Gpr158 mediates osteocalcin's regulation of cognition

BBPs-functionalized tetrahedral framework nucleic acid hydrogel scaffold captures endogenous BMP-2 to promote bone regeneration

Bone Morphogenetic Protein-2 (BMP-2) is a key growth factor for inducing osteogenic differentiation and promoting bone remodeling. However, the exogenous application of delivery systems for BMP-2 has been hampered by various postoperative complications, poor stability and high price. Hence, in situ enrichment of endogenous BMP-2 is promising. The discovery of a small molecule BMP-2 binding peptide (BBP) that binds specifically to BMP-2 with high affinity lays the foundation for the construction of bioactive materials that capture endogenous BMP-2. In contrast, conventional enrichment strategies have low binding efficiency due to steric hindrance caused by the disordered arrangement of BBPs. Tetrahedral framework nucleic acid (tFNA) exhibits good editability and unique three-dimensional spatial structure that enables topological control of multivalent ligands in spatial distribution. The BBPs are further designed to be stably modified on tFNA (BBPs-tFNA) via click chemistry of the azide-alkyne addition to achieve the orderly arrangement of BBPs in spatial organization, to improve the binding efficiency of BMP-2. Therefore, in this study, BBPs-tFNA is modified on biocompatible hyaluronic acid methacryloyl (HAMA) to construct the functionalized bioactive composite hydrogel scaffolds, with the aim of achieving precise and efficient capture of endogenous BMP-2, stimulating osteogenic differentiation and promoting in situ osteogenesis for bone defect repair.

Relationships among osteoporosis, redox homeostasis, and alcohol addiction: Importance of the brain-bone axis

Overabundance of reactive oxygen species (oxidative distress) leads to redox homeostasis disturbance and is associated with many pathological conditions. Accumulating evidence suggests that oxidative distress may contribute to osteoporosis. This review thoroughly outlines the relationships among osteoporosis, redox homeostasis, and alcohol addiction, since these relations are not sufficiently known and subsequently summarized. The brain-bone axis plays a crucial role in alcohol-induced damage to the nervous and skeletal systems. Alterations in the nervous system can lead to osteoporosis because the central nervous system is involved in bone remodeling through various neural pathways. Conversely, as an endocrine organ, bone secretes a number of bone-derived factors (osteokines), which can influence brain function and behavior. As a result, osteoporosis is more common in individuals with neurological disorders, and sudden neurological events can rapidly increase the risk of osteoporosis. Excessive alcohol consumption is linked to many neurological complications, as well as osteoporosis, which are manifested by disrupted redox homeostasis, inflammation, neurodegeneration, inhibition of neurogenesis, decreased bone mineral density, impaired bone microarchitecture, altered mineral homeostasis, raising fracture risk, hormonal dysregulation, and altered gut microbiota composition. Compared to men, alcohol dependence has more negative consequences for women, including an increased risk of liver, cardiovascular, metabolic, mental disorders, and breast cancer. Abstinence has been demonstrated to improve bone and brain health in alcohol addiction. The discovery of the brain-bone axis may lead to the development of new therapeutic approaches for alcohol and other substance addictions. Further research is needed in this direction, as many questions remain unanswered.

Beyond the Brain: Exploring the multi-organ axes in Parkinson's disease pathogenesis

BACKGROUND

Parkinson's Disease (PD), a complex neurodegenerative disorder, is increasingly recognized as a systemic condition involving multi-organ interactions. Emerging evidence highlights roles of organ-brain axes (lung-, liver-, heart-, muscle-, bone-, and gut-brain) in PD pathogenesis. These axes communicate via neural, circulatory, endocrine, and inflammatory pathways, collectively driving neurodegeneration. For example, lung dysfunction in PD involves respiratory impairment and inflammatory signaling, while gut dysbiosis triggers α-synuclein aggregation via the vagus nerve. Such cross-organ interactions underscore PD's systemic nature, challenging traditional brain-centric models.

AIM OF REVIEW

1. Decipher mechanisms linking peripheral organs (e.g., lung, gut) to PD via shared pathways. 2. Explore bidirectional organ-brain interactions (e.g., liver metabolism affecting neurotoxin clearance). 3. Propose multi-organ therapeutic strategies targeting integrated signaling networks. Key Scientific Concepts of Review. 1. Lung-Brain Axis: Respiratory dysfunction (motor impairment, inflammation) exacerbates neurodegeneration. 2. Liver-Brain Axis: Metabolic dysregulation alters neurotoxin clearance; drugs (e.g., levodopa) impact liver function. 3. Heart-Brain Axis: Autonomic dysfunction reduces cerebral blood flow; neuroendocrine changes promote α-synuclein pathology. 4. Muscle-Brain Axis: Neuromuscular/metabolic disruptions worsen motor symptoms. 5. Bone-Brain Axis: Bone-derived hormones (osteocalcin, OCN) and inflammation influence cognition. 6. Gut-Brain Axis: Dysbiosis drives α-synuclein misfolding; gut metabolites modulate neuroinflammation. Integrated Mechanisms: Shared pathways (neuroinflammation, oxidative stress) create a regulatory network, suggesting therapies targeting multi-organ crosstalk (e.g., probiotics, anti-inflammatory agents).

A postsynaptic GPR158-PLCXD2 complex controls spine apparatus abundance and dendritic spine maturation

The spine apparatus (SA), an endoplasmic reticulum (ER)-related organelle present in a subset of dendritic spines, plays a key role in postsynaptic development and is implicated in various neurological disorders. The molecular mechanisms that dictate SA localization at selected synapses remain elusive. Here, we identify a postsynaptic signaling complex comprising the G protein-coupled receptor (GPCR)- GPR158 and a constitutively active phospholipase C (PLC) family member, PLC X-domain containing 2 (PLCXD2), that controls SA abundance. Sparse genetic manipulations of mouse cortical neurons in vivo demonstrate that, in the absence of GPR158, unrestrained PLCXD2 activity impedes postsynaptic SA incorporation and hampers structural and functional dendritic spine maturation. Extracellular heparan sulfate proteoglycan (HSPG) binding modulates the GPR158-PLCXD2 interaction, providing spatiotemporal control over GPR158 signaling. Together, our findings uncover a direct GPCR-like receptor-to-PLC signaling pathway that bypasses canonical PLC regulation via G proteins. This GPR158-PLCXD2 module regulates SA abundance, essential for proper postsynaptic structure and function.

Circulatory factors in stroke protection and recovery

Over the past decade, the management of acute ischemic stroke has undergone a paradigm shift, especially a longer time-window and a wider indication for endovascular treatments. However, many patients still have long-term dysfunction despite the best medical care at present. Based on findings from innovative proteomic and transcriptomic technologies, researchers have identified an array of novel or previously underappreciated circulatory factors that play pivotal roles in mediating post-injuries brain communication. Thus, the previous concept of the brain as a privileged compartment isolated from the rest of the body has been replaced by the novel consensus that brain bidirectionally interacts with the other organs after brain diseases. In this review, we make a summary of several axes that connect the brain with the rest of the body after stroke. More importantly, we summarize several circulatory factors that play pivotal roles in fostering post-stroke functional recovery in the chronic stage. Special attention is given to the instrumental role of circulatory signals, positing them as significant contributors to the complex process of brain function recovery and as translational therapeutic targets for ischemic stroke in future studies.

