The metabolism of low-density lipoprotein (LDL) was studied in six insulin-dependent (type I) diabetic patients during a 7-wk period of conventional and intensive therapy with insulin. Plasma glucose and HbA1c were normalized, demonstrating the effectiveness of our intensive treatment program. Plasma lipoprotein profiles and LDL apolipoprotein B kinetic parameters were estimated during conventional and then during intensive therapy for each patient. Intensive therapy resulted in a significant reduction of plasma and LDL cholesterol and an increase in high-density lipoprotein (HDL) cholesterol. The lower LDL levels resulted from a decreased production of lipoprotein rather than an increased fractional catabolic rate. These results are consistent with our previous observations of very-low-density lipoprotein (VLDL) metabolism during intensive therapy. VLDL production is significantly reduced; thus, a decreased production of LDL supports the contention that intensive therapy with insulin in normolipemic type I diabetic patients reduces the production of lipoproteins containing apolipoprotein B rather than increasing the clearance, and therapy also increases HDL cholesterol. Both of these effects may be beneficial in reducing the risk for coronary heart disease in type I diabetes.

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