Fasting Glucagon Research Articles

Postprandial fatty acid-binding protein4 is associated with muscle insulin resistance.

Fatty acid-binding protein4 (FABP4) has been reported to act as a hepatic insulin resistance factor. We previously reported that fasting FABP4 was correlated with insulin resistance measurements derived from the glucose clamp, and another study reported that postprandial FABP4 levels were decreased in healthy volunteers but were not reported (or known) in participants with type 2 diabetes. We have limited knowledge about the direct effect of FABP4 on muscle cells. We investigated the postprandial FABP4 levels in participants with type 2 diabetes, and the basic mechanism of muscle insulin resistance and FABP4. We performed a meal tolerance test and hyperinsulinaemic-euglycaemic clamp in 22 participants with type 2 diabetes and 26 participants without diabetes. We measured fasting and postprandial serum FABP4. We cultured mouse C2C12 muscle cells, and investigated the effect of FABP4 on glucose uptake. We analysed insulin signalling by western blot and insulin binding assay. The postprandial FABP4 level in participants with type 2 diabetes was higher than that in participants without diabetes. Participants without diabetes had lower postprandial FABP4 than fasting except for one participant, whereas one-third of participants with type 2 diabetes had higher postprandial FABP4 than fasting. Postprandial FABP4 was correlated with the muscle insulin resistance M/I value from a glucose clamp in participants without diabetes (r=-0.42, p<0.05). The increase in FABP4 after a meal correlated with the muscle insulin resistance M/I value (r=-0.44, p<0.05) and the difference between fasting and postprandial glucagon in participants with type 2 diabetes (r=0.36, p<0.05). FABP4 alone appears to increase glucose uptake, and the combination of FABP4 and insulin decreases glucose uptake when compared with insulin alone. FABP4 inhibits insulin signalling of muscle cells through decreases in phosphorylation of insulin receptor substrate1 and Akt. The physiological concentration of FABP4 did not inhibit insulin binding to muscle cells. These results suggested that the postprandial FABP4 level is associated with insulin resistance, and FABP4 may suppress insulin signals.

Inadequate Glucagon Suppression During OGTT in Prediabetes: A Systematic Review and Meta-analysis.

Glucagon plays a role in the development of type 2 diabetes, yet its role in prediabetes (preDM) remains uncertain. To evaluate glucagon levels in the fasting state and its response to glucose inhibition in preDM through meta-analysis. A systematic search across Pubmed, Embase, Web of Science, and Cochrane Library identified studies assessing glucagon levels during 75 g oral glucose tolerance test (OGTT) in both preDM and normal glucose tolerance (NGT) cohorts. Data on glucagon, glucose, and insulin were pooled using a random-effect model. Although glucagon levels decreased in both preDM and NGT groups upon glucose challenge, glucagon levels at 0 hours, 0.5 hours, 1 hour, and 1.5 hours in preDM were significantly higher compared to NGT, despite higher glucose levels at all time points and higher insulin levels at 0 hours, 1 hour, 1.5 hours, and 2 hours during OGTT. Subgroup analysis revealed that in studies using the radioimmunoassay method, glucagon levels in preDM were higher at 0.5 hours and 1 hour than NGT, while in studies using the ELISA method, glucagon levels were similar to those of the NGT group despite higher glucose in preDM compared to NGT. Fasting glucagon level was inadequately suppressed in both impaired glucose tolerance (IGT) and impaired fasting glucose (IFG). Responsiveness to glucose inhibition was preserved in IFG, while glucagon level in IGT group at 0.5 hours after glucose intake was not suppressed and was higher than NGT. Glucagon was not adequately suppressed during OGTT in preDM. Glucagon dysregulation is a contributing mechanism underlying both IFG and IGT.

Sex differences in the plasma glucagon responses to a high carbohydrate meal and a glucose drink in type 2 diabetes

Elevated fasting glucagon concentrations and/or attenuated postprandial glucagon suppression are characteristics of type 2 diabetes (T2D) and contribute to hyperglycaemia. This study shows that hyperglucagonaemia is more prominent in males than females after a nutrient load in T2D, adding insights into sex differences in relation to the pathophysiology of T2D.

Impairments of insulin and glucagon sensitivity in Chinese women with gestational diabetes mellitus.

