Inhibition of lipolysis stimulates peripheral glucose uptake but has no effect on endogenous glucose production in HIV lipodystrophy.
HIV-infected patients with lipodystrophy (HIV lipodystrophy) are insulin resistant and have elevated plasma free fatty acid (FFA) concentrations. We aimed to explore the mechanisms underlying FFA-induced insulin resistance in patients with HIV lipodystrophy. Using a randomized, placebo-controlled, cross-over design, we studied the effects of an overnight acipimox-induced suppression of FFAs on glucose and FFA metabolism by using stable isotope-labeled tracer techniques during basal conditions and a two-stage euglycemic-hyperinsulinemic clamp (20 and 50 mU insulin/m(2) per min, respectively) in nine patients with nondiabetic HIV lipodystrophy. All patients received antiretroviral therapy. Biopsies from the vastus lateralis muscle were obtained during each stage of the clamp. Acipimox treatment reduced basal FFA rate of appearance by 68.9% (95% CI 52.6-79.5) and decreased plasma FFA concentration by 51.6% (42.0-58.9) (both, P < 0.0001). Endogenous glucose production was not influenced by acipimox. During the clamp, the increase in glucose uptake was significantly greater after acipimox treatment compared with placebo (acipimox: 26.85 micromol x kg(-1) x min(-1) [18.09-39.86] vs. placebo: 20.30 micromol x kg(-1) x min(-1) [13.67-30.13]; P < 0.01). Insulin increased phosphorylation of Akt Thr(308) and glycogen synthase kinase-3beta Ser(9), decreased phosphorylation of glycogen synthase (GS) site 3a + b, and increased GS activity (percent I-form) in skeletal muscle (P < 0.01). Acipimox decreased phosphorylation of GS (site 3a + b) (P < 0.02) and increased GS activity (P < 0.01) in muscle. The present study provides direct evidence that suppression of lipolysis in patients with HIV lipodystrophy improves insulin-stimulated peripheral glucose uptake. The increased glucose uptake may in part be explained by increased dephosphorylation of GS (site 3a + b), resulting in increased GS activity.
Lindegaard
Birgitte
B
Centre of Inflammation and Metabolism, Department of Infectious Diseases, Rigshospitalet, Copenhagen Ø, Denmark. blm@rh.dk
Frøsig
Christian
C
Petersen
Anne Marie W
AM
Plomgaard
Peter
P
Ditlevsen
Susanne
S
Mittendorfer
Bettina
B
Van Hall
Gerrit
G
Wojtaszewski
Jørgen F P
JF
Pedersen
Bente K
BK
D001706:Biopsy; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005947:Glucose / Q000008:administration & dosage / Q000096:biosynthesis* / Q000378:metabolism*; D006006:Glycogen Synthase / Q000378:metabolism; D039682:HIV-Associated Lipodystrophy Syndrome / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007328:Insulin; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D010168:Palmitates / Q000097:blood / Q000494:pharmacology; D011719:Pyrazines / Q000627:therapeutic use; D015398:Signal Transduction / Q000187:drug effects
D005230:Fatty Acids, Nonesterified; D007328:Insulin; D010168:Palmitates; D011719:Pyrazines; D006006:Glycogen Synthase; D005947:Glucose; C027696:acipimox