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

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.

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.

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.

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.

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.

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.

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.

Biomimetic Therapeutics for Bone Regeneration: A Perspective on Antiaging Strategies

Advances in modern medicine and the significant reduction in infant mortality have steadily increased the population's lifespan. As more and more people in the world grow older, incidence of chronic, noncommunicable disease is anticipated to drastically increase. Recent studies have shown that improving the health of the aging population is anticipated to provide the most cost-effective and impactful improvement in quality of life during aging-driven disease. In bone, aging is tightly linked to increased risk of fracture, and markedly decreased regenerative potential, deeming it critical to develop therapeutics to improve aging-driven bone regeneration. Biomimetics offer a cost-effective method in regenerative therapeutics for bone, where there are numerous innovations improving outcomes in young models, but adapting biomimetics to aged models is still a challenge. Chronic inflammation, accumulation of reactive oxygen species, and cellular senescence are among three of the more unique challenges facing aging-induced defect repair. This review dissects many of the innovative biomimetic approaches research groups have taken to tackle these challenges, and discusses the further uncertainties that need to be addressed to push the field further. Through these research innovations, it can be noted that biomimetic therapeutics hold great potential for the future of aging-complicated defect repair.

Emerging epigenetic insights into aging mechanisms and interventions

Epigenetic dysregulation emerges as a critical hallmark and driving force of aging. Although still an evolving field with much to explore, it has rapidly gained significance by providing valuable insights into the mechanisms of aging and potential therapeutic opportunities for age-related diseases. Recent years have witnessed remarkable strides in our understanding of the epigenetic landscape of aging, encompassing pivotal elements, such as DNA methylation, histone modifications, RNA modifications, and noncoding (nc) RNAs. Here, we review the latest discoveries that shed light on new epigenetic mechanisms and critical targets for predicting and intervening in aging and related disorders. Furthermore, we explore burgeoning interventions and exemplary clinical trials explicitly designed to foster healthy aging, while contemplating the potential ramifications of epigenetic influences.

α-Ketoglutarate improves cardiac insufficiency through NAD+-SIRT1 signaling-mediated mitophagy and ferroptosis in pressure overload-induced mice

BACKGROUND

In heart failure (HF), mitochondrial dysfunction and metabolic remodeling lead to a reduction in energy productivity and aggravate cardiomyocyte injury. Supplementation with α-ketoglutarate (AKG) alleviated myocardial hypertrophy and fibrosis in mice with HF and improved cardiac insufficiency. However, the myocardial protective mechanism of AKG remains unclear. We verified the hypothesis that AKG improves mitochondrial function by upregulating NAD+ levels and activating silent information regulator 2 homolog 1 (SIRT1) in cardiomyocytes.

METHODS

In vivo, 2% AKG was added to the drinking water of mice undergoing transverse aortic constriction (TAC) surgery. Echocardiography and biopsy were performed to evaluate cardiac function and pathological changes. Myocardial metabolomics was analyzed by liquid chromatography‒mass spectrometry (LC‒MS/MS) at 8 weeks after surgery. In vitro, the expression of SIRT1 or PINK1 proteins was inhibited by selective inhibitors and siRNA in cardiomyocytes stimulated with angiotensin II (AngII) and AKG. NAD+ levels were detected using an NAD test kit. Mitophagy and ferroptosis levels were evaluated by Western blotting, qPCR, JC-1 staining and lipid peroxidation analysis.

RESULTS

AKG supplementation after TAC surgery could alleviate myocardial hypertrophy and fibrosis and improve cardiac function in mice. Metabolites of the malate-aspartate shuttle (MAS) were increased, but the TCA cycle and fatty acid metabolism pathway could be inhibited in the myocardium of TAC mice after AKG supplementation. Decreased NAD+ levels and SIRT1 protein expression were observed in heart of mice and AngII-treated cardiomyocytes. After AKG treatment, these changes were reversed, and increased mitophagy, inhibited ferroptosis, and alleviated damage in cardiomyocytes were observed. When the expression of SIRT1 was inhibited by a selective inhibitor and siRNA, the protective effect of AKG was suppressed.

CONCLUSION

Supplementation with AKG can improve myocardial hypertrophy, fibrosis and chronic cardiac insufficiency caused by pressure overload. By increasing the level of NAD+, the SIRT-PINK1 and SIRT1-GPX4 signaling pathways are activated to promote mitophagy and inhibit ferroptosis in cardiomyocytes, which ultimately alleviates cardiomyocyte damage.

Emerging roles of mitochondrial functions and epigenetic changes in the modulation of stem cell fate

Mitochondria serve as essential organelles that play a key role in regulating stem cell fate. Mitochondrial dysfunction and stem cell exhaustion are two of the nine distinct hallmarks of aging. Emerging research suggests that epigenetic modification of mitochondria-encoded genes and the regulation of epigenetics by mitochondrial metabolites have an impact on stem cell aging or differentiation. Here, we review how key mitochondrial metabolites and behaviors regulate stem cell fate through an epigenetic approach. Gaining insight into how mitochondria regulate stem cell fate will help us manufacture and preserve clinical-grade stem cells under strict quality control standards, contributing to the development of aging-associated organ dysfunction and disease.

