Follicle-stimulating hormone (FSH) coordinates ovarian follicle development by aligning mitochondrial biogenesis with increased metabolic demand. Although FSH is known to stimulate glycolysis in granulosa cells (GCs), the mechanism by which glycolytic flux coupled to mitochondrial biogenesis remains unclear. Here, we demonstrate that histone lactylation functions as a lactate-sensitive epigenetic mediator linking FSH-driven metabolic alterations to mitochondrial biogenesis in GCs. Mechanistically, FSH increases intracellular lactate levels through glycolytic activation, thereby promoting P300/CBP-dependent lactylation of histone H4 at lysine 5 (H4K5la). H4K5la directly enhances HDAC4 expression, and HDAC4 subsequently deacetylates PGC-1α at lysine residues 329/330. Deacetylated PGC-1α cooperates with nuclear respiratory factors NRF1/2 to drive transcription of key mitochondrial regulators (TFAM, TFB1M, TFB2M), ultimately promoting mitochondrial biogenesis. Disruption of the H4K5la/HDAC4/PGC-1α axis markedly impaired mitochondrial biogenesis and follicular development, evidenced by reduced ovarian weight, smaller follicle size, decreased antral follicle number, and impaired GC proliferation and estradiol (E2) production in FSH-treated mice. These findings identify a metabolic–epigenetic regulatory pathway in which histone lactylation links glycolysis to mitochondrial adaptation, providing mechanistic insight into FSH-dependent reproductive physiology.

Allele-specific expression (ASE) is a key regulatory mechanism linking genetic variation to phenotypic diversity. This study conducted a genome-wide ASE analysis in embryonic (brain, kidney, liver) and extraembryonic (chorion) tissues of Landrace × Meishan crossbred pigs. By integrating DNA sequencing of parental and F1 hybrids and RNA-sequencing of F1 tissues, a high-resolution ASE landscape was built via strict allele-specific SNP identification. Genomically, ASE genes (ASEG) were enriched on chromosomes 6, 7, 12, X and sparse on chromosome 11, and can be classified into extreme/moderate types by expression pattern and parental bias. Paternal ASEGs had higher expression levels, while maternal ones had higher abundance. Functionally, tissue-concordant ASEGs supported embryo/placenta basal development, tissue-specific ones matched organ core functions; maternal ASEGs were enriched in mitochondrial pathways, paternal ones in cell motility and RNA transcription. Besides, chorion had more allele-specific methylated regions than embryonic tissues, with opposite ASE directions. We proposed "orthogonal dual regulatory dimensions" for the relationship between ASE and tissue-specific expression. We also proposed regulatory models of extreme and moderate ASEGs, functional division modes between embryo and extraembryonic tissues, and between paternal and maternal alleles. This study clarifies tissue-specific ASE patterns and mechanisms, providing a framework for future ASE research.

Mitochondrial biogenesis is a fundamental process that ensures energy supply and supports steroidogenesis in ovarian cells. Lactate has recently been identified as a signaling metabolite that promotes mitochondrial biogenesis; however, the underlying regulatory mechanisms remain poorly defined. Here, we identify Heat Shock Protein 90 Alpha Family Class A Member 1 (HSP90α) lactylation as a key mediator that links glycolytic metabolism to mitochondrial function. Specifically, lactylation of HSP90α at K58 recruits ULK1, thereby enhancing phosphorylation at S39; lactylation at K616 prevents CDK5-mediated phosphorylation at S596. This dual regulation facilitates the nuclear translocation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) and its isoform LRPGC1, which activate NRF1/2-dependent transcription of mitochondrial biogenesis genes, such as Tfb1m, Tfb2m, and Tfam. Functionally, mitochondrial mass expansion both enhances cellular energy metabolism and promotes cholesterol import into mitochondria, thereby driving estrogen biosynthesis. Together, these findings reveal a lactate-HSP90α-PGC1α/LRPGC1 axis that metabolically couples glycolysis to mitochondrial biogenesis and reproductive hormone production, providing insights into the epigenetic regulation of follicular development.

