Intermuscular adipose tissue rivals visceral adipose tissue in independent associations with cardiovascular risk

Skeletal muscle and MASLD: Mechanistic and clinical insights

Metabolic dysfunction-associated steatotic liver disease (MASLD) is intrinsically linked with widespread metabolic perturbations, including within skeletal muscle. Indeed, MASLD is associated with a range of skeletal muscle abnormalities, including insulin resistance, myosteatosis, and sarcopenia, which all converge on the liver to drive disease progression and adverse patient outcomes. This review explores the mechanistic links between skeletal muscle and MASLD, including the role of abnormal glycemic control, systemic inflammation, and disordered myokine signaling. In turn, we discuss how intrinsic liver pathology can feed back to further exacerbate poor skeletal muscle health. Given the central importance of skeletal muscle in MASLD pathogenesis, it offers clinicians an opportunity to intervene for therapeutic benefit. We, therefore, summarize the role of nutrition and physical activity on skeletal muscle mass, quality, and metabolic function and discuss the knock-on effect this has on the liver. An awareness of these treatment strategies is particularly important in the era of effective pharmacological and surgical weight loss interventions, which can be associated with the development of sarcopenia. Finally, we highlight a number of promising drug agents in the clinical trial pipeline that specifically target skeletal muscle in an attempt to improve metabolic and physical functioning.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Mediating effect of physical activity on the association between body fat distribution, dysmobility syndrome, and cognitive impairment in older women in the community

PURPOSE

To examine the association between body fat distribution, dysmobility syndrome, and cognitive impairment in 181 community-dwelling older women and assess physical activity's mediating role.

METHODS

Body composition was assessed using dual-energy X-ray absorptiometry, and the android-to-gynoid (A/G) fat ratio was calculated as the android fat proportion divided by the gynoid fat proportion. Participants were categorized into high and low 50 % groups based on the A/G fat ratio. Dysmobility syndrome was defined as the presence of at least three of the following: increased body fat percentage, decreased muscle mass, osteoporosis, slow gait speed, reduced grip strength, or a history of falls. Cognitive impairment was defined as a Mini-Mental State Examination for Dementia Screening score ≤ 23. Physical activity was measured using the International Physical Activity Questionnaire, with ≥600 metabolic equivalent of task-minutes per week classified as active and < 600 as inactive. Binary logistic regression was used to compute odds ratios (OR) and 95 % confidence intervals (CI) for the A/G fat ratio and physical activity. The mediating effects of physical activity were analyzed using Process Macro Model 4.

RESULTS

Participants in the low 50 % A/G fat ratio group had higher odds of dysmobility syndrome (crude OR = 3.500, p < 0.001; adjusted OR = 3.678, p = 0.002) and cognitive impairment (crude OR = 2.714, p = 0.005; adjusted OR = 3.293, p = 0.005) than did those in the high 50 % group, even after covariate adjustments. The inactive group had higher odds of dysmobility syndrome (crude OR = 4.185, p < 0.001; adjusted OR = 3.199, p = 0.005) and cognitive impairment (crude OR = 3.190, p = 0.001; adjusted OR = 2.551, p = 0.022) than did the active group. Mediation analysis indicated that physical activity partially mediated the association between the A/G fat ratio and dysmobility syndrome (indirect effect = -0.5099, 95 % CI = -0.9045 to -0.1786) and cognitive impairment (indirect effect = 0.1446, 95 % CI = 0.0554 to 0.2582).

CONCLUSION

A lower A/G fat ratio increases the risks of dysmobility syndrome and cognitive impairment in older women; physical activity may mitigate these effects.

Health Implications Associated with Fat-Free Mass: A Phenome-Wide Mendelian Randomization Study

INTRODUCTION

Fat-free mass (FFM) is a critical component of the human body, with implications for various diseases.

METHODS

We conducted a comprehensive analysis integrating a phenome-wide association study (PheWAS), a two-sample Mendelian randomization (MR) analysis, and a systematic review to investigate the associations between FFM and health outcomes.

RESULTS

PheWAS identified 183 phenotypes enriched for FFM associations, including diseases, body composition, and lifestyle factors. A two-sample MR analysis using the FinnGen and UK Biobank dataset revealed significant associations between genetically determined FFM and 36 disease outcomes, including cardiovascular diseases, metabolic disorders, and musculoskeletal conditions. The mediation MR analysis indicates that FFM indirectly influences the levels of five biomarkers in visceral adipose tissue. A systematic review identified consistent associations between FFM and several diseases, including type 2 diabetes and cervical disc disorders. Moreover, new associations such as low back pain and ovarian cancer were discovered.

CONCLUSION

These findings challenge the conventional notion of FFM as a protective factor in health, suggesting that higher FFM levels may be linked to an increased risk of various diseases. Further clinical studies are warranted to validate these findings and elucidate the underlying mechanisms.

Skeletal muscle adiposity, coronary microvascular dysfunction, and adverse cardiovascular outcomes

BACKGROUND AND AIMS

Skeletal muscle (SM) fat infiltration, or intermuscular adipose tissue (IMAT), reflects muscle quality and is associated with inflammation, a key determinant in cardiometabolic disease. Coronary flow reserve (CFR), a marker of coronary microvascular dysfunction (CMD), is independently associated with body mass index (BMI), inflammation and risk of heart failure, myocardial infarction, and death. The relationship between SM quality, CMD, and cardiovascular outcomes is not known.

METHODS

Consecutive patients (n = 669) undergoing evaluation for coronary artery disease with cardiac stress positron emission tomography demonstrating normal perfusion and preserved left ventricular ejection fraction were followed over a median of 6 years for major adverse cardiovascular events (MACEs), including death and hospitalization for myocardial infarction or heart failure. Coronary flow reserve was calculated as stress/rest myocardial blood flow. Subcutaneous adipose tissue (SAT), SM, and IMAT areas (cm2) were obtained from simultaneous positron emission tomography attenuation correction computed tomography using semi-automated segmentation at the 12th thoracic vertebra level.

RESULTS

Median age was 63 years, 70% were female, and 46% were nonwhite. Nearly half of patients were obese (46%, BMI 30-61 kg/m2), and BMI correlated highly with SAT and IMAT (r = .84 and r = .71, respectively, P < .001) and moderately with SM (r = .52, P < .001). Decreased SM and increased IMAT, but not BMI or SAT, remained independently associated with decreased CFR (adjusted P = .03 and P = .04, respectively). In adjusted analyses, both lower CFR and higher IMAT were associated with increased MACE [hazard ratio 1.78 (95% confidence interval 1.23-2.58) per -1 U CFR and 1.53 (1.30-1.80) per +10 cm2 IMAT, adjusted P = .002 and P < .0001, respectively], while higher SM and SAT were protective [hazard ratio .89 (.81-.97) per +10 cm2 SM and .94 (.91-.98) per +10 cm2 SAT, adjusted P = .01 and .003, respectively]. Every 1% increase in fatty muscle fraction [IMAT/(SM + IMAT)] conferred an independent 2% increased odds of CMD [CFR <2, odds ratio 1.02 (1.01-1.04), adjusted P = .04] and a 7% increased risk of MACE [hazard ratio 1.07 (1.04-1.09), adjusted P < .001]. There was a significant interaction between CFR and IMAT, not BMI, such that patients with both CMD and fatty muscle demonstrated highest MACE risk (adjusted P = .02).

CONCLUSIONS

Increased intermuscular fat is associated with CMD and adverse cardiovascular outcomes independently of BMI and conventional risk factors. The presence of CMD and SM fat infiltration identified a novel at-risk cardiometabolic phenotype.

Impact of body fat composition on liver iron overload severity in hemochromatosis: a retrospective MRI analysis

PURPOSE

To evaluate the correlation between ectopic adipose tissue and iron overload severity in patients with hemochromatosis.

MATERIAL AND METHODS

A retrospective cohort of 52 patients who underwent liver iron concentration quantification from January 2015 to October 2023 using a 3.0T MRI scanner. R2* relaxation times and proton density fat fraction (PDFF) were assessed for the entire liver volume and a specific region of interest (ROI) placed in the right lobe. Total body fat (TF), subcutaneous fat (SCF), intermuscular fat (IMF), and visceral fat (VSF) percentages were calculated from a single axial slice at the level of the third lumbar vertebra. Additionally, ratios of IMF-to-VSF, IMF-to-SCF, and SCF-to-VSF were calculated. Standard iron laboratory parameters were collected at least one month prior to MRI. Pearson correlation coefficient was used for correlation analysis.

RESULTS

The mean age of participants was 53.9 ± 19.6 years. IMF positively correlated with R2* values in the ROI (p = 0.005, rs = 0.382) and entire liver (p = 0.016, rs = 0.332). Conversely, VSF negatively correlated with R2* values from the ROI (p = < 0.001, rs = - 0.488) and entire liver (p = < 0.001, rs = - 0.459). Positive correlations were also found between IMF-to-VSF and R2* of the ROI (p = 0.003, rs = 0.400) and whole liver (p = 0.008, rs = 0.364). Ferritin levels positively correlated with R2* values calculated from ROI (p = 0.002, rs = 0.417) and whole liver volume (p = 0.004, rs = 0.397). A positive correlation was noted between PDFF of the entire liver and TF (p = 0.024, rs = 0.313).

