Association of plasma FGF21 levels with muscle mass and muscle strength in a national multicentre cohort study: Korean Frailty and Aging Cohort Study

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.

Biomarkers of frailty

Several biomarkers have been proposed to identify frailty, a multisystemic age-related syndrome. However, the complex pathophysiology and the absence of a consensus on a comprehensive and universal definition make it challenging to pinpoint a singular biomarker or set of biomarkers that conclusively characterize frailty. This review delves into the main laboratory biomarkers, placing special emphasis on those associated with various pathways closely tied to the frailty condition, such as inflammation, oxidative stress, mitochondrial dysfunction, metabolic and endocrine alterations and microRNA. Additionally, we provide a summary of different clinical biomarkers encompassing different tools that have been proposed to assess frailty. We further address various imaging biomarkers such as Dual Energy X-ray Absorptiometry, Bioelectrical Impedance analysis, Computed Tomography and Magnetic Resonance Imaging, Ultrasound and D3 Creatine dilution. Intervention to treat frailty, including non-pharmacological ones, especially those involving physical exercise and nutrition, and pharmacological interventions, that include those targeting specific mechanisms such as myostatin inhibitors, insulin sensitizer metformin and with special relevance for hormonal treatments are mentioned. We further address the levels of different biomarkers in monitoring the potential positive effects of some of these interventions. Despite the availability of numerous biomarkers, their performance and usefulness in the clinical arena are far from being satisfactory. Considering the multicausality of frailty, there is an increasing need to assess the role of sets of biomarkers and the combination between laboratory, clinical and image biomarkers, in terms of sensitivity, specificity and predictive values for the diagnosis and prognosis of the different outcomes of frailty to improve detection and monitoring of older people with frailty or at risk of developing it, being this a need in the everyday clinical practice.

The role of mitochondrial dynamics and mitophagy in skeletal muscle atrophy: from molecular mechanisms to therapeutic insights

Skeletal muscle is the largest metabolic organ of the human body. Maintaining the best quality control and functional integrity of mitochondria is essential for the health of skeletal muscle. However, mitochondrial dysfunction characterized by mitochondrial dynamic imbalance and mitophagy disruption can lead to varying degrees of muscle atrophy, but the underlying mechanism of action is still unclear. Although mitochondrial dynamics and mitophagy are two different mitochondrial quality control mechanisms, a large amount of evidence has indicated that they are interrelated and mutually regulated. The former maintains the balance of the mitochondrial network, eliminates damaged or aged mitochondria, and enables cells to survive normally. The latter degrades damaged or aged mitochondria through the lysosomal pathway, ensuring cellular functional health and metabolic homeostasis. Skeletal muscle atrophy is considered an urgent global health issue. Understanding and gaining knowledge about muscle atrophy caused by mitochondrial dysfunction, particularly focusing on mitochondrial dynamics and mitochondrial autophagy, can greatly contribute to the prevention and treatment of muscle atrophy. In this review, we critically summarize the recent research progress on mitochondrial dynamics and mitophagy in skeletal muscle atrophy, and expound on the intrinsic molecular mechanism of skeletal muscle atrophy caused by mitochondrial dynamics and mitophagy. Importantly, we emphasize the potential of targeting mitochondrial dynamics and mitophagy as therapeutic strategies for the prevention and treatment of muscle atrophy, including pharmacological treatment and exercise therapy, and summarize effective methods for the treatment of skeletal muscle atrophy.

Late-life isoleucine restriction promotes physiological and molecular signatures of healthy aging

In defiance of the paradigm that calories from all sources are equivalent, we and others have shown that dietary protein is a dominant regulator of healthy aging. The restriction of protein or the branched-chain amino acid isoleucine promotes healthspan and extends lifespan when initiated in young or adult mice. However, many interventions are less efficacious or even deleterious when initiated in aged animals. Here, we investigate the physiological, metabolic, and molecular consequences of consuming a diet with a 67% reduction of all amino acids (Low AA), or of isoleucine alone (Low Ile), in male and female C57BL/6J.Nia mice starting at 20 months of age. We find that both diet regimens effectively reduce adiposity and improve glucose tolerance, which were benefits that were not mediated by reduced calorie intake. Both diets improve specific aspects of frailty, slow multiple molecular indicators of aging rate, and rejuvenate the aging heart and liver at the molecular level. These results demonstrate that Low AA and Low Ile diets can drive youthful physiological and molecular signatures, and support the possibility that these dietary interventions could help to promote healthy aging in older adults.

