Phase Of Insulin Secretion Research Articles

Kinetics of insulin and C-peptide and estimation of prehepatic insulin secretion rates after intravenous glucose stimulation using arterial versus venous blood sampling in healthy males

An intravenous glucose-infusion of 0.3 g glucose per Kg body weight was administered over 1 min in nine healthy males with simultaneous blood sampling from the hepatic vein, femoral artery and a peripheral vein. Insulin secretion rates (ISR) were determined by the Eaton method and the ISEC method using C-peptide concentrations from arterial and peripheral venous blood. First phase (0–10 min), second phase (10–60 min), and total insulin secretion (0–60 min) were calculated as the incremental areas (iAUC) above baseline. The primary endpoint was first phase insulin response. The first phase insulin response in artery and venous blood did not differ with the Eaton method (p = 0.25), but was significantly greater with the ISEC method in arterial compared with venous blood (p < 0.05). The first phase insulin responses did not differ between methods in artery (p = 0.73) or venous blood (p = 0.73). The first phase responses of insulin and C-peptide were significant higher in the hepatic vein compared with those in the artery (p < 0.05) and peripheral vein (p < 0.05) but did not differ significantly between the artery compared with the peripheral vein for insulin (p = 0.09) or C-peptide (p = 0.26). Prehepatic insulin secretion rates did not differ between the Eaton and ISEC methods, but with the ISEC method the first phase insulin response was significantly greater in arterial compared with venous blood. The first phase insulin response differs when calculated from plasma insulin or C-peptide and depends on sample sites.

Improvement of early-phase insulin secretion is an independent factor for achieving glycaemic control: A pooled analysis of SEED and DAWN study.

To investigate the effect of improving early phase insulin secretion function for glycaemic control in patients with type 2 diabetes mellitus treated with a new class of antidiabetic drug dorzagliatin. Early insulin secretion function was studied in 726 participants of which 414 were treated with dorzagliatin in the SEED and DAWN study. The early insulinogenic index (IGI30min ) and disposition index (DI) were used to assess early-phase insulin secretion function in this study. Logistic regression analysis was performed to verify the importance of IGI30min and DI indices for achieving effective glycaemic control. The reduction in HbA1c has a significant correlation with the improvement of IGI30min for patients that received 24 weeks of dorzagliatin treatment (p < .001), and this correlation was not observed in the placebo group (p = .364). In the dorzagliatin treatment group, the responders showed significant improvements in homeostasis model assessment 2-β, IGI30min and DI compared with the non-responders. Logistic regression analysis revealed that the odds ratio (OR) for achieving glycaemic control was 1.28 (95% CI 1.14-1.43) for baseline IGI30min , and 1.24 (95% CI 1.14-1.35) for the 24-week incremental IGI30min from baseline. The OR for baseline DI and 24-week changes in DI from baseline were 1.39 (95% CI 1.2-1.6) and 1.30 (95% CI 1.19-1.43) respectively. The timing of insulin secretion analysis showed the significant contribution of early-phase insulin secretion, rather than late-phase insulin secretion, to postprandial glucose control with the OR for the incremental IGI30min and IGI2h to postprandial glucose control were 1.3 (95% CI 1.19-1.42) and 1 (95% CI 1-1.01) respectively. Restoring the impaired early-phase insulin secretion function in patients with type 2 diabetes mellitus is a critical factor for improving the glycaemic control by dorzagliatin treatment.

