Fat Distribution,Aerobic Fitness,Blood Lipids,and Insulin Sensitivity in African‐American and European‐American Women

The purpose of this study was to determine independent relationships of intra‐abdominal adipose tissue (IAAT), leg fat, and aerobic fitness with blood lipids and insulin sensitivity (S_i) in European‐American (EA) and African‐American (AA) premenopausal women. Ninety‐three EA and ninety‐four AA with BMI between 27 and 30 kg/m² had IAAT by computed tomography, total fat and leg fat by dual‐energy X‐ray absorptiometry, aerobic fitness by a graded exercise test, African admixture (AFADM) by ancestry informative markers, blood lipids by the Ektachem DT system, and S_i by glucose tolerance test. Independent of age, aerobic fitness, AFADM, and leg fat, IAAT was positively related to low‐density lipoprotein–cholesterol (LDL‐C), cholesterol‐high‐density lipoprotein (HDL) ratio, triglycerides (TGs), and fasting insulin (standardized β varying 0.16–0.34) and negatively related to HDL‐cholesterol (HDL‐C) and S_i (standardized β ?0.15 and ?0.25, respectively). In contrast, independent of age, aerobic fitness, AFADM, and IAAT, leg fat was negatively related to total cholesterol, LDL‐C, cholesterol‐HDL ratio, TGs, and fasting insulin (standardized β varying ?0.15 to ?0.21) and positively related to HDL‐C and S_i (standardized β 0.16 and 0.23). Age was not independently related to worsening of any blood lipid but was related to increased S_i (standardized β for S_i 0.25, insulin ?0.31). With the exception of total cholesterol and LDL‐C, aerobic fitness was independently related to worsened blood lipid profile and increased S_i (standardized β varying 0.17 to ?0.21). Maintenance of favorable fat distribution and aerobic fitness may be important strategies for healthy aging, at least in premenopausal EA and AA women.     

Acquired liver fat is a key determinant of serum lipid alterations in healthy monozygotic twins

Objective: The effects of acquired obesity on lipid profile and lipoprotein composition in rare BMI‐discordant monozygotic (MZ) twin pairs were studied. Design and Methods: Abdominal fat distribution, liver fat (magnetic resonance imaging and spectroscopy), fasting serum lipid profile (ultracentrifugation, gradient gel‐electrophoresis, and colorimetric enzymatic methods), and lifestyle factors (questionnaires and diaries) were assessed in 15 BMI‐discordant (within‐pair difference [Δ] in BMI >3 kg/m²) and nin concordant (ΔBMI <3 kg/m²) MZ twin pairs, identified from two nationwide cohorts of Finnish twins. Results: Despite a strong similarity of MZ twins in lipid parameters (intra‐class correlations 0.42‐0.90, P < 0.05), concentrations of apolipoprotein B (ApoB), intermediate‐density lipoprotein cholesterol, low‐density lipoprotein cholesterol (LDL‐C), high‐density lipoprotein 3a% (HDL3a%), and HDL3c% were higher (P < 0.05) and those of HDL cholesterol, HDL2‐C, and HDL2b% were lower (P < 0.01) in the heavier co‐twins of BMI‐discordant pairs. The composition of lipoprotein particles was similar in the co‐twins. When BMI‐discordant pairs were further divided into liver fat‐discordant and concordant (based on median for Δliver fat, 2.6%), the adverse lipid profile was only seen in those heavy co‐twins who also had high liver fat. Conversely, BMI‐discordant pairs concordant for liver fat did not differ significantly in lipid parameters. In multivariate analyses controlling for Δsubcutaneous, Δintra‐abdominal fat, sex, Δsmoking and Δphysical activity, Δliver fat was the only independent variable explaining the variation in ΔApoB, Δtotal cholesterol, and ΔLDL‐C concentration. Conclusions: Several pro‐atherogenic changes in the amounts of lipids but not in the composition of lipoprotein particles were observed in acquired obesity. In particular, accumulation of liver fat was associated with lipid disturbances, independent of genetic effects.     

