Celiac and superior mesenteric ganglia removal improves glucose tolerance and reduces pancreas islet size.

The sympathetic nervous system is crucial for the regulation of visceral organ function. For instance, the activation of the sympathetic nervous system promotes glycogenolysis in the liver and modulates glucagon and insulin release from the pancreas, thereby raising blood glucose levels. A decrease in sympathetic nerve activity has the opposite effect. Although such acute effects of sympathetic activity changes have been studied, their long-term outcomes have not been previously examined. In this study, we removed the celiac/superior mesenteric ganglia, where sympathetic postganglionic neurons innervating pancreas and liver locate, and examined its effects on glucose homeostasis and islet size several weeks after surgery. Consistent with the reduction in gluconeogenesis, glucose tolerance improved in gangliectomized mice. However, contrary to our expectation that the inhibition of pancreatic function by sympathetic nerves would be relieved with gangliectomy, insulin or C-peptide release did not increase. Examining the size distribution of pancreatic islets, we identified that the gangliectomy led to a size reduction in large islets and a decrease in the proportion of α and ß cells within each islet, as analyzed by immunostaining for insulin and glucagon, respectively. These results indicate that the absence of sympathetic nerve activity reduces the size of the pancreatic islets within a few weeks to reinstate the homeostatic mechanism of blood glucose levels.

Fish-hunting cone snail disrupts prey's glucose homeostasis with weaponized mimetics of somatostatin and insulin.

Venomous animals have evolved diverse molecular mechanisms to incapacitate prey and defend against predators. Most venom components disrupt nervous, locomotor, and cardiovascular systems or cause tissue damage. The discovery that certain fish-hunting cone snails use weaponized insulins to induce hypoglycemic shock in prey highlights a unique example of toxins targeting glucose homeostasis. Here, we show that, in addition to insulins, the deadly fish hunter, Conus geographus, uses a selective somatostatin receptor 2 (SSTR2) agonist that blocks the release of the insulin-counteracting hormone glucagon, thereby exacerbating insulin-induced hypoglycemia in prey. The native toxin, Consomatin nG1, exists in several proteoforms with a minimized vertebrate somatostatin-like core motif connected to a heavily glycosylated N-terminal region. We demonstrate that the toxin's N-terminal tail closely mimics a glycosylated somatostatin from fish pancreas and is crucial for activating the fish SSTR2. Collectively, these findings provide a stunning example of chemical mimicry, highlight the combinatorial nature of venom components, and establish glucose homeostasis as an effective target for prey capture.

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

Background: 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. Methods: 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. Results: 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. Conclusion: 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.

Should we routinely assess hypothalamic-pituitary-adrenal axis in pediatric patients with Prader-Willi syndrome?

Background: It has been reported that central adrenal insufficiency (CAI) in pediatric patients (pts) with Prader-Willi syndrome (PWS) may be a potential cause of their sudden death. In addition, the risk of CAI may increase during treatment with recombinant human growth hormone (rhGH). Objective: To prevent both over- and undertreatment with hydrocortisone, we evaluated the prevalence of CAI in a large multicenter cohort of pediatric pts with PWS analyzing adrenal response in the low-dose ACTH test (LDAT) and/or the glucagon stimulation test (GST) and reviewing the literature. Methods: A total of 46 pts with PWS were enrolled to the study, including 34 treated with rhGH with a median dose of 0.21 mg/kg/week. LDAT was performed in 46 pts, and GST was carried out in 13 pts. Both tests were conducted in 11 pts. The tests began at 8:00 a.m. Hormones were measured by radioimmunoassays. Serum cortisol response >181.2 ng/mL (500 nmol/L) in LDAT and >199.3 ng/mL (550 nmol/L) in GST was considered a normal response. Additionally, cortisol response delta (the difference between baseline and baseline) >90 ng/mL and doubling/tripling of baseline cortisol were considered indicators of normal adrenal reserve. Results: Three GSTs were not diagnostic (no hypoglycemia obtained). LDAT results suggested CAI in four pts, but in two out of four pts, and CAI was excluded in GST. GST results suggested CAI in only one patient, but it was excluded in LDAT. Therefore, CAI was diagnosed in 2/46 pts (4.3%), 1 treated and 1 untreated with rhGH, with the highest cortisol values of 162 and 175 ng/dL, but only in one test. However, in one of them, the cortisol delta response was >90 ng/mL and peak cortisol was more than tripled from baseline. Finally, CAI was diagnosed in one patient treated with rhGH (2.2%). Conclusion: We present low prevalence of CAI in pediatric pts with PWS according to the latest literature. Therefore, we do not recommend to routinely screen the function of the hypothalamic-pituitary-adrenal axis (HPAA) in all pts with PWS, both treated and untreated with rhGH. According to a review of the literature, signs and symptoms or low morning ACTH levels suggestive of CAI require urgent and appropriate diagnosis of HPAA by stimulation test. Our data indicate that the diagnosis of CAI should be confirmed by at least two tests to prevent overtreatment with hydrocortisone.