OR34-05 Second Phase Insulin Secretion Varies By Time Of Day And Body Mass Index

Abstract Disclosure: S. Naaman: None. S. Sintetas: None. E. Van Cauter: None. E.C. Hanlon: None. Diurnal variation in insulin secretion (ISR) is documented in healthy adults with and without obesity. However, in previous studies, the caloric content of meals varied across the day or the analysis focused solely on morning versus evening differences. It remains unclear if dietary intake timing is associated with metabolic response differences to the same dietary challenge if presented across a full day in individuals categorized as lean (L), with overweight (OW) or obesity (OB). Thus, we examined ISR following consumption of identical meals, equally spaced across the day, in a lab setting with controlled sleep and energy expenditure. Our study included 74 individuals; 41 lean (19 women), 14 overweight (4 women), and 19 obese (14 women). Obstructive sleep apnea (OSA), a known confounder of glucose metabolism, was an exclusion criterion. Mean age between groups was similar (L, 25.2 ± 5.3yrs vs OW, 27.0 ± 6.6yrs vs OB, 32.2 ± 7.6yrs). BMI was 38 ± 5.9 kg/m2 in the OB, 27 ± 1.2 kg/m2 in the OW, vs 22 ± 1.8 kg/m2 in the L groups, respectively (p &amp;lt; 0.0001). We collected blood samples continuously at regular intervals over a 24hr period in which participants ate isocaloric identical high carbohydrate meals (20% fat, 68% carbohydrate, 12% protein) at 0900, 1400, and 1900; each meal was 33% of total caloric intake. Serum C-peptide was measured using high-sensitivity chemiluminescence assays (Immulite). ISR was derived from plasma C-peptide levels by mathematical deconvolution using a two-compartment model for C-peptide clearance. Each profile was expressed as a percentage of individual 24hr mean ISR to examine the profile wave shape independently of individual differences in mean ISR. We examined 2 phases of ISR following meal ingestion; 1st phase (AUC, 0 - 1.5hrs) and 2nd phase (AUC, 1.5hrs - 3.5hrs). The profiles were analyzed with ANOVA for repeated measures with participants as a random factor and mealtime, group (L, OW, OB), and interaction “mealtime by group” as fixed effects. Despite 3 equally spaced identical meals, significant differences emerged. Irrespective of BMI, 1st phase relative ISR was similar across breakfast, lunch and dinner. Second phase relative ISR, however, revealed significant time of day effects; with midday eliciting the highest relative ISR for all groups (p = 0.0002). Significant time x group effects emerged in the 2nd phase such that relative ISR varied across the day, differently for each group (p &amp;lt; 0.0001). Specifically, 2nd phase relative ISR was lowest following dinner in those with obesity. This is the first study to compare 24hr profiles of ISR in healthy individuals at multiple BMI ranges, without OSA, in an experimental setting of 3 equally spaced identical meals. These findings imply that the midday meal elicits the highest ISRs, irrespective of BMI. Further, BMI impacts ISR across the day in response to identical meals. These findings have implications for obesity management. Presentation: Sunday, June 18, 2023

1102-P: Joint Effect of GLP-1R and Exposure to Gestational Diabetes on Glucose Regulation in Adolescents—The EPOCH Study

Exposure to gestational diabetes (GDM) and polymorphisms of the glucagon-like-peptide-1 receptor gene (GLP-1R) are both associated with type 2 diabetes risk. In adults, GLP-1R mutations were associated with altered first phase insulin secretion and glucose levels during an oral glucose tolerance test (OGTT). We explored a potential joint association between GLP-1R and GDM exposure on glucose regulation in youth. Exploring Perinatal Outcomes among Children (EPOCH) participants with (N = 86) and without (N = 189) GDM exposure had 2-hour 75g OGTT at ~17 years. DNA was genotyped by microarray. Plink 2.0 was used to extract genotyped and imputed GLP-1R polymorphisms. Glucose and insulin measured at 0, 30 and 120 minutes were used to calculate areas under the curve (AUC), Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), insulinogenic index (IGI), and disposition index (DI). Linear models tested the interaction of GLP-1R rs1042044 homozygosity of the minor allele and GDM on each outcome. Homozygotes exposed to GDM had higher baseline, 30, 120 minute and AUC for glucose (p &amp;lt; 0.0001), and lower insulin AUC (p = 0.046) than others (Figure 1), but not significantly different HOMA-IR, IGI and DI. Our data indicates a joint effect of GDM exposure and GLP-1R on glucose levels in youth, potentially due to reduced first phase insulin secretion. Further studies are needed to replicate this finding. Disclosure K.K.Harrall: None. D.H.Glueck: None. K.A.Sauder: None. M.Cree-green: Consultant; Pollie Inc, Research Support; Amino Corp LLC. D.Dabelea: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK068001)

1526-P: Cephalic Phase Insulin Release Requires Alpha Cells

The glucose-independent rise of insulin levels immediately at the start of a meal is known as the cephalic phase of insulin release and is a neurally mediated physiological reflex. We recently found that IL-1β mediates cephalic phase insulin secretion by modulating parasympathetic neuronal transmission. It has been established that pancreatic islets are richly innervated by the parasympathetic nervous system, yet the mechanism underlying neuronally mediated insulin release at basal glucose, as seen in cephalic phase, remain to be studied. Methods: We assessed the role of glucagon in cephalic phase insulin secretion using a transgenic mouse model in which alpha cells are selectively ablated. Further, we isolated pancreatic islets of wild-type mice, as well as alpha cell-ablated mice, and assessed insulin and glucagon secretion at low glucose after stimulation with IL-1β, a muscarinic agonist (carbachol) and both combined. Results: We observed that mice lacking glucagon-producing alpha cells fail to exhibit a cephalic phase insulin response. In vitro, we found that muscarinic activation stimulated glucagon secretion at basal glucose, but not insulin secretion. Co-stimulating islets with the muscarinic agonist and IL-1β stimulated insulin secretion at basal glucose, and strikingly this was not the case in alpha cell-ablated islets. Conclusion: Cephalic phase of insulin release mediated by IL-1β stimulation of parasympathetic nerves requires pancreatic alpha cells. This beta-cell response may be mediated by glucagon. Disclosure K.A.Trimigliozzi: None. S.J.Wiedemann: None. D.T.Meier: None. L.Rachid: None. H.Mereau: None. M.Böni-schnetzler: None. M.Y.Donath: Consultant; Boehringer Ingelheim International GmbH, Eli Lilly and Company, Novo Nordisk.

