Statin therapy is associated with lower prevalence of gut microbiota dysbiosis.

Microbiome community typing analyses have recently identified the Bacteroides2 (Bact2) enterotype, an intestinal microbiota configuration that is associated with systemic inflammation and has a high prevalence in loose stools in humans1,2. Bact2 is characterized by a high proportion of Bacteroides, a low proportion of Faecalibacterium and low microbial cell densities1,2, and its prevalence varies from 13% in a general population cohort to as high as 78% in patients with inflammatory bowel disease2. Reported changes in stool consistency3 and inflammation status4 during the progression towards obesity and metabolic comorbidities led us to propose that these developments might similarly correlate with an increased prevalence of the potentially dysbiotic Bact2 enterotype. Here, by exploring obesity-associated microbiota alterations in the quantitative faecal metagenomes of the cross-sectional MetaCardis Body Mass Index Spectrum cohort (n = 888), we identify statin therapy as a key covariate of microbiome diversification. By focusing on a subcohort of participants that are not medicated with statins, we find that the prevalence of Bact2 correlates with body mass index, increasing from 3.90% in lean or overweight participants to 17.73% in obese participants. Systemic inflammation levels in Bact2-enterotyped individuals are higher than predicted on the basis of their obesity status, indicative of Bact2 as a dysbiotic microbiome constellation. We also observe that obesity-associated microbiota dysbiosis is negatively associated with statin treatment, resulting in a lower Bact2 prevalence of 5.88% in statin-medicated obese participants. This finding is validated in both the accompanying MetaCardis cardiovascular disease dataset (n = 282) and the independent Flemish Gut Flora Project population cohort (n = 2,345). The potential benefits of statins in this context will require further evaluation in a prospective clinical trial to ascertain whether the effect is reproducible in a randomized population and before considering their application as microbiota-modulating therapeutics.

Determinants of plasma levels of proglucagon and the metabolic impact of glucagon receptor signalling: a UK Biobank study.

AIMS/HYPOTHESES: Glucagon and glucagon-like peptide-1 (GLP-1) are derived from the same precursor; proglucagon, and dual agonists of their receptors are currently being explored for the treatment of obesity and metabolic dysfunction-associated steatotic liver disease (MASLD). Elevated levels of endogenous glucagon (hyperglucagonaemia) have been linked with hyperglycaemia in individuals with type 2 diabetes but are also observed in individuals with obesity and MASLD. GLP-1 levels have been reported to be largely unaffected or even reduced in similar conditions. We investigated potential determinants of plasma proglucagon and associations of glucagon receptor signalling with metabolic diseases based on data from the UK Biobank. METHODS: We used exome sequencing data from the UK Biobank for ~410,000 white participants to identify glucagon receptor variants and grouped them based on their known or predicted signalling. Data on plasma levels of proglucagon estimated using Olink technology were available for a subset of the cohort (~40,000). We determined associations of glucagon receptor variants and proglucagon with BMI, type 2 diabetes and liver fat (quantified by liver MRI) and performed survival analyses to investigate if elevated proglucagon predicts type 2 diabetes development. RESULTS: Obesity, MASLD and type 2 diabetes were associated with elevated plasma levels of proglucagon independently of each other. Baseline proglucagon levels were associated with the risk of type 2 diabetes development over a 14 year follow-up period (HR 1.13; 95% CI 1.09, 1.17; n=1562; p=1.3×10-12). This association was of the same magnitude across strata of BMI. Carriers of glucagon receptor variants with reduced cAMP signalling had elevated levels of proglucagon (ß 0.847; 95% CI 0.04, 1.66; n=17; p=0.04), and carriers of variants with a predicted frameshift mutation had higher levels of liver fat compared with the wild-type reference group (ß 0.504; 95% CI 0.03, 0.98; n=11; p=0.04). CONCLUSIONS/INTERPRETATION: Our findings support the suggestion that glucagon receptor signalling is involved in MASLD, that plasma levels of proglucagon are linked to the risk of type 2 diabetes development, and that proglucagon levels are influenced by genetic variation in the glucagon receptor, obesity, type 2 diabetes and MASLD. Determining the molecular signalling pathways downstream of glucagon receptor activation may guide the development of biased GLP-1/glucagon co-agonist with improved metabolic benefits. DATA AVAILABILITY: All coding is available through https://github.com/nicwin98/UK-Biobank-GCG.

Exercise-induced increase in muscle insulin sensitivity in men is amplified when assessed using a meal test.

