有氧和抗阻运动对糖尿病脂肪肝大鼠肝脏内质网应激的影响

Effects of aerobic and resistance exercise on hepatic endoplasmic reticulum stress in diabetic rats combined with fatty liver diseases

目的:对比两种不同运动方式——有氧运动和抗阻运动对2型糖尿病(T2D)脂肪肝大鼠肝脏内质网应激(ERS)及其介导的细胞凋亡的影响。方法:雄性SD大鼠随机分为对照组(CON,n=10)、模型组(T2D,n=10)、有氧运动组(T2D+AE,n=10)和抗阻运动组(T2D+RE,n=10)。对照组予普通饲料喂养,其余组予高糖高脂饲料喂养。7周后,T2D组、T2D+AE组和T2D+RE组给予腹腔内小剂量链脲佐菌素(STZ)注射1周,诱导T2D模型。T2D模型造模成功后,T2D+AE和T2D+RE组分别给予有氧运动和抗阻运动干预,连续8周。有氧运动方式为跑台训练:先适应性训练3天,速度15m/min,训练时间20min;以后逐渐增加训练速度和时间,直至速度达到20m/min,持续时间至60 min,每天训练1次,每周训练6天。抗阻运动方式为递增负荷爬梯训练,爬梯长1.0 m,负重装置固定于大鼠尾部,初始负荷为体重的50%,之后不断增加负荷,每3天进行1次。各组在最后一次训练结束48h后取材。HE和油红O染色检测肝脏病理形态,Western Blot检测内质网应激及其介导凋亡蛋白表达变化。结果:与CON组比较,T2D组肝细胞脂肪变性和脂滴数量显著增加(P<0.01),T2D+AE和T2D+RE组肝细胞脂肪变性和脂滴数量介于CON组和T2D组之间(P<0.05);与CON组比较,T2D组大鼠肝脏ERS标志物GRP78及凋亡蛋白CHOP、JNK、Caspase 12表达增加(均P<0.05)。与T2D组比较,T2D+AE和T2D+RE组GRP78及凋亡蛋白CHOP、JNK、Caspase 12表达下降(均P<0.05)。与T2D+RE组比较,T2D+AE组GRP78表达显著降低(P<0.05)。结论:肝脏内质网应激及其介导细胞凋亡参与2型糖尿病脂肪肝形成。有氧运动和抗阻运动均能有效改善糖尿病脂肪肝,其机制与有氧运动和抗阻运动能显著降低肝脏内质网应激及其介导的细胞凋亡有关。

Objective:To compare the effect of aerobic and resistance exercise on hepatic endoplasmic reticulum stress and apoptosis in diabetic rats combined with fatty liver diseases.Method:Sprague-Dawley rats were randomly assigned to four groups:control group(CON),Type 2 diabetes group(T2 D),aerobic exercise group(T2 D+AE) and resistant exercise group(T2 D+RE). Rats in CON group were fed with normal chow diet and the other rats were fed with high fat and high sucrose diet for 7 weeks.After that,rats feeding with high fat and fructose were injected with a single dose of streptozotocin to induce Type 2 Diabetes(T2 D) for one week. The rats in T2 D+AE group performed treadmill exercise. The speed increased from 15 m/min to 20 m/min, and the time increased from 20 min to 60 min for 8 weeks. Training were performed once a day,6 days per week. The rats in T2 D+RE group were allowed to climb a 1.0 m vertical ladder with loads attached to their tails and the loads were progressively increased from 50% body weight. Sessions were performed one time per three days for 8 weeks. The rats were sacrificed after 48 hours when finishing the last training session. Hematoxylin and eosin(HE) staining and Oil Red O staining was used to observe the morphology of liver. Western Blot was used to detect the protein expression of endoplasmic reticulum stress.Result:Hepatic lipid droplet density was elevated following the induction of T2 D,but was decreased following both types of exercise training. In addition,the protein contents of hepatic ER stress marker GRP78 and downstream apoptotic pathways(CHOP,JNK and Caspase 12) were upregulated in diabetic rats. Both types of exercise training effectively reduced these markers with greater reduction of GRP78 in T2 D+AE group in comparison to T2 D+RE group.Conclusion:Hepatic ER stress response and ER stress-induced apoptotic pathways are activated in an animal model of T2 D. Both aerobic and resistance exercise training are effective in reducing ER stress and ER stressinduced apoptosis,which may contribute to mitigating NAFLD in rats with T2 D.