Intermuscular Fat Research Articles

MYOSTEATOSIS AS A RISK FACTOR FOR HEPATOCELULAR CARCINOMA RECURRENCE AFTER DECEASED DONOR LIVER TRANSPLANTATION

NTRODUCTION: Sarcopenia is defined as loss of muscle mass. Besides, myosteatosis is characterized by increased proportion of intermuscular and intramuscular fat. We aimed evaluate the impact of sarcopenia and myosteatosis in hepatocellular carcinoma (HCC) recurrence after liver transplantation. METHODS: Retrospective study of consecutive patients with HCC who underwent liver transplantation in a single institution. Right psoas attenuation (PAt) was measured in Hounsfield units at the level of the third lumbar vertebra. Partial volume of the right psoas (PV) was measured up to the level of the iliac crest. Sarcopenia was defined based on the median values found in each measured parameter. RESULTS: Our study sample included 206 patients. The median follow-up was 4.83 years (IQR 2.35–7.82 years). Overall survival was 84% at 1 year and 75% at 3 years. There were 16 patients (7.76%) with HCC recurrence. Sarcopenia had no impact on overall survival (p<0.68) or disease-free survival (p<0.679). The continuous value of psoas attenuation was negatively associated with the risk of HCC recurrence (p=0.017). Univariate analysis for HCC recurrence identified micro- and macrovascular invasion, preoperative AFP greater than 200, pathological staging beyond Milan Criteria and presence of myosteatosis as significant risk factors. Multivariate analysis only confirmed myosteatosis as an independent risk factor for recurrence (HH 5.88, 95% CI 1.52; 25, and p=0.005). CONCLUSIONS: Myosteatosis was associated with HCC recurrence after liver transplantation.

EPIGENETIC AGE AND MUSCLE CHARACTERISTICS IN BALTIMORE LONGITUDINAL STUDY OF AGING PARTICIPANTS

Abstract Changes in muscle, including loss of muscle mass and fat infiltration, contribute to loss of muscle strength and subsequent declines in physical function in later life. Measures of body composition are consistently associated with DNA methylation (DNAm) in cross sectional studies. Whether differences in DNAm are informative with respect to longitudinal muscle characteristics has not been fully explored. Here we evaluate the relationship between epigenetic age metrics and computed tomography (CT) derived measures, including areas of muscle, subcutaneous fat, and intermuscular fat, as well as the mean and standard deviation of muscle intensity at mid-femur, in the Baltimore Longitudinal Study of Aging. Participants were at least 50 years old at the evaluation of DNAm (n = 471, 51% female), 61.8% of participants had three or more CT scans and mean follow up time was 6.0 years. Relationships between epigenetic age metrics including Horvath and Hannum DNAm age, PhenoAge, GrimAge and DunedinPACE at the index visit, and the trajectory of muscle composition were evaluated using multivariable mixed effects models adjusted for key demographic characteristics, health behaviors and body size. Epigenetic age metrics at the index visit were negatively correlated with the trajectory of muscle area over follow-up. Higher GrimAge at the index visit was associated with faster loss in muscle area and faster increase in fat areas (p < .05). Our analyses suggest that further exploration of DNAm with trajectories of muscle parameters may elucidate novel pathways of muscle dysfunction.

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

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. 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. 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, 400m 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%). 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.

Diabetes in South Asians: Uncovering Novel Risk Factors With Longitudinal Epidemiologic Data: Kelly West Award Lecture 2023.