Higher post-absorptive skeletal muscle LPL activity in African American vs. non-Hispanic White pre-menopausal women

Objective: Higher post‐absorptive post‐heparin plasma lipoprotein lipase (LPL) activity has been reported in African Americans as compared to non‐Hispanic whites but differences in tissue‐specific LPL activity are unclear. Methods and Procedures: Post‐absorptive skeletal muscle (SM)‐LPL (vastus lateralis) and subcutaneous abdominal adipose tissue (AT)‐LPL activity was measured in overweight, sedentary African American females (n = 11) as well as in their non‐Hispanic white counterparts (n = 6) during a period of controlled low fat (30%) diet (for 10 days) combined with physical activity (for days 8–10). Post‐absorptive substrate utilization was measured on day 10; fasting blood levels and SM and AT biopsies were obtained on day 11. Results: African Americans had significantly greater post‐absorptive SM‐LPL activity (P = 0.04) when compared to non‐Hispanic whites. There were no significant differences in post‐absorptive AT‐LPL activity, free fatty acids, and systemic fat oxidation or respiratory quotient between African American and white non‐Hispanic women in this study (P > 0.2 for all). Discussion: During a controlled low fat (30%) diet post‐absorptive vastus lateralis SM‐LPL activity is higher in sedentary pre‐menopausal African American as compared to non‐Hispanic white women.     

Impacts of Visceral Adipose Tissue and Subcutaneous Adipose Tissue on Metabolic Risk Factors in Middle‐aged Japanese

Regional fat distribution rather than overall fat volume has been considered to be important to understanding the link between obesity and metabolic disorders. We aimed to evaluate the independent associations of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) with metabolic risk factors in apparently healthy middle‐aged Japanese. Participants were 1,119 men and 854 women aged 38–60 years who were not taking medications for diabetes, hypertension, or dyslipidemia. VAT and SAT were measured by use of computed tomography (CT) scanning. VAT and SAT were significantly and positively correlated with each other in men (r = 0.531, P < 0.001) and women (r = 0.589, P < 0.001). In multiple regression analyses, either measure of abdominal adiposity (VAT or SAT) was positively associated with blood pressure, fasting plasma glucose, and log triglyceride (P < 0.001) and inversely with high‐density lipoprotein (HDL)‐cholesterol (P < 0.001). When VAT and SAT were simultaneously included in the model, the association of VAT with triglycerides was maintained (P < 0.001) but that of SAT was lost. The same was true for HDL‐cholesterol in women. For fasting plasma glucose, the association with VAT was strong (P < 0.001) and the borderline association with SAT was maintained (P = 0.060 in men and P = 0.020 in women). Both VAT and SAT were independently associated with blood pressure (P < 0.001). Further adjustment for anthropometric indices resulted in the independent association only with VAT for all risk factors. In conclusion, impacts of VAT and SAT differed among risk factors. VAT showed dominant impacts on triglyceride concentrations in both genders and on HDL‐cholesterol in women, while SAT also had an independent association with blood pressure.     

Low Fasting Triglycerides: Hallmark of the Healthy Large Hip?

Body fat distribution modulates risk for type 2 diabetes mellitus. We evaluated potentially involved metabolic risk factors. In a population of 282 male and 157 female healthy subjects (data from the San Antonio and the European Group of Insulin Resistance (EGIR) study cohorts), we evaluated associations between body fat distribution (assessed by waist and hip circumference) and parameters of lipid‐ and glucose metabolism, including clamp measurements of insulin sensitivity. After stratification for BMI, fasting triglycerides were lower in the presence of a large hip, and higher in a large waist. Persons with the largest BMI (3rd tertile) showed a difference in triglyceride levels of 1.5 vs. 2.4 mmol/l in large vs. small hip circumference groups (P < 0.038), and a difference of 1.5 vs. 1.2 mmol/l in large vs. small waist circumference groups (P < 0.025). A similar analysis did not reveal a difference in insulin sensitivity. Linear regression analyses confirmed the findings; they revealed negative associations between triglycerides and hip, and (for women borderline statistically significant) positive associations between triglycerides and waist, after adjustment for BMI, mutual confounding, and age (β ± s.e.; men: ?0.48 ± 0.005, P < 0.001, and 0.21 ± 0.005, P < 0.05; women: ?0.78 ± 0.007, P < 0.001, and 0.24 ± 0.005, P < 0.065), respectively. Linear regression analyses revealed similar opposite associations with high‐density lipoprotein (HDL)‐cholesterol, though not with glucose, insulin, or insulin sensitivity as measured with the clamp method. In our study population of healthy persons, body fat distribution is associated with fasting triglycerides and HDL‐cholesterol, and not with insulin sensitivity. Metabolic risk of unfavorable body fat distribution may be modulated by lower triglyceride storage capacity.     

