The Journal of clinical endocrinology and metabolism
-
J. Clin. Endocrinol. Metab. · Oct 1997
Insulin resistance does not change the ratio of proinsulin to insulin in normal volunteers.
Plasma glucose, insulin, and proinsulin concentrations were measured before and after an oral glucose challenge in 57 nondiabetic individuals. In addition, insulin-mediated glucose disposal was estimated by determining the steady state plasma glucose (SSPG) concentration after a 180-min iv infusion of somatostatin, insulin, and glucose. The plasma glucose concentration after oral glucose administration was used to divide the population into those with normal (n = 36) or impaired glucose tolerance (IGT; n = 21), and the 36 normal glucose-tolerant individuals were further subdivided into an insulin-sensitive (SSPG, < 9.0 mmol/L; n = 15) and an insulin-resistant (SSPG, > 10 mmol/L; n = 21) group. ⋯ These results demonstrate that fasting proinsulin and insulin concentrations are increased in insulin-resistant, nondiabetic subjects, and the more insulin resistant, the greater the increase. In contrast, the ratio of proinsulin to insulin did not vary as a function of insulin resistance. Thus, neither insulin resistance nor the need to secrete more insulin to maintain glucose tolerance necessarily leads to abnormal insulin processing by the beta-cell.
-
J. Clin. Endocrinol. Metab. · Oct 1997
Altered composition of high density lipoproteins in women with the polycystic ovary syndrome.
Women with polycystic ovary syndrome (PCOS) appear at increased cardiovascular risk due in part to a dyslipidemia characterized by increased plasma triglyceride and reduced high density lipoprotein (HDL) cholesterol levels. This is a detailed exploratory study of HDL composition in 35 obese [body mass index (BMI), > 27] and 22 nonobese subjects with PCOS and in 14 healthy obese and 18 nonobese women. Although we found reduced levels of total and HDL2 cholesterol in obese women with PCOS, HDL composition was modified by depletion of lipid relative to protein, with reduced ratios of HDL total cholesterol and HDL phospholipids to apolipoprotein A-I (apoA-I) compared to those in obese controls (P = 0.008 and P = 0.012, respectively). ⋯ Among the controls, total, low density lipoprotein cholesterol, triglycerides, and apoB were related to aspects of insulin sensitivity independent of age and BMI. Lipid metabolism in PCOS is dependent on several related factors, but subjects with PCOS who are obese show a specific reduction in HDL lipid, suggesting a reduced capacity for cholesterol removal from tissues with diminished antiatherogenic potential. Efforts should be directed toward reducing obesity in PCOS to improve the metabolic disturbance in addition to ameliorating the presenting symptoms.