South Asian populations have a higher prevalence and earlier age of onset of type 2 diabetes and atherosclerotic cardiovascular diseases than other race and ethnic groups. To better understand the pathophysiology and multilevel risk factors for diabetes and cardiovascular disease, we established the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study in 2010. The original MASALA study cohort (n = 1,164) included 83% Asian Indian immigrants, with an ongoing expansion of the study to include individuals of Bangladeshi and Pakistani origin. We have found that South Asian Americans in the MASALA study had higher type 2 diabetes prevalence, lower insulin secretion, more insulin resistance, and an adverse body composition with higher liver and intermuscular fat and lower lean muscle mass compared with four other U.S. race and ethnic groups. MASALA study participants with diabetes were more likely to have the severe hyperglycemia subtype, characterized by β-cell dysfunction and lower body weight, and this subtype was associated with a higher incidence of subclinical atherosclerosis. We have found several modifiable factors for cardiometabolic disease among South Asians including diet and physical activity that can be influenced using specific social network members and with cultural adaptations to the U.S. context. Longitudinal data with repeat cardiometabolic measures that are supplemented with qualitative and mixed-method approaches enable a deeper understanding of disease risk and resilience factors. Studying and contrasting Asian American subgroups can uncover the causes for cardiometabolic disease heterogeneity and reveal novel methods for prevention and treatment.

Association of sex-specific abdominal adipose tissue with WHO/ISUP grade in clear cell renal cell carcinoma

ObjectivesTo explore the association between computed tomography (CT)-measured sex-specific abdominal adipose tissue and the pathological grade of clear cell renal cell carcinoma (ccRCC).MethodsThis retrospective study comprised 560 patients (394 males and 166 females) with pathologically proven ccRCC (467 low- and 93 high-grade). Abdominal CT images were used to assess the adipose tissue in the subcutaneous, visceral, and intermuscular regions. Subcutaneous fat index (SFI), visceral fat index (VFI), intermuscular fat index (IFI), total fat index (TFI), and relative visceral adipose tissue (rVAT) were calculated. Univariate and multivariate logistic regression analyses were performed according to sex to identify the associations between fat-related parameters and pathological grade.ResultsIFI was significantly higher in high-grade ccRCC patients than in low-grade patients for both men and women. For male patients with high-grade tumors, the SFI, VFI, TFI, and rVAT were significantly lower, but not for female patients. In both univariate and multivariate studies, the IFI continued to be a reliable and independent predictor of high-grade ccRCC, regardless of sex.ConclusionsIntermuscular fat index proved to be a valuable biomarker for the pathological grade of ccRCC and could be used as a reliable independent predictor of high-grade ccRCC for both males and females.Critical relevance statementSex-specific fat adipose tissue can be used as a new biomarker to provide a new dimension for renal tumor-related research and may provide new perspectives for personalized tumor management decision-making approaches.Key points• There are sex differences in distribution of subcutaneous fat and visceral fat.• The SFI, VFI, TFI, and rVAT were significantly lower in high-grade ccRCC male patients, but not for female patients.• Intermuscular fat index can be used as a reliable independent predictor of high-grade ccRCC for both males and females.Graphical

Effects of fermented bamboo powder on growth performance, apparent digestibility, carcass traits, and meat quality in growing-finishing pigs

The purpose of this experiment is to study the effects of fermented bamboo powder (FBP) on growth performance, apparent digestibility, carcass traits, and meat quality in growing-finishing pigs. A total of 72 barrows (initial body weight, 90.37 ± 0.73 kg) were randomly allocated to 4 dietary treatments in a 42 d trial, including a control (CON) diet and 3 FBP supplementation diets. In this experiment, the CON group was fed the basic diet, whereas, in the FBP group, wheat bran was replaced with different proportions of FBP, which were 2.5 % (FBP 2.5 %), 5.0 % (FBP 5 %), 10.0 % (FBP 10 %), respectively. The results showed that FBP of 2.5 % and 5 % had no negative effect on the performance of growing-finishing pigs (P > 0.05), FBP could increase the digestibility of feed, decrease the average backfat thickness, increase the loin eye muscle area, and make the meat color fresher (P < 0.05), more in line with Chinese consumers' buying habits. Adding 10 % FBP increased the feed-to-gain ratio; increased water holding capacity and drip loss of pork (P < 0.05) and decreased the content of intermuscular fat of pork (P < 0.05), thus decreasing the taste of pork. To sum up, FBP can be used as a feed raw material to replace part of the grain, and the recommended addition ratio is 5 %.

