Mas receptor deficiency is associated with worsening of lipid profile and severe hepatic steatosis in ApoE-knockout mice.

The classical renin-angiotensin system pathway has been recently updated with the identification of additional molecules [such as angiotensin converting enzyme 2, ANG-(1-7), and Mas receptor] that might improve some pathophysiological processes in chronic inflammatory diseases. In the present study, we focused on the potential protective role of Mas receptor activation on mouse lipid profile, liver steatosis, and atherogenesis. Mas/apolipoprotein E (ApoE)-double-knockout (DKO) mice (based on C57BL/6 strain of 20 wk of age) were fed under normal diet and compared with aged-matched Mas and ApoE-single-knockout (KO), as well as wild-type mice. Mas/ApoE double deficiency was associated with increased serum levels of atherogenic fractions of cholesterol, triglycerides, and fasting glucose compared with wild-type or single KO. Serum levels of HDL or leptin in DKO were lower than in other groups. Hepatic lipid content as well as alanine aminotransferase serum levels were increased in DKO compared with wild-type or single-KO animals. Accordingly, the hepatic protein content of mediators related to atherosclerotic inflammation, such as peroxisome proliferator-activated receptor-α and liver X receptor, was altered in an adverse way in DKO compared with ApoE-KO. On the other hand, DKO mice did not display increased atherogenesis and intraplaque inflammation compared with ApoE-KO group. In conclusion, Mas deletion in ApoE-KO mice was associated with development of severe liver steatosis and dyslipidemia without affecting concomitant atherosclerosis. Mas receptor activation might represent promising strategies for future treatments targeting both hepatic and metabolic alterations in chronic conditions clustering these disorders.

Brown adipose tissue transcriptome unveils an important role of the Beta-alanine/alamandine receptor, MrgD, in metabolism.

Alamandine is a recently described heptapeptide component of the renin-angiotensin system (RAS), and its effects are mediated by the receptor Mas-related G protein-coupled receptor D (MrgD) RAS represents an important link between obesity and its consequences by directly modulating the thermogenesis and brown adipose tissue (BAT) function. The alamandine/MrgD metabolic effects and signaling remain unexplored. In this context, the main goal of the present study was to assess the metabolic consequences of MrgD genetic ablation in C57BL6/J mice by evaluating brown adipose tissue RNA sequencing. The main results showed that MrgD-KO mice have diminished brown adipose tissue and that a high-glucose diet (HG) decreased both circulating alamandine levels and MrgD expression in BAT from wild-type mice (WT). BAT transcriptome reveals that MrgD-KO HG mice regulated 45 genes, while WT HG mice regulated 1,148 genes. MrgD-KO mice fed a standard diet (ST) compared with WT ST mice regulated 476 genes, of which 445 genes were downregulated. BAT uses the MrgD receptor to display a normal pattern of gene expression and to respond, like WT mice, to an HG diet. In conclusion, the MrgD signaling is important for the metabolic regulation and manutention of BAT functionality.

Genetic deletion of Mas receptor in FVB/N mice impairs cardiac use of glucose and lipids.

Angiotensin-(1-7) is a biologically active product of the renin-angiotensin system cascade and exerts inhibitory effects on inflammation, vascular and cellular growth mechanisms signaling through the G protein-coupled Mas receptor. The major purpose of the present study was to investigate the use of glucose and fatty acids by cardiac tissue in Mas knockout mice models. Serum levels of glucose, lipids, and insulin were measured in Mas-deficient and wild-type FVB/N mice. To investigate the cardiac use of lipids, the lipoprotein lipase, the gene expression of peroxisome proliferator-activated receptor alpha; carnitine palmitoyltransferase I and acyl-CoA oxidase were evaluated. To investigate the cardiac use of glucose, the insulin signaling through Akt/GLUT4 pathway, glucose-6-phosphate (G-6-P) and fructose-6-phosphate (F-6-P) glycolytic intermediates, in addition to ATP, lactate and the glycogen content were measured. Despite normal body weight, cholesterol and insulin, Mas-Knockout mice presented hyperglycemia and hypertriglyceridemia, impaired insulin signaling, through reduced phosphorylation of AKT and decreased translocation of GLUT4 in response to insulin, with subsequent decrease of the cardiac G-6-P and F-6-P. Lactate production and glycogen content were not altered in Mas-KO hearts. Mas-KO presented reduced cardiac lipoprotein lipase activity and decreased translocation of CD36 in response to insulin. The expression of peroxisome proliferator-activated receptor alpha and carnitine palmitoyltransferase I genes were lower in Mas-KO animals compared to wild-type animals. The ATP content of Mas-KO hearts was smaller than in wild-type. The present results suggest that genetic deletion of Mas produced a devastating effect on cardiac use of glucose and lipids, leading to lower energy efficiency in the heart.

