Biomedical subjects

Stanley Heshka

Publications and source records attributed to Stanley Heshka.

At least 19 recordsLinked to original sources

PubMed2006

Estimating whole body intermuscular adipose tissue from single cross-sectional magnetic resonance images.

Intermuscular adipose tissue (IMAT), a novel fat depot linked with metabolic abnormalities, has been measured by whole body MRI. The cross-sectional slice location with the strongest relation to total body IMAT volume has not been established. The aim was to determine the predictive value of each slice location and which slice locations provide the best estimates of whole body IMAT. MRI quantified total adipose tissue of which IMAT, defined as adipose tissue visible within the boundary of the muscle fascia, is a subcomponent. Single-slice IMAT areas were calculated for the calf, thigh, buttock, waist, shoulders, upper arm, and forearm locations in a sample of healthy adult women, African-American [n = 39; body mass index (BMI) 28.5 +/- 5.4 kg/m2; 41.8 +/- 14.8 yr], Asian (n = 21; BMI 21.6 +/- 3.2 kg/m2; 40.9 +/- 16.3 yr), and Caucasian (n = 43; BMI 25.6 +/- 5.3 kg/m2; 43.2 +/- 15.3 yr), and Caucasian men (n = 39; BMI 27.1 +/- 3.8 kg/m2; 45.2 +/- 14.6 yr) and used to estimate total IMAT groups using multiple-regression equations. Midthigh was the best, or near best, single predictor in all groups with adjusted R2 ranging from 0.49 to 0.84. Adding a second and third slice further increased R2 and reduced the error of the estimate. Menopausal status and degree of obesity did not affect the location of the best single slice. The contributions of other slice locations varied by sex and race, but additional slices improved predictions. For group studies, it may be more cost-effective to estimate IMAT based on one or more slices than to acquire and segment for each subject the numerous images necessary to quantify whole body IMAT.

Adipose Tissue↗

PubMed2006

Metabolically active portion of fat-free mass: a cellular body composition level modeling analysis.

The proportion of fat-free mass (FFM) as body cell mass (BCM) is highly related to whole body resting energy expenditure. However, the magnitude of BCM/FFM may have been underestimated in previous studies. This is because Moore's equation [BCM (kg) = 0.00833 x total body potassium (in mmol)], which was used to predict BCM, underestimates BCM by approximately 11%. The aims of the present study were to develop a theoretical BCM/FFM model at the cellular level and to explore the influences of sex, age, and adiposity on the BCM/FFM. Subjects were 112 adults who had the following measurements: total body water by (2)H(2)O or (3)H(2)O dilution; extracellular water by NaBr dilution; total body nitrogen by in vivo neutron activation analysis; and bone mineral by dual-energy X-ray absorptiometry. FFM was calculated using a multicomponent model and BCM as the difference between FFM and the sum of extracellular fluid and solids. The developed theoretical model revealed that the proportion of BCM to FFM is mainly determined by water distribution (i.e., E/I, the ratio of extracellular to intracellular water). A significant correlation (r = 0.90, P < 0.001) was present between measured and model-predicted BCM/FFM for all subjects pooled. Measured BCM/FFM [mean (SD)] was 0.584 +/- 0.041 and 0.529 +/- 0.041 for adult men and women (P < 0.001), respectively. A multiple linear regression model showed that there are independent significant associations of sex, age, and fat mass with BCM/FFM.

Adult↗

PubMed2006

Serum iron and body fat distribution in a multiethnic cohort of adults living in New York City.

OBJECTIVE: To examine the relationship between serum iron and body composition in a multiracial adult cohort. METHODS: The analysis consisted of 670 participants on whom blood analysis and anthropometric data were available. The participants were recruited as part of the Rosetta Study (1990-2000), which was designed to assess body composition in a multiethnic cohort of healthy adults. Fasting iron level was measured as part of a biochemistry panel. Dual x-ray absorptiometry was used to assess fat mass. Anthropometric measures included waist circumference and body mass index (BMI; calculated as kg/m(2)) as an index of abdominal adiposity and overall body fatness, respectively. RESULTS: In the study cohort the mean age was 54+/-17 years and 60.9% were overweight or obese (BMI > or =25). Men had higher serum iron levels (94.91+/-34.52 microg/dL [16.99+/-6.18 micromol/L] vs 82.17+/-32.62 microg/dL [14.71+/-5.84 micromol/L]) and larger waist circumference (91.98+/-11.87 cm vs 85.24+/-12.37 cm) compared with women (P<0.001). Iron was inversely correlated with BMI (r=-0.23, P<0.001), waist circumference (r=-0.19, P<0.05), and fat mass (r=-0.19, P<0.05) among Hispanic women but not among African-American, white, or Asian women or in men of any race/ethnic group. CONCLUSIONS: The results of this study show an inverse association of measures of body fat distribution and total fat mass with serum iron level in Hispanic women. Studies designed to explore how micronutrients are used by the body at varying degrees of body fatness could provide useful information on the micronutrient-related comorbidities of obesity.

