Sarcopenia and increased adipose tissue infiltration of muscle in elderly African American women

A Nomogram Incorporating Intermuscular Adipose Tissue to Predict Chemotherapy Toxicity in Older Adults With Early-Stage Breast Cancer

PURPOSE

Recent studies have shown that intermuscular adipose tissue (IMAT) is a significant prognostic factor for breast cancer. To date, no clinical studies have investigated whether IMAT can be used to predict chemotherapy toxicity in older adult patients with early-stage breast cancer.

METHODS

We included 304 patients diagnosed with stage I-III breast cancer between January 2020 and December 2022 in Harbin Medical University Cancer Hospital. All patients were aged ≥ 65 years and treated with neoadjuvant or adjuvant chemotherapy. IMAT within the pectoralis muscle was measured using computed tomography imaging. Logistic regression analysis was used to identify independent predictors of chemotherapy toxicity. A nomogram was built, and the model performance was assessed using accuracy, discrimination, and clinical benefits. The net reclassification index (NRI) and integrated discrimination improvement (IDI) were used to evaluate changes in model performance after the addition of adipose tissue.

RESULTS

Of the 304 patients (184 in the training cohort and 120 in the validation cohort), 30.3% developed grade 3-5 chemotherapy toxicities. Three independent predictors were identified in the multivariate analysis: hemoglobin level, IMAT area, and primary prophylaxis with granulocyte colony-stimulating factor. The nomogram demonstrated area under the receiver operating characteristic curve values of 0.708 (95% confidence interval [CI], 0.616-0.801) and 0.751 (95% CI, 0.655-0.846) in the training and validation cohorts, respectively. The nomogram showed good calibration (Hosmer-Lemeshow test, p > 0.05), and incorporating IMAT improved nomogram performance in both cohorts (all NRI and IDI > 0, p < 0.05). Decision curve analysis revealed that the nomogram was clinically useful.

CONCLUSION

A nomogram including IMAT may be useful for predicting the individual probability of chemotherapy toxicity and guiding therapy in older adults with early-stage breast cancer.

Age- and sex-specific reference values for CT-based low skeletal muscle quantity and quality in healthy living kidney donors

Background

Computed tomography (CT) imaging is a useful tool for assessing skeletal muscle mass and quality. The present study aimed to determine age- and sex-specific reference values for CT-based skeletal muscle markers in a healthy population, and to correlate them with serum creatinine and 24-h urinary creatinine excretion (24h-UCE).

Methods

Skeletal muscle index (SMI) - a marker of muscle mass/quantity - and skeletal muscle radiation attenuation (SMRA) and intermuscular adipose tissue index (IMATI) - markers of muscle quality/myosteatosis - were determined using a deep-learning-based method from axial CT images at the level of the 3rd lumbar vertebra in living kidney donors assessed between 01/2005 and 05/2023. Age- and sex-specific reference values were determined by the 5th percentile, and correlation was tested with the Pearson correlation coefficient.

Results

CT scans of 394 healthy individuals were included. The mean age was 53 years (SD 12), mean BMI was 25.2 kg/m2 (SD 3.9), and 130 patients (33%) were male. The reference values for low skeletal muscle mass (SMI) in males were 43.7 cm2/m2 (20-39 years), 44.9 cm2/m2 (40-59 years), and 39.7 cm2/m2 (≥60 years). In females, the corresponding values were 33.8 cm2/m2 (20-39 years), 34.8 cm2/m2 (40-59 years), and 31.2 cm2/m2 (≥60 years). SMI showed a moderate correlation with serum creatinine (r = 0.452, p < 0.001) but a weak correlation with 24h-UCE (r = 0.188, p = 0.003). Correlations were all weak for SMRA (creatinine: r = 0.220, p < 0.001; 24h-UCE: r = 0.177, p = 0.006) and IMATI (creatinine: r = -0.101, p = 0.054; 24h-UCE, r = -0.108, p = 0.093).

Conclusion

The age- and sex-specific reference values reported here could be used in clinical practice and future studies to identify patients at risk of muscle decline.

Correlation study on gut microbiota and myosteatosis in patients with liver cirrhosis

Objective

To investigate the features of gut microbiota in cirrhotic patients with myosteatosis and identify specific bacterial species that may be involved in the pathogenesis of myosteatosis.

Methods

80 patients with liver cirrhosis were categorized into the myosteatosis group (n = 44) and the non-myosteatosis group (n = 36). Metagenomic sequencing was used to analyze the differences in gut microbiota composition between the two groups. Subsequently, the value of meaningful gut microbiota in the diagnosis of myosteatosis in patients with liver cirrhosis was analyzed.

Results

At the species level, however, 15 bacterial species exhibited significant differences in relative abundance between these two groups. The relative abundance of Roseburia hominis and Subdoligranulum unclassified was inversely associated with mean muscle attenuation density at the L3 level (p < 0.05). Assessement of the diagnostic potential of Roseburia hominis and Subdoligranulum unclassified for the development of myosteatosis showed that the areas under the ROC curves (AUCs) was 0.869 [95% confidence interval (CI): 0.709-1.029; p < 0.05] for Roseburia hominis and 0.828 (95% CI: 0.6472-1.009; p < 0.05) for Subdoligranulum unclassified.

Conclusion

Our study establishes compositional alterations of gut microbiota in patients with liver cirrhosis combined with myosteatosis and suggests the diagnostic potential for using gut microbiota as noninvasive biomarkers.

Umbilical cord mesenchymal stem cell-derived exosomal Follistatin inhibits fibrosis and promotes muscle regeneration in mice by influencing Smad2 and AKT signaling

BACKGROUND

Promoting muscle regeneration through stem cell therapy has potential risks. We investigated the effect of umbilical cord mesenchymal stem cells (UMSCs) Exosomes (Exo) Follistatin on muscle regeneration.

METHODS

The Exo was derived from UMSCs cells and was utilized to affect the mice muscle injury model and C2C12 cells myotubes atrophy model. The Western blot, qRT-PCR and IF were utilized to determine the effects of Exo on the levels of Follistatin, MyHC, MyoD, Myostatin, MuRF1, MAFbx, α-SMA, Collagen I, Smad2, and AKT. In addition, HE and Masson staining were used to assess muscle tissue damage in mice.

RESULTS

The level of Follistatin in Exo was significantly higher than that in UMSCs. UMSCs-Exo increased the levels of Follistatin, MyHC, MyoD, and p-Smad2 and decreased the levels of Myostatin, MuRF1, MAFbx, α-SMA, Collagen I, p-AKT, and p-mTOR in mice or C2C12 cells. In addition, UMSCs-Exo decreased levels of inflammation and fibrosis in mice. However, UMSCs-Exo-si-Follistatin reversed the effect of UMSCs-Exo. Transfection of oe-Smad2 up-regulated the protein levels of Collagen I, α-SMA, and changed the ratio of p-Smad2/Smad2 expression to 0.33, and 0.34, 0.73. LY294002 decreased the levels of MyHC, MyoD, and the ratio of p-AKT/AKT and p-mTOR/mTOR expression to 0.12, 0.17, 0.33, and 0.41, increased the levels of MuRF1 and MAFbx to 0.36 and 0.34.

CONCLUSION

This study demonstrated that Follistatin in UMSCs-Exo inhibits fibrosis and promotes muscle regeneration in mice by regulating Smad and AKT signaling.

Altered body composition in obesity: Prevalence, associated factors and comparison of two methods

BACKGROUND & AIMS

There is still some uncertainty towards the best method to diagnose the sarcopenic obesity, and specifically, altered body composition. A recent international consensus proposes the association of increased fat mass (FM) with reduced skeletal muscle mass adjusted by weight (SMM/W) (method 1). The ratio of fat mass index (FMI)/fat free mass index (FFMI) (method 2) has also been proposed.

AIMS

to determine and compare the prevalence of altered body composition by the two methods, and its associated factors, in obese patients referred to a specialized center.

METHODS

Anthropometry, single-frequency bioimpedance analysis (BIA), and risk factors for sarcopenia were collected. SMM, according to the Janssen equation, and the FMI/FFMI ratio, were calculated. The agreement between the two methods was determined by the kappa coefficient. Multivariable analysis identified the factors associated with altered body composition according to the two methods.

RESULTS

253 consecutive patients were retrospectively included: 81 % women, age 44.4 ± 13 yr, body mass index (BMI) 43.0 ± 6.8 kg/m2, severe obesity, 94 %. Altered body composition was reported in 90 % of the obese patients (n = 227/253) with method 1, and 35 % (83/253) with method 2. The agreement between the two methods was very low (kappa = 0.10). The factors associated with altered body composition were: method 1, age (odds ratio = 1.05 [95 % confidence interval, 1.01; 1.10], P = 0.02), arterial hypertension (0.18 [0.06; 0.57], P = 0.04), hip circumference (1.13 [1.07; 1.20], P < 0.0001), previous obesity follow-up (3.78 [1.30; 10.96], P = 0.002); method 2, female gender (3.12 [1.02; 9.5], P = 0.04), age (1.10 [1.06; 1.14], P < 0.0001), BMI (1.37 [1.26; 1.50], P < 0.0001), history of cancer (5.35 [1.20; 23.84], P < 0.028), phase angle (0.42 [0.27; 0.66], P < 0.001).

