Sarcopenia and Muscle Aging: A Brief Overview

Supplementation of low-protein diets with plant protein and probiotics enhances muscle health by regulating gut microbiota and metabolomic profiles in SAMP8 mice

Muscle health is crucial, especially for aging populations. This study investigates how plant protein and probiotic supplementation in a low-protein (LP) diet affects the gut microbiota, metabolome, and muscle health in aging SAMP8 mice, emphasizing the gut-muscle axis in older populations. Twenty-four 8-month-old male SAMP8 mice were divided into four groups: control (CON, standard diet), low-protein (LP), LP supplemented with plant protein (LP + P), and LP supplemented with plant protein and probiotics (LP + P + B). The experimental treatment lasted 8 weeks. Results showed that, by week 6, body weight increased significantly in all LP groups, with a trend toward higher body fat. Protein utilization and muscle strength improved significantly in the supplemented groups compared to the LP group (P < 0.05). The LP group showed elevated levels of inflammatory cytokines (IL-12p70, IL-6, TNF-α) (P < 0.05) in serum, which were reduced in the supplemented groups, especially in the LP + P + B group (P < 0.05). Gene expression related to muscle protein synthesis (mTOR, S6K1) and oxidative stress (CAT, Nrf2) was upregulated in the LP group but downregulated in the supplemented groups (P < 0.05). Immune-related genes followed similar patterns, with inflammation markers being significantly reduced after supplementation (P < 0.05). After supplementation, fecal beneficial bacteria (Bifidobacterium, Roseburia) and metabolites (butyric acid, indole-3-propionic acid, kyotorphin) increased, indicating enhanced gut health (P < 0.05). Specific bacterial species were correlated with metabolites and immune markers, highlighting their role in immune modulation (P < 0.05). These results show that supplementing plant protein and probiotics into an LP diet improved muscle strength, reduced inflammation, optimized gut microbiota, and boosted beneficial metabolism. The findings suggest that plant protein and probiotics can maintain muscle health and regulate immune responses in the elderly.

Systematic transcriptomics analysis of calorie restriction and rapamycin unveils their synergistic interaction in prolonging cellular lifespan

Aging is a multifaceted biological process marked by the decline in both mitotic and postmitotic cellular function, often central to the development of age-related diseases. In the pursuit of slowing or even reversing the aging process, a prominent strategy of significant interest is calorie restriction (CR), also known as dietary restriction, and the potential influence of a drug called rapamycin (RM). Both CR and RM have demonstrated the capacity to extend healthspan and lifespan across a diverse array of species, including yeast, worms, flies, and mice. Nevertheless, their individual and combined effects on mitotic and postmitotic cells, as well as their comparative analysis, remain areas that demand a thorough investigation. In this study, we employ RNA-sequencing methodologies to comprehensively analyze the impact of CR, RM, and their combination (CR + RM) on gene expression in yeast cells. Our analysis uncovers distinctive, overlapping, and even contrasting patterns of gene regulation, illuminating the unique and shared effects of CR and RM. Furthermore, the transcriptional synergistic interaction of CR + RM is validated in extending the lifespan of both yeast and human cells.

Analysis of alterations in the composition of the intestinal microbiota in frail older individuals

BACKGROUND

Frailty is an ageing-associated geriatric syndrome that severely affects the functional status, quality of life and life expectancy of older adults. Immune dysfunction and chronic inflammation play crucial roles in frailty, and this study aimed to explore the correlation between the intestinal microbiota and frailty.

METHODS

A cross-sectional survey was conducted using a comprehensive geriatric assessment of older individuals who underwent medical checkups at the Health Management Center from April 2023 to May 2024. A total of 672 older individuals who met the inclusion criteria were included and divided into a healthy control group and a frail case group. Clinical data, as well as blood and stool samples, were collected. The data from the two groups were analysed with 16S rRNA sequencing in 20 and 30 cases, respectively. SPSS 25.0 was used for statistical analysis.

RESULTS

There were significant differences in income, smoking, and globulin levels between the two groups, while there were no differences in age or sex. There was no significant difference in the abundance or species evenness of intestinal bacteria between the two groups. However, the abundance of accessory bacteria, bifidobacteria, and Escherichia coli in the frail group was greater than that in the control group. Specifically, Escherichia-Shigella was significantly upregulated and fit well into the prediction model of frailty.

CONCLUSION

The gut microbiota of frail older individuals underwent significant changes in structural composition, and the presence of Escherichia-Shigella may be a diagnostic marker for debilitating diseases. These findings provide an essential clinical reference value for developing methods for preventing or alleviating frailty based on specific microbial communities.

Risk of sarcopenia in women with breast cancer: a comparative analysis of screening tools

BACKGROUND

Sarcopenia is characterized by the loss of muscle strength and mass and is associated with poorer clinical outcomes in women with breast cancer. However, no specific tool is capable of assessing the risk of sarcopenia in this population. Therefore, the aim of the present study was to compare the performance of SARC-F, SARC-CalF, and BMI-adjusted SARC-CalF as screening tools for the risk of sarcopenia in women with breast cancer.

METHODS

An observational cross-sectional study was conducted involving women with breast cancer diagnosed in the previous 12 months. The risk of sarcopenia was identified by SARC-F, SARC-CalF, and BMI-adjusted SARC-CalF. As proposed by the EWGSOP2, sarcopenia was defined as low muscle strength (grip strength: <23.0 kg) and appendicular skeletal muscle mass index < 6.38 kg/m2 (determined by dual-energy X-ray absorptiometry). The performance of the screening tools was assessed by calculating specificity, sensitivity, positive and negative predictive values, and area under the ROC curve (AUC). AUC values were compared using DeLong's test.

RESULTS

This study included 168 women with a mean age of 54.8 ± 11.3 years. The prevalence of sarcopenia risk ranged from 10.1 to 36.6%, depending on the screening tool employed. The prevalence of sarcopenia was 8.3%. Using the presence of sarcopenia as reference, the SARC-F had an AUC of 0.550 [(0.396-0.703) p = 0.54], sensitivity of 21.4%, and specificity of 85.7%; the SARC-CalF had an AUC of 0.790 [(0.654-0.927) p < 0.001], sensitivity of 42.8%, and specificity of 92.2%; the BMI-adjusted SARC-CalF had an AUC of 0.521 [(0.385-0.658) p = 0.08], sensitivity of 28.6%, and specificity of 63.0%. Therefore, the SARC-CalF tool had low sensitivity and high specificity.

CONCLUSION

SARC-CalF performed the best compared to the alternatives provided. However, based on the current results, it may be necessary to reconsider the use of either of these instruments as a screening option for sarcopenia risk in women with breast cancer.

Predictors of gait speed post-stroke: A systematic review and meta-analysis

BACKGROUND

While gait speed serves as a clinical marker and health indicator, there is a paucity of a consolidated review of the factors that are most predictive of gait speed across the clinical stages of stroke recovery.

RESEARCH QUESTION

What are predictors of gait speed in the acute, subacute and chronic phase of stroke, categorized according to International Classification of Functioning, Health, and Disability (ICF)?

METHODS

A systematic search was conducted using four electronic databases following the PRISMA guideline. Included studies were cross-sectional, cohort and case-control reporting the predictors of gait speed, published from January 2000 to July 2024, and involved participants 18 years or older with diagnosis of stroke. Four meta-analyses were performed.

RESULTS

The initial search yielded 311 articles. After screening, 32 articles were included in the final analysis. In all clinical stages of stroke, age was the most common predictor of gait speed, followed by admission walking speed, Berg Balance Scale (BBS) score and time since onset. Knee extensor strength emerged as a predictor in three studies, all in the chronic stage. The meta-analyses indicated that older age was associated with slower discharge gait speed (SMD: -0.004 [-0.01, -0.001]; p < 0.0001) while higher BBS scores at admission were associated with a larger change in gait speed between admission and discharge (SMD: 0.17 [0.06, 0.28]; p = 0.002).

SIGNIFICANCE

Understanding the modifiable factors can help clinicians target interventions and seek additional care while non-modifiable factors can guide the prognosis of walking function in people post stroke.

Dyrk1b as a potential biomarker for sarcopenia in older adults

BACKGROUND

Sarcopenia is characterized by the progressive loss of muscle mass and function due to aging. Dual-specificity tyrosine-regulated kinase 1b (Dyrk1b) plays a key role in muscle differentiation by regulating transcription, cell cycle progression, and cell survival. However, the relationship between Dyrk1b levels and sarcopenia is unclear. This study aimed to evaluate the association of serum Dyrk1b level with sarcopenia in the elderly of community-dwelling.

METHODS

A total of 939 community-dwelling elderly people (median age = 76.0 years) were recruited, including 524 men and 415 women. Serum Dyrk1b was measured by enzyme-linked immunosorbent assay. Appendicular skeletal muscle mass index (ASMI), grip strength, and gait speed were taken to assess sarcopenia.

