Cardiovascular disease remains a worldwide public health concern, despite decades of research and the availability of numerous targeted therapies. While the intrinsic physiological mechanisms regulating cardiovascular function are similar between males and females, marked sex differences are established in terms of cardiovascular disease onset, pathophysiology, manifestation, susceptibility, prevalence, treatment responses and outcomes in animal models and clinical populations. Premenopausal females are generally protected from cardiovascular disease when compared to men of similar age, and tend to develop cardiovascular complications later in life following menopause. Emerging evidence suggests this cardioprotection in females is, in part, attributed to sex differences in hormonal regulators such as the renin-angiotensin system. To date, research has largely focused on canonical renin-angiotensin system pathways, and shown that premenopausal females are protected from cardiovascular derangements produced by activation of angiotensin II pathways. More recently, a vasodilatory arm of the renin-angiotensin system has emerged that is characterized by angiotensin-(1-7), angiotensin-converting enzyme 2, and Mas receptors. Emerging studies provide evidence for a shift towards these cardioprotective angiotensin-(1-7) pathways in females, with effects modulated by interactions with estrogen. Despite well-established sex differences, female comparison studies on cardiovascular outcomes are lacking at both the preclinical and clinical levels. Furthermore, there are no specific guidelines in place for treatment of cardiovascular disease in men versus women, including for therapies targeting the renin-angiotensin system. This review summarizes current knowledge of sex differences in cardiovascular actions of the renin-angiotensin system, focusing on interactions with gonadal hormones, emerging data for protective angiotensin-(1-7) pathways, and potential clinical implications for established and novel therapies.Terms of use and reuse: academic research for non-commercial purposes, see here for full terms. https://www.springer.com/aamterms-v1

Obesity is a chronic state of energy imbalance that represents a major public health problem and greatly increases the risk for developing hypertension, hyperglycemia, and a multitude of related pathologies that encompass the metabolic syndrome. The underlying mechanisms and optimal treatment strategies for obesity, however, are still not fully understood. The control of energy balance involves the actions of circulating hormones on a widely distributed network of brain regions involved in the regulation of food intake and energy expenditure, including the arcuate nucleus of the hypothalamus. While obesity is known to disrupt neurocircuits controlling energy balance, including those in the hypothalamic arcuate nucleus, the pharmacological targeting of these central mechanisms often produces adverse cardiovascular and other off-target effects. This highlights the critical need to identify new anti-obesity drugs that can activate central neurocircuits to induce weight loss without negatively impacting blood pressure control. The renin–angiotensin system may provide this ideal target, as recent studies show this hormonal system can engage neurocircuits originating in the arcuate nucleus to improve energy balance without elevating blood pressure in animal models. This review will summarize the current knowledge of renin–angiotensin system actions within the arcuate nucleus for control of energy balance, with a focus on emerging roles for angiotensin II, prorenin, and angiotensin-(1–7) pathways.

Angiotensin (Ang)‐(1‐7), a protective hormone of the renin‐angiotensin system, has emerged as a novel target to improve cardiovascular and metabolic functions in animal models. In addition to blood pressure lowering effects, recent studies from our laboratory and others have shown that Ang‐(1‐7) can promote insulin sensitization and weight loss in obese rodents. Our recent preliminary findings suggest these effects are centrally‐mediated, with Ang‐(1‐7) mas receptors (MasR) widely distributed to the arcuate nucleus of the hypothalamus. In particular, we found that MasR are highly colocalized with proopiomelanocortin (POMC)‐containing neurons in this brain region, neurons which when activated reduce food intake and increase energy expenditure to promote weight loss as well as improve insulin sensitivity. The importance of MasR localized to POMC neurons in metabolic functions, however, is currently unknown. In this study, we tested the hypothesis MasR expressed in POMC neurons are important for normal control of energy balance and glucose homeostasis. To test this, mice containing conditional knockout alleles of the Ang‐(1‐7) MasR were crossed with POMC‐Cre mice to specifically delete MasR from POMC neurons (POMCMasR‐KO). Body mass and composition, insulin sensitivity, and glucose tolerance were measured in male and female POMCMasR‐KO mice and wild‐type littermates (n=6‐11/group) at 8 weeks of age on a standard chow diet. Despite similar fasting glucose and insulin levels, male POMCMasR‐KO mice had worsened insulin sensitivity compared with wild‐type littermates (area under the curve for decrease in glucose from baseline in response to intraperitoneal insulin: ‐2134±1071 vs. ‐6531±1507, respectively; p=0.029), with no differences in body mass, adiposity, lean mass, or glucose tolerance. In female mice, there was no effect of POMC MasR deletion on any of the metabolic outcomes tested. These findings suggest that MasR localized to POMC neurons provide tonic and sex‐specific modulation of insulin sensitivity in mice. Additional studies are needed to determine if altered MasR signaling in POMC neurons could contribute to insulin resistance in disease states such as obesity and type II diabetes.

