Integrative control of cardiometabolic functions by AT1R in AgRP neurons in the VCD model of menopause

Angiotensin II type 1 receptors (AT1R) stimulate resting metabolic rate (RMR) via Gi-mediated inhibition of agouti-related peptide (AgRP) neurons in the hypothalamic arcuate nucleus (ARC). During diet-induced obesity, AT1R signaling in these cells is plastic in a sex-dependent manner. Males exhibit plasticity of AT1R signaling (from Gi to Gq) that correlates with RMR suppression and weight gain, while intact cycling females exhibit resistance to this plasticity. Thus, we hypothesized that 17β-estradiol (E2) provides protection against AT1R second messenger signaling plasticity in AgRP neurons. First, to examine the role of E2 in the modulation of RMR control and weight gain, female C57BL/6J mice were randomized to receive 4-vinylcyclohexene diepoxide (VCD) or sesame oil (SO) vehicle with or without 17β-estradiol (E2) supplementation via subcutaneous pellets (0.25 mg/90d). VCD induces ovarian failure and a progressive decline in E2, thereby modeling menopause. Starting at 12 weeks of age, mice were injected once daily for 20 days with SO or VCD (160 mg/kg/d, ip). At 0, 35, and 70 days after start of VCD treatment, mice underwent comprehensive metabolic phenotyping, including analyses of body composition (by nuclear magnetic resonance, NMR) and multiplexed home-cage measures of energy expenditure, intake behaviors, and physical activity using a Promethion system (Sable Systems). Body mass (BM) and composition were similar across VCD and E2 treatments at the start of the study, however, by 35d E2 supplementation caused trends toward reduced adiposity. No changes in food intake were observed, but VCD caused suppressed energy expenditure (EE; 0.52±0.05 vs. 0.44±0.01 kcal/h; p=0.02, n=4-5) and this suppression was prevented in the E2 supplemented group (0.51±0.04 kcal/h; p=0.03 vs VCD, n=5). Second, to explore the contribution of AT1R-Gi signaling within AgRP neurons to RMR control in the VCD model, VCD-treated female BAC-AT1R-Cre mice (that express Cre via the Agtr1a promoter) or Cre-deficient littermates received bilateral ARC injection of an AAV encoding Cre-dependent expression of the Gi-coupled designer receptor exclusively activated by designer drugs (hM4Di; 120 nL, 1x1012 pfu). As AT1R expression in the ARC is limited to AgRP neurons, this results in the expression of hM4Di only in these cells. RMR was then evaluated before and after activation of hM4Di via clozapine N-oxide (2 μg/g) at 50 and 80d after VCD treatment, via respirometry. Preliminary results indicate activation of Gi strongly stimulates RMR regardless of VCD treatment. These results support our working hypothesis that E2 protects against AT1R signaling plasticity within AgRP neurons. By extension, E2 likely acts at these cells to prevent diet-induced obesity via the maintenance of RMR. Ultimately, these findings may also help explain the observation that menopause in humans is associated with reduced RMR and accelerated adipose gains. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.