Rapid Quantification of First and Second Phase Insulin Secretion Dynamics using an In vitro Platform for Improving Insulin Therapy

High-throughput quantification of the first- and second-phase insulin secretion dynamics is intractable with current methods. The fact that independent secretion phases play distinct roles in metabolism necessitates partitioning them separately and performing high-throughput compound screening to target them individually. We developed an insulin-nanoluc luciferase reporter system to dissect the molecular and cellular pathways involved in the separate phases of insulin secretion. We validated this method through genetic studies, including knockdown and overexpression, as well as small-molecule screening and their effects on insulin secretion. Furthermore, we demonstrated that the results of this method are well correlated with those of single-vesicle exocytosis experiments conducted on live cells, providing a quantitative reference for the approach. Thus, we have developed a robust methodology for screening small molecules and cellular pathways that target specific phases of insulin secretion, resulting in a better understanding of insulin secretion, which in turn will result in a more effective insulin therapy through the stimulation of endogenous glucose-stimulated insulin secretion.

Acute pharmacodynamic responses to exenatide: Drug-induced increases in insulin secretion and glucose effectiveness.

Glucagon-like peptide-1 receptor agonists provide multiple benefits to patients with type 2 diabetes, including improved glycaemic control, weight loss and decreased risk of major adverse cardiovascular events. Because drug responses vary among individuals, we initiated investigations to identify genetic variants associated with the magnitude of drug responses. Exenatide (5 μg, subcutaneously) or saline (0.2 ml, subcutaneously) was administered to 62 healthy volunteers. Frequently sampled intravenous glucose tolerance tests were conducted to assess the impact of exenatide on insulin secretion and insulin action. This pilot study was a crossover design in which participants received exenatide and saline in random order. Exenatide increased first phase insulin secretion 1.9-fold (p = 1.9 × 10-9 ) and accelerated the rate of glucose disappearance 2.4-fold (p = 2 × 10-10 ). Minimal model analysis showed that exenatide increased glucose effectiveness (Sg ) by 32% (p = .0008) but did not significantly affect insulin sensitivity (Si ). The exenatide-induced increase in insulin secretion made the largest contribution to interindividual variation in exenatide-induced acceleration of glucose disappearance while interindividual variation in the drug effect on Sg contributed to a lesser extent (β = 0.58 or 0.27, respectively). This pilot study provides validation for the value of a frequently sampled intravenous glucose tolerance test (including minimal model analysis) to provide primary data for our ongoing pharmacogenomic study of pharmacodynamic effects of semaglutide (NCT05071898). Three endpoints provide quantitative assessments of the effects of glucagon-like peptide-1 receptor agonists on glucose metabolism: first phase insulin secretion, glucose disappearance rates and glucose effectiveness.

Insulin Secretion and β-Cell Function Are Preserved in Patients with Treated Hematological Malignancies