Abdominal Fat↗

PubMed2006

Waist circumference correlates with metabolic syndrome indicators better than percentage fat.

OBJECTIVE: Percent fat is often considered the reference for establishing the magnitude of adipose tissue accumulation and the risk of excess adiposity. However, the increasing recognition of a strong link between central adiposity and metabolic disturbances led us to test whether waist circumference (WC) is more highly correlated with metabolic syndrome components than percent fat and other related anthropometric measures such as BMI. RESEARCH METHODS AND PROCEDURES: BMI, WC, and percent fat, measured by DXA, were evaluated in 1010 healthy white and African-American men and women [age, 48.3 +/- 17.2 (standard deviation) years; BMI, 27.0 +/- 5.3 kg/m(2)]. The associations of BMI, WC, and percent fat with age and laboratory-adjusted health risk indicators (i.e., serum glucose, insulin, triglycerides, high-density lipoprotein cholesterol, blood pressure) in each sex and ethnicity group were examined. RESULTS: For 18 of 24 comparisons, the age- and laboratory-adjusted correlations were lowest for percent fat and in 16 of 24 comparisons were highest for WC. Fifteen of the between-method differences reached statistical significance. With health risk indicator as the dependent variable and anthropometric measures as the independent variable, the contribution of percent fat to the WC regression model was not statistically significant; in contrast, adding WC to the percent fat regression model did make a significant independent contribution for most health risk indicators. DISCUSSION: WC had the strongest associations with health risk indicators, followed by BMI. Although percent fat is a useful measure of overall adiposity, health risks are best represented by the simply measured WC.

Adiposity↗

PubMed2006

Serum magnesium and type-2 diabetes in African Americans and Hispanics: a New York cohort.

OBJECTIVES: The aim of this study was to examine the relationship of serum Mg with stage of diabetes measured by fasting serum glucose in a cohort of 485 African American and Hispanic adults. METHODS: The cross sectional Rosetta study was designed to assess body composition in a multi-racial cohort of healthy adults living in New York City. The data utilized for the current analyses were collected during the years 1990 to 2000. Serum Mg and glucose were measured after a 10-12 hour fast. Dual-energy x-ray absorptiometry was used to measure fat mass (FM) and fat free mass (FFM). RESULTS: The mean age of the cohort was 53 +/- 16 years. Hispanics had significantly lower (p < 0.05) mean serum Mg levels (0.82 +/- 0.07 mmol/L vs. 0.85 +/- 0.07 mmol/L) and FFM (48.8 +/- 10.9 kg vs. 50.9 +/- 10.3 kg) compared to African Americans. In both race/ethnic groups, individuals classified as having diabetes had significantly (p < 0.001) lower serum concentrations of Mg (0.80 +/- 0.07 mmol/L) compared to the normal group (0.84 +/- 0.07 mmol/L). CONCLUSIONS: These results show that in African American and Hispanic adults, those with diabetes have lower serum Mg levels compared to those classified as pre-diabetic or those with normal fasting glucose levels.

Adipose Tissue↗

PubMed2006

Small organs with a high metabolic rate explain lower resting energy expenditure in African American than in white adults.

