[Effect of Gegen Qinlian Decoction on methylation and expression of Scd1gene in adipose tissue of insulin resistant rats and correlations between methylation and physiological and biochemical parameters].

This study aimed to explore the effect of Gegen Qinlian Decoction(GQD) on the methylation and mRNA expression level of stearoyl CoA desaturase(SCD) gene in the adipose tissue of rats with insulin resistance(IR) induced by high-fat diet as well as the correlations between methylation and physiological and biochemical indicators. The animals were divided into seven groups, namely, blank control(C) group, IR model group, low-(1.65 g·kg~(-1)), medium-(4.95 g·kg~(-1)), and high(14.85 g·kg~(-1))-dose GQD(GQDL, GQDM, and GQDH) groups, rosiglitazone(RGN, 5 mg·kg~(-1)) group, and simvastatin(SVT, 10 mg·kg~(-1)) group. The rat epididymal adipose tissue was collected for detecting all the cytosine methylation levels in two fragments of Scd1 gene by bisulfite sequencing PCR(BSP). Scd1-1 was located in CG shores and Scd1-2 in CG islands, including the transcriptional start site(TSS). The Scd1 mRNA level was determined by quantitative real-time PCR(q-PCR). Spearman correlation coefficient was used to analyze the correlations between amplified fragment C methylation and physiological and biochemical indicators. The results showed that GQDM remarkably reversed the elevated CG7 methylation in the TSS upstream region of Scd1-2 triggered by high-fat diet. GQDL significantly reversed the lowered total CG methylation in the downstream region of Scd1-2 induced by the high-fat diet. GQD did not significantly improve the decreased Scd1 mRNA expression caused by high-fat diet. Changes in methylation of the total CG, CG5 and CT11 of Scd1-1 in CG shores exhibited significant negative correlations with the serum triglyceride(TG) but positive correlation with the Scd1 mRNA level. The methylation of several C sites in the TSS upstream region of Scd1-2 was positively correlated with physiological and biochemical parameters. The methylation of several CG sites in the TSS downstream region of Scd1-2 was negatively associated with physiological and biochemical parameters. Besides, the methylation of several CH sites in the downstream fragment was positively correlated with physiological and biochemical parameters. All these have demonstrated that GQD may exert the therapeutic effect by regulating the methylation of CG7 in the TSS upstream region and total CG site in the TSS downstream region of Scd1 gene. The methylation of total CG, CG5 and CT11 sites in CG shores of Scd1 gene may be important targets for regulating Scd1 mRNA level and affecting serum TG.

[Preliminary study on effect of Gegen Qinlian Decoction on enzyme activity, gene expression and methylation level of FASN in adipose tissue of rats with insulin resistance].

To investigate the effect of Gegen Qinlian Decoction(GQD) on enzyme activity, gene expression and methylation level of fatty acid synthase(FASN) in adipose tissue from rats with insulin resistance induced by high-fat diet. The 60% fat-powered high-fat diet was continuously given to male SD rats to induce the insulin resistance model. Then, they were divided into five groups randomly and administrated by gavage every day for 16 weeks with following drugs respectively: 10 mL·kg~(-1)water for control group(C) and insulin resistance model control group(IR), 1.65 g·kg~(-1)GQD per day for low-dose group(GQDL), 4.95 g·kg~(-1)GQD per day for medium-dose group(GQDM), 14.85 g·kg~(-1)GQD per day for high-dose group(GQDH), and 5 mg·kg~(-1) rosiglitazone per day for rosiglitazone group(RGN). Epididymal adipose tissue was taken to determine enzyme activity of FASN by colorimetric method, mRNA expression level of Fasn by quantitative Real-time PCR(Q-PCR) and CpGs methylation level between +313 and +582 by bisulfite sequencing PCR(BSP). These results showed that Fasn expression was significantly lowered in IR model rats compared with the control rats(P<0.01). Enzymatic activity and CpGs methylation level of Fasn in IR group showed downward trends. Low and medium-dose GQD can increase enzyme activity of FASN(P<0.05). Moreover, low-dose GQD increased the total CpGs methylation level of Fasn fragment between +313 and +582 in insulin resistance rats(P<0.05). For GQDM group, the methylation frequency of CpGs at positions +506 and +508(P<0.01) as well as the methylation frequency of CpGs on the binding sites of transcription factorzinc finger protein 161(P<0.05) were significantly increased. The methylation frequency of CpG at +442 position was positively correlated with Fasn expression(P<0.01, r=0.735), and methylation frequencies of CpGs at +345 and +366 positions were positively associated to enzyme activity of FASN respectively(P<0.05, r=0.479; P<0.01, r=0.640). In conclusion, GQD can reverse enzyme activity of FASN and methylation level of Fasn in adipose tissue of insulin resistant rats, and CpG sites at positions +506 and +508 may be the targets of GQD. The methylation level of CpGs at + 345 and + 366 sites were possibly related to FASN activity, while methylation of CpG at + 442 site may be closely correlated with mRNA level of Fasn. In addition, GQD did not significantly change mRNA expression level of Fasn, but effectively reversed enzymatic activity, suggesting that GQD may regulate the post transcriptional expression of Fasn.