Oral Glucose Tolerance Test with Insulin Assay and the evaluation of Insulin Resistance and Impaired Beta-cell function in primary prevention for Type 2 Diabetes

Abstract

Background: Insulin resistance and impaired beta-cell function are associated with type 2 diabetes mellitus (T2DM). Many insulin resistance and beta-cell function indices have been developed using the data from an oral glucose tolerance test (OGTT) with insulin assay. However, insulin assays are not widely used along with the OGTT in primary prevention outpatient clinics. We aimed to evaluate the association of having impaired fasting glucose (IFG), impaired glucose tolerance (IGT), isolated or combined, with insulin resistance and impaired beta-cell function in subjects at risk for T2DM. Methods: This is a cross-sectional study that included 376 subjects who underwent an OGTT who had at least two risk factors for T2DM without any chronic disease. Results: Participants were 51.6±8.2 years old, 71.8% were women, had a mean body mass index (BMI) of 30.1±6.5 kg/m2, 42.4% had obesity and 26.7% hypertension. A HOMA-IR ≥2.5 was independently associated with male sex, BMI>25kg/m2, and with isolatedIFG, isolated-IGT, or combined (p<0.05 for all). On the other hand, only overweight, but not obesity, was independently associated with impaired beta-cell function (disposition index <1.24). Additionally, combined IFG and IGT had 29.7 higher odds to have impaired beta-cell function compared with those that had a normal OGTT. Conclusions: IFG alone, IGT alone, or the presence of both, are associated with higher odds to have insulin resistance and impaired beta-cell function in asymptomatic subjects at risk for T2DM without any chronic disease. Further studies are needed to evaluate this associations with the risk to develop T2DM, cardiovascular events and mortality.