Mice subjected to aP2-Cre mediated ablation of microsomal triglyceride transfer protein are resistant to high fat diet induced obesity.
Mice subjected to aP2-Cre mediated ablation of microsomal triglyceride transfer protein are resistant to high fat diet induced obesity.
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DOI：
10.1186/s12986-016-0061-6
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发表时间：
2016
影响因子：
4.5
通讯作者：
Hussain MM
中科院分区：
文献类型：
--
作者：
Bakillah A;Hussain MM
微粒体甘油三酯转移蛋白（MTP）对于脂蛋白的组装至关重要。 MTP已显示在脂肪细胞脂滴表面；然而，其在脂肪组织中的功能尚不明确。我们假设 MTP 可能在脂肪脂滴的形成和扩张中发挥关键作用。在 3T3-L1 前脂肪细胞中进行质粒介导的 Mttp 基因过表达和 siRNA 介导的敲低，以评估 MTP 对细胞分化和甘油三酯积累的影响。通过将 MTP floxed (Mttpfl/fl) 小鼠与 aP2-Cre 重组酶转基因小鼠交配，在小鼠中实现了 MTP 的脂肪特异性敲除。脂肪特异性MTP缺陷（A-Mttp-/-）小鼠被喂食60%高脂饮食（HFD），研究MTP敲低对体重、体脂肪成分、血浆和组织脂质成分、葡萄糖代谢、脂肪生成和肠道吸收的影响。使用比色测定法测量总空腹血浆和大小分级血浆中的脂质。通过实时定量PCR研究基因表达。所有数据均使用 t 检验、方差分析进行评估。 MTP 表达在 3T3-L1 细胞分化早期增加，随后下降。 MTP 表达的增加先于 PPARγ 表达的增加。 MTP 过表达增强了脂滴的形成，而敲低则减弱了细胞脂质积累。这些研究表明 MTP 对脂肪生成有积极影响。当给小鼠喂食 HFD 时，使用 aP2-Cre (A-Mttp-/-) 消除 Mttp 基因会导致小鼠出现瘦表型。与野生型 Mttpfl/fl 小鼠相比，这些小鼠的白色脂肪组织减少。 A-Mttp-/-小鼠的脂肪组织中较小尺寸的脂肪细胞数量增加，巨噬细胞浸润减少。此外，这些小鼠还可以免受 HFD 诱导的脂肪肝的影响。 A-Mttp-/-小鼠血浆甘油三酯中度升高，但胆固醇、葡萄糖和胰岛素水平正常。基因表达分析显示，A-Mttp-/-小鼠的脂肪组织中PPARγ及其下游靶标的mRNA水平显着降低。这些数据表明，MTP 可能通过影响 PPARγ 表达来调节脂肪生成，并在脂质积聚形成更大的脂滴中发挥作用。因此，灭活脂肪 MTP 的药物可能是有用的抗肥胖药物。
Microsomal triglyceride transfer protein (MTP) is essential for the assembly of lipoproteins. MTP has been shown on the surface of lipid droplets of adipocytes; however its function in adipose tissue is not well defined. We hypothesized that MTP may play critical role in adipose lipid droplet formation and expansion. Plasmids mediated overexpression and siRNA mediated knockdown of Mttp gene were performed in 3T3-L1 pre-adipocytes to evaluate the effects of MTP on cell differentiation and triglyceride accumulation. Adipose-specific knockdown of MTP was achieved in mice bybreeding MTP floxed (Mttpfl/fl) mice with aP2-Cre recombinase transgenic mice. Adipose-specific MTP deficient (A-Mttp-/-) mice were fed 60 % high-fat diet (HFD), and the effects of MTP knockdown on body weight, body fat composition, plasma and tissues lipid composition, glucose metabolism, lipogenesis and intestinal absorption was studied. Lipids were measured in total fasting plasma and size fractionated plasma using colorimetric assays. Gene expression was investigated by Real-Time quantitative PCR. All data was assessed using t-test, ANOVA. MTP expression increased during early differentiation in 3T3-L1 cells, and declined later. The increases in MTP expression preceded PPARγ expression. MTP overexpression enhanced lipid droplets formation, and knockdown attenuated cellular lipid accumulation. These studies indicated that MTP positively affects adipogenesis. The ablation of the Mttp gene using aP2-Cre (A-Mttp-/-) in mice resulted in a lean phenotype when fed a HFD. These mice had reduced white adipose tissue compared with wild-type Mttpfl/fl mice. The adipose tissue of A-Mttp-/- mice had increased number of smaller size adipocytes and less macrophage infiltration. Further, these mice were protected from HFD-induced fatty liver. The A-Mttp-/- mice had moderate increase in plasma triglyceride, but normal cholesterol, glucose and insulin levels. Gene expression analysis showed that the adipose tissue of the A-Mttp-/- mice had significantly lower mRNA levels of PPARγ and its downstream targets. These data suggest that MTP might modulate adipogenesis by influencing PPARγ expression, and play a role in the accretion of lipids to form larger lipid droplets. Thus, agents that inactivate adipose MTP may be useful anti-obesity drugs.