The Ameliorative Effects of Carnosine on the In Vitro Developmental Competence of Bovine Oocytes

Carnosine is a naturally occurring endogenous dipeptide with great potential to improve reproductive function and fertility. In this study, supplementation of 1 μg/mL carnosine during in vitro maturation (IVM) significantly enhanced the developmental competence and quality of the resulting bovine embryos. Carnosine treatment effectively elevated mitochondrial membrane potential, mitochondrial activity, and ATP content in oocytes. Moreover, it strengthened the antioxidant and anti-apoptotic capacities of oocytes, as evidenced by reduced intracellular reactive oxygen species (ROS) levels, lowered DNA damage and an early apoptosis rate, alongside increased glutathione (GSH) content, an elevated BCL2/BAX mRNA ratio, and upregulation of antioxidant genes SOD1, CAT, GPx1, and GPx4. Notably, combined application of 1 μg/mL carnosine during IVM and 10−7 M melatonin during in vitro culture (IVC) synergistically improved both blastocyst development and quality. Collectively, these findings provide novel evidence supporting the therapeutic potential of carnosine in optimizing in vitro embryo production in bovine, and highlight the value of stage-specific supplementation strategies to further improve embryonic development efficiency.