Lactic acid promotes nucleus pulposus cell senescence and corresponding intervertebral disc degeneration via interacting with Akt

The accumulation of metabolites in the intervertebral disc is considered an important cause of intervertebral disc degeneration (IVDD). Lactic acid, which is a metabolite that is produced by cellular anaerobic glycolysis, has been proven to be closely associated with IVDD. However, little is known about the role of lactic acid in nucleus pulposus cells (NPCs) senescence and oxidative stress. The aim of this study was to investigate the effect of lactic acid on NPCs senescence and oxidative stress as well as the underlying mechanism. A puncture-induced disc degeneration (PIDD) model was established in rats. Metabolomics analysis revealed that lactic acid levels were significantly increased in degenerated intervertebral discs. Elimination of excessive lactic acid using a lactate oxidase (LOx)-overexpressing lentivirus alleviated the progression of IVDD. In vitro experiments showed that high concentrations of lactic acid could induce senescence and oxidative stress in NPCs. High-throughput RNA sequencing results and bioinformatic analysis demonstrated that the induction of NPCs senescence and oxidative stress by lactic acid may be related to the PI3K/Akt signaling pathway. Further study verified that high concentrations of lactic acid could induce NPCs senescence and oxidative stress by interacting with Akt and regulating its downstream Akt/p21/p27/cyclin D1 and Akt/Nrf2/HO-1 pathways. Utilizing molecular docking, site-directed mutation and microscale thermophoresis assays, we found that lactic acid could regulate Akt kinase activity by binding to the Lys39 and Leu52 residues in the PH domain of Akt. These results highlight the involvement of lactic acid in NPCs senescence and oxidative stress, and lactic acid may become a novel potential therapeutic target for the treatment of IVDD.

Stress, epigenetics, and aging: Unraveling the intricate crosstalk

Aging, as a complex process involving multiple cellular and molecular pathways, is known to be exacerbated by various stresses. Because responses to these stresses, such as oxidative stress and genotoxic stress, are known to interplay with the epigenome and thereby contribute to the development of age-related diseases, investigations into how such epigenetic mechanisms alter gene expression and maintenance of cellular homeostasis is an active research area. In this review, we highlight recent studies investigating the intricate relationship between stress and aging, including its underlying epigenetic basis; describe different types of stresses that originate from both internal and external stimuli; and discuss potential interventions aimed at alleviating stress and restoring epigenetic patterns to combat aging or age-related diseases. Additionally, we address the challenges currently limiting advancement in this burgeoning field.

A bone-targeting near-infrared luminescence nanocarrier facilitates alpha-ketoglutarate efficacy enhancement for osteoporosis therapy

Osteoporosis (OP), which largely increases the risk of fractures, is the most common chronic degenerative orthopedic disease in the elderly due to the imbalance of bone homeostasis. Alpha-ketoglutaric acid (AKG), an endogenous metabolic intermediate involved in osteogenesis, plays critical roles in osteogenic differentiation and mineralization and the inhibition of osteoclastogenic differentiation. However, the low bioavailability and poor bone-targeting efficiency of AKG seriously limit its efficacy in OP treatment. In this work, a bone-targeting, near-infrared emissive lanthanide luminescence nanocarrier loaded with AKG (β-NaYF4:7%Yb, 60%Nd@NaLuF4@mSiO2-EDTA-AKG, abbreviated as LMEK) is developed for the enhancement of AKG efficacy in OP therapy. By utilizing the NIR-II luminescence (>1000 nm) of LMEK, whole-body bone imaging with high spatial resolution is achieved to confirm the bone enrichment of AKG noninvasively in vivo. The results reveal that LMEK exhibits a remarkable OP therapeutic effect in improving the osseointegration of the surrounding bone in the ovariectomized OP mice models, which is validated by the enhanced inhibition of osteoclast through hypoxia-inducible factor-1α suppression and promotion of osteogenic differentiation in osteoblast. Notably, the dose of AKG in LMEK can be reduced to only 0.2 % of the dose when pure AKG is used in therapy, which dramatically improves the bioavailability of AKG and mitigates the metabolism burden. This work provides a strategy to conquer the low utilization of AKG in OP therapy, which not only overcomes the challenges in AKG efficacy for OP treatment but also offers insights into the development and application of other potential drugs for skeletal diseases. STATEMENT OF SIGNIFICANCE: Alpha-ketoglutarate (AKG) is an intermediate within the Krebs cycle, participating in diverse metabolic and cellular processes, showing potential for osteoporosis (OP) therapy. However, AKG's limited bioavailability and inefficient bone-targeting hinder its effectiveness in treating OP. Herein, a near-infrared emissive nanocarrier is developed that precisely targets bones and delivers AKG, bolstering its effectiveness in OP therapy. Thanks to this efficient bone-targeting delivery, the AKG dosage is reduced to 0.2 % of the conventional treatment level. This marks the first utilization of a bone-targeting nanocarrier to amplify AKG's bioavailability and OP therapy efficacy. Furthermore, the mechanism of AKG-loaded nanocarrier regulating the biological behavior of osteoclasts and osteoblasts mediated is tentatively explored.

