Alpha-ketoglutarate ameliorates age-related osteoporosis via regulating histone methylations

The addition of alpha-ketoglutarate to NT-proBNP improves the prediction of long-term all-cause mortality in acute heart failure patients

BACKGROUND AND OBJECTIVE

Alpha-ketoglutarate (AKG), is a major intermediate metabolite of the tricarboxylic acid cycle, and is closely associated with cardiometabolic disease prognosis. Previous studies indicated that AKG is related to myocardial energy expenditure levels and reflects adverse short-term outcomes in heart failure (HF) patients. In this prospective cohort study, we examined the long-term prognostic value of AKG levels in acute HF (AHF) patients.

METHODS

Plasma AKG levels were assessed in patients hospitalized with AHF. Hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality were calculated via multiple Cox regression. All-cause mortality was compared between patients with NT-proBNP < 1000 pg/ml and those with NT-proBNP ≥ 1000 pg/ml via subgroup analysis.

RESULTS

Patients with AKG ≥ 9.83 μg/ml had higher heart rates and NT-proBNP and lower left ventricular ejection fraction (LVEF) and systolic blood pressure (SBP). After multiple adjustment, higher AKG was associated with an increased all-cause mortality risk (HR = 1.078, p < 0.001). Compared with AKG < 9.83 μg/ml, AKG ≥ 9.83 μg/ml nearly doubled (HR = 1.929, p < 0.001) and quadrupled (HR = 4.160, p < 0.001) the all-cause mortality risk in patients with NT-proBNP ≥ 1000 pg/ml and those with NT-proBNP < 1000 pg/ml, respectively.

CONCLUSIONS AND RELEVANCE

Plasma AKG was independently associated with greater all-cause mortality risk in patients with AHF. Higher AKG levels retained prognostic value for patients with relatively low NT-proBNP.

Inosine from purine metabolism enhances fracture healing by coupling fibrinolysis and angiogenesis of type H vessels

Fibrinolysis-angiogenesis coupling is crucial for successful fracture healing, in which type H vessels play an indispensable role. However, the metabolic control of fibrinolysis-type H angiogenesis coupling in fracture healing remains unclear. We used a metabolomics approach to gain metabolic insights from mouse fracture models (0.3 mm and 1.0 mm femur defects). Furthermore, human umbilical vein endothelial cells (HUVECs) and MC3T3-E1 cells were employed as in vitro models to examine the effects of identified metabolites on endothelial events and osteogenesis, respectively. CD31 and endomucin (Emcn) were used for detecting type H markers, and tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) for fibrinolysis. A femur defect of 1.5 mm in mice was included to validate the therapeutic potential of identified metabolites by bone imaging and micro-CT. Purine metabolism is the most significant pathway in fracture healing; three purinergic metabolites, adenosine, adenine, and inosine, are regulated in mouse serum. According to the in vivo results, CD31HiEmcnHi type H vessels are upregulated near the defect site in mouse femur and are associated with tPA expression, but not PAI-1. Additionally, in vitro experiments examining the endothelial functions of HUVECs demonstrated that these three metabolites promote cell migration and tube formation rather than proliferation. Fibrinolytic activity and type H phenotype in HUVECs were induced only by inosine through activation of the adenosine A2A receptor. Inosine, regulated during fracture healing, has the capacity to synchronously induce fibrinolysis and type H phenotype in line with osteogenesis, indicating its role in enhancing fracture healing.

Calcium phosphate bone cements with α-ketoglutarate polyester microspheres promote osteoporotic bone defect repair

Excessive oxidative stress and inflammation are prevalent in osteoporotic bone defects, significantly impairing the efficacy of bone regeneration in such defects. Calcium phosphate bone cements (CPC) are a commonly employed material for repairing bone defects. However, the slow rate of osteogenic mineralization and biodegradation presents a significant challenge in meeting the requirements of osteoporotic bone treatment. In this study, α-ketoglutarate (α-KG) polyester microspheres were synthesized from α-KG. By introducing different mass ratios of α-KG polyester microspheres, we constructed CPC with α-KG polyester microspheres (CPC/α-KG) that exhibited an improved microenvironment, enhanced osteogenic differentiation, and increased biomineralization. The incorporation of α-KG polyester microspheres was instrumental in enhancing the physicochemical attributes, biodegradability, biocompatibility, osteogenic differentiation potential, and biomineralization of α-KG. Mechanistically, the CPC/α-KG improves the osteogenic microenvironment by inhibiting the inflammatory response and reducing oxidative stress through the PI3K/AKT signaling pathway. Notably, the addition of 10 wt% α-KG polyester microspheres resulted in the optimal osteogenic capacity for CPC/α-KG. In conclusion, the modified α-KG composites show potential as effective candidates for bone defect repair and regeneration.

Role and mechanisms of histone methylation in osteogenic/odontogenic differentiation of dental mesenchymal stem cells

Dental mesenchymal stem cells (DMSCs) are pivotal for tooth development and periodontal tissue health and play an important role in tissue engineering and regenerative medicine because of their multidirectional differentiation potential and self-renewal ability. The cellular microenvironment regulates the fate of stem cells and can be modified using various optimization techniques. These methods can influence the cellular microenvironment, activate disparate signaling pathways, and induce different biological effects. "Epigenetic regulation" refers to the process of influencing gene expression and regulating cell fate without altering DNA sequences, such as histone methylation. Histone methylation modifications regulate pivotal transcription factors governing DMSCs differentiation into osteo-/odontogenic lineages. The most important sites of histone methylation in tooth organization were found to be H3K4, H3K9, and H3K27. Histone methylation affects gene expression and regulates stem cell differentiation by maintaining a delicate balance between major trimethylation sites, generating distinct chromatin structures associated with specific downstream transcriptional states. Several crucial signaling pathways associated with osteogenic differentiation are susceptible to modulation via histone methylation modifications. A deeper understanding of the regulatory mechanisms governing histone methylation modifications in osteo-/odontogenic differentiation and immune-inflammatory responses of DMSCs will facilitate further investigation of the epigenetic regulation of histone methylation in DMSC-mediated tissue regeneration and inflammation. Here is a concise overview of the pivotal functions of epigenetic histone methylation at H3K4, H3K9, and H3K27 in the regulation of osteo-/odontogenic differentiation and renewal of DMSCs in both non-inflammatory and inflammatory microenvironments. This review summarizes the current research on these processes in the context of tissue regeneration and therapeutic interventions.

Metabolism-epigenetic interaction-based bone and dental regeneration: From impacts and mechanisms to treatment potential

Metabolic pathways exhibit fluctuating activities during bone and dental loss and defects, suggesting a regulated metabolic plasticity. Skeletal remodeling is an energy-demanding process related to altered metabolic activities. These metabolic changes are frequently associated with epigenetic modifications, including variations in the expression or activity of enzymes modified through epigenetic mechanisms, which directly or indirectly impact cellular metabolism. Metabolic reprogramming driven by bone and dental conditions alters the epigenetic landscape by modulating the activities of DNA and histone modification enzymes at the metabolite level. Epigenetic mechanisms modulate the expression of metabolic genes, consequently influencing the metabolome. The interplay between epigenetics and metabolomics is crucial in maintaining bone and dental homeostasis by preserving cell proliferation and pluripotency. This review, therefore, aims to examine the effects of metabolic reprogramming in bone and dental-related cells on the regulation of epigenetic modifications, particularly acetylation, methylation, and lactylation. We also discuss the effects of chromatin-modifying enzymes on metabolism and the potential therapeutic benefits of dietary compounds as epigenetic modulators. In this review, we highlight the inconsistencies in current research findings and suggest potential approaches to translate fundamental insights into clinical treatments for bone and tooth diseases.

Essential role of the metabolite α-ketoglutarate in bone tissue and bone-related diseases

Bone metabolism in bone tissue is constantly maintained in a state of dynamic equilibrium. The mass of bone and joint tissues is determined by both bone formation and bone resorption. It is hypothesized that disrupted metabolic balance leads to osteoporosis, osteoarthritis, rheumatoid arthritis, and bone tumors. Such disruptions often manifest as either a reduction or abnormality in bone mass and are frequently accompanied by pathological changes such as inflammation, fractures, and pain. α-Ketoglutarate (α-KG) serves as a pivotal intermediate in various metabolic pathways in mammals, significantly contributing to cellular energy metabolism, amino acid metabolism, and other physiological processes. α-KG may be a therapeutic target for a variety of bone-related diseases, such as osteoporosis, osteoarthritis, and rheumatoid arthritis, because of its role in maintaining the metabolic balance of bone. After the application of α-KG, bone loss and inflammation in bone tissue are alleviated. This review focuses on the regulatory effects of α-KG on various cells in bone and joint tissues. Owing to the regulatory effect of α-KG on the balance of bone metabolism, the application of α-KG in the treatment of osteoporosis, osteoarthritis, rheumatoid arthritis, bone tumors, and other bone tissue diseases has been clarified.

