Reduction in Endothelial Leptin Signaling in Congenital Generalized Lipodystrophy Leads to Endothelial Dysfunction via PPARγ‐Mediated Increases in Nox1 in the Vasculature

Absence of the adipose tissue in congenital generalized lipodystrophy is associated with a very early mortality from cardiovascular disease. However, the underlying mechanisms are unknown. Mice deficient in Berardinelli‐Seip gene (gBscl2−/−), which recapitulate the phenotype of human lipodystrophic patients, were used to characterize their cardiovascular phenotype. Here we tested the hypothesis that reduction of leptin plasma levels in congenital lipodystrophy reduces PPARγ expression and elevates Nox1‐derived ROS in the vasculature leading to endothelial dysfunction. gBscl2−/− mice presented reduced fat mass [% of fat: wild‐type (WT): 8.9 ± 0.4 vs gBscl2−/−: 1.7 ± 0.1* (*P<0.05 vs WT)] and leptin plasma levels [ng/mL: WT: 4.6 ± 0.2 vs gBscl2−/−: 0.4 ± 0.1* (*P<0.05 vs WT)], which was associated with reduction of acetylcholine (Ach)‐induced vascular relaxation. Nitric oxide synthase (NOS) inhibitor (L‐NAME, 10μmol/l) blunted the vascular relaxation in WT and gBscl2−/− to the same magnitude, but no difference was observed for endothelial NOS phosphorylation. Moreover, gBscl2−/− mice presented elevated Nox1, NoxA1 and NoxO1, vascular –O 2 and H 2 O 2 and plasma lipid peroxidation, Inhibtion of Nox1 in vitro by GKT771 (10 μmol/l) restored the endothelial function in gBscl2−/− mice. Furthermore, lipodystrophy reduced PPARγ gene expression in the aorta. The endothelial dysfunction in gBscl2−/− mice was blunted by pioglitazone pre‐incubation (PPARγ activator, 10 μmol/l). Leptin treatment in vivo via osmotic mini pump (10ug/day for 7 days) restored endothelial function, reduced Nox1, NoxA1 and NoxO1, vascular oxidative stress and plasma lipid peroxidation, increased the PPARγ expression, but did not change eNOS phosphorylation levels. In order to check whether leptin replacement exerts vascular protective effects by acting directly in the vasculature in lipodystrophy aortic rings were pre‐incubated with leptin (1ug/mL for 2h), leptin in vitro improved the endothelial dysfunction in aortic rings from gBscl2−/− mice, this effect was blunted by pre‐incubating concomitantly leptin and PPARγ antagonist (GW9662, 5 μmol/l). In addition, human leptin increased PPARγ gene expression in HUVEC and aortic segments, which were obtained from humans during cardiovascular surgeries. To confirm that vascular leptin signaling is important for the vascular homeostasis we used endothelial leptin receptor knockout mice (LepR EC−/− ), these mice presented impaired vascular relaxation to Ach, elevated Nox1, NoxA1 and NoxO1 and reduced PPARγ expression in aorta. Our data demonstrate that leptin replacement therapy restores endothelial function by directly regulating PPARγ activity in the vasculature and reducing oxidative stress via downregulation of Nox1 and increasing NO bioavailability. Our data also show that leptin plays major role on maintain the vascular homeostasis in physiological conditions. Support or Funding Information Work supported by 1K99HL140139‐01A1 and 17POST33410363 to TBN and 1R01HL13030101 to EJ.BdC. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .