Plasma C-peptide Concentrations Research Articles

Secretion of glucagon, GLP-1 and GIP may be affected by circadian rhythm in healthy males.

Glucagon is secreted from pancreatic alpha cells in response to low blood glucose and increases hepatic glucose production. Furthermore, glucagon enhances hepatic protein and lipid metabolism during a mixed meal. Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are secreted from gut endocrine cells during meals and control glucose homeostasis by potentiating insulin secretion and inhibiting food intake. Both glucose homeostasis and food intake have been reported to be affected by circadian rhythms and vice versa. In this study, we investigated whether the secretion of glucagon, GLP-1 and GIP was affected by circadian rhythms. A total of 24 healthy men with regular sleep schedules were examined for 24h at the hospital ward with 15h of wakefulness and 9h of sleep. Food intake was standardized, and blood samples were obtained every third hour. Plasma concentrations of glucagon, GLP-1 and GIP were measured, and data were analyzed by rhythmometric statistical methods. Available data on plasma glucose and plasma C-peptide were also included. Plasma concentrations of glucagon, GLP-1, GIP, C-peptide and glucose fluctuated with a diurnal 24-h rhythm, with the highest levels during the day and the lowest levels during the night: glucagon (p < 0.0001, peak time 18:26h), GLP-1 (p < 0.0001, peak time 17:28h), GIP (p < 0.0001, peak time 18:01h), C-peptide (p < 0.0001, peak time 17.59h), and glucose (p < 0.0001, peak time 23:26h). As expected, we found significant correlations between plasma concentrations of C-peptide and GLP-1 and GIP but did not find correlations between glucose concentrations and concentrations of glucagon, GLP-1 and GIP. Our results demonstrate that under meal conditions that are similar to that of many free-living individuals, plasma concentrations of glucagon, GLP-1 and GIP were observed to be higher during daytime and evening than overnight. These findings underpin disturbed circadian rhythm as a potential risk factor for diabetes and obesity. ClinicalTrials.gov Identifier: NCT06166368. Registered 12 December 2023.

Differential effects of fish-oil and cocoa-butter based high-fat/high-sucrose diets on endocrine pancreas morphology and function in mice.

A high-fat/high-sucrose diet leads to adverse metabolic changes that affect insulin sensitivity, function, and secretion. The source of fat in the diet might inhibit or increase this adverse effect. Fish oil and cocoa butter are a significant part of our diets. Yet comparisons of these commonly used fat sources with high sucrose on pancreas morphology and function are not made. This study investigated the comparative effects of a fish oil-based high-fat/high-sucrose diet (Fish-HFDS) versus a cocoa butter-based high-fat/high-sucrose diet (Cocoa-HFDS) on endocrine pancreas morphology and function in mice. C57BL/6 male mice (n=12) were randomly assigned to dietary intervention either Fish-HFDS (n=6) or Cocoa-HFDS (n=6) for 22 weeks. Intraperitoneal glucose and insulin tolerance tests (IP-GTT and IP-ITT) were performed after 20-21 weeks of dietary intervention. Plasma concentrations of c-peptide, insulin, glucagon, GLP-1, and leptin were measured by Milliplex kit. Pancreatic tissues were collected for immunohistochemistry to measure islet number and composition. Tissues were multi-labelled with antibodies against insulin and glucagon, also including expression on Pdx1-positive cells. Fish-HFDS-fed mice showed significantly reduced food intake and body weight gain compared to Cocoa-HFDS-fed mice. Fish-HFDS group had lower fasting blood glucose concentration and area under the curve (AUC) for both GTT and ITT. Plasma c-peptide, insulin, glucagon, and GLP-1 concentrations were increased in the Fish-HFDS group. Interestingly, mice fed the Fish-HFDS diet displayed higher plasma leptin concentration. Histochemical analysis revealed a significant increase in endocrine pancreas β-cells and islet numbers in mice fed Fish-HFDS compared to the Cocoa-HFDS group. Taken together, these findings suggest that in a high-fat/high-sucrose dietary setting, the source of the fat, especially fish oil, can ameliorate the effect of sucrose on glucose homeostasis and endocrine pancreas morphology and function.