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).

Biomarkers of aging in frailty and age-associated disorders: State of the art and future perspective

According to the Geroscience concept that organismal aging and age-associated diseases share the same basic molecular mechanisms, the identification of biomarkers of age that can efficiently classify people as biologically older (or younger) than their chronological (i.e. calendar) age is becoming of paramount importance. These people will be in fact at higher (or lower) risk for many different age-associated diseases, including cardiovascular diseases, neurodegeneration, cancer, etc. In turn, patients suffering from these diseases are biologically older than healthy age-matched individuals. Many biomarkers that correlate with age have been described so far. The aim of the present review is to discuss the usefulness of some of these biomarkers (especially soluble, circulating ones) in order to identify frail patients, possibly before the appearance of clinical symptoms, as well as patients at risk for age-associated diseases. An overview of selected biomarkers will be discussed in this regard, in particular we will focus on biomarkers related to metabolic stress response, inflammation, and cell death (in particular in neurodegeneration), all phenomena connected to inflammaging (chronic, low-grade, age-associated inflammation). In the second part of the review, next-generation markers such as extracellular vesicles and their cargos, epigenetic markers and gut microbiota composition, will be discussed. Since recent progresses in omics techniques have allowed an exponential increase in the production of laboratory data also in the field of biomarkers of age, making it difficult to extract biological meaning from the huge mass of available data, Artificial Intelligence (AI) approaches will be discussed as an increasingly important strategy for extracting knowledge from raw data and providing practitioners with actionable information to treat patients.

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.

Increased serum fibroblast growth factor 21 levels are associated with adverse clinical outcomes after intracerebral hemorrhage

Introduction

Intracerebral hemorrhage (ICH) is the most prevalent cause of death. We sought to explore whether serum Fibroblast growth factor 21 (FGF21) is of substantial benefit in predicting poor prognosis in ICH patient.

Methods

A prospective, multicenter cohort analysis of serum FGF21 levels in 418 ICH patients was carried out. At three months following ICH start, the primary endpoint was death or major disability, whereas the secondary endpoint was death. We investigated the association between serum FGF21 and clinical outcomes. We added FGF21 to the existing rating scale to assess whether it enhanced the prediction ability of the original model. Effectiveness was determined by calculating the C-statistic, net reclassification index (NRI), absolute integrated discrimination improvement (IDI) index.

Results

Among 418 enrolled patients, 217 (51.9%) of the all subjects had death or significant disability. Compared with patients in the lowest quartile group, those in the first quartile group had higher risk of the primary outcome (Odds ratio, 2.73 [95%CI,1.42-5.26, p < 0.05]) and second outcome (Hazard ratio, 4.28 [95%CI,1.61-11.42, p < 0.001]). The integration of FGF21 into many current ICH scales improved the discrimination and calibration quality for the integrated discrimination index's prediction of main and secondary findings (all p < 0.05).

Conclusion

Elevated serum FGF21 is associated with increased risks of adverse clinical outcomes at 3 months in ICH patients, suggesting FGF21 may be a valuable prognostic factor.

