The effect of exogenous glucagon on circulating amino acids in individuals with and without type 2 diabetes and obesity.

Objective: In obesity and type 2 diabetes, hyperglucagonaemia may be caused by elevated levels of glucagonotropic amino acids due to hepatic glucagon resistance at the level of amino acid turnover. Here, we investigated the effect of exogenous glucagon on circulating amino acids in obese and non-obese individuals with and without type 2 diabetes. Design: This was a post hoc analysis in a glucagon infusion study performed in individuals with type 2 diabetes (n = 16) and in age, sex, and body mass index-matched control individuals without diabetes (n = 16). Each group comprised two subgroups of eight individuals with and without obesity, respectively. Methods: All participants received a 1-h glucagon infusion (4 ng/kg/min) in the overnight fasted state. Plasma amino acid concentrations were measured with frequent intervals. Results: Compared to the control subgroup without obesity, baseline total amino acid levels were elevated in the control subgroup with obesity and in the type 2 diabetes subgroup without obesity. In all subgroups, amino acid levels decreased by up to 20% in response to glucagon infusion, which resulted in high physiological steady-state glucagon levels (mean concentration: 74 pmol/L, 95% CI [68;79] pmol/L). Following correction for multiple testing, no intergroup differences in changes in amino acid levels reached significance. Conclusion: Obesity and type 2 diabetes status was associated with elevated fasting levels of total amino acids. The glucagon infusion decreased circulating amino acid levels similarly in all subgroups, without significant differences in the response to exogenous glucagon between individuals with and without obesity and type 2 diabetes. Significance statement: The hormone glucagon stimulates glucose production from the liver, which may promote hyperglycaemia if glucagon levels are abnormally elevated, as is often seen in type 2 diabetes and obesity. Glucagon levels are closely linked to, and influenced by, the levels of circulating amino acids. To further investigate this link, we measured amino acid levels in individuals with and without obesity and type 2 diabetes before and during an infusion of glucagon. We found that circulating amino acid levels were higher in type 2 diabetes and obesity, and that glucagon infusion decreased amino acid levels in both individuals with and without type 2 diabetes and obesity. The study adds novel information to the link between circulating levels of glucagon and amino acids.

An extended minimal model of OGTT: estimation of α- and ß-cell dysfunction, insulin resistance, and the incretin effect.

Loss of insulin sensitivity, α- and ß-cell dysfunction, and impairment in incretin effect have all been implicated in the pathophysiology of type 2 diabetes (T2D). Parsimonious mathematical models are useful in quantifying parameters related to the pathophysiology of T2D. Here, we extend the minimum model developed to describe the glucose-insulin-glucagon dynamics in the isoglycemic intravenous glucose infusion (IIGI) experiment to the oral glucose tolerance test (OGTT). The extended model describes glucose and hormone dynamics in OGTT including the contribution of the incretin hormones, glucose-dependent insulinotropic polypeptide (GIP), and glucagon-like peptide-1 (GLP-1), to insulin secretion. A new function describing glucose arrival from the gut is introduced. The model is fitted to OGTT data from eight individuals with T2D and eight weight-matched controls (CS) without diabetes to obtain parameters related to insulin sensitivity, ß- and α-cell function. The parameters, i.e., measures of insulin sensitivity, a1, suppression of glucagon secretion, k1, magnitude of glucagon secretion, γ2, and incretin-dependent insulin secretion, γ3, were found to be different between CS and T2D with P values < 0.002, <0.017, <0.009, <0.004, respectively. A new rubric for estimating the incretin effect directly from modeling the OGTT is presented. The average incretin effect correlated well with the experimentally determined incretin effect with a Spearman rank test correlation coefficient of 0.67 (P < 0.012). The average incretin effect was found to be different between CS and T2D (P < 0.032). The developed model is shown to be effective in quantifying the factors relevant to T2D pathophysiology.NEW & NOTEWORTHY A new extended model of oral glucose tolerance test (OGTT) has been developed that includes glucagon dynamics and incretin contribution to insulin secretion. The model allows the estimation of parameters related to α- and ß-cell dysfunction, insulin sensitivity, and incretin action. A new function describing the influx of glucose from the gut has been introduced. A new rubric for estimating the incretin effect directly from the OGTT experiment has been developed. The effect of glucose dose was also investigated.

