Loss Of Cd36 Protects Skeletal Muscle Cells From PA-Induced Apoptosis By Enhancing Autophagy

Abstract

Studies have shown that skeletal muscle mass was declined with diabetes and obesity. Skeletal muscle mass declines resulting in sarcopenia and metabolic diseases. CD36 is also reported to play a pivotal role in Type 2 Diabetes. Therefore, the apoptosis of skeletal muscle cells plays a vital role in maintaining the functional muscle mass of type 2 diabetes. PURPOSE: To investigate the protective effect of Fatty Acid Translocase (FAT/CD36) against PA-induced apoptosis. METHODS: Cells were differentiated when they reached 80%–90% confluence. Once the long shape occurred in 80%–90% cells, lipofectamine RNAiMAX was used to transfect siCtrl or siCD36.The whole term for knockdown is 72 h. Skeletal muscle cells were harvested after treatment with PA (200 μM) for 16 h. The apoptosis of differentiated skeletal muscle cells induced by PA treatment was monitored by flow cytometry. The gene expression level of endoplasmic reticulum stress-related genes was detected by QPCR. The protein expression level of autophagy-related genes was detected by Western blotting. The t-test was used as the statistical test. RESULTS: Compared with the PA-free culture medium group, skeletal muscle cells treated with PA had increased apoptosis (18.75% ± 1.25% vs. 12.74% ± 0.19%, p < 0.001). Whereas skeletal muscle cells treated with siCD36 transfection can resist apoptosis under PA and PA-free condition (15.86% ± 0.96% vs. 18.75% ± 1.25%, p < 0.05; 9.92% ± 0.37% vs. 12.74% ± 0.19%, p < 0.001) especially in the late stage (10.83% ± 0.49% vs. 13.4% ± 1.52%, p < 0.05; 6.18% ± 0.69% vs. 9.5% ± 0.15%, p < 0.01). The mRNA expression level of Grp78 and Ire1a were increased in CD36 deficiency group (1.23 ± 0.09 vs. 1 ± 0.05, p < 0.05; 1.25 ± 0.07 vs. 1 ± 0.05, p < 0.05). The protein expression level of LC3-II, Beclin1 were significantly increased in CD36 deficiency group (201.71 ± 3.13 vs. 160.40 ± 6.76, p < 0.05, 193.84 ± 2.92 vs. 176.94 ± 1.41, p < 0.05). CONCLUSIONS: CD36, as a signaling molecule, can activate the autophagy pathway through the endoplasmic reticulum, thereby attenuating apoptosis in PA-stimulated skeletal muscle cells, implicating a promising target for metabolic diseases. Supported by the National Natural Science Foundation of China (No. 32071172, 31600966).