The role of lactate on the immunomodulatory properties of the nonbacterial fraction of kefir

Probiotic Potential of Yeasts Isolated from Fermented Beverages: Assessment of Antagonistic Strategies Against Salmonella enterica Serovar Enteritidis

Global concern about pathogenic resistance to antibiotics is prompting interest in probiotics as a strategy to prevent or inhibit infections. Fermented beverages are promising sources of probiotic yeasts. This study aimed to evaluate the antagonistic effects of Kluyveromyces marxianus, Wickerhamomyces anomalus, and Pichia manshurica strains from kefir and wine against Salmonella enterica serovar Enteritidis in intestinal epithelial cells. The ability of these yeasts to adhere to Caco-2/TC-7 cells was evaluated, as well as their influence on the ability of Salmonella to associate and invade these cells. The behavior of the pathogen was analyzed by (a) incubation of enterocytes with yeast before adding Salmonella, (b) co-incubation of Salmonella with yeast before contact with the enterocytes, and (c) incubation of Salmonella with yeast metabolites before contact with enterocytes. All yeast strains demonstrated adherence to Caco-2/TC-7 cells (33-100%) and effectively inhibited Salmonella invasion. Among the treatments, co-culture showed the greatest effect, reducing Salmonella association and invasion by more than 50%. Additionally, these yeasts modulated the epithelial immune response, significantly decreasing CCL20-driven luminescence by 60-81% (p < 0.0001). These results highlight the potential of yeasts from fermented beverages as probiotics to counteract Salmonella infections, offering a promising alternative in the fight against antibiotic resistance.

Mitigation of chemotherapy-induced experimental intestinal mucositis through postbiotic lactate

Postbiotic lactate modulates the immune system in inflammatory bowel diseases. However, its role in experimental intestinal mucositis (IM) has not been elucidated. This study aimed to evaluate the effects of lactate supplementation (1 and 2 × 10-1 mol/l) in a 5-fluorouracil (5-FU)-induced IM model. Male BALB/c mice (6-8 weeks old) were randomly divided into four groups: control (CTL), mucositis (MUC), mucositis with 1 × 10-1 mol/l lactate solution (MUC10), and mucositis with 2 × 10-1 mol/l lactate solution (MUC200). Lactate was administered via oral gavage for 10 days. Following the treatment period, the animals were subjected to an intraperitoneal injection of 300 mg/kg 5-FU to induce IM and were euthanized 72 h later for analysis. The MUC group presented intestinal damage with a poor histological score and decreased morphometric parameters as well as decreased mucus production and increased inflammatory infiltration and intestinal permeability compared to those of the CTL group (P < .05). However, the MUC200 group exhibited better results for the evaluated parameters than the MUC group (P < .05). Notably, the results in the MUC10 group were similar to those in the MUC group (P > .05). In conclusion, lactate supplementation attenuates mucositis-induced damage in a dose-dependent manner.

Yogurt Prevents Colitis-Associated Colorectal Cancer in Mice

SCOPE

Epidemiological studies indicate an inverse correlation between yogurt consumption and colorectal cancer (CRC), but whether there is a cause-and-effect relationship has not yet been validated. This study aims to investigate the effects and possible mechanisms of yogurt on colitis-associated colorectal cancer (CAC) in mice.

METHODS AND RESULTS

Experimental CAC is induced by azoxymethane (AOM, 10 mg kg-1 , ip) followed by three cycles of dextran sulfate sodium (DSS, 3%) treatment. Colitis is induced by adding DSS (3%) in drinking water for 5 days. Primary mouse macrophages are isolated for mechanistic studies. Data clearly show that yogurt (15 g kg-1 body weight) significantly reduces the multiplicity of colonic neoplasms by 38.83% in mice. Yogurt protects mice from colitis dependent on lactate receptor GPR81. The deficiency of Gpr81 exacerbates colitis and CAC in mice. Further investigation reveals that GPR81 may be dispensable for gut barrier function but essential for colonic mucosal repair. d-lactate in yogurt can activate GPR81 to suppress proinflammatory macrophage polarization, thereby facilitating inflammatory resolution after colonic injury and consequently suppressing CAC progression.

CONCLUSION

Yogurt effectively protects against colitis-associated colorectal tumorigenesis in mice, and this study provides a rationale for introducing yogurt supplementation to patients with chronic inflammatory bowel diseases.