Association Between Alcohol Consumption and Ectopic Fat in the Multi-Ethnic Study of Atherosclerosis.

Background The relationship between alcohol consumption and ectopic fat distribution, both known factors for cardiovascular disease, remains understudied. Therefore, we aimed to examine the association between alcohol consumption and ectopic adiposity in adults at risk for cardiovascular disease. Methods and Results In this cross-sectional analysis, we categorized alcohol intake among participants in MESA (Multi-Ethnic Study of Atherosclerosis) as follows (drinks/day): <1 (light drinking), 1 to 2 (moderate drinking), >2 (heavy drinking), former drinking, and lifetime abstention. Binge drinking was defined as consuming ≥5 drinks on 1 occasion in the past month. Visceral, subcutaneous, and intermuscular fat area, pericardial fat volume, and hepatic fat attenuation were measured using noncontrast computed tomography. Using multivariable linear regression, we examined the associations between categories ofalcohol consumption and natural log-transformed fat in ectopic depots. We included 6756 MESA participants (62.1±10.2 years; 47.2% women), of whom 6734 and 1934 had chest computed tomography (pericardial and hepatic fat) and abdominal computed tomography (subcutaneous, intermuscular, and visceral fat), respectively. In adjusted analysis, heavy drinking, relative to lifetime abstention, was associated with a higher (relative percent difference) pericardial 15.1 [95% CI, 7.1-27.7], hepatic 3.4 [95% CI, 0.1-6.8], visceral 2.5 [95% CI, -10.4 to 17.2], and intermuscular 5.2 [95% CI, -6.6 to 18.4] fat but lower subcutaneous fat -3.5 [95% CI, -15.5 to 10.2]). The associations between alcohol consumption and ectopic adiposity exhibited a J-shaped pattern. Binge drinking, relative to light-to-moderate drinking, was also associated with higher ectopic fat. Conclusions Alcohol consumption had a J-shaped association with ectopic adiposity. Both heavy alcohol intake and binge alcohol drinking were associated with higher ectopic fat.

Diet composition, nutrient substitutions and circulating fatty acids in relation to ectopic and visceral fat depots

Short-term randomized trials have demonstrated that replacing saturated fat (SFA) with polyunsaturated fat (PUFA) causes a reduction or prevention of liver fat accumulation, but population-based studies on diet and body fat distribution are limited. We investigated cross-sectional associations between diet, circulating fatty acids and liver fat, visceral adipose tissue (VAT), intermuscular adipose tissue (IMAT) and other fat depots using different energy-adjustment models. Sex-stratified analyses of n=9119 (for serum fatty acids) to 13849 (for nutrients) participants in UK Biobank were conducted. Fat depots were assessed by MRI, circulating fatty acids by NMR spectroscopy and diet by repeated 24-h recalls. Liver fat, VAT and IMAT were primary outcomes; total adipose tissue (TAT) and abdominal subcutaneous adipose tissue (ASAT) were secondary outcomes. Three a priori defined models were constructed: the all-components model, standard model and leave-one-out model (main model including specified nutrient substitutions). Imiomics (MRI-derived) was used to confirm and visualize associations. In women, substituting carbohydrates and free sugars with saturated fat (SFA) was positively associated with liver fat (β (95% CI)=0.19 (0.02, 0.36) and β (95% CI)=0.20 (0.05-0.35), respectively) and IMAT (β (95% CI)=0.07 (0.00, 0.14) and β (95% CI)=0.08 (0.02, 0.13), respectively), whereas substituting animal fat with plant fat was inversely associated with IMAT, ASAT and TAT. In the all-components and standard models, SFA and animal fat were positively associated with liver fat, IMAT and VAT whereas plant fat was inversely associated with IMAT in women. Few associations were observed in men. Circulating polyunsaturated fatty acids (PUFA) were inversely associated with liver fat, IMAT and VAT in both men and women, whereas SFA and monounsaturated fatty acids were positively associated. Type of dietary fat may be an important determinant of ectopic fat in humans consuming their habitual diet. Plant fat and PUFA should be preferred over animal fat and SFA. This is corroborated by circulating fatty acids and overall consistent through different energy adjustment models. In UK Biobank, intake of saturated- and animal fat were positively whereas biomarkers of polyunsaturated fat were inversely associated with liver-, visceral- and intermuscular fat. Type of dietary fat may be a determinant of ectopic fat, a risk factor for cardiometabolic disease.

