Intermuscular fat: a review of the consequences and causes

Mitochondrial quality control measures, systemic inflammation, and lower-limb muscle power in older adults: a PROMPT secondary analysis

OBJECTIVES

The study was conducted to explore associations between markers of mitochondrial quality control (MQC) from vastus lateralis muscle biopsies, serum inflammatory markers, and measures of muscle power assessed by two different tools in a sample of older adults.

DESIGN

Secondary analysis of data collected in the PeppeR develOpMental ProjecT (PROMPT) at the University of Florida (Gainesville, FL, USA).

METHODS

Forty-three older adults (n = 20 women) were included in the study. Muscle volume of the calf and thigh was quantified by three-dimensional magnetic resonance imaging. Lower-limb muscle power was estimated using 5-time sit-to-stand (5STS) muscle power equations and isokinetic test. Protein markers of MQC were measured in muscle samples by Western immoblotting (n = 12-23), while type I and II fiber cross-sectional area (CSA) and their proportion were quantified using immunohistochemistry (n = 12). Cytochrome C oxidase enzyme activity was measured spectrophotometrically. Finally, inflammatory markers were quantified in the serum using a multiplex immunoassay (n = 39).

RESULTS

Mean age of participants was 78.1 ± 5.5 years, and the average body mass index was 26.2 ± 4.5 kg/m2. Markers of mitochondrial biogenesis (i.e., PGC-1α), mitochondrial import proteins (i.e., cHsp70 and mtHsp70), and type I fiber CSA were significantly associated with muscle power estimated via both 5STS muscle power equations and isokinetic test (p < 0.05). Specific associations were also found according to the muscle power assessment method. 5STS muscle power measures were negatively correlated with ClvCasp3, P-AMPK, T-AMPK, P-p38, GM-CSF, INF-γ, IL1b, IL6, IL8, and TNF-α, whereas positive associations were found with BAX (p < 0.05). In contrast, isokinetic measures were significantly and positively correlated with RIP140, Hsp60, and type II muscle fiber CSA (p < 0.05).

CONCLUSIONS

Markers of mitochondrial biogenesis (PGC-1α), mitochondrial import proteins (cHsp70 and mtHsp70), and type I muscle fiber CSA were significantly linked to lower-limb muscle power in older adults. These results suggest that muscle power is influenced by mitochondrial signaling. We also found that the relationship between mitochondrial mediators, inflammatory markers, and muscle power varied according to the assessment tool used.

Intramuscular condition of swallowing-related muscles using shear-wave elastography: A preliminary study in healthy adults

BACKGROUND

Assessing the internal condition of swallowing-related muscles and muscle strength and size is important because their deterioration may lead to dysphagia. However, there are few reports on stiffness of swallowing-related muscles measured using shear-wave elastography (SWE) and their qualitative characteristics.

OBJECTIVES

We measured stiffness of swallowing-related muscles using SWE to investigate the relationship between muscle stiffness and body composition as well as other relevant variables in healthy adults.

METHODS

Thirty healthy adults were included in this cross-sectional study. We evaluated stiffness of the genioglossus muscle (GGM) and geniohyoid muscle (GHM) using SWE. Skeletal muscle mass index, body mass index (BMI), handgrip strength, tongue pressure, and cross-sectional areas of the muscles were measured, and we determined their relationship with muscle stiffness.

RESULTS

For muscle stiffness, the mean value for the middle GGM was 7.08 ± 1.92 kPa, that for the posterior GGM was 9.31 ± 2.68 kPa, and that for the GHM was 8.84 ± 2.15 kPa. In multiple regression analysis, with stiffness of the posterior GGM as the dependent variable, BMI (β = -.473, p = .039) was a significant negative explanatory variable. However, with the GHM stiffness as the dependent variable, BMI (β = .419, p = .033) was a significant positive explanatory variable.

CONCLUSION

Stiffness of the posterior GGM was positively correlated with BMI and that of the GHM was negatively correlated with BMI. Stiffness, as measured using SWE, has the potential to capture the intramuscular characteristics of swallowing-related muscles, particularly the posterior GGM.

Mastication and oral myofunctional status in excess weight children and adolescents: A cross-sectional observational study

BACKGROUND

Masticatory function seems to play a role in the aetiology of obesity. However, literature on the association between oral myofunctional status and overweight and obesity in children and adolescents is scarce and contrasting.

OBJECTIVE

To compare masticatory performance, orofacial myofunctional status and tongue strength and endurance between children and adolescents with overweight and obesity and those with normal weight.

METHODS

Thirty children and adolescents with overweight and obesity and 30 subjects with normal weight matched for age and sex were recruited. All subjects were evaluated with the Test of Masticating and Swallowing Solids in Children (TOMASS-C) for masticatory performance and with the Italian Orofacial Myofunctional Evaluation with Scores (I-OMES) for the orofacial myofunctional status. Anterior and posterior maximum tongue pressures and tongue endurance were measured. Parents-reported (PRO) duration of meals was recorded. Data were compared between the groups through the paired samples t-test or the Wilcoxon signed-rank test.

RESULTS

Children and adolescents with overweight showed significantly lower number of bites (p = .033), lower I-OMES scores (p < .05), and shorter meal duration (p = .005) compared to their peers with normal weight. No significant differences were found between the two groups for the number of swallows, the number of masticatory cycles and the total time of the TOMASS-C, and none of the tongue pressure measurements.

CONCLUSIONS

Eating in children and adolescents with overweight and obesity is characterised by a larger bolus sizes and shorter PRO meal duration. Additionally, overweight and obesity seem to be associated with poorer orofacial skills and structures in the paediatric population.

Beyond weakness: Exploring intramuscular fat and quadriceps atrophy in ACLR recovery

Muscle weakness following anterior cruciate ligament reconstruction (ACLR) increases the risk of posttraumatic osteoarthritis (OA). However, focusing solely on muscle weakness overlooks other aspects like muscle composition, which could hinder strength recovery. Intramuscular fat is a non-contractile element linked to joint degeneration in idiopathic OA, but its role post-ACLR has not been thoroughly investigated. To bridge this gap, we aimed to characterize quadriceps volume and intramuscular fat in participants with ACLR (male/female = 15/9, age = 22.8 ± 3.6 years, body mass index [BMI] = 23.2 ± 1.9, time since surgery = 3.3 ± 0.9 years) and in controls (male/female = 14/10, age = 22.0 ± 3.1 years, BMI = 23.3 ± 2.6) while also exploring the associations between intramuscular fat and muscle volume with isometric strength. Linear mixed effects models assessed (I) muscle volume, (II) intramuscular fat, and (III) strength between limbs (ACLR vs. contralateral vs. control). Regression analyses were run to determine if intramuscular fat or volume were associated with quadriceps strength. The ACLR limb was 8%-11% smaller than the contralateral limb (p < 0.05). No between-limb differences in intramuscular fat were observed (p = 0.091-0.997). Muscle volume but not intramuscular fat was associated with strength in the ACLR and control limbs (p < 0.001-0.002). We demonstrate that intramuscular fat does not appear to be an additional source of quadriceps dysfunction following ACLR and that muscle size only explains some of the variance in muscle strength.

Histological changes in skeletal muscle induced by heart failure in human patients and animal models: A scoping review

OBJECTIVE

This scoping review aimed to characterize the histological changes in skeletal muscle after heart failure (HF) and to identify gaps in knowledge.

METHODS

On April 03, 2024, systematic searches were performed for papers in which histological analyses were conducted on skeletal muscle sampled from patients with HF or animal models of HF. Screening and data extraction were conducted by two independent authors.

RESULTS AND CONCLUSION

A total of 118 papers were selected, including 33 human and 85 animal studies. Despite some disagreements among studies, some trends were observed. These trends included a slow-to-fast transition, a decrease in muscle fiber size, capillary to muscle fiber ratio, and mitochondrial activity and content, and an increase in apoptosis. These changes may contribute to the fatigability and decrease in muscle strength observed after HF. Although there were some disagreements between the results of human and animal studies, the results were generally similar. Animal models of HF will therefore be useful in elucidating the histological changes in skeletal muscle that occur in human patients with HF. Because the muscles subjected to histological analysis were mostly thigh muscles in humans and mostly lower leg muscles in animals, it remains uncertain whether changes similar to those seen in lower limb (hindlimb) muscles after HF also occur in upper limb (forelimb) muscles. The results of this review will consolidate the current knowledge on HF-induced histological changes in skeletal muscle and consequently aid in the rehabilitation of patients with HF and future studies.

Cachexia in preclinical rheumatoid arthritis: Longitudinal observational study of thigh magnetic resonance imaging from osteoarthritis initiative cohort

BACKGROUND

Preclinical rheumatoid arthritis (Pre-RA) is defined as the early stage before the development of clinical RA. While cachexia is a well-known and potentially modifiable complication of RA, it is not known if such an association exists also in the Pre-RA stage. To investigate such issue, we aimed to compare the longitudinal alterations in the muscle composition and adiposity of participants with Pre-RA with the matched controls.

METHODS

In this observational cohort study, the Osteoarthritis Initiative (OAI) participants were categorized into Pre-RA and propensity score (PS)-matched control groups. Pre-RA was retrospectively defined as the absence of RA from baseline to year-2, with progression to physician-diagnosed clinical RA between years 3-8 of the follow-up period. Using a validated deep learning algorithm, we measured MRI biomarkers of thigh muscles and adiposity at baseline and year-2 follow-ups of the cohort. The outcomes were the differences between Pre-RA and control groups in the 2-year rate of change for thigh muscle composition [cross-sectional area (CSA) and intramuscular adipose tissue (Intra-MAT)] and adiposity [intermuscular adipose tissue (Inter-MAT) and subcutaneous adipose tissue (SAT)]. Linear mixed-effect regression models were used for comparison.

