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目的探讨高脂饲养SD大鼠脂肪分存的顺序及其与胰岛素抵抗的关系。方法将8周龄雄性SD大鼠随机分为2组:正常饲养组(NC,n=40)、高脂饲养组(HF,n=40)。在不同周龄测定血清、肝脏、肌肉组织中甘油三酯(TG)含量;进行正常血糖高胰岛素钳夹试验评估胰岛素的敏感性;并用定量PCR方法分析肝脏和肌肉中脂代谢调控基因mRNA表达的变化。结果(1)与NC组比较,高脂饲养4周、8周时血TG无明显变化,12周时明显增高[0.52(0.15-1.00)mmol/L vs 0.31(0.09-0.53)mmol/L,P<0.01],持续至20周。(2)HF组肝脏TG含量从高脂饲养4周始便明显增高[(34.38±11.12)mg/g vs(1.65±0.37)mg/g,p<0.01],一直持续至20周;肌肉TG在高脂饲养4、8、12周均无明显变化,高脂饲养20周时明显增高[(32.24±7.24)mg/g vs(2.77±0.76)mg/g,P<0.01]。(3)正常血糖高胰岛素钳夹试验表明,HF组高脂饲养4周始葡萄糖输注率(GIR)呈下降趋势,高脂饲养8周时明显下降[(21.81±7.20)mg·kg~(-1)·min~(-1)vs(8.44±1.77)mg·kg~(-1)·min~(-1),p<0.01],一直持续至20周。(4)脂代谢调控基因的检测表明,高脂饲养4周时肝脏中合成基因乙酰辅酶A羧化酶(ACCl)的表达无明显增高而氧化基因肉毒碱酰基转移酶(CPT-1)的表达下降20.3%(P<0.05),肌肉组织ACC2、CPT-1的表达均无明显变化(P>0.05);高脂饲养8周时肝脏中ACCl的表达增高20.6%、CPT-1的表达下降27.1%(P<0.05),肌肉组织ACC2的表达增高18.6%、CPT-1的表达下降19.2%(P<0.05);高脂饲养20周时肝脏ACCl表达增高48.3%(P<0.05)、CPT-l表达无明显变化(p>0.05),肌肉ACC2表达增高101.1%、CPT-1的表达下降71%(P<0.05)。结论高脂饲养SD大鼠脂肪分存过程中,肝脏早于肌肉,肝脏TG含量增加可能是胰岛素抵抗的早期标志之一。脂代谢调控基因的表达可能在其中起了重要作用。
Objective To investigate the order of fat storage in high fat diet SD rats and its relationship with insulin resistance. Methods 8-week-old male Sprague-Dawley rats were randomly divided into two groups: normal feeding group (NC, n = 40) and high fat feeding group (HF, n = 40). The contents of triglyceride (TG) in serum, liver and muscle tissue were measured at different weeks of age. The insulin sensitivity was evaluated by normal hyperglycemic insulin test. The mRNA expression of lipid metabolism regulatory genes in liver and muscle was analyzed by quantitative PCR Variety. RESULTS: Compared with NC group, the blood TG level did not change significantly at 4 weeks and 8 weeks after hyperlipidemia, and significantly increased at 12 weeks [0.52 (0.15-1.00) mmol / L vs 0.31 (0.09-0.53) mmol / L, P <0.01] for up to 20 weeks. (2) The content of TG in the liver of HF group increased significantly from 4 weeks after high fat diet [(34.38 ± 11.12) mg / g vs (1.65 ± 0.37) mg / g, p <0.01] There was no significant change in high fat diets at 4, 8, and 12 weeks. High fat diets were significantly increased at 20 weeks [(32.24 ± 7.24) mg / g vs (2.77 ± 0.76) mg / g, P <0.01]. (3) The hyperglycemic hyperinsulinaemia test showed that the HFG group had a decreasing trend of GIR at 4 weeks, and decreased significantly at 8 weeks ([(21.81 ± 7.20) mg · kg ~ (-1)] -1) · min -1 (8.44 ± 1.77) mg · kg -1 · min -1, p <0.01], which lasted for 20 weeks. (4) The test of lipid metabolism regulation gene showed that the expression of acetylcholinesterase A (ACCl) in the liver was not significantly increased at 4 weeks after high-fat diet and the level of oxidative gene carnitine acyltransferase (CPT-1) (P <0.05). The expression of ACC2 and CPT-1 in muscle tissue showed no significant change (P> 0.05). The expression of ACCl in liver increased by 20.6% and the expression of CPT-1 decreased 27.1% (P <0.05). The expression of ACC2 in muscle increased by 18.6% and the expression of CPT-1 decreased by 19.2% (P <0.05) (P> 0.05). The expression of ACC2 in muscle increased by 101.1% and the expression of CPT-1 decreased by 71% (P <0.05). Conclusions During the process of fat storage in SD rats fed with high-fat diet, the increase of TG content in liver earlier than muscle and liver may be one of the early markers of insulin resistance. Lipid metabolism regulation of gene expression may play an important role.