RESULTS

We found that serum Dyrk1b levels in patients with sarcopenia [median (IQR) = 67.37 (55.13-82.56) pg/mL] were lower than those in elderly people without sarcopenia [70.40 (58.34-92.35) pg/mL, P < 0.001]. Receiver operating characteristic curve analysis indicated that the optimal cutoff value of serum Dyrk1b level for predicting sarcopenia was 44.73 pg/mL, with a sensitivity of 94.8% and a specificity of 14.7% (AUC = 0.577, 95% CI = 0.540-0.613, P < 0.001. Multivariate logistic regression analysis showed that high serum Dyrk1b levels (> 44.73 pg/mL) were related to decreased risk of sarcopenia (adjusted OR = 0.342, 95%CI = 0.194-0.603, P < 0.001). Moreover, serum Dyrk1b concentration was positively correlated with ASMI (r = 0.169, P < 0.001), grip strength (r = 0.157, P < 0.001) and gait speed (r = 0.164, P < 0.001).

CONCLUSIONS

In summary, our results indicate that low serum Dyrk1b level is associated with an increased risk of sarcopenia in the elderly, suggesting that Dyrk1b may be valuable as a surrogate biomarker for screening and evaluation of sarcopenia.

Age-defying swallowing

Swallowing disorders, which are generally underdiagnosed, affect the elderly, leading to a decreased quality of life and complications, including aspiration pneumonia and death. Understanding the neurophysiology of swallowing and the causes of its dysfunction is a fundamental tool for the prevention, early diagnosis, and treatment of dysphagia. New technologies open a wide range of possibilities for the implementation of new care protocols for this disorder.

Association between atherogenic index of plasma, body mass index, and sarcopenia: a cross-sectional and longitudinal analysis study based on older adults in China

OBJECTIVE

To investigate the correlation between the atherogenic index of plasma (AIP), body mass index (BMI), and sarcopenia in the older adults in China, and to analyze the predictive ability of AIP and BMI for sarcopenia.

METHODS

This study utilized data from the 2011-2015 CHARLS database (China Health and Retirement Longitudinal Study, CHARLS), focusing on participants aged 60 years and older. The cross-sectional analysis included 7,744 samples, with 2,398 in the sarcopenia group and 5,346 in the non-sarcopenia group. In the retrospective cohort study, 1,441 participants without sarcopenia at baseline were selected and followed for the development of sarcopenia. Multivariable logistic regression was employed to analyze the association between AIP, BMI, and sarcopenia risk. A restricted cubic spline regression model was used to evaluate the dose-response association, and ROC curve analysis was performed to assess the predictive ability of individual and combined indicators (AIP and BMI). Additionally, subgroup analysis was conducted to explore the association between AIP, BMI, and sarcopenia risk across different demographic groups.

RESULTS

The cross-sectional analysis demonstrated that sarcopenia was significantly associated with various factors, including age, marital status, education level, residence, smoking, BMI, uric acid (UA), glycosylated hemoglobin (HbA1c), total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), AIP, as well as hypertension, diabetes, dyslipidemia, and heart disease (p < 0.05). Logistic regression analysis, adjusted for potential confounders, revealed that the low AIP group was significantly associated with an increased risk of sarcopenia (OR = 1.22, 95% CI 1.03-1.44, p = 0.02), while no significant difference was observed in the high AIP group (OR = 0.83, 95% CI 0.69-1.01, p = 0.07). In the retrospective cohort study, the low AIP group showed a positive association with sarcopenia risk (OR = 1.79, 95% CI 1.18-2.72, p = 0.01), and a similar trend was observed in the high AIP group (OR = 1.69, 95% CI 1.03-2.77, p = 0.04). BMI was inversely associated with sarcopenia incidence, consistent with the cross-sectional findings. Both AIP and BMI showed a nonlinear dose-response relationship with sarcopenia risk, with AIP approximating a U-shaped curve and BMI approximating an L-shaped curve. Subgroup analysis indicated that, in the 65-69 age group, low AIP levels were significantly associated with an increased risk of sarcopenia. In participants aged 70 and above, as well as in females, both low and high AIP levels were significantly associated with higher incidence risk. ROC curve analysis showed that the combined use of AIP and BMI for predicting sarcopenia had an Area Under the Curve (AUC) of 0.8913, which was moderately better than the use of AIP (0.6499) or BMI (0.8888) alone.

CONCLUSION

The changes in AIP and BMI are associated with the risk of sarcopenia, and both provide some predictive value for sarcopenia. Taken together, the combined prediction using AIP and BMI appears to be somewhat more effective than using either indicator alone in assessing the risk of sarcopenia.

Optimizing electrical field stimulation parameters reveals the maximum contractile function of human skeletal muscle microtissues

Skeletal muscle microtissues are engineered to develop therapies for restoring muscle function in patients. However, optimal electrical field stimulation (EFS) parameters to evaluate the function of muscle microtissues remain unestablished. This study reports a protocol to optimize EFS parameters for eliciting contractile force of muscle microtissues cultured in micropost platforms. Muscle microtissues were produced across an opposing pair of microposts in polydimethylsiloxane and polymethyl methacrylate culture platforms using primary, immortalized, and induced pluripotent stem cell-derived myoblasts. In response to EFS between needle electrodes, contraction deflects microposts proportional to developed force. At 5 V, pulse durations used for native muscle (0.1-1 ms) failed to elicit contraction of microtissues; durations reported for engineered muscle (5-10 ms) failed to elicit peak force. Instead, pulse durations of 20-80 ms were required to elicit peak twitch force across microtissues derived from five myoblast lines. Similarly, although peak tetanic force occurs at 20-50 Hz for native human muscles, it varied across microtissues depending on the cell line type, ranging from 7 to 60 Hz. A new parameter, the dynamic oscillation of force, captured trends during rhythmic contractions, whereas quantifying the duration-at-peak force provides an extended kinetics parameter. Our findings indicate that muscle microtissues have cell line type-specific contractile properties, yet all contract and relax more slowly than native muscle, implicating underdeveloped excitation-contraction coupling. Failure to optimize EFS parameters can mask the functional potential of muscle microtissues by underestimating force production. Optimizing and reporting EFS parameters and metrics is necessary to leverage muscle microtissues for advancing skeletal muscle therapies.NEW & NOTEWORTHY Electrical field stimulation (EFS) parameters remain to be standardized for engineered skeletal muscle. Herein, we report a protocol for defining EFS parameters that elicit the maximal contractile force of muscle microtissues cultivated in micropost devices and highlight the value of developing appropriate metrics. The dynamic oscillation of force and duration-at-peak force are introduced as novel metrics of contraction kinetics.

Knee strength balance ratios are not affected by aging among male runners

Objectives

This study aimed to assess thigh muscular strength, conventional and functional strength balance ratios, and muscle quality in well-trained male runners aged 20-70 yr.

Methods

Eighty-nine male runners were divided into five age categories: 20-29, 30-39, 40-49, 50-59, and 60-70 yr. Participants underwent an isokinetic strength test for knee flexor and extensor muscles and a body composition analysis via dual-energy X-ray absorptiometry.

Results

No significant difference was observed in concentric peak torque of the knee extensor muscles between the 20-29 and 40-49 age groups. However, the 50-59 age group showed significantly lower strength than the 20-29 age group (p = 0.049), and the 60-70 age group demonstrated significantly lower strength than the 40-49 group (p < 0.001). The conventional and functional balance ratios remain stable across all age groups.

Conclusion

Knee flexor and extensor strength in male runners decreases significantly after the age of 50, while conventional and functional strength balance ratios remain stable.

Puerarin Delays the Progression of Muscle Atrophy in Mice With Dexamethasone-Induced Sarcopenia Through Inhibiting the TNF-α/NF-κB Pathway

Sarcopenia, marked by the loss of muscle mass and function, is a chronic condition that worsens with age. Currently, there are no effective drugs for its treatment. Puerarin, a potent natural compound extracted from the root of Pueraria lobata, exhibits various pharmacological properties, including anti-inflammatory, antioxidative, and anti-apoptotic effects. It remains unclear whether puerarin possesses anti-muscle atrophy capabilities. This study aims to evaluate the effectiveness of puerarin in delaying the development of muscle atrophy in mice with dexamethasone-induced sarcopenia and to explore the underlying molecular mechanisms. Experimental findings reveal that puerarin effectively alleviates a range of physiological and behavioral changes caused by dexamethasone, including weight loss, deterioration in muscle mass and function, and destruction of the ultrastructure of muscle fibers. Notably, puerarin significantly enhances muscle mass and function in mice with dexamethasone-induced sarcopenia, reduces the release of pro-inflammatory cytokines while promoting the production of anti-inflammatory factors, lowers oxidative stress, inhibits the expression of muscle apoptosis proteins, and decelerates muscle atrophy development by suppressing the TNF-α/NF-κB signaling pathway. In conclusion, these findings not only further confirm the potential value of puerarin as a therapeutic drug for sarcopenia but also provide new directions and theoretical foundations for future research.

