Skeletal Muscle Fat Infiltration Research Articles

Prognostic impact of myosteatosis in patients with colorectal cancer undergoing curative surgery: an updated systematic review and meta-analysis.

Colorectal cancer (CRC) is a global health concern, and identifying prognostic factors can improve outcomes. Myosteatosis is fat infiltration into muscles and is a potential predictor of the survival of patients with CRC. This systematic review and meta-analysis aimed to assess the prognostic role of myosteatosis in CRC. PubMed, Embase, and Cochrane CENTRAL were searched up to 1 August 2023, for relevant studies, using combinations of the keywords CRC, myosteatosis, skeletal muscle fat infiltration, and low skeletal muscle radiodensity. Case-control, prospective, and retrospective cohort studies examining the association between myosteatosis and CRC outcomes after curative intent surgery were eligible for inclusion. Primary outcomes were overall survival (OS), disease-free survival (DFS), and cancer-specific survival (CSS). A total of 10 studies with a total of 9,203 patients were included. The pooled hazard ratio (HR) for OS (myosteatosis vs. no myosteatosis) was 1.52 [95% confidence interval (CI), 1.38-1.67); for CSS, 1.67 (95% CI, 1.40-1.99); and for DFS, 1.89 (95% CI, 1.35-2.65). In patients with CRC undergoing curative intent surgery, myosteatosis is associated with worse OS, CSS, and DFS. These findings underscore the importance of evaluating myosteatosis in patients with CRC to improve outcomes.

The adverse impact of perioperative body composition abnormalities on outcomes after split liver transplantation: a multi-center retrospective cohort study.

Split liver transplantation increases graft availability, but its safe and effective utilization is insufficiently documented. This study aimed to investigate the association between perioperative body composition abnormalities and outcomes in adult split liver transplantation. 240 recipients who underwent split liver transplantation in three centers were enrolled in this retrospective cohort study. Body composition abnormalities including sarcopenia, myosteatosis, visceral obesity, and sarcopenic obesity were evaluated at baseline and one month after surgery using computed tomography. Their impact on outcomes including early allograft dysfunction, early complications, intensive care unit stay, graft regeneration rate and survival was analyzed. Recipients with sarcopenia or myosteatosis had a higher risk of early allograft dysfunction, higher early complication rate, and longer length of intensive care unit stay (all P<0.05), while there was no difference in graft regeneration rate. Recipient and graft survival were significantly worse for recipients with body composition abnormalities (all P<0.05). In multivariable Cox-regression analysis, sarcopenia (hazard ratio=1.765, P=0.015), myosteatosis (hazard ratio=2.066, P=0.002), and visceral obesity (hazard ratio=1.863, P=0.008) were independently associated with shorter overall survival. Piling up of the three factors increased the mortality risk stepwise (P<0.001). Recipients experienced skeletal muscle loss and muscle fat infiltration one month after surgery. Postoperative worsening sarcopenia (hazard ratio=2.359, P=0.009) and myosteatosis (hazard ratio=1.878, P=0.026) were also identified as independent risk factors for mortality. Sarcopenia, myosteatosis and their progression negatively affect outcomes including early allograft dysfunction, early complications, intensive care unit stay and survival after SLT. Systemic evaluation and dynamic monitoring of body composition are valuable.

Associations between regional adipose tissue distribution and skeletal muscle bioenergetics in older men and women.

