Association between serum FGF21 level and sarcopenia in older adults

Bone and muscle crosstalk in ageing and disease

Interorgan communication between bone and skeletal muscle is central to human health. A dysregulation of bone-muscle crosstalk is implicated in several age-related diseases. Ageing-associated changes in endocrine, inflammatory, nutritional and biomechanical stimuli can influence the differentiation capacity, function and survival of mesenchymal stem cells and bone-forming and muscle-forming cells. Consequently, the secretome phenotype of bone and muscle cells is altered, leading to impaired crosstalk and, ultimately, catabolism of both tissues. Adipose tissue acts as a third player in the bone-muscle interaction by secreting factors that affect bone and muscle cells. Physical exercise remains the key biological stimulus for bone-muscle crosstalk, either directly via the release of cytokines from bone, muscle or adipocytes, or indirectly through extracellular vesicles. Overall, bone-muscle crosstalk is considered an inherent process necessary to maintain the structure and function of both tissues across the life cycle. This Review summarizes the latest biomedical advances in bone-muscle crosstalk as it pertains to human ageing and disease. We also outline future research priorities to accommodate the understanding of this rapidly emerging field.

FGF-based drug discovery: advances and challenges

The fibroblast growth factor (FGF) family comprises 15 paracrine-acting and 3 endocrine-acting polypeptides, which govern a multitude of processes in human development, metabolism and tissue homeostasis. Therapeutic endocrine FGFs have recently advanced in clinical trials, with FGF19 and FGF21-based therapies on the cusp of approval for the treatment of primary sclerosing cholangitis and metabolic syndrome-associated steatohepatitis, respectively. By contrast, while paracrine FGFs were once thought to be promising drug candidates for wound healing, burns, tissue repair and ischaemic ailments based on their potent mitogenic and angiogenic properties, repeated failures in clinical trials have led to the widespread perception that the development of paracrine FGF-based drugs is not feasible. However, the observation that paracrine FGFs can exert FGF hormone-like metabolic activities has restored interest in these FGFs. The recent structural elucidation of the FGF cell surface signalling machinery and the formulation of a new threshold model for FGF signalling specificity have paved the way for therapeutically harnessing paracrine FGFs for the treatment of a range of metabolic diseases.

TSG attenuated NAFLD and facilitated weight loss in HFD-fed mice via activating the RUNX1/FGF21 signaling axis

Non-alcoholic fatty liver disease (NAFLD) is a chronic liver disease characterized by steatosis in hepatocytes and is now becoming the major cause of liver-related mortality. Fibroblast growth factor 21 (FGF21) is an endocrine hormone mainly secreted by the liver, which can bind to its receptor (FGFR) and co-receptor beta klotho (KLB) to form a receptor complex, exerting its lipid-lowering function. 2,3,5,4'-Tetrahydroxy-stilbene-2-O-β-D-glucoside (TSG), a natural compound isolated from Polygonum multiflorum Thunb, has shown excellent activity in lowering lipid content and efficacy in improving NAFLD. In this study we investigated whether FGF21 was implicated in the therapeutic effect of TSG in NAFLD mice. NAFLD was induced in mice by feeding with a high-fat diet (HFD) for 12 weeks, and treated with TSG (20, 40 mg·kg-1·d-1, i.g.) during the last 4 weeks. We showed that TSG treatment significantly alleviated NAFLD in HFD-fed mice evidenced by reduced hepatic triglyceride (TG) and non-esterified fatty acids (NEFA), diminished lipid droplets and decreased NAFLD activity score (NAS) in liver tissues. We demonstrated that TSG treatment significantly increased the mRNA and protein levels of FGF21 in vitro and in vivo, and reduced lipid accumulation in both the liver and adipose tissues. Transcriptomics analysis revealed that TSG treatment significantly increased the nuclear translocation of a transcription factor RUNX1. Knockdown of Runx1 in HFD-fed mice eliminated the efficacy of TSG in alleviating NAFLD, reducing hepatic lipid accumulation and regulating FGF21 signaling pathway in liver and adipose tissues. In conclusion, TSG alleviates NAFLD by enhancing the FGF21-mediated lipid metabolism in a RUNX1-dependent manner.

3D Mitochondrial Structure in Aging Human Skeletal Muscle: Insights Into MFN-2-Mediated Changes

Age-related skeletal muscle atrophy, known as sarcopenia, is characterized by loss of muscle mass, strength, endurance, and oxidative capacity. Although exercise has been shown to mitigate sarcopenia, the underlying governing mechanisms are poorly understood. Mitochondrial dysfunction is implicated in aging and sarcopenia; however, few studies explore how mitochondrial structure contributes to this dysfunction. In this study, we sought to understand how aging impacts mitochondrial three-dimensional (3D) structure and its regulators in skeletal muscle. We hypothesized that aging leads to remodeling of mitochondrial 3D architecture permissive to dysfunction and is ameliorated by exercise. Using serial block-face scanning electron microscopy (SBF-SEM) and Amira software, mitochondrial 3D reconstructions from patient biopsies were generated and analyzed. Across five human cohorts, we correlate differences in magnetic resonance imaging, mitochondria 3D structure, exercise parameters, and plasma immune markers between young (under 50 years) and old (over 50 years) individuals. We found that mitochondria are less spherical and more complex, indicating age-related declines in contact site capacity. Additionally, aged samples showed a larger volume phenotype in both female and male humans, indicating potential mitochondrial swelling. Concomitantly, muscle area, exercise capacity, and mitochondrial dynamic proteins showed age-related losses. Exercise stimulation restored mitofusin 2 (MFN2), one such of these mitochondrial dynamic proteins, which we show is required for the integrity of mitochondrial structure. Furthermore, we show that this pathway is evolutionarily conserved, as Marf, the MFN2 ortholog in Drosophila, knockdown alters mitochondrial morphology and leads to the downregulation of genes regulating mitochondrial processes. Our results define age-related structural changes in mitochondria and further suggest that exercise may mitigate age-related structural decline through modulation of mitofusin 2.

