Role Of CypD-Mitochondria-ER Pathway In NAFLD Induced By OSAHS Combined With Obesity And Its Mechanisms

Objective:In this study,we established a CIH mouse model simulating OSAHS to investigate the effects of CIH and high-fat diet(HFD)-induced obesity on liver injury in mice,and explored the possible roles and mechanisms of mitochondrial key regulator CypD,mitochondrial function and endoplasmic reticulum stress in liver injury induced by OSAHS combined with obesity.Methods: 1.The CIH mouse model and HFD mouse model was established and all the mice were randomly divided into four groups: CON group(Control)?CIH group?HFD group and HFD+CIH group;2.Biochemical assay was used to detect the liver enzyme activity in serum as well as lipid metabolism-related indicators in serum and liver;3.The liver histopathology was examined by HE staining of liver tissue;4.The liver/body weight ratio was calculated by weighing the body weight and liver weight of each mouse;5.Gene expression level of fatty acid accumulation,cholesterol breakdown and synthesis in the livers of mice from different treatment groups were detected by Real-time PCR;6.Hepatic fibrosis was examined by Masson staining and Sirius staining;7.CypD protein and mitochondrial function-related proteins,endoplasmic reticulum function-related genes and proteins in the liver were examined by Western blot and Real-time PCR,to explore the possible role of CypD-Mitochondria-ER in liver injury induced by CIH combined with obesity.Results: 1.It was found that both CIH and HFD can increase the serum level of liver enzymes in mice,among which the increase of liver enzymes in CIH+HFD group was most obvious;2.By HE staining,significant adipose deposition and vacuole-like changes in the liver cells could be observed in CIH or HFD group.CIH+HFD group suffered the most severe tissue structural damage;3.Both CIH and HFD could significantly increase the liver weight of mice.HFD had a greater effect on the body weight of mice than CIH,and the liver/body weight ratio of CIH group was the highest;4.According to the analysis of the biochemical indicators of lipid metabolism,both CIH and HFD could up-regulate liver triglycerides(TG)and cholesterol(TC),serum TG and TC,and serum low-density lipoprotein,among which the most significant increase happened in HFD+CIH group;5.By RT-PCR,it was found that HFD+CIH group had increased fatty acid accumulation, increased cholesterol synthesis and decreased cholesterol catabolism,which altogether promoted the development of liver steatosis;6.No significant liver fibrosis was found in each group by Masson staining or Sirius staining;7.It was found that compared with control group,mice treated with HFD+CIH showed a significant increase in CypD protein level,as well as an up-regulation of mitochondrial fission protein FIS1 and MTP18 and a down-regulation of fusion protein MFN1, suggesting that mitochondrial dysfunction occurred under this stress;8.Both CIH and HFD could up-regulate the endoplasmic reticulum function-related genes and protein levels in mice,with HFD+CIH group being the most obvious up-regulated.Conclusion:By studying the CIH and HFD mouse model,we demonstrate that CIH-and HFD-treated mice undergo significant liver injury,and the CypD-Mitochondria-ER pathway may mediate NAFLD induced by OSAHS combined with obesity.