Detrimental Effects of β2-Microglobulin on Muscle Metabolism: Evidence From In Vitro, Animal and Human Research

BACKGROUND

β2-Microglobulin (B2M) has garnered considerable interest as a potential pro-ageing factor, leading to speculation about its involvement in muscle metabolism and the development of sarcopenia, a key component of ageing phenotypes. To explore this hypothesis, we conducted a comprehensive investigation into the impact of B2M on cellular and animal muscle biology, as well as its clinical implications concerning sarcopenia parameters in older individuals.

METHODS

In vitro myogenesis was induced in mouse C2C12 myoblasts with 2% horse serum. For in vivo research, C57BL/6 mice aged 3 months were intraperitoneally given 250 μg of B2M daily, and muscular alterations were assessed one month later. Human blood samples were obtained from 158 participants who underwent assessments of muscle mass and function at an outpatient geriatric clinic affiliated with a teaching hospital. Sarcopenia and associated parameters were assessed using cut-off values specifically tailored for the Asian population. The concentration of serum B2M was quantified through an enzyme-linked immunosorbent assay.

RESULTS

Recombinant B2M inhibited in vitro myogenesis by increasing intracellular reactive oxygen species (ROS) production. Furthermore, B2M significantly induced differential myotube atrophy via ROS-mediated ITGB1 downregulation, leading to impaired activation of the FAK/AKT/ERK signalling cascade and enhanced nuclear translocation of FoxO transcription factors. Animal experiments showed that mice with systemic B2M treatment exhibited significantly smaller cross-sectional area of tibialis anterior and soleus muscle, weaker grip strength, shorter grid hanging time, and decreased latency time to fall off the rotating rod, compared to untreated controls. In a clinical study, serum B2M levels were inversely associated with grip strength, usual gait speed and short physical performance battery (SPPB) total score after adjustment for age, sex, and body mass index, whereas sarcopenia phenotype score showed a positive association. Consistently, higher serum B2M levels were associated with higher risk for weak grip strength, slow gait speed, low SPPB total score, and poor physical performance.

CONCLUSION

These results provide experimental evidence that B2M exerted detrimental effects on muscle metabolism mainly by increasing oxidative stress. Furthermore, we made an effort to translate the results of in vitro and animal research into clinical implication and found that circulating B2M could be one of blood-based biomarkers to assess poor muscle health in older adults.

Puerarin Ameliorates Sarcopenia in Aged Mice via Modulation of Inflammation and Oxidative Stress: Insights from Proteomics and Transcriptomics

Sarcopenia, a chronic degenerative condition associated with aging, is characterized by a significant decline in muscle mass and strength. Puerarin, a major active isoflavone extracted from Pueraria lobata, exhibits potent anti-inflammatory and antioxidant properties. However, its therapeutic effects on sarcopenia remain unclear. Thus, the purpose of this study was to evaluate the therapeutic effects and underlying molecular mechanisms of puerarin in ameliorating sarcopenia in naturally aged mice. Twenty-month-old male C57BL/6 J aged mice were randomly divided into two groups based on body weight: the puerarin group (puerarin dissolved in double-distilled water, 150 mg/kg/day) and the control group (equal volume of double-distilled water). After an 8-week intervention, changes in muscle mass and function between the two groups were compared. Techniques such as HE staining, immunofluorescence staining, ELISA, transmission electron microscopy, Western blot, and qRT-PCR were employed to evaluate the positive effects of puerarin on sarcopenia in naturally aged mice. Furthermore, serum proteomics and muscle transcriptomics were used to analyze the molecular mechanisms underlying the anti-muscle atrophy effects of puerarin. The results demonstrated that puerarin significantly improved body composition, enhanced muscle mass and function, and exerted its effects by modulating inflammatory cytokines, reducing oxidative stress, and inhibiting the expression of apoptosis proteins in skeletal muscle. Additionally, integrated proteomics and transcriptomics analyses suggested that the anti-muscle atrophy mechanisms of puerarin might be related to the TNF-α/NF-κB signaling pathway. These findings highlight puerarin's potential as a therapeutic agent for sarcopenia, providing a foundation for further research and clinical application.

Mid- and long-term associations between food insecurity and sarcopenia

BACKGROUND

Sarcopenia is a complex geriatric syndrome characterized by progressive and generalized loss of skeletal muscle mass, muscle strength, and physical performance. Nutritional factors, including food insecurity, have been reported to be important in the development of sarcopenia. However, evidence on the relationship between sarcopenia and food insecurity is limited, especially with longitudinal data.

AIMS

This study aimed to examine the longitudinal association between sarcopenia, severe sarcopenia, and food insecurity in a nationally representative sample of older adults in Mexico.

METHODS

We used data from the four waves (2009, 2014, 2017, 2021) of the World Health Organization Study on Global Ageing and Adult Health in Mexico. The sample consisted of 1,484 older adults aged 50 years or older. Sarcopenia was defined according to the criteria of the European Working Group on Sarcopenia in Older People. Food insecurity was assessed with two questions related to frequency of eating less and hunger due to lack of food in the last 12 months.

RESULTS

Moderate (OR = 1.13; 95%CI: 1.09-1.20) and severe food insecurity (OR = 1.19; 95%CI: 1.11-1.27) significantly increased the longitudinal rates of sarcopenia or severe sarcopenia. Meanwhile, the incidence of severe food insecurity increased the cumulative incidence rate of sarcopenia and severe sarcopenia (OR = 1.91; 95%CI: 1.24-2.94).

DISCUSSION

Since food insecurity is a modifiable structural factor, the implementation of specific programs to alleviate its deleterious consequences is warranted.

CONCLUSIONS

This study shows that moderate and severe food insecurity are associated with an increase in the rates of sarcopenia and severe sarcopenia over time.

Pathological and Inflammatory Consequences of Aging

Aging is a complex, progressive, and irreversible biological process that entails numerous structural and functional changes in the organism. These changes affect all bodily systems, reducing their ability to respond and adapt to the environment. Chronic inflammation is one of the key factors driving the development of age-related diseases, ultimately causing a substantial decline in the functional abilities of older individuals. This persistent inflammatory state (commonly known as "inflammaging") is characterized by elevated levels of pro-inflammatory cytokines, an increase in oxidative stress, and a perturbation of immune homeostasis. Several factors, including cellular senescence, contribute to this inflammatory milieu, thereby amplifying conditions such as cardiovascular disease, neurodegeneration, and metabolic disorders. Exploring the mechanisms of chronic inflammation in aging is essential for developing targeted interventions aimed at promoting healthy aging. This review explains the strong connection between aging and chronic inflammation, highlighting potential therapeutic approaches like pharmacological treatments, dietary strategies, and lifestyle changes.

Rest-to-work and work-to-rest transients of interstitial PO2 in spinotrapezius muscle of young and old male rats

Muscle function declines with age. Since the primary energy source for contraction is aerobic, this study investigated age-related changes in muscle oxygenation dynamics to: characterize PO2 transients during rest-work transitions, identify age-specific differences in oxygen delivery/utilization balance, and examine the relationship between interstitial and arterial oxygen tension (PO2). Interstitial PO2 was measured with a high-resolution stroboscopic phosphorescence quenching technique to map intra-contractile dynamics during changes in muscle activity-rest-to-work (RtW) and work-to-rest (WtR) in rats aged three (young) and 23 (old) months. RtW (τw) and WtR (τr) PO2 transitions had lag periods and mono-exponential time constants. In young muscles, lag was 4 s, τw = 9.0 ± 3.7 s, and τr = 15.4 ± 3.9 s. For old, lag was also 4 s with increases to τw = 15.9 ± 3.5 s and τr = 41.4 ± 8.3 s. Resting PO2's were higher for young than for old (66.7 ± 13.7 vs. 60.2 ± 13.0 mmHg; p < 0.05). Work reduced PO2 with a greater effect on old (42.5 ± 14.0 vs. 28.3 ± 16.5 mmHg; p < 0.05). Intra-contractile measurements revealed a spike in PO2 (11 mmHg amplitude for >200 ms), which was absent in old. Further, sustained exercise in young showed a rising trend in PO2, while old remained at nadir. The missing PO2 spike in aged muscle contributes to reduced PO2 during work and may explain age-related loss of endurance.

A Retrospective Study on the Incidence of Periprosthetic Fractures Related to Total Hip Arthroplasty and Postoperative Complications During Hospitalization

Background/Objectives: Periprosthetic fractures (PFs) are serious complications that can occur after total hip arthroplasty (THA), particularly in elderly patients who often have multiple comorbidities and low bone density. The surgical treatment of PFs typically involves internal fixation or revision arthroplasty, depending on the fracture type categorized by the Vancouver classification. This study examines the annual incidence of PFs and the complications that arise during hospitalization, as well as the predictive role of age in the occurrence of these fractures and their associated complications. Methods: Based on a retrospective observational study conducted over three years (2021-2023) at the Bihor County Emergency Hospital in Oradea, we analyzed 783 patients who underwent various hip surgeries. Results: The retrospective analysis identified 38 cases of PF out of 768 hip surgeries, resulting in an incidence of PF of 4.5%. Most PFs were classified as Vancouver B, with surgeries mainly involving internal fixation. Complications occurred in 23.68% of cases, including a mortality rate of 7.90%. A correlation analysis examining the relationship between age and post-surgical complications demonstrates a weak and statistically insignificant association (r = 0.120, p = 0.478). To highlight whether age is a predictive factor for PFs, we used the linear regression model; this suggests that older age explains 2.7% of the total variability in the incidence of PFs, being statistically significant ([F(1, 766) = 20.923], p < 0.001). Conclusions: The rising incidence of periprosthetic fractures is closely linked to the increasing number of total hip arthroplasties and the aging population. Fractures of this type are more common in elderly women, with no statistically significant differences have been found between the sexes.

