The functional differences were evident within the first year and widened throughout follow-up. At 12 months, grip strength in the dominant hand, measured with a calibrated dynamometer, increased by 1.45 kilograms on average in the denosumab group versus 0.66 kilograms in the zoledronic acid group, a between-group difference of 0.79 kilograms. Usual gait speed over a 10-metre walkway improved by 0.041 metres per second with denosumab versus 0.017 with zoledronic acid, and the time needed to complete five rises from a standard chair fell by 0.82 seconds versus 0.32 seconds. All three between-group differences at 12 months were statistically significant at p < 0.001. By 36 months the gaps had grown: grip strength had improved by 2.52 kilograms with denosumab versus 0.99 kilograms with zoledronic acid, gait speed by 0.070 versus 0.027 metres per second, and chair-stand time had shortened by 1.47 versus 0.63 seconds. Linear mixed-effects models showed significant group-by-time interactions for all three primary functional outcomes, indicating that the trajectories genuinely diverged rather than differing only at isolated visits.

Changes in muscle mass followed a later and more nuanced course. Whole-body dual-energy X-ray absorptiometry, or DXA, showed no significant between-group difference in the appendicular skeletal muscle mass index at 12 months. A difference emerged at 24 months, when the index had risen by 0.161 kilograms per square metre with denosumab versus 0.076 with zoledronic acid, and it persisted at 36 months at 0.192 versus 0.089. Bone mineral density told a mixed story: lumbar spine density increased more with denosumab at every visit, while femoral neck density showed slightly greater gains in the zoledronic acid group at 24 and 36 months. The authors note that functional improvement appeared earlier, whereas separation in DXA-defined muscle mass emerged later, a staged pattern that has practical implications because DXA alone may miss early treatment effects when muscle function improves before measurable changes in appendicular lean mass appear.

Computed tomography added a structural dimension that DXA cannot capture. Using clinically acquired whole-abdomen CT scans and an open-source deep-learning segmentation tool called TotalSegmentator, with all outputs reviewed by a musculoskeletal radiologist blinded to treatment group, the researchers quantified a volumetric T12-L4 skeletal muscle volume index, skeletal muscle density, and indices of subcutaneous, visceral and intermuscular fat, each normalized to height squared. At 12 months, denosumab was associated with a greater increase in skeletal muscle volume index (1.19 versus 0.45), greater increase in muscle density (1.47 versus 0.47) and greater reduction in intermuscular fat volume index (−0.10 versus −0.04), all p < 0.001. By 24 and 36 months these differences remained pronounced, and the reduction in visceral fat also became significant, while subcutaneous fat did not differ between groups at any time point. The coordinated decline in intermuscular fat alongside rising muscle volume and density points to an improvement in muscle quality rather than a nonspecific shift in body composition.

The biologic rationale for the comparison rests on the receptor activator of nuclear factor-kappa B ligand pathway, commonly abbreviated RANKL. Denosumab is a monoclonal antibody that inhibits RANKL, an established antiresorptive mechanism with robust evidence for suppressing bone turnover, increasing bone mineral density and reducing fracture risk. But experimental work has shown that skeletal muscle also expresses components of the RANK/RANKL/osteoprotegerin axis, and that RANK signalling influences calcium handling, sarcoplasmic and endoplasmic reticulum calcium-ATPase activity, oxidative programming and muscle performance. Preclinical studies have further suggested that RANKL inhibition can improve muscle strength and insulin sensitivity, raising the possibility that denosumab has clinically relevant effects beyond fracture prevention.

The study’s biomarker data fit this framework. Denosumab produced a larger reduction in soluble RANKL, a larger increase in osteoprotegerin, and a substantially greater rise in the OPG/sRANKL ratio at every follow-up visit; at 12 months the ratio had increased by a median of 2.503 with denosumab versus 0.807 with zoledronic acid, and by 36 months the figures were 5.677 versus 1.448. Bone turnover markers, serum C-terminal telopeptide of type I collagen and procollagen type I N-terminal propeptide, fell further with denosumab throughout. Downstream, myostatin declined more and irisin rose more in the denosumab group, as did the follistatin-to-myostatin ratio, while inflammatory markers including high-sensitivity C-reactive protein, interleukin-6 and tumour necrosis factor alpha, along with fasting insulin and the HOMA-IR insulin-resistance index, all decreased more with denosumab. Brain-derived neurotrophic factor did not differ significantly in longitudinal change at any visit.

