ACE2 pathway regulates thermogenesis and energy metabolism

Glycolipid Metabolic Disorders, Metainflammation, Oxidative Stress, and Cardiovascular Diseases: Unraveling Pathways

Glycolipid metabolic disorders (GLMDs) are various metabolic disorders resulting from dysregulation in glycolipid levels, consequently leading to an increased risk of obesity, diabetes, liver dysfunction, neuromuscular complications, and cardiorenal vascular diseases (CRVDs). In patients with GLMDs, excess caloric intake and a lack of physical activity may contribute to oxidative stress (OxS) and systemic inflammation. This study aimed to review the connection between GLMD, OxS, metainflammation, and the onset of CRVD. GLMD is due to various metabolic disorders causing dysfunction in the synthesis, breakdown, and absorption of glucose and lipids in the body, resulting in excessive ectopic accumulation of these molecules. This is mainly due to neuroendocrine dysregulation, insulin resistance, OxS, and metainflammation. In GLMD, many inflammatory markers and defense cells play a vital role in related tissues and organs, such as blood vessels, pancreatic islets, the liver, muscle, the kidneys, and adipocytes, promoting inflammatory lesions that affect various interconnected organs through their signaling pathways. Advanced glycation end products, ATP-binding cassette transporter 1, Glucagon-like peptide-1, Toll-like receptor-4, and sphingosine-1-phosphate (S1P) play a crucial role in GLMD since they are related to glucolipid metabolism. The consequences of this is system organ damage and increased morbidity and mortality.

Polygenic subtype identified in ACCORD trial displays a favorable type 2 diabetes phenotype in the UKBiobank population

INTRODUCTION

We previously identified a genetic subtype (C4) of type 2 diabetes (T2D), benefitting from intensive glycemia treatment in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial. Here, we characterized the population of patients that met the C4 criteria in the UKBiobank cohort.

RESEARCH DESIGN AND METHODS

Using our polygenic score (PS), we identified C4 individuals in the UKBiobank and tested C4 status with risk of developing T2D, cardiovascular disease (CVD) outcomes, and differences in T2D medications.

RESULTS

C4 individuals were less likely to develop T2D, were slightly older at T2D diagnosis, had lower HbA1c values, and were less likely to be prescribed T2D medications (P < .05). Genetic variants in MAS1 and IGF2R, major components of the C4 PS, were associated with fewer overall T2D prescriptions.

CONCLUSION

We have confirmed C4 individuals are a lower risk subpopulation of patients with T2D.

Adipose tissue plasticity mediated by the counterregulatory axis of the renin-angiotensin system: Role of Mas and MrgD receptors

The renin-angiotensin system (RAS) is an endocrine system composed of two main axes: the classical and the counterregulatory, very often displaying opposing effects. The classical axis, primarily mediated by angiotensin receptors type 1 (AT1R), is linked to obesity-associated metabolic effects. On the other hand, the counterregulatory axis appears to exert antiobesity effects through the activation of two receptors, the G protein-coupled receptor (MasR) and Mas-related receptor type D (MrgD). The local RAS in adipose organ has prompted extensive research into white adipose tissue and brown adipose tissue (BAT), with a key role in regulating the cellular and metabolic plasticity of these tissues. The MasR activation favors the brown plasticity signature in the adipose organ by improve the thermogenesis, adipogenesis, and lipolysis, decrease the inflammatory state, and overall energy homeostasis. The MrgD metabolic effects are related to the maintenance of BAT functionality, but the signaling remains unexplored. This review provides a summary of RAS counterregulatory actions triggered by Mas and MrgD receptors on adipose tissue plasticity. Focus on the effects related to the morphology and function of adipose tissue, especially from animal studies, will be given targeting new avenues for treatment of obesity-associated metabolic effects.

Angiotensin II participates in mitochondrial thermogenic functions via the activation of glycolysis in chemically induced human brown adipocytes