CONCLUSION

Altered body composition is common in severely obese patients. The two methods are not comparable. Further work will aim at refining the methods of body composition measurements in the obese patients, and especially for the sarcopenic obesity diagnosis.

Sarcopenia and cachexia: molecular mechanisms and therapeutic interventions

Sarcopenia is defined as a muscle-wasting syndrome that occurs with accelerated aging, while cachexia is a severe wasting syndrome associated with conditions such as cancer and immunodeficiency disorders, which cannot be fully addressed through conventional nutritional supplementation. Sarcopenia can be considered a component of cachexia, with the bidirectional interplay between adipose tissue and skeletal muscle potentially serving as a molecular mechanism for both conditions. However, the underlying mechanisms differ. Recognizing the interplay and distinctions between these disorders is essential for advancing both basic and translational research in this area, enhancing diagnostic accuracy and ultimately achieving effective therapeutic solutions for affected patients. This review discusses the muscle microenvironment's changes contributing to these conditions, recent therapeutic approaches like lifestyle modifications, small molecules, and nutritional interventions, and emerging strategies such as gene editing, stem cell therapy, and gut microbiome modulation. We also address the challenges and opportunities of multimodal interventions, aiming to provide insights into the pathogenesis and molecular mechanisms of sarcopenia and cachexia, ultimately aiding in innovative strategy development and improved treatments.

Glucagon-like peptide-1 receptor agonist-based agents and weight loss composition: Filling the gaps

Excess adiposity is at the root of type 2 diabetes (T2D). Glucagon-like peptide-1 receptor agonists (GLP-1RAs) have emerged as first-line treatments for T2D based on significant weight loss results. The composition of weight loss using most diets consists of <25% fat-free mass (FFM) loss, with the remainder from fat stores. Higher amounts of weight loss (achieved with metabolic bariatric surgery) result in greater reductions in FFM. Our aim was to assess the impact that GLP-1RA-based treatments have on FFM. We analysed studies that reported changes in FFM with the following agents: exenatide, liraglutide, semaglutide, and the dual incretin receptor agonist tirzepatide. We performed an analysis of various weight loss interventions to provide a reference for expected changes in FFM. We evaluated studies using dual-energy X-ray absorptiometry (DXA) for measuring FFM (a crude surrogate for skeletal muscle). In evaluating the composition of weight loss, the percentage lost as fat-free mass (%FFML) was equal to ΔFFM/total weight change. The %FFML using GLP-1RA-based agents was between 20% and 40%. In the 28 clinical trials evaluated, the proportion of FFM loss was highly variable, but the majority reported %FFML exceeding 25%. Our review was limited to small substudies and the use of DXA, which does not measure skeletal muscle mass directly. Since FFM contains a variable amount of muscle (approximately 55%), this indirect measure may explain the heterogeneity in the data. Assessing quantity and quality of skeletal muscle using advanced imaging (magnetic resonance imaging) with functional testing will help fill the gaps in our current understanding.

The association between weight-adjusted-waist index and muscle strength in adults: a population-based study

Background

The relationship between the weight-adjusted-waist index (WWI) and grip strength, a crucial marker in assessing sarcopenia, lacks clarity. We aimed to explore the relationship between WWI and muscle strength across genders.

Methods

The cross-sectional study involved adults with complete data on WWI and grip strength from the 2011-2014 National Health and Nutrition Examination Survey. WWI was derived by dividing waist circumference by the square root of weight. Weighted multivariable logistic regression and smooth curve fitting techniques were used to examine the independent association and potential non-linear relationship between WWI and grip strength. A two-piecewise linear regression model was utilized to determine the threshold effect. Additionally, subgroup analyses and interaction tests were conducted.

Results

The study encompassed 9,365 participants, including 4,661 males and 4,704 females. Multivariate logistic regression analysis revealed a negative correlation between WWI and grip strength among males (β = -11.49, 95% CI: -12.38, -10.60, p < 0.001) as well as females (β = -2.53, 95% CI: -2.98, -2.08, p < 0.001). Subgroup analysis showed that the negative correlation of WWI with grip strength remained consistent across various age groups and levels of obesity for both males and females.

Conclusion

An increase in WWI correlates with reduced muscle strength in both males and females. WWI was negatively associated not only with muscle mass but also with muscle strength. WWI may serve as an assessment tool for sarcopenia, but further large-scale studies are needed to clarify causality.

Intermuscular adipose tissue accumulation is associated with higher tissue sodium in healthy individuals

BACKGROUND AND AIMS

High tissue sodium accumulation and intermuscular adipose tissue (IMAT) are associated with aging, type 2 diabetes, and chronic kidney disease. In this study, we aim to investigate whether high lower-extremity tissue sodium accumulation relates to IMAT quantity and whether systemic inflammatory mediators and adipocytokines contribute to such association.

METHODS

Tissue sodium content and IMAT accumulation (percentage of IMAT area to muscle area) were measured in 83 healthy individuals using sodium imaging (23Na-MRI) and proton (1H-MRI) imaging of the calf. Insulin sensitivity was assessed by glucose disposal rate (GDR) measured with the hyperinsulinemic-euglycemic clamp.

RESULTS

Median (interquartile range) muscle and skin sodium contents were 16.6 (14.9, 19.0) and 12.6 (10.9, 16.7) mmol/L, respectively. Median IMAT was 3.69 (2.80, 5.37) %. In models adjusted for age, sex, BMI, GDR, adiponectin, and high-sensitivity C-reactive protein, increasing tissue sodium content was significantly associated with higher IMAT quantity (p = 0.018 and 0.032 for muscle and skin tissue sodium, respectively). In subgroup analysis stratified by sex, skin sodium was significantly associated with IMAT only among men. In interaction analysis, the association between skin sodium and IMAT was greater with increasing levels of high-sensitivity C-reactive protein and interleukin-6 (p for interaction = 0.022 and 0.006, respectively).

CONCLUSIONS

Leg muscle and skin sodium are associated with IMAT quantity among healthy individuals. The relationship between skin sodium and IMAT may be mediated by systemic inflammation.

Fibro-adipogenic progenitors in physiological adipogenesis and intermuscular adipose tissue remodeling

Excessive accumulation of intermuscular adipose tissue (IMAT) is a common pathological feature in various metabolic and health conditions and can cause muscle atrophy, reduced function, inflammation, insulin resistance, cardiovascular issues, and unhealthy aging. Although IMAT results from fat accumulation in muscle, the mechanisms underlying its onset, development, cellular components, and functions remain unclear. IMAT levels are influenced by several factors, such as changes in the tissue environment, muscle type and origin, extent and duration of trauma, and persistent activation of fibro-adipogenic progenitors (FAPs). FAPs are a diverse and transcriptionally heterogeneous population of stromal cells essential for tissue maintenance, neuromuscular stability, and tissue regeneration. However, in cases of chronic inflammation and pathological conditions, FAPs expand and differentiate into adipocytes, resulting in the development of abnormal and ectopic IMAT. This review discusses the role of FAPs in adipogenesis and how they remodel IMAT. It highlights evidence supporting FAPs and FAP-derived adipocytes as constituents of IMAT, emphasizing their significance in adipose tissue maintenance and development, as well as their involvement in metabolic disorders, chronic pathologies and diseases. We also investigated the intricate molecular pathways and cell interactions governing FAP behavior, adipogenesis, and IMAT accumulation in chronic diseases and muscle deconditioning. Finally, we hypothesize that impaired cellular metabolic flexibility in dysfunctional muscles impacts FAPs, leading to IMAT. A deeper understanding of the biology of IMAT accumulation and the mechanisms regulating FAP behavior and fate are essential for the development of new therapeutic strategies for several debilitating conditions.

The Association between Sarcopenic Obesity and DXA-Derived Visceral Adipose Tissue (VAT) in Adults

Many people with overweight and obesity are affected by sarcopenia, which is represented by a phenotype known as sarcopenic obesity (SO), characterized by excessive body fat (BF), combined with reduced muscle mass and strength. In this population, it is vital to identify the factors associated with SO. With this aim in mind, we investigated the association between visceral adipose tissue (VAT) mass and SO in patients with overweight or obesity in a nutritional setting. A total of 256 participants (23.8% female) with overweight or obesity were involved and completed a body composition assessment, including VAT mass, using dual-energy X-ray absorptiometry (DXA). The sample was initially categorized according to whether the individual had the SO phenotype; they were then classified according to their VAT mass into three tertiles (lowest, medium, and highest). Among the 256 participants, who had a median body mass index (BMI) of 29.3 (interquartile range (IQR): 27.0-32.4) kg/m2 and a median age of 51.0 (IQR: 47.0-54.0) years, 32.4% were identified as having SO, and they displayed a higher median VAT mass (517.0 (IQR: 384.5-677.0) vs. 790.0 (IQR: 654.0-1007.0) g; p < 0.05). The logistic regression model that accounted for age, sex and BMI revealed that a higher VAT mass increases the risk of SO (odds ratio (OR) = 1.003; 95% confidence interval (CI): 1.001-1.004; p < 0.05). In conclusion, VAT mass appears to be an independent factor associated with SO in people with overweight or obesity. However, due to the cross-sectional design, no information regarding any causality between higher VAT mass and SO can be provided. Additional longitudinal research in this direction should therefore be conducted.

