PDF(Pubmed)
Abstract：
In obesity, circulating saturated fatty acids (SFAs) and inflammatory cytokines interfere with skeletal muscle insulin signaling, leading to whole body insulin resistance. Further, obese skeletal muscle is characterized by macrophage infiltration and polarization to the inflammatory M1 phenotype, which is central to the development of local inflammation and insulin resistance. While skeletal muscle-infiltrated macrophage-myocyte crosstalk is exacerbated by SFA, the effects of other fatty acids, such as n-3 and n-6 polyunsaturated fatty acids (PUFAs), are less studied. Thus, the objective of this study was to determine the effects of long-chain n-3 and n-6 PUFAs on macrophage M1 polarization and subsequent effects on myocyte inflammation and metabolic function compared to SFA. Using an in vitro model recapitulating obese skeletal muscle cells, differentiated L6 myocytes were cultured for 24 h with RAW 264.7 macrophage-conditioned media (MCM), followed by insulin stimulation (100 nM, 20 min). MCM was generated by pre-treating macrophages for 24 h with 100 μM palmitic acid (16:0, PA-control), arachidonic acid (20:4n-6, AA), or docosahexaenoic acid (22:6n-3, DHA). Next, macrophage cultures were stimulated with a physiological dose (10 ng/mL) of lipopolysaccharide for an additional 12 h to mimic in vivo obese endotoxin levels. Compared to PA, both AA and DHA reduced mRNA expression and/or secreted protein levels of markers for M1 (TNFα, IL-6, iNOS; p < 0.05) and increased those for M2 (IL-10, TGF-β; p < 0.05) macrophage polarization. In turn, AA- and DHA-derived MCM reduced L6 myocyte-secreted cytokines (TNFα, IL-6; p < 0.05) and chemokines (MCP-1, MIP-1β; p < 0.05). Only AA-derived MCM increased L6-myocyte phosphorylation of Akt (p < 0.05), yet this was inconsistent with improved insulin signaling, as only DHA-derived MCM improved L6 myocyte glucose uptake (p < 0.05). In conclusion, dietary n-3 and n-6 PUFAs may be a useful strategy to modulate macrophage-myocyte inflammatory crosstalk and improve myocyte insulin sensitivity in obesity.
摘要：
在肥胖症中，循环饱和脂肪酸（SFAs）和炎性细胞因子干扰骨骼肌胰岛素信号，导致全身胰岛素抵抗。Further,肥胖骨骼肌的特征是巨噬细胞浸润和极化为炎性M1表型，这是局部炎症和胰岛素抵抗发展的核心。虽然SFA会加剧骨骼肌浸润的巨噬细胞-心肌细胞串扰，其他脂肪酸的影响，如n-3和n-6多不饱和脂肪酸（PUFA），研究较少。因此，这项研究的目的是确定长链n-3和n-6PUFA对巨噬细胞M1极化的影响以及随后对肌细胞炎症和代谢功能的影响。使用体外模型概括肥胖骨骼肌细胞，分化的L6肌细胞用RAW264.7巨噬细胞条件培养基（MCM）培养24小时，其次是胰岛素刺激（100nM，20分钟）。通过用100μM棕榈酸(16:0,PA对照)预处理巨噬细胞24小时产生MCM,花生四烯酸(20:4n-6,AA),或二十二碳六烯酸（22：6n-3，DHA）。接下来,用生理剂量（10ng/mL）的脂多糖再刺激巨噬细胞培养物12小时，以模拟体内肥胖内毒素水平。与PA相比，AA和DHA均降低M1标志物的mRNA表达和/或分泌蛋白水平(TNFα，IL-6、iNOS;p<0.05)和增加M2(IL-10、TGF-β;p<0.05)巨噬细胞极化。反过来,AA和DHA衍生的MCM减少了L6肌细胞分泌的细胞因子（TNFα，IL-6；p<0.05）和趋化因子（MCP-1，MIP-1β；p<0.05）。只有AA来源的MCM增加了Akt的L6-心肌细胞磷酸化（p<0.05），然而这与胰岛素信号的改善不一致，因为只有DHA来源的MCM改善了L6肌细胞葡萄糖摄取(p<0.05)。总之,饮食中的n-3和n-6PUFAs可能是一个有用的策略，以调节巨噬细胞-肌细胞的炎症串扰和提高肌细胞胰岛素敏感性的肥胖。