Exploring the Link Between Vitamin K and Depression: A Systematic Review

Background and Objectives: Depression is a multifactorial mental health disorder involving inflammation, oxidative stress, neuroplasticity deficits, and metabolic dysfunction. Emerging research suggests that vitamin K, beyond its classical roles in coagulation and bone metabolism, may influence neurobiological processes relevant to mood regulation. This systematic review evaluates the association between vitamin K and depressive symptoms and explores potential underlying mechanisms. Materials and Methods: A systematic search was conducted across PubMed, Scopus, Cochrane Library, ScienceDirect, and Google Scholar, following PRISMA 2020 guidelines. Eligible studies included human or animal research examining associations between vitamin K status (dietary intake or serum levels) and depression-related outcomes. Fourteen studies met the inclusion criteria: eleven observational studies, one randomized controlled trial (RCT), and two preclinical animal studies. Results: Most observational studies reported an inverse association between vitamin K intake or serum levels and depressive symptoms across diverse populations. One small RCT demonstrated modest improvements in depression scores following vitamin K2 (menaquinone-7) supplementation in women with polycystic ovary syndrome. Two preclinical studies using non-depression models reported behavioral improvements and reduced oxidative stress following vitamin K2 administration. Conclusions: While preliminary findings suggest a potential role for vitamin K in pathways relevant to depression, the current evidence is limited by cross-sectional designs, lack of isoform-specific analyses, and the absence of depression-focused preclinical models. Mechanisms including inflammation reduction, oxidative stress modulation, sphingolipid regulation, and vitamin K-dependent protein signaling (e.g., GAS6 and osteocalcin) were discussed based on indirect evidence and require further investigation in depression-specific contexts.

Bone-derived factors mediate crosstalk between skeletal and extra-skeletal organs

Bone has long been acknowledged as a fundamental structural entity that provides support and protection to the body's organs. However, emerging research indicates that bone plays a crucial role in the regulation of systemic metabolism. This is achieved through the secretion of a variety of hormones, cytokines, metal ions, extracellular vesicles, and other proteins/peptides, collectively referred to as bone-derived factors (BDFs). BDFs act as a medium through which bones can exert targeted regulatory functions upon various organs, thereby underscoring the profound and concrete implications of bone in human physiology. Nevertheless, there remains a pressing need for further investigations to elucidate the underlying mechanisms that inform the effects of bone on other body systems. This review aims to summarize the current findings related to the roles of these significant modulators across different organs and metabolic contexts by regulating critical genes and signaling pathways in vivo. It also addresses their involvement in the pathogenesis of various diseases affecting the musculoskeletal system, circulatory system, glucose and lipid metabolism, central nervous system, urinary system, and reproductive system. The insights gained from this review may contribute to the development of innovative therapeutic strategies through a focused approach to bone secretomes. Continued research into BDFs is expected to enhance our understanding of bone as a multifunctional organ with diverse regulatory roles in human health.

Osteocalcin and GPR158: linking bone and brain function

Osteocalcin (OCN), a small protein secreted by osteoblasts, has attracted significant attention for its role as an endocrine factor in regulating the central nervous system (CNS) via the bone-brain axis. As a critical receptor for OCN, G protein-coupled receptor 158 (GPR158) facilitates the proliferation, differentiation, and survival of neural cells while directly influencing neurons' structural and functional plasticity, thereby modulating cognitive function. Additionally, GPR158 is involved in cellular energy metabolism and interacts with proteins such as regulators of G protein signaling 7 (RGS7), broadening the understanding of OCN's impact on neural activity. Notably, GPR158 displays region- and cell type-specific bidirectional effects under certain pathological conditions, such as tumor development and mood regulation, adding complexity to its mechanisms of action. Although the precise biological mechanisms underlying the OCN/GPR158 signaling pathway remain incompletely understood, its association with neurodegenerative diseases (NDs), including Alzheimer's disease (AD) and Parkinson's disease (PD), is becoming increasingly evident. Thus, a systematic summary of OCN/GPR158 in CNS regulation and NDs will deepen understanding of its role in brain function and support the development of new therapeutic targets and strategies.

Molecular dynamics of amyloid-β transport in Alzheimer's disease: Exploring therapeutic plasma exchange with albumin replacement - Current insights and future perspectives

INTRODUCTION

The complex process of amyloid-β (Aβ) transportation across the blood-brain and blood-cerebrospinal fluid barriers is crucial for preventing Aβ accumulation, which linked to dementia and neurodegeneration. This review explores therapeutic plasma exchange with albumin replacement in Alzheimer's disease, based on the dynamics of amyloid-β between the brain, plasma, and cerebrospinal fluid.

METHODOLOGY

A comprehensive literature review was conducted using PubMed/Medline, Cochrane Library, and open databases (bioRxiv, MedRixv, preprint.org) up to April 30, 2023. The first search utilized the following MeSH terms and keywords: 'Plasma Exchange', 'Plasmapheresis', 'Therapeutic plasma exchange', 'Apheresis', 'Aβ', 'p-tau', 'Total-tau', 'Alzheimer's disease', 'Cognitive dysfunction', 'neurodegenerative diseases', 'centrifugation', 'membranous', and 'filtration' in the Title/Abstract, yielding 146 results. A second search with the keywords: 'Albumin', 'Aβ', 'BBB', 'Alzheimer's dementia', and 'Nerve degeneration' resulted in 125 additional articles for analysis. Finally, a third search using keywords: 'Albumin structural domains', 'Albumin-Aβ interactions', 'Albumin-endothelial interactions', and 'Post-Translational Modification' produced 193 results for further review.

RESULTS/DISCUSSION

Therapeutic plasma exchange shows potential as a disease-modifying therapy for dementia, specifically for Alzheimer's disease. Additionally, the promising role of albumin supplementation in cognitive improvement has attracted attention. However, clinical evidence supporting therapeutic plasma exchange for dementia remains limited, necessitating further research and development to mitigate potential adverse effects. A deeper understanding of the molecular dynamics of Aβ transportation and the mechanisms of therapeutic plasma exchange is essential. A critical evaluation of existing evidence highlights the importance of balancing potential benefits with associated risks, which will guide the development and application of these treatments in neurodegenerative diseases.

Pharmacological and resting state fMRI reveal Osteocalcin's effects on mouse brain regions with high Gpr37 and Gpr158 expression

Osteocalcin (OCN) is an endocrine hormone that signals in the periphery, regulating male fertility, energy expenditure and glucose homeostasis. It can also cross the blood-brain-barrier and act on the brain via receptors GPR37 and GPR158. In the brain, OCN influences neurotransmitter synthesis of serotonin, norepinephrine, and dopamine. OCN's function is related to cognitive and memory performance and lack of OCN is associated with anxiety and depression-like behavior in mice. We used multiparametric magnetic resonance imaging (MRI) including pharmacological MRI and resting state functional MRI, along with gene expression data for Gpr37 and Gpr158 to investigate the physiological effects of intravenously administered OCN on the wild type mouse brain. We found four core brain regions (brainstem, limbic output, association cortex, and basal ganglia) that are highly relevant in all three analytical modalities (i.e. pharmacological, resting state MRI and gene expression) and play therefore a major role in mediating OCN's effect in the brain. This study provides the first imaging data of the physiological impact of OCN on the mouse brain, suggesting its potential role in modulating brain function and its relevance as a candidate for further investigation in anxiety, depression, and cognitive impairments.

Bone-brain interaction: mechanisms and potential intervention strategies of biomaterials

Following the discovery of bone as an endocrine organ with systemic influence, bone-brain interaction has emerged as a research hotspot, unveiling complex bidirectional communication between bone and brain. Studies indicate that bone and brain can influence each other's homeostasis via multiple pathways, yet there is a dearth of systematic reviews in this area. This review comprehensively examines interactions across three key areas: the influence of bone-derived factors on brain function, the effects of brain-related diseases or injuries (BRDI) on bone health, and the concept of skeletal interoception. Additionally, the review discusses innovative approaches in biomaterial design inspired by bone-brain interaction mechanisms, aiming to facilitate bone-brain interactions through materiobiological effects to aid in the treatment of neurodegenerative and bone-related diseases. Notably, the integration of artificial intelligence (AI) in biomaterial design is highlighted, showcasing AI's role in expediting the formulation of effective and targeted treatment strategies. In conclusion, this review offers vital insights into the mechanisms of bone-brain interaction and suggests advanced approaches to harness these interactions in clinical practice. These insights offer promising avenues for preventing and treating complex diseases impacting the skeleton and brain, underscoring the potential of interdisciplinary approaches in enhancing human health.

