The plasma amino acid response to cafeteria feeding in the rat: influence of hyperphagia, sucrose intake, and exercise.

The plasma amino acid response to voluntary hyperphagia was evaluated in rats fed a "cafeteria" diet for 4 to 8 weeks and compared to chow-fed controls. The influence of the sucrose content of the cafeteria diet was examined by studying rats given a low-sucrose, highly palatable, liquid diet (Magnacal). In a second series of studies the cafeteria diet was fed to rats housed in wheel cages and who ran 2.0 +/- 0.1 milles per day and compared with a sedentary cafeteria-fed group housed in standard cages. As expected, the cafeteria diet resulted in hyperphagia (45% to 55%) and in increased weight gain (35% to 50%). In response to cafeteria feeding there was an increase in plasma threonine, serine, proline, citrulline, alpha-amino butyric acid (ABA), and tyrosine. Significant decreases were observed in the branched chain amino acids (BCAA), valine and leucine. All of these changes were also observed when hyperphagia was induced with the low-sucrose diet, with the exception of the rise in ABA. In the exercised cafeteria-fed rats, excessive weight gain did not occur. Nevertheless, the amino acid response to the cafeteria diet was the same as in sedentary rats with excessive weight gain. The plasma amino acid pattern in those rats that developed glucose intolerance during cafeteria feeding and those that maintained normal glucose tolerance was similar. We conclude that hyperphagia induced by cafeteria feeding in the rat results in a specific plasma amino acid profile characterized by elevations in some amino acids (threonine, serine, proline, citrulline, ABA, and tyrosine) and reductions in the BCAA.(ABSTRACT TRUNCATED AT 250 WORDS)