INTRODUCTION:Hypoxia, a condition characterized by inadequate oxygen supply to tissues, triggers various cellular responses, including apoptosis. The RNA demethylase FTO has been shown to exert anti-apoptotic effects, but its functions independent of RNA demethylase-particularly those involving protein-protein interactions-during hypoxia remain unclear. OBJECTIVES:This study aimed to elucidate the cytoprotective mechanism of FTO in preventing apoptosis under hypoxic stress. METHODS:NIH/3T3 cells, MEF cells, and mouse granulosa cells were cultured under hypoxia (1 % O2) and treated with inhibitors (chloroquine, MG132, cycloheximide) to identify FTO degradation pathways. RNA interference was used to knock down atg7, nedd4, and fto. Mass spectrometry identified FTO-associated proteins, and their interactions with FTO were analyzed with immunoprecipitation assays. FTO localization was examined through nuclear and cytoplasmic fractionation and fluorescence microscopy. Apoptosis was evaluated by flow cytometry (annexin V/PI). The role of FTO independent of its m6A demethylase activity was determined by inhibiting FTO function using FB23-2 or an H228A/D230A mutant lacking m6A demethylase activity. RESULTS:Upon hypoxia exposure, FTO relocated from the nucleus to the cytoplasm and underwent degradation through a regulatory pathway in which the E1-like ubiquitin-activating enzyme ATG7 and the E3 ubiquitin ligase NEDD4 cooperatively activated both the ubiquitin-proteasome system (UPS) and the autophagic-lysosomal pathway (ALP) in NIH/3T3 cells, MEF cells, and mouse granulosa cells. Furthermore, knocking down atg7 resulted in FTO accumulation in the cytoplasm, where FTO exerted its protective effect by binding with RACK1, which impairs the interaction between RACK1 and MTK1, thereby blocking activation of JNK1/2 and subsequently preventing apoptosis in hypoxic cells. CONCLUSION:This study reveals a novel function of cytoplasmic FTO in disrupting the RACK1-MTK1-JNK1/2-apoptosis cascade during hypoxia, positioning the functional context of FTO at the layer of protein-protein interactions, which extends its mechanistic role beyond RNA demethylation.

Background/Objectives: The avascular nature of the follicle creates a hypoxic microenvironment, establishing a niche where granulosa cells (GCs) rely on glycolysis to produce energy in the form of lactate (L-lactate). Autophagy, an evolutionarily conserved stress-response process, involves the formation of autophagosomes to encapsulate intracellular components, delivering them to lysosomes for degradation. This process plays a critical role in maintaining optimal follicular development. However, whether hypoxia regulates autophagy in GCs via lactate remains unclear. Methods: In this study, we investigated lactate-induced autophagy under hypoxia by utilizing glycolysis inhibitors or silencing related genes. Results: We observed a significant increase in autophagy in ovarian GCs under hypoxic conditions, indicated by elevated LC3II levels and reduced P62 levels. Suppressing lactate production through glycolytic inhibitors (2-DG and oxamate) or silencing lactate dehydrogenase (LDHA/LDHB) effectively reduced hypoxia-induced autophagy. Further investigation revealed that the HIF1-α/BNIP3/Beclin-1 axis is essential for lactate-induced autophagy under hypoxic conditions. Inhibiting HIF-1α activity using siRNAs or PX-478 downregulated BNIP3 expression and subsequently suppressed autophagy. Similarly, BNIP3 silencing with siRNAs repressed lactate-induced autophagy in hypoxic conditions. Mechanistically, immunoprecipitation experiments showed that BNIP3 disrupted pre-existing Bcl-2/Beclin-1 complexes by competing with Bcl-2 to form Bcl-2/BNIP3 complexes. This interaction released Beclin-1, which subsequently triggered lactate-induced autophagy under hypoxic conditions. Conclusions: These findings unveil a novel mechanism by which hypoxia regulates GC autophagy through lactate production, highlighting its potential role in sustaining follicular development under hypoxic conditions.

