Arginine-stimulated C-peptide Research Articles

65-OR: Effects of Treatment with Metformin and/or Sitagliptin on Beta-Cell Function and Insulin Resistance in Prediabetic Women with Previous Gestational Diabetes

Gestational diabetes (GDM) enhances the risk of type 2 diabetes (T2D) with 20-50% of women progressing to T2D within 10-years after pregnancy. Preventative strategies, including use of pharmacologic agents, are worth considering. We assessed, in a randomized double-blind study, the effect of 16-week therapy with sitagliptin (SITA, 100 mg qd), metformin (MET, 850 mg bid), and SITA+MET (50+850 mg bid) on beta-cell function and insulin sensitivity in women (n=40, age 30-49 y) with recent GDM and impaired glucose regulation (IGR: IFG and/or IGT). A 75gr OGTT and +125 mg/dl hyperglycemic clamp followed by 5 gr i.v. L-arginine were performed at baseline and study-end. Baseline characteristics were comparable in the 3 groups. At week 16, BMI declined in all groups (-1.2±0.2 Kg/m2; p<0.05). First phase(2-10 min) insulin secretion and arginine-stimulated C-peptide response increased with SITA+MET (1.0±0.2 to 1.3±0.3 ng/ml/min and 3.2±0.6 to 4.8±1.0 pmol/min, respectively, both p<0.05) while no changes occurred with MET and SITA. SITA+MET increased OGTT-based glucose sensitivity (55.7±11.3 to 108±56.2 pmol x min-1m-2 x mM-1; p=0.04) but no changes occurred with MET and SITA. No change occurred for rate sensitivity and potentiation factor in any group. SITA+MET increased insulin sensitivity (M/I: 2.2±0.5 to 4.6±1.3 mg/kg/min÷μIU/min/ml; p=0.04; OGIS: 351.9±11.4 to 375.7±9.6 ml x min-1m-2; p=0.08) but it was not affected by MET or SITA. Disposition Index increased with SITA+MET (10.8±1.1 to 13.6±1.6 μIU/ml/min÷mg/dl/min) and SITA (8.6±1.0 to 10.6±1.3; both p<0.05). Among SITA+MET women, 33% reverted to NGT compared to 14% with MET and 7% with SITA (p<0.05). This proof of concept study shows that SITA+MET is superior to SITA and MET monotherapy on beta-cell function and insulin sensitivity improvement in IGR women with previous GDM. It may offer a potential pharmacologic intervention to reduce risk of T2D in this high-risk population. Disclosure S. Barone: None. A. Dardano: None. A. Tura: None. J.J. Kurumthodathu: None. A. Bertolotto: Speaker's Bureau; Self; Abbott, Lilly Diabetes. C. Bianchi: None. L. Giusti: None. E. Lacaria: None. M. Romano: None. R. Miccoli: None. G. Penno: None. S. Del Prato: Advisory Panel; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, GlaxoSmithKline plc., Merck Sharp & Dohme Corp., Novartis Pharmaceuticals Corporation, Novo Nordisk A/S, Sanofi, Servier, Takeda Pharmaceutical Company Limited. Board Member; Self; AstraZeneca. Research Support; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc. Speaker's Bureau; Self; Boehringer Ingelheim Pharmaceuticals, Inc., Takeda Pharmaceutical Company Limited. G. Daniele: None.

Metabolic Contrasts Between Youth and Adults With Impaired Glucose Tolerance or Recently Diagnosed Type 2 Diabetes: I. Observations Using the Hyperglycemic Clamp

OBJECTIVETo compare insulin sensitivity (M/I) and β-cell responses in youth versus adults with impaired glucose tolerance (IGT) or drug-naïve, recently diagnosed type 2 diabetes.RESEARCH DESIGN AND METHODSIn 66 youth (80.3% with IGT) and 355 adults (70.7% IGT), hyperglycemic clamps were used to measure 1) M/I, 2) acute (0–10 min [first phase]) C-peptide (ACPRg) and insulin (AIRg) responses to glucose, 3) steady-state C-peptide and insulin concentrations at plasma glucose of 11.1 mmol/L, and 4) arginine-stimulated maximum C-peptide (ACPRmax) and insulin (AIRmax) responses at plasma glucose >25 mmol/L. The fasting C-peptide–to–insulin ratio was used as an estimate of insulin clearance.RESULTSInsulin sensitivity was 46% lower in youth compared with adults (P < 0.001), and youth had greater acute and steady-state C-peptide (2.3- and 1.3-fold, respectively; each P < 0.001) and insulin responses to glucose (AIRg 3.0-fold and steady state 2.2-fold; each P < 0.001). Arginine-stimulated C-peptide and insulin responses were also greater in youth (1.6- and 1.7-fold, respectively; each P < 0.001). After adjustment for insulin sensitivity, all β-cell responses remained significantly greater in youth. Insulin clearance was reduced in youth (P < 0.001). Participants with diabetes had greater insulin sensitivity (P = 0.026), with lesser C-peptide and insulin responses than those with IGT (all P < 0.001) but similar insulin clearance (P = 0.109).CONCLUSIONSIn people with IGT or recently diagnosed diabetes, youth have lower insulin sensitivity, hyperresponsive β-cells, and reduced insulin clearance compared with adults. Whether these age-related differences contribute to declining β-cell function and/or impact responses to glucose-lowering interventions remains to be determined.