Brown adipocytes are potential therapeutic targets for the prevention of obesity-associated metabolic diseases because they consume circulating glucose and fatty acids for heat production. Angiotensin II (Ang II) peptide is involved in the pathogenesis of obesity- and cold-induced hypertension; however, the mechanism underlying the direct effects of Ang II on human brown adipocytes remains unclear. Our transcriptome analysis of chemical compound-induced brown adipocytes (ciBAs) showed that the Ang II type 1 receptor (AGTR1), but not AGTR2 and MAS1 receptors, was expressed. The Ang II/AGTR1 axis downregulated the expression of mitochondrial uncoupling protein 1 (UCP1). The simultaneous treatment with β-adrenergic receptor agonists and Ang II attenuated UCP1 expression, triglyceride lipolysis, and cAMP levels, although cAMP response element-binding protein (CREB) phosphorylation was enhanced by Ang II mainly through the protein kinase C pathway. Despite reduced lipolysis, both coupled and uncoupled mitochondrial respiration was enhanced in Ang II-treated ciBAs. Instead, glycolysis and glucose uptake were robustly activated upon treatment with Ang II without a comprehensive transcriptional change in glucose metabolic genes. Elevated mitochondrial energy status induced by Ang II was likely associated with UCP1 repression. Our findings suggest that the Ang II/AGTR1 axis participates in mitochondrial thermogenic functions via glycolysis.

Alternative Renin-Angiotensin System

The renin-angiotensin system is the most important peptide hormone system in the regulation of cardiovascular homeostasis. Its classical arm consists of the enzymes, renin, and angiotensin-converting enzyme, generating angiotensin II from angiotensinogen, which activates its AT1 receptor, thereby increasing blood pressure, retaining salt and water, and inducing cardiovascular hypertrophy and fibrosis. However, angiotensin II can also activate a second receptor, the AT2 receptor. Moreover, the removal of the C-terminal phenylalanine from angiotensin II by ACE2 (angiotensin-converting enzyme 2) yields angiotensin-(1-7), and this peptide interacts with its receptor Mas. When the aminoterminal Asp of angiotensin-(1-7) is decarboxylated, alamandine is generated, which activates the Mas-related G-protein-coupled receptor D, MrgD (Mas-related G-protein-coupled receptor type D). Since Mas, MrgD, and the AT2 receptor have opposing effects to the classical AT1 receptor, they and the enzymes and peptides activating them are called the alternative or protective arm of the renin-angiotensin system. This review will cover the historical aspects and the current standing of this recent addition to the biology of the renin-angiotensin system.

Maternal Brown Rice Diet during Pregnancy Promotes Adipose Tissue Browning in Offspring via Reprogramming PKA Signaling and DNA Methylation

SCOPE

Brown rice, the most consumed food worldwide, has been shown to possess beneficial effects on the prevention of metabolic diseases. However, the way in which maternal brown rice diet improves metabolism in offspring and the regulatory mechanisms remains unclear. The study explores the epigenetic regulation of offspring energy metabolic homeostasis by maternal brown rice diet during pregnancy.

METHODS AND RESULTS

Female mice are fed brown rice during pregnancy, and then body phenotypes, the histopathological analysis, and adipose tissues biochemistry assay of offspring mice are detected. It is found that maternal brown rice diet significantly reduces body weight and fat mass, increases energy expenditure and heat production in offspring. Maternal brown rice diet increases uncoupling protein 1 (UCP1) protein level and upregulates the mRNA expression of thermogenic genes in adipose tissues. Mechanistically, protein kinase A (PKA) signaling is likely responsible in the induced thermogenic program in offspring adipocytes, and the progeny adipocytes browning program is altered due to decreased level of DNA methyltransferase 1 protein and hypomethylation of the transcriptional coregulator positive regulatory domain containing 16 (PRDM16).

CONCLUSIONS

These findings demonstrate that maternal brown rice during pregnancy improves offspring mice metabolic homeostasis via promoting adipose browning, and its mechanisms may be mediated by DNA methylation reprogramming.

The Role Played by Mitochondria in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) refers to an endocrine disorder syndrome that are correlated with multiple organs and systems. PCOS has an effect on women at all stages of their lives, and it has an incidence nearly ranging from 6% to 20% worldwide. Mitochondrial dysfunctions (e.g., oxidative stress, dynamic imbalance, and abnormal quality control system) have been identified in patients and animal models of PCOS, and the above processes may play a certain role in the development of PCOS and its associated complications. However, their specific pathogenic roles should be investigated in depth. In this review, recent studies on the mechanisms of action of mitochondrial dysfunction in PCOS and its associated clinical manifestations are summarized from the perspective of tissues and organs, and some studies on the treatment of the disease by improving mitochondrial function are reviewed to highlight key role of mitochondrial dysfunction in this syndrome.