Understanding Glucagon Aggregation: In Silico Insights and Experimental Validation.

Peptide aggregation poses a significant challenge in biopharmaceutical development and neurodegenerative diseases. This study combines computational simulations and experimental validation to uncover the underlying mechanisms and countermeasures for the aggregation of glucagon, a peptide with a high tendency to aggregate. In silico simulations demonstrate that lactose and 2-hydroxypropyl-ß-cyclodextrin (2-HPßCD) influence glucagon aggregation differently: lactose stabilizes glucagon by increasing the α-helical content, while 2-HPßCD disrupts protein-protein interactions. According to the simulations, 2-HPßCD is particularly effective at preserving the monomeric form of glucagon. Experimental validation with microfluidic modulation spectroscopy (MMS) confirms these findings, showing that glucagon in the presence of 2-HPßCD remains structurally stable, supporting the antiaggregation effect of this excipient. This research provides essential insights into glucagon aggregation obtained through a new powerful tool for monitoring the critical properties of peptide aggregation, suggesting new strategies for addressing this challenge in therapeutic peptide development.

Randomised comparison of intravenous and subcutaneous routes of glucagon-like peptide-1 administration for lowering plasma glucose in hyperglycaemic subjects with type 2 diabetes.

AIM: To perform a direct, double-blind, randomised, crossover comparison of subcutaneous and intravenous glucagon-like peptide-1 (GLP-1) in hyperglycaemic subjects with type 2 diabetes naïve to GLP-1-based therapy. MATERIALS AND METHODS: Ten fasted, hyperglycaemic subjects (1 female, age 63 ± 10 years [mean ± SD], glycated haemoglobin 73.5 ± 22.0 mmol/mol [8.9% ± 2.0%], both mean ± SD) received subcutaneous GLP-1 and intravenous saline, or intravenous GLP-1 and subcutaneous saline. Infusion rates were doubled every 120 min (1.2, 2.4, 4.8 and 9.6 pmol·kg-1·min-1 for subcutaneous, and 0.3, 0.6, 1.2 and 2.4 pmol·kg-1·min-1 for intravenous). Plasma glucose, total and intact GLP-1, insulin, C-peptide, glucagon and gastrointestinal symptoms were evaluated over 8 h. The results are presented as mean ± SEM. RESULTS: Plasma glucose decreased more with intravenous (by ~8.0 mmol/L [144 mg/dL]) than subcutaneous GLP-1 (by ~5.6 mmol/L [100 mg/dL]; p < 0.001). Plasma GLP-1 increased dose-dependently, but more with intravenous than subcutaneous for both total (∆max 154.2 ± 3.9 pmol/L vs. 85.1 ± 3.8 pmol/L; p < 0.001), and intact GLP-1 (∆max 44.2 ± 2.2 pmol/L vs. 12.8 ± 2.2 pmol/L; p < 0.001). Total and intact GLP-1 clearance was higher for subcutaneous than intravenous GLP-1 (p < 0.001 and p = 0.002, respectively). The increase in insulin secretion was greater, and glucagon was suppressed more with intravenous GLP-1 (p < 0.05 each). Gastrointestinal symptoms did not differ (p > 0.05 each). CONCLUSIONS: Subcutaneous GLP-1 administration is much less efficient than intravenous GLP-1 in lowering fasting plasma glucose, with less stimulation of insulin and suppression of glucagon, and much less bioavailability, even at fourfold higher infusion rates.