To evaluate insulin and glucagon sensitivity in Han Chinese women with and without gestational diabetes mellitus (GDM). In total, 81 women with GDM and 81 age-matched healthy controls were evaluated with a 75 g oral glucose tolerance test (OGTT) at gestational weeks 24-28. Plasma glucose concentrations were measured at fasting and 1 h and 2 h post-OGTT. Fasting plasma insulin, glucagon and amino acids were also measured. Insulin and glucagon sensitivity were assessed by the homeostatic model assessment of insulin resistance (HOMA-IR) and glucagon-alanine index, respectively. As expected, plasma glucose concentrations were higher at fasting and 1 h and 2 h post-OGTT in GDM participants (p < .001 each). Both the HOMA-IR and the glucagon-alanine index were higher in GDM participants. There was a weak positive correlation between HOMA-IR and glucagon-alanine index (r = 0.24, p = .0024). Combining the HOMA-IR and the glucagon-alanine index yielded better capacity (area under the curve = 0.878) than either alone (area under the curve = 0.828 for HOMA-IR and 0.751 for glucagon-alanine index, respectively) in differentiating GDM from healthy participants. While the majority of GDM participants (64%) exhibited both reduced insulin and glucagon sensitivity, a third of them presented either reduced insulin (20%) or glucagon (14%) sensitivity alone. HOMA-IR and glucagon-alanine index correlated differentially with fasting glucose, triglycerides, low-density lipoprotein cholesterol, sum of amino acids and hepatic steatosis index. Impairments of both insulin and glucagon sensitivity occur frequently in Chinese women with GDM, which may, individually or together, drive metabolic derangements in GDM. These observations provide new insights into the pathophysiology of GDM and support the need to target insulin or glucagon resistance, or both, in the management of GDM.

The association of fasting and postprandial GIP and glucagon levels with glycemic variability evaluated by flash glucose monitoring system in type 1 diabetes

The association of fasting and postprandial GIP and glucagon levels with glycemic variability evaluated by flash glucose monitoring system in type 1 diabetes

Tirzepatide Improved Markers of Islet Cell Function (Fasting Glucagon and HOMA2-B) and Insulin Sensitivity (Fasting Insulin and HOMA2-IR) Compared to Semaglutide in People with Type 2 Diabetes

Tirzepatide Improved Markers of Islet Cell Function (Fasting Glucagon and HOMA2-B) and Insulin Sensitivity (Fasting Insulin and HOMA2-IR) Compared to Semaglutide in People with Type 2 Diabetes

Effects of Tirzepatide vs Semaglutide on β-cell Function, Insulin Sensitivity, and Glucose Control During a Meal Test.

In a clinical study, tirzepatide, a glucose-dependent insulinotropic polypeptide/glucagon-like peptide-1 receptor agonist (GIP/GLP-1RA), provided superior glycemic control vs the GLP-1RA semaglutide. The physiologic mechanisms are incompletely understood. To evaluate treatment effects by model-based analyses of mixed-meal tolerance test (MMTT) data. A 28-week double-blind, randomized, placebo-controlled trial. Two clinical research centers in Germany. Patients with type 2 diabetes treated with metformin. Tirzepatide 15 mg, semaglutide 1 mg, placebo. Glycemic control, model-derived β-cell function indices including insulin secretion rate (ISR) at 7.2-mmol/L glucose (ISR7.2), β-cell glucose (β-CG) sensitivity, insulin sensitivity, and estimated hepatic insulin-to-glucagon ratio. Tirzepatide significantly reduced fasting glucose and MMTT total glucose area under the curve (AUC) vs semaglutide (P < 0.01). Incremental glucose AUC did not differ significantly between treatments; therefore, greater total glucose AUC reduction with tirzepatide was mainly attributable to greater suppression of fasting glucose. A greater reduction in total ISR AUC was achieved with tirzepatide vs semaglutide (P < 0.01), in the context of greater improvement in insulin sensitivity with tirzepatide (P < 0.01). ISR7.2 was significantly increased with tirzepatide vs semaglutide (P < 0.05), showing improved β-CG responsiveness. MMTT-derived β-CG sensitivity was increased but not significantly different between treatments. Both treatments reduced fasting glucagon and total glucagon AUC, with glucagon AUC significantly reduced with tirzepatide vs semaglutide (P < 0.01). The estimated hepatic insulin-to-glucagon ratio did not change substantially with either treatment. These results suggest that the greater glycemic control observed for tirzepatide manifests as improved fasting glucose and glucose excursion control, due to improvements in ISR, insulin sensitivity, and glucagon suppression.

