SIRT1基因缺陷对肥胖小鼠棕色脂肪功能的影响

Effect of SIRT1 deficiency on function of brown adipose tissue in obese mice

目的探讨沉默信息调节因子2相关酶1（SIRTl）基因缺陷对高脂饮食诱导的肥胖小鼠棕色脂肪功能的影响。方法雄性12周龄SIRT1基因敲除杂合子小鼠和同窝的野生型对照小鼠（每组6只），分别给予高脂饮食饲养16周以构建肥胖模型。能量代谢笼测定氧耗量和产热量，冷刺激试验评估适应性产热功能。干预结束后留取棕色脂肪组织，HE染色观察形态学改变，免疫组化染色和Western印迹法检测解偶联蛋白1（UCP1）的表达水平，实时定量PCR检测线粒体DNA相对含量。结果与对照组相比，SIRTl基因敲除杂合子小鼠的氧耗量和产热量均明显降低[（2681±297）比（3017±313）ml·kg^-1·h^-1、（19．05±2．40）比（21．15±2．49）kcal·kg^-1·h^-1，均P〈0．05l，冷刺激时维持体温的能力受损。HE染色显示SIRT1杂合子小鼠棕色脂肪组织内的脂滴空泡较对照组更大，免疫组化染色及Western印迹检测结果表明其UCPl的表达水平显著降低（P〈0．05）。实时定量PCR结果显示，SIRT1杂合子小鼠棕色脂肪组织的线粒体DNA相对含量明显减少（0．38±0．10比1．00±0．40，P〈0．05）。结论SIRT1基因缺陷加剧高脂饮食诱导的肥胖小鼠的棕色脂肪功能障碍，即加重棕色脂肪白色化。

Objective To investigate the effect of silent mating type information regulation 2 homolog 1 （SIRT1） deficiency on function of brown adipose tissue （BAT） in high-fat diet （HFD）-induced obese mice. Methods Male SIRT1 deficient heterozygous （ SIRT1 ＋/- ） mice and their wild-type （WT） littermates were challenged with a HFD diet for 16 weeks to induce obesity model. Energy metabolic cages were used to measure oxygen consumption and heat production, and cold tolerance test was to evaluate the adaptive thermogenic function. With brown fat collected after the diet intervention, determination techniques were adopted included HE staining for morphologic changes, immunohistochemical staining and Western blotting for uncoupling protein 1 （UCP1） expression, quantitative real-time PCR for relative content of mitochondria DNA （mtDNA）. Results Compared to WT controls, SIRT1 ＋/- mice displayed significant decreases in both oxygen consumption and heat production[ （2 681 ±297） vs （3 017 ±313） ml·kg^-1·h^-1 , （19.05±2.40） vs （21.15±2.49） kcal·kg^-1·h^-1, both P〈0.05）], as well as an impairment in maintaining their body temperature during the cold challenge. HE staining revealed the accumulation of larger lipid droplets in BAT of SIRT1 ＋/- mice, and both immunohistochemical staining and Western blotting indicated an obvious reduction in expression of UCP1 （ P 〈 0.05 ）. Quantitative real-time PCR showed a significant decrease in the relative mtDNA content in BAT of SIRT1 ＋/- mice （0. 38 ±0.10 vs 1.00 ±0.40, P 〈 0. 05 ）. Conclusion SIRT1 deficiency promotes BAT dysfunction, meaning that whitening in obese