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.

INTERVENTION: 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). CONDITION: Diet and Nutrition ‐ Obesity Metabolic and Endocrine ‐ Diabetes Obesity;Diabetes; ; Obesity ; Diabetes Oral and Gastrointestinal ‐ Normal oral and gastrointestinal development and function PRIMARY OUTCOME: Plasma glucose response to the mixed nutrient Resource Plus drink. [Plasma glucose will be assessed from blood samples taken at t = ‐31, ‐20, ‐10, ‐1, 15, 30, 45, 60, 90, 120 min, where t = ‐31 is just prior to the time of the bolus administration and t = ‐1 is just prior to nutrient drink consumption.] INCLUSION CRITERIA: A total of 16 healthy, lean (BMI 19‐25 kg/m2) male subjects, aged between 18 ‐ 55 years will be included. Subjects will be required to be weight stable (ie <5% fluctuation) at study entry, which will be ascertained by a stable body weight in the preceding 4 weeks. SECONDARY OUTCOME: Appetite perceptions using a VAS questionnaire: amount of food desired to eat.[VAS questionnaires will be completed at t = ‐31, ‐20, ‐10, ‐1, 15, 30, 45, 60, 90, and 120 min.] Appetite perceptions using a VAS questionnaire: desire to eat.[VAS questionnaires will be completed at t = ‐31, ‐20, ‐10, ‐1, 15, 30, 45, 60, 90, and 120 min.] Appetite perceptions using a VAS questionnaire: fullness.[VAS questionnaires will be completed at t = ‐31, ‐20, ‐10, ‐1, 15, 30, 45, 60, 90, and 120 min.] Appetite perceptions using a VAS questionnaire: hunger.[VAS questionnaires will be completed at t = ‐31, ‐20, ‐10, ‐1, 15, 30, 45, 60, 90, and 120 min.] Gastric emptying (measurement of 13CO2 in breath samples).[Breath samples will be collected at t = ‐31 min, every 5 minutes from t = 0 to 60 min, and every 15 minutes from t = 60 to 120 min.] Plasma concentrations of gastrointestinal hormones (e.g. GLP‐1, GIP ), insulin and 3‐OMG (composite secondary outcome)[Gut hormone release will be assessed from blood samples taken at t = ‐31, ‐20, ‐10, ‐1, 15, 30, 45, 60, 90, and 120 min.]