Fat distribution, aerobic fitness, blood lipids, and insulin sensitivity in African-American and European-American women

Current state of unhealthy living characteristics in White, African American and Latinx populations

The United States (US) is similar to most industrialized countries in that it falls short on many of the basic metrics related to cardiovascular and overall health. These metrics include nutritional patterns, levels of physical activity (PA), cardiorespiratory fitness (CRF), and prevalence of overweight and obesity. These issues are even more apparent in underserved communities, among whom unhealthy living characteristics cluster and contribute to a disproportionate chronic disease burden. The reasons for these inequities are complex and include social and economic factors as well as reduced access to health care. CRF has been demonstrated to be a critically important risk factor that tends to be lower in disadvantaged groups. In this article we discuss the current state of health & lifestyle characteristics in the US, the impact of social inequality on health, and the particular role that CRF and PA patterns play in the current state of unhealthy living characteristics as they relate to underserved populations.

The Association of Upper Body Obesity with Insulin Resistance in the Newfoundland Population

Body-fat distribution is a primary risk factor for insulin resistance and cardiovascular disease. Visceral fat explains only a portion of this risk. The link between upper-body fat and insulin resistance is uncertain. Furthermore, upper-body fat is not clearly defined. Dual-energy X-ray absorptiometry (DXA) can accurately quantify body fat. In this study, we explored the relationship between non-visceral upper-body adiposity and insulin resistance and other markers of metabolic syndrome. Fat proportions in the upper body, leg, and visceral regions were quantified by using DXA in 2547 adult Newfoundlanders aged 19 and older. Adjusting for remaining fat regions, we performed partial correlation analysis for each body region and insulin resistance defined by the Homeostatic Model of Assessment (HOMA). Similarly, partial correlation analysis was also performed between each fat region and other markers of metabolic syndrome, including high-density lipoprotein cholesterol (HDL), triglycerides (TG), body mass index (BMI), and blood pressure. Major confounding factors, including age, caloric intake, and physical activity, were statistically controlled by using partial correlation analysis. Interactions between sex, menopausal status, and medication status were also tested. Arm adiposity was correlated with HOMA-IR (R = 0.132, p < 0.001) and HOMA-β (R = 0.134, p < 0.001). Visceral adiposity was correlated with HOMA-IR (R = 0.230, p < 0.001) and HOMA-β (R = 0.160, p < 0.001). No significant correlation between non-visceral trunk adiposity and insulin resistance was found. Non-visceral trunk adiposity was negatively correlated with HDL in men (R = −0.110, p < 0.001) and women (R = −0.117, p < 0.001). Non-visceral trunk adiposity was correlated with TG (total: R = 0.079, p < 0.001; men: R = 0.105, p = 0.012; women: R = 0.078, p = 0.001). In menopausal women, leg adiposity was negatively correlated with HOMA-IR (R = −0.196, p < 0.001) and HOMA-β (R = −0.101, p = 0.012). Upper-body adiposity in the arms is an independent contributor to insulin resistance. Upper-body adiposity in the non-visceral trunk region is an independent contributor to metabolic syndrome. Leg adiposity is protective against metabolic syndrome in women.

Age-specific markers of adiposity in patients with obstructive sleep apnea

OBJECTIVES

Adiposity can have varying effects on the individual depending upon its distribution pattern. We assessed age-related distribution of adipose tissue by anthropometric measures and bioelectrical impedance analysis, as well as their association with obstructive sleep apnea (OSA) severity.

METHODS

Participants were 169 elderly (aged ≥ 65 years) and 142 non-elderly (aged < 65 years) referred for overnight polysomnography. The associations between obesity parameters and apnea-hypopnea index (AHI) were determine by univariate and multivariate linear regression analyses. Area under receiver operating characteristic curve (AUC) was used to access the predicting performance of some parameters.

