Lactate promotes myogenesis via activating H3K9 lactylation-dependent up-regulation of Neu2 expression

Protein lactylation in broiler breast: Insights on occurrence mechanisms and the correlations with meat quality

This study investigated the effects of lactate levels in broiler breast on protein lactylation modification, meat quality, and their correlation. High lactate injections led to increased lactate levels in both serum and breast muscle, and significantly reduced the values of pH0, pH45min and pH24h. Additionally, the lactylation levels in breast muscle were increased both post-slaughter and post-mortem. Protein lactylation in breast muscle occurred through enzymatic and non-enzymatic pathways at these stages, with the underlying mechanisms varying according to lactate levels and the muscle aging process. Correlation analysis revealed that post-slaughter lactylation contributed to breast muscle morphometry, whereas post-mortem lactylation was associated with meat quality and texture profile. These findings could demonstrate the presence and dynamic patterns of protein lactylation in broiler breast muscles, offering new insights into the role of lactate accumulation in meat quality variation.

Role of lysine lactylation in neoplastic and inflammatory pulmonary diseases (Review)

Protein lysine lactylation is a ubiquitous and post‑translational modification of lysine residues that involves the addition of a lactyl group on both histone and non‑histone proteins. This process plays a pivotal role in human health and disease and was first discovered in 2019. This epigenetic modification regulates gene transcription from chromatin or directly influences non‑histone proteins by modulating protein‑DNA/protein interactions, activity and stability. The dual functions of lactylation in both histone and non‑histone proteins establish it as a crucial mechanism involved in various cellular processes, such as cell proliferation, differentiation, immune and inflammatory responses and metabolism. Specific enzymes, referred to as 'writers' and 'erasers', catalyze the addition or removal of lactyl groups at designated lysine sites, thereby dynamically modulating lactylation through alterations in their enzymatic activities. The respiratory system has a remarkably intricate metabolic profile. Numerous pulmonary diseases feature an atypical transition towards glycolytic metabolism, which is linked to an overproduction of lactate, a possible substrate for lactylation. However, there has yet to be a comprehensive review elucidating the full impact of lactylation on the onset, progression and potential treatment of neoplastic and inflammatory pulmonary diseases. In the present review, an extensive overview of the discovery of lactylation and advancements in research on the existing lactylation sites were discussed. Furthermore, the review particularly investigated the potential roles and mechanisms of histone and non‑histone lactylation in various neoplastic and inflammatory pulmonary diseases, including non‑small cell lung cancers, malignant pleural effusion, pulmonary fibrosis, acute lung injury and asthma, to excavate the new therapeutic effects of post‑translational modification on various pulmonary diseases.

Emerging roles of lysine lactyltransferases and lactylation

Given its various roles in cellular functions, lactate is no longer considered a waste product of metabolism and lactate sensing is a pivotal step in the transduction of lactate signals. Lysine lactylation is a recently identified post-translational modification that serves as an intracellular mechanism of lactate sensing and transfer. Although acetyltransferases such as p300 exhibit general acyl transfer activity, no bona fide lactyltransferases have been identified. Recently, the protein synthesis machinery, alanyl-tRNA synthetase 1 (AARS1), AARS2 and their Escherichia coli orthologue AlaRS, have been shown to be able to sense lactate and mediate lactyl transfer and are thus considered pan-lactyltransferases. Here we highlight the mechanisms and functions of these lactyltransferases and discuss potential strategies that could be exploited for the treatment of human diseases.