Comparison of the Relative Contributions of Intra‐Abdominal and Liver Fat to Components of the Metabolic Syndrome

Abdominally obese individuals with the metabolic syndrome often have excess fat deposition both intra‐abdominally (IA) and in the liver, but the relative contribution of these two deposits to variation in components of the metabolic syndrome remains unclear. We determined the mutually independent quantitative contributions of IA and liver fat to components of the syndrome, fasting serum (fS) insulin, and liver enzymes and measures of hepatic insulin sensitivity in 356 subjects (mean age 42 years, mean BMI 29.7 kg/m²) in whom liver fat and abdominal fat volumes were measured. IA and liver fat contents were correlated (r = 0.65, P < 0.0001). In multivariate linear regression analyses including either liver or IA fat, liver fat or IA fat explained variation in fS‐triglyceride (TG) and high‐density lipoprotein (HDL) cholesterol, plasma glucose, insulin and liver enzyme concentrations, and hepatic insulin sensitivity independent of age, gender, subcutaneous (SC) fat, and/or lean body mass (LBM). Including both liver and IA fat, liver and IA fat both explained variation in TG, HDL cholesterol, insulin and hepatic insulin sensitivity independent of each other and of age, gender, SC fat, and LBM. Liver fat independently predicted glucose and liver enzymes. SC fat and age explained variation in blood pressure. In conclusion, both IA and liver fat independently of each other explain variation in serum TG, HDL cholesterol, insulin concentrations and hepatic insulin sensitivity, thus supporting that both fat depots are important predictors of these components of the metabolic syndrome.     

Relation of epicardial fat and alanine aminotransferase in subjects with increased visceral fat

Background: Increased visceral adipose tissue (VAT) is a risk factor for an unfavorable cardio‐metabolic profile and fatty liver. Individuals with human immunodeficiency virus (HIV) on highly active antiretroviral therapy (HAART) can be associated with metabolic syndrome (MS) and higher visceral fat. However, the potential link between cardiac adiposity, emerging index of visceral adiposity, and fatty liver is still unexplored. Objective: To evaluate whether echocardiographic epicardial adipose tissue, index of cardiac adiposity, could be related to serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity, surrogate markers of fatty liver, in HIV‐infected patients with (HIV+MS+) and without HAART‐associated MS (HIV+MS‐). Methods and Procedures: This was a cross‐sectional observational study on 57 HIV+MS+ patients, 52 HIV+MS? and 57 HIV‐negative subjects with MS (HIV?MS+), as control group. Epicardial fat thickness and intra‐abdominal VAT were obtained by echocardiography and magnetic resonance imaging (MRI), respectively. Serum ALT and AST activity, plasma adiponectin levels, and MS biochemical parameters were measured. Results: Echocardiographic epicardial fat thickness was correlated with MRI‐VAT (r = 0.83, P < 0.01), AST/ALT ratio (r = 0.77, P < 0.01), ALT (r = 0.58, P < 0.01), AST (r = 0.56, P < 0.01), and adiponectin (r = ?0.45, P < 0.01) in HIV+MS+. MRI‐VAT and AST/ALT ratio were the best correlates of epicardial fat thickness (r ² = 0.45, P < 0.01). Discussion: This study shows for the first time a clear relationship of epicardial fat, index of cardiac and visceral adiposity, and serum ALT and AST activity, markers of fatty liver, in subjects with increased visceral adiposity and cardio‐metabolic risk. This correlation seems to be independent of overall adiposity and rather function of excess visceral adiposity.     

