Regulation Of CD36/LKB1/AMPK On Fatty Acid Oxidative Metabolism Under High-fat Diet Conditions

Abstract

Activation of AMP-activated kinase (AMPK) in skeletal muscle increases FA oxidation by inducing Acetyl-CoA Carboxylaze (ACC) deactivation. However, the upstream signal molecules that activate AMPK/ACC signaling remains unclear. It is expected that Fatty Acid Translocase (FAT/CD36) will become another potential target for diabetic therapy after AMPK. PURPOSE: To explore the role of CD36, as a signal molecule, in regulating the upstream signaling pathway of AMPK/ACC in skeletal muscle under HFD conditions. METHODS: First, siRNA interference was used to knock down CD36 gene in C2C12 cells to investigate the effect of CD36 deficiency on the phosphorylation of AMPK/ACC signaling in skeletal muscle cells. Then, twelve 8-week-old C57BL/6 male mice were randomly divided into two groups: control group (CON; n = 6), and high-fat diet group (HFD; n = 6). The expression levels of CD36 protein and phosphorylation of AMPK/ACC signaling under HFD conditions were detected by Western blotting method; the translocation of Liver kinase B1 (LKB1) in nucleus was detected by immunofluorescence method; the ultrastructural changes of skeletal muscle were detected by transmission electron microscopy; and the activity of mitochondrial respiratory chain enzyme was detected by colorimetry. RESULTS: CD36 deficiency activated AMPK (0.129 ± 0.009 vs. 0.417 ± 0.055, p < 0.05), ACC (0.044 ± 0.008 vs. 0.081 ± 0.010, p < 0.05) signaling in skeletal muscle cells. Compared with the CON group, the expression levels of CD36 protein in HFD group were significantly increased (0.225± 0.041 vs. 0.506 ± 0.022, p < 0.01), the phosphorylation levels of AMPK (0.142 ± 0.020 vs. 0.079 ± 0.010, p < 0.05) and ACC (0.229 ± 0.023 vs. 0.119 ± 0.028, p < 0.05) were significantly decreased, and induced LKB1 translocation from cytoplasm to nucleus. In addition, electron microscopic results showed that HFD intervention damaged the mitochondrial structure of skeletal muscle to a certain extent, and significantly decreased CS activity (411.32 ± 22.15 vs. 310.20 ± 44.09, p < 0.01). CONCLUSION: CD36, as a signaling molecule, promotes LKB1 to translocate from cytoplasm to nucleus, which inhibits AMPK/ACC signaling activation, thereby regulating FA oxidation under HFD condition. Supported by the National Natural Science Foundation of China (No. 31600966).