The purpose of this study is to determine the effects of the drug, sitagliptin, on the rate at which the stomach empties, and the release of gut hormones and blood glucose concentrations, after a mashed potato meal in healthy subjects. Sitagliptin has been shown to reduce the blood glucose (sugar) response to a meal and this may potentially be due to slowing of stomach emptying. This is particularly relevant to people who have diabetes, in whom normalization of elevated blood glucose levels is important to maintain health.

The purpose of this study is to evaluate the effect of sitagliptin on gastric emptying, intragastric meal distribution, postprandial glycemia and insulinemia in healthy subjects. Glucagon-like peptide-1 (GLP-1) inhibits gastric emptying, thereby slowing the delivery of nutrients, and their absorption, across the small intestine. The rate of entry of carbohydrate into the small intestine is especially important in patients with diabetes mellitus. Sitagliptin is an orally administered inhibitor of dipeptidyl-peptidase-IV (DPP-IV), the enzyme responsible for the degradation of GLP-1. It is hypothesized that sitagliptin will increase the GLP-1 response to, and thereby slow gastric emptying and diminish the glycemic response to, a carbohydrate-containing meal.

Fifteen healthy subjects (male and female) will be studied. Each subject will be studied on two occasions following treatment for 2 days with sitagliptin (100mg once daily) or matching placebo in a randomized, double blind, crossover design. Measurements of gastric emptying, intragastric meal distribution, blood glucose concentrations, gut hormones and appetite will be measured for 4 hours following ingestion of a mashed potato meal.

Inclusion Criteria:

• Male or female (females must be using an appropriate contraceptive method)
• 18 - 45 years
• Body mass index (BMI) 19 - 25 kg/m2.

Exclusion criteria:

• Subjects with gastrointestinal disease, history of gastrointestinal surgery and/or significant gastrointestinal symptoms
• Subjects taking medication known to influence gastrointestinal function
• Alcohol intake > 20 g per day
• Smoking > 10 cigarettes per day
• Pregnant and/or lactating females
• Calculated creatinine clearance < 60 ml/min
• Exposure to ionising radiation for research purposes in the previous 12 months.