Protection of FGF21 as well as metallothionein for high fat diet induced cardiomyocyte impairment.

Abstract

Background Obesity and diabetes induced cardiomyocyte impairment lead to left ventricular hypertrophy and diastolic dysfunction. Hyperlipidemia induced large numbers of circulating fatty acid followed into cardiomyocyte lead to abnormal lipid accumulation in the myocardium. Lipid accumulation in cardiomyocyte correlates with insulin resistance, mitochondrial impairments and increased oxidative stress. Increased oxidative stress could induce cardiomyocyte apoptosis, myocardium fibrosis and derangements in calcium homeostasis, which finally induce cardiomyocyte hypertrophy and left ventricular diastolic dysfunction. Fibroblast growth factor 21 (FGF21) as an important regulator in energy homeostasis, which has a good effect for obesity or diabetes induced metabolic disease. In this study, we investigated whether FGF21 has protection effect for HFD induced cardiomyocyte impairment and to explore the synergistic protection effect of FGF21 and Tat-MT in HFD induced cardiomyocyte impairment.

Methods To produce mice with diet-induced DCMP, 6 weeks old C57BL/6 mice were fed a high fat (45% kcal fat) diet (HFD) for 12 weeks, low fat (10% kcal fat) diet fed mice as control. FGF21 or Tat-MT was treated in HFD fed mice to investigate their protection effects to DCMP and further investigate FGF21 and Tat-MT had synergistic protection effect to DCMP. H9C2 cells cultured in high glucose and palmitate (HG+PA) contained DMEM medium as surrogate for cardiomyocyte which impaired by HFD. FGF21 and/or Tat-MT were also treated simultaneously to explore their protection effect for HG+PA induced cardiomyocyte impairments in vitro.

Results From in vitro experiment, we observed serious impairment was caused by HG+PA treatment in H9C2 cells and FGF21 signaling was suppressed by HG+PA treatment. We also found large numbers of lipid was accumulated in cardiomyocyte and expression changes of lipid metabolism was observed. FGF21 treatment could improve HG+PA induced H9C2 cell impairment and abnormal lipid metabolism was also restored by FGF21 treatment. We observed FGF21 could effectively reduce lipogenesis and lipid uptake genes expression. Tat-MT treatment could also effectively improve HG+PA induced H9C2 cell impairment and restore abnormal lipid metabolism through modulate lipogenesis and lipid uptake gene expression. When simultaneously treat FGF21 and Tat-MT, we observed a synergistic protection effect for lipid accumulation. MAPK and WNT signaling activation was observed in HG+PA treated H9C2 cells and both FGF21 and Tat-MT could effectively suppress MAPK and WNT signaling, however FGF21 has better suppression effect for WNT signaling and FGF21 and Tat-MT co-treatment showed synergistic suppression effect for MAPK and WNT signaling. In HFD fed mice serious hyperglycemia, hyperlipidemia and insulin resistance were observed and it’s cause serious cardiomyocte impairment and FGF21 signaling resistance. FGF21 treatment could effectively improve HFD induced cardiomyocyte impairment and FGF21 signaling resistance as good as Tat-MT treatment. Like invitro experiment showed abnormal lipid metabolism was restored by FGF21 and Tat-MT and there has synergistic improvement effect for abnormal lipid accumulation and expression changes of lipogenesis and lipid uptake genes in myocardium of HFD fed mice. MAPK and WNT signaling were also activated by HFD, however FGF21 treatment could effectively reduce MAPK and WNT signaling activation as good as Tat-MT treatment. Different with HG+PA treated H9C2 cells, we didn’t observed a significant synergistic protection effect for MAPK and WNT signaling activation.

Conclusion HFD induced hyperlipidemia lead to large numbers of free fatty acid followed into cardiomyocyte induce abnormal lipid metabolism resulted in lipotoxicity conditions which could induce large numbers of ROS production in cardiomyocyte. With increased oxidative stress and deterioration of pathological impairments eventually lead to functional impairments. FGF21 could effectively improve cardiomyocyte impairment through improvement of abnormal lipid metabolism and modulate MAPK and WNT signaling and its therapeutic mechanism was similar with antioxidant, although FGF21 couldn’t direct eliminate ROS. There has synergistic protection effect for lipid accumulation, but significantly synergistic protection effect for cardiomyocyte impairment didn’t observed.