Immunomodulatory Properties of Probiotics and Their Derived Bioactive Compounds

Immune system modulation is an intriguing part of scientific research. It is well established that the immune system plays a crucial role in orchestrating cellular and molecular key mediators, thus establishing a powerful defense barrier against infectious pathogens. Gut microbiota represent a complex community of approximately a hundred trillion microorganisms that live in the mammalian gastrointestinal (GI) tract, contributing to the maintenance of gut homeostasis via regulation of the innate and adaptive immune responses. However, impairment in the crosstalk between intestinal immunity and gut microbiota may reflect on detrimental health issues. In this context, many studies have indicated that probiotics and their bioactive compounds, such as bacteriocins and short chain fatty acids (SCFAs), display distinct immunomodulatory properties through which they suppress inflammation and enhance the restoration of microbial diversity in pathological states. This review highlights the fundamental features of probiotics, bacteriocins, and SCFAs, which make them ideal therapeutic agents for the amelioration of inflammatory and autoimmune diseases. It also describes their underlying mechanisms on gut microbiota modulation and emphasizes how they influence the function of immune cells involved in regulating gut homeostasis. Finally, it discusses the future perspectives and challenges of their administration to individuals.

Effects of kefir fermented milk beverage on sodium dextran sulfate (DSS)-induced colitis in rats

Background and aim

The etiopathogenesis of inflammatory bowel disease (IBD) is associated with different factors such as genetic, infectious, immunological, and environmental, including modification of the gut microbiota. IBD's conventional pharmacological therapeutic approaches have become a challenge due to side effects, complications from prolonged use, and higher costs. Kefir fermented milk beverage is a functional food that has demonstrated multiple beneficial effects including anti-inflammatory and antioxidant activity. Alternative therapeutic strategies have been used for IBD as more natural products with low-cost and easy acquisition. The aim of this study is to evaluate the anti-inflammatory effects of kefir fermented milk beverage on sodium dextran sulfate (DSS)-induced colitis in rats.

Methods

We used 4 groups to perform this study: baseline control (BC), kefir control (KC), 5% untreated DSS-induced colitis (DSS), and 5% DSS-induced colitis treated with kefir (DSSK). The animals received fermented kefir milk beverage ad libitum for six days and the disease activity index was recorded daily. Colon samples were processed for Transmission Electron Microscopy and histopathological evaluation. We analyzed short fatty chain acids through the fecal sample using gas chromatography.

Results

Kefir supplementation was able to reduce the clinical activity index and inflammatory process evidenced by decreased neutrophil accumulation, decreased reticulum edema, and increased autophagosomes. Also, showed a trend to increase the levels of acetate and propionate.

Conclusions

Our results suggest that kefir fermented milk beverage may have an anti-inflammatory effect minimizing the intestinal damage of DSS-induced colitis.

Characterization of autochthonous lactobacilli from goat dairy products with probiotic potential for metabolic diseases

The present study aimed to design functional fermented goat milk with probiotic potential for metabolic diseases. Thereby, autochthonous lactobacilli from goat dairy products that target improving the inflammatory, lipid, and glycemic profile were characterized. We designed fermented goat milk using Lactobacillus delbrueckii subsp. indicus CRL1447 as starter strain, supplemented with different probiotic consortia formed by Limosilactobacillus fermentum CRL1446, Lactiplantibacillus paraplantarum CRL1449, and CRL1472 strains. These lactobacilli were selected for their positive effects on inhibition of α-glucosidase, bile salts hydrolase activity, cholesterol assimilation, and decreased triglyceride percentage in Caenorhabditis elegans. Furthermore, the lactobacilli oral administration to obese mice caused a significant decrease in body weight gain and ameliorated hyperglycemia and hyperlipemia. These results reveal the potential of this goat dairy product as a functional food to prevent obesity and related pathologies. Goat milk-derived products stand out for their marketing potential. Hence, fermented goat milk incorporating novel probiotics represents a group of food products with broad prospects by their promising nutritive and therapeutic properties for metabolic diseases. The goat dairy product designed in this study could be used in the prevention of dyslipidemia and hyperglycemia in obese people.

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New probiotic consortium (CRL1449, CRL1472, and ​CRL1446) was selected.

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The probiotic consortium showed in vitro immuno and adipomodulatory properties.