CONCLUSION

The percentage of Intermuscular and visceral adipose tissues correlates with the severity of liver iron overload in hemochromatosis patients.

Sarcopenia and cachexia: molecular mechanisms and therapeutic interventions

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

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

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

Prevalence of disability and associated functional limitations among older adults in Brazil

INTRODUCTION

Disabilities are a serious public health, social and human rights issue. Few studies address the relationship between disabilities and functioning among older adults. The study aimed to estimate the prevalence of disability and its' association with comorbidities and functional limitations in Brazilian elderly individuals.

METHODS

Data from the National Health Survey-PNS 2019 was used. Prevalence rates with its corresponding 95% confidence intervals (CI) were estimated for variables of interest. Chi-squared tests and multiple logistic regression were conducted to investigate associations and estimate crude and adjusted odds ratios (OR) using Stata 17.0 software. The critical value (p<0.05) was considered.

RESULTS

The overall prevalence of disability was 58.3% (95% CI 57.2-59.4). Moderate/severe disabilities accounted for 24.1 (95% CI 23.1-25.1) and was high among elderly people females (27.9%, 95% CI 26.5-29.3), unemployed (28.4%, 95% CI 27.3-29.6), with an income of up to one minimum wage (30.6%, 95% CI 29.1-32.2), lower education (28.7%, 95% CI 27.5-29.9) and not married (28.5%, 95% CI 27.1-29.9). Crude odds ratios of having functional limitations were 4.5 times higher among individuals with three or more comorbidities, and 32.5 times higher among those with two or more disabilities, compared to those without these conditions.

CONCLUSION

Having a disability is an important predictor of functional limitations, especially among women, and people with lower income and education. To address this problem, public health policies such as encouraging physical activity among the elderly in Brazil should be implemented.

Uremic sarcopenia: the role of intramuscular adipose tissue as a potential early identifier

Introduction

Sarcopenia is a chronic pathological condition, first defined in 2010 and revised in 2018. The most recent definition of sarcopenia focuses mostly on "low muscle strength." A secondary form of sarcopenia is represented by uremic sarcopenia (US), a condition that characterizes end-stage kidney disease (ESKD) patients. The intramuscular adipose tissue (IMAT) seems to impact negatively on muscle strength, as it would seem to replace muscle fibers with a non-contractile component. The study aims to compare body composition parameters-both standardized and innovative-related to the diagnosis of US in hemodialysis (HD) patients, stratified by sarcopenia diagnosis. Furthermore, the different indices of sarcopenia are compared in order to evaluate their predictive capacity.

Methods

We analyzed 48 ESKD patients according to the sarcopenia diagnosis, obtained using dual-energy X-ray absorptiometry (DXA). Moreover, we assessed the presence of IMAT and calculated the sarcopenia index (SI).

Results

For the study, the enrolled population was divided according to the sarcopenia diagnosis: no sarcopenic patients had higher transferrin (p = 0.03), total proteins (p = 0.04), and azotemia pre-dialysis (p = 0.05) values. On the contrary, atherogenic indices were lower in no sarcopenic patients. Moreover, we observed an indirect correlation between the SI and parathyroid hormone (PTH) (p = 0.00138, R 2 = 0.54). Finally, we calculated the prevalence of sarcopenia and sarcopenia adjusted for IMAT. We showed a different prevalence between sarcopenia diagnosed with a standard index and an index adjusted for IMAT (p = 0.043). In conclusion, we believe that the most important result obtained is the indirect correlation between SI and PTH. These data corroborate the theories, in which PTH seems to play a central role in the cachexia genesis. Moreover, the SI adjusted for IMAT seems to be a more reliable parameter for the early identification of subjects at risk of developing US, allowing timely implementation of targeted therapeutic strategies.

Myosteatosis: diagnostic significance and assessment by imaging approaches

Myosteatosis has emerged as an important concept in muscle health as it is associated with an increased risk of adverse health outcomes, a higher rate of complications, and increased mortality associated with ageing, chronic systemic and neuromuscular diseases, cancer, metabolic syndromes, degenerative events, and trauma. Myosteatosis involves ectopic infiltration of fat into skeletal muscle, and it exhibits a negative correlation with muscle mass, strength, and mobility representing a contributing factor to decreased muscle quality. While myosteatosis serves as an additional biomarker for sarcopenia, cachexia, and metabolic syndromes, it is not synonymous with sarcopenia. Myosteatosis induces proinflammatory changes that contribute to decreased muscle function, compromise mitochondrial function, and increase inflammatory response in muscles. Imaging techniques such as computed tomography (CT), particularly opportunistic abdominal CT scans, and magnetic resonance imaging (MRI) or magnetic resonance spectroscopy (MRS), have been used in both clinical practice and research. And in recent years, ultrasound has emerged as a promising bedside tool for measuring changes in muscle tissue. Various techniques, including CT-based muscle attenuation (MA) and intermuscular adipose tissue (IMAT) quantification, MRI-based proton density fat fraction (PDFF) and T1-T2 mapping, and musculoskeletal ultrasound (MSUS)-based echo intensity (EI) and shear wave elastography (SWE), are accessible in clinical practice and can be used as adjunct biomarkers of myosteatosis to assess various debilitating muscle health conditions. However, a stan¬dard definition of myosteatosis with a thorough understanding of the pathophysiological mechanisms, and a consensus in assessment methods and clinical outcomes has not yet been established. Recent developments in image acquisition and quantification have attempted to develop an appropriate muscle quality index for the assessment of myosteatosis. Additionally, emerging studies on artificial intelligence (AI) may provide further insights into quantification and automated assessment, including MRS analysis. In this review, we discuss the pathophysiological aspects of myosteatosis, all the current imaging techniques and recent advances in imaging assessment as potential biomarkers of myosteatosis, and the most common clinical conditions involved.

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

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

Body Composition Analysis Techniques and Its Application in Oncology: A Review

The oncology community has shown growing interest to understand how body composition measures can be utilized to improve cancer treatment and survivorship care for about 20 million individuals diagnosed with cancer annually. Recent observational studies demonstrate that muscle and adipose tissue distribution are risk factors for clinical outcomes such as postoperative complications, and worse overall survival. There is an emergent recognition that body mass index (BMI) is neither adequate to identify patients with adverse health outcomes due to poor muscle health or excess adiposity, nor does BMI accurately classify the distribution of adiposity. Abdominal CT is a most frequently imaging examination for a wide variety of clinical indications, but it is only used to diagnose the immediate problem. Additionally, each CT examination contains very robust data on body composition which generally goes unused in routine clinical practice. The field is eager to identify therapeutic interventions that modify body composition and reduce the incidence of poor clinical outcomes in this population. Large scale population based screening is feasible now by making all of these relevant biometric measures fully automated through the use of artificial intelligence algorithms, which provide rapid and objective assessment.

Associations of relative fat mass and BMI with all-cause mortality: Confounding effect of muscle mass

OBJECTIVE

The study objective was to examine associations of relative fat mass (RFM) and BMI with all-cause mortality in the Dutch general population and to investigate whether additional adjustment for muscle mass strengthened these associations.

METHODS

A total of 8433 community-dwelling adults from the PREVEND general population cohort (1997-1998) were included. Linear regression models were used to examine associations of RFM and BMI with 24-h urinary creatinine excretion, a marker of total muscle mass. Cox regression models were used to examine associations of RFM and BMI with all-cause mortality.

RESULTS

The mean age of the cohort was 49.8 years (range: 28.8-75.7 years), and 49.9% (n = 4209) were women. In age- and sex-adjusted models, both RFM and BMI were associated with total muscle mass (24-h urinary creatinine excretion), and these associations were stronger with BMI (standardized beta [Sβ]RFM : 0.29; 95% CI: 0.27-0.31 vs. SβBMI : 0.38; 95% CI: 0.36-0.40; pdifference  < 0.001). During a median follow-up period of 18.4 years, 1640 deaths (19.4%) occurred. In age- and sex-adjusted models, RFM was significantly associated with all-cause mortality (hazard ratio per 1-SD [HRRFM ]: 1.16; 95% CI: 1.09-1.24), whereas BMI was not (HRBMI : 1.04; 95% CI: 0.99-1.10). After additional adjustment for muscle mass, associations of both RFM and BMI with all-cause mortality increased in magnitude (HRRFM : 1.24; 95% CI: 1.16-1.32 and HRBMI : 1.12; 95% CI: 1.06-1.19). Results were broadly similar in multivariable adjusted models.

CONCLUSIONS

In the general population, a higher RFM was significantly associated with mortality risk, whereas a higher BMI was not. Adjusting for total muscle mass increased the strength of associations of both RFM and BMI with all-cause mortality.