Glibenclamide targets MDH2 to relieve aging phenotypes through metabolism-regulated epigenetic modification

Mitochondrial metabolism-regulated epigenetic modification is a driving force of aging and a promising target for therapeutic intervention. Mitochondrial malate dehydrogenase (MDH2), an enzyme in the TCA cycle, was identified as an anti-aging target through activity-based protein profiling in present study. The expression level of MDH2 was positively correlated with the cellular senescence in Mdh2 knockdown or overexpression fibroblasts. Glibenclamide (Gli), a classic anti-glycemic drug, was found to inhibit the activity of MDH2 and relieve fibroblast senescence in an MDH2-dependent manner. The anti-aging effects of Gli were also further validated in vivo, as it extended the lifespan and reduced the frailty index of naturally aged mice. Liver specific Mdh2 knockdown eliminated Gli's beneficial effects in naturally aged mice, reducing p16INK4a expression and hepatic fibrosis. Mechanistically, MDH2 inhibition or knockdown disrupted central carbon metabolism, then enhanced the methionine cycle flux, and subsequently promoted histone methylation. Notably, the tri-methylation of H3K27, identified as a crucial methylation site in reversing cellular senescence, was significantly elevated in hepatic tissues of naturally aged mice with Mdh2 knockdown. Taken together, these findings reveal that MDH2 inhibition or knockdown delays the aging process through metabolic-epigenetic regulation. Our research not only identified MDH2 as a potential therapeutic target and Gli as a lead compound for anti-aging drug development, but also shed light on the intricate interplay of metabolism and epigenetic modifications in aging.

Rejuvenation of Bone Marrow Mesenchymal Stem Cells: Mechanisms and Their Application in Senile Osteoporosis Treatment

Bone marrow mesenchymal stromal cells (BM-MSCs) are multipotent cells present in bone marrow; they play a crucial role in the process of bone formation. Cellular senescence is defined as a stable state of cell cycle arrest that impairs the functioning of cells. Research has shown that aging triggers a state of senescence in BM-MSCs, leading to a reduced capacity for osteogenic differentiation and the accumulation of senescent cells, which can accelerate the onset of various diseases. Therefore, it is essential to explore mechanisms and strategies for the rejuvenation of senescent BM-MSCs. Senile osteoporosis (SOP) is a metabolic bone disease characterized by reduced bone formation. The senescence of BM-MSCs is considered one of the most important factors in the occurrence and development of SOP. Therefore, the rejuvenation of BM-MSCs for the treatment of SOP represents a promising strategy. This work provides a summary of the functional alterations observed in senescent BM-MSCs and a systematic review of the mechanisms that facilitate the rejuvenation of senescent BM-MSCs. Additionally, we analyze the progress in and the limitations associated with the application of rejuvenated senescent BM-MSCs to treat SOP, with the aim of providing new insights for the prevention and treatment of SOP.

SIRT3 alleviates mitochondrial dysfunction and senescence in diabetes-associated periodontitis by deacetylating LRPPRC

Diabetes-associated periodontitis (DP) is recognized as an inflammatory disease that can lead to teeth loss. Uncontrolled chronic low-grade inflammation-induced senescence impairs the stemness of human periodontal stem cells (hPDLSCs). Sirtuin 3 (SIRT3), an NAD+-dependent deacetylase, is pivotal in various biological processes and is closely linked to aging and aging-related diseases. This study aims to explore the mechanism of SIRT3-related senescence and osteogenic differentiation of hPDLSCs under DP and explored the novelty therapeutic targets. Our study revealed that SIRT3 expression was markedly inhibited in periodontal ligament stem cells (PDLSCs) stimulated by high glucose and lipopolysaccharide. Both in vitro and in vivo, reduced SIRT3 expression accelerated cell senescence and impaired osteogenic differentiation of hPDLSCs. We demonstrated that SIRT3 binds to and deacetylates leucine-rich pentatricopeptide repeat-containing protein (LRPPRC), thereby modulating senescence. Additionally, we found that LRPPRC regulates senescence by modulating oxidative phosphorylation and oxidative stress. The activation of SIRT3 by honokiol significantly delayed senescence and promoted alveolar bone regeneration in mice after DP. Our findings indicate that the activation of SIRT3 negatively regulates hPDLSCs senescence by deacetylating LRPPRC, suggesting SIRT3 as a promising therapeutic target for DP.

Metabolism and metabolomics in senescence, aging, and age-related diseases: a multiscale perspective

The pursuit of healthy aging has long rendered aging and senescence captivating. Age-related ailments, such as cardiovascular diseases, diabetes, and neurodegenerative disorders, pose significant threats to individuals. Recent studies have shed light on the intricate mechanisms encompassing genetics, epigenetics, transcriptomics, and metabolomics in the processes of senescence and aging, as well as the establishment of age-related pathologies. Amidst these underlying mechanisms governing aging and related pathology metabolism assumes a pivotal role that holds promise for intervention and therapeutics. The advancements in metabolomics techniques and analysis methods have significantly propelled the study of senescence and aging, particularly with the aid of multiscale metabolomics which has facilitated the discovery of metabolic markers and therapeutic potentials. This review provides an overview of senescence and aging, emphasizing the crucial role metabolism plays in the aging process as well as age-related diseases.

α-Ketoglutaric Acid Reprograms Macrophages by Altering Energy Metabolism to Promote the Regeneration of Small-Diameter Vascular Grafts

Small-diameter vascular grafts still cannot clinically replace autologous blood vessels due to high restenosis rates caused by long-term inflammatory infiltration. Foreign body reactions to vascular grafts induce macrophages to adopt the pro-inflammatory M1 phenotype, releasing inflammatory factors such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). This induces a phenotypic switch in smooth muscle cells, eventually leading to intimal hyperplasia. Herein, we constructed small-diameter artificial vascular grafts capable of modulating immune responses through the controlled release of α-ketoglutaric acid (α-KG). Our findings verify that the delivery of α-KG reprograms the macrophage phenotype from a pro-inflammatory M1 to an anti-inflammatory and pro-repair M2 phenotype by regulating the energy metabolism of the tricarboxylic acid cycle (TAC). More interestingly, the delivery of α-KG positively influences the behavior of vascular cells by enhancing the proliferation of human umbilical vein endothelial cells (HUVECs) and inhibiting the expansion of mouse aortic vascular smooth muscle cells (MOVAS), thereby reducing vascular restenosis. In vivo evaluation in rabbit carotid artery replacement confirms the optimal performance of α-KG-doped vascular grafts in terms of endothelial coverage and long-term patency. Collectively, our work presents a promising approach for creating artificial vascular grafts with inflammatory regulation to ensure rapid endothelialization and sustained patency.

Cordycepin-Loaded Dental Pulp Stem Cell-Derived Exosomes Promote Aged Bone Repair by Rejuvenating Senescent Mesenchymal Stem Cells and Endothelial Cells

Aging impairs bone marrow mesenchymal stem cell (BMSC) functions as well as associated angiogenesis which is critical for bone regeneration and repair. Hence, repairing bone defects in elderly patients poses a formidable challenge in regenerative medicine. Here, the engineered dental pulp stem cell-derived exosomes loaded with the natural derivative of adenosine Cordycepin (CY@D-exos) are fabricated by means of the intermittent ultrasonic shock, which dually rejuvenates both senescent BMSCs and endothelial cells and significantly improve bone regeneration and repair in aged animals. CY@D-exos can efficiently overcome the senescence of aged BMSCs and enhance their osteogenic differentiation by activating NRF2 signaling and maintaining heterochromatin stability. Importantly, CY@D-exos also potently overcomes the senescence of vascular endothelial cells and promotes angiogenesis. In vivo injectable gelatin methacryloyl (GelMA) hydrogels with sustained release of CY@D-exos can accelerate bone injury repair and promote new blood vessel formation in aged animals. Taken together, these results thus demonstrate that cordycepin-loaded dental pulp stem cell-derived exosomes display considerable potential to be developed as a next-generation therapeutic agent for promoting aged bone regeneration and repair.

Glutamic-pyruvic transaminase 1 deficiency-mediated metabolic reprogramming facilitates colorectal adenoma-carcinoma progression

The tumorigenesis of colorectal cancer (CRC) often follows the normal-adenoma-carcinoma (N-A-C) sequence. However, the molecular mechanisms underlying colorectal adenoma carcinogenesis remain largely unknown. Here, we analyzed transcriptomic profile changes in normal, advanced adenoma, and carcinoma tissues from patients with CRC, revealing that glutamic-pyruvic transaminase 1 (GPT1) in colorectal tissues was down-regulated during the N-A-C process and correlated with poor CRC prognosis. Mechanistically, GPT1 was transcriptionally activated by Krüppel-like factor 4 (KLF4). GPT1 reprogrammed metabolism and suppressed CRC tumorigenesis in cells and mouse models not only through enzyme-dependent α-ketoglutarate (α-KG) production and WNT signaling inhibition but also through enzyme-independent disruption of the folate cycle through binding with methylenetetrahydrofolate dehydrogenase 1-like (MTHFD1L). Furthermore, we identified poliumoside as a GPT1 activator that restrained CRC progression in cells, patient-derived CRC organoids, and patient-derived xenograft (PDX) models of CRC. Our study uncovers a role for GPT1 in CRC tumorigenesis and shows that poliumoside is a potential drug for the prevention and treatment of CRC.