Alpha-ketoglutarate supplementation reduces inflammation and thrombosis in type 2 diabetes by suppressing leukocyte and platelet activation

The interplay between platelets and leukocytes contributes to the pathogenesis of inflammation, thrombosis, and cardiovascular diseases (CVDs) in type 2 diabetes (T2D). Our recent studies described alpha-ketoglutarate (αKG), a Krebs cycle intermediate metabolite as an inhibitor to platelets and leukocytes activation by suppressing phosphorylated-Akt (pAkt) through augmentation of prolyl hydroxylase-2 (PHD2). Dietary supplementation with a pharmacological concentration of αKG significantly inhibited lung inflammation in mice with either SARS-CoV-2 infection or exposed to hypoxia treatment. We therefore investigated if αKG supplementation could suppress hyperactivation of these blood cells and reduce thromboinflammatory complications in T2D. Our study describes that dietary supplementation with αKG (8 mg/100 g body wt. daily) for 7 days significantly reduced the activation of platelets and leukocytes (neutrophils and monocytes), and accumulation of IL1β, TNFα, and IL6 in peripheral blood of T2D mice. αKG also reduced the infiltration of platelets and leukocytes, and accumulation of inflammatory cytokines in lungs by suppressing pAkt and pP65 signaling. In a cross-sectional investigation, our study also described the elevated platelet-leukocyte aggregates and pro-inflammatory cytokines in circulation of T2D patients. T2D platelets and leukocytes showed an increased aggregation and thrombus formation in vitro. Interestingly, a pre-incubation of T2D blood samples with octyl αKG significantly suppressed the activation of these blood cells and ameliorated aggregate/thrombus formation in vitro. Thus, suggesting a potential therapeutic role of αKG against inflammation, thrombosis, and CVDs in T2D.

Inokosterone activates the BMP2 to promote the osteogenic differentiation of bone marrow mesenchymal stem cells and improve bone loss in ovariectomized rats

Evidence suggests that enhancing the osteogenic ability of bone marrow-derived mesenchymal stem cells (BMSCs) may be beneficial in the fight against osteoporosis (OP) effects. Inokosterone (IS) is a major active constituent of Achyranthis bidentatae radix (ABR), which stimulates osteogenic differentiation of mouse embryonic osteoblasts. This study aims to investigate effect of IS on OP using osteogenic differentiated BMSCs and ovariectomy (OVX)-induced OP rats. The BMSCs were treated with 50, 100, or 200 mg/L IS and OP rats were given 2 or 4 mg/kg of IS by gavage. Cell viability, the osteogenic differentiation marker protein expression level, and mineralization were observed. This study proved that IS improved cell viability, osteogenic differentiation, and cellular mineralization in BMSCs and raised expression levels of bone morphogenetic protein-2 (BMP2), Smad1, runt-related transcription factor 2 (RUNX2), collagen I, ALP, and OCN. By BMP2 knockdown/overexpression, this study also proved the BMP2 signaling pathway activation is a potential biological mechanism of IS to improve osteogenic differentiation and mineralization in osteogenic differentiated BMSCs. In OVX-induced OP rats, IS was observed to antagonize bone loss, improve osteogenic differentiation marker protein expression levels, and activate BMP-2, smad1, and RUNX2. These findings provide scientific support for further investigation of the biological mechanisms of IS in ameliorating OP.

Mitochondria pleiotropism in stem cell senescence: Mechanisms and therapeutic approaches

Aging is a complex biological process characterized by a progressive decline in cellular and tissue function, ultimately leading to organismal aging. Stem cells, with their regenerative potential, play a crucial role in maintaining tissue homeostasis and repair throughout an organism's lifespan. Mitochondria, the powerhouses of the cell, have emerged as key players in the aging process, impacting stem cell function and contributing to age-related tissue dysfunction. Here are discuss the mechanisms through which mitochondria influence stem cell fate decisions, including energy production, metabolic regulation, ROS signalling, and epigenetic modifications. Therefore, this review highlights the role of mitochondria in driving stem cell senescence and the subsequent impact on tissue function, leading to overall organismal aging and age-related diseases. Finally, we explore potential anti-aging therapies targeting mitochondrial health and discuss their implications for promoting healthy aging. This comprehensive review sheds light on the critical interplay between mitochondrial function, stem cell senescence, and organismal aging, offering insights into potential strategies for attenuating age-related decline and promoting healthy longevity.

Altitude-dependent metabolite biomarkers reveal the mechanism of plateau pika adaptation to high altitudes

The harsh environment in the Tibetan plateau, the highest place in the world, poses thermoregulatory challenges and hypoxic stress to animals. The impacts of plateau environment on animal physiology and reproduction include external factors such as strong ultraviolet radiation and low temperature, and internal factors such as animal metabolites and gut microbiota. However, it remains unclear how plateau pika adapt to high altitudes through the combination of serum metabolites and gut microbiota. To this end, we captured 24 wild plateau pikas at the altitudes of 3400, 3600, or 3800 m a.s.l. in a Tibetan alpine grassland. Using the machine learning algorithms (random forest), we identified five biomarkers of serum metabolites indicative of the altitudes, that is, dihydrotestosterone, homo-l-arginine, alpha-ketoglutaric-acid, serotonin, and threonine, which were related to body weight, reproduction, and energy metabolism of pika. Those metabolic biomarkers were positively correlated with Lachnospiraceae_ Agathobacter, Ruminococcaceae, or Prevotellaceae_Prevotella, suggesting the close relationship between metabolites and gut microbiota. By identifying the metabolic biomarkers and gut microbiota analysis, we reveal the mechanisms of adaptation to high altitudes in plateau pika.

