Changes In Glucagon Secretion Research Articles

1224-P: Glucagon Secretion Increases with Age in People with Type 2 Diabetes

It has been shown that the decline in the number of pancreatic beta cells and the insulin-secreting capacity of individual pancreatic beta cells progressively decreases with age, and this functional decline is accelerated by the addition of hyperglycemia. While, glucagon (GCG) is elevated in diabetes, and elevated GCG not only increases blood glucose levels (GLUs), but also decreases muscle mass due to protein metabolism leading to decrease in muscle glucose uptake, making blood glucose control more difficult. However, there are no reports yet regarding to age-related changes in GCG secretion. In this study, we analyze the age-related changes in GCG secretion in people with type 2 diabetes (T2D) after insulin treatment to remove glucose toxicity. A retrospective analysis was performed on people with T2D hospitalized for a period of 5 years from December 2017 in whom a test meal load (carbohydrate 75.5-70g, protein 8.5g, fat 28.5g) was performed before and after insulin treatment, and GLUs and GCG were measured. Insulin (IRI) and/or C-peptide (CPR) were also measured. A total of 121 patients (70 males, age 64.2 ± 11.6 years) were included in the analysis. After insulin treatment, GCG secretion was almost all lower than before treatment. GCG secretion increased with age (P=0.014). Insulinogenic Index decreased with age (R=-0.286 P=0.004), and IRI/GLU and CPR/GLU at 120 minutes after the test meal load also decreased with age (R=-0.314 P=0.001, R=-0.324 P=0.001). We confirmed that there is an increase in GCG secretion with aging in people with T2D. This might be one of the reasons for the decrease in muscle mass and physical activity in elderly people with T2D. Further studies are needed to expand the number including people with normal glucose and impaired glucose tolerance. Acknowledgments:The Cookie Testing Study Group provided support. Disclosure S.Kaneko: Advisory Panel; Lilly Diabetes, Speaker's Bureau; AstraZeneca, Novo Nordisk, Sumitomo Dainippon Pharma Co., Ltd., Mitsubishi Tanabe Pharma Corporation, Lilly Diabetes, Bayer Inc., Kowa Company, Ltd., Kyowa Kirin Co., Ltd. K.Motohashi: None. Y.Ueba: None. S.Tokumoto: None. Funding Cookie Testing Study Group

Changes in glucagon secretion induced by food intake in fulminant type 1 diabetes mellitus: a case report

Fulminant type 1 diabetes mellitus (FT1DM) is a subtype of type 1 diabetes mellitus and is characterized by a remarkably abrupt onset and almost complete destruction of β-cells within a few days. Here, we report a case of diabetic ketoacidosis in a 63-year-old man with no history of hyperglycemia. The patient was diagnosed with FT1DM and had almost no insulin secretion. We examined his insulin and glucagon secretions induced by a liquid meal test at the onset of FT1DM and 1year later. The results suggested severely attenuated insulin secretion and an undetectable level of serum insulin 1year after onset. In contrast, glucagon secretion, which was highly impaired at onset, increased in response to food intake. Although previous reports have suggested that both β- and α-cells of pancreatic islets are damaged in patients with FT1DM, the number of α-cells may increase over time after the onset of FT1DM.

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.

2222-PUB: Differences In Clinical Background between Patients with and without Increased Glucagon Secretion while on SGLT2 Inhibitors: A Comparison of Canagliflozin and Other SGLT2 Inhibitors