AIMS/HYPOTHESIS: Exercise has a profound effect on insulin sensitivity in skeletal muscle. The euglycaemic-hyperinsulinaemic clamp (EHC) is the gold standard for assessment of insulin sensitivity but it does not reflect the hyperglycaemia that occurs after eating a meal. In previous EHC investigations, it has been shown that the interstitial glucose concentration in muscle is decreased to a larger extent in previously exercised muscle than in rested muscle. This suggests that previously exercised muscle may increase its glucose uptake more than rested muscle if glucose supply is increased by hyperglycaemia. Therefore, we hypothesised that the exercise-induced increase in muscle insulin sensitivity would appear greater after eating a meal than previously observed with the EHC. METHODS: Ten recreationally active men performed dynamic one-legged knee extensor exercise for 1 h. Following this, both femoral veins and one femoral artery were cannulated. Subsequently, 4 h after exercise, a solid meal followed by two liquid meals were ingested over 1 h and glucose uptake in the two legs was measured for 3 h. Muscle biopsies from both legs were obtained before the meal test and 90 min after the meal test was initiated. Data obtained in previous studies using the EHC (n=106 participants from 13 EHC studies) were used for comparison with the meal-test data obtained in this study. RESULTS: Plasma glucose and insulin peaked 45 min after initiation of the meal test. Following the meal test, leg glucose uptake and glucose clearance increased twice as much in the exercised leg than in the rested leg; this difference is twice as big as that observed in previous investigations using EHCs. Glucose uptake in the rested leg plateaued after 15 min, alongside elevated muscle glucose 6-phosphate levels, suggestive of compromised muscle glucose metabolism. In contrast, glucose uptake in the exercised leg plateaued 45 min after initiation of the meal test and there were no signs of compromised glucose metabolism. Phosphorylation of the TBC1 domain family member 4 (TBC1D4; p-TBC1D4Ser704) and glycogen synthase activity were greater in the exercised leg compared with the rested leg. Muscle interstitial glucose concentration increased with ingestion of meals, although it was 16% lower in the exercised leg than in the rested leg. CONCLUSIONS/INTERPRETATION: Hyperglycaemia after meal ingestion results in larger differences in muscle glucose uptake between rested and exercised muscle than previously observed during EHCs. These findings indicate that the ability of exercise to increase insulin-stimulated muscle glucose uptake is even greater when evaluated with a meal test than has previously been shown with EHCs.

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.

Healthy Weight Loss Maintenance with Exercise, Liraglutide, or Both Combined.

BACKGROUND: Weight regain after weight loss is a major problem in the treatment of persons with obesity. METHODS: In a randomized, head-to-head, placebo-controlled trial, we enrolled adults with obesity (body-mass index [the weight in kilograms divided by the square of the height in meters], 32 to 43) who did not have diabetes. After an 8-week low-calorie diet, participants were randomly assigned for 1 year to one of four strategies: a moderate-to-vigorous-intensity exercise program plus placebo (exercise group); treatment with liraglutide (3.0 mg per day) plus usual activity (liraglutide group); exercise program plus liraglutide therapy (combination group); or placebo plus usual activity (placebo group). End points with prespecified hypotheses were the change in body weight (primary end point) and the change in body-fat percentage (secondary end point) from randomization to the end of the treatment period in the intention-to-treat population. Prespecified metabolic health-related end points and safety were also assessed. RESULTS: After the 8-week low-calorie diet, 195 participants had a mean decrease in body weight of 13.1 kg. At 1 year, all the active-treatment strategies led to greater weight loss than placebo: difference in the exercise group, -4.1 kg (95% confidence interval [CI], -7.8 to -0.4; P = 0.03); in the liraglutide group, -6.8 kg (95% CI, -10.4 to -3.1; P<0.001); and in the combination group, -9.5 kg (95% CI, -13.1 to -5.9; P<0.001). The combination strategy led to greater weight loss than exercise (difference, -5.4 kg; 95% CI, -9.0 to -1.7; P = 0.004) but not liraglutide (-2.7 kg; 95% CI, -6.3 to 0.8; P = 0.13). The combination strategy decreased body-fat percentage by 3.9 percentage points, which was approximately twice the decrease in the exercise group (-1.7 percentage points; 95% CI, -3.2 to -0.2; P = 0.02) and the liraglutide group (-1.9 percentage points; 95% CI, -3.3 to -0.5; P = 0.009). Only the combination strategy was associated with improvements in the glycated hemoglobin level, insulin sensitivity, and cardiorespiratory fitness. Increased heart rate and cholelithiasis were observed more often in the liraglutide group than in the combination group. CONCLUSIONS: A strategy combining exercise and liraglutide therapy improved healthy weight loss maintenance more than either treatment alone. (Funded by the Novo Nordisk Foundation and others; EudraCT number, 2015-005585-32; ClinicalTrials.gov number, NCT04122716.).

The role of empagliflozin-induced metabolic changes for cardiac function in patients with type 2 diabetes. A randomized cross-over magnetic resonance imaging study with insulin as comparator.