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Lactobacillus delbrueckii subsp. indicus CRL1447 was selected as a starter culture for fermented milk elaboration.

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Manufacturing of a functional fermented goat milk with a new probiotic consortium.

Isolation and Identification of Lactose-Degrading Yeasts and Characterisation of Their Fermentation-Related Ability to Produce Ethanol

Kefir is traditionally produced by fermenting cow’s milk using kefir grains as a starter culture. As the viability of microbes within kefir grains is limited and preparing the grains for kefir fermentation is laborious, here, a single starter that ferments lactose and produces ethanol is developed. For this purpose, it is important to isolate yeasts that can ferment lactose and subsequently produce alcohol. This study aimed to isolate and identify yeasts from kefir and characterise their ability as single starters to produce kefir. Based on morphological and physiological evaluations, 15 presumptive yeast isolates were obtained, 10 of which grew well on lactose-containing media. Those that were able to grow on lactose using only carbon sources were subjected to molecular identification based on the internal transcribed spacer (ITS) of the 5.8 rDNA using PCR technology. Molecular identification confirmed four isolates—namely, KFA 3, KFA 7, KFA 9 and KFB 1—as belonging to Kluyveromyces marxianus. The batch fermentation data of these strains were fitted on a logistic model to obtain the carrying capacity coefficients and strain performances were compared. The kinetic modelling revealed that KFA 9 had the highest values for the carrying capacity coefficient, biomass yield and product yield, indicating that, among the four K. marxianus strains, this was superior due to its relatively fast growth and good ethanol productivity.

Gut Microbiota and Immune Modulatory Properties of Human Breast Milk Streptococcus salivarius and S. parasanguinis Strains

Human breast milk Streptococcus spp. are transferred to infant guts via breast feeding, but their effects on the gut microbiota and immunity remain unclear. In this study, we characterized gut microbiota and immune modulatory properties of human breast milk S. salivarius F286 and S. parasanguinis F278 that had been shown to be able to colonize gut. The two Streptococcus strains were orally administered to mouse pups individually at 1 × 10⁷ cells/day from postnatal Days 1 to 21. At postnatal week 3 (the weaning period), S. salivarius F286 reduced the colonic microbiota α-diversity, increased 21 amplicon sequence variants (ASVs), including bacteria from Akkermansia, Intestinimonas, and Lachnospiraceae, and decreased 52 ASVs, including bacteria from Eubacterium, Bifidobacterium, Escherichia-Shigella, and Turicibacter; however, S. parasanguinis F278 didn't change the colonic microbiota. Both Streptococcus strains reduced the ileal mRNA expression of cytokine/transcription factor representatives of T helper (Th) cells, including IFN-γ (Th1), Gata3 (Th2), and TGF-β (Treg) in 2-week-old suckling mice, and promoted the ileal expression of Foxp3 and TGF-β, which are representatives of anti-inflammatory Treg cells, in 3-week-old weaning mice. The two Streptococcus strains exhibited anti-inflammatory potential when incubated in vitro with human peripheral blood mononuclear cells and TNF-α-treated gut epithelial HT29 cells. In C. elegans, both strains activated immune response genes, which was associated with their lifespan-prolonging effects. Our results suggest that S. salivarius F286 and S. parasanguinis F278 may exert regulatory (anti-inflammatory) roles in gut immunity and S. salivarius F286 can modulate gut microbiota, and highlight the probiotic potential of milk S. salivarius and S. parasanguinis strains.

Lactate content, total polyphenols and antioxidant activity of selected commercial yogurts from the Serbian market

One of the most popular dairy products worldwide is yogurt, which flavor is highly influenced by lactic acid content. Yogurts with fruit preparations contain polyphenols, secondary plant metabolites with proven antioxidant properties. As there is no data regarding neither lactate nor polyphenol content in commercial yogurts in Serbia, this study aimed to determine lactate and polyphenol levels, as well as antioxidant activity in selected yogurts. A total of 15 plain and 5 fruit yogurts with strawberry preparations were analyzed. Lactate contents were from 0.83 to 1.33%. Three plain yogurts in plastic containers differed in lactate content. There was no difference in lactate content among the same plain yogurts packed in plastic and Tetra Pack containers. Fruit yogurts with strawberry preparations differed in total polyphenol content in the range from 6.84 to 29.11mg GAE/100 g and antioxidant properties were determined by reducing power test (from 0.22 to 0.79) and DPPH assay (from 28.13 to 87.23%), while there was no difference regarding lactate. Our results provided new information about the levels of lactate, total polyphenols and antioxidant activity of selected commercial yogurts available on the Serbian market.

