PHD2/HIF‐1α signaling mediates hepatic metabolic responses to moderate exercise in cholestasis mouse model
Authors: Luo Beibei , Chen Peijie , Xiang Dao , Wu Die , Hu Yiping 
Published: November 2023

Moderate exercise increases the energy demand, maintaining hepatic metabolic homeostasis, and promoting the recovery of cholestasis and chronic liver disease in both human and rodents. Exercise induces tissue blood flow redistribution by which the blood flow is decreased in the splanchnic circulation. The hypoxia‐inducible factor (HIF) and its prolyl hydroxylases (PHDs) are pivotal in the transcriptional response to oxygen flux. Therefore, we hypothesize that PHD2/HIF‐1α signaling pathway is engaged in the moderate exercise intervention in a mouse model of cholestasis. Mice were subjected to a 4‐week 3.5‐diethoxycarbonyl‐1.4‐dihydrocollidine (DDC) feeding for inducing cholestasis with biliary obstruction and bile duct injury. 30min voluntary swimming in warm water (37±1□) was used as a moderate exercise intervention method. The noninvasive in vivo bioluminescence imaging was applied to monitor HIF‐1α expression after exercise in ROSA26 ODD‐Luc/+ mouse model (ODD‐Luc) that ubiquitously expresses a bioluminescent reporter consisting of firefly luciferase fused to a region of HIF‐1α. We found that in vivo hepatic HIF‐1α markedly increases in the liver of DDC fed ODD‐Luc mice. One session of 30min swimming exercise also moderately enhances in vivo HIF‐1α in the abdominal area of control ODD‐Luc mice. Next, we developed Albumin Cre mediated, hepatocyte specific deletions of HIF‐1α (Alb‐Hif1a−/−) and PHD2 (Alb‐Phd2−/−) mouse models to verify the role of PHD2/HIF‐1α signaling pathway in moderate exercise intervention for cholestasis. Wild‐type (D‐WT), hepatic HIF‐1α knockout (D‐Alb‐Hif1a−/−) and hepatic PHD2 knockout (D‐Alb‐Phd2−/−) mice were fed by DDC for 4 weeks. Another two groups of WT (SD‐WT) and Alb‐Hif1a−/− (SD‐Alb‐Hif1a−/−) swam 30min per day during DDC feeding. The data was shown that D‐WT and D‐Alb‐Hif1a−/− and SD‐Alb‐Hif1a−/− mice were suffered from cholestasis with no group differences. However, the cholestasis induced body weight reduction and liver injury related makers in SD‐WT and D‐Alb‐Phd2−/− groups were attenuated (P<0.05), compared to D‐WT. These results suggest that moderate exercise and hepatic PHD2 knockout partially prevent mice from DDC feeding induced cholestasis; hepatic HIF‐1α knockout blocks the protection of moderate exercise. To explore the possible mechanisms, the Alb‐Hif1a−/−, Alb‐Phd2−/− mice and their controls were kept in metabolic chambers for 48 hours, swam for 30 min, and kept back in for another 48 hours. The mRNA expression profile related to glucose metabolism, fatty acid metabolism, and cholesterol metabolism were assessed. It was found that the energy expenditure, VO2 and VCO2 of Alb‐Hif1a−/− mice was elevated after swim (P<0.01). The hepatic metabolism related gene expression patterns were significantly different among the groups. In conclusion, moderate exercise intervention attenuates the cholestasis in mice. PHD2/HIF‐1α signaling pathway mediating hepatic metabolic responses to exercise is one possible explanation.Support or Funding InformationThe National Natural Science Foundation of China (31471135) and the China Postdoctoral Science Foundation funded project.