BACKGROUND: Metabolic effects of empagliflozin treatment include lowered glucose and insulin concentrations, elevated free fatty acids and ketone bodies and have been suggested to contribute to the cardiovascular benefits of empagliflozin treatment, possibly through an improved cardiac function. We aimed to evaluate the influence of these metabolic changes on cardiac function in patients with T2D. METHODS: In a randomized cross-over design, the SGLT2 inhibitor empagliflozin (E) was compared with insulin (I) treatment titrated to the same level of glycemic control in 17 patients with type 2 diabetes, BMI of > 28 kg/m2, C-peptide > 500 pM. Treatments lasted 5 weeks and were preceded by 3-week washouts (WO). At the end of treatments and washouts, cardiac diastolic function was determined with magnetic resonance imaging from left ventricle early peak-filling rate and left atrial passive emptying fraction (primary and key secondary endpoints); systolic function from left ventricle ejection fraction (secondary endpoint). Coupling between cardiac function and fatty acid concentrations, was studied on a separate day with a second scan after reduction of plasma fatty acids with acipimox. Data are Mean ± standard error. Between treatment difference (ΔT: E-I) and treatments effects (ΔE: E-WO or ΔI: I -WO) were evaluated using Students' t-test or Wilcoxon signed rank test as appropriate. RESULTS: Glucose concentrations were similar, fatty acids, ketone bodies and lipid oxidation increased while insulin concentrations decreased on empagliflozin compared with insulin treatment. Cardiac diastolic and systolic function were unchanged by either treatment. Acipimox decreased fatty acids with 35% at all visits, and this led to reduced cardiac diastolic (ΔT: -51 ± 22 ml/s (p < 0.05); ΔE: -33 ± 26 ml/s (ns); ΔI: 37 ± 26 (ns, p < 0.05 vs ΔE)) and systolic function (ΔT: -3 ± 1% (p < 0.05); ΔE: -3 ± 1% (p < 0.05): ΔI: 1 ± 2 (ns, ns vs ΔE)) under chronotropic stress during empagliflozin compared to insulin treatment. CONCLUSIONS: Despite significant metabolic differences, cardiac function did not differ on empagliflozin compared with insulin treatment. Impaired cardiac function during acipimox treatment, could suggest greater cardiac reliance on lipid metabolism for proper function during empagliflozin treatment in patients with type 2 diabetes. TRIAL REGISTRATION: EudraCT 2017-002101-35, August 2017.

Canagliflozin or acarbose versus placebo to ameliorate post-bariatric hypoglycaemia - The HypoBar I randomized clinical trial protocol.

INTRODUCTION: Post-bariatric hypoglycaemia (PBH) is a rare yet disabling clinical condition, mostly reported after Roux-en-Y gastric bypass (RYGB) surgery. RYGB is one of the most widely used and effective bariatric procedures. The pathophysiology of PBH remains unclear, and treatment options are limited in effectiveness and/or carry significant side effects. Acarbose slows carbohydrates digestion and absorption and is generally considered first-line pharmacological treatment for PBH but its gastrointestinal side effects limit patient compliance. Canagliflozin inhibits intestinal and renal sodium-dependent glucose absorption and reduces postprandial excursions of glucose, insulin and incretins after RYGB - effects that could be beneficial in ameliorating PBH. AIMS: The trial aims to investigate how blood glucose levels are affected during daily living in subjects with PBH during treatment with canagliflozin or acarbose compared with placebo, and to study the meal-induced entero-endocrine mechanisms implied in the treatment responses. METHODS: In a double-blinded, randomized, crossover clinical trial, HypoBar I will investigate the effectiveness in reducing the risk of PBH, safety, ambulatory glucose profile and entero-endocrine responses when PBH is treated with canagliflozin 300 mg twice daily during a 4-week intervention period, compared with acarbose 50 mg thrice daily or placebo. ETHICS AND DISSEMINATION: HypoBar I is approved by the Local regulatory entities. Results will be published in peer-reviewed journals. CONCLUSION: If effective, well-tolerated and safe, canagliflozin could be a novel treatment for people with PBH. HypoBar I might also unravel new mechanisms underlying PBH, potentially identifying new treatment targets. TRIAL REGISTRATION: EudraCT number 2022-000157-87.

Glucagon agonism in the treatment of metabolic diseases including type 2 diabetes mellitus and obesity.

