IMPROVED LIPOPROTEIN SURFACE AND CORE LIPID-COMPOSITION FOLLOWING INTRAPERITONEAL INSULIN DELIVERY IN INSULIN-DEPENDENT DIABETES-MELLITUS

To determine whether insulin delivered into portal circulation by an i mplanted pump reversed abnormalities in lipoprotein composition in ins ulin-dependent diabetes mellitus, 10 well-controlled normolipidaemic p atients were studied after conventional intensive subcutaneous (ISC) i nsulin management and then 3 and 6 months after intraperitoneal pump i mplantation (IP). Glycated haemoglobin (ISC: 6.9 +/- 1.7 % vs. IP-3 mo nths 6.3 +/- 0.7; IP-6 months 6.3 +/- 0.8, mean +/- S.D.), plasma trig lyceride and cholesterol levels, and the cholesterol content of HDL(2) and HDL(3) were normal and not significantly changed during these tre atments. Fasting free insulin concentrations measured before and after 6 months of IP fell by more than half (ISC 8.22 +/- 6.5 vs IP 2.77 +/ - 2.4 mU/ml; p < 0.025). The plasma free cholesterol/lecithin ratio, a potential new cardiovascular risk factor, was increased during ISC, d eclined progressively after 3 months of IP, and approached normal by 6 months (ISC 0.96 +/- 0.37 mol/mol vs.IP - 3 months 0.91 +/- 0.34; IP 6 months 0.86 +/- 0.10; reference group 0.83 +/- 0.33). In all lipopro tein fractions, sphingomyelin concentrations tended to fall, and lecit hin concentrations to rise progressively during IP. As a result, the s phingomyelin/lecithin ratio, an index of the surface rigidity of lipop roteins, declined. The fact that some of the compositional modificatio ns associated with ISC were reversed when insulin was administered int raperitoneally suggests that they may have been iatrogenic and resulte d from high systemic insulin levels.