No effect of the turmeric root phenol curcumin on prednisolone-induced glucometabolic perturbations in men with overweight or obesity.

Objectives: Preclinically, curcumin has been shown to protect against glucocorticoid-induced insulin resistance. We evaluated the effect of curcumin administered with prednisolone in healthy overweight or obese men. Methods: In a double-blind, parallel-group trial, 24 overweight/obese non-diabetic men were randomised to one of three intervention groups (A) prednisolone placebo+curcumin placebo, (B) prednisolone (50 mg/day)+curcumin placebo or (C) prednisolone and curcumin (400 mg/day). Curcumin or curcumin placebo treatment started 1 day prior to 10-day prednisolone or prednisolone placebo treatment. The primary endpoint was change in prednisolone-induced insulin resistance assessed by homeostatic model assessment of insulin resistance (HOMA2-IR). Other endpoints included anthropometric measurements, magnetic resonance spectroscopy-assessed hepatic fat content, blood pressure, circulating metabolic markers and continuous glucose monitoring measures. Results: Baseline characteristics (mean ± s.d): age 44.2 ± 13.7 years, BMI 30.1 ± 3.5 kg/m2, HbAlc 33.3 ± 3.2 mmol/mol, HOMA2-IR 1.10 ± 0.45 and fasting plasma glucose 5.2 ± 0.4 mmol/L. Prednisolone significantly increased HOMA2-IR (estimated treatment difference 0.36 (95% CI 0.16; 0.57)). Co-treatment with curcumin had no effect on HOMA2-IR (estimated treatment difference 0.08 (95% CI -0.13; 0.39)). Prednisolone increased HbAlc, insulin, C-peptide, glucagon, blood pressure, mean interstitial glucose, time spent in hyperglycaemia and glucose variability, but no protective effect of curcumin on any of these measures was observed. Conclusions: In this double-blind, placebo-controlled parallel-group study involving 24 overweight or obese men randomised to one of three treatment arms, curcumin treatment had no protective effect on prednisolone-induced insulin resistance or other glucometabolic perturbations.

A glucose-insulin-glucagon coupled model of the isoglycemic intravenous glucose infusion experiment.

Type 2 diabetes (T2D) is a pathophysiology that is characterized by insulin resistance, beta- and alpha-cell dysfunction. Mathematical models of various glucose challenge experiments have been developed to quantify the contribution of insulin and beta-cell dysfunction to the pathophysiology of T2D. There is a need for effective extended models that also capture the impact of alpha-cell dysregulation on T2D. In this paper a delay differential equation-based model is developed to describe the coupled glucose-insulin-glucagon dynamics in the isoglycemic intravenous glucose infusion (IIGI) experiment. As the glucose profile in IIGI is tailored to match that of a corresponding oral glucose tolerance test (OGTT), it provides a perfect method for studying hormone responses that are in the normal physiological domain and without the confounding effect of incretins and other gut mediated factors. The model was fit to IIGI data from individuals with and without T2D. Parameters related to glucagon action, suppression, and secretion as well as measures of insulin sensitivity, and glucose stimulated response were determined simultaneously. Significant impairment in glucose dependent glucagon suppression was observed in patients with T2D (duration of T2D: 8 (6-36) months) relative to weight matched control subjects (CS) without diabetes (k1 (mM)-1: 0.16 ± 0.015 (T2D, n = 7); 0.26 ± 0.047 (CS, n = 7)). Insulin action was significantly lower in patients with T2D (a1 (10 pM min)-1: 0.000084 ± 0.0000075 (T2D); 0.00052 ± 0.00015 (CS)) and the Hill coefficient in the equation for glucose dependent insulin response was found to be significantly different in T2D patients relative to CS (h: 1.4 ± 0.15; 1.9 ± 0.14). Trends in parameters with respect to fasting plasma glucose, HbA1c and 2-h glucose values are also presented. Significantly, a negative linear relationship is observed between the glucagon suppression parameter, k1, and the three markers for diabetes and is thus indicative of the role of glucagon in exacerbating the pathophysiology of diabetes (Spearman Rank Correlation: (n = 12; (-0.79, 0.002), (-0.73,.007), (-0.86,.0003)) respectively).

The effect of curcumin on hepatic fat content in individuals with obesity.