Antiageing strategy for neurodegenerative diseases: from mechanisms to clinical advances

In the context of global ageing, the prevalence of neurodegenerative diseases and dementia, such as Alzheimer's disease (AD), is increasing. However, the current symptomatic and disease-modifying therapies have achieved limited benefits for neurodegenerative diseases in clinical settings. Halting the progress of neurodegeneration and cognitive decline or even improving impaired cognition and function are the clinically meaningful goals of treatments for neurodegenerative diseases. Ageing is the primary risk factor for neurodegenerative diseases and their associated comorbidities, such as vascular pathologies, in elderly individuals. Thus, we aim to elucidate the role of ageing in neurodegenerative diseases from the perspective of a complex system, in which the brain is the core and peripheral organs and tissues form a holistic network to support brain functions. During ageing, the progressive deterioration of the structure and function of the entire body hampers its active and adaptive responses to various stimuli, thereby rendering individuals more vulnerable to neurodegenerative diseases. Consequently, we propose that the prevention and treatment of neurodegenerative diseases should be grounded in holistic antiageing and rejuvenation means complemented by interventions targeting disease-specific pathogenic events. This integrated approach is a promising strategy to effectively prevent, pause or slow down the progression of neurodegenerative diseases.

The Effects of Electrical Stimulation on a 3D Osteoblast Cell Model

Electrical stimulation has been used with tissue engineering-based models to develop three-dimensional (3D), dynamic, research models that are more physiologically relevant than static two-dimensional (2D) cultures. For bone tissue, the effect of electrical stimulation has focused on promoting healing and regeneration of tissue to prevent bone loss. However, electrical stimulation can also potentially affect mature bone parenchymal cells such as osteoblasts to guide bone formation and the secretion of paracrine or endocrine factors. Due to a lack of physiologically relevant models, these phenomena have not been studied in detail. In vitro electrical stimulation models can be useful for gaining an understanding of bone physiology and its effects on paracrine tissues under different physiological and pathological conditions. Here, we use a 3D, dynamic, in vitro model of bone to study the effects of electrical stimulation conditions on protein and gene expression of SaOS-2 human osteosarcoma osteoblast-like cells. We show that different stimulation regimens, including different frequencies, exposure times, and stimulation patterns, can have different effects on the expression and secretion of the osteoblastic markers alkaline phosphatase and osteocalcin. These results reveal that electrical stimulation can potentially be used to guide osteoblast gene and protein expression.

The Power of Exercise: Unlocking the Biological Mysteries of Peripheral-Central Crosstalk in Parkinson's Disease

BACKGROUND

Exercise is a widely recognized non-pharmacological treatment for Parkinson's Disease (PD). The bidirectional regulation between the brain and peripheral organs has emerged as a promising area of research, with the mechanisms by which exercise impacts PD closely linked to the interplay between peripheral signals and the central nervous system.

AIM OF REVIEW

This review aims to summarize the mechanisms by which exercise influences peripheral-central crosstalk to improve PD, discuss the molecular processes mediating these interactions, elucidate the pathways through which exercise may modulate PD pathophysiology, and identify directions for future research.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review examines how exercise-induced cytokine release promotes neuroprotection in PD. It discusses how exercise can stimulate cytokine secretion through various pathways, including the gut-brain, muscle-brain, liver-brain, adipose-brain, and bone-brain axes, thereby alleviating PD symptoms. Additionally, the potential contributions of the heart-brain, lung-brain, and spleen-brain axes, as well as multi-axis crosstalk-such as the brain-gut-muscle and brain-gut-bone axes-are explored in the context of exercise therapy. The study highlights the need for further research into peripheral-central crosstalk and outlines future directions to address challenges in clinical PD therapy.

A primary cilia-autophagy axis in hippocampal neurons is essential to maintain cognitive resilience

Blood-borne factors are essential to maintain neuronal synaptic plasticity and cognitive resilience throughout life. One such factor is osteocalcin (OCN), a hormone produced by osteoblasts that influences multiple physiological processes, including hippocampal neuronal homeostasis. However, the mechanism through which this blood-borne factor communicates with neurons remains unclear. Here we show the importance of a core primary cilium (PC) protein-autophagy axis in mediating the effects of OCN. We found that the OCN receptor GPR158 is present at the PC of hippocampal neurons and mediates the regulation of autophagy machinery by OCN. During aging, autophagy and PC core proteins are reduced in neurons, and restoring their levels is sufficient to improve cognitive impairments in aged mice. Mechanistically, the induction of this axis by OCN is dependent on the PC-dependent cAMP response element-binding protein signaling pathway. Altogether, this study demonstrates that the PC-autophagy axis is a gateway to mediate communication between blood-borne factors and neurons, and it advances understanding of the mechanisms involved in age-related cognitive decline.

Osteocalcin: may be a useful biomarker for early identification of rapidly progressive central precocious puberty in girls

OBJECTIVE

To assess serum osteocalcin (OC) as a potential biomarker for the early detection of rapidly progressive central precocious puberty (RP-CPP) in girls.

METHODS

Serum OC levels were quantified using enzyme-linked immunosorbent assays (ELISAs). In the retrospective analysis, receiver operating characteristic (ROC) curve analysis was employed to evaluate the ability of OC to identify RP-CPP. A prospective study and screening tests were utilized to assess the potential of OC for use in the early prediction of RP-CPP. Variable selection in the multivariate analysis was conducted using the Bayesian Information Criterion (BIC) and binary logistic regression was employed to construct the diagnostic prediction model.

RESULTS

Girls with RP-CPP had significantly higher serum OC levels compared to girls with non-rapidly progressive central precocious puberty (NRP-CPP) (149.04±40.50 vs. 89.10±31.83 ng/mL, P < 0.001). The optimal OC cut-off point for differentiating RP-CPP from NRP-CPP was 107.05 ng/mL, the area under the ROC curve (AUC) was 0.90 (95%CI: 0.851-0.949; P < 0.001), with a sensitivity of 91.1% and specificity of 70.7%. The results of the prospective study indicated that changes in OC precede alterations in estradiol (E2) and bone age (BA). A diagnostic prediction model that includes duration of breast development, BA, OC, high-density lipoprotein cholesterol (HDL-C), and uterine length achieved an AUC of 0.961, with a sensitivity of 94.1% and specificity of 91.5% for the detection of RP-CPP. If OC is excluded from the model, the AUC decreases to 0.894, with sensitivity and specificity declining to 80.5% and 83.1%, respectively.

CONCLUSIONS

Serum OC levels may serve as a promising biomarker for the early differentiation between RP-CPP and NRP-CPP in girls. The diagnostic prediction model that incorporates duration of breast development, BA, OC, HDL-C, and uterine length effectively identifies girls with RP-CPP.

Bone-brain communication mediates the amelioration of Polgonatum cyrtonema Hua polysaccharide on fatigue in chronic sleep-deprived mice

This study aimed to investigate the anti-fatigue efficacy and underlying mechanisms of Polygonatum cyrtonema Hua polysaccharide (PCP) in chronic sleep-deprived mice. Following three weeks of oral administration, PCP demonstrated significant efficacy in alleviating fatigue symptoms. This was evidenced by the prolonged swimming and rotarod time in the high-dose group of PCP, which increased by 73 % and 64 %, respectively. Additionally, serum activities of CAT, GSH-Px, and SOD enzymes rose by 53.56 %, 37.69 % and 53.67 %, respectively, while MDA, lactic acid and BUN levels decreased by 22.90 %, 17.48 % and 24.61 %. The crosstalk between bone and brain is crucial for maintaining energy homeostasis. Molecular docking studies indicated a spontaneous and strong mutual binding between PCP and the bone-promoting target protein BMPR1A. Furthermore, it was observed that PCP enhanced osteogenic differentiation via the BMP-2/Smad1 pathway, leading to an upregulation of osteocalcin expression, which in turn regulated neurotransmitter balance and improved central arousal capacity. Moreover, PCP treatment stimulated neurogenesis by activating the CREB/BDNF/Akt signaling cascade, exhibiting neurotrophic effects. Additionally, PCP increased AMPK phosphorylation and destabilized TXNIP, facilitating astrocyte glucose uptake, glycolysis, and lactate conversion to support neuronal activity. These findings suggested that PCP could effectively respond to energy demands through bone-brain crosstalk, ultimately exerting anti-fatigue properties.

