NORMALIZATION OF LIPOPROTEIN COMPOSITION BY INTRAPERITONEAL INSULIN IN IDDM - ROLE OF INCREASED HEPATIC LIPASE ACTIVITY

OBJECTIVE- To characterize the effects of intraperitoneal insulin pump therapy on lipoprotein composition and lipolytic enzyme activity in p atients with insulin- dependent diabetes mellitus (IDDM). RESEARCH DES IGN AND METHODS- Ten IDDM patients were studied 3 times: when receivin g conventional subcutaneous insulin therapy and at 3 and 9 months from the initiation of intraperitoneal insulin regimen. Ten nondiabetic su bjects matched for age, sex, and body weight were studied as controls. Levels of cholesterol, triglycerides, apolipoprotein A-I (apoA-I) and B (apoB) were measured in total plasma and lipoprotein fractions (ver y-low-density lipoprotein [VLDL], intermediate-density lipoprotein [ID L], low-density lipoprotein [LDL], and high-density lipoprotein [HDL]: HDL(2) and HDL(3)). Postheparin plasma lipoprotein lipase and hepatic lipase activities were determined by an immunochemical method. RESULT S- IDDM patients showed higher levels of HDL, and lower levels of HDL, particles during intraperitoneal insulin therapy in comparison with s ubcutaneous insulin therapy. Both cholesterol and apoA-I significantly increased in HDL, and decreased in HDL, during intraperitoneal treatm ent. Plasma total cholesterol significantly decreased in the diabetic patients at 3 months of intraperitoneal insulin therapy compared with both subcutaneous insulin regimen and control subjects. IDL triglyceri de concentrations during intraperitoneal treatment were significantly lower than those seen with subcutaneous therapy. Furthermore, triglyce ride:apoB ratio in VLDL and cholesterol:apoB ratio in LDL significantl y decreased in IDDM patients treated by intraperitoneal insulin. A sig nificant increase in the activity of hepatic lipase with intraperitone al insulin therapy by 9 months compared with subcutaneous insulin ther apy has been shown. CONCLUSIONS- The increased activity of hepatic lip ase after intraperitoneal insulin administration in IDDM patients appe ars to be one of the main determinants of lipoprotein changes observed , resulting in the normalization of lipoprotein composition during thi s mode of therapy. The normal inverse relationship between VLDL trigly cerides and HDL cholesterol, which was not present in IDDM patients wi th subcutaneous therapy, was restored with intraperitoneal insulin reg imen.