AIM: To evaluate the effect of curcumin treatment on hepatic fat content in obese individuals. MATERIALS AND METHODS: In a double-blind, parallel-group trial, 37 obese, non-diabetic individuals were randomized to placebo or curcumin treatment for 6 weeks. Curcumin was dosed as lecithin-formulated tablet; 200 mg twice daily. The primary endpoint was hepatic fat content as assessed by magnetic resonance spectroscopy (MRS). Other endpoints included anthropometric measurements, hepatic biomarkers including FibroScan measurements, metabolic variables, inflammation markers, appetite measures and ad libitum food intake. RESULTS: Baseline characteristics (mean ± SD) were age 46 ± 14 years, hepatic fat content 12.2% ± 8.8% points, body mass index 38.8 ± 6.1 kg/m2 and waist circumference 125.8 ± 12.3 cm. After 6 weeks of treatment with curcumin, hepatic fat content was changed by -0.86% points (95% CI -3.65; 1.94) compared with 0.71% points (95% CI - 2.08; 3.51) with placebo, thus resulting in a non-significant estimated treatment difference of -1.57% points (95% CI -5.36; 2.22, P = .412). Compared with placebo, curcumin treatment caused small reductions in fasting plasma glucose (estimated treatment difference [ETD] - 0.24 mmol/L [95% CI -0.45; -0.03]), triglycerides (ETD [percentage change] -20.22% [95% CI -33.21; -6.03]) and gamma glutamyltransferase (ETD [percentage change] -15.70% [95% CI -23.32; -7.32]), but except for gamma glutamyltransferase, none of these differences remained statistically significant after adjusting for multiple testing. Treatment was well tolerated. CONCLUSIONS: Compared with placebo, curcumin treatment for 6 weeks had no significant effect on MRS-assessed hepatic fat content in obese individuals with primarily mild steatosis. Curcumin was well tolerated.

Acute changes in plasma glucose increases left ventricular systolic function in insulin-treated patients with type 2 diabetes and controls.

AIMS: We aimed to evaluate the effect of acute hyperglycaemia and hypoglycaemia on cardiac function in patients with type 2 diabetes (T2D) and a control group. MATERIALS AND METHODS: In a nonrandomized interventional study, insulin-treated patients with T2D (N = 21, mean ± SD age 62.8 ± 6.5 years, body mass index [BMI] 29.0 ± 4.2 kg/m2 , glycated haemoglobin [HbA1c] 51.0 ± 5.4 mmol/mol [6.8 ± 0.5%]) and matched controls (N = 21, mean ± SD age 62.2 ± 8.3 years, BMI 29.2 ± 3.5 kg/m2 , HbA1c 34.3 ± 3.3 mmol/L [5.3 ± 0.3%]) underwent one experimental day with plasma glucose (PG) clamped at three different 30-minute steady-state levels: (1) fasting plasma glucose (FPG); (2) hyperglycaemia (FPG + 10 mmol/L); and (3) hyperinsulinaemic hypoglycaemia (PG <3.0 mmol/L). Cardiac function was evaluated during each steady state by echocardiography. RESULTS: Acute hyperglycaemia increased left ventricular (LV) ejection fraction from baseline in patients with T2D (mean [95% confidence interval] 4.5 percentage points [1.1; 7.9]) but not in controls (2.0 percentage points [-1.4; 5.4]). Mitral annular peak systolic velocity (s') increased during hyperglycaemia in both patients and controls (0.4 m/s [0.2;0.6] and 0.6 m/s [0.4; 0.8], respectively), whereas global longitudinal strain rate only increased in the controls (-0.05 s-1 [-0.12; 0.02] and -0.11 s-1 [-0.18; -0.03], respectively). All measures of LV systolic function increased markedly during hypoglycaemia (P <0.01 for all). No interaction between group and PG level on cardiac function was observed. CONCLUSIONS: Acute hyperglycaemia and hypoglycaemia increase LV systolic function, with no difference between patients with T2D and controls. Standardization of PG may improve reproducibility when evaluating LV systolic function in patients with T2D.

THERAPY OF ENDOCRINE DISEASE: Amylin and calcitonin - physiology and pharmacology.