Volume and quality of the gluteal muscles are associated with early physical function after total hip arthroplasty

PURPOSE

Identifying muscles linked to postoperative physical function can guide protocols to enhance early recovery following total hip arthroplasty (THA). This study aimed to evaluate the association of preoperative pelvic and thigh muscle volume and quality with early physical function after THA in patients with unilateral hip osteoarthritis (HOA).

METHODS

Preoperative Computed tomography (CT) images of 61 patients (eight males and 53 females) with HOA were analyzed. Six muscle groups were segmented from CT images, and muscle volume and quality were calculated on the healthy and affected sides. Muscle quality was quantified using the mean CT values (Hounsfield units [HU]). Early postoperative physical function was evaluated using the Timed Up & Go test (TUG) at three weeks after THA. The effect of preoperative muscle volume and quality of both sides on early postoperative physical function was assessed.

RESULTS

On the healthy and affected sides, mean muscle mass was 9.7 cm3/kg and 8.1 cm3/kg, and mean muscle HU values were 46.0 HU and 39.1 HU, respectively. Significant differences in muscle volume and quality were observed between the affected and healthy sides. On analyzing the function of various muscle groups, the TUG score showed a significant association with the gluteus maximum volume and the gluteus medius/minimus quality on the affected side.

CONCLUSION

Patients with HOA showed significant muscle atrophy and fatty degeneration in the affected pelvic and thigh regions. The gluteus maximum volume and gluteus medius/minimus quality were associated with early postoperative physical function. Preoperative rehabilitation targeting the gluteal muscles on the affected side could potentially enhance recovery of physical function in the early postoperative period.

Melatonin and Exercise Restore Myogenesis and Mitochondrial Dynamics Deficits Associated With Sarcopenia in iMS-Bmal1-/- Mice

Sarcopenia, a condition associated with aging, involves progressive loss of muscle mass, strength, and function, leading to impaired mobility, health, and increased mortality. The underlying mechanisms remain unclear, which limits the development of effective therapeutic interventions. Emerging evidence implicates chronodisruption as a key contributor to sarcopenia, emphasizing the role of Bmal1, a circadian clock gene critical for muscle integrity and mitochondrial function. In a skeletal muscle-specific and inducible Bmal1 knockout model (iMS-Bmal1-/-), we observed hallmark features of sarcopenia, including disrupted rhythms, impaired muscle function, and mitochondrial dysfunction. Exercise and melatonin treatment reversed these deficits independently of Bmal1. Building on these findings, the present study elucidates several mechanisms underlying these changes and the pathways by which melatonin and exercise exert their beneficial effects. Our findings indicate that iMS-Bmal1-/- mice exhibit reduced expression of satellite cell and muscle regulatory factors, indicating impaired muscle regeneration. While mitochondrial respiration remained unchanged, notable alterations in mitochondrial dynamics disrupted mitochondria in skeletal muscle. In addition, these mice showed alterations in muscle energy metabolism, compromised antioxidant defense, and inflammatory response. Remarkably, exercise and/or melatonin successfully mitigated these deficits, restoring muscle health in Bmal1-deficient mice. These findings position exercise and melatonin as promising therapeutic candidates for combating sarcopenia and emphasize the need to elucidate the molecular pathways underlying their protective effects.

Myokines as potential mediators of changes in glucose homeostasis and muscle mass after bariatric surgery

Myokines are bioactive peptides released by skeletal muscle. Myokines exert auto-, para-, or endocrine effects, enabling them to regulate many aspects of metabolism in various tissues. However, the contribution of myokines to the dramatic changes in glucose homeostasis and muscle mass induced by bariatric surgery has not been established. Our review highlights that myokines such as brain-derived neurotrophic factor (BDNF), meteorin-like protein (Metrnl), secreted protein acidic and rich in cysteine (SPARC), apelin (APLN) and myostatin (MSTN) may mediate changes in glucose homeostasis and muscle mass after bariatric surgery. Our review also identifies myonectin as an interesting candidate for future studies, as this myokine may regulate lipid metabolism and muscle mass after bariatric surgery. These myokines may provide novel therapeutic targets and biomarkers for obesity, type 2 diabetes and sarcopenia.

Plasma biomarkers in patients with age-related sarcopenia: a proteomic exploration and experimental validation

BACKGROUND

Various biomarkers associated with sarcopenia have been identified. However, there is a scarcity of studies exploring and validating biomarkers in individuals with age-related sarcopenia.

AIMS

This study aimed to investigate the proteome and identify potential biomarkers for age-related sarcopenia.

METHODS

Proteomic analysis and experimental validation were conducted using plasma from hospitalized older adults. Sarcopenia diagnosis was based on the Asian Working Group for Sarcopenia 2019 criteria. Data-independent acquisition-based proteomics was performed on plasma from 60 participants, with 30 diagnosed with sarcopenia and 30 without sarcopenia. Differentially expressed proteins (DEPs) were selected and evaluated by Receiver Operating Characteristic (ROC) analysis. Biomarker candidates were further quantitatively validated by enzyme-linked immunosorbent assay (ELISA) utilizing plasma from 6 participants with sarcopenia and 6 without sarcopenia.

RESULTS

A total of 39 DEPs were identified and 12 DEPs were selected for ROC analysis. 8 DEPs were included for ELISA validation based on their predictive performance. Paraoxonase-3 (PON3) consistently showed down-regulation in the sarcopenic group across both methodologies. Insulin-like growth factor-binding protein-2 (IGFBP2) showed inconsistency in the sarcopenic group, with up-regulation observed in proteomic analysis but down-regulation in ELISA.

