α-ketoglutarate produced by lactic acid bacteria inhibits hyaluronidase activity

In Japan, the growing interest in anti-aging skin care is associated with the unprecedented aging society. Skin aging can be attributed to various factors, including the activation of hyaluronidase enzyme in subcutaneous tissues exposed to ultraviolet radiation. This enzyme breaks down hyaluronic acid, leading to skin sagging. Therefore, hyaluronidase inhibitors can effectively prevent skin aging. Previously, food components have been actively explored to search for hyaluronidase inhibitors considering the high safety of these materials. Although lactic acid bacteria (LAB)-fermented foods inhibit this enzyme, their active compounds responsible for hyaluronidase inhibition remain unknown. Thus, in this study, we aimed to explore the mechanism underlying the LAB-mediated inhibition of hyaluronidase activity. Supernatants of a LAB-fermented milk-based beverage were subjected to a hyaluronidase inhibition assay, followed by purification and separation using hydrophobic adsorbents and high-performance liquid chromatography, respectively. Subsequently, liquid chromatograph time-of-flight mass analysis was performed, revealing alpha-ketoglutarate (AKG) as the inhibitor of this enzyme. The half-maximal inhibitory concentration (IC50) of AKG was approximately 0.13-fold that of the known strong hyaluronidase inhibitor disodium cromoglycate (DSCG). To the best of our knowledge, this is the first report on hyaluronidase inhibition mediated by AKG, a metabolic product of LAB. Additionally, Lactobacillus acidophilus JCM1132 was identified as a highly effective AKG-producing LAB (63.9 mu g/mL) through LC-MS/MS-based quantitative analyses using various LAB-fermented milk samples. We anticipate that the findings of this study will potentially support the development of functional foods and cosmetics enriched with AKG.