Spatial alteration of metabolites in diabetic cortical cataracts: New insight into lactate

This study aimed to use metabolomics to accurately reveal alterations in metabolites and potential regulatory mechanisms in patients with diabetic cortical cataracts (DCC). We first collected cortical samples from different pathological areas of the same lens in DCC patients for metabolomics. Then, we used transcriptomic analysis to study lactate's effect on gene expression in human lens epithelial cells (HLECs). An in vitro rat lens culture assay evaluated lactate's impact on lens transparency, and WB and immunofluorescence assessed lactate-induced apoptosis and oxidative damage in rat LECs. Furthermore, CHIP sequencing and LC-MS identified H3K18la separately modified genes and potential lactylation proteins in HLECs. Immunoprecipitation validated lactylation levels of proteins. Our findings identified 11 upregulated and 18 downregulated metabolites in the opacity zone of LFCs (OZ-LFCs) compared to the clear zone (CZ-LFCs) in DCC patients. We confirmed the differential lactate content between OZ-LFCs and CZ-LFCs and, through transcriptomic analysis, discovered that lactate affects gene expression, protein metabolism, and DNA repair in primary Human Lens epithelial cells (HLECs). Lactate-induced apoptosis and DNA repair hastened lens opacity in a high-sugar rat lens culture model. Lactylation-MS and H3K18la-ChIP sequencing revealed 591 H3K18la-modified genes and 953 lactylation proteins in HLECs. PKM2 and NPM1 lactylation was confirmed through immunoprecipitation. These findings improve our grasp of spatial dynamics in DCC patient metabolomics and suggest a new research path into lactylation modification to understand lactate's role in cataract formation.

Lactylation: a promising therapeutic target in ischemia-reperfusion injury management

Ischemia-reperfusion injury (IRI) is a critical condition that poses a significant threat to patient safety. The production of lactate increases during the process of IRI, and lactate serves as a crucial indicator for assessing the severity of such injury. Lactylation, a newly discovered post-translational modification in 2019, is induced by lactic acid and predominantly occurs on lysine residues of histone or nonhistone proteins. Extensive studies have demonstrated the pivotal role of lactylation in the pathogenesis and progression of various diseases, including melanoma, myocardial infarction, hepatocellular carcinoma, Alzheimer's disease, and nonalcoholic fatty liver disease. Additionally, a marked correlation between lactylation and inflammation has been observed. This article provides a comprehensive review of the mechanism underlying lactylation in IRI to establish a theoretical foundation for better understanding the interplay between lactylation and IRI.

Lactylation modification in cardio-cerebral diseases: A state-of-the-art review

Cardio-cerebral diseases (CCDs), encompassing conditions such as coronary heart disease, myocardial infarction, stroke, Alzheimer's disease, et al., represent a significant threat to human health and well-being. These diseases are often characterized by metabolic abnormalities and remodeling in the process of pathology. Glycolysis and hypoxia-induced lactate accumulation play critical roles in cellular energy dynamics and metabolic imbalances in CCDs. Lactylation, a post-translational modification driven by excessive lactate accumulation, occurs in both histone and non-histone proteins. It has been implicated in regulating protein function across various pathological processes in CCDs, including inflammation, angiogenesis, lipid metabolism dysregulation, and fibrosis. Targeting key proteins involved in lactylation, as well as the enzymes regulating this modification, holds promise as a therapeutic strategy to modulate disease progression by addressing these pathological mechanisms. This review provides a holistic picture of the types of lactylation and the associated modifying enzymes, highlights the roles of lactylation in different pathological processes, and synthesizes the latest clinical evidence and preclinical studies in a comprehensive view. We aim to emphasize the potential of lactylation as an innovative therapeutic target for preventing and treating CCD-related conditions.

Lactylation in health and disease: physiological or pathological?