Lactate content, total polyphenols and antioxidant activity of selected commercial yogurts from the Serbian market

One of the most popular dairy products worldwide is yogurt, which flavor is highly influenced by lactic acid content. Yogurts with fruit preparations contain polyphenols, secondary plant metabolites with proven antioxidant properties. As there is no data regarding neither lactate nor polyphenol content in commercial yogurts in Serbia, this study aimed to determine lactate and polyphenol levels, as well as antioxidant activity in selected yogurts. A total of 15 plain and 5 fruit yogurts with strawberry preparations were analyzed. Lactate contents were from 0.83 to 1.33%. Three plain yogurts in plastic containers differed in lactate content. There was no difference in lactate content among the same plain yogurts packed in plastic and Tetra Pack containers. Fruit yogurts with strawberry preparations differed in total polyphenol content in the range from 6.84 to 29.11mg GAE/100 g and antioxidant properties were determined by reducing power test (from 0.22 to 0.79) and DPPH assay (from 28.13 to 87.23%), while there was no difference regarding lactate. Our results provided new information about the levels of lactate, total polyphenols and antioxidant activity of selected commercial yogurts available on the Serbian market.

Bioactive Compounds from Kefir and Their Potential Benefits on Health: A Systematic Review and Meta-Analysis

Despite evidence of health benefits from kefir administration, a systematic review with meta-analysis on bioactive compounds associated with these benefits is still absent in the literature. Kefir is fermented milk resulting from the metabolism of a complex microbiota in symbiosis. Recent researches have investigated the bioactive compounds responsible for the preventive and therapeutic effects attributed to kefir. However, differences in functional potential between industrial and artisanal kefir are still controversial. Firstly, we identified differences in the microbial composition among both types of kefir. Available evidence concerning the action of different bioactive compounds from kefir on health, both from in vitro and in vivo studies, was subsequently summarized to draw a primary conclusion of the dose and the intervention time for effect, the producer microorganisms, the precursor in the milk, and the action mechanism. Meta-analysis was performed to investigate the statistically significant differences (P < 0.05) between intervention and control and between both types of kefir for each health effect studied. In summary, the bioactive compounds more commonly reported were exopolysaccharides, including kefiran, bioactive peptides, and organic acids, especially lactic acid. Kefir bioactive compounds presented antimicrobial, anticancer, and immune-modulatory activities corroborated by the meta-analysis. However, clinical evidence is urgently needed to strengthen the practical applicability of these bioactive compounds. The mechanisms of their action were diverse, indicating that they can act by different signaling pathways. Still, industrial and artisanal kefir may differ regarding functional potential-OR of 8.56 (95% CI: 2.27-32.21, P ≤ .001)-according to the observed health effect, which can be associated with differences in the microbial composition between both types of kefir.

Health-Promoting Properties of Lacticaseibacillus paracasei: A Focus on Kefir Isolates and Exopolysaccharide-Producing Strains

Among artisanal fermented beverages, kefir (fermented milk drink) and water kefir (fermented nondairy beverage) are of special interest because their grains can be considered natural reservoirs of safe and potentially probiotic strains. In the last years, several reports on Lacticaseibacillus paracasei (formerly Lactobacillus paracasei) isolated from both artisanal fermented beverages were published focusing on their health-promoting properties. Although this is not the predominant species in kefir or water kefir, it may contribute to the health benefits associated to the consumption of the fermented beverage. Since the classification of L. paracasei has been a difficult task, the selection of an adequate method for identification, which is essential to avoid mislabeling in products, publications, and some publicly available DNA sequences, is discussed in the present work. The last findings in health promoting properties of L. paracasei and the bioactive compounds are described and compared to strains isolated from kefir, providing a special focus on exopolysaccharides as effector molecules. The knowledge of the state of the art of Lacticaseibacillus paracasei from kefir and water kefir can help to understand the contribution of these microorganisms to the health benefits of artisanal beverages as well as to discover new probiotic strains for applications in food industry.