FRI032 Cellular Insights Into Metabolically Healthy And Unhealthy Obesity

Abstract Disclosure: M.C. Petersen: None. G.I. Smith: None. J. Yu: None. R.A. Barve: Other; Self; Royalties; PercayAI. J. Yoshino: None. G.I. Shulman: None. S. Klein: Advisory Board Member; Self; Merck, Altimmune. Some people with obesity are resistant to the adverse metabolic effects of excess adiposity and are considered to have “metabolically healthy obesity” (MHO). However, the mechanisms responsible for MHO are not clear. We evaluated whole-body insulin sensitivity (glucose infusion rate/plasma insulin during a hyperinsulinemic-euglycemic clamp) and several putative factors that regulate insulin action, including skeletal muscle diacylglycerol (DAG) and ceramide content and transcriptomic profiles in abdominal subcutaneous adipose tissue (ASAT) and muscle, in three groups separated by adiposity and metabolic function: i) 20 adults with MHO (BMI = 38.6 ± 1.2 kg/m2, normal fasting glucose, oral glucose tolerance, hemoglobin A1c, and intrahepatic triglyceride content); ii) 20 adults with MUO (BMI= 39.5 ± 1.1 kg/m2, prediabetes and hepatic steatosis); and iii) 15 adults who were metabolically-healthy and lean (MHL, BMI= 22.7 ± 0.4 kg/m2). Insulin sensitivity progressively decreased from MHL to MHO to MUO [109 ± 7 to 72 ± 7 to 30 ± 2 (μg glucose/kg FFM/min)/(μU/mL), respectively]. Muscle plasma membrane and total cellular sn-1,2-DAG contents were greater in the MHO and MUO groups compared with the MHL group, with no difference between MHO and MUO groups. In contrast, muscle ceramide content in multiple compartments progressively increased from MHL to MHO to MUO and were inversely correlated with insulin sensitivity among all subjects (plasma membrane, r = -0.61; mitochondria, r = -0.56; endoplasmic reticulum, r = -0.51, all P &amp;lt; 0.001). In ASAT, the expression of genes involved in extracellular matrix (ECM) remodeling and inflammation were greater in MUO than MHO, whereas the expression of genes involved in lipogenesis was greater in MHO than MUO. Sparse partial least-squares discriminant analysis, a classification algorithm, was used to identify the features that best discriminated the MHO and MUO groups. Of 125 variables, fasting plasma C-peptide concentration and skeletal muscle mitochondrial ceramide content were the best discriminants of MHO and MUO. Muscle mitochondrial ceramide content was negatively correlated with muscle transcripts involved in mitochondrial structure/function (e.g., ATP5MG [r = -0.69, P &amp;lt; 0.0001] and MPC1 [r = -0.67, P &amp;lt; 0.0001]) and PAQR4 (r = -0.71, P &amp;lt; 0.0001), which encodes a ceramidase in the adiponectin receptor family. In addition, the muscle transcripts that positively correlated with muscle mitochondrial ceramide content were strongly enriched for ECM and TGFβ-related pathways. Conclusions: Greater whole-body insulin sensitivity in people with MHO than MUO is associated with alterations in adipose tissue and skeletal muscle biology, namely decreased markers of ASAT ECM remodeling and inflammation, decreased skeletal muscle ceramide content, and increased skeletal muscle expression of PAQR4 and genes associated with mitochondrial content/function. Presentation: Friday, June 16, 2023

Oral glucose sensing in cephalic phase insulin release

Oral stimulation with foods or food components elicits cephalic phase insulin release (CPIR), which limits postprandial hyperglycemia. Despite its physiological importance, the specific gustatory mechanisms that elicit CPIR have not been clearly defined. While most studies point to glucose and glucose-containing saccharides (e.g., sucrose, maltodextrins) as being the most consistent elicitors, it is not apparent whether this is due to the detection of glucose per se, or to the perceived taste cues associated with these stimuli (e.g., sweetness, starchiness). This study investigated potential sensory mechanisms involved with eliciting CPIR in humans, focusing on the role of oral glucose detection and associated taste. Four stimulus conditions possessing different carbohydrate and taste profiles were designed: 1) glucose alone; 2) glucose mixed with lactisole, a sweet taste inhibitor; 3) maltodextrin, which is digested to starchy- and sweet-tasting products during oral processing; and 4) maltodextrin mixed with lactisole and acarbose, an oral digestion inhibitor. Healthy adults (N = 22) attended four sessions where blood samples were drawn before and after oral stimulation with one of the target stimuli. Plasma c-peptide, insulin, and glucose concentrations were then analyzed. Whereas glucose alone elicited CPIR (one-sample t-test, p < 0.05), it did not stimulate the response in the presence of lactisole. Likewise, maltodextrin alone stimulated CPIR (p < 0.05), but maltodextrin with lactisole and acarbose did not. Together, these findings indicate that glucose is an effective CPIR stimulus, but that an associated taste sensation also serves as an important cue for triggering this response in humans.

Suppression of Endogenous Insulin Secretion by Euglycemic Hyperinsulinemia.

The impact of insulin, particularly exogenous hyperinsulinemia, on insulin secretion in humans is debated. We assessed the effects of exogenous hyperinsulinemia on insulin secretion and whether the response is altered in insulin resistance associated with obesity. Insulin secretion rates (ISRs) during euglycemic hyperinsulinemic clamp studies (52 volunteers) were calculated using a model that employs plasma C-peptide concentrations. One study involved a 2-step insulin clamp and the other study was a single step insulin clamp. For both studies the goal was to achieve plasma glucose concentrations of 95 mg/dL during the clamp irrespective of fasting glucose concentrations. The percent change in ISR from fasting to the end of the insulin clamp interval was the main outcome. Linear regression and analysis of covariance were used to test for the effects of insulin on ISR and to test for group differences. ISR was greater in obese volunteers (P < .001) under fasting and hyperinsulinemic clamp conditions. The change in plasma glucose from baseline to the end of the insulin clamp interval was highly correlated with the change in ISR (r = 0.61, P < .001). From baseline to the end of the clamp we observed a 27% (SD 20) suppression of ISR. The participants who underwent a 2-step insulin clamp had greater suppression of ISR during the second step than the first step (P < .001). The proportional suppression of ISR during euglycemic hyperinsulinemia was not different between nonobese and obese groups (P = .19). Hyperinsulinemia suppresses endogenous insulin secretion and the relative change in insulin secretion produced by exogenous insulin did not differ between nonobese and obese people.

