Liu Mei Fang, Zu Lu Xia, Xu Chong, Pu Shen Shen, Xu Guo Heng
Department of Physiology and Pathophysiology, Peking University School of Basic Medical Sciences, Beijing, China.
Beijing Da Xue Xue Bao Yi Xue Ban. 2008 Dec 18;40(6):578-82.
To investigate the effect and basis of tumor necrosis factor-alpha (TNF-alpha) on the lipid droplet associating protein adipose differentiation-related protein(ADRP) in rat differentiated adipocytes.
Differentiated rat adipocytes derived from epididymal fat pads of Sprague-Dawley rats were incubated in the presence or absence of TNF-alpha (25 microg/L). Glycerol level released in the culture medium was determined by a colorimetric assay and served as an index of lipolysis. The protein levels of two lipid droplet associating proteins, perilipin and adipose differentiation-related protein, were examined by immunoblotting analysis. The intracellular lipid droplets were stained by nile red and the localizations of perilipin and ADRP on the lipid droplets were determined by immunostaining.
On day 5 or day 8 after the differentiation of adipocytes, TNF-alpha significantly stimulated lipolysis. The lipolysis response to TNF-alpha occurred apparently at hour 8 and remained high 48 h after the stimulation. TNF-alpha increased the protein levels of ADRP, downregulated perilipin proteins but promoted its phosphorylation level. TNF-alpha caused the lipid droplet dispersion, whereas ADRP and perilipin proteins were remained to associate with the surface of the dispersed lipid droplets.
Chronic stimulation of lipolysis by TNF-alpha resulted in the dispersion of the lipid droplets and therefore upregulated the levels of ADRP proteins.
研究肿瘤坏死因子-α（TNF-α）对大鼠分化脂肪细胞中脂滴相关蛋白脂肪分化相关蛋白（ADRP）的影响及其作用机制。
取Sprague-Dawley大鼠附睾脂肪垫来源的分化脂肪细胞，分别在有无TNF-α（25μg/L）的条件下进行培养。采用比色法测定培养基中释放的甘油水平，作为脂解指标。通过免疫印迹分析检测两种脂滴相关蛋白——周脂素和脂肪分化相关蛋白的蛋白水平。用尼罗红对细胞内脂滴进行染色，并通过免疫染色确定周脂素和ADRP在脂滴上的定位。
在脂肪细胞分化后的第5天或第8天，TNF-α显著刺激脂解。对TNF-α的脂解反应明显在刺激后8小时出现，并在刺激后48小时保持高水平。TNF-α增加了ADRP的蛋白水平，下调了周脂素蛋白水平，但促进了其磷酸化水平。TNF-α导致脂滴分散，而ADRP和周脂素蛋白仍与分散的脂滴表面相关联。
TNF-α对脂解的长期刺激导致脂滴分散，从而上调了ADRP蛋白水平。