Oral Probiotic Bifidobacterium Longum Supplementation Improves Metabolic Parameters and Alters the Expression of the Renin-Angiotensin System in Obese Mice Liver.

BACKGROUND: Obesity and non-alcoholic fatty liver disease (NAFLD) have been increasing at an alarming rate worldwide. Bifidobacterium longum (BL), a common member of the human gut microbiota, has important health benefits through several mechanisms. OBJECTIVES: We evaluated the BL supplementation effects on body metabolism and renin-angiotensin components hepatic expression in mice fed a high-fat diet. METHODS: Thirty-two male mice were divided into four groups: standard diet + placebo (ST), standard diet + Bifidobacterium longum (ST + BL), high-fat diet + placebo (HFD) and high-fat diet + Bifidobacterium longum (HFD + BL). Following the obesity induction period, the ST + BL and HFD + BL groups were supplemented with Bifidobacterium longum for 4 weeks. Then, body, biochemical, histological and molecular parameters were evaluated. RESULTS: HFD + BL mice had a significant decrease in adipose tissue mass and blood glucose levels, as well as a significant reduction in blood glucose during an intraperitoneal glucose tolerance test. The treatment also resulted in reduced levels of total cholesterol and hepatic fat accumulation. Moreover, we observed an increase in angiotensin converting enzyme 2 (ACE2) and Mas receptor (MASR) expression levels in BL-treated obese mice. CONCLUSIONS: These data demonstrate that BL may have the potential to prevent obesity and NAFLD by modulating the mRNA expression of renin-angiotensin system components.

Oral Angiotensin-(1-7) Peptide Modulates Intestinal Microbiota Improving Metabolic Profile in Obese Mice.

BACKGROUND: Obesity is a serious health problem that dysregulate Renin-Angiotensin System (RAS) and intestinal microbiota. OBJECTIVE: The present study aimed to evaluate the Angiotensin-(1-7) [ANG-(1-7)] oral formulation effects on obese mice intestinal microbiota. METHODS: Mice were divided into four groups: obese and non-obese treated with ANG-(1-7) and obese and non-obese without ANG-(1-7) during four weeks. RESULTS: We observed a significant decrease in the fasting plasma glucose, total cholesterol, triglycerides, and Low-density lipoprotein levels and increased High-density lipoprotein in animals treated with ANG-(1-7). The histological analysis showed intestinal villi height reduction in mice treated with ANG-(1-7). Additionally, increased Bacteroidetes and decreased Firmicutes (increased Bacteroidetes/ Firmicutes ratio) and Enterobacter cloacae populations were observed in the High-Fat Diet + ANG-(1-7) group. Receptor toll-like 4 (TLR4) intestinal mRNA expression was reduced in the HFD+ANG-(1-7) group. Finally, the intestinal expression of the neutral amino acid transporter (B0AT1) was increased in animals treated with ANG-(1-7), indicating a possible mechanism associated with tryptophan uptake. CONCLUSION: The results of the present study suggest for the first time an interaction between oral ANG-(1-7) and intestinal microbiota modulation.

Localization of angiotensin-(1-7) and Mas receptor in the rat ovary throughout the estrous cycle.