Association of daily carbohydrate intake with intermuscular adipose tissue in Korean individuals with obesity: a cross-sectional study

BACKGROUND/OBJECTIVES

The prevalence of obesity, a worldwide pandemic, has been increasing steadily in Korea. Reports have shown that increased intermuscular adipose tissue (IMAT) is associated with an increased risk of cardiovascular disease, independent of body mass index. However, the relationship between dietary intake and IMAT accumulation in the Korean population remains undetermined. The objective of this study was to evaluate regional fat compartments using advanced magnetic resonance imaging (MRI) techniques. We also aimed to investigate the association between IMAT amounts and dietary intake, including carbohydrate intake, among Korean individuals with obesity.

SUBJECTS/METHODS

This cross-sectional study, performed at a medical center in South Korea, recruited 35 individuals with obesity (15 men and 20 women) and classified them into 2 groups according to sex. Anthropometry was performed, and body fat distribution was measured using MRI. Blood parameters, including glucose and lipid profiles, were analyzed using commercial kits. Linear regression analysis was used to test whether the IMAT was associated with daily carbohydrate intake.

RESULTS

Carbohydrate intake was positively associated with IMAT in all individuals, with adjustments for age, sex, height, and weight. No significant differences in blood indicators were found between the sexes.

CONCLUSIONS

Regardless of sex and age, higher carbohydrate intake was strongly correlated with greater IMAT accumulation. This suggests the need to better understand sex differences and high carbohydrate diet patterns in relation to the association between obesity and metabolic risk, which may help reduce obesity prevalence.

The association of body composition and fat distribution with dysmobility syndrome in community-dwelling older adults: Bushehr Elderly Health (BEH) program

BACKGROUND AND OBJECTIVE

Dysmobility Syndrome (DS) is characterized as an accumulation of clinical risk factors for functional disability, such as osteoporosis, sarcopenia, and obesity. Neurological disorders that affect the motor and sensory systems can also contribute to the condition, resulting in gait and muscle strength disturbances, as well as a history of falls and fractures. The study aimed to determine the association between fat distribution in different body areas and the odds of older adults developing DS, as there is still uncertainty about the accumulation of fat in which area is most closely linked to the condition.

METHODS

This cross-sectional study was conducted according to the data from the second phase of the Bushehr Elderly Health Cohort (BEH). Dysmobility Syndrome was defined based on the co-occurrence of at least three outcomes of its criteria. Body composition was measured using dual-energy X-ray absorptiometry (DXA) and anthropometric studies. For evaluating the relationship, multivariate logistic regression and adjusted univariate linear regression were used.

RESULTS

Of 2,359 who were recruited in the study, 1,277 participants (54.13%) had DS. According to the final logistic regression model in the limb region, FM and FM to FFM ratios were significantly associated with DS [OR (95%CI) = 1.04 (1.02 to 1.05), and 3.42 (1.95 to 5.99), respectively]. Also, In the trunk region, the FM and FM to FFM ratio were significantly related to the odds of DS, although this relationship was weaker than in the limbs region [OR (95%CI) = 1.02 (1.00 to 1.03), and 2.45 (1.36 to 4.39), respectively].

CONCLUSION

Our findings indicate that a higher regional and whole-body amount of fat mass rather than fat-free mass is closely linked to an increased risk of DS, particularly in the elderly population. Notably, higher fat mass in the limbs (especially in the legs) is associated with greater odds of DS, while a higher android-to-gynoid fat mass ratio is associated with lower DS risk. Screening fat mass distribution in older individuals can be a valuable strategy for promptly diagnosing DS, implementing interventions to prevent disabilities, and improving their quality of life.

Elucidating the primary mechanisms of high-intensity interval training for improved cardiac fitness in obesity

Obesity is a global and rising multifactorial pandemic associated with the emergence of several comorbidities that are risk factors for malignant cardiac remodeling and disease. High-intensity interval training (HIIT) has gained considerable attention due to its favorable outcomes of cardiometabolic health in individuals with overweight or obese. The primary aim of this review is to discuss the fundamental processes through which HIIT improves cardiac impairment in individuals with obesity to develop viable treatments for obesity management. In this review, a multiple database search and collection were conducted from the earliest record to January 2013 for studies included the qualitative component of HIIT intervention in humans and animals with overweight/obesity related to cardiac remodeling and fitness. We attempt to integrate the main mechanisms of HIIT in cardiac remolding improvement in obesity into an overall sequential hypothesis. This work focus on the ameliorative effects of HIIT on obesity-induced cardiac remodeling with respect to potential and pleiotropic mechanisms, including adipose distribution, energy metabolism, inflammatory response, insulin resistance, and related risk profiles in obesity. In conclusion, HIIT has been shown to reduce obesity-induced risks of cardiac remodeling, but the long-term effects of HIIT on obesity-induced cardiac injury and disease are presently unknown. Collective understanding highlights numerous specific research that are needed before the safety and effectiveness of HIIT can be confirmed and widely adopted in patient with obesity.

Intermuscular Adiposity is Associated with Coronary Microvascular Dysfunction Independently of Body Mass Index and Modifies its Effect on Adverse Cardiovascular Outcomes

Background: Skeletal muscle (SM) fat infiltration, or intermuscular adipose tissue (IMAT), reflects muscle quality and is associated with inflammation, a key determinant in cardiometabolic disease. Coronary flow reserve (CFR), a marker of coronary microvascular dysfunction (CMD), is independently associated with BMI, inflammation and risk of heart failure, myocardial infarction and death. We sought to investigate the relationship between skeletal muscle quality, CMD and cardiovascular outcomes. Methods: Consecutive patients (N=669) undergoing evaluation for CAD with cardiac stress PET demonstrating normal perfusion and preserved left ventricular ejection fraction were followed over median 6 years for major adverse cardiovascular events (MACE), including death and hospitalization for myocardial infarction or heart failure. CFR was calculated as stress/rest myocardial blood flow and CMD defined as CFR<2. Subcutaneous adipose tissue (SAT), SM and IMAT areas (cm ² ) were obtained from simultaneous PET attenuation correction CTs using semi-automated segmentation at the twelfth thoracic vertebra (T12) level. Results: Median age was 63 years, 70% were female and 46% nonwhite. Nearly half of patients were obese (46%, BMI 30-61) and BMI correlated highly with SAT and IMAT (r=0.84 and 0.71, respectively, p<0.001) and moderately with SM (r=0.52, p<0.001). Decreased SM and increased IMAT, but not BMI or SAT, remained independently associated with decreased CFR (adjusted p=0.03 and p=0.04, respectively). In adjusted analyses, both lower CFR and higher IMAT were associated with increased MACE [HR 1.78 (1.23-2.58) per -1U CFR and 1.53 (1.30-1.80) per +10 cm ² IMAT, adjusted p=0.002 and p<0.0001, respectively], while higher SM and SAT were protective [HR 0.89 (0.81-0.97) per +10 cm ² SM and 0.94 (0.91-0.98) per +10 cm ² SAT, adjusted p=0.01 and 0.003, respectively]. Every 1% increase in fatty muscle fraction [IMAT/(SM+IMAT)] conferred an independent 2% increased odds of CMD [CFR<2, OR 1.02 (1.01-1.04), adjusted p=0.04] and a 7% increased risk of MACE [HR 1.07 (1.04-1.09), adjusted p<0.001]. There was a significant interaction between CFR and IMAT, not BMI, such that patients with both CMD and fatty muscle demonstrated highest MACE risk (adjusted p=0.02). Conclusion: Increased intermuscular fat is associated with CMD and adverse cardiovascular outcomes independently of BMI and conventional risk factors. The presence of CMD and skeletal muscle fat infiltration identified a novel at-risk cardiometabolic phenotype.

Abdominal fat and muscle distributions in different stages of colorectal cancer

BACKGROUND

The purpose of this study is to explore the difference of abdominal fat and muscle composition, especially subcutaneous and visceral adipose tissue, in different stages of colorectal cancer (CRC).

MATERIALS AND METHODS

Patients were divided into 4 groups: healthy controls (patients without colorectal polyp), polyp group (patients with colorectal polyp), cancer group (CRC patients without cachexia), and cachexia group (CRC patients with cachexia). Skeletal muscle (SM), subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and intermuscular adipose tissue (IMAT) were assessed at the third lumbar level on computed tomography images obtained within 30 days before colonoscopy or surgery. One-way ANOVA and linear regression were used to analyze the difference of abdominal fat and muscle composition in different stages of CRC.

RESULTS

A total of 1513 patients were divided into healthy controls, polyp group, cancer group, and cachexia group, respectively. In the development of CRC from normal mucosa to polyp and cancer, the VAT area of the polyp group was significantly higher than that of the healthy controls both in male (156.32 ± 69.71 cm² vs. 141.97 ± 79.40 cm², P = 0.014) and female patients (108.69 ± 53.95 cm² vs. 96.28 ± 46.70 cm², P = 0.044). However, no significant differences were observed of SAT area between polyp group and healthy controls in both sexes. SAT area decreased significantly in the male cancer group compared with the polyp group (111.16 ± 46.98 cm² vs. 126.40 ± 43.52 cm², P = 0.001), while no such change was observed in female patients. When compared with healthy controls, the SM, IMAT, SAT, and VAT areas of cachexia group was significantly decreased by 9.25 cm² (95% CI: 5.39-13.11 cm², P < 0.001), 1.93 cm² (95% CI: 0.54-3.32 cm², P = 0.001), 28.84 cm² (95% CI: 17.84-39.83 cm², P < 0.001), and 31.31 cm² (95% CI: 18.12-44.51 cm², P < 0.001) after adjusting for age and gender.