RESULTS

Compared with non-elderly, elderly showed higher conicity index and visceral adiposity (VA)/subcutaneous adiposity (SA), lower body mass index (BMI), neck circumference, waist circumference, hip circumference and SA. Multiple regression analyses revealed that VA and VA/SA were independently associated with AHI in elderly (explained 17.2% of the AHI ^0.5 variability), while BMI and VA/SA were independently associated with AHI in non-elderly (explained 25.9% of the AHI ^0.5 variability), after adjusting for age, sex, cigarette smoking, alcohol drinking and main comorbidities. In elderly, VA over 128 cm² and VA/SA less than 0.41 resulted in sensitivity, specificity and AUC of 0.382, 0.790, 0.580 and 0.176, 0.947, 0.553 in predicting moderate-to-severe OSA, respectively. In non-elderly, BMI over 24.7 kg/m² and VA/SA over 0.54 resulted in sensitivity, specificity and AUC of 0.883, 0.484, 0.704 and 0.550, 0.710, 0.667 in predicting moderate-to-severe OSA, respectively.

CONCLUSIONS

VA is strongly associated with OSA severity in elderly, independently of general obesity as per BMI standards, while general adiposity appears to be more strongly associated with OSA severity in non-elderly. Our study supports age-specific approaches should be developed with respect to prediction and treatment of OSA.

High-intensity exercise to promote accelerated improvements in cardiorespiratory fitness (HI-PACE): study protocol for a randomized controlled trial

Background

African Americans have a disproportionate prevalence and incidence of type 2 diabetes compared with Caucasians. Recent evidence indicates that low cardiorespiratory fitness (CRF) level, an independent risk factor for type 2 diabetes, is also more prevalent in African Americans than Caucasians. Numerous studies in Caucasian populations suggest that vigorous exercise intensity may promote greater improvements in CRF and other type 2 diabetes risk factors (e.g., reduction of glucose/insulin levels, pulse wave velocity, and body fat) than moderate intensity. However, current evidence comparing health benefits of different aerobic exercise intensities on type 2 diabetes risk factors in African Americans is negligible. This is clinically important as African Americans have a greater risk for type 2 diabetes and are less likely to meet public health recommendations for physical activity than Caucasians. The purpose of the HI-PACE (High-Intensity exercise to Promote Accelerated improvements in CardiorEspiratory fitness) study is to evaluate whether high-intensity aerobic exercise elicits greater improvements in CRF, insulin action, and arterial stiffness than moderate-intensity exercise in African Americans.

Methods/Design

A randomized controlled trial will be performed on overweight and obese (body mass index of 25–45 kg/m²) African Americans (35–65 years) (n = 60). Participants will be randomly assigned to moderate-intensity (MOD-INT) or high-intensity (HIGH-INT) aerobic exercise training or a non-exercise control group (CON) for 24 weeks. Supervised exercise will be performed at a heart rate associated with 45–55% and 70–80% of VO₂ max in the MOD-INT and HIGH-INT groups, respectively, for an exercise dose of 600 metabolic equivalents of task (MET)-minutes per week (consistent with public health recommendations). The primary outcome is change in CRF. Secondary outcomes include change in insulin sensitivity (measured via an intravenous glucose tolerance test), skeletal muscle mitochondrial oxidative capacity (via near-infrared spectroscopy), skeletal muscle measurements (i.e., citrate synthase, COX IV, GLUT-4, CPT-1, and PGC1-α), arterial stiffness (via carotid-femoral pulse wave velocity), body fat, C-reactive protein, and psychological outcomes (quality of life/exercise enjoyment).

Discussion

The anticipated results of the HI-PACE study will provide vital information on the health effects of high-intensity exercise in African Americans. This study will advance health disparity research and has the potential to influence future public health guidelines for physical activity.

Trial registration

ClinicalTrials.gov identifier: NCT02892331. Registered on September 8, 2016.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3611-1) contains supplementary material, which is available to authorized users.

