探索脂肪组织特异性敲除Sirt6小鼠的代谢表型及SIRT6调控产热的分子机制

发布时间：2018-03-21 18:43

本文选题：SIRT6　切入点：脂肪组织　出处：《北京协和医学院》2017年博士论文　论文类型：学位论文

【摘要】：肥胖是诱发Ⅱ型糖尿病、动脉粥样硬化和肿瘤的危险因素。虽然肥胖的发病率在30年间翻了一倍,但是目前的医疗界仍然缺乏有效的手段治疗肥胖。考虑到棕色和米色脂肪能够解偶联氧化磷酸化,将化学能转化成热能,增加机体的能量消耗,它们成为了人类战胜肥胖的新希望。SIRT6与Sirtuins家族的其他成员不同,它位于细胞核内的染色质上,是具有ADP-核糖基转移酶和依赖于NAD+的去乙酰化酶活性的蛋白酶。研究表明,SIRT6在调控基因组稳定性、衰老、糖代谢、应激反应、寿命、昼夜节律、心肌肥大和肿瘤的发生及发展中扮演重要角色,但是SIRT6在脂肪组织中的功能还有待发掘。我们的研究表明,SIRT6在棕色脂肪组织中的表达量明显高于其在白色脂肪组织的表达水平,并且肥胖小鼠棕色脂肪组织中SIRT6的表达量显著降低。冷刺激和β-激动剂能够促进SIRT6在棕色和白色皮下脂肪组织中的表达。脂肪组织特异性敲除Sirt6会削弱小鼠棕色脂肪的产热功能,使小鼠的棕色脂肪发生明显的“白色化”,同时小鼠的氧气消耗速率降低、体温下降,并导致敲除小鼠的肥胖。此外,敲除小鼠还有高血脂症、胰岛素抵抗和脂肪肝等异常的代谢表型。脂肪组织特异性敲除Sirt6使得小鼠的能量消耗减少,脂肪酸氧化和产热受到抑制。我们还发现敲除Sirt6致使小鼠缺乏对冷刺激和β3肾上腺素受体激动剂CL316,243介导的产热产生响应。在原代小鼠棕色脂肪细胞中敲除Sirt6,会显著抑制产热相关基因的表达和线粒体呼吸,反过来,过表达SIRT6则会促进产热基因的表达和线粒体呼吸,基于这些体外实验,我们认为SIRT6对脂肪组织产热功能的调控具有细胞自主性。对于分子机制的探索,我们发现SIRT6通过与磷酸化的ATF2发生相互作用,招募磷酸化的ATF2结合到PGC-1α的启动子区,进而增强PGC-1α的表达。因此,脂肪细胞内敲除Sirt6会因磷酸化的ATF2对PGC-1α启动子区的结合减少,从而抑制PGC-1α及其下游基因的表达。我们的研究表明SIRT6对于具有产热功能的脂肪细胞维持其产热作用具有决定性作用,这使得SIRT6成为治疗肥胖和Ⅱ型糖尿病的潜在靶点。
[Abstract]:Obesity is a risk factor for type 2 diabetes, atherosclerosis and cancer, although the incidence of obesity has doubled in 30 years. But the current medical community still lacks effective means to treat obesity. Considering that brown and beige fats can uncouple oxidative phosphorylation, converting chemical energy into heat energy and increasing the body's energy consumption, They became the new hope for a human fight against obesity. SIRT6, unlike other members of the Sirtuins family, is located on the chromatin in the nucleus. It is a protease with ADP- ribonyltransferase and deacetylase activity dependent on NAD. Studies have shown that SIRT6 regulates genomic stability, senescence, glucose metabolism, stress response, longevity, circadian rhythm, Myocardial hypertrophy and tumor play an important role in the occurrence and development of tumor, but the function of SIRT6 in adipose tissue remains to be explored. Our study shows that the expression of SIRT6 in brown adipose tissue is significantly higher than that in white adipose tissue. Cold stimulation and 尾 -agonist can promote the expression of SIRT6 in brown and white subcutaneous adipose tissue. The specific knockout of Sirt6 in adipose tissue can weaken the brown of mice. The heat production function of fat, "Whitening" of brown fat in mice, at the same time reducing the rate of oxygen consumption, lowering body temperature, and leading to obesity in knockout mice. In addition, the knockout mice also have hyperlipidemia. Abnormal metabolic phenotypes such as insulin resistance and fatty liver. Fatty tissue specific knockout of Sirt6 reduces energy consumption in mice. Fatty acid oxidation and heat production were inhibited. We also found that knockout of Sirt6 caused a lack of response to cold stimulation and 尾 3 adrenergic receptor agonist CL316243 mediated heat production. Knockout of Sirt6 in primary mouse brown adipocytes showed significant results. Inhibit the expression of heat-producing genes and mitochondrial respiration, In turn, overexpression of SIRT6 promotes the expression of heat-producing genes and mitochondrial respiration. Based on these in vitro experiments, we believe that SIRT6 has cellular autonomy in regulating heat production in adipose tissue. We found that SIRT6, by interacting with phosphorylated ATF2, recruited phosphorylated ATF2 to the promoter region of PGC-1 伪, thereby enhancing the expression of PGC-1 伪. As a result, Sirt6 knockout in adipocytes decreased the binding of PGC-1 伪 promoter by phosphorylated ATF2. Our results show that SIRT6 plays a decisive role in maintaining the heat production of adipocytes with heat production, which makes SIRT6 a potential target for the treatment of obesity and type 2 diabetes.
【学位授予单位】：北京协和医学院
【学位级别】：博士
【学位授予年份】：2017
【分类号】：R589.2

【相似文献】