DISCUSSION

Decline in PON3 may result in an overload of oxidative stress in skeletal muscles and contribute to sarcopenia. Protein modifications of IGFBP2 might exhibit during sarcopenia pathogenesis.

CONCLUSIONS

Plasma proteins are implicated in sarcopenia pathogenesis. PON3 is highlighted as a potential biomarker for patients with age-related sarcopenia. Further studies are imperative to gain an in-depth understanding of PON3 and IGFBP2.

Obesity, Osteoarthritis, and Myokines: Balancing Weight Management Strategies, Myokine Regulation, and Muscle Health

Obesity and osteoarthritis (OA) are increasingly prevalent conditions that are intricately linked, with each exacerbating the other's pathogenesis and worsening patient outcomes. This review explores the dual impact of obesity on OA, highlighting the role of excessive weight in aggravating joint degeneration and the limitations OA imposes on physical activity, which further perpetuates obesity. The role of muscle tissue, particularly the release of myokines during physical activity, is examined in the context of OA and obesity. Myokines such as irisin, IL-6, and myostatin are discussed for their roles in metabolic regulation, inflammation, and tissue repair, offering insights into their potential therapeutic targets. This review emphasizes the importance of supervised weight management methods in parallel with muscle rehabilitation in improving joint health and metabolic balance. The potential for myokine modulation through targeted exercise and weight loss interventions to mitigate the adverse effects of obesity and OA is also discussed, suggesting avenues for future research and therapy development to reduce the burden of these chronic conditions.

Oleuropein mitigates non-alcoholic fatty liver disease (NAFLD) and modulates liver metabolites in high-fat diet-induced obese mice via activating PPARα

BACKGROUND

This study aimed to elucidate the mechanism of oleuropein (OLE) ameliorates non-alcoholic fatty liver disease (NAFLD) and its underlying mechanisms.

RESULTS

Male C57BL/6J mice were fed either a low-fat diet (LFD), a high-fat diet (HFD), or a HFD supplemented with 0.03% (w/w) OLE for 16 weeks. OLE supplementation decreased body weight and liver weight, improved serum lipid profiles, and ameliorated HFD-induced hepatic dysfunction. Liver metabolomics analysis revealed that OLE increased the levels of nicotinamide, tauroursodeoxycholic acid, taurine, and docosahexaenoic acid, which were beneficial for lipid homeostasis and inflammation regulation. OLE exerted its protective effects by activating peroxisome proliferator-activated receptor alpha (PPARα), a key transcription factor that regulates fibroblast growth factor 21 (FGF21) expression and modulates lipid oxidation, lipogenesis and inflammation pathways. Importantly, OLE supplementation did not significantly affect body weight or liver weight in PPARα knockout (PPARα KO) mice, indicating that PPARα is essential for OLE-mediated NAFLD prevention.

CONCLUSION

Our results suggest that OLE alleviates NAFLD in mice by activating PPARα and modulating liver metabolites. © 2024 Society of Chemical Industry.

Metabolomic profiles of ovariectomized mice and their associations with body composition and frailty-related parameters in postmenopausal women

BACKGROUND

Menopause, a dramatical estrogen-deficient condition, is considered the most significant milestone in women's health.

PURPOSE

To investigate the metabolite changes attributed to estrogen deficiency using random forest (RF)-based machine learning (ML) modeling strategy in ovariectomized (OVX) mice as well as determine the clinical relevance of selected metabolites in older women.

METHODS AND RESULTS

Untargeted and targeted metabolomic analyses revealed that metabolites related to TCA cycle, sphingolipids, phospholipids, fatty acids, and amino acids, were significantly changed in the plasma and/or muscle of OVX mice. Subsequent ML classifiers based on RF algorithm selected alpha-ketoglutarate (AKG), arginine, carnosine, ceramide C24, phosphatidylcholine (PC) aa C36:6, and PC ae C42:3 in plasma as well as PC aa 34:1, PC aa C34:3, PC aa C36:5, PC aa C32:1, PC aa C36:2, and sphingosine in muscle as top featured metabolites that differentiate the OVX mice from the sham-operated group. When circulating levels of AKG, arginine, and carnosine, which showed the most significant changes in OVX mice blood, were measured in postmenopausal women, higher plasma AKG levels were associated with lower bone mass, weak grip strength, poor physical performance, and increased frailty risk.

CONCLUSIONS

Metabolomics- and ML-based methods identified the key metabolites of blood and muscle that were significantly changed after ovariectomy in mice, and the clinical implication of several metabolites was investigated by looking at their correlation with body composition and frailty-related parameters in postmenopausal women. These findings provide crucial context for understanding the diverse physiological alterations caused by estrogen deficiency in women.

Dietary Protein and Physical Exercise for the Treatment of Sarcopenia

Sarcopenia is a multifactorial age-related disorder that causes a decrease in muscle mass, strength, and function, leading to alteration of movement, risk of falls, and hospitalization. This article aims to review recent findings on the factors underlying sarcopenia and the strategies required to delay and counteract its symptoms. We focus on molecular factors linked to ageing, on the role of low-grade chronic and acute inflammatory conditions such as cancer, which contributes to the onset of sarcopenia, and on the clinical criteria for its diagnosis. The use of drugs against sarcopenia is still subject to debate, and the suggested approaches to restore muscle health are based on adequate dietary protein intake and physical exercise. We also highlight the difference in the amount and quality of amino acids within animal- and plant-based diets, as studies have often shown varying results regarding their effect on sarcopenia in elderly people. In addition, many studies have reported that non-pharmacological approaches, such as an optimization of dietary protein intake and training programs based on resistance exercise, can be effective in preventing and delaying sarcopenia. These approaches not only improve the maintenance of skeletal muscle function, but also reduce health care costs and improve life expectancy and quality in elderly people.