Beyond energy balance regulation: The underestimated role of adipose tissues in host defense against pathogens

Although the adipose tissue (AT) is a central metabolic organ in the regulation of whole-body energy homeostasis, it is also an important endocrine and immunological organ. As an endocrine organ, AT secretes a variety of bioactive peptides known as adipokines - some of which have inflammatory and immunoregulatory properties. As an immunological organ, AT contains a broad spectrum of innate and adaptive immune cells that have mostly been studied in the context of obesity. However, overwhelming evidence supports the notion that AT is a genuine immunological effector site, which contains all cell subsets required to induce and generate specific and effective immune responses against pathogens. Indeed, AT was reported to be an immune reservoir in the host's response to infection, and a site of parasitic, bacterial and viral infections. In addition, besides AT's immune cells, preadipocytes and adipocytes were shown to express innate immune receptors, and adipocytes were reported as antigen-presenting cells to regulate T-cell-mediated adaptive immunity. Here we review the current knowledge on the role of AT and AT's immune system in host defense against pathogens. First, we will summarize the main characteristics of AT: type, distribution, function, and extraordinary plasticity. Second, we will describe the intimate contact AT has with lymph nodes and vessels, and AT immune cell composition. Finally, we will present a comprehensive and up-to-date overview of the current research on the contribution of AT to host defense against pathogens, including the respiratory viruses influenza and SARS-CoV-2.

Central angiotensin 1-7 triggers brown fat thermogenesis

We tested the hypothesis that third ventricular (3V) injections of angiotensin 1-7 (Ang 1-7) increases thermogenesis in brown adipose tissue (BAT), and whether the Mas receptor mediates this response. First, in male Siberian hamsters (n = 18), we evaluated the effect of Ang 1-7 in the interscapular BAT (IBAT) temperature and, using selective Mas receptor antagonist A-779, the role of Mas receptor in this response. Each animal received 3V injections (200 nL), with 48 h intervals: saline; Ang 1-7 (0.03, 0.3, 3, and 30 nmol); A-779 (3 nmol); and Ang 1-7 (0.3 nmol) + A-779 (3 nmol). IBAT temperature increased after 0.3 nmol Ang 1-7 compared with Ang 1-7 + A-779 at 20, 30, and 60 min. Also, 0.3 nmol Ang 1-7 increased IBAT temperature at 10 and 20 min, and decreased at 60 min compared with pretreatment. IBAT temperature decreased after A-779 at 60 min and after Ang 1-7 + A-779 at 30 and 60 min compared with the respective pretreatment. A-779 and Ang 1-7 + A-779 decreased core temperature at 60 min compared with 10 min. Then, we evaluated blood and tissue Ang 1-7 levels, and the expression of hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL) in IBAT. Male Siberian hamsters (n = 36) were killed 10 min after one of the injections. No changes were observed in blood glucose, serum and IBAT Ang 1-7 levels, and ATGL. Ang 1-7 (0.3 nmol) increased p-HSL expression compared with A-779 and increased p-HSL/HSL ration compared with other injections. Ang 1-7 and Mas receptor immunoreactive cells were found in brain regions that coincide with the sympathetic nerves outflow to BAT. In conclusion, 3V injection of Ang 1-7 induced thermogenesis in IBAT in a Mas receptor-dependent manner.

Angiotensin(1-7) attenuates visceral adipose tissue expansion and lipogenesis by suppression of endoplasmic reticulum stress via Mas receptor

BACKGROUND

White adipose tissue can be classified based on its location as subcutaneous and visceral fat, and the latter accumulation is reported to be more detrimental to metabolism. Endoplasmic reticulum (ER) stress has been demonstrated to regulate lipogenesis. The peptide angiotensin(1-7) [Ang(1-7)], which can be produced from angiotensin II (AngII) by angiotensin-converting enzyme 2 (ACE2), plays its role through Mas receptor, also participates in the regulation of lipid metabolism in adipose tissue, however, whether ER stress is involved in the mechanism remains unclear. Therefore, we aimed to explore the role of Ang(1-7) pathway in regulating visceral adipose tissue expansion and ER stress.

METHODS

ACE2 knockout (KO), Mas KO and C57BL/6 J mice were fed with high fat diet. Db/db mice were treated with either normal saline, Ang(1-7) or Ang(1-7) combined with Mas receptor inhibitor A779 using mini osmotic pumps. Fat mass was weighted, fat distribution was evaluated by MRI, and lipid profile and adipokines in epididymal adipose tissue were measured by ELISA kits, and histology of epididymal adipose tissue was also analyzed in multiple animal models. Additionally, differentiated 3T3-L1 cells were pre-loaded with palmitic acid to induce ER stress, then treated with drugs as those administrated to db/db mice. ER stress and lipogenesis related proteins in mice adipose and differentiated 3T3L-1 cells were analyzed by Western blot.