Within the denosumab group, the 12-month change in the OPG/sRANKL ratio correlated with later clinical gains: it was associated with change in grip strength (r = 0.520), gait speed (r = 0.364), chair-stand time (r = −0.470) and the DXA-derived muscle mass index (r = 0.316). A prespecified responder analysis split denosumab-treated participants at the within-group median of the 12-month OPG/sRANKL increase. High responders, who did not differ from low responders in baseline high-sRANKL prevalence, showed greater 36-month gains in grip strength (2.80 versus 2.21 kilograms), CT-defined muscle volume index (2.816 versus 2.199) and DXA-derived muscle mass index, and a markedly higher sarcopenia remission rate at 36 months (91.7 percent versus 55.0 percent). Exploratory mediation analyses, using bootstrap resampling with 5,000 iterations, found that the 12-month OPG/sRANKL change accounted for 37.0 percent of the association between treatment and 36-month grip-strength gain, and 39.9 percent of the association with CT-defined muscle volume gain, with significant residual direct effects in both models.

Sarcopenia outcomes, re-evaluated retrospectively under the updated Asian Working Group for Sarcopenia 2025 framework using prospectively collected data, followed the same staged pattern. Low muscle strength was less common with denosumab at 12 months (61.8 percent versus 79.1 percent), 24 months (38.8 versus 71.2 percent) and 36 months (26.7 versus 69.6 percent), while the prevalence of low muscle mass did not differ significantly between groups at any visit. Overall study-defined sarcopenia, defined by concurrent low muscle strength and low muscle mass, was less prevalent with denosumab at every visit, reaching 20.0 percent versus 46.0 percent at 36 months, and among participants with sarcopenia at baseline, remission was more frequent with denosumab at all time points, reaching 75.0 percent versus 37.0 percent at 36 months. Falls and new fragility fractures, by contrast, did not differ significantly between groups at any time point, with cumulative three-year fracture frequencies of 5.0 percent versus 10.1 percent that were directionally favourable but not statistically significant.

The researchers took several steps to address the inherent limitation that treatment was chosen by physicians rather than randomly assigned. Sensitivity analyses adjusted for age, baseline vitamin D supplementation and baseline variables that differed between groups, and additional models incorporated regular physical activity, resistance exercise and physical therapy as time-varying covariates; the primary functional findings were materially unchanged. A propensity score-weighted analysis using stabilized inverse probability of treatment weighting improved covariate balance, reducing the maximum absolute standardized mean difference from 0.446 to 0.110, and the weighted 36-month between-group differences remained significant for grip strength (1.607 kilograms, 95 percent confidence interval 1.386 to 1.828), gait speed (0.0455 metres per second) and chair-stand time (−0.863 seconds). An exploratory age-stratified analysis found no evidence of treatment-by-age interaction for any functional outcome.

The authors are careful about what the data do and do not establish. The mediation analyses are exploratory and hypothesis-generating, and the OPG/sRANKL response patterns are best interpreted as statistically compatible with partial mediation rather than proof that the pathway directly caused the later functional or structural benefits. Residual confounding from unmeasured clinical or lifestyle factors cannot be excluded in an observational cohort, and the cohort was intentionally enriched for women prescreened for sarcopenia risk, most commonly because of low handgrip strength, so the high baseline prevalence of low muscle strength and sarcopenia, roughly 84 percent in both groups, does not reflect an unselected osteoporosis population. With those caveats, the study describes a coherent sequence in which denosumab was associated first with stronger biologic pathway activation, then earlier gains in muscle strength and physical performance, coordinated CT-defined remodelling of muscle and fat compartments, later gains in DXA-defined muscle mass, and ultimately a lower study-defined sarcopenia burden, supporting further prospective evaluation of RANKL inhibition as a strategy for osteosarcopenic phenotypes.