Objective: This study was conducted to characterize differences in clinical background between patients with and without increased glucagon secretion while on SGLT2 inhibitors (S). Methods: Of the 75 type 2 diabetic patients admitted for glycemic control who were not receiving incretin-related drugs nor S at admission, 22 patients received S but no incretin-related drugs after admission and were subjected to meal tolerance tests (MTTs) during early morning fasting hours at admission and after improving glycemic control. Blood samples were drawn from these patients preprandially and 30, 60, and 120 minutes postprandially to measure their glucose, C-peptide, and glucagon (Mercodia) values. First, based on changes in glucagon secretion observed in MTTs, they were divided into those with increased AUC glucagon (n = 13) and those without (n = 9) and compared for changes in MTT parameters. Then, they were also divided canagliflozin (Cana) group (n = 12) and other S (non-Cana) group (n = 10) and compared for changes in MTT parameters. Results: Although those without increased AUC glucagon showed a significant increase in ΔCPR/Δglucose 0-30 min after improving glycemic control, those with increased AUC glucagon did not. Increased Δ CPR/Δ glucose 0-30 min values were noted in 5 of 13 of those with increased AUC glucagon but in 9/9 of those without, suggesting that those without increased AUC glucagon were more likely to be associated with increased Δ CPR/Δ glucose 0-30 min values. On the other hand, no significant difference was seen in changes in AUC glucagon or in the proportion of patients with increased AUC glucagon between the Cana and non-Cana groups. Conclusions: Study results suggest that differences in the recovery of insulin secretion between patients may affect glucagon secretion to a greater extent than differences between S with or without SGLT1-inhibitory properties. Disclosure M. Ishiguro: None. Y. Mori: None. R. Nishimura: Research Support; Self; Boehringer Ingelheim Pharmaceuticals, Inc. Speaker’s Bureau; Self; Abbott, AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly Japan K.K., Medtronic, Merck & Co., Inc., Novo Nordisk Inc., Sanofi K.K., Takeda Pharmaceutical Company Limited.

Obesity dysregulates fasting-induced changes in glucagon secretion.

Hyperglucagonemia, a hallmark in obesity and insulin resistance promotes hepatic glucose output, exacerbating hyperglycemia and thus predisposing to the development type 2 diabetes. As such, glucagon signaling is a key target for new therapeutics to manage insulin resistance. We evaluated glucagon homeostasis in lean and obese mice and people. In lean mice, fasting for 24 h caused a rise in glucagon. In contrast, a decrease in serum glucagon compared to baseline was observed in diet-induced obese mice between 8 and 24 h of fasting. Fasting decreased serum insulin in both lean and obese mice. Accordingly, the glucagon:insulin ratio was unaffected by fasting in obese mice but increased in lean mice. Re-feeding (2 h) restored hyperglucagonemia in obese mice. Pancreatic perfusion studies confirm that fasting (16 h) decreases pancreatic glucagon secretion in obese mice. Consistent with our findings in the mouse, a mixed meal increased serum glucagon and insulin concentrations in obese humans, both of which decreased with time after a meal. Consequently, fasting and re-feeding less robustly affected glucagon:insulin ratios in obese compared to lean participants. The glucoregulatory disturbance in obesity may be driven by inappropriate regulation of glucagon by fasting and a static glucagon:insulin ratio.

Fasting-Induced Changes in Glucagon Secretion Are Dysregulated in Obesity

Hyperglucagonemia is a hallmark in obesity and type 2 diabetes (T2DM). Suppression of glucagon signaling improves glycemic control in T2DM. We evaluated glucagon homeostasis in lean and obese mice and people. Discordant with the canonical rise in glucagon with fasting, our studies show that fasting (4, 8, 16 and 24 h) caused a progressive decrease in serum glucagon in diet-induced obese, hyperglucagonemic mice (P<0.01), yet a progressive increase in serum glucagon in lean mice (P<0.01). Serum insulin decreased with fasting in both lean and obese mice (P<0.01). Accordingly, fasting increased the glucagon:insulin ratio in the lean mouse (P<0.01), but did not affect the glucagon:insulin ratio in the obese mouse. Two hours of re-feeding restored hyperglucagonemia in obese mice (P<0.01). Pancreatic perfusion studies in obese, hyperglucagonemic mice confirm that 16 h of fasting decreases pancreatic glucagon secretion (P<0.01). Consistent with our findings in the mouse, fasting decreased (P<0.05) serum glucagon in obese participants. In contrast, fasting increased serum glucagon concentrations in lean participants (P<0.05). As expected, fasting decreased serum insulin in both lean and obese participants (P<0.05 for both). As a result, fasting induced a more robust rise in the glucagon:insulin ratio in lean compared to obese participants (P<0.01). In addition, mixed meal feeding increased serum glucagon in people with obesity. These findings suggest that the metabolic pathophysiology of obesity may be driven by inappropriate meal-induced regulation of glucagon, resulting in a relatively static glucagon:insulin ratio. Disclosure J.H. Stern: None. G.I. Smith: None. R.H. Unger: None. S. Klein: Stock/Shareholder; Self; Aspire Bariatrics. Consultant; Self; Pfizer Inc.. Research Support; Self; Merck & Co., Inc., Johnson & Johnson Services, Inc., REMD Biotherapeutics. P.E. Scherer: None.