IGF-1 c.258 A > G synonymous mutation ameliorates senile osteoporosis

Senile osteoporosis (SOP) is a multifactorial, age-related progressive phenomenon with a considerable morbidity and mortality. IGF-1 is an important regulator of bone reconstruction and metabolism throughout life. Nevertheless, our previous study unexpectedly found there is no change in the peak bone mass with a altered IGF-1 gene expression leaded by IGF-1 c.258 A > G synonymous mutation. Considering its involvement in the cellular senescence, we suspected c.258 A > G may participate in SOP. Therefore, the effect of IGF-1 c.258 A > G on SOP was firstly detected, the changes of bone formation and bone resorption index in SOP mice with two genotypes indicated it improved SOP. Then, the in vitro study confirmed the mutation ameliorates SOP by promoting the growth and development of senescent osteoblasts. At last, co-culture of osteoblast and osteoclast further verified the mutation prevents SOP by increasing the bone formation capacity of senescent osteoblasts. Collectively, this study illuminated the role of IGF-1 c.258 A > G in ameliorating SOP.

Glutamine-αKG axis affects dentin regeneration and regulates osteo/odontogenic differentiation of mesenchymal adult stem cells via IGF2 m6A modification

BACKGROUND

Multi-lineage differentiation of mesenchymal adult stem cells (m-ASCs) is crucial for tissue regeneration and accompanied with metabolism reprogramming, among which dental-pulp-derived m-ASCs has obvious advantage of easy accessibility. Stem cell fate determination and differentiation are closely related to metabolism status in cell microenvironment, which could actively interact with epigenetic modification. In recent years, glutamine-α-ketoglutarate (αKG) axis was proved to be related to aging, tumorigenesis, osteogenesis etc., while its role in m-ASCs still lack adequate research evidence.

METHODS

We employed metabolomic analysis to explore the change pattern of metabolites during dental-pulp-derived m-ASCs differentiation. A murine incisor clipping model was established to investigate the influence of αKG on dental tissue repairment. shRNA technique was used to knockdown the expression of related key enzyme-dehydrogenase 1(GLUD1). RNA-seq, m6A evaluation and MeRIP-qPCR were used to dig into the underlying epigenetic mechanism.

RESULTS

Here we found that the glutamine-αKG axis displayed an increased tendency along with the osteo/odontogenic differentiation of dental-pulp-derived m-ASCs, same as expression pattern of GLUD1. Further, the key metabolite αKG was found able to accelerate the repairment of clipped mice incisor and promote dentin formation. Exogenous DM-αKG was proved able to promote osteo/odontogenic differentiation of dental-pulp-derived m-ASCs, while the inhibition of glutamine-derived αKG level via GLUD1 knockdown had the opposite effect. Under the circumstance of GLUD1 knockdown, extracellular matrix (ECM) function and PI3k-Akt signaling pathway was screened out to be widely involved in the process with insulin-like growth factor 2 (IGF2) participation via RNA-seq. Inhibition of glutamine-αKG axis may affect IGF2 translation efficiency via m6A methylation and can be significantly rescued by αKG supplementation.

CONCLUSION

Our findings indicate that glutamine-αKG axis may epigenetically promote osteo/odontogenic differentiation of dental-pulp-derived m-ASCs and dentin regeneration, which provide a new research vision of potential dental tissue repairment therapy method or metabolite-based drug research.

Exploration of Key Regulatory Factors in Mesenchymal Stem Cell Continuous Osteogenic Differentiation via Transcriptomic Analysis

BACKGROUND/OBJECTIVES

Mesenchymal stem cells (MSCs) possess the remarkable ability to differentiate into various cell types, including osteoblasts. Understanding the molecular mechanisms governing MSC osteogenic differentiation is crucial for advancing clinical applications and our comprehension of complex disease processes. However, the key biological molecules regulating this process remain incompletely understood.

METHODS

In this study, we conducted systematic re-analyses of published high-throughput transcriptomic datasets to identify and validate key biological molecules that dynamically regulate MSC osteogenic differentiation. Our approach involved a comprehensive analysis of gene expression patterns across human tissues, followed by the rigorous experimental validation of the identified candidates.

RESULTS

Through integrated analytical and experimental approaches, we utilized high-throughput transcriptomics to identify four critical regulators of MSC osteogenic differentiation: PTBP1, H2AFZ, BCL6, and TTPAL (C20ORF121). Among these, PTBP1 and H2AFZ functioned as positive regulators, while BCL6 and TTPAL acted as negative regulators in osteogenesis. The regulatory roles of these genes in osteogenesis were further validated via overexpression experiments.

CONCLUSIONS

Our findings advance our understanding of MSC differentiation fate determination and open new therapeutic possibilities for bone-related disorders. The identification of these regulators provides a foundation for developing targeted interventions in regenerative medicine.

Roles of chromatin and genome instability in cellular senescence and their relevance to ageing and related diseases

Ageing is a complex biological process in which a gradual decline in physiological fitness increases susceptibility to diseases such as neurodegenerative disorders and cancer. Cellular senescence, a state of irreversible cell-growth arrest accompanied by functional deterioration, has emerged as a pivotal driver of ageing. In this Review, we discuss how heterochromatin loss, telomere attrition and DNA damage contribute to cellular senescence, ageing and age-related diseases by eliciting genome instability, innate immunity and inflammation. We also discuss how emerging therapeutic strategies could restore heterochromatin stability, maintain telomere integrity and boost the DNA repair capacity, and thus counteract cellular senescence and ageing-associated pathologies. Finally, we outline current research challenges and future directions aimed at better comprehending and delaying ageing.

Foxk1 promotes bone formation through inducing aerobic glycolysis

Transcription factor Foxk1 can regulate cell proliferation, differentiation, metabolism, and promote skeletal muscle regeneration and cardiogenesis. However, the roles of Foxk1 in bone formation is unknown. Here, we found that Foxk1 expression decreased in the bone tissue of aged mice and osteoporosis patients. Knockdown of Foxk1 in primary murine calvarial osteoblasts suppressed osteoblast differentiation and proliferation. Conditional knockout of Foxk1 in preosteoblasts and mature osteoblasts in mice exhibited decreased bone mass and mechanical strength due to reduced bone formation. Mechanistically, we identified Foxk1 targeted the promoter region of many genes of glycolytic enzyme by CUT&Tag analysis. Lacking of Foxk1 in primary murine calvarial osteoblasts resulted in reducing aerobic glycolysis. Inhibition of glycolysis by 2DG hindered osteoblast differentiation and proliferation induced by Foxk1 overexpression. Finally, specific overexpression of Foxk1 in preosteoblasts, driven by a preosteoblast specific osterix promoter, increased bone mass and bone mechanical strength of aged mice, which could be suppressed by inhibiting glycolysis. In summary, these findings reveal that Foxk1 plays a vital role in the osteoblast metabolism regulation and bone formation stimulation, offering a promising approach for preventing age-related bone loss.

Unlocking the potential of histone modification in regulating bone metabolism

Bone metabolism plays a crucial role in maintaining normal bone tissue homeostasis and function. Imbalances between bone formation and resorption can lead to osteoporosis, osteoarthritis, and other bone diseases. The dynamic and complex process of bone remodeling is driven by various factors, including epigenetics. Histone modification, one of the most important and well-studied components of epigenetic regulation, has emerged as a promising area of research in bone metabolism. Different histone proteins and modification sites exert diverse effects on osteogenesis and osteoclastogenesis. In this review, we summarize recent progress in understanding histone modifications in bone metabolism, including specific modification sites and potential regulatory enzymes. Comprehensive knowledge of histone modifications in bone metabolism could reveal new therapeutic targets and treatment strategies for bone diseases.

Decoding senescence of aging single cells at the nexus of biomaterials, microfluidics, and spatial omics

Aging has profound effects on the body, most notably an increase in the prevalence of several diseases. An important aging hallmark is the presence of senescent cells that no longer multiply nor die off properly. Another characteristic is an altered immune system that fails to properly self-surveil. In this multi-player aging process, cellular senescence induces a change in the secretory phenotype, known as senescence-associated secretory phenotype (SASP), of many cells with the intention of recruiting immune cells to accelerate the clearance of these damaged senescent cells. However, the SASP phenotype results in inducing secondary senescence of nearby cells, resulting in those cells becoming senescent, and improper immune activation resulting in a state of chronic inflammation, called inflammaging, in many diseases. Senescence in immune cells, termed immunosenescence, results in further dysregulation of the immune system. An interdisciplinary approach is needed to physiologically assess aging changes of the immune system at the cellular and tissue level. Thus, the intersection of biomaterials, microfluidics, and spatial omics has great potential to collectively model aging and immunosenescence. Each of these approaches mimics unique aspects of the body undergoes as a part of aging. This perspective highlights the key aspects of how biomaterials provide non-cellular cues to cell aging, microfluidics recapitulate flow-induced and multi-cellular dynamics, and spatial omics analyses dissect the coordination of several biomarkers of senescence as a function of cell interactions in distinct tissue environments. An overview of how senescence and immune dysregulation play a role in organ aging, cancer, wound healing, Alzheimer's, and osteoporosis is included. To illuminate the societal impact of aging, an increasing trend in anti-senescence and anti-aging interventions, including pharmacological interventions, medical procedures, and lifestyle changes is discussed, including further context of senescence.