We have previously demonstrated the presence of Angiotensin (Ang)-(1-7) in rat ovary homogenates and its stimulatory effect on estradiol and progesterone production. The present study was undertaken to identify the cellular localization of Ang-(1-7) and its receptor Mas in the rat ovary in the different phases of the estrous cycle. Ang-(1-7) and Mas were localized by immunohistochemistry and Mas mRNA expression was assessed by RT-PCR. Immunostaining for both Ang-(1-7) and Mas was found in all phases of the estrous cycle, particularly in the thecal and interstitial cells, as well as in regressing corpora lutea. However, granulosa cells were positive only in antral and preovulatory follicles at proestrus and estrus phases. This pattern contrasted with the distribution of the octapeptide Ang II, which was abundant in granulosa but not in theca cells. In addition, the expression of Mas mRNA was demonstrated in all estrous cycle phases. Angiotensin-converting enzyme activity did not vary between estrous cycle phases, whereas prolyl endopeptidase activity was significantly higher in diestrus and neutral endopeptidase activity was significantly higher in metestrus. These data provide the first evidence that new RAS components are dynamically expressed in the ovary across the rat estrous cycle. Further functional studies should clarify the role of Ang-(1-7) signaling through Mas receptor in the regulation of ovarian physiology.

Genetic deletion of the angiotensin-(1-7) receptor Mas leads to glomerular hyperfiltration and microalbuminuria.

Angiotensin-(1-7), an active fragment of both angiotensins I and II, generally opposes the vascular and proliferative actions of angiotensin II. Here we evaluated effects of the angiotensin-(1-7) receptor Mas on renal physiology and morphology using Mas-knockout mice. Compared to the wild-type animals, Mas knockout mice had significant reductions in urine volume and fractional sodium excretion without any significant change in free-water clearance. A significantly higher inulin clearance and microalbuminuria concomitant with a reduced renal blood flow suggest that glomerular hyperfiltration occurs in the knockout mice. Histological analysis found reduced glomerular tuft diameter and increased expression of collagen IV and fibronectin in the both the mesangium and interstitium, along with increased collagen III in the interstitium. These fibrogenic changes and the renal dysfunction of the knockout mice were associated with an upregulation of angiotensin II AT1 receptor and transforming growth factor-beta mRNA. Our study suggests that Mas acts as a critical regulator of renal fibrogenesis by controlling effects transduced through angiotensin II AT1 receptors in the kidney.

The role of the angiotensin II type I receptor blocker telmisartan in the treatment of non-alcoholic fatty liver disease: a brief review.

Non-alcoholic fatty liver disease (NAFLD) is currently considered an important component of metabolic syndrome (MetS). The spectrum of NAFLD includes conditions that range from simple hepatic steatosis to non-alcoholic steatohepatitis. NAFLD is correlated with liver-related death and is predicted to be the most frequent indication for liver transplantation by 2030. Insulin resistance is directly correlated to the central mechanisms of hepatic steatosis in NAFLD patients, which is strongly correlated to the imbalance of the renin-angiotensin system, that is involved in lipid and glucose metabolism. Among the emerging treatment approaches for NAFLD is the anti-hypertensive agent telmisartan, which has positive effects on liver, lipid, and glucose metabolism, especially through its action on the renin-angiotensin system, by blocking the ACE/AngII/AT1 axis and increasing ACE2/Ang(1-7)/Mas axis activation. However, treatment with this drug is only recommended for patients with an established indication for anti-hypertensive therapy. Thus, there is an increased need for large randomized controlled trials with the aim of elucidating the effects of telmisartan on liver disease, especially NAFLD. From this perspective, the present review aims to provide a brief examination of the pathogenesis of NAFLD/NASH and the role of telmisartan on preventing liver disorders and thus to improve the discussion on potential therapies.

Oral administration of angiotensin-(1-7) ameliorates type 2 diabetes in rats.

