15. Tissues were collected at GD18 or at postnatal day (PN)15. Among HFSTZ-treated dams, 34% developed PDM and 66% developed GDM, characterized by impaired glucose-induced insulin release and inadequate suppression of endogenous glucose production. No increased adiposity or overt insulin resistance was observed. Furthermore, markers of non-alcoholic fatty liver disease (NAFLD) were significantly increased in PDM at GD18 and were positively correlated with basal glucose levels at GD18 in GDM dams. By PN15, NAFLD markers were also increased in GDM dams. Only PDM affected pregnancy outcomes such as litter size. Our findings indicate that GDM and PDM, resulting in disturbances of maternal glucose homeostasis, increase the risk of postpartum NAFLD development, related to the onset and severity of pregnancy hyperglycemia. These findings signal a need for earlier monitoring of maternal glycemia and more rigorous follow-up of maternal health after GDM and PDM pregnancy in humans. KEY POINTS: We studied the impact of high-fat diet/streptozotocin induced hyperglycemia in pregnancy (HIP) in mice and found that this impaired glucose tolerance and insulin release. Litter size and embryo survival were compromised by pre-gestational, but not by gestational diabetes. Despite postpartum recovery from hyperglycemia in a majority of dams, liver disease markers were further elevated by PN15. Maternal liver disease markers were associated with the severity of hyperglycemia at GD18. The association between hyperglycemic exposure and NAFLD signal a need for more rigorous monitoring and follow-up of maternal glycemia and health in diabetic pregnancy in humans. Abstract figure legend Streptozotocin and high fat diet were used to induce GDM in female BL6/NTac mice. Pregnant dams underwent an OGTT at GD15 to confirm GDM diagnosis. By GD18, dams were hyperglycemic and showed a reduction in pancreatic beta cells. By PN15, dams additionally had developed an increase in NAFLD markers, despite the majority of the dams having recovered from hyperglycemia. This article is protected by copyright. All rights reserved.

Antipsychotics impair regulation of glucose metabolism by central glucose.

Hypothalamic detection of elevated circulating glucose triggers suppression of endogenous glucose production (EGP) to maintain glucose homeostasis. Antipsychotics alleviate symptoms associated with schizophrenia but also increase the risk for impaired glucose metabolism. In the current study, we examined whether two acutely administered antipsychotics from different drug classes, haloperidol (first generation antipsychotic) and olanzapine (second generation antipsychotic), affect the ability of intracerebroventricular (ICV) glucose infusion approximating postprandial levels to suppress EGP. The experimental protocol consisted of a pancreatic euglycemic clamp, followed by kinomic and RNA-seq analyses of hypothalamic samples to determine changes in serine/threonine kinase activity and gene expression, respectively. Both antipsychotics inhibited ICV glucose-mediated increases in glucose infusion rate during the clamp, a measure of whole-body glucose metabolism. Similarly, olanzapine and haloperidol blocked central glucose-induced suppression of EGP. ICV glucose stimulated the vascular endothelial growth factor (VEGF) pathway, phosphatidylinositol 3-kinase (PI3K) pathway, and kinases capable of activating KATP channels in the hypothalamus. These effects were inhibited by both antipsychotics. In conclusion, olanzapine and haloperidol impair central glucose sensing. Although results of hypothalamic analyses in our study do not prove causality, they are novel and provide the basis for a multitude of future studies.

