Oxidative stress, which can cause imbalance in the body by damaging cells and tissues, arises from the immoderate production of reactive oxygen species (ROS)/reactive nitrogen species (RNS). Therefore, external supplements having antioxidant activity are required for reducing oxidative stress. In our study, we investigated DPPH and ABTS radical scavenging ability, and the inhibition effect on the nitric oxide (NO) production of 15 food-derived bacterial strains in LPS-activated RAW264.7 cells. Among these LAB strains, eight strains with an excellent inhibition effect on NO production were selected through comparisons within the same genera. Moreover, the selected strains, including Leuconostoc mesenteroides MG860, Leu. citreum MG210, Pediococcus acidilactici MG5001, P. pentosaceus MG5078, Weissella cibaria MG5090, Levilactobacillus brevis MG5306, Latilactobacillus curvatus MG5020, and Latilactobacillus sakei MG5048 diminished the inducible nitric oxide synthase (iNOS)/cyclooxygenase-2 (COX-2) expression. In addition, the stability and adhesion ability of the eight LAB strains in the gastrointestinal tract were determined. In conclusion, the selected strains have potential as new probiotics with antioxidant effects.

In this study, lactic acid bacteria (LAB) strains derived from human and fermented food sources were examined to identify their properties related to obesity, as well as establish their safety and stability as probiotics. LAB (Lacticaseibacillus rhamnosus MG4502, Lactobacillus gasseri MG4524, Limosilactobacillus reuteri MG5149, and Weissella cibaria MG5285) exhibited antioxidant activity through DPPH (>26.1%) and ABTS (>40.1%) radical scavenging assays and α-glucosidase inhibitory activities (>60.3%), respectively. The LAB strains promoted anti-adipogenesis by reducing lipid accumulation in 3T3-L1 cells by Oil Red O staining (>70.3%). In addition, we found that these LAB strains were resistant to simulated gastric and intestinal fluids (pH 3, 4, 7, and 8) and showed potential for health promotion, based on hemolysis, cell adhesion, antibiotic susceptibility, and enzyme production. Thus, LAB may be used as probiotic ingredients with beneficial effects.

Antioxidants protect against oxidative stress that can damage proteins, the cellular immune system, and DNA. In recent studies, probiotics have been shown to impart a microbial balance to the gastrointestinal tract, demonstrating significant antioxidant capacity. In this study, the probiotic properties and antioxidant mechanism of probiotics were evaluated in HepG2 cells and in an animal model. The characteristics of Lactococcus lactis MG5125, Bifidobacterium bifidum MG731, and Bifidobacterium animalis subsp. lactis MG741, which were used as lactic acid bacteria in this study, were analyzed. The results revealed the safety and stability of these probiotics in the gastrointestinal tract because they did not cause hemolysis and had excellent intestinal adhesion (75–84%). In HepG2 cells, the three probiotics alleviated H₂O₂-induced oxidative stress by mediating lipid peroxidation and glutathione levels and upregulating antioxidant enzymes, including catalase, superoxide dismutase, and glutathione peroxidase. In the tBHP-induced mouse model, administration of the three probiotics reduced hepatic aspartate transaminase, alanine transaminase, and lipid peroxidation levels. In conclusion, Lc. lactis MG5125, B. bifidum MG731, and B. lactis MG741 showed considerable antioxidant activity both in vitro and in vivo.

The skin acts as a physical and physiological barrier, thereby protecting the body from various environmental components and stimuli. Cell-free supernatants (CFS) derived from probiotics can improve skin functions and retain moisture. In this study, to assess the efficacy of CFS derived from Ligilactobacillus salivarius and Limosilactobacillus fermentum, we investigated the barrier strengthening and moisturizing effects of CFS in keratinocytes along with their antibacterial effects. We also determined the adhesive effects of probiotics on colorectal cells. To confirm improvements in moisturization and barrier function mediated by CFS in keratinocytes, hyaluronic acid (HA) production, and mRNA expression of HA synthases (HAS)2, HAS3, and FLG were measured. The results showed that CFS from L. salivarius MG242 and L. fermentum MG901 increased the expression of these genes along with the production of HA (2.40- and 1.95-fold of control). Additionally, CFS derived from L. salivarius MG242 and L. fermentum MG901 inhibited the growth of S. aureus and E. coli, thereby demonstrating inhibitory effects against harmful pathogens observed on the skin. These results indicate that the use of CFS derived from L. salivarius MG242 and L. fermentum MG901 may increase moisturization in the skin and improve barrier function of keratinocytes along with elimination of potential pathogens.

Alcoholic liver fatty disease (ALFD) is caused by excessive and chronic alcohol consumption. Alcohol consumption causes an imbalance in the intestinal microflora, leading to liver disease induced by the excessive release of endotoxins into the hepatic portal vein. Therefore, research on the intestinal microflora to identify treatments for ALFD is increasing. In this study, the protective effects of lactic acid bacteria (LAB) strains, including Levilactobacillus brevis, Limosilactobacillus reuteri, and Limosilactobacillus fermentum, were evaluated in ethanol-induced HepG2 cells. Among the evaluated LAB, nine strains increased aldehyde dehydrogenase (ALDH) levels and downregulated lipid peroxidation and liver transferase in the ethanol-induced HepG2 cells. Moreover, L. brevis MG5280 and MG5311, L. reuteri MG5458, and L. fermentum MG4237 and MG4294 protected against ethanol-induced HepG2 cell damage by regulating CYP2E1, antioxidant enzymes (SOD, CAT, and GPX), lipid synthesis factors (SREBP1C and FAS), and lipid oxidation factors (PPARα, ACO, and CPT-1). Moreover, five LAB were confirmed to be safe probiotics based on antibiotic susceptibility and hemolysis assays; their stability and adhesion ability in the gastrointestinal tract were also established. In conclusion, L. brevis MG5280 and MG5311, L. reuteri MG5458, and L. fermentum MG4237 and MG4294 may be useful as new probiotic candidates for ALFD prevention.

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease and the leading cause of liver-related deaths worldwide. It has been established that microorganisms are involved in the interaction between the intestinal lumen and the liver; therefore, studies on probiotics as potential candidates are increasing. This study evaluated the effects of Limosilactobacillus fermentum MG4294 and Lactiplantibacillus plantarum MG5289 on NAFLD. The MG4294 and MG5289 reduced lipid accumulation in FFA-induced HepG2 by suppressing the adipogenic proteins through the regulation of AMP-activated protein kinase (AMPK). The administration of these strains in the HFD-induced mice model lowered body weight, serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and cholesterol levels. In particular, MG4294 and MG5289 restored liver TG and TC to normal levels by lowering lipid and cholesterol-related proteins via the modulation of AMPK in the liver tissue. In addition, the administration of MG4294 and MG5289 reduced pro-inflammatory cytokines (tumor necrosis factor (TNF)-α and interleukin (IL)-1β-, and IL6) in the intestinal tissues of the HFD-induced mouse model. In conclusion, MG4294 and MG5289 can be presented as probiotics with the potential to prevent NAFLD.