Fibrosis of Peritoneal Membrane, Molecular Indicators of Aging and Frailty Unveil Vulnerable Patients in Long-Term Peritoneal Dialysis

Peritoneal membrane status, clinical data and aging-related molecules were investigated as predictors of long-term peritoneal dialysis (PD) outcomes. A 5-year prospective study was conducted with the following endpoints: (a) PD failure and time until PD failure, (b) major cardiovascular event (MACE) and time until MACE. A total of 58 incident patients with peritoneal biopsy at study baseline were included. Peritoneal membrane histomorphology and aging-related indicators were assessed before the start of PD and investigated as predictors of study endpoints. Fibrosis of the peritoneal membrane was associated with MACE occurrence and earlier MACE, but not with the patient or membrane survival. Serum α-Klotho bellow 742 pg/mL was related to the submesothelial thickness of the peritoneal membrane. This cutoff stratified the patients according to the risk of MACE and time until MACE. Uremic levels of galectin-3 were associated with PD failure and time until PD failure. This work unveils peritoneal membrane fibrosis as a window to the vulnerability of the cardiovascular system, whose mechanisms and links to biological aging need to be better investigated. Galectin-3 and α-Klotho are putative tools to tailor patient management in this home-based renal replacement therapy.

Luteolin Protects Against Obese Sarcopenia in Mice with High-Fat Diet-Induced Obesity by Ameliorating Inflammation and Protein Degradation in Muscles

SCOPE

Although sarcopenia is mainly caused by aging, sarcopenia due to obesity has become an emerging issue given the increase in obesity among people of various ages. There are studies on obesity or sarcopenia, our understanding of obesity-mediated sarcopenia is insufficient. Luteolin (LU) has exhibited antiobesity effects, but no studies have investigated the LU effects on antisarcopenia. This study therefore investigated the effects of LU on obese sarcopenia in mice with high-fat diet (HFD)-induced obesity.

METHODS AND RESULTS

To evaluate its inhibitory efficacy against obese sarcopenia, 5-week-old mice are fed an HFD supplemented with LU for 20 weeks. LU exerts suppressive effects on obesity, inflammation, and protein degradation in the HFD-fed obese mice. It also inhibits lipid infiltration into the muscle and decreases p38 activity and the mRNA expression of inflammatory factors, including TNF-α, Tlr2, Tlr4, MCP1, and MMP2, in the muscle. The suppression of muscle inflammation by LU leads to the inhibition of myostatin, FoxO, atrogin, and MuRF expression. These effects of LU affect inhibition of protein degradation and improvement of muscle function.

CONCLUSION

Here, it demonstrates that LU's antiobesity and antiinflammatory functionality affect inhibition of muscle protein degradation, and consequently, these interactions by LU exerts a protective effect against obese sarcopenia.

Markers for the Prediction of Probably Sarcopenia in Middle-Aged Individuals

Sarcopenia is a condition that is characterized by a progressive loss of muscle mass, strength, and function, resulting in reduced quality of life. The aim of the study was to analyze the significance of pro-inflammatory markers in the prognostic diagnosis of sarcopenia. The participants were divided into two groups: the main group of 146 people and the control-75 people. The complex of examinations included neuropsychological testing (Hospital Anxiety and Depression Scale (HADS), quality-of-life questionnaire for patients with sarcopenia (SarQoL), and short health assessment form (MOS SF-36)), a 6 m walking speed test, manual dynamometry, bioimpedancemetry, and metabolic markers (nitrates, fibroblast growth factor 21, and malondialdehyde). When analyzing metabolic markers in the main group, a twofold increase in nitrates in the main group was recorded in a subsequent analysis adjusted for multiple variables, there was a negative association between the nitrate levels for weak grip strength and appendicular muscle mass. An additional analysis revealed that the complaint of pain in the lower extremities was more frequent in patients of the main group, as well as constipation and the pathology of thyroid gland, and they were more frequently diagnosed with arterial hypertension. At the same time, patients from the main group more frequently took vitamin D. When conducting body composition, the main group recorded a higher weight visceral fat content, as well as a decrease in appendicular and skeletal muscle mass; these changes were accompanied by a decrease in protein and minerals. Among the markers that differed significantly were nitrates, and it was this that was associated with decreased muscle strength and appendicular mass, which may indicate both a possible mechanism and a possible predictive marker. The results of this study can be used to develop a screening method for diagnosing sarcopenia at the outpatient stage.

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.