Targeting Alpha-Ketoglutarate Disruption Overcomes Immunoevasion and Improves PD-1 Blockade Immunotherapy in Renal Cell Carcinoma

The Warburg effect-related metabolic dysfunction of the tricarboxylic acid (TCA) cycle has emerged as a hallmark of various solid tumors, particularly renal cell carcinoma (RCC). RCC is characterized by high immune infiltration and thus recommended for immunotherapeutic interventions at an advanced stage in clinical guidelines. Nevertheless, limited benefits of immunotherapy have prompted investigations into underlying mechanisms, leading to the proposal of metabolic dysregulation-induced immunoevasion as a crucial contributor. In this study, a significant decrease is found in the abundance of alpha-ketoglutarate (αKG), a crucial intermediate metabolite in the TCA cycle, which is correlated with higher grades and a worse prognosis in clinical RCC samples. Elevated levels of αKG promote major histocompatibility complex-I (MHC-I) antigen processing and presentation, as well as the expression of β2-microglobulin (B2M). While αKG modulates broad-spectrum demethylation activities of histone, the transcriptional upregulation of B2M is dependent on the demethylation of H3K4me1 in its promoter region. Furthermore, the combination of αKG supplementation and PD-1 blockade leads to improved therapeutic efficacy and prolongs survival in murine models when compared to monotherapy. Overall, the findings elucidate the mechanisms of immune evasion in anti-tumor immunotherapies and suggest a potential combinatorial treatment strategy in RCC.

Methylation across the central dogma in health and diseases: new therapeutic strategies

The proper transfer of genetic information from DNA to RNA to protein is essential for cell-fate control, development, and health. Methylation of DNA, RNAs, histones, and non-histone proteins is a reversible post-synthesis modification that finetunes gene expression and function in diverse physiological processes. Aberrant methylation caused by genetic mutations or environmental stimuli promotes various diseases and accelerates aging, necessitating the development of therapies to correct the disease-driver methylation imbalance. In this Review, we summarize the operating system of methylation across the central dogma, which includes writers, erasers, readers, and reader-independent outputs. We then discuss how dysregulation of the system contributes to neurological disorders, cancer, and aging. Current small-molecule compounds that target the modifiers show modest success in certain cancers. The methylome-wide action and lack of specificity lead to undesirable biological effects and cytotoxicity, limiting their therapeutic application, especially for diseases with a monogenic cause or different directions of methylation changes. Emerging tools capable of site-specific methylation manipulation hold great promise to solve this dilemma. With the refinement of delivery vehicles, these new tools are well positioned to advance the basic research and clinical translation of the methylation field.

Lipid and glucose metabolism in senescence

Senescence is an inevitable biological process. Disturbances in glucose and lipid metabolism are essential features of cellular senescence. Given the important roles of these types of metabolism, we review the evidence for how key metabolic enzymes influence senescence and how senescence-related secretory phenotypes, autophagy, apoptosis, insulin signaling pathways, and environmental factors modulate glucose and lipid homeostasis. We also discuss the metabolic alterations in abnormal senescence diseases and anti-cancer therapies that target senescence through metabolic interventions. Our work offers insights for developing pharmacological strategies to combat senescence and cancer.

Therapeutic effects of different intervention forms of human umbilical cord mesenchymal stem cells in the treatment of osteoarthritis

Osteoarthritis (OA) is a common and disabling disease. For advanced OA, surgical treatment is still the main treatment. Human umbilical cord mesenchymal stem cells (hUC-MSCs) are self-regenerative pluripotent cells, that coordinate cartilage regeneration by secreting various trophic factors, which adjust the injured tissue environment. hUC-MSCs secret extracellular vesicles and participates in OA treatment by transmitting bioactive molecules related to migration, proliferation, apoptosis, inflammatory reaction, extracellular matrix synthesis and cartilage repair. In addition, the combination of multiple substances represented by cartilage matrix and hUC-MSCs also have a significant synergistic effect on OA treatment. Because hUC-MSCs have shown considerable promise in cartilage repair, some scholars have proposed transplanting mesenchymal stem cells into damaged cartilage to delay OA progression. This article reviews the application of hUC-MSCs as a treatment for OA. With the continuous development of routine clinical applications, more reliable intervention modalities for hUC-MSCs in OA treatment will be discovered for the time to come.

Amino Acid Metabolism in Bone Metastatic Disease

PURPOSE OF REVIEW

Breast and prostate tumors frequently metastasize to the bone, but the underlying mechanisms for osteotropism remain elusive. An emerging feature of metastatic progression is metabolic adaptation of cancer cells to new environments. This review will summarize the recent advances on how cancer cells utilize amino acid metabolism during metastasis, from early dissemination to interactions with the bone microenvironment.

RECENT FINDINGS

Recent studies have suggested that certain metabolic preferences for amino acids may be associated with bone metastasis. Once in the bone microenvironment, cancer cells encounter a favorable microenvironment, where a changing nutrient composition of the tumor-bone microenvironment may alter metabolic interactions with bone-resident cells to further drive metastatic outgrowth. Enhanced amino acid metabolic programs are associated with bone metastatic disease and may be further augmented by the bone microenvironment. Additional studies are necessary to fully elucidate the role of amino acid metabolism on bone metastasis.

