Bone and Muscle Endocrine Functions: Unexpected Paradigms of Inter-organ Communication

Activation of the osteoblastic HIF-1α pathway partially alleviates the symptoms of STZ-induced type 1 diabetes mellitus via RegIIIγ

The hypoxia-inducible factor-1α (HIF-1α) pathway coordinates skeletal bone homeostasis and endocrine functions. Activation of the HIF-1α pathway increases glucose uptake by osteoblasts, which reduces blood glucose levels. However, it is unclear whether activating the HIF-1α pathway in osteoblasts can help normalize glucose metabolism under diabetic conditions through its endocrine function. In addition to increasing bone mass and reducing blood glucose levels, activating the HIF-1α pathway by specifically knocking out Von Hippel‒Lindau (Vhl) in osteoblasts partially alleviated the symptoms of streptozotocin (STZ)-induced type 1 diabetes mellitus (T1DM), including increased glucose clearance in the diabetic state, protection of pancreatic β cell from STZ-induced apoptosis, promotion of pancreatic β cell proliferation, and stimulation of insulin secretion. Further screening of bone-derived factors revealed that islet regeneration-derived protein III gamma (RegIIIγ) is an osteoblast-derived hypoxia-sensing factor critical for protection against STZ-induced T1DM. In addition, we found that iminodiacetic acid deferoxamine (SF-DFO), a compound that mimics hypoxia and targets bone tissue, can alleviate symptoms of STZ-induced T1DM by activating the HIF-1α-RegIIIγ pathway in the skeleton. These data suggest that the osteoblastic HIF-1α-RegIIIγ pathway is a potential target for treating T1DM.

Research progress in Alzheimer's disease and bone-brain axis

Alzheimer's disease (AD) is the most common type of cognitive impairment. AD is closely related to orthopedic diseases, such as osteoporosis and osteoarthritis, in terms of epidemiology and pathogenesis. Brain and bone tissues can regulate each other in different manners through bone-brain axis. This article reviews the research progress of the relationship between AD and orthopedic diseases, bone-brain axis mechanisms of AD, and AD therapy by targeting bone-brain axis, in order to deepen the understanding of bone-brain communication, promote early diagnosis and explore new therapy for AD patients.

The single point insulin sensitivity estimator (SPISE) is associated with bone health in Arab adults

BACKGROUND

The Single Point Insulin Sensitivity Estimator (SPISE) index is a surrogate marker for insulin sensitivity. Given the emerging role of bone as an active endocrine organ, its associations with non-invasive measures of extra-skeletal functions such as insulin sensitivity warrant investigation.

AIMS

This study aimed to explore the relationship between the SPISE index and Bone Mineral Density (BMD) in an adult population.

METHODS

Data from a total of 1270 Arab adults (84% females, mean age 56.7 ± 8.1 years) from the Osteoporosis Registry Database of the Chair for Biomarkers of Chronic Diseases in King Saud University, Riyadh, Saudi Arabia was used in this study. T-scores and SPISE were calculated. Regression models were used to determine associations between SPISE and bone health indices.

RESULTS

The low BMD group (N = 853; T-score <-1.0) had significantly higher SPISE values than those with normal BMD (N = 417; T-score - 1.0 and above) (4.6 ± 1.3 vs. 4.3 ± 1.2, p < 0.001). Multivariate linear regression, adjusted for covariates, confirmed a significant inverse association between SPISE and BMD for all participants (β=-0.22, p < 0.001), as well as both groups [normal BMD (β = -0.10, p = 0.02) and low BMD groups (β = -0.15, p < 0.001)]. SPISE, family history of T2DM, and history of fractures collectively account for 17% of the variances perceived in T-score for all participants (p < 0.001).

CONCLUSIONS

A significant inverse association between the SPISE index and BMD was observed in adults, suggesting a link between BMD and extra-skeletal health. Underlying mechanisms need to be investigated prospectively using BMD as secondary outcomes in lifestyle modification programs.

Muscle-bone cross-talk through the FNIP1-TFEB-IGF2 axis is associated with bone metabolism in human and mouse

Clinical evidence indicates a close association between muscle dysfunction and bone loss; however, the underlying mechanisms remain unclear. Here, we report that muscle dysfunction-related bone loss in humans with limb-girdle muscular dystrophy is associated with decreased expression of folliculin-interacting protein 1 (FNIP1) in muscle tissue. Supporting this finding, murine gain- and loss-of-function genetic models demonstrated that muscle-specific ablation of FNIP1 caused decreased bone mass, increased osteoclastic activity, and mechanical impairment that could be rescued by myofiber-specific expression of FNIP1. Myofiber-specific FNIP1 deficiency stimulated expression of nuclear translocation of transcription factor EB, thereby activating transcription of insulin-like growth factor 2 (Igf2) at a conserved promoter-binding site and subsequent IGF2 secretion. Muscle-derived IGF2 stimulated osteoclastogenesis through IGF2 receptor signaling. AAV9-mediated overexpression of IGF2 was sufficient to decrease bone volume and impair bone mechanical properties in mice. Further, we found that serum IGF2 concentration was negatively correlated with bone health in humans in the context of osteoporosis. Our findings elucidate a muscle-bone cross-talk mechanism bridging the gap between muscle dysfunction and bone loss. This cross-talk represents a potential target to treat musculoskeletal diseases and osteoporosis.

Association between surrogate marker of insulin resistance and bone mineral density in US adults without diabetes

This study examines the relationship between TyG-BMI, an indicator of insulin resistance, and bone mineral density in US adults without diabetes, revealing a positive association. The findings suggest that higher TyG-BMI levels may be linked to a lower risk of osteoporosis, providing a basis for future research in this area.

OBJECTIVE

Patients with osteoporosis are often diagnosed with type 2 diabetes or prediabetes. Insulin resistance is a prediabetic state, and triglyceride glucose-body mass index (TyG-BMI) has been recognized as a potential predictor of it, valuable in assessing prediabetes, atherosclerosis, and other diseases. However, the validity of TyG-BMI in osteoporosis studies remains inadequate.

PURPOSE

The purpose of this study was to evaluate the relationship between TyG-BMI and BMD as well as the effect of TyG-BMI on the odds of developing osteoporosis in US adults without diabetes.

METHODS

National Health and Nutrition Examination Survey data were obtained. The relationship between TyG-BMI and BMD was evaluated via multivariate linear regression models. Smoothed curve fitting and threshold effect analysis explored potential non-linear relationships, and age, gender, and race subgroup analyses were performed. In addition, multivariate logistic regression models were employed to analyze its potential role in the development of osteoporosis.

RESULTS

In a study of 6501 participants, we observed a significant positive correlation between the TyG-BMI index and BMD, even after adjusting for covariates and categorizing TyG-BMI. The study identified specific TyG-BMI folding points-112.476 for the total femur BMD, 100.66 for the femoral neck BMD, 107.291 for the intertrochanter BMD, and 116.58 for the trochanter BMD-indicating shifts in the relationship's strength at these thresholds. While the association's strength slightly decreased after the folding points, it remained significant. Subgroup analyses further confirmed the positive TyG-BMI and BMD correlation. Multivariate linear regression analyses indicated a lower osteoporosis risk in participants with higher TyG-BMI levels, particularly in menopausal women over 40 and men over 60.

CONCLUSION

This study suggests a positive correlation between BMD and TyG-BMI in US adults without diabetes. Individuals with higher levels of TyG-BMI may have a lower risk of osteoporosis.

An integrated multi-omics analysis reveals osteokines involved in global regulation

Bone secretory proteins, termed osteokines, regulate bone metabolism and whole-body homeostasis. However, fundamental questions as to what the bona fide osteokines and their cellular sources are and how they are regulated remain unclear. In this study, we analyzed bone and extraskeletal tissues, osteoblast (OB) conditioned media, bone marrow supernatant (BMS), and serum, for basal osteokines and those responsive to aging and mechanical loading/unloading. We identified 375 candidate osteokines and their changes in response to aging and mechanical dynamics by integrating data from RNA-seq, scRNA-seq, and proteomic approaches. Furthermore, we analyzed their cellular sources in the bone and inter-organ communication facilitated by them (bone-brain, liver, and aorta). Notably, we discovered that senescent OBs secrete fatty-acid-binding protein 3 to propagate senescence toward vascular smooth muscle cells (VSMCs). Taken together, we identified previously unknown candidate osteokines and established a dynamic regulatory network among them, thus providing valuable resources to further investigate their systemic roles.