RESULTS

After 1:3 PS-matching of the groups for confounding variables (demographics, risk factors, co-morbidities, and knee osteoarthritis status), 408 thighs (102 Pre-RA and 306 control) of 322 participants were included (age mean ± SD: 61.7 ± 8.9 years; female/male: 1.8). Over a 2-year period, Pre-RA was associated with a larger decrease in total thigh muscle CSA [estimate, 95% confidence interval (CI): -180.13 mm2/2-year, -252.80 to -107.47, P-value < 0.001]. Further examination of thigh muscle composition showed that the association of the presence of Pre-RA with a larger decrease in muscle CSA over 2 years was noticeable in the quadriceps, flexors, and sartorius muscle groups (P-values < 0.05). Comparison of changes in total adipose tissue showed no difference between Pre-RA and control participants (estimate, 95% CI: 48.48 mm2/2-year, -213.51 to 310.47, P-value = 0.691). However, in the detailed analysis of thigh adiposity, Pre-RA presence was associated with a larger increase in Inter-MAT (estimate, 95% CI: 150.55 mm2/2-year, 95.58 to 205.51, P-value < 0.001).

CONCLUSIONS

Preclinical rheumatoid arthritis is associated with a decrease in muscle cross-sectional area and an increase in intermuscular adipose tissue, similar to rheumatoid cachexia in clinical rheumatoid arthritis. These findings suggest the presence of cachexia in the preclinical phase of rheumatoid arthritis. Given that cachexia, which can exacerbate health outcomes, is potentially modifiable, this study emphasizes the importance of early identification of patients in their preclinical phase.

Multimodal three-dimensional characterization of murine skeletal muscle micro-scale elasticity, structure, and composition: Impact of dysferlinopathy, Duchenne muscular dystrophy, and age on three hind-limb muscles

Skeletal muscle tissue function is governed by the mechanical properties and organization of its components, including myofibers, extracellular matrix, and adipose tissue, which can be modified by the onset and progression of many disorders. This study used a novel combination of quantitative micro-elastography and clearing-enhanced three-dimensional (3D) microscopy to assess 3D micro-scale elasticity and micro-architecture of muscles from two muscular dystrophies: dysferlinopathy and Duchenne muscular dystrophy, using male BLA/J and mdx mice, respectively, and their wild-type (WT) controls. We examined three muscles with varying proportions of slow- and fast-twitch myofibers: the soleus (predominantly slow), extensor digitorum longus (EDL; fast), and quadriceps (mixed), from BLA/J and WTBLA/J mice aged 3, 10, and 24 months, and mdx and WTmdx mice aged 10 months. Both dysferlin deficiency and age reduced the elasticity and variability of elasticity of the soleus and quadriceps, but not EDL. Overall, the BLA/J soleus was 20% softer than WT and less mechanically heterogeneous (-14% in standard deviation of elasticity). The BLA/J quadriceps at 24 months was 72% softer than WT and less mechanically heterogeneous (-59% in standard deviation), with substantial adipose tissue accumulation. While mdx muscles did not differ quantitatively from WT, regional heterogeneity was evident in micro-scale elasticity and micro-architecture of quadriceps (e.g., 11.2 kPa in a region with marked pathology vs 3.8 kPa in a less affected area). These results demonstrate differing biomechanical changes in hind-limb muscles of two distinct muscular dystrophies, emphasizing the potential for this novel multimodal technique to identify important differences between various myopathies.

Myosteatosis: an underrecognized risk factor for mortality in non-dialysis chronic kidney disease patients

BACKGROUND

Low muscle mass quantity and quality (myosteatosis) can be evaluated by computed tomography (CT) by measuring skeletal muscle area and muscular attenuation, respectively, at the third lumbar vertebra. We aimed to define cut-off points of skeletal muscle area and muscular attenuation to predict mortality in non-dialysis chronic kidney disease (CKD) patients.

METHODS

We conducted a retrospective study including non-dialysis CKD patients over two years, who underwent an opportunistic computed tomography within a two year period, and for whom creatinine was measured within 90 days of CT. Skeletal muscle area was normalized for stature to calculate the skeletal muscle index. Area under the receiver operating characteristic (AuROC) curve and Youden's index were used, to identify the cut-point, separately according to sex.

RESULTS

One hundred sixty-seven patients (50.9% male, mean age of 68.3 ± 16.4 years) were included, most with CKD stages 3 and 4. During a median follow-up of 4.9 (4.2) years, 39 (23.4%) patients died. Muscular attenuation showed a better ability to predict mortality (AuROC curve 0.739 [95% CI 0.623-0.855] in women and 0.744 in men [95% CI 0.618-0.869]) than skeletal muscle index (AuROC curve 0.491 [95% CI 0.332-0.651] in women and 0.711 [95% CI 0.571-0.850] in men). For muscular attenuation, the best cut-off values to predict mortality were 27.56 Hounsfield units in women and 24.58 Hounsfield units in men. For skeletal muscle index, the best cut-off values were 38.47 cm2/m2 in women and 47.81 cm2/m2 in men. In univariable Cox-regression both low muscle mass and myosteatosis were associated with increased mortality. In multivariable Cox-regression models only myosteatosis maintained a significant association with mortality (Hazard Ratio 2.651 (95% CI 1.232-5.703, p = 0.013)).

CONCLUSIONS

We found sex-specific cut-off values for muscle parameters using CT analysis in non-dialysis CKD patients that were associated with mortality. In this population, myosteatosis may be more closely associated with mortality than muscle quantity.

Short-term mortality prediction in acute pulmonary embolism: Radiomics values of skeletal muscle and intramuscular adipose tissue

BACKGROUND

Acute pulmonary embolism (APE) is a potentially life-threatening disorder, emphasizing the importance of accurate risk stratification and survival prognosis. The exploration of imaging biomarkers that can reflect patient survival holds the potential to further enhance the stratification of APE patients, enabling personalized treatment and early intervention. Therefore, in this study, we develop computed tomography pulmonary angiography (CTPA) radiomic signatures for the prognosis of 7- and 30-day all-cause mortality in patients with APE.

METHODS

Diagnostic CTPA images from 829 patients with APE were collected. Two hundred thirty-four features from each skeletal muscle (SM), intramuscular adipose tissue (IMAT) and both tissues combined (SM + IMAT) were calculated at the level of thoracic vertebra 12. Radiomic signatures were derived using 10 times repeated three-fold cross-validation on the training data for SM, IMAT and SM + IMAT for predicting 7- and 30-day mortality independently. The performance of the radiomic signatures was then evaluated on held-out test data and compared with the simplified pulmonary embolism severity index (sPESI) score, a well-established biomarker for risk stratification in APE. Predictive accuracy was assessed by the area under the receiver operating characteristic curve (AUC) with a 95% confidence interval (CI), sensitivity and specificity.

RESULTS

The radiomic signatures based on IMAT and a combination of SM and IMAT (SM + IMAT) achieved moderate performance for the prediction of 30-day mortality on test data (IMAT: AUC = 0.68, 95% CI [0.57-0.78], sensitivity = 0.57, specificity = 0.73; SM + IMAT: AUC = 0.70, 95% CI [0.60-0.79], sensitivity = 0.74, specificity = 0.54). Radiomic signatures developed for predicting 7-day all-cause mortality showed overall low performance. The clinical signature, that is, sPESI, achieved slightly better performance in terms of AUC on test data compared with the radiomic signatures for the prediction of both 7- and 30-day mortality on the test data (7 days: AUC = 0.73, 95% CI [0.67-0.79], sensitivity = 0.92, specificity = 0.16; 30 days: AUC = 0.74, 95% CI [0.66-0.82], sensitivity = 0.97, specificity = 0.16).

CONCLUSIONS

We developed and tested radiomic signatures for predicting 7- and 30-day all-cause mortality in APE using a multicentric retrospective dataset. The present multicentre work shows that radiomics parameters extracted from SM and IMAT can predict 30-day all-cause mortality in patients with APE.

Injection of Adipose-Derived Mesenchymal Stem/Stromal Cells Suppresses Muscle Atrophy Markers and Adipogenic Markers in a Rat Fatty Muscle Degeneration Model

Fatty muscle degeneration and muscle atrophy have not been successfully treated due to their irreversible pathology. This study evaluated the efficacy of rat adipose-derived mesenchymal stem/stromal cells (ADP MSCs) in treating fatty muscle degeneration (FD). A total of 36 rats were divided into three groups: the control (C) group (n = 12); FD model group, generated by sciatic nerve crushing (n = 12); and the group receiving ADP MSC treatment for FD (FD+MSCs) (n = 12). In Group FD+MSCs, ADP MSCs were injected locally into the gastrocnemius muscle one week after the FD model was created (Day 8). On Day 22 (n = 18) and Day 43 (n = 18), muscle morphology, histopathology, and molecular analyses (inflammation, muscle atrophy, adipocytes, and muscle differentiation markers) were performed. In Group FD+MSCs, the formation of immature myofibers was observed on Day 22, and mitigation of fatty degeneration and muscle atrophy progression was evident on Day 43. Gene expression of muscle atrophy markers (FBXO32, TRIM63, and FOXO1) and adipogenic markers (ADIPOQ, PPARG, FABP4, and PDGFRA) was lower in Group FD+MSCs than Group FD on Day 43. ADP MSCs induce anti-inflammatory effects, inhibit fat accumulation, and promote muscle regeneration, highlighting their potential as promising therapy for FD and atrophy.

Frailty in patients on dialysis

Frailty is a condition that is frequently observed among patients undergoing dialysis. Frailty is characterized by a decline in both physiological state and cognitive state, leading to a combination of symptoms, such as weight loss, exhaustion, low physical activity level, weakness, and slow walking speed. Frail patients not only experience a poor quality of life, but also are at higher risk of hospitalization, infection, cardiovascular events, dialysis-associated complications, and death. Frailty occurs as a result of a combination and interaction of various medical issues in patients who are on dialysis. Unfortunately, frailty has no cure. To address frailty, a multifaceted approach is necessary, involving coordinated efforts from nephrologists, geriatricians, nurses, allied health practitioners, and family members. Strategies such as optimizing nutrition and chronic kidney disease-related complications, reducing polypharmacy by deprescription, personalizing dialysis prescription, and considering home-based or assisted dialysis may help slow the decline of physical function over time in subjects with frailty. This review discusses the underlying causes of frailty in patients on dialysis and examines the methods and difficulties involved in managing frailty among this group.