Insulin:Glucagon Bipolar Axis in Obesity With a Glimpse Into Its Association With Insulin Resistance in Different Glucose Tolerance States.

Dysregulation of insulin and glucagon secretion alters the normal insulin:glucagon ratio (IGR) in type 2 diabetes mellitus, obesity, and metabolic syndrome. This study explores the scope of construing the role of these two diametrically opposing hormones on the glucose level not just in obesity but in different glucose tolerance states by looking at the hormone levels and at the insulin glucagon bipolar axis itself. This is an analytical cross-sectional study of 60 healthy adults consisting of an equal number of adults who are lean and adults who are obese. It was conducted at North Eastern Indira Gandhi Regional Institute of Health and Medical Sciences (NEIGRIHMS), located in Shillong City, Meghalaya, India. Fasting glucose, insulin, glucagon, and lipids were estimated. Postprandial estimation of glucose was done two hours after oral administration of 75 grams of glucose solution. The study demonstrated a state of hyperinsulinemia and hyperglucagonemia prevailing in obesity and all sub-categories of the group of persons who are obese. The study showed a higher fasting IGRin the group consisting of adults who were obese (with a mean of 4.11) when compared with the group of adults who are lean (with a mean of 2.24). Fasting IGRwas seen to increase with increasing levels of insulin resistance and increasing impairment in glucose tolerance. IGR showed a positive correlation with the homeostatic model assessment for insulin resistance (HOMA-IR) in the impaired fasting glucose (IFG) category and strongly in the impaired glucose tolerance (IGT) category. Hyperglucagonemia in the group of adult persons who are obese indicates a decreased sensitivity of alpha cells to insulin failing insulin to adequately suppress the secretion of glucagon. The study also demonstrated a positive correlation between IGR and HOMA-IR in obesity and all glucose tolerance states of the group of adults who are obese. It is telltale that the sturdier the insulin resistance, the higher the IGR.

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.

Decreased glucagon in diabetic peripheral neuropathy patients with long duration type 2 diabetes.

The aim of this study was to investigate the association of fasting C-peptide and glucagon with diabetic peripheral neuropathy (DPN) in patients with type 2 diabetes (T2DM). A comprehensive evaluation was conducted on 797 patients with T2DM to assess the various risk factors affecting DPN. The subjects were categorized into short duration and long duration group according to the duration of diabetes with a threshold of 10years. Logistic regression analysis was employed to examine the association between DPN and islet function, as well as other parameters. Receiver operating characteristic curve analysis was performed to evaluate the predictive capability of glucagon. The fasting C-peptide levels were significantly lower in the DPN patients with short duration of diabetes, but lost significance in the long duration group. Conversely, a decreased level of glucagon was only observed in DPN patients with long duration of diabetes. For the group with long duration of diabetes, glucagon was the sole risk factor associated with DPN. The receiver operating characteristic curve analysis revealed that glucagon in the long duration group exhibited a moderate area under the curve of 0.706. The serum glucagon levels in T2DM patients with DPN exhibited bidirectional changes based on the duration of diabetes. Decreased glucagon was associated with DPN in T2DM patients with long duration of diabetes.

High fat diet is associated with gut microbiota dysbiosis and decreased gut microbial derived metabolites related to metabolic health in young Göttingen Minipigs.

