Leucine assimilation in patients with diabetes mellitus.

To estimate leucine metabolism in patients with absolute or relative insulin deficiency, elimination of an iv leucine load (50 mg/kg) was determined in 5 insulin-dependent diabetics, in obese (n = 5) as well as in ideal weight maturity onset diabetics (n = 5). Following leucine administration a marked rise of plasma insulin levels in obese diabetics, but lack of insulin response in insulin-dependent diabetics was observed compared to healthy controls (n = 6). Elimination half-life of leucine was similar in controls (34 +/- 5 min), in obese (40 +/- 4 min) and in ideal weight maturity onset diabetics (37 +/- 2 min), but significantly prolonged in insulin-dependent diabetics (60 +/- 3 min; P less than 0.01). Thus in obese diabetics elevated plasma insulin levels and near normal elimination half-life of leucine suggest peripheral insulin resistance regarding leucine assimilation. In insulin-dependent diabetics, however, it appears that insulin deficiency is associated not only with elevated plasma leucine levels, but also with delayed elimination by peripheral tissues following administration of this amino acid.