| Background:Many human physiological and biochemical processes such as: glucose and lipid metabolism, sleep-wake, cardiovascular activities showed a light-dark rhythm.The biological rhythm is mainly under the control of the circadian clock system.The central clock system, mainly locates in the SCN area, which mainly accepts the stimulation from the light. Accepted the central pacemaker, numerous subsidiary clocks also exist in human peripheral organs (liver, heart, kidney, etc.) Peripheral clock system activted when accepted output singals from SCN or diet, hunger, cold and other stimuli. The peripheral circadian clocks and he central pacemakers share the similar molecular bases.The clock machinery is composed by a train of complex transcriptionnal-translational feedback loops. The circadian clock system is mainly composed of several genes(bmall,clock etc.) participate in maintaining normal biological rhythms.Accumulating evidence shows that there is extensive interplay between circadian rhythm and metabolism.Disordered circadian genes expression would induce irregular metablic prosesses such as glucolipid metabolic disorder. Similarly, metabolic disruptions also have reciprocal effects on circadian rhythm.?-klotho is the obligate co-receptor of the FGF15 and FGF21.FGF15 plays an important role in the process of metabolism of bile acids. FGF21 is involved in a variety of metabolic processes, such as glucose intake and lipolysis.Objective:To explore the impact of high-fat diet on the biological rhythm of ?-klotho and the regulation effects of the clock gene bmallMethods:In vitro experiment:HepG2 cells, after serum shock, treaed free fatty acids to intimated high fat environment, to explore whether the free fatty caids would influence the biological rhythms of ?-klotho through RT-PCR. HepG2 cells, after transfected ?-klotho siRNA or expression plasmid, treaed free fatty acids, to detect ?-klotho expresion levels in different circumstance by RT-PCR.In vivo experiment:Male C57BL6 mice were supplied, and housed under the constant dark with ad libitum access to standard chow diet or a high-fat diet(60% calories from fat) for 8 weeks. The tissues were collected every four/six hours. RT-PCR were used to detect the mRNA expression of P-klotho and the protein expression level were evaluated by westerern-blotting.Bmall knockout mice were fed with high-fat diet, and ?-klotho mRNA expression levels were evaluated by RT-PCR method.Results:In vitro experiment:After serum shock,?-klotho showed a oscillated expression pattern. Free fatty acids had a stronger effect leading to a disruption of ?-klotho mRNA oscillation(p<0.01).When exposed to free fatty acids,the expression of ?-klotho increased(p<0.05). While after transfection of siRNA targeting bamllgene, ?-klotho was suppressed compared with the group only received free fatty acids(p<0.01). When transfected plasmids with bmall,we find that the expression of ?-klotho was also increased,but can't resume the effect of the high fat exposure(P>0.05).In vivo experiment:?-klotho showed robust rhythm expression patterns in different organs. Compared with the chow diet group, the circadian pattern of ?-klotho significantly disrupted in liver when the wild-type and bmall-/- mice treated high fat diet or not.Notably, higher expression of ?-klotho was observed in the high fat food feeding group(P<0.01),while, the bmall-/- mice feeding high fat diet, the expression of ?-klotho was significantly reduced compared the normal high fat diet mice(P<0.01).Conclusions:P-klotho showed a rhythmic and oscillated expression.High-fat diets disturbed ?-klotho rhythms.Suppression of Bmall expression improves high- fat induced ?-klotho expression disordered. |
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