Increase of the lipoprotein-lipase activity in human skeletal muscle during clofibrate administration

Lipoprotein-lipase activity was determined in tissue from the skeletal muscle of the leg and the subcutaneous adipose tissue of the abdomen in fourteen patients before and after 1 month of clofibrate administration. The concentrations of serum triglycerides decreased by, on the average, 37% in a group of thirteen patients which mainly consisted of subjects with type-IV hyperlipoproteinaemia. Clofibrate administration was associated with an average increase of the skeletal muscle-tissue lipoprotein-lipase activity of 50% (P less than 0.005). There was a significant correlation between the percentage changes in skeletal muscle-tissue lipoprotein-lipase activity and those of the triglycerides concentrations and the K2-values in an intravenous fat tolerance test during clofibrate treatment. Adipose-tissue lipoprotein-lipase activity did not change significantly. One patient with type-I hyperlipoproteinaemia had very low values of skeletal muscle-tissue lipoprotein-lipase activity and moderately low adipose-tissue lipoprotein-lipase activity. In this patient, neither the tissue lipoprotein-lipase activity nor the triglycerides concentration changed during clofibrate therapy. Fasting serum insulin concentrations decreased significantly during clofibrate administration and the percentage decrease was significantly correlated to the percentage increase of skeletal-muscle lipoprotein-lipase activity. It is suggested that the lowering of insulin levels is a possible mechanism through which glucagon activity is enhanced and this may increase skeletal muscle-tissue lipoprotein-lipase activity.