Type 2 diabetes is a common manifestation of metabolic dysfunction due to obesity and constitutes a major burden for modern health care systems, in concert with the alarming rise in obesity worldwide. In recent years, several successful pharmacotherapies improving glucose metabolism have emerged and some of these also promote weight loss, thus, ameliorating insulin resistance. However, the progressive nature of type 2 diabetes is not halted by these new anti-diabetic pharmacotherapies. Therefore, novel therapies promoting weight loss further and delaying diabetes progression are needed. Amylin, a beta cell hormone, has satiating properties and also delays gastric emptying and inhibits postprandial glucagon secretion with the net result of reducing postprandial glucose excursions. Amylin acts through the six amylin receptors, which share the core component with the calcitonin receptor. Calcitonin, derived from thyroid C cells, is best known for its role in humane calcium metabolism, where it inhibits osteoclasts and reduces circulating calcium. However, calcitonin, particularly of salmon origin, has also been shown to affect insulin sensitivity, reduce the gastric emptying rate and promote satiation. Preclinical trials with agents targeting the calcitonin receptor and the amylin receptors, show improvements in several parameters of glucose metabolism including insulin sensitivity and some of these agents are currently undergoing clinical trials. Here, we review the physiological and pharmacological effects of amylin and calcitonin and discuss the future potential of amylin and calcitonin-based treatments for patients with type 2 diabetes and obesity.

Long-acting amylin analogues for the management of obesity.

PURPOSE OF REVIEW: To summarize recent developments of long-acting amylin analogues for the treatment of obesity and to outline their mode of action. RECENT FINDINGS: Amylin is a pancreatic hormone acting to control energy homeostasis and body weight. Activity at the calcitonin and amylin receptors in the area postrema seems to - at least partly - be responsible for these effects of amylin. Both preclinical and early-stage clinical studies investigating long-acting amylin receptor analogues demonstrate beneficial effects on body weight in obesity. Cagrilintide, a novel amylin analogue suitable for once-weekly administration, is in phase II clinical development and has shown promising body weight reducing effects alone and in combination with the glucagon-like peptide 1 receptor agonist semaglutide. SUMMARY: Long-acting amylin analogues have emerged as a possible pharmacotherapy against obesity, but more studies are needed to support the utility and long-term effects of this strategy in relevant populations.

Associations of hypoglycemia, glycemic variability and risk of cardiac arrhythmias in insulin-treated patients with type 2 diabetes: a prospective, observational study.

BACKGROUND: Insulin-treated patients with type 2 diabetes (T2D) are at risk of hypoglycemia, which is associated with an increased risk of cardiovascular disease and mortality. Using a long-term monitoring approach, we investigated the association between episodes of hypoglycemia, glycemic variability and cardiac arrhythmias in a real-life setting. METHODS: Insulin-treated patients with T2D (N = 21, [mean ± SD] age 66.8 ± 9.6 years, BMI 30.1 ± 4.5 kg/m2, HbA1c 6.8 ± 0.4% [51.0 ± 4.8 mmol/mol]) were included for a one-year observational study. Patients were monitored with continuous glucose monitoring ([mean ± SD] 118 ± 6 days) and an implantable cardiac monitor (ICM) during the study period. RESULTS: Time spend in hypoglycemia was higher during nighttime than during daytime ([median and interquartile range] 0.7% [0.7-2.7] vs. 0.4% [0.2-0.8]). The ICMs detected 724 episodes of potentially clinically significant arrhythmias in 12 (57%) participants, with atrial fibrillation and pauses accounting for 99% of the episodes. No association between hypoglycemia and cardiac arrhythmia was found during daytime. During nighttime, subject-specific hourly incidence of cardiac arrhythmias tended to increase with the occurrence of hypoglycemia (incident rate ratio [IRR] 1.70 [95% CI 0.36-8.01]) but only slightly with increasing time in hypoglycemia (IRR 1.04 [95% CI 0.89-1.22] per 5 min). Subject-specific incidence of cardiac arrhythmias during nighttime increased with increasing glycemic variability as estimated by coefficient of variation whereas it decreased during daytime (IRR 1.33 [95% CI 1.05-1.67] and IRR 0.77 [95% CI 0.59-0.99] per 5% absolute increase, respectively). CONCLUSIONS: Cardiac arrhythmias were common in insulin-treated patients with T2D and were associated with glycemic variability, whereas arrhythmias were not strongly associated with hypoglycemia. TRIAL REGISTRATION: NCT03150030, ClinicalTrials.gov, registered May 11, 2017. https://clinicaltrials.gov/ct2/show/NCT03150030.

