Relationship between trunk intramuscular adipose tissue content and prevalence of metabolic syndrome in middle-aged Japanese men.

OBJECTIVES: The aim of the present study was to examine the dose-response relationship between trunk tissue composition and prevalence of metabolic syndrome (MetS) in middle-aged Japanese men. METHODS: The 1026 men (between 35 and 59 y of age) who participated in the present study were divided into two groups: those with metabolic syndrome (MetS) and those without (non-MetS). Intramuscular adipose tissue (IntraMAT) content and the cross-sectional areas (CSAs) of visceral adipose tissue and skeletal muscle tissue were calculated using low-dose computed tomography images acquired at the level of the third lumbar vertebra. Height, body mass, body fat, waist circumference, the presence of MetS, and lifestyle habits were also assessed. RESULTS: IntraMAT content was significantly higher in MetS than in non-MetS men. A 10% increase in IntraMAT content correlated with the prevalence of MetS (odds ratio, 4.197; 95% confidence interval, 3.108-7.088; P < 0.001), even after adjustments for age, height, adjusted skeletal muscle CSA, sleeping time, alcohol consumption, exercise habit, and cigarette smoking. Skeletal muscle CSA did not correlate with the prevalence of MetS after adjustments for IntraMAT content and other cofactors. CONCLUSIONS: Increase in IntraMAT content, not in skeletal muscle CSA, significantly correlated with the prevalence of MetS. These results suggest that countermeasures against the accumulation of trunk IntraMAT effectively prevent MetS in middle-aged Japanese men.

Factors related to trunk intramuscular adipose tissue content - A comparison of younger and older men.

The present study investigated factors related to trunk intramuscular adipose tissue (IntraMAT) content in younger and older men. Twenty-three healthy younger (20 to 29 years) and 20 healthy older men (63 to 79 years) participated in this study. The trunk IntraMAT content was measured using magnetic resonance imaging at the height of the 3rd lumbar vertebra. In addition to blood properties and physical performance, dietary intake was assessed by a self-administered diet history questionnaire. The dietary intake status was quantified using the nutrient adequacy score for the intake of 10 selected nutrients by summing the number of items that met the criteria of dietary reference intakes for Japanese individuals. The results obtained revealed that the trunk IntraMAT content was significantly higher in the older group than in the younger group (p < 0.05). In the younger group, the trunk IntraMAT content significantly correlated with systolic and diastolic blood pressure and HbA1c (rs = 0.443 to 0.464, p < 0.05). In the older group, significant and negative correlations were observed between the trunk IntraMAT content and 5-m usual walking speed, handgrip strength, and nutrient adequacy scores (rs = -0.485 to -0.713, p < 0.05). These results indicate that factors associated with the trunk IntraMAT content differed in an age dependent manner. In the younger group, the trunk IntraMAT content correlated with the metabolic status such as blood pressure and HbA1c. In the older group, physical performance and the dietary intake status negatively correlated with the trunk IntraMAT content.

Comparison of metabolic risk factors, physical performances, and prevalence of low back pain among categories determined by visceral adipose tissue and trunk skeletal muscle mass in middle-aged men.

The present study compared metabolic risk factors, physical performances, and musculoskeletal impairment among categories determined by visceral adipose tissue (VAT) and trunk skeletal muscle (SM) mass in middle-aged Japanese men. In total, 1026 healthy Japanese males aged between 35 and 59 years were categorized into 4 groups according to the amount of VAT and SM in the trunk measured using low-dose computed tomography (LowVAT-HighSM, LowVAT-LowSM, HighVAT-HighSM, and HighVAT-LowSM). Height, body mass waist circumference, body fat, intramuscular adipose tissue (IntraMAT), subcutaneous adipose tissue, biochemical blood profiles (triglycerides, high-density lipoprotein cholesterol, fasting blood glucose, aspartate transaminase, alanine transaminase and γ-glutamyl trans peptidase), physical performances (trunk flexibility, the chair-stand test, two-step length and hand-grip strength), the prevalence of low back pain, and lifestyle habits for exercise, alcohol intake and smoking, were compared among the groups. The results showed that LowVAT-HighSM had significantly superior biochemical blood profiles and physical performances to the other groups. HighVAT-LowSM had significantly higher %IntraMAT and the prevalence of low back pain. The two-step length, which is an index of walking ability, significantly differed according to the four subject categories. These results indicate that metabolic risk factors, physical performances, and prevalence of low back pain in middle-aged Japanese men may differ among four categories determined by VAT and trunk SM.