Role of signaling pathways in age-related orthopedic diseases: focus on the fibroblast growth factor family

Fibroblast growth factor (FGF) signaling encompasses a multitude of functions, including regulation of cell proliferation, differentiation, morphogenesis, and patterning. FGFs and their receptors (FGFR) are crucial for adult tissue repair processes. Aberrant FGF signal transduction is associated with various pathological conditions such as cartilage damage, bone loss, muscle reduction, and other core pathological changes observed in orthopedic degenerative diseases like osteoarthritis (OA), intervertebral disc degeneration (IVDD), osteoporosis (OP), and sarcopenia. In OA and IVDD pathologies specifically, FGF1, FGF2, FGF8, FGF9, FGF18, FGF21, and FGF23 regulate the synthesis, catabolism, and ossification of cartilage tissue. Additionally, the dysregulation of FGFR expression (FGFR1 and FGFR3) promotes the pathological process of cartilage degradation. In OP and sarcopenia, endocrine-derived FGFs (FGF19, FGF21, and FGF23) modulate bone mineral synthesis and decomposition as well as muscle tissues. FGF2 and other FGFs also exert regulatory roles. A growing body of research has focused on understanding the implications of FGF signaling in orthopedic degeneration. Moreover, an increasing number of potential targets within the FGF signaling have been identified, such as FGF9, FGF18, and FGF23. However, it should be noted that most of these discoveries are still in the experimental stage, and further studies are needed before clinical application can be considered. Presently, this review aims to document the association between the FGF signaling pathway and the development and progression of orthopedic diseases. Besides, current therapeutic strategies targeting the FGF signaling pathway to prevent and treat orthopedic degeneration will be evaluated.

3D Mitochondrial Structure in Aging Human Skeletal Muscle: Insights into MFN-2 Mediated Changes

Age-related atrophy of skeletal muscle, is characterized by loss of mass, strength, endurance, and oxidative capacity during aging. Notably, bioenergetics and protein turnover studies have shown that mitochondria mediate this decline in function. Although exercise has been the only therapy to mitigate sarcopenia, the mechanisms that govern how exercise serves to promote healthy muscle aging are unclear. Mitochondrial aging is associated with decreased mitochondrial capacity, so we sought to investigate how aging affects mitochondrial structure and potential age-related regulators. Specifically, the three-dimensional (3D) mitochondrial structure associated with morphological changes in skeletal muscle during aging requires further elucidation. We hypothesized that aging causes structural remodeling of mitochondrial 3D architecture representative of dysfunction, and this effect is mitigated by exercise. We used serial block-face scanning electron microscopy to image human skeletal tissue samples, followed by manual contour tracing using Amira software for 3D reconstruction and subsequent analysis of mitochondria. We then applied a rigorous in vitro and in vivo exercise regimen during aging. Across 5 human cohorts, we correlate differences in magnetic resonance imaging, mitochondria 3D structure, exercise parameters, and plasma immune markers between young (under 50 years) and old (over 50 years) individuals. We found that mitochondria we less spherical and more complex, indicating age-related declines in contact site capacity. Additionally, aged samples showed a larger volume phenotype in both female and male humans, indicating potential mitochondrial swelling. Concomitantly, muscle area, exercise capacity, and mitochondrial dynamic proteins showed age-related losses. Exercise stimulation restored mitofusin 2 (MFN2), one such of these mitochondrial dynamic proteins, which we show is required for the integrity of mitochondrial structure. Furthermore, we show that this pathway is evolutionarily conserved as Marf, the MFN2 ortholog in Drosophila, knockdown alters mitochondrial morphology and leads to the downregulation of genes regulating mitochondrial processes. Our results define age-related structural changes in mitochondria and further suggest that exercise may mitigate age-related structural decline through modulation of mitofusin 2.

Differences in Type 2 Fiber Composition in the Vastus Lateralis and Gluteus Maximus of Patients with Hip Fractures

BACKGRUOUND

Aging leads to sarcopenia, which is characterized by reduced muscle mass and strength. Many factors, including altered muscle protein turnover, diminished neuromuscular function, hormonal changes, systemic inflammation, and the structure and composition of muscle fibers, play a crucial role in age-related muscle decline. This study explored differences in muscle fiber types contributing to overall muscle function decline in aging, focusing on individuals with hip fractures from falls.

METHODS

A pilot study at Chungnam National University Hospital collected muscle biopsies from hip fracture patients aged 20 to 80 undergoing surgical treatment. Muscle biopsies from the vastus lateralis and gluteus maximus were obtained during hip arthroplasty or internal fixation. Handgrip strength, calf and thigh circumference, and bone mineral density were evaluated in individuals with hip fractures from falls. We analyzed the relationships between each clinical characteristic and muscle fiber type.

RESULTS

In total, 26 participants (mean age 67.9 years, 69.2% male) were included in this study. The prevalence of sarcopenia was 53.8%, and that of femoral and lumbar osteoporosis was 19.2% and 11.5%, respectively. Vastus lateralis analysis revealed an age-related decrease in type IIx fibers, a higher proportion of type IIa fibers in women, and an association between handgrip strength and type IIx fibers in men. The gluteus maximus showed no significant correlations with clinical parameters.

CONCLUSION

This study identified complex associations between age, sex, handgrip strength, and muscle fiber composition in hip fracture patients, offering insights crucial for targeted interventions combating age-related muscle decline and improving musculoskeletal health.

