Leucine balance, metabolic and satiety responses to a leucinerich meal in healthy elderly women

Abstract

Many older adults experience a decline of appetite and may not meet their protein needs; a strategy to optimize protein retention is thus essential. Leucine has anabolic potential by stimulating protein synthesis via mRNA translation and insulin secretion. Postprandial responses to leucine‐rich versus isonitrogenous mixed meals were assessed in 9 healthy older women (70.1±2 y, BMI 23.7±2.7 kg/m2) by double‐blinded, randomized, crossover studies. Test meals provided 0.6 g protein and 16.0 kcal/kg LBM, once with added leucine (0.07 g/kg LBM), once without.ResultsFive‐hour whole‐body postprandial leucine oxidation response, measured by constant infusion of [1‐13C]leucine and enrichment of plasma 13C‐KIC and expired 13CO2 was further increased with meal+leucine. Yet, the resulting balance (intake‐oxidation) was greater (18.1±1.4 vs. without 11.3±1.3 mmol/5h, p<0.001) suggesting more protein retention. Serum insulin and C‐peptide AUC were greater post meal+leucine, indicating more secretion. Plasma glucose excursions and free fatty acids suppression did not differ between meals. Addition of leucine had no effect on meal‐induced thermogenesis, satiety and gut peptide responses (GLP‐1, PYY 3–36, ghrelin). This study shows the anabolic potential of a leucine‐rich mixed meal in older women, a dietary strategy that may be used to promote protein anabolism without affecting appetite. (Funded by CIHR)