Deep learning–based assessment of CT markers of sarcopenia and myosteatosis for outcome assessment in patients with advanced pancreatic cancer after high-intensity focused ultrasound treatment

ObjectivesTo evaluate the prognostic value of CT-based markers of sarcopenia and myosteatosis in comparison to the Eastern Cooperative Oncology Group (ECOG) score for survival of patients with advanced pancreatic cancer treated with high-intensity focused ultrasound (HIFU).Materials and methodsFor 142 retrospective patients, the skeletal muscle index (SMI), skeletal muscle radiodensity (SMRD), fatty muscle fraction (FMF), and intermuscular fat fraction (IMFF) were determined on superior mesenteric artery level in pre-interventional CT. Each marker was tested for associations with sex, age, body mass index (BMI), and ECOG. The prognostic value of the markers was examined in Kaplan-Meier analyses with the log-rank test and in uni- and multivariable Cox proportional hazards (CPH) models.ResultsThe following significant associations were observed: Male patients had higher BMI and SMI. Patients with lower ECOG had lower BMI and SMI. Patients with BMI lower than 21.8 kg/m2 (median) also showed lower SMI and IMFF. Patients younger than 63.3 years (median) were found to have higher SMRD, lower FMF, and lower IMFF. In the Kaplan-Meier analysis, significantly lower survival times were observed in patients with higher ECOG or lower SMI. Increased patient risk was observed for higher ECOG, lower BMI, and lower SMI in univariable CPH analyses for 1-, 2-, and 3-year survival. Multivariable CPH analysis for 1-year survival revealed increased patient risk for higher ECOG, lower SMI, lower IMFF, and higher FMF. In multivariable analysis for 2- and 3-year survival, only ECOG and FMF remained significant.ConclusionCT-based markers of sarcopenia and myosteatosis show a prognostic value for assessment of survival in advanced pancreatic cancer patients undergoing HIFU therapy.Clinical relevance statementThe results indicate a greater role of myosteatosis for additional risk assessment beyond clinical scores, as only FMF was associated with long-term survival in multivariable CPH analyses along ECOG and also showed independence to ECOG in group analysis.Key Points• This study investigates the prognostic value of CT-based markers of sarcopenia and myosteatosis for patients with pancreatic cancer treated with high-intensity focused ultrasound.• Markers for sarcopenia and myosteatosis showed a prognostic value besides clinical assessment of the physical status by the Eastern Cooperative Oncology Group score. In contrast to muscle size measurements, the myosteatosis marker fatty muscle fraction demonstrated independence to the clinical score.• The results indicate that myosteatosis might play a greater role for additional patient risk assessments beyond clinical assessments of physical status.