Type 2 diabetes mellitus related sarcopenia: a type of muscle loss distinct from sarcopenia and disuse muscle atrophy

Muscle loss is a significant health concern, particularly with the increasing trend of population aging, and sarcopenia has emerged as a common pathological process of muscle loss in the elderly. Currently, there has been significant progress in the research on sarcopenia, including in-depth analysis of the mechanisms underlying sarcopenia caused by aging and the development of corresponding diagnostic criteria, forming a relatively complete system. However, as research on sarcopenia progresses, the concept of secondary sarcopenia has also been proposed. Due to the incomplete understanding of muscle loss caused by chronic diseases, there are various limitations in epidemiological, basic, and clinical research. As a result, a comprehensive concept and diagnostic system have not yet been established, which greatly hinders the prevention and treatment of the disease. This review focuses on Type 2 Diabetes Mellitus (T2DM)-related sarcopenia, comparing its similarities and differences with sarcopenia and disuse muscle atrophy. The review show significant differences between the three muscle-related issues in terms of pathological changes, epidemiology and clinical manifestations, etiology, and preventive and therapeutic strategies. Unlike sarcopenia, T2DM-related sarcopenia is characterized by a reduction in type I fibers, and it differs from disuse muscle atrophy as well. The mechanism involving insulin resistance, inflammatory status, and oxidative stress remains unclear. Therefore, future research should further explore the etiology, disease progression, and prognosis of T2DM-related sarcopenia, and develop targeted diagnostic criteria and effective preventive and therapeutic strategies to better address the muscle-related issues faced by T2DM patients and improve their quality of life and overall health.

The association between weight-adjusted-waist index and sarcopenia in adults: a population-based study

This study aims to investigate the relationship between weight-adjusted-waist index (WWI), a new body index, and sarcopenia, while also assessing the potential of WWI as a tool for screening sarcopenic patients. The cross-sectional study involved adults who possessed complete data on WWI and appendicular skeletal muscle mass from the 1999-2006 and 2011-2018 National Health and Nutrition Examination Surveys. Weighted multivariate regression and logistic regression analyses were employed to explore the independent relationship between WWI and sarcopenia. The study included 26,782 participants. The results showed that WWI demonstrated a positive correlation with sarcopenia risk. In the fully adjusted model, with each 1 unit increase in WWI, the risk of developing sarcopenia rose 14.55 times higher among males (OR: 14.55, 95% CI 12.33, 17.15) and 2.86 times higher among females (OR: 2.86, 95% CI 2.59, 3.15). The optimal cutoff values of WWI for sarcopenia were 11.26 cm/√kg for males and 11.39 cm/√kg for females. Individuals with a higher WWI have an increased risk of developing sarcopenia, and a high WWI functions as a risk factor for sarcopenia. Assessing WWI could assist in identifying individuals at risk of sarcopenia.

Racial differences in body composition and survival among older adults with gastrointestinal malignancies

INTRODUCTION

Muscle and adipose tissue measures can be quantified from routinely obtained computed tomography (CT) images and are predictors of chemotherapy-related toxicities and survival among patients with gastrointestinal (GI) malignancies. Most studies to date have consisted of predominantly White patients, and the role of body composition among minoritized racial groups is unknown. We examined racial differences in body composition and survival among patients with GI malignancies.

MATERIALS AND METHODS

This was a prospective cohort study of patients with GI malignancies. Single slices of axial CT images from L3 segments were analyzed using Slice-O-Matic software. The skeletal muscle area (cm2) was divided by height to obtain the skeletal muscle index (SMI, cm2/m2). Skeletal muscle radiodensity (SMD) in Hounsfield units (HU) was used for muscle composition. We compared body composition parameters between non-Hispanic (NH)-White and NH-Black participants. Cox models were used to examine the impact of body composition on survival. We proposed new race-specific cutoffs for body composition using optimal stratification.

RESULTS

Five hundred forty patients were included, of which 24% were NH-Black. In Cox models stratified by race, each 5 cm2/m2 decrease in SMI was associated with increase in risk of all-cause mortality in NH-Black patients (hazard ratio [HR] 1.25; 95% confidence interval [CI] 1.04-1.49 p = 0.02). With the existing cut points, neither sarcopenia nor myosteatosis was associated with worse survival. Using a new cutoff for sarcopenia in NH-Black patients, NH-Black patients with sarcopenia (HR 2.31 95%CI 1.10-4.88 p = 0.03) and myosteatosis (HR 2.63 95% CI 1.25-5.53 p = 0.01) had worse survival.

DISCUSSION

NH-Black older patients with GI cancers and sarcopenia or myosteatosis have worse overall survival.

Effect of Sarcopenia on 10-Year Risk of Atherosclerotic Cardiovascular Disease in Patients with Type 2 Diabetes Mellitus

Objective

To investigate the impact of sarcopenia on the 10-year risk of atherosclerotic cardiovascular disease (ASCVD) among individuals with type 2 diabetes mellitus (T2DM).

Methods

This study included the clinical, laboratory, and body composition data of 1491 patients with T2DM who were admitted to the Department of Endocrinology and Metabolism at Tianjin Union Medical Center from July 2018 to July 2023. The China-PAR model was utilized to evaluate cardiovascular disease risk. Associations between ASCVD risk and various clinical parameters were analyzed, and the relationship between body composition parameters and ASCVD risk was assessed using logistic regression.

Results

The analysis revealed that T2DM patients with sarcopenia had a higher 10-year ASCVD risk compared to those without sarcopenia, with reduced muscle mass independently predicting an increased risk of cardiovascular disease. This association was significant among female T2DM patients, while male T2DM patients with sarcopenia showed a marginally higher median ASCVD risk compared to their non-sarcopenic counterparts. ASCVD risk inversely correlated with body muscle parameters and positively correlated with fat content parameters. Specifically, height- and weight-adjusted fat mass (FM, FM%, FMI) were identified as risk factors for ASCVD. Conversely, muscle parameters adjusted for weight and fat (ASM%, SMM%, FFM%, ASM/FM, SMM/FM, FMM/FM) were protective against ASCVD risk. These findings highlight the critical role of sarcopenia in influencing cardiovascular disease risk among Chinese patients with T2DM, as predicted by the China-PAR model.

Conclusion

This study highlights the importance of sarcopenia in T2DM patients, not only as an indicator of ASCVD risk, but possibly as an independent risk factor in this demographics.

Aging-Related Sarcopenia: Metabolic Characteristics and Therapeutic Strategies

The proportion of the elderly population is gradually increasing as a result of medical care advances, leading to a subsequent surge in geriatric diseases that significantly impact quality of life and pose a substantial healthcare burden. Sarcopenia, characterized by age-related decline in skeletal muscle mass and quality, affects a considerable portion of older adults, particularly the elderly, and can result in adverse outcomes such as frailty, fractures, bedridden, hospitalization, and even mortality. Skeletal muscle aging is accompanied by underlying metabolic changes. Therefore, elucidating these metabolic profiles and specific mechanisms holds promise for informing prevention and treatment strategies for sarcopenia. This review provides a comprehensive overview of the key metabolites identified in current clinical studies on sarcopenia and their potential pathophysiological alterations in metabolic activity. Besides, we examine potential therapeutic strategies for sarcopenia from a perspective focused on metabolic regulation.

A review of dairy food intake for improving health among black geriatrics in the US

The transition to older adulthood is generally marked by progressive declines in body composition, metabolism, cognitive function, and immunity. For socially disadvantaged geriatric populations such as Black Americans, this life stage may also include additional stressors, including dealing with discrimination, poor access to healthcare, and food insecurity. These types of chronic stressors are linked to a higher allostatic load, which is associated with accelerated biological aging, higher rates of adverse health outcomes, and an overall lower quality of life. Of the numerous factors involved in healthy aging, a growing body of research indicates that consuming a higher quality diet that is rich in fruits, vegetables, whole grains, protein foods, and dairy foods, is one of the most potent factors for helping to protect against age-related disease progression. Among the food groups listed above that are recommended by the 2020-2025 Dietary Guidelines for Americans dairy foods are unique in their ability to provide several of the essential nutrients (e.g., high-quality protein, calcium, potassium, vitamin B12, and vitamin D in fortified products) that are most often inadequately consumed by older Black Americans. However, dairy is the most inadequately consumed food group in the US, with older Black adults consuming fewer than half of the 3 daily recommended servings. Therefore, this review examines the current body of evidence exploring the links between dairy intake and age-related disease risk, with a special focus on health and disparities among older Black Americans. Overall, the evidence from most systematic reviews and/or meta-analyses focused on dairy intake and musculoskeletal health suggest that higher dairy intake across the life span, and especially from fermented and fortified products, is associated with better bone and muscle health outcomes in older adults. The evidence on dairy intake and neurocognitive and immune outcomes among older adults holds significant promise for potential benefits, but most of these results are sourced from individual studies or narrative reviews and are not currently corroborated in systematic reviews or meta-analyses. Additionally, most of the research on dairy intake and age-related disease risk has been performed in White populations and can only be extrapolated to Black populations. Nonetheless, older Black populations who do not meet the DGA recommended 3 servings of dairy per day due to lactose intolerance, restrictive dietary patterns, or for other reasons, are likely falling short of several of the nutritional requirements necessary to support healthy aging.