CONCLUSION

Abdominal fat and muscle composition, especially SAT and VAT, was differently distributed in different stages of CRC. It is necessary to pay attention to the different roles of subcutaneous and visceral adipose tissue in the development of CRC.

Intermuscular adipose tissue in metabolic disease

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

The Pathological Links between Adiposity and the Carpal Tunnel Syndrome

An association between obesity and carpal tunnel syndrome is found in many epidemiological studies. Therefore, there is a need to evaluate the physiopathological links that could explain the association between these two entities. Ectopic adipose tissue is responsible for metabolic syndrome and inflammation, and is a major risk factor for diabetes and cardiovascular diseases. Taking these elements into consideration, we conducted an extensive literature revision of the subject, considering as ectopic fat-related mechanisms the following: (a) the direct compression and the association with the metabolic syndrome of the fat deposition around the wrist, (b) the insulin resistance, dyslipidemia, inflammatory, and oxidative mechanisms related to the central deposition of the fat, (c) the impaired muscle contraction and metabolism related to myosteatosis. Each section presents the cellular pathways which are modified by the ectopic deposition of the adipose tissue and the impact in the pathogeny of the carpal tunnel syndrome. In conclusion, the experimental and clinical data support the epidemiological findings. Efforts to reduce the obesity epidemics will improve not only cardio-metabolic health but will reduce the burden of the disability-free life expectancy due to the carpal tunnel syndrome.

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

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

Intermuscular adipose tissue in Type 2 diabetes mellitus: Non-invasive quantitative imaging and clinical implications

Intermuscular adipose tissue (IMAT) is an ectopic fat depot found beneath the fascia and within the muscles. IMAT modulates muscle insulin sensitivity and triggers local and systemic chronic low-grade inflammation by producing cytokines and chemokines, which underlie the pathogenesis of Type 2 diabetes mellitus (T2DM). Imaging techniques have been increasingly used to non-invasively quantify IMAT in patients with diabetes in research and healthcare settings. In this study, we systematically reviewed the cell of origin and definition of IMAT, and the use of quantitative and functional imaging technology pertinent to the etiology, risk factors, lifestyle modification, and therapeutic treatment of diabetes. The purpose of this article is to provide important insight into the current understanding of IMAT and future prospects of targeting IMAT for T2DM control.

A Portable Band-shaped Bioimpedance System to Monitor the Body Fat and Fasting Glucose Level

With better quality of life, obesity is becoming a worldwide disease due to over-eating and sedentary lifestyle. Therefore, daily monitoring of the glucose and body fat percentage (%) is vital to keep track of one's health. Currently, separated devices are required to monitor each parameter at home and some are still invasive to measure the glucose level. In this study, a portable band-shaped bioimpedance system is proposed to measure both parameters. The system is battery run with two main modules: the current source and the voltage recording, with minimal design to fit into a band of 150 mm x 40 mm in dimension. The impedance is measured at the frequency of 1 kHz at 30 kHz sampling frequency and in 1000 signal cycles to flatten noises. The final average impedance is calculated and evaluated in correlation with the body fat and the fasting glucose. The system was tested on 21 volunteers and 4 locations were picked for the impedance measurement: the arm under the triceps, the side of the belly, the back on one side and the thigh under the bicep femoris. The results show promising results with the arm being the best location for predicting the body fat (correlation coefficient: 0.89, 95% CI: 0.73-0.95), while the thigh impedance best correlated with the fasting glucose (correlation coefficient: 0.92, 95% CI: 0.81-0.97). These preliminary results indicate the feasibility and capacity of the proposed system as a home-based, portable and convenient system in monitoring the body fat and glucose. The system's performance will be verified and replicated in a future larger study.

Investigation of the Relationship between the Mid_Thigh Adipose Tissue Distribution Measured by MRI and Serum Osteocalcin—A Sex-Based Approach

Osteocalcin, in its non-carboxylated form, has a positive effect on glucose metabolism. Additionally, osteocalcin levels are related to body composition, especially muscle mass. The relation to the distribution of different adipose tissue types, such as subcutaneous, intermuscular, and visceral adipose tissue, is unclear. This study aimed to investigate associations between serum osteocalcin and the distribution of subcutaneous and intermuscular adipose tissue of the mid-thigh. Furthermore, the influence of different training methods on osteocalcin levels was investigated. We performed adipose tissue quantification of subcutaneous adipose tissue (SAT) and intramuscular adipose tissue (IMAT) using MRI measurements of the mid-thigh in 128 volunteers (63 male/65 female). Laboratory analysis included blood lipid panel, serum insulin, adiponectin, and osteocalcin measurements. The main observation was a significant correlation of total serum osteocalcin (TOC) and the distribution of adipose tissue of the mid-thigh (SAT/(SAT + IMAT)) (cc = −0.29/p-value = 0.002), as well as the cross-sectional muscle area (MA), increasing with the weekly resistance training duration in males. Additionally, TOC (p-value = 0.01) and MA (p-value = 0.03) were negatively related to serum insulin. The significant relationship between TOC and SAT/(SAT + IMAT) is a new finding and confirms the negative influence of IMAT on glucose metabolism in a sex-specific approach. We could substantiate this by the negative relation of TOC with serum insulin.

Body Composition and Metabolomics in the Alberta Physical Activity and Breast Cancer Prevention Trial

BACKGROUND

Obesity is correlated with many biomarkers, but the extent to which these correlate with underlying body composition is poorly understood.

OBJECTIVES

Our objectives were to 1) describe/compare distinct contributions of fat/lean mass with BMI-metabolite correlations and 2) identify novel metabolite biomarkers of fat/lean mass.

METHODS

The Alberta Physical Activity and Breast Cancer Prevention Trial was a 2-center randomized trial of healthy, inactive, postmenopausal women (n = 304). BMI (in kg/m2) was calculated using weight and height, whereas DXA estimated fat/lean mass. Ultra-performance liquid chromatography and mass spectrometry measured relative concentrations of serum metabolite concentrations. We estimated partial Pearson correlations between 1052 metabolites and BMI, adjusting for age, smoking, and site. Fat mass index (FMI; kg/m2) and lean mass index (LMI; kg/m2) correlations were estimated similarly, with mutual adjustment to evaluate independent effects.

RESULTS

Using a Bonferroni-corrected α level <4.75 × 10-5,  we observed 53 BMI-correlated metabolites (|r| = 0.24-0.42). Of those, 21 were robustly correlated with FMI (|r| > 0.20), 25 modestly (0.10 ≤ |r| ≤ 0.20), and 7 virtually null (|r| < 0.10). Ten of 53 were more strongly correlated with LMI than with FMI. Examining non-BMI-correlated metabolites, 6 robustly correlated with FMI (|r| = 0.24-0.31) and 2 with LMI (r = 0.25-0.26). For these, correlations for fat and lean mass were in opposing directions compared with BMI-correlated metabolites, in which correlations were mostly in the same direction.

CONCLUSIONS

Our results demonstrate how a thorough evaluation of the components of fat and lean mass, along with BMI, provides a more accurate assessment of the associations between body composition and metabolites than BMI alone. Such an assessment makes evident that some metabolites correlated with BMI predominantly reflect lean mass rather than fat, and some metabolites related to body composition are not correlated with BMI. Correctly characterizing these relations is important for an accurate understanding of how and why obesity is associated with disease.

Distribution of subcutaneous and intermuscular fatty tissue of the mid-thigh measured by MRI-A putative indicator of serum adiponectin level and individual factors of cardio-metabolic risk

Obesity and metabolic syndrome (MetS) are associated with hypoadiponectinemia. On the contrary, studies revealed correlations between the amount of subcutaneous adipose tissue (SAT) and higher serum adiponectin levels. Furthermore, independent association of intermuscular adipose tissue (IMAT) deposit in the thigh with cardiometabolic risk factors (including total blood cholesterol, low-density lipoprotein (LDL), and triglycerides), and decreased insulin sensitivity, as MetS components, are sufficiently described. The combined relationship of thigh IMAT and SAT with serum adiponectin, leptin levels, and cardiometabolic risk factors have not been investigated till date. Since both SAT and IMAT play a role in fat metabolism, we hypothesized that the distribution pattern of SAT and IMAT in the mid-thigh might be related to adiponectin, leptin levels, and serum lipid parameters. We performed adipose tissue quantification using magnetic resonance imaging (MRI) of the mid-thigh in 156 healthy volunteers (78 male/78 female). Laboratory measurements of lipid panel, serum adiponectin, and leptin levels were conducted. Total serum adiponectin level showed a significant correlation with the percentage of SAT of the total thigh adipose tissue (SAT/ (IMAT+SAT)) for the whole study population and in sex-specific analysis. Additionally, SAT/(IMAT+SAT) was negatively correlated with known cardiometabolic risk factors such as elevated total blood cholesterol, LDL, and triglycerides; but positively correlated with serum high-density lipoprotein. In multiple linear regression analysis, (SAT/(IMAT+SAT)) was the most strongly associated variable with adiponectin. Interestingly, leptin levels did not show a significant correlation with this ratio. Adipose tissue distribution in the mid-thigh is not only associated to serum adiponectin levels, independent of sex. This proposed quantitative parameter for adipose tissue distribution could be an indicator for individual factors of a person`s cardiometabolic risk and serve as additional non-invasive imaging marker to ensure the success of lifestyle interventions.