Metabolic disruption exacerbates intestinal damage during sleep deprivation by abolishing HIF1α-mediated repair

Sleep deprivation (SD) has been reported to induce intestinal damage by several mechanisms, yet its role in modulating epithelial repair remains unclear. In this study, we find that chronic SD leads to colonic damage through continuous hypoxia. However, HIF1α, which generally responds to hypoxia to modulate barrier integrity, was paradoxically dysregulated in the colon. Further investigation revealed that a metabolic disruption during SD causes accumulation of α-ketoglutarate in the colon. The excessive α-ketoglutarate degrades HIF1α protein through PHD2 (prolyl hydroxylase 2) to abolish the intestinal repair functions of HIF1α. Collectively, these findings provide insights into how SD can exacerbate intestinal damage by fine-tuning metabolism to abolish HIF1α-mediated repair.

STING regulates aging-related osteoporosis by mediating the Hk2-Vdac1 mitochondrial axis

Metabolic abnormalities and mild inflammation are hallmarks of aging and major driving factors for aging-related damage and bone metabolic diseases. Mitochondria are crucial links in energy metabolism and immune homeostasis regulation. Mitochondrial dysfunction is considered one of the pathogenic factors of aging-related osteoporosis, but its mechanism of action needs further research. Here, we demonstrated that the interaction between stimulator of interferon genes (STING)-mediated regulation of hexokinase 2 (Hk2)-voltage-dependent anion channel-1 (Vdac1) is a critical factor contributing to mitochondrial dysfunction and osteogenic abnormalities during aging. As the aging process progresses, factors related to aging cause an increase in STING expression, which disrupts the interaction between Hk2 and Vdac1. Dissociation of Hk2 from Vadc1 triggered the opening of the mitochondrial inner mitochondrial permeability transition pore (mPTP), leading to mitochondrial dysfunction and abnormal osteogenic differentiation, thereby disrupting bone homeostasis. In brief, this study demonstrates that STING acts as an intracellular metabolic Checkpoint, influencing mitochondrial function to promote the development of osteoporosis. These findings significantly enhance the development of STING-targeted treatments for aging-related osteoporosis.

Fumarate Restrains Alveolar Bone Restoration via Regulating H3K9 Methylation

Nonresolving inflammation causes irreversible damage to periodontal ligament stem cells (PDLSCs) and impedes alveolar bone restoration. The impaired tissue regeneration ability of stem cells is associated with abnormal mitochondrial metabolism. However, the impact of specific metabolic alterations on the differentiation process of PDLSCs remains to be understood. In this study, we found that inflammation altered the metabolic flux of the tricarboxylic acid cycle and induced the accumulation of fumarate through metabolic testing and metabolic flux analysis. Transcriptome sequencing revealed the potential of fumarate in modulating epigenetics. Specifically, histone methylation typically suppresses the expression of genes related to osteogenesis. Fumarate was found to impede the osteogenic differentiation of PDLSCs that exhibited high levels of H3K9me3. Various techniques, including assay for transposase-accessible chromatin with high-throughput sequencing, chromatin immunoprecipitation sequencing, and RNA sequencing, were used to identify the target genes regulated by H3K9me3. Mechanistically, accumulated fumarate inhibited lysine-specific demethylase 4B (KDM4B) activity and increased H3K9 methylation, thus silencing asporin gene transcription. Preventing fumarate from binding to the histone demethylase KDM4B with α-ketoglutarate effectively restored the impaired osteogenic capacity of PDLSCs and improved alveolar bone recovery. Collectively, our research has revealed the significant impact of accumulated fumarate on the regulation of osteogenesis in stem cells, suggesting that inhibiting fumarate production could be a viable therapeutic approach for treating periodontal diseases.

Extracellular vesicles from neural stem cells safeguard neurons in intracerebral hemorrhage by suppressing reactive astrocyte neurotoxicity

Extracellular vesicles (EVs) derived from stem cells have shown therapeutic potential in various diseases, but their use in treating neurological disorders remains limited. In this study, we observed neurotoxic activation of reactive astrocytes and lipoapoptosis pathways in both mice and patients with intracerebral hemorrhage (ICH) and found that EVs derived from neural stem cells (EVs-NSC) could suppress this activation. Using loss- and gain-of-function approaches, we identified interferon-β (IFNβ) as a key regulator in neurotoxic activation of astrocytes. In addition, we demonstrated that the microRNA (miRNA) miR-124-3p within EVs-NSC degrades IFNβ mRNA and inhibits ELOVL1 expression via miRNA-coding sequence (CDS) and miRNA-3' UTR binding mechanisms, respectively. This dual action likely reduces astrocyte neurotoxicity by lowering saturated lipid secretion. These mechanisms enable EVs-NSC or miR-124-3p overexpression to inhibit astrocyte neurotoxicity, reduce neural damage, and promote recovery in ICH models, offering strategies for treating neurological disorders by targeting neurotoxic reactive astrocytes.

Impacts of Hyperglycemia on Epigenetic Modifications in Human Gingival Fibroblasts and Gingiva in Diabetic Rats

Periodontal disease is considered one of the diabetic complications with high morbidity and severity. Recent studies demonstrated the involvement of the epigenome on diabetic complications. Histone modifications change chromatin architecture and gene activation. Histone modifications have been reported to alter chromatin structure and regulate gene transcription. In this study, we investigated the impacts of H3 lysine 4 trimethylation (H3K4me3) and specific histone methyltransferases of H3K4 methylation, su(var)3-9, enhancer-of-zeste, and trithorax domain 1A (SETD1A) on periodontal tissue affected by the diabetic condition. We observed the increase in H3K4me3 and SETD1A in gingival tissue of diabetic rats compared with the normal rats. Cultured human fibroblasts (hGFs) confirmed a high glucose-induced increase in H3K4me3 and SETD1A. We further demonstrated that high glucose increased the gene expression of matrix metalloproteinase (MMP) 1 and MMP13, which were canceled by sinefungin, an SETD1A inhibitor. Our investigation suggests that diabetes triggers histone modifications in the gingival tissue, resulting in gingival inflammation. Histone modifications may play crucial roles in the development of periodontal disease in diabetes.

Anti-aging Metabolite-Based Polymeric Microparticles for Intracellular Drug Delivery and Bone Regeneration

Alpha-ketoglutarate (AKG), a key component of the tricarboxylic acid (TCA) cycle, has attracted attention for its anti-aging properties. Our recent study indicates that locally delivered cell-permeable AKG significantly promotes osteogenic differentiation and mouse bone regeneration. However, the cytotoxicity and rapid hydrolysis of the metabolite limit its application. In this study, we synthesize novel AKG-based polymeric microparticles (PAKG MPs) for sustained release. In vitro data suggest that the chemical components, hydrophilicity, and size of the MPs can significantly affect their cytotoxicity and pro-osteogenic activity. Excitingly, these biodegradable PAKG MPs are highly phagocytosable for nonphagocytic pre-osteoblasts MC3T3-E1 and primary bone marrow mesenchymal stem cells (BMSCs), significantly promoting their osteoblastic differentiation. RNAseq data suggest that PAKG MPs strongly activate Wnt/β-catenin and PI3K-Akt pathways for osteogenic differentiation. Moreover, PAKG enables poly (L-lactic acid) and poly (lactic-co-glycolic acid) MPs (PLLA & PLGA MPs) for efficient phagocytosis. Our data indicate that PLGA-PAKG MPs-mediated intracellular drug delivery can significantly promote stronger osteoblastic differentiation compared to PLGA MPs-delivered phenamil. Notably, PAKG MPs significantly improve large bone regeneration in a mouse cranial bone defect model. Thus, the novel PAKG-based MPs show great promise to improve osteogenic differentiation, bone regeneration, and enable efficient intracellular drug delivery for broad regenerative medicine.

L-arginine loading porous PEEK promotes percutaneous tissue repair through macrophage orchestration

Infection and poor tissue repair are the key causes of percutaneous implantation failure. However, there is a lack of effective strategies to cope with due to its high requirements of sterilization, soft tissue healing, and osseointegration. In this work, l-arginine (L-Arg) was loaded onto a sulfonated polyetheretherketone (PEEK) surface to solve this issue. Under the infection condition, nitric oxide (NO) and reactive oxygen species (ROS) are produced through catalyzing L-Arg by inducible nitric oxide synthase (iNOS) and thus play a role in bacteria sterilization. Under the tissue repair condition, L-Arg is catalyzed to ornithine by Arginase-1 (Arg-1), which promotes the proliferation and collagen secretion of L929 and rBMSCs. Notably, L-Arg loading samples could polarize macrophages to M1 and M2 in infection and tissue repair conditions, respectively. The results in vivo show that the L-Arg loading samples could enhance infected soft tissue sealing and bone regeneration. In summary, L-Arg loading sulfonated PEEK could polarize macrophage through metabolic reprogramming, providing multi-functions of antibacterial abilities, soft tissue repair, and bone regeneration, which gives a new idea to design percutaneous implantation materials.