The aim of this study was to examine associations of ectopic adipose tissue (AT) with skeletal muscle (SM) mitochondrial bioenergetics in older adults. Cross-sectional data from 829 adults ≥70 years of age were used. Abdominal, subcutaneous, and visceral AT and thigh muscle fat infiltration (MFI) were quantified by magnetic resonance imaging. SM mitochondrial energetics were characterized in vivo (31P-magnetic resonance spectroscopy; ATPmax) and ex vivo (high-resolution respirometry maximal oxidative phosphorylation [OXPHOS]). ActivPal was used to measure physical activity ([PA]; step count). Linear regression adjusted for covariates was applied, with sequential adjustment for BMI and PA. Independent of BMI, total abdominal AT (standardized [Std.] β = -0.21; R2 = 0.09) and visceral AT (Std. β = -0.16; R2 = 0.09) were associated with ATPmax (p < 0.01; n = 770) but not following adjustment for PA (p ≥ 0.05; n = 658). Visceral AT (Std. β = -0.16; R2 = 0.25) and thigh MFI (Std. β = -0.11; R2 = 0.24) were associated with carbohydrate-supported maximal OXPHOS independent of BMI and PA (p < 0.05; n = 609). Total abdominal AT (Std. β = -0.19; R2 = 0.24) and visceral AT (Std. β = -0.17; R2 = 0.24) were associated with fatty acid-supported maximal OXPHOS independent of BMI and PA (p < 0.05; n = 447). Skeletal MFI and abdominal visceral, but not subcutaneous, AT are inversely associated with SM mitochondrial bioenergetics in older adults independent of BMI. Associations between ectopic AT and in vivo mitochondrial bioenergetics are attenuated by PA.

#1458 Adverse muscle composition predicts all-cause mortality in CKD

Abstract Background and Aims Sarcopenia is common in CKD and associates with morbidity and mortality. A rapid and standardized MRI (Magnetic Resonance Imaging) scan protocol allows an accurate muscle composition analysis by quantification of skeletal muscle volume and muscle fat infiltration (MFI). The combined observation of low muscle volume and high muscle fat infiltration, i.e. adverse muscle composition (AMC), is a prevalent muscle composition phenotype within CKD and associates to poor function, high prevalence of comorbidity, and an increased risk for coronary heart disease (CHD). It has also been shown that AMC is an independent predictor of all-cause mortality in patients with non-alcoholic fatty liver disease and in general population. In this study we aimed to investigate muscle composition as predictor of all-cause mortality within participants with CKD in the UK Biobank imaging study (UKB). Method This is a prospective study including UKB participants with CKD defined as having an eGFR cystatin C &amp;lt; 60 ml/min/1, 73 m2. A control group was created by matching each participant with CKD for sex, age, and BMI to four participants with normal eGFR. Cystatin C was analyzed based on blood samples at time of study enrolment 7-9 years prior to the MRI. Fat-tissue free thigh muscle volume and MFI were quantified using a rapid neck-to-knee water and fat separated MRI protocol and automated image analysis (AMRA® Researcher). For each participant, a personalized muscle volume z-score (sex- and body size-specific) was calculated and combined with MFI to divide the participants into four muscle composition phenotype groups; 1) normal muscle composition, 2) only low muscle volume, 3) only high MFI and 4) AMC, using previously published thresholds based on the whole UKB cohort. The thresholds were the 25th percentile (&amp;lt; -0.68 SD) for muscle volume z-score and the 75th percentile (men &amp;gt;7.69%; women &amp;gt;8.82%) for MFI. The mortality data were obtained through the UKB´s linkage to national death registries. All-cause mortality was investigated using Kaplan-Meier curves and Cox regression. Models within participants with CKD were crude and subsequently adjusted for sex, age, BMI, low hand grip strength (&amp;lt;16/27 kg for females/males), physical activity, smoking, alcohol, and previous diagnosis of cancer, prevalent CHD and type 2 diabetes, all assessed at the time of imaging. Results Conclusion AMC, determined by standardized MRI, was a strong predictor of all-cause mortality in CKD. The study results indicate that CKD patients with poor muscle health, identified as having both low muscle volume z-score and high MFI, have a significantly higher mortality risk. This vulnerable group would potentially benefit from targeted interventions and is also of specific interest when evaluating new treatments for CKD.

