In the present study we have compared the effects of leucine supplementation and its metabolite β-hydroxy-β-methyl butyrate (HMB) on the ubiquitin-proteasome system and the PI3K/Akt pathway during two distinct atrophic conditions, hindlimb immobilization and dexamethasone treatment. Leucine supplementation was able to minimize the reduction in rat soleus mass driven by immobilization. On the ot...

Dexamethasone (DEXA) is a potent immunosupressant and anti-inflammatory agent whose main side effects are muscle atrophy and insulin resistance in skeletal muscles. In this context, leucine supplementation may represent a way to limit the DEXA side effects. In this study, we have investigated the effects of a low and a high dose of leucine supplementation (via a bolus) on glucose homeostasis, m...

To evaluate the role of blood cells in interorgan amino acid transport and in the estimates of regional protein turnover, we studied the effects of plasma vs. whole blood sampling on regional leucine kinetics in postabsorptive humans. Studies were carried out by combining the arteriovenous difference technique with the measurement of [14C]- and [15N]leucine isotope exchange across the human kid...

Leucine metabolism in cultured skin fibroblasts from patients with isovaleric acidemia was compared with that in normal fibroblasts and in cells from patients with maple syrup urine disease using [1-(14)C] and [2-(14)C] leucine as substrates. Inhibitory effects of methylenecyclopropylacetic acid on leucine metabolism in normal cells were also investigated. Production of 14CO2 from [2-(14)C] leu...

Lactic acid bacteria are characterized by numerous nutritional requirements. The influence of amino acids and peptides on the growth of Pediococcus pentosaceus c1 isolated from argentinean wines was determined. Cells were growth in synthetic media and in the same media added with the following dipeptides: leucine-leucine; leucine-proline; methionine-proline and glycineglycine. In the complete m...

The kinetics of K(+)-leucine cotransport in the midgut of lepidopteran larvae was investigated using brush border membrane vesicles. Initial rate (3 s) of leucine uptake was determined under experimental conditions similar to those occurring in vivo, i.e. in the presence of delta psi much greater than 0 (inside negative) and a delta pH of 1.4 units (7.4in/8.8out). Leucine and K+ bind to the car...

An enzyme which catalyzes acetylation of L-leucine with acetyl-CoA was partially purified from a cell extract of Streptomyces roseus MA839-A1, a leupeptin producer. The molecular weight of this enzyme is about 27,000 daltons. The enzyme has fairly broad specificity for acyl donors (I) and acceptors (II): as for I, propionyl-CoA was 1/10 as active as acetyl-CoA with L-leucine as the acceptor; as...

Skeletal muscle in the neonate grows at a rapid rate due in part to an enhanced sensitivity to the postprandial rise in amino acids, particularly leucine. To elucidate the molecular mechanism by which leucine stimulates protein synthesis in neonatal muscle, overnight-fasted 7-day-old piglets were treated with rapamycin [an inhibitor of mammalian target of rapamycin (mTOR) complex (mTORC)1] for ...

Pompe disease is due to a deficiency in acid-α-glucosidase (GAA) and results in debilitating skeletal muscle wasting, characterized by the accumulation of glycogen and autophagic vesicles. Given the role of lysosomes as a platform for mTORC1 activation, we examined mTORC1 activity in models of Pompe disease. GAA-knockdown C2C12 myoblasts and GAA-deficient human skin fibroblasts of infantile Pom...