Type 2 diabetes mellitus (T2DM) is associated with obesity and, therefore, it is important to target both overweight and hyperglycaemia. Glucagon plays important roles in glucose, amino acid and fat metabolism and may also regulate appetite and energy expenditure. These physiological properties are currently being exploited therapeutically in several compounds, most often in combination with glucagon-like peptide-1 (GLP-1) agonism in the form of dual agonists. With this combination, increases in hepatic glucose production and hyperglycaemia, which would be counterproductive, are largely avoided. In multiple randomized trials, the co-agonists have been demonstrated to lead to significant weight loss and, in participants with T2DM, even improved glycated haemoglobin (HbA1c) levels. In addition, significant reductions in hepatic fat content have been observed. Here, we review and discuss the studies so far available. Twenty-six randomized trials of seven different GLP-1 receptor (GLP-1R)/glucagon receptor (GCGR) co-agonists were identified and reviewed. GLP-1R/GCGR co-agonists generally provided significant weight loss, reductions in hepatic fat content, improved lipid profiles, insulin secretion and sensitivity, and in some cases, improved HbA1c levels. A higher incidence of adverse effects was present with GLP-1R/GCGR co-agonist treatment than with GLP-1 agonist monotherapy or placebo. Possible additional risks associated with glucagon agonism are also discussed. A delicate balance between GLP-1 and glucagon agonism seems to be of particular importance. Further studies exploring the optimal ratio of GLP-1 and glucagon receptor activation and dosage and titration regimens are needed to ensure a sufficient safety profile while providing clinical benefits.

Elucidating the glucose-lowering effect of the bile acid sequestrant sevelamer.

AIM: Bile acid sequestrants are cholesterol-lowering drugs, which also improve glycaemic control in people with type 2 diabetes. The mechanism behind the glucose-lowering effect is unknown but has been proposed to be mediated by increased glucagon-like peptide-1 (GLP-1) secretion. Here, we investigated the glucose-lowering effects of sevelamer including any contribution from GLP-1 in people with type 2 diabetes. MATERIALS AND METHODS: In a randomized, double-blind, placebo-controlled, crossover study, 15 people with type 2 diabetes on metformin monotherapy underwent two 17-day treatment periods with the bile acid sequestrant sevelamer and placebo, respectively, in a randomized order and with an interposed wash-out period of minimum 6 weeks. On days 15 and 17 of each treatment period, participants underwent experimental days with 4-h liquid meal tests and application of concomitant infusion of exendin(9-39)NH2 or saline. RESULTS: Compared with placebo, sevelamer improved insulin sensitivity (assessed by homeostatic model assessment of insulin resistance) and beta-cell sensitivity to glucose and lowered fasting and postprandial plasma glucose concentrations. In both treatment periods, exendin(9-39)NH2 increased postprandial glucose excursions compared with saline but without absolute or relative difference between the two treatment periods. In contrast, exendin(9-39)NH2 abolished the sevelamer-induced improvement in beta-cell glucose sensitivity. CONCLUSIONS: The bile acid sequestrant sevelamer improved insulin sensitivity and beta-cell sensitivity to glucose, but using the GLP-1 receptor antagonist exendin(9-39)NH2 we were not able to detect a GLP-1-mediated glucose-lowering effect of sevelamer in individuals with type 2 diabetes. Nevertheless, the sevelamer-induced improvement of beta-cell sensitivity to glucose was shown to be GLP-1-dependent.

Liraglutide treatment for the prevention of glucose tolerance deterioration in women with prior gestational diabetes mellitus: A 52-week randomized controlled clinical trial.

AIM: We investigated the effect of 52-week treatment with liraglutide, a glucagon-like peptide 1 receptor agonist, on glucose tolerance and incretin effect in women with previous gestational diabetes mellitus (pGDM). MATERIALS AND METHODS: Women with overweight/obesity and pGDM were randomized to once daily subcutaneous liraglutide 1.8 mg or placebo for 52 weeks. Participants underwent oral glucose tolerance test (OGTT) and isoglycaemic intravenous glucose infusion at baseline and at 52 weeks, and an additional OGTT after the drug wash-out. RESULTS: In total, 104 women [age: mean ± SD, 38 ± 5 years; fasting plasma glucose (FPG): 5.5 ± 0.4 mmol/L; glycated haemoglobin (HbA1c): 33 ± 4 mmol/mol, bodyweight: 88.2 ± 14.8 kg, body mass index: 31.1 ± 4.3 kg/m2 ] were assigned to liraglutide (n = 49) or placebo (n = 55). Estimated treatment difference (ETD) for area under curve during OGTT was -173 (95% confidence interval -250 to -97) mmol/L × min, p < .0001, but after wash-out the difference disappeared [ETD 58 (-30 to 146) mmol/L × min, p = .536]. Liraglutide reduced FPG [ETD -0.2 (-0.4 to -0.1) mmol/L, p = .018], HbA1c [-2.2 (-3.5 to -0.8) mmol/mol, p = .018] and bodyweight [-3.9 (-6.2 to -1.6) kg, p = .012]. No change in the incretin effect was observed. The number of women with prediabetes was reduced from 64% to 10% with liraglutide vs. 50% with placebo [adjusted odds ratio 0.10 (0.03-0.32), p = .002]. CONCLUSIONS: Treatment with liraglutide for 52 weeks improved glucose tolerance, FPG, HbA1c and bodyweight in women with overweight/obesity and pGDM. Progression to prediabetes while on drug was markedly reduced, but after a 1-week drug wash-out, the effect was lost.