Lactate is an indispensable substance in various cellular physiological functions and plays regulatory roles in different aspects of energy metabolism and signal transduction. Lactylation (Kla), a key pathway through which lactate exerts its functions, has been identified as a novel posttranslational modification (PTM). Research indicates that Kla is an essential balancing mechanism in a variety of organisms and is involved in many key cellular biological processes through different pathways. Kla is closely related to disease development and represents a potential and important new drug target. In line with existing reports, we searched for newly discovered Kla sites on histone and nonhistone proteins; reviewed the regulatory mechanisms of Kla (particularly focusing on the enzymes directly involved in the reversible regulation of Kla, including "writers" (modifying enzymes), "readers" (modification-binding enzymes), and "erasers" (demodifying enzymes); and summarized the crosstalk between different PTMs to help researchers better understand the widespread distribution of Kla and its diverse functions. Furthermore, considering the "double-edged sword" role of Kla in both physiological and pathological contexts, this review highlights the "beneficial" biological functions of Kla in physiological states (energy metabolism, inflammatory responses, cell fate determination, development, etc.) and its "detrimental" pathogenic or inducive effects on pathological processes, particularly malignant tumors and complex nontumor diseases. We also clarify the molecular mechanisms of Kla in health and disease, and discuss its feasibility as a therapeutic target. Finally, we describe the detection technologies for Kla and their potential applications in diagnosis and clinical settings, aiming to provide new insights for the treatment of various diseases and to accelerate translation from laboratory research to clinical practice.

Histone lactylation in macrophage biology and disease: from plasticity regulation to therapeutic implications

Epigenetic modifications have been identified as critical molecular determinants influencing macrophage plasticity and heterogeneity. Among these, histone lactylation is a recently discovered epigenetic modification. Research examining the effects of histone lactylation on macrophage activation and polarization has grown substantially in recent years. Evidence increasingly suggests that lactate-mediated changes in histone lactylation levels within macrophages can modulate gene transcription, thereby contributing to the pathogenesis of various diseases. This review provides a comprehensive analysis of the role of histone lactylation in macrophage activation, exploring its discovery, effects, and association with macrophage diversity and phenotypic variability. Moreover, it highlights the impact of alterations in macrophage histone lactylation in diverse pathological contexts, such as inflammation, tumorigenesis, neurological disorders, and other complex conditions, and demonstrates the therapeutic potential of drugs targeting these epigenetic modifications. This mechanistic understanding provides insights into the underlying disease mechanisms and opens new avenues for therapeutic intervention.

Lactate and lysine lactylation of histone regulate transcription in cancer

Histone lysine modifications were well-established epigenetic markers, with many types identified and extensively studied. The discovery of histone lysine lactylation had revealed a new form of epigenetic modification. The intensification of this modification was associated with glycolysis and elevated intracellular lactate levels, both of which were closely linked to cellular metabolism. Histone lactylation plays a crucial role in multiple cellular homeostasis, including immune regulation and cancer progression, thereby significantly influencing cell fate. Lactylation can modify both histone and non-histone proteins. This paper provided a comprehensive review of the typical epigenetic effects and lactylation on classical transcription-related lysine sites and summarized the known enzymes involved in histone lactylation and delactylation. Additionally, some discoveries of histone lactylation in tumor biology were also discussed, and some prospects for this field were put forward.

Acute and Chronic Resistance Training, Acute Endurance Exercise, nor Physiologically Plausible Lactate In Vitro Affect Skeletal Muscle Lactylation

We examined changes in skeletal muscle protein lactylation and acetylation in response to acute resistance exercise, chronic resistance training (RT), and a single endurance cycling bout. Additionally, we performed in vitro experiments to determine if different sodium lactate treatments affect myotube protein lactylation and acetylation. The acute and chronic RT study (12 college-aged participants) consisted of 10 weeks of unilateral leg extensor RT with vastus lateralis (VL) biopsies taken at baseline, 24 h following the first RT bout, and the morning of the last day of the RT bout. For the acute cycling study (9 college-aged participants), VL biopsies were obtained before, 2 h after, and 8 h after 60 min of cycling. For in vitro experiments, C2C12 myotubes were treated with varying levels of sodium lactate, including LOW (1 mM for 24 h), HIGH (10 mM for 24 h), and PULSE (10 mM for 30 min followed by 1 mM for 23.5-h). Neither acute nor chronic RT significantly affected nuclear or cytoplasmic protein lactylation. However, cytoplasmic protein acetylation was significantly reduced following one RT bout (-15%, p = 0.002) and chronic RT (-16%, p = 0.006). Cycling did not acutely alter post-exercise global protein lactylation or acetylation patterns. Lastly, varying 24 h lactate treatments did not alter nuclear or cytoplasmic protein lactylation or acetylation, cytoplasmic protein synthesis levels, or myotube diameters. These findings continue to support the idea that exercise induces more dynamic changes in skeletal muscle protein acetylation, but not lactylation. However, further human research with more sampling timepoints and a lactylomics approach are needed to determine if, at all, different exercise modalities affect skeletal muscle protein lactylation.

