miR-34a及其下游基因在铁超载大鼠非酒精性脂肪肝发生过程中的作用

目的：探讨miR-34a及其下游基因在铁超载大鼠非酒精性脂肪肝（NAFLD）发生过程中的作用。方法：将36只5周龄雄性SD大鼠随机分为对照组（基础饲料）、高铁组（含1% FeSO₄的基础饲料）、高脂组（脂肪供能比为35%的高脂饲料）和高脂高铁组（含1% FeSO₄的高脂饲料）。干预12周后，称取大鼠体质量；肝脏油红O染色观察大鼠肝脏中脂质堆积程度；测定大鼠血清中丙氨酸氨基转移酶（ALT）和天门冬氨酸氨基转移酶（AST）含量；实时荧光定量PCR（qPCR）检测大鼠肝脏中miR-34a、沉默信息调节因子1（SIRT1）及过氧化物酶体增殖物激活受体α（PPARα）的mRNA表达水平，并用Western blot方法检测SIRT1和PPARα的蛋白表达水平。结果：与对照组相比，高脂组和高脂高铁组大鼠体质量、血清ALT及miR-34a表达水平均显著增加（P均 < 0.05），SIRT1及其下游PPARα的mRNA和蛋白表达水平均降低（P均 < 0.05），肝脏脂质堆积程度加重；与高脂组比较，高脂高铁组SIRT1和PPARα的mRNA和蛋白表达水平均显著降低（P均 < 0.05）。结论：高脂高铁联合作用，可进一步激活miR-34a的表达，进而抑制其下游基因的表达，从而加重NAFLD大鼠肝脏脂代谢紊乱。

Involvement of miR-34a and its downstream genes plus iron overload in rats with nonalcoholic fatty liver disease

OBJECTIVE:To explore the roles of miR-34a and its downstream genes plus iron overload in rats with nonalcoholic fatty liver disease. METHODS:Thirty-six male SD rats of 5 weeks old were randomly divided into control diet group (basal diet),high iron diet group (basal diet containing 1% FeSO₄),high fat diet group (high fat diet 35% energy supply from fat) and high fat plus high iron diet group (high fat diet containing 1% FeSO₄). These rats were sacrificed after 12 weeks. Body weights were measured and liver lipid accumulation was observed by oil red O staining. The contents of ALT and AST in rat serum were detected. Quantitative real-time PCR (qPCR) was used to detect mRNA levels of miR-34a, silent information regulator (SIRT1) and peroxisome proliferator-activated receptor α (PPARα). SIRT1 and PPARα protein levels were detected by Western blot. RESULTS:Compared with control diet group,the body weight,the serum ALT level and the level of miR-34a in high fat diet group and high fat plus high iron diet group were increased significantly (P < 0.05). The levels of mRNA and protein expression of SIRT1 and its downstream PPARα were decreased (P < 0.05). The degree of lipid accumulation in the liver was gradually aggravated. Compared with high fat diet group,the levels of mRNA and protein expression of SIRT1 and PPARα in high fat plus high iron diet group were decreased significantly (P < 0.05). CONCLUSION:The combined effect of high fat and high iron diets could activate the expression of miR-34a and then inhibit the expression of downstream genes, thus aggravating liver lipid disorder in NAFLD rats.