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

AIM: To evaluate insulin and glucagon sensitivity in Han Chinese women with and without gestational diabetes mellitus (GDM). METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

α- or ß-Adrenergic blockade does not affect transplanted islet cell responses to hypoglycemia in type 1 diabetes.

Type 1 diabetes recipients of intrahepatic islet transplantation exhibit glucose-dependent suppression of insulin and activation of glucagon secretion in response to insulin-induced hypoglycemia associated with clinical protection from hypoglycemia. Whether sympathetic activation of adrenergic receptors on transplanted islets is required for these responses in defense against hypoglycemia is not known. To evaluate the adrenergic contribution to posttransplant glucose counterregulation, we performed a randomized, double-blind crossover study of responses during a hyperinsulinemic euglycemic-hypoglycemic clamp under phentolamine (α-adrenergic blockage), propranolol (ß-adrenergic blockage), or placebo infusion. Characteristics of participants (5 females/4 males) were as follows: median (range) age 53 (34-63) yr, diabetes duration 29 (18-56) yr, posttransplant 7.0 (1.9-8.4) yr, HbA1c 5.8 (4.5-6.8)%, insulin in-/dependent 5/4, all on tacrolimus-based immunosuppression. During the clamp, blood pressure was lower with phentolamine and heart rate was lower with propranolol versus placebo (P < 0.05). There was no difference in the suppression of endogenous insulin secretion (derived from C-peptide measurements) during the euglycemic or hypoglycemic phases, and although levels of glucagon were similar with phentolamine or propranolol vs. placebo, the increase in glucagon from eu- to hypoglycemia was greater with propranolol vs. placebo (P < 0.05). Pancreatic polypeptide was greater with phentolamine versus placebo during the euglycemic phase (P < 0.05), and free fatty acids were lower and the glucose infusion rate was higher with propranolol versus placebo during the hypoglycemic phase (P < 0.05 for both). These results indicate that neither physiological α- nor ß-adrenergic blockade attenuates transplanted islet responses to hypoglycemia, suggesting sympathetic reinnervation of the islet graft is not necessary for posttransplant glucose counterregulation.NEW & NOTEWORTHY Whether adrenergic input to islets is necessary for glucose homeostasis in humans is debated. Here, the adrenergic contribution to intrahepatically transplanted islet cell responses to hypoglycemia in individuals with type 1 diabetes was investigated through α- or ß-adrenergic receptor blockade during hyperinsulinemic euglycemic-hypoglycemic clamps. Neither α- nor ß-adrenergic blockage affected the suppression of endogenous insulin or activation of glucagon secretion, suggesting that sympathetic reinnervation of islet grafts is not required for posttransplant defense against hypoglycemia.

NCLX controls hepatic mitochondrial Ca2+ extrusion and couples hormone-mediated mitochondrial Ca2+ oscillations with gluconeogenesis.

OBJECTIVE: Hepatic Ca2+ signaling has been identified as a crucial key factor in driving gluconeogenesis. The involvement of mitochondria in hormone-induced Ca2+ signaling and their contribution to metabolic activity remain, however, poorly understood. Moreover, the molecular mechanism governing the mitochondrial Ca2+ efflux signaling remains unresolved. This study investigates the role of the Na+/Ca2+ exchanger, NCLX, in modulating hepatic mitochondrial Ca2+ efflux, and examines its physiological significance in hormonal hepatic Ca2+ signaling, gluconeogenesis, and mitochondrial bioenergetics. METHODS: Primary mouse hepatocytes from both an AAV-mediated conditional hepatic-specific and a total mitochondrial Na+/Ca2+ exchanger, NCLX, knockout (KO) mouse models were employed for fluorescent monitoring of purinergic and glucagon/vasopressin-dependent mitochondrial and cytosolic hepatic Ca2+ responses in cultured hepatocytes. Isolated liver mitochondria and permeabilized primary hepatocytes were used to analyze the ion-dependence of Ca2+ efflux. Utilizing the conditional hepatic-specific NCLX KO model, the rate of gluconeogenesis was assessed by first monitoring glucose levels in fasted mice, and subsequently subjecting the mice to a pyruvate tolerance test while monitoring their blood glucose. Additionally, cultured primary hepatocytes from both genotypes were assessed in vitro for glucagon-dependent glucose production and cellular bioenergetics through glucose oxidase assay and Seahorse respirometry, respectively. RESULTS: Analysis of Ca2+ responses in isolated liver mitochondria and cultured primary hepatocytes from NCLX KO versus WT mice showed that NCLX serves as the principal mechanism for mitochondrial calcium extrusion in hepatocytes. We then determined the role of NCLX in glucagon and vasopressin-induced Ca2+ oscillations. Consistent with previous studies, glucagon and vasopressin triggered Ca2+ oscillations in WT hepatocytes, however, the deletion of NCLX resulted in selective elimination of mitochondrial, but not cytosolic, Ca2+ oscillations, underscoring NCLX's pivotal role in mitochondrial Ca2+ regulation. Subsequent in vivo investigation for hepatic NCLX role in gluconeogenesis revealed that, as opposed to WT mice which maintained normoglycemic blood glucose levels when fasted, conditional hepatic-specific NCLX KO mice exhibited a faster drop in glucose levels, becoming hypoglycemic. Furthermore, KO mice showed deficient conversion of pyruvate to glucose when challenged under fasting conditions. Concurrent in vitro assessments showed impaired glucagon-dependent glucose production and compromised bioenergetics in KO hepatocytes, thereby underscoring NCLX's significant contribution to hepatic glucose metabolism. CONCLUSIONS: The study findings demonstrate that NCLX acts as the primary Ca2+ efflux mechanism in hepatocytes. NCLX is indispensable for regulating hormone-induced mitochondrial Ca2+ oscillations, mitochondrial metabolism, and sustenance of hepatic gluconeogenesis.