Genetic perturbation of mitochondrial function reveals functional role for specific mitonuclear genes, metabolites, and pathways that regulate lifespan

Altered mitochondrial function is tightly linked to lifespan regulation, but underlying mechanisms remain unclear. Here, we report the chronological and replicative lifespan variation across 167 yeast knock-out strains, each lacking a single nuclear-coded mitochondrial gene, including 144 genes with human homologs, many associated with diseases. We dissected the signatures of observed lifespan differences by analyzing profiles of each strain's proteome, lipidome, and metabolome under fermentative and respiratory culture conditions, which correspond to the metabolic states of replicative and chronologically aging cells, respectively. Examination of the relationships among extended longevity phenotypes, protein, and metabolite levels revealed that although many of these nuclear-encoded mitochondrial genes carry out different functions, their inhibition attenuates a common mechanism that controls cytosolic ribosomal protein abundance, actin dynamics, and proteasome function to regulate lifespan. The principles of lifespan control learned through this work may be applicable to the regulation of lifespan in more complex organisms, since many aspects of mitochondrial function are highly conserved among eukaryotes.

The Therapeutic Potential of a Strategy to Prevent Acute Myeloid Leukemia Stem Cell Reprogramming in Older Patients

Acute myeloid leukemia (AML) is the most common and incurable leukemia subtype. Despite extensive research into the disease's intricate molecular mechanisms, effective treatments or expanded diagnostic or prognostic markers for AML have not yet been identified. The morphological, immunophenotypic, cytogenetic, biomolecular, and clinical characteristics of AML patients are extensive and complex. Leukemia stem cells (LSCs) consist of hematopoietic stem cells (HSCs) and cancer cells transformed by a complex, finely-tuned interaction that causes the complexity of AML. Microenvironmental regulation of LSCs dormancy and the diagnostic and therapeutic implications for identifying and targeting LSCs due to their significance in the pathogenesis of AML are discussed in this review. It is essential to perceive the relationship between the niche for LSCs and HSCs, which together cause the progression of AML. Notably, methylation is a well-known epigenetic change that is significant in AML, and our data also reveal that microRNAs are a unique factor for LSCs. Multiple-targeted approaches to reduce the risk of epigenetic factors, such as the administration of natural compounds for the elimination of local LSCs, may prevent potentially fatal relapses. Furthermore, the survival analysis of overlapping genes revealed that specific targets had significant effects on the survival and prognosis of patients. We predict that the multiple-targeted effects of herbal products on epigenetic modification are governed by different mechanisms in AML and could prevent potentially fatal relapses. Thus, these strategies can facilitate the incorporation of herbal medicine and natural compounds into the advanced drug discovery and development processes achievable with Network Pharmacology research.

Dysregulation of histone modifications in bone marrow mesenchymal stem cells during skeletal ageing: roles and therapeutic prospects

Age-associated bone diseases such as osteoporosis (OP) are common in the elderly due to skeletal ageing. The process of skeletal ageing can be accelerated by reduced proliferation and osteogenesis of bone marrow mesenchymal stem cells (BM-MSCs). Senescence of BM-MSCs is a main driver of age-associated bone diseases, and the fate of BM-MSCs is tightly regulated by histone modifications, such as methylation and acetylation. Dysregulation of histone modifications in BM-MSCs may activate the genes related to the pathogenesis of skeletal ageing and age-associated bone diseases. Here we summarize the histone methylation and acetylation marks and their regulatory enzymes that affect BM-MSC self-renewal, differentiation and senescence. This review not only describes the critical roles of histone marks in modulating BM-MSC functions, but also underlines the potential of epigenetic enzymes as targets for treating age-associated bone diseases. In the future, more effective therapeutic approaches based on these epigenetic targets will be developed and will benefit elderly individuals with bone diseases, such as OP.

Mitochondrial homeostasis: a potential target for delaying renal aging

Mitochondria, which are the energy factories of the cell, participate in many life activities, and the kidney is a high metabolic organ that contains abundant mitochondria. Renal aging is a degenerative process associated with the accumulation of harmful processes. Increasing attention has been given to the role of abnormal mitochondrial homeostasis in renal aging. However, the role of mitochondrial homeostasis in renal aging has not been reviewed in detail. Here, we summarize the current biochemical markers associated with aging and review the changes in renal structure and function during aging. Moreover, we also review in detail the role of mitochondrial homeostasis abnormalities, including mitochondrial function, mitophagy and mitochondria-mediated oxidative stress and inflammation, in renal aging. Finally, we describe some of the current antiaging compounds that target mitochondria and note that maintaining mitochondrial homeostasis is a potential strategy against renal aging.

Metabolic regulation by biomaterials in osteoblast

The repair of bone defects resulting from high-energy trauma, infection, or pathological fracture remains a challenge in the field of medicine. The development of biomaterials involved in the metabolic regulation provides a promising solution to this problem and has emerged as a prominent research area in regenerative engineering. While recent research on cell metabolism has advanced our knowledge of metabolic regulation in bone regeneration, the extent to which materials affect intracellular metabolic remains unclear. This review provides a detailed discussion of the mechanisms of bone regeneration, an overview of metabolic regulation in bone regeneration in osteoblasts and biomaterials involved in the metabolic regulation for bone regeneration. Furthermore, it introduces how materials, such as promoting favorable physicochemical characteristics (e.g., bioactivity, appropriate porosity, and superior mechanical properties), incorporating external stimuli (e.g., photothermal, electrical, and magnetic stimulation), and delivering metabolic regulators (e.g., metal ions, bioactive molecules like drugs and peptides, and regulatory metabolites such as alpha ketoglutarate), can affect cell metabolism and lead to changes of cell state. Considering the growing interests in cell metabolic regulation, advanced materials have the potential to help a larger population in overcoming bone defects.