197-OR: Glucagon Receptor Agonism Stimulates Time-Dependent Glycemic Regulation

Historically, glucagon is proposed to be a key factor in the development of diabetes. However, we demonstrated that while chronic glucagon receptor (GCGR) agonism induces hyperglycemia and glucose intolerance, it also improves insulin secretion and insulin action. These paradoxical actions suggest the mechanisms regulating GCGR-mediated glucose metabolism have yet to be fully elucidated. Glucose metabolism and glucagon-stimulated glucose production are both regulated in a circadian manner. Thus, we hypothesized that chronic GCGR signaling regulates glycemia in a time-of-day dependent manner. We treated lean mice for 4d with vehicle or the GCGR agonist IUB288 administered either during the early (ZT 3) or late (ZT9) light period. Ad libitum glycemia was assessed every 4h over a 24h period after the last injection. Independent of the time injected, IUB288-treated mice displayed improved glycemia 4h after the last injection and hyperglycemia after 12h, compared to vehicle-treated controls. This suggests that chronic GCGR agonism is not exclusively hyperglycemic and variations in GCGR-stimulated glycemia are dependent on the time after treatment, rather than the time of day. Interestingly, ad libitum insulin levels were no different between IUB288 and vehicle-treated mice, suggesting differences in insulin sensitivity. Surprisingly, 4d IUB288 treatment in diet-induced obese (DIO) mice reduced ad libitum glycemia for a greater duration than chow IUB288-treated mice. We used hyperinsulinemic-euglycemic clamps to further dissect the mechanisms of these benefits. In DIO mice, IUB288 treatment increased glucose infusion rate, suppression of endogenous glucose production, and phosphorylation of AKT (S473 and T308) . Together, these data increase our understanding of GCGR pharmacology and its therapeutic role in diabetes and obesity treatment. Disclosure S.Nason: None. T.Kim: None. J.P.Antipenko: None. B.Finan: Employee; Novo Nordisk. R.Dimarchi: None. K.M.Habegger: Consultant; Glyscend Inc., Research Support; Eli Lilly and Company, Novo Nordisk, Stock/Shareholder; Glyscend Inc. Funding T32 AI007051

The Effect of Diabetes-Associated Variation in TCF7L2 on Postprandial Glucose Metabolism When Glucagon and Insulin Concentrations Are Matched.

Background: The rs7903146 variant in the TCF7L2 gene is associated with defects in postprandial insulin and glucagon secretion and increased risk of type 2 diabetes. However, it is unclear if this variant has effects on glucose metabolism that are independent of islet function. Methods: We studied 54 nondiabetic subjects on two occasions where endogenous hormone secretion was inhibited by somatostatin. Twenty-nine subjects were homozygous for the diabetes-associated allele (TT) and 25 for the diabetes-protective allele (CC) at rs7903146, but otherwise matched for anthropometric characteristics. On 1 day, glucagon infused at a rate of 0.65 ng/kg/min, and at 0 min prevented a fall in glucagon (nonsuppressed day). On the contrary, infusion commenced at 120 min to create a transient fall in glucagon (suppressed day). Subjects received glucose (labeled with [3-3H]-glucose) infused to mimic the systemic appearance of oral glucose. Insulin was infused to mimic a prandial insulin response. Endogenous glucose production (EGP) was measured using the tracer dilution technique. Results: Lack of glucagon suppression increased postchallenge glucose concentrations and impaired EGP suppression. However, in the presence of matched insulin and glucagon concentrations, genetic variation in TCF7L2 did not alter glucose metabolism. Conclusion: These data suggest that genetic variation in TCF7L2 alters glucose metabolism through changes in islet hormone secretion.

Plasma Imidazole Propionate Is Positively Correlated with Blood Pressure in Overweight and Obese Humans.

Background: The gut microbiota and its metabolites are essential for host health and dysbiosis has been involved in several pathologic conditions such as type 2 diabetes (T2D) and cardiovascular disease (CVD). Recent studies have identified that plasma imidazole propionate (ImP), a microbial-produced metabolite, is increased in patients with prediabetes and T2D. More recently, ImP was found to be significantly increased in patients with overt CVD. Here, we aimed to investigate the association between ImP and CVD risk factors: blood pressure, HDL-cholesterol, LDL-cholesterol and insulin-resistance in overweight and obese subjects without T2D or use of any metabolic diseases-related medication. Methods: Plasma metabolites, including ImP, were determined in 107 male or post-menopausal women with overweight/obesity, but without T2D. Insulin-sensitivity was assessed with the gold standard method: the hyperinsulinemic-euglycemic clamp using the isotope [6,6-2H2] glucose and expressed as glucose rate of disposal (Rd) for peripheral insulin sensitivity and suppression of endogenous glucose production (EGP) for hepatic insulin sensitivity. Results: Partial correlation analysis controlled for BMI and age showed a significant correlation between ImP and diastolic blood pressure (rs = 0.285, p = 0.004) and a borderline significance with systolic blood pressure (rs = 0.187, p = 0.060); however, systolic and diastolic blood pressure did not correlate with ImP precursor histidine (rs = 0.063, p = 0.526 and r = −0.038, p = 0.712, respectively). We did not find a correlation between ImP with LDL-cholesterol or HDL-cholesterol (rs = −0.181, p = 0.064 and rs = 0.060, p = 0.546, respectively). Furthermore, there was no association between plasma ImP concentrations and Rd and EGP suppression. Conclusion: In this cohort with overweight/obese subjects without T2D, plasma ImP concentrations were positively correlated with diastolic blood pressure but not with insulin-sensitivity.