Fear of hypoglycemia in parents of children with type 1 diabetes trained for intranasal glucagon use.

OBJECTIVE: To investigate fear of hypoglycemia (FoH) in parents of children with type 1 diabetes (T1D) before and after undergoing training to learn intranasal (IN) glucagon administration. METHOD: In this pre-test/post-test uncontrolled study 364 caregivers of patients with T1D (6-18 years) completed questionnaires measuring sociodemographic characteristics, diabetes-related factors (e.g., type of insulin therapy, glycemic control), and parents' trait anxiety. Parents' FoH was assessed at baseline (T0, training) and after nine months (T1). Two repeated-measure mixed analyses of covariance (ANCOVA) compared the FoH at T0 and at T1 and analyzed the moderating roles of anxiety proneness and type of insulin therapy, as well as of anxiety proneness and use of sensor. Age, T1D duration, HbA1c values, and SES were included as covariates. RESULTS: Parental FoH at T1 (M = 1.72; SE = 0.06/M = 1.57; SE = 0.09) was significantly lower than parental FoH at T0 (M = 1.89; SE = 0.06/M = 1.77; SE = 0.09). The group with high trait-anxiety had a higher level of FoH (M = 2.05; SE = 0.08/M = 1.89; SE = 0.12) than the group with low trait-anxiety (M = 1.57; SE = 0.08/M = 1.46; SE = 0.09) at both time points. SES was negatively associated with FoH at T0 (t = -2.87; p = .004/t = -2.87; p = .005). No other significant effects were found. CONCLUSIONS: Training and educating parents on IN glucagon use can help them effectively manage hypoglycemic episodes and alleviate the fear that generally accompany such events.

Beta-Hydroxybutyrate Promotes Basal Insulin Secretion While Decreasing Glucagon Secretion in Mouse and Human Islets.

Dietary carbohydrates raise blood glucose levels, and limiting carbohydrate intake improves glycemia in patients with type 2 diabetes. Low carbohydrate intake (< 25 g) allows the body to utilize fat as its primary fuel. As a consequence of increased fatty acid oxidation, the liver produces ketones to serve as an alternative energy source. ß-Hydroxybutyrate (ßHB) is the most abundant ketone. While ßHB has a wide range of functions outside of the pancreas, its direct effects on islet cell function remain understudied. We examined human islet secretory response to acute racemic ßHB treatment and observed increased insulin secretion at a low glucose concentration of 3 mM. Because ßHB is a chiral molecule, existing as both R and S forms, we further studied insulin and glucagon secretion following acute treatment with individual ßHB enantiomers in human and C57BL/6J mouse islets. We found that acute treatment with R-ßHB increased insulin secretion and decreased glucagon secretion at physiological glucose concentrations in both human and mouse islets. Proteomic analysis of human islets treated with R-ßHB over 72 hours showed altered abundance of proteins that may promote islet cell health and survival. Collectively, our data show that physiological concentrations of ßHB influence hormone secretion and signaling within pancreatic islets.