BACKGROUND: African Americans have a lower resting energy expenditure (REE) relative to fat-free mass (FFM) than do whites. Whether the composition of FFM at the organ-tissue level differs between African Americans and whites and, if so, whether that difference could account for differences by race in REE are unknown. OBJECTIVE: The objectives were to quantify FFM in vivo in women and men at the organ-tissue level and to ascertain whether the mass of specific high-metabolic-rate organs and tissues differs between African Americans and whites and, if so, whether that difference can account for differences in REE. DESIGN: The study was a cross-sectional evaluation of 64 women (n = 34 African Americans, 30 whites) and 35 men (n = 8 African Americans, 27 whites). Magnetic resonance imaging measures of liver, kidney, heart, spleen, brain, skeletal muscle, and adipose tissue and dual-energy X-ray absorptiometry measures of fat and FFM were acquired. REE was measured by using indirect calorimetry. RESULTS: The mass of selected high-metabolic-rate organs (sum of liver, heart, spleen, kidneys, and brain) after adjustment for fat, FFM, sex, and age was significantly (P < 0.001) smaller in African Americans than in whites (3.1 and 3.4 kg, respectively; x +/- SEE difference: 0.30 +/- 0.06 kg). In a multiple regression analysis with fat, FFM, sex, age, and race as predictors of REE, the addition of the total mass rendered race nonsignificant. CONCLUSIONS: Racial differences in REE were reduced by >50% and were no longer significant when the mass of specific high-metabolic-rate organs was considered. Differences in FFM composition may be responsible for the reported REE differences.

Absorptiometry, Photon↗

PubMed2006

Total-body skeletal muscle mass: estimation by dual-energy X-ray absorptiometry in children and adolescents.

BACKGROUND: Skeletal muscle (SM) is an important compartment but is difficult to quantify in children and adolescents. OBJECTIVE: We investigated the potential of dual-energy X-ray absorptiometry (DXA) for measuring total-body SM in pediatric subjects. DESIGN: A previously published adult DXA SM prediction formula was evaluated in children and adolescents aged 5-17 y (n = 99) who varied in pubertal maturation stage. SM estimated by whole-body magnetic resonance imaging (MRI) was used as the reference. The adult SM model was not accurate for subjects below Tanner stage 5 (n = 65; aged 5-14 y). New pediatric SM prediction models were therefore developed and validated in a separate group (n = 18). RESULTS: The adult DXA SM prediction model was valid in subjects at Tanner stage 5 but significantly (P < 0.001) overestimated SM in subjects below Tanner stage 5. New SM prediction formulas were developed with appendicular lean soft tissue (ALST) estimates by DXA as the main predictor variable (eg, model 1, ALST alone: R(2) = 0.982, SEE = 0.565 kg, P < 0.001). The new models were validated by the leave-one-out method and were cross-validated in a separate validation group. CONCLUSIONS: A previously reported adult DXA SM prediction model is applicable in children and adolescents late in pubertal development (Tanner stage 5). A new DXA SM prediction model was developed for prepubertal and pubertal subjects (Tanner stage </=4) aged >/=5 y. DXA thus provides an important opportunity for quantifying total-body SM mass across most of the human life span.

Absorptiometry, Photon↗

PubMed2006

Total body protein mass: validation of total body potassium prediction model in children and adolescents.

Protein is an important body component for monitoring growth, development, and nutritional status. We previously developed a total body potassium (TBK, in mmol) and bone mineral (Mo, in kg) model for predicting total body protein (TBPro, in kg) in adults (TBPro = 0.00252 x TBK + 0.732 x Mo). However, the applicability of the TBK-Mo model for children is unknown. The study aims were to develop a TBK-independent 6-component (6-C) TBPro approach as the criterion, and then to validate the TBK-Mo model in children. The following measurements were made in adolescents and children (n = 62, 38 boys and 24 girls, aged 5-17 y): body weight (BW, in kg), body volume (BV, in liters) by air displacement plethysmography, total body water (TBW, in kg) by 2H2O dilution, Mo by dual-energy X-ray absorptiometry, and TBK by whole-body counting. A 6-C model was derived as TBPro = 2.922 x BW - 0.301 x TBW - 2.039 x Mo - 2.632 x BV. The TBPro estimates did not differ between the 6-C and TBK-Mo models (mean +/- SD, 0.20 +/- 0.86 kg). There was a significant correlation between TBPro by the 6-C and TBK-Mo models (r = 0.94, P < 0.001). Bland-Altman analysis indicated that the differences between TBPro by 6-C and TBK-Mo models were not significantly correlated with the mean TBPro estimates by the 2 models (r = 0.032, P > 0.05). The TBK-Mo model can thus be used to estimate TBPro in healthy adults, adolescents, and children > 5 y old.

Absorptiometry, Photon↗

PubMed2005

Excessive weight gain in cardiac transplant recipients.