Shared genetic architecture and causal relationship between liver and heart disease

This study investigates the relationship and genetic mechanisms of liver and heart diseases, focusing on the liver-heart axis (LHA) as a fundamental biological basis. Through genome-wide association study analysis, we explore shared genes and pathways related to LHA. Shared genetic factors are found in 8 out of 20 pairs, indicating genetic correlations. The analysis reveals 53 loci with pleiotropic effects, including 8 loci exhibiting shared causality across multiple traits. Based on SNP-p level tissue-specific multi-marker analysis of genomic annotation (MAGMA) analysis demonstrates significant enrichment of pleiotropy in liver and heart diseases within different cardiovascular tissues and female reproductive appendages. Gene-specific MAGMA analysis identifies 343 pleiotropic genes associated with various traits; these genes show tissue-specific enrichment primarily in the liver, cardiovascular system, and other tissues. Shared risk loci between immune cells and both liver and cardiovascular diseases are also discovered. Mendelian randomization analyses provide support for causal relationships among the investigated trait pairs.

Direct-Acting Oral Anticoagulant/Vitamin K Antagonists: Do They Affect the Trabecular and Cortical Structure of the Mandible?

BACKGROUND

This study aimed to evaluate the mandibular bone structure of patients using oral anticoagulants (OACs) vitamin K antagonist drugs (warfarin) and other OACs including direct oral anticoagulants [(DOACs) apixaban, rivaroxaban, dabigatran, edoxaban]. Analyses were based upon the fractal dimension (FD), the panoramic mandibular index (PMI) and the Klemetti index (KI), which is also known as the mandibular cortical index (MCI).

METHODOLOGY

Ninety participants were divided into three groups: group 1: 30 systemically healthy individuals who had not used any anticoagulants before, group 2: 30 individuals using warfarin, and group 3: 30 individuals using DOACs. FD was used to analyze trabecular bone architecture in the condyle, angle, and two sites in the alveolar bone. PMI was used to evaluate the quantity of cortical bone and KI was used to evaluate the cortical bone quality.

RESULTS

There was no difference between the groups regarding FD analysis and KI; however, a difference was found between groups 1, 2, and 3 in the PMI (P≤ 0.001). The PMI in group 1 was higher than in groups 2 and 3.

CONCLUSION

Mandibular radiomorphometric indices can be used on panoramic radiographs to evaluate the quantity of mandibular cortical bone in patients using oral anticoagulants.

Inter-organ steroid hormone signaling promotes myoblast fusion via direct transcriptional regulation of a single key effector gene

Steroid hormones regulate tissue development and physiology by modulating the transcription of a broad spectrum of genes. In insects, the principal steroid hormones, ecdysteroids, trigger the expression of thousands of genes through a cascade of transcription factors (TFs) to coordinate developmental transitions such as larval molting and metamorphosis. However, whether ecdysteroid signaling can bypass transcriptional hierarchies to exert its function in individual developmental processes is unclear. Here, we report that a single non-TF effector gene mediates the transcriptional output of ecdysteroid signaling in Drosophila myoblast fusion, a critical step in muscle development and differentiation. Specifically, we show that the 20-hydroxyecdysone (commonly referred to as "ecdysone") secreted from an extraembryonic tissue, amnioserosa, acts on embryonic muscle cells to directly activate the expression of antisocial (ants), which encodes an essential scaffold protein enriched at the fusogenic synapse. Not only is ants transcription directly regulated by the heterodimeric ecdysone receptor complex composed of ecdysone receptor (EcR) and ultraspiracle (USP) via ecdysone-response elements but also more strikingly, expression of ants alone is sufficient to rescue the myoblast fusion defect in ecdysone signaling-deficient mutants. We further show that EcR/USP and a muscle-specific TF Twist synergistically activate ants expression in vitro and in vivo. Taken together, our study provides the first example of a steroid hormone directly activating the expression of a single key non-TF effector gene to regulate a developmental process via inter-organ signaling and provides a new paradigm for understanding steroid hormone signaling in other developmental and physiological processes.

Oncogenic miR-106b-5p promotes cisplatin resistance in triple-negative breast cancer by targeting GDF11

BACKGROUND

Cytoplatin (CDDP) is a standard treatment for triple-negative breast cancer (TNB), but patient resistance to CDDP limits its efficacy. A growing study confirms that microRNAs (miRNAs) are significantly important in breast cancer, especially TNBC. This research was carried out to examine the function of miR-106b-5p in CDDP resistance of TNBC as well as the downstream mechanism.

METHODS

The miR-106b-5p and growth-differentiation factor 11 (GDF11) expressions in the tissues from TNBC patients and CDDP-treated TNBC cell lines were measured by RT-qPCR. Thereafter, cell proliferation and migration in the presence of CDDP treatment were evaluated via CCK-8 and Transwell assays in the TNBC cells. A xenograft mice model was also established to verify the miR-106b-5p silencing effect on the growth of CDDP resistance TNBC cells in vivo. Luciferase reporter experiments were performed to predict the relationship between miR-106b-5p and GDF11 expression.

RESULTS

The results showed that miR-106b-5p was upregulated in the TNBC tumor cells and TNBC cells treated with CDDP and knockdown of this caused inhibition of the TNBC cell lines' proliferation, migration and suppressed the growth of the TNBC xenografted tumors, in the presence of CDDP treatment. In addition, it was observed that miR-106b-5p can bind to GDF11; as a result in the TNBC tissues and CDDP-treated TNBC cell lines the down-regulation of GDF11 was observed. Moreover, GDF11 silencing promoted CDDP-treated TNBC cell lines' proliferation and migration and reversed the interference effect of miR-106b-5p.

CONCLUSIONS

MiR-106b-5p was upregulated in TNBC and this upregulation may promote CDDP resistance of the TNBC cells by targeting GDF11 and inhibiting its expression.

Effect of sarcopenia on refractures of adjacent vertebra after percutaneous kyphoplasty

PURPOSE

To explore the effect of sarcopenia on recurrent fractures of adjacent vertebra after percutaneous kyphoplasty (PKP).

METHODS

A total of 376 osteoporotic vertebral compression fractures (OVCFs) patients over 55 years old who were admitted to the Hospital from August 2020 to January 2021 were selected. Among them, 38 patients with recurrent fractures in adjacent vertebra after PKP were selected as the refracture group (RG), and the remaining 338 patients were selected as the non-refracture group (NRG). The age, gender, grip strength, body mass index (BMI), bone mineral density (BMD), visual analogue scale (VAS) of pain before and one month after surgery, Oswestry disability index (ODI) before and one month after surgery and the occurrence of sarcopenia were compared between the two groups. Logistic regression analysis was used to evaluate the effect of related risk factors on refracture after vertebral PKP.

RESULTS

The results of t-test and Chi-square test showed that there were no obvious differences in gender, BMI, preoperative VAS score (t=-0.996, P = 0.320) and ODI (t=-0.424, P = 0.671), one month postoperative VAS score (t=-0.934, P = 0.355) and ODI score (t=-0.461, P = 0.645). while the age and grip strength showed significant differences between the two groups. Logistic regression analysis showed that BMI and gender had no significant effect on refracture after PKP, while sarcopenia and advanced age were independent risk factors for refracture after PKP. Also, increased BMD was a protective factor for refracture after PKP.

CONCLUSION

Sarcopenia is an independent risk factor for recurrent fractures after PKP in OVCF patients. The screening and diagnosis of sarcopenia should be strengthened. At the same time, anti-sarcopenia treatment should be actively performed after surgery.

