Metabolic syndrome and small dense LDL-cholesterol

Recently, small dense low-density lipoprotein (sd-LDL) has been highlighted as a new risk factor for CHD. Sd-LDL is also closely associated with insulin resistance and hypertriglyceridemia, suggesting a high prevalence of these atherogenic particles in metabolic syndrome. It has been proposed that increased triglyceride (TG) production in the liver due to insulin resistance preferentially produces TG-rich very-low density lipoproteins (VLDL1), which finally generate sd-LDL particles. Sd-LDL is usually measured by electrophoresis or ultracentrifugation, but these methods are too laborious for general clinical use. Recently, we established a simple method for the quantification of sd-LDL-cholesterol (C) using heparin-magnesium precipitation with a filter, which selectively detects cholesterol in the denser LDL fraction with a density(d) =1.044-1.063g/ml. Patients with coronary heart disease (CHD) had substantially increased sd LDL-C levels, while their LDL-C levels were comparable to those of controls. Sd-LDL-C levels were positively correlated with TG, LDL C, and apolipoprotein B, and were inversely with HDL-C. Sd-LDL-C levels were also correlated positively with waist circumference, blood pressure, and insulin resistance index, and negatively with adiponectin level. Patients with type 2 diabetes and metabolic syndrome had substantially increased sd-LDL-C level. These results suggest that measurement of sdLDL-C is useful to evaluate overall atherogenic risks associated with metabolic syndrome and may be applicable to routine clinical examination.