Impact of Obesity and Body Fat Distribution on Cardiovascular Risk Factors in Hong Kong Chinese

Objective: Body fat distribution has been reported to differentially contribute to the development of cardiovascular risk. We report the relative associations between general and central obesity and risk factors in 2893 Chinese subjects recruited from the Hong Kong population. Research Methods and Procedures: Anthropometric parameters [waist circumference (WC) and BMI], surrogate measures of insulin resistance (fasting plasma glucose and insulin, oral glucose tolerance test, 2 hours glucose and insulin), fasting lipids (total, low‐density lipoprotein‐cholesterol, high‐density lipoprotein‐cholesterol, and triglycerides) and systolic and diastolic blood pressure were measured. General obesity was classified as BMI ≥25.0 kg/m² and central obesity as a WC ≥80 or ≥90 cm in women and men, respectively. Results: A total of 39.2% of the population was found to be obese. Obesity per se increased the levels of the risk factors, but central adiposity contributed to a greater extent to adverse high‐density lipoprotein‐cholesterol, triglyceride, and insulin resistance levels. There was a continuous relationship between increasing obesity, both general and central, and cardiovascular risk, with lowest risk associated with the lowest indices of obesity. In the 1759 nonobese subjects divided into quartiles of BMI or WC, the levels of the cardiovascular risk factors still significantly increased with increasing quartiles of adiposity. Discussion: Central adiposity appears to contribute to a greater extent than general adiposity to the development of cardiovascular risk in this population. The relationship between obesity parameters and risk is a continuum, with risk factors significantly increasing even at levels usually considered nonobese. These observations support the proposed redefinition of overweight and obesity in Asian populations using lower cut‐off points.     

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/m²]. 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.     

Truncal and Abdominal Fat as Determinants of High Triglycerides and Low HDL‐cholesterol in Adolescents

We examined whether abdominal and truncal adiposity, assessed with simple anthropometric indices, determines serum triglycerides and high‐density lipoprotein (HDL)–cholesterol levels independently of total adiposity amount in adolescents. A total of 547 Spanish adolescents (284 males and 263 females) aged 13–18.5 years were included in this study. Measures of truncal adiposity included subscapular to triceps ratio, and trunk‐to‐total skinfolds ratio (TTS%). Waist circumference was used as a surrogate of abdominal adiposity, and BMI was used as a measure of total adiposity. The results of the regression models indicated that levels of triglycerides were positively associated with waist circumference and TTS% after controlling for age and Tanner stage in both sexes. Once BMI was entered in the model, these associations remained significant for waist circumference in females. HDL‐cholesterol levels were negatively associated with waist circumference in both sexes, and with subscapular to triceps ratio and TTS% in males, after controlling for age and Tanner stage. Once BMI was entered in the model, these associations remained significant for subscapular to triceps ratio and for TTS% in males. The results of this study suggest that in male adolescents, truncal adiposity is negatively associated with levels of HDL‐cholesterol, whereas in females, abdominal adiposity is positively associated with levels of triglycerides independently of total adiposity. These findings highlight the deleterious effect of both truncal and abdominal fat depots on the lipid profile already from the first decades of life.     