Effect of Aerobic or Resistance Exercise, or Both, on Intermuscular and Visceral Fat and Physical and Metabolic Function in Older Adults with Obesity While Dieting

BACKGROUND

Obesity exacerbates age-related effects on body composition, physical and metabolic function. Which exercise mode is most effective in mitigating these deleterious changes in dieting obese older adults is unknown.

METHODS

In a randomized controlled trial, we performed a head-to-head comparison of aerobic (AEX), resistance (REX), or combination (COMB) exercise during matched weight loss in 160 obese older adults. Prespecified analyses compared 6-month changes in intermuscular adipose tissue (IMAT) and visceral adipose tissue (VAT) assessed using MRI, insulin sensitivity index (ISI) by oral glucose tolerance test, physical function using Modified Physical Performance Test (PPT), VO2peak, gait-speed, and knee strength by dynamometry.

RESULTS

IMAT and VAT decreased more in COMB than AEX and REX groups (IMAT; -41% vs. -28% and -23% and VAT: -36% vs. -19% and -21%; p=.003 to .01); IMAT and VAT decreased in all groups more than control (CON) (between-group p<.001). ISI increased more in COMB than AEX and REX groups (86% vs. 50% and 39%; p=.005 to .03). PPT improved more in COMB than AEX and REX groups, while VO2peak improved more in COMB and AEX than REX group (all p<.05). Knee strength improved more in COMB and REX than AEX group (all p<.05). Changes in IMAT and VAT correlated with PPT (r=-.28 and -.39), VO2peak (r=-.49 and -.52), gait-speed (r=-.25 and -.36), and ISI (r=-.49 and -.52) (all p<.05).

CONCLUSIONS

Weight loss plus combination aerobic and resistance exercise was most effective in improving ectopic fat deposition and physical and metabolic function in older adults with obesity.

A high lean body mass is not protecting from type 2 diabetes in the presence of a high body fat mass

AIM

Most studies examining the associations between body composition and type 2 diabetes have been cross-sectional with prevalent diabetes diagnosis or they have analyzed only fat or lean body mass. Hence, the combined effect of fat and lean body mass on the risk of developing type 2 diabetes remains unclear. We investigated whether baseline lean and fat body mass taken simultaneously into account are associated with incidence of type 2 diabetes over a 15-year follow-up in older adults.

METHODS

We studied 704 men (n = 297) and women (n = 407) from the Helsinki Birth Cohort Study (mean age 61 years at baseline) without diabetes at baseline. Bioelectrical impedance analysis was used to derive baseline fat mass index (FMI, fat mass/height²) and lean mass index (LMI, lean mass/height²), dichotomized at sex-specific medians. Incident diabetes was defined as the composite of fasting plasma glucose (FPG) ≥ 7.0 mmol/l, haemoglobin A_1c (HbA_1C) ≥ 6.5% (48 mmol/mol) or physician-based diagnosis.

RESULTS

After a median 14.8 (range 12.5-16.8) years of follow-up, 110 incident diabetes cases occurred (15.6%). Participants with high FMI and LMI at baseline had higher composite incidence of type 2 diabetes (P < 0.001), and significantly increased risk of type 2 diabetes after adjustment for potential confounding factors (sex, physical activity, education and body mass index) compared to the other participants.

CONCLUSION

Contrary to a general belief greater muscle mass is not protective against type 2 diabetes. High LMI accompanied with high FMI seem to predict subsequent development of type 2 diabetes.

Intermuscular Fat Content in Young Chinese Men With Newly Diagnosed Type 2 Diabetes: Based on MR mDIXON-Quant Quantitative Technique

OBJECTIVE

Skeletal muscle fat content is one of the important contributors to insulin resistance (IR), but its diagnostic value remains unknown, especially in the Chinese population. Therefore, we aimed to analyze differences in skeletal muscle fat content and various functional MRI parameters between diabetic patients and control subjects to evaluate the early indicators of diabetes. In addition, we aimed to investigate the associations among skeletal muscle fat content, magnetic resonance parameters of skeletal muscle function and IR in type 2 diabetic patients and control subjects.

METHODS

We enrolled 12 patients (age:29-38 years, BMI: 25-28 kg/m²) who were newly diagnosed with type 2 diabetes (intravenous plasma glucose concentration≥11.1mmol/l or fasting blood glucose concentration≥7.0mmol/l) together with 12 control subjects as the control group (age: 26-33 years, BMI: 21-28 kg/m²). Fasting blood samples were collected for the measurement of glucose, insulin, 2-hour postprandial blood glucose (PBG2h), and glycated hemoglobin (HbAlc). The magnetic resonance scan of the lower extremity and abdomen was performed, which can evaluate visceral fat content as well as skeletal muscle metabolism and function through transverse relaxation times (T2), fraction anisotropy (FA) and apparent diffusion coefficient (ADC) values.

RESULTS

We found a significant difference in intermuscular fat (IMAT) between the diabetes group and the control group (p<0.05), the ratio of IMAT in thigh muscles of diabetes group was higher than that of control group. In the entire cohort, IMAT was positively correlated with HOMA-IR, HbAlc, T2, and FA, and the T2 value was correlated with HOMA-IR, PBG2h and HbAlc (p<0.05). There were also significant differences in T2 and FA values between the diabetes group and the control group (p<0.05). According to the ROC, assuming 8.85% of IMAT as the cutoff value, the sensitivity and specificity of IMAT were 100% and 83.3%, respectively. Assuming 39.25ms as the cutoff value, the sensitivity and specificity of T2 value were 66.7% and 91.7%, respectively. All the statistical analyses were adjusted for age, BMI and visceral fat content.

CONCLUSION

Deposition of IMAT in skeletal muscles seems to be an important determinant for IR in type 2 diabetes. The skeletal muscle IMAT value greater than 8.85% and the T2 value greater than 39.25ms are suggestive of IR.

Treatment of Hepatitis C Virus Infection with Direct-acting Antiviral Agents Elevates the Serum Small-dense Low-density Lipoprotein Cholesterol Level

Objective The low-density lipoprotein cholesterol (LDL) level is known to increase following the treatment of hepatitis C virus (HCV) infection using direct-acting antiviral agents (DAAs). This study aimed to investigate the changes in the lipid profiles, including small-dense LDL cholesterol (sdLDL), in HCV patients treated with DAAs. Patients We retrospectively assessed 67 HCV patients who achieved sustained virological response with DAA administration and were observed for more than 2 years, of whom 32 were on daclatasvir/asunaprevir, 14 were on sofosbuvir/ledipasvir, and 21 were on sofosbuvir/ribavirin. Methods We evaluated the lipid profiles, including sdLDL, every 6 months until 2 years after the start of treatment and analyzed the factors related to changes in the sdLDL level. Results The median sdLDL value at baseline was 12.8 mg/dL, which increased to 19.5 mg/dL at 6 months (p<0.001) and remained elevated at 25.4 mg/dL at 2 years later (p<0.001). The Kaplan-Meier curve indicated that patients with high values of LDL, albumin, muscle attenuation and visceral to subcutaneous adipose tissue area ratio were at increased risk for elevation of sdLDL over 35 mg/dL (log-rank test: p<0.001; p=0.008, p=0.002 and p=0.042, respectively). A multivariate analysis performed on the factors contributing to elevation of sdLDL 2 years after DAA treatment (≥35.0 mg/dL) revealed pretreatment LDL (≥91.0 mg/dL) and muscle attenuation (≥33.7 HU) as significant factors (p=0.007 and p=0.032, respectively). Conclusion SdLDL increased continuously after DAA treatment, and high LDL levels and low intramuscular fat deposition before treatment contributed to elevated sdLDL levels after treatment.

Sarcopenia during COVID-19 lockdown restrictions: long-term health effects of short-term muscle loss

The COVID-19 pandemic is an extraordinary global emergency that has led to the implementation of unprecedented measures in order to stem the spread of the infection. Internationally, governments are enforcing measures such as travel bans, quarantine, isolation, and social distancing leading to an extended period of time at home. This has resulted in reductions in physical activity and changes in dietary intakes that have the potential to accelerate sarcopenia, a deterioration of muscle mass and function (more likely in older populations), as well as increases in body fat. These changes in body composition are associated with a number of chronic, lifestyle diseases including cardiovascular disease (CVD), diabetes, osteoporosis, frailty, cognitive decline, and depression. Furthermore, CVD, diabetes, and elevated body fat are associated with greater risk of COVID-19 infection and more severe symptomology, underscoring the importance of avoiding the development of such morbidities. Here we review mechanisms of sarcopenia and their relation to the current data on the effects of COVID-19 confinement on physical activity, dietary habits, sleep, and stress as well as extended bed rest due to COVID-19 hospitalization. The potential of these factors to lead to an increased likelihood of muscle loss and chronic disease will be discussed. By offering a number of home-based strategies including resistance exercise, higher protein intakes and supplementation, we can potentially guide public health authorities to avoid a lifestyle disease and rehabilitation crisis post-COVID-19. Such strategies may also serve as useful preventative measures for reducing the likelihood of sarcopenia in general and in the event of future periods of isolation.