Subject of Research: Comparative effects of denosumab versus zoledronic acid on muscle strength, physical performance and body composition in postmenopausal osteoporosis

Article Title: Denosumab Versus Zoledronic Acid for Muscle Strength and Physical Performance in Postmenopausal Osteoporosis: A 3‐Year Prospective Study

Article References: Li, X., Yuan, Z., Ma, N., Huang, B., Tao, H., & Chen, S. (2026). Denosumab Versus Zoledronic Acid for Muscle Strength and Physical Performance in Postmenopausal Osteoporosis: A 3‐Year Prospective Study. Journal of Cachexia, Sarcopenia and Muscle, 17(5), Article e70406. https://doi.org/10.1002/jcsm.70406

Image Credits: AI Generated

DOI: 10.1002/jcsm.70406

Keywords: denosumab, zoledronic acid, osteoporosis, sarcopenia, osteosarcopenia, RANKL inhibition, grip strength, physical performance, body composition, DXA, computed tomography, postmenopausal women

Exosomes belong to the broader family of extracellular vesicles, but they have a specific origin story that distinguishes them from other secreted particles. They form inside cells within compartments called multivesicular bodies, which are essentially endosomes studded with internal buds known as intraluminal vesicles. When these multivesicular bodies fuse with the cell’s outer membrane, the intraluminal vesicles are released into the surrounding fluid as exosomes. The process is orchestrated in large part by the endosomal sorting complexes required for transport, or ESCRT, a molecular machinery that decides which proteins are packed into each vesicle. Because the cargo is selected during biogenesis, exosomes are not random debris; they are curated snapshots of the physiological state of the cell that released them. That property is precisely what makes them so interesting to researchers studying tissues that communicate across anatomical boundaries.

The review’s first major theme is the pathway running from skeletal muscle to bone. Muscle-derived exosomes carry a payload rich in microRNAs, short RNA molecules that do not encode proteins but instead regulate gene expression by silencing target messenger RNAs. When muscle-derived exosomes are taken up by bone cells, these myogenic microRNAs can tip the balance of bone remodeling, the perpetual tug-of-war between osteoblasts, the cells that build bone, and osteoclasts, the cells that resorb it. According to the review, specific muscle-derived microRNAs and proteins influence the activity of both osteoblasts and osteoclasts, meaning that a healthy, contracting muscle can actively encourage bone formation while suppressing excessive breakdown. This provides a molecular explanation for a clinical observation that has long puzzled researchers: people who lose muscle mass almost invariably lose bone mass as well, and exercise that strengthens muscle tends to strengthen bone in parallel.

The reverse direction of the conversation is equally consequential. Bone is not a passive recipient of muscle-derived signals; it sends its own exosomal messages back. The review highlights exosomes derived from bone marrow mesenchymal stem cells, the regenerative cells resident in bone marrow, as particularly influential on muscle. These bone-derived vesicles affect myogenesis, the formation of new muscle fibers, and influence the process of muscle atrophy, the wasting that follows disuse, disease, or aging. In other words, the bone marrow appears to function as an endocrine-like organ in its own right, dispatching nanoscale couriers that help determine whether muscle tissue is maintained or lost. This bidirectional loop helps explain why osteosarcopenia behaves as a single coupled syndrome rather than two coincidental conditions, and why treating one tissue in isolation often fails to rescue the other.

Several specific molecular players illustrate how granular this communication can be. The review’s abbreviation list points to factors such as paired-related homeobox 2, a transcriptional regulator implicated in bone cell behavior, and lactate dehydrogenase A, a key enzyme of glycolytic metabolism, as components of the vesicular cargo that has drawn attention. Fluid flow shear stress, the mechanical stimulus that bone cells experience when interstitial fluid is pushed through the bone matrix during loading, also appears in the discussion, underscoring that mechanical forces and vesicular signals are intertwined rather than separate channels. Markers such as procollagen type I N-terminal propeptide and the beta-isomer of C-terminal telopeptide of type I collagen, standard clinical indicators of bone formation and resorption respectively, represent the kind of measurable endpoints that exosome research ultimately hopes to complement or refine. The chemokine receptor CXCR4, known for guiding stem cell migration and homing, hints at how vesicle-mediated signals might direct regenerative cells to where they are needed.