Transient Increase in HDL‐Cholesterol During Weight Gain by Hyperalimentation in Healthy Subjects

Determination of lipid levels is fundamental in cardiovascular risk assessment. We studied the short‐term effects of fast food‐based hyperalimentation on lipid levels in healthy subjects. Twelve healthy men and six healthy women with a mean age of 26 ± 6.6 years and an aged‐matched control group were recruited for this prospective interventional study. Subjects in the intervention group aimed for a body weight increase of 5–15% by doubling the baseline caloric intake by eating at least two fast food‐based meals a day in combination with adoption of a sedentary lifestyle for 4 weeks. This protocol induced a weight gain from 67.6 ± 9.1 kg to 74.0 ± 11 kg (P < 0.001). A numerical increase in the levels of high‐density lipoprotein (HDL)‐cholesterol occurred in all subjects during the study and this was apparent already at the first week in 16/18 subjects (mean increase at week 1: +22.0 ± 16%, range from ?7 to +50%), whereas the highest level of HDL during the study as compared with baseline values varied from +6% to +58% (mean +31.6 ± 15%). The intake of saturated fat in the early phase of the trial related positively with the HDL‐cholesterol‐increase in the second week (r = 0.53, P = 0.028). Although the levels of insulin doubled at week 2, the increase in low‐density lipoprotein (LDL)‐cholesterol was only +12 ± 17%, and there was no statistically significant changes in fasting serum triglycerides. We conclude that hyperalimentation can induce a fast but transient increase in HDL‐cholesterol that is of clinical interest when estimating cardiovascular risk based on serum lipid levels.     

Association of the CPT1B Gene with Skeletal Muscle Fat Infiltration in Afro‐Caribbean Men

Skeletal muscle fat is greater in African ancestry individuals compared with whites, is associated with diabetes, and is a heritable polygenic trait. However, specific genetic factors contributing to skeletal muscle fat in humans remain to be defined. Muscle carnitine palmitoyltransferase‐1B (CPT1B) is a key enzyme in the regulation of skeletal muscle mitochondrial β‐oxidation of long‐chain fatty acids, and as such is a reasonable biological candidate gene for skeletal muscle fat accumulation. Therefore, we examined the association of three nonsynonymous coding variants in CPT1B (G531L, I66V, and S427C; a fourth, A320G, could not be genotyped) and quantitative computed tomography measured tibia skeletal muscle composition and BMI among 1,774 Afro‐Caribbean men aged ≥40, participants of the population‐based Tobago Health Study. For all variants, no significant differences were observed for BMI or total adipose tissue. Among individuals who were homozygous for the minor allele at G531L or I66V, intermuscular adipose tissue (IMAT) was 87% (P = 0.03) and 54% lower (P = 0.03), respectively. In contrast, subcutaneous adipose tissue (SAT) was 11% (P = 0.017) and 7% (P = 0.049) higher, respectively, than among individuals without these genotypes. These associations were independent of age, body size, and muscle area. Finally, no individuals with type 2 diabetes were found among those who were homozygous for the minor allele of either at G531L and I66V whereas 14–18% of men with the major alleles had type 2 diabetes (P = 0.03 and 0.007, respectively). Our results suggest a novel association between common nonsynonymous coding variants in CPT1B and ectopic skeletal muscle fat among middle‐aged and older African ancestry men.     

Objectively measured sedentary behavior,physical activity,and plasma lipids in overweight and obese children

Objective:

This study examines the associations between objectively measured sedentary behavior, light physical activity (LPA), and moderate‐to‐vigorous physical activity (MVPA), and plasma lipids in overweight and obese children.

Design and Methods:

Cross‐sectional analyses were conducted among 126 children aged 5.5‐9.9 years. Sedentary behavior, LPA, and MVPA were assessed using accelerometry. Fasting blood samples were analyzed for plasma lipids (high‐density lipoprotein cholesterol [HDL‐C], low‐density lipoprotein cholesterol [LDL‐C], total cholesterol [TC], and triglycerides [TG]).

Results:

MVPA was not related to plasma lipids (P > 0.05). Independent of age, sex, energy intake, and waist circumference z‐score, sedentary behavior and LPA were associated with HDL‐C (β = ?0.23, 95% CI ?0.42 to ?0.04, P = 0.020; β = 0.20, 95% CI 0.14 to 0.39, P = 0.036, respectively). The strength of the associations remained after additionally adjusting for MVPA (sedentary behavior: β = ?0.22, 95% CI ?0.44 to 0.006, P = 0.056; LPA: β = 0.19, 95% CI ?0.005 to 0.38, P = 0.056, respectively).