The objectives were 1) to characterize a Göttingen Minipig model of metabolic syndrome regarding its colon microbiota and circulating microbial products, and 2) to assess whether ovariectomized female and castrated male minipigs show similar phenotypes. Twenty-four nine-week-old Göttingen Minipigs were allocated to four groups based on sex and diet: ovariectomized females and castrated males fed either chow or high-fat diet (HFD) for 12 weeks. At study end, body composition and plasma biomarkers were measured, and a mixed meal tolerance test (MMT) and an intravenous glucose tolerance test (IVGTT) were performed. The HFD groups had significantly higher weight gain, fat percentage, fasting plasma insulin and glucagon compared to the chow groups. Homeostatic model assessment of insulin resistance index (HOMA-IR) was increased and glucose effectiveness derived from the IVGTT and Matsuda´s insulin sensitivity index from the MMT were decreased in the HFD groups. The HFD groups displayed dyslipidemia, with significantly increased total-, LDL- and HDL-cholesterol, and decreased HDL/non-HDL cholesterol ratio. The colon microbiota of HFD minipigs clearly differed from the lean controls (GuniFrac distance matrix). The main bacteria families driving this separation were Clostridiaceae, Fibrobacteraceae, Flavobacteriaceae and Porphyromonadaceae. Moreover, the species richness was significantly decreased by HFD. In addition, HFD decreased the circulating level of short chain fatty acids and beneficial microbial metabolites hippuric acid, xanthine and trigonelline, while increasing the level of branched chain amino acids. Six and nine metabolically relevant genes were differentially expressed between chow-fed and HFD-fed animals in liver and omental adipose tissue, respectively. The HFD-fed pigs presented with metabolic syndrome, gut microbial dysbiosis and a marked decrease in healthy gut microbial products and thus displayed marked parallels to human obesity and insulin resistance. HFD-fed Göttingen Minipig therefore represents a relevant animal model for studying host-microbiota interactions. No significant differences between the castrated and ovariectomized minipigs were observed.

Effect of preoperative oral carbohydrates on insulin resistance in patients undergoing laparoscopic cholecystectomy: a randomized controlled trial

PurposeThe present research seeks to clarify the consequences of two specific preoperative oral carbohydrate (POC) amounts on insulin resistance (IR) and stomach evacuation in laparoscopic cholecystectomy (LC) patients.MethodsA total of 129 patients set for elective LC procedures were randomly assigned to a control group (C, n = 45), a 200 mL POC group (P1, n = 42), and a 400 mL POC group (P2, n = 42). The C group was fasted from midnight until surgery, whereas the P1 and P2 groups received their respective carbohydrate volumes 2–4 h before anesthesia. Fasting blood glucose, insulin, and glucagon concentrations were measured at three junctures. IR metrics were derived by employing the homeostasis model assessment. Gastric volume was measured before anesthesia using gastric ultrasound. Inter-group comparisons included IR indicators, subjective comfort scores, and hemodynamic data.ResultsAt T2, the C group exhibited reduced glucose concentrations compared to the P2 group (4.73 ± 0.64 vs. 5.26 ± 1.02 mmol/L, p < 0.05). The Perlas grading indicated that grade 1 was more prevalent in the P2 group than in the P1 and C groups (18 [42.9%] vs. 6 [14.3%] and 1 [2.2%], p < 0.05). Additionally, thirst and hunger metrics for the P2 group were notably reduced compared to the C group at both T2 and T3.ConclusionAdministering either 200 mL or 400 mL of carbohydrates 2–4 h pre-surgery had no detectable impact on IR or gastric volume in LC patients.Trial registrationChiCTR, ChiCTR2200065648. Registered January 13, 2023, http://www.chictr.org.cn.

Tirzepatide Improved Markers of Islet Cell Function and Insulin Sensitivity in People With T2D (SURPASS-2).

In previous SURPASS studies tirzepatide reduced hemoglobin glycated A1c (HbA1c) and body weight and improved markers of insulin sensitivity and β-cell function to a greater extent than comparators. Explore changes in biomarkers of β-cell function and insulin sensitivity and in efficacy profiles in baseline biomarker quartile analyses with tirzepatide compared to semaglutide. Post hoc analysis of SURPASS-2 phase 3 trial (participants randomly assigned to receive weekly subcutaneous tirzepatide or semaglutide for 40 weeks). Post hoc analysis of 128 sites in 8 countries. A total of 1879 participants with type 2 diabetes. Once-weekly tirzepatide (5, 10, 15 mg) or semaglutide 1 mg. Change in homeostatic model assessment indices for pancreatic β-cell function (HOMA2-B) and for insulin resistance (HOMA2-IR), fasting glucagon, fasting C-peptide, and fasting insulin. At week 40, a greater increase in HOMA2-B was seen with tirzepatide (5, 10, 15 mg) doses (96.9-120.4%) than with semaglutide 1 mg (84.0%) (P < .05). There was a greater reduction in HOMA2-IR with all doses of tirzepatide (15.5%-24.0%) than with semaglutide 1 mg (5.1%) (P < .05). Tirzepatide 10 and 15 mg resulted in a significant reduction in both fasting C-peptide (5.2%-6.0%) and fasting glucagon (53.0%-55.3%) compared with an increase of C-peptide (3.3%) and a reduction of glucagon (47.7%) with semaglutide 1 mg (P < .05). HbA1c and body weight reductions were greater with all tirzepatide doses than semaglutide within each HOMA2-B and HOMA2-IR baseline quartile. In this post hoc analysis, improvements in HbA1c and weight loss were consistent and significantly higher with tirzepatide, regardless of baseline β-cell function and insulin resistance, compared with semaglutide.

