Metabolic characteristics and insulin resistance of impaired fasting glucose among the middle-aged and elderly Taiwanese.

Impaired fasting glucose (IFG), a newly defined category of glycemic metabolism, has gained extensive attentions after the introduction of the diagnostic criteria of diabetes mellitus (DM) by the American Diabetes Association. To explore the metabolic characteristics of IFG, we conducted this prospective community-based study among people aged more than 40 years residing in three major townships of I-Lan, an agricultural county in Taiwan. People attending the annual health examinations in community health stations were recruited for study. Experienced research staff recorded the past medical history, performed comprehensive physical examinations, and drew blood for further laboratory tests for each subject. Insulin resistance was evaluated by homeostasis model assessment (HOMA), and the renal hemodynamics was evaluated by estimated glomerular filtration rate (GFR). In total, 824 subjects (mean age=64.4+/-11.3 years, M:F=366:458) participated this study, the overall prevalence of DM was 15.3% (8.7% previously undiagnosed), and the prevalence of IFG was 7.2%. Lipid profiles including serum levels of total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglyceride of subjects with IFG were basically indistinguishable from subjects with DM. Insulin resistance was significantly associated with the progression of glycemic metabolism (HOMA-IR of subjects with normal fasting glucose, IFG, and DM were 1.12+/-1.24, 1.88+/-1.64, 4.47+/-5.12, P<0.001). However, the prevalence of metabolic syndrome was similar among subjects of IFG and DM (86.4 versus 85.6%). The prevalence of overt proteinuria was significantly increased as the glycemic metabolism progressed. The mean GFR was slightly increased in subjects with IFG, which may represent hyperfiltration in this category. In conclusion, metabolic characteristics of IFG were complex. Lipid profile and prevalence of metabolic syndrome of IFG were indistinguishable from DM, but renal hemodynamics and prevalence of overt proteinuria were intermediate between NFG and DM. To prevent or delay the onset of type 2 DM, aggressive lifestyle modifications should be engaged in our clinical practice for subjects with IFG.