Dietary intake of α-ketoglutarate ameliorates α-synuclein pathology in mouse models of Parkinson's disease

Parkinson's disease (PD) is a progressive movement disorder characterized by dopaminergic (DA) neuron degeneration and the existence of Lewy bodies formed by misfolded α-synuclein. Emerging evidence supports the benefits of dietary interventions in PD due to their safety and practicality. Previously, dietary intake of α-ketoglutarate (AKG) was proved to extend the lifespan of various species and protect mice from frailty. However, the mechanism of dietary AKG's effects in PD remains undetermined. In the present study, we report that an AKG-based diet significantly ameliorated α-synuclein pathology, and rescued DA neuron degeneration and impaired DA synapses in adeno-associated virus (AAV)-loaded human α-synuclein mice and transgenic A53T α-synuclein (A53T α-Syn) mice. Moreover, AKG diet increased nigral docosahexaenoic acid (DHA) levels and DHA supplementation reproduced the anti-α-synuclein effects in the PD mouse model. Our study reveals that AKG and DHA induced microglia to phagocytose and degrade α-synuclein via promoting C1q and suppressed pro-inflammatory reactions. Furthermore, results indicate that modulating gut polyunsaturated fatty acid metabolism and microbiota Lachnospiraceae_NK4A136_group in the gut-brain axis may underlie AKG's benefits in treating α-synucleinopathy in mice. Together, our findings propose that dietary intake of AKG is a feasible and promising therapeutic approach for PD.

METTL5 regulates cranial suture fusion via Wnt signaling

METTL5 is a methyltransferase that mediates eukaryotic 18S ribosomal RNA m6A modification, and its mutations lead to intellectual disability, microcephaly, and facial dysmorphism in patients. However, the role of METTL5 in craniofacial development remains poorly understood. This study demonstrates that Mettl5 knockout mice exhibit poor ossification, widened cranial sutures, and a cleidocranial dysplasia-like phenotype. Deletion of Mettl5 leads to increased proliferation and decreased osteogenic differentiation of suture mesenchymal stem cells. Mechanistically, we find that Wnt signaling is significantly downregulated after Mettl5 knockout. Overall, we reveal an essential role of METTL5 in craniofacial development and osteogenic differentiation of suture mesenchymal stem cells, making METTL5 a potential diagnostic and therapeutic target for craniofacial developmental diseases.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Nutritional Factors: Benefits in Glaucoma and Ophthalmologic Pathologies

Glaucoma is a chronic optic neuropathy that can lead to irreversible functional and morphological damage if left untreated. The gold standard therapeutic approaches in managing patients with glaucoma and limiting progression include local drops, laser, and/or surgery, which are all geared at reducing intraocular pressure (IOP). Nutrients, antioxidants, vitamins, organic compounds, and micronutrients have been gaining increasing interest in the past decade as integrative IOP-independent strategies to delay or halt glaucomatous retinal ganglion cell degeneration. In our minireview, we examine the various nutrients and compounds proposed in the current literature for the management of ophthalmology diseases, especially for glaucoma. With respect to each substance considered, this minireview reports the molecular and biological characteristics, neuroprotective activities, antioxidant properties, beneficial mechanisms, and clinical studies published in the past decade in the field of general medicine. This study highlights the potential benefits of these substances in glaucoma and other ophthalmologic pathologies. Nutritional supplementation can thus be useful as integrative IOP-independent strategies in the management of glaucoma and in other ophthalmologic pathologies. Large multicenter clinical trials based on functional and morphologic data collected over long follow-up periods in patients with IOP-independent treatments can pave the way for alternative and/or coadjutant therapeutic options in the management of glaucoma and other ocular pathologies.

Dysregulated Gln-Glu-α-ketoglutarate axis impairs maternal decidualization and increases the risk of recurrent spontaneous miscarriage

Recurrent spontaneous miscarriage (RSM) affects 1%-2% of fertile women worldwide and poses a risk of future pregnancy complications. Increasing evidence has indicated that defective endometrial stromal decidualization is a potential cause of RSM. Here, we perform liquid chromatography with mass spectrometry (LC-MS)-based metabolite profiling in human endometrial stromal cells (ESCs) and differentiated ESCs (DESCs) and find that accumulated α-ketoglutarate (αKG) derived from activated glutaminolysis contributes to maternal decidualization. Contrarily, ESCs obtained from patients with RSM show glutaminolysis blockade and aberrant decidualization. We further find that enhanced Gln-Glu-αKG flux decreases histone methylation and supports ATP production during decidualization. In vivo, feeding mice a Glu-free diet leads to a reduction of αKG, impaired decidualization, and an increase of fetal loss rate. Isotopic tracing approaches demonstrate Gln-dependent oxidative metabolism as a prevalent direction during decidualization. Our results demonstrate an essential prerequisite of Gln-Glu-αKG flux to regulate maternal decidualization, suggesting αKG supplementation as a putative strategy to rectify deficient decidualization in patients with RSM.

