Sulfate production depicts fed-state adaptation to protein restriction in humans

One feature of the adaptation to dietary protein restriction is reduced ure a production over the hours after consumption of a test meal of fixed compo sition. This adaptation is impaired in conventionally treated insulin-depen dent diabetes mellitus (Hoffer LJ, Taveroff A, and Schiffrin A. Am J Physio l Endocrinol Metab 272: E59-E67, 1997). We have now tested the response to a test meal containing less protein and included as a main outcome variable the production of sulfate, a specific indicator of sulfur amino acid catab olism. Six normal men consumed a mixed test meal containing 0.25 g protein/ kg and 10 kcal/kg while adapted to high (1.5 g.kg(-1).day(-1)) and low (0.3 g.kg(-1).day(-1)) protein intakes. They followed the identical protocol tw ice. Six subjects with insulin-dependent diabetes consumed the test meal wh ile adapted to their customary high-protein diet. Adaptation to protein res triction reproducibly reduced 9-h cumulative postmeal urea N and S producti on by 22-29% and 49-52%, respectively (both P < 0.05). Similar results were obtained for a postmeal collection period of 6 h. The response of the diab etic subjects was normal. We conclude that reductions in postmeal urea and sulfate production after protein restriction are reproducible and are evide nt using a postmeal collection period as short as 6 h. Sulfate production e ffectively depicts fed-state adaptation to protein restriction.