Effects of Lactobacillus kefiri fermentation supernatant on skin aging caused by oxidative stress

Lactobacillus kefiri is a beneficial bacteria that is often used to make yogurt only, and is beneficial to human health when it is used in food fermentation. In this article, a fermentation supernatant (LAF) is prepared by culturing Lactobacillus kefiri, and the anti-aging effects of LAF are evaluated at the biochemical, cellular, and molecular biology levels. The antioxidant activity of LAF is comprehensively evaluated by three free radical scavenging tests and the total antioxidant capacity (ABTS method) test. The toxicity of LAF on human skin fibroblasts (HSF) is detected using the MTT method, and the effects of LAF on H2O2-induced oxidative stress in terms of intracellular reactive oxygen species (ROS), Malondialdehyde (MDA) content, antioxidant enzyme activity are evaluated. The gene expression levels of LC3 and Beclin-1 are detected using the real-time reverse transcription-polymerase chain reaction (qRT-PCR) method, and the protein expression levels of LC3 are detected using the Western blot method to evaluate the effects of LAF on HSF autophagy. The expression of type I collagen (COL-1), Matrix metalloproteinase-1(MMP-1), AKT pathway, MAPK pathway, and other genes are detected by qRT-PCR to study the anti-aging effects of LAF. From the experimental results, it is found that LAF can delay the aging of HSF at the biochemical, cellular, and molecular biology levels, and can be utilized as a functional food ingredient.