Skeletal Muscle Pathology in Pulmonary Arterial Hypertension and Its Contribution to Exercise Intolerance

Pulmonary arterial hypertension is a disease of the pulmonary vasculature, resulting in elevated pressure in the pulmonary arteries and disrupting the physiological coordination between the right heart and the pulmonary circulation. Exercise intolerance is one of the primary symptons of pulmonary arterial hypertension, significantly impacting the quality of life. The pathophysiology of exercise intolerance in pulmonary arterial hypertension is complex and likely multifactorial. Although the significance of right ventricle impairment and perfusion/ventilation mismatch is widely acknowledged, recent studies suggest pathophysiology of the skeletal muscle contributes to reduced exercise capacity in pulmonary arterial hypertension, a concept explored herein.

The effect of biocide chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT) mixture on C2C12 muscle cell damage attributed to mitochondrial reactive oxygen species overproduction and autophagy activation

The mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one (CMIT/MIT) is a biocide widely used as a preservative in various commercial products. This biocide has also been used as an active ingredient in humidifier disinfectants in South Korea, resulting in serious health effects among users. Recent evidence suggests that the underlying mechanism of CMIT/MIT-initiated toxicity might be associated with defects in mitochondrial functions. The aim of this study was to utilize the C2C12 skeletal muscle model to investigate the effects of CMIT/MIT on mitochondrial function and relevant molecular pathways associated with skeletal muscle dysfunction. Data demonstrated that exposure to CMIT/MIT during myogenic differentiation induced significant mitochondrial excess production of reactive oxygen species (ROS) and a decrease in intracellular ATP levels. Notably, CMIT/MIT significantly inhibited mitochondrial oxidative phosphorylation (Oxphos) and reduced mitochondrial mass at a lower concentration than the biocide amount, which diminished the viability of myotubes. CMIT/MIT induced activation of autophagy flux and decreased protein expression levels of myosin heavy chain (MHC). Taken together, CMIT/MIT exposure produced damage in C2C12 myotubes by impairing mitochondrial bioenergetics and activating autophagy. Our findings contribute to an increased understanding of the underlying mechanisms associated with CMIT/MIT-induced adverse skeletal muscle health effects.

The role of chronic low-grade inflammation in the development of sarcopenia: Advances in molecular mechanisms

With the exacerbation of global population aging, sarcopenia has become an increasingly recognized public health issue. Sarcopenia, characterized by a progressive decline in skeletal muscle mass, strength, and function, significantly impacts the quality of life in the elderly. Herein, we explore the role of chroniclow-gradeinflammation in the development of sarcopenia and its underlying molecular mechanisms, including chronic inflammation-associated signaling pathways, immunosenescence, obesity and lipid infiltration, gut microbiota dysbiosis and intestinal barrier disruption, and the decline of satellite cells. The interplay and interaction of these molecular mechanisms provide new perspectives on the complexity of the pathogenesis of sarcopenia and offer a theoretical foundation for the development of future therapeutic strategies.

The BET inhibitor JQ1 targets fat metabolism and counteracts obesity

INTRODUCTION

Obesity, one of the most frequent health problems in the adult population, is a condition characterized by excessive white adipose tissue accumulation and accompanied by the increased risk to develop other disorders such as type II diabetes, cardiovascular disorders, physical disability, frailty and sarcopenia. Total fat mass frequently increases during aging, often coexisting with sarcopenia, thus resulting in an emerging condition defined sarcopenic obesity (SO). Our previous data demonstrated the relevant role of the bromo and extra-terminal domain (BET) proteins inhibitor JQ1 in attenuating inflammation and fibrosis in sarcopenic mice. Moreover, we preliminarily observed that JQ1 administration markedly reduces white adipose tissue mass, suggesting a potential role of BET proteins on visceral fat deposition during aging.

OBJECTIVES

Starting from those observations, the aim of this study was to investigate the ability of JQ1 to reduce adiposity in a chronic diet-induced obesity (DIO) mouse model mimicking the human metabolic syndrome.

METHODS

Male C57BL/6J mice were divided in subgroups, either fed a standard diet or a high fat diet for 22 or 12 weeks, treated over the last 14 days with JQ1 or with vehicle.

RESULTS

The results showed that JQ1 administration reduces fat mass, preserving skeletal muscle mass and function. A direct JQ1 lipolytic effect was demonstrated on mature adipocyte cultures. JQ1-mediated loss of adipose tissue mass was not associated with systemic inflammation or with lipid accumulation in muscle and liver. JQ1 administration did not impinge on skeletal muscle metabolism and oxidative capability, as shown by the lack of significant impact on mitochondrial mass and biogenesis.

CONCLUSION

In conclusion, the current data highlight a potential benefit of JQ1 administration to counteract obesity, suggesting epigenetic modulation as a prospective target in the treatment of obesity and sarcopenic obesity, despite the underlying multiorgan molecular mechanism is still not completely elucidated.

Gut microbiota in patients with sarcopenia: a systematic review and meta-analysis

Background

Intestinal dysbiosis was considered a pivotal pathological mechanism underlying sarcopenia. Despite the fervor surrounding research in this domain, substantial controversy persists regarding the obtained outcomes.

Objective

To systematically summarized the disparities in gut microbiota composition between the group afflicted by sarcopenia and non-sarcopenia controls.

Methods

PubMed, Medline, CINAHL, EMBASE, Scopus, Web of Science and Google Scholer, Cochrane Library and gray literature sources were systematically searched for in randomized controlled trials. Meta-analysis and random-effects meta-regression were conducted using Rev. Man 5.3. Overall effect was measured using Hedges's g and determined using Z-statistics. Cochran's Q test and I 2 were used to investigate heterogeneity. The Newcastle-Ottawa Scale was used to assess overall quality of evidence.

Results

Ten studies, including 421 cases of sarcopenia and 1,642 cases of controls, were included in the meta-analysis. Patients with sarcopenia showed significantly reduced gut microbiota in α diversity, and β diversity was significantly different in 8/9 of included studies. We also found more abundance of phylum Proteobacteria and genus Escherichia-Shigella, and less abundance of phylum Firmicutes and genus Faecalibacterium, Prevotella 9, Blautia in the sarcopenia group.

Conclusion

The gut microbiota composition in patients with sarcopenia has undergone alterations, serving as a fundamental reference for further investigation into the potential pathogenic mechanisms and treatment strategies for sarcopenia.

Intramuscular administration of fractalkine modulates mitochondrial properties and promotes fast glycolytic phenotype

A newly categorized myokine called fractalkine (CX3CL1) has been associated with divergent conditions such as obesity, tissue inflammation, and exercise. CX3CL1 works through specific membrane-bound receptors (CX3CR1) found in various tissues including skeletal muscles. Studies indicate CX3CL1 induces muscles to uptake energy substrates thereby improving glucose utilization and countering diabetes. Here, we tested if the administration of purified CX3CL1 directly into mice skeletal muscles affects its histoarchitecture, mitochondrial activity, and expression of metabolic proteins. We analyzed four muscles: two upper-limb (quadriceps, hamstrings) and two lower-limb (tibialis anterior, gastrocnemius), contralateral leg muscles were taken as controls. The effects of CX3CL1 treatment on histoarchitecture, mitochondrial activity, and expression of metabolic proteins in muscles were characterized. We used histochemical staining succinate dehydrogenase (SDH)/cytochrome c oxidase (COX), myosin ATPase, alkaline phosphatase (ALP) to evaluate the mitochondrial activity, fiber types, and vascularization in the muscles, respectively. Western blotting was used to evaluate the expression of proteins associated with mitochondrial metabolism (OXPHOS), glycolysis, and vascularization. Overall, this study indicates CX3CL1 primarily modulates mitochondrial metabolism and shifts substrate preference toward glucose in the skeletal muscle. Evidence also supports that CX3CL1 stimulates the relative composition of fast fiber types, influencing selection of energy substrates in the skeletal muscle.

Prospective Intervention Strategies Between Skeletal Muscle Health and Mitochondrial Changes During Aging

Sarcopenia is a geriatric condition characterized by a decrease in skeletal muscle mass and function, significantly impacting both quality of life and overall health. Mitochondria are the main sites of energy production within the cell, and also produce reactive oxygen species (ROS), which maintain mitochondrial homeostasis-mitophagy (clearing damaged mitochondria); mitochondrial dynamics, which involve fusion and fission to regulate mitochondrial morphology; mitochondrial biogenesis, which ensures the functionality and homeostasis of mitochondria. Sarcopenia is linked to mitochondrial dysfunction, suggesting that muscle mitochondrial function therapy should be investigated. Extrinsic therapies are extensively examined to identify new treatments for muscular illnesses including sarcopenia. Changes in muscle physiology and lifestyle interventions, such as pharmacological treatments and exercise, can modulate mitochondrial activity in older adults. This PubMed review encompasses the most significant mitophagy and sarcopenia research from the past five years. Animal models, cellular models, and human samples are well covered. The review will inform the development of novel mitochondria-targeted therapies aimed at combating age-related muscle atrophy.