Validity of Extended-Field-of-View Ultrasound Imaging to Evaluate Quantity and Quality of Trunk Skeletal Muscles.

This study examined the validity of extended-field-of-view (EFOV) ultrasound imaging for evaluating the quantity (cross-sectional area [CSA]) and quality (accumulation of intramuscular fat) of trunk skeletal muscles (rectus abdominis, abdominal oblique and erector spinae) using magnetic resonance imaging (MRI) as a reference. Thirty healthy young men participated in this study. Cross-sectional images of the trunk at the height of the third lumbar vertebra were acquired and compared by EFOV ultrasound imaging and MRI. No significant differences were observed in CSAs between the two methods (0.74 ≤ R2 ≤ 0.85). Echo intensities significantly correlated with MRI-derived accumulation of intramuscular fat in each skeletal muscle group. However, the correlation coefficients were relatively low (0.37 ≤ r ≤0.47; p < 0.05). These results indicate that EFOV ultrasound imaging is a reliable method for assessing trunk skeletal muscle CSA. Further research is warranted to find the optimal ultrasound setting for evaluating muscle quality.

Quadriceps echo intensity can be an index of muscle size regardless of age in 65 or more years old.

Although age-related deterioration of skeletal muscle strength and size has gained much attention, the age-related increase in adipose tissue within skeletal muscle has not received the same level of attention, especially in older individuals. It is not well known how echo intensity (EI), which is an index of intramuscular adipose tissue (IntraMAT) and connective tissue, is associated with demographic, functional, and morphological characteristics in older individuals. The purpose of this study was to assess the relationships between the EI of the quadriceps femoris (QF) and demographic, functional, and morphological characteristics in pre-old (65-74 years) and old (75 years or older) individuals. One hundred thirty-two men and women aged 65 to 74 years (45 men and 51 women; Pre-old group) or 75 years and older (17 men and 19 women, Old group) participated in this study. The EI and muscle thickness (MT) of the QF were measured using B-mode ultrasonography. Sit-up, supine-up, sit-to-stand, 5-m maximal walk, and 6-min walk tests were performed. The EI of the QF in the Old group (73.1 ± 9.0 a.u.) was significantly higher than that in the Pre-old group (67.6 ± 9.1 a.u.). The EI of the QF was significantly correlated with the MT of the QF in both the Pre-old (r = -0.542, P < 0.01) and Old (r = -0.622, P < 0.01) groups. Stepwise multiple linear regression analysis with the EI of the QF as a dependent variable showed that the MT of the QF was a significant variable in both the Pre-old and Old groups. These results suggest that MT is an extremely valuable factor for explaining the EI of the QF regardless of age group. Exercise interventions are recommended to decrease the risks of metabolic impairment by increasing muscle size and decreasing IntraMAT in individuals aged 65 years or older.

Effects of 1-year weight loss intervention on abdominal skeletal muscle mass in Japanese overweight men and women.

BACKGROUND AND OBJECTIVES: Limited information is available on how weight loss intervention programs affect skeletal muscle mass especially in trunk. METHODS AND STUDY DESIGN: A total of 235 overweight Japanese men and women aged 40-64 years with a body mass index of 28.0 to 44.8 kg/m2 participated in this randomized controlled intervention study. They were randomly divided into a lifestyle intervention group and control group. Before and after the one-year lifestyle intervention for weight loss an abdominal transverse image was acquired by computed tomography. The cross-sectional areas (CSAs) of visceral fat, subcutaneous fat, and skeletal muscle of rectus abdominis, abdominal oblique, iliopsoas, and erector spinae muscle were calculated. RESULTS: The body weight changed by approximately -5% in the intervention groups. The corresponding values for subcutaneous fat and visceral fat CSAs were -10.8 to -17.5% in both sexes. The reductions observed in skeletal muscle CSAs were significantly less (-6.0% and -7.2% in the men and women intervention groups respectively) than those in fat tissue CSAs. The CSA of each of the four skeletal muscle groups also significantly decreased; however, after adjustments for body weight at each time point, only reductions in the iliopsoas muscle in both sex and abdominal oblique muscles in men remained significant. CONCLUSIONS: The lifestyle weight loss intervention might reduce the relative amount of the abdominal skeletal muscles especially in iliopsoas muscle.