Dynamic monitoring of glucagon secretion from living cells on a microfluidic chip

A rapid microfluidic based capillary electrophoresis immunoassay (CEIA) was developed for on-line monitoring of glucagon secretion from pancreatic islets of Langerhans. In the device, a cell chamber containing living islets was perfused with buffers containing either high or low glucose concentration. Perfusate was continuously sampled by electroosmosis through a separate channel on the chip. The perfusate was mixed on-line with fluorescein isothiocyanate-labeled glucagon (FITC-glucagon) and monoclonal anti-glucagon antibody. To minimize sample dilution, the on-chip mixing ratio of sampled perfusate to reagents was maximized by allowing reagents to only be added by diffusion. Every 6 s, the reaction mixture was injected onto a 1.5-cm separation channel where free FITC-glucagon and the FITC-glucagon-antibody complex were separated under an electric field of 700 V cm(-1). The immunoassay had a detection limit of 1 nM. Groups of islets were quantitatively monitored for changes in glucagon secretion as the glucose concentration was decreased from 15 to 1 mM in the perfusate revealing a pulse of glucagon secretion during a step change. The highly automated system should be enable studies of the regulation of glucagon and its potential role in diabetes and obesity. The method also further demonstrates the potential of rapid CEIA on microfluidic systems for monitoring cellular function.

α-Cells of the Endocrine Pancreas: 35 Years of Research but the Enigma Remains

Glucagon, a hormone secreted from the alpha-cells of the endocrine pancreas, is critical for blood glucose homeostasis. It is the major counterpart to insulin and is released during hypoglycemia to induce hepatic glucose output. The control of glucagon secretion is multifactorial and involves direct effects of nutrients on alpha-cell stimulus-secretion coupling as well as paracrine regulation by insulin and zinc and other factors secreted from neighboring beta- and delta-cells within the islet of Langerhans. Glucagon secretion is also regulated by circulating hormones and the autonomic nervous system. In this review, we describe the components of the alpha-cell stimulus secretion coupling and how nutrient metabolism in the alpha-cell leads to changes in glucagon secretion. The islet cell composition and organization are described in different species and serve as a basis for understanding how the numerous paracrine, hormonal, and nervous signals fine-tune glucagon secretion under different physiological conditions. We also highlight the pathophysiology of the alpha-cell and how hyperglucagonemia represents an important component of the metabolic abnormalities associated with diabetes mellitus. Therapeutic inhibition of glucagon action in patients with type 2 diabetes remains an exciting prospect.

Etiology and pathophysiology of gestational diabetes mellitus.

In pregnancy, several physiologic changes take place, the sum of which tends to reset the glucose homeostasis in the direction of diabetes. About 1-2% of all pregnant women develop an abnormal glucose tolerance in pregnancy, but most often glucose tolerance returns to normal postpartum. This condition is called gestational diabetes mellitus (GDM). The possibility that glucose tolerance deteriorates in pregnancy because of diabetes-like changes in the secretory function of the endocrine pancreas has been investigated in healthy controls and in normal-weight gestational diabetic subjects. The insulin responses to oral glucose and mixed meals are equally large in these two groups, but the insulin response per unit of glycemic stimulus is significantly lower in the gestational diabetic subjects than in the controls. Diabetes-like changes in glucagon secretion are not observed in either group. Insulin degradation is unaffected by human pregnancy and the proinsulin share of the total plasma insulin immunoreactivity does not increase in pregnancy. Insulin receptor binding to monocytes from normal pregnant women is increased in midpregnancy but is significantly decreased in late pregnancy. No difference in insulin binding (at tracer insulin concentration) to monocytes from healthy pregnant controls and gestational diabetic subjects is found. The insulin concentration necessary to reduce tracer insulin binding by 50% (ID50) is lower in the gestational diabetic subjects diagnosed in late pregnancy than in the pregnant controls. Together, these findings indicate that the number of insulin receptors on monocytes is decreased in GDM at this stage of pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Potassium ion concentration alters glucagon secretion independently of insulin secretion in the isolated rat pancreas.

