Effect of short-term phenformin administration on the pattern of free amino acids in the plasma of healthy subjects and patients with non insulin-dependent diabetes.

Administration of phenformin to healthy subjects in a daily dose of 150 mg for a four day period caused a significant increase of 30% in the alanine level, as well as significant increases in the branched-chain amino acids valine, isoleucine, and a selective lowering in the level of arginine. Dexamethasone administered to healthy subjects in a daily dose of 3 mg over a four day period caused significant increases in alanine and methionine levels (26%) as well as a rise in arginine. Simultaneous administration of phenformin and dexamethasone resulted in significant changes in levels of glutamine, alanine, methionine and isoleucine. The highest rise (55%) was observed in alanine and methionine rose by 34%. The level of arginine decreased by 13% and glutamic acid by 39%. The fasting levels of plasma free amino acids in diabetics were similar to those in healthy subjects. The changes in the levels of plasma free amino acids after phenformin were also similar. The observed results support the suggestion that phenformin inhibits gluconeogenesis.