Fat infiltration in skeletal muscle: Influential triggers and regulatory mechanism

Fat infiltration in skeletal muscle (also known as myosteatosis) is now recognized as a distinct disease from sarcopenia and is directly related to declining muscle capacity. Hence, understanding the origins and regulatory mechanisms of fat infiltration is vital for maintaining skeletal muscle development and improving human health. In this article, we summarized the triggering factors such as aging, metabolic diseases and metabolic syndromes, nonmetabolic diseases, and muscle injury that all induce fat infiltration in skeletal muscle. We discussed recent advances on the cellular origins of fat infiltration and found several cell types including myogenic cells and non-myogenic cells that contribute to myosteatosis. Furthermore, we reviewed the molecular regulatory mechanism, detection methods, and intervention strategies of fat infiltration in skeletal muscle. Based on the current findings, our review will provide new insight into regulating function and lipid metabolism of skeletal muscle and treating muscle-related diseases.

Integrative cross-species analysis reveals conserved and unique signatures in fatty skeletal muscles

Fat infiltration in skeletal muscle is now recognized as a standard feature of aging and is directly related to the decline in muscle function. However, there is still a limited systematic integration and exploration of the mechanisms underlying the occurrence of myosteatosis in aging across species. Here, we re-analyzed bulk RNA-seq datasets to investigate the association between fat infiltration in skeletal muscle and aging. Our integrated analysis of single-nucleus transcriptomics in aged humans and Laiwu pigs with high intramuscular fat content, identified species-preference subclusters and revealed core gene programs associated with myosteatosis. Furthermore, we found that fibro/adipogenic progenitors (FAPs) had potential capacity of differentiating into PDE4D+/PDE7B+ preadipocytes across species. Additionally, cell-cell communication analysis revealed that FAPs may be associated with other adipogenic potential clusters via the COL4A2 and COL6A3 pathways. Our study elucidates the correlation mechanism between aging and fat infiltration in skeletal muscle, and these consensus signatures in both humans and pigs may contribute to increasing reproducibility and reliability in future studies involving in the field of muscle research.

Imaging of Sarcopenia in Type 2 Diabetes Mellitus

Sarcopenia is an age-related condition characterized by the loss of skeletal muscle mass, muscular strength, and muscle function. In older adults, type 2 diabetes mellitus (T2DM) constitutes a significant health burden. Skeletal muscle damage and deterioration have emerged as novel chronic complications in patients with diabetes, often linked to their increased longevity. Diabetic sarcopenia has been associated with increased rates of hospitalization, cardiovascular events, and mortality. Nevertheless, effectively managing metabolic disorders in patients with T2DM through appropriate therapeutic interventions could potentially mitigate the risk of sarcopenia. Utilizing imaging technologies holds substantial clinical significance in the early detection of skeletal muscle mass alterations associated with sarcopenia. Such detection is pivotal for arresting disease progression and preserving patients' quality of life. These imaging modalities offer reproducible and consistent patterns over time, as they all provide varying degrees of quantitative data. This review primarily delves into the application of dual-energy X-ray absorptiometry, computed tomography, magnetic resonance imaging, and ultrasound for both qualitative and quantitative assessments of muscle mass in patients with T2DM. It also juxtaposes the merits and limitations of these four techniques. By understanding the nuances of each method, clinicians can discern how best to apply them in diverse clinical scenarios.

Skeletal muscle-focused guideline development: hierarchical model incorporating muscle form, function, and clinical outcomes

Sarcopenia, sarcopenic obesity, malnutrition, and cachexia clinical guidelines were created by expert consensus over the past decade. These pathological states all share in common deficits in skeletal muscle mass, and in some cases muscle function, which adversely impact patient outcomes. Early identification is key as some detrimental outcomes are potentially preventable with available treatments. The four guidelines share common design features: patients suspected of having the condition are first screened with a focused clinical history; if positive, the next step is evaluation with either a measure of body "form" (e.g., mass, shape, and composition) or function (e.g., mechanical, endurance, and metabolic); combined form and functional criteria are also recognized. The form and functional "gateway" nodes establish whether or not to proceed with further evaluations and treatments. Intensive discussions among experts focus on selection of these gateway nodes and the final choice is made when consensus is reached. Form and functional measures are often treated as equivalent alternatives when framed in the context of "outcomes" for which they are intended to predict. Here we adapt a classic biological concept stating that "function follows form" to show that pathophysiological links are present between these two different muscle qualities and clinical outcomes. We argue that a hierarchy exists such that outcomes closely follow functions that, in turn, follow form…the OFF rule. The OFF rule explains why functional measures often show stronger associations with outcomes than those quantifying form, helps to frame debates on how to structure the gateway nodes used to identify patients for further evaluation and treatment, and sets out a pathophysiological structure for developing future outcome prediction models.

Temporal trends in obesity defined by the relative fat mass (RFM) index among adults in the United States from 1999 to 2020: a population-based study

OBJECTIVES

The body mass index (BMI) largely underestimates excess body fat, suggesting that the prevalence of obesity could be underestimated. Biologically, women are known to have higher body fat than men. This study aimed to compare the temporal trends in general obesity by sex, ethnicity and age among adults in the USA using the relative fat mass (RFM), a validated surrogate for whole-body fat percentage and BMI.

DESIGN

Population-based study.

SETTING

US National Health and Nutrition Examination Survey, from 1999-2000 to 2017-March 2020.

PARTICIPANTS

A representative sample of adults 20-79 years in the USA.

MAIN OUTCOME MEASURES

Age-adjusted prevalence of general obesity. RFM-defined obesity was diagnosed using validated cut-offs to predict all-cause mortality: RFM≥40% for women and ≥30% for men. BMI-defined obesity was diagnosed using a cut-off of 30 kg/m2.

RESULTS

Analysis included data from 47 667 adults. Among women, RFM-defined obesity prevalence was 64.7% (95% CI 62.1% to 67.3%) in 2017-2020, a linear increase of 13.9 percentage points (95% CI 9.0% to 18.9%; p<0.001) relative to 1999-2000. In contrast, the prevalence of BMI-defined obesity was 42.2% (95% CI 39.4% to 45.0%) in 2017-2020. Among men, the corresponding RFM-defined obesity prevalence was 45.8% (95% CI 42.0% to 49.7%), a linear increase of 12.0 percentage points (95% CI 6.6% to 17.3%; p<0.001). In contrast, the prevalence of BMI-defined obesity was 42.0 (95% CI 37.8% to 46.3%). The highest prevalence of RFM-defined obesity across years was observed in older adults (60-79 years) and Mexican Americans, in women and men. Conversely, the highest prevalence of BMI-defined obesity across years was observed in middle-age (40-59 years) and older adults, and in African American women.

CONCLUSIONS

The use of a surrogate for whole-body fat percentage revealed a much higher prevalence of general obesity in the USA from 1999 to 2020, particularly among women, than that estimated using BMI, and detected a disproportionate higher prevalence of general obesity in older adults and Mexican Americans.

Unraveling age-related impairment of the neuromuscular system: exploring biomechanical and neurophysiological perspectives

With extended life expectancy, the quality of life of elders is a priority. Loss of mobility, increased morbidity and risks of falls have dramatic individual and societal impacts. Here we consider the age-related modifications of gait, from a biomechanical and neurophysiological perspective. Among the many factors of frailty involved (e.g., metabolic, hormonal, immunological), loss of muscle strength and neurodegenerative changes inducing slower muscle contraction may play a key role. We highlight that the impact of the multifactorial age-related changes in the neuromuscular systems results in common features of gait in the immature gait of infants and older adults. Besides, we also consider the reversibility of age-related neuromuscular deterioration by, on the one hand, exercise training, and the other hand, novel techniques such as direct spinal stimulation (tsDCS).

Pathogenesis, Intervention, and Current Status of Drug Development for Sarcopenia: A Review

Sarcopenia refers to the loss of muscle strength and mass in older individuals and is a major determinant of fall risk and impaired ability to perform activities of daily living, often leading to disability, loss of independence, and death. Owing to its impact on morbidity, mortality, and healthcare expenditure, sarcopenia in the elderly has become a major focus of research and public policy debates worldwide. Despite its clinical importance, sarcopenia remains under-recognized and poorly managed in routine clinical practice, partly owing to the lack of available diagnostic testing and uniform diagnostic criteria. Since the World Health Organization and the United States assigned a disease code for sarcopenia in 2016, countries worldwide have assigned their own disease codes for sarcopenia. However, there are currently no approved pharmacological agents for the treatment of sarcopenia; therefore, interventions for sarcopenia primarily focus on physical therapy for muscle strengthening and gait training as well as adequate protein intake. In this review, we aimed to examine the latest information on the epidemiology, molecular mechanisms, interventions, and possible treatments with new drugs for sarcopenia.