A microbiota-derived metabolite, 3-phenyllactic acid, prolongs healthspan by enhancing mitochondrial function and stress resilience via SKN-1/ATFS-1 in C. elegans

The mechanisms underlying the impact of probiotic supplementation on health remain largely elusive. While previous studies primarily focus on the discovery of novel bioactive bacteria and alterations in the microbiome environment to explain potential probiotic effects, our research delves into the role of living Lactiplantibacillus (formerly known as Lactobacillus) and their conditioned media, highlighting that only the former, not dead bacteria, enhance the healthspan of Caenorhabditis elegans (C. elegans). To elucidate the underlying mechanisms, we conduct transcriptomic profiling through RNA-seq analysis in C. elegans exposed to GTB1, a strain of Lactiplantibacillus plantarum or 3-phenyllactic acid (PLA), mimicking the presence of key candidate metabolites of GTB1 and evaluating healthspan. Our findings reveal that PLA treatment significantly extends the healthspan of C. elegans by promoting energy metabolism and stress resilience in a SKN-1/ATFS-1-dependent manner. Moreover, PLA-mediated longevity is associated with a novel age-related parameter, the Healthy Aging Index (HAI), introduced in this study, which comprises healthspan-related factors such as motility, oxygen consumption rate (OCR), and ATP levels. Extending the relevance of our work to humans, we observe an inverse correlation between blood PLA levels and physical performance in patients with sarcopenia, when compared to age-matched non-sarcopenic controls. Our investigation thus sheds light on the pivotal role of the metabolite PLA in probiotics-mediated enhancement of organismal healthspan, and also hints at its potential involvement in age-associated sarcopenia. These findings warrant further investigation to delineate PLA's role in mitigating age-related declines in healthspan and resilience to external stressors.

Perindopril erbumine-entrapped ultradeformable liposomes alleviate sarcopenia via effective skin delivery in muscle atrophy mouse model

Sarcopenia is a pertinent challenge in the super-aged societies causing reduced functional performance, poor quality of life and increased morbidity. In this study, the potential of perindopril erbumine-loaded ultradeformable liposomes (PE-UDLs) against sarcopenia was investigated. PE-UDLs were prepared by thin-film hydration and extrusion method using egg yolk L-α-phosphatidylcholine (EPC) as a lipid bilayer former and Tween 80 or sodium deoxycholate as an edge activator. Owing to the smallest particle size (75.0 nm) and the highest deformability (54.2) and entrapment efficiency (35.7 %), PE-UDLs with EPC to Tween 80 ratio of 8:2 was selected as the optimized formulation. The optimized PE-UDLs showed substantially higher cumulative amount of drug permeated and permeation rate across the rat skin compared to PE solution (485.7 vs. 50.1 µg and 13.4 vs. 2.3 µg/cm2/h, respectively). Topically applied PE-UDLs successfully ameliorated the effects of lipopolysaccharide (LPS)-induced sarcopenia in mice by improving body weight changes, grip strength and muscle weight. Furthermore, PE-UDLs reduced the shrinkage of muscle fibers as demonstrated by higher cross-sectional area than PE solution. PE-UDLs also increased the expression of myosin heavy chain (MHC) protein and reduced the expression of muscle atrophy F-box (Atrogin-1) and muscle ring-finger protein-1 (MuRF1), thereby improving muscles atrophy. In conclusion, these results demonstrate the therapeutic potential of PE-UDLs against sarcopenia.

FAPs orchestrate homeostasis of muscle physiology and pathophysiology

As a common clinical manifestation, muscle weakness is prevalent in people with mobility disorders. Further studies of muscle weakness have found that patients with muscle weakness present with persistent muscle inflammation, loss of muscle fibers, fat infiltration, and interstitial fibrosis. Therefore, we propose the concept of muscle microenvironment homeostasis, which explains the abnormal pathological changes in muscles through the imbalance of muscle microenvironment homeostasis. And we identified an interstitial progenitor cell FAP during the transition from normal muscle microenvironment homeostasis to muscle microenvironment imbalance caused by muscle damage diseases. As a kind of pluripotent stem cell, FAPs do not participate in myogenic differentiation, but can differentiate into fibroblasts, adipocytes, osteoblasts, and chondrocytes. As a kind of mesenchymal progenitor cell, it is involved in the generation of extracellular matrix, regulate muscle regeneration, and maintain neuromuscular junction. However, the muscle microenvironment is disrupted by the causative factors, and the abnormal activities of FAPs eventually contribute to the complex pathological changes in muscles. Targeting the mechanisms of these muscle pathological changes, we have identified appropriate signaling targets for FAPs to improve and even treat muscle damage diseases. In this review, we propose the construction of muscle microenvironmental homeostasis and find the key cells that cause pathological changes in muscle after homeostasis is broken. By studying the mechanism of abnormal differentiation and apoptosis of FAPs, we found a strategy to inhibit the abnormal pathological changes in muscle damage diseases and improve muscle regeneration.

An immunohistochemical evaluation of fast twitch muscle formation induced by repeated administration of flavan 3-ols in mice

Flavan-3-ols (FL) are poorly bioavailable astringent polyphenols that induce hyperactivation of the sympathetic nervous system. The aim of this study was to investigate the effects of repeated oral administration of FL on mice hindlimb skeletal muscle using immunohistochemical techniques. C57BL/6J male mice were orally administered 50 mg/kg of FL for a period of 2 weeks, and bromideoxyuridine (BrdU) was administered intraperitoneally 3 days prior to the dissection. The soleus and extensor digitorum longus (EDL) were excised and prepared for frozen sections. Myosin heavy chain (MHC) antibodies were used to classify muscle types, in addition, muscle cross-sectional areas (CSA) were measured. We observed a shift in the peak of CSA in the soleus muscle and to a larger extent in the EDL. In addition, a distinct shift toward fast muscle was detected, documented by a reduction in type I and an increase in type IIb in the soleus muscle, whereas in the EDL, we observed a decline in type IIa and an expansion in type IIb. Incorporation of BrdU into cells was significantly increased in all skeletal muscles, with a significant increase in cells co-expressing pair box 7 (Pax7), a marker of differentiation, as observed in the EDL. Given the evidence that β2-adrenergic receptors in skeletal muscles regulate differentiation and size, we measured plasma catecholamine (CA) concentrations following a single differentiation of FL. A single oral dose of FL was observed to significantly increase plasma CA. These findings indicate that catecholamines secreted into the bloodstream from the adrenal gland following oral administration of FL may influence skeletal muscle size and type via β2-receptors.

Sphingolipid metabolites as potential circulating biomarkers for sarcopenia in men

BACKGROUND

Sarcopenia is an age-related progressive loss of muscle mass and function. Sarcopenia is a multifactorial disorder, including metabolic disturbance; therefore, metabolites may be used as circulating biomarkers for sarcopenia. We aimed to investigate potential biomarkers of sarcopenia using metabolomics.

METHODS

After non-targeted metabolome profiling of plasma from mice of an aging mouse model of sarcopenia, sphingolipid metabolites and muscle cells from the animal model were evaluated using targeted metabolome profiling. The associations between sphingolipid metabolites identified from mouse and cell studies and sarcopenia status were assessed in men in an age-matched discovery (72 cases and 72 controls) and validation (36 cases and 128 controls) cohort; women with sarcopenia (36 cases and 36 controls) were also included as a discovery cohort.

RESULTS

Both non-targeted and targeted metabolome profiling in the experimental studies showed an association between sphingolipid metabolites, including ceramides (CERs) and sphingomyelins (SMs), and sarcopenia. Plasma SM (16:0), CER (24:1), and SM (24:1) levels in men with sarcopenia were significantly higher in the discovery cohort than in the controls (all P < 0.05). There were no significant differences in plasma sphingolipid levels for women with or without sarcopenia. In men in the discovery cohort, an area under the receiver-operating characteristic curve (AUROC) of SM (16:0) for low muscle strength and low muscle mass was 0.600 (95% confidence interval [CI]: 0.501-0.699) and 0.647 (95% CI: 0.557-0.737). The AUROC (95% CI) of CER (24:1) and SM (24:1) for low muscle mass in men was 0.669 (95% CI: 0.581-0.757) and 0.670 (95% CI: 0.582-0.759), respectively. Using a regression equation combining CER (24:1) and SM (16:0) levels, a sphingolipid (SphL) score was calculated; an AUROC of the SphL score for sarcopenia was 0.712 (95% CI: 0.626-0.798). The addition of the SphL score to HGS significantly improved the AUC from 0.646 (95% CI: 0.575-0.717; HGS only) to 0.751 (95% CI: 0.671-0.831, P = 0.002; HGS + SphL) in the discovery cohort. The predictive ability of the SphL score for sarcopenia was confirmed in the validation cohort (AUROC = 0.695, 95% CI: 0.591-0.799).