A view on the skin-bone axis: unraveling similarities and potential of crosstalk

The phrase "skin as a mirror of internal medicine," which means that the skin reflects many of the diseases of the internal organs, is a well-known notion. Despite the phenotypic differences between the soft skin and hard bone, the skin and bone are highly associated. Skin and bone consist of fibroblasts and osteoblasts, respectively, which secrete collagen and are involved in synthesis, while Langerhans cells and osteoclasts control turnover. Moreover, the quality and quantity of collagen in the skin and bone may be modified by aging, inflammation, estrogen, diabetes, and glucocorticoids. Skin and bone collagen are pathologically modified by aging, drugs, and metabolic diseases, such as diabetes. The structural similarities between the skin and bone and the crosstalk controlling their mutual pathological effects have led to the advocacy of the skin-bone axis. Thus, the skin may mirror the health of the bones and conversely, the condition of the skin may be reflected in the bones. From the perspective of the skin-bone axis, the similarities between skin and bone anatomy, function, and pathology, as well as the crosstalk between the two, are discussed in this review. A thorough elucidation of the pathways governing the skin-bone axis crosstalk would enhance our understanding of disease pathophysiology, facilitating the development of new diagnostics and therapies for skin collagen-induced bone disease and of new osteoporosis diagnostics and therapies that enhance skin collagen to increase bone quality and density.

Effects of 12 weeks of neuromuscular electrical stimulation of the quadriceps muscles on the function and physio-biochemical traits in functionally fit female nursing-home residents aged 75 + years: a pilot study

PURPOSE

Muscular changes induced by neuromuscular electrical stimulation (NMES) are well recognized, but knowledge of how NMES influences the physio-biochemical traits of the oldest old is still limited. This study investigated the effect of NMES applied for 12 weeks to the quadriceps muscles of female nursing-home residents aged 75 + on their functional capability and inflammatory, bone metabolism, and cardiovascular traits.

METHODS

Nineteen women regularly taking part in two body conditioning sessions per week were randomized into an electrical stimulation group (ES; n = 10; 30 min sessions, 3 times per week) or a control group (CON; n = 9). At baseline and study week 12, all women performed the 30 s chair stand test (30sCST), the 6-minute walk test (6MWT), and the instrumented timed up and go test (iTUG). Resting heart rates, blood pressure, and the blood concentrations of inflammatory and bone metabolism markers were also measured twice.

RESULTS

NMES increased the strength of participants' quadriceps muscles and their performance on the 30sCST and 6MWT while lowering resting arterial blood pressure and inflammatory marker levels; osteoclast activity showed a tendency to decrease. Changes in the iTUG results were not observed. A multiple regression analysis found that the results of functional tests in the ES group were best correlated with pulse pressure (the 30sCST and iTUG tests) and diastolic blood pressure (the 6MWT test).

CONCLUSION

Twelve weeks of NMES treatment improved participants' functional capacity and inflammatory, bone metabolism, and cardiovascular traits. The ES group participants' performance on functional tests was best predicted by hemodynamic parameters.

The multi-faceted nature of age-associated osteoporosis

Age-associated osteoporosis (AAOP) poses a significant health burden, characterized by increased fracture risk due to declining bone mass and strength. Effective prevention and early treatment strategies are crucial to mitigate the disease burden and the associated healthcare costs. Current therapeutic approaches effectively target the individual contributing factors to AAOP. Nonetheless, the management of AAOP is complicated by the multitude of variables that affect its development. Main intrinsic and extrinsic factors contributing to AAOP risk are reviewed here, including mechanical unloading, nutrient deficiency, hormonal disbalance, disrupted metabolism, cognitive decline, inflammation and circadian disruption. Furthermore, it is discussed how these can be targeted for prevention and treatment. Although valuable as individual targets for intervention, the interconnectedness of these risk factors result in a unique etiology for every patient. Acknowledgement of the multifaceted nature of AAOP will enable the development of more effective and sustainable management strategies, based on a holistic, patient-centered approach.

Interorgan communication in neurogenic heterotopic ossification: the role of brain-derived extracellular vesicles

Brain-derived extracellular vesicles participate in interorgan communication after traumatic brain injury by transporting pathogens to initiate secondary injury. Inflammasome-related proteins encapsulated in brain-derived extracellular vesicles can cross the blood‒brain barrier to reach distal tissues. These proteins initiate inflammatory dysfunction, such as neurogenic heterotopic ossification. This recurrent condition is highly debilitating to patients because of its relatively unknown pathogenesis and the lack of effective prophylactic intervention strategies. Accordingly, a rat model of neurogenic heterotopic ossification induced by combined traumatic brain injury and achillotenotomy was developed to address these two issues. Histological examination of the injured tendon revealed the coexistence of ectopic calcification and fibroblast pyroptosis. The relationships among brain-derived extracellular vesicles, fibroblast pyroptosis and ectopic calcification were further investigated in vitro and in vivo. Intravenous injection of the pyroptosis inhibitor Ac-YVAD-cmk reversed the development of neurogenic heterotopic ossification in vivo. The present work highlights the role of brain-derived extracellular vesicles in the pathogenesis of neurogenic heterotopic ossification and offers a potential strategy for preventing neurogenic heterotopic ossification after traumatic brain injury. Brain-derived extracellular vesicles (BEVs) are released after traumatic brain injury. These BEVs contain pathogens and participate in interorgan communication to initiate secondary injury in distal tissues. After achillotenotomy, the phagocytosis of BEVs by fibroblasts induces pyroptosis, which is a highly inflammatory form of lytic programmed cell death, in the injured tendon. Fibroblast pyroptosis leads to an increase in calcium and phosphorus concentrations and creates a microenvironment that promotes osteogenesis. Intravenous injection of the pyroptosis inhibitor Ac-YVAD-cmk suppressed fibroblast pyroptosis and effectively prevented the onset of heterotopic ossification after neuronal injury. The use of a pyroptosis inhibitor represents a potential strategy for the treatment of neurogenic heterotopic ossification.

Heat shock response during the resolution of inflammation and its progressive suppression in chronic-degenerative inflammatory diseases

The heat shock response (HSR) is a crucial biochemical pathway that orchestrates the resolution of inflammation, primarily under proteotoxic stress conditions. This process hinges on the upregulation of heat shock proteins (HSPs) and other chaperones, notably the 70 kDa family of heat shock proteins, under the command of the heat shock transcription factor-1. However, in the context of chronic degenerative disorders characterized by persistent low-grade inflammation (such as insulin resistance, obesity, type 2 diabetes, nonalcoholic fatty liver disease, and cardiovascular diseases) a gradual suppression of the HSR does occur. This work delves into the mechanisms behind this phenomenon. It explores how the Western diet and sedentary lifestyle, culminating in the endoplasmic reticulum stress within adipose tissue cells, trigger a cascade of events. This cascade includes the unfolded protein response and activation of the NOD-like receptor pyrin domain-containing protein-3 inflammasome, leading to the emergence of the senescence-associated secretory phenotype and the propagation of inflammation throughout the body. Notably, the activation of the NOD-like receptor pyrin domain-containing protein-3 inflammasome not only fuels inflammation but also sabotages the HSR by degrading human antigen R, a crucial mRNA-binding protein responsible for maintaining heat shock transcription factor-1 mRNA expression and stability on heat shock gene promoters. This paper underscores the imperative need to comprehend how chronic inflammation stifles the HSR and the clinical significance of evaluating the HSR using cost-effective and accessible tools. Such understanding is pivotal in the development of innovative strategies aimed at the prevention and treatment of these chronic inflammatory ailments, which continue to take a heavy toll on global health and well-being.

Osteocalcin of maternal and embryonic origins synergize to establish homeostasis in offspring

Many physiological osteocalcin-regulated functions are affected in adult offspring of mothers experiencing unhealthy pregnancy. Furthermore, osteocalcin signaling during gestation influences cognition and adrenal steroidogenesis in adult mice. Together these observations suggest that osteocalcin may broadly function during pregnancy to determine organismal homeostasis in adult mammals. To test this hypothesis, we analyzed in unchallenged wildtype and Osteocalcin-deficient, newborn and adult mice of various genotypes and origin maintained on different genetic backgrounds, the functions of osteocalcin in the pancreas, liver and testes and their molecular underpinnings. This analysis revealed that providing mothers are Osteocalcin-deficient, Osteocalcin haploinsufficiency in embryos hampers insulin secretion, liver gluconeogenesis, glucose homeostasis, testes steroidogenesis in adult offspring; inhibits cell proliferation in developing pancreatic islets and testes; and disrupts distinct programs of gene expression in these organs and in the brain. This study indicates that osteocalcin exerts dominant functions in most organs it influences. Furthermore, through their synergistic regulation of multiple physiological functions, osteocalcin of maternal and embryonic origins contributes to the establishment and maintenance of organismal homeostasis in newborn and adult offspring.