Serum alanine transaminase is predictive of fasting and postprandial insulin and glucagon concentrations in type 2 diabetes

The liver plays a key role in glucose homeostasis. Serum liver enzyme levels, including alanine transaminase (ALT), aspartate transaminase (AST) and gamma-glutamyl transferase (GGT), are reportedly predictive of the risk of type 2 diabetes (T2D). However, the link between the liver enzyme profile and metabolic derangements in T2D, particularly the secretion of both insulin and glucagon, is not clear. This study evaluated its relationships with glycemia, insulin and glucagon both during fasting and after an oral glucose load or a mixed meal in T2D. 15 healthy and 43 T2D subjects ingested a 75 g glucose drink. 86 T2D subjects consumed a mixed meal. Venous blood was sampled for measurements of blood glucose and plasma insulin, C-peptide and glucagon. Blood glucose, plasma insulin, C-peptide and glucagon concentrations, both fasting and after oral glucose, correlated directly with ALT, while fewer and weaker correlations were observed with GGT or AST. Subgroup analysis in T2D subjects ascertained that plasma insulin, C-peptide and glucagon concentrations after oral glucose were higher with increasing ALT. Similar findings were observed in the T2D subjects who received a mixed meal. In conclusion, serum liver enzyme profile, particularly ALT, reflects dysregulated fasting and nutrient-stimulated plasma insulin and glucagon concentrations in T2D.

The effect of pre-dosing with metformin on the insulin response to oral sugar in insulin-dysregulated horses.

A single dose of metformin administered 1 h prior to oral glucose challenge was previously shown to reduce insulinaemic responses in horses with experimentally-induced insulin dysregulation (ID). Targeted administration could be useful for controlling post-prandial hyperinsulinaemia in horses with naturally-occurring ID. The objective was to compare the insulinaemic and glycaemic responses to oral sugar testing (OST) performed at different intervals after a single dose of metformin in horses with naturally-occurring ID. We hypothesised that pre-treatment with one dose of metformin would significantly decrease the insulinaemic response to OST. Randomised cross-over in vivo experiment. Eight university-owned adult horses with naturally-occurring ID underwent OST 1, 2 and 6 h following a single oral dose of metformin (30 mg/kg) or 1 h after placebo (240 mL water) with a 7-day washout between treatments over a period of 3 weeks. Plasma insulin, C-peptide and glucose concentrations were measured at 0, 60 and 90 min after 0.45 mL/kg light corn syrup and the effect of treatment (and the interval since dosing) examined using a mixed effects linear regression model. Metformin treatment had no significant effect on plasma glucose, insulin or C-peptide concentrations at any time point compared with placebo (p > 0.05). For OST 1 h post metformin, median (IQR) plasma insulin was 91.3 (62.4-114.9) μIU/mL at 60 min versus 76.2 (59.1-134.5) for placebo (p = 0.8) and 62.7 (31.4-109.7) at 90 min versus 51.8 (29.2-126.3) for placebo (p = 0.9). Small sample size may limit identification of more subtle decreases in insulin concentration with metformin pre-dosing. The results of this study are relevant only for one pre-treatment dose (30 mg/kg) which limits extrapolation to predictions about the effects of longer-term metformin administration on insulin and glucose dynamics in the horse. The results do not support the use of targeted metformin treatment to reduce post-prandial hyperinsulinaemia in horses with naturally-occurring ID.

1586-P: Post-OGTT Low Blood Glucose in Individuals with Metabolic Syndrome, Metabolic Phenotypes, and Metabolic-Associated Fatty Liver Disease