Obesity, but not high-fat diet, is associated with bone loss that is reversed via CD4+CD25+Foxp3+ Tregs-mediated gut microbiome of non-obese mice

Osteoporosis is characterized by decreased bone mass, microarchitectural deterioration, and increased bone fragility. High-fat diet (HFD)-induced obesity also results in bone loss, which is associated with an imbalanced gut microbiome. However, whether HFD-induced obesity or HFD itself promotes osteoclastogenesis and consequent bone loss remains unclear. In this study, we developed HFD-induced obesity (HIO) and non-obesity (NO) mouse models to evaluate the effect of HFD on bone loss. NO mice were defined as body weight within 5% of higher or lower than that of chow diet fed mice after 10 weeks HFD feeding. NO was protected from HIO-induced bone loss by the RANKL /OPG system, with associated increases in the tibia tenacity, cortical bone mean density, bone volume of cancellous bone, and trabecular number. This led to increased bone strength and improved bone microstructure via the microbiome-short-chain fatty acids (SCFAs) regulation. Additionally, endogenous gut-SCFAs produced by the NO mice activated free fatty acid receptor 2 and inhibited histone deacetylases, resulting in the promotion of Treg cell proliferation in the HFD-fed NO mice; thereby, inhibiting osteoclastogenesis, which can be transplanted by fecal microbiome. Furthermore, T cells from NO mice retain differentiation of osteoclast precursors of RAW 264.7 macrophages ex vivo. Our data reveal that HFD is not a deleterious diet; however, the induction of obesity serves as a key trigger of bone loss that can be blocked by a NO mouse-specific gut microbiome.

Osteoporosis remission via an anti-inflammaging effect by icariin activated autophagy

The pace of bone formation slows down with aging, which leads to the development of osteoporosis. In addition to senescent bone marrow mesenchymal stem cells (S-BMSCs), senescent macrophages (S-MΦs) present in the bone marrow produce numerous inflammatory cytokines that contribute to the inflammaged microenvironment and are involved in the development of osteoporosis. Although autophagy activation has shown a significant anti-aging effect, its influence on inflammaging and its role in osteoporosis treatment remain unclear. Traditional Chinese herbal medicine contains bioactive components that exhibit remarkable advantages in bone regeneration. We have demonstrated that icariin (ICA), a bioactive component of traditional Chinese herbal medicine, activates autophagy, exerts a significant anti-inflammaging effect on S-MΦs, and rejuvenates osteogenesis of S-BMSCs, thereby alleviating bone loss in osteoporotic mice. The transcriptomic analysis further reveals that the TNF-α signaling pathway, which is significantly associated with the level of autophagy, regulates this effect. Moreover, the expression of senescence-associated secretory phenotype (SASP) is significantly reduced after ICA treatment. In summary, our findings suggest that bioactive components/materials targeting autophagy can effectively modulate the inflammaging of S-MΦs, offering an innovative treatment strategy for osteoporosis remission and various age-related comorbidities.

Apoptotic Vesicles Regulate Bone Metabolism via the miR1324/SNX14/SMAD1/5 Signaling Axis

Mesenchymal stem cells (MSCs) are widely used in the treatment of diseases. After their in vivo application, MSCs undergo apoptosis and release apoptotic vesicles (apoVs). This study investigates the role of apoVs derived from human bone marrow mesenchymal stem cells (hBMMSCs) in bone metabolism and the molecular mechanism of the observed effects. The results show that apoVs can promote osteogenesis and inhibit osteoclast formation in vitro and in vivo. ApoVs may therefore attenuate the bone loss caused by primary and secondary osteoporosis and stimulate bone regeneration in areas of bone defect. The mechanisms responsible for apoV-induced bone regeneration include the release of miR1324, which inhibit expression of the target gene Sorting Nexin 14 (SNX14) and thus activate the SMAD1/5 pathway in target cells. Given that MSC-derived apoVs are easily obtained and stored, with low risks of immunological rejection and neoplastic transformation, The findings suggest a novel therapeutic strategy to treat bone loss, including via cell-free approaches to bone tissue engineering.

Metformin Ameliorates D-Galactose-Induced Senescent Human Bone Marrow-Derived Mesenchymal Stem Cells by Enhancing Autophagy

Human bone marrow-derived mesenchymal stem cells (hBMSCs) are promising candidates for stem cell therapy in clinical trials. Applications of hBMSCs in clinical therapy are limited by cellular senescence due to long-term ex vivo expansion. Metformin, an oral hypoglycemic drug for type 2 diabetes, has been shown to have antiaging effects. However, the mechanisms of metformin in antiaging treatment remain controversial. Here, we used D-galactose (D-gal) to establish an appropriate model of senescent hBMSCs to explore the antiaging effects of metformin. Following metformin treatment with a low concentration range, senescence phenotypes induced by D-gal significantly changed, including generation of reactive oxygen species (ROS), loss of mitochondrial membrane potential (MMP), and cell cycle arrest. In contrast, no apparent change was found in unsenescent hBMSCs. Furthermore, the results show that activation of 5 $\prime$ AMP-activated protein kinase (AMPK) by metformin enhances cell autophagy in senescent hBMSCs. These findings suggest that metformin exerts antiaging function within the low concentration range by enhancing autophagy and exhibits potential benefits for clinical stem cell therapy by ameliorating the ex vivo replicative senescence of hBMSCs.