Infiltration of intramuscular adipose tissue impairs skeletal muscle contraction

KEY POINTS

Muscle infiltration with adipose tissue (IMAT) is common and associated with loss of skeletal muscle strength and physical function across a diverse set of pathologies. Whether the association between IMAT and muscle weakness is causative or simply correlative remains an open question that needs to be addressed to effectively guide muscle strengthening interventions in people with increased IMAT. In the present studies, we demonstrate that IMAT deposition causes decreased muscle strength using mouse models. These findings indicate IMAT is a novel therapeutic target for muscle dysfunction.

ABSTRACT

Intramuscular adipose tissue (IMAT) is associated with deficits in strength and physical function across a wide array of conditions, from injury to ageing to metabolic disease. Due to the diverse aetiologies of the primary disorders involving IMAT and the strength of the associations, it has long been proposed that IMAT directly contributes to this muscle dysfunction. However, infiltration of IMAT and reduced strength could both be driven by muscle disuse, injury and systemic disease, making IMAT simply an 'innocent bystander.' Here, we utilize novel mouse models to evaluate the direct effect of IMAT on muscle contraction. First, we utilize intramuscular glycerol injection in wild-type mice to evaluate IMAT in the absence of systemic disease. In this model we find that, in isolation from the neuromuscular and circulatory systems, there remains a muscle-intrinsic association between increased IMAT volume and decreased contractile tension (r2  > 0.5, P < 0.01) that cannot be explained by reduction in contractile material. Second, we utilize a lipodystrophic mouse model which cannot generate adipocytes to 'rescue' the deficits. We demonstrate that without IMAT infiltration, glycerol treatment does not reduce contractile force (P > 0.8). Taken together, this indicates that IMAT is not an inert feature of muscle pathology but rather has a direct impact on muscle contraction. This finding suggests that novel strategies targeting IMAT may improve muscle strength and function in a number of populations.

Neck circumference is associated with adipose tissue content in thigh skeletal muscle in overweight and obese premenopausal women

Neck circumference (NC) has been proposed as a simple and practical tool, independently associated with cardiometabolic risk factors. However, the association of NC with inter-muscular adipose tissue (IMAT) is still to be determined. We aimed to examine the association of NC with thigh IMAT, and visceral adipose tissue (VAT) measured with computed tomography (CT) in overweight/obese women. 142 premenopausal overweight and obese Caucasian women participated in this cross-sectional study. NC was measured with an inextensible metallic tape above the thyroid cartilage according to International Society for Advancement of Kinanthropometry protocol. Thigh IMAT and VAT volumes were measured with a single cross-sectional CT. Regarding the covariates, fat mass (FM) was assessed with dual-energy x-ray absorptiometry and physical activity was objectively measured with accelerometry. NC was positively associated with thigh IMAT and VAT volumes (standardized β coefficient: β = 0.45, P-value = ≤0.001, β = 0.60, P = ≤ 0.001; respectively), which persisted after adjusting for age, height, overall FM or moderate-to-vigorous physical activity. Our findings show that NC is associated with thigh IMAT volume in overweight and obese premenopausal Caucasian women, regardless of the amount of lower-body fatness. These results suggest underscoring the relevance of NC as a marker of adipose tissue content in thigh skeletal muscle.

Muscle transcriptome analysis identifies genes involved in ciliogenesis and the molecular cascade associated with intramuscular fat content in Large White heavy pigs

Intramuscular fat content (IMF) is a complex trait influencing the technological and sensorial features of meat products and determining pork quality. Thus, we aimed at analyzing through RNA-sequencing the Semimembranosus muscle transcriptome of Italian Large White pigs to study the gene networks associated with IMF deposition. Two groups of samples were used; each one was composed of six unrelated pigs with extreme and divergent IMF content (0.67 ± 0.09% in low IMF vs. 6.81 ± 1.17% in high IMF groups) that were chosen from 950 purebred individuals. Paired-end RNA sequences were aligned to Sus scrofa genome assembly 11.1 and gene counts were analyzed using WGCNA and DeSeq2 packages in R environment. Interestingly, among the 58 differentially expressed genes (DEGs), several were related to primary cilia organelles (such as Lebercilin 5 gene), in addition to the genes involved in the regulation of cell differentiation, in the control of RNA-processing, and G-protein and ERK signaling pathways. Together with cilia-related genes, we also found in high IMF pigs an over-expression of the Fibroblast Growth Factor 2 (FGF2) gene, which in other animal species was found to be a regulator of ciliogenesis. Four WGCNA gene modules resulted significantly associated with IMF deposition: grey60 (P = 0.003), darkturquoise (P = 0.022), skyblue1 (P = 0.022), and lavenderblush3 (P = 0.030). The genes in the significant modules confirmed the results obtained for the DEGs, and the analysis with “cytoHubba” indicated genes controlling RNA splicing and cell differentiation as hub genes. Among the complex molecular processes affecting muscle fat depots, genes involved in primary cilia may have an important role, and the transcriptional reprogramming observed in high IMF pigs may be related to an FGF-related molecular cascade and to ciliogenesis, which in the literature have been associated with fibro-adipogenic precursor differentiation.

Comparing intramuscular adipose tissue on T1-weighted and two-point Dixon images

Purpose

The purpose of this study was to compare intramuscular adipose tissue content determined by two-point Dixon imaging and T1-weighted imaging, calculated using thresholding techniques.

Methods

In total, 19 nonobese younger adults (26.2 ± 4.9 years) and 13 older adults (72.2 ± 6.0 years) were recruited. Axial images of the mid-thigh were taken using T1-weighted and two-point Dixon sequences with a 3.0 T whole-body magnetic resonance device and used to measure intramuscular adipose tissue content of the vastus lateralis, adductor magnus, and long head of the biceps femoris.

Results

There was no significant difference in intramuscular adipose tissue content between T1-weighted and two-point Dixon imaging for the vastus lateralis (11.0 ± 4.4% and 12.2 ± 2.4%); however, intramuscular adipose tissue content determined by T1-weighted imaging was significantly higher than that of two-point Dixon imaging for the other muscles. Bland-Altman analysis showed a proportional bias for intramuscular adipose tissue calculations in all three muscles.

Conclusion

The validity of intramuscular adipose tissue content measurements between T1-weighted and two-point Dixon imaging is muscle-specific. This study showed discrepancies of intramuscular adipose tissue content between T1-weighted and two-point Dixon imaging.

Advances in knowledge

This study’s results suggest that care should be taken when selecting an imaging modality for intramuscular adipose tissue, especially for patients who would be suspected to have higher intramuscular adipose tissue values.

Adipose Tissue Distribution, Inflammation and Its Metabolic Consequences, Including Diabetes and Cardiovascular Disease

Adipose tissue plays essential roles in maintaining lipid and glucose homeostasis. To date several types of adipose tissue have been identified, namely white, brown, and beige, that reside in various specific anatomical locations throughout the body. The cellular composition, secretome, and location of these adipose depots define their function in health and metabolic disease. In obesity, adipose tissue becomes dysfunctional, promoting a pro-inflammatory, hyperlipidemic and insulin resistant environment that contributes to type 2 diabetes mellitus (T2DM). Concurrently, similar features that result from adipose tissue dysfunction also promote cardiovascular disease (CVD) by mechanisms that can be augmented by T2DM. The mechanisms by which dysfunctional adipose tissue simultaneously promote T2DM and CVD, focusing on adipose tissue depot-specific adipokines, inflammatory profiles, and metabolism, will be the focus of this review. The impact that various T2DM and CVD treatment strategies have on adipose tissue function and body weight also will be discussed.

Computed Tomography-Based Body Composition Is Not Consistently Associated with Outcome in Older Patients with Colorectal Cancer

Background

Current literature is inconsistent in the associations between computed tomography (CT)‐based body composition measures and adverse outcomes in older patients with colorectal cancer (CRC). Moreover, the associations with consecutive treatment modalities have not been studied. This study compared the associations of CT‐based body composition measures with surgery‐ and chemotherapy‐related complications and survival in older patients with CRC.