Enhancement of the Antibacterial Properties of Kefir by Adding Lactobacillus fermentum grx08

ABSTRACT

Kefir is an acidic-alcoholic fermented milk that can provide probiotic benefits, such as intestinal microecological balance regulation, antibacterial activity, and anti-inflammatory activity. In this study, Lactobacillus fermentum grx08 isolated from longevous people was used to further improve the health properties of kefir. L. fermentum grx08 and kefir grains obtained from Xinjiang, People's Republic of China, were mixed at ratios of 1:1, 5:1, and 25:1 as starters. The six gram-positive and gram-negative foodborne pathogens were able to grow in the supernatant of kefir but not in the supernatant of kefir with L. fermentum grx08. With increasing amounts of inoculated L. fermentum grx08, the antibacterial activity of the mixed fermented kefir gradually increased. The contents of lactic acid, fumaric acid, and malic acid in the mixed fermented milk were significantly increased by adding L. fermentum grx08 (P < 0.05), while the content of acetic acid decreased with the increase of L. fermentum grx08 and the content of citric acid was unaffected. This study suggests that the addition of L. fermentum grx08 shortened the fermentation time, improved the acidity, and retained the quality of fermented milk. Moreover, the antibacterial properties of kefir is enhanced by increasing the production of certain acids.

HIGHLIGHTS

Characterization of Kefir Produced in Household Conditions: Physicochemical and Nutritional Profile, and Storage Stability

Kefir, a traditional fermented food, has numerous health benefits due to its unique chemical composition, which is reflected in its excellent nutritional value. Physicochemical and microbial composition of kefir obtained from fermented milk are influenced by the type of the milk, grain to milk ratio, time and temperature of fermentation, and storage conditions. It is crucial that kefir characteristics are maintained during storage since continuous metabolic activities of residual kefir microbiota may occur. This study aimed to examine the nutritional profile of kefir produced in traditional in use conditions by fermentation of ultra-high temperature pasteurized (UHT) semi-skimmed cow milk using argentinean kefir grains and compare the stability and nutritional compliance of freshly made and refrigerated kefir. Results indicate that kefir produced under home use conditions maintains the expected characteristics with respect to the physicochemical parameters and composition, both after fermentation and after refrigerated storage. This work further contributes to the characterization of this food product that is so widely consumed around the world by focusing on kefir that was produced in a typical household setting.

A biorefinery concept for the production of fuel ethanol, probiotic yeast, and whey protein from a by-product of the cheese industry

Agroindustrial by-products and residues can be transformed into valuable compounds in biorefineries. Here, we present a new concept: production of fuel ethanol, whey protein, and probiotic yeast from cheese whey. An initial screening under industrially relevant conditions, involving thirty Kluyveromyces marxianus strains, was carried out using spot assays to evaluate their capacity to grow on cheese whey or on whey permeate (100 g lactose/L), under aerobic or anaerobic conditions, in the absence or presence of 5% ethanol, at pH 5.8 or pH 2.5. The four best growing K. marxianus strains were selected and further evaluated in a miniaturized industrial fermentation process using reconstituted whey permeate (100 g lactose/L) with cell recycling (involving sulfuric acid treatment). After five consecutive fermentation cycles, the ethanol yield on sugar reached 90% of the theoretical maximum in the best cases, with 90% cell viability. Cells harvested at this point displayed probiotic properties such as the capacity to survive the passage through the gastrointestinal tract and capacity to modulate the innate immune response of intestinal epithelium, both in vitro. Furthermore, the CIDCA 9121 strain was able to protect against histopathological damage in an animal model of acute colitis. Our findings demonstrate that K. marxianus CIDCA 9121 is capable of efficiently fermenting the lactose present in whey permeate to ethanol and that the remaining yeast biomass has probiotic properties, enabling an integrated process for the obtainment of whey protein (WP), fuel ethanol, and probiotics from cheese whey.Key points• K. marxianus-selected strains ferment whey permeate with 90% ethanol yield.• Industrial fermentation conditions do not affect selected yeast probiotic capacity.• Whey permeate, fuel ethanol, and probiotic biomass can be obtained in a biorefinery.