Beyond mechanism, the review devotes substantial attention to translation, and this is where the story becomes genuinely exciting for clinicians. Because exosomal cargo mirrors the state of the source tissue, circulating exosomes could serve as liquid biopsy markers for musculoskeletal health. A blood test that reads the molecular signatures of muscle-derived and bone-derived vesicles might one day detect the earliest shifts toward osteosarcopenia, long before a dual-energy X-ray scan registers meaningful loss of tissue. The review assesses this biomarker potential explicitly, positioning exosomes alongside established biochemical markers of bone turnover as a next generation of diagnostics. Early detection matters enormously in this field, because interventions that preserve muscle and bone are far more effective before irreversible structural damage has accumulated.

The therapeutic possibilities are equally striking. Exosomes are natural delivery vehicles: they are small, stable in circulation, protected by a lipid membrane, and capable of crossing biological barriers that defeat many synthetic drugs. Researchers are exploring two parallel strategies. The first uses naturally occurring exosomes, for example those secreted by mesenchymal stem cells, as ready-made therapeutics whose intrinsic cargo promotes regeneration. The second is engineering: loading exosomes with chosen microRNAs, proteins, or drugs and, ideally, decorating their surface with targeting molecules so that they home to muscle or bone specifically. The review also references work on exosomes from human fetal cartilage-derived progenitor cells, an example of how vesicles from unusual source tissues are being evaluated for regenerative applications. If either strategy matures, a single injectable product could theoretically stimulate osteoblasts, calm osteoclasts, and revive failing muscle fibers at once, addressing both faces of osteosarcopenia with one intervention.

The authors are careful, however, not to oversell the promise, and their discussion of limitations is one of the most valuable parts of the review. Isolation and characterization of exosomes remain inconsistent across laboratories, with different separation techniques yielding vesicle populations of varying purity and potency, which complicates comparisons between studies. Biodistribution is poorly understood: once injected, engineered or native exosomes may accumulate in the liver or spleen rather than reaching the intended tissue, and achieving reliable tissue-specific delivery is still an unsolved problem. Manufacturing at clinical scale under Good Manufacturing Practice conditions poses further hurdles, and the regulatory landscape is still taking shape. The review notes that exosome-based products would likely navigate frameworks developed for advanced therapy medicinal products in Europe and for Investigational New Drug and Biologics License Application pathways at the United States Food and Drug Administration, routes that demand rigorous control of identity, purity, and potency. Safety questions, including the possibility that vesicles could transfer harmful cargo or provoke immune reactions, remain open.

What emerges from the review is a picture of a field in rapid ascent but not yet at the clinic. The authors conclude that exosomes are critical mediators of muscle-bone crosstalk and that their cargo reflects the physiological state of the source cells, a foundation solid enough to justify serious investment in both diagnostics and therapeutics. They also argue that future progress will depend on integrating multi-omics approaches, which profile the full complement of RNAs, proteins, and metabolites in vesicle populations, with artificial intelligence tools capable of finding predictive patterns in those enormous datasets. Such combinations could identify which specific vesicle signatures predict fracture risk or muscle decline, and which cargo molecules are the true therapeutic effectors among thousands of passengers. For the millions of people facing osteosarcopenia, the prospect that the body’s own nanoscale messengers could be read like a lab report and reprogrammed like a drug is no longer science fiction; it is a research agenda with a clear roadmap, published as an open-access article that invites the global research community to build on it.