Interorgan communication networks in the kidney-lung axis

The homeostasis and health of an organism depend on the coordinated interaction of specialized organs, which is regulated by interorgan communication networks of circulating soluble molecules and neuronal connections. Many diseases that seemingly affect one primary organ are really multiorgan diseases, with substantial secondary remote organ complications that underlie a large part of their morbidity and mortality. Acute kidney injury (AKI) frequently occurs in critically ill patients with multiorgan failure and is associated with high mortality, particularly when it occurs together with respiratory failure. Inflammatory lung lesions in patients with kidney failure that could be distinguished from pulmonary oedema due to volume overload were first reported in the 1930s, but have been largely overlooked in clinical settings. A series of studies over the past two decades have elucidated acute and chronic kidney-lung and lung-kidney interorgan communication networks involving various circulating inflammatory cytokines and chemokines, metabolites, uraemic toxins, immune cells and neuro-immune pathways. Further investigations are warranted to understand these clinical entities of high morbidity and mortality, and to develop effective treatments.

Deciphering Immune Landscape Remodeling Unravels the Underlying Mechanism for Synchronized Muscle and Bone Aging

Evidence from numerous studies has revealed the synchronous progression of aging in bone and muscle; however, little is known about the underlying mechanisms. To this end, human muscles and bones are harvested and the aging-associated transcriptional dynamics of two tissues in parallel using single-cell RNA sequencing are surveyed. A subset of lipid-associated macrophages (triggering receptor expressed on myeloid cells 2, TREM2+ Macs) is identified in both aged muscle and bone. Genes responsible for muscle dystrophy and bone loss, such as secreted phosphoprotein 1 (SPP1), are also highly expressed in TREM2+ Macs, suggesting its conserved role in aging-related features. A common transition toward pro-inflammatory phenotypes in aged CD4+ T cells across tissues is also observed, activated by the nuclear factor kappa B subunit 1 (NFKB1). CD4+ T cells in aged muscle experience Th1-like differentiation, whereas, in bone, a skewing toward Th17 cells is observed. Furthermore, these results highlight that degenerated myocytes produce BAG6-containing exosomes that can communicate with Th17 cells in the bone through its receptor natural cytotoxicity triggering receptor 3 (NCR3). This communication upregulates CD6 expression in Th17 cells, which then interact with TREM2+ Macs through CD6-ALCAM signaling, ultimately stimulating the transcription of SPP1 in TREM2+ Macs. The negative correlation between serum exosomal BCL2-associated athanogene 6 (BAG6) levels and bone mineral density further supports its role in mediating muscle and bone synchronization with aging.

Causal effects of osteoporosis on structural changes in specific brain regions: a Mendelian randomization study

Observational studies have reported that osteoporosis is associated with cortical changes in the brain. However, the inherent limitations of observational studies pose challenges in eliminating confounding factors and establishing causal relationships. And previous observational studies have not reported changes in specific brain regions. By employing Mendelian randomization, we have been able to infer a causal relationship between osteoporosis and a reduction in the surficial area (SA) of the brain cortical. This effect is partially mediated by vascular calcification. We found that osteoporosis significantly decreased the SA of global brain cortical (β = -1587.62 mm2, 95%CI: -2645.94 mm2 to -529.32 mm2, P = 0.003) as well as the paracentral gyrus without global weighted (β = - 19.42 mm2, 95%CI: -28.90 mm2 to -9.95 mm2, P = 5.85 × 10-5). Furthermore, we estimated that 42.25% and 47.21% of the aforementioned effects are mediated through vascular calcification, respectively. Osteoporosis leads to a reduction in the SA of the brain cortical, suggesting the presence of the bone-brain axis. Vascular calcification plays a role in mediating this process to a certain extent. These findings establish a theoretical foundation for further investigations into the intricate interplay between bone, blood vessels, and the brain.

Crosstalk Between the Neuroendocrine System and Bone Homeostasis

The homeostasis of bone microenvironment is the foundation of bone health and comprises 2 concerted events: bone formation by osteoblasts and bone resorption by osteoclasts. In the early 21st century, leptin, an adipocytes-derived hormone, was found to affect bone homeostasis through hypothalamic relay and the sympathetic nervous system, involving neurotransmitters like serotonin and norepinephrine. This discovery has provided a new perspective regarding the synergistic effects of endocrine and nervous systems on skeletal homeostasis. Since then, more studies have been conducted, gradually uncovering the complex neuroendocrine regulation underlying bone homeostasis. Intriguingly, bone is also considered as an endocrine organ that can produce regulatory factors that in turn exert effects on neuroendocrine activities. After decades of exploration into bone regulation mechanisms, separate bioactive factors have been extensively investigated, whereas few studies have systematically shown a global view of bone homeostasis regulation. Therefore, we summarized the previously studied regulatory patterns from the nervous system and endocrine system to bone. This review will provide readers with a panoramic view of the intimate relationship between the neuroendocrine system and bone, compensating for the current understanding of the regulation patterns of bone homeostasis, and probably developing new therapeutic strategies for its related disorders.

Multiorgan locked-state model of chronic diseases and systems pharmacology opportunities

With increasing human life expectancy, the global medical burden of chronic diseases is growing. Hence, chronic diseases are a pressing health concern and will continue to be in decades to come. Chronic diseases often involve multiple malfunctioning organs in the body. An imminent question is how interorgan crosstalk contributes to the etiology of chronic diseases. We conceived the locked-state model (LoSM), which illustrates how interorgan communication can give rise to body-wide memory-like properties that 'lock' healthy or pathological conditions. Next, we propose cutting-edge systems biology and artificial intelligence strategies to decipher chronic multiorgan locked states. Finally, we discuss the clinical implications of the LoSM and assess the power of systems-based therapies to dismantle pathological multiorgan locked states while improving treatments for chronic diseases.

Skeletal muscle-derived extracellular vesicles transport glycolytic enzymes to mediate muscle-to-bone crosstalk

Identification of cues originating from skeletal muscle that govern bone formation is essential for understanding the crosstalk between muscle and bone and for developing therapies for degenerative bone diseases. Here, we identified that skeletal muscle secreted multiple extracellular vesicles (Mu-EVs). These Mu-EVs traveled through the bloodstream to reach bone, where they were phagocytized by bone marrow mesenchymal stem/stromal cells (BMSCs). Mu-EVs promoted osteogenic differentiation of BMSCs and protected against disuse osteoporosis in mice. The quantity and bioactivity of Mu-EVs were tightly correlated with the function of skeletal muscle. Proteomic analysis revealed numerous proteins in Mu-EVs, some potentially regulating bone metabolism, especially glycolysis. Subsequent investigations indicated that Mu-EVs promoted the glycolysis of BMSCs by delivering lactate dehydrogenase A into these cells. In summary, these findings reveal that Mu-EVs play a vital role in BMSC metabolism regulation and bone formation stimulation, offering a promising approach for treating disuse osteoporosis.

To investigate the association of serum osteocalcin with cognitive functional status in patients with type 2 diabetes: A systematic review with meta-analysis

BACKGROUND

To systematically evaluate the correlation between serum osteocalcin levels and cognitive function status in type 2 diabetes mellitus (T2D) patients.

METHODS

This review was conducted according to the PRISMA guidelines, and was developed and submitted to PROSPERO (CRD42022339295). We comprehensively searched PubMed, EMBASE, Web of Science, Scopus, ProQuest, and Chinese Databases (China National Knowledge Infrastructure, Wan Fang, Chinese Science and Technology Periodical Database, and China Biology Medicine) up to 1 June 2023. 3 investigators performed independent literature screening and data extraction of the included literature, and 2 investigators performed an independent quality assessment of case-control studies using the Newcastle-Ottawa-Scale tool. Data analysis was performed using Review Manager 5.4 software. For continuous various outcomes, mean difference (MD) or standardized MD with 95% confidence intervals (CIs) was applied for assessment by fixed-effect or random-effect model analysis. The heterogeneity test was performed by the Q statistic and quantified using I2, and publication bias was evaluated using a funnel plot.

