Table 1_Vitamin D3 promotes white fat beige through IL-27/P38MAPK/PGC-1α pathway.docx

BackgroundObesity is turning into a more critical problem for public health. Vitamin D3 (VD3) may be strongly linked to obesity.
ObjectivesThe study aims to examine the influence of VD3 on IL-27 levels and the molecular mechanism by which VD3 affects white fat beige through the IL-27/P38MAPK/PGC-1α pathway.
MethodsFirstly, a small sample population study was conducted to compare the disparities in serum 25(OH)D3 and IL-27 between individuals with obesity and healthy control groups. Secondly, twenty-four Wistar rats were separated into three groups: CON, HFD, and HFD + VD3 groups. Following 7 weeks of intervention, detection of biochemical indicators in serum by enzyme-linked immunosorbent assay (ELISA), mRNA, and protein expression of vitamin D receptor (VDR), IL-27R, P38MAPK, PGC-1α, and UCP-1 in inguinal adipose tissue by RT-qPCR and western blot. Finally, 3T3-L1 cells were induced into a hypertrophic adipose model, knock down IL-27 or PGC-1α using small interfering RNA, treated with 100 nM Calcitriol for 24 h, and divided into CON, PA, PA + 1,25(OH)2D3, PA + si IL-27, PA + si IL-27 + 1,25(OH)2D3, PA + si PGC-1α, and PA + si PGC-1α + 1,25(OH)2D3 groups. Detection of TC, TG, and IL-27 levels by ELISA, mRNA, and protein expression of VDR, IL-27R, P38MAPK, PGC-1α, UCP-1, and CD137 in cell supernatant by RT-qPCR and western blot.
ResultsA correlation was identified between serum 25(OH)D3 and IL-27 in the population-based study. However, no statistically significant difference in serum 25(OH)D3 or IL-27 levels was observed between the observation group and the control group. After VD3 intervention, TC, TG, and the number of LDs were significantly reduced in both HFD rats and 3T3-L1 cells, and serum IL-6 and MCP-1 in HFD rats were decreased. Meanwhile, there was a significant increase in mRNA and protein expression for VDR, IL-27R, P38MAPK, and PGC-1α. The expressions of the UCP-1 protein and the CD137 mRNA dramatically increased. Knockdown of IL-27 eliminated the increasing effect of calcitriol on the expression of P38MAPK, PGC-1α, UCP-1, and CD137 in 3T3-L1 cells, and knockdown of PGC-1α eliminated the increasing effect of calcitriol on the expression of UCP-1 and CD137 in 3T3-L1 cells.
ConclusionThe study shows that VD3 may promote white fat beige through the IL-27/P38MAPK/PGC-1α pathway.

背景 肥胖已成为日益严峻的公共卫生问题。维生素D3（Vitamin D3, VD3）可能与肥胖存在密切关联。
目的 本研究旨在探讨维生素D3（Vitamin D3, VD3）对白细胞介素27（Interleukin-27, IL-27）水平的影响，以及VD3通过IL-27/P38MAPK/PGC-1α通路调控白色脂肪米色化的分子机制。
方法 首先开展小样本人群研究，对比肥胖人群与健康对照组人群血清25-羟维生素D3[25(OH)D3]及IL-27水平差异。其次，将24只Wistar大鼠随机分为对照组（CON）、高脂饮食组（HFD）及高脂饮食+VD3干预组（HFD+VD3）。干预7周后，采用酶联免疫吸附试验（enzyme-linked immunosorbent assay, ELISA）检测血清生化指标，通过实时荧光定量聚合酶链反应（RT-qPCR）和蛋白质印迹法（western blot）检测腹股沟脂肪组织中维生素D受体（Vitamin D Receptor, VDR）、IL-27受体（IL-27R）、P38丝裂原活化蛋白激酶（P38MAPK）、过氧化物酶体增殖物激活受体γ辅激活因子1α（PGC-1α）和解偶联蛋白1（UCP-1）的mRNA及蛋白表达水平。最后，将3T3-L1细胞诱导为肥大脂肪细胞模型，采用小干扰RNA（small interfering RNA, siRNA）敲低IL-27或PGC-1α，用100nM骨化三醇（Calcitriol）处理24小时，随后分为对照组（CON）、棕榈酸处理组（PA）、PA+1,25-二羟维生素D3[1,25(OH)2D3]组、PA+siIL-27组、PA+siIL-27+1,25(OH)2D3组、PA+siPGC-1α组及PA+siPGC-1α+1,25(OH)2D3组。采用ELISA检测细胞上清液中总胆固醇（TC）、甘油三酯（TG）及IL-27水平，通过RT-qPCR和western blot检测细胞中VDR、IL-27R、P38MAPK、PGC-1α、UCP-1及CD137的mRNA和蛋白表达水平。
结果 人群研究发现血清25(OH)D3与IL-27存在相关性，但肥胖组与健康对照组的血清25(OH)D3及IL-27水平未出现统计学显著差异。经VD3干预后，高脂饮食大鼠及3T3-L1细胞中的TC、TG及脂滴（LDs）数量均显著降低，高脂饮食大鼠的血清IL-6及单核细胞趋化蛋白1（MCP-1）水平亦有所下降。同时，VDR、IL-27R、P38MAPK及PGC-1α的mRNA与蛋白表达水平均显著升高，UCP-1蛋白及CD137的mRNA表达量亦显著上调。敲低IL-27可消除骨化三醇对3T3-L1细胞中P38MAPK、PGC-1α、UCP-1及CD137表达的上调作用；敲低PGC-1α则可消除骨化三醇对3T3-L1细胞中UCP-1及CD137表达的上调作用。
结论 本研究表明，VD3可通过IL-27/P38MAPK/PGC-1α通路促进白色脂肪米色化。