MME+ fibro-adipogenic progenitors are the dominant adipogenic population during fatty infiltration in human skeletal muscle

Fatty infiltration, the ectopic deposition of adipose tissue within skeletal muscle, is mediated via the adipogenic differentiation of fibro-adipogenic progenitors (FAPs). We used single-nuclei and single-cell RNA sequencing to characterize FAP heterogeneity in patients with fatty infiltration. We identified an MME⁺ FAP subpopulation which, based on ex vivo characterization as well as transplantation experiments, exhibits high adipogenic potential. MME⁺ FAPs are characterized by low activity of WNT, known to control adipogenic commitment, and are refractory to the inhibitory role of WNT activators. Using preclinical models for muscle damage versus fatty infiltration, we show that many MME⁺ FAPs undergo apoptosis during muscle regeneration and differentiate into adipocytes under pathological conditions, leading to a reduction in their abundance. Finally, we utilized the varying fat infiltration levels in human hip muscles and found less MME⁺ FAPs in fatty infiltrated human muscle. Altogether, we have identified the dominant adipogenic FAP subpopulation in skeletal muscle.

Intermuscular adipose tissue in metabolic disease

Intermuscular adipose tissue (IMAT) is a distinct adipose depot described in early reports as a 'fatty replacement' or 'muscle fat infiltration' that was linked to ageing and neuromuscular disease. Later studies quantifying IMAT with modern in vivo imaging methods (computed tomography and magnetic resonance imaging) revealed that IMAT is proportionately higher in men and women with type 2 diabetes mellitus and the metabolic syndrome than in people without these conditions and is associated with insulin resistance and poor physical function with ageing. In parallel, agricultural research has provided extensive insight into the role of IMAT and other muscle lipids in muscle (that is, meat) quality. In addition, studies using rodent models have shown that IMAT is a bona fide white adipose tissue depot capable of robust triglyceride storage and turnover. Insight into the importance of IMAT in human biology has been limited by the dearth of studies on its biological properties, that is, the quality of IMAT. However, in the past few years, investigations have begun to determine that IMAT has molecular and metabolic features that distinguish it from other adipose tissue depots. These studies will be critical to further decipher the role of IMAT in health and disease and to better understand its potential as a therapeutic target.

The acromegaly lipodystrophy

Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are essential to normal growth, metabolism, and body composition, but in acromegaly, excesses of these hormones strikingly alter them. In recent years, the use of modern methodologies to assess body composition in patients with acromegaly has revealed novel aspects of the acromegaly phenotype. In particular, acromegaly presents a unique pattern of body composition changes in the setting of insulin resistance that we propose herein to be considered an acromegaly-specific lipodystrophy. The lipodystrophy, initiated by a distinctive GH-driven adipose tissue dysregulation, features insulin resistance in the setting of reduced visceral adipose tissue (VAT) mass and intra-hepatic lipid (IHL) but with lipid redistribution, resulting in ectopic lipid deposition in muscle. With recovery of the lipodystrophy, adipose tissue mass, especially that of VAT and IHL, rises, but insulin resistance is lessened. Abnormalities of adipose tissue adipokines may play a role in the disordered adipose tissue metabolism and insulin resistance of the lipodystrophy. The orexigenic hormone ghrelin and peptide Agouti-related peptide may also be affected by active acromegaly as well as variably by acromegaly therapies, which may contribute to the lipodystrophy. Understanding the pathophysiology of the lipodystrophy and how acromegaly therapies differentially reverse its features may be important to optimizing the long-term outcome for patients with this disease. This perspective describes evidence in support of this acromegaly lipodystrophy model and its relevance to acromegaly pathophysiology and the treatment of patients with acromegaly.

Quantifying the inflammatory secretome of human intermuscular adipose tissue

Adipose tissue secretes an abundance of lipid and protein mediators, and this secretome is depot-specific, with local and systemic effects on metabolic regulation. Intermuscular adipose tissue (IMAT) accumulates within the skeletal muscle compartment in obesity, and is associated with insulin resistance and metabolic disease. While the human IMAT secretome decreases insulin sensitivity in vitro, its composition is entirely unknown. The current study was conducted to investigate the composition of the human IMAT secretome, compared to that of the subcutaneous (SAT) and visceral adipose tissue (VAT) depots. IMAT, SAT, and VAT explants from individuals with obesity were used to generate conditioned media. Proteomics analysis of conditioned media was performed using multiplex proximity extension assays, and eicosanoid analysis using liquid chromatography-tandem mass spectrometry. Compared to SAT and/or VAT, IMAT secreted significantly more cytokines (IL2, IL5, IL10, IL13, IL27, FGF23, IFNγ and CSF1) and chemokines (MCP1, IL8, CCL11, CCL20, CCL25 and CCL27). Adipokines hepatocyte growth factor and resistin were secreted significantly more by IMAT than SAT or VAT. IMAT secreted significantly more eicosanoids (PGE2, TXB2 , 5-HETE, and 12-HETE) compared to SAT and/or VAT. In the context of obesity, IMAT is a distinct adipose tissue with a highly immunogenic and inflammatory secretome, and given its proximity to skeletal muscle, may be critical to glucose regulation and insulin resistance.

The effect of ageing on fat infiltration of thigh and paraspinal muscles in men

Background

Myosteatosis, skeletal muscle fat infiltration, is associated with inflammation and fibrosis. The age-related increase of myosteatosis is an important characteristic of sarcopenia and contributes to fragility.

Aims

To investigate the impact of healthy aging on intermuscular adipose tissue (IMAT) and muscle fat fraction (FF) in the thigh and the paraspinal muscles in males.

Methods

In 54 healthy males (age 20–70), all active hobby golfers, magnetic resonance imaging was performed to determine volume of IMAT, volume of muscle tissue (MT) and of percentage of FF.

Results

Between ages 20–70, at the thigh, IMAT/MT volume and MT FF increased annually by 2.9% and 1.3%, respectively. At the psoas IMAT/Psoas volume did not change with age. MT FF increased by 1.5% annually. At the erector spinae IMAT/Erector volume decreased by 0.3% and MT FF increased by 2.8% annually.

Discussion

With increasing age, in males, thigh muscle atrophied, muscle tissue was partly replaced by adipose tissue and remaining muscle tissue also contained more fat. Similar effects were observed in the erector spinae. The psoas muscle did not atrophy, although MT FF also increased with age. Overall correlations with age were weak to moderate with higher correlations observed in the paraspinal muscles.

Conclusions

Age-related increases of muscle fat infiltration were observed in the thigh and in the spine. Muscle atrophy did not occur in the psoas. In cross-sectional studies, an adjustment of volumetric parameters by muscle volume is advisable when comparing age-dependent results.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40520-022-02149-1.

Skeletal muscle and abdominal circumference explain intramuscular fat, independent of exercise frequency, in middle-aged Japanese men

The purpose of this study was to examine how intramuscular adipose tissue (IntraMAT) can be characterized using physical and functional characteristics, muscle size, and/or adipose tissue in four different exercise frequency groups of middle-aged Japanese men. One thousand twenty-eight middle-aged men (age, 47.5 ± 8.1 years; height, 170.5 ± 5.8 cm; body mass, 67.0 ± 9.3 kg; body mass index, 21.9 ± 5.3 kg/m²) were allocated to four groups on the basis of their weekly exercise frequency: Group 1, no exercise, n = 334; Group 2, once a week, n = 271; Group 3, a few days a week, n = 269; and Group 4, every day, n = 154. Their body composition, blood pressure, and handgrip strength were assessed. A single-slice computerized tomography image at the level of the umbilicus was acquired and the CSAs of IntraMAT, muscle tissue, and subcutaneous and visceral adipose tissues (SCAT and VAT) were calculated. The %IntraMAT significantly correlated with physical characteristics, such as age, BMI, abdominal circumference, and muscle tissue CSA. Stepwise multiple regression analysis was performed, with the %IntraMAT as the dependent variable. Muscle tissue CSA and abdominal circumference were the common independent variables across groups to explain the variability of the %IntraMAT. It was also extracted %body fat and age for Group 2, age, handgrip strength, and BMI for Group 3, and smoking category for Group 4. These results suggested that muscle tissue size and abdominal circumference would be the strong predictors to explain %IntraMAT of the trunk muscle across four groups, and that age, %body fat, BMI, and SCAT, handgrip strength and smoking category were also good predictors for each group with different exercise frequency in middle-aged Japanese men.

Additive Effect of Sarcopenia and Anemia on the 10-Year Risk of Cardiovascular Disease in Patients with Type 2 Diabetes

OBJECTIVE

To investigate the association between sarcopenia and anemia and the 10-year cardiovascular disease risk in diabetic patients.

METHODS

A cross-sectional study was conducted involving 4673 hospitalized patients (2271 men and 2402 women) with type 2 diabetes mellitus, with an average age of 60.66 ± 11.93 years, of whom 542 were followed up for a median follow-up period of 24 months. All participants underwent body composition measurements, and they were grouped by sex and presence of sarcopenia using the Framingham risk model to assess their 10-year cardiovascular risk. According to the changes in the cardiovascular risk during follow-up, the patients were divided into four groups: low-low, low-high, high-low, and high-high.