Features of acute COVID-19 associated with post-acute sequelae of SARS-CoV-2 phenotypes: results from the IMPACC study

Post-acute sequelae of SARS-CoV-2 (PASC) is a significant public health concern. We describe Patient Reported Outcomes (PROs) on 590 participants prospectively assessed from hospital admission for COVID-19 through one year after discharge. Modeling identified 4 PRO clusters based on reported deficits (minimal, physical, mental/cognitive, and multidomain), supporting heterogenous clinical presentations in PASC, with sub-phenotypes associated with female sex and distinctive comorbidities. During the acute phase of disease, a higher respiratory SARS-CoV-2 viral burden and lower Receptor Binding Domain and Spike antibody titers were associated with both the physical predominant and the multidomain deficit clusters. A lower frequency of circulating B lymphocytes by mass cytometry (CyTOF) was observed in the multidomain deficit cluster. Circulating fibroblast growth factor 21 (FGF21) was significantly elevated in the mental/cognitive predominant and the multidomain clusters. Future efforts to link PASC to acute anti-viral host responses may help to better target treatment and prevention of PASC.

Fibroblast Growth Factor 21: A Fascinating Perspective on the Regulation of Muscle Metabolism

Fibroblast growth factor 21 (FGF21) plays a vital role in normal eukaryotic organism development and homeostatic metabolism under the influence of internal and external factors such as endogenous hormone changes and exogenous stimuli. Over the last few decades, comprehensive studies have revealed the key role of FGF21 in regulating many fundamental metabolic pathways, including the muscle stress response, insulin signaling transmission, and muscle development. By coordinating these metabolic pathways, FGF21 is thought to contribute to acclimating to a stressful environment and the subsequent recovery of cell and tissue homeostasis. With the emphasis on FGF21, we extensively reviewed the research findings on the production and regulation of FGF21 and its role in muscle metabolism. We also emphasize how the FGF21 metabolic networks mediate mitochondrial dysfunction, glycogen consumption, and myogenic development and investigate prospective directions for the functional exploitation of FGF21 and its downstream effectors, such as the mammalian target of rapamycin (mTOR).

Integrated procedures for accelerating, deepening, and leading genetic inquiry: A first application on human muscle secretome

PURPOSE

Beyond classical procedures, bioinformatic-assisted approaches and computational biology offer unprecedented opportunities for scholars. However, these amazing possibilities still need epistemological criticism, as well as standardized procedures. Especially those topics with a huge body of data may benefit from data science (DS)-assisted methods. Therefore, the current study dealt with the combined expert-assisted and DS-assisted approaches to address the broad field of muscle secretome. We aimed to apply DS tools to fix the literature research, suggest investigation targets with a data-driven approach, predict possible scenarios, and define a workflow.

METHODS

Recognized scholars with expertise on myokines were invited to provide a list of the most important myokines. GeneRecommender, GeneMANIA, HumanNet, and STRING were selected as DS tools. Networks were built on STRING and GeneMANIA. The outcomes of DS tools included the top 5 recommendations. Each expert-led discussion has been then integrated with an DS-led approach to provide further perspectives.

RESULTS

Among the results, 11 molecules had already been described as bona-fide myokines in literature, and 11 molecules were putative myokines. Most of the myokines and the putative myokines recommended by the DS tools were described as present in the cargo of extracellular vesicles.

CONCLUSIONS

Including both supervised and unsupervised learning methods, as well as encompassing algorithms focused on both protein interaction and gene represent a comprehensive approach to tackle complex biomedical topics. DS-assisted methods for reviewing existent evidence, recommending targets of interest, and predicting original scenarios are worth exploring as in silico recommendations to be integrated with experts' ideas for optimizing molecular studies.

Lack of association between serum myonectin levels and sarcopenia in older Asian adults

Myonectin is a muscle-secreted factor that helps maintain homeostasis in the body by regulating several functions, including lipid metabolism. Previous studies suggested that myonectin may play a role in muscle health in an autocrine manner, but its impact on human skeletal muscle is still unclear. We aimed to investigate the relationship of serum myonectin levels with sarcopenia and related muscle parameters. We conducted a cross-sectional study of 142 older adults whose muscle mass, grip strength, gait speed, chair stands, and short physical performance battery (SPPB) were evaluated in the geriatric clinic of a tertiary medical center. Sarcopenia was defined based on Asian-specific cutoff values, and circulating myonectin levels were measured using an enzyme immunoassay. Before and after adjusting for age, sex, and body mass index, the serum myonectin level was not significantly different when the patients were stratified by status of sarcopenia, muscle mass, muscle strength, and physical performance. Furthermore, whether given as a continuous variable or divided into quartile groups, the serum myonectin level had no association with the skeletal muscle mass, grip strength, gait speed, chair stand test, or SPPB score. Our findings did not confirm the potential role of myonectin in muscle metabolism observed in experimental research. Thus, serum myonectin levels cannot predict the risk of sarcopenia in older Asian adults.

Sarcopenic obesity: epidemiology, pathophysiology, cardiovascular disease, mortality, and management

Sarcopenic obesity is defined as the coexistence of sarcopenia and obesity in the same individual, characterized by of the co-presence of body fat accumulation and muscle loss. This condition is currently a major concern as it is associated with frailty and disabilities such as cardiovascular disease, fractures, dementia, cancer, and increased all-cause mortality. Particularly, older individuals remain at risk of sarcopenic obesity. Progress at several levels is needed to improve the global prognostic outlook for this condition, including the elaboration and implementation of a more uniform definition that may favor the identification and specification of prevalence by age group. Furthermore, improvements in the understanding of the pathogenesis of sarcopenic obesity may lead to the development of more specific therapeutic interventions to improve prognosis. We reviewed the knowledge on sarcopenic obesity and its associations with cardiovascular diseases and mortality.

