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BACKGROUND - Smokers have lower risk of obesity, which some consider a "beneficial" side effect of smoking. However, some studies suggest that smoking is simultaneously associated with higher central adiposity and, more specifically, ectopic adipose deposition. Little is known about the association of smoking with intermuscular adipose tissue (IMAT), an ectopic adipose depot associated with cardiovascular disease (CVD) risk and a key determinant of muscle quality and function. We tested the hypothesis that smokers have higher abdominal IMAT and lower lean muscle quality than never smokers.
METHODS AND FINDINGS - We measured abdominal muscle total, lean, and adipose volumes (in cubic centimeters) and attenuation (in Hounsfield units [HU]) along with subcutaneous (SAT) and visceral adipose tissue (VAT) volumes using computed tomography (CT) in 3,020 middle-aged Coronary Artery Risk Development in Young Adults (CARDIA) participants (age 42-58, 56.3% women, 52.6% white race) at the year 25 (Y25) visit. The longitudinal CARDIA study was initiated in 1985 with the recruitment of young adult participants (aged 18-30 years) equally balanced by female and male sex and black and white race at 4 field centers located in Birmingham, AL, Chicago, IL, Minneapolis, MN, and Oakland, CA. Multivariable linear models included potential confounders such as physical activity and dietary habits along with traditional CVD risk factors. Current smokers had lower BMI than never smokers. Nevertheless, in the fully adjusted multivariable model with potential confounders, including BMI and CVD risk factors, adjusted mean (95% CI) IMAT volume was 2.66 (2.55-2.76) cm3 in current smokers (n = 524), 2.36 (2.29-2.43) cm3 in former smokers (n = 944), and 2.23 (2.18-2.29) cm3 in never smokers (n = 1,552) (p = 0.007 for comparison of former versus never smoker, and p < 0.001 for comparison of current smoker versus never and former smoker). Moreover, compared to participants who never smoked throughout life (41.6 [41.3-41.9] HU), current smokers (40.4 [39.9-40.9] HU) and former smokers (40.8 [40.5-41.2] HU) had lower lean muscle attenuation suggesting lower muscle quality in the fully adjusted model (p < 0.001 for comparison of never smokers with either of the other two strata). Among participants who had ever smoked, pack-years of smoking exposure were directly associated with IMAT volume (β [95% CI]: 0.017 [0.010-0.025]) (p < 0.001). Despite having less SAT, current smokers also had higher VAT/SAT ratio than never smokers. These findings must be viewed with caution as residual confounding and/or reverse causation may contribute to these associations.
CONCLUSIONS - We found that, compared to those who never smoked, current and former smokers had abdominal muscle composition that was higher in adipose tissue volume, a finding consistent with higher CVD risk and age-related physical deconditioning. These findings challenge the belief that smoking-associated weight loss or maintenance confers a health benefit.
OBJECTIVE - Decreased radiodensity of adipose tissue (AT) located in the visceral AT (VAT), subcutaneous AT (SAT), and intermuscular AT (IMAT) abdominal depots is associated with hyperglycemia, hyperinsulinemia, and insulin resistance independent of AT volumes. These associations were sought in African-ancestry men, who have higher risk for type 2 diabetes and have been underrepresented in previous studies.
METHODS - This cross-sectional analysis included 505 nondiabetic men of African-Caribbean ancestry (median age: 61 years; median BMI: 26.8 kg/m ) from the Tobago Health Study. AT volumes and radiodensities were assessed using computed tomography, including abdominal (VAT and SAT) and thigh (IMAT) depots. Associations between AT radiodensities were assessed with fasting serum glucose and insulin and with insulin resistance (updated homeostatic model assessment of insulin resistance, HOMA2-IR).
RESULTS - Higher radiodensity in any AT depot was associated with lower log-insulin and log-HOMA2-IR (β range: -0.16 to -0.18 for each; all P < 0.0001). No AT radiodensity was associated with glucose. Thigh IMAT radiodensity associations were independent of, and similar in magnitude to, VAT radiodensities. Model fit statistics suggested that AT radiodensities were a better predictor for insulin and insulin resistance compared with AT volumes in individuals with overweight and obesity.
CONCLUSIONS - AT radiodensities at multiple depots are significantly associated with insulin and insulin resistance in African-ancestry men.
© 2019 The Obesity Society.