Introduction: Post-prandial low blood glucose (LBG) is usually associated with late postprandial hyperinsulinemia in metabolic syndrome (MetS), but have not been well studied. Objectives: We aimed to 1) characterize insulin/glucose metabolism associated with LBG post 75g OGTT in a sample of individuals with MetS; and 2) assess the association between MAFLD (≥ 5% liver fat at MRI) and LBG. Methods: Plasma glucose, insulin and c-peptide concentrations were measured on OGTT over 180 mins. Insulin sensitivity and secretion were assessed with the Oral Minimal Model. During OGTT, we defined glucose ≤ 50 mg/dl as LBG, glucose &amp;gt; 70 mg/dl as no LBG and glucose 51-70 mg/dl as undefined status and were excluded from this analysis. Results: Of 82 participants, 50 were included and 15 (18 %) experienced LBG. Of the 33 participants who underwent MRI, 48% had MAFLD. Median age and BMI were 59 [IQR: 49-74] years and 28 [IQR: 26-31] kg/m2 respectively. Women represented 70% (n=35) of participants and experienced less LBG (p=0.0002) than men. Individuals experiencing LBG had higher insulin sensitivity (p=0.02), higher ß cell function (p=0.03), earlier glucose peaks (p&amp;lt;0.0001) and lower c-peptide peaks (p=0.007) than those without LBG. MAFLD was not associated with more LBG (p=0.7), but was associated with a different insulin curve. LBG+MAFLD status was associated with higher and later c-peptide and insulin levels compared to LBG without MAFLD status. Conclusion: In contrary to our hypothesis, individuals with MetS without MAFLD experiencing glucose ≤ 50 mg/dl during OGTT displayed a healthier metabolic profile. However, individuals with MAFLD experiencing a LBG during OGTT had a glucose phenotype similar to the late post-prandial hyperinsulinemic hypoglycemia often found in prediabetes state and associated with worst metabolic parameters. This suggests that MAFLD may be an important feature of MetS associated with a different post-OGTT glucose metabolism. Disclosure T.Gignac: None. A.Morissette: None. A.Agrinier: None. C.Gagnon: Advisory Panel; Novo Nordisk, Other Relationship; Ascendis Pharma A/S, Research Support; Novo Nordisk. M.Vohl: None. A.Marette: Advisory Panel; Valbiotis, Amancia, Plexus, Acasti. A.Carreau: Advisory Panel; Novartis, Consultant; Valbiotis, Speaker's Bureau; Novo Nordisk Canada Inc.

Hyperinsulinemia and risk of lethal prostate cancer.

e17008 Background: Epidemiologic studies have found that insulin-like growth factor (IGF)-1 causally increases prostate cancer incidence and mortality, but the effect of insulin is less clear. IGF-1 and insulin act as mitogens by binding non-selectively to their receptors. To this end, this study tests the hypothesis that high circulating insulin increases risk for lethal (fatal or metastatic) prostate cancer among men with non-metastatic prostate cancer. Methods: The study population was drawn from two U.S.-based longitudinal cohorts: the Health Professionals Follow-Up Study (HPFS) of 51,529 health professionals and the Physicians’ Health Study (PHS) of 29,067 physicians. Pre-diagnostic plasma concentration of C-peptide was used as a proxy for insulin and measured on blood collected in 1993-1995 (HPFS) or 1982 (PHS) and stratified into quartiles for analysis. The empiric lifestyle index (based on body mass index (BMI), physical activity, and diet) for hyperinsulinemia (ELIH) was calculated from questionnaire data. Covariates of interest (age and fasting status at blood draw, BMI, height, clinical stage, and tumor grade) were attained from questionnaires and medical records. We followed patients for development of metastasis or death (lethal) through 2019 (HPFS) and 2015 (PHS). SAS 9.4 and R Studio were used for analyses. Chi-squared tests and Mann Whitney U tests were used to compare differences between groups, and Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% CI. Results: The sample included 2,812 men with 353 lethal prostate cancer events and a mean follow-up of 164 months from diagnosis to death. The mean time from blood draw to cancer diagnosis was 8.1 years. Compared to men with non-lethal prostate cancer, those with lethal disease had significantly more severe clinical grade and stage at diagnosis, higher BMI (25.1 vs 24.6), older age at blood draw (64.5 vs 61.9 years), and higher ELIH index. There were no differences by other covariates. There was no association between pre-diagnostic c-peptide levels and cancer-specific survival in a multivariable model that included clinical stage and grade (HR, 95% CI for high vs. low quartiles: 1.17, 0.83, 1.67). High ELIH was positively associated with risk of lethal prostate cancer (HR, 95% CI: 2.41, 1.36, 4.28), even when controlling for C-peptide (HR, 95% CI: 2.18, 1.20, 3.96). Conclusions: C-peptide levels measured prior to cancer diagnosis were not associated with increased mortality from prostate cancer. Higher ELIH was associated with increased risk of lethal prostate cancer among those diagnosed with prostate cancer, which could be partly mediated by hyperinsulinemia, but other dietary, physical activity, or BMI mechanisms could contribute.

Umbilical cord-derived mesenchymal stromal cells preserve endogenous insulin production in type 1 diabetes: a Phase I/II randomised double-blind placebo-controlled trial