Materials and Methods

A retrospective single‐center cohort study was conducted in patients with CRC aged ≥65 years who underwent elective surgery between 2010 and 2014. Gender‐specific standardized scores of preoperative CT‐based skeletal muscle (SM), muscle density, intermuscular adipose tissue (IMAT), visceral adipose tissue (VAT), subcutaneous adipose tissue, IMAT percentage, SM/VAT, and body mass index (BMI) were tested for their associations with severe postoperative complications, prolonged length of stay (LOS), readmission, and dose‐limiting toxicity using logistic regression and 1‐year and long‐term survival (range 3.7–6.6 years) using Cox regression. Bonferroni correction was applied to account for multiple testing.

Results

The study population consisted of 378 patients with CRC with a median age of 73.4 (interquartile range 69.5–78.4) years. Severe postoperative complications occurred in 13.0%, and 39.4% of patients died during follow‐up. Dose‐limiting toxicity occurred in 77.4% of patients receiving chemotherapy (n = 53). SM, muscle density, VAT, SM/VAT, and BMI were associated with surgery‐related complications, and muscle density, IMAT, IMAT percentage, and SM/VAT were associated with long‐term survival. After Bonferroni correction, no CT‐based body composition measure was significantly associated with adverse outcomes. Higher BMI was associated with prolonged LOS.

Conclusion

The associations between CT‐based body composition measures and adverse outcomes of consecutive treatment modalities in older patients with CRC were not consistent or statistically significant.

Implications for Practice

Computed tomography (CT)‐based body composition, including muscle mass, muscle density, and intermuscular, visceral, and subcutaneous adipose tissue, showed inconsistent and nonsignificant associations with surgery‐related complications, dose‐limiting toxicity, and overall survival in older adults with colorectal cancer. This study underscores the need to verify whether CT‐based body composition measures are worth implementing in clinical practice.

Colorectal cancer is prevalent in older individuals. This article compares the associations of computed tomography‐based body composition measures with surgery‐ and chemotherapy‐related complications and survival in older patients with colorectal cancer.

Skeletal muscle fat in individuals with rheumatoid arthritis compared to healthy adults

OBJECTIVE

To compare skeletal muscle fat (SMF), intermuscular adipose tissue (IMAT) and subcutaneous adipose tissue (SAT) between individuals with rheumatoid arthritis (RA), and healthy individuals of the same age, and healthy individuals at least 10 years older than those with RA.

METHODS

Two cross-sectional studies. In the first study, RA subjects were matched by age, sex, and BMI with healthy adults. In the second, RA subjects were matched by sex and BMI to adults 10-20 years older. SMF, IMAT and SAT were measured with Computed Tomography images of the mid-thigh region. We used parametric or non-parametric related-sample tests to compare fat accumulation between RA subjects and healthy adults.

RESULTS

In the first study SMF was significantly higher in the RA cohort compared to their age-matched healthy counterparts (mean difference = -3.5 HU (95% -6.2, -0.9), p = 0.011), but IMAT and SAT were similar between cohorts. In the second study, SMF, IMAT and SAT were not significantly different between the RA and matched older healthy cohorts. In both studies, there were no significant differences in mid-thigh muscle area between RA subjects and healthy adults.

CONCLUSION

SMF accumulation in RA was higher than in healthy individuals of similar age, sex, BMI. Accumulation of fat within and around the muscles in RA was not different compared to the matched healthy older individuals, indicating that muscle fat accumulation in RA might mimic a pattern not different from healthy aging.

Intermuscular adipose tissue directly modulates skeletal muscle insulin sensitivity in humans

Intermuscular adipose tissue (IMAT) is negatively related to insulin sensitivity, but a causal role of IMAT in the development of insulin resistance is unknown. IMAT was sampled in humans to test for the ability to induce insulin resistance in vitro and characterize gene expression to uncover how IMAT may promote skeletal muscle insulin resistance. Human primary muscle cells were incubated with conditioned media from IMAT, visceral (VAT), or subcutaneous adipose tissue (SAT) to evaluate changes in insulin sensitivity. RNAseq analysis was performed on IMAT with gene expression compared with skeletal muscle and SAT, and relationships to insulin sensitivity were determined in men and women spanning a wide range of insulin sensitivity measured by hyperinsulinemic-euglycemic clamp. Conditioned media from IMAT and VAT decreased insulin sensitivity similarly compared with SAT. Multidimensional scaling analysis revealed distinct gene expression patterns in IMAT compared with SAT and muscle. Pathway analysis revealed that IMAT expression of genes in insulin signaling, oxidative phosphorylation, and peroxisomal metabolism related positively to donor insulin sensitivity, whereas expression of macrophage markers, inflammatory cytokines, and secreted extracellular matrix proteins were negatively related to insulin sensitivity. Perilipin 5 gene expression suggested greater IMAT lipolysis in insulin-resistant individuals. Combined, these data show that factors secreted from IMAT modulate muscle insulin sensitivity, possibly via secretion of inflammatory cytokines and extracellular matrix proteins, and by increasing local FFA concentration in humans. These data suggest IMAT may be an important regulator of skeletal muscle insulin sensitivity and could be a novel therapeutic target for skeletal muscle insulin resistance.

pQCT- and Ultrasound-based Muscle and Fat Estimate Errors after Resistance Exercise

PURPOSE

Resistance exercise increases blood flow, induces osmotic and hydrostatic fluid shifts during and immediately after exercise, and may trigger inflammatory responses for several days in the working muscle. The resultant muscle swelling can subsequently affect muscle size and quality assessments. However, the effects of muscle swelling on x-ray attenuation of adipose estimate errors are unknown.

METHODS

Peripheral quantitative computed tomography (pQCT) and ultrasonography were used to assess muscle and adipose tissue properties of both upper arms before, 24, 48, and 72 h after unilateral resistance exercise. Recreationally active participants (n = 17) completed the exercise while their contralateral limb served as a control.

RESULTS

Resistance exercise resulted in a significant increase in pQCT-derived muscle cross-sectional area (includes intermuscular adipose tissue [IMAT] area), muscle area (excludes IMAT area) and IMAT area, and ultrasound-derived muscle thickness at 24, 48, and 72 h. A significant decrease in pQCT-derived muscle density was also detected as well as an increase in ultrasound-derived echo intensity at 48 and 72 h. The changes in muscle area, IMAT area, and muscle density were significantly correlated with changes in echo intensity, whereas the changes in muscle cross-sectional area and IMAT area were significantly correlated with changes in muscle thickness.

CONCLUSION

Unaccustomed resistance exercise can cause errors in pQCT- and ultrasound-based muscle and adipose estimates for at least 72 h. These errors are the result of muscle swelling likely caused by muscle blood flow and inflammation-dependent fluid shifts in muscle. These findings may have implications for measurements in other inflammatory conditions.

Thigh and abdominal adipose tissue depot associations with testosterone levels in postmenopausal females

OBJECTIVE

Research findings on the relationship between serum androgens and adipose tissue in older females are inconsistent. We aimed to clarify the relationship using state-of-the-art techniques to evaluate associations between body fat distribution and plasma testosterone (T) levels in older postmenopausal women.

DESIGN

Observational, cross-sectional study of healthy, community dwelling postmenopausal women.

PATIENTS AND MEASUREMENTS

Postmenopausal women (60-80 years old) were included in this study. Overall body composition was evaluated by dual-energy X-ray absorptiometry. Abdominal and thigh fat depots were measured by magnetic resonance imaging. Circulating T concentrations were analysed by liquid chromatography-tandem mass spectrometry.

RESULTS

Thirty-five women (66.6 ± 0.8 years) participated in this study. T levels were positively associated with clinical proxy measures of adiposity including weight (ρ = 0.39), BMI (ρ = 0.43) and waist circumference (ρ = 0.39) (all P < 0.05). Fat mass and % body fat were correlated with T levels (ρ = 0.42 and 0.38 respectively, both P < 0.05). T correlated with overall and superficial abdominal fat (ρ = 0.34 and 0.37 respectively, both P < 0.05) but not with visceral adipose tissue. T increased with greater thigh fat (ρ = 0.49, P < 0.05) in both superficial and deep depots (ρ = 0.50 and 0.35 respectively, both P < 0.05).

CONCLUSION

Our results suggest that postmenopausal women with higher circulating T levels have both higher regional and overall body adiposity. These findings underscore the sexual dimorphism in the relationship between serum androgen levels and adiposity.

The Dual Role of the Pervasive "Fattish" Tissue Remodeling With Age

Human aging is characterized by dramatic changes in body mass composition that include a general increase of the total fat mass. Within the fat mass, a change in the proportions of adipose tissues also occurs with aging, affecting body metabolism, and playing a central role in many chronic diseases, including insulin resistance, obesity, cardiovascular diseases, and type II diabetes. In mammals, fat accumulates as white (WAT) and brown (BAT) adipose tissue, which differ both in morphology and function. While WAT is involved in lipid storage and immuno-endocrine responses, BAT is aimed at generating heat. With advancing age BAT declines, while WAT increases reaching the maximum peak by early old age and changes its distribution toward a higher proportion of visceral WAT. However, lipids tend to accumulate also within lipid droplets (LDs) in non-adipose tissues, including muscle, liver, and heart. The excess of such ectopic lipid deposition and the alteration of LD homeostasis contribute to the pathogenesis of the above-mentioned age-related diseases. It is not clear why age-associated tissue remodeling seems to lean toward lipid deposition as a "default program." However, it can be noted that such remodeling is not inevitably detrimental. In fact, such a programmed redistribution of fat throughout life could be considered physiological and even protective, in particular at extreme old age. In this regard, it has to be considered that an excessive decrease of subcutaneous peripheral fat is associated with a pro-inflammatory status, and a decrease of LD is associated with lipotoxicity leading to an increased risk of insulin resistance, type II diabetes and cardiovascular diseases. At variance, a balanced rate of fat content and distribution has beneficial effects for health and metabolic homeostasis, positively affecting longevity. In this review, we will summarize the present knowledge on the mechanisms of the age-related changes in lipid distribution and we will discuss how fat mass negatively or positively impacts on human health and longevity.