BACKGROUND: Substantial weight gain frequently occurs after cardiac transplant (CT) and increases the risk of secondary disease. It is unclear, however, if weight gain after CT is related to glucocorticoid immunosuppressive therapy. METHODS: A retrospective chart review was performed on the first 200 patients undergoing CT and the first 200 patients undergoing renal transplant (RT) at Columbia Presbyterian Medical Center, starting in January 2000. Patients who survived 1 year and had their weight recorded at transplant were included in the study. Rejection episodes and prednisone treatment was recorded for CT patients. Regression analysis was used to determine predictors of weight gain. RESULTS: A total of 158 CT patients and 128 RT patients were included in the data analysis. The weight of CT patients at time of transplant was (mean +/- SD) 76.3 +/- 14.6 kg and increased by 10.3 +/- 10.6 kg (p < 0.05) by 1-year post-transplant. Pre-transplant weight of the RT patients was 74.1 +/- 20.1 kg; by 1-year post-RT, weight increased by 3.5 +/- 8.6 kg (p < 0.05). The weight gain in CT patients was significantly greater than in the RT patients (p < 0.001). Post-transplant weight change in multiple regression models was related to age, gender (male) and transplant type (cardiac), but not to prednisone dose or pre-transplant weight. CONCLUSIONS: CT results in substantial post-surgical weight gain, which is greater than that observed for RT. Overweight and obesity development was not related to prednisone dose alone. This observation may have important clinical and research implications.

Adult↗

PubMed2005

Extracellular water: greater expansion with age in African Americans.

Aging is associated with the onset of chronic diseases that lead to pathological expansion of the extracellular water (ECW) compartment. Healthy aging, in the absence of disease, is also reportedly accompanied by a relative expansion of the ECW compartment, although the studies on which this observation is based are few in number, applied different ECW measurement methods, included small ethnically homogeneous subject samples, and failed to adjust ECW for non-age-related influencing factors. The aim of the current study was to examine, in a large (n = 1,538) ethnically diverse [African American (AA), Asian, Caucasian, Hispanic] subject group the cross-sectional relationships between ECW and age after controlling first for other potential factors that may influence fluid distribution. ECW and intracellular water (ICW) were derived from measured total body water (isotope dilution) and potassium (40K whole body counting). The cross-sectional relationships between ECW, ICW, and ECW/ICW (E/I), and age were developed using multiple regression modelling methods. Body weight, weight squared, height, age, sex, race, and interactions were all significant ECW predictors. The slope of the observed race x age interaction was significantly greater in AA (beta = 0.0005, P = 0.005) than in the three other race groups. Race, sex, and age differences in fluid distribution persisted after adjusting for body composition in a subgroup (n = 994) with dual-energy X-ray absorptiometry lean soft tissue and fat measurements. A relative ECW expansion (i.e., E/I) was present with greater age in most sex-race groups, although the effect was not significantly larger in AA males (P > 0.05) compared with the other race groups, except Asians (P < 0.05). For females, a larger E/I-age effect was found in AA compared with the other race groups, but only the comparison against Hispanics was significant (P < 0.05). The ECW compartment and E/I are thus variably larger, according to race, in healthy older subjects independent of sex, lean soft tissue, and fat mass.

Black or African American↗

PubMed2005

Air displacement plethysmography: validation in overweight and obese subjects.

OBJECTIVE: Patients with moderate and severe obesity, because of their physical size, often cannot be evaluated with conventional body composition measurement systems. The BOD POD air displacement plethysmography (ADP) system can accommodate a large body volume and may provide an opportunity for measuring body density (D(b)) in obese subjects. D(b) can be used in two- or three-compartment body composition models for estimating total body fat in patients with severe obesity. The purpose of this study was to compare D(b) measured by ADP to D(b) measured by underwater weighing (UWW) in subjects ranging from normal weight to severely obese. RESEARCH METHODS AND PROCEDURES: D(b) was measured with UWW and BOD POD in 123 subjects (89 men and 34 women; age, 46.5 +/- 16.9 years; BMI, 31.5 +/- 7.3 kg/m2); 15, 70, and 10 subjects were overweight (25 < or = BMI < 30 kg/m2), obese (30 < or = BMI < 40 kg/m2), and severely obese (BMI > or = 40 kg/m2), respectively. RESULTS: There was a strong correlation between D(b) (kilograms per liter) measured by UWW and ADP (r = 0.94, standard error of the estimate = 0.0073 kg/L, p < 0.001). Similarly, percent fat estimates from UWW and ADP using the two-compartment Siri equation were highly correlated (r = 0.94, standard error of the estimate = 3.58%, p < 0.001). Bland-Altman analysis showed no significant bias between D(b) measured by UWW and ADP. After controlling for D(b) measured by ADP, no additional between-subject variation in D(b) by UWW was accounted for by subject age, sex, or BMI. DISCUSSION: Body density, an important physical property used in human body composition models, can be accurately measured by ADP in overweight and obese subjects.