Quantification of volumetric thigh and paravertebral muscle fat content: comparison of quantitative Dixon (Q-Dixon) magnetic resonance imaging (MRI) with high-speed T2-corrected multiecho MR spectroscopy

Background

Muscle fat infiltration (MFI) is increasingly recognized as a critical factor influencing muscle function and metabolic health. Accurate quantification of MFI is essential for diagnosing and monitoring various muscular and metabolic disorders. Quantitative Dixon (Q-Dixon) magnetic resonance imaging (MRI) and high-speed T2-corrected multi-echo (HISTO) magnetic resonance spectroscopy (MRS) are both advanced imaging techniques that offer potential for detailed assessment of MFI. However, the validity and reliability of these methods in measuring volumetric changes in muscle composition, particularly in both thigh and paravertebral muscles, have not been thoroughly compared. This study aims to validate volumetric measurements using Q-Dixon MRI against HISTO MRS in thigh and paravertebral muscles, taking into account the heterogeneity of MFI.

Methods

A retrospective study was conducted with 54 subjects [mean age, 60 years; 38 male (M)/16 female (F)] for thigh muscle and 56 subjects (mean age, 50 years; 22 M/34 F) for paravertebral muscle assessment using a 3-Tesla MRI. The proton density fat fraction (PDFF) was measured with Q-Dixon MRI and HISTO MRS within the upper-middle part of quadriceps femoris and paravertebral muscles at L4/5 level in volumes-of-interest (VOIs). The corresponding volumetric Q-Dixon freehand VOI PDFF was measured. Scatterplots, Bland-Altman plots, Spearman correlation coefficients, and Wilcoxon signed rank test with Bonferroni correction were employed. The Kruskal-Wallis H tests followed by Bonferroni-corrected post hoc tests were analyzed to compare parameter differences with visual MFI grades.

Results

Q-Dixon cubic VOI PDFF correlated positively with HISTO MRS PDFF in thigh (r=0.96, P<0.001) and paravertebral groups (r=0.98, P<0.001), with insignificant differences (P=0.29, 0.82, respectively). Both PDFF values from cubic VOIs in Q-Dixon and HISTO MRS differed from the freehand Q-Dixon PDFF (all P<0.001). Only for <5% HISTO MRS PDFF, there was a difference between HISTO MRS PDFF and Q-Dixon cubic VOI PDFF (P=0.002).

Conclusions

Volumetric Q-Dixon cubic VOI PDFF exhibited good correlation and consistency with HISTO MRS PDFF for quantitative fat assessment in thigh and paravertebral muscles except for muscles with fat fraction <5%, and the Q-Dixon freehand VOI PDFF offers a more comprehensive assessment of the actual MFI compared to cubic VOI.

Fatty infiltration of gastrocnemius-soleus muscle complex: Considerations for myosteatosis rehabilitation

Although previous studies have reported fatty infiltration of the gastrocnemius-soleus complex, little is known about the volumetric distribution and patterns of fatty infiltration. The purpose of this anatomical study was to document and quantify the frequency, distribution, and pattern of fatty infiltration of the gastrocnemius-soleus complex. One hundred formalin-embalmed specimens (mean age 78.1 ± 12.3 years; 48F/52M) were serially dissected to document the frequency, distribution, and pattern of fatty infiltration in the medial and lateral heads of gastrocnemius and soleus muscles. Fatty infiltration was found in 23% of specimens, 13 unilaterally (8F/5M) and 10 (5M/5F) bilaterally. The fatty infiltration process was observed to begin medially from the medial aspect of the medial head of gastrocnemius and medial margin of soleus and then progressed laterally throughout the medial head of gastrocnemius and the marginal, anterior, and posterior soleus. The lateral head of gastrocnemius remained primarily muscular in all specimens. Microscopically, the pattern of infiltration was demonstrated as intramuscular with intact aponeuroses, and septa. The remaining endo-, peri-, and epimysium preserved the overall contour of the gastrocnemius-soleus complex, even in cases of significant fatty replacement. Since the external contour of the calf is preserved, the presence of fatty infiltration may be underdiagnosed in the clinic without imaging. Myosteatosis is associated with gait and balance challenges in the elderly, which can impact quality of life and result in increased risk of falling. The findings of the study have implications in the rehabilitation management of elderly patients with sarcopenia and myosteatosis.

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.

Omega-3 polyunsatured fatty acids and physical performance across the lifespan: a narrative review

Background and Aims

Physical performance is a major contributor of mobility and independence during older life. Despite a progressive decline in musculoskeletal function starts from middle age, several factors acting during the life-course can negatively influence musculoskeletal functional capacities. Lifestyle interventions incorporating nutrition and physical exercise can help maximizing the muscle functional capacities in early life as well as preserving them later in life. Among various dietary compounds, omega-3 polyunsaturated fatty acids (PUFAs) are gaining growing attention for their potential effects on muscle membrane composition and muscle function. Indeed, several pathways are enhanced, such as an attenuation of pro-inflammatory oxidative stress, mitochondrial function, activation of the mammalian target of rapamycin (mTOR) signaling and reduction of insulin resistance.

Methods

We performed a narrative review to explore the existing literature on the relationship between omega-3 PUFAs and physical performance across the life-course.

Results

Growing evidence from randomized controlled trials (RCTs) suggests beneficial effects of omega-3 PUFAs on muscle function, including physical performance parameters in mid to later life. On the other hand, despite a direct association in early life is not available in literature, some mechanisms by which omega-3 PUFAs may contribute to improved adult physical performance could be hypothesized.

Conclusion

Omega-3 PUFAs are gaining growing attention for their positive effect on muscle function parameters. The integration of physical function measures in future studies would be of great interest to explore whether omega-3 PUFAs could contribute to improved muscle function, starting from early life and extending throughout the lifespan. However, larger and high-quality RCTs are needed to fully elucidate the beneficial effects of omega-3 PUFAs supplementation on muscle mass and function.

Association of body composition and survival in patients with locally advanced breast cancer: a historical cohort study

BACKGROUND

Altered body composition has been attributed to major health problems globally, particularly in patients with cancer. To date, there have not been sufficient indices for body compositions in predicting the survival of locally advanced breast cancer (LABC).

PURPOSE

To assess the association between body composition and overall survival (OS) as well as disease-free survival (DFS) in patients with LABC.

MATERIAL AND METHODS

A retrospective study was conducted of patients with LABC diagnosed between 2010 and 2018. Body composition parameters, including skeletal muscle and adiposity parameters, were measured using computed tomography at the L3 vertebra using in-house software developed by MATLAB and freeware Python 3.6.13. The association between body composition and OS and DFS were analyzed using a log-rank test and multivariate Cox-proportional hazard regression.

RESULTS

Of 199 patients, 72 (36%) died during the follow-up period (range = 3.8-150.7 months). Median survival was 101 months. Low visceral-to-subcutaneous ratio ≤0.3 (adjusted hazard ratio [aHR] = 2.57, 95% confidence interval [CI] = 1.51-4.37; aHR = 2.46, 95% CI = 1.33-4.56), and high composite fat (aHR = 3.26, 95% CI = 1.69-6.29; aHR = 2.19, 95% CI = 1.11-4.3) were associated with lower OS and DFS. Positive lymph nodes ≥3, progesterone receptor negative, and total radiation dose >5000 cGy significantly decreased both OS and DFS. A history of previous treatment before body composition assessment and surgery had a protective effect on OS and DFS. No association of sarcopenia, body mass index, and adiposity areas with survival outcomes was observed.

CONCLUSION

Low visceral-to-subcutaneous ratio and high composite fat were independent prognostic factors for OS and DFS in patients with LABC. However, other body composition parameters showed no effect on survival.

Muscle attenuation, not skeletal muscle index, is an independent prognostic factor for survival in gastric cancer patients with overweight and obesity

OBJECTIVES

Skeletal muscle index (SMI) is insufficient for evaluating muscle in obesity, and muscle attenuation (MA) may be a preferred indicator. This study aimed to investigate whether MA has greater prognostic value than SMI in gastric cancer patients with overweight and obesity.

METHODS

Clinical parameters of 1312 patients with gastric cancer who underwent radical gastrectomy were prospectively collected between 2013 and 2019. MA and SMI were analyzed by computed tomography scan. Overweight/obesity was defined as body mass index (BMI) ≥24 kg/m2. The hazard ratio (HR) for death was calculated using Cox regression analysis.

RESULTS

Among all patients, 405 were identified as overweight and obese, and 907 were identified as normal and underweight. MA was inversely associated with BMI and visceral fat area. Among the 405 patients with overweight and obesity, 212 patients (52%) were diagnosed with low MA. In the overweight/obese group, MA was an independent predictor for overall survival (HR, 1.610; P = 0.021) in multivariate Cox regression analyses, whereas SMI did not remain in the model. In the normal/underweight group, both low MA (HR, 1.283; P = 0.039) and low SMI (HR, 1.369; P = 0.008) were independent factors of overall survival. Additionally, 318 patients were identified as having visceral obesity in the overweight/obese group, and low MA was also an independent prognostic factor for survival in these patients (HR, 1.765; P = 0.013).

CONCLUSION

MA had a higher prognostic value than SMI in overweight and obese patients with gastric cancer after radical gastrectomy.

Studying intramuscular fat deposition and muscle regeneration: insights from a comparative analysis of mouse strains, injury models, and sex differences

Intramuscular fat (IMAT) infiltration, pathological adipose tissue that accumulates between muscle fibers, is a shared hallmark in a diverse set of diseases including muscular dystrophies and diabetes, spinal cord and rotator cuff injuries, as well as sarcopenia. While the mouse has been an invaluable preclinical model to study skeletal muscle diseases, they are also resistant to IMAT formation. To better understand this pathological feature, an adequate pre-clinical model that recapitulates human disease is necessary. To address this gap, we conducted a comprehensive in-depth comparison between three widely used mouse strains: C57BL/6J, 129S1/SvlmJ and CD1. We evaluated the impact of strain, sex and injury type on IMAT formation, myofiber regeneration and fibrosis. We confirm and extend previous findings that a Glycerol (GLY) injury causes significantly more IMAT and fibrosis compared to Cardiotoxin (CTX). Additionally, females form more IMAT than males after a GLY injury, independent of strain. Of all strains, C57BL/6J mice, both females and males, are the most resistant to IMAT formation. In regard to injury-induced fibrosis, we found that the 129S strain formed the least amount of scar tissue. Surprisingly, C57BL/6J of both sexes demonstrated complete myofiber regeneration, while both CD1 and 129S1/SvlmJ strains still displayed smaller myofibers 21 days post injury. In addition, our data indicate that myofiber regeneration is negatively correlated with IMAT and fibrosis. Combined, our results demonstrate that careful consideration and exploration are needed to determine which injury type, mouse model/strain and sex to utilize as preclinical model especially for modeling IMAT formation.