RESULTS

9 studies with T2D were included (a total of 1310 subjects). Meta-analysis results indicated that cognitive function was more impaired in patients with lower serum osteocalcin levels [MD = 9.91, 95% CI (8.93, -10.89), I2 = 0%]. Serum osteocalcin levels were also significantly different between the 2 groups of T2D patients based on the degree of cognitive impairment [MD = -0.93, 95% CI (-1.09, -0.78), I2 = 41%]. It summarized the statistical correlation between serum osteocalcin and cognitive function scores in patients with T2D at r = 0.43 [summary Fisher's Z = 0.46, 95% CI (0.39, -0.50), I2 = 41%). After sensitivity analysis, the heterogeneity I2 decreased to 0%, indicating that the results of the meta-analysis are more reliable.

CONCLUSION SUBSECTIONS

Based on a meta-analysis of included studies, we concluded that there is a moderately strong positive correlation between serum osteocalcin levels and patients' cognitive function in T2D. An intervention to increase serum osteocalcin levels can contribute to delaying and improving cognitive decline in patients with T2D.

Analysis of the association between osteoporosis and muscle strength in Korean adults: a national cross-sectional study

BACKGROUND

This study aimed to examine the associations between osteoporosis and hand grip strength (HGS), a surrogate marker of muscular strength, among Korean adults stratified by body mass index (BMI), age, and renal function.

METHODS

This study was conducted using the data obtained from the Korea National Health and Nutrition Examination Survey 2015-2019, a cross-sectional and nationally representative survey performed by the Korea Centers for Diseases Control and Prevention.

RESULTS

Of the 26,855 subjects included in this study, those with low muscle strength (LMS) and normal muscle strength were showed in 4,135 (15.4%) and 22,720 (84.6%) subjects, respectively. The osteoporotic subjects had a higher prevalence rate for LMS than those without osteoporosis after adjusting for age [odds ratio (OR), 1.684; 95% confidence interval (CI), 1.500-1.890). The subjects with osteoporosis and BMI < 18.5 kg/m2 also had a higher prevalence rate for LMS after adjusting for age compared to those with non-osteoporosis and BMI < 18.5 kg/m2 (OR, 1.872; 95% CI, 1.043-3.359). Compared to the non-osteoporotic subjects with estimated glomerular filtration rate (eGFR) ≥ 60 mL/min/1.73 m2, those with osteoporosis and eGFR ≥ 60 mL/min/1.73 m2 had a higher prevalence rate for LMS after controlling for age and sex (OR, 1.630; 95% CI, 1.427-1.862).

CONCLUSIONS

The results showed that osteoporosis was likely to contribute to an increased prevalence rate of LMS in terms of HGS. Aging, BMI, and renal function also had significant effects on the association between osteoporosis and LMS. This association is likely to assist in developing better strategies to estimate bone health in clinical or public health practice.

Osteocalcin of maternal and embryonic origins synergize to establish homeostasis in offspring

Many physiological functions regulated by osteocalcin are affected in adult offspring of mothers experiencing an unhealthy pregnancy. Furthermore, osteocalcin signaling during gestation influences cognition and adrenal steroidogenesis in adult mice. Together these observations suggest that osteocalcin functions during pregnancy may be a broader determinant of organismal homeostasis in adult mammals than previously thought. To test this hypothesis, we analyzed in unchallenged wildtype and Osteocalcin -deficient, newborn, and adult mice of various genotypes and origin, and that were maintained on different genetic backgrounds, the functions of osteocalcin in the pancreas, liver and testes and their molecular underpinnings. This analysis revealed that providing mothers are themselves Osteocalcin -deficient, Osteocalcin haploinsufficiency in embryos hampers insulin secretion, liver gluconeogenesis, glucose homeostasis, testes steroidogenesis in adult offspring; inhibits cell proliferation in developing pancreatic islets and testes; and disrupts distinct programs of gene expression in these organs and in the brain. This study indicates that through their synergistic regulation of multiple physiological functions, osteocalcin ofmaternal and embryonic origins contributes to the establishment and maintenance of organismal homeostasis in newborn and adult offspring.

Secondary Osteoporosis: A Still Neglected Condition

The condition of "secondary osteoporosis" is defined as a bone loss that results from specific well-defined clinical disorders [...].

An IL-6/STAT3/MR/FGF21 axis mediates heart-liver cross-talk after myocardial infarction

The liver plays a protective role in myocardial infarction (MI). However, very little is known about the mechanisms. Here, we identify mineralocorticoid receptor (MR) as a pivotal nexus that conveys communications between the liver and the heart during MI. Hepatocyte MR deficiency and MR antagonist spironolactone both improve cardiac repair after MI through regulation on hepatic fibroblast growth factor 21 (FGF21), illustrating an MR/FGF21 axis that underlies the liver-to-heart protection against MI. In addition, an upstreaming acute interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) pathway transmits the heart-to-liver signal to suppress MR expression after MI. Hepatocyte Il6 receptor deficiency and Stat3 deficiency both aggravate cardiac injury through their regulation on the MR/FGF21 axis. Therefore, we have unveiled an IL-6/STAT3/MR/FGF21 signaling axis that mediates heart-liver cross-talk during MI. Targeting the signaling axis and the cross-talk could provide new strategies to treat MI and heart failure.

The Impact of Plasma Membrane Ion Channels on Bone Remodeling in Response to Mechanical Stress, Oxidative Imbalance, and Acidosis

The extracellular milieu is a rich source of different stimuli and stressors. Some of them depend on the chemical–physical features of the matrix, while others may come from the ‘outer’ environment, as in the case of mechanical loading applied on the bones. In addition to these forces, a plethora of chemical signals drives cell physiology and fate, possibly leading to dysfunctions when the homeostasis is disrupted. This variety of stimuli triggers different responses among the tissues: bones represent a particular milieu in which a fragile balance between mechanical and metabolic demands should be tuned and maintained by the concerted activity of cell biomolecules located at the interface between external and internal environments. Plasma membrane ion channels can be viewed as multifunctional protein machines that act as rapid and selective dual-nature hubs, sensors, and transducers. Here we focus on some multisensory ion channels (belonging to Piezo, TRP, ASIC/EnaC, P2XR, Connexin, and Pannexin families) actually or potentially playing a significant role in bone adaptation to three main stressors, mechanical forces, oxidative stress, and acidosis, through their effects on bone cells including mesenchymal stem cells, osteoblasts, osteoclasts, and osteocytes. Ion channel-mediated bone remodeling occurs in physiological processes, aging, and human diseases such as osteoporosis, cancer, and traumatic events.

Muscle regeneration in gilthead sea bream: Implications of endocrine and local regulatory factors and the crosstalk with bone

Fish muscle regeneration is still a poorly known process. In the present study, an injury was done into the left anterior epaxial skeletal muscle of seventy 15 g gilthead sea bream (Sparus aurata) juveniles to evaluate at days 0, 1, 2, 4, 8, 16 and 30 post-wound, the expression of several muscle genes. Moreover, transcripts' expression in the bone (uninjured tissue) was also analyzed. Histology of the muscle showed the presence of dead tissue the first day after injury and how the damaged fibers were removed and replaced by new muscle fibers by day 16 that kept growing up to day 30. Gene expression results showed in muscle an early upregulation of igf-2 and a downregulation of ghr-1 and igf-1. Proteolytic systems expression increased with capn2 and ctsl peaking at 1 and 2 days post-injury, respectively and mafbx at day 8. A pattern of expression that fitted well with active myogenesis progression 16 days after the injury was then observed, with the recovery of igf-1, pax7, cmet, and cav1 expression; and later on, that of cav3 as well. Furthermore, the first days post-injury, the cytokines il-6 and il-15 were also upregulated confirming the tissue inflammation, while tnfα was only upregulated at days 16 and 30 to induce satellite cells recruitment; overall suggesting a possible role for these molecules as myokines. The results of the bone transcripts showed an upregulation first, of bmp2 and ctsk at days 1 and 2, respectively; then, ogn1 and ocn peaked at day 4 in parallel to mstn2 downregulation, and runx2 and ogn2 increased after 8 days of muscle injury, suggesting a possible tissue crosstalk during the regenerative process. Overall, the present model allows studying the sequential involvement of different regulatory molecules during muscle regeneration, as well as the potential relationship between muscle and other tissues such as bone to control musculoskeletal development and growth, pointing out an interesting new line of research in this group of vertebrates.