Comparative Cardiorespiratory Fitness in Children: Racial Disparity May Begin Early in Childhood

African American (AA) adults are reported to have lower levels of cardiorespiratory fitness (CRF) as compared to Caucasian adults. CRF is linked to cardiovascular morbidity and mortality. We hypothesized that the disparities start early in childhood. This was a retrospective analysis of the cardiopulmonary exercise test (CPET). We included normal healthy children, ≤ 18 years of age, who had normal electrocardiograms and normal cardiac function. We excluded patients with congenital heart disease, obesity and suboptimal exercise test. The entire cohort was divided into two groups based on race (Caucasian vs. AA) and then further subcategorized by gender. The cohort of 248 patients had a mean ± SD age of 14.4 ± 2.1 years. 158 (60.8%) were males and 158 (60.8%) were Caucasians. Oxygen consumption was higher among Caucasian children when compared to the AA children (48.7 ± 7.9 vs. 45.4 ± 7 mL/kg/min, p = 0.01). This racial disparity continued to persist when comparisons were performed separately for girls and boys. Upon comparing the four groups, the AA females were found to have the lowest values of VO_2max, exercise time and METS (p = 0.001). Thus, in conclusion, the AA children have significantly lower level of CRF, as measured by VO_2max and exercise time. The racial disparity is independent of gender. African American females show the lowest level of aerobic capacity. The findings of our study suggest that the racial disparity in the CRF levels seen in the adult population may begin early in childhood.

Utilizing a low-carbohydrate/high-protein diet to improve metabolic health in individuals with spinal cord injury (DISH): study protocol for a randomized controlled trial

Background

Metabolic disorders (e.g., impaired glucose tolerance, insulin resistance, and type 2 diabetes) are more prevalent in people with spinal cord injury (SCI) than able-bodied individuals. Dietary modification is a more cost-effective treatment option than pharmacological therapies for reducing the risk of metabolic dysfunction. Lowering carbohydrate, increasing protein, and maintaining a proper dietary fat intake are expected to induce favorable adaptations in glucose control, body fat distribution, and the composition of the gut microbiome. However, dietary modification has not been rigorously investigated in people with SCI. The purpose of this study is to determine if an 8-week low-carbohydrate/high-protein (LC/HP) dietary intervention will show improvements in clinically important metrics of metabolic function, body composition, the composition of gut bacteria, and quality of life.

Methods/design

We intend to recruit 100 participants with chronic traumatic SCI (3 years postinjury, C5–L2, American Spinal Injury Association impairment scale A–D, and aged 18–65 years) and insulin resistance, impaired glucose tolerance or untreated type 2 diabetes and randomly assign them to an 8-week LC/HP dietary intervention group or a control group. The daily LC/HP dietary intervention includes ~ 30% total energy as protein (1.6 g/kg per day) with a carbohydrate-to-protein ratio < 1.5 and fat intake set at ~ 30% of the total energy intake. The control group does not receive any dietary intervention and are continuing with their regular daily diets. Glucose tolerance, insulin sensitivity, β-cell function, body composition, gut microbiome composition, and quality of life measures are assessed at week 1, before starting the LC/HP dietary intervention, and at week 8, after completion of the LC/HP dietary intervention.

Discussion

New information derived from this project will result in the development of a low-cost, simple, self-administered LC/HP dietary intervention for improving metabolic function in individuals with chronic SCI, improved understanding of the composition of gut bacteria in SCI, and how a LC/HP dietary intervention alters gut bacteria composition. In addition, this project will improve our understanding of the relationship between metabolic function and quality of life in individuals with long-standing SCI.

Trial registration

ClinicalTrials.gov, NCT03207841. Registered on 5 June 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3520-3) contains supplementary material, which is available to authorized users.

Adiposity-Independent Effects of Aging on Insulin Sensitivity and Clearance in Mice and Humans

OBJECTIVE

Aging is associated with impaired insulin sensitivity and increased prevalence of type 2 diabetes. However, it remains unclear whether aging-associated insulin resistance is due to increased adiposity or other age-related factors. To address this question, the impact of aging on insulin sensitivity was investigated independently of changes in body composition.