INTRODUCTION Cancer survivors are at elevated risk for developing type 2 diabetes mellitus, which decreases quality of life and increases mortality during cancer survivorship. Type 2 diabetes results from a combination of insulin resistance and decreased insulin secretion. Assessing pancreatic β-cell function by measuring insulin secretion dynamics in response to hyperglycemia can provide insight into the pathogenesis of type 2 diabetes. We investigated insulin secretion in patients with treated hematological malignancies and compared them to non-diabetic controls without cancer. We hypothesized that patients with hematological malignancies will have decreased insulin secretion compared to controls without cancer due to β-cell toxicity from previous treatment and chemotherapy. METHODS We evaluated insulin secretion in 16 non-diabetic adult patients with treated hematological malignancies using a hyperglycemic clamp, which assesses pancreatic β-cell function by measuring insulin secretion in response to hyperglycemia (200 mg/dL) maintained by a dextrose infusion. Clamp outcomes included first phase (T0-10 minutes), second phase (T90-120 minutes), and maximal (L-arginine stimulated) insulin response. The insulin sensitivity index (ISI) and disposition index (DI, a measure of the β-cell function to compensate for insulin resistance) were calculated. Controls (n=32) matched for age, sex, race, and body mass index (BMI) were selected 2:1 from a database of 154 hyperglycemic clamps in participants without diabetes or cancer. Demographic characteristics and clamp outcomes were compared using χ2, Wilcoxon rank-sum test, or linear regression. RESULTS Hyperglycemic clamps were performed in 48 individuals without diabetes (16 patients with treated hematological malignancies and 32 matched controls without cancer). Cancer survivors and controls without malignancy were well-matched for age, sex, race (Table 1). Myeloid malignancies were the most common diagnosis (n=11; 69%) with a median time from diagnosis to metabolic testing of 6 months. Treatment included cytotoxic chemotherapy (n=15; 94%), glucocorticoids (n=7; 44%), and radiation (n=1; 6%) with 7 (44%) patients achieving a remission prior to testing. Compared to controls, patients with malignancy had lower fasting glucose levels (93.0 mg/dL [IQR 86.3-96.6] vs 101.5 [IQR 94.9-107.6], p<0.001) and lower fasting insulin levels (11.5 uU/mL [IQR 9.3-15.0] vs 16.3 [IQR 12.3-21.5], p=0.023), suggesting greater insulin sensitivity within the cancer cohort. In univariable analysis, there were no significant differences between first and second phase insulin response between patients with or without treated hematological malignancies (Table 1). Cancer survivors had a higher maximal (L-arginine stimulated) insulin secretion (3606 uU/mL [IQR 3255-4594] vs 2278 [IQR 1900-3555], p=0.026) and a higher disposition index (2521 mg/kg/min [IQR 1986-3360] vs 1300 [IQR 939-1923], p=0.01) than in controls. Cancer survivors demonstrated a trend toward greater insulin sensitivity compared to controls (6.82 mg/kg/min per uU/mL [IQR 5.53-10.83] vs 4.98 [IQR 3.65-7.28], p=0.092). After adjustment for BMI and fasting glucose in linear regression models, both second phase (β=242.5, p=0.005) and maximal insulin secretion (β=1225.6, p=0.019) were greater in cancer survivors then in controls without cancer (Table 2). CONCLUSION Cancer survivors had higher maximal phase insulin secretion and disposition index (a measure of β-cell function adjusted for insulin resistance) compared to non-diabetic controls without cancer. Our data suggests that cancer survivors have preserved β-cell function following treatment of their hematological malignancies, contrary to our hypothesis. Longitudinal follow-up is needed to determine factors that promote diabetes susceptibility in cancer survivors. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

LBODP051 Relation Of The Quadrumvirate ― Hepatic Steatosis, High Normal Fasting Glucose, And Attenuated Whole Body-insulin Sensitivity And Glucose-stimulated Acute Insulin Secretion ― To Incident Prediabetes, The Beginning Of Type 2 Diabetes

Abstract Type 2 diabetes begins as conversion of normal glucose metabolism (NGM) to prediabetes, and 5-10% per year of people with prediabetes progress to diabetes. Therefore, understanding evolution of prediabetes is mandatory to know how type 2 diabetes starts. However, the process of conversion of NGM to prediabetes, which may be ethnicity-specific, has poorly been investigated. We analyzed 599 Japanese adults with NGM (fasting plasma glucose (FPG) &amp;lt;100 mg·dL-1 and 2-h PG at 75 g oral glucose tolerance (OGTT) &amp;lt;140 mg·dL-1) (male 62%, the mean age, body mass index (BMI), fasting IRI/FPG and 2-h IRI/PG, 52 years, 23.1 kg·m-2, 4.1 μU·mL-1/92 mg·dL-1 and 24.5 μU·mL-1/104 mg·dL-1, respectively). They received follow-up OGTTs at a mean of 3.7 years later (2,061 person-years observation). Prediabetes developed in 179 (impaired fasting glucose 102, impaired glucose tolerance 39, and impaired fasting glucose/impaired glucose tolerance 28). By the screening univariate analysis, Fatty Liver Index (FLI), FPG, ISIMATSUDA (index of basal and post-glucose whole body insulin sensitivity (Si) and Stumvoll's first phase (Stumvoll-1, an index of glucose-stimulated acute (∼10 min) insulin secretion (Isec) were robust risk factors for incident prediabetes. In contrast, indices of basal Si such as HOMA-IR, and basal, 30 min, or later phase index of Isec such as HOMAbeta and insulinogenic index, respectively, were not significant risk for prediabetes. In multivariate Cox model adjusted for age and sex, HR (95%CI) per 1 IQR increase were FLI 1.303 (1. 063-1.586), P &amp;lt;0. 01; FPG 1.400 (1. 076-1.840), P &amp;lt;0. 01; ISIMATSUDA 0.841 (0.712-0.963), P = 0. 03; Stumvoll-1 0.764 (0.622-0.935) P &amp;lt;0. 01. Note that FLI and FPG are risk factors and ISIMATSUDA and Stumvoll-1 are protective factors. Notably, FLI was a risk even after adjustment for BMI. The best cutoff values differentiating prediabetes Progressors from Nonprogressors obtained by the ROC curve using entire range of each risk factor was ≥12.4 for FLI, ≥95 mg·dL-1 for FPG, ≤11.99 for ISIMATSUDA and ≤486.3 for Stumvoll-1, and incidence of prediabetes was progressively high as 10/127 (6%), 34/153 (22%), 56/189 (30%), 53/106 (50%) and 16/24 (67%) among the participants with no, one, two, three and four unfavorable discriminating values for progression, respectively. AUC of ROC curve (AUROC) for the combination of the quadrumvirate was as large as 0.729 (0.661-0.788) with high precision as sensitivity 73.4% and specificity 63.8%. In conclusion, at the beginning of type 2 diabetes in the Japanese population who are non-obese and insulin-sensitive as shown, hepatic steatosis, the high normal FPG, attenuation of whole-body insulin sensitivity, lowered acute phase glucose-induced insulin release (the quadrumvirate) are synergistically and independently, with comparable strength each other, related to the development of prediabetes. Presentation: No date and time listed

