[Disorders of lipid metabolism in insulin resistance]

Insulin resistance with consecutive hyperinsulinemia is associated with dyslipidemia in individuals with metabolic syndrome or "syndrome x". This dyslipidemia is characterized by a hypertriglyceridemia and reduced levels of HDL-(high density lipoprotein)cholesterol in plasma. Table 1 summarizes the alterations of lipoproteins in insulin resistance. In severe forms of insulin resistance LDL-(low density lipoprotein)cholesterol can be elevated as well. The hypertriglyceridemia is caused by an elevated synthesis and secretion of VLDL (very low density lipoprotein) in the liver and by reduced metabolism, mediated e.g. by lipoprotein lipase. The alterations of VLDL-metabolism are associated with a reduced concentration of HDL-cholesterol. In addition the composition of lipoprotein particles can be altered, which might interfere with their normal metabolism. Furthermore addition direct effects of insulin on cellular cholesterol metabolism have been described. These alterations in lipid metabolism which are due to an insulin resistance and hyperinsulinemia might be related to the increased coronary risk which has been observed in patients with metabolic syndrome. Therefore the diagnostic approach in patients with hypertriglyceridemia should consider the possibility of an underlying glucose intolerance or Type 2 diabetes. Therapeutic aims and strategies are discussed. In accordance to guidelines of the American Heart Association the goals of lipid-lowering therapy take into account the prevalence of various cardiovascular risk factors in an individual patient (Table 2). Principle actions of lipid-lowering drugs on plasma lipids are outlined in Table 3. Table 4 summarizes the effect of antihypertensive drugs on plasma lipids and lipoproteins, which should be considered in the treatment of patients with dyslipidemia.