Hypoxia-inducible factor 1α (HIF-1α) is a master regulator of cellular adaptation to hypoxia. Although prolyl hydroxylation-mediated degradation via the von Hippel–Lindau (VHL) ubiquitination complex is a well-established regulatory mechanism, the role of lactate-induced posttranslational modifications in HIF-1α stabilization remains incompletely understood. Here, we demonstrate that lactate induces lysine lactylation of HIF-1α at distinct residues across species—specifically, K644 in mice and K12 in humans and pigs—to increase protein stability by impairing VHL recognition. Mass spectrometry and mutagenesis analyses revealed that lactylation at these sites reduces K48-linked ubiquitination and proteasomal degradation, even when HIF-1α is hydroxylated. Structural modeling and functional assays revealed that lactylation sterically hinders VHL binding without affecting hydroxylation. Notably, lactylated HIF-1α exhibited increased transcriptional activity, as evidenced by increased promoter occupancy and upregulation of hypoxia-responsive genes (Vegfa, Glut1). Cross-species comparisons highlighted evolutionary divergence in lactylation sites while preserving the functional conservation of this modification. Our findings reveal that lactylation is a universal regulatory mechanism that overrides classical hydroxylation-dependent degradation, expanding our understanding of metabolic control over hypoxic signaling.

HMGB1, one of the most abundant nuclear non-histone proteins, also performs extracellular functions, and its nuclear export mechanisms have been extensively studied. Here, a novel mechanism of nuclear export for HMGB1 driven by lactylation is proposed. In addition, it is revealed that hypoxia-induced lactylation of HMGB1 facilitates its nuclear export in a complex with TIAR, promoting stress granule (SG) formation in the cytosol. Mass spectrometry revealed 12 lysine residues in HMGB1 undergoing lactylation, with K172 and K177 being the most susceptible. Functional studies using lysine-to-arginine mutants (K→R) demonstrated that lactylation at K177 is crucial for HMGB1-TIAR complex export, as K177R mutation completely blocked this export and subsequent SG formation. Notably, this lactylation-mediated mechanism is specific to hypoxic stress, while other stressors, such as sodium arsenite exposure and heat shock, triggered TIAR nuclear export and SG assembly independently of HMGB1. These findings reveal a previously unrecognized role of HMGB1 lactylation in mediating nuclear export and SG formation under hypoxia.

BACKGROUND:Neonatal hypoxic-ischemic encephalopathy (HIE) has a high incidence and mortality rate, representing a significant patient burden. Therefore, treatment strategies that work synergistically with hypothermic therapies are urgently required. Punicalagin (PUN) is a natural and safe polyphenol with anti-inflammatory functions whose excellent water solubility and safety make it an advantageous perinatal medication. However, its underlying mechanisms of action in HIE remain unclear. OBJECTIVES:This study investigated the role and associated mechanism of action PUN in HIE. METHODS:We used the Rice Vannucci method to construct an in vivo HIE model in rats, from which we extracted primary cortical neurons to construct an in vitro oxygen and glucose deprivation/reoxygenation (OGD/R) model. The mechanisms of action of PUN were investigated using transcriptome sequencing, laser speckle contrast imaging, 2,3,5-triphenyltetrazolium chloride-staining, the Morris water maze test, western blotting, qPCR, immunofluorescence, and histochemistry. RESULTS:HIE rats demonstrated excessive autophagy and inflammation. PUN reduced brain tissue damage and neuronal apoptosis, and improved cerebral blood flow perfusion, learning, and cognitive abilities. PUN attenuated autophagic overexpression following HIE and inhibited the AKT-FOXO4 (forkhead box O4) signaling pathway. The neuroprotective effects of PUN were inhibited by treatment with the AKT signaling pathway and autophagy inhibitor 3-MA. Furthermore, brain tissue damage was significant and PUN was ineffective in siFOXO4 rats. CONCLUSIONS:PUN significantly reduces cerebral infarction, neuroinflammation, and excessive autophagy caused by HIE, thereby exerting short- and long-term neuroprotective effects. Mechanistically, the neuroprotective effect of PUN is mediated by activation of the AKT-FOXO4 pathway. Therefore, PUN may be a potential therapy for HIE.

