Factor analysis of the metabolic syndrome: obesity vs insulin resistance as the central abnormality

Objectives: To evaluate whether there is one central abnormality contributi ng to the conditions associated with the metabolic syndrome (MES), or wheth er one abnormality is contributing on multiple levels. Methods: We recruited 145 Chinese subjects aged 17-68 y with varying degree s of insulin-sensitivity (IS): 33 healthy, 59 with type 2 diabetes mellitus , 32 essential hypertensives and 21 dyslipidaemics. IS was evaluated by the short insulin sensitivity test using a 0.1 U/kg intravenous bolus dose of insulin. Blood pressure, anthropometric measures and biochemical parameters associated with IS were also measured. Exploratory factor analyses (EFA) w ere performed in the entire group of 145 subjects and in the 76 with normal glucose tolerance. Results: EFA in all 145 subjects defined three distinct, independent factor s. Factor 1 was interpreted as general and central adiposity, impaired IS a nd glucose intolerance, Factor 2 was associated with hypertension and gener al and central obesity, whilst Factor 3 was strongly related to low HDL-cho lesterol and high triglyceride concentrations and weakly to waist circumfer ence. In patients with impaired glucose tolerance, only two factors were id entified; factor I related to reduced IS, impaired glucose tolerance, dysli pidaemia and general and central adiposity, and factor 2 which was related to blood pressure and general and central adiposity. Conclusions: These models suggest that the clustering of variables in MES i s a result of multiple factors linked by adiposity and not a single aetiolo gy. Furthermore, increases in blood pressure are related to obesity in thes e Chinese subjects rather than decreased IS per se.