Aim/hypothesisThis study aimed to investigate the safety and efficacy of treatment with allogeneic Wharton’s jelly-derived mesenchymal stromal cells (MSCs) in recent-onset type 1 diabetes.MethodsA combined Phase I/II trial, composed of a dose escalation followed by a randomised double-blind placebo-controlled study in parallel design, was performed in which treatment with allogeneic MSCs produced as an advanced therapy medicinal product (ProTrans) was compared with placebo in adults with newly diagnosed type 1 diabetes. Inclusion criteria were a diagnosis of type 1 diabetes <2 years before enrolment, age 18–40 years and a fasting plasma C-peptide concentration >0.12 nmol/l. Randomisation was performed with a web-based randomisation system, with a randomisation code created prior to the start of the study. The randomisation was made in blocks, with participants randomised to ProTrans or placebo treatment. Randomisation envelopes were kept at the clinic in a locked room, with study staff opening the envelopes at the baseline visits. All participants and study personnel were blinded to group assignment. The study was conducted at Karolinska University Hospital, Stockholm, Sweden.ResultsThree participants were included in each dose cohort during the first part of the study. Fifteen participants were randomised in the second part of the study, with ten participants assigned to ProTrans treatment and five to placebo. All participants were analysed for the primary and secondary outcomes. No serious adverse events related to treatment were observed and, overall, few adverse events (mainly mild upper respiratory tract infections) were reported in the active treatment and placebo arms. The primary efficacy endpoint was defined as Δ-change in C-peptide AUC for a mixed meal tolerance test at 1 year following ProTrans/placebo infusion compared with baseline performance prior to treatment. C-peptide levels in placebo-treated individuals declined by 47%, whereas those in ProTrans-treated individuals declined by only 10% (p<0.05). Similarly, insulin requirements increased in placebo-treated individuals by a median of 10 U/day, whereas insulin needs of ProTrans-treated individuals did not change over the follow-up period of 12 months (p<0.05).Conclusions/interpretationThis study suggests that allogeneic Wharton’s jelly-derived MSCs (ProTrans) is a safe treatment for recent-onset type 1 diabetes, with the potential to preserve beta cell function.Trial registrationClinicalTrials.gov NCT03406585FundingThe sponsor of the clinical trial is NextCell Pharma AB, Stockholm, Sweden.Graphical

Non-invasive imaging of functional pancreatic islet beta-cell mass in people with type 1 diabetes mellitus.

To investigate whether manganese-enhanced magnetic resonance imaging can assess functional pancreatic beta-cell mass in people with type 1 diabetes mellitus. In a prospective case-control study, 20 people with type 1 diabetes mellitus (10 with low (≥50 pmol/L) and 10 with very low (<50 pmol/L) C-peptide concentrations) and 15 healthy volunteers underwent manganese-enhanced magnetic resonance imaging of the pancreas following an oral glucose load. Scan-rescan reproducibility was performed in 10 participants. Mean pancreatic manganese uptake was 31 ± 6 mL/100 g of tissue/min in healthy volunteers (median 32 [interquartile range 23-36] years, 6 women), falling to 23 ± 4 and 13 ± 5 mL/100 g of tissue/min (p ≤ 0.002 for both) in people with type1 diabetes mellitus (52 [44-61] years, 6 women) and low or very low plasma C-peptide concentrations respectively. Pancreatic manganese uptake correlated strongly with plasma C-peptide concentrations in people with type1 diabetes mellitus (r = 0.73, p < 0.001) but not in healthy volunteers (r = -0.054, p = 0.880). There were no statistically significant correlations between manganese uptake and age, body-mass index, or glycated haemoglobin. There was strong intra-observer (mean difference: 0.31 (limits of agreement -1.42 to 2.05) mL/100 g of tissue/min; intra-class correlation, ICC = 0.99), inter-observer (-1.23 (-5.74 to 3.27) mL/100 g of tissue/min; ICC = 0.85) and scan-rescan (-0.72 (-2.9 to 1.6) mL/100 g of tissue/min; ICC = 0.96) agreement for pancreatic manganese uptake. Manganese-enhanced magnetic resonance imaging provides a potential reproducible non-invasive measure of functional beta-cell mass in people with type 1 diabetes mellitus. This holds major promise for investigating type 1 diabetes, monitoring disease progression and assessing novel immunomodulatory interventions.

Postprandial Metabolic Responses to High-fat Feeding in Healthy Adults Following Ingestion of Oolong Tea–Derived Polymerized Polyphenols: A Randomized, Double-blinded, Placebo-controlled Crossover Study

BackgroundPolymerized polyphenols (PP) found in oolong tea can inhibit pancreatic lipase activity in vitro, and pilot work indicates that this may reduce postprandial lipemia. Since tea contains caffeine and catechins, the interactions between these ingredients and PP warrant investigation. ObjectivesTo assess whether PP ingested alone or with caffeine and catechins lowers postprandial lipemia. MethodsFifty healthy adults [mean (SD) age: 26 (7) y; BMI (in kg/m2): 24.0 (2.7); female: n = 16] completed 4 oral lipid tolerance tests in a placebo-controlled randomized, crossover design. Participants ingested 40 g of fat with either 1) placebo, 2) 100 mg PP, 3) 150 mg PP, or 4) 100 mg PP plus 50 mg caffeine and 63 mg catechins (PP + CC). Blood was sampled for 3 h postprandially to assess concentrations of serum and plasma triacylglycerol and plasma markers of lipid (NEFA; glycerol; LDL and HDL cholesterol; and ApoA-I, A-II, B, C-II, C-III, and E) and glucose metabolism (glucose, insulin, and C-peptide). ResultsSerum and plasma triacylglycerol concentrations and lipid metabolism variables generally increased following any test drink ingestion (main effect of time, p < 0.001). Nevertheless, for the lipid metabolism responses, there were no statistically significant condition–time interactions and no statistically significant differences in incremental or total area under the curve between conditions, apart from HDL cholesterol (p = 0.021). Ingesting 100 mg PP + CC lowered peak plasma glucose, insulin, and C-peptide concentrations compared with all other conditions 30 min postingestion (p < 0.001), with persistent alterations in glucose concentrations observed for 90 min compared with placebo and 100 mg PP conditions. ConclusionsPP ingested at doses ≤150 mg does not clearly alter early-phase postprandial triacylglycerol concentrations in healthy adults, irrespective of the presence or absence of caffeine and catechins. Nevertheless, caffeine and catechins added to PP lowered postprandial glucose and insulin concentrations.This trial was registered in ClinicalTrials.gov as NCT03324191 (https://clinicaltrials.gov/ct2/show/NCT03324191).

