Extra-pancreatic effects of incretin-based therapies: potential benefit for cardiovascular-risk management in type 2 diabetes.

Development of cardiovascular disease is one of the major complications of type 2 diabetes mellitus (T2DM). The chronic hyperglycaemic state is often accompanied by dyslipidaemia, hypertension, low-grade systemic inflammation and oxidative stress which collectively result in a high risk of micro- and macrovascular complications. Current glucose-lowering agents do not sufficiently address fore-mentioned macrovascular-risk factors. Recently, new therapeutic agents were introduced, based on the incretin hormone glucagon-like peptide-1 (GLP-1), that is, the GLP-1 receptor agonists (GLP-1RA) and dipeptidyl-peptidase 4 (DPP-4) inhibitors. Beside its effect on pancreatic insulin secretion, GLP-1 exerts several extra-pancreatic effects such as slowing down gastric emptying, promoting satiety and reducing food intake and weight loss. Also, GLP-1 and GLP-1RA were shown to improve cardiovascular-risk profiles, by reducing body fat content, blood pressure, circulating lipids and inflammatory markers in patients with T2DM. This review summarizes the presently known evidence with regard to extra-pancreatic effects of the incretin-based agents, focusing on the actions that improve the cardiovascular-risk profile. We present available data from clinical trials of at least 24 week duration, but also findings from small-sized clinical 'proof of principle' studies. We conclude that GLP-1 RA and to a lesser extent DPP-4 inhibitors are promising agents with regard to their effects on body weight, blood pressure and lipids, which collectively ameliorate the cardiovascular-risk profile and as such may have added value in the treatment of T2DM. However, large-sized long-term outcome studies are warranted to show the true added value of these agents in the treatment of patients with T2DM.

Lowering of postprandial lipids in individuals with type 2 diabetes treated with alogliptin and/or pioglitazone: a randomised double-blind placebo-controlled study.

AIMS/HYPOTHESIS: Pharmacological augmentation of glucagon-like peptide 1 receptor signalling by dipeptidyl peptidase 4 (DPP-4) inhibition reduced intestinal lipoprotein secretion in experimental studies, suggesting that DPP-4 inhibitors may ameliorate dyslipidaemia and thus reduce cardiovascular risk in patients with type 2 diabetes. We assessed the effects of alogliptin (Alo) and Alo co-administered with pioglitazone (Pio) vs placebo (Pbo) on triacylglycerol (TG)-rich lipoproteins in type 2 diabetes before and following a high-fat meal. METHODS: Seventy-one patients (age 18-70 years), who did not reach HbA(1c) 6.5% (48 mmol/mol) with lifestyle and/or metformin, sulfonylurea or glinide therapy, participated in this 16 week, double-centre (university hospitals) Pbo-controlled parallel-group study. All participants, people doing measurements or examinations, and people assessing the outcomes were blinded to group assignment. Fasting TG 1.7-5.0 mmol/l was among the entry criteria. Patients received a high-fat mixed meal before and 4 and 16 weeks after randomisation (allocation by central office) to Alo (n = 25), Alo/Pio (n = 22) or Pbo (n = 24). Blood was sampled at pre-specified intervals, starting at 15 min before and ending 8 h after meal ingestion. RESULTS: At week 16, Alo (n = 25) and Alo/Pio (n = 21) vs Pbo (n = 24) produced similar significant reductions in total postprandial TG response (incremental AUC [iAUC]; p < 0.001), as well as in chylomicron TG (p < 0.001) and VLDL1 TG iAUCs (p < 0.001 and p = 0.012, respectively). Postprandial chylomicron apolipoprotein B-48 iAUC showed a significant decrease after Alo treatment (p = 0.028), and a non-significant trend towards a decrease with Alo/Pio (p = 0.213). The incidence of adverse events was low and consistent with previous studies. CONCLUSIONS/INTERPRETATION: Treatment with Alo and Alo/Pio produced significant reductions in postprandial TG and TG-rich lipoproteins, contributing to an improved overall cardiometabolic risk profile in type 2 diabetes. The data support the concept that incretins not only modulate glucose metabolism but also influence chylomicron metabolism in intestinal cells. TRIAL REGISTRATION: ClinicalTrials.gov number NCT00655863.

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/HYPOTHESIS: Traditional 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. METHODS: This 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 HbA(1c) ≤7.5% and BMI of 22-45 kg/m(2). 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). RESULTS: Fifty-two week vildagliptin 100 mg (n = 26) treatment increased the primary efficacy variable, combined hyperglycaemia and arginine-stimulated C-peptide secretion (AIR(arg)), 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 AIR(arg) 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 HbA(1c) and fasting plasma glucose, respectively. There were no suspected drug treatment-related serious adverse events. CONCLUSIONS/INTERPRETATION: One 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 NCT00260156.