Insulinogenic index and early phase insulin secretion predict increased risk of worsening glucose tolerance and of cystic fibrosis-related diabetes

ObjectiveMeasures of stimulated insulin secretion are emerging as important predictors of diabetes mellitus in at-risk populations. We analyzed the utility of clinical estimates of insulin secretion in a prospective cohort at risk for cystic fibrosis-related diabetes (CFRD). MethodsWe divided the profiles of 189 people with CF (pwCF) followed longitudinally in the Montreal CF cohort (mean follow up 6.6 ± 1.2 years) according to quartiles of the insulinogenic index (IGI; (I30-I0)/(G30-G0)); area under the curve for insulin normalized for glucose (AUCins/glu), and HOMA-B at baseline to compare clinical characteristics and risk of CFRD according to quartiles for each measure. We also compared characteristics of 40 pwCF found to have de novo CFRD at baseline. ResultsAt baseline, IGI and AUCins/glu were lower in subjects with de novo CFRD and those who later developed CFRD than those who never developed CFRD (p < 0.0001 for each). Subjects with the lowest quartiles of IGI, AUCins/glu, and AUCins/glu 0–30 had increased risk of developing CFRD by Kaplan-Meier analysis (p = 0.0244, p = 0.0024, and p = 0.0338, respectively). There was no significant difference in risk between quartiles of HOMA-B. Subjects in the lowest quartile of IGI showed a significant increase in 2-hour OGTT glucose and AUCglu between the initial and final study visits (p = 0.0027 and p = 0.0044, respectively). ConclusionIGI is easily measured in a clinical setting and needs to be validated in prospective studies as a potential tool to improve risk stratification in CFRD with direct relevance to pathogenesis.

Clinical relevance of dual agonist of glucagon and glucagon-like peptide-1 receptors to achieve functional restoration of first- and second-phase insulin secretion.

The role of glucagon and GLP-1 receptors in first and second phase insulin secretion.

722-P: Tirzepatide Improves Multiple Aspects of Beta-Cell Function

We investigated the effect of tirzepatide (TZP) 15 mg (novel GIP-GLP-1 dual receptor agonist) , placebo and semaglutide 1 mg (SEMA) on beta-cell function using euglycaemic and hyperglycemic glucose clamps (EGC, HGC) and Mixed Meal Tolerance Tests (MMTT) in a 28-week double-blind randomized controlled trial of people with type 2 diabetes. During EGC and HGC, TZP improved insulin sensitivity (M-value) , first and second phase insulin secretion (ISR) and beta-cell glucose sensitivity (ratio of ISR and glucose increments) more than SEMA and placebo (Table; EASD symposium 2021) . During MMTT, both fasting and AUC glucose were reduced more with TZP than with SEMA or placebo, while incremental glucose AUC was reduced with TZP and SEMA vs. placebo similarly. Despite similarly reduced incremental glucose AUC, insulin AUC and incremental insulin AUC were reduced by TZP but not by SEMA. Model-derived beta-cell glucose sensitivity was increased with TZP and SEMA from baseline similarly. In contrast, ISR at 7.2 mmol/L glucose increased more with TZP than with placebo and SEMA (Table) . The glucose-lowering effect of TZP is mediated through improvements in multiple aspects of beta-cell function, including beta-cell glucose sensitivity and ISR, and in insulin sensitivity, resulting in pronounced lowering of fasting and postprandial glucose. These effects help explain the superior improvement in glucose control seen with TZP vs. comparators in clinical trials. Disclosure A. Mari: Consultant; Lilly. Research Support; Lilly. J. Li: Employee; Eli Lilly and Company. Stock/Shareholder; Eli Lilly and Company. S. Urva: Employee; Eli Lilly and Company. T. Heise: Advisory Panel; Novo Nordisk A/S. Research Support; ADOCIA, AstraZeneca, Biocon, Boehringer Ingelheim International GmbH, Crinetics Pharmaceuticals, Inc., Eli Lilly and Company, Gan &amp; Lee Pharmaceuticals, Genova, Nestlé, Neuraly Inc., Novo Nordisk A/S, Sanofi, Zealand Pharma A/S. Speaker's Bureau; Eli Lilly and Company, Gan &amp; Lee Pharmaceuticals, Novo Nordisk A/S. J. De Vries: Advisory Panel; ADOCIA, Novo Nordisk A/S, Zealand Pharma A/S. Speaker's Bureau; Novo Nordisk A/S. E.J. Pratt: Employee; Eli Lilly and Company. R.J. Heine: Employee; Eli Lilly and Company. M.K. Thomas: Employee; Eli Lilly and Company. Stock/Shareholder; Eli Lilly and Company. Z. Milicevic: Employee; Eli Lilly and Company. K.J. Mather: Employee; Eli Lilly and Company. Stock/Shareholder; Eli Lilly and Company. Funding Eli Lilly and Company