Muscle quality and not quantity as a predictor of survival in head and neck squamous cell carcinoma

BackgroundSarcopenia is frequent in head and neck squamous cell carcinoma (HNSCC), as a consequence of malnutrition related to risk factors or tumoral mass. Treatment is associated with toxicities that lead to reduced calories intake and muscle mass wasting. Sarcopenia has been negatively associated with tumor control and survival outcomes. PurposeOur aim is to evaluate the prognostic impact of sarcopenia on overall survival (OS) and progression free survival (PFS) in HNSCC patients undergoing chemoradiation therapy within a prospective clinical trial of chemoradiation vs induction chemotherapy followed by radiation and cetuximab (INTERCEPTOR). Materials and methodsOn baseline CT or MRI, we investigated the association between OS and PFS with radiological markers of sarcopenia, measured at the third cervical vertebra level. We studied paravertebral skeletal muscles area (cm2), muscle density (HU), muscle index (cm2/m2), and intermuscular adipose tissue (IMAT) area (cm2). ResultsImaging of 128 patients was evaluable. We found out that higher body mass index (BMI) was associated with better OS (p = 0.02), and PFS (p = 0.04). Skeletal muscle area (p = 0.02), and IMAT (p = 0.02) were negatively associated with PFS. IMAT was positively correlated with muscle area (Correlation coefficient 0.6, CI95% 0.47–0.7), and negatively associated with muscle density (Correlation coefficient −0.37, CI95% −0.53 – −0.18). ConclusionsIMAT can be used as predictor of PFS in HNC patients undergoing chemoradiation therapy. The amount of intermuscular fat deposits induces alterations of muscle quality, without alterations of muscle quantity, influencing patients’ prognosis.

Deep Learning-Based Fully Automated Segmentation of Regional Muscle Volume and Spatial Intermuscular Fat Using CT

Rationale and ObjectivesWe aim to develop a CT-based deep learning (DL) system for fully automatic segmentation of regional muscle volume and measurement of the spatial intermuscular fat distribution of the gluteus maximus muscle. Materials and MethodsA total of 472 subjects were enrolled and randomly assigned to one of three groups: a training set, test set 1, and test set 2. For each subject in the training set and test set 1, we selected six slices of the CT images as the region of interest for manual segmentation by a radiologist. For each subject in test set 2, we selected all slices of the gluteus maximus muscle on the CT images for manual segmentation. The DL system was constructed using Attention U-Net and the Otsu binary thresholding method to segment the muscle and measure the fat fraction of the gluteus maximus muscle. The segmentation results of the DL system were evaluated using the Dice similarity coefficient (DSC), Hausdorff distance (HD), and the average surface distance (ASD) as metrics. Intraclass correlation coefficients (ICCs) and Bland-Altman plots were used to assess agreement in the measurements of fat fraction between the radiologist and the DL system. ResultsThe DL system showed good segmentation performance on the two test sets, with DSCs of 0.930 and 0.873, respectively. The fat fraction of the gluteus maximus muscle measured by the DL system was in agreement with the radiologist (ICC=0.748). ConclusionThe proposed DL system showed accurate, fully automated segmentation performance and good agreement with the radiologist at fat fraction evaluation, and can be further used for muscle evaluation.

Preoperative CT-Based Skeletal Muscle Mass Depletion and Outcomes after Total Laryngectomy.

To assess the role of preoperative CT-based skeletal muscle mass depletion on postoperative clinical outcomes and survival in patients who underwent total laryngectomy for cancer. Patients operated on between January 2011 and March 2020 were retrospectively included. Skeletal muscle area and intra- and inter-muscular fat accumulation were measured at the third lumbar vertebral level on preoperative CT scans. Skeletal muscle mass depletion was defined based on pre-established cut-off values. Their association with postoperative morbidity, length of stay (LOS), costs, and survival was assessed. A total of 84 patients were included, of which 37 (44%) had preoperative skeletal muscle mass depletion. The rate of postoperative fistula (23% vs. 35%, p = 0.348), cutaneous cervical dehiscence (17% vs. 11%, p = 0.629), superficial incisional surgical site infections (SSI) (12% vs. 10%, p = 1.000), and unplanned reoperation (38% vs. 37%, p = 1.000) were comparable between the two patient groups. No difference in median LOS was observed (41 vs. 33 days, p = 0.295), nor in treatment costs (119,976 vs. 109,402 CHF, p = 0.585). The median overall survival was comparable between the two groups (3.43 vs. 4.95 years, p = 0.09). Skeletal muscle mass depletion alone had no significant impact on postoperative clinical outcomes or survival.