Association between recent exposure to continuous glucose monitoring-recorded hypoglycaemia and counterregulatory and symptom responses to subsequent controlled hypoglycaemia in people with type 1 diabetes.

AIM: Experimental hypoglycaemia blunts the counterregulatory hormone and symptom responses to a subsequent episode of hypoglycaemia. In this study, we aimed to assess the associations between antecedent exposure and continuous glucose monitoring (CGM)-recorded hypoglycaemia during a 1-week period and the counterregulatory responses to subsequent experimental hypoglycaemia in people with type 1 diabetes. MATERIALS AND METHODS: Forty-two people with type 1 diabetes (20 females, mean ± SD glycated haemoglobin 7.8% ± 1.0%, diabetes duration median (interquartile range) 22.0 (10.5-34.9) years, 29 CGM users, and 19 with impaired awareness of hypoglycaemia) wore an open intermittently scanned CGM for 1 week to detect hypoglycaemic exposure before a standardized hyperinsulinaemic-hypoglycaemic [2.8 ± 0.1 mmol/L (50.2 ± 2.3 mg/dl)] glucose clamp. Symptom responses and counterregulatory hormones were measured during the clamp. The study is part of the HypoRESOLVE project. RESULTS: CGM-recorded hypoglycaemia in the week before the clamp was negatively associated with adrenaline response [ß -0.09, 95% CI (-0.16, -0.02) nmol/L, p = .014], after adjusting for CGM use, awareness of hypoglycaemia, glycated haemoglobin and total daily insulin dose. This was driven by level 2 hypoglycaemia [<3.0 mmol/L (54 mg/dl)] [ß -0.21, 95% CI (-0.41, -0.01) nmol/L, p = .034]. CGM-recorded hypoglycaemia was negatively associated with total, autonomic, and neuroglycopenic symptom responses, but these associations were lost after adjusting for potential confounders. CONCLUSIONS: Recent exposure to CGM-detected hypoglycaemia was independently associated with an attenuated adrenaline response to experimental hypoglycaemia in people with type 1 diabetes.

Bone remodeling in survivors of pediatric hematopoietic stem cell transplantation: Impact of heavy resistance training.

BACKGROUND: Early-onset osteoporosis is a frequent late effect after pediatric hematopoietic stem cell transplantation (HSCT). It remains unknown if physical training can improve bone formation in these patients, as the transplantation procedure may cause sustained dysregulation of the bone-forming osteoblast progenitor cells. OBJECTIVE: We aimed to explore the effect of resistance training on bone remodeling in long-term survivors of pediatric HSCT. PROCEDURE: In this prospective, controlled intervention study, we included seven HSCT survivors and 15 age- and sex-matched healthy controls. The participants completed a 12-week heavy load, lower extremity resistance training intervention with three weekly sessions. We measured fasting serum levels of the bone formation marker "N-terminal propeptide of type I procollagen" (P1NP), and the bone resorption marker "C-terminal telopeptide of type I collagen" (CTX). The hypothesis was planned before data collection began. The trial was registered at Clinicaltrials.gov before including the first participant, with trial registration no. NCT04922970. RESULTS: Resistance training led to significantly increased levels of fasting P1NP in both patients (from 57.62 to 114.99 ng/mL, p = .03) and controls (from 66.02 to 104.62 ng/mL, p < .001). No significant changes in fasting CTX levels were observed. CONCLUSIONS: Despite previous high-dose cytotoxic therapy, long-term survivors of pediatric HSCT respond to resistance training with improvement of bone formation, comparable to that of healthy controls. This suggests that resistance training might be a promising non-pharmacological approach to prevent the early decline in bone mass, and should be considered as part of a follow-up program to counteract long-term sequela after pediatric HSCT.

Loss of the Secretin Receptor Impairs Renal Bicarbonate Excretion and Aggravates Metabolic Alkalosis in Mice during Acute Base-Loading.

