OBJECTIVESTo evaluate relationship between serum level of leptin and the components of risk factors for metabolic syndrome and to analyze the characteristics and laws of clustering of the risk factors.

METHODSTotally, 795 non-diabetic adult Chinese subjects (691 men and 104 women, aged 40 - 75 years) from a diabetes prevalence survey in 2000 were involved in this study. Measurements included serum levels of true insulin (TI), leptin, fasting lipids, fasting glucose (FBG) and 2 h postchallenge glucose, as well as seated blood pressure (BP), body mass index (BMI), ratio of waist circumference to hip circumference (WHR), calculated quantitative insulin sensitivity check index (QUICKI), etc. Relationship between serum level of leptin and all the variables mentioned above was studied by statistical methods such as factor analysis, etc.

RESULTSSerum level of leptin in the study subjects increased with the number of components of abnormal metabolism they had. Detection rates of obesity, hypertension, dyslipidemia and metabolic syndrome were significantly higher in those with the upper tertile of serum leptin level than in those with the lower tertile. Factor analysis revealed that variation of the 11 variables including serum level of leptin was affected by the three factors, i.e., the central factor associated with BMI, WHR, FTI, QUICKI and higher serum level of triglyceride (TG) and lower serum level of high-density lipoprotein-cholesterol (HDL-C), the glucose intolerance factor loaded with blood glucose level, FTI, QUICKI and higher serum level of TG (in women only) and the hypertension factor loaded with blood pressure and BMI (in men only), which could explain 62.0% and 66.7% of total variance in men and women, respectively, and higher serum level of TI and insulin resistance also loaded with both the central factor and glucose tolerance factor.

CONCLUSIONSSerum level of leptin was significantly associated with the key markers of metabolic syndrome. Hyperleptinaemia could be a new component of metabolic syndrome. Clustering of the risk factors for metabolic syndrome could be affected by many factors, and although insulin resistance played an important role in it, insulin resistance alone could not explain its etiology.