Effects of leucine and isoleucine on nicotinamide nucleotides of erythrocytes
Belavady, B.; Rao, P.U.; Khan, L.
International Journal for Vitamin and Nutrition Research. Internationale Zeitschrift für Vitamin- und Ernahrungsforschung. Journal International de Vitaminologie et de Nutrition 43(4): 442-453
1973
ISSN/ISBN: 0300-9831 PMID: 4149066 Document Number: 59375
For 10 days 10 men were given a diet supplying 2500 to 2700 kcal and containing 50 g protein derived mainly from rice and wheat, the leucine:isoleucine ratio of which was 1.7. Each subject then received a dietary supplement of 10 g of L-leucine for 5, 10 or 15 days after which he received 5 or 0.7 g DL-isoleucine and 10 g L-leucine for a further 5 or 10 days. When leucine alone was given, in erythrocytes synthesis of nicotinamide nucleotides decreased, the proportion of nicotinamide mononucleotide increased, oxidation of glucose by the hexose monophosphate shunt (HMS) pathway was stimulated and the production of lactate decreased; all those effects were reversed when isoleucine was included in the diet simultaneously with leucine. Excretion of quinolinic acid in urine increased with leucine administration but was reduced to normal when isoleucine was also given. The effect of 7.0 or 14.0 mu moles of L-leucine and 1.4 or 2.8 mu moles of L-isoleucine, added separately or together, on synthesis of nicotinamide nucleotides and glucose oxidation by HMS and glycolytic pathways was studied on erythrocytes in vitro. Leucine at high concentration inhibited synthesis of nicotinamide nucleotides and reduced the production of lactate but the simultaneous addition of isoleucine did not reverse those effects in vitro as it did in vivo.