Amino acid metabolism in human subcutaneous adipose tissue in vivo.

1. Arteriovenous differences for alanine, glutamate and glutamine were measured across subcutaneous adipose tissue and forearm muscle in normal subjects. 2. After an overnight fast, adipose tissue showed net production of alanine and glutamine and uptake of glutamate in each of 11 subjects. 3. In seven subjects, adipose tissue blood flow was measured and the measurements were continued for 6 h after eating a mixed meal. The pattern of amino acid metabolism across the adipose tissue was remarkably little disturbed after the meal, except for a short period of apparent uptake of alanine as the concentration of that amino acid rose. 4. The pattern of amino acid metabolism across adipose tissue was qualitatively similar to that across the forearm, although it differed quantitatively in that glutamate uptake was more prominent (compared with glutamine release) in the adipose tissue. 5. The rates of alanine and glutamine release observed suggest that adipose tissue may play a substantial role in the whole-body production of these amino acids.