RESULTS

The prevalence of anemia was higher in the sarcopenia group than in the nonsarcopenia group (11.5% vs. 24.1% for men, P < 0.001; 13.9% vs. 19.7% for women, P < 0.05), and the difference remained significant after adjusting for confounders. Patients with sarcopenia and without anemia had a 46.2% increased risk of high 10-year cardiovascular disease (CVD) (odds ratio (OR) = 1.462, 95% confidence interval (CI) 1.085-1.972, P = 0.013), and the risk was twofold higher in patients with sarcopenia and anemia than in those without (OR = 3.283, 95% CI 2.038-5.289, P < 0.001). In follow-up studies, sarcopenia was associated with an increased risk of CVD at 10 years, and a reduction in appendicular skeletal muscle mass index independently predicted the increased risk of CVD.

CONCLUSION

Sarcopenia is associated with an increased risk of anemia, and the presence of both has an additive effect on the 10-year CVD risk in patients with type 2 diabetes. Loss of muscle mass can independently predict an increased CVD risk in diabetic patients.

Growth hormone/IGF-I-dependent signaling restores decreased expression of the myokine SPARC in aged skeletal muscle

Skeletal muscle exerts many beneficial effects on the human body including the contraction-dependent secretion of peptides termed myokines. We have recently connected the myokine secreted protein acidic and rich in cysteine (SPARC) to the formation of intramuscular adipose tissue (IMAT) in skeletal muscle from aged mice and humans. Here, we searched for inducers of SPARC in order to uncover novel treatment approaches for IMAT. Endurance exercise in mice as well as forskolin treatment in vitro only modestly activated SPARC levels. However, through pharmacological treatments in vitro, we identified IGF-I as a potent inducer of SPARC expression in muscle cells, likely through a direct activation of its promoter via phosphatidylinositol 4,5-bisphospate 3-kinase (PI3K)-dependent signaling. We employed two different mouse models of growth hormone (GH)/IGF-I deficiency to solidify our understanding of the relationship between IGF-I and SPARC in vivo. GH administration robustly increased intramuscular SPARC levels (3.5-fold) in GH releasing hormone receptor-deficient mice and restored low intramuscular SPARC expression in skeletal muscle from aged mice. Intramuscular glycerol injections induced higher levels of adipocyte markers (adiponectin, perilipin) in aged compared to young mice, which was not prevented by GH treatment. Our study provides a roadmap for the study of myokine regulation during aging and demonstrates that the GH/IGF-I axis is critical for SPARC expression in skeletal muscle. Although GH treatment did not prevent IMAT formation in the glycerol model, targeting SPARC by exercise or by activation of IGF-I signaling might offer a novel therapeutic strategy against IMAT formation during aging. KEY MESSAGES : IGF-I regulates the myokine SPARC in muscle cells directly at the promoter level. GH/IGF-I is able to restore the decreased SPARC levels in aged skeletal muscle. The glycerol model induces higher adipocyte markers in aged compared to young muscle. GH treatment does not prevent IMAT formation in the glycerol model.

Quality Matters as Much as Quantity of Skeletal Muscle: Clinical Implications of Myosteatosis in Cardiometabolic Health

Although age-related changes in skeletal muscles are closely associated with decreases in muscle strength and functional decline, their associations with cardiometabolic diseases in the literature are inconsistent. Such inconsistency could be explained by the fact that muscle quality-which is closely associated with fatty infiltration of the muscle (i.e., myosteatosis)-is as important as muscle quantity in cardiometabolic health. However, muscle quality has been less explored compared with muscle mass. Moreover, the standard definition of myosteatosis and its assessment methods have not been established yet. Recently, some techniques using single axial computed tomography (CT) images have been introduced and utilized in many studies, as the mass and quality of abdominal muscles could be measured opportunistically on abdominal CT scans obtained during routine clinical care. Yet, the mechanisms by which myosteatosis affect metabolic and cardiovascular health remain largely unknown. In this review, we explore the recent advances in the assessment of myosteatosis and its changes associated with aging. We also review the recent literature on the clinical implication of myosteatosis by focusing on metabolic and cardiovascular diseases. Finally, we discuss the challenges and unanswered questions that need addressing to set myosteatosis as a therapeutic target for the prevention or treatment of cardiometabolic diseases.

Skeletal Muscle Deconditioning in Breast Cancer Patients Undergoing Chemotherapy: Current Knowledge and Insights From Other Cancers

Breast cancer represents the most commonly diagnosed cancer while neoadjuvant and adjuvant chemotherapies are extensively used in order to reduce tumor development and improve disease-free survival. However, chemotherapy also leads to severe off-target side-effects resulting, together with the tumor itself, in major skeletal muscle deconditioning. This review first focuses on recent advances in both macroscopic changes and cellular mechanisms implicated in skeletal muscle deconditioning of breast cancer patients, particularly as a consequence of the chemotherapy treatment. To date, only six clinical studies used muscle biopsies in breast cancer patients and highlighted several important aspects of muscle deconditioning such as a decrease in muscle fibers cross-sectional area, a dysregulation of protein turnover balance and mitochondrial alterations. However, in comparison with the knowledge accumulated through decades of intensive research with many different animal and human models of muscle atrophy, more studies are necessary to obtain a comprehensive understanding of the cellular processes implicated in breast cancer-mediated muscle deconditioning. This understanding is indeed essential to ultimately lead to the implementation of efficient preventive strategies such as exercise, nutrition or pharmacological treatments. We therefore also discuss potential mechanisms implicated in muscle deconditioning by drawing a parallel with other cancer cachexia models of muscle wasting, both at the pre-clinical and clinical levels.

Correlation between Psoas Muscle Index and Degeneration of Spinal Back Muscle in Patients with Back Pain

Sarcopenia is characterized by a decline in systemic muscle mass and physical performance. Disc degeneration also causes back muscle atrophy. Therefore, we aimed to evaluate the influence of systemic muscle mass decline on back muscle atrophy and fatty infiltration compared to disc degeneration. We included 127 patients (65.54 ± 14.93 years) with back pain who underwent lumbar spine magnetic resonance imaging (MRI). Axial T2-weighted MRI data of the L4-5 and L5-S1 levels were used to measure the cross-sectional area (CSA) of the psoas and spinal muscles. The psoas index (cm²/m²) was used as a surrogate for systemic muscle mass. The Pfirrmann grading system was used to evaluate intervertebral disc degeneration. The functional area of the back muscles was calculated by subtracting the fat infiltration area from the CSA; the functional CSA ratio was calculated by dividing the functional CSA by the CSA. Image-processing software (ImageJ; National Institutes of Health, Bethesda, MD, USA) was used for analysis. Psoas index and aging significantly affected CSA and the ratio of functional CSA of the back muscles and multifidi. Disc degeneration did not significantly affect the back muscles beyond aging in patients with back pain. Males showed substantially higher CSA of the back muscles and multifidi than females; however, sex did not affect the functional CSA ratio of these muscles. Systemic muscle mass decline showed a more powerful influence on back muscle atrophy and fatty infiltration than disc degeneration. Therefore, proper evaluation of sarcopenia is needed for patients with chronic back pain and back muscle degeneration.

MRI-Determined Psoas Muscle Fat Infiltration Correlates with Severity of Weight Loss during Cancer Cachexia

PURPOSE

To evaluate the suitability of psoas and erector spinae muscle proton density fat fraction (PDFF) and fat volume as biomarkers for monitoring cachexia severity in an oncological cohort, and to evaluate regional variances in muscle parameters over time.

METHODS

In this prospective study, 58 oncological patients were examined by a 3 T MRI receiving between one and five scans. Muscle volume and PDFF were measured, segmentation masks were divided into proximal, middle and distal muscle section.

RESULTS

A regional variation of fat distribution in erector spinae muscle at baseline was found (p < 0.01). During follow-ups significant relative change of muscle parameters was observed. Relative maximum change of erector spinae muscle showed a significant regional variation. Correlation testing with age as a covariate revealed significant correlations for baseline psoas fat volume (r = -0.55, p < 0.01) and baseline psoas PDFF (r = -0.52, p = 0.02) with maximum BMI change during the course of the disease.

CONCLUSION

In erector spinae muscles, a regional variation of fat distribution at baseline and relative maximum change of muscle parameters was observed. Our results indicate that psoas muscle PDFF and fat volume could serve as MRI-determined biomarkers for early risk stratification and disease monitoring regarding progression and severity of weight loss in cancer cachexia.

Suppression of MyoD induces spontaneous adipogenesis in skeletal muscle progenitor cell culture

The degree of intramuscular adipose tissue accumulation is one of the factors affecting meat quality. Accumulation of adipocytes is also observed under the pathological condition of skeletal muscle such as muscular dystrophy and sarcopenia. The origin of adipocytes seen in skeletal muscle is mesenchymal progenitor cells that can give rise to both adipocytes and fibroblasts. In the present study, we demonstrated that siRNA-mediated suppression of MyoD expression in rat skeletal muscle progenitor cell culture, which comprises both myogenic satellite cells and mesenchymal progenitor cells, resulted in diminished myotube formation and an unexpected spontaneous appearance of white adipocytes. Suppressing myomaker expression also resulted in complete absence of myotube formation without reducing MyoD expression, but no adipogenesis was seen in this scenario, indicating that decline in MyoD expression rather than decreased myotube formation is necessary to induce adipogenesis. In addition, spontaneous adipogenesis induced by suppressing MyoD expression in culture was inhibited by the conditioned medium from control culture, indicating that anti-adipogenic factor(s) are secreted from MyoD-positive myogenic cells. These results indicate the presence of regulatory mechanism on adipogenesis by myogenic cells.