Mettl14, a key component of the m6A methyltransferase complex, plays a crucial role in regulating mRNA stability and splicing. Reduced expression of Mettl14 is associated with hepatocellular carcinoma and liver regeneration, yet the molecular mechanisms by which it regulates the hepatocyte cell cycle remain unclear. Using RNA-Seq and MeRIP-Seq in liver-specific Mettl14 knockout mice, we found that Mettl14 deficiency stabilizes Fam32a mRNA through m6A modifications, resulting in increased Fam32a protein levels. Elevated Fam32a expression accelerates the G1/S transition by modulating Cdkn1a splicing, specifically downregulating its variant 2. These findings uncover a novel m6A-dependent mechanism that regulates hepatocyte cell cycle progression and highlight the previously unrecognized role of Fam32a in promoting the G1/S transition.

Follicle-stimulating hormone (FSH) promotes follicular development by inducing the proliferation and differentiation of granulosa cells (GCs). This process is primarily attributed to the activation of the canonical G protein-coupled receptor (GPCR)/adenylyl cyclase/cAMP/PKA/CREB signaling pathway. Here, we revealed a novel mechanism wherein FSH promotes GCs proliferation and differentiation by stimulating cAMP response element-binding protein (CREB) lactylation. Specifically, FSH induced CREB lactylation at lysine 136 (K136la), leading to CREB phosphorylation at serine 133, which facilitated CREB/CBP/P300 complex formation for transcription activation. Moreover, K136la alone directly recruited CBP/P300, triggering transcriptional surges of proliferation and differentiation genes by binding with the cAMP response element (CRE), thereby stimulating GCs proliferation and differentiation. By contrast, a CREB mutation at K136 eliminated these effects. Blocking CREB lactylation using oxamate or C646 in vivo suppressed GCs proliferation, differentiation, and follicular development in mouse ovaries. These findings highlight the important role of lactylation between metabolic regulation and folliculogenesis, and its importance in mediating GPCR signaling, providing a theoretical basis for treating female infertility associated with defective follicular development.

Extensive research has been conducted on the role of CXCR3 in immune responses and inflammation. However, the role of CXCR3 in the reproductive system, particularly in oocyte development, remains unknown. In this study, we present findings on the involvement of CXCR3 in the meiotic division process of mouse oocytes. We found CXCR3 was expressed consistently throughout the entire maturation process of mouse oocyte. Inhibition of CXCR3 impaired the asymmetric division of oocyte, while the injection of Cxcr3 mRNA was capable of restoring these defects. Further study showed that inhibition of CXCR3 perturbed spindle migration by affecting LIMK/cofilin pathway-mediated actin remodeling. Knockout of CXCR3 led to an upregulation of actin-binding protein and an increased ATP level in GV-stage oocytes, while maintaining normal actin dynamics during the process of meiosis. Additionally, we noticed the expression level of DYNLT1 is markedly elevated in CXCR3-null oocytes. DYNLT1 bound with the Arp2/3 complex, and knockdown of DYNLT1 in CXCR3-null oocytes impaired the organization of cytoplasmic actin, suggesting the regulatory role of DYNLT1 in actin organization, and the compensatory expression of DYNLT1 may contribute to maintain normal actin dynamics in CXCR3-knockout oocytes. In summary, our findings provide insights into the intricate network of actin dynamics associated with CXCR3 during oocyte meiosis.