Angiotensin (Ang)-(1-7) is a protective hormone of the renin-angiotensin system that improves insulin sensitivity, glucose tolerance, and energy balance in obese rodents. Our recent findings suggest that Ang-(1-7) activates mas receptors (MasR) in the arcuate nucleus of the hypothalamus (ARC), a brain region critical to control of energy balance and glucose homeostasis, to induce these positive metabolic effects. The distribution of MasR in the ARC and their role in metabolic regulation, however, is unknown. We hypothesized: (1) MasR are expressed in the ARC; and (2) deletion of ARC MasR leads to worsened metabolic outcomes following high fat diet (HFD). To test this, male and female C57Bl/6J mice were fed a 60% HFD or matched control diet ad libitum for 12 weeks. RNAscope in situ hybridization was performed on coronal ARC sections in rostral-middle-caudal regions to determine percentage of MasR positive neurons (n=5/group). In a second experiment, we assessed body composition and insulin and glucose tolerance in transgenic mice with deletion of MasR in ARC neurons (MasR-flox with AAV5-hsyn-GFP-Cre). RNAscope revealed a wide distribution on MasR-positive cells throughout the rostral to caudal extent of the ARC. The average percentage of MasR positive neurons was increased in females versus males, with HFD tending to increase MasR expression in both sexes (control diet male: 11±2; control diet female: 17±3; HFD male: 15±5; HFD female: 24±2; p sex : 0.030; p diet : 0.066; p int : 0.615; two-way ANOVA). Deletion of MasR in ARC neurons worsened insulin sensitivity in HFD but not control diet females (area under the curve for change in glucose from baseline: -1989±1359 HFD control virus vs. 2530±1762 HFD Cre virus; p=0.016), while fasting glucose, glucose tolerance, and body composition did not change. There was no effect of ARC MasR deletion on metabolic outcomes in control diet or HFD male mice. These findings suggest females have more MasR positive neurons in the ARC compared to males, which may be a sex-specific protective mechanism for glucose homeostasis. While further studies are needed to explore the role of ARC MasR in metabolic regulation, these findings support targeting Ang-(1-7) as an innovative strategy in obesity.

Introduction The control of energy balance involves communication of peripheral hormones with brain regions controlling food intake and energy expenditure such as the arcuate nucleus of the hypothalamus (ARC). Within the ARC, two primary neuronal subpopulations control energy balance: proopiomelanocortin (POMC) neurons, which reduce food intake and increase energy expenditure; and agouti‐related protein (AgRP) neurons, which inhibit POMC neurons and conversely increase food intake and suppress energy expenditure. These circuits are typically disrupted by high fat diet (HFD) leading to a chronic state of energy imbalance and obesity. Accumulating evidence suggests that HFD‐induced obesity is associated with deficiency of angiotensin (Ang)‐(1‐7), a protective renin‐angiotensin system hormone. Our recent data show that systemically administered Ang‐(1‐7) induces adipose thermogenesis to enhance energy expenditure and promote weight loss. We propose that effects of Ang‐(1‐7) on energy balance involve activation of ARC neurocircuits, but this has not been tested. Additionally, the localization and neuronal subpopulations expressing Ang‐(1‐7) mas receptors (MasR) in the ARC is unknown. In this study, we hypothesized that: Ang‐(1‐7) activates ARC neurons; MasR are expressed in the ARC and are primarily colocalized with POMC neurons; and the ability of Ang‐(1‐7) to activate ARC neurons as well as co‐localization of MasR with POMC neurons is disrupted following chronic HFD. Methods Male C57Bl/6J mice were fed a 60% HFD or matched control diet ad libitum for 12 weeks. Mice then received subcutaneous injection of Ang‐(1‐7) [2 mg/kg] to induce neuronal activation in the ARC, as measured by c‐fos gene expression (n=4‐6/group). In a second cohort of mice, RNAscope in situ hybridization was performed on coronal ARC sections to determine co‐localization of MasR mRNA within POMC versus AgRP neurons (n=5/group). Results We found that Ang‐(1‐7) increases the number of c‐fos positive cells in the ARC (39±6 vs. 19±3 saline; p=0.022) in control diet mice. Ang‐(1‐7)‐mediated activation of ARC neurons was attenuated in HFD mice (34±3 vs. 23±4 saline; p=0.185). The rostral‐medial‐caudal distribution of ARC MasR was similar between control diet and HFD mice, with no difference in percentage of MasR positive neurons between groups (18±1 and 15±5%, respectively; p=0.733). MasR were more highly co‐localized to POMC versus AgRP neurons, with HFD tending to reduce these co‐localizations (MasR/POMC: 49±10 control vs. 33±5% HFD, p=0.199; MasR/AgRP: 36±11 control vs.16±7% HFD, p=0.209). Conclusions These findings suggest that chronic HFD reduces the ability of Ang‐(1‐7) to acutely activate neurons in the ARC. Further, HFD disrupts co‐localization of MasR with POMC and AgRP neurons in the ARC indicating disconnect in the endogenous neurocircuitry controlling energy balance. Further studies are needed to explore the importance of MasR in these neuronal subpopulations for energy balance, to determine the potential for targeting of Ang‐(1‐7) as an in...

Angiotensin (Ang)-(1-7) is a beneficial renin–angiotensin system (RAS) hormone that elicits protective cardiometabolic effects in young animal models of hypertension, obesity, and metabolic syndrome. The impact of Ang-(1-7) on cardiovascular and metabolic outcomes during aging, however, remains unexplored. This study tested the hypothesis that Ang-(1-7) attenuates age-related elevations in blood pressure and insulin resistance in mice. Young adult (two-month-old) and aged (16-month-old) male C57BL/6J mice received Ang-(1-7) (400 ng/kg/min) or saline for six-weeks via a subcutaneous osmotic mini-pump. Arterial blood pressure and metabolic function indices (body composition, insulin sensitivity, and glucose tolerance) were measured at the end of treatment. Adipose and cardiac tissue masses and cardiac RAS, sympathetic and inflammatory marker gene expression were also measured. We found that chronic Ang-(1-7) treatment decreased systolic and mean blood pressure, with a similar trend for diastolic blood pressure. Ang-(1-7) also improved insulin sensitivity in aged mice to levels in young mice, without effects on glucose tolerance or body composition. The blood pressure–lowering effects of Ang-(1-7) in aged mice were associated with reduced sympathetic outflow to the heart. These findings suggest Ang-(1-7) may provide a novel pharmacological target to improve age-related cardiometabolic risk.