Connections between body composition and dysregulation of islet α- and β-cells in type 2 diabetes

BackgroundAccompanying islet α- and β-cell dysregulation in type 2 diabetes (T2D) at the microscopic scale, alterations in body composition at the macroscopic scale may affect the pathogenesis of T2D. However, the connections between body composition and islet α-cell and β-cell functions in T2D have not been thoroughly explored.MethodsFor this cross-sectional study, we recruited a total of 729 Chinese Han patients with T2D in a consecutive manner. Dual-energy X-ray absorptiometry (DXA) was used to measure body composition, which included total bone-free mass, total fat and lean mass, trunk fat and lean mass and limb fat and lean mass. Every patient underwent an oral glucose tolerance test to simultaneously detect glucose, C-peptide and glucagon. The indices of islet α-cell function included fasting glucagon levels and the area under the curve of glucagon after a challenge (AUCglucagon), while the indices of β-cell function included the insulin sensitivity index derived from C-peptide (ISIC-peptide) and the area under the curve of C-peptide after a challenge (AUCC-peptide).ResultsAmong all patients, fat mass, especially trunk fat mass, was significantly correlated with ISIC-peptide and AUCC-peptide levels (r = − 0.330 and 0.317, respectively, p < 0.001), while lean mass, especially limb lean mass, was significantly correlated with fasting glucagon and AUCglucagon levels (r = − 0.196 and − 0.214, respectively, p < 0.001). Moreover, after adjusting for other relevant variables via multivariate linear regression analysis, increased trunk fat mass was independently associated with decreased ISIC-peptide (β = − 0.247, t = − 3.628, p < 0.001, partial R2 = 10.9%) and increased AUCC-peptide (β = 0.229, t = 3.581, p < 0.001, partial R2 = 8.2%), while decreased limb lean mass was independently associated with increased fasting glucagon (β = − 0.226, t = − 2.127, p = 0.034, partial R2 = 3.8%) and increased AUCglucagon (β = − 0.218, t = − 2.050, p = 0.041, partial R2 = 2.3%). Additionally, when separate analyses were performed with the same concept for both sexes, we found that increased trunk fat mass was still independently associated with decreased ISIC-peptide and increased AUCC-peptide, while decreased limb lean mass was still independently associated with increased fasting glucagon and AUCglucagon.ConclusionsIncreased trunk fat mass may partly account for decreased insulin sensitivity and increased insulin secretion, while decreased limb lean mass may be connected to increased fasting glucagon and postprandial glucagon secretion.

Abnormal late postprandial glucagon response in type 1 diabetes is a function of differences in stimulated C-peptide concentrations.

