High Fat Diet-Induced Constitutive Caveolin-1 Activation in Mouse Jejunum Promotes LPS Transport with Consequent Metabolic Syndrome
Authors: Pokala Nikita , Akiba Yasutada , Kaunitz Jonathan 
Published: May 2024

Lipopolysaccharides (LPS) entry from the intestinal lumen to the circulation is associated with systemic inflammation. We have found that LPS is transcellularly transported from the gut lumen to the portal vein (PV) in the presence of luminal long-chain fatty acid (LCFA) via CD36- and lipid raft-mediated pathways. Furthermore, LCFA-induced LPS transport is abolished in caveolin-1 (Cav1) knockout (KO) jejunum, suggesting the involvement of caveolae-mediated endocytosis. Here, we examined the effects of diets of varying FA composition on the development of the metabolic syndrome (MetS) and on LPS transport in murine jejunum. Male and female C57Bl6 wild type (WT) and Cav1 KO mice were fed a standard high CHO, high protein, low fat diet (SD), or one of 3 high fat-high sugar diets (34% sucrose, 42% fat) that were enriched in saturated LCFA (LCD), medium-chain FA (MCD) and polyunsaturated FA (PUD) for 6 wks. FITC-LPS was added to the mucosal (m) bath of Ussing-chambered muscle-stripped jejunum. Serosal (s) appearance of FITC-LPS was measured with or without luminal addition of oleic acid (OA, 10 mM)/taurocholic acid (TCA, 0.1 mM). FD4 m-to-s permeability and transepithelial electrical resistance (TER) were also measured. PV LPS levels were measured by a limulus amœbocyte lysate test kit. LCD-induced MetS (increased body weight, blood glucose levels, perigonadal fat weight, and liver weight), predominantly in male, whereas MCD and PUD did not induce MetS in WT. Nevertheless, LCD failed to induce MetS in KO, confirming that Cav1 KO mice are resistant to diet-induced obesity. PV LPS levels were elevated only in male WT LCD with no change in KO. There was no FITC-LPS m-to-s movement in WT SD jejunum, whereas luminal addition of OA/TCA increased LPS m-to-s movement. Interestingly, FITC-LPS m-to-s movement was increased in jejunum from WT LCD with no further increase after OA/TCA challenge, suggesting that LCD constitutively upregulated LPS transport. FD4 permeability was significantly higher in WT LCD than in WT SD, but not in KO. MCD but no other diet somewhat increased TER, compared with WT SD or KO SD. Constitutive LPS transport in WT LCD jejunum was abolished by luminal addition of the lipid raft inhibitor methyl-β-cyclodextrin (0.1 mM), suggesting the involvement of transcytotic rather than paracellular transport mechanisms. No LPS transport was observed in KO SD and KO LCD jejunum, further suggesting that LCD-induced LPS transport is Cav1 dependent. These results suggest that LCD constitutively activates Cav1-mediated endocytotic LPS transport in the small intestine, resulting in metabolic endotoxemia and the MetS. Cav1-mediated LPS transport is a promising therapeutic target for diet-induced, LPS-associated MetS. VA Merit Review and DoD grants. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.