In nondiabetic, human immunodeficiency virus-infected patients with lipodystrophy, hepatic insulin extraction and posthepatic insulin clearance rate are decreased in proportion to insulin resistance

Abstract

In healthy, nondiabetic individuals with insulin resistance, fasting insulin is inversely correlated to the posthepatic insulin clearance rate (MCRi) and the hepatic insulin extraction (HEXi). We investigated whether similar early mechanisms to facilitate glucose homeostasis exist in nondiabetic, human immunodeficiency virus (HIV)-infected patients with and without lipodystrophy. We studied 18 HIV-infected patients with lipodystrophy (LIPO) on antiretroviral therapy and 25 HIV-infected patients without lipodystrophy (controls) of whom 18 were on antiretroviral therapy and 7 were not. Posthepatic insulin clearance rate was estimated as the ratio of posthepatic insulin appearance rate to steady-state plasma insulin concentration during a euglycemic hyperinsulinemic clamp (40 mU.m-2 .min-1). Posthepatic insulin appearance rate during the clamp was calculated, taking into account the remnant endogenous insulin secretion, which was estimated by deconvolution of C-peptide concentrations. Hepatic extraction of insulin was calculated as 1 minus the ratio of fasting posthepatic insulin delivery rate to fasting endogenous insulin secretion rate. Compared with controls, LIPO displayed increased fasting insulin (130%, P < .001), impaired insulin sensitivity index (M value, -29%, P < .001), and reduced MCRi (-17%, P < .01). Hepatic extraction of insulin was similar between groups (LIPO, 55%; controls, 57%; P > .8). In LIPO, HEXi and MCRi correlated inversely with fasting insulin (r = -0.56, P < .02 and r = -0.68, P < .002) and positively with M value (r = 0.63, P < .01 and r = 0.65, P < .004). In controls, MCRi correlated inversely with fasting insulin (r = -0.47, P < .02) and positively with M value (r = 0.57, P < .004); however, the correlations between HEXi and these parameters were insignificant (P > .1). Our data suggest that HEXi and MCRi are decreased in proportion to the degree of insulin resistance in nondiabetic HIV-infected patients with lipodystrophy.