Glucagon Clearance is Preserved in Type 2 Diabetes.

Hyperglucagonemia is a common observation in both obesity and type 2 diabetes, and the etiology is primarily thought to be hypersecretion of glucagon. We investigated whether altered elimination kinetics of glucagon could contribute to the hyperglucagonemia in type 2 diabetes and obesity. Individuals with type 2 diabetes and preserved kidney function (8 with and 8 without obesity) and matched control individuals (8 with and 8 without obesity) were recruited. Each participant underwent a 1-hour glucagon infusion (4 ng/kg/min), achieving steady-state plasma glucagon concentrations, followed by a 1-hour wash-out period. Plasma levels, the metabolic clearance rate (MCR), half-life (T½) and volume of distribution of glucagon were evaluated and a pharmacokinetic model was constructed. Glucagon MCR and volume of distribution were significantly higher in the type 2 diabetes group compared to the control group, while no significant differences between the groups were found in glucagon T½. Individuals with obesity had neither a significantly decreased MCR, T½, nor volume of distribution of glucagon. In our pharmacokinetic model, glucagon MCR associated positively with fasting plasma glucose and negatively with body weight. In conclusion, our results suggest that impaired glucagon clearance is not a fundamental part of the hyperglucagonemia observed in obesity and type 2 diabetes.

Glucagon Clearance is Preserved in Type 2 Diabetes.

Hyperglucagonemia is a common observation in both obesity and type 2 diabetes, and the etiology is primarily thought to be hypersecretion of glucagon. We investigated whether altered elimination kinetics of glucagon could contribute to the hyperglucagonemia in type 2 diabetes and obesity. Individuals with type 2 diabetes and preserved kidney function (8 with and 8 without obesity) and matched control individuals (8 with and 8 without obesity) were recruited. Each participant underwent a 1-hour glucagon infusion (4 ng/kg/min), achieving steady-state plasma glucagon concentrations, followed by a 1-hour wash-out period. Plasma levels, the metabolic clearance rate (MCR), half-life (T½) and volume of distribution of glucagon were evaluated and a pharmacokinetic model was constructed. Glucagon MCR and volume of distribution were significantly higher in the type 2 diabetes group compared to the control group, while no significant differences between the groups were found in glucagon T½ Individuals with obesity had neither a significantly decreased MCR, T½, nor volume of distribution of glucagon. In our pharmacokinetic model, glucagon MCR associated positively with fasting plasma glucose and negatively with body weight. In conclusion, our results suggest that impaired glucagon clearance is not a fundamental part of the hyperglucagonemia observed in obesity and type 2 diabetes.

MECHANISMS IN ENDOCRINOLOGY: The physiology of neuronostatin.

In 2008, the first evidence of a new hormone called neuronostatin was published. The hormone was discovered using a bioinformatic method and found to originate from the same preprohormone as somatostatin. This small peptide hormone of 13 amino acids and a C-terminal amidation was soon found to exert pleiotropic physiological effects. In animal studies, neuronostatin has been shown to reduce food intake and delay gastric emptying and gastrointestinal transit. Furthermore, neuronostatin has been shown to affect glucose metabolism by increasing glucagon secretion during situations when glucose concentrations are low. Additionally, neuronostatin has been shown to affect neural tissue and cardiomyocytes by suppressing cardiac contractility. The effects of neuronostatin have not yet been delineated in humans, but if the effects found in animal studies translate to humans it could position neuronostatin as a promising target in the treatment of obesity, hypertension and diabetes. In this review, we describe the discovery of neuronostatin and the current understanding of its physiological role and potential therapeutic applicability.

Acute hypoglycemia and risk of cardiac arrhythmias in insulin-treated type 2 diabetes and controls.

