Lactylation of HADHA Promotes Sepsis-Induced Myocardial Depression.

Background: Serum lactate levels are used to evaluate tissue hypoxia and predict outcomes in cases of sepsis and septic shock. Lactate can participate in a posttranslational modification known as lactylation. Myocardial depression during sepsis and septic shock is common. Here, we investigated the role of lactate in sepsis-induced myocardial depression.

Methods: Septic myocardial depression in rats was induced by lipopolysaccharide administration or cecal ligation and puncture. Lactylation and protein profiles of heart tissues from the control and lipopolysaccharide groups were analyzed using proteomic analysis. Lactylation of the HADHA (trifunctional enzyme subunit alpha) at K166 and K728 was detected in septic heart tissues and lipopolysaccharide-induced cultured cells. Mutation of K166 and K728 HADHA were used to clarify the effects of HADHA lactylation on mitochondrial function, ATP production, energy metabolism, and heart function. Transcriptomic and metabolomic analyses were used to identify differentially expressed genes and differential metabolites in H9c2 (rat cardiomyoblast cell line) cells.

Results: We identified 1127 lysine lactylation sites, with 83 differentially lactylated lysine sites. By integrating multifeature hybrid learning and protein language models, we identified lactylation at K166 and K728 of the HADHA as functionally important. We confirmed that lactylation at these sites was influenced by lactate levels and inhibited the HADHA activity, which disturbed mitochondrial function, ATP production, and energy metabolism. This reduction in the contraction force of cardiomyocytes can influence heart function in vitro and in vivo. Furthermore, this study revealed that sirtuin 1 and sirtuin 3 regulated the lactylation of HADHA at K166 and K728.

Conclusions: This study reveals the significant impact of lactylation on cardiomyocyte metabolism. Lactate-induced HADHA lactylation disturbs cardiomyocyte mitochondrial function and metabolism and promotes sepsis-induced cardiac dysfunction. These findings inform the development of new therapeutic targets for sepsis-induced myocardial depression.