The Role of H3K27me3-Mediated Th17 Differentiation in Ankylosing Spondylitis

Ankylosing spondylitis (AS) is a common chronic progressive inflammatory autoimmune disease. T helper 17 (Th17) cells are the major effector cells mediating AS inflammation. Histone 3 Lys 27 trimethylation (H3K27me3) is an inhibitory histone modification that silences gene transcription and plays an important role in Th17 differentiation. The objective of this study was to investigate the expression of H3K27me3 in patients with AS and to explore its epigenetic regulation mechanism of Th17 differentiation during AS inflammation. We collected serum samples from 45 patients with AS at various stages and 10 healthy controls to measure their Interleukin-17 (IL-17) levels using ELISA. A quantitative polymerase chain reaction was used to quantify the mRNA levels of RORc and the signaling molecules of the JAK2/STAT3 pathway, JMJD3, and EZH2. Additionally, Western blot analysis was performed to quantify the protein levels of H3K27me3, RORγt, JAK2, STAT3, JMJD3, and EZH2 in cell protein extracts. The results showed that H3K27me3 expression in peripheral blood mononuclear cells (PBMCs) was significantly lower in patients with active AS compared to both the normal control groups and those with stable AS. Moreover, a significant negative correlation was observed between H3K27me3 expression and the characteristic transcription factor of Th17 differentiation, RORγt. We also discovered that patients with active AS exhibited significantly higher levels of JMJD3, an inhibitor of H3K27 demethylase, compared to the normal control group and patients with stable AS, while the expression of H3K27 methyltransferase (EZH2) was significantly lower. These findings suggest that H3K27me3 may be a dynamic and important epigenetic modification in AS inflammation, and JMJD3/EZH2 regulates the methylation level of H3K27me3, which may be one of the key regulatory factors in the pathogenesis of AS. These findings contribute to our understanding of the role of epigenetics in AS and may have implications for the development of novel therapeutic strategies for AS.

Dissecting Causal Relationships Between Plasma Metabolites and Osteoporosis: A Bidirectional Mendelian Randomization Study

OBJECTIVES

To investigate the causal relationships between plasma metabolites and osteoporosis via Mendelian randomization (MR) analysis.

METHODS

Bidirectional MR was used to analyze pooled data from different genome-wide association studies (GWAS). The causal effect of plasma metabolites on osteoporosis was estimated using the inverse variance weighted method, intersections of statistically significant metabolites obtained from different sources of osteoporosis-related GWAS aggregated data was determined, and then sensitivity analysis was performed on these metabolites. Heterogeneity between single nucleotide polymorphisms was evaluated by Cochran's Q test. Horizontal pleiotropy was assessed through the application of the MR-Egger intercept method and the MR-PRESSO method. The causal effect of osteoporosis on plasma metabolites was also evaluated using the inverse variance weighted method. Additionally, pathway analysis was conducted to identify potential metabolic pathways involved in the regulation of osteoporosis.

RESULTS

Primary analysis and sensitivity analysis showed that 77 and 61 plasma metabolites had a causal relationship with osteoporosis from the GWAS data in the GCST90038656 and GCST90044600 datasets, respectively. Five common metabolites were identified via intersection. X-13684 levels and the glucose-to-maltose ratio were negatively associated with osteoporosis, whereas glycoursodeoxycholate levels and arachidoylcarnitine (C20) levels were positively associated with osteoporosis (all P < 0.05). The relationship between X-11299 levels and osteoporosis showed contradictory results (all P < 0.05). Pathway analysis indicated that glycine, serine, and threonine metabolism, valine, leucine, and isoleucine biosynthesis, galactose metabolism, arginine biosynthesis, and starch and sucrose metabolism pathways were participated in the development of osteoporosis.

CONCLUSIONS

We found a causal relationship between plasma metabolites and osteoporosis. These results offer novel perspectives with important implications for targeted metabolite-focused interventions in the management of osteoporosis.

The Role of Mitochondrial Homeostasis in Mesenchymal Stem Cell Therapy-Potential Implications in the Treatment of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a hereditary disorder characterized by bones that are fragile and prone to breaking. The efficacy of existing therapies for OI is limited, and they are associated with potentially harmful side effects. OI is primarily due to a mutation of collagen type I and hence impairs bone regeneration. Mesenchymal stem cell (MSC) therapy is an attractive strategy to take advantage of the potential benefits of these multipotent stem cells to address the underlying molecular defects of OI by differentiating osteoblasts, paracrine effects, or immunomodulation. The maintenance of mitochondrial homeostasis is an essential component for improving the curative efficacy of MSCs in OI by affecting the differentiation, signaling, and immunomodulatory functions of MSCs. In this review, we highlight the MSC-based therapy pathway in OI and introduce the MSC regulation mechanism by mitochondrial homeostasis. Strategies aiming to modulate the metabolism and reduce the oxidative stress, as well as innovative strategies based on the use of compounds (resveratrol, NAD+, α-KG), antioxidants, and nanomaterials, are analyzed. These findings may enable the development of new strategies for the treatment of OI, ultimately resulting in improved patient outcomes.

Metabolic rewiring during bone development underlies tRNA m7G-associated primordial dwarfism

Translation of mRNA to protein is tightly regulated by transfer RNAs (tRNAs), which are subject to various chemical modifications that maintain structure, stability, and function. Deficiency of tRNA N7-methylguanosine (m7G) modification in patients causes a type of primordial dwarfism, but the underlying mechanism remains unknown. Here we report that the loss of m7G rewires cellular metabolism, leading to the pathogenesis of primordial dwarfism. Conditional deletion of the catalytic enzyme Mettl1 or missense mutation of the scaffold protein Wdr4 severely impaired endochondral bone formation and bone mass accrual. Mechanistically, Mettl1 knockout decreased abundance of m7G-modified tRNAs and inhibited translation of mRNAs relating to cytoskeleton and Rho GTPase signaling. Meanwhile, Mettl1 knockout enhanced cellular energy metabolism despite incompetent proliferation and osteogenic commitment. Further exploration revealed that impairment of Rho GTPase signaling upregulated the level of branched-chain amino acid transaminase 1 (BCAT1) that rewired cell metabolism and restricted intracellular α-ketoglutarate (αKG). Supplementation of αKG ameliorated the skeletal defect of Mettl1-deficient mice. In addition to the selective translation of metabolism-related mRNAs, we further revealed that Mettl1 knockout globally regulated translation via integrated stress response (ISR) and mammalian target of rapamycin complex 1 (mTORC1) signaling. Restoring translation by targeting either ISR or mTORC1 aggravated bone defects of Mettl1-deficient mice. Overall, our study unveils a critical role of m7G tRNA modification in bone development by regulation of cellular metabolism and indicates suspension of translation initiation as a quality control mechanism in response to tRNA dysregulation.

Recent progress of methods for cuproptosis detection

Varying from other identified cell death pathways, cuproptosis is a new type of regulated cell death characterized by excess Cu ions, abnormal aggregation of lipoylated proteins in TCA cycle, loss of Fe-S cluster proteins, upregulation of HSP70, leading to proteotoxic and oxidative stress. Cuproptosis is highly concerned by scientific community and as the field of cuproptosis further develops, remarkable progress has been made in the verification and mechanism of cuproptosis, and methods used to detect cuproptosis have been continuously improved. According to the characteristic changes of cuproptosis, techniques based on cell death verification, Cu content, morphology, molecular biology of protein levels of cuproptosis-related molecules and biochemical pathways of cuproptosis-related enzyme activity and metabolites of oxidative stress, lipoic acid, TCA cycle, Fe-S cluster proteins, oxidative phosphorylation, cell respiration intensity have been subject to cuproptosis verification and research. In order to further deepen the understanding of detecting cuproptosis, the principle and application of common cuproptosis detection methods are reviewed and categorized in cellular phenomena and molecular mechanism in terms of cell death, Cu content, morphology, molecular biology, biochemical pathways with a flow chart. All the indicating results have been displayed in response to the markers of cuproptosis, their advantages and limitations are summaried, and comparison of cuproptosis and ferroptosis detection is performed in this study. Our collection of methods for cuproptosis detection will provide a great basis for cuproptosis verification and research in the future.

Alpha-ketoglutarate is required for chronic hypoxia-induced cardiac remodeling

Chronic hypoxia (CH) is commonly associated with various cardiovascular diseases, with cardiac hypertrophy being the most frequently observed alteration. Metabolic remodeling is another consequence seen in the hypoxic heart. However, the mechanistic linkage between metabolic remodeling and cardiac hypertrophy in the hypoxic heart remains unclear. In this study, wild-type C57BL/6J mice were subjected to CH for 4 wk. Echocardiography and morphological analysis were used to assess the cardiac effects. We found that 4 wk of CH led to significant cardiac hypertrophy in the mice, whereas cardiac function remained unchanged compared with normoxic mice. In addition, CH induced an elevation in cardiac alpha-ketoglutarate (α-KG) content. Promoting α-KG degradation in the CH hearts prevented CH-induced cardiac hypertrophy but led to noticeable cardiac dysfunction. Mechanistically, α-KG promoted the transcription of hypertrophy-related genes by regulating histone methylation. Silencing lysine-specific demethylase 5 (KDM5), a histone demethylation enzyme, blunted α-KG-induced transcription of hypertrophy-related genes. These data suggest that α-KG is required for CH-induced cardiac remodeling, thus establishing a connection between metabolic changes and cardiac remodeling in hypoxic hearts.NEW & NOTEWORTHY We reported that alpha-ketoglutarate (α-KG) is indispensable for chronic hypoxia (CH)-induced cardiac remodeling, which builds the bridge between metabolic intermediates and cardiac remodeling.