Sarcopenic obesity and its relation with muscle quality and mortality in patients on chronic hemodialysis

Sarcopenia is prevalent in patients with end-stage kidney disease (ESKD) on hemodialysis (HD), and is associated with poor outcomes, while obesity may be protective. Sarcopenic obesity is associated with increased frailty, morbidity and mortality in the general population. Myosteatosis, i.e., muscle fat infiltration, has major effects on muscle strength and physical performance, but is poorly investigated in the nephrology setting. In the present study we aimed to assess the association between sarcopenic obesity, as diagnosed by abdominal CT, and mortality. Moreover, the relationship between myosteatosis, sarcopenic obesity and mortality was also investigated. This is a retrospective study in which ESKD patients on HD submitted to unenhanced abdominal CT for clinical reasons at least 6 months after dialysis initiation were evaluated for sarcopenic obesity and myosteatosis, defined as intermuscular fat area and low attenuation muscle area. Sarcopenic obesity was diagnosed in cases of low abdominal skeletal muscle area and high total fat area. Receiver-operating characteristics (ROC) analysis with Youden index was used to determine the cut-off for high total fat area. Intermuscular fat area and low attenuation muscle area were evaluated by applying the Hounsfield unit of interest (-190;-30, and-29;+29 respectively). Cox regression analysis was used to evaluate the association between predictors and mortality risk. We enrolled 212 patients, aged 68.8 (±14.7) years, 65.5% (139/212) male. Median follow-up was 19.7 (interquartile range [IQR] 2.7-35) months. Sarcopenic obesity was diagnosed in 19.8% of patients and was associated with increased mortality (HR: 3.29 (1.72; 6.27), P<0.001), and with the presence of myosteatosis. Both intermuscular fat area and low attenuation muscle area were associated with increased mortality in adjusted analyses. Patients with sarcopenic obesity have increased myosteatosis. Sarcopenic obesity and myosteatosis are associated with increased mortality in patients on HD.

Molecular Pathways for Muscle and Adipose Tissue Are Altered between Beef Steers Classed as Choice or Standard.

Targets for finished livestock are often determined by expected fat, either subcutaneous or intramuscular. These targets are used frequently to improve eating quality. Lower intramuscular fat, lack of product uniformity, and insufficient tenderness can negatively impact beef acceptability. This study aimed to investigate the differences in gene expression that alter metabolism and intercellular signaling in the muscle and adipose tissue in beef carcasses at different fat endpoints. In this study, longissimus thoracis muscle samples and adipose tissue were collected at harvest, and RNA was extracted and then sequenced using RNAseq. Differential expression was determined using edgeR, and p-values were adjusted using the Benjamini-Hochberg method. A corrected p-value of 0.005 and log2 (fold change) of >1 were the threshold to identify differential expression. Comparison between intermuscular and subcutaneous fat showed no differences in the genes activated in the two adipose tissue depots, suggesting that subcutaneous fat was an adequate sample. Carcass data allowed the classification of carcasses by USDA quality grades (marbling targets). In comparing muscle from Standard and Choice carcasses, 15 genes were downregulated, and 20 were upregulated. There were 49 downregulated and 113 upregulated genes comparing adipose tissue from Standard and Choice carcasses. These genes are related to the metabolism of fat and energy. This indicates that muscle transcript expression varies less than adipose. In addition, subcutaneous fat can be used to evaluate transcript changes in fat. However, it is unclear whether these fat tissues can be used as surrogates for marbling.

Influence of internal muscle properties on muscle shape change and gearing in the human gastrocnemii.