Lactate-mediated lactylation in human health and diseases: Progress and remaining challenges

BACKGROUND

Lactate was once considered as metabolic waste for a long time. In 2019, Professor Zhao Yingming's team from the University of Chicago found that lactate could also be used as a substrate to induce histone lactylation and regulate gene expression. Since then, researchers have discovered that lactate-mediated lactylation play important regulatory roles in various physiological and pathological processes.

AIM OF REVIEW

In this review, we aim to discuss the roles and mechanisms of lactylation in human health and diseases, as well as the effects of lactylation on proteins and metabolic modulators targeting lactylation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this work, we emphasize the crucial regulatory roles of lactylation in the development of numerous physiological and pathological processes. Of relevance, we discuss the current issues and challenges pertaining to lactylation. This review provides directions and a theoretical basis for future research and clinical translation of lactylation.

Lactylation drives hCG-triggered luteinization in hypoxic granulosa cells

Hypoxia that occurs during the luteinization process of granulosa cells (GC) contributes to the formation of lactate in follicles. Lysine lactylation (Kla), a post-translational modification directly regulated by lactate levels, is a metabolic sensor that converts metabolic information into gene expression patterns. In this study, we employed human chorionic gonadotropin (hCG) to induce GCs luteinization and discovered that hypoxia enhances hCG-mediated GCs luteinization by stimulating lactate production/lactylation. The elevated levels of luteinization markers (including progesterone synthesis, expression of CYP11A1 and STAR) were accompanied by increased lactate production as well as enhanced lactylation in mouse ovarian GCs after the injection of hCG in vivo. By treating GCs with hypoxia in vitro, we found that hypoxia accelerated hCG-induced GCs luteinization, which was inhibited after blocking lactate production/lactylation. Further investigations revealed that H3K18la might contribute to hCG-induced luteinization in hypoxic GCs by upregulating CYP11A1 and STAR transcription. Additionally, we identified that CREB K136la is also required for hCG-induced GCs luteinization under hypoxia. Finally, the in vitro findings were verified in vivo, which showed impaired GCs luteinization and corpus luteum formation after blocking the lactate/lactylation by intraperitoneal injection of oxamate/C646 in mice. Taken together, this study uncovered a novel role of protein lactylation in the regulation of GCs luteinization.

Transcriptome Analysis of Differentially Expressed Genes and Molecular Pathways Involved in C2C12 Cells Myogenic Differentiation

Muscles are essential tissues responsible for movement, stability, and metabolism, playing a crucial role in human health and well-being. A comprehensive understanding of muscle differentiation processes is imperative for combating muscle degenerative diseases such as muscular dystrophy. In this study, C2C12 cells were induced to differentiate into myotubes in vitro. Phenotypic changes were observed utilizing Gimsa and immunofluorescent staining techniques. RNA sequencing was conducted at distinct time points (0, 2, 4, and 7 days) during the differentiation process. To elucidate the underlying molecular mechanisms, differential expression analysis, gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and Gene Set Enrichment Analysis (GSEA) were performed. Soft clustering of time series gene expression was employed to establish the expression patterns of differentially expressed genes (DEGs) at various time points during myogenesis. Additionally, quantitative reverse transcription PCR was utilized to validate gene expression from RNA-seq data at the mRNA level. Throughout the myogenic differentiation of C2C12 cells, notable morphological changes were observed, with myoblasts forming multinucleated myotubes by day 4 and plump elongated structures by day 7. Gene expression analysis revealed a substantial increase in DEGs as differentiation progressed, with a significant rise in DEGs from day 0 to day 7. Enrichment analysis highlighted key biological processes and pathways involved, including signal transduction and immune system processes, as well as pathways like chemokine and calcium signaling. Noise-robust soft clustering identified distinct temporal gene expression patterns, categorizing genes into upregulated, downregulated, and biphasic response clusters. The MYH family exhibited diverse expression changes, with Myh3, Myh13, Myh6, Myh7, Myh2, Myh8, Myh14, Myh7b, Myh1, and Myh4 upregulated, Myh10, Myh9, and Myh12 downregulated. Key transcription factors displayed dynamic expression patterns, which was crucial for the regulation of myoblast differentiation. A comprehensive and dynamic transcriptomic analysis of the C2C12 myoblast differentiation process has significantly enhanced our understanding of the key genes and biological pathways involved in myogenesis.

