The Effects And Mechanism Of Niacin On The Expression Of Apolipoprotein M And Apolipoprotein E

Objective: To investigate the effects of niacin on apolipoprotein M(apoM)and apolipoprotein E(apoE)in HepG2 cells,and explore the possible mechanism.Methods: Cultured HepG2 cells were divided into 5 groups(control group,0.1,1,3 and 10 mmol/L niacin)for 24 h,respectively.HepG2 cells were incubated with niacin at 10 mmol/L concentration for 0,6,12,24 and 48 h.Total RNA of HepG2 cells were extracted and reverse transcriped.The expression levels of apoM,apoE and GAPDH mRNA of HepG2 cells were measured bv real time RT-PCR.Meanwhile,HepG2 cells were treated with experiment medium containing niacin(10mM)and/or PI-3K inhibitor LY294002(10μM),respectively.Western blot was used to detect the protein expression of apoM.Results: Niacin up-regulated apoM and apoE in a dose-dependent manner,and the results were significantly higher than that of the control group(P <0.05)when the nicotinic acid concentration exceeded 1mmol/L.Meanwhile,the levels of apoM and apoE mRNA expression in HepG2 cells showed a time-dependent increase as stimulated by niacin in time-course experiment for 0,6,12,24,48 h.ApoM and apoE mRNA were gradually increased and the highest at 24 h.The levels of apoM and apoE mRNA and protein expression in HepG2 cells were significantly higher than control by the effects of niacin and LY(P<0.05).Two-Way ANOVA showed that there were no interaction between niacin and LY on apoM and apoE expression in HepG2 cells.Meanwhiles,compared with the control group,the apoM protein expression in niacin and / or LY group was significantly increased.Conclusions: Niacin up-regulated apoM and apoE gene expressions in HepG2 cells,but not through PI-3K pathway.