METHODS

Cohorts of mice aged 4 to 8 months ("young") and 18 to 27 months ("aged") exhibiting similar body composition were characterized for glucose metabolism on chow and high-fat diets. Insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp analyses. The relationship between aging and insulin resistance in humans was investigated in 1,250 nondiabetic Mexican Americans who underwent hyperinsulinemic-euglycemic clamps.

RESULTS

In mice with similar body composition, age had no detrimental effect on plasma glucose and insulin levels. While aging did not diminish glucose tolerance, hyperinsulinemic-euglycemic clamps demonstrated impaired insulin sensitivity and reduced insulin clearance in aged mice on chow and high-fat diets. Consistent with results in the mouse, age remained an independent determinant of insulin resistance after adjustment for body composition in Mexican American males.

CONCLUSIONS

This study demonstrates that in addition to altered body composition, adiposity-independent mechanisms also contribute to aging-associated insulin resistance in mice and humans.

Association between carbohydrate intake and body composition: The Korean National Health and Nutrition Examination Survey

OBJECTIVE

Several studies have investigated the effects of dietary carbohydrate intake on body composition. However, the results are controversial and few studies have been conducted on an Asian population. The aim of this study was to investigate whether dietary carbohydrate intake is associated with body composition in Korean adults.

METHODS

The present study used data from the Korean National Health and Nutrition Examination Survey, a cross-sectional survey of Korean civilians, conducted from 2008 to 2011. The study analyzed 9594 participants. Carbohydrate intake was defined as the proportion of energy consumed from carbohydrate. Waist circumference, body mass index, and lean and fat mass using a whole-body dual-energy x-ray absorptiometry scanner were measured as body composition parameters.

RESULTS

After adjusting for age, household income, smoking, alcohol consumption, physical activity, history of diabetes, hypertension, dyslipidemia, and intake of energy and fiber per day, the proportion of carbohydrate intake was positively correlated with total limb lean mass in men (β = 0.141, P = 0.046), and in women, the proportion of carbohydrate intake was positively associated with appendicular skeletal muscle mass index (β = 0804, P = 0.003) but negatively associated with trunk fat percentage (β = -0.075, P = 0.026). Total limb lean mass and appendicular skeletal muscle mass index in women showed an increasing trend as the proportion of carbohydrate intake increased.

CONCLUSIONS

No positive association was found between the proportion of carbohydrate intake and any measure of obesity or body fat mass in either men or women. Further studies are needed to evaluate the effects of quantity and quality of carbohydrate intake on body composition.

Differences in Glucose Metabolism Among Women With Spinal Cord Injury May Not Be Fully Explained by Variations in Body Composition

OBJECTIVE

To investigate the differences in glucose metabolism among women with paraplegic, and tetraplegic spinal cord injury (SCI) in comparison to their able-bodied (AB) counterparts after adjusting for differences in body composition.

DESIGN

Cross-sectional study. After an overnight fast, each participant consumed a 75-g glucose solution for oral glucose tolerance test (OGTT). Blood glucose, insulin, and C-peptide concentrations were analyzed before and 30, 60, 90, and 120 minutes after ingesting glucose solution. Insulin sensitivity index (ISI) was estimated using the Matsuda index. Percentage fat mass (%FM) and total body lean mass (TBLM) were estimated using data from dual-energy x-ray absorptiometry. Visceral fat (VF) was quantified using computed tomography. Outcome measures were compared among groups using analysis of covariance with %FM (or VF) and TBLM as covariates.

SETTING

Research university.

PARTICIPANTS

Women (N=42) with SCI (tetraplegia: n=8; paraplegia: n=14) and their race-, body mass index-, and age-matched AB counterparts (n=20).