Abstract P147: Alcohol Consumption and Its Relation to Ectopic Adiposity in African Caribbean Men

Introduction: Alcohol intake and ectopic fat are associated with cardiometabolic diseases. While previous studies primarily focused on visceral and/or liver fat, few studies to date have investigated the associations of alcohol intake with skeletal muscle fat infiltration, a fat depot which might contribute to the increased risk of diabetes and hypertension in African ancestry populations. Methods: Alcohol intake (drinks/day) was assessed using a 146-item semi-quantitative food frequency questionnaire in the Tobago Health Study (N=800). Ectopic fat was measured in the abdomen and thigh in a subset of this cohort (N=706, mean age=63.94 (8.66) years, mean BMI=27.72 (4.65) kg/m 2 ) using computed tomography. Men were divided into current drinkers/not current drinkers, and the current drinkers were further subdivided into types of alcohol consumed (wine, beer/stout, or liquor). Results: A majority of men (56.1%) were not current drinkers. Of drinking men, 76.1% were light drinkers (&lt;1 drink/day), 17.4% were moderate drinkers (1-3 drinks/day), and 6.5% were heavy drinkers (&gt;3 drinks/day). Men who did not drink were slightly older (65.1 vs 62.5, p&lt;0.001), with less visceral adiposity (91.4 vs. 101.9 cm 3 , p=0.002) and less psoas muscle fat (0.59 vs 0.64 cm 3 , p=0.017) than men who drank, independent of age. In fully adjusted models, drinking liquor was positively associated with BMI, waist circumference, visceral and subcutaneous adiposity, while drinking beer was positively associated with thigh muscle fat (Table). Conclusion: Alcohol intake was associated with greater ectopic fat accumulation in all studied compartments, except in the liver, in this cohort of African Caribbean men, who mostly had low alcohol consumption. We also report a novel finding that observed relationships differ by type of alcohol. † Adjusted for total energy intake, age, walking (hours/week), TV watching (≥14 hours/week), current smoking, diabetes, hypertension, and statin use status. * Additional adjustment for BMIHU = Houndsfield Units

Abstract P151: Increased Gain of Skeletal Muscle Adiposity in Middle-Aged African Caribbean Men With Type 2 Diabetes

While type 2 diabetes (T2D) is a known risk factor for the acceleration of muscle loss with aging, less is known about the impact of T2D on skeletal muscle fat infiltration (i.e., myosteatosis) and overall adiposity. Myosteatosis increases with aging, is greater in African as compared to European ancestry individuals, and plays an important role in the development of T2D. Thus, we investigated the association of T2D with changes in body adiposity distribution, with a particular interest in myosteatosis. T2D was identified by self-report, use of hypoglycemic agents, or fasting glucose levels of ≥ 126 mg/dL. Longitudinal changes in computed tomography-measured calf skeletal muscle density [as an inverse surrogate measure of intramuscular adiposity (mg/cm 3 )] and dual-energy X-ray absorptiometry-measured regional and whole body fat were examined by T2D status over an average of 6 years in 724 African-Caribbean men aged 40-54 years from the Tobago Health Study. Total body, arm, leg, and trunk adiposity increased to a significantly greater extent among men without compared to with T2D. In contrast, men with T2D had a 1.6 times greater decrease in calf skeletal muscle density compared with their non-diabetic counterparts (p=0.03). T2D is associated with lower gains in general adiposity, but an increased gain in skeletal muscle adiposity among middle aged African Caribbean men. Our novel findings suggest that middle-aged African Caribbean men with T2D might be at especially high risk for increased gain of myosteatosis. Interventions targeted for men in this age group could focus on controlling diabetes, slowing myosteatosis, and promoting healthy aging.

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

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

Intravoxel Incoherent Motion Diffusion-Weighted MRI, Fat Quantification, and Electromyography: Correlation in Polymyositis and Dermatomyositis.