Intranasal Insulin Diminishes Postoperative Delirium and Elevated Osteocalcin and Brain Derived Neurotrophic Factor in Older Patients Undergoing Joint Replacement: A Randomized, Double-Blind, Placebo-Controlled Trial

Background

Brain energy metabolism disorders, including glucose utilization disorders and abnormal insulin sensitivity, are linked to the pathogenesis of postoperative delirium. Intranasal insulin has shown significant benefits in improving glucose metabolism, insulin sensitivity and cognitive function. However, its impact on postoperative delirium and insulin sensitivity biomarkers remains unknown.

Aim

This randomized, double-blind, placebo-controlled trial was to evaluate whether intranasal insulin reduces the incidence and severity of postoperative delirium (POD) in older patients undergoing joint replacement, and its effect on insulin sensitivity-related biomarkers.

Methods

212 older patients (≥65 years) were randomly assigned to receive either 40 IU of intranasal insulin (n=106) or a placebo (n=106) for 8 days. The primary objective was to determine the incidence and severity of POD within 5 days after surgery, estimated using the Confusion Assessment Method (CAM) and the Delirium Rating Scale (DRS)-98. The secondary objective was insulin sensitivity, which was assessed using the homeostasis model Assessment of Insulin Resistance (HOMA-IR) and biomarkers, including total osteocalcin (tOC), uncarboxylated osteocalcin (ucOC), and brain-derived neurotrophic factor (BDNF).

Main Results

Compared to placebo, intranasal insulin significantly reduced the incidence of delirium within 5 days after surgery (8 [8.33%] vs 23 [23.23%], P = 0.004, odds ratio [OR] = 3.33 [95% CI 1.41-7.88]) and the severity of delirium (P<0.001). Intranasal insulin elevated the levels of tOC, ucOC, and BDNF in the CSF on D0 (all P<0.001) and tOC levels in the plasma on D0, D1 and D3 (all P<0.001). It elevated ucOC levels in the plasma of the insulin group on D0 but not on D1 and D3 (all P<0.001). Intranasal insulin administration reduced the HOMA-IR on D3 (P=0.002).

Conclusion

Intranasal insulin notably reduced the incidence and severity of POD in older patients undergoing joint replacement, which may be related to the elevation in osteocalcin and BDNF levels.

Trial Registry Numbers

Chinese Clinical Trial Registry (ChiCTR2300068073).

Total osteocalcin levels are independently associated with worse testicular function and a higher degree of hypothalamic-pituitary-gonadal axis activation in Klinefelter syndrome

PURPOSE

The role of osteocalcin (OCN) in pubertal development, male hypogonadism, and the effect of testosterone (Te) replacement therapy (TRT) remains unclear. We aimed to investigate the total OCN (tOCN) concentrations in male patients with Klinefelter syndrome (KS), a model of adult hypergonadotropic hypogonadism.

METHODS

This retrospective longitudinal study investigated 254 male patients with KS (47,XXY) between 2007 and 2021 at an academic referral center, categorized as (1) prepubertal, (2) pubertal, and (3) adults. All prepubertal patients were Te-naïve. Adult patients were subcategorized as (1) eugonadal, (2) hypogonadal, and (3) receiving TRT. We also analyzed 18 adult patients with available tOCN levels before and 3 months after TRT commencement.

RESULTS

The tOCN levels varied throughout the lifespan according to pubertal status, were highest in eugonadal and significantly lower in TRT subjects, correlated with both LH (p = 0.017) and FSH levels (p = 0.004) in adults, and significantly declined after 3 months of TRT (p = 0.006) in the adult KS cohort. HPG-axis hormones levels demonstrated no correlation in prepubertal boys. Adjustment for age and body mass index confirmed previous results and revealed significant inverse correlations with total Te (p = 0.004), calculated free Te (p = 0.016), the Te/LH (p = 0.010), and calculated free Te/LH ratios (p = 0.031).

CONCLUSION

In KS, a model of male hypergonadotropic hypogonadism, tOCN levels were not associated with gonadal function during normal prepuberty and pubertal development but were associated with worse testicular function and a higher degree of HPG stimulation in adults. TRT acutely reduced tOCN levels in adults.

Lipoteichoic Acid Rescued Age-Related Bone Loss by Enhancing Neuroendocrine and Growth Hormone Secretion Through TLR2/COX2/PGE2 Signalling Pathway

The phenomenon of brain-bone crosstalk pertains to the intricate interaction and communication pathways between the central nervous system and the skeletal system. Disruption in brain-bone crosstalk, particularly in disorders such as osteoporosis, can result in skeletal irregularities. Consequently, investigating and comprehending this communication network holds paramount importance in the realm of bone disease prevention and management. In this study, we found that Staphylococcus aureus lipoteichoic acid promoted the conversion of arachidonic acid to PGE2 by interacting with TLR2 receptors acting on the surface of microglial cells in the pituitary gland, leading to the upregulation of COX-2 expression. Subsequently, PGE2 bound to the EP4 receptor of growth hormone-secreting cells and activated the intracellular CREB signalling pathway, promoting GH secretion and ameliorating age-related bone loss.

Blood-derived factors to brain communication in brain diseases

Brain diseases, mainly including acute brain injuries, neurodegenerative diseases, and mental disorders, have posed a significant threat to human health worldwide. Due to the limited regenerative capability and the existence of the blood-brain barrier, the brain was previously thought to be separated from the rest of the body. Currently, various cross-talks between the central nervous system and peripheral organs have been widely described, including the brain-gut axis, the brain-liver axis, the brain-skeletal muscle axis, and the brain-bone axis. Moreover, several lines of evidence indicate that leveraging systemic biology intervention approaches, including but not limited to lifestyle interventions, exercise, diet, blood administration, and peripheral immune responses, have demonstrated a significant influence on the progress and prognosis of brain diseases. The advancement of innovative proteomic and transcriptomic technologies has enriched our understanding of the nuanced interplay between peripheral organs and brain diseases. An array of novel or previously underappreciated blood-derived factors have been identified to play pivotal roles in mediating these communications. In this review, we provide a comprehensive summary of blood-to-brain communication following brain diseases. Special attention is given to the instrumental role of blood-derived signals, positing them as significant contributors to the complex process of brain diseases. The insights presented here aim to bridge the current knowledge gaps and inspire novel therapeutic strategies for brain diseases.

Molecular and Cellular Foundations of Aging of the Brain: Anti-aging Strategies in Alzheimer's Disease

Alzheimer's disease (AD) is a condition characterized by the gradual degeneration of the nervous system that poses significant challenges to cognitive function and overall mental health. Given the increasing global life expectancy, there is an urgent need for effective strategies to prevent and manage Alzheimer's disease, with a particular focus on anti-aging interventions. Recent scientific advancements have unveiled several promising strategies for combating Alzheimer's disease (AD), ranging from lifestyle interventions to cutting-edge pharmacological treatments and therapies targeting the underlying biological processes of aging and AD. Regular physical exercise, cognitive engagement, a balanced diet, and social interaction serve as key pillars in maintaining brain health. At the same time, therapies target key pathological mechanisms of AD, such as amyloid-beta accumulation, tau abnormalities, neuroinflammation, mitochondrial dysfunction, and synaptic loss, offering potential breakthroughs in treatment. Moreover, cutting-edge innovations such as gene therapy, stem cell transplantation, and novel drug delivery systems are emerging as potential game-changers in the fight against AD. This review critically evaluates the latest research on anti-aging interventions and their potential in preventing and treating Alzheimer's disease (AD) by exploring the connections between aging mechanisms and AD pathogenesis. It provides a comprehensive analysis of both well-established and emerging strategies, while also identifying key gaps in current knowledge to guide future research efforts.