CONCLUSIONS

SM (16:0), reflecting low muscle strength, and CER (24:1) and SM (16:0), reflecting low muscle mass, are potential circulating biomarkers for sarcopenia in men. Further research on sphingolipid metabolites is required to confirm these results and provide additional insights into the metabolomic changes relevant to the pathogenesis and diagnosis of sarcopenia.

Aging Biomarker Consortium, Huang N, Ge M, Liu X, Tian X, Yin P, Bao Z, Cao F, Shyh-Chang N, Dong B, Dai L, Gan Z, Hu P, Qu J, Wang S, Wang H, Xiao Q, Yue R, Yue J, Zhang L, Zhang Y, Zhang H, Zhang W, Liu GH, Pei G, Liu Y, Zhu D, Dong B. A framework of biomarkers for skeletal muscle aging: a consensus statement by the Aging Biomarker Consortium

The skeletal muscle is an important organ for movement and metabolism in human body, and its physiological aging underlies the occurrence of muscle atrophy and sarcopenia. China has the largest aging population in the world and is facing a grand challenge with how to prevent and treat skeletal muscle aging-related diseases. To address this difficult problem, the Aging Biomarker Consortium (ABC) of China has reached an expert consensus on biomarkers of skeletal muscle aging by synthesizing literatures and insights from scientists and clinicians. This consensus attempts to provide a comprehensive assessment of biomarkers associated with skeletal muscle aging, and proposes a systematic framework to classify them into three dimensions: functional, structural, and humoral. Within each dimension, the experts recommend clinically relevant biomarkers for skeletal muscle aging. This consensus aims to lay the foundation for future research on skeletal muscle aging, facilitating precise prediction, diagnosis, and treatment of skeletal muscle aging and sarcopenia. It is anticipated to make significant contributions to healthy aging of skeletal muscle in the elderly population in China and around the world as well.

Irisin in degenerative musculoskeletal diseases: Functions in system and potential in therapy

Degenerative musculoskeletal diseases are a class of diseases related to the gradual structural and functional deterioration of muscles, joints, and bones, including osteoarthritis (OA), osteoporosis (OP), sarcopenia (SP), and intervertebral disc degeneration (IDD). As the proportion of aging people around the world increases, degenerative musculoskeletal diseases not only have a multifaceted impact on patients, but also impose a huge burden on the medical industry in various countries. Therefore, it is crucial to find key regulatory factors and potential therapeutic targets. Recent studies have shown that irisin plays an important role in degenerative musculoskeletal diseases, suggesting that it may become a key molecule in the prevention and treatment of degenerative diseases of the musculoskeletal system. Therefore, this review provides a comprehensive description of the release and basic functions of irisin, and summarizes the role of irisin in OA, OP, SP, and IDD from a cellular and tissue perspective, providing comprehensive basis for clinical application. In addition, we summarized the many roles of irisin as a key information molecule in bone-muscle-adipose crosstalk and a regulatory molecule involved in inflammation, senescence, and cell death, and proposed the interesting possibility of irisin in degenerative musculoskeletal diseases.

The recent development, application, and future prospects of muscle atrophy animal models

Muscle atrophy, characterized by the loss of muscle mass and function, is a hallmark of sarcopenia and cachexia, frequently associated with aging, malignant tumors, chronic heart failure, and malnutrition. Moreover, it poses significant challenges to human health, leading to increased frailty, reduced quality of life, and heightened mortality risks. Despite extensive research on sarcopenia and cachexia, consensus in their assessment remains elusive, with inconsistent conclusions regarding their molecular mechanisms. Muscle atrophy models are crucial tools for advancing research in this field. Currently, animal models of muscle atrophy used for clinical and basic scientific studies are induced through various methods, including aging, genetic editing, nutritional modification, exercise, chronic wasting diseases, and drug administration. Muscle atrophy models also include in vitro and small organism models. Despite their value, each of these models has certain limitations. This review focuses on the limitations and diverse applications of muscle atrophy models to understand sarcopenia and cachexia, and encourage their rational use in future research, therefore deepening the understanding of underlying pathophysiological mechanisms, and ultimately advancing the exploration of therapeutic strategies for sarcopenia and cachexia.

Effects and mechanisms of APP and its cleavage product Aβ in the comorbidity of sarcopenia and Alzheimer's disease

Sarcopenia and AD are both classic degenerative diseases, and there is growing epidemiological evidence of their comorbidity with aging; however, the mechanisms underlying the biology of their commonality have not yet been thoroughly investigated. APP is a membrane protein that is expressed in tissues and is expressed not only in the nervous system but also in the NMJ and muscle. Deposition of its proteolytic cleavage product, Aβ, has been described as a central component of AD pathogenesis. Recent studies have shown that excessive accumulation and aberrant expression of APP in muscle lead to pathological muscle lesions, but the pathogenic mechanism by which APP and its proteolytic cleavage products act in skeletal muscle is less well understood. By summarizing and analyzing the literature concerning the role, pathogenicity and pathological mechanisms of APP and its cleavage products in the nervous system and muscles, we aimed to explore the intrinsic pathological mechanisms of myocerebral comorbidities and to provide new perspectives and theoretical foundations for the prevention and treatment of AD and sarcopenia comorbidities.

Experimental models as a tool for research on sarcopenia: A narrative review

Sarcopenia is a musculoskeletal disorder related to muscle mass and function; as the worldwide population ages, its growing prevalence means a decline in quality of life and an increased burden for public health systems. As sarcopenia is a reversible condition, its early diagnosis is of utmost importance. Consensus definitions and diagnosis protocols for sarcopenia have been evolving for a long time, and the identification of molecular pathways subjacent to sarcopenia is a growing research area. The use of liquid biopsies to identify circulating molecules does not provide information about specific regulatory pathways or biomarkers in relevant tissue, and the use of skeletal muscle biopsies from older people has many limitations. Complementary tools are therefore necessary to advance the knowledge of relevant molecular aspects. The development of experimental models, such as animal, cellular, or bioengineered tissue, together with knock-in or knock-out strategies, could therefore be of great interest. This narrative review will explore experimental models of healthy muscle and aged muscle cells as a tool for research on sarcopenia. We will summarize the literature and present relevant experimental models in terms of their advantages and disadvantages. All of the presented approaches could potentially contribute to the accurate and early diagnosis, follow-up, and possible treatment of sarcopenia.

Exploring the Relationship Between Gut Microbiota and Sarcopenia Based on Gut-Muscle Axis

Sarcopenia, as a disease characterized by progressive decline of quality, strength, and function of muscles, has posed an increasingly significant threat to the health of middle-aged and elderly individuals in recent years. With the continuous deepening of studies, the concept of gut-muscle axis has attracted widespread attention worldwide, and the occurrence and development of sarcopenia are believed to be closely related to the composition and functional alterations of gut microbiota. In this review, combined with existing literatures and clinical reports, we have summarized the role and impacts of gut microbiota on the muscle, the relevance between gut microbiota and sarcopenia, potential mechanisms of gut microbiota in the modulation of sarcopenia, potential methods to alleviate sarcopenia by modulating gut microbiota, and relevant advances and perspectives, thus contributing to adding more novel knowledge to this research direction and providing certain reference for future related studies.

Body Composition and Senescence: Impact of Polyphenols on Aging-Associated Events

Aging is a dynamic and progressive process characterized by the gradual accumulation of cellular damage. The continuous functional decline in the intrinsic capacity of living organisms to precisely regulate homeostasis leads to an increased susceptibility and vulnerability to diseases. Among the factors contributing to these changes, body composition-comprised of fat mass and lean mass deposits-plays a crucial role in the trajectory of a disability. Particularly, visceral and intermuscular fat deposits increase with aging and are associated with adverse health outcomes, having been linked to the pathogenesis of sarcopenia. Adipose tissue is involved in the secretion of bioactive factors that can ultimately mediate inter-organ pathology, including skeletal muscle pathology, through the induction of a pro-inflammatory profile such as a SASP, cellular senescence, and immunosenescence, among other events. Extensive research has shown that natural compounds have the ability to modulate the mechanisms associated with cellular senescence, in addition to exhibiting anti-inflammatory, antioxidant, and immunomodulatory potential, making them interesting strategies for promoting healthy aging. In this review, we will discuss how factors such as cellular senescence and the presence of a pro-inflammatory phenotype can negatively impact body composition and lead to the development of age-related diseases, as well as how the use of polyphenols can be a functional measure for restoring balance, maintaining tissue quality and composition, and promoting health.

Exploring SGLT-2 inhibitors and sarcopenia in FAERS: a post-marketing surveillance study

BACKGROUND

The sodium-dependent glucose transporters 2 inhibitors (SGLT-2i) is associated with body weight loss but the composition of the losing weight remains unclear.

