HFHS Cav1 paper data

The entry of lipopolysaccharides (LPS) from the intestinal lumen to the circulation is associated with metabolic syndrome (MetS). We have reported that LPS is transcellularly transported from the jejunal lumen in the presence of luminal long-chain fatty acid (LCFA) via caveolin-1 (Cav1)-mediated endocytotic pathways. Here, we examined the effects of diets of varying FA composition on the MetS induction and LPS transport in murine jejunum.Male and female C57Bl6 wild type (WT) and global Cav1 knockout (KO) mice were fed a standard diet (SD), or one of 3 high fat-high sucrose diets enriched in saturated LCFA (LCD), medium-chain FA (MCD) and polyunsaturated FA (PUD) for 6 wks. FITC-LPS or FITC-dextran (FD4) m-to-s transport with transepithelial electrical resistance (TEER) was measured in Ussing chambers.MetS was predominantly induced in male WT LCD with increased portal venous LPS levels, but less induced in WT MCD and PUD or in KO. Interestingly, basal FITC-LPS and FD4 transport was increased in the jejunum of male WT LCD without TEER change, compared with WT SD, but not in KO LCD. The LCD-induced enhanced LPS and FD4 transports were abolished by luminal inhibitors of lipid rafts, CD36, or Src kinase. In vivo imaging demonstrated intracellular vesicular uptake of dextran and LPS in the jejunal villous enterocytes with absent paracellular staining in male WT LCD, but not in WT SD or KO LCD. In proximal colonic mucosa, there was no LPS or FD4 transport in WT SD or LCD.These results suggest that LCD constitutively activates Cav1-mediated endocytotic LPS transport in the small intestine, with consequent metabolic endotoxemia and MetS. Cav1-mediated LPS transport is a promising therapeutic target for diet-induced, LPS-associated MetS.

肠道腔隙中的脂多糖（lipopolysaccharides, LPS）进入血液循环系统，与代谢综合征（metabolic syndrome, MetS）密切相关。本团队此前已报道，在肠腔内长链脂肪酸（long-chain fatty acid, LCFA）存在的条件下，LPS可通过窖蛋白-1（caveolin-1, Cav1）介导的内吞途径，从空肠腔完成跨细胞转运。本研究旨在探讨不同脂肪酸组成的饲料对小鼠空肠内MetS诱导过程及LPS转运的影响。
将雄性与雌性C57BL/6野生型（wild type, WT）及全身Cav1敲除（knockout, KO）小鼠分为四组，分别饲喂标准饲料（standard diet, SD），或三种分别富集饱和长链脂肪酸（saturated LCFA, LCD）、中链脂肪酸（medium-chain FA, MCD）与多不饱和脂肪酸（polyunsaturated FA, PUD）的高脂高糖饲料，造模周期为6周。采用尤斯灌流室（Ussing chambers）检测FITC标记LPS（FITC-LPS）与FITC标记葡聚糖（FITC-dextran, FD4）的黏膜侧到浆膜侧转运效率，并同步测定跨上皮电阻（transepithelial electrical resistance, TEER）。
实验结果显示：雄性野生型小鼠饲喂LCD饲料后可显著诱导MetS，伴随门静脉LPS水平升高；而饲喂MCD或PUD饲料的WT小鼠，以及所有KO小鼠均未出现明显的MetS表型。有趣的是，与WT SD组相比，雄性WT LCD组小鼠的空肠组织中基础FITC-LPS及FD4转运水平均显著升高，且跨上皮电阻未发生明显改变，但该现象在KO LCD组中并未观测到。LCD诱导的LPS与FD4转运增强效应，可被脂筏、分化簇36（CD36）或Src激酶的肠腔内抑制剂所阻断。活体成像结果表明，雄性WT LCD组小鼠的空肠绒毛肠上皮细胞内可见葡聚糖与LPS的囊泡摄取现象，且无细胞旁染色信号；而WT SD组与KO LCD组均未观察到该特征。在近端结肠黏膜中，WT SD组与WT LCD组均未检测到LPS或FD4的跨黏膜转运。
综上，本研究结果提示，LCD饲料可持续激活小肠内Cav1介导的内吞型LPS转运通路，进而引发代谢性内毒素血症与MetS。Cav1介导的LPS转运有望成为饮食诱导的、与LPS相关的MetS的潜在治疗靶点。