Differences in insulin resistance and pancreatic B-cell function in obese subjects with isolated impaired glucose tolerance and isolated impaired fasting glucose.

AIMS: To investigate changes in insulin action and insulin secretion in obese subjects with different categories of impaired glucose regulation (IGR): impaired glucose tolerance (IGT), impaired fasting glucose (IFG), and combined IFG/IGT (CGI). METHODS: A total of 222 subjects underwent an oral glucose tolerance test and a frequently sampled intravenous glucose tolerance test (FSIGTT); 100 had normal glucose tolerance (subdivided into 32 lean NGT, 68 obese NGT), and 122 were obese with IGR (82 IGT, 14 IFG and 26 CGI). The insulin sensitivity index (S(I)) was assessed by Bergman's minimal model method with FSIGTT; insulin secretion was determined by acute insulin response to glucose (AIRg). The disposition index (DI), the product of AIRg and S(I), was used to determine whether AIRg was adequate to compensate for insulin resistance. RESULTS: S(I) was similar in NGT and IGR obese subgroups. AIRg was significantly increased in obese NGT as compared with lean NGT, significantly reduced in IGT, and further reduced in IFG and CGI subjects as compared with obese NGT subgroups. DI was reduced in NGT obese individuals. Within the obese IGR subgroups, IFG and CGI subjects had even lower DI value than IGT subjects. CONCLUSIONS: Obese Chinese subjects with IGR have a similar degree of insulin resistance but differ in insulin secretion. Subjects with IFG and CGI have a more prominent deficiency in insulin secretion than subjects with IGT.

Increased serum retinol-binding protein-4 levels in pregnant women with and without gestational diabetes mellitus.

OBJECTIVE: Retinol-binding protein 4 (RBP4) is thought to be associated with insulin resistance in humans, while pregnancy is normally characterized by progressive insulin resistance. Gestational diabetes (GDM) occurs when pancreatic beta-cell function is unable to compensate for insulin resistance. This study aimed to determine whether or not serum RBP4 levels are elevated in pregnancy, and to explore the relationship between RBP4 levels and insulin resistance during pregnancy. METHODS: Serum RBP4 was measured at median gestational week 26 in 121 pregnant women, including 63 with GDM (GDM group) and 58 normal, glucose-tolerant pregnant women (P-NGT group), as well as 65 non-pregnant normal, glucose-tolerant women (NP-NGT group). Multiple stepwise regression analysis was used to explore the independent factors of RBP4. RESULTS: Serum RBP4 levels in the P-NGT and GDM groups were significantly higher than in the NP-NGT group (34.50±9.80 mg/L and 41.64±12.21 mg/L vs 30.64±9.46 mg/L, respectively; P<0.05) after adjusting for age, body mass index (BMI) and blood pressure. Furthermore, RBP4 levels were much higher in the GDM vs P-NGT group. Spearman's correlation analysis showed that serum RBP4 levels were positively correlated with triglycerides (TG), fasting plasma glucose, postprandial 2h plasma glucose and HOMA-IR in pregnancy. Of these, TG and HOMA-IR (r(2)=0.312) were independent factors of serum RBP4. CONCLUSION: Serum RBP4 levels are significantly increased in pregnancy, independent of age and BMI, and are also considerably higher in pregnant women with GDM than in those with normal glucose tolerance. In addition, serum RBP4 levels appear to be a valuable marker of insulin resistance and dysfunctional lipid metabolism in pregnancy.