Abstract:

Objective    To investigate metabolic characteristics, insulin resistance (IR) and islet B-cell function in elderly subjects with different thresholds for impaired fasting glucose(IFG). Methods    A cohort of 830 nondiabetic subjects older than 60 years with fasting plasma glucose(FPG)＜7.0mmol/L were divided into three groups：the normal glucose tolerance(NGT) group(n=510) with FPG＜5.6mmol/L, the IFG1group(n=167) with 5.6mmol/L ≤FPG＜6.1mmol/L, and the IFG2 group(n=153) with 6.1 mmol/L ≤FPG＜7.0mmol/L.  Height, weight, blood pressure, waist circumference and hip circumference were measured, and the body mass index(BMI) and waist hip ratio(WHR) were calculated. Triglyceride(TG), total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol(LDL -C), FPG and 2h post-75g oral glucose tolerance test(OGTT) plasma glucose(2hPG) were determined. Fasting insulin(FINS) and 2h post-OGTT insulin(PINS)were measured by radioimmunoassay.The homeostasis model assessment (HOMA) was applied to assess the status of insulin resistance (HOMA-IR) and islet B-cell function (HOMA-B). Associations of IFG1 and IFG2 with risks of post-challenge glucose intolerance and metabolic syndrome (MS) were tested by logistic regression analysis with adjustment for age and gender. Results     Compared with the NGT group, age, WHR, BMI, blood pressure, TC, LDL-C, TG, FPG and 2hPG were elevated in the IFG1 and IFG2 groups(P<0.05). Subjects with IFG2 had  significantly higher 2hPG than those with IFG1(P<0.05). After adjustment for age, sex and BMI, HOMA-IR increased in subjects with IFG(P<0.05), and subjects with IFG2 had higher HOMA-IR(P<0.05). Compared with subjects with NGT, subjects with IFG had lower HOMA-B, while there was no significant difference between IFG1 and IFG2(P>0.05). In logistic regression analysis with adjustment for age and gender, IFG2 was associated with higher risks of post-challenge glucose intolerance and MS compared with IFG1. Conclusions    Insulin resistance and B cell dysfuction are present in elderly subjects with different thresholds for IFG. IFG2 is associated with more serious metabolic disorders and insulin resistance, and it is much more likely to have risks of post-challenge glucose intolerance and MS.

Key words: Impaired fasting glucose;  Insulin resistance;  Islet B-cell function;    Metabolic syndrome