Lipoprotein lipase in diabetes.

Lipoprotein lipase has a central role in the metabolism of both triglyceride-rich particles and high density lipoproteins, and it is one determinant of both serum triglyceride and HDL concentrations. In man the enzyme activity in both adipose tissue and skeletal muscle is insulin dependent, and therefore it varies in diabetes according to ambient insulin level and insulin sensitivity. In insulin deficiency (untreated Type 1 diabetes) the enzyme activity in both adipose tissue and muscle tissue is low but increases upon insulin therapy. In chronically insulin-treated patients with good control, the enzyme activity in postheparin plasma is increased. In untreated Type 2 diabetic patients, the average enzyme activity in adipose tissue and postheparin plasma is normal or subnormal. Therapy with oral agents or insulin, resulting in good glycemic control, is followed by an increase of LPL activity in both adipose tissue and postheparin plasma. In both Types 1 and 2 diabetes, changes of LPL activity are associated with relevant alterations in lipoprotein pattern. In insulin deficiency with low LPL, serum total and VLDL triglyceride levels are elevated, and HDL concentration is reduced. In chronically insulin-treated patients with high LPL activity, VLDL triglyceride concentrations are normal or subnormal, and HDL level is increased. In untreated Type 2 diabetic patients subnormal LPL activity may contribute to the elevation of serum triglycerides and to the reduction of HDL level.