Subject of Research: Exosome-mediated molecular communication between skeletal muscle and bone and its therapeutic potential for osteosarcopenia

Article Title: Exosome-mediated muscle-bone crosstalk: mechanisms and therapeutic potential

Article References: Chen, D., Liu, J., Liang, X., Zhang, X., Bai, L., Qin, G., Min, T., Xiang, J., Li, K., & Xu, D. (2026). Exosome-mediated muscle-bone crosstalk: mechanisms and therapeutic potential. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-08994-2

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08994-2

Keywords: exosomes, extracellular vesicles, muscle-bone crosstalk, osteosarcopenia, skeletal muscle, bone metabolism, osteoblasts, osteoclasts, microRNAs, bone marrow mesenchymal stem cells, biomarkers, drug delivery

The scale of the problem is staggering. In 2019 alone, an estimated 4.3 million new fragility fractures occurred across the EU27, Switzerland, and the United Kingdom, including approximately 827,000 hip fractures. The direct cost of these new fractures reached 36.3 billion euros, with an additional 19.0 billion euros attributable to long-term disability from fractures sustained in previous years. When pharmacological assessment and treatment costs of 1.6 billion euros are added, the total direct cost climbed to 56.9 billion euros in a single year. Healthcare costs remain elevated above pre-fracture levels for five full years after the injury, placing an unsustainable strain on health systems already stretched by aging populations.

What makes these figures particularly troubling is how preventable many of these fractures are. More than 95 percent of hip fractures are caused by falling, yet the clinical systems designed to prevent falls and those designed to prevent fractures operate almost entirely in isolation from one another. Hip fracture outcomes are grim: one-year mortality reaches 20 to 24 percent, and among survivors, 40 percent are unable to walk independently while 60 percent still require assistance a full year after injury. Approximately one-third of patients become fully dependent or require residential care within twelve months of sustaining a hip fracture.

The biological logic for integration is compelling. The paper presents a conceptual framework showing how bone fragility and fall risk jointly determine fracture probability, with their relative contributions shifting over time. A common geriatric syndrome called osteosarcopenia—the combination of sarcopenia and osteopenia or osteoporosis—illustrates this overlap, affecting an estimated 5 to 37 percent of community-dwelling older adults and elevating the risk of both falls and fractures simultaneously. Crucially, researchers have documented an imminent subsequent fracture risk after both an incident fracture and an incident fall, and conversely, an increased risk of falling soon after a fracture. This bidirectional cascade means that missing one risk dimension inevitably undermines the other.

Despite this, clinical practice lags badly. In a recent survey among European healthcare professionals, fewer than 60 percent of respondents reported including fracture risk assessment often or always within the multifactorial fall risk assessment. On the fracture side, fall risk assessment is not routinely performed in many Fracture Liaison Services, the specialized secondary prevention programs established after a first fracture. In a 2025 national UK evaluation, only about 65 percent of FLS patients received or were referred for a fall risk assessment, with substantial variation between services, and the picture is likely worse or entirely absent in many other countries. The authors contend that FLS programs are uniquely positioned to operationalize integrated care but frequently remain predominantly bone-focused rather than comprehensively risk-focused.

The paper lays out a detailed technical roadmap for how fracture risk assessment can be embedded within fall prevention services, drawing on the 2022 World Guidelines for Fall Prevention and Management. These guidelines introduce a fall risk stratification algorithm for community-dwelling older adults and recommend that those at moderate to high risk of falls undergo bone health assessment using validated tools. Fracture risk calculators such as FRAX, Garvan, and QFracture can identify older adults at high fracture risk, with Garvan and QFracture already incorporating falls as a predictor. FRAXplus further refines conventional FRAX estimates by accounting for the number of falls in the previous year, allowing clinicians to treat fall history as a modifiable fracture risk amplifier that directly informs both risk stratification and therapeutic choice.

Conversely, established osteoporosis management pathways should embed fall prevention. An internationally applicable algorithm for postmenopausal women categorizes fracture risk into low, intermediate, and very high zones using FRAX, with bone densitometry and recalculation refining intermediate cases. Women with a prior fragility fracture are automatically considered at least high risk. The authors emphasize that fall prevention strategies must be embedded within treatment pathways for patients at high and very high fracture risk, and that cognitively impaired and dementia patients should never be denied fracture prevention measures, including pharmacological osteoporosis treatments. This population deserves particular attention: 60 to 80 percent of people with dementia fall annually, and cognitive impairment is present in approximately 40 percent of all older adults with hip fractures.