OBJECTIVE: Hypoglycemia is associated with an increased risk of cardiovascular disease including cardiac arrhythmias. We investigated the effect of hypoglycemia in the setting of acute glycemic fluctuations on cardiac rhythm and cardiac repolarization in insulin-treated patients with type 2 diabetes compared with matched controls without diabetes. DESIGN: A non-randomized, mechanistic intervention study. METHODS: Insulin-treated patients with type 2 diabetes (n = 21, age (mean ± s.d.): 62.8 ± 6.5 years, BMI: 29.0 ± 4.2 kg/m2, HbA1c: 6.8 ± 0.5% (51.0 ± 5.4 mmol/mol)) and matched controls (n = 21, age: 62.2 ± 8.3 years, BMI 29.2 ± 3.5 kg/m2, HbA1c: 5.3 ± 0.3% (34.3 ± 3.3 mmol/mol)) underwent a sequential hyperglycemic and hypoglycemic clamp with three steady-states of plasma glucose: (i) fasting plasma glucose, (ii) hyperglycemia (fasting plasma glucose +10 mmol/L) and (iii) hyperinsulinemic hypoglycemia (plasma glucose < 3.0 mmol/L). Participants underwent continuous ECG monitoring and blood samples for counterregulatory hormones and plasma potassium were obtained. RESULTS: Both groups experienced progressively increasing heart rate corrected QT (Fridericia's formula) interval prolongations during hypoglycemia ((∆mean (95% CI): 31 ms (16, 45) and 39 ms (24, 53) in the group of patients with type 2 diabetes and controls, respectively) with similar increases from baseline at the end of the hypoglycemic phase (P = 0.43). The incidence of ventricular premature beats increased significantly in both groups during hypoglycemia (P = 0.033 and P < 0.0001, respectively). One patient with type 2 diabetes developed atrial fibrillation during recovery from hypoglycemia. CONCLUSIONS: In insulin-treated patients with type 2 diabetes and controls without diabetes, hypoglycemia causes clinically significant and similar increases in cardiac repolarization that might increase vulnerability for serious cardiac arrhythmias and sudden cardiac death.

Metabolic effects of 1-week binge drinking and fast food intake during Roskilde Festival in young healthy male adults.

AIMS/HYPOTHESIS: Metabolic effects of intermittent unhealthy lifestyle in young adults are poorly studied. We investigated the gluco-metabolic and hepatic effects of participation in Roskilde Festival (1 week of binge drinking and junk food consumption) in young, healthy males. METHODS: Fourteen festival participants (FP) were studied before, during and after 1 week's participation in Roskilde Festival. Fourteen matched controls (CTRL) who did not participate in Roskilde Festival or change their lifestyle in other ways were investigated along a similar timeline. RESULTS: The FP group consumed more alcohol compared to their standard living conditions (2.0 ± 3.9 vs 16.3 ± 8.3 units/day, P < 0.001). CTRLs did not change their alcohol consumption. AUC for glucose during OGTT did not change in either group. C-peptide responses increased in the FP group (206 ± 24 vs 236 ± 17 min × nmol/L, P = 0.052) and the Matsuda index of insulin sensitivity decreased (6.2 ± 2.4 vs 4.7 ± 1.4, P = 0.054). AUC for glucagon during oral glucose tolerance test (OGTT) increased in the FP group (1037 ± 90 vs 1562 ± 195 min × pmol/L, P = 0.003) together with fasting fibroblast growth factor 21 (FGF21) (62 ± 30 vs 132 ± 72 pmol/L, P < 0.001), growth differentiation factor 15 (GDF5) (276 ± 78 vs 330 ± 83 pg/mL, P = 0.009) and aspartate aminotransferase (AST) levels (37.6 ± 6.8 vs 42.4 ± 11 U/L, P = 0.043). Four participants (29%) developed ultrasound-detectable steatosis and a mean strain elastography-assessed liver stiffness increased (P = 0.026) in the FP group. CONCLUSIONS/INTERPRETATION: Participation in Roskilde Festival did not affect oral glucose tolerance but was associated with a reduction in insulin sensitivity, increases in glucagon, FGF21, GDF15 and AST and lead to increased liver stiffness and, in 29% of the participants, ultrasound-detectable hepatic steatosis.

Glucagonostatic Potency of GLP-1 in Patients With Type 2 Diabetes, Patients With Type 1 Diabetes, and Healthy Control Subjects.