In the arginine-stimulated perfused rat pancreas, elevated concentrations of potassium ion inhibited glucagon secretion while stimulating the secretion of insulin. Decreased potassium ion produced the reverse effect. The observed inverse correlation between changes in insulin and glucagon secretion (r = -0.64; p less than 0.001) was suggestive of local interactions between islet hormones, and prompted us to determine whether potassium-induced changes in glucagon secretion were dependent upon concurrent changes in insulin release. We found that when insulin secretion was greatly suppressed, either through acute induction of diabetes with streptozotocin or by utilization of a glucose-free perfusate, no qualitative differences in glucagon responsiveness to altered potassium ion were evident, although the amplitude of these glucagon changed was enhanced. Similarly, when exogenous insulin (20,000 mU/l) was added to the perfusate in order to render potassium-induced changes in endogenous insulin secretion insignificant, glucagon responsiveness to altered potassium ion was maintained. Exogenous insulin alone had no effect on arginine-stimulated glucagon secretion. We conclude that any indirect effects of potassium ion on arginine-stimulated glucagon secretion are not mediated by insulin, but could be related to changes in somatostatin secretion.

Effect of pregnancy on the glucagon response to protein ingestion.

Plasma glucose, insulin and glucagon concentrations were measured before and after the ingestion of a protein-rich meal in 11 healthy pregnant women in the last trimester of pregnancy, and again in the same subjects postpartum. Compared to postpartum, basal levels of plasma glucose were lower in late pregnancy whereas basal insulin and glucagon concentrations were both enhanced. After the meal, insulin and glucagon concentrations in plasma increased in gestation as well as postpartum. Plasma glucose increased slightly in pregnancy but remained unchanged postpartum. The mean insulin response to the meal was unaffected by pregnancy whereas that of glucagon was reduced. Thus following protein ingestion, plasma glucose rose in pregnancy in spite of unchanged levels of insulin and depressed levels of glucagon. Favouring analbolism, the reduced glucagon response to protein ingestion in pregnancy fits in the concept of 'facilitated anabolism' in late pregnancy and, moreover, it lend further support to the idea that changes in glucagon secretion per se are not involved in the pathogenesis of the diabetogenicity of pregnancy.

Interaction of calcium and glucose on glucagon secretion.

The interrelationship between calcium ion and glucose on glucagon release was studied in the in vitro perfused pancreas. Spontaneous release during perfusion with glucose-free, calcium-depleted (0.2 mEq/l calcium) medium was completely abolished by ethylene glycol bis (beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA; 0.2 mM). Glucose added to calcium-depleted perfusate caused only partial inhibition of glucagon release, even at concentrations of 500 mg/dl, and there was no evidence of a paradoxical increase in secretion with time. When calcium was added in a series of steps (in the absence of additional secretagogues) more than half of the increased glucagon released was elicited by the first step (0.5 mEq/l). Release patterns at subsequent steps suggested that higher concentrations of calcium may cause mixed stimulation and inhibition. With 70 mg/dl glucose, calcium-stimulated release was partially suppressed at all calcium concentrations up through 9 mEq/l. With 150 mg/dl glucose, addition of the normally stimulating 0.5 mEq/l calcium caused abrupt and complete inhibition of glucagon secretion, and this persisted at all higher calcium concentrations. Insulin release, when high enough to be detected, did not correlate with the glucose/calcium suppression of glucagon. In other experiments, control results and all insulin secretion patterns were qualitatively similar to those reported by other investigators; however, various attempts to demonstrate a paradoxical increase glucagon secretion by glucose during calcium deprivation were unsuccessful. It is concluded that small amounts of calcium are normally required for glucagon secretion, although at higher concentrations the effects become complex. In addition, glucagon suppression by glucose is calcium-requiring. Thus, changes in glucagon secretion caused by addition or depletion of calcium can depend on the relative amount of glucose in the milieu.