RESEARCH DESIGN AND METHODS

Disproportionality analyses, including the reporting odds ratio (ROR), the proportional reporting ratio (PRR), the Bayesian confidence propagation neural network (BCPNN), and the multi- item gamma Poisson shrinker (MGPS) algorithms, were employed to quantify the signals of SGLT-2i-associated musculoskeletal and connective tissue disorders AEs.

RESULTS

The search retrieved a total of 3,206 cases of musculoskeletal and connective tissue disorder-related AEs during the reporting period. This included 1,061 cases for Canagliflozin, 1,052 cases for Dapagliflozin, 1,074 cases for Empagliflozin, and 19 cases for Ertugliflozin. Fifteen preferred terms (PTs) with significant disproportionality were retained. No musculoskeletal and connective tissue system-related AE signals were reported for Ertugliflozin. We identified a risk of muscle necrosis with Canagliflozin use, a risk of sarcopenia with Dapagliflozin use, and a chance of muscle atrophy with Dapagliflozin and Empagliflozin prescriptions. Most cases occurred within the first month after SGLT-2i initiation, and AEs can persist beyond 360 days of use.

CONCLUSIONS

Our study identified potential new musculoskeletal and connective tissue disorder-related AE signals associated with SGLT-2 inhibitors.

Effects of household solid fuel use on sarcopenia in middle-aged and older adults: evidence from a nationwide cohort study

Background

Household solid fuel use is common in global households and has been linked to changes in handgrip strength and muscle mass. However, whether household solid fuel use results in sarcopenia over time is not well elaborated.

Methods

This study employed data from the 2011-2015 China Health and Retirement Longitudinal Study (CHARLS) that recruited 4,932 participants ≥45 years. The Cox proportional hazards regression model was conducted to estimate the impact of household solid fuel use for cooking and heating on sarcopenia development. The analysis was further stratified based on geographic position. Mediation analysis was employed to estimate the potential mediating effects of cognitive function and depressive symptoms associated with household solid fuel use and sarcopenia.

Results

Over the 4-year follow-up, 476 cases of sarcopenia were reported (9.65%), with 254 in males (10.82%) and 222 in females (8.59%). Cooking and heating with solid fuels increased the risk of sarcopenia (Cooking: HR 1.401, 95% CI 1.138-1.724; Heating: HR 1.278, 95% CI 1.040-1.571). Crop residue/wood burning correlated with higher sarcopenia risk (Cooking: 1.420, 95% CI 1.147-1.758; Heating: 1.318, 95% CI 1.062-1.635). Switching to clean cooking fuels significantly reduced sarcopenia risk (HR 0.766, 95% CI 0.599-0.979). Heating with solid fuels was associated with higher sarcopenia risk only in southern China (HR 1.375, 95% CI 1.102-1.715). Additionally, cognitive function and depressive symptoms partially mediated the link between household solid fuel use and sarcopenia.

Conclusion

Household use of solid fuels is associated with an increased risk of sarcopenia. Restricting the use of solid fuels and focusing on cognitive function and depressive symptoms in solid fuel users can help decrease sarcopenia development.

Particulate matter 2.5 accelerates aging: Exploring cellular senescence and age-related diseases

Exposure to Particulate matter 2.5 (PM2.5) accelerates aging, causing declines in tissue and organ function, and leading to diseases such as cardiovascular, neurodegenerative, and musculoskeletal disorders. PM2.5 is a major environmental pollutant and an exogenous pathogen in air pollution that is now recognized as an accelerator of human aging and a predisposing factor for several age-related diseases. In this paper, we seek to elucidate the mechanisms by which PM2.5 induces cellular senescence, such as genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, and mitochondrial dysfunction, and age-related diseases. Our goal is to increase awareness among researchers within the field of the toxicity of environmental pollutants and to advocate for personal and public health initiatives to curb their production and enhance population protection. Through these endeavors, we aim to promote longevity and health in older adults.

Vascular Impairment, Muscle Atrophy, and Cognitive Decline: Critical Age-Related Conditions

The triad of vascular impairment, muscle atrophy, and cognitive decline represents critical age-related conditions that significantly impact health. Vascular impairment disrupts blood flow, precipitating the muscle mass reduction seen in sarcopenia and the decline in neuronal function characteristic of neurodegeneration. Our limited understanding of the intricate relationships within this triad hinders accurate diagnosis and effective treatment strategies. This review analyzes the interrelated mechanisms that contribute to these conditions, with a specific focus on oxidative stress, chronic inflammation, and impaired nutrient delivery. The aim is to understand the common pathways involved and to suggest comprehensive therapeutic approaches. Vascular dysfunctions hinder the circulation of blood and the transportation of nutrients, resulting in sarcopenia characterized by muscle atrophy and weakness. Vascular dysfunction and sarcopenia have a negative impact on physical function and quality of life. Neurodegenerative diseases exhibit comparable pathophysiological mechanisms that affect cognitive and motor functions. Preventive and therapeutic approaches encompass lifestyle adjustments, addressing oxidative stress, inflammation, and integrated therapies that focus on improving vascular and muscular well-being. Better understanding of these links can refine therapeutic strategies and yield better patient outcomes. This study emphasizes the complex interplay between vascular dysfunction, muscle degeneration, and cognitive decline, highlighting the necessity for multidisciplinary treatment approaches. Advances in this domain promise improved diagnostic accuracy, more effective therapeutic options, and enhanced preventive measures, all contributing to a higher quality of life for the elderly population.

New insights into the function of the NLRP3 inflammasome in sarcopenia: mechanism and therapeutic strategies

Sarcopenia is one of the most common skeletal muscle disorders and is characterized by infirmity and disability. While extensive research has focused on elucidating the mechanisms underlying the progression of sarcopenia, further comprehensive insights into its pathogenesis are necessary to identify new preventive and therapeutic approaches. The involvement of inflammasomes in sarcopenia is widely recognized, with particular emphasis on the NLRP3 (NLR family pyrin domain containing 3) inflammasome. In this review, we aim to elucidate the underlying mechanisms of the NLRP3 inflammasome and its relevance in sarcopenia of various etiologies. Furthermore, we highlight interventions targeting the NLRP3 inflammasome in the context of sarcopenia and discuss the current limitations of our knowledge in this area.

Impact of Gut Microbiota on Aging and Frailty: A Narrative Review of the Literature

Aging is a natural, complex, and individual process that focuses on the progressive decay of the body and a decrease in cell function that begins in approximately the sixth decade of life and ends with death. Current scientific evidence shows that the aging process is mostly related to genetic load and varies because of the environment. Therefore, aging can be adjusted through the intervention of factors that control homeostasis in genetic, biochemical, and immunological processes, including those involving the gut microbiota. Indeed, the diversity of the gut microbiota decreases during aging, based on the presence of modifications in the hormonal, immunological, and operational processes of the gastrointestinal tract. These modifications lead to a state of dysbiosis. However, altering bacterial communities remains complicated due to the great diversity of factors that influence their modification. Alterations caused by the aging process are known to foster dysbiosis and correspond to conditions that determine the degree of frailty in senior citizens. Consequently, the microbial structure can be used as a biomarker for geriatric care in the promotion of healthy aging.

Muscle-specific PGC-1α modulates mitochondrial oxidative stress in aged sarcopenia through regulating Nrf2

BACKGROUND

Aged sarcopenia is characterized by loss of skeletal muscle mass and strength, and mitochondrial dysregulation in skeletal myocyte is considered as a major factor. Here, we aimed to analyze the effects of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) on mitochondrial reactive oxygen species (ROS) and nuclear factor erythroid 2-related factor 2 (Nrf2) in aged skeletal muscles.

METHODS

C2C12 cells were stimulated by 50 μM 7β-hydroxycholesterol (7β-OHC) to observe the changes of cellular ROS, mitochondrial ROS, and expression of PGC-1α and Nrf2. Different PGC-1α expression in cells was established by transfection with small interfering RNA (siRNA) or plasmids overexpressing PGC-1α (pEX-3-PGC-1α). The effects of different PGC-1α expression on cellular ROS, mitochondrial ROS and Nrf2 expression were measured in cells. Wild type (WT) mice and PGC-1α conditional knockout (CKO) mice were used to analyze the effects of PGC-1α on aged sarcopenia and expression of Nrf2 and CD38 in gastrocnemius muscles. Diethylmaleate, a Nrf2 activator, was used to analyze the connection between PGC-1α and Nrf2 in cells and in mice.

RESULTS

In C2C12 cells, the expressions of PGC-1α and Nrf2 were declined by the 7β-OHC treatment or PGC-1α silence. Moreover, PGC-1α silence increased the harmful ROS and decreased the Nrf2 protein expression in the 7β-OHC-treated cells. PGC-1α overexpression decreased the harmful ROS and increased the Nrf2 protein expression in the 7β-OHC-treated cells. Diethylmaleate treatment decreased the harmful ROS in the 7β-OHC-treated or PGC-1α siRNA-transfected cells. At the same age, muscle-specific PGC-1α deficiency aggravated aged sarcopenia, decreased Nrf2 expression and increased CD38 expression in gastrocnemius muscles compared with the WT mice. Diethylmaleate treatment improved the muscle function and decreased the CD38 expression in the old two genotypes.