Translating glucose tolerance data from mice to humans: Insights from stable isotope labelled glucose tolerance tests

ObjectiveThe glucose tolerance test (GTT) is widely used in human and animal biomedical and pharmaceutical research. Despite its prevalent use, particularly in mouse metabolic phenotyping, to the best of our knowledge we are not aware of any studies that have attempted to qualitatively compare the metabolic events during a GTT in mice with those performed in humans. MethodsStable isotope labelled oral glucose tolerance tests (siOGTTs; [6,6-2H2]glucose) were performed in both human and mouse cohorts to provide greater resolution into postprandial glucose kinetics. The siOGTT allows for the partitioning of circulating glucose into that derived from exogenous and endogenous sources. Young adults spanning the spectrum of normal glucose tolerance (n = 221), impaired fasting (n = 14), and impaired glucose tolerance (n = 19) underwent a 75g siOGTT, whereas a 50 mg siOGTT was performed on chow (n = 43) and high-fat high-sucrose fed C57Bl6 male mice (n = 46). ResultsDuring the siOGTT in humans, there is a long period (>3hr) of glucose absorption and, accordingly, a large, sustained insulin response and robust suppression of lipolysis and endogenous glucose production (EGP), even in the presence of glucose intolerance. In contrast, mice appear to be highly reliant on glucose effectiveness to clear exogenous glucose and experience only modest, transient insulin responses with little, if any, suppression of EGP. In addition to the impaired stimulation of glucose uptake, mice with the worst glucose tolerance appear to have a paradoxical and persistent rise in EGP during the OGTT, likely related to handling stress. ConclusionsThe metabolic response to the OGTT in mice and humans is highly divergent. The potential reasons for these differences and their impact on the interpretation of mouse glucose tolerance data and their translation to humans are discussed.

Insulin resistance in type 1 diabetes managed with metformin (INTIMET): Study protocol of a double-blind placebo-controlled, randomised trial.

Insulin resistance is an under-recognised metabolic defect and cardiovascular risk factor in Type 1 diabetes. Whether metformin improves hepatic, muscle or adipose tissue insulin sensitivity has not been studied in adults with Type 1 diabetes. We initiated the INTIMET study (INsulin resistance in Type 1 diabetes managed with METformin), a double-blind randomised, placebo-controlled trial to measure the effect of metformin on tissue-specific insulin resistance in adults with Type 1 diabetes. We will study 40 adults aged 20-55years with Type 1 diabetes (HbA1c 80mmol/mol [9.5%], fasting C-peptide <0.3nmol/L) and 20 age-, gender- and body mass index (BMI)-matched controls. Insulin sensitivity will be determined by the two-step hyperinsulinaemic-euglycaemic clamp method with deuterated glucose to document liver, muscle and adipose insulin sensitivity. Subjects with Type 1 diabetes will be randomised to metformin extended-release 1500mg daily or matched placebo for 26weeks. The primary outcome is change in hepatic insulin sensitivity, assessed by change in basal rate of appearance (Ra) of glucose and suppression of endogenous glucose production (EGP) during the low-dose stage of the clamp. The INTIMET study is the first clinical trial to quantify the impact of metformin on liver, muscle and adipose insulin resistance in adults with Type 1 diabetes. This study may identify factors that predict an individual's response to metformin in Type 1 diabetes. ACTRN12619001440112.