GPR37 and its neuroprotective mechanisms: bridging osteocalcin signaling and brain function

Osteocalcin (OCN) is a hormone secreted by osteoblasts and has attracted widespread attention for its role in regulating brain function. Clinical studies indicate a positive correlation between levels of circulating OCN and cognitive performance. Indeed, lower circulating OCN has been detected in various neurodegenerative diseases (NDs), while OCN supplementation under certain conditions may improve cognitive function. GPR37, a G protein-coupled receptor, has recently been identified as a receptor for OCN. It exhibits distinct expression patterns across various brain regions and cell types, potentially influencing its functional roles within the brain. Research indicates that GPR37 regulates neuronal migration, cell proliferation, differentiation, and myelination. Furthermore, GPR37 has been shown to mitigate inflammation and apoptosis through various mechanisms, exerting neuroprotective effects. However, its regulatory influence on brain function exhibits inconsistency, highlighting a duality in its actions. Therefore, this review thoroughly summarizes the roles and mechanisms of GPR37 in modulating cellular physiological activities and its involvement in immune responses, stress reactions, and neuroprotection. It aims to enhance the understanding of how GPR37 modulates brain function and facilitate the identification of novel therapeutic targets or strategies for related diseases.

The Quest for Eternal Youth: Hallmarks of Aging and Rejuvenating Therapeutic Strategies

The impressive achievements made in the last century in extending the lifespan have led to a significant growth rate of elderly individuals in populations across the world and an exponential increase in the incidence of age-related conditions such as cardiovascular diseases, diabetes mellitus type 2, and neurodegenerative diseases. To date, geroscientists have identified 12 hallmarks of aging (genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, impaired macroautophagy, mitochondrial dysfunction, impaired nutrient sensing, cellular senescence, stem cell exhaustion, defective intercellular communication, chronic inflammation, and gut dysbiosis), intricately linked among each other, which can be targeted with senolytic or senomorphic drugs, as well as with more aggressive approaches such as cell-based therapies. To date, side effects seriously limit the use of these drugs. However, since rejuvenation is a dream of mankind, future research is expected to improve the tolerability of the available drugs and highlight novel strategies. In the meantime, the medical community, healthcare providers, and society should decide when to start these treatments and how to tailor them individually.

Effects of exercise on brain-derived neurotrophic factor in Alzheimer's disease models: A systematic review and meta-analysis

A growing body of research examining effects of exercise on brain-derived neurotrophic factor (BDNF) in Alzheimer's disease (AD) models, while due to differences in gender, age, disease severity, brain regions examined, and type of exercise intervention, findings of available studies were conflicting. In this study, we aimed to evaluate current evidence regarding effects of exercise on BDNF in AD models. Searches were performed in PubMed, Web of Science, Cochrane, and EBSCO electronic databases, through July 20, 2023. We included studies that satisfied the following criteria: eligible studies should (1) report evidence on experimental work with AD models; (2) include an exercise group and a control group (sedentary); (3) use BDNF as the outcome indicator; and (4) be randomized controlled trials (RCTs). From 1196 search records initially identified, 36 studies met the inclusion criteria. There was a significant effect of exercise on increasing BDNF levels in AD models [standardized mean differences (SMD) = 0.98, P < 0.00001]. Subgroup analysis showed that treadmill exercise (SMD = 0.92, P< 0.0001), swimming (SMD = 1.79, P< 0.0001), and voluntary wheel running (SMD = 0.51, P= 0.04) were all effective in increasing BDNF levels in AD models. In addition, exercise significantly increased BDNF levels in the hippocampus (SMD = 0.92, P< 0.00001) and cortex (SMD = 1.56, P= 0.02) of AD models. Exercise, especially treadmill exercise, swimming, and voluntary wheel running, significantly increased BDNF levels in hippocampus and cortex of AD models, with swimming being the most effective intervention type.

Supraspinal glycinergic neurotransmission in pain: A scoping review of current literature

The neurotransmitter glycine is an agonist at the strychnine-sensitive glycine receptors. In addition, it has recently been discovered to act at two new receptors, the excitatory glycine receptor and metabotropic glycine receptor. Glycine's neurotransmitter roles have been most extensively investigated in the spinal cord, where it is known to play essential roles in pain, itch, and motor function. In contrast, less is known about supraspinal glycinergic functions, and their contributions to pain circuits are largely unrecognized. As glycinergic neurons are absent from cortical regions, a clearer understanding of how supraspinal glycine modulates pain could reveal new pharmacological targets. This review aims to synthesize the published research on glycine's role in the adult brain, highlighting regions where glycine signaling may modulate pain responses. This was achieved through a scoping review methodology identifying several key regions of supraspinal pain circuitry where glycine signaling is involved. Therefore, this review unveils critical research gaps for supraspinal glycine's potential roles in pain and pain-associated responses, encouraging researchers to consider glycinergic neurotransmission more widely when investigating neural mechanisms of pain.

GPR158 in pyramidal neurons mediates social novelty behavior via modulating synaptic transmission in male mice

Impairment in social communication skills is a hallmark feature of autism spectrum disorder (ASD). The role of G-protein-coupled receptor 158 (GPR158) in ASD remains largely unexplored. In this study, we observed that both constitutive and cell-/tissue-specific knockouts of Gpr158 in pyramidal neurons or the medial prefrontal cortex (mPFC) result in impaired novelty preference, while sociability remains unaffected in male mice. Notably, the loss of GPR158 leads to a significant decline in excitatory synaptic transmission, characterized by a reduction in glutamate vesicles, as well as the expression and phosphorylation of GluN2B in the mPFC. We successfully rescue the phenotype of social novelty deficits either by reintroducing GPR158 in the mPFC of Gpr158 deficient mice or by chemogenetic activation of pyramidal neurons where Gpr158 is specifically ablated. Our findings indicate that GPR158 in pyramidal neurons plays a specific role in modulating social novelty and may represent a potential target for treating social disorders.

Polygenic proxies of age-related plasma protein levels reveal TIMP2 role in cognitive performance

Background

While numerous studies have identified blood proteins that modulate brain aging in mice, the direct translation of these findings to human health remains a substantial challenge. Bridging this gap is critical for developing interventions that can effectively target human brain aging and associated diseases.

Methods

We first identified 12 proteins with aging or rejuvenating properties in murine brains through a systematic review. Using protein quantitative trait loci data for these proteins, we developed polygenic scores to predict plasma protein levels, which we then validated in two independent human cohorts. We employed association models to explore the association between these genetically predicted protein levels and cognitive performance, focusing specifically on their interaction with key genetic markers such as sex, APOE-ε4 and Aβ42 status.

Results

Predicted plasma levels of Tissue Inhibitor of Metalloproteinases 2 (TIMP2) were significantly associated with improved global cognition and memory performance in humans, also when the models were stratified by sex, APOE-ε4, and Aβ42 status.

Conclusions

This finding aligns with TIMP2's brain-rejuvenating role in murine models, suggesting it as a promising therapeutic target for brain aging and age-related brain diseases in humans.

Osteocalcin: A potential marker to identify and monitor girls with rapidly progressive central precocious puberty

AIM

To evaluate the suitability of serum osteocalcin (OC) as a marker to distinguish between rapidly and non-rapidly progressive central precocious puberty (RP-CPP and NRP-CPP), as well as its potential to assess growth rates following treatment with gonadotropin-releasing hormone agonist (GnRHa).

METHODS

Serum levels of OC were measured using enzyme-linked immunosorbent assays in girls diagnosed with either RP-CPP or NRP-CPP as well as in normal control subjects. Receiver operating characteristic (ROC) curve analysis was performed to determine the cut-off value for OC. Multivariate linear regression analysis was used to analyse the main influencing factors associated with OC.

RESULTS

Serum OC levels were higher in the CPP girls when compared to normal controls (110.76 ± 43.69 vs 55.97 ± 20.96 ng/mL, P < 0.001). The level in the RP-CPP group was higher than the NRP-CPP group (153.28 ± 33.89 vs 88.33 ± 29.26 ng/mL, P < 0.001). The cut-off value of OC levels for distinguishing between RP-CPP and NRP-CPP was 107.05 ng/mL, the sensitivity was 94.7% and the specificity was 77.8%, which was superior to using the basal luteinising hormone (B-LH) levels, and the area under ROC curve (AUC) were 0.933 versus 0.695, respectively. Following 1-2 years of treatment with GnRHa for girls with CPP, both OC levels and the growth rates decreased to pre-pubertal values. B-LH levels, bone age and body weight were also significant factors, which affected OC levels.

