The Impact of a Large Bolus Dose of l-leucine and l-isoleucine on Enteroendocrine and Pancreatic Hormones, and Glycemia in Healthy, Inactive Adults.

BACKGROUND: The ingestion of whey protein and amino acids with carbohydrate (CHO) enhances the release of glucagon-like peptide-1 (GLP-1) and glucose-dependent-insulinotropic peptide (GIP) that promote insulin secretion. It is unknown if L-isoleucine (Ile) and L-leucine (Leu) have this same effect. The purpose of this study was to examine how Ile and Leu influence both GLP-1 and GIP, subsequent pancreatic hormones, and glycemia in healthy, inactive adults. METHODS: Twelve adults (6F/6M; age 27.4 ± 2 years; BMI 26.3 ± 2 kg/m2; lean body mass 53.2 ± 5 kg; body fat 34.1 ± 3%) completed four conditions in a randomized, cross-over fashion. Treatments standardized (0.3 g/kg·LBM-1) (1) Leu, (2) Ile, (3) Equal (1:1 g) of Leu + Ile, and (4) placebo (Pla, 3.5 g inert stevia) ingested 30 min prior to an oral glucose tolerance test (OGTT). Samples of plasma glucose, insulin, glucagon, GIPTotal, and GLP-1Active were assessed. RESULTS: A treatment (p = 0.01) effect comparing Ile vs. Leu (p = 0.02) in GIPTotal. Area under the curve showed an increase in GIPTotal from Ile compared to Leu and Pla (p = 0.03). No effect was found on GLP-1. The ingestion of Ile prior to CHO augmented GIP concentration greater than Leu or Pla. No correlation was found between GIP, insulin, and glucose between conditions. CONCLUSIONS: Ile impacts GIP concentration, which did not relate to either insulin or glucose concentrations. Neither Ile, nor Leu seem to have an effect on hyperglycemia ingested prior to a CHO drink.

Plasma Somatomedin-C in 8- to 10-Year-Old Swimmers.

Plasma somatomedin-C (SM-C), important for linear growth, is reduced under conditions of caloric deficit whether induced by diet or exercise. The purpose of this study was to determine the effect of diet and exercise on plasma SM-C levels in 37 8- to 10-year-old children, 18 swimmers (SWM) and 19 control children (CTL). All children kept a 3-day dietary record for 2 weeks prior to collection of a fasted, resting blood sample. Both groups showed RDA-normal total kcal intake (SWM = 2301 ± 664; CTL = 2072 ± 449) and twice the RDA for protein for this age group (SWM = 3.1 ± 2.3 g • kg-1; CTL = 3.0 ± 2.4 g • kg-1). Plasma SM-C levels for SWM (1.39 ± .84 U • ml-1) and CTL (.91 ± .33 U • ml-1) were significantly different (P<.01) but within the normal range for this age group. These data suggest that 8- to 10-year-old children who are training regularly, in combination with adequate energy and protein intake, show SM-C levels within the normal range expected for this age.