Education represents another critical pillar. Among nearly 4,000 European healthcare professionals surveyed, approximately 12 percent reported low or very low knowledge of both falls and bone health, and 35.9 percent reported low knowledge of orthogeriatric care. Only about a quarter of surveyed professionals agreed that their undergraduate education adequately prepared them for fall prevention in clinical practice. The authors call for interprofessional training that bridges medicine, physiotherapy, nursing, pharmacy, and dietetics, alongside a core set of competencies for integrated fall and fracture assessment that local teams can adapt to their resources while remaining evidence-based.

On the policy front, the paper argues that integrated fall and fracture prevention must be recognized as a public health priority and incorporated into national healthy aging strategies aligned with the WHO’s Decade of Healthy Ageing. Promising national initiatives already exist: France launched a 2022 plan targeting a 20 percent reduction in fall-related fractures and deaths; the Netherlands has introduced an Integrated Approach to Fall Prevention strategy; and Belgium operates a dedicated Center of Expertise for Falls and Fracture Prevention in Flanders. Hip fracture registries, another policy instrument, should include fall prevention quality markers, as the Danish National Hip Fracture Database has done since 2010.

Emerging technologies offer powerful new tools. Wearable sensors capturing real-world balance and mobility data, combined with AI-driven predictive models, demonstrate superior fall prediction performance compared with traditional approaches, while in silico clinical trials enable simulation of virtual populations to optimize preventive interventions before deployment. Emerging pharmacological findings add intrigue: pooled analyses suggest that romosozumab and denosumab may each reduce fall risk in postmenopausal women with osteoporosis, hinting at mechanisms that might involve muscle mass, though the authors caution that studies with falls as the primary outcome are still needed. The WHO and ESCEO have signed a five-year collaboration agreement to develop a strategic global roadmap on bone health and aging, signaling that momentum toward truly integrated prevention may finally be building. The authors’ message is unambiguous: unify the science, unify the services, and millions of preventable fractures and falls could be avoided.

Subject of Research: Integrated fall and fragility fracture prevention in older adults through coordinated international clinical, educational, policy, and research strategies

Article Title: Position paper: a coordinated approach to fracture and fall prevention from seven international organizations

Article References: van der Velde, N., Seppala, L. J., Bahat, G., Blain, H., Casas Herrero, A., Harvey, N. C., Masud, T., Rizzoli, R., Reginster, J.-Y., Ruggiero, C., Barbagallo, M., de Lima, A. B., Bonnici, M., Bousquet, J., Cortet, B., Chiari, L., Dionyssiotis, Y., Dreinhöfer, K., Duque, G., … Öztürk, Y. (2026). Position paper: a coordinated approach to fracture and fall prevention from seven international organizations. European Geriatric Medicine. https://doi.org/10.1007/s41999-026-01596-7

Image Credits: AI Generated

DOI: 10.1007/s41999-026-01596-7

Keywords: fall prevention, fragility fractures, osteoporosis, geriatric medicine, Fracture Liaison Services, hip fracture, osteosarcopenia, integrated care, healthy aging, bone health, wearable sensors, public health policy

The clearest longitudinal signal ran from muscle traits to later osteoporosis. Participants with higher appendicular lean mass, stronger hand grips or faster usual walking speeds had lower observed risks of developing osteoporosis. For each standardised increase in the three measures, the reported hazard ratios were 0.830 for adjusted lean mass, 0.544 for grip strength and 0.735 for walking pace. A hazard ratio below one indicates a lower event rate in the model, although it does not by itself prove that improving the trait would prevent disease. When the three muscle measures were adjusted for one another, grip strength and walking pace remained independently associated with lower osteoporosis risk, with hazard ratios of 0.593 and 0.788. The exposure–response patterns were broadly monotonic for these functional measures: risk fell as strength and walking speed increased. Analyses also detected interactions with age, sex and body-mass index. The associations were generally stronger in younger adults; lean mass and walking pace had larger effects in men, while lean mass showed a stronger relationship among people with lower BMI. Even within these subgroups, however, favourable muscle traits were consistently associated with lower risk.