INTRODUCTION - Cross-sectional data note lower levels of testosterone and sex hormone-binding globulin (SHBG) levels in men with nonalcoholic fatty liver disease (NAFLD). Whether sex hormone levels in young men are predictive of later risk of NAFLD is not known.
METHODS - Among men in the prospective population-based multicenter Coronary Artery Risk Development in Young Adults study (mean age 50; n = 837), we assessed whether testosterone and SHBG levels measured at study year 10 (median age 35 years) were associated with prevalent NAFLD at study year 25. NAFLD was defined using noncontrast abdominal computed tomography (CT) scan after excluding other causes of hepatic steatosis. The association of testosterone and SHBG with prevalent NAFLD was assessed by logistic regression.
RESULTS - Total testosterone levels in young men were inversely associated with subsequent prevalent NAFLD on unadjusted analysis (odds ratio [OR] 0.64, 95% confidence interval 0.53-0.7, P < 0.001), although no longer significant after adjustment for year 10 metabolic covariates as well as change in metabolic covariates from years 10 to 25 (OR 0.99, 95% confidence interval 0.76-1.27). In contrast, there was a significant inverse association of SHBG with prevalent NAFLD, independent of testosterone and metabolic covariates (OR 0.68, OR 0.51-0.92, P = 0.013). On formal mediation testing, visceral adiposity was found to explain ∼41.0% (95% confidence interval 27%-73%) of the association of lower SHBG with prevalent NAFLD.
CONCLUSIONS - Lower levels of SHBG in young men are associated with increase in prevalent NAFLD in middle age, independent of comprehensive metabolic risk factors. SHBG may provide a novel marker of NAFLD risk in young men.
BACKGROUND - Obesity is highly prevalent among blacks and is associated with a greater risk of heart failure (HF). However, the contribution of regional adiposity depots such as visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue toward risk of HF in blacks is unknown.
METHODS AND RESULTS - We included 2602 participants (mean age: 59 years, 35% men) from the Jackson Heart Study without prevalent HF who underwent computed tomography quantification of VAT and subcutaneous adipose tissue during the second visit (2005-2009). The associations between different adiposity measures and HF were evaluated using adjusted Cox models. There were 122 incident HF events over a median follow-up of 7.1 years. Higher amounts of VAT were associated with greater risk of HF in age- and sex-adjusted analyses (hazard ratio [95% CI] per 1-SD higher VAT: 1.29 [1.09-1.52]). This association was attenuated and not significant after additional adjustment for traditional HF risk factors and body mass index. Overall obesity, represented by body mass index, was associated with higher risk of HF independent of risk factors and VAT (hazard ratio [95% CI] per 1-kg/m higher body mass index: 1.06 [1.02-1.11]). Subcutaneous adipose tissue was not associated with risk of HF in adjusted analyses.
CONCLUSIONS - In a community-dwelling black population, higher amounts of overall and visceral adiposity are associated with higher risk of HF. The association between VAT and HF risk in blacks may reflect differences in traditional HF risk factor burden. Future studies are needed to confirm this observation and clarify the independent role of different measures of adiposity on HF outcomes.
AIM - To evaluate the relationship of abdominal muscle lean tissue and adipose tissue volumes with prediabetes and diabetes.
RESEARCH DESIGN AND METHODS - We measured abdominal muscle composition in 3170 participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study who underwent computed tomography (CT) at Year 25 of follow-up (ages, 43-55 years). Multinomial regression analysis was used to evaluate the associations of CT-measured intermuscular adipose tissue (IMAT), lean muscle tissue (lean) and visceral adipose tissue (VAT) volumes with diabetes at any point during the CARDIA study, newly detected prediabetes, prior history of prediabetes, and normal glucose tolerance. Models were adjusted for potential confounding factors: age, sex, race, height, smoking status, hypertension, hyperlipidaemia, cardiorespiratory fitness and study centre.
RESULTS - Higher IMAT, lean and VAT volumes were all separately associated with a higher prevalence of prediabetes and diabetes. Inclusion of VAT volume in models with both IMAT volume and lean volume attenuated the association of IMAT with both prediabetes and diabetes, but higher lean volume retained its association with prediabetes and diabetes. Individuals in the highest IMAT quartile, coupled with VAT in its lower three quartiles, had a higher prevalence of diabetes, but not of prediabetes, than those with both IMAT and VAT in their respective lower three quartiles. Adjusting for cardiorespiratory fitness did not substantially change the findings.
