Vitamin B₆ nutritional status of pellagrins and their leucine tolerance¹

Abstract

Disturbances in tryptophan-nicotinamide adenine dinucleotide pathway, seen in pellagrins whose staple is sorghum have been ascribed to an amino acid imbalance caused by excess intake of leucine. Studies in normal human volunteers and in experimental animals have shown that administration of vitamin B6 will counteract some of the metabolic effects of leucine. In view of these observations, two clinical studies were conducted--one to investigate the vitamin B6 nutritional status of pellagrins and the other to determine whether plasma leucine clearance in pellagrins is different from that of normals. Vitamin B6 nutritional status of pellagrins was found to be far from satisfactory, as indicated by elevated levels of xanthurenic acid and kynurenic acid in urine after a tryptophan load and low plasma pyridoxal phosphate levels. Plasma leucine concentrations at 1, 2, and 4 hr after a leucine load were significantly higher in pellagrins than those in normals. Administration of 25 mg of vitamin B6, intramuscularly 30 min before leucine load significantly decreased plasma leucine concentration in pellagrins. However, the leucine concentration at 4th hr did not return to basal level. Administration of vitamin B6 10 TO 20 mg/day orally for 10 to 15 days normalized leucine tolerance in pellagrins. Data presented here suggest that when the diets contain excess leucine, additional amounts of vitamin B6 are required.