UNLABELLED: Diabetes mellitus type 2 (DM2) is a disease with increasing importance in modern societies and insufficient treatment options. Pharmacological stimulation of insulin signaling, which is blunted in DM2, is a promising approach to treat this disease. It has been shown that activation of the angiotensin (Ang)-(1-7)/Mas axis of the renin-angiotensin system leads to an improved glucose uptake. In this study, we intended to evaluate, whether this effect could be exploited therapeutically. We first confirmed that Ang-(1-7) improves insulin signaling and glucose uptake in vitro in cultured cardiomyocytes. We then evaluated the therapeutic effect of a newly developed hydro-xypropyl-ß-cyclodextrin-based Ang-(1-7) nano-formulation in a novel transgenic rat model of inducible insulin resistance and DM2. The chronic administration of this compound prevented the marked elevation in blood glucose levels in these rats at a dose of 30 µg/kg, reversed the established hyperglycemic state at a dose of 100 µg/kg, and resulted in improved insulin sensitivity, reduced plasma insulin and decreased diabetic nephropathy. In conclusion, an oral Ang-(1-7) formulation reverses hyperglycemia and its consequences in an animal model of DM2 and represents a novel therapeutic option for the treatment of DM2 and other cardio-metabolic diseases. KEY MESSAGE: A novel rat model with inducible diabetes can be used to evaluate new therapies. Angiotensin-(1-7) is effective in an oral formulation packaged in cyclodextrine. Angiotensin-(1-7) is a promising antidiabetic drug.

An orally active angiotensin-(1-7) inclusion compound and exercise training produce similar cardiovascular effects in spontaneously hypertensive rats.

Low angiotensin-(1-7) (Ang-(1-7)) concentration is observed in some cardiovascular diseases and exercise training seems to restore its concentration in the heart. Recently, a novel formulation of an orally active Ang-(1-7) included in hydroxy-propyl-beta-cyclodextrin (HPB-CD) was developed and chronically administered in experimental models of cardiovascular diseases. The present study examined whether chronic administration of HPB-CD/Ang-(1-7) produces beneficial cardiovascular effects in spontaneously hypertensive rats (SHR), as well as to compare the results obtained with those produced by exercise training. Male SHR (15-week old) were divided in control (tap water) or treated with HPB-CD/Ang-(1-7) (corresponding to 30µgkg(-1)day(-1) of Ang-(1-7)) by gavage, concomitantly or not to exercise training (treadmill, 10 weeks). After chronic treatment, hemodynamic, morphometric and molecular analysis in the heart were performed. Chronic HPB-CD/Ang-(1-7) decreased arterial blood pressure (BP) and heart rate in SHR. The inclusion compound significantly improved left ventricular (LV) end-diastolic pressure, restored the maximum and minimum derivatives (dP/dT) and decreased cardiac hypertrophy index in SHR. Chronic treatment improved autonomic control by attenuating sympathetic modulation on heart and vessels and the SAP variability, as well as increasing parasympathetic modulation and HR variability. Overall results were similar to those obtained with exercise training. These results show that chronic treatment with the HPB-CD/Ang-(1-7) inclusion compound produced beneficial effects in SHR resembling the ones produced by exercise training. This observation reinforces the potential cardiovascular therapeutic effect of this novel peptide formulation.

Association of an oral formulation of angiotensin-(1-7) with atenolol improves lipid metabolism in hypertensive rats.

The ß-adrenergic blockers and antagonists of the renin-angiotensin system (RAS) are among the drugs that present better results in the control of cardio-metabolic diseases. The aim of the present study was to evaluate the effect of the association of the ß-blocker, atenolol, and an oral formulation of Ang-(1-7) on lipid metabolism in spontaneously hypertensive rats (SHR). The main results showed that SHR treated with oral formulation of Ang-(1-7) in combination to atenolol have an improvement of lipid metabolism with a reduction of total plasma cholesterol, improvement of oral fat load tolerance and an increase in the lipolytic response stimulated by the ß-adrenergic agonist, isoproterenol, without modification of resting glucose or insulin sensitivity in adipocytes. In conclusion, we showed that administration of an Ang-(1-7) oral formulation in association with a ß-blocker induces beneficial effects on dyslipidemia treatment associated with hypertension.

Immunohistochemical analysis of TIMP-3 and MMP-9 in actinic keratosis, squamous cell carcinoma of the skin, and basal cell carcinoma.

