Increased mTORC1 signaling in the vasculature of diet‐induced obese mice and obese humans

Obesity‐induced hypertension is associated with vascular endothelial dysfunction. Recently our laboratory has implicated the mammalian target of rapamycin complex 1 (mTORC1) signaling in the regulation of the cardiovascular system. Specifically, activation of central mTORC1 triggered a significant increase in arterial pressure. Therefore, we tested the hypothesis that dysregulation of mTORC1 signaling is involved in the vascular endothelial dysfunction associated with obesity in mice and human patients. In diet induced obese mice (DIO), whole aortic homogenates demonstrated a significant increase in the mTORC1 signaling pathway compared to control as indicated by the increased phosphorylated levels of mTOR and its downstream targets S6‐kinase and S6 ribosomal protein (p<0.05) by Western blot. Immunohistochemical analysis, using a phospho‐S6 ribosomal protein antibody, of aortas from DIO mice revealed a substantial increase in mTORC1 signaling in the smooth muscle and the endothelium. Next, we isolated venous endothelial cells from normal‐weight (body mass index, BMI <25 kg/m 2 ) and obese (BMI ≥30 kg/m 2 ) humans and found increased levels of phosphorylated S6 ribosomal protein in obese compared with normal weight subjects (p<0.05), consistent with increased mTORC1 signaling. Stimulation of mTORC1 in cultured mouse aortas and resistance mesenteric arteries with the branched amino acid Leucine significantly increased mTORC1 signaling in both the endothelium and smooth muscle. Interestingly, cultured aortas stimulated with Leucine exhibited impairment in acetylcholine induced relaxation (Max. relaxation: 71.3 ± 2.1% vs 63.5 ± 1.9%; p<0.05), but no changes in relaxation responses evoked by sodium nitroprusside (Max. relaxation: 77.3 ± 2.3% vs 76.0 ± 4.5%) suggesting endothelial, but not smooth muscle, dysfunction. In order to selectively disrupt mTORC1 signaling in the vascular endothelium, we have generated endothelial‐specific mTORC1 knockout mice by breeding Tie‐2 Cre mice with mice harboring floxed alleles of the unique regulatory associated protein of mTOR (Raptor) subunit (Tie‐2 Cre /raptor f/f ). Preliminary immunohistochemical analysis suggests endothelial specific knockout of mTORC1 signaling in these mice. Studies are ongoing to characterize the vascular function of these mice. We speculate that selective dysregulation of endothelial mTORC1 signaling is contributes to obesity‐induced endothelial dysfunction in both mice and humans. Support or Funding Information P01 HL084207