CONCLUSIONS

Serum OC levels may be a useful marker for distinguishing RP-CPP from NRP-CPP. In addition, it was also found to be a useful predictor for growth rate during GnRHa treatment.

Roles of osteocalcin in the central nervous system

BACKGROUND

Bone-derived protein osteocalcin, which has beneficial effects on brain function, may be a future research direction for neurological disorders. A growing body of evidence suggests a link between osteocalcin and neurological disorders, but the exact relationship is contradictory and unclear.

SCOPE OF REVIEW

The aim of this review is to summarize the current research on the interaction between osteocalcin and the central nervous system and to propose some speculative future research directions.

MAJOR CONCLUSIONS

In the normal central nervous system, osteocalcin is involved in neuronal structure, neuroprotection, and the regulation of cognition and anxiety. Studies on osteocalcin-related abnormalities in the central nervous system are divided into animal model studies and human studies, depending on the subject. In humans, the link between osteocalcin and brain function is inconsistent. These conflicting data may be due to methodological inconsistencies. By reviewing the related literature on osteocalcin, some comorbidities of the bone and nervous system and future research directions related to osteocalcin are proposed.

Aging insights from heterochronic parabiosis models

Heterochronic parabiosis consists of surgically connecting the circulatory systems of a young and an old animal. This technique serves as a model to study circulating factors that accelerate aging in young organisms exposed to old blood or induce rejuvenation in old organisms exposed to young blood. Despite the promising results, the exact cellular and molecular mechanisms remain unclear, so this study aims to explore and elucidate them in more detail.

Crosstalk between bone and brain in Alzheimer's disease: Mechanisms, applications, and perspectives

Alzheimer's disease (AD) is a neurodegenerative disease that involves multiple systems in the body. Numerous recent studies have revealed bidirectional crosstalk between the brain and bone, but the interaction between bone and brain in AD remains unclear. In this review, we summarize human studies of the association between bone and brain and provide an overview of their interactions and the underlying mechanisms in AD. We review the effects of AD on bone from the aspects of AD pathogenic proteins, AD risk genes, neurohormones, neuropeptides, neurotransmitters, brain-derived extracellular vesicles (EVs), and the autonomic nervous system. Correspondingly, we elucidate the underlying mechanisms of the involvement of bone in the pathogenesis of AD, including bone-derived hormones, bone marrow-derived cells, bone-derived EVs, and inflammation. On the basis of the crosstalk between bone and the brain, we propose potential strategies for the management of AD with the hope of offering novel perspectives on its prevention and treatment. HIGHLIGHTS: The pathogenesis of AD, along with its consequent changes in the brain, may involve disturbing bone homeostasis. Degenerative bone disorders may influence the progression of AD through a series of pathophysiological mechanisms. Therefore, relevant bone intervention strategies may be beneficial for the comprehensive management of AD.

Astrocytes control quiescent NSC reactivation via GPCR signaling-mediated F-actin remodeling

The transitioning of neural stem cells (NSCs) between quiescent and proliferative states is fundamental for brain development and homeostasis. Defects in NSC reactivation are associated with neurodevelopmental disorders. Drosophila quiescent NSCs extend an actin-rich primary protrusion toward the neuropil. However, the function of the actin cytoskeleton during NSC reactivation is unknown. Here, we reveal the fine filamentous actin (F-actin) structures in the protrusions of quiescent NSCs by expansion and super-resolution microscopy. We show that F-actin polymerization promotes the nuclear translocation of myocardin-related transcription factor, a microcephaly-associated transcription factor, for NSC reactivation and brain development. F-actin polymerization is regulated by a signaling cascade composed of G protein-coupled receptor Smog, G protein αq subunit, Rho1 guanosine triphosphatase, and Diaphanous (Dia)/Formin during NSC reactivation. Further, astrocytes secrete a Smog ligand folded gastrulation to regulate Gαq-Rho1-Dia-mediated NSC reactivation. Together, we establish that the Smog-Gαq-Rho1 signaling axis derived from astrocytes, an NSC niche, regulates Dia-mediated F-actin dynamics in NSC reactivation.

Polygenic proxies of age-related plasma protein levels reveal TIMP2 role in cognitive performance

Several studies have identified blood proteins that influence brain aging performance in mice, yet translating these findings to humans remains challenging. Here we found that higher predicted plasma levels of Tissue Inhibitor of Metalloproteinases 2 (TIMP2) were significantly associated with improved global cognition and memory performance in humans. We first identified 12 proteins with aging or rejuvenating effects on murine brains through a systematic review. Using protein quantitative trait loci data for these proteins, we computed polygenic scores as proxies for plasma protein levels and validated their prediction accuracy in two independent cohorts. Association models between genetic proxies and cognitive performance highlighted the significance of TIMP2, also when the models were stratified by sex, APOE -ε4, and Aβ42 status. This finding aligns with TIMP2's brain-rejuvenating role in murine models, suggesting it as a promising therapeutic target for brain aging and age-related brain diseases in humans.

Hyperglycemia from Diabetes Potentiates Uncarboxylated Osteocalcin-Stimulated Insulin Secretion in Rat INS-1 Pancreatic β-Cells

Uncarboxylated osteocalcin (ucOC) is a hormone secreted by osteoblasts that strengthens bone during mineralization and is a biomarker for ongoing bone formation. It also regulates glucose homeostasis by stimulating insulin secretion from pancreatic β-cells. However, its effect on β-cells under hyperglycemic diabetic conditions is unclear. The objective of this study was to investigate ucOC's effect on insulin secretion in β-cells maintained under high glucose conditions. We hypothesized that hyperglycemia potentiates insulin secretion in response to ucOC stimulation. Using INS-1 cells, we performed insulin secretion experiments, intracellular calcium recordings, and RT-qPCR to determine ucOC's effect on glucose-stimulated insulin secretion (GSIS)-related genes. The results reveal that ucOC significantly increased insulin secretion under hyperglycemic conditions compared to lower glucose levels. High glucose conditions also potentiated the effect of ucOC on calcium signals, which enhanced insulin secretion. The increase in intracellular calcium was due to an influx from the extracellular space via voltage-dependent calcium channels (VDCCs). Interestingly, the treatment of cells with NPS-2143, a GPRC6A blocker, failed to abolish the calcium signals. Uncarboxylated osteocalcin upregulated the expression of GSIS-related genes under high glucose conditions (450 mg/dL) compared to cells under standard culture conditions (200 mg/dL). In conclusion, hyperglycemia potentiates ucOC-induced insulin secretion in β-cells by opening VDCCs and upregulating GSIS genes. These findings provide a better understanding of ucOC's mechanism in the diabetic state and could lead to alternative treatments to stimulate insulin secretion.

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.

Glycine-induced activation of GPR158 increases the intrinsic excitability of medium spiny neurons in the nucleus accumbens

It has been recently established that GPR158, a class C orphan G protein-coupled receptor, serves as a metabotropic glycine receptor. GPR158 is highly expressed in the nucleus accumbens (NAc), a major input structure of the basal ganglia that integrates information from cortical and subcortical structures to mediate goal-directed behaviors. However, whether glycine modulates neuronal activity in the NAc through GPR158 activation has not been investigated yet. Using whole-cell patch-clamp recordings, we found that glycine-dependent activation of GPR158 increased the firing rate of NAc medium spiny neurons (MSNs) while it failed to significantly affect the excitability of cholinergic interneurons (CIN). In MSNs GPR158 activation reduced the latency to fire, increased the action potential half-width, and reduced action potential afterhyperpolarization, effects that are all consistent with negative modulation of potassium M-currents, that in the central nervous system are mainly carried out by Kv7/KCNQ-channels. Indeed, we found that the GPR158-induced increase in MSN excitability was associated with decreased M-current amplitude, and selective pharmacological inhibition of the M-current mimicked and occluded the effects of GPR158 activation. In addition, when the protein kinase A (PKA) or extracellular signal-regulated kinase (ERK) signaling was pharmacologically blocked, modulation of MSN excitability by GPR158 activation was suppressed. Moreover, GPR158 activation increased the phosphorylation of ERK and Kv7.2 serine residues. Collectively, our findings suggest that GPR158/PKA/ERK signaling controls MSN excitability via Kv7.2 modulation. Glycine-dependent activation of GPR158 may significantly affect MSN firing in vivo, thus potentially mediating specific aspects of goal-induced behaviors.