Impact of functional electrical stimulation on nerve-damaged muscles by quantifying fat infiltration using deep learning

Quantitative imaging in life sciences has evolved into a powerful approach combining advanced microscopy acquisition and automated analysis of image data. The focus of the present study is on the imaging-based evaluation of the posterior cricoarytenoid muscle (PCA) influenced by long-term functional electrical stimulation (FES), which may assist the inspiration of patients with bilateral vocal fold paresis. To this end, muscle cross-sections of the PCA of sheep were examined by quantitative image analysis. Previous investigations of the muscle fibers and the collagen amount have not revealed signs of atrophy and fibrosis due to FES by a laryngeal pacemaker. It was therefore hypothesized that regardless of the stimulation parameters the fat in the muscle cross-sections would not be significantly altered. We here extending our previous investigations using quantitative imaging of intramuscular fat in cross-sections. In order to perform this analysis both reliably and faster than a qualitative evaluation and time-consuming manual annotation, the selection of the automated method was of crucial importance. To this end, our recently established deep neural network IMFSegNet, which provides more accurate results compared to standard machine learning approaches, was applied to more than 300 H&E stained muscle cross-sections from 22 sheep. It was found that there were no significant differences in the amount of intramuscular fat between the PCA with and without long-term FES, nor were any significant differences found between the low and high duty cycle stimulated groups. This study on a human-like animal model not only confirms the hypothesis that FES with the selected parameters has no negative impact on the PCA, but also demonstrates that objective and automated deep learning-based quantitative imaging is a powerful tool for such a challenging analysis.

Intramuscular adipose tissue, muscle area, and power as predictors of performance in breast cancer survivors

PURPOSE

The decline in physical performance, assessed by physical tests such as the timed up and go (TUG) test, is a consequence of reduced physiological reserves at higher levels of a hierarchical process. This occurs due to changes in muscle architecture, including atrophy and fat infiltration into the muscles, which in turn lead to changes in muscle function, resulting in reduced muscle strength and power and, consequently, affecting physical performance. This study investigated predictive factors for physical performance in breast cancer survivor (BCS), focusing on intramuscular adipose tissue (IMAT), quadríceps muscle area (QMA), and muscular power.

METHODS

This observational, analytical, and cross-sectional study included 23 women without a history of cancer (age, 58.5 ± 8.3 years; BMI, 27.2 ± 5.1 kg/m2) and 56 BCS (age, 58.5 ± 8.3 years; BMI, 27.2 ± 5.1 kg/m2). QMA and IMAT were assessed using computed tomography images. Muscular power and physical performance were measured using the 5-repetition sit-to-stand and TUG tests, respectively.

RESULTS

IMAT (r = 0.4, P < 0.01) and muscular power (r =  - 0.4, P < 0.01) were associated with TUG performance in BCS, whereas QMA (r =  - 0.22, P = 0.10) showed no significant association. QMA (r = 0.55, P < 0.01) was associated with muscular power, while no significant association was found between IMAT and muscular power (r =  - 0.05, P = 0.73). Age explained 19% (P < 0.01) of TUG performance variability. Adding muscular power increased explanatory power by 12% (P < 0.01), and including IMAT further increased it by 7% (P = 0.02) for TUG performance. Collectively, age, muscular power, and IMAT accounted for 38% of the performance variance in the TUG test (age, B = 0.06, P = 0.043; muscular power, B =  - 0.01, P = 0.002; IMAT, B =  - 0.05, P = 0.020).

CONCLUSIONS

Our findings suggest that IMAT and muscular power predict the physical performance of BCS, while QMA does not have the same predictive capability.

Skeletal Muscle Injury in Chronic Kidney Disease-From Histologic Changes to Molecular Mechanisms and to Novel Therapies

Chronic kidney disease (CKD) is associated with significant reductions in lean body mass and in the mass of various tissues, including skeletal muscle, which causes fatigue and contributes to high mortality rates. In CKD, the cellular protein turnover is imbalanced, with protein degradation outweighing protein synthesis, leading to a loss of protein and cell mass, which impairs tissue function. As CKD itself, skeletal muscle wasting, or sarcopenia, can have various origins and causes, and both CKD and sarcopenia share common risk factors, such as diabetes, obesity, and age. While these pathologies together with reduced physical performance and malnutrition contribute to muscle loss, they cannot explain all features of CKD-associated sarcopenia. Metabolic acidosis, systemic inflammation, insulin resistance and the accumulation of uremic toxins have been identified as additional factors that occur in CKD and that can contribute to sarcopenia. Here, we discuss the elevation of systemic phosphate levels, also called hyperphosphatemia, and the imbalance in the endocrine regulators of phosphate metabolism as another CKD-associated pathology that can directly and indirectly harm skeletal muscle tissue. To identify causes, affected cell types, and the mechanisms of sarcopenia and thereby novel targets for therapeutic interventions, it is important to first characterize the precise pathologic changes on molecular, cellular, and histologic levels, and to do so in CKD patients as well as in animal models of CKD, which we describe here in detail. We also discuss the currently known pathomechanisms and therapeutic approaches of CKD-associated sarcopenia, as well as the effects of hyperphosphatemia and the novel drug targets it could provide to protect skeletal muscle in CKD.

The effects of myosteatosis on skeletal muscle function in older adults

Myosteatosis, or the infiltration of fatty deposits into skeletal muscle, occurs with advancing age and contributes to the health and functional decline of older adults. Myosteatosis and its inflammatory milieu play a larger role in adipose tissue dysfunction, muscle tissue dysfunction, and increased passive muscle stiffness. Combined with the age-related decline of sex hormones and development of anabolic resistance, myosteatosis also contributes to insulin resistance, impaired muscle mechanics, loss of force production from the muscle, and increased risk of chronic disease. Due to its highly inflammatory secretome and the downstream negative effects on muscle metabolism and mechanics, myosteatosis has become an area of interest for aging researchers and clinicians. Thus far, myosteatosis treatments have had limited success, as many lack the potency to completely rescue the metabolic and physical consequences of myosteatosis. Future research is encouraged for the development of reliable assessment methods for myosteatosis, as well as the continued exploration of pharmacological, nutritional, and exercise-related interventions that may lead to the success in attenuating myosteatosis and its clinical consequences within the aging population.

Effects of neuromuscular control and strengthening exercises on MRI-measured thigh tissue composition and muscle properties in people with knee osteoarthritis - an exploratory secondary analysis from a randomized controlled trial

OBJECTIVE

To investigate the effects of adding strength training to neuromuscular control exercises on thigh tissue composition and muscle properties in people with radiographic-symptomatic knee osteoarthritis (KOA).

METHODS

In this exploratory secondary analysis of a randomized controlled trial, using a complete-case approach, participants performed 12 weeks of twice-weekly neuromuscular control exercise and patient education (NEMEX, n = 34) or NEMEX plus quadriceps strength training (NEMEX+ST, n = 29). Outcomes were MRI-measured inter- and intramuscular adipose tissue (InterMAT, IntraMAT), quadriceps muscle cross-sectional area (CSA), knee-extensor strength, specific strength (strength/lean CSA) and 30 s chair-stands. Between-group effects were compared using a mixed model analysis of variance.

RESULTS

At 12 weeks, responses to NEMEX+ST overlapped with NEMEX for all outcomes. Both groups reduced InterMAT (NEMEX+ST=25 %, NEMEX=21 %); between-group difference: 0.8cm2 (95 % CI: -0.1, 1.7). NEMEX+ST decreased IntraMAT (2 %) and NEMEX increased IntraMAT (4 %); between-group difference 0.1 %-points (-0.3, 0.5). Both groups increased quadriceps CSA and lean CSA (CSA minus IntraMAT), improved knee-extensor strength and specific strength, and improved chair-stand performance with a trend towards greater effects in NEMEX+ST.

CONCLUSION

Adding strength training to 12 weeks of neuromuscular control exercises provided largely similar effects to neuromuscular control exercises alone in decreasing InterMAT and IntraMAT, in improving knee-extensor strength, CSA and in improving performance-based function in KOA persons, with a trend towards greater effects with additional strength training. Notably, both groups substantially reduced InterMAT and improved specific strength (an index of muscle quality). Our hypothesis-generating work warrants exploration of the roles played by InterMAT and IntraMAT in exercise effects in KOA.

Influence of skeletal muscle and intermuscular fat on postoperative complications and long-term survival in rectal cancer patients

BACKGROUND

The body composition of patients with rectal cancer potentially affects postoperative outcomes. This study explored the correlations between skeletal muscle and adipose tissue quantified by computed tomography (CT) with postoperative complications and long-term prognosis in patients with rectal cancer after surgical resection.

METHODS

This retrospective cohort study included patients with rectal cancer who underwent surgical resection at the Wuhan Union Hospital between 2014 and 2018. CT images within 3 months prior to the surgery were used to quantify the indices of skeletal muscle and adipose tissue at the levels of the third lumbar vertebra (L3) and umbilicus. Optimal cut-off values for each index were defined separately for males and females. Associations between body composition and postoperative complications, overall survival (OS), and disease-free survival (DFS) were evaluated using logistic and Cox proportional hazards models.

RESULTS

We included 415 patients (240 males and 175 females; mean age: 57.8 ± 10.5 years). At the L3 level, a high skeletal muscle density (SMD; hazard ratio [HR]: 0.357, 95% confidence interval [CI]: 0.191-0.665, P = 0.001; HR: 0.571, 95% CI: 0.329-0.993, P = 0.047) and a high skeletal muscle index (SMI; HR: 0.435, 95% CI 0.254-0.747, P = 0.003; HR: 0.568, 95% CI: 0.359-0.897, P = 0.015) were independent prognostic factors for better OS and DFS. At the umbilical level, a large intermuscular fat area (IMFA; HR: 1.904, 95% CI: 1.068-3.395, P = 0.029; HR: 2.064, 95% CI: 1.299-3.280, P = 0.002) was an independent predictive factor for worse OS and DFS, and a high SMI (HR: 0.261, 95% CI: 0.132-0.517, P < 0.001; HR: 0.595, 95% CI: 0.387-0.913, P = 0.018) was an independent prognostic factor for better OS and DFS. The models combining body composition and clinical indicators had good predictive abilities for OS. The receiver operating characteristic areas under the curve were 0.848 and 0.860 at the L3 and umbilical levels, respectively (both P < 0.05).

