Insulin sensitivity in adipocytes from subjects with varying degrees of glucose tolerance

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Abstract
Previous studies showed that the sensitivity of glucose transport to insulin is lower in adipocytes isolated from subjects with noninsulin-dependent diabetes mellitus and impaired glucose tolerance compared with subjects with normal glucose tolerance. This study analyzed the relationship between insulin sensitivity of glucose transport and glycemia in a large group of nondiabetic-nonglucose-intolerant subjects with a wide range of glycemic response to oral glucose. Seventy-four Pima Indians with 2-h postglucose load glucoses between 77 and 197 mg/100 ml, fasting plasma glucoses between 76 and 108 mg/100 ml, and no postload glucoses less than 199 mg/100 ml were studied. Isolated adipocytes were prepared in vitro after an abdominal fat biopsy, ED50 of insulin for glucose transport was correlated with 2-h postload glucoses, but not between insulin binding per cell or per cell surface area or in ED50 of insulin for antilipolysis and 2-h postglucose load glucoses. Although only 17% of the variation in glucose tolerance could be explained by a change in the sensitivity of glucose transport to insulin, the data suggests that a postinsulin-binding defect in the coupling of insulin binding to glucose transport may be an early step in the development of insulin resistance in human adipocytes.