不同脂肪酸饮食对大鼠肝脏XBP-1的影响

Effects of dietary fatty acids on XBP-1 in liver tissues of rats

目的:探讨饱和脂肪酸、单不饱和脂肪酸、多不饱和脂肪酸饮食对大鼠肝脏X盒结合蛋白-1(XBP-1)的影响。方法:48只雄性Wistar大鼠随机分为4组:正常对照组(N组)、饱和脂肪酸饮食组(S组)、单不饱和脂肪酸饮食组(M组)、多不饱和脂肪酸饮食组(P组)。正常对照组给基础饲料(脂肪占10.3%);饱和脂肪酸饮食组的饲料是在基础饲料中添加15%猪油;单不饱和脂肪酸饮食组的饲料是在基础饲料中添加15%茶油;多不饱和脂肪酸饮食组的饲料是在基础饲料中添加15%豆油(脂肪占35.4%)。8周后4组各随机选8只大鼠行高胰岛素-正葡萄糖钳夹试验,同时留取空腹状态血清测定血脂、胰岛素等指标。肝脏XBP-1蛋白表达分别用Western blot法和免疫组化法测定。结果:①实验第8周末,与N组相比,P、M、S组大鼠进食量有所减少(P<0.05)。除外进食量的影响,与N组相比,S组血清总胆固醇(TC)、甘油三酯(TG)升高(P<0.05),M、P组差异无统计学意义(P>0.05);S、P组空腹胰岛素(FINS)、空腹血糖(FBG)升高,葡萄糖输注率(GIR)明显下降(P均<0.05),但S、P两组间无统计学意义(P>0.05);M组血清FINS、FBG有升高趋势,差异无统计学意义(P>0.05),GIR明显下降(P<0.05)。与M组相比,S、P组GIR明显下降(P<0.05)。②XBP-1在细胞浆和细胞核均有表达,呈棕黄色或棕褐色染色。N、M组主要在细胞核表达,而P、S组在细胞浆和细胞核均有表达,但是4组间无统计学意义(P>0.05);Western blot显示XBP-1蛋白相对表达的量分别是:M组(0.85±0.15)、N组(0.79±0.14)、P组(1.09±0.16)、S组(1.15±0.21)。与N组比较,P、S组肝脏XBP-1蛋白表达升高,差异有统计学意义(P<0.05);但P、S两组间及N、M两组间比较均无统计学意义(P>0.05)。结论:饱和脂肪酸和多不饱和脂肪酸饮食喂养所致大鼠肝脏中XBP-1蛋白表达明显高于正常对照和单不饱和脂肪酸饮食大鼠组,说明内质网应激可能参与了胰岛素抵抗的发生。

Objective： To explore the effects of saturated fats diets,polyunsaturated fats diets and monounsaturated fats diets on the expression of X-box binding protein 1（XBP-1）in liver tissues of rats.Methods：Wistar rats（n=48）were randomly divided into normal control group（N）,saturated fatty acid diets group（S）,monounsaturated fatty acid diets group（M）,polyunsaturated fatty acid diets group（P）.The rats in group N were fed with a regular lower fatty acids diet containing 10.3% fat,24.2% protein,and 65.5% carbohydrate as percentage of total calories.The rats in group M,P and S were fed with regular diets mixed with 15% tea oil,soybean oil,lard oil respectively,containing 35.4% fat,17.4% protein and 47.2% carbohydrate as percentages of total calories.The blood sample was collected by cardiac puncture after rats were anesthetized with diethyl ether for the biochemical analysis,insulin resistance was evaluated by glucose infusion rate（GIR） of hyperinsulinemic euglycemic clamp technique.After 8 weeks,the rats were killed with phenobarbital sodium after hyperinsulinemic euglycemic clamp test,hepatic XBP-1 were detected by Western blot and immunohistochemistry.Results：① Compared with group N,the amounts of food intake were significantly lower in group S,M and P（P 0.05）.Adjusted for the amount of food intake,serum TC,TG in group S were significantly higher than group N（P 0.05）,but there was no detectable difference among N,P and M groups（P 0.05）.Compared with group N,FINS and FBG were significantly higher in group S and P groups（P 0.05）,GIR was significantly lower in S,P and M groups（P 0.05）.②Immunohistochemistry analysis showed positive XBP-1 localized in both cytoblast and cytoplasm with intense brown staining.Further more,Western blot for XBP-1 in liver tissues showed that XBP-1 protein levels increased in group P and S [（1.09±0.16）,（1.15±0.21）]compared with group N and M [（0.85±0.15）,（0.79±0.14）,P 0.05].Conclusion：It may be one of the mechanisms of insulin resistance that the higher expression of XBP-1 and in liver tissues induced by polyunsaturated fatty acid and saturated fatty acid diets,simultaneously,it suggested that endoplasmic reticulum stress（ERS）can be a core mechanism involved in triggering insulin resistance.