CONCLUSIONS

No correlations existed between CT-quantified body composition parameters and postoperative complications. However, a high SMD and high SMI were significantly associated with longer OS and DFS at the L3 level, whereas a large IMFA and low SMI were associated with worse OS and DFS at the umbilical level. Combining CT-quantified body composition and clinical indicators could help physicians predict the prognosis of patients with rectal cancer after surgery.

Association Between Typologies of Sedentary Behavior and Muscle Strength, Gait Speed, and Balance in Community-Dwelling Older Adults

Knowledge of how the different types of sedentary behaviors (SB) are associated with functional limitations can guide professionals who work with older adults on better recommendations about the amount of daily time that should be encouraged in each type of SB. The objective was to estimate the associations between two SB typologies (SB television [TV] and SB computer/internet) and the presence of handgrip strength, lower limb strength, gait speed, and balance limitations in Brazilian community-dwelling older adults. This is a cross-sectional study with 1,298 community-dwelling older adults (≥60 years). SB was assessed by self-reporting daily time spent watching TV or using computer/internet (categorized into <2, 3-4, and ≥5 hr/day). Outcomes were handgrip strength, lower limb strength, gait speed, and balance limitations considering referenced cutoff points. Older adults in SB TV ≥5 hr/day had 1.75 (95% confidence interval [CI] [1.07, 2.86]) and 1.88 (95% CI [1.02, 3.46]) times more chances of handgrip strength and gait speed limitations, respectively. On the other hand, those who spent 3-4 and ≥5 hr/day in SB computer/internet had 0.45 (95% CI [0.20, 0.99]) and 0.37 (95% CI [0.15, 0.93]) had less chances of lower limb strength and balance limitations, respectively. In conclusion, functional limitations would be associated differently depending on the type of SB in the older adults sampled.

Reciprocal communication between FAPs and muscle cells via distinct extracellular vesicle miRNAs in muscle regeneration

Muscle regeneration is a complex process relying on precise teamwork between multiple cell types, including muscle stem cells (MuSCs) and fibroadipogenic progenitors (FAPs). FAPs are also the main source of intramuscular adipose tissue (IMAT). Muscles without FAPs exhibit decreased IMAT infiltration but also deficient muscle regeneration, indicating the importance of FAPs in the repair process. Here, we demonstrate the presence of bidirectional crosstalk between FAPs and MuSCs via their secretion of extracellular vesicles (EVs) containing distinct clusters of miRNAs that is crucial for normal muscle regeneration. Thus, after acute muscle injury, there is activation of FAPs leading to a transient rise in IMAT. These FAPs also release EVs enriched with a selected group of miRNAs, a number of which come from an imprinted region on chromosome 12. The most abundant of these is miR-127-3p, which targets the sphingosine-1-phosphate receptor S1pr3 and activates myogenesis. Indeed, intramuscular injection of EVs from immortalized FAPs speeds regeneration of injured muscle. In late stages of muscle repair, in a feedback loop, MuSCs and their derived myoblasts/myotubes secrete EVs enriched in miR-206-3p and miR-27a/b-3p. The miRNAs repress FAP adipogenesis, allowing full muscle regeneration. Together, the reciprocal communication between FAPs and muscle cells via miRNAs in their secreted EVs plays a critical role in limiting IMAT infiltration while stimulating muscle regeneration, hence providing an important mechanism for skeletal muscle repair and homeostasis.

[Association between birth conditions and bone mineral density in adults from the 1982 and 1993 birth cohorts in Pelotas, Rio Grande do Sul State, Brazil]

This study assessed the association of birth weight, gestational age, and intrauterine growth with bone mineral density (BMD) at 22 and 30 years of age in the 1982 and 1993 birth cohorts in Pelotas, Rio Grande do Sul State, Brazil. BMD was measured by dual-energy X-ray absorptiometry (DXA) and the association was assessed using analysis of variance. Multiple linear regression was used to control for confounding factors: sex; household income at birth; maternal smoking during pregnancy; maternal schooling; maternal ethnicity/skin color; and pre-pregnancy body mass index. The study tested whether body fat in adulthood was a mediator of the association analyzed, using the G-computation Formula. A total of 6,803 participants from the 1982 and 1993 cohorts were evaluated at 30 and 22 years of age, respectively. Birth weight was associated with BMD at all sites, with a greater difference at the femoral neck. Individuals born weighing less than 2,000g had on average -0.036g/cm2 (95%CI: -0.064; -0.008) of BMD in the femoral neck than individuals weighing more than 3,500g. Individuals with an intrauterine growth z-score at least 1.28 standard deviation below the mean had an average of -0.013g/cm2 (95%CI: -0.024; -0.002) of BMD in the lumbar spine compared with individuals with an above-average z-score. The mediation analysis showed that body fat in adulthood did not mediate the association. Birth conditions have been associated with BMD in adulthood and the identification of early factors related to bone loss is essential due to the demographic inversion that has been taking place in low- and middle-income countries.

Impact of obesity on the structures and functions of the stomatognathic system: A morphofunctional approach

OBJECTIVE

The prevalence of obesity is increasing significantly worldwide, raising great concern among health professionals. This observational study evaluated the electromyographic activity and thickness of the masseter and temporalis muscles, in addition to the maximum molar bite force, in obese and eutrophic subjects.

METHODS

Sixty subjects were divided into three groups: I (7-12 years), II (13-20 years), III (21-40 years) and sex: with 10 men and 10 women for each group. Electromyographic recordings of the masticatory muscles were obtained during mandibular tasks. The masticatory muscles thicknesses were obtained at rest and during dental clenching. The maximum molar bite forces were measured on the right and left sides. The difference in outcome measures between the groups and sex was analyzed using Mann-Whitney U test (p < 0.05) and analysis of covariance (ANCOVA).

RESULTS

Electromyographic activity in the masseter and temporal muscles consistently displayed lower levels in obese subjects of both sexes across all three age groups during mandibular tasks. Additionally, greater thickness of the masticatory muscles was observed in obese subjects of both sexes across all three age groups. Obese women in Group II displayed higher values of molar bite force, both on the right and left sides, compared to eutrophic women. On the other hand, women in Group III exhibited higher values of molar bite force on the right side in comparison to eutrophic women.

CONCLUSIONS

This study underscores the potential impact of obesity on the morphofunctional aspects of the stomatognathic system in subjects aged 7 to 40 years.

Associations between muscle quality and N-terminal pro-B-type natriuretic peptide (NT-proBNP): The multi-ethnic study of atherosclerosis

INTRODUCTION

N-terminal pro-B-type natriuretic peptide (NT-proBNP) is widely used in clinical settings to identify cardiac stress, diagnose, and manage heart failure (HF). We explored the associations between NT-proBNP and both muscle area and density.

METHODS

A cross-sectional analysis including 1,489 participants from the MESA. Plasma NT-proBNP concentrations and inflammatory biomarkers and health history questionnaires were analyzed. Computed tomography quantified abdominal body composition. Separate multivariable linear regression models were used to assess the associations between both muscle (MA) area and density (MD) and NT-proBNP.

RESULTS

In models adjusted for sociodemographic characteristics, risk factors for cardiovascular disease, anthropometric variables, and subcutaneous and visceral adiposity, NT-proBNP was inversely associated with total abdominal and psoas MAs. Adjustment for inflammatory markers and MD attenuated these associations to the null. Stabilization MA and NT-proBNP were not significantly associated. Analyses per quartiles of MA confirmed lack of a consistent association between stabilization and total abdominal MAs and NT-proBNP. While the third and fourth quartiles of psoas MA were inversely associated with NT-proBNP, adding inflammation biomarkers and MD to the model attenuated the association to the null. Conversely, after full adjustment, NT-proBNP was inversely and significantly associated with total abdominal, stabilization and psoas MDs. For psoas MD, but not the other muscle density variables, the addition of MA to the model attenuated the association to the null. The quartiles of MD were consistently inversely associated with NT-proBNP, where higher MDs showed larger estimates of the association compared to the lowest quartiles, for all muscle groups investigated.

CONCLUSION

Muscle density is inversely associated with NT-proBNP, while muscle area is not after adjustment for inflammation and muscle density.

SARC-F and modified versions using arm and calf circumference: Diagnostic performance for sarcopenia screening and the impact of obesity

AIM

SARC-F is limited by low sensitivity for sarcopenia identification. As surrogates of muscle mass, mid-arm circumference (MAC) and/or calf circumference have been proposed as additions to SARC-F to enhance sarcopenia identification. The aim of this study was to evaluate the diagnostic performance of SARC-F, SARC-CalF, SARC-F + MAC, and SARC-CalF + MAC in sarcopenia detection, and to assess the impact of obesity on their diagnostic performance.

METHODS

We studied 230 healthy non-frail community-dwelling older adults age >50 years. We performed receiver operating characteristic curve analysis for SARC-F, SARC-CalF, SARC-F + MAC and SARC-CalF + MAC against sarcopenia diagnosed by the Asian Working Group for Sarcopenia (AWGS) 2019 as the reference standard. Obesity was defined by high waist circumference (men ≥90 cm, women ≥80 cm). We performed subgroup analysis to compare between obese and non-obese groups.

RESULTS

The prevalence of sarcopenia was 27.0% by AWGS 2019. SARC-CalF + MAC had the best diagnostic performance (area under the curve [AUC] 0.74, 95% confidence interval [CI] 0.67-0.81; sensitivity 66.1%; specificity 69.1%), followed by SARC-CalF (AUC 0.70, 95% CI 0.62-0.78; sensitivity 21.0%; specificity 95.8%). SARC-F (AUC 0.57, 95% CI 0.49-0.66; sensitivity 0%; specificity 100%) performed significantly worsethan its modified versions (P < 0.05). There was higher accuracy of sarcopenia identification in obese compared with non-obese groups for SARC-F + MAC (AUC 0.75, 95% CI 0.65-0.85 vs. 0.58, 95% CI 0.46-0.70) and SARC-CalF + MAC (AUC 0.75, 95% CI 0.66-0.85 vs. 0.70, 95% CI 0.59-0.81).