Lactate: a multifunctional signaling molecule

Since its discovery in 1780, lactate has long been misunderstood as a waste by-product of anaerobic glycolysis with multiple deleterious effects. Owing to the lactate shuttle concept introduced in the early 1980s, a paradigm shift began to occur. Increasing evidence indicates that lactate is a coordinator of whole-body metabolism. Lactate is not only a readily accessible fuel that is shuttled throughout the body but also a metabolic buffer that bridges glycolysis and oxidative phosphorylation between cells and intracellular compartments. Lactate also acts as a multifunctional signaling molecule through receptors expressed in various cells and tissues, resulting in diverse biological consequences including decreased lipolysis, immune regulation, anti-inflammation, wound healing, and enhanced exercise performance in association with the gut microbiome. Furthermore, lactate contributes to epigenetic gene regulation by lactylating lysine residues of histones, accounting for its key role in immune modulation and maintenance of homeostasis.

Isolation, purification, characterization and immunostimulatory activity of an exopolysaccharide produced by Lactobacillus pentosus LZ-R-17 isolated from Tibetan kefir

In this study, three strains of lactic acid bacteria isolated from Tibetan kefir grains, including two strains of Lactobacillus pentosus LZ-R-17 and L. helveticus LZ-R-5, and one strain of Lactococcus lactis subsp. lactis LZ-R-12. The ability of three strains to produce exopolysaccharide (EPS) was tested, and L. pentosus LZ-R-17 was found to have the highest EPS yield. One EPS (R-17-EPS) was isolated from the fermented milk by L. pentosus LZ-R-17 and purified by DEAE-52 anion exchange chromatography. Furthermore, R-17-EPS preliminary structure and macrophage immunomodulatory activity in vitro were investigated. On the basis of the analytical results of ultraviolet-visible spectrum, Fourier transform-infrared spectrum, monosaccharide composition analysis and one-dimensional and two-dimensional nuclear magnetic resonance (NMR) spectra, R-17-EPS was found to have an average molecular weight of 1.20 × 106 Da and was composed of galactose and glucose residues with a molar ratio of 1.00:3.15. NMR analysis revealed that the R-17-EPS was a linear hetero-galactoglucan containing repeating units of →2)-α-D-Galp-(1 → 4)-β-D-Glcp-(1 → 4)-β-D-Glcp-(1 → 4)-β-D-Glcp-(1→. In addition, R-17-EPS could effectively enhanced the proliferation, phagocytosis, nitric oxide and cytokines production of RAW264.7 cells, suggesting that R-17-EPS had potent immunostimulatory activity and could be explored as immunomodulator in functional food and/or medicine fields.

Ready to Use Therapeutical Beverages: Focus on Functional Beverages Containing Probiotics, Prebiotics and Synbiotics

The growing global interest in functional foods containing nutrients capable of adding possible beneficial health effects is rapidly increasing both interest and consumer demand. In particular, functionalized beverages for their potential positive effect on health e.g., decreasing cholesterol level, lowering sugar, high fiber content, ability to enhance the immune system, and help digestion, have recently received special attention. Among the different beverages available on the market, probiotic dairy and non-dairy products have attracted much attention because of their affordable cost and their numerous therapeutic activities. Fermented milk and yogurt are currently worth €46 billion, with 77% of the market reported in Europe, North America, and Asia. Consumption of dairy beverages has some limitations due for example to lactose intolerance and allergy to milk proteins, thereby leading consumers to use non-dairy beverages such as fruit, grains, and vegetable juices to add probiotics to diet as well as driving the manufacturers to food matrices-based beverages containing probiotic cultures. The purpose of this review article is to evaluate the therapeutic performance and properties of dairy and non-dairy beverages in terms of probiotic, prebiotic, and synbiotic activities.

"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.

The Science and Translation of Lactate Shuttle Theory

Once thought to be a waste product of anaerobic metabolism, lactate is now known to form continuously under aerobic conditions. Shuttling between producer and consumer cells fulfills at least three purposes for lactate: (1) a major energy source, (2) the major gluconeogenic precursor, and (3) a signaling molecule. "Lactate shuttle" (LS) concepts describe the roles of lactate in delivery of oxidative and gluconeogenic substrates as well as in cell signaling. In medicine, it has long been recognized that the elevation of blood lactate correlates with illness or injury severity. However, with lactate shuttle theory in mind, some clinicians are now appreciating lactatemia as a "strain" and not a "stress" biomarker. In fact, clinical studies are utilizing lactate to treat pro-inflammatory conditions and to deliver optimal fuel for working muscles in sports medicine. The above, as well as historic and recent studies of lactate metabolism and shuttling, are discussed in the following review.

