Lactate and short chain fatty acids produced by microbial fermentation downregulate proinflammatory responses in intestinal epithelial cells and myeloid cells

The use of short chain fatty acids to modulate gastrointestinal inflammatory conditions such as ulcerative colitis has produced encouraging results either in animal models or also in clinical trials. Identifying the key cellular and molecular targets of this activity will contribute to establish the appropriate combinations/targeting strategies to maximize the efficacy of anti-inflammatory interventions. In the present work, we evaluated in vitro the interaction of lactate, acetate, propionate and butyrate on cells relevant for innate immune response of the gastrointestinal tract. All molecules tested regulate the production of proinflammatory cytokines by TLR-4 and TLR-5 activated intestinal epithelial cells in a dose response manner. Furthermore SCFAs and lactate modulate cytokine secretion of TLR-activated bone marrow derived macrophages and also TLR-dependent CD40 upregulation in bone marrow derived dendritic in a dose-dependent manner. Butyrate and propionate have been effective at concentrations of 1 to 5mM whereas acetate and lactate produced modulatory effects at concentrations higher than 20-50mM in different assays. Our results indicate that in concentrations similar to found in large bowel lumen, all SCFAs tested and lactate can modulate activity of relevant sentinel cell types activated by TLR signals. Modulatory activity was not inhibited by pertussis toxin treatment indicating that the effects are not related to Gi signaling. The use of these molecules in combined or separately as intervention strategy in conditions where epithelial or myeloid cells are main triggers of the inflammatory situation seems appropriate.

Local Treatment with Lactate Prevents Intestinal Inflammation in the TNBS-Induced Colitis Model

Lactate has long been considered as a metabolic by-product of cells. Recently, this view has been changed by the observation that lactate can act as a signaling molecule and regulates critical functions of the immune system. We previously identified lactate as the component responsible for the modulation of innate immune epithelial response of fermented milk supernatants in vitro. We have also shown that lactate downregulates proinflammatory responses of macrophages and dendritic cells. So far, in vivo effects of lactate on intestinal inflammation have not been reported. We evaluated the effect of intrarectal administration of lactate in a murine model of colitis induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS). The increase in lactate concentration in colon promoted protective effects against TNBS-induced colitis preventing histopathological damage, as well as bacterial translocation and rise of IL-6 levels in serum. Using intestinal epithelial reporter cells, we found that flagellin treatment induced reporter gene expression, which was abrogated by lactate treatment as well as by glycolysis inhibitors. Furthermore, lactate treatment modulated glucose uptake, indicating that high levels of extracellular lactate can impair metabolic reprograming induced by proinflammatory activation. These results suggest that lactate could be a potential beneficial microbiota metabolite and may constitute an overlooked effector with modulatory properties.

"Physicochemical, immunomodulatory and safety aspects of milks fermented with Lactobacillus paracasei isolated from kefir"

The use of Lactobacillus paracasei strains isolated from kefir grains as starters for the development of functional dairy products was evaluated. The physicochemical and immunomodulatory properties of milks fermented with L. paracasei CIDCA8339, CIDCA83123 and CIDCA83124 were analyzed. The three strains produced bioactive metabolites during fermentation, since the fermented milk supernatants were able to downregulate >75% of the induced innate immune response in vitro. Although all strains presented absence of hemolytic activity and susceptibility to antibiotics, L. paracasei CIDCA8339 presented more attractive probiotic and technological properties. Mice consuming the fermented milk with L. paracasei CIDCA 8339 did not present significant modifications in sIgA levels or TNF-α, TGF-β and IL-10 mRNA expression in ileum. Additionally, a decrease of INF-γ level in ileum and no microbiological translocation to liver and spleen was observed. These results demonstrate that L. paracasei CIDCA8339 represents a safe promising potential probiotic strain for the development of functional foods.

Water kefir: Factors affecting grain growth and health-promoting properties of the fermented beverage

Nowadays, the interest in the consumption of healthy foods has increased as well as the homemade preparation of artisanal fermented product. Water kefir is an ancient drink of uncertain origin, which has been passed down from generation to generation and is currently consumed practically all over the world. Considering the recent and extensive updates published on sugary kefir, this work aims to shed light on the scientific works that have been published so far in relation to this complex ecosystem. We focused our review evaluating the factors that affect the beverage microbial and chemical composition that are responsible for the health attribute of water kefir as well as the grain growth. The microbial ecosystem that constitutes the grains and the fermented consumed beverage can vary according to the fermentation conditions (time and temperature) and especially with the use of different substrates (source of sugars, additives as fruits and molasses). In this sense, the populations of microorganisms in the beverage as well as the metabolites that they produce varies and in consequence their health properties. Otherwise, the knowledge of the variables affecting grain growth are also discussed for its relevance in maintenance of the starter biomass as well as the use of dextran for technological application.