CONCLUSIONS

The addition of arm circumference to SARC-CalF confers better diagnostic accuracy for sarcopenia identification, especially in the obese group. Thus, MAC may complement SARC-CalF for community screening of sarcopenia amongst healthy community-dwelling older adults by increasing sensitivity for the detection of sarcopenic obesity. Geriatr Gerontol Int 2024; 24: 182-188.

The association of body composition on chemotherapy toxicities in non-metastatic colorectal cancer patients: a systematic review

BACKGROUND

In recent years, certain body composition measures, assessed by computed tomography (CT), have been found to be associated with chemotherapy toxicities. This review aims to explore available data on the relationship between skeletal muscle and adiposity, including visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), intramuscular and intermuscular adipose tissue and their association with chemotherapy toxicity in non-metastatic colorectal cancer (CRC) patients.

METHODS

A systematic literature search following PRISMA guidelines was conducted in Medline, Embase, Cochrane and Web of Science, for papers published between 2011 and 2023. The search strategy combined keywords and MESH terms relevant to 'body composition', 'chemotherapy toxicities', and 'non-metastatic colorectal cancer'.

RESULTS

Out of 3868 studies identified, six retrospective studies fulfilled the inclusion criteria with 1024 eligible patients. Low skeletal muscle mass was strongly associated with increased incidence of both chemotherapy toxicities and dose-limiting toxicity (DLT). The association of VAT, intramuscular and intermuscular adiposity was heterogeneous and inconclusive. There was no association between SAT and chemotherapy intolerance. No universal definitions or cut-offs for sarcopenia and obesity were noted. All studies utilized 2-dimensional (2D) CT slices for CT body composition assessment with varied selection on the vertebral landmark and inconsistent reporting of tissue-defining Hounsfield unit (HU) measurements.

CONCLUSION

Low skeletal muscle is associated with chemotherapy toxicities in non-metastatic CRC. However, quality evidence on the role of adiposity is limited and heterogeneous. More studies are needed to confirm these associations with an emphasis on a more coherent body composition definition and an approach to its assessment, especially regarding sarcopenia.

Exploring the Interplay between Bone Marrow Stem Cells and Obesity

Obesity, a complex disorder with rising global prevalence, is a chronic, inflammatory, and multifactorial disease and it is characterized by excessive adipose tissue accumulation and associated comorbidities. Adipose tissue (AT) is an extremely diverse organ. The composition, structure, and functionality of AT are significantly influenced by characteristics specific to everyone, in addition to the variability connected to various tissue types and its location-related heterogeneity. Recent investigation has shed light on the intricate relationship between bone marrow stem cells and obesity, revealing potential mechanisms that contribute to the development and consequences of this condition. Mesenchymal stem cells within the bone marrow, known for their multipotent differentiation capabilities, play a pivotal role in adipogenesis, the process of fat cell formation. In the context of obesity, alterations in the bone marrow microenvironment may influence the differentiation of mesenchymal stem cells towards adipocytes, impacting overall fat storage and metabolic balance. Moreover, bone marrow's role as a crucial component of the immune system adds another layer of complexity to the obesity-bone marrow interplay. This narrative review summarizes the current research findings on the connection between bone marrow stem cells and obesity, highlighting the multifaceted roles of bone marrow in adipogenesis and inflammation.

Effects of high-intensity training on fatty infiltration in paraspinal muscles in elderly males with osteosarcopenia - the randomized controlled FrOST study

BACKGROUND

Osteosarcopenia is a common geriatric syndrome with an increasing prevalence with age, leading to secondary diseases and complex consequences such as falls and fractures, as well as higher mortality and frailty rates. There is a great need for prevention and treatment strategies.

METHODS

In this analysis, we used magnetic resonance imaging (MRI) data from the randomised controlled FrOST trial, which enrolled community-dwelling osteosarcopenic men aged > 72 years randomly allocated to 16 months of twice-weekly high-intensity resistance training (HIRT) or a non-training control group. MR Dixon imaging was used to quantify the effects of HIRT on muscle fat infiltration in the paraspinal muscles, determined as changes in muscle tissue, fat faction and intermuscular adipose tissue (IMAT) in the erector spinae and psoas major muscles. Intention-to-treat analysis with multiple imputation was used to analyse the data set.

RESULTS

After 16 months of intervention, 15 men from the HIRT and 16 men from the CG were included in the MRI analysis. In summary, no positive effects on the fat infiltration of the erector spinae and psoas major muscles were observed.

CONCLUSIONS

The previously reported positive effects on lumbar spine bone mineral density (BMD) suggest that mechanotransduction induces tropic effects on bone, but that fat infiltration of the erector spinae and psoas major muscles are either irreversible or, for some unknown reason, resistant to exercise. Because of the beneficial effects on spinal BMD, HIRT is still recommended in osteosarcopenic older men, but further research is needed to confirm appropriate age-specific training exercises for the paraspinal muscles. The potential of different MRI sequences to quantify degenerative and metabolic changes in various muscle groups must be better characterized.

TRIAL REGISTRATIONS

FrOST was approved by the University Ethics Committee of the Friedrich-Alexander University of Erlangen-Nürnberg (number 67_15b and 4464b) and the Federal Office for Radiation Projection (BfS, number Z 5-2,246,212 - 2017-002). Furthermore, it fully complies with the Declaration of Helsinki and is registered at ClinicalTrials.gov: NCT03453463 (05/03/2018). JAMA 310:2191-2194, 2013.

Shape phenotype of thigh fat and muscle and risk of major adverse cardiovascular events after fragility hip fracture

BACKGROUND

Although sarcopenia has been recognized as a predictor of mortality in elderly patients with hip fracture, the association of thigh fat and muscle with cardiovascular (CV) outcome remains unclear. We examined the impact of computed tomography (CT)-derived shape features of thigh fat and muscle on major adverse CV events (MACE) in elderly patients with hip fracture.

METHODS

We conducted a retrospective analysis of consecutive patients aged ≥65 years who presented with hip fracture confirmed on pelvic bone CT scan and underwent hip fracture surgery at our institution from April 2019 to December 2021. The cross-sectional area (CSA) and compactness (CM) of both the muscle and fat at the upper-thigh level were calculated from two-dimensional CT images using AVIEW Research (v1.1.38, Coreline Soft, Co. Ltd, Seoul, South Korea). The shape features of thigh fat and muscle were categorized into four groups based on the combination of CSA and CM: fat CSA (fat area [FA])/fat CM (FCM), muscle CSA (muscle area [MA])/muscle CM (MCM), FA/MCM and MA/FCM. In each of them, subjects were categorized into four subgroups: high CSA/high CM, high CSA/low CM, low CSA/high CM and low CSA/low CM. The primary outcome was MACE after 30 days of surgery, defined as a composite of all-cause death, acute myocardial infarction, stroke or hospitalization for heart failure.

RESULTS

Of 356 patients enrolled (median age, 82 years; 76.7% females), 72 (20.2%) had MACE over a median follow-up of 13.1 months (ranges 5.9-21.0 months). Patients with MACE had a significantly lower median FA (193.7 vs. 226.2 cm2 , P < 0.0001) and FCM (0.443 vs. 0.513, P = 0.001) compared with those without MACE, but no significant differences were found in MA, MCM and FA-MA ratio between the two groups. In a multivariate Cox regression analysis, low FA (<240.1 cm2 ) (adjusted hazard ratio [HR] 2.99, 95% confidence interval [CI] 1.39-6.44, P = 0.005) and low FCM (<0.477) (adjusted HR 2.00, 95% CI 1.10-3.63, P = 0.023) were associated with an increased risk of MACE. Among the shape phenotypes of thigh fat and muscle, the thigh fat phenotype of low FA/low FCM (adjusted HR 3.13, 95% CI 1.81-5.42, P < 0.0001 [reference, high FA/high FCM]) was found to be an independent predictor of MACE.

CONCLUSIONS

In elderly patients with fragility hip fracture, thigh CT-derived measures of FA and FCM may provide useful prognostic information for predicting adverse CV outcomes.

The mediation roles of intermuscular fat and inflammation in muscle mitochondrial associations with cognition and mobility

BACKGROUND

Mitochondrial dysfunction may contribute to brain and muscle health through inflammation or fat infiltration in the muscle, both of which are associated with cognitive function and mobility. We aimed to examine the association between skeletal muscle mitochondrial function and cognitive and mobility outcomes and tested the mediation effect of inflammation or fat infiltration.

METHODS

We analysed data from 596 Baltimore Longitudinal Study of Aging participants who had concurrent data on skeletal muscle oxidative capacity and cognitive and mobility measures of interest (mean age: 66.1, 55% women, 24% Black). Skeletal muscle oxidative capacity was assessed as post-exercise recovery rate (kPCr) via P31 MR spectroscopy. Fat infiltration was measured as intermuscular fat (IMF) via CT scan and was available for 541 participants. Inflammation markers [IL-6, C-reactive protein (CRP), total white blood cell (WBC), neutrophil count, erythrocyte sedimentation rate (ESR), or albumin] were available in 594 participants. We examined the association of kPCr and cognitive and mobility measures using linear regression and tested the mediation effect of IMF or inflammation using the mediation package in R. Models were adjusted for demographics and PCr depletion.

RESULTS

kPCr and IMF were both significantly associated with specific cognitive domains (DSST, TMA-A, and pegboard dominant hand performance) and mobility (usual gait speed, HABCPPB, 400 m walk time) (all P < 0.05). IMF significantly mediated the relationship between kPCr and these cognitive and mobility measures (all P < 0.05, proportion mediated 13.1% to 27%). Total WBC, neutrophil count, and ESR, but not IL-6 or CRP, also mediated at least one of the cognitive and mobility outcomes (all P < 0.05, proportion mediated 9.4% to 15.3%).

CONCLUSIONS

Skeletal muscle mitochondrial function is associated with cognitive performance involving psychomotor speed. Muscle fat infiltration and specific inflammation markers mediate the relationship between muscle mitochondrial function and cognitive and mobility outcomes. Future studies are needed to confirm these associations longitudinally and to understand their mechanistic underpinnings.