Gait disturbances and muscle dysfunction in fibroblast growth factor 2 knockout mice

Fibroblast growth factor 2 (FGF2) is important in musculoskeletal homeostasis, therefore the impact of reduction or Fgf2 knockout on skeletal muscle function and phenotype was determined. Gait analysis as well as muscle strength testing in young and old WT and Fgf2KO demonstrated age-related gait disturbances and reduction in muscle strength that were exacerbated in the KO condition. Fgf2 mRNA and protein were significantly decreased in skeletal muscle of old WT compared with young WT. Muscle fiber cross-sectional area was significantly reduced with increased fibrosis and inflammatory infiltrates in old WT and Fgf2KO vs. young WT. Inflammatory cells were further significantly increased in old Fgf2KO compared with old WT. Lipid-related genes and intramuscular fat was increased in old WT and old Fgf2KO with a further increase in fibro-adipocytes in old Fgf2KO compared with old WT. Impaired FGF signaling including Increased β-Klotho, Fgf21 mRNA, FGF21 protein, phosphorylated FGF receptors 1 and 3, was observed in old WT and old Fgf2KO. MAPK/ ERK1/2 was significantly increased in young and old Fgf2KO. We conclude that Fgf2KO, age-related decreased FGF2 in WT mice, and increased FGF21 in the setting of impaired Fgf2 expression likely contribute to impaired skeletal muscle function and sarcopenia in mice.

Age-related changes in muscle quality and development of diagnostic cutoff points for myosteatosis in lumbar skeletal muscles measured by CT scan

BACKGROUND & AIMS

We have sought to develop proper and useful indices for muscle quality measurements other than muscle attenuation (Hounsfield unit; HU) and to determine the diagnostic cutoff points for myosteatosis by using those indices measured at the L3 lumbar vertebrae level by CT scan.

METHODS

This cross-sectional analysis included 20,664 healthy adult subjects (12,697 men and 7967 women) who underwent abdominal CT scans. Total abdominal muscle area (TAMA), on the L3 vertebra was demarcated using predetermined thresholds. Intermuscular adipose tissue area (IMAT) and skeletal muscle area (SMA) were measured. SMA was divided into normal attenuation muscle area (NAMA) and low attenuation muscle area (LAMA). Their various indices were calculated. We identified the sex-specific mean values of NAMA, LAMA, IMAT, and their indices and the cutoff points equivalent to the T-scores in the young reference group.

RESULTS

The mean values of the NAMA and NAMA indices decreased with age in both sexes, LAMA, IMAT, and their indices showed an increasing tendency with age in both sexes. When using T-score < -2.0 as the cutoff for myosteatosis, the sex-specific cutoff points of NAMA, NAMA/BMI, NAMA/TAMA index, and SMA and TAMA attenuation in men and women were 103.0 and 64.5 cm², 4.0 and 2.8, 66.4 and 65.1, 40.2 and 39.9 HU, and 34.1 and 33.5 HU, respectively. Using these cutoff points, the prevalence of myosteatosis by NAMA, NAMA/BMI, NAMA/TAMA index, or SMA or TAMA attenuation ranged from 5.9 to 8.8% in men and from 10.2 to 20.5% in women.

CONCLUSIONS

The NAMA/TAMA index developed in this study was useful for assessing myosteatosis. This is the first study to report the sex-specific diagnostic cutoff points for myosteatosis of trunk muscles based on T-scores measured by CT scans in healthy population. These diagnostic cutoff points may be particularly useful in the treatment and prevention of sarcopenia and myosteatosis.

Longitudinal changes in skeletal muscle mass in patients with advanced squamous cell lung cancer

Background

Skeletal muscle depletion (sarcopenia) is associated with poor prognosis in patients with lung cancer. We analyzed changes in skeletal muscle area using serial computed tomography (CT) until the death of patients with advanced squamous cell lung cancer (SQCLC).

Methods

This retrospective study comprised 70 consecutive patients who underwent palliative chemotherapy for SQCLC. The cross‐sectional area of the skeletal muscle at the level of the first lumbar vertebra (L1) was measured using chest CT. An artificial intelligence algorithm was developed and used for the serial assessment of the muscle area. Sarcopenia was defined as an L1 skeletal muscle index <46 cm²/m² in men and < 29 cm²/m² in women.

Results

The median age was 69 years; 62 patients (89%) had metastatic disease at the time of initial diagnosis. Sarcopenia was present in 58 patients (82.9%) at baseline; all patients experienced net muscle loss over the disease trajectory. The median overall survival was 8.7 (95% confidence interval 5.9–11.5) months. The mean percentage loss of skeletal muscle between the first and last CT was 16.5 ± 11.0%. Skeletal muscle loss accelerated over time and was the highest in the last 3 months of life (p < 0.001). Patients losing skeletal muscle rapidly (upper tertile, >3.24 cm²/month) had shorter overall survival than patients losing skeletal muscle slowly (median, 5.7 vs. 12.0 months, p < 0.001).

Conclusions

Patients with advanced SQCLC lose a significant amount of skeletal muscle until death. The rate of muscle area reduction is faster at the end of life.

Patients with advanced SQCLC lose a significant amount of skeletal muscle until death. The rate of muscle area reduction is faster at the end of life.

Impact of adiposity on muscle function and clinical events among elders with dynapenia, presarcopenia and sarcopenia: a community-based cross-sectional study

INTRODUCTION

Low muscle function determined unfavorable clinical outcome than low muscle mass; nevertheless, comparison of detrimental parameters among dynapenia, presarcopenia and sarcopenia was sparse. We hypothesized that adiposity is implicated in low muscle function related adverse events.

METHODS

We recruited community elders to measure handgrip strength and walking speed. Using bioelectronics impedance analyzer to examine body compositions. The faller is indicated of having a fall event in the past one year. Associations of different obesity parameters, metabolic syndrome (MetS) and fall among the groups were analyzed.

RESULTS

Among 765 participants, the dynapenia group had higher metabolic profiles, body fat percentage (BFP), waist circumference, and fat to muscle ratio (FMR) than the other groups, whereas the presarcopenia subjects had the lowest obesity parameters. The fallers tended to have poorer muscle function than non-fallers (p<0.001). The dynapenia individuals had the highest risk for MetS (odds ratio [OR]= 5.79; 95% confidence interval [CI]= 2.45-13.73), and the highest fall risk (OR= 3.11; 95% CI=1.41-6.87). Among obesity parameters, FMR had better diagnostic performance to estimate low muscle function, followed by BFP.

CONCLUSION

Dynapenia individual had higher risk of obese-related adverse events. Increased adiposity irrespective of muscle mass is relevant to reduced muscle function among elders.

Geriatric syndromes in an urban elderly population in Cameroon: a focus on disability, sarcopenia and cognitive impairment

Introduction

geriatric syndromes are multifactorial conditions that are associated with substantial disability, poor quality of life and mortality in the elderly. The patterns of these conditions are poorly described in sub-Saharan Africa. This study aimed to determine the prevalence and correlates of common geriatric syndromes in Cameroon.

Methods

we conducted a cross-sectional study in the geriatrics unit of a university hospital in Cameroon. All people aged ≥55 who attended a health promotion and screening campaign in September 2019 were included. Geriatric syndromes including functional decline, cognitive impairment and sarcopenia were assessed. We also examined sociodemographic characteristics and comorbidities.

Results

overall, 104 participants were enrolled with median age of 65 (IQR: 62.2 - 70.8). About 67% of participants presented at least one geriatric syndrome. Disability in activities of daily living and instrumental activities of daily living were present in 10% and 38% of participants respectively and associated factors were male gender (OR 4.7, p=0.005), age 75 and above (OR 5.7, p=0.027), osteoarthritis (OR 3.3, p=0.055) and polypharmacy (OR 7.7, p=0.012). Sarcopenia occurs in 26% with female gender (OR 3.1, p=0.029) and SARC-F ≥4 (OR 4.9, p=0.002) as associated factors. Cognitive impairment was present in 20% of participants and associated with illiteracy (p=0.008).

Conclusion

our study shows a high prevalence of geriatric syndromes in older adults in an urban area. Geriatric principles and frailty awareness should be considered in clinical care of older adults in our setting.

Relationship between muscle mass index and LDL cholesterol target levels: Analysis of two studies of the Korean population

BACKGROUND AND AIMS

Decreased skeletal muscle mass is an important change in body composition with aging. Maintaining the optimal low-density lipoprotein (LDL) cholesterol level is crucial for the prevention of cardiovascular diseases (CVD). We investigated whether muscle mass was associated with dyslipidemia.