Follicular fluid meiosis-activating sterol (FF-MAS) is a small molecule compound found in FF, named for its ability to induce oocyte resumption of meiosis. Granulosa cells (GCs) within the follicle are typically located in a hypoxic environment under physiologic conditions due to limited vascular distribution. Previous research suggests that hypoxia-induced cell cycle arrest and apoptosis in GCs may be crucial triggering factors in porcine follicular atresia. However, the impact of FF-MAS on GCs within follicles has not been explored so far. In this study, we uncovered a novel role of FF-MAS in facilitating GC survival under hypoxic conditions by inhibiting STAT4 expression. We found that STAT4 expression was upregulated in porcine GCs exposed to 1% O2. Both gain and loss of function assays confirmed that STAT4 was required for cell apoptosis under hypoxia conditions, and that the GC apoptosis caused by hypoxia was markedly attenuated following FF-MAS treatment through inhibition of STAT4 expression. Correlation analysis in vivo revealed that GC apoptosis was associated with increased STAT4 expression, while the FF-MAS content in follicular fluid was negatively correlated with STAT4 mRNA levels and cell apoptosis. These findings elucidate a novel role of FF-MAS-mediated protection of GCs by inhibiting STAT4 expression under hypoxia, which might contribute to the mechanistic understanding of follicular development.

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.

Follicle development, a crucial process in reproductive biology, hinges upon the dynamic proliferation of granulosa cells (GCs). Growth differentiation factor-8 (GDF8) is well-known as myostatin for inhibiting skeletal muscle growth, and it also exists in ovarian GCs and follicle fluid. However, the relationship between GCs proliferation and GDF8 remains elusive. Sulforaphane (SFN) is a potent bioactive compound, which in our study has been demonstrated to induce the expression of GDF8 in GCs. Meanwhile, we discover a novel role of SFN in promoting the proliferation of porcine GCs. Specifically, SFN enhances GCs proliferation by accelerating the progression of the cell cycle through the G1 phase to the S phase. By performing gene expression profiling, we showed that the promoting proliferative effects of SFN are highly correlated with the TGF-β signaling pathways and cell cycle. Among the ligand factors of TGF-β signaling, we identify GDF8 as a critical downstream effector of SFN, which acts through ALK5 to mediate SFN-induced proliferation and G1/S transition. In addition, we identify a noncanonical downstream pathway by which GDF8 induces the activation of MAPK/ERK to facilitate the cell cycle progression in GCs. Moreover, we reveal that the expression of GDF8 is regulated by SFN through epigenetic modifications of H3K27 acetylation. These findings not only provide mechanistic insights into the regulation of GCs proliferation but also establish a previously unrecognized role of GDF8 in follicle development, which have significant implications for developing strategies to improve female fertility.

FOXO proteins, especially FOXO1 and FOXO3, are recognized for their roles in controlling apoptosis and autophagy. Both apoptosis and autophagy have been induced in granulosa cells (GCs) by hypoxic conditions in ovarian follicles; however, the exact contribution of FOXO proteins and autophagy to the regulation of GCs apoptosis under hypoxia remains unclear. In this investigation of porcine GCs, we reveal that FOXO1 promotes apoptosis in response to hypoxia through FOXO3-dependent autophagy. We describe how mechanistically, FOXO1 forms a complex with the transcription factor STAT3 during hypoxia. Guided by FOXO1, this complex undergoes nuclear translocation and effectively attaches to the STAT3-responsive element (SRE) located in the FOXO3 promoter region, thereby enhancing the transcriptional expression of FOXO3. Simultaneously, FOXO1 associates with AKT1, thus facilitating its nuclear entry and subsequently reducing the Ser253 phosphorylation of FOXO3, leading to FOXO3 detachment from 14-3-3 and promoting FOXO3 translocation into the nucleus. FOXO3 subsequently stimulates the upregulation of ATG3, ultimately initiating autophagy and autophagy-dependent apoptosis. Our results suggest that hypoxia acts through FOXO1 to induce autophagic death in porcine GCs by promoting the expression and nuclear import of FOXO3.