Exploring the correlation between serum fibroblast growth factor-21 levels and Sarcopenia: a systematic review and meta-analysis

BACKGROUND

Fibroblast growth factor 21 (FGF-21) plays an important role in the growth and metabolism of skeletal muscle cells. This study aims to systemically review the evidence regarding the relationship between FGF-21 levels and Sarcopenia, as well as the related influential factors.

METHODS

This review was conducted according to the PRISMA guidelines. We comprehensively searched PubMed, EMBASE, the Web of Science, Scopus, and Chinese Databases (CNKI, Wan Fang, VIP, and CBM) up to 1 May 2023. 3 investigators performed independent literature screening and data extraction of the included literature, and two investigators performed an independent quality assessment of case-control studies using the Joanna Briggs Institute (JBI) tool. Data analysis was performed using Review Manager 5.4 software. For continuous various outcomes, mean difference (MD) or standard mean difference (SMD) with 95% confidence intervals (CIs) was applied for assessment by fixed-effect or random-effect model analysis. The heterogeneity test was performed by the Q-statistic and quantified using I², and publication bias was evaluated using a funnel plot.

RESULTS

Five studies with a total of 625 cases were included in the review. Meta-analysis showed lower BMI in the sarcopenia group [MD= -2.88 (95% CI, -3. 49, -2.27); P < 0.00001; I² = 0%], significantly reduced grip strength in the sarcopenia group compared to the non-sarcopenia group [MD = -7.32(95% CI, -10.42,-4.23); P < 0.00001; I² = 93%]. No statistically significant differences in serum FGF21 levels were found when comparing the two groups of subjects [SMD = 0.31(95% CI, -0.42, 1.04); P = 0.41; I² = 94%], and no strong correlation was found between the onset of sarcopenia and serum FGF21 levels.

CONCLUSION

The diagnosis of sarcopenia is followed by a more significant decrease in muscle mass and strength, but there is a lack of strong evidence to support a direct relationship between elevated organismal FGF21 and sarcopenia, and it is not convincing to use FGF21 as a biological or diagnostic marker for sarcopenia. The currently used diagnostic criteria for sarcopenia and setting of cut-off values for each evaluation parameter no longer seem to match clinical practice.

Interplay of skeletal muscle and adipose tissue: sarcopenic obesity

Sarcopenic obesity is becoming a global health concern, owing to the rising older population, causing cardiometabolic morbidity and mortality. Loss of muscle exceeding normal age-related changes has been revealed to be associated with obesity, aggravating each other through complex interactions. Physiological regeneration and proliferation of muscle tissue are achieved through harmonious processes of regulated inflammation, autophagy, muscle satellite cell proliferation, and signaling molecule function. Adipokines and myokines are signaling molecules from adipose tissue and muscle, respectively, that exert autocrine, paracrine, and endocrine effects on fat and muscle tissues. These signaling molecules interact with each other to regulate metabolic homeostasis. However, excessive adiposity creates pro-inflammatory conditions, leading to metabolic disorders and the disorganization of systemic homeostasis. Therefore, obesity impedes muscle tissue regeneration and induces the loss of muscle mass and function. Numerous studies have attempted to demonstrate the pathophysiological interaction between sarcopenia and obesity, but the interwoven matrix of the relationship between myokines and adipokines has made it difficult for researchers to understand them. This review briefly describes updated information about the crosstalk between muscle and adipose tissue.

Biochemical Markers of Musculoskeletal Health and Aging to be Assessed in Clinical Trials of Drugs Aiming at the Treatment of Sarcopenia: Consensus Paper from an Expert Group Meeting Organized by the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) and the Centre Académique de Recherche et d'Expérimentation en Santé (CARES SPRL), Under the Auspices of the World Health Organization Collaborating Center for the Epidemiology of Musculoskeletal Conditions and Aging

In clinical trials, biochemical markers provide useful information on the drug's mode of action, therapeutic response and side effect monitoring and can act as surrogate endpoints. In pharmacological intervention development for sarcopenia management, there is an urgent need to identify biomarkers to measure in clinical trials and that could be used in the future in clinical practice. The objective of the current consensus paper is to provide a clear list of biochemical markers of musculoskeletal health and aging that can be recommended to be measured in Phase II and Phase III clinical trials evaluating new chemical entities for sarcopenia treatment. A working group of the European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases (ESCEO) proposed classifying biochemical markers into 2 series: biochemical markers evaluating musculoskeletal status and biochemical markers evaluating causal factors. For series 1, the group agreed on 4 biochemical markers that should be assessed in Phase II or Phase III trials (i.e., Myostatin-Follistatin, Brain Derived Neurotrophic Factor, N-terminal Type III Procollagen and Serum Creatinine to Serum Cystatin C Ratio - or the Sarcopenia Index). For series 2, the group agreed on 6 biochemical markers that should be assessed in Phase II trials (i.e., the hormones insulin-like growth factor-1 (IGF-I), dehydroepiandrosterone sulphate, and cortisol, and the inflammatory markers C-reactive protein (CRP), interleukin-6 and tumor necrosis factor-α), and 2 in Phase III trials (i.e., IGF-I and CRP). The group also proposed optional biochemical markers that may provide insights into the mode of action of pharmacological therapies. Further research and development of new methods for biochemical marker assays may lead to the evolution of these recommendations.