CONCLUSIONS

Our study demonstrated that PGC-1α modulated mitochondrial oxidative stress in aged sarcopenia through regulating Nrf2.

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.

The Combination of Lactoferrin and Creatine Ameliorates Muscle Decay in a Sarcopenia Murine Model

BACKGROUND

Sarcopenia is an age-related condition characterized by progressive loss of muscle mass, strength, and function. The occurrence of sarcopenia has a huge impact on physical, psychological, and social health. Therefore, the prevention and treatment of sarcopenia is becoming an important public health issue.

METHOD

35 six-week-old male C57BL/6 mice were randomly divided into five groups, one of which served as a control group, while the rest of the groups were constructed as a model of sarcopenia by intraperitoneal injection of D-galactose. The intervention with lactoferrin, creatine, and their mixtures, respectively, was carried out through gavage for 8 weeks. Muscle function was assessed based on their endurance, hanging time, and grip strength. The muscle tissues were weighed to assess the changes in mass, and the muscle RNA was extracted for myogenic factor expression and transcriptome sequencing to speculate on the potential mechanism of action by GO and KEGG enrichment analysis.

RESULT

The muscle mass (lean mass, GAS index), and muscle function (endurance, hanging time, and grip strength) decreased, and the size and structure of myofiber was smaller in the model group compared to the control group. The intervention with lactoferrin and creatine, either alone or combination, improved muscle mass and function, restored muscle tissue, and increased the expression of myogenic regulators. The combined group demonstrated the most significant improvement in these indexes. The RNA-seq results revealed enrichment in the longevity-regulated pathway, MAPK pathway, focal adhesion, and ECM-receptor interaction pathway in the intervention group. The intervention group may influence muscle function by affecting the proliferation, differentiation, senescence of skeletal muscle cell, and contraction of muscle fiber. The combined group also enriched the mTOR-S6K/4E-BPs signaling pathway, PI3K-Akt signaling pathway, and energy metabolism-related pathways, including Apelin signaling, insulin resistance pathway, and adipocytokine signaling pathway, which affect energy metabolism in muscle.

CONCLUSIONS

Lactoferrin and creatine, either alone or in combination, were found to inhibit the progression of sarcopenia by influencing the number and cross-sectional area of muscle fibers and muscle protein synthesis. The combined intervention appears to exert a more significant effect on energy metabolism.

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.

Telomere Length is Associated with the Prevalence, Persistence, and Incidence of Sarcopenia

BACKGROUND

Telomere length (TL) shortening has been identified as a marker of aging and associated with adverse health outcomes, but evidence of its association with sarcopenia is inconclusive.

AIMS

Estimate the cross-sectional and prospective associations between TL and sarcopenia.

METHODS

We used data from Waves 3 and 4 (2017, 2021) of the Study on Global Aging and Adult Health in Mexico (SAGE-Mexico). The cross-sectional sample consisted of 1,738 adults aged 50 and older, and the longitudinal sample consisted of 1,437. Relative TL was determined by real-time quantitative polymerase chain reaction (qPCR) on DNA extracted from saliva samples and quantified as the telomere/single-copy gene (T/S) ratio. Sarcopenia was defined according to the European Working Group on Sarcopenia in Older People (EWGSOP2).

RESULTS

The mean salivary TL was 1.50 T/S units (95% CI: 1.49-1.52). The baseline prevalence of sarcopenia was 13.3% (95% CI: 9.8-16.8%). The incidence and persistence of sarcopenia were 6.8% (95% CI: 5.0-9.5%) and 7.0% (95% CI: 5.1-9.6%), respectively. The results showed that a one standard deviation decrease in TL was cross-sectionally associated with higher odds of sarcopenia (OR = 1.31; 95% CI: 1.03-1.67) and prospectively with a higher incidence (RRR = 1.55; 95% CI: 1.06-2.25) and persistence (RRR = 1.50; 95% CI: 1.01-2.24) of sarcopenia.

CONCLUSIONS

Older adults with shorter TL had higher rates of incident and persistent sarcopenia. Implementation of interventions to delay the decline of TL in older adults is warranted. Further translational studies are needed to elucidate the effects of exercise or diet on DNA repair in the telomeric region and their associations with sarcopenia.

A randomized, controlled clinical trial demonstrates improved owner-assessed cognitive function in senior dogs receiving a senolytic and NAD+ precursor combination

Age-related decline in mobility and cognition are associated with cellular senescence and NAD + depletion in dogs and people. A combination of a novel NAD + precursor and senolytic, LY-D6/2, was examined in this randomized controlled trial. Seventy dogs with mild to moderate cognitive impairment were enrolled and allocated into placebo, low or full dose groups. Primary outcomes were change in cognitive impairment measured with the owner-reported Canine Cognitive Dysfunction Rating (CCDR) scale and change in activity measured with physical activity monitors. Fifty-nine dogs completed evaluations at the 3-month primary endpoint, and 51 reached the 6-month secondary endpoint. There was a significant difference in CCDR score across treatment groups from baseline to the primary endpoint (p = 0.02) with the largest decrease in the full dose group. No difference was detected between groups using in house cognitive testing. There were no significant differences between groups in changes in measured activity. The proportion of dogs that improved in frailty and owner-reported activity levels and happiness was higher in the full dose group than other groups, however this difference was not significant. Adverse events occurred equally across groups. All groups showed improvement in cognition, frailty, and activity suggesting placebo effect and benefits of trial participation. We conclude that LY-D6/2 improves owner-assessed cognitive function over a 3-month period and may have broader, but more subtle effects on frailty, activity and happiness as reported by owners.

Association between the systemic immune-inflammation index and sarcopenia: a systematic review and meta-analysis

BACKGROUND

Sarcopenia is associated with increased morbidity and mortality. The systemic immune-inflammation index (SII) has been correlated to a variety of disorders. The present study conducted a systematic review and meta-analysis to investigate the relationship between SII and sarcopenia.

METHODS

A literature search was performed in Web of Science, PubMed, Embase, Cochrane Library, CINAHL, China National Knowledge Infrastructure, Chinese Biomedical Literature Database, Wanfang Database, and VIP Chinese Science and Technology Database, from inception to March 2024. Then, the literature quality was assessed. After the heterogeneity test, a random effects or fixed effects model was applied to establish the forest plot, and investigate the relationship between SII and sarcopenia. Then, the sensitivity analysis and publication bias were examined.

RESULTS

Nine articles, which included 18,634 adults, were analyzed. Sarcopenic adults had higher SII levels, when compared to non-sarcopenic adults (standardized mean difference [SMD] = 0.66, 95% confidence interval [CI] = 0.22 - 0.19, p = 0.003). The high SII level was associated to the increased risk of sarcopenia (odds ratio = 1.52, 95% CI = 1.09-2.13, p = 0.01). In addition, the subgroup analysis revealed that the SII levels were higher in the sarcopenic group, when compared to the non-sarcopenic group, in elderly adults, as well as in adults with or without gastrointestinal disorders. The analysis was robust with a low risk of publication bias.

CONCLUSIONS

SII is closely associated to sarcopenia. Sarcopenic adults had elevated SII levels. The high SII level increased the risk of sarcopenia. Large scale multi-center prospective studies are required to validate these study findings.

Establishing an optimal diagnostic criterion for respiratory sarcopenia using peak expiratory flow rate

BACKGROUND

The skeletal muscle changes as aging progresses, causing sarcopenia in the older adult population, which affects the respiratory muscles' mass, strength, and function. The optimal cut-off point of peak expiratory flow rate (PEFR) for respiratory sarcopenia (RS) diagnosis in accordance with sarcopenia identification is needed.

AIM

To establish an optimal cut-off point of PEFR for RS diagnosis in community-dwelling Asian older women.

METHODS

Sarcopenia diagnostic indicators were evaluated according to the Asian Working Group for Sarcopenia 2019 (AWGS) criteria. The respiratory parameters composed of respiratory muscle strength and respiratory function were evaluated by assessing maximal inspiratory pressure (MIP), percent predicted forced vital capacity (Pred FVC), and PEFR.

RESULTS

A total of 325 community-dwelling older women were included in this study. PEFR was negatively associated with RS (OR: 0.440; 95% CI: 0.344-0.564). The area under the curve (AUC) of PEFR was 0.772 (p < 0.001). The optimal cut-off point of PEFR for RS diagnosis was 3.4 l/s (sensitivity, 63.8%; specificity, 77.3%). Significant differences were found between the robust, possible sarcopenia, sarcopenia, and RS groups in terms of both sarcopenia diagnostic indicators and respiratory parameters (p < 0.05).

CONCLUSIONS

The cut-off point of PEFR can be used as a reasonable standard for RS diagnosis. This study finding can serve as a cornerstone for developing concrete criteria of RS in older women, supporting clinical judgment, which is crucial for providing appropriate treatment through accurate diagnosis.