INTRODUCTION:Granulosa cells (GCs) is essential for maintaining follicular development. Follicle-stimulating Hormone (FSH) has been demonstrated to effectively promote GCs proliferation, driving the establishment of various superovulation techniques for animal husbandry. However, these techniques face challenges, such as high costs, hormonal imbalances, and an increased risk of early ovarian dysfunction. Therefore, it is important to investigate new methods to improve GCs proliferation. OBJECTIVES:This study aimed to investigate the effect of sulforaphane (SFN) on ovarian GCs proliferation and the underlying mechanisms. METHODS:A comparative transcriptomic analysis of ovaries from the control, SFN, and FSH groups was conducted to identify the primary factors contributing to high proliferative capacity. The role of SFN in the regulation of cell proliferation has been examined in mouse ovarian GCs. Gene interference, overexpression, CUT&TAG technology, and transcriptome analyses were performed to elucidate the underlying mechanisms of the nuclear factor E2-related factor 2 (NRF2)-transketolase (TKT) axis in mediating GCs proliferation. RESULTS:Our research revealed a previously unknown function of SFN, an isothiocyanate of plant origin that is prevalent in cruciferous vegetables, in facilitating the proliferation of mouse ovarian GCs. The efficacy of SFN in enhancing GCs proliferation is similar to that of FSH. At the mechanistic level, SFN promotes NRF2 to transport to the nucleus, which subsequently activates the key enzyme of the non-oxidative pentose phosphate pathway TKT. This activation is instrumental in generating ribose 5-phosphate, a critical precursor for amino acid and nucleotide biosynthesis that underpins the proliferation of GCs. CONCLUSION:Collectively, our findings delineate a novel pathway by which SFN, through the NRF2-TKT axis, enhances the nucleotide pool and thereby supports the proliferation of mouse GCs, presenting novel avenues for exploration in reproductive biology and agricultural sciences.

The developmental fate of ovarian follicles is primarily determined by the survival status (proliferation or apoptosis) of granulosa cells (GCs). Owing to the avascular environment within follicles, GCs are believed to live in a hypoxic niche. Follicle‐stimulating hormone (FSH) has been reported to improve GCs survival by governing hypoxia‐inducible factor‐1α (HIF‐1α)‐dependent hypoxia response, but the underlying mechanisms remain poorly understood. Growth arrest‐specific gene 6 (GAS6) is a secreted ligand of tyrosine kinase receptors, and has been documented to facilitate tumor growth. Here, we showed that the level of GAS6 was markedly increased in mouse ovarian GCs after the injection of FSH. Specifically, FSH‐induced GAS6 expression was accompanied by HIF‐1α accumulation under conditions of hypoxia both in vivo and in vitro, whereas inhibition of HIF‐1α with small interfering RNAs/antagonist repressed both expression and secretion of GAS6. As such, Luciferase reporter assay and chromatin immunoprecipitation assay showed that HIF‐1α directly bound to a hypoxia response element site within the Gas6 promoter and contributed to the regulation of GAS6 expression in response to FSH. Notably, blockage of GAS6 and/or its receptor Axl abrogated the pro‐survival effects of FSH under hypoxia. Moreover, phosphorylation of Axl by GAS6 is required for FSH‐mediated Akt activation and the resultant pro‐survival phenotypes. Finally, the in vitro findings were verified in vivo, which showed that FSH‐induced proliferative and antiapoptotic effects in ovarian GCs were diminished after blocking GAS6/Axl using HIF‐1α antagonist. These findings highlight a novel function of FSH in preserving GCs viability against hypoxic stress by activating the HIF‐1a‐GAS6‐Axl‐Akt pathway.

