Insulin-stimulated glucose uptake, leucine incorporation into protein, and uridine incorporation into RNA in skin fibroblast cultures from patients with diabetes mellitus

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Abstract
Since intrinsic cellular abnormalities have previously been reported in diabetes mellitus, skin fibroblasts from patients with insulin-dependent diabetes and non-insulin-dependent diabetes, and from age-matched young and old controls, were examined for stimulation by insulin (4–4000 ng/ml) of glucose uptake, leucine incorporation into protein, and uridine incorporation into RNA. No differences in insulin-stimulated glucose uptake were seen between donor types. At 40 and 400 ng/ml, insulin did not stimulate as much leucine incorporation into protein in insulin-dependent diabetics as in young controls (p<0.05) and at 4000 ng/ml, less insulinstimulated leucine incorporation was seen in insulindependent diabetics than in young controls or noninsulin dependent diabetics (p<0.01). Lower insulin-stimulated uridine incorporation into RNA in old controls than in other cell lines appeared to be largely secondary to a two-fold increase in basal incorporation in these old controls. These results provide additional evidence for intrinsic cellular abnormalities in diabetes mellitus. Whether the differences in basal or insulin-stimulated response between fibroblasts of different donor types are attributable to alterations in protein or RNA synthesis, metabolite pool size or turnover have yet to be determined.