Glutamine nitrogen kinetics in insulin-dependent diabetic humans.

To assess the effect of insulin deficiency on whole body glutamine kinetics, five young adults with type I (insulin-dependent) diabetes received 4-h primed continuous infusions of L-[1-13C]leucine and L-[2-15N]glutamine in the postabsorptive state after blood glucose had been clamped overnight at either a normoglycemic level (approximately 85 mg/dl) or a moderate hyperglycemic level (approximately 260 mg/dl) by means of an automated glucose control insulin infusion system. The hyperglycemic state was associated with a significant rise in leucine level [from 165 +/- 23 to 242 +/- 62 (SD) microM], appearance rate (from 125 +/- 11 to 142 +/- 17 mumol.kg-1.

Role of leucine as a precursor of glutamine alpha-amino nitrogen in vivo in humans.

To assess the role of leucine as a precursor of glutamine alpha-amino N in vivo, five healthy men received primed continuous intravenous infusions of L-[15N]leucine, L-[15N]alanine, and L-[2-15N]glutamine in the postabsorptive state on three separate days and over 7, 4, and 4 h, respectively. A steady state in isotopic enrichment was observed in every amino acid during the last hour of each isotope infusion and was used to calculate the rates of amino acid appearance (Ra) and interconversion. Leucine, alanine, and glutamine Ra values were 137 +/- 18, 234 +/- 42, and 320 +/- 18 (SD) mumol.