Leptin调控Hh信号通路抑制脂肪生成的作用和机制的研究

Obesity is characterized by the accumulation of adipose tissue, which expands due to an increase in adipocyte size (hypertrophy) and number (hyperplasia). Therefore, inhibition of adipogenesis from preadipocytes can regulate the amount of adipose tissue. There are evidences that both leptin and Hedgehog（Hh）pathway are expressed in adipose tissue, and they all regulate the differentiation and maturation of adipocytes independently and inhibit adipogenesis. Their effects are closely related to inhibiting key transcription factors peroxisome proliferator-activated receptor gamma (PPARγ) and lipid droplet related protein perilipin expression. Those support that there may be cross or link between leptin and Hh signal pathway. Our experiment results showed that leptin could promote the Gli1 mRNA and protein expression in 3T3-L1 preadipocytes, which is one of Hh pathway target genes and has been characterized as a reliable marker of Hedgehog signaling activity. That illustrates leptin can activate Hh pathway.Then,during the differentiation and maturation of adipocytes,whether could leptin inhibit adipogenesis through up-regulating expression and function of Hh signal molecules? What is its mechanism? So, we will use many research techniques and methods to investigate the role of Hh pathway in leptin's inhibition on adipogenesis in preadipocytes and its mechanism, and to explore whether that effect is alterative and one of mechanisms to promote adipogenesis during the formation of obesity. This research can enhance our understanding about regulation ways of fat formation and action mechanism of leptin. And it has the important meaning for exploring occurrence, development and treatment of clinical disease such as obesity.

肥胖的特征是脂肪的累积，抑制前脂肪细胞的脂肪生成可调节脂肪组织量。leptin和Hedgehog(Hh)信号通路均分布在脂肪组织，两者也均能通过降低关键转录因子PPARγ及脂肪代谢关键分子perilipin的表达降低脂肪生成，表明两条信号通路之间可能具有联系。我们前期研究显示，在3T3-L1前脂肪细胞，leptin可以促进Hh信号通路的关键分子Gli1的mRNA和蛋白表达，激活Hh信号通路。那么，在脂肪细胞的分化成熟中，leptin是否能通过上调Hh通路信号分子的表达和功能抑制脂肪的生成？其作用机制如何？本研究拟以前脂肪细胞为研究对象，研究Hh信号通路在leptin抑制脂肪生成中的作用及其调节机制，探讨在肥胖形成中leptin对Hh通路的调控作用是否改变并参与脂肪增加，该研究有助于加深对脂肪形成调控方式和leptin作用机制的深入理解，对于肥胖等临床疾病的发生发展机制和治疗有重要探索意义。

Leptin和Hedgehog(Hh)信号通路均分布在脂肪组织，调控着脂肪的分化和成熟，具有抑制成脂作用，两者之间可能具有相互联系。本研究利用3T3-L1前脂肪细胞的培养和诱导分化模型为研究对象，研究Hh信号通路在leptin抑制脂肪生成中的作用及其调节机制。结果显示，在脂肪细胞分化过程中Hh信号通路逐渐受到抑制，leptin对Hh信号通路具有激活作用，尤其是脂肪细胞分化中后期。随后研究了Hh通路在leptin抑制脂肪生成中的作用，发现leptin与Hh信号通路激活均能减少前脂肪细胞存活率，促进脂肪细胞凋亡，诱导分化后发现leptin与Hh信号通路激活可减小脂肪细胞面积、脂质含量，GPDH活性，促进脂肪细胞中游离脂肪酸和甘油的释放，抑制脂肪合成相关酶（FAS、ACC）、促进脂肪分解相关酶（HSL、ATGL）mRNA和蛋白的表达，从而抑制脂肪合成，促进脂肪分解。另外Hh通路激活和leptin能抑制脂肪生成转录因子PPARγ和C/EBPα 、抑制脂肪细胞特异分子perilipin、aP2、Adipsin mRNA和蛋白的表达，促进抗脂肪生成转录因子Gata2/3、Gliz、Ncor2 mRNA和蛋白的表达，leptin与Hh信号通路激活共同作用抑制脂肪生成作用进一步增强，阻断Hh信号通路则可以逆转部分leptin的作用，说明leptin抑制成脂的作用部分是通过激活Hh通路发挥的。进一步我们研究了leptin及其信号通路对Hh通路中信号分子的作用，发现诱导脂肪细胞分化，Hh信号通路被抑制，leptin可激活Hh信号通路，阻断leptin受体、JAK、PI3K/Akt通路后发现leptin对Hh信号通路的激活作用被减弱，以上结果表明：在前脂肪细胞的分化成熟过程中，leptin通过激活Hh信号通路抑制脂肪细胞的分化成熟，抑制脂肪合成，促进脂肪分解，从而抑制脂肪生成。该作用是通过leptin受体-JAK/STAT/-PI3K/Akt通路激活Hh信号通路从而参与调节脂肪生成。研究结果有助于加深对脂肪形成调控方式和leptin作用机制的理解，对于肥胖等临床疾病的发生发展机制和治疗有重要探索意义。