250-LB: Tead1—A Regulator of Adult ß-Cell Proliferation and Function

The transcriptional factor, Tead1, mediates the transcriptional output of the Hippo pathway. Tead1 activates the transcription of downstream genes including many cell cycle promoting genes that lead to cell proliferation in many tissues, but its role in β-cells is unknown. To test if Tead1 is required for β-cell proliferation and function, we deleted Tead1 in β-cell. Deletion of Tead1 in β-cells was confirmed in these β-cell Tead1 KO (β-Tead1-/-) , by a significant decrease in transcript and protein from whole islet lysates. The β-Tead1-/- mice had normal body weight but developed significantly higher fasting and fed glucose levels starting at 5 weeks of age and progressed to frank diabetes by 8 weeks, with fasting blood glucose &amp;gt;300 mg/dl, accompanied by hypoinsulinemia, as compared to floxed control mice. 8wk β-Tead1-/- mice display severe glucose intolerance due to an abrogation of GSIS during GTT, with a loss of first phase insulin secretion. Pancreatic insulin content was decreased by ∼50%, due to a decrease in expression of mature β-cell genes including, Pdx1, Nkx6.1 and MafA, all of which, we show to be direct transcriptional targets of Tead1. Tead1 also binds to the proximal promoter at the Ink4a locus to regulate p16/p19, critical cell cycle inhibitors, and this loss of activation in Tead1-deficient β-cells leads to an enhanced entry into cell cycle. Furthermore, to test if Tead1 has a similar regulatory role in human β-cells, we deleted TEAD1 knockout in human iPS cell-derived β-cells using CRISPR/Cas9 system. Tead1 deficient iPS cell-derived β-cells displayed a significant decrease in vitro GSIS. Our results demonstrate Tead1 to be a transcriptional switch required for β-cells to maintain mature function and remain in proliferative quiescence. This novel regulatory pathway could be targeted for β-cell replacement therapy to achieve β-cell proliferation without a loss of mature function. Disclosure J. Lee: None. V. Yechoor: n/a. R. Liu: None. F. Li: None. V. Negi: None. R. Jagannathan: None. M. Huising: Consultant; Crinetics Pharmaceuticals, Inc., Research Support; Crinetics Pharmaceuticals, Inc. K. Ma: None. B. Shih: None. M. Moulik: None. Funding VA-MERIT Grant (I01BX002678)

1323-P: Insulin Secretion at Diabetes Remission in Obese Blacks Presenting with Diabetic Ketoacidosis

In obese Blacks presenting with diabetic ketoacidosis (DKA) at new-onset of diabetes, intensive insulin treatment improves β-cell function so that ˜70% achieve near-normoglycemia remission (HbA1c &amp;lt; 7%, fasting blood glucose [BG]&amp;lt;130 mg/dl while off insulin for ≥1 week) and maintain glycemic control without medications. The 2021 American Diabetes Association (ADA) consensus defined diabetes remission as HbA1c &amp;lt;6.5% or BG 126 mg/dl while off medications for &amp;gt;3 months. It is unknown whether glycemic measures and insulin secretion differ between patients who achieve the new ADA definition of remission (intensive remission [IR]) compared to near-normoglycemia remission (non-intensive remission [NIR]) .We performed 75-g, 240-minute (min) oral glucose tolerance tests (OGTT) in 13 obese (BMI&amp;gt;30 kg/m2) Blacks who presented with DKA (BG&amp;gt;250 mg/dl, HCO3&amp;lt;18 mEq/L, pH&amp;lt;7.3) and achieved remission from insulin. Glucose and C-peptide levels were measured at -15, 0, 10, 20, 30, 60, 90, 120, 180 and 240 min during OGTT. Insulin secretory rates (ISR) , first phase (Φdynamic) , second phase (Φstatic) and total (Φtotal) insulin secretion were calculated using a previously published model. Data was compared between IR, (HbA1c&amp;lt;6.5%, n=7) vs. NIR, (HbA1c≥6.5%, n=6)) There were no differences in age, BMI and mean BG levels during OGTT between groups. Model estimates of Φdynamic were significant (P=0.046) and 5-fold higher in IR (Marginal Mean: 514.00, 95% CI: 134.53-893.47 [109]) vs. NIR (Marginal Mean: 100, 95% CI: 100.45, 95% CI: -41.97-242.87 [109]) . Estimates of Φstatic were significant (P=0.022) and 2-fold higher in the IR (Marginal Mean: 31.84, 95% CI: 19.88-43.80 [min-1]) vs. NIR (Marginal Mean: 14.59, 95% CI: 6.79-22.39 [min-1]) with no significant (P=0.058) group differences between Φtotal.In comparison to NIR, obese Blacks with IR exhibit marked preservation of β-cell function suggesting that HbA1c &amp;lt;6.5% should be targeted for insulin remission after presentation with DKA. Disclosure D.Stefanovski: None. O.Oladejo: None. G.E.Umpierrez: Research Support; AstraZeneca, Dexcom, Inc., Novo Nordisk. P.Vellanki: n/a. Funding NIH/NIDDK K23 DK11324-01A1

