Influence of insulin on albumin and non-albumin protein fractional synthetic rates in post-absorptive type I diabetic patients.

Two 8-h primed continuous infusions of L-[1-13C] leucine were used to determine fractional synthesis rates of albumin and non-albumin plasma protein in post-absorptive Type I diabetic patients during insulin infusion and its withdrawal. Fractional protein synthetic rates were calculated from the rate of incorporation of 13C-label into protein and employing plasma 13C-alpha-ketoisocaproic acid enrichment to represent the precursor pools label. Incorporation of 13C into albumin and non-albumin plasma protein was linear over the latter 6 h of the 8-h L-[1-13C] leucine infusion. Fractional synthetic rates of plasma albumin and non-albumin proteins were similar during insulin withdrawal and its infusion. The increased whole-body protein synthesis observed during insulin withdrawal in Type I diabetic patients appears unrelated to events in albumin and non-albumin plasma protein fractions. These data are further evidence that insulin per se does not stimulate protein synthesis in man.