The brain-bone axis: unraveling the complex interplay between the central nervous system and skeletal metabolism

The brain-bone axis has emerged as a captivating field of research, unveiling the intricate bidirectional communication between the central nervous system (CNS) and skeletal metabolism. This comprehensive review delves into the current state of knowledge surrounding the brain-bone axis, exploring the complex mechanisms, key players, and potential clinical implications of this fascinating area of study. The review discusses the neural regulation of bone metabolism, highlighting the roles of the sympathetic nervous system, hypothalamic neuropeptides, and neurotransmitters in modulating bone remodeling. In addition, it examines the influence of bone-derived factors, such as osteocalcin and fibroblast growth factor 23, on brain function and behavior. The therapeutic potential of targeting the brain-bone axis in the context of skeletal and neurological disorders is also explored. By unraveling the complex interplay between the CNS and skeletal metabolism, this review aims to provide a comprehensive resource for researchers, clinicians, and students interested in the brain-bone axis and its implications for human health and disease.

Osteocalcin: Beyond Bones

Apart from basic roles such as supporting the body, protecting internal organs, and storing calcium, the skeletal system also performs hormonal functions. In recent years, several reports have been published on proteins secreted by bones and their impact on the homeostasis of the entire body. These proteins include fibroblast growth factor 23, sclerostin, lipocalin 2, and osteocalcin. Osteocalcin, the most abundant non-collagenous protein in bone tissue, is routinely measured as a clinical marker for diagnosing bone metabolism disorders. Its molecule undergoes numerous transformations, with decarboxylation being the critical process. Decarboxylation occurs in the acidic environment typical of bone resorption, facilitating the release of the molecule into the bloodstream and enabling its hormonal action. Decarboxylated osteocalcin promotes insulin secretion and stimulates the proliferation of pancreatic islet β-cells. It also plays a role in reducing the accumulation of visceral fat and decreasing fat storage in the liver. Furthermore, decarboxylated osteocalcin levels are inversely correlated with fasting serum glucose levels, total body fat, visceral fat area, and body mass index. Apart from its role in energy metabolism, osteocalcin affects testosterone production and the synthesis of glucagon-like peptide-1. It is also actively involved in muscle-bone crosstalk and influences cognitive function.

Impact of menopause-associated frailty on traumatic brain injury

Navigating menopause involves traversing a complex terrain of hormonal changes that extend far beyond reproductive consequences. Menopausal transition is characterized by a decrease in estradiol-17β (E2), and the impact of menopause resonates not only in the reproductive system but also through the central nervous system, musculoskeletal, and gastrointestinal domains. As women undergo menopausal transition, they become more susceptible to frailty, amplifying the risk and severity of injuries, including traumatic brain injury (TBI). Menopause triggers a cascade of changes leading to a decline in muscle mass, accompanied by diminished tone and excitability, thereby restricting the availability of irisin, a crucial hormone derived from muscles. Concurrently, bone mass undergoes reduction, culminating in the onset of osteoporosis and altering the dynamics of osteocalcin, a hormone originating from bones. The diminishing levels of E2 during menopause extend their influence on the gut microbiota, resulting in a reduction in the availability of tyrosine, tryptophan, and serotonin metabolites, affecting neurotransmitter synthesis and function. Understanding the interplay between menopause, frailty, E2 decline, and the intricate metabolisms of bone, gut, and muscle is imperative when unraveling the nuances of TBI after menopause. The current review underscores the significance of accounting for menopause-associated frailty in the incidence and consequences of TBI. The review also explores potential mechanisms to enhance gut, bone, and muscle health in menopausal women, aiming to mitigate frailty and improve TBI outcomes.

Small extracellular vesicles from young plasma reverse age-related functional declines by improving mitochondrial energy metabolism

Recent investigations into heterochronic parabiosis have unveiled robust rejuvenating effects of young blood on aged tissues. However, the specific rejuvenating mechanisms remain incompletely elucidated. Here we demonstrate that small extracellular vesicles (sEVs) from the plasma of young mice counteract pre-existing aging at molecular, mitochondrial, cellular and physiological levels. Intravenous injection of young sEVs into aged mice extends their lifespan, mitigates senescent phenotypes and ameliorates age-associated functional declines in multiple tissues. Quantitative proteomic analyses identified substantial alterations in the proteomes of aged tissues after young sEV treatment, and these changes are closely associated with metabolic processes. Mechanistic investigations reveal that young sEVs stimulate PGC-1α expression in vitro and in vivo through their miRNA cargoes, thereby improving mitochondrial functions and mitigating mitochondrial deficits in aged tissues. Overall, this study demonstrates that young sEVs reverse degenerative changes and age-related dysfunction, at least in part, by stimulating PGC-1α expression and enhancing mitochondrial energy metabolism.

Approximation of bone mineral density and subcutaneous adiposity using T1-weighted images of the human head

Bones and brain are intricately connected and scientific interest in their interaction is growing. This has become particularly evident in the framework of clinical applications for various medical conditions, such as obesity and osteoporosis. The adverse effects of obesity on brain health have long been recognised, but few brain imaging studies provide sophisticated body composition measures. Here we propose to extract the following bone- and adiposity-related measures from T1-weighted MR images of the head: an approximation of skull bone mineral density (BMD), skull bone thickness, and two approximations of subcutaneous fat (i.e., the intensity and thickness of soft non-brain head tissue). The measures pertaining to skull BMD, skull bone thickness, and intensi-ty-based adiposity proxy proved to be reliable ( r =.93/.83/.74, p <.001) and valid, with high correlations to DXA-de-rived head BMD values (rho=.70, p <.001) and MRI-derived abdominal subcutaneous adipose volume (rho=.62, p <.001). Thickness-based adiposity proxy had only a low retest reliability ( r =.58, p <.001).The outcomes of this study constitute an important step towards extracting relevant non-brain features from available brain scans.

In vitro heterochronic parabiosis identifies pigment epithelium-derived factor as a systemic mediator of rejuvenation by young blood

Several decades of heterochronic parabiosis (HCPB) studies have demonstrated the restorative impact of young blood, and deleterious influence of aged blood, on physiological function and homeostasis across tissues, although few of the factors responsible for these observations have been identified. Here we develop an in vitro HCPB system to identify these circulating factors, using replicative lifespan (RLS) of primary human fibroblasts as an endpoint of cellular health. We find that RLS is inversely correlated with serum donor age and sensitive to the presence or absence of specific serum components. Through in vitro HCPB, we identify the secreted protein pigment epithelium-derived factor (PEDF) as a circulating factor that extends RLS of primary human fibroblasts and declines with age in mammals. Systemic administration of PEDF to aged mice reverses age-related functional decline and pathology across several tissues, improving cognitive function and reducing hepatic fibrosis and renal lipid accumulation. Together, our data supports PEDF as a systemic mediator of the effect of young blood on organismal health and homeostasis and establishes our in vitro HCPB system as a valuable screening platform for the identification of candidate circulating factors involved in aging and rejuvenation.

Interpreting the molecular mechanisms of RBBP4/7 and their roles in human diseases (Review)

Histone chaperones serve a pivotal role in maintaining human physiological processes. They interact with histones in a stable manner, ensuring the accurate and efficient execution of DNA replication, repair and transcription. Retinoblastoma binding protein (RBBP)4 and RBBP7 represent a crucial pair of histone chaperones, which not only govern the molecular behavior of histones H3 and H4, but also participate in the functions of several protein complexes, such as polycomb repressive complex 2 and nucleosome remodeling and deacetylase, thereby regulating the cell cycle, histone modifications, DNA damage and cell fate. A strong association has been indicated between RBBP4/7 and some major human diseases, such as cancer, age‑related memory loss and infectious diseases. The present review assesses the molecular mechanisms of RBBP4/7 in regulating cellular biological processes, and focuses on the variations in RBBP4/7 expression and their potential mechanisms in various human diseases, thus providing new insights for their diagnosis and treatment.