Numerous studies have established that the hypoxic conditions within ovarian follicles induce apoptosis in granulosa cells (GCs), a pivotal hallmark of follicular atresia. Melatonin (N-acetyl-5-methoxytryptamine, MT), a versatile antioxidant naturally present in follicular fluid, acts as a safeguard for maintaining GCs' survival during stress exposure. In this study, we unveil an innovative protective mechanism of melatonin against hypoxia-triggered GC apoptosis by selectively inhibiting mitochondrial ROS (mtROS) generation. Specifically, under hypoxic conditions, a gradual accumulation of mitochondrial ROS occurred, consequently activating the JNK-FOXO1 pathway, and driving GCs toward apoptosis. The blocking of JNK or FOXO1 diminished hypoxia-induced GC apoptosis, but this effect was nullified in the presence of GSH, indicating that mtROS instigates apoptosis through the JNK-FOXO1 pathway. Consistent with this, hypoxic GCs treated with melatonin exhibited decreased levels of mtROS, reduced JNK-FOXO1 activation, and mitigated apoptosis. However, the protective capabilities of melatonin were attenuated upon inhibiting its receptor MTNR1B, accompanied by the decreased expression of antioxidant genes. Notably, SOD2, a key mitochondrial antioxidant gene modulated by the melatonin-MTNR1B axis, effectively inhibited the activation of mtROS-JNK-FOXO1 and subsequent apoptosis, whereas SOD2 knockdown abrogated the protective role of melatonin in hypoxic GCs. In conclusion, our study elucidates that melatonin, through MTNR1B activation, fosters SOD2 expression, effectively quelling mtROS-JNK-FOXO1-mediated apoptosis in follicular GCs under hypoxic stress.

Our previous study with artificial intelligence (AI)-assisted screening found that diosmin, a natural flavonoid extracted from citrus, may affect myoblast proliferation and differentiation. At present, few studies have been conducted regarding the biological function of diosmin in muscle cells. Here, using molecular biological techniques, we found that diosmin elevated the proliferation ability of C2C12 myoblasts via activating the Akt/FOXO1 pathway to promote FOXO1 nuclear export, thus repressing p27 protein expression, increasing CDK2, CDK4, and cyclin D1 and cyclin E1 protein expression and accelerating cell cycle transformation, which contributed to myogenesis. Moreover, diosmin suppressed differentiation of C2C12 myoblasts by delaying the terminal exit of the cell cycle in early differentiated myoblasts and inhibiting autophagic flux in mature myotubes. Furthermore, diosmin promoted myogenesis by activating the Akt/FOXO1 pathway to facilitate myoblast proliferation, which had a positive biological effect on the repair of muscle injury. This study revealed the effect and mechanism of diosmin on skeletal muscle cells and simultaneously provided a new candidate drug for the treatment of myopathy.

Abstract Background Lactate, a glycolytic metabolite mainly produced in muscles, has been suggested to regulate myoblast differentiation, although the underlying mechanism remains elusive. Recently, lactate‐mediated histone lactylation is identified as a novel epigenetic modification that promotes gene transcription. Methods We used mouse C2C12 cell line and 2‐month‐old male mice as in vitro and in vivo models, respectively. These models were treated with lactate to explore the biological function and latent mechanism of lactate‐derived histone lactylation on myogenic differentiation by quantitative real‐time PCR, western blotting, immunofluorescence staining, chromatin immunoprecipitation, cleavage under targets and tagmentation assay and RNA sequencing. Results Using immunofluorescence staining and western blotting, we proposed that lactylation might occur in the histones. Inhibition of lactate production or intake both impaired myoblast differentiation, accompanied by diminished lactylation in the histones. Using lactylation site‐specific antibodies, we demonstrated that lactate preferentially increased H3K9 lactylation (H3K9la) during myoblast differentiation (CT VS 5, 10, 15, 20, 25 mM lactate treatment, P = 0.0012, P = 0.0007, and the rest of all P < 0.0001). Notably, inhibiting H3K9la using P300 antagonist could block lactate‐induced myogenesis. Through combined omics analysis using cleavage under targets and tagmentation assay and RNA sequencing, we further identified Neu2 as a potential target gene of H3K9la. IGV software analysis (P = 0.0013) and chromatin immunoprecipitation‐qPCR assay (H3K9la %Input, LA group = 9.0076, control group = 2.7184, IgG = 0.3209) confirmed that H3K9la is enriched in the promoter region of Neu2. Moreover, siRNAs or inhibitors against Neu2 both abrogated myoblast differentiation despite lactate treatment, suggesting that Neu2 is required for lactate‐mediated myoblast differentiation. Conclusions Our findings provide novel understanding of histone lysine lactylation, suggesting its role in myogenesis, and as potential therapeutic targets for muscle diseases.