Adipose Tissue↗

PubMed2005

Four-compartment cellular level body composition model: comparison of two approaches.

OBJECTIVE: The aim of this study was to develop and compare two DXA-based four-compartment [body weight=body cell mass (BCM)+extracellular fluid (ECF)+extracellular solids (ECS)+fat] cellular level models. RESEARCH METHODS AND PROCEDURES: Total body potassium (TBK) model: BCM from TBK by whole-body counting-ECF(TBK)=LST-[BCM(TBK)+0.73 x osseous mineral (Mo)]. Bromide model: ECF from sodium bromide dilution-BCM(BROMIDE)=LST-(ECF(BROMIDE)+0.73xMo); Mo and LST measurements came from DXA. The two approaches were evaluated in 99 healthy men and 118 women. RESULTS: BCM estimates were highly correlated (r=0.97, p<0.001), as were ECF estimates (r=0.87, p<0.001); a small statistically significant mean difference was present (mean+/-SD; BCM(TBK) model, 30.4+/-8.9 kg; BCM(BROMIDE), 31.4+/-9.3 kg; Delta=1.0+/-2.8 kg; p<0.001; ECF(TBK), 18.5+/-4.2 kg; ECF(BROMIDE), 17.5+/-3.6 kg; Delta=1.0+/-2.8 kg; p<0.001). A high correlation (r=0.97, p<0.001) and good agreement (38.9+/-9.5 vs. 38.9+/-9.5 kg; Delta=0.0+/-2.4 kg; p=0.39) were present between TBW, derived as the sum of intracellular water from TBK and ECW from bromide, and measured TBW by 2H2O dilution. DISCUSSION: Two developed four-compartment cellular level DXA models, one of which is appropriate for use in most clinical and research settings, provide comparable results and are applicable for BCM and ECF estimation of subject groups with hydration disturbances.

Absorptiometry, Photon↗

PubMed2005

Race-ethnicity-specific waist circumference cutoffs for identifying cardiovascular disease risk factors.

BACKGROUND: Waist circumferences (WCs) in white men and women that represent a risk of cardiovascular disease (CVD) equivalent to that of body mass indexes (BMIs; in kg/m2) of 25 and 30 have been identified. However, WC cutoffs for other race-ethnicity groups remain unknown. OBJECTIVE: The objective was to determine WC cutoffs for CVD risk in non-Hispanic blacks (blacks), Mexican Americans (MA), and non-Hispanic whites (whites). DESIGN: Data from 10,969 participants in the third National Health and Nutrition Examination Survey (1988-1994) were analyzed. The presence of CVD risk factors was the main outcome. Sex- and race-ethnicity-specific WC cutoffs were determined with logistic regression models by linking WC cutoffs with equivalent CVD risk based on BMI cutoffs for overweight and obesity. WC cutoffs for metabolic syndrome risk factors were similarly calculated. RESULTS: Correlations between WC and lipid profiles, blood pressure, and glucose were significantly higher than those between BMI and these same variables in all groups. The WC cutoffs were approximately 5-6 cm greater for white than for black men at BMIs between 25 and 40, and those for MA were intermediate. In women, few differences in WC cutoffs were observed between the groups. Simplified WC cutoffs corresponding to BMIs of 25 and 30, largely independent of age, for the 3 race-ethnicity groups were 89 and 101 cm for men and 83 and 94 cm for women. Minimal distances in receiver operating characteristic curves tended to be shorter when WC cutoffs rather than BMI cutoffs were used. CONCLUSIONS: WC is a better indicator of CVD risk than is BMI in the 3 race-ethnicity groups studied. The proposed WC cutoffs are more sensitive than are BMI cutoffs in predicting CVD risk.