SIGNIFICANCE STATEMENT: During acute base excess, the renal collecting duct ß -intercalated cells ( ß -ICs) become activated to increase urine base excretion. This process is dependent on pendrin and cystic fibrosis transmembrane regulator (CFTR) expressed in the apical membrane of ß -ICs. The signal that leads to activation of this process was unknown. Plasma secretin levels increase during acute alkalosis, and the secretin receptor (SCTR) is functionally expressed in ß -ICs. We find that mice with global knockout for the SCTR lose their ability to acutely increase renal base excretion. This forces the mice to lower their ventilation to cope with this challenge. Our findings suggest that secretin is a systemic bicarbonate-regulating hormone, likely being released from the small intestine during alkalosis. BACKGROUND: The secretin receptor (SCTR) is functionally expressed in the basolateral membrane of the ß -intercalated cells of the kidney cortical collecting duct and stimulates urine alkalization by activating the ß -intercalated cells. Interestingly, the plasma secretin level increases during acute metabolic alkalosis, but its role in systemic acid-base homeostasis was unclear. We hypothesized that the SCTR system is essential for renal base excretion during acute metabolic alkalosis. METHODS: We conducted bladder catheterization experiments, metabolic cage studies, blood gas analysis, barometric respirometry, perfusion of isolated cortical collecting ducts, immunoblotting, and immunohistochemistry in SCTR wild-type and knockout (KO) mice. We also perfused isolated rat small intestines to study secretin release. RESULTS: In wild-type mice, secretin acutely increased urine pH and pendrin function in isolated perfused cortical collecting ducts. These effects were absent in KO mice, which also did not sufficiently increase renal base excretion during acute base loading. In line with these findings, KO mice developed prolonged metabolic alkalosis when exposed to acute oral or intraperitoneal base loading. Furthermore, KO mice exhibited transient but marked hypoventilation after acute base loading. In rats, increased blood alkalinity of the perfused upper small intestine increased venous secretin release. CONCLUSIONS: Our results suggest that loss of SCTR impairs the appropriate increase of renal base excretion during acute base loading and that SCTR is necessary for acute correction of metabolic alkalosis. In addition, our findings suggest that blood alkalinity increases secretin release from the small intestine and that secretin action is critical for bicarbonate homeostasis.

The feedback cycles between glucose, amino acids and lipids and alpha cell secretion and their role in metabolic fatty liver disease.

PURPOSE OF REVIEW: Glucagon increases hepatic glucose production and in patients with metabolic diseases, glucagon secretion is increased contributing to diabetic hyperglycemia. This review explores the role of amino acids and lipids in the regulation of glucagon secretion and how it may be disturbed in metabolic diseases such as obesity and metabolic associated fatty liver disease (MAFLD). RECENT FINDINGS: Human and animal studies have shown that MAFLD is associated with glucagon resistance towards amino acid catabolism, resulting in elevated plasma levels of amino acids. A recent clinical study showed that MAFLD is also associated with glucagon resistance towards lipid metabolism. In contrast, MAFLD may not decrease hepatic sensitivity to the stimulatory effects of glucagon on glucose production. SUMMARY: Elevated plasma levels of amino acids and lipids associated with MAFLD may cause diabetogenic hyperglucagonemia. MAFLD and glucagon resistance may therefore be causally linked to hyperglycemia and the development of type 2 diabetes.

The expanding incretin universe: from basic biology to clinical translation.

Incretin hormones, principally glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1(GLP-1), potentiate meal-stimulated insulin secretion through direct (GIP + GLP-1) and indirect (GLP-1) actions on islet ß-cells. GIP and GLP-1 also regulate glucagon secretion, through direct and indirect pathways. The incretin hormone receptors (GIPR and GLP-1R) are widely distributed beyond the pancreas, principally in the brain, cardiovascular and immune systems, gut and kidney, consistent with a broad array of extrapancreatic incretin actions. Notably, the glucoregulatory and anorectic activities of GIP and GLP-1 have supported development of incretin-based therapies for the treatment of type 2 diabetes and obesity. Here we review evolving concepts of incretin action, focusing predominantly on GLP-1, from discovery, to clinical proof of concept, to therapeutic outcomes. We identify established vs uncertain mechanisms of action, highlighting biology conserved across species, while illuminating areas of active investigation and uncertainty that require additional clarification.

100 years of glucagon and 100 more.

The peptide hormone glucagon, discovered in late 1922, is secreted from pancreatic alpha cells and is an essential regulator of metabolic homeostasis. This review summarises experiences since the discovery of glucagon regarding basic and clinical aspects of this hormone and speculations on the future directions for glucagon biology and glucagon-based therapies. The review was based on the international glucagon conference, entitled 'A hundred years with glucagon and a hundred more', held in Copenhagen, Denmark, in November 2022. The scientific and therapeutic focus of glucagon biology has mainly been related to its role in diabetes. In type 1 diabetes, the glucose-raising properties of glucagon have been leveraged to therapeutically restore hypoglycaemia. The hyperglucagonaemia evident in type 2 diabetes has been proposed to contribute to hyperglycaemia, raising questions regarding underlying mechanism and the importance of this in the pathogenesis of diabetes. Mimicry experiments of glucagon signalling have fuelled the development of several pharmacological compounds including glucagon receptor (GCGR) antagonists, GCGR agonists and, more recently, dual and triple receptor agonists combining glucagon and incretin hormone receptor agonism. From these studies and from earlier observations in extreme cases of either glucagon deficiency or excess secretion, the physiological role of glucagon has expanded to also involve hepatic protein and lipid metabolism. The interplay between the pancreas and the liver, known as the liver-alpha cell axis, reflects the importance of glucagon for glucose, amino acid and lipid metabolism. In individuals with diabetes and fatty liver diseases, glucagon's hepatic actions may be partly impaired resulting in elevated levels of glucagonotropic amino acids, dyslipidaemia and hyperglucagonaemia, reflecting a new, so far largely unexplored pathophysiological phenomenon termed 'glucagon resistance'. Importantly, the hyperglucagonaemia as part of glucagon resistance may result in increased hepatic glucose production and hyperglycaemia. Emerging glucagon-based therapies show a beneficial impact on weight loss and fatty liver diseases and this has sparked a renewed interest in glucagon biology to enable further pharmacological pursuits.