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.

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.

Background: 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). Materials and methods: 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. Results and conclusion: 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.

Impaired islet function and normal exocrine enzyme secretion occur with low inter-regional variation in type 1 diabetes.

Histopathological heterogeneity in the human pancreas is well documented; however, functional evidence at the tissue level is scarce. Herein, we investigate in situ glucose-stimulated islet and carbachol-stimulated acinar cell secretion across the pancreas head (PH), body (PB), and tail (PT) regions in donors without diabetes (ND; n = 15), positive for one islet autoantibody (1AAb+; n = 7), and with type 1 diabetes (T1D; <14 months duration, n = 5). Insulin, glucagon, pancreatic amylase, lipase, and trypsinogen secretion along with 3D tissue morphometrical features are comparable across regions in ND. In T1D, insulin secretion and beta-cell volume are significantly reduced within all regions, while glucagon and enzymes are unaltered. Beta-cell volume is lower despite normal insulin secretion in 1AAb+, resulting in increased volume-adjusted insulin secretion versus ND. Islet and acinar cell secretion in 1AAb+ are consistent across the PH, PB, and PT. This study supports low inter-regional variation in pancreas slice function and, potentially, increased metabolic demand in 1AAb+.

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.

Correlation between islet α cell function and peripheral neuropathy in patients with type 2 diabetes mellitus.

BACKGROUND: This study explored the correlation between pancreatic islet α cell function, as reflected by the plasma glucagon levels, and Diabetic Peripheral Neuropathy (DPN) in patients with Type 2 Diabetes Mellitus (T2DM). METHODS: A total of 358 patients with T2DM were retrospectively enrolled in this study and divided into the Non-DPN (NDPN) group (n = 220) and the DPN group (n = 138). All patients underwent an oral glucose tolerance test to detect levels of blood glucose, insulin and glucagon, and the Area Under the Curve (AUC) for Glucagon (AUCglu) was used to estimate the overall glucagon level. The Peripheral Nerve Conduction Velocity (PNCV), Amplitude (PNCA) and Latency (PNCL) were obtained with electromyography, and their Z scores were calculated. RESULTS: There were significant differences regarding the age, disease duration, serum levels of alanine aminotransferase, aspartate aminotransferase, urea nitrogen, high-density lipoprotein, and 2h-C peptide between these two groups (p < 0.05). The NDPN group had higher glucagon levels at 30, 60 and 120 min and AUCglu (p < 0.05). The Z-scores of PNCV and PNCA showed an increasing trend (p < 0.05), while the Z-score of PNCL showed a decreasing trend (p < 0.05). The glucagon levels were positively correlated with PNCV and PNCA, but negatively correlated with PNCL, with Gluca30min having the strongest correlation (p < 0.05). Gluca30min was independently related to PNCV, PNCL, PNCA and DPN, respectively (p < 0.05). The function of pancreatic α islet cells, as reflected by the plasma glucagon level, is closely related to the occurrence of DPN in T2DM patients. CONCLUSION: Gluca30min may be a potentially valuable independent predictor for the occurrence of DPN.

Intra-islet α-cell Gs signaling promotes glucagon release.

Glucagon, a hormone released from pancreatic α-cells, is critical for maintaining euglycemia and plays a key role in the pathophysiology of diabetes. To stimulate the development of new classes of therapeutic agents targeting glucagon release, key α-cell signaling pathways that regulate glucagon secretion need to be identified. Here, we focused on the potential importance of α-cell Gs signaling on modulating α-cell function. Studies with α-cell-specific mouse models showed that activation of α-cell Gs signaling causes a marked increase in glucagon secretion. We also found that intra-islet adenosine plays an unexpected autocrine/paracrine role in promoting glucagon release via activation of α-cell Gs-coupled A2A adenosine receptors. Studies with α-cell-specific Gαs knockout mice showed that α-cell Gs also plays an essential role in stimulating the activity of the Gcg gene, thus ensuring proper islet glucagon content. Our data suggest that α-cell enriched Gs-coupled receptors represent potential targets for modulating α-cell function for therapeutic purposes.