(1) Background: The intravoxel incoherent motion (IVIM) model can provide information about both molecular diffusion and blood flow for the evaluation of skeletal muscle inflammation. MRI-based fat quantification is advantageous for assessing fat infiltration in skeletal muscle. (2) Purpose: We aimed to quantitatively measure various parameters associated with IVIM diffusion-weighted imaging (DWI) and fat quantification in the muscles of patients with polymyositis and dermatomyositis using magnetic resonance imaging and to investigate the relationship between these parameters and electromyography (EMG) findings. (3) Material and methods: Data were retrospectively evaluated for 12 patients with polymyositis and dermatomyositis who underwent thigh MRI, including IVIM-DWI and fat quantification. The IVIM-derived parameters included the pure diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (f). Fat fraction values were assessed using the six-point Dixon technique. Needle EMG was performed within 9 days of the MRI. (4) Results: The f values (19.02 ± 4.87%) in muscles with pathological spontaneous activity on EMG were significantly higher than those (14.60 ± 5.31) in muscles without pathological spontaneous activity (p < 0.027). There were no significant differences in D, D*, ADC, or fat fraction between muscles with and without pathologic spontaneous activity. Significant negative correlations were observed between fat fraction and amplitude (r = -0.402, p < 0.015) and between fat fraction and duration (r = -0.360, p < 0.031). (5) Conclusion: The current study demonstrates that IVIM-DWI and fat quantification using 3.0 T MRI may aid in predicting EMG findings in patients with polymyositis and dermatomyositis and promote the pathophysiological study of idiopathic inflammatory myopathies.

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.

Hepatocellular carcinoma in patients with non-alcoholic fatty liver disease is associated with heterogeneous pattern of fat infiltration in skeletal muscles.

To evaluate the association between fat infiltration in skeletal muscles (myosteatosis) and hepatocellular carcinoma (HCC) in patients with non-alcoholic fatty liver disease (NAFLD). In a cross-sectional cohort of 72 histologically proven NAFLD patients (n = 38 with non-alcoholic steatohepatitis; NASH), among which 20 had HCC diagnosed on biopsy, we used proton density fat fraction (PDFF) at MRI to evaluate myosteatosis in skeletal muscles (mean fat fraction and first order radiomic-based pattern) at the third lumbar level, namely in erector spinae (ES), quadratus lumborum (QL), psoas, oblique, and rectus muscles. PDFFES was 70% higher in patients with HCC when compared to those without HCC (9.6 ± 5.5% versus 5.7 ± 3.0%, respectively, p < 0.001). In multivariate logistic regression, PDFFES was a significant predictor of the presence of HCC (AUC = 0.72, 95% CI 0.57-0.86, p = 0.002) independently from age, sex, visceral fat area, and liver fibrosis stage (all p < 0.05). The relationship between PDFFES and HCC was exacerbated in patients with NASH (AUC = 0.79, 95% CI 0.63-0.86, p = 0.006). In patients with NASH, radiomics features of heterogeneity such as energy and entropy in any of the paraspinal muscles (i.e., ES, QL, or psoas) were independent predictors of HCC. EnergyES identified patients with HCC (n = 13) in the NASH population with AUC = 0.92 (95% CI 0.82-1.00, p < 0.001). In patients with NAFLD, and more specifically in those with NASH, the degree and heterogeneity of myosteatosis is independently associated with HCC irrespective of liver fibrosis stage. Our data suggest that myosteatosis could be used as a biomarker of HCC in the ever-expanding NAFLD population and pave the way for further investigation in longitudinal studies. • HCC in patients with non-alcoholic fatty liver disease, and more specifically in those with non-alcoholic steatohepatitis, is independently associated with severe fatty infiltration (myosteatosis) of paravertebral skeletal muscles. • Association between myosteatosis and HCC is independent from liver fibrosis stage. • Histogram-based radiomics features of myosteatosis predicts the risk of HCC in patients with non-alcoholic steatohepatitis.

The prevalence and associated factors of myocardial involvement in Duchenne muscular dystrophy patients in the first decade of life.

The prevalence and associated factors of myocardial involvement in Duchenne muscular dystrophy patients in the first decade of life.

Growth arrest and DNA damage-inducible alpha regulates muscle repair and fat infiltration through ATP synthase F1 subunit alpha.