Adult↗

PubMed2005

A cellular-level approach to predicting resting energy expenditure across the adult years.

BACKGROUND: We previously derived a whole-body resting energy expenditure (REE) prediction model by using organ and tissue mass measured by magnetic resonance imaging combined with assumed stable, specific resting metabolic rates of individual organs and tissues. Although the model predicted REE well in young persons, it overpredicted REE by approximately 11% in elderly adults. This overprediction may occur because of a decline in the fraction of organs and tissues as cell mass with aging. OBJECTIVE: The aim of the present study was to develop a cellular-level REE prediction model that would be applicable across the adult age span. Specifically, we tested the hypothesis that REE can be predicted from a combination of organ and tissue mass, the specific resting metabolic rates of individual organs and tissues, and the cellular fraction of fat-free mass. DESIGN: Fifty-four healthy subjects aged 23-88 y had REE, organ and tissue mass, body cell mass, and fat-free mass measured by indirect calorimetry, magnetic resonance imaging, whole-body (40)K counting, and dual-energy X-ray absoptiometry, respectively. RESULTS: REE predicted by the cellular-level model was highly correlated with measured REE (r = 0.92, P < 0.001). The mean difference between measured REE (x+/- SD: 1487 +/- 294 kcal/d) and predicted REE (1501 +/- 300 kcal/d) for the whole group was not significant, and the difference between predicted and measured REE was not associated with age (r = 0.009, NS). CONCLUSION: The present approach establishes an REE-body composition link with the use of a model at the cellular level. The combination of 2 aging-related factors (ie, decline in both the mass and the cellular fraction of organs and tissues) may account for the lower REE observed in elderly adults.

Absorptiometry, Photon↗

PubMed2005

Adipose tissue in muscle: a novel depot similar in size to visceral adipose tissue.

BACKGROUND: The manner in which fat depot volumes and distributions, particularly the adipose tissue (AT) between the muscles, vary by race is unknown. OBJECTIVE: The objective was to quantify a previously unstudied and novel intermuscular AT (IMAT) depot and subcutaneous AT, visceral AT (VAT), and total-body skeletal muscle mass in healthy sedentary African American (AA), Asian, and white adults by whole-body magnetic resonance imaging. IMAT is the AT between muscles and within the boundary of the muscle fascia. DESIGN: Analyses were conducted on 227 women [AA (n = 79): body mass index (BMI; in kg/m(2)), 29.0 +/- 5.5; age, 45.7 +/- 16.9 y; Asian (n = 38): BMI, 21.7 +/- 2.9; age, 47.2 +/- 19.9 y; whites (n = 110): BMI, 24.9 +/- 5.4; age, 43.7 +/- 16.2 y]) and 111 men [AA (n = 39): BMI, 25.6 +/- 3.2; age, 45.5 +/- 18.8 y; Asian (n = 13): BMI, 24.9 +/- 2.5; age, 45.6 +/- 25.0 y; white (n = 59): BMI, 25.8 +/- 3.8; age 44.5 +/- 16.3 y]. RESULTS: IMAT depots were not significantly different in size between race groups at low levels of adiposity; however, with increasing adiposity, AAs had a significantly greater increment in the proportion of total AT (TAT) than did the whites and Asians (58, 46, and 44 g IMAT/kg TAT, respectively; P = 0.001). VAT depots were not significantly different in size at low levels of adiposity but, with increasing adiposity, VAT accumulation was greater than IMAT accumulation in the Asians and whites; no significant differences were observed in AAs. CONCLUSION: Race differences in AT distribution extend to IMAT, a depot that may influence race-ethnicity differences in dysglycemia.

Adipose Tissue↗

PubMed2005

Independent association of insulin resistance with larger amounts of intermuscular adipose tissue and a greater acute insulin response to glucose in African American than in white nondiabetic women.