Chronic physiologic hyperglycemia impairs insulin-mediated suppression of plasma glucagon concentration in healthy humans

Background and aimsHyperglucagonemia is a characteristic feature of type 2 diabetes mellitus (T2DM). We examined the effect of chronic (48–72 h) physiologic increase (+50 mg/dl) in plasma glucose concentration on suppression of plasma glucagon concentration by insulin and by hyperglycemia in normal glucose tolerance (NGT) individuals. Materials and methodsStudy One: 16 NGT subjects received OGTT and 3-step hyperinsulinemic (10, 20, 40 mU/m2·min) euglycemic clamp before and after 48 hour glucose infusion to increase plasma glucose by ~50 mg/dl. Study Two: 20 NGT subjects received OGTT and 2-step hyperglycemic (+125 and + 300 mg/dl) clamp before and after 72 hour glucose infusion. Plasma insulin, C-peptide and glucagon concentrations were measured during OGTT, euglycemic hyperinsulinemic and hyperglycemic clamps. Ratio of plasma glucagon/insulin was used as an index of insulin-mediated suppression of glucagon secretion. ResultsDuring all 3 insulin clamp steps (Study 1), plasma glucagon concentration was increased compared to baseline study, and plasma glucagon/insulin ratio was significantly reduced by 24 % (p < 0.05). The rate of insulin-stimulated glucose disposal was inversely correlated with plasma glucagon/insulin ratio (r = −0.44, p < 0.05) and with glucagon AUC (r = −0.48, p < 0.05). During the 2-step hyperglycemic clamp (Study 2) plasma glucagon was similar before and after 72 h of glucose infusion; however, glucagon/insulin ratio was significantly reduced (p < 0.05). Incremental area under plasma insulin curve during the first (r = −0.74, p < 0.001) and second (r = −0.85, p < 0.001) hyperglycemic clamp steps was strongly and inversely correlated with plasma glucagon/insulin ratio. ConclusionSustained (48–72 h) physiologic hyperglycemia (+50 mg/dl) caused whole body insulin resistance and impaired insulin-mediated suppression of glucagon secretion, suggesting a role for glucotoxicity in development of hyperglucagonemia in T2DM.

The Effect of Glucagon-Like Peptide 1 Receptor Blockade on Glucagon-Induced Stimulation of Insulin Secretion.

Data from transgenic rodent models suggest that glucagon acts as an insulin secretagogue by signaling through the glucagon-like peptide 1 receptor (GLP-1R) present on β-cells. However, its net contribution to physiologic insulin secretion in humans is unknown. To address this question, we studied individuals without diabetes in two separate experiments. Each subject was studied on two occasions in random order. In the first experiment, during a hyperglycemic clamp, glucagon was infused at 0.4 ng/kg/min, increasing by 0.2 ng/kg/min every hour for 5 h. On one day, exendin-9,39 (300 pmol/kg/min) was infused to block GLP-1R, while on the other, saline was infused. The insulin secretion rate (ISR) was calculated by nonparametric deconvolution from plasma concentrations of C-peptide. Endogenous glucose production and glucose disappearance were measured using the tracer-dilution technique. Glucagon concentrations, by design, did not differ between study days. Integrated ISR was lower during exendin-9,39 infusion (213 ± 26 vs. 191 ± 22 nmol/5 h, saline vs. exendin-9,39, respectively; P = 0.02). In the separate experiment, exendin-9,39 infusion, compared with saline infusion, also decreased the β-cell secretory response to a 1-mg glucagon bolus. These data show that, in humans without diabetes, glucagon partially stimulates the β-cell through GLP-1R.

Preclinical pharmacology of RA15127343: In vitro and in vivo activity of a novel ultralong-acting basal insulin.

To report the in vitro and in vivo preclinical pharmacokinetic (PK) and pharmacodynamic (PD) properties of RA15127343, a novel ultralong-acting insulin analogue targeting once-weekly administration, in female Göttingen minipigs. In vitro binding and activation of human insulin receptor isoforms (IR-A/IR-B), glucose uptake in rat myocytes, as well as mitogenic activity of RA15127343 were evaluated. In vivo, the PK and PD activities of RA15127343 were assessed in female, normoglycaemic Göttingen minipigs. The half-life (t1/2 ) and time to maximum plasma concentration (Tmax ) of subcutaneously (SC) administered RA15127343 (10/30/45/60 nmol/kg) were estimated. In vivo blood glucose and endogenous plasma C-peptide concentrations after single SC administration (10/30/45/60 nmol/kg) or repeated dosing (15 nmol/kg) were analysed. In comparison to human insulin, RA15127343 showed lower in vitro binding affinity (19.9/6.31 μM vs. 1.10/1.14 nM) and activation (2.054 μM/669.6nM vs. 26.04/18.24 nM) of IR-A/IR-B, lower potency to activate glucose uptake (855.2 vs. 3.37 nM) and lower mitogenic activity (17.92 μM vs. 10.78 nM; proliferation in MCF7 cells). In vivo, the mean t1/2 and Tmax of RA15127343 after SC administration ranged from 48 to 59 and 30 to 39 hours, respectively. Blood glucose and plasma C-peptide concentrations were significantly lower with RA15127343 (single/repeated doses) versus vehicle. RA15127343 showed an ultra-long t1/2 with a slow onset of action. The preclinical pharmacological outcomes suggest RA15127343 could be a potential ultralong-acting insulin analogue with low risk of hypoglycaemia in humans.