Does dipeptidyl peptidase-4 inhibition prevent the diabetogenic effects of glucocorticoids in men with the metabolic syndrome? A randomized controlled trial

Anti-inflammatory glucocorticoid (GC) therapy often induces hyperglycemia due to insulin resistance and islet-cell dysfunction. Incretin-based therapies may preserve glucose tolerance and pancreatic islet-cell function. In this study, we hypothesized that concomitant administration of the dipeptidyl peptidase-4 inhibitor sitagliptin and prednisolone in men at high risk to develop type 2 diabetes could protect against the GC-induced diabetogenic effects. Men with the metabolic syndrome but without diabetes received prednisolone 30 mg once daily plus sitagliptin 100 mg once daily (n=14), prednisolone (n=12) or sitagliptin alone (n=14) or placebo (n=12) for 14 days in a double-blind 2 × 2 randomized-controlled study. Glucose, insulin, C-peptide, and glucagon were measured in the fasted state and following a standardized mixed-meal test. β-cell function parameters were assessed both from a hyperglycemic-arginine clamp procedure and from the meal test. Insulin sensitivity (M-value) was measured by euglycemic clamp. Prednisolone increased postprandial area under the curve (AUC)-glucose by 17% (P<0.001 vs placebo) and postprandial AUC-glucagon by 50% (P<0.001). Prednisolone reduced 1st and 2nd phase glucose-stimulated- and combined hyperglycemia-arginine-stimulated C-peptide secretion (all P ≤ 0.001). When sitagliptin was added, both clamp-measured β-cell function (P=NS for 1st and 2nd phase vs placebo) and postprandial hyperglucagonemia (P=NS vs placebo) remained unaffected. However, administration of sitagliptin could not prevent prednisolone-induced increment in postprandial glucose concentrations (P<0.001 vs placebo). M-value was not altered by any treatment. Fourteen-day treatment with high-dose prednisolone impaired postprandial glucose metabolism in subjects with the metabolic syndrome. Concomitant treatment with sitagliptin improved various aspects of pancreatic islet-cell function, but did not prevent deterioration of glucose tolerance by GC treatment.

Beta cell function following 1 year vildagliptin or placebo treatment and after 12 week washout in drug-naive patients with type 2 diabetes and mild hyperglycaemia: a randomised controlled trial

Aims/hypothesisTraditional blood glucose lowering agents do not prevent the progressive loss of beta cell function in patients with type 2 diabetes. The dipeptidylpeptidase (DPP)-4 inhibitor vildagliptin improves beta cell function both acutely and chronically (up to 2 years). Whether this effect persists after cessation of treatment remains unknown. Here, we assessed the insulin secretory capacity in drug-naive patients with type 2 diabetes after a 52 week treatment period with vildagliptin or placebo, and again after a 12 week washout period.MethodsThis study was conducted at a single university medical centre, and was a double-blind, randomised clinical trial in 59 drug-naive patients with type 2 diabetes and mild hyperglycaemia to either vildagliptin 100 mg (n = 29) or placebo (n = 30). Randomisation was performed by a validated 1:1 system. Neither patient, nor caregiver, was informed about the assigned treatment. Inclusion criteria were drug-naive patients ≥30 years, with HbA1c ≤7.5% and BMI of 22–45 kg/m2. The mildly hyperglycaemic patient population was chosen to minimise glucose toxicity as a confounding variable. Beta-cell function was measured during an arginine-stimulated hyperglycaemic clamp at week 0, week 52 and after a 12 week washout period. All patients with at least one post-randomisation measure were analysed (intent-to-treat).ResultsFifty-two week vildagliptin 100 mg (n = 26) treatment increased the primary efficacy variable, combined hyperglycaemia and arginine-stimulated C-peptide secretion (AIRarg), by 5.0 ± 1.8 nmol/l × min, while it decreased by 0.8 ± 1.8 nmol/l × min with placebo (n = 25) (between-group difference p = 0.030). No significant between-group difference in AIRarg was seen after the 12 week washout period. The between-group difference adjusted mean 52 week changes from baseline was −0.19 ± 0.11, p = 0.098 and −0.22 ± 0.23%, p = 0.343 for HbA1c and fasting plasma glucose, respectively. There were no suspected drug treatment-related serious adverse events.Conclusions/interpretationOne year treatment with vildagliptin significantly increased beta cell secretory capacity. This effect was not maintained after the washout, indicating that this increased capacity was not a disease modifying effect on beta cell mass and/or function.Trial registration:ClinicalTrials.gov NCT00260156Funding:This study was sponsored by the Novartis Pharmaceutical Cooperation.

