Abstract 514: Knockout of Rictor in Adipocytes Compromises Anticontractile Function of PVAT and Increases Mean Arterial Pressure

Abstract

Introduction: Mammalian target of rapamycin (mTOR) is a kinase found in two distinct complexes: mTORC1 and mTORC2. The latter is activated by growth factors such as insulin and characterized by the adaptor protein rictor. mTORC2 controls essential functions in white adipose tissue, while little is known about its role in perivascular adipose tissue (PVAT), surrounding most arteries. PVAT is an important regulator of the vascular tone and we have shown that mTORC2 is necessary for normal PVAT function. In the present study we assessed whether adipose mTORC2 contributes to blood pressure regulation and investigated the diurnal expression of mTORC2 phosphorylation targets and circadian clock in PVAT. Methods: Experiments were performed with male adipose-specific rictor knockout mice ( rictor ad-/- ) and control littermates (18-23 weeks of age). Vascular function was assessed ex vivo using aortic rings with or without PVAT treated with 5-hydroxytrypthamine (5-HT; 10 -9 - 3x10 -6 mol/l). Blood pressure recordings were performed using radiotelemetry monitoring hemodynamic parameters over 7 days (n = 5-6). mRNA and protein levels were analyzed by performing qRT-PCR and Western Blot. Results: In rictor ad-/- mice, vascular maximal contractions of aortic rings in the presence of PVAT were 2-fold higher after stimulation with 5-HT compared with control mice (43.4% ± 6.8% vs. 26.0% ± 3.5%, n= 13 ) . Removal of PVAT resulted in increased contraction with similar maximum levels in both mice groups. Blood pressure recordings revealed a significant increase in the 24-h average of mean arterial pressure (103.9 ± 1.1 vs. 98.5 ± 1.4 mmHg) and diastolic arterial pressure (94.6 ± 1.4 vs. 90.2 ± 0.6 mmHg) in rictor ad -/- mice, while systolic arterial pressure and pulse pressure were not significantly different between groups. Interestingly, differences in mean and diastolic arterial pressure were slightly higher during dark as compared to light period. Expression levels of clock genes were similar while expression of mTORC2 phosphorylation targets such as Foxo1 and Sgk1 was dampened in rictor ad-/- mice. Conclusion: mTORC2 in adipose tissue regulates mean arterial pressure potentially by affecting diurnal expression and activation of phosphorylation targets such as Foxo1.