Conclusion:

Substituting at least LPA for sedentary time may contribute to the development of healthy HDL‐C levels among overweight and obese children, independent of their adiposity. Comprehensive prevention and treatment strategies to improve plasma HDL‐C among overweight and obese children should target reductions in total sedentary time and promote the benefits of LPA, in addition to promoting healthy levels of adiposity, healthy dietary behaviors, and MVPA.

     

Visceral fat and liver fat are independent predictors of metabolic risk factors in men

We examined the independent associations among abdominal adipose tissue (AT), liver fat, cardiorespiratory fitness (CRF), and lipid variables in 161 Caucasian men who had a wide variation in adiposity. We measured AT and liver fat by computed tomography and CRF by a maximal exercise test on a treadmill. Visceral AT remained a significant (P or= 0.05) correlate of any lipid variable after control for visceral AT and CRF. Furthermore, subdivision of subcutaneous AT into deep and superficial depots did not alter these observations. Visceral AT was the strongest correlate of liver fat and remained so after control for abdominal subcutaneous AT, CRF, and alcohol consumption (r = -0.34, P < 0.01). In contrast, abdominal subcutaneous AT and CRF were not significant (P > 0.10) correlates of liver fat after control for visceral AT. Visceral AT remained a significant (P < 0.01) correlate of TG, HDL-C, and TC/HDL-C independent of liver fat. However, liver fat was also a significant correlate (P 相似文献   

Visceral adiposity is associated with serum retinol binding protein-4 levels in healthy women

Objective: Retinol binding protein‐4 (RBP4) has been reported to impair insulin sensitivity throughout the body. We investigated the relationship between serum RBP4 levels and adiposity indices as well as metabolic risk variables. Research Methods and Procedure: We recruited a total of 102 healthy women 21 to 67 years old. We assessed body composition by computed tomography and divided the study population into four groups based on body weight and visceral fat area (non‐obese without visceral adiposity, non‐obese with visceral adiposity, obese without visceral adiposity, and obese with visceral adiposity). Serum RBP4 levels were measured by radioimmunoassay. Results: Despite similar levels of total body fat, non‐obese women had lower systolic blood pressure, total cholesterol, triglyceride (TG), low‐density lipoprotein (LDL)‐cholesterol levels, insulin resistance indices, and RBP4 levels than non‐obese women with visceral adiposity and had higher high‐density lipoprotein‐cholesterol levels. Similarly, obese women without visceral adiposity had lower blood pressure, total cholesterol, TG levels, insulin resistance indices, and RBP4 levels than obese women with visceral adiposity. In addition, despite having increased body fat, obese women without visceral adiposity had lower TGs, insulin resistance indices, and serum RBP4 levels than non‐obese women with visceral adiposity. By step‐wise multiple regression analysis, visceral fat areas and LDL‐cholesterol levels independently affected RBP4 levels. Discussion: We determined that serum RBP4 levels are independently associated with visceral fat and LDL‐cholesterol levels. These results suggest that, irrespective of body weight, visceral obesity is an independent predictor of serum RBP4 levels, and RBP4 may represent a link between visceral obesity and cardiovascular disease.     