Effects of the SGLT2 Inhibitor Dapagliflozin on Energy Metabolism in Patients With Type 2 Diabetes: A Randomized, Double-Blind Crossover Trial.

SGTL2 inhibitors increase urinary glucose excretion and have beneficial effects on cardiovascular and renal outcomes. The underlying mechanism may involve caloric restriction-like metabolic effects due to urinary glucose loss. We investigated the effects of dapagliflozin on 24-h energy metabolism and insulin sensitivity in patients with type 2 diabetes. There were 26 patients with type 2 diabetes randomized to a 5-week double-blind, crossover study with a 6- to 8-week washout. Indirect calorimetry was used to measure 24-h energy metabolism and the respiratory exchange ratio (RER), both by whole-room calorimetry and by ventilated hood during a two-step euglycemic-hyperinsulinemic clamp. Results are presented as the differences in least squares mean (95% CI) between treatments. Evaluable patients (n = 24) had a mean (SD) age of 64.2 (4.6) years, BMI of 28.1 (2.4) kg/m2, and HbA1c of 6.9% (0.7) (51.7 [6.8] mmol/mol). Rate of glucose disappearance was unaffected by dapagliflozin, whereas fasting endogenous glucose production (EGP) increased by dapagliflozin (+2.27 [1.39, 3.14] μmol/kg/min, P < 0.0001). Insulin-induced suppression of EGP (-1.71 [-2.75, -0.63] μmol/kg/min, P = 0.0036) and plasma free fatty acids (-21.93% [-39.31, -4.54], P = 0.016) was greater with dapagliflozin. Twenty-four-hour energy expenditure (-0.11 [-0.24, 0.03] MJ/day) remained unaffected by dapagliflozin, but dapagliflozin reduced the RER during daytime and nighttime, resulting in an increased day-to-nighttime difference in the RER (-0.010 [-0.017, -0.002], P = 0.016). Dapagliflozin treatment resulted in a negative 24-h energy and fat balance (-20.51 [-27.90, -13.12] g/day). Dapagliflozin treatment for 5 weeks resulted in major adjustments of metabolism mimicking caloric restriction, increased fat oxidation, improved hepatic and adipose insulin sensitivity, and improved 24-h energy metabolism.

Mechanisms by which adiponectin reverses high fat diet-induced insulin resistance in mice

Adiponectin has emerged as a potential therapy for type 2 diabetes mellitus, but the molecular mechanism by which adiponectin reverses insulin resistance remains unclear. Two weeks of globular adiponectin (gAcrp30) treatment reduced fasting plasma glucose, triglyceride (TAG), and insulin concentrations and reversed whole-body insulin resistance, which could be attributed to both improved insulin-mediated suppression of endogenous glucose production and increased insulin-stimulated glucose uptake in muscle and adipose tissues. These improvements in liver and muscle sensitivity were associated with ∼50% reductions in liver and muscle TAG and plasma membrane (PM)-associated diacylglycerol (DAG) content and occurred independent of reductions in total ceramide content. Reductions of PM DAG content in liver and skeletal muscle were associated with reduced PKCε translocation in liver and reduced PKCθ and PKCε translocation in skeletal muscle resulting in increased insulin-stimulated insulin receptor tyrosine1162 phosphorylation, IRS-1/IRS-2-associated PI3-kinase activity, and Akt-serine phosphorylation. Both gAcrp30 and full-length adiponectin (Acrp30) treatment increased eNOS/AMPK activation in muscle and muscle fatty acid oxidation. gAcrp30 and Acrp30 infusions also increased TAG uptake in epididymal white adipose tissue (eWAT), which could be attributed to increased lipoprotein lipase (LPL) activity. These data suggest that adiponectin and adiponectin-related molecules reverse lipid-induced liver and muscle insulin resistance by reducing ectopic lipid storage in these organs, resulting in decreased plasma membrane sn-1,2-DAG-induced nPKC activity and increased insulin signaling. Adiponectin mediates these effects by both promoting the storage of TAG in eWAT likely through stimulation of LPL as well as by stimulation of AMPK in muscle resulting in increased muscle fat oxidation.