Effects of intragastric administration of L-leucine, L-isoleucine and L-valine on gastric emptying, gut hormone release and blood glucose in healthy, lean volunteers.

Assessment of blood glucose and gastric emptying, following administration of control, 10g L-Leucine, 10g L-Isoleucine or 10g L-Valine 30 min prior to a standardised mixed nutrient drink. Subjects will receive, in randomized, double-blind fashion, a 100 ml intragastric bolus infusion of: i) 10g L-Leucine; ii) 10g L-Isoleucine; iii) 10g L-Valine; iv) saline (control). Subjects will receive one infusion per visit. All bolus infusions will be administered by the primary researcher. Study visits will be separated by 3-7 days. In addition, during study visits, the primary researcher will be present in order to closely monitor adherence to study protocol. For each study visit a baseline blood sample, VAS, and breath sample will be collected (t = -31). At t = -31 the infusion will be administered over 1 minute using a feeding tube. At t = -20, -10, and -1 min further blood samples will be collected and VAS completed. At t = -1 min, subjects will consume, within 1 minute, a mixed-nutrient drink (Resource Plus, 500 kcal, 325 ml) labeled with 100 mg of 13C-acetate for measurement of gastric emptying by breath sampling, and 3g 3-OMG for measurement of glucose absorption. Blood samples and VAS will be taken every 15 minutes, and breath samples will be taken every 5 min, over the next hour (t = 0 to 60 min). Over the following hour, VAS and blood samples will be collected every half hour (t = 90, 120), and breath samples collected every 15 min (t = 75, 90, 105, 120).