[Advances in the study of the role and mechanisms of endogenous hormones in the development of myopia].

With the increasing prevalence of myopia among adolescents, the pathogenesis of this condition has garnered significant attention. Studies have discovered the expression of various hormone receptors in ocular tissues of both animals and humans. Additionally, changes in hormone levels accompany the development of myopia, although the exact relationships remain inconclusive. This article reviews the potential influences and mechanisms of action of endogenous hormones such as melatonin, serotonin, insulin, glucagon, sex hormones, vitamin D, and prostaglandins in ocular tissues including the retina, choroid, and sclera. It elaborates on the relationship between fluctuations in these hormone levels and the progression of myopia, aiming to provide guidance for exploring targets for myopia prevention and control.

Amylin-like immunoreactivity in the extra-islet peptide YY-producing and glucagon-immunoreactive cells in Japanese quail pancreas.

In this study, we investigated amylin-like substance distribution in the pancreas of Japanese quail (Coturnix japonica) using a specific anti-rat amylin serum. We detected amylin-immunoreactive cells dispersed in the pancreatic extra-islet region but not in the islet region. The synthetic rat amylin-containing serum pre-absorption abolished the staining profile. Almost all amylin-immunoreactive cells were immuno-positive for peptide YY (PYY). In addition, certain amylin-immunoreactive cells stained immuno-positive for glucagon. Amylin and PYY co-secreted from the extra-islet cells might participate in the insulin and glucagon release regulation in the pancreas and food intake modulation through the central nervous system.

Regulatory Role of Fatty Acid Metabolism on Glucose-Induced Changes in Insulin and Glucagon Secretion by Pancreatic Islet Cells.

A detailed study of palmitate metabolism in pancreatic islets subject to different experimental conditions, like varying concentrations of glucose, as well as fed or starved conditions, has allowed us to explore the interaction between the two main plasma nutrients and its consequences on hormone secretion. Palmitate potentiates glucose-induced insulin secretion in a concentration-dependent manner, in a physiological range of both palmitate (0-2 mM) and glucose (6-20 mM) concentrations; at glucose concentrations lower than 6 mM, no metabolic interaction with palmitate was apparent. Starvation (48 h) increased islet palmitate oxidation two-fold, and the effect was resistant to its inhibition by glucose (6-20 mM). Consequently, labelled palmitate and glucose incorporation into complex lipids were strongly suppressed, as well as glucose-induced insulin secretion and its potentiation by palmitate. 2-bromostearate, a palmitate oxidation inhibitor, fully recovered the synthesis of complex lipids and insulin secretion. We concluded that palmitate potentiation of the insulin response to glucose is not attributable to its catabolic mitochondrial oxidation but to its anabolism to complex lipids: islet lipid biosynthesis is dependent on the uptake of plasma fatty acids and the supply of α-glycerol phosphate from glycolysis. Islet secretion of glucagon and somatostatin showed a similar dependence on palmitate anabolism as insulin. The possible mechanisms implicated in the metabolic coupling between glucose and palmitate were commented on. Moreover, possible mechanisms responsible for islet gluco- or lipotoxicity after a long-term stimulation of insulin secretion were also discussed. Our own data on the simultaneous stimulation of insulin, glucagon, and somatostatin by glucose, as well as their modification by 2-bromostearate in perifused rat islets, give support to the conclusion that increased FFA anabolism, rather than its mitochondrial oxidation, results in a potentiation of their stimulated release. Starvation, besides suppressing glucose stimulation of insulin secretion, also blocks the inhibitory effect of glucose on glucagon secretion: this suggests that glucagon inhibition might be an indirect or direct effect of insulin, but not of glucose. In summary, there seems to exist three mechanisms of glucagon secretion stimulation: 1. glucagon stimulation through the same secretion coupling mechanism as insulin, but in a different range of glucose concentrations (0 to 5 mM). 2. Direct or indirect inhibition by secreted insulin in response to glucose (5-20 mM). 3. Stimulation by increased FFA anabolism in glucose intolerance or diabetes in the context of hyperlipidemia, hyperglycemia, and hypo-insulinemia. These conclusions were discussed and compared with previous published data in the literature. Specially, we discussed the mechanism for inhibition of glucagon release by glucose, which was apparently contradictory with the secretion coupling mechanism of its stimulation.