Genetic versus environmental aetiology of the metabolic syndrome among male and female twins

Aims/hypothesis. The aetiology of the metabolic syndrome including hyperins ulinaemia, glucose intolerance, dyslipidaemia? hypertension and obesity is not known. We studied the relative impact of genetic versus environmental f actors for the development of the components in the syndrome among male and female twins. Methods. A total of 303 elderly twin pairs participated in the study. We re port concordances and heritability estimates of the components by classic t win analysis to assess the proportion of variation attributed to genetic fa ctors. Results. AII components correlated significantly. The concordance rates for glucose intolerance, overall obesity and low HDL-cholesterol were signific antly higher among monozygotic than dizygotic twins indicating a genetic in fluence on the development of these phenotypes. The heritability estimates for glucose concentration. BMI and HDL-cholesterol among monozygotic twins confirmed these findings. The heritability estimates for waist-to-hip ratio , fasting insulin and triglycerides, however were low, indicating a major e nvironmental influence. We found a higher genetic influence on glucose into lerance and systolic blood pressure and a lower genetic influence on low HD L-cholesterol and diastolic blood pressure among male twins compared to fem ale twins. Conclusion/interpretation. Based on the correlations between the components in the syndrome, we propose a core complex including hyperinsulinaemia, ob esity hypertriglyceridaemia and low HDL-cholesterol with only weak associat ions to glucose concentrations and blood pressure levels, The study confirm s the notion of a multifactorial aetiology of the components including gene tic and non-genetic factors. The differences in aetiology between male and female twins indicate an influence of sex on several of the components in t he metabolic syndrome.