Relationships of BMI to Cardiovascular Risk Factors Differ by Ethnicity

The burden of cardiovascular risk associated with obesity disproportionately affects African Americans and little is known about ethnic/racial differences in the relationship of obesity to cardiometabolic risk. This report assesses whether obesity is similarly associated with cardiometabolic risk factors in African Americans and whites of European ancestry. Cross‐sectional observational data from the Jackson Heart Study (JHS) and the Framingham Heart Study (FHS) were compared. This analysis uses participants aged 35–74 years with BMI >18.5 kg/m², and free of prevalent cardiovascular disease (CVD), from the initial JHS clinical examination (2000–2004) and the FHS Offspring (1998–2001) and Third Generation (2002–2005) cohorts. Participants were evaluated for the presence of lipid abnormalities, hypertension, and diabetes. Overall, 4,030 JHS (mean age 54 years, 64% women) and 5,245 FHS (mean age 51 years, 54% women) participants were available for analysis. The prevalence of all risk factors except high triglycerides and low high‐density lipoprotein (HDL) was substantially higher in JHS (all P < 0.001) and BMI was associated with increasing prevalence of most CVD risk factors within each race. For diabetes mellitus, hypertension, and low HDL, steeper relationships to BMI were observed in FHS than in JHS (P values <0.001–0.016). There were larger proportional increases in risk factor prevalence with increasing BMI in whites than in African Americans. The higher prevalence rates of cardiometabolic risk factors at nearly all levels of BMI in African Americans, however, suggest that additional factors contribute to the burden of CVD risk in African Americans.     

Comparison of bioelectrical impedance and BMI in predicting obesity-related medical conditions

Objective : To determine the relative validity of specific bioelectrical impedance analysis (BIA) prediction equations and BMI as predictors of physiologically relevant general adiposity. Research Methods and Procedures : Subjects were >12, 000 men and women from the Third National Health and Nutrition Examination Survey population. We examined the correlations between BMI and percentage body fat based on 51 different predictive equations, blood pressure, and blood levels of glucose, high‐density lipoprotein cholesterol, and triglycerides, which are known to reflect adiposity, while controlling for other determinants of these physiological measures. Results : BMI consistently had one of the highest correlations across biological markers, and no BIA‐based measure was superior. Percent body fat estimated from BIA was minimally predictive of the physiological markers independent of BMI. Discussion : These results suggest that BIA is not superior to BMI as a predictor of overall adiposity in a general population.     

Association analysis of 33 lipoprotein candidate genes in multi-generational families of African ancestry

African ancestry individuals have a more favorable lipoprotein profile than Caucasians, although the mechanisms for these differences remain unclear. We measured fasting serum lipoproteins and genotyped 768 tagging or potentially functional single nucleotide polymorphisms (SNPs) across 33 candidate gene regions in 401 Afro-Caribbeans older than 18 years belonging to 7 multi-generational pedigrees (mean family size 51, range 21–113, 3,426 relative pairs). All lipoproteins were significantly heritable (P < 0.05). Gender-specific analysis showed that heritability for triglycerides was much higher (P < 0.01) in women than in men (women, 0.62 ± 0.18, P < 0.01; men, 0.13 ± 0.17, P > 0.10), but the heritability for LDL cholesterol (LDL-C) was higher (P < 0.05) in men than in women (men, 0.79 ± 0.21, P < 0.01; women, 0.39 ± 0.12, P < 0.01). The top 14 SNPs that passed the false discovery rate threshold in the families were then tested for replication in an independent population-based sample of 1,750 Afro-Caribbean men aged 40+ years. Our results revealed significant associations for three SNPs in two genes (rs5929 and rs6511720 in LDLR and rs7517090 in PCSK9) and LDL-C in both the family study and in the replication study. Our findings suggest that LDLR and PCSK9 variants may contribute to a variation in LDL-C among African ancestry individuals. Future sequencing and functional studies of these loci may advance our understanding of genetic factors contributing to LDL-C in African ancestry populations.Lipoprotein abnormalities, characterized by elevated levels of LDL cholesterol (LDL-C) and triglycerides (TRIG) and low levels of HDL cholesterol (HDL-C), have a central role in the development of atherosclerotic coronary heart disease (CHD). A recent meta-analysis, including 3,000 individuals with CHD-related deaths, showed that HDL-C and LDL-C are independently associated with CHD risk (1). There is also considerable evidence that high levels of TRIG are an additional, independent risk factor for CHD (2, 3), although this is still controversial (4).Individuals of African ancestry have a more favorable lipoprotein profile than Caucasians, characterized by lower levels of TRIG and higher levels of HDL-C (5–8). The mechanisms responsible for these ethnic differences remain to be defined. In particular, the differences in TRIG levels are independent of the greater degree of obesity among individuals of African ancestry and several other risk factors and appear to be consistent across African populations in different environments (9), indicating a possible role of genetic factors. Although genetic factors are important in determining lipoprotein levels, little data exists regarding the importance of heredity and specific genetic factors in determining lipoprotein levels in populations of African ancestry, especially outside the US, and the findings from previous studies in African-Americans may not necessarily apply to other African ancestry populations. Recently, several genome-wide association studies identified a number of loci contributing to inter-individual variation in lipoprotein levels (10, 11). However, the majority of these studies were restricted to Caucasian populations. Given the ethnic differences in lifestyle and environmental factors, as well as in genetic background, it is important to examine genes related to lipoprotein metabolism in different ethnic groups. Therefore, we examined the heritability of fasting, serum levels of HDL-C, LDL-C, and TRIG and systematically screened for association with 33 positional and biological candidate genes in large, multigenerational families of African ancestry.     