The Multiple Roles of Lactate in the Skeletal Muscle

Believed for a long time to be merely a waste product of cell metabolism, lactate is now considered a molecule with several roles, having metabolic and signalling functions together with a new, recently discovered role as an epigenetic modulator. Lactate produced by the skeletal muscle during physical exercise is conducted to the liver, which uses the metabolite as a gluconeogenic precursor, thus generating the well-known "Cori cycle". Moreover, the presence of lactate in the mitochondria associated with the lactate oxidation complex has become increasingly clear over the years. The signalling role of lactate occurs through binding with the GPR81 receptor, which triggers the typical signalling cascade of the G-protein-coupled receptors. Recently, it has been demonstrated that lactate regulates chromatin state and gene transcription by binding to histones. This review aims to describe the different roles of lactate in skeletal muscle, in both healthy and pathological conditions, and to highlight how lactate can influence muscle regeneration by acting directly on satellite cells.

Comprehensive review of histone lactylation: Structure, function, and therapeutic targets

Histone lysine lactylation (Kla) has emerged as a distinct epigenetic modification that differs markedly from established acylation modifications through the unique addition of a lactyl group to a lysine residue. Such modifications not only alter nucleosome structure but also significantly impact chromatin dynamics and gene expression, thus playing a crucial role in cellular metabolism, inflammatory responses, and embryonic development. The association of histone Kla with various metabolic processes, particularly glycolysis and glutamine metabolism, underscores its pivotal role in metabolic reprogramming, including in cancerous tissues, where it contributes to tumorigenesis, immune evasion, and angiogenesis. In addition, histone Kla is involved in the pathogenesis of various diseases, particularly several cancers and neurodegenerative diseases. The identification of histone Kla opens new avenues for therapeutic interventions targeting specific Kla sites. In this review, we summarize the differences between histone Kla modifications and other acylation modifications, discuss the mechanisms and roles of histone Kla in disease, and conclude by describing existing drugs and potential targets. This study provides new insights into the mechanisms linking histone Kla to diseases and into the discovery of new drugs and targets.

The role of platelet desialylation as a biomarker in primary immune thrombocytopenia: mechanisms and therapeutic perspectives

Primary immune thrombocytopenia (ITP) is an acquired autoimmune disorder characterized by the destruction of platelets. Although it was long believed that the critical role of autoantibodies in platelet destruction, primarily through the Fc-dependent platelet clearance pathway, recent findings indicate that the significance of the Fc-independent platelet clearance pathway mediated by hepatocytes, thus shedding light on a previously obscure aspect of ITP pathogenesis. Within this context, the desialylation of platelets has emerged as a pivotal biochemical marker. Consequently, targeting platelet desialylation emerges as a novel therapeutic strategy in the pathogenesis of ITP. Notably, prevailing research has largely focused on antiplatelet antibodies and the glycosylation-associated mechanisms of platelet clearance, while comprehensive analysis of platelet desialylation remains scant. In response, we retrospectively discuss the historical progression, inducing factors, generation process, and molecular regulatory mechanisms underlying platelet desialylation in ITP pathogenesis. By systematically evaluating the most recent research findings, we contribute to a comprehensive understanding of the intricate processes involved. Moreover, our manuscript delves into the potential application of desialylation regulatory strategies in ITP therapy, heralding novel therapeutic avenues. In conclusion, this manuscript not only fills a critical void in existing literature but also paves the way for future research by establishing a systematic theoretical framework. By inspiring new research ideas and offering insights into the development of new therapeutic strategies and targeted drugs, our study is poised to significantly advance the clinical management of ITP.