The functional changes in alpha cells in patients with type 1 diabetes (T1D) with different residual beta cell functions remain poorly elucidated. The study aimed to investigate the relationship between glucagon secretion and C-peptide levels and to explore the relationship between glucagon response and glucose increment in respond to a secretagogue in a steamed bread meal tolerance test (BMTT) in T1D. The study enrolled 43 adult patients with T1D and 24 healthy control subjects. Patients with T1D who underwent BMTT were divided into two groups based on peak C-peptide levels: C peptide low (CPL; C-peptide < 200 pmol/L; n=14) and high (CPH; C peptide ≥ 200 pmol/L; n=29). Plasma glucose, C-peptide, glucagon levels at 0, 30, 60, 120, and 180 min were measured. The glucagon response to the BMTT was defined by areas under the curve (AUC) as early (AUC0-30), late (AUC30-180), or total (AUC0-180) glucagon. Compared to healthy individuals, fasting plasma glucagon was lower and postprandial plasma glucagon level was increased in patients with T1D. Glucagon levels after BMTT between the CPL and CPH group showed significant group by time interaction. Peak glucagon and glucagon at 60-180 min, total and late glucagon response were higher in CPL than CPH group, while fasting glucagon and early glucagon response adjusted for glucose were comparable between CPL and CPH group. The higher late glucagon response and late glucagon response adjusted for glucose were associated with lower peak C-peptide in T1D. The higher late glucagon response and lower peak C-peptide were associated with the higher value of ▵glucose at 180 min. Stimulated C-peptide levels affect the paradoxical increase in postprandial glucagon secretion in patients with T1D, especially late glucagon response. The exaggerated postprandial glucagon secretion further stimulates the elevation of postprandial glucose in patients with T1D.

Rise in fasting and dynamic glucagon levels in children and adolescents with obesity is moderate in subjects with impaired fasting glucose but accentuated in subjects with impaired glucose tolerance or type 2 diabetes.

Fasting levels of glucagon are known to be elevated in youth and adults with type 2 diabetes mellitus (T2D). Children and adolescents with obesity were previously reported to show increasing fasting and post-glucose-challenge hyperglucagonemia across the spectrum of glucose tolerance, while no data are available in those with impaired fasting glucose (IFG). Individuals from the Beta-JUDO study population (Uppsala and Salzburg 2010-2016) (n=101, age 13.3 ± 2.8, m/f =50/51) were included (90 with overweight or obesity, 11 with normal weight). Standardized OGTT were performed and plasma glucose, glucagon and insulin concentrations assessed at baseline, 5, 10, 15, 30, 60, 90 and 120 minutes. Patients were grouped according to their glycemic state in six groups with normal glucose metabolism (NGM) and normal weight (NG-NW), NGM with obesity or overweight (NG-O), impaired glucose tolerance (IGT), impaired fasting glucose (IFG), IGT+IFG and T2D, and in two groups with NGM and impaired glucose metabolism (IGM), for statistical analysis. Glucagon concentrations were elevated in young normoglycemic individuals with overweight or obesity (NG-O) compared to normoglycemic individuals with normal weight. Glucagon levels, fasting and dynamic, increased with progressing glycemic deterioration, except in IFG, where levels were comparable to those in NG-O. All glycemic groups showed an overall suppression of glucagon during OGTT. An initial increase of glucagon could be observed in T2D. In T2D, glucagon showed a strong direct linear correlation with plasma glucose levels during OGTT. Glucagon in adolescents, as in adults, may play a role in the disease progression of T2D.

Carotid body denervation improves hyperglycemia in obese mice.

The carotid bodies (CBs) have been implicated in glucose abnormalities in obesity via elevation of activity of the sympathetic nervous system. Obesity-induced hypertension is mediated by insulin receptor (INSR) signaling and by leptin, which binds to the leptin receptor (LEPRb) in CB and activates transient receptor potential channel subfamily M member 7 (TRPM7). We hypothesize that in mice with diet-induced obesity, hyperglycemia, glucose intolerance, and insulin resistance will be attenuated by the CB denervation (carotid sinus nerve dissection, CSND) and by knockdown of Leprb, Trpm7, and Insr gene expression in CB. In series of experiments in 75 male diet-induced obese (DIO) mice, we performed either CSND (vs. sham) surgeries or shRNA-induced suppression of Leprb, Trpm7, or Insr gene expression in CB, followed by blood pressure telemetry, intraperitoneal glucose tolerance and insulin tolerance tests, and measurements of fasting plasma insulin, leptin, corticosterone, glucagon and free fatty acids (FFAs) levels, hepatic expression of gluconeogenesis enzymes phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6-phosphatase (G-6-Pase) mRNA and liver glycogen levels. CSND decreased blood pressure, fasting blood glucose levels and improved glucose tolerance without any effect on insulin resistance. CSND did not affect any hormone levels and gluconeogenesis enzymes, but increased liver glycogen level. Genetic knockdown of CB Leprb, Trpm7, and Insr had no effect on glucose metabolism. We conclude that CB contributes to hyperglycemia of obesity, probably by modulation of the glycogen-glucose equilibrium. Diabetogenic effects of obesity on CB in mice do not occur via activation of CB Leprb, Trpm7, and Insr.NEW & NOTEWORTHY This paper provides first evidence that carotid body denervation abolishes hypertension and improves fasting blood glucose levels and glucose tolerance in mice with diet-induced obesity. Furthermore, we have shown that this phenomenon is associated with increased liver glycogen content, whereas insulin sensitivity and enzymes of gluconeogenesis were not affected.

