Propranolol and low-dose isoproterenol ameliorate insulin resistance, enhance β-arrestin2 signaling, and reduce cardiac remodeling in high-fructose, high-fat diet-fed mice: Comparative study with metformin

AIMS

β-Arrestin2 signaling has emerged as a promising therapeutic target for the management of insulin resistance and related complications. Moreover, recent studies have shown that certain G protein-coupled receptor (GPCR) ligands can modulate β-arrestin2 signaling. The current study examined the effects of the β-blocker propranolol and a low dose of the agonist isoproterenol (L-D-ISOPROT) on β-arrestin2 signaling, insulin resistance, and cardiac remodeling in high-fructose, high-fat diet (HFrHFD)-fed mice. In addition, the effects of these agents were compared to those of the clinical antidiabetic agent, metformin.

MATERIALS AND METHODS

Insulin resistance was induced by HFrHFD feeding for 16 weeks. Mice were then randomly allocated to groups receiving propranolol, L-D-ISOPROT, metformin, or vehicle (control) for 4 weeks starting on week 13 of HFrHFD feeding. Survival rate, body weight, visceral fat weight, blood glucose, serum insulin, insulin resistance index, hepatic β-arrestin2 signaling, heart weight, left and right ventricular thicknesses, cardiac fibrosis severity, serum endothelin-1, cardiac cardiotrophin-1, and cardiac β-arrestin2 signaling were then compared among groups.

KEY FINDINGS

HFrHFD for 16 weeks significantly increased insulin resistance index, cardiac fibrosis area, and serum endothelin-1, and reduced hepatic β-arrestin2 signaling, cardiac cardiotrophin-1, and cardiac β-arrestin2 signaling without significant changes in survival rate, body weight, visceral fat weight, heart weight, or left and right ventricular thicknesses. All three drugs reduced insulin resistance and cardiac remodeling parameters and enhanced β-arrestin2 signaling with variable efficacies.

SIGNIFICANCE

Propranolol and L-D-ISOPROT, like metformin, can reduce insulin-resistance and cardiac remodeling in HFrHFD-fed mice, possibly by upregulating β-arrestin2 signaling activity. Therefore, β-arrestin2-signaling modulation might be a promising strategy for insulin-resistance treatment.

Antiproliferative and Apoptotic Effects of Shemamruthaa, a Herbal Preparation, in 7,12-Dimethylbenz(a)Anthracene-Induced Breast Cancer Rats

A herbal preparation, Shemamruthaa (SM), was formulated to investigate the molecular mechanism by which it exhibits anticancer effects in mammary carcinoma bearing rats. Female Sprague-Dawley rats were used for the study, and mammary carcinoma was induced by administration of 7,12-dimethylbenz(a)anthracene, intragastrically. After 3 months of induction period, the rats were treated with SM (400 mg/kg body weight) for 14 days. Our study shows that SM-treated mammary carcinoma rats showed regression in tumor volume with concomitant increase in p(53), Bax, caspase-3, and caspase-9 mRNA and protein levels compared with mammary carcinoma-induced rats. Proliferating cell nuclear antigen and anti-apoptotic Bcl-2 were markedly increased in mammary carcinoma-induced rats, whereas the SM treatment significantly decreased the expression of these proteins. The expression pattern of apoptotic signaling molecules analyzed in the present study signifies the therapeutic efficacy of SM against breast cancer.