Alpha-ketoglutarate as a potent regulator for lifespan and healthspan: Evidences and perspectives

Aging is a natural process that determined by a functional decline in cells and tissues as organisms are growing old, resulting in an increase at risk of disease and death. To this end, many efforts have been made to control aging and increase lifespan and healthspan. These efforts have led to the discovery of several anti-aging drugs and compounds such as rapamycin and metformin. Recently, alpha-ketoglutarate (AKG) has been introduced as a potential anti-aging metabolite that can control several functions in organisms, thereby increases longevity and improves healthspan. Unlike other synthetic anti-aging drugs, AKG is one of the metabolites of the tricarboxylic acid (TCA) cycle, also known as the Krebs cycle, and synthesized in the body. It plays a crucial role in the cell energy metabolism, amino acid/protein synthesis, epigenetic regulation, stemness and differentiation, fertility and reproductive health, and cancer cell behaviors. AKG exerts its effects through different mechanisms such as inhibiting mTOR and ATP-synthase, modulating DNA and histone demethylation and reducing ROS formation. Herein, we summarize the recent findings of AKG-related lifespan and healthspan studies and discuss AKG associated cell and molecular mechanisms involved in increasing longevity, improving reproduction, and modulating stem cells and cancer cells behavior. We also discuss the promises and limitations of AKG for delaying aging and other potential applications.

Mesenchymal stem cells: Emerging concepts and recent advances in their roles in organismal homeostasis and therapy

Stem cells play a crucial role in re-establishing homeostasis in the body, and the search for mechanisms by which they interact with the host to exert their therapeutic effects remains a key question currently being addressed. Considering their significant regenerative/therapeutic potential, research on mesenchymal stem cells (MSCs) has experienced an unprecedented advance in recent years, becoming the focus of extensive works worldwide to develop cell-based approaches for a variety of diseases. Initial evidence for the effectiveness of MSCs therapy comes from the restoration of dynamic microenvironmental homeostasis and endogenous stem cell function in recipient tissues by systemically delivered MSCs. The specific mechanisms by which the effects are exerted remain to be investigated in depth. Importantly, the profound cell-host interplay leaves persistent therapeutic benefits that remain detectable long after the disappearance of transplanted MSCs. In this review, we summarize recent advances on the role of MSCs in multiple disease models, provide insights into the mechanisms by which MSCs interact with endogenous stem cells to exert therapeutic effects, and refine the interconnections between MSCs and cells fused to damaged sites or differentiated into functional cells early in therapy.

Using mass spectrometry imaging to visualize age-related subcellular disruption

Metabolic homeostasis balances the production and consumption of energetic molecules to maintain active, healthy cells. Cellular stress, which disrupts metabolism and leads to the loss of cellular homeostasis, is important in age-related diseases. We focus here on the role of organelle dysfunction in age-related diseases, including the roles of energy deficiencies, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, changes in metabolic flux in aging (e.g., Ca2+ and nicotinamide adenine dinucleotide), and alterations in the endoplasmic reticulum-mitochondria contact sites that regulate the trafficking of metabolites. Tools for single-cell resolution of metabolite pools and metabolic flux in animal models of aging and age-related diseases are urgently needed. High-resolution mass spectrometry imaging (MSI) provides a revolutionary approach for capturing the metabolic states of individual cells and cellular interactions without the dissociation of tissues. mass spectrometry imaging can be a powerful tool to elucidate the role of stress-induced cellular dysfunction in aging.

Alpha-ketoglutarate promotes alveolar bone regeneration by modulating M2 macrophage polarization

Objectives

Alpha-ketoglutarate (αKG) is an essential metabolite that plays a crucial role in skeletal homeostasis. Here we aim to investigate the effect of αKG on alveolar socket healing and reveal the underlying mechanism in the view of macrophage polarization.

Methods

In a murine model pretreated with or without αKG, mandibular first molars were extracted. Mandibular tissues were harvested for microCT and histological analyses. Immunofluorescence was used to evaluate macrophage polarization during healing process. Macrophages with αKG/vehicle supplementation in vitro were proceeded to quantitative real-time PCR and flow cytometry to further elucidate the mechanism.

Results

MicroCT and histological analyses showed accelerated healing and enhanced bone regeneration of extraction sockets in experimental group. αKG increased new bone volume in alveolar sockets and promoted the activity of both osteoblastogenesis and osteoclastogenesis. αKG administration reduced M1 pro-inflammatory macrophages in an early phase and promoted anti-inflammatory M2 macrophage polarization in a later phase. Consistently, the expressions of M2 marker genes were augmented in αKG group, while M1 marker genes were downregulated. Flow cytometry revealed the increased ratio of M2/M1 macrophages in cells treated with αKG.

Conclusions

αKG accelerates the healing process of extraction sockets via orchestrating macrophage activation, with promising therapeutic potential in oral clinics.

Efficacy, Mechanism, and Structure-Activity Relationship of 6-Methoxy Benzofuran Derivatives as a Useful Tool for Senile Osteoporosis

Most patients with senile osteoporosis (SOP) are severely deficient in bone mass, and treatments using bone resorption inhibitors, such as bisphosphonates, have shown limited efficacy. Small-molecule osteogenesis-promoting drugs are required to improve the treatment for this disease. Previously, we demonstrated that a compound with a benzofuran-like structure promoted bone formation by upregulating BMP-2, and it exhibited a therapeutic effect in SAMP-6 mice, glucocorticoid-induced osteoporosis rats, and ovariectomized rats. In this study, aged C57 and SAMP-6 mice models were used to investigate the therapeutic and preventive effects of compound 125 on SOP. scRNA-seq analysis showed that BMP-2 upregulation is the mechanism through which 125 accelerates bone turnover and increases the proportion of osteoblasts. We evaluated the structure-activity relationship of the candidate drugs and found that the derivative I-9 showed significantly higher efficacy than 125 and teriparatide in the zebrafish osteoporosis model. This study provides a foundation for the development of SOP drugs.