Glucagon-Like Peptide-1 Receptor Agonist Treatment Prevents Glucocorticoid-Induced Glucose Intolerance and Islet-Cell Dysfunction in Humans

OBJECTIVEGlucocorticoids (GCs) are regarded as diabetogenic because they impair insulin sensitivity and islet-cell function. This study assessed whether treatment with the glucagon-like peptide receptor agonist (GLP-1 RA) exenatide (EXE) could prevent GC-induced glucose intolerance.RESEARCH DESIGN AND METHODSA randomized, placebo-controlled, double-blind, crossover study in eight healthy men (age: 23.5 [20.0–28.3] years; BMI: 26.4 [24.3–28.0] kg/m2) was conducted. Participants received three therapeutic regimens for 2 consecutive days: 1) 80 mg of oral prednisolone (PRED) every day (q.d.) and intravenous (IV) EXE infusion (PRED+EXE); 2) 80 mg of oral PRED q.d. and IV saline infusion (PRED+SAL); and 3) oral placebo-PRED q.d. and intravenous saline infusion (PLB+SAL). On day 1, glucose tolerance was assessed during a meal challenge test. On day 2, participants underwent a clamp procedure to measure insulin secretion and insulin sensitivity.RESULTSPRED+SAL treatment increased postprandial glucose levels (vs. PLB+SAL, P = 0.012), which was prevented by concomitant EXE (vs. PLB+SAL, P = NS). EXE reduced PRED-induced hyperglucagonemia during the meal challenge (P = 0.018) and decreased gastric emptying (vs. PRED+SAL, P = 0.028; vs. PLB+SAL, P = 0.046). PRED+SAL decreased first-phase glucose- and arginine-stimulated C-peptide secretion (vs. PLB+SAL, P = 0.017 and P = 0.05, respectively), whereas PRED+EXE improved first- and second-phase glucose- and arginine-stimulated C-peptide secretion (vs. PLB+SAL; P = 0.017, 0.012, and 0.093, respectively).CONCLUSIONSThe GLP-1 RA EXE prevented PRED-induced glucose intolerance and islet-cell dysfunction in healthy humans. Incretin-based therapies should be explored as a potential strategy to prevent steroid diabetes.

Ectopic Fat Storage in the Pancreas, Liver, and Abdominal Fat Depots: Impact on β-Cell Function in Individuals with Impaired Glucose Metabolism

Pancreatic fat content (PFC) may have deleterious effects on β-cell function. We hypothesized that ectopic fat deposition, in particular pancreatic fat accumulation, is related to β-cell dysfunction in individuals with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT). This was a cross-sectional study in 64 age- and body mass index-matched individuals, with normal glucose tolerance (NGT; n = 16, 60% males), IFG (n = 29, 52% males), or IFG/IGT (n = 19, 63% males) was conducted. Participants underwent the following: 1) a combined hyperinsulinemic-euglycemic and hyperglycemic clamp, with subsequent arginine stimulation to quantify insulin sensitivity and β-cell function; 2) proton-magnetic resonance spectroscopy to assess PFC and liver fat content (LFC); and 3) magnetic resonance imaging to quantify visceral (VAT) and sc (SAT) adipose tissue. The disposition index (DI; insulin sensitivity adjusted β-cell function) was assessed. IFG and IFG/IGT were more insulin resistant (P < 0.001) compared with NGT. Individuals with IFG/IGT had the lowest values of glucose- and arginine-stimulated C-peptide secretion (both P < 0.03) and DI (P < 0.001), relative to IFG and NGT. PFC and LFC gradually increased between NGT, IFG, and IFG/IGT (P = 0.02 and P = 0.01, respectively), whereas VAT and SAT were similar between groups. No direct associations were found between PFC, LFC, VAT, and SAT and C-peptide secretion. The DI was inversely correlated with PFC, LFC, and VAT (all P < 0.05). PFC was increased in individuals with IFG and/or IGT, without a direct relation with β-cell function.

