丁酸鈉對脂肪細胞分化之調控

Abstract

游離短鏈脂肪酸為微生物於腸道發酵後的主要產物,包含乙酸、丙酸、丁酸 和戊酸,此類脂肪酸除了提供能量外也會影響腸道上皮細胞黏膜和菌相的生長, 除此之外也具有調控免疫系統、癌細胞生長、胰臟分泌胰島素以及細胞分化的作 用。目前已有許多研究指出丁酸能夠對脂肪細胞的分化有所作用,而其效果卻不 一致,因此本研究的目在釐清丁酸對小鼠、豬等脂肪細胞分化的影響,期能瞭解 其作用途徑和機制。我們發現丁酸會抑制小鼠基質血管細胞 (SVCs) 分化成成熟 的脂肪細胞,減少脂肪堆積於脂肪細胞中,也會抑制脂肪細胞標的基因表現,包 含 Adipoq (adiponectin)、Glut4 (glucose transporter type 4)、Fasn (fatty acid synthase)、 Fabp4 (fatty acid binding protein 4) 和 Srebf1 (sterol regulatory element-binding transcription factor 1) 等,但卻對 3T3-L1 細胞株的分化沒有明顯的影響。相反的, 我們發現丁酸會促進豬基質血管細胞分化脂肪細胞,並且會增進脂肪細胞標的基 因的表現,包含 Adipoq、Fabp4 以及 Cebpa (CCAAT/enhancer binding protein, alpha) 等,而增加細胞累積油滴。我們進一步探討丁酸對脂肪細胞分化的作用途徑,在 小鼠 SVCs 分化過程中額外添加對游離脂肪酸二型受體 (FFAR2) 具有專一性的配 體 (4-chloro-α-(1-methylethyl)-N-2-thiazolylbenzeneacetamide, 4-CMTB) , 發 現 4-CMTB 也會減少小鼠基質血管細胞的分化,qPCR 分析也顯示脂肪細胞標的基因 有下降的情形。綜合上述結果,丁酸對不同物種的脂肪細胞有不一樣的效果,在 小鼠中丁酸可能藉由游離脂肪酸二型受體這個路徑來抑制脂肪細胞的分化過程。

Butyric acid, a short-chain fatty acid (SCFA), is one of the main products from microbial fermentation in the gastrointestinal tract. Free fatty acid receptor 2 (FFAR2) and FFAR3 were found to be receptors for SCFA. In recent years, SCFAs have been shown to play an important role in the prevention and regulation of the metabolic syndrome, certain types of cancer and bowel disorders. Although, the functions of butyrate on adipogenesis were investigated, the results were not consistent. Therefore, we designed the current study to clarify the effects of butyrate on adipocyte differentiation. In the current study, stromal vascular cells (SVC) from murine and porcine subcutaneous adipose tissue (SAT) were used as the preadipocyte model. Adipocyte differentiation degree was assessed by Oil Red O staining and mRNA expression analysis of adipogenic genes. In addition to SVC of mouse and porcine SAT, we also used 3T3-L1 cell line as an in vitro model. 4-CMTB, an agonist of FFAR2, was used to determine whether the effects of butyrate are mediated through FFAR2. Compared with control, butyrate inhibited the differentiation of mouse adipocytes. The mRNA expression of adipogenesis related genes, Adipoq (adiponectin), Glut4 (glucose transporter type 4), Fasn (fatty acid synthase), Fabp4 (fatty acid binding protein 4), and Srebf1 (sterol regulatory element-binding transcription factor 1), were inhibited in mouse adipocytes. In porcine adipocytes, butyrate enhanced the expression of adipogenic genes. On the other hand, 3T3-L1 cell differentiation was not affected by butyrate. 4-CMTB decreased the formation of adipocytes in mouse SVC and the expression of Adipoq, Fabp4 and Cebpa (CCAAT/enhancer binding protein, alpha).Our research demonstrated that butyrate inhibited mouse adipogenesis but enhanced adipogenesis in porcine SVC. Furthermore, the effect of butyrate on adipogenesis may be through the FFAR2 pathway. Further research is required to demonstrate the function of butyrate and the involvement of FFAR2 in regulating human adipogenesis. Such information can support whether murine or porcine model can be used as a better human model in coping with obesity.