RESULTS

ACE2 or Mas KO mice exhibited increased visceral adipose tissue, adipocyte size and protein expression of lipogenesis and ER stress related markers in epididymal adipose tissue compared to wild-type mice. Db/db mice treated with Ang(1-7) displayed decreased visceral fat mass, adipocyte size and protein expression of lipogenesis and ER stress markers in epididymal adipose tissue compared to those treated with normal saline, while A779 partly attenuated these effects. Additionally, Ang(1-7) improved ER stress and lipogenesis markers in differentiated 3T3-L1 cells pre-loaded with palmitic acid.

CONCLUSIONS

Our findings indicated that Ang(1-7) attenuated visceral adipose tissue expansion and lipogenesis by suppression of ER stress via Mas receptor. The present study provides a potential perspective for Ang(1-7) for the therapeutics of obesity and related disorders.

Maternal Supplementation of Probiotics, Prebiotics or Postbiotics to Prevent Offspring Metabolic Syndrome: The Gap between Preclinical Results and Clinical Translation

Metabolic syndrome (MetS) is an extremely prevalent complex trait and it can originate in early life. This concept is now being termed the developmental origins of health and disease (DOHaD). Increasing evidence supports that disturbance of gut microbiota influences various risk factors of MetS. The DOHaD theory provides an innovative strategy to prevent MetS through early intervention (i.e., reprogramming). In this review, we summarize the existing literature that supports how environmental cues induced MetS of developmental origins and the interplay between gut microbiota and other fundamental underlying mechanisms. We also present an overview of experimental animal models addressing implementation of gut microbiota-targeted reprogramming interventions to avert the programming of MetS. Even with growing evidence from animal studies supporting the uses of gut microbiota-targeted therapies start before birth to protect against MetS of developmental origins, their effects on pregnant women are still unknown and these results require further clinical translation.

Angiotensin II Promotes White Adipose Tissue Browning and Lipolysis in Mice

Emerging evidence has revealed that all components of the renin-angiotensin system (RAS) are present in adipose tissue. Angiotensin II (Ang II), the major bioactive component of the RAS, has been recognized as an adipokine involved in regulating energy homeostasis. However, the precise role of Ang II in white adipose tissue (WAT) remodeling remains to be elucidated. In this present study, C57BL/C male mice were continuously infused with different doses of Ang II (1.44 mg/kg/d or 2.5 mg/kg/d) or saline for 2 weeks and treated with or without the Ang II type 1 receptor blocker valsartan. H&E staining and immunohistochemistry were conducted to investigate the white-to-brown fat conversion. The level of serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) was measured. RNA sequencing was employed to explore the differentially expressed genes and their enriched pathways between control and Ang II groups. Our results showed that Ang II substantially resulted in loss of body weight and fat mass. Most importantly, Ang II treatment induced WAT browning in mice, which was partially attenuated by valsartan treatment. Furthermore, Ang II perturbed the serum lipid profiles. Ang II treatment elevated serum levels of TC, TG, LDL-C, and HDL-C in mice. Mechanistically, thermogenesis, cell respiration, and lipid metabolism-associated mRNAs showed significantly increased expression profiling in Ang II-treated WATs compared with control WATs. Moreover, we found that Ang II treatment enhanced AMPK phosphorylation in adipocytes. Therefore, Ang II promotes WAT browning and lipolysis via activating the AMPK signaling pathway.

Amino acid sensor GCN2 promotes SARS-CoV-2 receptor ACE2 expression in response to amino acid deprivation

Angiotensin-converting enzyme 2 (ACE2) has been identified as a primary receptor for severe acute respiratory syndrome coronaviruses 2 (SARS-CoV-2). Here, we investigated the expression regulation of ACE2 in enterocytes under amino acid deprivation conditions. In this study, we found that ACE2 expression was upregulated upon all or single essential amino acid deprivation in human colonic epithelial CCD841 cells. Furthermore, we found that knockdown of general control nonderepressible 2 (GCN2) reduced intestinal ACE2 mRNA and protein levels in vitro and in vivo. Consistently, we revealed two GCN2 inhibitors, GCN2iB and GCN2-IN-1, downregulated ACE2 protein expression in CCD841 cells. Moreover, we found that increased ACE2 expression in response to leucine deprivation was GCN2 dependent. Through RNA-sequencing analysis, we identified two transcription factors, MAFB and MAFF, positively regulated ACE2 expression under leucine deprivation in CCD841 cells. These findings demonstrate that amino acid deficiency increases ACE2 expression and thereby likely aggravates intestinal SARS-CoV-2 infection.

Amino acid deprivation increases ACE2 expression in the gut, potentially aggravating SARS-CoV-2 infection.