Hypertriglyceridaemic waist phenotype and β-cell function in subjects with normal and impaired glucose tolerance

Abstract

To determine the association between the hypertriglyceridaemic waist phenotype, a combination of enlarged waist circumference and increased triglyceride levels, and β-cell function in subjects with normal glucose tolerance and those with impaired glucose tolerance. We studied 1344 outpatients clinic without diabetes. Overnight fasting blood samples were obtained to measure plasma glucose, insulin and lipids. An oral glucose tolerance test was performed in all subjects. All patients were divided in four groups, two groups with normal glucose tolerance and two with impaired glucose tolerance, with or without the hypertriglyceridaemic waist phenotype. Insulin resistance and β-cell function were calculated by homeostatsis model assessment 2 indices. Twenty per cent of subjects showed the hypertriglyceridaemic waist phenotype and 23.8% had impaired glucose tolerance. We found a progressive significant increase (P < 0.001) of insulin resistance from subjects with normal glucose tolerance without the hypertriglyceridaemic waist phenotype with respect to patients with impaired glucose tolerance with the hypertriglyceridaemic waist phenotype. In subjects with normal glucose tolerance, the hypertriglyceridaemic waist phenotype was associated with a mild, but not significant, increase of homeostatsis model assessment 2-β levels; but, in patients with impaired glucose tolerance, the hypertriglyceridaemic waist phenotype was associated with significantly lower homeostatsis model assessment 2-β levels [127.0 (103.0-162.7) vs. 123.0 (96.0-147.0); P < 0.05]. The hypertriglyceridaemic waist phenotype displayed a higher (odds ratio 95% CI) β-cell dysfunction of 1.8 (1.3-2.6) and insulin resistance of 5.0 (2.7-8.5) compared with 1.3 (0.9-1.9) and 2.4 (1.8-3.2), respectively, of waist circumference alone. In this study, the hypertriglyceridaemic waist phenotype is associated with increased insulin resistance and an overstimulation of β-cell function in subjects with normal glucose tolerance, while patients with impaired glucose tolerance with the hypertriglyceridaemic waist phenotype showed a reduction in β-cell function. These data suggest the importance of the identification of patients with impaired glucose tolerance combined with the hypertriglyceridaemic waist phenotype for an early intervention in relation to the high risk of developing Type 2 diabetes.