Skeletal muscle fat infiltration is a common feature during ageing, obesity and several myopathies associated with muscular dysfunction and sarcopenia. However, the regulatory mechanisms of intramuscular adipogenesis and strategies to reduce fat infiltration in muscle remain unclear. Here, we identified the growth arrest and DNA damage-inducible alpha (GADD45A), a stress-inducible histone folding protein, as a critical regulator of intramuscular fat (IMAT) infiltration. To explore the role of GADD45A on IMAT infiltration and muscle regeneration, the gain or loss function of GADD45A in intramuscular preadipocytes was performed. The adipocyte-specific GADD45A knock-in (KI) mice and high IMAT-infiltrated muscle model by glycerol injection (50μL of 50% v/v GLY) were generated. RNA-sequencing, histological changes, gene expression, lipid metabolism, mitochondrial function and the effect of dietary factor epigallocatechin-3-gallate (EGCG) treatment (100mg/kg) on IMAT infiltration were studied. The unbiased transcriptomics data analysis indicated that GADD45A expression positively correlates with IMAT infiltration and muscle metabolic disorders in humans (correlation: young vs. aged people, Gadd45a and Cebpa, r2 =0.20, P<0.05) and animals (correlation: wild-type [WT] vs. mdx mice, Gadd45a and Cebpa, r2 =0.38, P<0.05; NaCl vs. GLY mice, Gadd45a and Adipoq/Fabp4, r2 =0.80/0.71, both P<0.0001). In vitro, GADD45A overexpression promotes intramuscular preadipocyte adipogenesis, upregulating the expression of adipogenic genes (Ppara: +47%, Adipoq: +28%, P<0.001; Cebpa: +135%, Fabp4: +16%, P<0.01; Pparg: +66%, Leptin: +77%, P<0.05). GADD45A knockdown robustly decreased lipid accumulation (Pparg: -57%, Adipoq: -35%, P<0.001; Fabp4: -37%, P<0.01; Leptin: -28%, P<0.05). GADD45A KI mice exhibit inhibited skeletal muscle regeneration (myofibres: -40%, P<0.01) and enhanced IMAT infiltration (adipocytes: +20%, P<0.05). These KI mice have impaired exercise endurance and mitochondrial function. Mechanistically, GADD45A affects ATP synthase F1 subunit alpha (ATP5A1) ubiquitination degradation (ubiquitinated ATP5A1, P<0.001) by recruiting the E3 ubiquitin ligase TRIM25, which decreases ATP synthesis (ATP production: -23%, P<0.01) and inactivates the cAMP/PKA/LKB1 signalling pathway (cAMP: -36%, P<0.01; decreased phospho-PKA and phospho-LKB1 protein content, P<0.01). The dietary factor EGCG can protect against muscle fat infiltration (triglyceride: -64%, P<0.05) via downregulating GADD45A (decreased GADD45A protein content, P<0.001). Our findings reveal a crucial role of GADD45A in regulating muscle repair and fat infiltration and suggest that inhibition of GADD45A by EGCG might be a potential strategy to combat fat infiltration and its associated muscle dysfunction.

Co-existence of hepatosteatosis and skeletal muscle fat infiltration

Co-existence of hepatosteatosis and skeletal muscle fat infiltration

Preoperative skeletal muscle fat infiltration is a strong predictor of poorer survival in gallbladder cancer underwent surgery

Recently, a decrease in skeletal muscle, termed sarcopenia, has been reported to be associated with poorer survival of patients in several types of cancer. However, few studies have investigated the association between sarcopenia and the survival of patients with gallbladder cancer. A total of 88 patients undergoing curative resection for advanced gallbladder cancer were included in this study. The quality of skeletal muscle was assessed by the intramuscular adipose tissue content (IMAC), and the quantity of skeletal muscle was assessed by the psoas muscle index (PMI), measured on preoperative computed tomography. The optimum cutoff values for IMAC and PMI for predicting the overall survival in each sex were determined using a minimum p value approach. Clinicopathological factors, IMAC and PMI were retrospectively analyzed to identify the predictors of overall survival (OS). The cutoff values for IMAC were-0.3 in males and 0.04 in females. The numbers of patients with low IMAC and high IMAC were 42 and 46, respectively. The cutoff values for PMI were 7.3cm2/m2 in males and 5.0cm2/m2 in females. The numbers of patients with low PMI and high PMI were 22 and 66, respectively. A multivariate analysis revealed that pT stage (pT3/4, hazard ratio [HR]=6.72, p=0.004), high IMAC (HR=4.12, p<0.001), Bile duct infiltration (present, HR=2.82, p=0.046), high age (≥72 years old, HR=2.64, p=0.010), major hepatectomy (performed, HR=2.50, p=0.031) and pN1/2 (HR=2.17, p=0.010) as independent prognostic factors. IMAC was independent prognostic factor for resected advanced gallbladder cancer, so the quality of skeletal muscle more strongly predicted survival than the quantity of skeletal muscle.