Altered Glucagon and GLP-1 Responses to Oral Glucose in Children and Adolescents With Obesity and Insulin Resistance.

Pediatric obesity is characterized by insulin resistance, yet it remains unclear whether insulin resistance contributes to abnormalities in glucagon and incretin secretion. To examine whether fasting and stimulated glucagon, glucagon-like peptide-1 (GLP-1), and glucose-dependent insulinotropic polypeptide (GIP) concentrations differ between children and adolescents with obesity and insulin resistance (OIR), obesity and normal insulin sensitivity (OIS), and controls with normal weight (NW). 80 (34 boys) children and adolescents, aged 7-17 years with OIR (n = 22), OIS (n = 22), and NW (n = 36) underwent an oral glucose tolerance test with measurements of serum insulin, plasma glucose, glucagon, total GLP-1, and total GIP. Homeostatic model assessment of insulin resistance (HOMA-IR), single point insulin sensitivity estimator (SPISE), Matsuda index, insulinogenic index (IGI), and oral disposition index (ODI) were calculated. Fasting concentrations of glucagon and GLP-1 were higher in the OIR group, with no significant differences for GIP. The OIR group had higher glucagon total area under the curve (tAUC0-120) and lower GLP-1 incremental AUC (iAUC0-120), with no significant differences in GIP iAUC0-120. Higher fasting glucagon was associated with higher HOMA-IR, lower Matsuda index, lower SPISE, higher IGI, and higher plasma alanine transaminase, whereas higher fasting GLP-1 was associated with higher HOMA-IR, lower Matsuda index, and lower ODI. Higher glucagon tAUC0-120 was associated lower SPISE and lower Matsuda index, whereas lower GLP-1 iAUC0-120 was associated with a higher HOMA-IR, lower Matsuda index, and lower ODI. Children and adolescents with OIR have elevated fasting concentrations of glucagon and GLP-1, higher glucagon and lower GLP-1 responses during an OGTT compared to those with OIS and NW. In contrast, individuals with OIS have similar hormone responses to those with NW.

The Ablation of Sensory Neurons Expressing the Nav1.8 Sodium Channel Improves Glucose Homeostasis and Amplifies the GLP-1 Signaling in Obese Female Mice.

Sensory neurons expressing the sodium channel Nav1.8 contain a repertoire of receptors for nutrient, hormonal, and inflammatory ligands. However, their function in key regulators of energy homeostasis control is not well understood and is completely unexplored in females. Mice lacking neurons expressing the sodium channel Nav1.8 were generated using an ablation strategy based on cre recombinase-mediated expression of diphtheria toxin fragment A (DTA) (Nav1.8-cre/DTA mice) to investigate whether these neurons modulate body weight, food intake, gut hormone secretion, gastrointestinal transit, and glucose tolerance in response to nutrient challenges in a sex-dependent manner. Male Nav1.8-cre/DTA mice show resistance to gain weight in response to high-fat high-sugar diet (HFHSD), whereas females lacking Nav1.8+ neurons have improved oral glucose tolerance accompanied by higher insulin levels and attenuated glucagon secretion after an oral glucose load. Female Nav1.8-cre/DTA mice also show higher fasting and postprandial glucagon like peptide-1 (GLP-1) levels with an increased number of GLP-1-positive cells. Finally, ablation of Nav1.8-expressing neurons accelerates the gastrointestinal transit in female mice under HFHSD. This data demonstrates sex-dependent differences in the Nav1.8-mediated regulation of energy metabolism, and provides new insights that may help in the design of sex-specific neuromodulation therapies for metabolic disorders induced by diets rich in fats and simple sugars.

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).