Versatile JMJD proteins: juggling histones and much more

Jumonji C domain-containing (JMJD) proteins are found in bacteria, fungi, animals, and plants. They belong to the 2-oxoglutarate-dependent oxygenase superfamily and are endowed with various enzymatic activities, including demethylation of histones and hydroxylation of non-histone proteins. Many JMJD proteins are involved in the epigenetic control of gene expression, yet they also modulate a myriad other cellular processes. In this review we focus on the 33 human JMJD proteins and their established and controversial catalytic properties, survey their epigenetic and non-epigenetic functions, emphasize their contribution to sex-specific disease differences, and highlight how they sense metabolic changes. All this underlines not only their key roles in development and homeostasis, but also that JMJD proteins are destined to become drug targets in multiple diseases.

Rejuvenation of BMSCs senescence by pharmacological enhancement of TFEB-mediated autophagy alleviates aged-related bone loss and extends lifespan in middle aged mice

Bone marrow stromal/stem cells (BMSCs) are generally considered as common progenitors for both osteoblasts and adipocytes in the bone marrow, but show preferential differentiation into adipocytes rather than osteoblasts under aging, thus leading to senile osteoporosis. Accumulated evidences indicate that rejuvenation of BMSCs by autophagic enhancement delays bone aging. Here we synthetized and demonstrated a novel autophagy activator, CXM102 that could induce autophagy in aged BMSCs, resulting in rejuvenation and preferential differentiation into osteoblasts of BMSCs. Furthermore, CXM102 significantly stimulated bone anabolism, reduced marrow adipocytes, and delayed bone loss in middle-age male mice. Mechanistically, CXM102 promoted transcription factor EB (TFEB) nuclear translocation and favored osteoblasts formation both in vitro and in vivo. Moreover, CXM102 decreased serum levels of inflammation and reduced organ fibrosis, leading to a prolonger lifespan in male mice. Our results indicated that CXM102 could be used as an autophagy inducer to rejuvenate BMSCs and shed new lights on strategies for senile osteoporosis and healthyspan improvement.

Solvent-Directed Bioactive Supramolecular Zinc(II)-Metallogels: Exploring Semiconducting Aptitudes of Fabricating p-n Junction and Schottky Devices

α-Ketoglutaric acid-based supramolecular Zn(II) metallogels in N,N'-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solvent (i.e., Zn-α-Glu-DMF and Zn-α-Glu-DMSO) were successfully achieved. Zinc(II) acetate salt and α-ketoglutaric acid directed a three-dimensional noncovalent supramolecular network individually entrapped with N,N'-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solvent to accomplish their respective semisolid flexible metallogel frameworks. The gel features of these synthesized materials were verified by rheological experiments such as amplitude sweep and frequency sweep measurements. The discrete morphological arrangements were analyzed for these metallogel samples through field emission scanning electron microscopic (FESEM) analysis. Highly stacked interconnected blocks of Zn-α-Glu-DMF with hierarchical arrays are found due to the occurrence of diverse noncovalent supramolecular interactions present in the metallogel framework. A distinct spherical shaped microstructure with interconnected hierarchical assembly has been observed for the FESEM pattern of Zn-α-Glu-DMSO. FTIR spectroscopic measurement was carried out to detect some important stretching vibrations of xerogel samples of different metallogels as well as gel-constructing chemical ingredients. A substantial amount of peak shifting of xerogel samples for both metallogels is observed in FTIR analysis, indicating the presence of different noncovalent interactions. ESI-mass analysis portrays a possible metallogel-constructing strategy. The antibacterial potentialities of both metallogels were investigated. These materials exhibited good antimicrobial efficacy toward Gram-positive and Gram-negative bacterial strains (including Escherichia coli, Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, and Salmonella typhimurium). Both synthesized metallogels were successfully implemented to fabricate the photoresponsive semiconducting diode. These materials offer excellent photodiode parameters including an ideality factor and rectification ratio (ON/OFF ratio). Synthesized metallogels are used to successfully fabricate photodiodes with an Al/p-Si/metallogel/Au structure. The ideality factors (η) for Zn-α-Glu-DMF and Zn-α-Glu-DMSO are found as 1.3 and 2.3, respectively, in dark conditions. The rectification ratios for Zn-α-Glu-DMF and Zn-α-Glu-DMSO metallogels are also determined, and these are found as 40 and 10, respectively.

Gamma-glutamyl transferase secreted by Helicobacter pylori promotes the development of gastric cancer by affecting the energy metabolism and histone methylation status of gastric epithelial cells

BACKGROUND

Helicobacter pylori (H. pylori) infection is critical in the development and occurrence of gastric cancer. H. pylori secretes gamma-glutamyl transferase (GGT), which affects energy metabolism and histone methylation in mesenchymal stem cells. However, its effect on human gastric epithelial cells remains unclear. This study aimed to investigate the effects of GGT on energy metabolism and histone methylation in gastric epithelial cells and determine its role in the development and progression of H. pylori-induced gastric cancer.

METHODS

A GGT knockout H. pylori strain and mouse gastric cancer model were constructed, and alpha-ketoglutarate (α-KG) was added. The underlying mechanism was investigated using proteomics, immunohistochemistry, Western blotting, and other experimental assays.

RESULTS

H. pylori can colonize the host's stomach and destroy the gastric epithelium. GGT secreted by H. pylori decreased the concentration of glutamine in the stomach and increased H3K9me3 and H3K27me3 expression, which promoted the proliferation and migration of gastric epithelial cells. Additionally, α-KG reversed this effect. GGT increased the tumorigenic ability of nude mice. GGT, secreted by H. pylori, promoted the expression of ribosomal protein L15 (RPL15), while GGT knockout and supplementation with α-KG and trimethylation inhibitors reduced RPL15 expression and Wnt signaling pathway expression.

CONCLUSIONS

H. pylori secreted GGT decreased the expression of glutamine and α-KG in gastric epithelial cells, increased the expression of histones H3K9me3 and H3K27me3, and activated the Wnt signaling pathway through RPL15 expression, ultimately changing the biological characteristics of the gastric epithelium and promoting the occurrence of gastric cancer. Altered energy metabolism and histone hypermethylation are important factors involved in this process.

α-ketoglutarate produced by lactic acid bacteria inhibits hyaluronidase activity

In Japan, the growing interest in anti-aging skin care is associated with the unprecedented aging society. Skin aging can be attributed to various factors, including the activation of hyaluronidase enzyme in subcutaneous tissues exposed to ultraviolet radiation. This enzyme breaks down hyaluronic acid, leading to skin sagging. Therefore, hyaluronidase inhibitors can effectively prevent skin aging. Previously, food components have been actively explored to search for hyaluronidase inhibitors considering the high safety of these materials. Although lactic acid bacteria (LAB)-fermented foods inhibit this enzyme, their active compounds responsible for hyaluronidase inhibition remain unknown. Thus, in this study, we aimed to explore the mechanism underlying the LAB-mediated inhibition of hyaluronidase activity. Supernatants of a LAB-fermented milk-based beverage were subjected to a hyaluronidase inhibition assay, followed by purification and separation using hydrophobic adsorbents and high-performance liquid chromatography, respectively. Subsequently, liquid chromatograph time-of-flight mass analysis was performed, revealing α-ketoglutarate (AKG) as the inhibitor of this enzyme. The half-maximal inhibitory concentration (IC50) of AKG was approximately 0.13-fold that of the known strong hyaluronidase inhibitor disodium cromoglycate (DSCG). To the best of our knowledge, this is the first report on hyaluronidase inhibition mediated by AKG, a metabolic product of LAB. Additionally, Lactobacillus acidophilus JCM1132 was identified as a highly effective AKG-producing LAB (63.9 µg/mL) through LC-MS/MS-based quantitative analyses using various LAB-fermented milk samples. We anticipate that the findings of this study will potentially support the development of functional foods and cosmetics enriched with AKG.

Anti-aging effects of medicinal plants and their rapid screening using the nematode Caenorhabditis elegans

BACKGROUND

Aging is the primary risk factor of most chronic diseases in humans, including cardiovascular diseases, osteoporosis and neurodegenerative diseases, which extensively damage the quality of life for elderly individuals. Aging is a multifaceted process with numerous factors affecting it. Efficient model organisms are essential for the research and development of anti-aging agents, particularly when investigating pharmacological mechanisms are needed.

PURPOSE

This review discusses the application of Caenorhabditis elegans for studying aging and its related signaling pathways, and presents an overview of studies exploring the mechanism and screening of anti-aging agents in C. elegans. Additionally, the review summarizes related clinical trials of anti-aging agents to inspire the development of new medications.

METHOD

Literature was searched, analyzed, and collected using PubMed, Web of Science, and Science Direct. The search terms used were "anti-aging", "medicinal plants", "synthetic compounds", "C. elegans", "signal pathway", etc. Several combinations of these keywords were used. Studies conducted in C. elegans or humans were included. Articles were excluded, if they were on studies conducted in silico or in vitro or could not offer effective data.