Semi-quantitative thigh magnetic resonance imaging scores in assessing disease activity and determining long-term clinical outcome in idiopathic inflammatory myopathies: a causal mediation analysis

OBJECTIVES

To evaluate the relationship of thigh MRI (t-MRI) with manual muscle testing-8 (MMT-8), muscle enzymes and autoantibodies. To determine the causal and mediating factors resulting in poor recovery of MMT-8 in inflammatory myositis (IIM).

METHODS

This was a single-centre retrospective study in IIM patients. t-MRI was semi-quantitatively scored for muscle oedema, fascial oedema, muscle atrophy and fatty infiltration. Spearman correlation of t-MRI scores was done with muscle enzymes at baseline, and MMT-8 at baseline and on follow-up. Causal mediation analysis was performed with age, sex, symptom duration, autoantibodies, diabetes and BMI as independent variables, follow-up MMT-8 as dependent and t-MRI scores as mediating variables.

RESULTS

Baseline evaluation was done on 59 and follow-up on 38 patients. Median follow-up of the cohort was 31 (10-57) months. Baseline MMT-8 negatively correlated with muscle oedema (r = -0755), fascial oedema (r = -0.443) and muscle atrophy (r = -0.343). Creatinine kinase (r = 0.422) and aspartate transaminase (r = 0.480) positively correlated with muscle oedema. Follow-up MMT-8 correlated negatively with baseline atrophy (r = -0.497) and fatty infiltration (r = -0.531). On follow-up, MMT-8 males had positive total effect (estimate (95%CI)) via atrophy [2.93 (0.44, 4.89)] and fatty infiltration [2.08 (0.54, 3.71)]. Antisynthetase antibody had a positive total effect via fatty infiltration [4.50 (0.37, 7.59)]. Age had a negative total effect via atrophy [-0.09 (0.19, -0.01)] and fatty infiltration [-0.07 (-0.15, -0.01)]. Disease duration had a negative total effect via fatty infiltration [-0.18 (-0.27, -0.02)].

CONCLUSION

Baseline fatty infiltration and muscle atrophy resulting from older age, female sex, longer disease duration and absent anti-synthetase antibodies, partly mediate muscle recovery in IIM.

The association between lateral hip muscle size/intramuscular fat infiltration and hip strength in active young adults with long standing hip/groin pain

OBJECTIVES

To investigate associations between lateral hip muscle size/intramuscular fat infiltration (MFI) and hip strength in active young adults with longstanding hip/groin pain.

DESIGN

Cross-sectional study.

SETTING

University/Clinical.

PARTICIPANTS

Sub-elite soccer and Australian Football players (n = 180; 37 female) with long standing hip/groin pain.

MAIN OUTCOME MEASURES

Muscle size (volume) and MFI of gluteus maximus, medius, and minimis, and tensor fascia latae (TFL) were assessed using magnetic resonance imaging. Isometric hip strength was measured with handheld dynamometry. Associations between muscle size/MFI were assessed using linear regression models, adjusted for body mass index and age, with sex-specific interactions.

RESULTS

Positive associations were identified between lateral hip muscle volume and hip muscle strength, particularly for gluteus maximus and gluteus minimus volume. For all muscles, hip abduction was associated with an increase in strength by up to 0.69 N (R2 ranging from 0.29 to 0.39). These relationships were consistent across sexes with no sex interactions observed. No associations were found between MFI and strength measures.

CONCLUSION

Greater lateral hip muscle volumes are associated with greater hip strength in active young adults with long standing hip/groin pain, irrespective of sex. Gluteus maximus and minimus volume showed the most consistent relationships with hip strength across multiple directions.

Handgrip Strength and Clinical Evolution of People Living with HIV: A Mini Narrative Review

HIV infection is a worldwide epidemic. Antiretroviral therapy allows people living with HIV (PLHIV) increased longevity and a better quality of life. Among the various ways of monitoring the clinical evolution of PLHIV, handgrip strength (HGS) is a promising strategy, as this test can be used to assess the health condition quickly and at a low cost. In this sense, the present study aims to describe, through a literature review, the relationship between HGS and the clinical evolution of PLHIV, especially with morbimortality. Initially, it is highlighted that aging, HIV infection, and excess body fat are related to the loss of HGS in PLHIV. Furthermore, PLHIV is more likely to present cardiometabolic diseases that can be aggravated by reduced HGS. Thus, in people without positive HIV serology, low HGS indirectly, through the presence of risk factors or cardiometabolic diseases, or directly increases the chance of mortality. In conclusion, the lack of studies on this topic for PLHIV is highlighted, and more longitudinal studies, including control groups, are needed.

Prognostic value of deep learning-derived body composition in advanced pancreatic cancer-a retrospective multicenter study

BACKGROUND

Despite the prognostic relevance of cachexia in pancreatic cancer, individual body composition has not been routinely integrated into treatment planning. In this multicenter study, we investigated the prognostic value of sarcopenia and myosteatosis automatically extracted from routine computed tomography (CT) scans of patients with advanced pancreatic ductal adenocarcinoma (PDAC).

PATIENTS AND METHODS

We retrospectively analyzed clinical imaging data of 601 patients from three German cancer centers. We applied a deep learning approach to assess sarcopenia by the abdominal muscle-to-bone ratio (MBR) and myosteatosis by the ratio of abdominal inter- and intramuscular fat to muscle volume. In the pooled cohort, univariable and multivariable analyses were carried out to analyze the association between body composition markers and overall survival (OS). We analyzed the relationship between body composition markers and laboratory values during the first year of therapy in a subgroup using linear regression analysis adjusted for age, sex, and American Joint Committee on Cancer (AJCC) stage.

RESULTS

Deep learning-derived MBR [hazard ratio (HR) 0.60, 95% confidence interval (CI) 0.47-0.77, P < 0.005] and myosteatosis (HR 3.73, 95% CI 1.66-8.39, P < 0.005) were significantly associated with OS in univariable analysis. In multivariable analysis, MBR (P = 0.019) and myosteatosis (P = 0.02) were associated with OS independent of age, sex, and AJCC stage. In a subgroup, MBR and myosteatosis were associated with albumin and C-reactive protein levels after initiation of therapy. Additionally, MBR was also associated with hemoglobin and total protein levels.

CONCLUSIONS

Our work demonstrates that deep learning can be applied across cancer centers to automatically assess sarcopenia and myosteatosis from routine CT scans. We highlight the prognostic role of our proposed markers and show a strong relationship with protein levels, inflammation, and anemia. In clinical practice, automated body composition analysis holds the potential to further personalize cancer treatment.

Cross-sectional area and fat infiltration of the lumbar spine muscles in patients with back disorders: a deep learning-based big data analysis

PURPOSE

Validated deep learning models represent a valuable option to perform large-scale research studies aiming to evaluate muscle quality and quantity of paravertebral lumbar muscles at the population level. This study aimed to assess lumbar spine muscle cross-sectional area (CSA) and fat infiltration (FI) in a large cohort of subjects with back disorders through a validated deep learning model.

METHODS

T2 axial MRI images of 4434 patients (n = 2609 females, n = 1825 males; mean age: 56.7 ± 16.8) with back disorders, such as fracture, spine surgery or herniation, were retrospectively collected from a clinical database and automatically segmented. CSA, expressed as the ratio between total muscle area (TMA) and the vertebral body area (VBA), and FI, in percentages, of psoas major, quadratus lumborum, erector spinae, and multifidus were analyzed as primary outcomes.

RESULTS

Male subjects had significantly higher CSA (6.8 ± 1.7 vs. 5.9 ± 1.5 TMA/VBA; p < 0.001) and lower FI (21.9 ± 8.3% vs. 15.0 ± 7.3%; p < 0.001) than females. Multifidus had more FI (27.2 ± 10.6%; p < 0.001) than erector spinae (22.2 ± 9.7%), quadratus lumborum (17.5 ± 7.0%) and psoas (13.7 ± 5.8%) whereas CSA was higher in erector spinae than other lumbar muscles. A high positive correlation between age and total FI was detected (rs = 0.73; p < 0.001) whereas a negligible negative correlation between total CSA and age was observed (rs =  - 0.24; p < 0.001). Subjects with fractures had lower CSA and higher FI compared to those with herniations, surgery and with no clear pathological conditions.

CONCLUSION

CSA and FI values of paravertebral muscles vary a lot in accordance with subjects' sex, age and clinical conditions. Given also the large inter-muscle differences in CSA and FI, the choice of muscles needs to be considered with attention by spine surgeons or physiotherapists when investigating changes in lumbar muscle morphology in clinical practice.

Body Composition Evaluation and Clinical Markers of Cardiometabolic Risk in Patients with Phenylketonuria

Cardiovascular diseases are the main cause of mortality worldwide. Patients with phenylketonuria (PKU) may be at increased cardiovascular risk. This review provides an overview of clinical and metabolic cardiovascular risk factors, explores the connections between body composition (including fat mass and ectopic fat) and cardiovascular risk, and examines various methods for evaluating body composition. It particularly focuses on nutritional ultrasound, given its emerging availability and practical utility in clinical settings. Possible causes of increased cardiometabolic risk in PKU are also explored, including an increased intake of carbohydrates, chronic exposure to amino acids, and characteristics of microbiota. It is important to evaluate cardiovascular risk factors and body composition in patients with PKU. We suggest systematic monitoring of body composition to develop nutritional management and hydration strategies to optimize performance within the limits of nutritional therapy.

Osteoporosis and Obesity

Introduction

This article concisely overviews the complex relationship between obesity and bone health. Obesity, characterized by excessive fat accumulation, has been traditionally associated with higher bone mineral density. Also, recent data suggest a favorable bone microarchitecture profile in these patients. However, the increase in bone mineral density does not necessarily confer protection against fractures, and the risk of fractures may vary depending on the skeletal sites.

Factors affecting bone health

Various factors, including mechanical factors, hormones, cytokines, inflammation, and bone marrow adiposity, contribute to the adverse effect of obesity on bone. The article explores these factors alongside non-invasive techniques and tools like the Fracture Risk Assessment (FRAX) to evaluate fracture risk.