CONCLUSION - Higher IMAT volume was associated with a higher prevalence of diabetes even after adjustment for VAT volume. However, further study is warranted to understand the complicated relationship between abdominal muscle and adipose tissues.
© 2018 John Wiley & Sons Ltd.
AIMS - We investigated the association between cumulative lifetime and current marijuana use with total abdominal adipose tissue (AT), visceral AT, subcutaneous AT, intermuscular AT, and mean liver attenuation (LA) at mid-life.
DESIGN - Longitudinal and cross-sectional secondary data analysis of participants in the Coronary Artery Risk Development in Young Adults (CARDIA) Study.
SETTING - CARDIA field centers in Birmingham, AL; Chicago, IL; Minneapolis, MN; and Oakland, CA, USA.
PARTICIPANTS - CARDIA participants, aged 18-30 years in 1985-1986, who were present at the clinic examination in 2010-2011 (n = 2902).
MEASUREMENTS - Marijuana use was assessed from responses to self-administered questionnaires at 8 CARDIA examinations over 25 years, determined as cumulative marijuana-years and current use status. Non-contrast computed tomography imaging of the abdomen was obtained in 2010-2011.
FINDINGS - In 2010-2011, 84% of participants reported a history of marijuana use with 11% reporting use within the past 30 days. Before adjustment, we observed greater cumulative marijuana use was associated with lower total abdominal and subcutaneous AT volume and lower LA and current marijuana use was associated with lower subcutaneous AT. However, after adjustment for age, sex, race, field center, cigarette pack-years and current use, regular alcohol consumption, cumulative drink-years, and physical activity, neither cumulative marijuana use nor current use showed an association with any abdominal adipose depot. Our estimates did not differ by age, sex, or race nor after accounting for cohort attrition.
CONCLUSION - Neither cumulative marijuana use nor current marijuana use is associated with total abdominal, visceral, subcutaneous, or intermuscular adipose tissue, or liver attenuation in mid-life.
© 2017 Society for the Study of Addiction.
OBJECTIVE - Excess deposition of fat within and around vital organs and nonadipose tissues is hypothesized to contribute to cardiovascular disease (CVD) risk. We evaluated the association of abdominal intermuscular adipose tissue (IMAT) volume with coronary artery calcification in the CARDIA study (Coronary Artery Risk Development in Young Adults) participants.
APPROACH AND RESULTS - We measured IMAT in the abdominal muscles, visceral adipose tissue and pericardial adipose tissue, and coronary artery calcification using computed tomography in 3051 CARDIA participants (56% women) at the CARDIA year 25 examination (2010-2011). Mean IMAT volume and mean IMAT/total muscle volume (IMAT normalized for muscle size) were calculated in a 10-mm block of slices centered at L3-L4. Multivariable analyses included potential confounders and traditional cardiovascular disease risk factors. Compared with the lowest quartile, the upper quartile of abdominal IMAT volume was associated with higher coronary artery calcification prevalence (odds ratio [95% confidence interval], 1.6 [1.2-2.1]) after adjusting for cardiovascular disease risk factors. Results were similar for highest versus lowest quartile of IMAT normalized to total muscle volume (odds ratio [95% confidence interval], 1.5 [1.1-2.0]). Significant associations of higher IMAT and normalized IMAT with coronary artery calcification prevalence persisted when body mass index, visceral adipose tissue, or pericardial adipose tissue were added to the models.
CONCLUSIONS - In a large, community-based, cross-sectional study, we found that higher abdominal skeletal muscle adipose tissue volume was associated with subclinical atherosclerosis independent of traditional cardiovascular disease risk factors and other adipose depots.
© 2017 American Heart Association, Inc.
Background - Adiposity depots may differentially affect cognition. African Americans (AA) have higher rates of obesity and dementia but lower visceral adipose tissue (VAT) than whites, yet are underrepresented in studies of adiposity and cognition. Our study compared relations of cognitive function to clinical adiposity measures and computed tomography (CT)-imaged abdominal adiposity in AA.
Methods - CT-imaged subcutaneous adipose tissue (SAT) and VAT measurements were obtained in the AA cohort of the Genetic Epidemiology Network of Arteriopathy Study (N = 652, mean age 68 ± 8.4 years, 74% females, 59% obese, 82% hypertensive). Clinical adiposity measures included waist circumference (WC) and body mass index (BMI). Global cognition was operationalized as a global cognitive z-score generated from the average of four cognitive domain z-scores. Generalized estimating equations were used to examine cross-sectional associations between individual standardized adiposity measures and cognition, accounting for age, sex, education, smoking status, and familial clustering. A collective model was constructed including multiple supported adiposity measures and age-by-adiposity interactions.