Biological activity of the non-microbial fraction of kefir: antagonism against intestinal pathogens

Kefir is a fermented milk obtained by the activity of kefir grains which are composed of lactic and acetic acid bacteria, and yeasts. Many beneficial health effects have been associated with kefir consumption such as stimulation of the immune system and inhibition of pathogenic microorganisms. The biological activity of kefir may be attributed to the presence of a complex microbiota as well as the microbial metabolites that are released during fermentation. The aim of this work was to characterise the non-microbial fraction of kefir and to study its antagonism againstEscherichia coli,Salmonellaspp. andBacillus cereus.During milk fermentation there was a production of organic acids, mainly lactic and acetic acid, with a consequent decrease in pH and lactose content. The non-microbial fraction of kefir added to nutrient broth at concentrations above 75% v/v induced a complete inhibition of pathogenic growth that could be ascribed to the presence of un-dissociated lactic acid. In vitro assays using an intestinal epithelial cell model indicated that pre-incubation of cells with the non-microbial fraction of kefir did not modify the association/invasion ofSalmonellawhereas pre-incubation ofSalmonellawith this fraction under conditions that did not affect their viability significantly decreased the pathogen's ability to invade epithelial cells. Lactate exerted a protective effect againstSalmonellain a mouse model, demonstrating the relevance of metabolites present in the non-microbial fraction of kefir produced during milk fermentation.

Deleterious Metabolic Effects of High Fructose Intake: The Preventive Effect of Lactobacillus kefiri Administration

Modern lifestyle and diets have been associated with metabolic disorders and an imbalance in the normal gut microbiota. Probiotics are widely known for their health beneficial properties targeting the gut microbial ecosystem. The aim of our study was to evaluate the preventive effect of Lactobacillus kefiri (L. kefiri) administration in a fructose-rich diet (FRD) mice model. Mice were provided with tap water or fructose-added (20% w/v) drinking water supplemented or not with L. kefiri. Results showed that probiotic administration prevented weight gain and epidydimal adipose tissue (EAT) expansion, with partial reversion of the adipocyte hypertrophy developed by FRD. Moreover, the probiotic prevented the increase of plasma triglycerides and leptin, together with the liver triglyceride content. Leptin adipocyte secretion was also improved by L. kefiri, being able to respond to an insulin stimulus. Glucose intolerance was partially prevented by L. kefiri treatment (GTT) and local inflammation (TNFα; IL1β; IL6 and INFγ) was completely inhibited in EAT. L. kefiri supplementation generated an impact on gut microbiota composition, changing Bacteroidetes and Firmicutes profiles. Overall, our results indicate that the administration of probiotics prevents the deleterious effects of FRD intake and should therefore be promoted to improve metabolic disorders.

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.

α-Defensin 5 gene expression is regulated by gut microbial metabolites

α-Defensin 5 is important to both maintenance of a gut microbiota and host immunity. While previous reports have shown that gut bacteria are able to upregulate α-defensin 5 through Toll-like receptor signaling, we demonstrate here that α-defensin 5 expression can also be regulated by microbial metabolites. Among these, lactate appeared to significantly suppress α-defensin 5 gene transcription. Actually, fractions of <3 kD compounds obtained from the ceca of SPF mice were suppressed α-defensin 5 gene transcription at specific concentrations. Our results also suggest that cecal content may include as yet unidentified factors that can enhance α-defensin 5 expression. Our data point to a novel function for the gut microbial metabolites in controlling the expression of antimicrobial peptides in the intestine.

The Microbiota and Health Promoting Characteristics of the Fermented Beverage Kefir

Kefir is a complex fermented dairy product created through the symbiotic fermentation of milk by lactic acid bacteria and yeasts contained within an exopolysaccharide and protein complex called a kefir grain. As with other fermented dairy products, kefir has been associated with a range of health benefits such as cholesterol metabolism and angiotensin-converting enzyme (ACE) inhibition, antimicrobial activity, tumor suppression, increased speed of wound healing, and modulation of the immune system including the alleviation of allergy and asthma. These reports have led to increased interest in kefir as a focus of research and as a potential probiotic-containing product. Here, we review those studies with a particular emphasis on the microbial composition and the health benefits of the product, as well as discussing the further development of kefir as an important probiotic product.

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.