Bone and Adipose tissue

This article also highlights the essential roles of hormones such as vitamin D, Parathormone (PTH), FGF-23 (Fibroblast Growth Factor 23), which affect bone health, and some of the hormones secreted from the adipose tissues such as adiponectin and leptin.

Obesity Paradox and Sarcopenic Obesity

The article delves into the intriguing obesity paradox, where an increased BMI correlates with higher bone mineral density but not necessarily reduced fracture risk. Sarcopenic obesity, a combination of excessive fat accumulation and reduced muscle mass, further complicates the relationship between obesity and bone health.

Conclusions

Physicians should keep a comprehensive approach to treating obese patients with osteoporosis, including lifestyle modifications, weight management, fall prevention strategies, and pharmacological interventions. Further research is needed to better understand the relationship between obesity and bone health.

Associations of Quantitative and Qualitative Muscle Parameters With Second Hip Fracture Risk in Older Women: A Prospective Cohort Study

Older women with a first hip fracture exhibit heightened susceptibility and incidence of second fracture and potentially severe consequences. This prospective study was to compare the predictive power of qualitative and quantitative muscle parameters for a second hip fracture in older women with a first hip fracture. A total of 206 subjects were recruited from the longitudinal Chinese Second Hip Fracture Evaluation study. Hip computed tomography (CT) scans were obtained immediately after the first fracture. Muscle fat infiltration was assessed according to the Goutallier classification qualitatively. Quantitative parameters included cross-sectional area and density of gluteus maximus (G.MaxM) and gluteus medius and minimus (G.Med/MinM) muscles. CT X-ray absorptiometry was used to measure the areal bone mineral density (aBMD) of the contralateral femur. Cox proportional hazards models were used to compute hazard ratios (HR) of second hip fracture risk. The mean age of subjects was 74.9 (±9.5) years at baseline. After 4.5 years, 35 had a second hip fracture, 153 without a second hip fracture, and 18 died. Except for the combined G.MinM Goutallier grade 3 and 4 groups before adjustment for covariates (HR = 5.83; 95% confidence interval [CI] 1.49-22.83), there were no significant HRs for qualitative classification to predict a second hip fracture. Among quantitative metrics, after adjustment for covariates, G.Med/MinM density was significant in the original (HR = 1.44; CI 1.02-2.04) and competing risk analyses (HR = 1.46; CI 1.02-2.07). After additional adjustment for femoral neck (FN) aBMD, G.Med/MinM density remained borderline significant for predicting a second hip fracture in competing risk analysis (HR = 1.43; CI 0.99-2.06; p = 0.057). Our study revealed that Goutallier classification was less effective than quantitative muscle metrics for predicting hip second fracture in this elderly female cohort. After adjustment for FN aBMD, G.Med/MinM density is a borderline independent predictor of second hip fracture risk. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Muscle fiber phenotype: a culprit of abnormal metabolism and function in skeletal muscle of humans with obesity

The proportion of the different types of fibers in a given skeletal muscle contributes to its overall metabolic and functional characteristics. Greater proportion of type I muscle fibers is associated with favorable oxidative metabolism and function of the muscle. Humans with obesity have a lower proportion of type I muscle fibers. We discuss how lower proportion of type I fibers in skeletal muscle of humans with obesity may explain metabolic and functional abnormalities reported in these individuals. These include lower muscle glucose disposal rate, mitochondrial content, protein synthesis, and quality/contractile function, as well as increased risk for heart disease, lower levels of physical activity, and propensity for weight gain/resistance to weight loss. We delineate future research directions and the need to examine hybrid muscle fiber populations, which are indicative of a transitory state of fiber phenotype within skeletal muscle. We also describe methodologies for precisely characterizing muscle fibers and gene expression at the single muscle fiber level to enhance our understanding of the regulation of muscle fiber phenotype in obesity. By contextualizing research in the field of muscle fiber type in obesity, we lay a foundation for future advancements and pave the way for translation of this knowledge to address impaired metabolism and function in obesity.

Loss of Muscle Mass and Strength After Hip Fracture: an Intervention Target for Nutrition Supplementation

PURPOSEOF REVIEW

To summarize what is known about the deleterious effect of hip fracture on muscle mass and strength as well as the scientific evidence for post-surgical nutrition supplementation to maintain muscle and improve function.

RECENT FINDINGS

This review provides a discussion of the relationship between muscle mass, strength, and physical function following hip fracture, briefly describes the approaches to measuring lean mass, discusses prevalence of sarcopenia and malnutrition among older men and women with hip fracture, and reviews the effects of essential amino acids on muscle. Loss of muscle mass and strength following hip fracture is substantial with consequences for recovery of functional independence. EAA-based nutrition supplementation, which directly effects muscle, has potential to improve outcomes.

Development and expansion of intramuscular adipose tissue is not dependent on UCP-1-lineage cells in mice

Accumulation of adipose tissue within and outside of skeletal muscle is associated with orthopedic injury and metabolic disease, where it is thought to impede muscle function. The close juxtaposition between this adipose and myofibers has led to hypotheses that paracrine interactions between the two regulate local physiology. Recent work suggests that intramuscular adipose tissue (IMAT) may have features of beige or brown fat, indicated by the expression of uncoupling protein-1 (UCP-1). However, this is contested by other studies. Clarification of this point is needed to inform our understanding of the relationship between IMAT and muscle health. To achieve this, we examined the effects of constitutive UCP-1+ cell ablation (UCP1-DTA) on IMAT development and homeostasis. IMAT developed normally in UCP1-DTA mice, with no significant differences in quantity compared with wild-type littermates. Likewise, IMAT accumulation in response to glycerol-induced injury was similar between genotypes, with no significant differences in adipocyte size, quantity, or dispersion. This suggests that neither physiological nor pathological IMAT express UCP-1 and that the development of IMAT does not depend on UCP-1 lineage cells. In response to β3-adrenergic stimulation, we find minor, localized UCP-1 positivity in wildtype IMAT, but the bulk of the adipocytes are unresponsive. In contrast, two depots of muscle-adjacent (epi-muscular) adipose tissue have reduced mass in UCP1-DTA mice and UCP-1 positivity in wildtype littermates, comparable to traditional beige and brown adipose depots. Taken together this evidence strongly supports a white adipose phenotype for mouse IMAT and a brown/beige phenotype for some adipose outside the muscle boundary.

Association of the visceral adiposity index with femur bone mineral density and osteoporosis among the U.S. older adults from NHANES 2005-2020: a cross-sectional study

Background

The visceral adiposity index (VAI) is a marker of abdominal fat distribution and adipose tissue function. However, the association between VAI and femur bone mineral density (BMD) and osteoporosis is unclear among the U.S. older adults.

Methods

Cross-sectional data for adults aged 60 years and older from the 2007-2020 National Health and Nutrition Examination Survey (NHANES) were included. Multivariable linear and logistic regression were used to evaluate the association between VAI and femur BMD and osteoporosis. We used the smooth curve fitting to address nonlinearity. Moreover, a two-piecewise linear regression model was used to explain the nonlinearity further.

Results

The findings of the multivariable logistic regression models showed that as the VAI value increased by one unit, the prevalence of osteoporosis decreased by 1.2% after adjusting for covariates associated with osteoporosis. The multivariable linear regression models demonstrated that VAI was positively correlated with femur BMD. Further analysis revealed an inverted L-shaped and inverted U-shaped relationship between VAI and femur BMD at different sites.

Conclusions

Our findings indicated that an increased VAI is independently linked to a higher prevalence of osteoporosis among the U.S. older adults. Further analysis reveals that once VAI reaches a certain threshold, femur BMD no longer increases and may even decrease. This suggests that a moderate accumulation of visceral fat may be beneficial for bone health, while excessive visceral fat could potentially have detrimental effects.

Type 2 Diabetes Mellitus and Sarcopenia as Comorbid Chronic Diseases in Older Adults: Established and Emerging Treatments and Therapies

Type 2 diabetes mellitus (T2DM) and sarcopenia (low skeletal muscle mass and function) share a bidirectional relationship. The prevalence of these diseases increases with age and they share common risk factors. Skeletal muscle fat infiltration, commonly referred to as myosteatosis, may be a major contributor to both T2DM and sarcopenia in older adults via independent effects on insulin resistance and muscle health. Many strategies to manage T2DM result in energy restriction and subsequent weight loss, and this can lead to significant declines in muscle mass in the absence of resistance exercise, which is also a first-line treatment for sarcopenia. In this review, we highlight recent evidence on established treatments and emerging therapies targeting weight loss and muscle mass and function improvements in older adults with, or at risk of, T2DM and/or sarcopenia. This includes dietary, physical activity and exercise interventions, new generation incretin-based agonists and myostatin-based antagonists, and endoscopic bariatric therapies. We also highlight how digital health technologies and health literacy interventions can increase uptake of, and adherence to, established and emerging treatments and therapies in older adults with T2DM and/or sarcopenia.

Association between body fat and bone mineral density in Korean adults: a cohort study

Although obesity was once considered protective against osteoporosis, various factors influence the relationship between fat and bone mineral density (BMD). To establish the importance of healthy body composition in decelerating declines in BMD, we conducted a study to compare the association between body fat composition and BMD in Korean adults. Using data collected from the Kangbuk Samsung Health Study from 2012 to 2019, this cohort study compared the incidence of decreased BMD among the following four groups: normal BMI and normal adiposity (NBMI-NA), normal BMI and high adiposity (NBMI-HA), overweight, and obesity. Decreased BMD was defined as a Z-score ≤  - 2.0 in premenopausal women and men < 50 years of age or a T-score <  - 1.0 in postmenopausal women and men ≥ 50 years of age. Individuals who were diagnosed with osteoporosis or compression fracture after their second visit were categorized as having decreased BMD. The incidence rate of decreased BMD in the NBMI-NA group was 3.37, and that in the NBMI-HA group was 4.81, which was the highest among all groups. After adjusting for confounding factors, NBMI-HA led to a significantly greater risk of decreased BMD compared to NBMI-NA (HR 1.47; 95% CI 1.09-1.99). Even with a normal BMI, a high BFP was associated with an increased risk of decreased BMD. Therefore, healthy body composition management, not simply BMI, is important in preventing decreased BMD.