RESULTS

Four compounds mainly derived through synthesis (metformin, rapamycin, nicotinamide mononucleotide, alpha-ketoglutarate) and four active ingredients chiefly obtained from plants (resveratrol, quercetin, Astragalus polysaccharide, ginsenosides) are introduced emphatically. These compounds and active ingredients exhibit potential anti-aging effects in preclinical and clinical studies. The screening of these anti-aging agents and the investigation of their pharmacological mechanisms can benefit from the use of C. elegans.

CONCLUSION

Medicinal plants provide valuable resource for the treatment of diseases. A wide source of raw materials for the particular plant medicinal compounds having anti-aging effects meet diverse pharmaceutical requirements, such as immunomodulatory, anti-inflammation and alleviating oxidative stress. C. elegans possesses advantages in scientific research including short life cycle, small size, easy maintenance, genetic tractability and conserved biological processes related to aging. C. elegans can be used for the efficient and rapid evaluation of compounds with the potential to slow down aging.

FoxO1 knockdown inhibits RANKL-induced osteoclastogenesis by blocking NLRP3 inflammasome activation

OBJECTIVES

This study aimed to elucidate the connection between osteoclastic forkhead transcription factor O1 (FoxO1) and periodontitis and explore the underlying mechanism by which FoxO1 knockdown regulates osteoclast formation.

MATERIALS AND METHODS

A conventional ligature-induced periodontitis model was constructed to reveal the alterations in the proportion of osteoclastic FoxO1 in periodontitis via immunofluorescence staining. Additionally, RNA sequencing (RNA-seq) was performed to explore the underlying mechanisms of FoxO1 knockdown-mediated osteoclastogenesis, followed by western blotting, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay.

RESULTS

FoxO1+ osteoclasts were enriched in the alveolar bone in experimental periodontitis. Moreover, FoxO1 knockdown led to impaired osteoclastogenesis with low expression of osteoclast differentiation-related genes, accompanied by an insufficient osteoclast maturation phenotype. Mechanistically, RNA-seq revealed that the nuclear factor kappa B (NF-κB) and nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome signaling pathways were inhibited in FoxO1-knockdown osteoclasts. Consistent with this, MCC950, an effective inhibitor of the NLRP3 inflammasome, substantially attenuated osteoclast formation.

CONCLUSIONS

FoxO1 knockdown contributed to the inhibition of osteoclastogenesis by effectively suppressing NF-κB signaling and NLRP3 inflammasome activation. This prospective study reveals the role of FoxO1 in mediating osteoclastogenesis and provides a viable therapeutic target for periodontitis treatment.

Mesenchymal Stem Cells Preconditioned with Hypoxia and Dexamethasone Promote Osteoblast Differentiation Under Stress Conditions

Bone marrow-derived mesenchymal stem cells (MSCs), which are capable of differentiating into osteoblasts, are used in effective regenerative therapies. MSCs must be prompted to differentiate into osteoblasts for MSC transplantation to be effective. In this study, osteoblast differentiation markers involved in bone formation were evaluated to investigate the stress resistance of bone marrow-derived rat MSCs to dexamethasone and hypoxia and their ability to differentiate into osteoblasts. MSCs were allowed to differentiate into osteoblasts for 21 days in three different environments (dexamethasone treatment, hypoxic conditions [1% oxygen], or both). Osteoblast differentiation potential was evaluated according to alkaline phosphatase levels and a mineralisation assay. Immunofluorescence staining was used to determine the protein expression of the osteoblast differentiation markers type I collagen and osteopontin. MSCs differentiated into osteoblasts under hypoxic conditions but differentiated more slowly upon treatment with dexamethasone and dexamethasone plus hypoxia relative to the control. MSCs preconditioned with dexamethasone or hypoxia and then allowed to differentiate into osteoblasts under similar conditions differentiated comparably to control MSCs. MSCs that developed resistance to dexamethasone or hypoxia differentiated more quickly into osteoblasts than those that did not. The findings suggest that increasing the resistance of MSCs to stress by preconditioning them via dexamethasone or hypoxia exposure could result in more rapid differentiation into osteoblasts following transplantation.

[Latest Findings on the Role of α-Ketoglutarate in Metabolic Syndrome]

Alpha-ketoglutarate (α-KG), an endogenous intermediate of the tricarboxylic acid cycle, is involved in a variety of cellular metabolic pathways. It serves as an energy donor, a precursor of amino acid biosynthesis, and an epigenetic regulator. α-KG plays physiological functions in immune regulation, oxidative stress, and anti-aging as well. In recent years, it has been reported that the level of α-KG in the body is closely associated with metabolic syndrome, including obesity, hyperglycemia, and other pathological factors. Exogenous supplementation of α-KG improves obesity, blood glucose levels, and cardiovascular disease risks associated with metabolic syndrome. Furthermore, α-KG regulates the common pathological mechanisms of metabolic syndrome, suggesting the potential application prospect of α-KG in metabolic syndrome. In order to provide a theoretical basis for further exploration of the application of α-KG in metabolic syndrome, we focused on α-KG and metabolic syndrome in this article and summarized the latest research progress in the role of α-KG in improving the pathological condition and disease progression of metabolic syndrome. For the next step, researchers may focus on the co-pathogenesis of metabolic syndrome and investigate whether α-KG can be used to achieve the therapeutic goal of "homotherapy for heteropathy" in the treatment of metabolic syndrome.

Role of epigenetic regulatory mechanisms in age-related bone homeostasis imbalance

Alterations to the human organism that are brought about by aging are comprehensive and detrimental. Of these, an imbalance in bone homeostasis is a major outward manifestation of aging. In older adults, the decreased osteogenic activity of bone marrow mesenchymal stem cells and the inhibition of bone marrow mesenchymal stem cell differentiation lead to decreased bone mass, increased risk of fracture, and impaired bone injury healing. In the past decades, numerous studies have reported the epigenetic alterations that occur during aging, such as decreased core histones, altered DNA methylation patterns, and abnormalities in noncoding RNAs, which ultimately lead to genomic abnormalities and affect the expression of downstream signaling osteoporosis treatment and promoter of fracture healing in older adults. The current review summarizes the impact of epigenetic regulation mechanisms on age-related bone homeostasis imbalance.

Tricarboxylic Acid Cycle Regulation of Metabolic Program, Redox System, and Epigenetic Remodeling for Bone Health and Disease

Imbalanced osteogenic cell-mediated bone gain and osteoclastic remodeling accelerates the development of osteoporosis, which is the leading risk factor of disability in the elderly. Harmonizing the metabolic actions of bone-making cells and bone resorbing cells to the mineralized matrix network is required to maintain bone mass homeostasis. The tricarboxylic acid (TCA) cycle in mitochondria is a crucial process for cellular energy production and redox homeostasis. The canonical actions of TCA cycle enzymes and intermediates are indispensable in oxidative phosphorylation and adenosine triphosphate (ATP) biosynthesis for osteogenic differentiation and osteoclast formation. Knockout mouse models identify these enzymes' roles in bone mass and microarchitecture. In the noncanonical processes, the metabolites as a co-factor or a substrate involve epigenetic modification, including histone acetyltransferases, DNA demethylases, RNA m6A demethylases, and histone demethylases, which affect genomic stability or chromatin accessibility for cell metabolism and bone formation and resorption. The genetic manipulation of these epigenetic regulators or TCA cycle intermediate supplementation compromises age, estrogen deficiency, or inflammation-induced bone mass loss and microstructure deterioration. This review sheds light on the metabolic functions of the TCA cycle in terms of bone integrity and highlights the crosstalk of the TCA cycle and redox and epigenetic pathways in skeletal tissue metabolism and the intermediates as treatment options for delaying osteoporosis.

Identification of PKM2 as a pyroptosis-related key gene aggravates senile osteoporosis via the NLRP3/Caspase-1/GSDMD signaling pathway

BACKGROUNDS

Senile osteoporosis-alternatively labeled as skeletal aging-encompasses age-induced bone deterioration and loss of bone microarchitecture. Recent studies have indicated a potential association between senile osteoporosis and chronic systemic inflammation, and pyroptosis in bone marrow-derived mesenchymal stem cells is speculated to contribute to bone loss and osteoporosis. Therefore, targeting pyroptosis in stem cells may be a potential therapeutic strategy for treating osteoporosis.

METHODS

Initially, we conducted bioinformatics analysis to screen the GEO databases to identify the key gene associated with pyroptosis in senile osteoporosis. Next, we analyzed the relationship between altered proteins and clinical data. In vitro experiments were then performed to explore whether the downregulation of PKM2 expression could inhibit pyroptosis. Additionally, an aging-related mouse model of osteoporosis was established to validate the efficacy of a PKM2 inhibitor in alleviating osteoporosis progression.

RESULTS

We identified PKM2 as a key gene implicated in pyroptosis in senile osteoporosis patients through bioinformatics analysis. Further analyses of bone marrow and stem cells demonstrated significant PKM2 overexpression in senile osteoporosis patients. Silencing PKM2 expression inhibited pyroptosis in senile stem cells, of which the osteogenesis potential and angiogenic function were also primarily promoted. Moreover, the results in vivo demonstrated that administering PKM2 inhibitors suppressed pyroptosis in senile osteoporosis mice and mitigated senile osteoporosis progression.