Endogenous Electric Field-Coupled PD@BP Biomimetic Periosteum Promotes Bone Regeneration through Sensory Nerve via Fanconi Anemia Signaling Pathway

To treat bone defects, repairing the nerve-rich periosteum is critical for repairing the local electric field. In this study, an endogenous electric field is coupled with 2D black phosphorus electroactive periosteum to explore its role in promoting bone regeneration through nerves. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to characterize the electrically active biomimetic periosteum. Here, the in vitro effects exerted by the electrically active periosteum on the transformation of Schwann cells into the repair phenotype, axon initial segment (AIS) and dense core vesicle (DCV) of sensory neurons, and bone marrow mesenchymal stem cells are assessed using SEM, immunofluorescence, RNA-sequencing, and calcium ion probes. The electrically active periosteum stimulates Schwann cells into a neuroprotective phenotype via the Fanconi anemia pathway, enhances the AIS effect of sensory neurons, regulates DCV transport, and releases neurotransmitters, promoting the osteogenic transformation of bone marrow mesenchymal stem cells. Microcomputed tomography and other in vivo techniques are used to study the effects of the electrically active periosteum on bone regeneration. The results show that the electrically active periosteum promotes nerve-induced osteogenic repair, providing a potential clinical strategy for bone regeneration.

Skeletal Muscle's Role in Prenatal Inter-organ Communication: A Phenogenomic Study with Qualitative Citation Analysis

Gene targeting in mice allows for a complete elimination of skeletal (striated or voluntary) musculature in the body, from the beginning of its development, resulting in our ability to study the consequences of this ablation on other organs. Here I focus on the relationship between the muscle and lung, motor neurons, skeleton, and special senses. Since the inception of my independent laboratory, in 2000, with my team, we published more than 30 papers (and a book chapter), nearly 400 pages of data, on these specific relationships. Here I trace, using Web of Science, nearly 600 citations of this work, to understand its impact. The current report contains a summary of our work and its impact, NCBI's Gene Expression Omnibus accession numbers of all our microarray data, and three clear future directions doable by anyone using our publicly available data. Together, this effort furthers our understanding of inter-organ communication during prenatal development.

ED-71 Prevents Glucocorticoid-Induced Osteoporosis by Regulating Osteoblast Differentiation via Notch and Wnt/β-Catenin Pathways

PURPOSE

Long-term glucocorticoid- usage can lead to glucocorticoid-induced osteoporosis (GIOP). The study focused on the preventative effects of a novel active vitamin D3 analog, eldecalcitol (ED-71), against GIOP and explored the underlying molecular mechanisms.

METHODS

Intraperitoneal injection of methylprednisolone (MPED) or dexamethasone (DEX) induced the GIOP model within C57BL/6 mice in vivo. Simultaneously, ED-71 was orally supplemented. Bone histological alterations, microstructure parameters, novel bone formation rates, and osteogenic factor changes were evaluated by hematoxylin-eosin (HE) staining, micro-computed tomography, calcein/tetracycline labeling, and immunohistochemical (IHC) staining. The osteogenic differentiation level and mineralization in pre-osteoblast MC3T3-E1 cells were evaluated in vitro using alkaline phosphatase (ALP) staining, alizarin red (AR) staining, quantitative polymerase chain reaction (qPCR), Western blotting, and immunofluorescence staining.

RESULTS

ED-71 partially prevented bone mass reduction and microstructure parameter alterations among GIOP-induced mice. Moreover, ED-71 also promoted new bone formation and osteoblast activity while inhibiting osteoclasts. In vitro, ED-71 promoted osteogenic differentiation and mineralization in DEX-treated MC3T3-E1 cells and boosted the levels of osteogenic-related factors. Additionally, GSK3-β and β-catenin expression levels were elevated after ED-71 was added to cells and were accompanied by reduced Notch expression. The Wnt signaling inhibitor XAV939 and Notch overexpression reversed the ED-71 promotional effects toward osteogenic differentiation and mineralization.

CONCLUSION

ED-71 prevented GIOP by enhancing osteogenic differentiation through Notch and Wnt/GSK-3β/β-catenin signaling. The results provide a novel translational direction for the clinical application of ED-71 against GIOP.

Connexin 43 Channels in Osteocytes Are Necessary for Bone Mass and Skeletal Muscle Function in Aged Male Mice

Osteoporosis and sarcopenia (termed "Osteosarcopenia"), the twin-aging diseases, are major contributors to reduced bone mass and muscle weakness in the elderly population. Connexin 43 (Cx43) in osteocytes has been previously reported to play vital roles in bone homeostasis and muscle function in mature mice. The Cx43-formed gap junctions (GJs) and hemichannels (HCs) in osteocytes are important portals for the exchange of small molecules in cell-to-cell and cell-to-extracellular matrix, respectively. However, the roles of Cx43-based GJs and HCs in both bone and muscle aging are still unclear. Here, we used two transgenic mouse models with overexpression of the dominant negative Cx43 mutants primarily in osteocytes driven by the 10-kb Dmp1 promoter, R76W mice (inhibited gap junctions but enhanced hemichannels) and Δ130-136 mice (both gap junction and hemichannels are inhibited), to determine the actions of Cx43-based hemichannels (HCs) and gap junctions (GJs) in the regulation of bone and skeletal muscle from aged mice (18 months) as compared with those from adult mice (10 months). We demonstrated that enhancement of Cx43 HCs reduces bone mass due to increased osteoclast surfaces while the impairment of Cx43 HCs increases osteocyte apoptosis in aged mice caused by reduced PGE2 levels. Furthermore, altered mitochondrial homeostasis with reduced expression of Sirt-1, OPA-1, and Drp-1 resulted in excessive ROS level in muscle soleus (SL) of aged transgenic mice. In vitro, the impairment of Cx43 HCs in osteocytes from aged mice also promoted muscle collagen synthesis through activation of TGFβ/smad2/3 signaling because of reduced PGE2 levels in the PO CM. These findings indicate that the enhancement of Cx43 HCs while GJs are inhibited reduces bone mass, and the impairment of Cx43 HCs inhibits PGE2 level in osteocytes and this reduction promotes muscle collagen synthesis in skeletal muscle through activation of TGFβ/smad2/3 signaling, which together with increased ROS level contributes to reduced muscle force in aged mice.

Exercise and Exercise Mimetics for the Treatment of Musculoskeletal Disorders

PURPOSE OF REVIEW

The incidence of musculoskeletal disorders affecting bones, joints, and muscles is dramatically increasing in parallel with the increased longevity of the worldwide population, severely impacting on the individual's quality of life and on the healthcare costs. Inactivity and sedentary lifestyle are nowadays considered the main drivers of age-associated musculoskeletal disorders and exercise may counteract such alterations also in other bone- and muscle-centered disorders. This review aims at clarifying the potential use of exercise training to improve musculoskeletal health.

RECENT FINDINGS

Both the skeletal muscle and the bone are involved in a complex crosstalk determining, in part through tissue-specific and inflammatory/immune released factors, the occurrence of musculoskeletal disorders. Exercise is able to modulate the levels of those molecules and several associated molecular pathways. Evidence from preclinical and clinical trials supports the adoption of exercise and the future use of exercise mimicking drugs will optimize the care of individuals with musculoskeletal disorders.