Protein Lactylation Profiles Provide Insights into Molecular Mechanisms Underlying Metabolism in Yak

Protein lysine lactylation, a recently discovered post-translational modification (PTM), is prevalent across tissues and cells of diverse species, serving as a regulator of glycolytic flux and biological metabolism. The yak (Bos grunniens), a species that has inhabited the Qinghai-Tibetan Plateau for millennia, has evolved intricate adaptive mechanisms to cope with the region's unique geographical and climatic conditions, exhibiting remarkable energy utilization and metabolic efficiency. Nonetheless, the specific landscape of lysine lactylation in yaks remains poorly understood. Herein, we present the first comprehensive lactylome profile of the yak, effectively identifying 421, 308, and 650 lactylated proteins in the heart, muscles, and liver, respectively. These lactylated proteins are involved in glycolysis/gluconeogenesis, the tricarboxylic acid cycle, oxidative phosphorylation, and metabolic process encompassing carbohydrates, lipids, and proteins during both anaerobic and aerobic glucose bio-oxidation, implying their crucial role in material and energy metabolism, as well as in maintaining homeostasis in yaks.

Regulation of newly identified lysine lactylation in cancer

Metabolic reprogramming is a typical hallmark of cancer. Enhanced glycolysis in tumor cells leads to the accumulation of lactate, which is traditionally considered metabolic waste. With the development of high-resolution liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), the lactate-derived, lysine lactylation(Kla), has been identified. Kla can alter the spatial configuration of chromatin and regulate the expression of corresponding genes. Metabolic reprogramming and epigenetic remodeling have been extensively linked. Accumulating studies have subsequently expanded the framework on the key roles of this protein translational modification (PTM) in tumors and have provided a new concept of cancer-specific regulation by Kla.

Hippocampal Lactate-Infusion Enhances Spatial Memory Correlated with Monocarboxylate Transporter 2 and Lactylation

Lactate has emerged as a key player in regulating neural functions and cognitive processes. Beyond its function as an energy substrate and signal molecule, recent research has revealed lactate to serve as an epigenetic regulator in the brain. However, the molecular mechanisms by which lactate regulates spatial memory and its role in the prevention of cognitive disorders remain unclear. Herein, we injected L-lactate (10 μmol/kg/d for 6 d) into the mouse's hippocampus, followed by the Morris water maze (MWM) test and molecular analyses. Improved spatial memory performances were observed in mice injected with lactate. Besides, lactate upregulated the expression of synaptic proteins post-synaptic density 95 (PSD95), synaptophysin (SYP), and growth associated protein 43 (GAP43) in hippocampal tissues and HT22 cells, suggesting a potential role in synaptic transmission and memory formation. The facilitative role of monocarboxylate transporter 2 (MCT2), a neuron-specific lactate transporter, in this process was confirmed, as MCT2 antagonists attenuated the lactate-induced upregulation of synaptic proteins. Moreover, lactate induced protein lactylation, a post-translational modification, which could be suppressed by MCT2 inhibition. RNA sequencing of lactated-injected hippocampal tissues revealed a comprehensive gene expression profile influenced by lactate, with significant changes in genes associated with transcriptional progress. These data demonstrate that hippocampal lactate injection enhances spatial memory in mice, potentially through the upregulation of synaptic proteins and induction of protein lactylation, with MCT2 playing a crucial role in these processes. Our findings shed light on the multi-faceted role of lactate in neural function and memory regulation, opening new avenues for therapeutic interventions targeting cognitive disorders.