CONCLUSION

Our study uncovered PKM2, a key pyroptosis marker of bone marrow mesenchymal stem cells in senile osteoporosis. Shikonin, a PKM2 inhibitor, was then identified as a potential drug candidate for the treatment of osteoporosis.

Identification and immunological role of cuproptosis in osteoporosis

Background

osteoporosis is a skeletal disorder disease features low bone mass and poor bone architecture, which predisposes to increased risk of fracture. Copper death is a newly recognized form of cell death caused by excess copper ions, which presumably involve in various disease. Accordingly, we intended to investigate the molecular clusters related to the cuproptosis in osteoporosis and to construct a predictive model.

Methods

we investigated the expression patterns of cuproptosis regulators and immune signatures in osteoporosis based on the GSE56815 dataset. Through analysis of 40 osteoporosis samples, we investigated molecular clustering on the basis of cuproptosis--related genes, together with the associated immune cell infiltration. The WGCNA algorithm was applied to detect cluster-specific differentially expressed genes. Afterwards, the optimum machine model was selected by calculating the performance of the support vector machine model, random forest model, eXtreme Gradient Boosting and generalized linear model. Nomogram, decision curve analysis, calibration curves, and the GSE7158 dataset was utilizing to confirm the prediction efficiency.

Results

Differences between osteoporotic and non-osteoporotic controls confirm poorly adjusted copper death-related genes and triggered immune responses. In osteoporosis, two clusters of molecules in connection with copper death proliferation were outlined. The assessed levels of immune infiltration showed prominent heterogeneity between the different clusters. Cluster 2 was characterized by a raised immune score accompanied with relatively high levels of immune infiltration. The functional analysis we performed showed a close relationship between the different immune responses and specific differentially expressed genes in cluster 2. The random forest machine model showed the optimum discriminatory performance due to relatively low residuals and root mean square errors. Finally, a random forest model based on 5 genes was built, showing acceptable performance in an external validation dataset (AUC = 0.750). Calibration curve, Nomogram, and decision curve analyses also evinced fidelity in predicting subtypes of osteoporosis.

Conclusion

Our study identifies the role of cuproptosis in OP and essentially illustrates the underlying molecular mechanisms that lead to OP heterogeneity.

Astragaloside IV alleviates macrophage senescence and d-galactose-induced bone loss in mice through STING/NF-κB pathway

BACKGROUND

Senile osteoporosis (SOP) is an age-related metabolic bone disease that currently lacks specific therapeutic interventions. Thus, this study aimed to investigate the effect of Astragaloside IV (AS-IV) on macrophage senescence, bone marrow mesenchymal stem cell (BMSC) osteogenesis, and SOP progression.

METHODS

A senescent macrophage model was established and treated with varying concentrations of AS-IV. Cell activity was measured using the CCK8 assay. The senescence levels of macrophages were evaluated through β-galactosidase staining, PCR, and immunofluorescence. Macrophage mitochondrial function was assessed using ROS and JC-1 staining. Macrophage polarization was evaluated through PCR, Western blot, and immunofluorescence. The inhibitory effects of AS-IV on macrophage senescence were investigated using Western blot analysis. Furthermore, the effects of macrophage conditioned medium (CM) on BMSCs osteogenic were detected using ALP, alizarin red, and PCR.

RESULTS

AS-IV inhibited macrophage senescence and M1 polarization, alleviated mitochondrial dysfunction, and promoted M2 polarization. Mechanistically, it suppressed the STING/NF-κB pathway in H2O2-activated macrophages. Conversely, the STING agonist c-di-GMP reversed the effects of AS-IV on macrophage senescence. Additionally, AS-IV-induced macrophage CM promoted BMSC osteogenic differentiation. In vivo, AS-IV treatment ameliorated aberrant bone microstructure and bone mass loss in the SOP mouse model, inhibited macrophage senescence, and promoted M2 polarization.

CONCLUSIONS

By modulating the STING/NF-κB signaling pathway, AS-IV potentially inhibited macrophage senescence and stimulated osteogenic differentiation of BMSCs, thus exerting an anti-osteoporotic effect. Consequently, AS-IV may serve as an effective therapeutic candidate for the treatment of osteoporosis.

Growing concerns about using hypoxia-inducible factor prolyl hydroxylase inhibitors for the treatment of renal anemia

Hypoxia-inducible factor prolyl hydroxylase inhibitors (HIF-PHIs) have emerged as a novel therapeutic class for treating anemia in patients with chronic kidney disease. Small molecule analogs of α-ketoglutarate (AKG), an essential substrate for 2-oxoglutarate-dependent dioxygenases (2-OGDDs), including prolyl hydroxylase domain proteins (PHDs), inhibit PHDs pharmacologically and thereby prevent HIF degradation. HIF stabilization alleviates anemia through several stimulatory effects on erythropoiesis, but it also affects the expression of many anemia-unrelated genes whose protein products exert important functions in vivo. Therefore, the pleiotropic effects of HIF stabilization under normoxic conditions deserve to be examined in more detail. Specifically, we believe that particular attention should be given to epigenetic modifications among the various AKG-based metabolic systems that may be altered by HIF-PHIs. It is noteworthy that AKG has been reported to exert health-protective actions. AKG-based metabolic systems include enzymes associated with the tricarboxylic acid cycle and amino acid metabolism, as well as 2-OGDD-mediated processes, which play important roles in many biological reactions. In this review, we examine the multifaceted effects of HIF-PHIs, encompassing not only their on-target effect of HIF stabilization but also their off-target inhibitory effects on various AKG-based metabolic systems. Furthermore, we examine its potential relevance to cardiovascular complications, based on clinical and animal studies suggesting its involvement in vascular calcification, thrombogenesis and heart failure. In conclusion, although HIF-PHIs offer a promising avenue for anemia treatment in CKD patients, their broader impact on multiple biological systems raises substantial concerns. The intricate interplay between HIF stabilization, AKG competition and cardiovascular complications warrants extensive, long-term investigations to ensure the safety and usefulness of HIF-PHIs in clinical practice.

Carnitine functions as an enhancer of NRF2 to inhibit osteoclastogenesis via regulating macrophage polarization in osteoporosis

Osteoporosis, which manifests as reduced bone mass and deteriorated bone quality, is common in the elderly population. It is characterized by persistent elevation of macrophage-associated inflammation and active osteoclast bone resorption. Currently, the roles of intracellular metabolism in regulating these processes remain unclear. In this study, we initially performed bioinformatics analysis and observed a significant increase in the proportion of M1 macrophages in bone marrow with aging. Further metabolomics analysis demonstrated a notable reduction in the expression of carnitine metabolites in aged macrophages, while carnitine was not detected in osteoclasts. During the differentiation process, osteoclasts took up carnitine synthesized by macrophages to regulate their own activity. Mechanistically, carnitine enhanced the function of Nrf2 by inhibiting the Keap1-Nrf2 interaction, reducing the proteasome-dependent ubiquitination and degradation of Nrf2. In silico molecular ligand docking analysis of the interaction between carnitine and Keap1 showed that carnitine binds to Keap1 to stabilize Nrf2 and enhance its function. In this study, we found that the decrease in carnitine levels in aging macrophages causes overactivation of osteoclasts, ultimately leading to osteoporosis. A decrease in serum carnitine levels in patients with osteoporosis was found to have good diagnostic and predictive value. Moreover, supplementation with carnitine was shown to be effective in the treatment of osteoporosis.

Inhibiting Glutaminase Exerts Opposite Effects on Ovariectomy-Induced and Age-Related Reductions in Murine Bone Mass

Recent studies have provided links between glutamine metabolism and bone remodeling, but little is known about its role in primary osteoporosis progression. We aimed to determine the effects of inhibiting glutaminase (GLS) on two types of primary osteoporosis and elucidate the related metabolism. To address this issue, age-related and ovariectomy (OVX)-induced bone loss mouse models were used to study the in vivo effects of CB-839, a potent and selective GLS inhibitor, on bone mass and bone turnover. We also studied the metabolic profile changes related with aging and GLS inhibition in primary bone marrow stromal cells (BMSC) and that related with OVX and GLS inhibition in primary bone marrow-derived monocytes (BMM). Besides, we studied the possible metabolic processes mediating GLS blockade effects during aging-impaired osteogenic differentiation and RANKL-induced osteoclast differentiation respectively via in vitro rescue experiments. We found that inhibiting GLS via CB-839 prevented OVX-induced bone loss while aggravated age-related bone loss. Further investigations showed that effects of CB-839 treatment on bone mass were associated with alterations of bone turnover. Moreover, CB-839 treatment altered metabolic profile in different orientations between BMSC of aged mice and BMM of ovariectomized mice. In addition, rescue experiments revealed that different metabolic processes mediated glutaminase blockade effects between aging-impaired osteogenic differentiation and RANKL-induced osteoclast differentiation. Taken together, our data demonstrated the different outcomes caused by CB-839 treatment between two types of osteoporosis in mice, which were tightly connected to the suppressive effects on both aging-impaired osteoblastogenesis and OVX-enhanced osteoclastogenesis mediated by different metabolic processes downstream of glutaminolysis.