Exercise training attenuates skeletal muscle fat infiltration and improves insulin pathway of patients with immune-mediated necrotizing myopathies and dermatomyositis.

This study aims to evaluate the effects of exercise training on intramuscular lipid content and genes related to insulin pathway in patients with systemic autoimmune myopathies (SAMs). Between January 2016 and May 2019, a total of seven patients with dermatomyositis (DM; 3 males, 4 females; mean age: 49.8±2.3 years; range, 43 to 54 years), six with immune mediated necrotizing myopathy (IMNM; 3 males, 3 females; mean age: 58.5±10.6 years; range, 46 to 74 years), and 10 control individuals (CTRL group; 4 males, 6 females; mean age: 48.7±3.9 years; range, 41 to 56 years) were included. The muscle biopsy before and after the intervention was performed to evaluate the intramuscular lipid content. Patients underwent a combined exercise training program for 12 weeks. Skeletal muscle gene expression was analyzed and the DM versus CTRL group, DM pre- and post-, and IMNM pre- and post-intervention were compared. The DM group had a higher intramuscular lipid content in type II muscle fibers compared to the CTRL group. After the intervention, there was a reduction of lipid content in type I and II fibers in DM and IMNM group. The CTRL group showed a significantly higher expression of genes related to insulin and lipid oxidation pathways (AMPKβ2, AS160, INSR, PGC1-α, PI3K, and RAB14) compared to the DM group. After exercise training, there was an increase gene expression related to insulin pathway and lipid oxidation in DM group (AMPKβ2, AS160, INSR, PGC1-α, PI3K, and RAB14) and in IMNM group (AKT2, AMPKβ2, RAB10, RAB14, and PGC1-α). Exercise training attenuated the amount of fat in type I and II muscle fibers in patients with DM and IMNM and increased gene expression related to insulin pathways and lipid oxidation in DM and IMNM. These results suggest that exercise training can improve the quality and metabolic functions of skeletal muscle in these diseases.

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

BackgroundMyosteatosis, skeletal muscle fat infiltration, is associated with inflammation and fibrosis. The age-related increase of myosteatosis is an important characteristic of sarcopenia and contributes to fragility.AimsTo investigate the impact of healthy aging on intermuscular adipose tissue (IMAT) and muscle fat fraction (FF) in the thigh and the paraspinal muscles in males.MethodsIn 54 healthy males (age 20–70), all active hobby golfers, magnetic resonance imaging was performed to determine volume of IMAT, volume of muscle tissue (MT) and of percentage of FF.ResultsBetween ages 20–70, at the thigh, IMAT/MT volume and MT FF increased annually by 2.9% and 1.3%, respectively. At the psoas IMAT/Psoas volume did not change with age. MT FF increased by 1.5% annually. At the erector spinae IMAT/Erector volume decreased by 0.3% and MT FF increased by 2.8% annually.DiscussionWith increasing age, in males, thigh muscle atrophied, muscle tissue was partly replaced by adipose tissue and remaining muscle tissue also contained more fat. Similar effects were observed in the erector spinae. The psoas muscle did not atrophy, although MT FF also increased with age. Overall correlations with age were weak to moderate with higher correlations observed in the paraspinal muscles.ConclusionsAge-related increases of muscle fat infiltration were observed in the thigh and in the spine. Muscle atrophy did not occur in the psoas. In cross-sectional studies, an adjustment of volumetric parameters by muscle volume is advisable when comparing age-dependent results.

