High fat diet downregulates regulatory T cells in the myocardium of spontaneous hypertensive rats

Background and aim: Regulatory T cells (Tregs) play an important role in cardiovascular complications with the immune response. However, the role of Tregs in high fat diet (HFD)-induced myocardial fibrosis has not been fully elucidated to date. Therefore, we investigated whether HFD suppresses Tregs activation in the myocardium of spontaneously hypertensive rats (SHRs), which aggregates myocardial fibrosis. Methods and results: Eight-week-old male SHRs were fed to either HFD or control diet (CHO) groups for 12 weeks. We measured Tregs (CD4+FoxP3+) in the heart and mediastinal lymph nodes (LNs). The flow cytometry analysis confirmed that SHR-HFD exhibited a decreased Tregs compared to that of SHR-CHO in the heart and mediastinal LNs. Furthermore, the CD4 and FoxP3 antigens were used in the immunofluorescence microscopy of Tregs in the heart tissues. In the heart, dual staining for the Treg population was increased more in SHR-CHO than it was in SHR-HFD rats. In line with these findings, SHR-HFD significantly exacerbated myocardial fibrosis. Conclusion: We found that diet-induced obesity typically showed an exacerbated myocardial fibrosis and down-regulation of Tregs pathway in the heart and mediastinal LNs. Therefore, we suggest that the up-regulation of Tregs may be a promising therapeutic approach to preventing obesity induced heart failure.