Effects of 10-week walking and walking with home-based resistance training on muscle quality, muscle size, and physical functional tests in healthy older individuals.

BACKGROUND: Older individuals have been shown to present muscle atrophy in conjunction with increased fat fraction in some muscles. The proportion of fat and connective tissue within the skeletal muscle can be estimated from axial B-mode ultrasound images using echo intensity (EI). EI was used to calculate the index of muscle quality. Walking, home-based weight-bearing resistance training, and its combinations are considered simple, easy, and practical exercise interventions for older adults. The purpose of this study was to quantify the effects of walking and walking with home-based resistance training on muscle quality of older individuals. METHODS: Thirty-one participants performed walking training only (W-group; 72 ± 5 years) and 33 participants performed walking and home-based resistance training (WR-group; 73 ± 6 years). This study was a non-randomized controlled trial with no control group. All participants were instructed to walk 2 or 3 sets per week for 10 weeks (one set: 30-min continuous walking). In addition, the WR-group performed home-based weight-bearing resistance training. EI was measured as a muscle quality index using axial B-mode ultrasound images of the rectus femoris and vastus lateralis of the mid-thigh. We further averaged these parameters to obtain the EI of the quadriceps femoris (QF). Participants further performed five functional tests: sit-ups, supine up, sit-to-stand, 5-m maximal walk, and 6-min walk. RESULTS: QF EI was significantly decreased in both groups after training (W-group 69.9 ± 7.4 a.u. to 61.7 ± 7.0 a.u., WR-group 64.0 ± 9.5 a.u. to 51.1 ± 10.0 a.u.; P < 0.05), suggesting improved muscle quality. QF EI was further decreased in the WR-group compared with the W-group. The sit-up test in both groups and the sit-to-stand and 5-m maximal walk tests in the W-group were significantly improved after training. CONCLUSION: These results suggest that training-induced stimulation is associated with a decrease in EI in some thigh regions. Furthermore, the addition of home-based resistance training to walking would be effective for a greater reduction of EI.

Association of visceral fat area with abdominal skeletal muscle distribution in overweight Japanese adults.

BACKGROUND: Quantitative evaluation of visceral fat mass and skeletal muscle mass is important for health promotion. Recently, some studies suggested the existence of adipocyte-myocyte negative crosstalk. If so, abdominal skeletal muscles may easily and negatively affected not only by the age but also the visceral fat because age-related reduction in abdominal region is greater compared with limbs. OBJECTIVE: We cross-sectionally examined the existence of quantitative associations between visceral fat area and abdominal skeletal muscle distribution in overweight people. METHODS: A total of 230 Japanese males and females who aged 40-64 years and whose body mass index (BMI) was 28.0-44.8kg/m2 participated in this study. The cross-sectional area (CSA) of the visceral fat, subcutaneous fat, and abdominal skeletal muscles, namely, the rectus abdominis, abdominal oblique, erector spinae, and iliopsoas muscles were measured by the computed tomography images. RESULTS: Stepwise regression analyses revealed the existence of sex difference in the relation between visceral fat CSA and other morphological variables. In males, BMI was a positive, and the iliopsoas muscle group CSA was a negative contributor of the visceral fat CSA. In females, both age and BMI were selected as positive contributors. CONCLUSION: These data suggested that the visceral fat CSA may negatively associated with iliopsoas muscle group CSA in males. In females, the visceral fat CSA was not significantly related to the distribution of the abdominal skeletal muscle groups.