METHODS

We analyzed the data of 17,546 adults from the 2008-2011 Korean National Health and Nutrition Examination Survey (KNHANES) and 5126 adults from the Korean Genome and Epidemiology Study (KoGES). Participants were classified into the lower skeletal muscle mass index (LSMI) group and normal group. LSMI was defined as body mass index (BMI)-adjusted appendicular skeletal muscle mass <0.789 (men) and <0.512 (women) in the KNHANES, and as sex-specific lowest quintile of the BMI-adjusted total skeletal muscle mass in the KoGES. Participants were defined as having dyslipidemia when the serum LDL cholesterol levels were higher than their LDL cholesterol management targets based on their CVD risk level.

RESULTS

The odds ratio with 95% confidence interval (CI) for dyslipidemia of the LSMI group was 1.230 (1.016-1.488, p = 0.034) after adjusting for confounding variables compared to the normal group in the 2008-2011 KNHANES. In the KoGES, the hazard ratio with 95% CI for incident dyslipidemia of the LSMI group compared to the normal group was 1.225 (1.101-1.364, p < 0.001). Regardless of abdominal obesity, LSMI was significantly associated with a higher risk of incident dyslipidemia.

CONCLUSIONS

LSMI was associated with dyslipidemia regardless of abdominal obesity. Prevention of muscle mass loss may be an important strategy for LDL cholesterol management.

Resistance Training in Hypoxia as a New Therapeutic Modality for Sarcopenia-A Narrative Review

Hypoxic training is believed to be generally useful for improving exercise performance in various athletes. Nowadays, exercise intervention in hypoxia is recognized as a new therapeutic modality for health promotion and disease prevention or treatment based on the lower mortality and prevalence of people living in high-altitude environments than those living in low-altitude environments. Recently, resistance training in hypoxia (RTH), a new therapeutic modality combining hypoxia and resistance exercise, has been attempted to improve muscle hypertrophy and muscle function. RTH is known to induce greater muscle size, lean mass, increased muscle strength and endurance, bodily function, and angiogenesis of skeletal muscles than traditional resistance exercise. Therefore, we examined previous studies to understand the clinical and physiological aspects of sarcopenia and RTH for muscular function and hypertrophy. However, few investigations have examined the combined effects of hypoxic stress and resistance exercise, and as such, it is difficult to make recommendations for implementing universal RTH programs for sarcopenia based on current understanding. It should also be acknowledged that a number of mechanisms proposed to facilitate the augmented response to RTH remain poorly understood, particularly the role of metabolic, hormonal, and intracellular signaling pathways. Further RTH intervention studies considering various exercise parameters (e.g., load, recovery time between sets, hypoxic dose, and intervention period) are strongly recommended to reinforce knowledge about the adaptational processes and the effects of this type of resistance training for sarcopenia in older people.

Salivary Testosterone and Cortisol as Biomarkers for the Diagnosis of Sarcopenia and Sarcopenic Obesity in Community-Dwelling Older Adults

Nowadays, the appearance of sarcopenia (S) or sarcopenic obesity (SO) is related to aging. According to the criteria of the European Working Group on Sarcopenia in Older People (EWGSOP), the feasibility of using salivary cortisol and testosterone levels was analyzed as diagnostic biomarkers of S or SO. One hundred and ninety non-institutionalized people aged ≥65 years were studied, independent of the activities of daily living (ADLs) (Barthel > 60), and sociodemographic variables were determined together with criteria for the diagnosis of S and SO including grip force, lower body strength, appendicular skeletal muscle mass, physical performance, total body fat percentage, body mass index (BMI), waist circumference, and triceps skinfold, together with the levels of salivary cortisol and testosterone. Our results reflected that women presented a higher prevalence of S and SO (21.2% and 30.2%, respectively). A significant difference was observed between salivary testosterone levels and the age of the participants with differences by sex. Testosterone values in men with S and SO were significantly lower (p = 0.043 and p = 0.048, respectively), which suggests a potential use of the biomarker for diagnostic purposes. No significant differences were shown with cortisol values.

Dynamics of hepatic steatosis resolution and changes in gut microbiome with weight loss in nonalcoholic fatty liver disease

Background

Weight loss is recommended as the primary treatment for nonalcoholic fatty liver disease (NAFLD). However, the magnitude and velocity of hepatic steatosis resolution with weight loss is unclear, making it difficult to counsel patients seeking weight loss for treatment of NAFLD. The aim of this study was to determine the rate of hepatic steatosis improvement and stool microbiome changes associated with rapid diet‐induced weight loss in NAFLD.

Methods

Fourteen NAFLD patients (mean ± standard deviation, body mass index [BMI] 36.4 ± 4 kg/m²) enrolled in a 12‐week meal replacement program underwent frequent measurement of Fibroscan‐controlled attenuation parameter (CAP). Magnetic resonance imaging (MRI‐Dixon method) for hepatic fat quantitation and stool microbiome analysis (16S rRNA gene sequencing) were completed in 11 subjects at baseline and Week 12.

Results

At Week 12, mean (95% confidence interval) weight loss was −13.4 (−15.2, −11.5)% and CAP score −26.6 (−35.6, −17.6)% (both Ps < 0.001). CAP scores changed at a rate of −4.9 dB/m/kg (−30.1 dB/m per unit BMI) in Weeks 1–4 and −0.6 dB/m/kg (−2.4 dB/m per unit BMI) in Weeks 8–12. MRI‐determined hepatic fat fraction decreased by −74.1% (p < 0.001) at a rate of −0.51%/kg (−3.19% per unit BMI), with complete steatosis resolution in 90% patients. BMI change was associated with decreased stool microbial diversity (coefficient = 0.17; Shannon Index), increased abundance of Prevotella_9 (Bacteroidetes; coefficient = 0.96) and decreased abundance of Phascolarctobacterium (Firmicutes; coefficient = −0.42) (both Ps < 0.05).

Conclusions

Diet‐induced intensive weight loss is associated with rapid improvement and complete resolution of hepatic steatosis and decreased stool microbial diversity. These findings highlight the dynamic nature of hepatic fat and may help clinicians to develop evidence‐based treatment goals for patients with NAFLD and obesity who undertake weight loss interventions. Further research is warranted to understand the effects of intensive weight loss and gut microbiome changes on long‐term NAFLD resolution.

Novel approaches to sarcopenic obesity and weight management before and after kidney transplantation

PURPOSE OF REVIEW

Although a widely recognized and complex pathophysiological condition, sarcopenic obesity remains less appreciated and may elude diagnosis and workup in both kidney transplant waitlisted candidates and kidney transplant recipients. The lack of consensus definition, and practical diagnostic tools for evaluating waitlisted candidates and transplant recipients are barriers to early detect and initiate therapeutic management for sarcopenic obesity. Although sarcopenia leads to poor clinical outcomes, posttransplant obesity yields conflicting results. Exercise and nutritional managements are common therapies for sarcopenic obese patients; however, surgery weight loss or bariatric surgery in both transplant candidates and potential living kidney donors shows promising benefits for kidney transplant access in waitlist obese candidates but may require to be selected for appropriate patients.

RECENT FINDINGS

Pathogenesis and management for sarcopenia and obesity are interconnected. The benefits of exercise to improve muscle mass and function is clear in waitlist kidney transplant candidates and transplant recipients. However, there are several barriers for those to increase exercise and improve physical activity including patient, provider, and healthcare or environmental factors. The advantages of fat mass reduction to lose weight can promote muscle mass and strength. However, epidemiological data regarding the obesity paradox in dialysis-dependent patients when overnutrition provides survival benefits for this population should be taken into account when performing weight loss especially bariatric surgery.

SUMMARY

Barriers in providing optimal care to kidney transplant waitlisted candidates and transplant recipients may partly result from underdiagnosis of sarcopenic obesity; notwithstanding that this entity has increasingly been more recognized. Mechanistic studies to better understand pathogenesis of sarcopenic obesity will help determine pathogenesis and clinical tools for diagnosis of this entity, which can facilitate further studies related to the outcomes and weight management to ultimately improve kidney transplant outcomes.

Habitual Miso (Fermented Soybean Paste) Consumption Is Associated with a Low Prevalence of Sarcopenia in Patients with Type 2 Diabetes: A Cross-Sectional Study

Insulin resistance is a risk of sarcopenia, and the presence of sarcopenia is high in patients with type 2 diabetes (T2DM). It has been reported that habitual miso soup consumption was associated with lower insulin resistance. However, the association between habitual miso consumption and the presence of sarcopenia in patients with T2DM, especially sex difference, was unclear. In this cross-sectional study, 192 men and 159 women with T2DM were included. Habitual miso consumption was defined as consuming miso soup regularly. Having both low skeletal muscle mass index (<28.64% for men, <24.12% for women) and low adjusted hand grip strength (<51.26% for men, <35.38% for women) was defined as sarcopenia. The proportions of sarcopenia were 8.7% in men and 22.6% in women. The proportions of habitual miso consumption were 88.0% in men and 83.6% in women. Among women, the presence of sarcopenia was lower in the group with habitual miso consumption (18.8% versus 42.3%, p = 0.018); however, there was no association between habitual miso consumption and the presence of sarcopenia in men. Habitual miso consumption was negatively associated with the presence of sarcopenia in women (adjusted odds ratio (OR), 0.20 (95% confidence interval (CI): 0.06-0.62), p = 0.005) but not in men. This study indicated that habitual miso consumption was associated with the presence of sarcopenia in women but not in men.