Dietary fat induced chylomicron-mediated LPS translocation in a bicameral Caco-2cell model.

BACKGROUND: There is increasing evidence that dietary fat, especially saturated fat, promotes the translocation of lipopolysaccharide (LPS) via chylomicron production in the gut. Chylomicrons can subsequently transport LPS to other parts of the body, where they can induce low-grade chronic inflammation that is linked to various metabolic and gut-related diseases. To identify promising (food) compounds that can prevent or ameliorate LPS-related low-grade inflammation, we developed and optimized a bicameral in vitro model for dietary fat-induced LPS translocation that closely mimics the in vivo situation and facilitates high-throughput screening. METHODS: Caco-2 cells were cultured in monolayers and differentiated to a small intestinal phenotype in 21 days. Thereafter, optimal conditions for fat-induced chylomicron production were determined by apical exposure of Caco-2 cells to a dilution range of in vitro digested palm oil and sunflower oil, optionally preceded by a 1-week apical FBS deprivation (cultured without apical fetal bovine serum). Chylomicron production was assessed by measuring basolateral levels of the chylomicron-related marker apolipoprotein B. Next, LPS was coincubated at various concentrations with the digested oils, and fat-induced LPS translocation to the basolateral side was assessed. RESULTS: We found that dietary fat-induced LPS translocation in Caco-2 cells was optimal after apical exposure to digested oils at a 1:50 dilution in combination with 750 ng/mL LPS, preceded by 1 week of apical FBS deprivation. Coincubation with the chylomicron blocker Pluronic L81 confirmed that fat-induced LPS translocation is mediated via chylomicron production in this Caco-2 cell model. CONCLUSION: We developed a robust Caco-2 cell model for dietary fat-induced LPS translocation that can be used for high-throughput screening of (food) compounds that can reduce LPS-related low-grade inflammation.

Post-sensitization administration of non-digestible oligosaccharides and Bifidobacterium breve M-16V reduces allergic symptoms in mice.

To support dietary management of severe cow's milk allergic infants, a synbiotic mixture of non-digestible oligosaccharides and Bifidobacterium breve M-16V (B. breve) was designed from source materials that are completely cow's milk-free. It was investigated whether this specific synbiotic concept can reduce an established food allergic response in a research model for hen's egg allergy. Mice were orally sensitized once a week for 5 weeks to ovalbumin (OVA) using cholera toxin (CT) as an adjuvant. Non-sensitized mice received CT in PBS only. Sensitized mice were fed a control diet or a diet enriched with short-chain- (scFOS) and long-chain fructo-oligosaccharides (lcFOS), B. breve or scFOSlcFOS + B. breve for 3 weeks starting after the last sensitization. Non-sensitized mice received the control diet. Anaphylactic shock symptoms, acute allergic skin responses and serum specific IgE, mMCP-1 and galectin-9 were measured upon OVA challenge. Activated Th2-, Th1-cells and regulatory T-cells were quantified in spleen and mesenteric lymph nodes (MLN) and cytokine profiles were analyzed. Short chain fatty acids (SCFA) were measured in ceacal samples. The acute allergic skin response was reduced in mice fed the scFOSlcFOS + B. breve diet compared to mice fed any of the other diets. A reduction in mast cell degranulation (mMCP-1) and anaphylactic shock symptoms was also observed in these mice. Unstimulated splenocyte cultures produced increased levels of IL10 and IFNg in mice fed the scFOSlcFOS + B. breve diet. Correspondingly, increased percentages of activated Th1 cells were observed in the spleen. Allergen-specific re-stimulation of splenocytes showed a decrease in IL5 production. In summary; post-sensitization administration of scFOSlcFOS + B. breve was effective in reducing allergic symptoms after allergen challenge. These effects coincided with changes in regulatory and effector T-cell subsets and increases in the SCFA propionic acid. These results suggest immune modulatory benefits of dietary intervention with a unique combination of scFOSlcFOS + B. breve in established food allergy. Whether these effects translate to human applications is subject for ongoing clinical studies.