117-LB: Glucokinase Activator Restores Glucose Sensitivity and Early-Phase Insulin Secretion in T2DM Patient—A Post Hoc Analysis of Dorzagliatin

Background: Insulinogenic index (IGI) and disposition index (DI) measures patient’s early phase insulin secretion ability and glucose sensitivity. Pervious clinical trials of dorzagliatin have showed excellent effect on glycemic control and good safety profile in Chinese T2DM patients. This post-hoc analysis was focused on evaluating the correlation between glycemic control and the restoration effect of glucokinase activator on β-cell function. Method: The analysis has involved two phase III clinical trials of dorzagliatin, monotherapy (SEED) (NCT03173391) and metformin add-on (DAWN) (NCT03141073) , respectively. The change of HOMA2-IR, IGI and DI from baseline to 24 weeks were analyzed. Correlation between glycemic control status and patient’s early phase insulin secretion ability as well as glucose sensitivity were further demonstrated by logistic regression analysis with IGI, DI, HOMA2-IR and other characteristics. Results: Totally 726 patients were included in the final analysis set, with 241 patients from SEED cohort and 485 patients from DAWN. After 24 weeks treatment, two cohorts showed the consistent result of IGI and DI improvement. Nevertheless, The improvement of IGI and DI for HbA1c controlled group (HbA1c &amp;lt;7%) were significantly higher than HbA1c uncontrolled group (HbA1c ≥ 7%) . The result was also consistent across different disease course groups in DAWN cohort considering the relatively longer disease course. Logistic regression analysis revealed that both the improvement of IGI and DI were independent influential factor of patient’s HbA1c controlled status after treatment of dorzagliatin. Conclusion: The post hoc analysis demonstrated the beneficial effect of dorzagliatin on early insulin secretion ability and glucose sensitivity on T2DM patients. The HbA1c control status were significantly affected by improvement of early insulin secretion ability and glucose sensitivity both for drug naïve patients and metformin tolerated patient. Disclosure L. Feng: Employee; Hua Medicine. Q. Guo: None. C. Chen: Employee; Hua Medicine. X. Liu: Employee; Hua Medicine. L. Chen: Employee; Hua Medicine. W. Yang: Advisory Panel; Hua Medicine. Funding Hua Medicine

314-OR: Synaptotagmin-9 Regulates Early Phase Insulin Secretion by Regulating Tomosyn-1

Insulin secretion from pancreatic β-cells occurs in a biphasic manner. The loss of insulin secretion, entailing the inability of insulin granules to fuse with the plasma membrane (PM) via the formation of the SNARE complex, is a key determinant in impaired glucose tolerance and development of type 2 diabetes (T2D) . Synaptotagmins (Syt) are calcium sensors that regulate insulin-containing granule fusion to the PM for insulin secretion. Syt9 is highly expressed in β-cells; however, its role in insulin secretion is not well-characterized. Our goal is to determine how Syt9 affects insulin secretion from pancreatic β-cells. Mice lacking Syt9 (Syt9-/-) have improved glucose clearance with no change in insulin action than wild-type control mice. Interestingly, Syt9-/- mice showed increased plasma insulin levels at 5 min and 15 min post-glucose challenge. Similarly, islets isolated from Syt9-/- mice demonstrate increased stimulation of insulin secretion in response to the early phase insulin secretagogues (KCl and tolbutamide) compared to WT control islets. Similarly, siRNA-mediated knockdown of Syt9 in INS1 cells increased KCL-stimulated insulin secretion at 5 min and min. Altogether, these data suggest that Syt9 regulates the early phase of insulin secretion from β-cells. Strikingly, Syt9-/- mouse islets have reduced Tomosyn-1 levels (∼50%) without altering the levels of other key SNARE proteins (Stx1A, Stx4A, SNAP25) . Tomosyn-1, an inhibitor of insulin secretion whose increased protein abundance is associated with reduced insulin secretion, binds, cofractionates, and colocalizes with Syt9 and Stx1A. The knockdown of Tomosyn-1 in INS1 β-cells treated with KCL prevents the localization of Syt9 with Stx1A. Further, the knockdown of Syt9 or Tomosyn-1 increases the SNARE complex formation. In sum, these data demonstrate the identification of a novel Stx1A-Tomosyn-1-Syt9 molecular complex that regulates the fusion of insulin granules in the early phase. Disclosure M.Rahman: None. H.Alsharif: n/a. S.Bhatnagar: None. Funding R01DK120684-01