BACKGROUND: African Americans (AAs) have a higher prevalence of obesity and type 2 diabetes than do whites. Higher insulin resistance and hyperinsulinemia have been reported in adult AAs than in whites. Differences in adipose tissue and its distribution may account for these findings. OBJECTIVE: The objective was to ascertain whether differences between AA and white women in adipose tissue (AT) and skeletal muscle (SM) volumes account for ethnic differences in insulin resistance. DESIGN: We used whole-body magnetic resonance imaging to measure AT and SM volumes and used the intravenous-glucose-tolerance test to measure insulin resistance. RESULTS: AAs (n = 32) were 29-42% more insulin resistant than were whites (n = 28) after adjustment for weight and height or any AT volumes (P < 0.05). After adjustment for SM volume, the difference decreased to 19% and became nonsignificant. AAs had a 163% greater acute insulin response to glucose than did whites; this difference was significant even after adjustment for insulin sensivitity index, weight, height, and any magnetic resonance imaging measures. With respect to regional AT volumes, an association independent of race, weight, height, and SM volume was found only between increased intermuscular AT and lower insulin sensitivity index. CONCLUSIONS: Premenopausal AA women had significantly higher insulin resistance and acute insulin response to glucose than did their white counterparts. Whereas the difference in insulin resistance was partially accounted for by a greater SM volume in the AAs than in the whites, the difference in the acute insulin response to glucose was independent of any AT and SM measures and was disproportionately larger than expected according to the difference in insulin resistance. In addition, whole-body intermuscular AT was an important independent correlate of insulin resistance.

Adipose Tissue↗

PubMed2004

Total body skeletal muscle and adipose tissue volumes: estimation from a single abdominal cross-sectional image.

A single abdominal cross-sectional computerized axial tomography and magnetic resonance image is often obtained in studies examining adipose tissue (AT) distribution. An abdominal image might also provide additional useful information on total body skeletal muscle (SM) and AT volumes with related physiological insights. We therefore investigated the relationships between abdominal SM and AT areas from single images and total body component volumes in a large and diverse sample of healthy adult subjects. Total body SM and AT volumes were derived by whole body multislice magnetic resonance imaging in 123 men [age (mean +/- SD) of 41.6 +/- 15.8 yr; body mass index of 25.9 +/- 3.4 kg/m(2)] and 205 women (age of 47.8 +/- 18.7 yr; body mass index of 26.7 +/- 5.6 kg/m(2)). Single abdominal SM and AT slice areas were highly correlated with total body SM (r = 0.71-0.92; r = 0.90 at L(4)-L(5) intervertebral space) and AT (r = 0.84-0.96; r = 0.94 at L(4)-L(5) intervertebral space) volumes, respectively. R(2) increased by only 5.7-6.1% for SM and 2.7-4.4% for AT with the inclusion of subject sex, age, ethnicity, scanning position, body mass index, and waist circumference in the model. The developed SM and AT models were validated in an additional 49 subjects. To achieve equivalent power to a study measuring total body SM or AT volumes, a study using a single abdominal image would require 17-24% more subjects for SM and 6-12% more subjects for AT. Measurement of a single abdominal image can thus provide estimates of total body SM and AT for group studies of healthy adults.

Abdomen↗

PubMed2004

Three-compartment model: critical evaluation based on neutron activation analysis.

There is renewed interest in Siri's classic three-compartment (3C) body composition model, requiring body volume (BV) and total body water (TBW) estimates, because dual-energy X-ray absorptiometry (DEXA) and in vivo neutron activation (IVNA) systems cannot accommodate subjects with severe obesity. However, the 3C model assumption of a constant ratio (alpha) of mineral (M) to total body protein (TBPro) and related residual mass density (D(RES)) based on cadaver analyses might not be valid across groups differing in sex, race, age, and weight. The aim of this study was to derive new 3C model coefficients in vivo and to compare these estimates to those derived by Siri. Healthy adults (n = 323) were evaluated with IVNA and DEXA and the measured components used to derive alpha and D(RES). For all subjects combined, values of alpha and D(RES) (means +/- SD, 0.351 +/- 0.043; 1.565 +/- 0.023 kg/l) were similar to Siri's proposed values of 0.35 and 1.565 kg/l, respectively. However, alpha and D(RES) varied significantly as a function of sex, race, weight, and age. Expected errors in percent body fat arising by application of Siri's model were illustrated in a second group of 264 adults, including some whose size exceeded DEXA limits but whose BV and TBW had been measured by hydrodensitometry and (2)H(2)O dilution, respectively. Extrapolation of predictions by newly developed models to very high weights allows percent fat error estimation when Siri's model is applied in morbidly obese subjects. The present study results provide a critical evaluation of potential errors in the classic 3C model and present new formulas for use in selected populations.

Absorptiometry, Photon↗