Hyperglucagonemia is a well-known contributor to diabetic hyperglycemia, and glucagon-like peptide 1 (GLP-1) suppresses glucagon secretion. Reduced inhibitory effects of glucose and GLP-1 on glucagon secretion may contribute to the hyperglucagonemia in diabetes and influence the success of GLP-1 receptor agonist therapy. We examined the dose-response relationship for GLP-1 on glucose-induced glucagon suppression in healthy individuals and patients with type 2 and type 1 diabetes. In randomized order, 10 healthy individuals with normal glucose tolerance, 10 patients with type 2 diabetes, and 9 C-peptide-negative patients with type 1 diabetes underwent 4 separate stepwise glucose clamps (five 30-min steps from fasting level to 15 mmol/L plasma glucose) during simultaneous intravenous infusions of saline or 0.2, 0.4, or 0.8 pmol GLP-1/kg/min. In healthy individuals and patients with type 2 diabetes, GLP-1 potentiated the glucagon-suppressive effect of intravenous glucose in a dose-dependent manner. In patients with type 1 diabetes, no significant changes in glucagon secretion were observed during the clamps whether with saline or GLP-1 infusions. In conclusion, the glucagonostatic potency of GLP-1 during a stepwise glucose clamp is preserved in patients with type 2 diabetes, whereas our patients with type 1 diabetes were insensitive to the glucagonostatic effects of both glucose and GLP-1.

No detectable effect of a type 2 diabetes-associated TCF7L2 genotype on the incretin effect.

The T allele of TCF7L2 rs7903146 is a common genetic variant associated with type 2 diabetes (T2D), possibly by modulation of incretin action. In this study, we evaluated the effect of the TCF7L2 rs7903146 T allele on the incretin effect and other glucometabolic parameters in normal glucose tolerant individuals (NGT) and participants with T2D. The rs7903146 variant was genotyped in cohorts of 61 NGT individuals (23 were heterozygous (CT) or homozygous (TT) T allele carriers) and 43 participants with T2D (20 with CT/TT). Participants were previously examined by an oral glucose tolerance test (OGTT) and a subsequent isoglycemic intravenous glucose infusion (IIGI). The incretin effect was assessed by quantification of the difference in integrated beta cell secretory responses during the OGTT and IIGI. Glucose and hormonal levels were measured during experimental days, and from these, indices of beta cell function and insulin sensitivity were calculated. No genotype-specific differences in the incretin effect were observed in the NGT group (P = 0.70) or the T2D group (P = 0.68). NGT T allele carriers displayed diminished glucose-dependent insulinotropic polypeptide response during OGTT (P = 0.01) while T allele carriers with T2D were characterized by lower C-peptide AUC after OGTT (P = 0.04) and elevated glucose AUC after OGTT (P = 0.04). In conclusion, our findings do not exclude that this specific TCF7L2 variant increases the risk of developing T2D via diminished incretin effect, but genotype-related defects were not detectable in these cohorts.

One Year's Treatment with the Glucagon-Like Peptide 1 Receptor Agonist Liraglutide Decreases Hepatic Fat Content in Women with Nonalcoholic Fatty Liver Disease and Prior Gestational Diabetes Mellitus in a Randomized, Placebo-Controlled Trial.

Prior gestational diabetes mellitus (pGDM) is associated with increased risk of nonalcoholic fatty liver disease (NAFLD). Treatment with glucagon-like peptide 1 (GLP-1) receptor agonists has shown beneficial effects in NAFLD patients. We evaluated the effect of the GLP-1 analogue liraglutide on NAFLD features in women with pGDM. Eighty-two overweight/obese, nondiabetic women with pGDM were included. We performed abdominal ultrasound, transient elastography with controlled attenuation parameter (CAP), and blood sampling at baseline and after 1 year. Thirty-seven women were randomized to liraglutide (1.8 mg once-daily) and 45 to placebo. Based on the ultrasound scan, 18 women (22%) had ultrasound-verified NAFLD at baseline and of these, 10 (56%) received liraglutide treatment. After 1 year, eight participants no longer had steatosis, four in each treatment group. The number of participants who developed NAFLD was similar in the two treatment groups; five in the liraglutide group and six in the placebo group (p = 0.74). Compared to placebo, liraglutide reduced the CAP-assessed intrahepatic fat content (-28 (-44;-11) vs. 2 (-13;18) dB/m, p < 0.01) and body weight (-4.7 (-6.4;-2.9) vs. -1.4 (-3;0.3) kg, p < 0.01). One-year's liraglutide treatment had no effect on the presence of ultrasound-diagnosed NAFLD in overweight/obese nondiabetic women with pGDM, but reduced body weight and steatosis assessed by transient elastography with CAP.

Circulating Levels of the Soluble Receptor for AGE (sRAGE) during Escalating Oral Glucose Dosages and Corresponding Isoglycaemic i.v. Glucose Infusions in Individuals with and without Type 2 Diabetes.