Results - In the collective model, higher WC was associated with worse global cognition, β = -0.12 (95%CI: -0.21, -0.03); higher SAT was associated with better cognition, β = 0.09 (0.01, 0.18); higher BMI was associated with worse cognition at younger ages with attenuation at older ages (BMI-by-age-interaction p = .004). VAT was not significantly associated with global cognition, β = -0.03 (-0.07, 0.02).
Conclusions - WC may be the simplest and most efficient measure of adiposity to assess with respect to cognition in clinical settings, although studies to determine mechanistic effects of subcutaneous and other adiposity depots on cognition are warranted.
RATIONALE - Adiposity is associated with low lung function, but the longitudinal relationship between lung function and adiposity is inadequately studied.
OBJECTIVE - To examine the bidirectional longitudinal associations between rapid decline in lung function and adiposity phenotypes in healthy adults.
METHODS - This secondary analysis used a 25-year longitudinal dataset from the Coronary Artery Risk Development in Young Adults (CARDIA) study that enrolled 5115 participants.
MEASUREMENTS - In the first analysis, metabolic syndrome at or before CARDIA year (Y) 10 (Y10) was the predictor, and subsequent rapid decline in forced vital capacity (FVC) or forced expiratory volume in 1 s (FEV) between Y10 and Y20 was the outcome. In the second analysis, rapid decline was the predictor, and incident metabolic syndrome at Y20 and/or Y25 was the outcome. In the third analysis, rapid decline was the predictor, and subsequent CT-assessed regional fat depots at Y25 were the outcome.
RESULTS - Metabolic syndrome at or before Y10 is temporally associated with rapid decline in FVC between Y10 and Y20 (adjusted p=0.04), but this association was explained by body mass index (BMI) at Y10. Rapid decline in FVC or FEV is temporally associated with greater incident metabolic syndrome at Y20 and/or Y25 (adjusted OR 2.10 (1.69, 2.61); p<0.001, and 1.56 (1.26, 1.94); p<0.001, respectively) and greater CT-assessed intrathoracic visceral adiposity at Y25 (adjusted standardised β 0.09; p<0.001 for both analyses). These associations were not explained by BMI levels prior to the outcome measurement.
CONCLUSIONS - Healthy adults with rapid decline in lung function are at risk for developing metabolic syndrome and for disproportionate accumulation of intrathoracic visceral fat. Metabolic abnormalities may be an early extrapulmonary manifestation of lung impairment that may be preventable by improving lung health.
© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.
BACKGROUND AND AIMS - There is strong evidence that fat accumulating in non-adipose sites, "ectopic fat", is associated with cardiovascular disease (CVD), including vascular calcification. Most previous studies of this association have assessed only a single ectopic fat depot. Therefore, our aim was to assess the association of total, regional, and ectopic fat with abdominal aorto-illiac calcification (AAC) and coronary artery calcification (CAC) in 798 African ancestry men.
METHODS - Participants (mean age 62) were from the Tobago Bone Health Study cohort. Adiposity was assessed via clinical examination, dual x-ray absorptiometry, and computed tomography (CT). Ectopic fat depots included: abdominal visceral adipose tissue (VAT), liver attenuation, and calf intermuscular adipose tissue (IMAT). Vascular calcification was assessed by CT and quantified as present versus absent. Associations were tested using multiple logistic regression adjusted for traditional cardiovascular risk factors. Models of ectopic fat were additionally adjusted for total body fat and standing height.
RESULTS - All adiposity measures, except VAT, were associated with AAC. Lower liver attenuation or greater calf IMAT was associated with 1.2-1.3-fold increased odds of AAC (p < 0.03 for both), though calf IMAT was a stronger predictor than liver attenuation (p < 0.001) when entered in a single model. No ectopic fat measure was associated with CAC.
CONCLUSIONS - Greater adiposity in the skeletal muscle and liver, but not in the visceral compartment, was associated with increased odds of AAC in African ancestry men. These results highlight the potential importance of both quantity and location of adiposity accumulation throughout the body.
Copyright © 2017 Elsevier B.V. All rights reserved.