Circulating plasma-derived extracellular vesicles expressing bone and kidney markers are associated with neurocognitive impairment in people living with HIV

Background

Although effective antiretroviral therapy (ART) has improved the life expectancy of people with HIV (PWH), the prevalence of milder forms of HIV-associated neurocognitive disorders (HAND) persist, and it is associated with systemic and neuro-inflammatory processes that could impact other organ systems. However, the complex signaling mechanisms between the bone-kidney systems and the brain in HAND remain unknown. Extracellular vesicles (EVs) play a potential role in inter-organ communication and are involved in regulating cell activity in distant tissues. In this study, we examined whether levels of EVs from bone-and kidney-related cells associate with cognitive dysfunction and explored the relationship between kidney-bone EV axis in PWH experiencing cognitive deficits.

Methods

EV subtypes were characterized in plasma from 61 PWH with either cognitive impairment (CI, n = 53) or normal cognition (NC, n = 8) based on the American Academy of Neurology criteria for HIV-associated dementia (HAD, n = 11), minor cognitive motor disorder (MCMD, n = 25) or asymptomatic neurocognitive impairment (ANI, n = 17) by spectral flow cytometry. EVs were profiled with markers reflecting bone and kidney cell origin. A support vector machine learning-based model was employed for analyses of EV phenotypes to predict the cognitive dysfunction.

Results

Plasma-EVs expressing osteocalcin, sclerostin, and nephrin were significantly higher in the cognitive impairment group compared to the normal cognition group. EVs bearing kidney cell markers correlated significantly with bone-derived EVs. A machine learning-based model, comprised of osteocalcin+, nephrin+, and CD24+ EVs predicted cognitive impairment in PWH on ART.

Conclusion

Our study reveals that neurocognitive impairment in PWH is associated with increased levels of plasma EVs enriched with the bone markers osteocalcin and sclerostin and the kidney marker nephrin, suggesting that these EV subtypes may be novel candidate biomarkers for disease-spanning neurocognitive dysfunction. Moreover, the relationship between bone-derived EVs with kidney-derived EVs may suggest their role in mediating inter-organ crosstalk in the pathogenesis of HIV-associated cognitive impairment.

Bone-nerve crosstalk: a new state for neuralizing bone tissue engineering-A mini review

Neuro bone tissue engineering is a multidisciplinary field that combines both principles of neurobiology and bone tissue engineering to develop innovative strategies for repairing and regenerating injured bone tissues. Despite the fact that regeneration and development are considered two distinct biological processes, yet regeneration can be considered the reactivation of development in later life stages to restore missing tissues. It is noteworthy that the regeneration capabilities are distinct and vary from one organism to another (teleost fishes, hydra, humans), or even in the same organism can vary dependent on the injured tissue itself (Human central nervous system vs. peripheral nervous system). The skeletal tissue is highly innervated, peripheral nervous system plays a role in conveying the signals and connecting the central nervous system with the peripheral organs, moreover it has been shown that they play an important role in tissue regeneration. Their regeneration role is conveyed by the different cells' resident in it and in its endoneurium (fibroblasts, microphages, vasculature associated cells, and Schwann cells) these cells secrete various growth factors (NGF, BDNF, GDNF, NT-3, and bFGF) that contribute to the regenerative phenotype. The peripheral nervous system and central nervous system synchronize together in regulating bone homeostasis and regeneration through neurogenic factors and neural circuits. Receptors of important central nervous system peptides such as Serotonin, Leptin, Semaphorins, and BDNF are expressed in bone tissue playing a role in bone homeostasis, metabolism and regeneration. This review will highlight the crosstalk between peripheral nerves and bone in the developmental stages as well as in regeneration and different neuro-bone tissue engineering strategies for repairing severe bone injuries.

Aging brain: exploring the interplay between bone marrow aging, immunosenescence, and neuroinflammation

Aging is a complex process characterized by a myriad of physiological changes, including alterations in the immune system termed immunosenescence. It exerts profound effects on both the bone marrow and the central nervous system, with significant implications for immunosenescence in neurological contexts. Our mini-review explores the complex relationship between bone marrow aging and its impact on immunosenescence, specifically within the context of neurological diseases. The bone marrow serves as a crucial hub for hematopoiesis and immune cell production, yet with age, it undergoes significant alterations, including alterations in hematopoietic stem cell function, niche composition, and inflammatory signaling. These age-related shifts in the bone marrow microenvironment contribute to dysregulation of immune cell homeostasis and function, impacting neuroinflammatory processes and neuronal health. In our review, we aim to explore the complex cellular and molecular mechanisms that link bone marrow aging to immunosenescence, inflammaging, and neuroinflammation, with a specific focus on their relevance to the pathophysiology of age-related neurological disorders. By exploring this interplay, we strive to provide a comprehensive understanding of how bone marrow aging impacts immune function and contributes to the progression of neurological diseases in aging individuals. Ultimately, this knowledge can hold substantial promise for the development of innovative therapeutic interventions aimed at preserving immune function and mitigating the progression of neurological disorders in the elderly population.

Current knowledge of bone-derived factor osteocalcin: its role in the management and treatment of diabetes mellitus, osteoporosis, osteopetrosis and inflammatory joint diseases

Osteocalcin (OC) is the most abundant non-collagenous and osteoblast-secreted protein in bone. It consists of two forms such as carboxylated OC (cOC) and undercarboxylated OC (ucOC). While cOC promotes bone mineralization and increases bone strength, ucOC is regarded an endocrinologically active form that may have several functions in multiple end organs and tissues. Total OC (tOC) includes both of these forms (cOC and ucOC) and is considered a marker of bone turnover in clinical settings. Most of the data on OC is limited to preclinical studies and therefore may not accurately reflect the situation in clinical conditions. For the stated reason, the aim of this review was not only to summarize current knowledge of all forms of OC and characterize its role in diabetes mellitus, osteoporosis, osteopetrosis, inflammatory joint diseases, but also to provide new interpretations of its involvement in the management and treatment of aforementioned diseases. In this context, special emphasis was placed on available clinical trials. Significantly lower levels of tOC and ucOC could be associated with the risk of type 2 diabetes mellitus. On the contrary, tOC level does not seem to be a good indicator of high bone turnover status in postmenopausal osteoporosis, osteoarthritis and rheumatoid arthritis. The associations between several pharmacological drugs used to treat all disorders mentioned above and OC levels have also been provided. From this perspective, OC may serve as a medium through which certain medications can influence glucose metabolism, body weight, adiponectin secretion, and synovial inflammation.

Astrocytes control quiescent NSC reactivation via GPCR signaling-mediated F-actin remodeling

The transitioning of neural stem cells (NSCs) between quiescent and proliferative states is fundamental for brain development and homeostasis. Defects in NSC reactivation are associated with neurodevelopmental disorders. Drosophila quiescent NSCs extend an actin-rich primary protrusion toward the neuropil. However, the function of the actin cytoskeleton during NSC reactivation is unknown. Here, we reveal the fine F-actin structures in the protrusions of quiescent NSCs by expansion and super-resolution microscopy. We show that F-actin polymerization promotes the nuclear translocation of Mrtf, a microcephaly-associated transcription factor, for NSC reactivation and brain development. F-actin polymerization is regulated by a signaling cascade composed of G-protein-coupled receptor (GPCR) Smog, G-protein αq subunit, Rho1 GTPase, and Diaphanous (Dia)/Formin during NSC reactivation. Further, astrocytes secrete a Smog ligand Fog to regulate Gαq-Rho1-Dia-mediated NSC reactivation. Together, we establish that the Smog-Gαq-Rho1 signaling axis derived from astrocytes, a NSC niche, regulates Dia-mediated F-actin dynamics in NSC reactivation.