Skeletal muscles bulge when they contract. These three-dimensional shape changes, coupled with fiber rotation, influence a muscle's mechanical performance by uncoupling fiber velocity from muscle belly velocity (i.e., gearing). Muscle shape change and gearing are likely mediated by the interaction between internal muscle properties and contractile forces. Muscles with greater stiffness and intermuscular fat, due to aging or disuse, may limit a muscle's ability to bulge in width, subsequently causing higher gearing. The aim of this study was to determine the influence of internal muscle properties on shape change, fiber rotation, and gearing in the medial (MG) and lateral gastrocnemii (LG) during isometric plantar flexion contractions. Multimodal imaging techniques were used to measure muscle shear modulus, intramuscular fat, and fat-corrected physiological cross-sectional area (PCSA) at rest, as well as synchronous muscle architecture changes during submaximal and maximal contractions in the MG and LG of 20 young (24 ± 3 yr) and 13 older (70 ± 4 yr) participants. Fat-corrected PCSA was positively associated with fiber rotation, gearing, and changes in thickness during submaximal contractions, but it was negatively associated with changes in thickness at maximal contractions. Muscle stiffness and intramuscular fat were related to muscle bulging and reduced fiber rotation, respectively, but only at high forces. Furthermore, the MG and LG had varied internal muscle properties, which may relate to the differing shape changes, fiber rotations, and gearing behaviors observed at each contraction level. These results indicate that internal muscle properties may play an important role in mediating in vivo muscle shape change and gearing, especially during high-force contractions.NEW & NOTEWORTHY Here, we measured internal muscle properties in vivo to determine their influence on the varying shape change and gearing behaviors in the synergistic gastrocnemii muscles. These relationships have previously only been hypothesized or examined within isolated muscles during supramaximal contractions. Our results contribute to a more comprehensive understanding of the factors that influence a muscle's mechanical response to force with implications for preventing or treating muscle deficits associated with aging, disease, and disuse.

Gender-specific data-driven adiposity subtypes using deep-learning-based abdominal CT segmentation.

The aim of this study was to quantify abdominal adiposity and generate data-driven adiposity subtypes with different diabetes risks. A total of 3817 participants from the Pinggu Metabolic Disease Study were recruited. A deep-learning-based recognition model on abdominal computed tomography (CT) images (A-CT model) was developed and validated in 100 randomly selected cases. The volumes and proportions of subcutaneous fat, visceral fat, liver fat, and muscle fat were automatically recognized in all cases. K-means clustering was used to identify subgroups using the proportions of the four fat components. The Dice indices among the measurements assessed by the A-CT model and manual evaluation to detect liver fat, muscle fat, and subcutaneous fat areaswere 0.96, 0.95, and 0.92, respectively. Three subtypes were generated separately in men and women: visceral fat dominant type (VFD); subcutaneous fat dominant type (SFD); and intermuscular fat dominant type (MFD). Compared with the SFD group, the MFD group had similar diabetes risk, and the VFD group had a 60% higher diabetes risk when age and BMI were adjusted for in men. The adjusted odds ratio for diabetes was 1.92 (95% CI: 1.32-2.78) in the MFD group and 6.14 (95% CI: 4.18-9.03) in the VFD group in women. This study identified gender-specific abdominal adiposity subgroups, which may help clinicians to distinguish diabetes risk quickly and automatically.

Influence of cattle category and slaughter age on Charolais-breed carcase and meat traits