The Contribution of Diet Therapy and Probiotics in the Treatment of Sarcopenia Induced by Prolonged Immobilization Caused by the COVID-19 Pandemic

The prolonged immobilization associated with COVID-19 infection and the restrictions imposed by the pandemic have determined major changes in physical activity and eating habits, with a negative impact on physical performance. This study monitored non-pharmacological interventions (diet therapy and probiotics) in managing sarcopenia for patients with recent SARS-CoV-2 history (14 days). A prospective study was performed on 200 patients (between December 2020−December 2021), with SPPB score < 9, randomly divided into: Group K—DP (93 patients) with dietary therapy (protein 1.2−1.5 g/kg) and probiotics for two months; and Group K—non-DP (107 patients) without diet therapy and probiotics. All patients were included in a specific physical training program (40 min), three sessions per week. Skeletal muscle index (SMI), serum albumin, and hemoglobin were determined. The SMI was initially low for both groups without significant statistical differences (6.5 ± 0.52 kg/m2 for Group K—non-DP vs. 6.7 ± 0.57 Kg/m2 for Group K—DP, p = 0.135). After two months, significant difference between initial and final SMI values was determined for Group K—DP (6.92 ± 0.50 kg/m2 vs. 6.77 ± 0.56 kg/m2, p = 0.048). In Group K—DP, at end of study, were more patients with normal SMI (n = 32 → N = 70) values (p < 0.001) and fewer sarcopenia patients (p < 0.001). The initial serum albumin means values in the two groups (Group K—non-DP, 4.17 ± 1.04 g/dL, and Group K—DP, 3.95 ± 0.98 g/dL) were not statistically significantly different (p = 0.122). The hemoglobin level improved significantly following a hyper protein diet enriched with pro-biotics (p = 0.003). Diet therapy, consisting of increased protein intake and specific probiotics and specific physical therapy, demonstrated superiority in improving the functional status of patients with recent COVID-19 infection.

Association between Plasma FGF21 Levels and Body Composition in Patients with Gastric Cancer

BACKGROUND

Accumulating evidence has suggested that Fibroblast growth factor 21 (FGF21) plays an important role in metabolic diseases. This study aimed to investigate the relationship between plasma FGF21 levels and body composition parameters in gastric cancer (GC) patients.

METHODS

This study was cross-sectional based on a prospective cohort of GC patients in a single center. Computer tomography (CT) and bioelectrical impedance analysis (BIA) were used to estimate skeletal muscle and adipose tissue mass. Blood samples were collected and plasma concentrations of FGF21 were measured by ELISA. Spearman's rank correlation test and logistic regression analysis were performed to assess associations between plasma FGF21 levels and these body composition parameters.

RESULTS

A total of 66 GC patients were enrolled in this study. Plasma FGF21 levels were significantly higher in women compared with men. The plasma FGF21 levels were positively correlated with fat mass index (FMI), fat mass percentage (FM%), and subcutaneous adipose tissue index (SATI). Furthermore, after adjustment for confounders, the lower plasma FGF21 levels were remain associated with increased odds for low SATI.

CONCLUSIONS

Plasma FGF21 levels were positively associated with FMI, FM%, and SATI in GC patients, suggesting a potential mechanistic link between FGF21 and subcutaneous adipose tissue in GC.

LKB1 acts as a critical brake for the glucagon-mediated fasting response

As important as the fasting response is for survival, an inability to shut it down once nutrients become available can lead to exacerbated disease and severe wasting. The liver is central to transitions between feeding and fasting states, with glucagon being a key initiator of the hepatic fasting response. However, the precise mechanisms controlling fasting are not well defined. One potential mediator of these transitions is liver kinase B1 (LKB1), given its role in nutrient sensing. Here, we show LKB1 knockout mice have a severe wasting and prolonged fasting phenotype despite increased food intake. By applying RNA sequencing and intravital microscopy, we show that loss of LKB1 leads to a dramatic reprogramming of the hepatic lobule through robust up-regulation of periportal genes and functions. This is likely mediated through the opposing effect that LKB1 has on glucagon pathways and gene expression. Conclusion: Our findings show that LKB1 acts as a brake to the glucagon-mediated fasting response, resulting in "periportalization" of the hepatic lobule and whole-body metabolic inefficiency. These findings reveal a mechanism by which hepatic metabolic compartmentalization is regulated by nutrient-sensing.

Muscle-to-tumor crosstalk: The effect of exercise-induced myokine on cancer progression

Physical exercise has gradually become a focus in cancer treatment due to its pronounced role in reducing cancer risk, enhancing therapeutic efficacy, and improving prognosis. In recent decades, skeletal muscles have been considered endocrine organs, exerting their biological functions via the endocrine, autocrine, and paracrine systems by secreting various types of myokines. The amount of myokines secreted varies depending on the intensity, type, and duration of exercise. Recent studies have shown that muscle-derived myokines are highly involved the effects of exercise on cancer. Multiple myokines, such as interleukin-6 (IL-6), oncostatin M (OSM), secreted protein acidic and rich in cysteine (SPARC), and irisin, directly mediate cancer progression by influencing the proliferation, apoptosis, stemness, drug resistance, metabolic reprogramming, and epithelial-mesenchymal transformation (EMT) of cancer cells. In addition, IL-6, interleukin-8 (IL-8), interleukin-15 (IL-15), brain-derived neurotrophic factor (BDNF), and irisin can improve obesity-induced inflammation by stimulating lipolysis of adipose tissues, promoting glucose uptake, and accelerating the browning of white fat. Furthermore, some myokines could regulate the tumor microenvironment, such as angiogenesis and the immune microenvironment. Cancer cachexia occurs in up to 80% of cancer patients and is responsible for 22%-30% of patient deaths. It is characterized by systemic inflammation and decreased muscle mass. Exercise-induced myokine production is important in regulating cancer cachexia. This review summarizes the roles and underlying mechanisms of myokines, such as IL-6, myostatin, IL-15, irisin, fibroblast growth factor 21 (FGF21) and musclin, in cancer cachexia. Through comprehensive analysis, we conclude that myokines are potential targets for inhibiting cancer progression and the associated cachexia.