Type 2 diabetes subgroups and response to glucose-lowering therapy: Results from the EDICT and Qatar studies.

To examine the efficacy of glucose-lowering medications in subgroups of patients with type 2 diabetes mellitus (T2DM). Cluster analysis was performed in participants in the Efficacy and Durability of Initial Combination Therapy for Type 2 Diabetes (EDICT) study and the Qatar study using age, body mass index (BMI), glycated haemoglobin (HbA1c), and homeostatic model assessment of insulin resistance (HOMA-IR) and beta-cell function (HOMA-β). Participants also underwent an oral glucose tolerance test with measurement of plasma glucose, insulin and C-peptide concentrations to derive independent measures of insulin secretion and insulin sensitivity. The response to glucose-lowering therapies (change in HbA1c) was measured in each participant cluster for 3 years. Three distinct and comparable clusters/groups of T2DM patients were identified in both the EDICT and Qatar studies. Participants in Group 1 had the highest HbA1c and manifested severe insulin deficiency. Participants in Group 3 had comparable insulin sensitivity to those in Group 1 but better beta-cell function and better glucose control. Participants in Group 2 had the highest BMI with severe insulin resistance accompanied by marked hyperinsulinaemia, which was primarily attributable to decreased insulin clearance. Unexpectedly, participants in Group 1 had better response to combination therapy with pioglitazone plus exenatide than with insulin therapy or metformin sequentially followed by glipizide and basal insulin, while participants in Group 2 responded equally well to both therapies despite very severe insulin resistance. Distinct metabolic phenotypes characterize different T2DM clusters and differential responses to glucose-lowering therapies. Participants with severe insulin deficiency respond better to agents that preserve beta-cell function, while, surprisingly, patients with severe insulin resistance did not respond favourably to insulin sensitizers.

ADPKD protects against diabetogenic effects associated with genetically-predicted lactase persistence.

IntroductionThe LCT: -13910C&gt;T (rs4988235) polymorphism is associated with lactase persistence. Our previous study revealed impairment of pancreatic beta-cell function after an oral glucose tolerance test (OGTT) without a significant decrease in insulin sensitivity in ADPKD patients. The aim of the present study was to analyse clinical and biochemical parameters including indices of insulin sensitivity in regard to LCT polymorphism both in ADPKD patients and controls.Material and methodsThe study group consisted of 49 ADPKD patients and the control group comprised 50 healthy subjects. Plasma glucose, insulin and C-peptide concentrations were measured during WHO OGTT. The LCT polymorphism was identified by PCR-RFLP assay of samples of genomic DNA extracted from peripheral blood leukocytes.ResultsIn the ADPKD group no significant differences in clinical and biochemical parameters were found between patients with lactase non-persistence (LNP) and individuals with lactase persistence (LP). In healthy subjects with LP (LCT: CT or TT genotype) body fat, the levels of insulin, C-peptide and insulin/glucose ratio (at OGTT times 0 and 120 minutes); area under curve ratios of secretory 1st and 2nd phase, homeostasis model assessment (HOMA)-insulin resistance and % beta, were significantly higher as compared with CC homozygotes (LNP). In addition, HOMA% sensitivity and indices of insulin sensitivity in LP controls were significantly lower as compared with healthy subjects with LNP.ConclusionsOur results suggest that ADPKD patients are protected against a lactase-persistence-associated diabetogenic increase in insulin resistance.

358-OR: The Effect of Glucagon-Like Peptide-1 Receptor Blockade on Glucagon-Induced Stimulation of Insulin Secretion