Relationship of visceral adiposity to cardiovascular disease risk factors in black and white teens

Objective: We tested the hypothesis that visceral adiposity, compared with general adiposity, would explain more of the variance in cardiovascular disease (CVD) risk factors. Research Method and Procedures: Subjects were 464 adolescents (238 black and 205 girls). Adiposity measures included visceral adipose tissue (VAT; magnetic resonance imaging), percent body fat (%BF; DXA), BMI, and waist girth (anthropometry). CVD risk factors were fasting insulin, fibrinogen, total to high‐density lipoprotein‐cholesterol ratio, triglycerides (TGs), systolic blood pressure, and left ventricular mass indexed to height^2.7. Results: After adjustment for age, race, and sex, all adiposity indices explained significant proportions of the variance in all of the CVD risk factors; %BF tended to explain more variance than VAT. Regression models that included both %BF and VAT found that both indices explained independent proportions of the variance only for total to high‐density lipoprotein‐cholesterol ratio. For TGs, the model that included both %BF and VAT found that only VAT was significant. For systolic blood pressure and left ventricular mass indexed to height^2.7, anthropometric measures explained more of the variance than VAT and %BF. Discussion: The hypothesis that visceral adiposity would explain more variance in CVD risk than general adiposity was not supported in this relatively large sample of black and white adolescents. Only for TGs did it seem that VAT was more influential than %BF. Perhaps the deleterious effect of visceral adiposity becomes greater later in life as it increases in proportion to general adiposity.     

Medium‐Chain Oil Reduces Fat Mass and Down‐regulates Expression of Adipogenic Genes in Rats

Objective: To test the hypothesis that adipose tissue could be one of the primary targets through which medium‐chain fatty acids (MCFAs) exert their metabolic influence. Research Methods and Procedures: Sprague‐Dawley rats were fed a control high‐fat diet compared with an isocaloric diet rich in medium‐chain triglycerides (MCTs). We determined the effects of MCTs on body fat mass, plasma leptin and lipid levels, acyl chain composition of adipose triglycerides and phospholipids, adipose tissue lipoprotein lipase activity, and the expression of key adipogenic genes. Tissue triglyceride content was measured in heart and gastrocnemius muscle, and whole body insulin sensitivity and glucose tolerance were also measured. The effects of MCFAs on lipoprotein lipase activity and adipogenic gene expression were also assessed in vitro using cultured adipose tissue explants or 3T3‐L1 adipocytes. Results: MCT‐fed animals had smaller fat pads, and they contained a considerable amount of MCFAs in both triglycerides and phospholipids. A number of key adipogenic genes were down‐regulated, including peroxisome proliferator activated receptor γ and CCAAT/enhancer binding protein α and their downstream metabolic target genes. We also found reduced adipose tissue lipoprotein lipase activity and improved insulin sensitivity and glucose tolerance in MCT‐fed animals. Analogous effects of MCFAs on adipogenic genes were found in cultured rat adipose tissue explants and 3T3‐L1 adipocytes. Discussion: These results suggest that direct inhibitory effects of MCFAs on adiposity may play an important role in the regulation of body fat development.