The expression of metalloproteinases and their inhibitors has been related to different invasive and metastatic potentials in cancer. This study aims to investigate the immunohistochemical expression of TIMP-3 and MMP-9 in samples of basal cell carcinoma (BCC), squamous cell carcinoma of the skin (SCC), and actinic keratosis (AK). Immunohistochemistry was performed to evaluate the expression of TIMP-3 and MMP-9 in samples of BCC (n=22), SCC (n=10), and AK (n=15). Ten fields of both tumor parenchyma and tumor stroma were photographed and counted in image software. The ratio of positive cells to total cells was used to quantify the staining. A higher expression of MMP-9 was found in tumor stroma of SCC compared to BCC and AK. No significant differences in TIMP-3 expression were observed among the groups. Considering the well-described differences between these neoplasms, these results provide additional evidence of the role of MMP-9 in tumor invasiveness of keratinocyte-derived tumors.

Exercise induces renin-angiotensin system unbalance and high collagen expression in the heart of Mas-deficient mice.

The renin-angiotensin system (RAS) is involved in the cardiac and vascular remodeling associated with cardiovascular diseases. Angiotensin (Ang) II/AT(1) axis is known to promote cardiac hypertrophy and collagen deposition. In contrast, Ang-(1-7)/Mas axis opposes Ang II effects in the heart producing anti-trophic and anti-fibrotic effects. Exercise training is known to induce cardiac remodeling with physiological hypertrophy without fibrosis. We hypothesize that cardiac remodeling induced by chronic exercise depends on the action of Ang-(1-7)/Mas axis. Thus, we evaluated the effect of exercise training on collagen deposition and RAS components in the heart of FVB/N mice lacking Mas receptor (Mas-KO). Male wild-type and Mas-KO mice were subjected to a moderate-intense swimming exercise training for 6 weeks. The left ventricle (LV) of the animals was sectioned and submitted to qRT-PCR and histological analysis. Circulating and tissue angiotensin peptides were measured by RIA. Sedentary Mas-KO presented a higher circulating Ang II/Ang-(1-7) ratio and an increased ACE2 expression in the LV. Physical training induced in Mas-KO and WT a similar cardiac hypertrophy accompanied by a pronounced increase in collagen I and III mRNA expression. Trained Mas-KO and trained WT presented increased Ang-(1-7) in the blood. However, only in trained-WT there was an increase in Ang-(1-7) in the LV. In summary, we showed that deletion of Mas in FVB/N mice produced an unbalance in RAS equilibrium increasing Ang II/AT(1) arm and inducing deleterious cardiac effects as deposition of extracellular matrix proteins. These data indicate that Ang-(1-7)/Mas axis is an important counter-regulatory mechanism in physical training mediate cardiac adaptations.

Oral administration of an angiotensin-converting enzyme 2 activator ameliorates diabetes-induced cardiac dysfunction.

We evaluated the hypothesis that activation of endogenous angiotensin-converting enzyme (ACE) 2 would improve cardiac dysfunction induced by diabetes. Ten days after diabetes induction (streptozotocin, 50 mg/kg, i.v.), male Wistar rats were treated with the ACE2 activator 1-[[2-(dimethylamino)ethyl]amino]-4-(hydroxymethyl)-7-[[(4-methylphenyl)sulfonyl]oxy]-9H-xanthen-9-one (XNT, 1 mg/kg/day, gavage) or saline (control) for 30 days. Echocardiography was performed to analyze the cardiac function and kinetic fluorogenic assays were used to determine cardiac ACE and ACE2 activities. Cardiac ACE2, ACE, Mas receptor, AT(1) receptor, AT(2) receptor and collagen types I and III mRNA and ACE2, ACE, Mas, AT(1) receptor, AT(2) receptor, ERK1/2, Akt, AMPK-α and AMPK-ß(1) protein were measured by qRT-PCR and western blotting techniques, respectively. Histological sections of hearts were analyzed to evaluate the presence of hypertrophy and fibrosis. Diabetic animals presented hyperglycemia and diastolic dysfunction along with cardiac hypertrophy and fibrosis. XNT treatment prevented further increase in glycemia and improved the cardiac function, as well as the hypertrophy and fibrosis. These effects were associated with increases in cardiac ACE2/ACE ratios (activity: ~26%; mRNA: ~113%; and protein: ~188%) and with a decrease in AT(1) receptor expression. Additionally, XNT inhibited ERK1/2 phosphorylation and prevented changes in AMPK-α and AMPK-ß(1) expressions. XNT treatment did not induce any significant change in AT(2) receptor and Akt expression. These results indicate that activation of intrinsic cardiac ACE2 by oral XNT treatment protects the heart against diabetes-induced dysfunction through mechanisms involving ACE, ACE2, ERK1/2, AMPK-α and AMPK-ß(1) modulations.