Postprandial glucose excursions are postulated to increase the risk for diabetes complications via the production of advanced glycation end products (AGEs). The soluble receptor of AGEs (sRAGE) likely acts as a decoy receptor, mopping up AGEs, diminishing their capacity for pro-inflammatory and pro-apoptotic signaling. Recent evidence suggests that AGEs and soluble receptor for AGEs (sRAGE) may be altered under postprandial and fasting conditions. Here, we investigated the effects of increasing oral glucose loads during oral glucose tolerance tests (OGTT) and matched isoglycaemic intravenous (i.v.) glucose infusions (IIGI) on circulating concentrations of sRAGE. Samples from eight individuals with type 2 diabetes and eight age-, gender-, and body mass index (BMI)-matched controls, all of whom underwent three differently dosed OGTTs (25 g, 75 g, and 125 g), and three matched IIGIs were utilised (NCT00529048). Serum concentrations of sRAGE were measured over 240 min during each test. For individuals with diabetes, sRAGE area under the curve (AUC0-240min) declined with increasing i.v. glucose dosages (p < 0.0001 for trend) and was lower during IIGI compared to OGTT at the 125 g dosage (p = 0.004). In control subjects, sRAGE AUC0-240min was only lower during IIGI compared to OGTT at the 25 g dose (p = 0.0015). sRAGE AUC0-240min was negatively correlated to AUC0-240min for the incretin hormone glucagon-like peptide -1 (GLP-1) during the 75 g OGTT and matched IIGI, but only in individuals with type 2 diabetes. These data suggest that gastrointestinal factors may play a role in regulating sRAGE concentrations during postprandial glucose excursions, thus warranting further investigation.

Glucagon Resistance at the Level of Amino Acid Turnover in Obese Subjects With Hepatic Steatosis.

Glucagon secretion is regulated by circulating glucose, but it has turned out that amino acids also play an important role and that hepatic amino acid metabolism and glucagon are linked in a mutual feedback cycle, the liver-α-cell axis. On the basis of this knowledge, we hypothesized that hepatic steatosis might impair glucagon's action on hepatic amino acid metabolism and lead to hyperaminoacidemia and hyperglucagonemia. We subjected 15 healthy lean and 15 obese steatotic male participants to a pancreatic clamp with somatostatin and evaluated hepatic glucose and amino acid metabolism when glucagon was at basal levels and at high physiological levels. The degree of steatosis was evaluated from liver biopsy specimens. Total RNA sequencing of liver biopsy specimens from the obese steatotic individuals revealed perturbations in the expression of genes predominantly involved in amino acid metabolism. This group was characterized by fasting hyperglucagonemia, hyperaminoacidemia, and no lowering of amino acid levels in response to high levels of glucagon. Endogenous glucose production was similar between lean and obese individuals. Our results suggest that hepatic steatosis causes resistance to the effect of glucagon on amino acid metabolism. This results in increased amino acid concentrations and increased glucagon secretion, providing a likely explanation for fatty liver-associated hyperglucagonemia.

Amylin and Calcitonin: Potential Therapeutic Strategies to Reduce Body Weight and Liver Fat.

The hormones amylin and calcitonin interact with receptors within the same family to exert their effects on the human organism. Calcitonin, derived from thyroid C cells, is known for its inhibitory effect on osteoclasts. Calcitonin of mammalian origin promotes insulin sensitivity, while the more potent calcitonin extracted from salmon additionally inhibits gastric emptying, promotes gallbladder relaxation, increases energy expenditure and induces satiety as well as weight loss. Amylin, derived from pancreatic beta cells, regulates plasma glucose by delaying gastric emptying after meal ingestion, and modulates glucagon secretion and central satiety signals in the brain. Thus, both hormones seem to have metabolic effects of relevance in the context of non-alcoholic fatty liver disease (NAFLD) and other metabolic diseases. In rats, studies with dual amylin and calcitonin receptor agonists have demonstrated robust body weight loss, improved glucose tolerance and a decreased deposition of fat in liver tissue beyond what is observed after a body weight loss. The translational aspects of these preclinical data currently remain unknown. Here, we describe the physiology, pathophysiology, and pharmacological effects of amylin and calcitonin and review preclinical and clinical findings alluding to the future potential of amylin and calcitonin-based drugs for the treatment of obesity and NAFLD.