High-fat Diet In The Evening Affects The Hepatic Circadian Clock And Lipogenic Gene Expressions In Mice And Osthole Intervention

Aim: To investigate whether timed high-fat diet in the evening affects the hepaticcircadian clock and PPARα-mediated lipogenic gene expressions and their rhythms infatty liver mice. On this basis, we further observe the differences of the interventioneffects of equal osthole at different time administration.Methods: ICR male mice were used in the study. A mouse model withhyperlipidemic fatty liver was established by timed high-fat diet in the evening and a12-h light (8:30-20:30) and12-h dark (20:30-8:30) cycle for4weeks. Whereafter, micewere either sacrificed at the different time-points (6:00,12:00,18:00and24:00) orsacrificed after treatment with equal osthole at different time administration (morning-,evening-, and mixed morning and evening-treated groups) for4weeks. The totalcholesterol (TC), triglycerides (TG), and free fatty acids (FFA) contents in liver weremeasured with the colorimetric methods, and hepatic morphological changes wereexamined under a light microscope. The hepatic mRNA expressions of Clock, Bmal1,Per1-2, Cry1-2, peroxisome proliferator-activated receptor α (PPARα), andPPARα-mediated lipogenic genes expressions, including cholesterol7α-hydroxylase(CYP7A1),3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), low densitylipoprotein receptor (LDLR), lipoprotein lipase (LPL), diacylglycerol acyltransferase(DGAT), and fatty acid synthase (FAS) were determined by the RT-PCR methods.Results: The present experimental results showed that the hepatic TC and TGcontents were higher in the evening timed high-fat diet-fed mice at all time-points ascompared with matched normal control group, especially at6:00,18:00, and24:00. Andthe peak was present in a6-h delay for TC and a12-h advance for TG relative tomatched control mice. At the same time, the hepatic circadian clock genes Clock, Bmal1,Per2, and Cry2mRNA expressions in the high-fat diet-fed mice had significant changesin the rhythms and/or amplitudes. The clock-controlled gene PPARα and PPARα-mediated lipogenic genes such as CYP7A1, HMGCR, LDLR, LPL, and DGATmRNA expressions in liver had also significant changes in the rhythms and/oramplitudes, especially CYP7A1and DGAT mRNA expressions.After treatment with equal osthole at different time for4weeks, the hepatic TC andTG contents were decreased in varying degrees in the evening timed high-fat diet-fedmice. Meanwhile, the hepatic clock genes Clock and Bmal1mRNA expressions in theosthole evening-treated group were notablely reduced, and the hepatic Per1mRNAexpression in the osthole morning-treated group was obviously down-regulated as well.In the osthole-treated groups, the hepatic Cry2mRNA expression was all significantlydecreased, while the PPARα mRNA expression in liver was increased, especiallyosthole mixed morning and evening-treated group. The hepatic CYP7A1mRNAexpression in the osthole-treated groups and LPL mRNA expression in the ostholemorning-treated group were significantly increased. Reversely, the hepatic LDLRmRNA expression in the osthole-treated groups, and DGAT mRNA expression in theosthole evening-treated and mixed morning and evening-treated groups weresignificantly decreased.Conclusion: Timed high-fat diet in the evening could change the hepatic circadianrhythmic expressions of some clock genes and PPARα-mediated lipogenic genes, andled to the hepatic lipid accumulation and its diurnal rhythmic alteration. Afteradministration of equal osthole at different time, the reduced degree of the hepatic lipidaccumulation was significantly different, the results might were from the differenteffects of different time administration on the hepatic clock gene expressions inhyperlipidemic fatty liver mice, which subsequently regulated the different expressionsof clock-controlled gene PPARα and its target genes, and resulted in the differenttherapeutic effects.