Abstract
Background: Angiotensin II (Ang II), released by the renin–angiotensin–aldosterone system (RAAS), contributes to the modulatory role of the RAAS in adipose tissue dysfunction. Investigators have shown that inhibition of AngII improved adipose tissue function and insulin resistance in mice with metabolic syndrome. Heme Oxygenase-1 (HO-1), a potent antioxidant, has been demonstrated to improve oxidative stress and adipocyte phenotype. Molecular effects of high oxidative stress include suppression of sirtuin-1 (SIRT1), which is amenable to redox manipulations. The mechanisms involved, however, in these metabolic effects of the RAAS remain incompletely understood. Hypothesis: We hypothesize that AngII-induced oxidative stress has the potential to suppress adipocyte SIRT1 via down regulation of HO-1. This effect of AngII will, in turn, upregulate mineralocorticoid receptor (MR). The induction of HO-1 will rescue SIRT1, hence improving oxidative stress and adipocyte phenotype. Methods and Results: We examined the effect of AngII on lipid accumulation, oxidative stress, and inflammatory cytokines in mouse pre-adipocytes in the presence and absence of cobalt protoporphyrin (CoPP), HO-1 inducer, tin mesoporphyrin (SnMP), and HO-1 inhibitor. Our results show that treatment of mouse pre-adipocytes with AngII increased lipid accumulation, superoxide levels, inflammatory cytokine levels, interleukin-6 (IL-6) and tumor necrosis factor α (TNFα), and adiponectin levels. This effect was attenuated by HO-1 induction, which was further reversed by SnMP, suggesting HO-1 mediated improvement in adipocyte phenotype. AngII-treated pre-adipocytes also showed upregulated levels of MR and suppressed SIRT1 that was rescued by HO-1. Subsequent treatment with CoPP and SIRT1 siRNA in mouse pre-adipocytes increased lipid accumulation and fatty acid synthase (FAS) levels, suggesting that beneficial effects of HO-1 are mediated via SIRT1. Conclusion: Our study demonstrates for the first time that HO-1 has the ability to restore cellular redox, rescue SIRT1, and prevent AngII-induced impaired effects on adipocytes and the systemic metabolic profile.
Highlights
The renin–angiotensin–aldosterone system (RAAS) has been described as a multi-organ endocrine axis that is governed by a negative feedback loop where elevated circulating AngII inhibits renal renin release
Our Western blot analysis demonstrated that the treatment with AngII induced significantly reduced expression of SIRT1 as compared to controls, which was rescued by the induction of Heme Oxygenase-1 (HO-1) (Figure 2B)
Our Western blot analysis further demonstrated that AngII significantly reduced insulin receptor-β (IR-β) expression, which was significantly improved by treatment with cobalt protoporphyrin (CoPP) (Figure 2E)
Summary
The RAAS has been described as a multi-organ endocrine axis that is governed by a negative feedback loop where elevated circulating AngII inhibits renal renin release. Hypothesis: We hypothesize that AngII-induced oxidative stress has the potential to suppress adipocyte SIRT1 via down regulation of HO-1 This effect of AngII will, in turn, upregulate mineralocorticoid receptor (MR). Methods and Results: We examined the effect of AngII on lipid accumulation, oxidative stress, and inflammatory cytokines in mouse pre-adipocytes in the presence and absence of cobalt protoporphyrin (CoPP), HO-1 inducer, tin mesoporphyrin (SnMP), and HO-1 inhibitor. Our results show that treatment of mouse pre-adipocytes with AngII increased lipid accumulation, superoxide levels, inflammatory cytokine levels, interleukin-6 (IL-6) and tumor necrosis factor α (TNFα), and adiponectin levels. This effect was attenuated by HO-1 induction, which was further reversed by SnMP, suggesting HO-1 mediated improvement in adipocyte phenotype. Subsequent treatment with CoPP and SIRT1 siRNA in mouse pre-adipocytes increased lipid accumulation and fatty acid synthase (FAS) levels, suggesting that beneficial effects of HO-1 are mediated via SIRT1
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