Data from transgenic rodent models suggest that glucagon acts as an insulin secretagogue by signalling through the Glucagon-Like Peptide-1 Receptor (GLP1R) present on β-cells. This occurs at high concentrations as are present within the islet. However, its net contribution to physiologic insulin secretion is unknown. To address this question, we studied 12 non-diabetic, weight-stable individuals (26±1 years,25±1 kg/m2) on 2 occasions. During a hyperglycemic clamp (∼8.9mmol/l) where glucose was labeled with [3-3H] glucose, glucagon was infused at 0.4ng/kg/min, for 1 hour, increasing by 0.2ng/kg/min every hour for a total of 5 hours. Subjects were studied on two occasions in random order. On one occasion Exendin-9,39 (300pmol/kg/min) was infused to block the GLP1R, while on the control day saline was infused. The insulin secretion rate (ISR) was calculated by nonparametric deconvolution from plasma concentrations of C-peptide. Endogenous glucose production (EGP) and glucose disappearance (Rd) were measured using the tracer-dilution technique. Glucagon concentrations rose from baseline (6.6±2.1 vs. 5.4±1.5 pmol/l, saline vs. exendin-9,39 respectively, p=0.22) to values that, by design, did not differ between study days (17.8±1.8 vs. 17.1±1.1 pmol/l, p&amp;gt;0.1) . This was accompanied by a rise in C-peptide from fasting concentrations. Integrated C-peptide concentrations were slightly, but significantly, decreased during exendin-9,39 infusion (721±65 vs. 648±55 nmol per 5hr, p=0.02) . In addition, integrated insulin secretion rate was lower during exendin-9,39 infusion (213±26 vs. 191±22 nmol per 5 hr, saline vs. exendin-9,39 respectively, p = 0.03) . Both EGP and Rd did not differ significantly on either experimental day. These data show that in non-diabetic humans, during hyperglycemia as seen in the postprandial period, glucagon partially stimulates the β-cell through GLP1R. It remains to be ascertained if this also applies to individuals with type 2 diabetes. Disclosure R.A. Farahani: None. A.A. Welch: None. M.C. Laurenti: None. C. Cobelli: None. C. Dalla Man: Research Support; Becton, Dickinson and Company, Sanofi-Aventis Deutschland GmbH. A. Vella: Advisory Panel; Crinetics Pharmaceuticals, Inc., Rezolute, Inc., vTv Therapeutics, Zealand Pharma A/S. Other Relationship; Novo Nordisk. Funding National Institutes of Health (DK126206)

684-P: Tracking Type 2 Diabetes Progression Using CGM Systems

Disposition index (DI) is an index quantifying the quality of glucose control, usable to track disease progression. It is usually calculated as the product of beta-cell function and insulin sensitivity, assessed, in hospitalized setting, either from clamp data, surrogate indices or model-based methods, like the Oral Minimal Model (OMM) . The increasing use of continuous glucose monitoring (CGM) systems, even in individuals with type 2 diabetes (T2D) , opens the door to the use of such devices to monitor glucose control in outpatients. Here, we propose a method to assess DI from CGM data, validated it against OMM and proved its usability to track disease progression. We studied 100 early stage (ES) and 100 advanced stage (AS) subjects with T2D of the Padova T2D simulator, matched for age (54 [42,75] y) and different BMI (33 [29,37] vs. 31 [28,34] kg/m2; p=0.016) , which underwent a mixed meal challenge (75g of carbohydrates) while wearing CGM. Plasma glucose, insulin and C-peptide concentrations were measured for 6 hours after the meal and used for the estimation of the DI with the OMM (DIMM) , while CGM sensor data were used to calculate DI with the sensor-based method (DISB) . DISB well correlated with DIMM (ρES = 0.81 and ρAS = 0.77; p&amp;lt;0.001) and both were significantly lower in AD than ES (p&amp;lt;0.001, Fig. 1) . We conclude that DISB is usable to assess DI in subjects with different stage of T2D wearing CGM and thus, potentially, to track disease progression in noninvasive way. Disclosure M.Schiavon: None. C.Dalla man: Research Support; Becton, Dickinson and Company, Sanofi-Aventis Deutschland GmbH. Funding MIUR (Italian Minister for Education) under the initiative "Departments of Excellence" (Law 232/2016)

Neither Incretin or Amino Acid Responses, nor Casein Content, Account for the Equal Insulin Response Following Iso-Lactose Loads of Natural Human and Cow Milk in Healthy Young Adults.

Human milk contains <50% less protein (casein) than cow milk, but is equally effective in insulin secretion despite lower postingestion hyperaminoacidemia. Such potency of human milk might be modulated either by incretins (glucagon-like polypeptide-1,GLP-1); glucose-inhibitory-polypeptide, GIP), and/or by milk casein content. Healthy volunteers of both sexes were fed iso-lactose loads of two low-protein milks, i.e., human [Hum] (n = 8) and casein-deprived cow milk (Cow [↓Cas]) (n = 10), as well as loads of two high-protein milks, i.e., cow (n = 7), and casein-added human-milk (Hum [↑Cas]) (n = 7). Plasma glucose, insulin, C-peptide, incretins and amino acid concentrations were measured for 240′. All milks induced the same transient hyperglycemia. The early [20′–30′] insulin and C-peptide responses were comparable among all milk types apart from the low-protein (Cow [↓Cas]) milk, where they were reduced by <50% (p < 0.05 vs. others). When comparing the two high-protein milks, GLP-1 and GIP [5’–20’] responses with the (Hum [↑Cas]) milk were lower (by ≈2–3 fold, p < 0.007 and p < 0.03 respectively) than those with cow milk, whereas incretin secretion was substantially similar. Plasma amino acid increments largely reflected the milk protein content. Thus, neither casein milk content, nor incretin or amino acid concentrations, can account for the specific potency of human milk on insulin secretion, which remains as yet unresolved.