Research Progress of Fibroblast Growth Factor 21 in Fibrotic Diseases

Fibrosis is a common pathological outcome of chronic injuries, characterized by excessive deposition of extracellular matrix components in organs, as seen in most chronic inflammatory diseases. At present, there is an increasing tendency of the morbidity and mortality of diseases caused by fibrosis, but the treatment measures for fibrosis are still limited. Fibroblast growth factor 21 (FGF21) belongs to the FGF19 subfamily, which also has the name endocrine FGFs because of their endocrine manner. In recent years, it has been found that plasma FGF21 level is significantly correlated with fibrosis progression. Furthermore, there is evidence that FGF21 has a pronounced antifibrotic effect in a variety of fibrotic diseases. This review summarizes the biological effects of FGF21 and discusses what is currently known about this factor and fibrosis disease, highlighting emerging insights that warrant further research.

Exercise Therapy for People With Sarcopenic Obesity: Myokines and Adipokines as Effective Actors

Sarcopenic obesity is defined as a multifactorial disease in aging with decreased body muscle, decreased muscle strength, decreased independence, increased fat mass, due to decreased physical activity, changes in adipokines and myokines, and decreased satellite cells. People with sarcopenic obesity cause harmful changes in myokines and adipokines. These changes are due to a decrease interleukin-10 (IL-10), interleukin-15 (IL-15), insulin-like growth factor hormone (IGF-1), irisin, leukemia inhibitory factor (LIF), fibroblast growth factor-21 (FGF-21), adiponectin, and apelin. While factors such as myostatin, leptin, interleukin-6 (IL-6), interleukin-8 (IL-8), and resistin increase. The consequences of these changes are an increase in inflammatory factors, increased degradation of muscle proteins, increased fat mass, and decreased muscle tissue, which exacerbates sarcopenia obesity. In contrast, exercise, especially strength training, reverses this process, which includes increasing muscle protein synthesis, increasing myogenesis, increasing mitochondrial biogenesis, increasing brown fat, reducing white fat, reducing inflammatory factors, and reducing muscle atrophy. Since some people with chronic diseases are not able to do high-intensity strength training, exercises with blood flow restriction (BFR) are newly recommended. Numerous studies have shown that low-intensity BFR training produces the same increase in hypertrophy and muscle strength such as high-intensity strength training. Therefore, it seems that exercise interventions with BFR can be an effective way to prevent the exacerbation of sarcopenia obesity. However, due to limited studies on adipokines and exercises with BFR in people with sarcopenic obesity, more research is needed.

Fibroblast Growth Factor 21 Facilitates the Homeostatic Control of Feeding Behavior

Fibroblast growth factor 21 (FGF21) is a stress hormone that is released from the liver in response to nutritional and metabolic challenges. In addition to its well-described effects on systemic metabolism, a growing body of literature now supports the notion that FGF21 also acts via the central nervous system to control feeding behavior. Here we review the current understanding of FGF21 as a hormone regulating feeding behavior in rodents, non-human primates, and humans. First, we examine the nutritional contexts that induce FGF21 secretion. Initial reports describing FGF21 as a 'starvation hormone' have now been further refined. FGF21 is now better understood as an endocrine mediator of the intracellular stress response to various nutritional manipulations, including excess sugars and alcohol, caloric deficits, a ketogenic diet, and amino acid restriction. We discuss FGF21's effects on energy intake and macronutrient choice, together with our current understanding of the underlying neural mechanisms. We argue that the behavioral effects of FGF21 function primarily to maintain systemic macronutrient homeostasis, and in particular to maintain an adequate supply of protein and amino acids for use by the cells.

Association of FGF-19 and FGF-21 levels with primary sarcopenia

AIM

Serum fibroblast growth factor (FGF)-19 and FGF-21 levels have been reported to be associated with muscle hemostasis. This study aims to explore the relationship between the levels of these markers and sarcopenia.

METHODS

In our single-center, cross-sectional study, patients over 65 years old presenting to the geriatric outpatient clinic were included. Patients with secondary sarcopenia were excluded. The Strength-Assistance with walking-Rising from a chair-Climbing stairs and Falls (SARC-F) questionnaire was applied to all patients. Sarcopenia was determined by handgrip strength (HGS), bioelectrical impedance analysis and 6-m walk test. Serum samples were stored at -80°C until measurement. The ELISA method was used to assess FGF-19 and FGF-21 levels.

RESULTS

In total, 88 patients (54 women) were included. There were 43 patients in the sarcopenia group and 45 patients without sarcopenia in the control group. In those with sarcopenia, FGF-19 was lower (P = 0.04) and FGF-21 was higher (P = 0.021). There was a direct correlation between FGF-19 with SARC-F and HGS (P = 0.04, B = 0.178, P = 0.006, B = 0.447) while FGF-21 was inversely correlated with HGS and positively correlated with 6-m walking time (P = 0.016, B = -0.428, P = 0.004, B = 0.506).

CONCLUSIONS

Our results reveal that low FGF-19 and high FGF-21 may be associated with sarcopenia and this finding could be explained by the impacted muscle strength. Geriatr Gerontol Int 2021; 21: 959-962.

Biomarkers for Cancer Cachexia: A Mini Review

Cancer cachexia is a common condition in many cancer patients, particularly those with advanced disease. Cancer cachexia patients are generally less tolerant to chemotherapies and radiotherapies, largely limiting their treatment options. While the search for treatments of this condition are ongoing, standards for the efficacy of treatments have yet to be developed. Current diagnostic criteria for cancer cachexia are primarily based on loss of body mass and muscle function. However, these criteria are rather limiting, and in time, when weight loss is noticeable, it may be too late for treatment. Consequently, biomarkers for cancer cachexia would be valuable adjuncts to current diagnostic criteria, and for assessing potential treatments. Using high throughput methods such as "omics approaches", a plethora of potential biomarkers have been identified. This article reviews and summarizes current studies of biomarkers for cancer cachexia.