Relationship between phytosterol levels and components of the metabolic syndrome in the PROCAM study

Background Components of the metabolic syndrome such as hypertriglyceridemia, low high-density lipoprotein (HDL) cholesterol and obesity have been shown to be associated with increased cholesterol synthesis and reduced cholesterol absorption. In the present study, we measured the lathosterol/cholesterol ratio as an index of cholesterol synthesis and the ratios of cholestanol, campesterol and sitosterol to cholesterol as indices of cholesterol absorption, as well as components of the metabolic syndrome, in 324 men and 168 women from the PROCAM study, an epidemiological study in which raised sitosterol was previously associated with increased coronary risk. Our aim was to determine if the indices of cholesterol synthesis and absorption show a graded relationship with severity of metabolic syndrome. Results No differences were seen between men and women with regard to the relationship of either the lathosterol/cholesterol or the sitosterol/cholesterol ratios and severity of metabolic syndrome. On multiple regression analysis in men and women together, body mass index showed a positive relationship with the lathosterol/cholesterol ratio (r=0.257, P<0.001) and a negative relationship with the sitosterol/cholesterol ratio (r=-0.221, P<0.001). HDL-cholesterol showed a negative relationship with the lathosterol/cholesterol ratio (r= -0.166, P=0.001). Triglycerides showed a negative relationship with the sitosterol/cholesterol ratio (r=0.141, P=0.005). Overall, these relationships were graded across quintiles of HDL cholesterol, body mass index and triglyceride and across an index of metabolic syndrome severity (number of components present). Only the cholestanol/cholesterol ratio showed a graded relationship with estimated overall coronary risk. Conclusions The metabolic syndrome is associated with increased cholesterol synthesis and reduced cholesterol absorption in a relationship that is graded across severity of the individual components of the syndrome and across an index of the severity of the metabolic syndrome as a whole.