Quantity versus quality: Age-related differences in muscle volume, intramuscular fat, and mechanical properties in the triceps surae.

With aging comes reductions in the quality and size of skeletal muscle. These changes influence the force-generating capacity of skeletal muscle and contribute to movement deficits that accompany aging. Although declines in strength remain a significant barrier to mobility in older adults, the association between age-related changes in muscle structure and function remain unresolved. In this study, we compared age-related differences in (i) muscle volume and architecture, (ii) the quantity and distribution of intramuscular fat, and (iii) muscle shear modulus (an index of stiffness) in the triceps surae in 21 younger (24.6±4.3years) and 15 older (70.4±2.4years) healthy adults. Additionally, we explored the relationship between muscle volume, architecture, intramuscular fat and ankle plantar flexion strength in young and older adults. Magnetic resonance imaging was used to determine muscle volume and intramuscular fat content. B-mode ultrasound was used to quantify muscle architecture, shear-wave elastography was used to measure shear modulus, and ankle strength was measured during maximal isometric plantar flexion contractions. We found that older adults displayed higher levels of intramuscular fat yet similar muscle volumes in the medial (MG) and lateral gastrocnemius (LG) and soleus, compared to younger adults. These age-related higher levels of intramuscular fat were associated with lower muscle shear modulus in the LG and MG. We also found that muscle physiological cross-sectional area (PCSA) that accounted for age-associated differences in intramuscular fat showed a modest increase in its association with ankle strength compared to PCSA that did not account for fat content. This highlights that skeletal muscle fat infiltration plays a role in age-related strength deficits, but does not fully explain the age-related loss in muscle strength, suggesting that other factors play a more significant role.

Psoriasis Is Associated With Myosteatosis but Not Sarcopenia: A Case-Control Study.

Background: The link between psoriasis and body fat (or obesity) has been well established. However, there are no reports detailing the possible relationship between psoriasis and fat infiltration in skeletal muscle, also known as myosteatosis. A recent study reported the possible association between psoriasis, arthritis, and sarcopenia (the loss of skeletal muscle mass or function). The present study aimed to explore the possible associations of chronic plaque psoriasis with myosteatosis and sarcopenia.Methods: We conducted a case-control study. In-patients with chronic plaque psoriasis were retrospectively recruited. Healthy controls were prospectively and continuously recruited. Unenhanced cross-sectional chest computed tomography images at the 12th thoracic vertebral level were analyzed using Mimics software. Skeletal muscle area (SMA), skeletal muscle radiodensity (SMD), and intermuscular adiposity tissue (IMAT) were measured. The skeletal muscle index (SMI) was calculated as SMA/height2. The percentage of IMAT (IMAT%) was calculated as IMAT/SMA × 100%. Myosteatosis was defined by SMD or IMAT%, whereas sarcopenia was defined by SMI. Propensity score matching was performed to adjust for the main confounders. Logistic regression models were used to evaluate the associations of psoriasis with myosteatosis and sarcopenia.Results: We included 155 psoriasis patients and 512 healthy controls. After propensity score matching, we retained 310 controls. The prevalence of sarcopenia was not significantly different between the psoriasis and control groups (men: 9.8% vs. 14.4%, p = 0.244; women: 7.0% vs. 11.7%, p = 0.548). Psoriasis patients were more prone to SMD-defined myosteatosis (men: 39.3% vs. 20.8%; women: 46.5% vs. 16.0%; both p < 0.001) and IMAT%-defined myosteatosis (men: 21.4% vs. 12.5%, p = 0.034; women: 46.5 vs. 28.7%, p = 0.042) than the control group. After adjustment for potential confounders, psoriasis was not significantly associated with sarcopenia (odds ratio [OR] 0.51, 95% confidence interval [CI] 0.25–1.19, p = 0.136). However, psoriasis was associated with SMD-defined myosteatosis (OR 3.16, 95% CI 1.86–5.37, p < 0.001) and IMAT%-defined myosteatosis (OR 1.76, 95% CI 1.04–3.00; p = 0.037).Conclusions: Chronic plaque psoriasis is independently associated with myosteatosis but not sarcopenia. Since fat and muscle are considered endocrine organs and can drive the inflammatory process, further studies detailing the interaction between psoriasis, fat, and skeletal muscle are warranted.