Cross-Sectional and Longitudinal Association between Glycemic Status and Body Composition in Men: A Population-Based Study

This study sought to evaluate the associations between changes in glycemic status and changes in total body (TB), trunk, and appendicular fat (FM) and lean mass (LM) in men. A population-based study of men aged 20⁻66 years at baseline were included in cross-sectional (n = 430) and three-year longitudinal (n = 411) analyses. Prediabetes was defined as fasting glucose 100⁻125 mg/dL. Type 2 diabetes (T2D) was determined by: self-reported diabetes, current anti-diabetic drug use (insulin/oral hypoglycemic agents), fasting glucose (≥126 mg/dL), or non-fasting glucose (≥200 mg/dL). Body composition was evaluated by dual-energy X-ray absorptiometry. Longitudinal analyses showed that changes in TB FM and LM, and appendicular LM differed among glycemic groups. Normoglycemic men who converted to prediabetes lost more TB and appendicular LM than men who remained normoglycemic (all, p < 0.05). Normoglycemic or prediabetic men who developed T2D had a greater loss of TB and appendicular LM than men who remained normoglycemic (both, p < 0.05). T2D men had greater gains in TB FM and greater losses in TB and appendicular LM than men who remained normoglycemic (all, p < 0.05). Dysglycemia is associated with adverse changes in TB and appendicular LM.

Validation of Peripheral Quantitative Computed Tomography-Derived Thigh Adipose Tissue Subcompartments in Young Girls Using a 3 T MRI Scanner

The ability to assess skeletal muscle adipose tissue is important given the negative clinical implications associated with greater fat infiltration of the muscle. Computed tomography and magnetic resonance imaging (MRI) are highly accurate for measuring appendicular soft tissue and muscle composition, but have limitations. Peripheral quantitative computed tomography (pQCT) is an alternative that investigators find valuable because of its low radiation, fast scan time, and comparatively lower costs. The present investigation sought to assess the accuracy of pQCT-derived estimates of total, subcutaneous, skeletal muscle, intermuscular, and calculated intramuscular adipose tissue areas, and muscle density in the midthigh of young girls using the gold standard, 3 T MRI, as the criterion. Cross-sectional data were analyzed for 26 healthy girls aged 9-12 years. Midthigh soft tissue composition was assessed by both pQCT and 3 T MRI. Mean tissue area for corresponding adipose compartments by pQCT and MRI was compared using t tests, regression analysis, and Bland-Altman plots. Muscle density was regressed on MRI skeletal muscle adipose tissue, intermuscular adipose tissue, and intramuscular adipose tissue, each expressed as a percentage of total muscle area. Correlations were high between MRI and pQCT for total adipose tissue (r² = 0.98), subcutaneous adipose tissue (r² = 0.95), skeletal muscle adipose tissue (r² = 0.83), and intermuscular adipose tissue (r² = 0.82), and pQCT muscle density correlated well with both MRI skeletal muscle adipose tissue (r² = 0.70) and MRI intermuscular adipose tissue (r² = 0.70). There was a slight, but statistically significant underestimation by pQCT for total and subcutaneous adipose tissue, whereas no significant difference was observed for skeletal muscle adipose tissue. Both pQCT-estimated intramuscular adipose tissue and muscle density were weakly correlated with MRI-intramuscular adipose tissue. We conclude that pQCT is a valid measurement technique for estimating all adipose subcompartments, except for intramuscular adipose tissue, for the midthigh region in young/adolescent girls.

Quantitative analysis of skeletal muscle by computed tomography imaging-State of the art

The radiological assessment of muscle properties-size, mass, density (also termed radiodensity), composition, and adipose tissue infiltration-is fundamental in muscle diseases. More recently, it also became obvious that muscle atrophy, also termed muscle wasting, is caused by or associated with many other diseases or conditions, such as inactivity, malnutrition, chronic obstructive pulmonary disorder, cancer-associated cachexia, diabetes, renal and cardiac failure, and sarcopenia and even potentially with osteoporotic hip fracture. Several techniques have been developed to quantify muscle morphology and function. This review is dedicated to quantitative computed tomography (CT) of skeletal muscle and only includes a brief comparison with magnetic resonance imaging. Strengths and limitations of CT techniques are discussed in detail, including CT scanner calibration, acquisition and reconstruction protocols, and the various quantitative parameters that can be measured with CT, starting from simple volume measures to advanced parameters describing the adipose tissue distribution within muscle. Finally, the use of CT in sarcopenia and cachexia and the relevance of muscle parameters for the assessment of osteoporotic fracture illustrate the application of CT in two emerging areas of medical interest.

[Antioxidant and anti-inflammatory modulation of exercise during aging]

Aging is characterised by a gradual loss of the functional reserve. This, along with the fostering of sedentary habits and the increase in risk factors, causes a deterioration of antioxidant defences and an increase of the circulatory levels of inflammatory and oxidative markers, boosting a low-rate chronic inflammation, defined as inflamm-aging. This phenomenon is present in the aetiopathology of chronic diseases, as well as in cognitive deterioration cases associated with aging. The objective of this review is to describe the modulation of antioxidant and anti-inflammatory effects of physical exercise of moderate intensity and volume in the elderly. Evidence of its effectiveness as a non-pharmacological resource is presented, which decreases some deleterious effects of aging. This is mainly due to its neuroprotective action, the increase in circulating anti-inflammatory markers, and the improvement of antioxidant defence derived from its practice.

Low grip strength predicts incident diabetes among mid-life women: the Michigan Study of Women's Health Across the Nation

Background

skeletal muscle is the primary site of glucose uptake, yet the impact of age-related changes in muscle strength on diabetes risk is unknown.

Methods

four hundred and twenty-four participants (60% Black, 40% White) from the Michigan site of the Study of Women's Health Across the Nation contributed annual grip strength measures and were followed from 1996 to 2012 to identify incident cases of diabetes. Diabetes was defined as self-reported physician-diagnosed diabetes, use of anti-diabetic medications or measured fasting glucose ≥126 mg/dl or haemoglobin A1c > 6.5%.

Results

the 16-year diabetes incidence was 37%. The average baseline weight-normalised grip strength (NGS, kg per kg body weight) was 0.41 ± 0.12 and a mean of 0.29 ± 0.14 kg of absolute grip strength was lost per year. Each 0.1 higher NGS was associated with a 19% lower hazard of incident diabetes (P = 0.006) after adjustment for age, race/ethnicity, economic strain, smoking, menopause status, hormone use, physical activity and waist-hip ratio. In race/ethnic-stratified models, each 0.10 increase in NGS was associated with a 54% lower hazard of incident diabetes (P < 0.0001) among White women but the association among Black women was not statistically significant. In models without adjustment for waist-hip ratio or restricted to women <48 years of age at baseline, there was a statistically significant association between baseline NGS and incident diabetes among Black women. The rate of change in grip strength was not associated with diabetes incidence.

Conclusion

the mid-life is an important risk period for diabetes onset. Improving muscle strength. during mid-life may contribute to preventing diabetes among women.

Inter-tissue expression patterns of the key metabolic biomarker PGC-1α in severely obese individuals: Implication in obesity-induced disease

OBJECTIVE

PGC-1α is already known as a significant regulator of mitochondrial biogenesis, oxidative phosphorylation and fatty acid metabolism. Our study focuses on the role of PGC1α in morbid obesity, in five different tissues, collected from 50 severely obese patients during planned bariatric surgery.

METHODS

The investigated tissues included subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), skeletal muscle (SM), extramyocellular adipose tissue (EMAT) and liver. PGC1α expression was investigated with immunohistochemistry and evaluated with microscopy.

RESULTS

Our findings highlighted significant positive inter-tissue correlations regarding PGC-1α expression between several tissue pairs (VAT-SAT, VAT-SM, VAT-EMAT, SAT-SM, SAT-EMAT, SM-EMAT). Moreover, we found significant negative correlations between PGC1α expression in VAT with CD68 expression in skeletal muscle and EMAT, implying a possible protective role of PGC1α against obesity-induced inflammation.

CONCLUSION

Unmasking the inter-tissue communication networks regarding PGC-1α expression in morbid obesity, will give more insight into its significant role in obesity-induced diseases. PGC1α could potentially represent a future preventive and therapeutic target against obesity-induced disease, probably through enhancing mitochondrial biogenesis and metabolism.