Carbohydrate-enriched diet impairs cardiac performance by decreasing the utilization of fatty acid and glucose.

AIMS: We hypothesized that a high-carbohydrate diet affects the cardiac performance by interfering in the metabolic steps involved in energy transfer in this organ. To verify this, we investigated the myocardial utilization of different substrates and contractile function in rats fed a high-carbohydrate diet, under normal flow and ischemia. METHODS: and RESULTS: Male Wistar rats were fed over 9 days with standard (39.5% carbohydrate, 8% fiber) or high-carbohydrate diet (58% carbohydrate) and, afterwards, their cardiac function was examined using isolated heart preparations. The high-carbohydrate diet decreased the activity of the lipoprotein lipase, utilization of fatty acids, expression of the gene of peroxisome proliferator-activated receptor α and its target enzymes. In addition, decreased GLUT4 mass, glucose uptake, glycogen content and glycolytic intermediates were also observed. High-carbohydrate hearts displayed weaker activation of the glycolytic pathway during ischemia, according to minor production of lactate, in relation to control hearts. The functional impairment caused by high-carbohydrate diet shown by the decrease in the ventricular systolic strength, +dT/dt and -dT/dt was, at least in part, due to the low availability of adenosine triphosphate (ATP). CONCLUSION: Our data suggest that a high-carbohydrate diet can damage myocardial contractile function by decreasing the cardiac utilization of glucose and fatty acids and, consequently, the ATP pool.

Gonadotropin stimulation increases the expression of angiotensin-(1--7) and MAS receptor in the rat ovary.

We have previously shown the presence of immunoreactive angiotensin-(1-7) [Ang-(1-7)] in rat ovary homogenate and its stimulatory effect on estradiol and progesterone production in vitro. In the current study, we investigated the presence and cellular distribution of Ang-(1-7) and the Mas receptor, the expression of Mas and angiotensin-converting enzyme 2 (ACE2) messenger RNA (mRNA), and the enzymatic activity in the rat ovary following gonadotropin stimulation in vivo. Immature female Wistar rats (25 days old) were injected subcutaneously (SC) with equine chorionic gonadotropin (eCG, 20 IU in 0.2 mL) or vehicle 48 hours before euthanasia. Tissue distributions of Ang-(1-7), Mas receptor, and ACE2 were evaluated by immunohistochemistry, along with angiotensin II (Ang II) localization, while the mRNA expression levels of Mas receptor and ACE2 were evaluated by real-time polymerase chain reaction (PCR). In addition, we determined the activity of neutral endopeptidase (NEP), prolyl endopeptidase (PEP), and ACE by fluorometric assays. After eCG treatment, we found strong immunoreactivity for Ang-(1-7) and Mas primarily in the theca-interstitial cells, while Ang II appeared in the granulosa but not in the thecal layer. Equine chorionic gonadotropin treatment increased Mas and ACE2 mRNA expression compared with control animals (3.3- and 2.1-fold increase, respectively; P < .05). Angiotensin-converting enzyme and NEP activities were lower, while PEP activity was higher in the eCG-treated rats (P < .05). These data show gonadotropin-induced changes in the ovarian expression of Ang-(1-7), Mas receptor, and ACE2. These findings suggest that the renin-angiotensin system (RAS) branch formed by ACE2/Ang-(1-7)/Mas, fully expressed in the rat ovary and regulated by gonadotropic hormones, could play a role in the ovarian physiology.