Muscle mass itself produced a less straightforward result. Adjusted appendicular lean mass showed a U-shaped association with osteoporosis, meaning that neither the lowest nor the highest levels appeared optimal in the statistical model. This finding is exploratory and does not demonstrate that unusually high muscle mass causes bone loss. The authors propose several possible explanations that require testing, including overtraining, inadequate energy availability and exercise-related hormonal disruption. Muscles normally load the skeleton through contraction, encouraging bone adaptation, but that response may reach a ceiling. Prolonged fatigue, irregular forces or abnormal stress distribution could alter the benefit of loading and contribute to skeletal microdamage. Intense training combined with low energy availability has also been linked to impaired bone health, while hormonal disruption may add to the risk. These possibilities should not be read as evidence that ordinary physical activity is harmful. Rather, the unusual curve highlights the limitations of interpreting a single measure of lean mass without detailed information about training intensity, nutrition, hormones, body composition and previous injuries. Replication in other populations will be needed before the pattern can influence advice or clinical practice.

The association also ran in the opposite direction. In longitudinal analyses, people with higher left- or right-heel BMD, or higher heel BMD T-scores, were less likely to develop probable sarcopenia. The relationship was broadly monotonic: as heel density rose, sarcopenia risk fell. Complementary analyses using BMD measured at the femoral neck and lumbar spine by dual-energy X-ray absorptiometry supported inverse associations with both probable sarcopenia and confirmed sarcopenia. The primary sarcopenia definition was “probable sarcopenia”, based on low grip strength alone—below 27 kilograms in men or 16 kilograms in women—while confirmed sarcopenia additionally required low adjusted appendicular lean mass. Genetic analyses added evidence of two-way effects. Mendelian randomisation indicated that most sarcopenia-related traits, but not usual walking pace, had effects on lumbar-spine BMD. In the reverse analysis, lumbar-spine BMD showed effects on most sarcopenia traits, again excluding walking pace. Mendelian randomisation uses genetic variants as instruments to reduce some confounding, but its validity depends on assumptions about those variants. It is not a substitute for a randomised intervention trial.

The investigators next searched for circulating molecules that might help explain how muscle status relates to bone. Mediation analysis identified 465 proteins associated with the lean-mass measure, 706 associated with grip strength and 697 associated with walking pace in pathways leading statistically towards osteoporosis risk. Of these, 352 were shared across all three muscle traits. The metabolite analysis identified 21 potential mediators for lean mass, 140 for grip strength and 127 for walking pace, including 17 shared across the three measures. Because exposure, mediator and outcome were not measured repeatedly in a way that established their temporal order, these results indicate statistical mediation consistent with a biological pathway, not proof that a particular protein or metabolite causes muscle loss to produce osteoporosis. To investigate where the proteins might arise, the researchers compared their signals with single-cell RNA-sequencing data from 90,902 cells taken from intercostal muscles of 17 donors in a human skeletal-muscle ageing atlas. Mediator-related expression was especially enriched in myeloid, endothelial and stromal cells. These cell groups participate in immune regulation, blood-vessel biology and connective-tissue maintenance, suggesting that muscle-to-bone communication may involve secreted signals and local cellular networks as well as mechanical loading.

Genetic and biomarker analyses pointed to a common background for the two disorders. Across the genome, the estimated genetic correlation between sarcopenia and osteoporosis risk was 0.25. Local analysis identified 102 genomic regions with significant heritability for both traits; 12 also showed significant local genetic correlation, and 10 of those correlations were positive. Polygenic risk scores provided a similar pattern: a higher genetic risk score for sarcopenia was associated with osteoporosis prevalence and incidence, while an osteoporosis score was associated with both the prevalence and incidence of sarcopenia. Circulating biomarkers overlapped extensively as well. Of 226 metabolites associated with sarcopenia, 164—71 per cent—were also associated with osteoporosis, all in the same direction. Among 1,576 sarcopenia-associated proteins, 502—31.3 per cent—were also linked to osteoporosis; 500 had concordant directions of association. Most of the shared proteins were secreted molecules whose gene activity was enriched in immune and lymphoid tissues. A protein–protein interaction network was far more connected than expected by chance, with immune-regulatory nodes including IL6, CXCL8 and TNF. These are associations, not diagnostic markers or validated treatment targets.