Effects of therapy in type 1 and type 2 diabetes mellitus with a peptide derived from islet neogenesis associated protein (INGAP)

Islet neogenesis associated protein (INGAP) has beta cell regenerating effects in experimental models. Subjects with T1DM (N = 63) and T2DM (N = 126) received 300 or 600 mg/day of INGAP peptide in a 90 day, randomized, double-blind, placebo-controlled trial. In T1DM, on-treatment Arginine-stimulated C-peptide (AUC(0-30)) significantly increased from baseline in the 600 mg group (p = 0.0058 versus placebo); no significant changes were seen in the 300 mg group. In T2DM, stimulated C-peptide was significantly better preserved in the 600 mg group compared to placebo at day 120, 30 days after washout (p = 0.031 versus placebo), but did not reach statistical significance during treatment or in the 300 mg group. In T2DM, A1C decreased significantly more in the 600 mg group compared to placebo at day 90 (-0.94% versus -0.47%, respectively, p = 0.009) and day 120, 30 days after washout (-0.73% versus -0.24%, respectively, p = 0.013). This was accompanied by significant reductions in mean glucose. No difference from placebo was detected in the 300 mg group or in T1DM. Injection site reactions were the most common adverse event, occurring in 8 (36%) of placebo, 19 (90%) of 300 mg, and 15 (75%) of 600 mg groups (T1DM) and 14 (33%) of placebo, 27 (64%) of 300 mg, and 29 (69%) of 600 mg groups (T2DM). INGAP peptide increases C-peptide secretion in T1DM and improves glycaemic control in T2DM. Longer-term exposure, more frequent dosing, better tolerated formulations or combination with other therapies may be necessary to achieve optimal clinical response.

One-year treatment with exenatide improves beta-cell function, compared with insulin glargine, in metformin-treated type 2 diabetic patients: a randomized, controlled trial.

OBJECTIVETraditional blood glucose–lowering agents do not sustain adequate glycemic control in most type 2 diabetic patients. Preclinical studies with exenatide have suggested sustained improvements in β-cell function. We investigated the effects of 52 weeks of treatment with exenatide or insulin glargine followed by an off-drug period on hyperglycemic clamp–derived measures of β-cell function, glycemic control, and body weight.RESEARCH DESIGN AND METHODSSixty-nine metformin-treated patients with type 2 diabetes were randomly assigned to exenatide (n = 36) or insulin glargine (n = 33). β-Cell function was measured during an arginine-stimulated hyperglycemic clamp at week 0, at week 52, and after a 4-week off-drug period. Additional end points included effects on glycemic control, body weight, and safety.RESULTSTreatment-induced change in combined glucose- and arginine-stimulated C-peptide secretion was 2.46-fold (95% CI 2.09–2.90, P < 0.0001) greater after a 52-week exenatide treatment compared with insulin glargine treatment. Both exenatide and insulin glargine reduced A1C similarly: −0.8 ± 0.1 and −0.7 ± 0.2%, respectively (P = 0.55). Exenatide reduced body weight compared with insulin glargine (difference −4.6 kg, P < 0.0001). β-Cell function measures returned to pretreatment values in both groups after a 4-week off-drug period. A1C and body weight rose to pretreatment values 12 weeks after discontinuation of either exenatide or insulin glargine therapy.CONCLUSIONSExenatide significantly improves β-cell function during 1 year of treatment compared with titrated insulin glargine. After cessation of both exenatide and insulin glargine therapy, β-cell function and glycemic control returned to pretreatment values, suggesting that ongoing treatment is necessary to maintain the beneficial effects of either therapy.

The Case for Intravenous Arginine Stimulation In Lieu of Mixed-Meal Tolerance Tests as Outcome Measure for Intervention Studies in Recent-Onset Type 1 Diabetes

Residual β-cell function in patients with type 1 diabetes has been generally determined by C-peptide response to stimulation by a liquid mixed-meal tolerance test (MMTT) or intravenous glucagon (1). Early trials assessed benefits of therapy by frequency and duration of the clinical remission phase in which minimal or no exogenous insulin was needed to maintain euglycemia (reviewed in 2). What is now needed is the most sensitive, and not necessarily the most physiologic measure, so that any improvement in β-cell function during a clinical trial can be detected. Both the MMTT and the intravenous glucagon test have practical limitations. The MMTT takes 2–4 h to complete, and the stimulus is subject to variations in gastrointestinal absorption, while the intravenous glucagon test often invokes nausea. In contrast, the use of intravenous arginine to stimulate and measure β-cell secretion takes only a few minutes to perform, circumvents gastrointestinal variation, and is clinically well tolerated. In addition, responses to this nonglucose secretagogue have been demonstrated to persist after the diagnosis of diabetes at a time when responses to glucose are gone (3–6). Our goal was to determine whether arginine-stimulated C-peptide could be used in lieu of MMTT as an outcome measure for intervention studies in recent-onset type 1 diabetes. Institutional review board approval and informed consent were obtained before the study began. Nineteen subjects between 7–42 and 1–24 …