Holstein cow milk–derived Lactobacillus plantarum L19 alleviates heat stress–induced liver injury in mice by modulating gut microbiota

Heat stress-induced liver injury is a common and potentially life-threatening complication of heat exposure in both humans and animals. With the ongoing rise in global temperatures, effective preventive strategies are urgently needed. Lactic acid bacteria have been extensively studied and shown to effectively alleviate various types of liver injury; however, their specific role in heat stress-induced liver damage remains unknown. In our previous work, we isolated Lactobacillus plantarum L19 (LP-19), a strain with strong heat resistance and antioxidant capacity, from Holstein cow milk, suggesting its potential to benefit animals and humans under heat stress. This study aimed to investigate the effects of LP-19 against heat stress-induced liver injury using a mouse model. The results showed that oral administration of LP-19 reduced serum alanine aminotransferase and aspartate aminotransferase levels and inhibited liver oxidative stress in mice with heat-stressed liver injury. Immunohistochemistry and quantitative real-time PCR results showed that LP-19 also reduced levels of heat shock proteins and inflammatory factors. Moreover, LP-19 improved intestinal morphology and modulated gut microbiota by increasing beneficial genera such as Lactobacillus and Dorea while decreasing harmful taxa, including Haemophilus and Desulfovibrionaceae. These changes in the microbiota were closely correlated with therapeutic indices. Functional prediction with PICRUSt2 indicated that the LP-19-regulated microbiota may exert its effects primarily through modulating membrane transport, carbohydrate metabolism, and amino acid metabolism. These findings suggest that LP-19 may help prevent heat stress-induced liver injury by modulating the gut microbiota. Consequently, the study highlights the potential of LP-19 as a novel food additive for preventing heat stress-induced liver injury, offering new prospects for the utilization and the development of cow milk-derived lactic acid bacteria.