The biological pathways highlighted by the analysis offer a plausible bridge between muscle and bone. Enriched pathways included T-helper-17-cell differentiation, interleukin-17 signalling and NF-κB signalling. Chronic inflammatory activity can promote muscle protein breakdown and atrophy, while inflammatory signalling in bone can stimulate osteoclasts, the cells responsible for bone resorption. Several regulatory factors identified in the analysis have established roles across these processes, including NFKB1, RELA, FOXO1, SIRT1 and the vitamin D receptor. Other candidates included TFAM, which is involved in mitochondrial DNA maintenance; MGP, a vitamin K-dependent protein involved in mineral regulation and also linked to muscle development; and COMMD7, which has been connected with NF-κB activity. However, the gene-expression results demand caution. Transcriptome-wide association and summary-data Mendelian-randomisation analyses found dozens of genes nominally associated with both conditions in several tissues, and about 70 per cent showed consistent effect directions. After correction for multiple testing, no single gene remained significantly associated with both diseases simultaneously. The authors therefore describe these findings as exploratory clues rather than confirmed mechanisms. Similar caution applies to the large lists of proteins and metabolites: shared statistical signals need experimental validation.

The study also found common patterns for several potentially modifiable factors. Greater adult smoking exposure, measured in pack-years, was associated with higher prevalence of both sarcopenia and osteoporosis. Sleep duration showed a U-shaped relationship: sleeping fewer than six hours or more than eight hours was associated with greater risk than sleeping six to eight hours. More physical activity was associated with lower prevalence of both disorders up to a point, after which the association was no longer statistically significant. These observations do not establish that changing sleep duration or activity to a particular level will prevent either condition, and the study cannot distinguish all the reasons why people sleep or exercise more or less. Still, the molecular analyses found substantial overlap in the proteins and metabolites associated with these exposures and both diseases—roughly 30.5 to 73 per cent depending on the factor and analysis. Smoking and short sleep shared mediators linked to inflammation, oxidative stress, lipid metabolism and gastrointestinal function. Physical activity shared metabolic mediators, particularly involving lipid metabolism. The patterns are consistent with a muscle–bone unit influenced by systemic inflammation and metabolic health, while supporting established preventive priorities such as avoiding tobacco and maintaining appropriate physical activity and sleep.

Several limitations define what can be concluded. The primary sarcopenia outcome relied on grip strength alone, which may misclassify people whose muscle mass or mobility differs from their hand strength. The timing of sarcopenia onset was also uncertain; people who developed it between the baseline and imaging visits may have been excluded from some analyses because of progression or death. Heel BMD, the main osteoporosis trait, was estimated with quantitative ultrasound because baseline measurements at other skeletal sites were unavailable. Heel ultrasound is not universally considered the diagnostic gold standard, so findings should be tested using femoral-neck or lumbar-spine DXA measurements. UK Biobank participants may not represent the wider population, and the genetic analyses were based on people of Caucasian ancestry, limiting generalisability. Residual confounding could also have inflated some overlaps among diseases, proteins and metabolites. The research therefore does not show that one condition inevitably causes the other, nor that a specific supplement, exercise programme or drug will treat both. Future work should replicate the associations in diverse cohorts, measure molecular intermediaries repeatedly over time, test candidate pathways in cells and animal models, and evaluate integrated interventions. Clinically, the results argue for viewing muscle strength, mobility and bone health together rather than as isolated features of ageing—and for determining whether that integrated approach can reduce the combined burden of osteosarcopenia.

Subject of Research: The bidirectional relationship and shared biological mechanisms between sarcopenia and osteoporosis.

Article Title: Bidirectional Relationship and Shared Mechanisms Between Sarcopenia and Osteoporosis: An Observational Study Integrating Genomic, Proteomic, and Metabolomic Data.

Article References: Original research article.

DOI: 10.1111/acel.70617.

Keywords: Sarcopenia; osteoporosis; osteosarcopenia; bone mineral density; muscle strength; proteomics; metabolomics; genetics; inflammation; ageing.