The beef consumed worldwide comes from different categories of cattle slaughtered at different ages. The aim of this work was to study the effects of the cattle category (young bulls, heifers, cull cows) and slaughter age on carcase and meat traits, using data on 721 Charolais cattle. At 24h post-mortem in slaughterhouse, 14 carcase traits were measured on each carcase. Then, 2 ribs were collected and aged 14 days. Ten measurements were performed on raw meat (longissimus or rhomboideus muscles) and ten others on longissimus cooked meat. Our results showed that young bulls produced carcases with higher conformation scores, lower fat and meat that had less juiciness, and flavour intensity compared to heifers and cull cows. The carcase traits were more sensitive to variation in the slaughter age than in meat traits. Heifers and cull cows slaughtered at an older age produced heavier carcases. Cull cows slaughtered at above 6 years of age produced carcases with darker muscle and yellower fat. Slaughter age had no effect on the sensory descriptors of cooked meat from all three cattle categories. Heifers slaughtered at earlier than 32 months or later than 36 months produced carcases and meat with similar traits, except for the carcase weight. For cull cows over 6 years old, there was no effect of age at slaughter age on carcase and meat traits. Whatever the cattle category, the slaughter age impacted weakly the traits of raw and cooked meat. Meat from heifers was the most appreciated by trained panellists. HIGHLIGHTS Cooked meat from heifers was better appreciated than cooked meat from young bulls or cull cows. In young bulls, slaughter age had no effect on any carcase and meat traits other than intermuscular fat assessed at the 6th rib. In cull cows, slaughter age affected mostly carcase traits and weakly meat traits.

Temporal changes in muscle characteristics during growth in the goat

This study aimed to explore the temporal accumulative process of functional components and take insight into their dynamic regulatory metabolic pathways in the longissimus during growth in goats. Results showed that the intermuscular fat content, cross-sectional area and fast- to slow-switch fiber ratio of the longissimus were synchronously increased from d1 to d90. The dynamic profiles of functional components and transcriptomic pathways of the longissimus both exhibited two distinct phases during animal development. Expression of genes involved in de novo lipogenesis was increased from birth to weaning, leading to the accumulation of palmitic acid in the first phase. Accumulation of functional oleic acid, linoleic acid and linolenic acid in the second phase was dominatingly driven by enhancement in expression of genes related to fatty acid elongation and desaturation after weaning. A shift from serine to glycine production was observed after weaning, which was linked to the expression profile of genes involved in their interconversion. Our findings systematically reported the key window and pivotal targets of the functional components' accumulation process in the chevon.

Intermuscular Fat Changes Are Related to Reduced Left Ventricular Ejection Fraction During Cancer Therapy (PREVENT-WF-98213)

Intermuscular Fat Changes Are Related to Reduced Left Ventricular Ejection Fraction During Cancer Therapy (PREVENT-WF-98213)

Effect of exercise modality and weight loss on changes in muscle and bone quality in older adults with obesity

BackgroundLittle is known about the effect of exercise modality during a dietary weight loss program on muscle size and quality, as measured by computed tomography (CT). Even less is known about how CT-derived changes in muscle track with changes in volumetric bone mineral density (vBMD) and bone strength. MethodsOlder adults (66 ± 5 years, 64 % women) were randomized to 18-months of diet-induced weight loss (WL), WL with aerobic training (WL + AT), or WL with resistance training (WL + RT). CT-derived muscle area, radio-attenuation and intermuscular fat percentage at the trunk and mid-thigh were determined at baseline (n = 55) and 18-month follow-up (n = 22–34), and changes were adjusted for sex, baseline value, and weight lost. Lumbar spine and hip vBMD and finite element-derived bone strength were also measured. ResultsAfter adjustment for the weight lost, muscle area losses at the trunk were −7.82 cm2 [−12.30, −3.35] for WL, −7.72 cm2 [−11.36, −4.07] for WL + AT, and −5.14 cm2 [−8.65, −1.63] for WL + RT (p < 0.001 for group differences). At the mid-thigh, decreases were −6.20 cm2 [−10.39, −2.02] for WL, −7.84 cm2 [−11.19, −4.48] for WL + AT, and −0.60 cm2 [−4.14, 2.94] for WL + RT; this difference between WL + AT and WL + RT was significant in post-hoc testing (p = 0.01). Change in trunk muscle radio-attenuation was positively associated with change in lumbar bone strength (r = 0.41, p = 0.04). ConclusionsWL + RT better preserved muscle area and improved muscle quality more consistently than WL + AT or WL alone. More research is needed to characterize the associations between muscle and bone quality in older adults undertaking weight loss interventions.