Abstract P070: Longer Sleep Duration Is Associated With Less Myosteatosis In African Caribbean Adults

Introduction: Skeletal muscle is the largest organ in the human body and vital to maintaining metabolic homeostasis. Increased skeletal muscle fat infiltration (i.e. myosteatosis) is now recognized as a major risk factor for cardio-metabolic diseases, independent of general obesity. Modifications in lifestyle, such as sleep, to reduce myosteatosis would be of great public health importance. However, studies of this relationship often use subjective data and are lacking in minority populations. The aim of this study was to examine the relation between objectively measured sleep duration and myosteatosis at the calf among African Caribbeans. Methods: Data were collected on men (n=393) and women (n=438) from the Tobago Health Study. Sleep duration and physical activity was collected using a SenseWear Pro Armband (BodyMedia, Inc.). Participants were instructed to wear the armband at all times, except in water, for 4-7 days. Measures of muscle density, intermuscular adipose tissue (IMAT), and area were obtained by peripheral QCT scans of the calf (Stratec XCT-2000). Model covariates included age, sex, BMI, diabetes, alcohol intake, smoking, and moderate to vigorous physical activity (MVPA). Linear regression was used to assess the relationship of sleep duration on skeletal muscle. Results: Mean sleep duration was 5.5 hours/day (Min 2.2, Max 11.6). Overall, participants were aged 58.7 years, had a BMI of 30.2 kg/m 2 , spent an average of 42 min/day in MVPA, and 18% were diabetic. In fully adjusted models, longer sleep duration was associated with smaller muscle area, but greater muscle density and less IMAT (all P&lt;0.03). There was no interaction of sleep and sex on muscle density, area and IMAT (p-value=0.5184; 0.2730; 0.0954). Conclusions: In African Caribbean men and women, longer sleep duration was associated with less myosteatosis, as well as, less muscle area at the calf. Further research is warranted to understand this relationship longitudinally in order to determine how it may inform lifestyle guidelines in the Caribbean.

Platelet releasate normalises the compromised muscle regeneration in a mouse model of hyperlipidaemia.

What is the central question of this study? What is the impact of obesity-independent hyperlipidaemia on skeletal muscle stem cell function of ApoE-deficient (ApoE-/- ) mice? What is the main finding and its importance? Compromised muscle stem cell function accounts for the impaired muscle regeneration in hyperlipidaemic ApoE-/- mice. Importantly, impaired muscle regeneration is normalised by administration of platelet releasate. Muscle satellite cells are important stem cells for skeletal muscle regeneration and repair after injury. ApoE-deficient mice, an established mouse model of hyperlipidaemia and atherosclerosis, show evidence of oxidative stress-induced lesions and fat infiltration in skeletal muscle followed by impaired repair after injury. However, the mechanisms underpinning attenuated muscle regeneration remain to be fully defined. Key to addressing the latter is to understand the properties of muscle stem cells from ApoE-deficient mice and their myogenic potential. Muscle stem cells from ApoE-deficient mice were cultured both ex vivo (on single fibres) and in vitro (primary myoblasts) and their myogenic capacity was determined. Skeletal muscle regeneration was studied on days 5 and 10 after cardiotoxin injury. ApoE-deficient muscle stem cells showed delayed activation and differentiation on single muscle fibres ex vivo. Impaired proliferation and differentiation profiles were also evident on isolated primary muscle stem cells in culture. ApoE-deficient mice displayed impaired skeletal muscle regeneration after acute injury in vivo. Administration of platelet releasate in ApoE-deficient mice reversed the deficits of muscle regeneration after acute injury to wild-type levels. These findings indicate that muscle stem cell myogenic potential is perturbed in skeletal muscle of a mouse model of hyperlipidaemia. We propose that platelet releasate could be a therapeutic intervention for conditions with associated myopathy such as peripheral arterial disease.