Effect of β-casomorphin-7 on myocardial hypertrophy in hyperthyroidism-induced cardiomyopathy

Objective The purpose of this study was to investigate the effect of β-casomorphin-7 (β-CM-7) on myocardial hypertrophy (MH) in hyperthyroidism-induced cardiomyopathy in vivo and in vitro. Materials and methods Thirty C56BL/6 mice were randomly divided into three groups: control group, hyperthyroidism group, and β-CM-7 treatment group. An animal model of cardiac hypertrophy of hyperthyroid heart disease (HHD) was constructed by continuous intraperitoneal injection of 100 μg of L-thyroxine (L-Thy) for 28 days, and the serum TT3 and TT4 concentrations were measured. After that, myocardial specimens were collected to measure left and right ventricular MH index, and the myocardial cell structure was observed under hematoxylin and eosin (HE) staining. Thereafter, Masson staining was adopted to determine collagen volume fraction, and hydroxylamine method was used to measure superoxide dismutase (SOD) activity, Meanwhile, DTNB direct method was applied to measure GSH-Px activity, thio-malonylurea method was utilized to measure malondialdehyde (MDA) content, and the level of reactive oxygen species (ROS) was detected by flow cytometry. Finally, the expressions of oxidative stress (OS) and inflammation-related factors in vivo and the nuclear factor-κB (NF-κB) pathway in vitro were detected by Western blot and quantitative real-time polymerase chain reaction (qRT-PCR). Results Compared with those in control group, TT3 and TT4 were remarkably increased, the structure of myocardial cells was disordered, the interstitial fibrosis and the ventricular MH index were significantly increased, the OS and inflammatory responses were increased, and the NF-κB pathway was activated in the Hyperthyroidism group. In the β-CM-7 group, the content of TT3 and TT4 was decreased, the myocardial cell structure was slightly disturbed, the fibrosis and the ventricular MH index were reduced, OS and inflammatory response were reduced, and the NF-κB pathway was inhibited. Conclusions β-CM-7 can prevent and treat MH in mice with L-Thy-induced HHD probably through regulating the NF-κB signaling pathway.