OBJECTIVE-We sought to determine whether alterations in meal absorption and gastric emptying contribute to the mechanism by which inhibitors of dipeptidyl peptidase-4 (DPP-4) lower postprandial glucose concentrations.RESEARCH DESIGN AND METHODS-We simultaneously measured gastric emptying, meal appearance, endogenous glucose production, and glucose disappearance in 14 subjects with type 2 diabetes treated with either vildaglipitin (50 mg b.i.d.) or placebo for 10 days using a double-blind, placebo-controlled, randomized, crossover design.RESULTS-Fasting (7.3 Ϯ 0.5 vs. 7.9 Ϯ 0.5 mmol/l) and peak postprandial (14.1 Ϯ 0.6 vs. 15.9 Ϯ 0.9 mmol/l) glucose concentrations were lower (P Ͻ 0.01) after vildagliptin treatment than placebo. Despite lower glucose concentrations, postprandial insulin and C-peptide concentrations did not differ during the two treatments. On the other hand, the integrated (area under the curve) postprandial glucagon concentrations were lower (20.9 Ϯ 1.6 vs. 23.7 Ϯ 1.3 mg/ml per 5 h, P Ͻ 0.05), and glucagon-like peptide 1 (GLP-1) concentrations were higher (1,878 Ϯ 270 vs. 1,277 Ϯ 312 pmol/l per 5 h, P ϭ 0.001) during vildagliptin administration compared with placebo. Gastric emptying and meal appearance did not differ between treatments.CONCLUSIONS-Vildagliptin does not alter gastric emptying or the rate of entry of ingested glucose into the systemic circulation in humans. DPP-4 inhibitors do not lower postprandial glucose concentrations by altering the rate of nutrient absorption or delivery to systemic circulation. Alterations in islet function, secondary to increased circulating concentrations of active GLP-1, are associated with the decreased postprandial glycemic excursion observed in the presence of vildagliptin.

OBJECTIVETo investigate the pharmacokinetics (PK), pharmacodynamics, and safety of single-dose RM-131 in type 2 diabetic patients with gastrointestinal cardinal symptoms (GCSI) and previously documented delayed gastric emptying (DGE).RESEARCH DESIGN AND METHODSIn a randomized crossover study, 10 female patients received RM-131 (100 μg s.c.) or placebo and underwent scintigraphic gastric emptying (GE) and colonic filling at 6 h (CF6) of a solid-liquid meal administered 30 min postdosing. Adverse events, plasma glucose, and hormonal levels were assessed. GCSI daily diary (GCSI-DD) was completed during treatments. PK was assessed in this cohort and healthy volunteers (HVs).RESULTSAt screening, HbA1c was 7.2 ± 0.4% (SEM) and total GCSI-DD score was 1.32 ± 0.21. RM-131 accelerated GE t1/2 of solids (P = 0.011); mean difference (Δ) in solid GE t1/2 was 68.3 min (95% CI 20–117) or 66.1%. There were numerical differences in GE lag time, CF6 solids, and GE t1/2 liquids (all P < 0.14). With a significant (P < 0.014) order effect, further analysis of the first treatment period (n = 5 per group) confirmed significant RM-131 effects on GE t1/2 (solids, P = 0.016; liquids, P = 0.024; CF6, P = 0.013). PK was similar in DGE patients and HVs. There were increases in 120-min blood glucose (P = 0.07) as well as 30–90-min area under the curve (AUC) levels of growth hormone, cortisol, and prolactin (all P < 0.02) with single-dose RM-131. Only light-headedness was reported more on RM-131.CONCLUSIONSRM-131 greatly accelerates the GE of solids in patients with type 2 diabetes and documented DGE. PK is similar in diabetic patients and HVs.

BACKGROUND/AIMS-Bile acid (BA) malabsorption of moderate severity is reported in 32% of patients with chronic unexplained diarrhea including diarrhea-predominant IBS (IBS-D). We hypothesize that variants of genes regulating hepatic BA synthesis play a role in IBS-D.

This study evaluated the effects of serotonergic psychoactive agents on gastrointestinal functions in healthy human subjects. Participants received one of four regimens in a randomized, double-blind manner: buspirone, a 5-HT1Areceptor agonist (10 mg twice daily); paroxetine, a selective serotonin reuptake inhibitor (20 mg daily); venlafaxine-XR, a selective serotonin and norepinephrine reuptake inhibitor (75 mg daily); or placebo for 11 days. Physiological testing performed on days 8–11included scintigraphic assessment of gastrointestinal and colonic transit, the nutrient drink test, and assessment of the postprandial change in gastric volume. Fifty-one healthy adults (40 females, 11 males) participated in this study. No effects on gastric emptying or colonic transit were identified with any agent. Small bowel transit of a solid meal was accelerated by paroxetine. Buspirone decreased postprandial aggregate symptom and nausea scores. Venlafaxine-XR increased the postprandial change in gastric volume. Buspirone, paroxetine, and venlafaxine-XR affect upper gastrointestinal functions in healthy humans. These data support the need for clinical and physiological studies of these agents in functional gastrointestinal disorders.

Background & Aims-NPSR1, the receptor for neuropeptide S (NPS), is expressed by gastrointestinal (GI) enteroendocrine (EE) cells, and is involved in inflammation, anxiety and nociception. NPSR1 polymorphisms are associated with asthma and inflammatory bowel disease. We aimed to determine whether NPS induces expression of GI neuropeptides; and to associate NPSR1 single nucleotide polymorphisms (SNPs) with symptom phenotype and GI functions in health and functional GI disorders (FGID).