Chronic angiotensin AT2R activation prevents high-fat diet-induced adiposity and obesity in female mice independent of estrogen.

ABSTRACT

OBJECTIVE: Obesity is a known risk factor for various metabolic disorders and cardiovascular diseases. Recently we demonstrated that female angiotensin AT2 receptor (AT2R) knockout mice on high-fat diet (HFD) had higher body weight and adiposity with a parallel reduction in estrogen (17,ß-estradiol/E2). The present study investigated whether the anti-adiposity effects of the AT2R are estrogen-dependent in female mice. METHODS: Female C57BL/6 ovary-intact (Ovi) mice were treated with an AT2R agonist (C21, 0.3 mg/kg, daily i.p.). Ovariectomized (Ovx) mice, supplemented with E2 (5 µg/day, pellets implanted subcutaneously), were treated with an AT2R agonist (C21, 0.3 mg/kg, daily i.p.) or vehicle. After 4-days of pre-treatment with C21, Ovi and Ovx mice were placed on either normal diet (ND) or HFD while the C21 treatment continued for the next 10 days. For a long-term study, Ovi mice were placed on HFD and treated with C21 for 12 weeks. RESULTS: Ovi mice fed the HFD had increased parametrial white adipose tissue (pWAT) weight, plasma free fatty acid and triglycerides compared to Ovi mice on ND. Ovariectomy alone caused similar changes in these parameters which were further increased by HFD-feeding. C21 treatment attenuated these HFD-induced changes in Ovi as well as Ovx mice. HFD also, increased the liver/body-weight ratio and decreased the liver expression of the ß-oxidation enzyme, carnitine palmitoyltransferase 1 (CPT1-A). C21 treatment attenuated these changes as well. The long-term C21 treatment of Ovi mice lowered the HFD-induced body weight gain, increase in pWAT weight, parametrial adipocyte size and hyperinsulinemia induced by HFD. Finally, HFD drastically reduced urinary estrogen and the beneficial metabolic changes in response to C21-treatment occurred without significantly increasing urinary estrogen. CONCLUSION: We suggest that the pharmacological activation of AT2R by the agonist C21 reduces adiposity and body weight gain independent of estrogen in female mice. Improvement in fatty acid metabolism is a potential mechanism by which the AT2R exerts anti-adiposity effects.