100 anni dopo l’insulina: cosa ancora non sappiamo della sua secrezione nel diabete di tipo 2

β-cell dysfunction is a well-known feature of type 2 diabetes mellitus. In particular, it has been shown that defects in 1st phase insulin secretion play a fundamental role in the natural history of the disease. In this review, we highlight the clinical relevance of 1st phase impairment, focusing on its connection with post meal hyperglycemia and diabetic complications; we further evaluate possible therapeutic strategies aimed at improving β-cell secretory machinery and providing a durable control of the disease. In conclusion, we discuss the clinical relevance of C-Peptide sampling in detecting secretory defects.

Effect of acute iron infusion on insulin secretion: A randomized, double-blind, placebo-controlled trial

SummaryBackgroundChronic exposure to high iron levels increases diabetes risk partly by inducing oxidative stress, but the consequences of acute iron administration on beta cells are unknown. We tested whether the acute administration of iron for the correction of iron deficiency influenced insulin secretion and the production of reactive oxygen species.MethodsSingle-center, double-blinded, randomized controlled trial conducted between June 2017 and March 2020. 32 women aged 18 to 47 years, displaying symptomatic iron deficiency without anaemia, were recruited from a community setting and randomly allocated (1:1) to a single infusion of 1000 mg intravenous ferric carboxymaltose (iron) or saline (placebo). The primary outcome was the between group mean difference from baseline to day 28 in first and second phase insulin secretion, assessed by a two-step hyperglycaemic clamp. All analyses were performed by intention to treat. This trial was registered in ClinicalTrials.gov NCT03191201.FindingsIron infusion did not affect first and second phase insulin release. For first phase, the between group mean difference from baseline to day 28 was 0 μU × 10 min/mL [95% CI, -22 to 22, P = 0.99]. For second phase, it was -5 μUx10min/mL [95% CI, -161 to 151; P = 0.95] at the first plateau of the clamp and -249 μUx10min/mL [95% CI, -635 to 137; P = 0.20] at the second plateau. Iron infusion increased serum ascorbyl/ascorbate ratio, a marker of plasma oxidative stress, at day 14, with restoration of normal ratio at day 28 relative to placebo. Finally, high-sensitive C-reactive protein levels remained similar among groups.InterpretationIn iron deficient women without anaemia, intravenous administration of 1000 mg of iron in a single sitting did not impair glucose-induced insulin secretion despite a transient increase in the levels of circulating reactive oxygen species.FundingThe Swiss National Science Foundation, University of Lausanne and Leenaards, Raymond-Berger and Placide Nicod Foundations.

Insulinogenic Index and Early Phase Insulin Secretion Predict Increased Risk of Worsening Glucose Tolerance and of Cystic Fibrosis-Related Diabetes

Determine whether clinical estimates of insulin secretion derived from oral glucose tolerance test (OGTT) might improve cystic fibrosis-related diabetes (CFRD) risk prediction.

Spontaneous and iatrogenic hypoglycemia in cystic fibrosis

Spontaneous episodes of hypoglycemia can occur in people with cystic fibrosis (CF) without diabetes, who are not on glucose lowering medications. Spontaneous hypoglycemia in CF could occur both in the fasting or postprandial state (reactive hypoglycemia). The pathophysiology of fasting hypoglycemia is thought to be related to malnutrition and increased energy expenditure in the setting of inflammation and acute infections. Reactive hypoglycemia is thought to be due to impaired first phase insulin release in response to a glucose load, followed by a delayed and extended second phase insulin secretion; ineffective counterregulatory response to dropping glucose levels may also play a role. The overall prevalence of spontaneous hypoglycemia varies from 7 to 69% as examined with oral glucose tolerance test (OGTT) or with continuous glucose monitoring (CGM) under free living conditions. Spontaneous hypoglycemia in CF is associated with worse lung function, higher hospitalization rates, and worse clinical status. In addition, patients with CF related diabetes on glucose-lowering therapies are at risk for iatrogenic hypoglycemia. In this article, we will review the pathophysiology, prevalence, risk factors, clinical implications, and management of spontaneous and iatrogenic hypoglycemia in patients with CF.