Angiotensin II Inhibits Adipogenic Differentiation and Promotes Mature Adipocyte Browning through the Corepressor CtBP1

Aerobic Exercise Training Protects Against Insulin Resistance, Despite Low-Sodium Diet-Induced Increased Inflammation and Visceral Adiposity

Dietary sodium restriction increases plasma triglycerides (TG) and total cholesterol (TC) concentrations as well as causing insulin resistance and stimulation of the renin-angiotensin-aldosterone system (RAAS) and the sympathetic nervous system. Stimulation of the angiotensin II type-1 receptor (AT1) is associated with insulin resistance, inflammation, and the inhibition of adipogenesis. The current study investigated whether aerobic exercise training (AET) mitigates or inhibits the adverse effects of dietary sodium restriction on adiposity, inflammation, and insulin sensitivity in periepididymal adipose tissue. LDL receptor knockout mice were fed either a normal-sodium (NS; 1.27% NaCl) or a low-sodium (LS; 0.15% NaCl) diet and were either subjected to AET for 90 days or kept sedentary. Body mass, blood pressure (BP), hematocrit, plasma TC, TG, glucose and 24-hour urinary sodium (UNa) concentrations, insulin sensitivity, lipoprotein profile, histopathological analyses, and gene and protein expression were determined. The results were evaluated using two-way ANOVA. Differences were not observed in BP, hematocrit, diet consumption, and TC. The LS diet was found to enhance body mass, insulin resistance, plasma glucose, TG, LDL-C, and VLDL-TG and reduce UNa, HDL-C, and HDL-TG, showing a pro-atherogenic lipid profile. In periepididymal adipose tissue, the LS diet increased tissue mass, TG, TC, AT1 receptor, pro-inflammatory macro-phages contents, and the area of adipocytes; contrarily, the LS diet decreased anti-inflammatory macrophages, protein contents and the transcription of genes related to insulin sensitivity. The AET prevented insulin resistance, but did not protect against dyslipidemia, adipose tissue pro-inflammatory profile, increased tissue mass, AT1 receptor expression, TG, and TC induced by the LS diet.

Dysregulation of HO-1-SIRT1 Axis is Associated with AngII-Induced Adipocyte Dysfunction

Angiotensin II (AngII), a component of the Renin-Angiotensin-Aldosterone System (RAAS), has been implicated in the dysregulation of adipose tissue function. Inhibition of AngII has been shown to improve adipose tissue function in mice with metabolic syndrome. It is well established that the Heme Oxygenase-1 (HO-1), an antioxidant improves oxidative stress and phenotypic change in adipocytes. Molecular effects of high oxidative stress include suppression of Sirtuin-1 (SIRT1), which is amenable to redox manipulations. However, the underlying mechanisms by which the Renin-Angiotensin-Aldosterone System (RAAS) exerts its metabolic effects are not fully understood. In this study, we propose that AngII-induced oxidative stress may suppress adipocyte SIRT1 through down-regulation of HO-1. Consequently, this suppression of SIRT1 may result in the up-regulation of the Mineralocorticoid Receptor (MR). We further hypothesize that the induction of HO-1 would rescue SIRT1, thereby improving oxidative stress and adipocyte phenotype. To establish this hypothesis, we conducted experiments using mouse preadipocytes treated with AngII, in the presence or absence of Cobalt Protoporphyrin (CoPP), an inducer of HO-1, and Tin Mesoporphyrin (SnMP), an inhibitor of HO-1. Our data demonstrate that treatment of mouse preadipocytes with AngII leads to increased lipid accumulation, elevated levels of superoxide and inflammatory cytokines (Interleukin-6 and Tumor necrosis factor alpha), and reduced levels of adiponectin. However, these effects were attenuated by the induction of HO-1, and this attenuation was reversed by SnMP, indicating that the beneficial effects on adipocyte phenotype are modulated by HO-1. Furthermore, our findings reveal that AngII-treated preadipocytes exhibit upregulated MR levels and suppressed SIRT1 expression, which are rescued by HO-1 induction. Following treatment with CoPP and SIRT1 siRNA in mouse preadipocytes resulted in increased lipid accumulation and elevated levels of fatty acid synthase, indicating that the beneficial effects of HO-1 are modulated through SIRT1. Our study provides evidence that HO-1 restores cellular redox balance, rescues SIRT1, and attenuates the detrimental effects of AngII on adipocytes and systemic metabolic profile.

Serum metabolome perturbation in relation to noise exposure: Exploring the potential role of serum metabolites in noise-induced arterial stiffness

Noise pollution has grown to be a major public health issue worldwide. We sought to profile serum metabolite expression changes related to occupational noise exposure by untargeted metabolomics, as well as to evaluate the potential roles of serum metabolites in occupational noise-associated arterial stiffness (AS). Our study involved 30 noise-exposed industrial personnel (Lipo group) and 30 noise-free controls (Blank group). The untargeted metabolomic analysis was performed by employing a UPLC-HRMS. The associations of occupational noise and significant differential metabolites (between Blank/Lipo groups) with AS were evaluated using multivariable-adjusted generalized linear models. We performed the least absolute shrinkage and selection operator regression analysis to further screen for AS's risk metabolites. We explored 177 metabolites across 21 categories significantly differentially expressed between Blank/Lipo groups, and these metabolites were enriched in 20 metabolic pathways. Moreover, 15 metabolites in 4 classes (including food, glycerophosphocholine, sphingomyelin [SM] and triacylglycerols [TAG]) were adversely associated with AS (all P < 0.05). Meanwhile, five metabolites (homostachydrine, phosphatidylcholine (PC) (32:1e), PC (38:6p), SM (d41:2) and TAG (45:1) have been proven to be useful predictors of AS prevalence. However, none of these 15 metabolites were found to have a mediating influence on occupational noise-induced AS. Our study reveals specific metabolic changes caused by occupational noise exposure, and several metabolites may have protective effects on AS. However, the roles of serum metabolites in noise-AS association remain to be validated in future studies.

The relationship between adipose tissue RAAS activity and the risk factors of prediabetes: a systematic review and meta-analysis

METHODS

This systematic review was developed in compliance with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-2020) standards. This was accomplished by searching clinical MeSH categories in MEDLINE with full texts, EMBASE, Web of Science, PubMed, Cochrane Library, Academic Search Complete, ICTRP and ClinicalTrial.gov. Reviewers examined all the findings and selected the studies that satisfied the inclusion criteria. The Downs and Black Checklist was used to assess for bias, followed by a Review Manager v5. A Forrest plot was used for the meta-analysis and sensitivity analysis. The protocol for this review was registered with PROSPERO CRD42022320252.

RESULTS

The clinical studies (n = 2) comprised 1065 patients with prediabetes and 1103 normal controls. The RAAS measurements were completed in the adipose tissue. The RAAS components, renin and aldosterone were higher in the prediabetic (PD) compared to the control [mean difference (MD) = 0.16, 95% CI 0.16 (-0.13, 0.45), p = 0.25]. Furthermore, the PD group demonstrated higher triglycerides mean difference [MD = 7.84, 95% CI 7.84 (-9.84, 25.51), p = 0.38] and increased BMI [MD = 0.13, 95% CI 0.13 (-0.74, 0.99), p = 0.77] compared to the control. The overall quality of the studies was fair with a median score and range of 17 (16-18).

CONCLUSION

The current study highlights the relationship between increased BMI, RAAS and insulin resistance which is a predictor of prediabetes. The renin is slightly higher in the prediabetes group without any statistical significance, aldosterone is rather negatively associated with prediabetes which may be attributed to the use of anti-hypertensive treatment.