Intramuscular injection of sotagliflozin promotes neovascularization in diabetic mice through enhancing skeletal muscle cells paracrine function

Diabetes mellitus is associated with series of macrovascular and microvascular pathological changes that cause a wide range of complications. Diabetic patients are highly susceptible to hindlimb ischemia (HLI), which remains incurable. Evidence shows that skeletal muscle cells secrete a number of angiogenic factors to promote neovascularization and restore blood perfusion, this paracrine function is crucial for therapeutic angiogenesis in diabetic HLI. In this study we investigated whether sotagliflozin, an anti-hyperglycemia SGLT2 inhibitor, exerted therapeutic angiogenesis effects in diabetic HLI in vitro and in vivo. In C2C12 skeletal muscle cells, we showed that high glucose (HG, 25 mM) under hypoxia markedly inhibited cell viability, proliferation and migration potentials, which were dose-dependently reversed by pretreatment with sotagliflozin (5-20 μM). Sotagliflozin pretreatment enhanced expression levels of angiogenic factors HIF-1α, VEGF-A and PDGF-BB in HG-treated C2C12 cells under hypoxia as well as secreted amounts of VEGF-A and PDGF-BB in the medium; pretreatment with the HIF-1α inhibitor 2-methoxyestradiol (2-ME2, 10 μM) or HIF-1α knockdown abrogated sotagliflozin-induced increases in VEGF-A and PDGF-BB expression, as well as sotagliflozin-stimulated cell proliferation and migration potentials. Furthermore, the conditioned media from sotagliflozin-treated C2C12 cells in HG medium enhanced the migration and proliferation capabilities of vascular endothelial and smooth muscle cells, two types of cells necessary for forming functional blood vessels. In vivo study was conducted in diabetic mice subjected to excising the femoral artery of the left limb. After the surgery, sotagliflozin (10 mg/kg) was directly injected into gastrocnemius muscle of the left hindlimb once every 3 days for 3 weeks. We showed that intramuscular injection of sotagliflozin effectively promoted the formation of functional blood vessels, leading to significant recovery of blood perfusion in diabetic HLI mice. Together, our results highlight a new indication of SGLT2 inhibitor sotagliflozin as a potential therapeutic angiogenesis agent for diabetic HLI.

Skeletal stem cells: a game changer of skeletal biology and regenerative medicine?

Skeletal stem cells (SSCs) were originally discovered in the bone marrow stroma. They are capable of self-renewal and multilineage differentiation into osteoblasts, chondrocytes, adipocytes, and stromal cells. Importantly, these bone marrow SSCs localize in the perivascular region and highly express hematopoietic growth factors to create the hematopoietic stem cell (HSC) niche. Thus, bone marrow SSCs play pivotal roles in orchestrating osteogenesis and hematopoiesis. Besides the bone marrow, recent studies have uncovered diverse SSC populations in the growth plate, perichondrium, periosteum, and calvarial suture at different developmental stages, which exhibit distinct differentiation potential under homeostatic and stress conditions. Therefore, the current consensus is that a panel of region-specific SSCs collaborate to regulate skeletal development, maintenance, and regeneration. Here, we will summarize recent advances of SSCs in long bones and calvaria, with a special emphasis on the evolving concept and methodology in the field. We will also look into the future of this fascinating research area that may ultimately lead to effective treatment of skeletal disorders.

Interaction between the nervous and skeletal systems

The skeleton is one of the largest organ systems in the body and is richly innervated by the network of nerves. Peripheral nerves in the skeleton include sensory and sympathetic nerves. Crosstalk between bones and nerves is a hot topic of current research, yet it is not well understood. In this review, we will explore the role of nerves in bone repair and remodeling, as well as summarize the molecular mechanisms by which neurotransmitters regulate osteogenic differentiation. Furthermore, we discuss the skeleton’s role as an endocrine organ that regulates the innervation and function of nerves by secreting bone-derived factors. An understanding of the interactions between nerves and bone can help to prevent and treat bone diseases caused by abnormal innervation or nerve function, develop new strategies for clinical bone regeneration, and improve patient outcomes.

Crosstalk between bone and other organs

Bone has long been considered as a silent organ that provides a reservoir of calcium and phosphorus, traditionally. Recently, further study of bone has revealed additional functions as an endocrine organ connecting systemic organs of the whole body. Communication between bone and other organs participates in most physiological and pathological events and is responsible for the maintenance of homeostasis. Here, we present an overview of the crosstalk between bone and other organs. Furthermore, we describe the factors mediating the crosstalk and review the mechanisms in the development of potential associated diseases. These connections shed new light on the pathogenesis of systemic diseases and provide novel potential targets for the treatment of systemic diseases.

Effect of active vitamin D treatment on development of type 2 diabetes: DPVD randomised controlled trial in Japanese population

OBJECTIVE

To assess whether eldecalcitol, an active vitamin D analogue², can reduce the development of type 2 diabetes among adults with impaired glucose tolerance.

DESIGN

Double blinded, multicentre, randomised, placebo controlled trial.

SETTING

Three hospitals in Japan, between June 2013 and August 2019.

PARTICIPANTS

People aged 30 years and older who had impaired glucose tolerance defined by using a 75 g oral glucose tolerance test and glycated haemoglobin level.

INTERVENTIONS

Participants were randomised to receive active vitamin D (eldecalcitol 0.75 μg per day; n=630) or matching placebo (n=626) for three years.

MAIN OUTCOMES

The primary endpoint was incidence of diabetes. Prespecified secondary endpoints were regression to normoglycaemia and incidence of type 2 diabetes after adjustment for confounding factors at baseline. In addition, bone densities and bone and glucose metabolism markers were assessed.

RESULTS

Of the 1256 participants, 571 (45.5%) were women and 742 (59.1%) had a family history of type 2 diabetes. The mean age of participants was 61.3 years. The mean serum 25-hydroxyvitamin D concentration at baseline was 20.9 ng/mL (52.2 nmol/L); 548 (43.6%) participants had concentrations below 20 ng/mL (50 nmol/L). During a median follow-up of 2.9 years, 79 (12.5%) of 630 participants in the eldecalcitol group and 89 (14.2%) of 626 in the placebo group developed type 2 diabetes (hazard ratio 0.87, 95% confidence interval 0.67 to 1.17; P=0.39). Regression to normoglycaemia was achieved in 145 (23.0%) of 630 participants in the eldecalcitol group and 126 (20.1%) of 626 in the placebo group (hazard ratio 1.15, 0.93 to 1.41; P=0.21). After adjustment for confounding factors by multivariable fractional polynomial Cox regression analysis, eldecalcitol significantly lowered the development of diabetes (hazard ratio 0.69, 0.51 to 0.95; P=0.020). In addition, eldecalcitol showed its beneficial effect among the participants with the lower level of basal insulin secretion (hazard ratio 0.41, 0.23 to 0.71; P=0.001). During follow-up, bone mineral densities of the lumbar spine and femoral neck and serum osteocalcin concentrations significantly increased with eldecalcitol compared with placebo (all P<0.001). No significant difference in serious adverse events was observed.

CONCLUSIONS

Although treatment with eldecalcitol did not significantly reduce the incidence of diabetes among people with pre-diabetes, the results suggested the potential for a beneficial effect of eldecalcitol on people with insufficient insulin secretion.

TRIAL REGISTRATION

UMIN Clinical Trials Registry UMIN000010758.

Growth differentiation factor 11 induces skeletal muscle atrophy via a STAT3-dependent mechanism in pulmonary arterial hypertension

Skeletal muscle wasting is a clinically remarkable phenotypic feature of pulmonary arterial hypertension (PAH) that increases the risk of mortality. Growth differentiation factor 11 (GDF11), centrally involved in PAH pathogenesis, has an inhibitory effect on skeletal muscle growth in other conditions. However, whether GDF11 is involved in the pathogenesis of skeletal muscle wasting in PAH remains unknown. We showed that serum GDF11 levels in patients were increased following PAH. Skeletal muscle wasting in the MCT-treated PAH model is accompanied by an increase in circulating GDF11 levels and local catabolic markers (Fbx32, Trim63, Foxo1, and protease activity). In vitro GDF11 activated phosphorylation of STAT3. Antagonizing STAT3, with Stattic, in vitro and in vivo, could partially reverse proteolytic pathways including STAT3/socs3 and iNOS/NO in GDF11-meditated muscle wasting. Our findings demonstrate that GDF11 contributes to muscle wasting and the inhibition of its downstream molecule STAT3 shows promise as a therapeutic intervention by which muscle atrophy may be directly prevented in PAH.