Reliability of size and echo intensity of abdominal skeletal muscles using extended field-of-view ultrasound imaging.

PURPOSE: This study aimed to examine the reliability of extended field-of-view (EFOV) ultrasound imaging to evaluate the cross-sectional area (CSA) and echo intensity of abdominal skeletal muscles. METHODS: Twenty-seven healthy young males (age 18.6 ± 1.0 years, body mass index 20.9 ± 2.8 kg/m2, waist circumference 75.0 ± 7.9 cm, body fat 16.6 ± 5.9%) visited the laboratory on 2 days. EFOV ultrasound images of the rectus abdominis, abdominal oblique, and erector spinae muscles were acquired at the height of the third lumbar vertebra with the subject lying on a bed. We then analyzed CSA and echo intensity using ImageJ software and calculated intra-class correlation coefficients (ICC) and the standard error of measurement (SEM). RESULTS: No significant differences (p = 0.149-0.679) were observed in CSA or echo intensity values for each skeletal muscle between days. ICC and SEM values in CSA for each skeletal muscle ranged between 0.944 and 0.958 and 4.9% and 7.3%, respectively. The corresponding values for echo intensity were 0.851-0.945 for ICC and 5.3-9.7% for SEM. CONCLUSIONS: The present results indicate that EFOV ultrasound imaging has high repeatability for measuring CSA and echo intensity of abdominal skeletal muscle groups in healthy college-aged males.

Relationship between quadriceps echo intensity and functional and morphological characteristics in older men and women.

The age-related decrease in human skeletal muscle mass; i.e. sarcopenia, has received much attention, but an age-related increase in the ratio of adipose tissue to muscle tissue has received noticeably less. A few studies have shown that ultrasonographic echo intensity, an index of the adipose-to-muscle ratio, is negatively associated with functional capacity, but the best parameters by which to predict this ratio have not yet been established for older individuals. The purpose of this study was to assess the relationships between quadriceps femoris (QF) echo intensity and demographic, functional and morphological characteristics of older men and women. Sixty-four healthy men (n=27) and women (n=37) aged 62-88 years (72.0±5.0years) participated in this study. The echo intensity and muscle thickness of the QF were calculated using ultrasonography. Sit-up, supine-up, sit-to-stand, 5-m maximal walk and 6-min walk tests were performed. There were no significant differences in QF echo intensity between sexes, but QF echo intensity was significantly correlated with QF muscle thickness. Stepwise multiple regression analysis with QF echo intensity as a dependent variable revealed QF muscle thickness, sit-to-stand test in men and age, and QF muscle thickness and sit-to-stand test in women, to be significant variables. These results suggest that QF echo intensity can be explained by QF muscle thickness, sit-to-stand and/or age in older men and women; however, an "age" effect was present only in men.

Accuracy of segmental bioelectrical impedance analysis for predicting body composition in pre- and postmenopausal women.

This study aimed to compare the accuracy for predicting body composition using single-frequent segmental bioelectrical impedance analysis (BIA) between pre- and postmenopausal women. A total f 559 Japanese women aged 30-88yr were divided into 4 groups by questionnaire: natural menopause, pathological menopause, regular menstruation, or irregular menstruation. The measurement values by dual-energy X-ray absorptiometry were used as a reference of the body composition. In terms of the results, regardless of the menopausal status, BIA slightly but significantly overestimated the percentage of body fat (standard error of estimate: 5.3%-6.7%) and the leg lean soft tissue mass (LSTM; 5.1%-6.1%), and underestimated the LSTM in the whole body (6.2%-7.6%) and arm (2.8%-3.7%). The absolute values of the predictive error for leg LSTM were significantly higher in postmenopausal groups than in the premenopausal ones. The corresponding values for the whole body and arm LSTM, and the percentage of body fat were higher in premenopausal groups than in postmenopausal ones. In conclusion, the predictive accuracy of BIA for postmenopausal women is not inferior to that for premenopausal ones, unless we target the leg LSTM.

Variability of limb muscle size in young men.