Molecular and in vivo phenotyping of missense variants of the human glucagon receptor.

Naturally occurring missense variants of G protein-coupled receptors with loss of function have been linked to metabolic disease in case studies and in animal experiments. The glucagon receptor, one such G protein-coupled receptor, is involved in maintaining blood glucose and amino acid homeostasis; however, loss-of-function mutations of this receptor have not been systematically characterized. Here, we observed fewer glucagon receptor missense variants than expected, as well as lower allele diversity and fewer variants with trait associations as compared with other class B1 receptors. We performed molecular pharmacological phenotyping of 38 missense variants located in the receptor extracellular domain, at the glucagon interface, or with previously suggested clinical implications. These variants were characterized in terms of cAMP accumulation to assess glucagon-induced Gαs coupling, and of recruitment of ß-arrestin-1/2. Fifteen variants were impaired in at least one of these downstream functions, with six variants affected in both cAMP accumulation and ß-arrestin-1/2 recruitment. For the eight variants with decreased Gαs signaling (D63ECDN, P86ECDS, V96ECDE, G125ECDC, R2253.30H, R3085.40W, V3686.59M, and R3787.35C) binding experiments revealed preserved glucagon affinity, although with significantly reduced binding capacity. Finally, using the UK Biobank, we found that variants with wildtype-like Gαs signaling did not associate with metabolic phenotypes, whereas carriers of cAMP accumulation-impairing variants displayed a tendency toward increased risk of obesity and increased body mass and blood pressure. These observations are in line with the essential role of the glucagon system in metabolism and support that Gαs is the main signaling pathway effecting the physiological roles of the glucagon receptor.

The effects of postprandial exercise and meal glycemic index on plasma glucose and glucoregulatory hormone responses after Roux-en-Y gastric bypass.

Postprandial hypoglycemia is a complication of Roux-en-Y gastric bypass (RYGB), but the effects of postprandial exercise and meal glycemic index (GI) on postprandial glucose and glucoregulatory hormone responses are unknown. Ten RYGB-operated and 10 age and weight-matched unoperated women completed four test days in random order ingesting mixed meals with high GI (HGI, GI = 93) or low GI (LGI, GI = 54), but matched on energy and macronutrient content. Ten minutes after meal completion, participants rested or cycled for 30 min at 70% of maximum oxygen uptake (V̇o2max). Blood was collected for 4 h. Postprandial exercise did not lower plasma nadir glucose in RYGB after HGI (HGI/rest 3.7 ± 0.5 vs. HGI/Ex 4.1 ± 0.4 mmol/L, P = 0.070). Replacing HGI with LGI meals raised glucose nadir in RYGB (LGI/rest 4.1 ± 0.5 mmol/L, P = 0.034) and reduced glucose excursions (Δpeak-nadir) but less so in RYGB (-14% [95% CI: -27; -1]) compared with controls (-33% [-51; -14]). Insulin responses mirrored glucose concentrations. Glucagon-like peptide 1 (GLP-1) responses were greater in RYGB versus controls, and higher with HGI versus LGI. Glucose-dependent insulinotropic polypeptide (GIP) responses were greater after HGI versus LGI in both groups. Postexercise glucagon responses were lower in RYGB than controls, and noradrenaline responses tended to be lower in RYGB, whereas adrenaline responses were similar between groups. In conclusion, moderate intensity cycling shortly after meal intake did not increase the risk of postprandial hypoglycemia after RYGB. The low GI meal increased nadir glucose and reduced glucose excursions compared with the high GI meal. RYGB participants had lower postexercise glucagon responses compared with controls.NEW & NOTEWORTHY We investigate the effect of moderate exercise after a high or a low glycemic index meal on nadir glucose and glucoregulatory hormones in gastric bypass-operated individuals and in matched unoperated controls. Cycling shortly after meal intake did not increase the risk of hypoglycemia in operated individuals. The low glycemic index meal increased glucose nadir and reduced excursions compared with the high glycemic index meal. Operated individuals had lower postexercise glucagon responses compared with controls.