Extracellular vesicle-mediated bidirectional communication between heart and other organs

In recent years, a wealth of studies has identified various molecular species released by cardiac muscle under physiological and pathological conditions that exert local paracrine and/or remote endocrine effects. Conversely, humoral factors, principally produced by organs such as skeletal muscle, kidney, or adipose tissue, may affect the function and metabolism of normal and diseased hearts. Although this cross communication within cardiac tissue and between the heart and other organs is supported by mounting evidence, research on the role of molecular mediators carried by exosomes, microvesicles, and apoptotic bodies, collectively defined as extracellular vesicles (EVs), is at an early stage of investigation. Once released in the circulation, EVs can potentially reach any organ where they transfer their cargo of proteins, lipids, and nucleic acids that exert potent biological effects on recipient cells. Although there are a few cases where such signaling was clearly demonstrated, the results from many other studies can only be tentatively inferred based on indirect evidence obtained by infusing exogenous EVs in experimental animals or by adding them to cell cultures. This area of research is in rapid expansion and most mechanistic interpretations may change in the near future; hence, the present review on the role played by EV-carried mediators in the two-way communication between heart and skeletal muscle, kidneys, bone marrow, lungs, liver, adipose tissue, and brain is necessarily limited. Nonetheless, the available data are already unveiling new, intriguing, and ample scenarios in cardiac physiology and pathophysiology.

Osteocalcin Alleviates Lipopolysaccharide-Induced Acute Inflammation via Activation of GPR37 in Macrophages

The G protein-coupled receptor 37 (GPR37) has been reported to be expressed in macrophages and the activation of GPR37 by its ligand/agonist, and it can regulate macrophage-associated functions and inflammatory responses. Since our previous work identified that osteocalcin (OCN) acts as an endogenous ligand for GPR37 and can elicit various intracellular signals by interacting with GPR37, we thus hypothesized that OCN may also play a functional role in macrophage through the activation of GPR37. To verify the hypothesis, we conducted a series of in vivo and in vitro studies in lipopolysaccharide (LPS)-challenged mice and primary cultured macrophages. Our results reveal that the OCN gene deletion (OCN−/−) and wild type (WT) mice showed comparable death rates and inflammatory cytokines productions in response to a lethal dose of LPS exposure. However, the detrimental effects caused by LPS were significantly ameliorated by exogenous OCN treatments in both WT and OCN−/− mice. Notably, the protective effects of OCN were absent in GPR37−/− mice. In coordination with the in vivo results, our in vitro studies further illustrated that OCN triggered intracellular responses via GPR37 in peritoneal macrophages by regulating the release of inflammatory factors and macrophage phagocytic function. Finally, we exhibited that the adoptive transfer of OCN-treated macrophages from WT mice significantly inhibits the release of pro-inflammatory cytokines in GPR37−/− mice exposed to LPS. Taken together, these findings suggest a protective role of OCN against LPS-caused acute inflammation, by the activation of GPR37 in macrophages, and provide a potential application of the activation of the OCN/GPR37 regulatory axis as a therapeutic strategy for inflammatory diseases.

Research Status of the Orphan G Protein Coupled Receptor 158 and Future Perspectives

G-protein-coupled receptors (GPCRs) remain one of the most successful targets for therapeutic drugs approved by the US Food and Drug Administration (FDA). Many novel orphan GPCRs have been identified by human genome sequencing and considered as putative targets for refractory diseases. Of note, a series of studies have been carried out involving GPCR 158 (or GPR158) since its identification in 2005, predominantly focusing on the characterization of its roles in the progression of cancer and mental illness. However, advances towards an in-depth understanding of the biological mechanism(s) involved for clinical application of GPR158 are lacking. In this paper, we clarify the origin of the GPR158 evolution in different species and summarize the relationship between GPR158 and different diseases towards potential drug target identification, through an analysis of the sequences and substructures of GPR158. Further, we discuss how recent studies set about unraveling the fundamental features and principles, followed by future perspectives and thoughts, which may lead to prospective therapies involving GPR158.

Deadenylase-dependent mRNA decay of GDF15 and FGF21 orchestrates food intake and energy expenditure

Hepatokines, secretory proteins from the liver, mediate inter-organ communication to maintain a metabolic balance between food intake and energy expenditure. However, molecular mechanisms by which hepatokine levels are rapidly adjusted following stimuli are largely unknown. Here, we unravel how CNOT6L deadenylase switches off hepatokine expression after responding to stimuli (e.g., exercise and food) to orchestrate energy intake and expenditure. Mechanistically, CNOT6L inhibition stabilizes hepatic Gdf15 and Fgf21 mRNAs, increasing corresponding serum protein levels. The resulting upregulation of GDF15 stimulates the hindbrain to suppress appetite, while increased FGF21 affects the liver and adipose tissues to induce energy expenditure and lipid consumption. Despite the potential of hepatokines to treat metabolic disorders, their administration therapies have been challenging. Using small-molecule screening, we identified a CNOT6L inhibitor enhancing GDF15 and FGF21 hepatokine levels, which dramatically improves diet-induced metabolic syndrome. Our discovery, therefore, lays the foundation for an unprecedented strategy to treat metabolic syndrome.

Association of decreased muscle mass with reduced bone mineral density in patients with Graves' disease

AIM

This study aimed to determine the association of decreased muscle mass with reduced bone mineral density in patients with Graves' disease.

METHODS

A total of 758 patients with Graves' disease at diagnosis (mean age 41.2 years) were enrolled for a cross-sectional study; of these, 287 were enrolled for a cohort study with a median follow-up of 24 months. Meanwhile, 1164 age- and sex-matched healthy controls were recruited. All participants underwent dual-energy x-ray absorptiometry and muscle mass index (ASMI) measurements. The changes in ASMI and bone mineral density (BMD) were calculated from the measurements made at a gap of 2 years.

RESULTS

The BMD of patients with Graves' disease was still significantly lower after normalizing serum thyroid hormone levels compared with that of healthy controls. ASMI positively correlated with BMD in patients with Graves' disease (lumbar BMD, r = 0.210; femoral neck BMD, r = 0.259; hip BMD, r = 0.235; P < 0.001), and this relationship persisted after successful anti-thyroid therapy (lumbar BMD, r = 0.169; femoral neck BMD, r = 0.281; hip BMD, r = 0.394; P < 0.001). Low muscle mass was associated with low BMD (OR, 1.436; 95% CI, 1.026-2.010). Improving the muscle mass led to changes in the bone mass of the femoral neck (OR, 0.420; 95% CI, 0.194-0.911) and hip (OR, 0.217; 95% CI, 0.092-0.511) during the follow-up. However, this phenomenon was not observed in lumbar and bone turnover markers.

CONCLUSIONS

The recovery of bone mass might be related to the recovery of the muscle mass. Patients with Graves' disease should be helped to regain their muscle mass and thus accelerate the recovery of bone mass while administering anti-thyroid therapy.

The role of polypeptide PDTLN1 in suppression of PI3K/AKT signaling causes cardiogenetic disorders in vitro and in vivo

AIMS

A new polypeptide, PDTLN1, derived from the human Talin-1 protein, which is highly expressed in both myocardial tissue and maternal peripheral blood of aborted fetuses with congenital heart disease (CHD). However, its role in cardiac developmental disorders has not been disclosed till now. In the present study, we aim to assess the functions of PDTLN1 in heart development of zebrafish and cellular viability, proliferation, and apoptosis of P19 cells.

MAIN METHODS

Cellular viability was assessed by Cell Counting Kit-8, the EdU Kit was used to evaluate cellular proliferation, and apoptosic rate of P19 was examined using FITC Annexin-V staining followed by flow cytometry. The zebrafish embryos were divided into three groups: PEP group and NC group were microinjected with polypeptides, WT group without any intervention. The protein expression of PI3K/AKT were evaluated by western blotting.

KEY FINDINGS

PDTLN1 could suppress the proliferation, and facilitate apoptosis. PDTLN1 caused abnormal heart development of zebrafish embryos and the PDTLN1 (50 μM)-injected group showed an aberrant expression pattern of vmhc, amhc and cmlc2. Compared to the CTL group and SC79 group of P19 cells, the PDTLN1 group had a lower phosphorylated PI3K/AKT proteins level, decreased cellular viability and lower proliferation activity.

SIGNIFICANCE

PDTLN1 caused cardiac developmental defects in zebrafish, inhibited cellular viability, proliferation, and promoted apoptosis of P19 cells via suppressing the PI3K/AKT signaling pathway. Our findings provide a fresh perspective on the functional mechanism of human-derived peptides and may promote novel diagnostic biomarkers detection and therapeutic targets in CHD.