Serum concentrations of vitamins A and E in impaired glucose tolerance.

Serum concentrations of vitamins A and E were measured in 32 subjects with impaired glucose tolerance (IGT) and 148 subjects with normal glucose tolerance using reversed-phase high-performance liquid chromatography. Fasting glucose, insulin and lipid concentrations were also measured. Serum vitamin A concentrations were higher in subjects with IGT 2.5 (1.1-3.4) vs. 2.1 (1.4-3.2) mumol/l [median (2.5-97.5 percentiles)] (P = 0.002), the difference remaining significant after adjustment for triglycerides (P = 0.028). There was a univariate association between vitamin A levels and insulin resistance (r = 0.164; P = 0.02) and in multivariate logistic regression analysis the relative risk of subjects with high vitamin A concentrations having IGT was 3.8 (P = 0.002). There were no differences in serum vitamin E concentrations between the groups. These data suggest that higher vitamin A concentrations found in non-insulin-dependent diabetes pre-date the onset of diabetes. Further studies are required to confirm this finding and to investigate the possibility of a role for vitamin A in the aetiology of diabetes and IGT.