Hubei Province Engineering Research Center of Healthy Food, School of Biology and Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan 430023, China.
Food Funct. 2020 Apr 1;11(4):3621-3631. doi: 10.1039/c9fo02606a. Epub 2020 Apr 15.
Disruptions to circadian rhythm have been associated with an increased risk of nonalcoholic fatty liver disease (NAFLD). DHA has been found to affect both circadian rhythm and lipid metabolism. In this study, the relationship between DHA substitution and improvements in lipid metabolism and circadian clock regulation was studied. Male C57BL/6 mice were fed a control, a high fat or a DHA substituted diet for 12 weeks. Biochemical analysis and H&E staining showed that the high-fat diet (HFD) could induce NAFLD, and DHA substitution (AOH) could attenuate NAFLD. The qPCR results showed that the expressions of core clock genes Clock and Bmal1 were significantly higher at zeitgeber (ZT) 0 (7:00 am) than those at ZT12 (7:00 pm) in the control group, while this difference in day and night disappeared in the HFD group, but was observed in the AOH group. Western blotting results indicated that the expressions of rhythm output molecules (RORα and REV-ERBα) and their downstream protein INSIG2 all showed the corresponding circadian changes. SREBP-regulated proteins were significantly increased in the HFD group at both ZT0 and ZT12, but decreased in the AOH group accompanied by the corresponding changes in the protein expressions of HMGCR, LXR, CYP7A1 and CYP27A1. Altogether, HFD can decrease or disrupt circadian rhythm fluctuation by up-regulating the expression of core circadian rhythm genes Clock and Bmal1 at ZT12, and induce metabolic abnormalities through the INSIG2-SREBP pathway regulated by RORα and REV-ERBα. DHA substitution seems to restore circadian rhythm similar to the normal circadian rhythm of "night-high, day-low" through the metabolic pathway regulated by rhythmic nuclear receptors, improving the lipid metabolism rhythm and reducing liver fat.
昼夜节律紊乱与非酒精性脂肪性肝病（NAFLD）的风险增加有关。已经发现 DHA 会影响昼夜节律和脂质代谢。在这项研究中，研究了 DHA 替代与脂质代谢和生物钟调节改善之间的关系。雄性 C57BL/6 小鼠喂食对照、高脂肪或 DHA 替代饮食 12 周。生化分析和 H&E 染色表明，高脂肪饮食（HFD）可诱导 NAFLD，而 DHA 替代（AOH）可减轻 NAFLD。qPCR 结果表明，在对照组中，核心时钟基因 Clock 和 Bmal1 的表达在 Zeitgeber（ZT）0（上午 7:00）时明显高于 ZT12（晚上 7:00）时，而这种昼夜差异在 HFD 组中消失，但在 AOH 组中观察到。Western blot 结果表明，节律输出分子（RORα 和 REV-ERBα）及其下游蛋白 INSIG2 的表达均表现出相应的昼夜变化。SREBP 调节蛋白在 HFD 组中的表达在 ZT0 和 ZT12 时均显著增加，但在 AOH 组中减少，同时 HMGCR、LXR、CYP7A1 和 CYP27A1 的蛋白表达也相应变化。总之，HFD 可以通过上调 ZT12 时核心昼夜节律基因 Clock 和 Bmal1 的表达来降低或破坏昼夜节律波动，并通过 RORα 和 REV-ERBα 调节的 INSIG2-SREBP 途径诱导代谢异常。DHA 替代似乎通过调节昼夜核受体的代谢途径恢复类似于“夜高、昼低”的正常昼夜节律，改善脂质代谢节律并减少肝脂肪。