Primary weight loss failure after Roux-en-Y gastric bypass is characterized by impaired gut-hormone mediated regulation of food intake.

BACKGROUND/OBJECTIVES: After Roux-en-Y gastric bypass (RYGB) a subset of patients never obtain excess BMI loss (EBMIL) > 50% and are categorized as having primary weight loss (WL) failure. We hypothesized that postprandial concentrations of glucagon-like peptide 1 (GLP-1) and peptide YY (PYY) would be lower in patients with primary WL failure compared with patients with successfully maintained WL. Furthermore, that inhibition of gut hormone secretions would increase ad libitum food intake less in patients with primary WL failure. SUBJECTS/METHODS: Twenty women with primary WL failure (LowEBMIL < 50%) were individually matched to twenty women with successful WL (HighEBMIL > 60%) on age, preoperative BMI and time from RYGB. On separate days performed in a random order, patient-blinded subcutaneous injections of octreotide or saline (placebo) were followed by a fixed breakfast and an ad libitum lunch with blood sampling for appetite regulating hormones and Visual-Analogue-Scale (VAS)-scoring of hunger/satiety. Furthermore, participants underwent gene variant analysis for GLP-1, PYY and their receptors, indirect calorimetry, dual-energy X-ray absorptiometry (DXA)-scans, 4-days at-home food registration and 14-days step counting. RESULTS: On placebo days, postprandial GLP-1, PYY and cholecystokinin (CCK) concentrations were similar between groups after breakfast. Fasting ghrelin was lower in LowEBMIL, but the postprandial suppression was similar. LowEBMIL had lower satiety VAS-scores and less suppression of hunger VAS-scores. Gene variants did not differ between groups. Octreotide diminished GLP-1, PYY, CCK and ghrelin concentrations in both groups. Octreotide did not affect ad libitum food intake in LowEBMIL (-1% [-13, 12], mean [95%CI]), while food intake increased in HighEBMIL (+23% [2,44]). CONCLUSIONS: Primary WL failure after RYGB was not characterized by impaired secretions of appetite regulating gut hormones. Interestingly, inhibition of gut hormone secretions with octreotide only increased food intake in patients with successful WL post-RYGB. Thus, an impaired central anorectic response to gut hormones may contribute to primary WL failure after RYGB.

Combination of exercise and GLP-1 receptor agonist treatment reduces severity of metabolic syndrome, abdominal obesity, and inflammation: a randomized controlled trial.

BACKGROUND: Identifying and reducing cardiometabolic risks driven by obesity remains a healthcare challenge. The metabolic syndrome is associated with abdominal obesity and inflammation and is predictive of long-term risk of developing type 2 diabetes and cardiovascular disease in otherwise healthy individuals living with obesity. Therefore, we investigated the effects of adherent exercise, a glucagon-like peptide 1 receptor agonist (GLP-1 RA), or the combination on severity of metabolic syndrome, abdominal obesity, and inflammation following weight loss. METHODS: This was a randomized, double-blinded, placebo-controlled trial. During an 8-week low-calorie diet (800 kcal/day), 195 adults with obesity and without diabetes lost 12% in body weight. Participants were then evenly randomized to four arms of one-year treatment with: placebo, moderate-to-vigorous exercise (minimum of 150 min/week of moderate-intensity or 75 min/week of vigorous-intensity aerobic physical activity or an equivalent combination of both), the GLP-1 RA liraglutide 3.0 mg/day, or a combination (exercise + liraglutide). A total of 166 participants completed the trial. We assessed the prespecified secondary outcome metabolic syndrome severity z-score (MetS-Z), abdominal obesity (estimated as android fat via dual-energy X-ray absorptiometry), and inflammation marker high-sensitivity C-reactive protein (hsCRP). Statistical analysis was performed on 130 participants adherent to the study interventions (per-protocol population) using a mixed linear model. RESULTS: The diet-induced weight loss decreased the severity of MetS-Z from 0.57 to 0.06, which was maintained in the placebo and exercise groups after one year. MetS-Z was further decreased by liraglutide (- 0.37, 95% CI - 0.58 to - 0.16, P < 0.001) and the combination treatment (- 0.48, 95% CI - 0.70 to - 0.25, P < 0.001) compared to placebo. Abdominal fat percentage decreased by 2.6, 2.8, and 6.1 percentage points in the exercise, liraglutide, and combination groups compared to placebo, respectively, and hsCRP decreased only in the combination group compared with placebo (by 43%, P = 0.03). CONCLUSION: The combination of adherent exercise and liraglutide treatment reduced metabolic syndrome severity, abdominal obesity, and inflammation and may therefore reduce cardiometabolic risk more than the individual treatments. Trial registration EudraCT number: 2015-005585-32, ClinicalTrials.gov: NCT04122716.