The purpose of this study was to determine the interindividual variability of the upper and lower limb muscle size in young men. Subjects were 655 Japanese men aged 18-39 years. They were sedentary and mildly to highly active individuals, including college athletes of various sports. Muscle thicknesses at each of the anterior and posterior portions of the upper arm, thigh, and lower leg were measured using B-mode ultrasonography. Interindividual variability of muscle thickness was evaluated by coefficients of variation (CVs). The CVs of muscle thicknesses were found to be in the order of upper arm posterior (17.7%), thigh anterior (14.8%), thigh posterior (12.6%), upper arm anterior (12.2%), lower leg anterior (9.8%), and lower leg posterior (9.4%). The CVs were significantly different between each pair of measurement sites except for those of upper arm anterior-thigh posterior and lower leg anterior-posterior. These differences remain significant even when the muscle thicknesses were normalized to the segment length. The observed differences in the size variability can be interpreted as muscle-related differences in hypertrophic responsiveness to resistance training. The muscle-dependent size variability may be related to the differences in the fiber-type composition and/or muscle usage in daily life among examined muscle groups.

Difference in abdominal muscularity at the umbilicus level between young and middle-aged men.

This study aimed to examine how the muscularity of the abdomen at the umbilicus level differs between sedentary middle-aged and young men. Magnetic resonance imaging was applied to determine the cross-sectional areas of skeletal muscle, subcutaneous fat, and interperitoneal tissue in 43 middle-aged (40 58yrs) and 38 young (21-29 yrs) men. The cross-sectional area of the skeletal muscle was analyzed as the sum of those of the rectus abdominis, abdominal oblique, lower back, and iliopsoas skeletal muscle groups. The middle-aged men showed greater waist circumference and whole abdominal cross-sectional area than the young men. In addition, the cross-sectional areas of subcutaneous fat and interperitoneal tissue were greater in the middle-aged men than in the young men. However, the total cross-sectional area of the skeletal muscle was similar between the two groups, although its percentage to the whole abdominal cross-sectional area was higher in the young men compared to the middle-aged men. Among the four skeletal muscle groups analyzed, the percentage of the cross-sectional areas in abdominal oblique muscles to that of total skeletal muscle was higher in the middle-aged men than in the young men and that of the lower back muscles was the reverse. These results were similar even when cross-sectional area data were analyzed using a subsample (33 middle-aged and 23 young men) matched for body height and mass. Thus, the present study indicated that the total muscularity of the abdomen at the umbilicus level was similar between the middle-aged and young men, but the relative distributions of lower back and abdominal oblique muscles varied between the two generations.

Applicability of a segmental bioelectrical impedance analysis for predicting the whole body skeletal muscle volume.

This study aimed to test the hypothesis that a segmental bioelectrical impedance (BI) analysis can predict whole body skeletal muscle (SM) volume more accurately than a whole body BI analysis. Thirty males (19-34 yr) participated in this study. They were divided into validation (n = 20) and cross-validation groups (n = 10). The BI values were obtained using two methods: whole body BI analysis, which determines impedance between the wrist and ankle; and segmental BI analysis, which determines the impedance of every body segment in both sides of the upper arm, lower arm, upper leg and lower leg, and five parts of the trunk. Using a magnetic resonance imaging method, whole body SM volume was determined as a reference (SMV(MRI)). Simple and multiple regression analyses were applied to (length)(2)/Z (BI index) for the whole body and for every body segment, respectively, to develop the prediction equations of SMV(MRI). In the validation group, there were no significant differences between the measured and estimated SMV and no systematic errors in either BI analysis. In the cross-validation group, the whole body BI analysis produced systematic errors and resulted in the overestimation of SMV(MRI), but the segmental BI analysis was cross-validated. In the pooled data, the segmental BI analysis produced a prediction equation, which involves the BI indexes of the trunk and upper thigh as independent variables, with a SE of estimation of 1,693.8 cm(3) (6.1%). Thus the findings obtained here indicated that the segmental BI analysis is superior to the whole body BI analysis for estimating SMV(MRI).