INTERVENTIONS

Not applicable.

RESULTS

At fasting, there was no difference in glucose homeostasis (glucose, insulin, C-peptide concentrations) among 3 groups of women. In contrast, glucose, insulin, and C-peptide concentrations at minute 120 during OGTT were higher in women with tetraplegia versus women with paraplegia and AB women (P<.05, adjusted for TBLM and %FM). In addition, women with tetraplegia had lower ISI (P<.05, adjusted for TBLM and %FM) versus AB women. These differences remained after adjusting for VF and TBLM.

CONCLUSION

Our study confirms that impaired glucose metabolism among women with tetraplegia may not be fully explained by changes in their body composition. Future studies exploring additional factors involved in glucose metabolism are warranted.

Central fat accretion and insulin sensitivity: differential relationships in parous and nulliparous women

BACKGROUND/OBJECTIVES

Childbearing is associated with a disproportionate accumulation of visceral fat and an increased risk of metabolic disease. However, it is unknown whether the visceral fat accretion associated with pregnancy modifies a woman's risk for metabolic disease. The purpose of this study was to test whether the association between abdominal fat and insulin sensitivity differs by parity status in healthy overweight women.

SUBJECTS/METHODS

Intra-abdominal adipose tissue (IAAT) via CT, body composition by DXA, insulin sensitivity via intravenous glucose tolerance test and minimal model (SI), HOMA-IR, and cardiorespiratory fitness (VO2max) were assessed in 212 non-diabetic, premenopausal, overweight non-Hispanic white and African-American women.

RESULTS

Nulliparous women (n=98) were younger, had less IAAT and higher VO2max, but similar SI, HOMA-IR and leg fat, compared to parous (n=114). In nulliparous women, IAAT was negatively associated with SI, controlling for age, race and body fat mass (r=-0.40, P<0.001), but this relationship was attenuated in parous women (r=-0.15, P=0.16). In multiple linear regression analysis, leg fat and IAAT were significant predictors of SI in nulliparous, but not parous women.

CONCLUSIONS

Results suggest that greater IAAT in parous women does not lead to greater insulin resistance; rather, transient insulin resistance during pregnancy may encourage intra-abdominal fat accumulation that is metabolically benign. This underscores the need to consider parity when assessing cardiometabolic risk.

Triglyceride glucose-waist circumference, a novel and effective predictor of diabetes in first-degree relatives of type 2 diabetes patients: cross-sectional and prospective cohort study

BACKGROUND

Body mass index (BMI), waist circumference (WC), visceral adiposity index (VAI), triglyceride glucose index (TyG), TyG-BMI, and TyG-WC have been reported as markers of insulin resistance or type 2 diabetes mellitus (T2DM). However, little is known about the associations between the aforementioned markers and the risk of prediabetes and diabetes in first-degree relatives (FDRs) of T2DM patients.

METHODS

1544 FDRs of T2DM patients (635 men and 909 women) were enrolled in the initial cross-sectional study and all of them finished corresponding examinations. Logistic regression analysis and receiver operating characteristic (ROC) curve were used to compare and identify the associations of the six parameters (BMI, WC, VAI, TyG, TyG-BMI and TyG-WC) with the prevalence of prediabetes and diabetes. Subsequently, 452 of them were followed-up for an average of 5 years. Cox proportional hazard regression model was applied to confirm the predictive value of the optimal marker.

RESULTS

Among the indices, TyG-WC was more strongly associated with the prevalence of prediabetes and diabetes. Compared with participants in the lowest quartile of TyG-WC, the adjusted odds ratio and 95 % CIs for prediabetes and diabetes was 11.19 (7.62-16.42) for those in the top quartile of TyG-WC. Moreover, the largest AUC was also observed in TyG-WC (0.765, 95 % CIs 0.741-0.789, P < 0.001). The robust predictive value of TyG-WC was further confirmed in the follow-up study (HR: 7.13, 95 % CIs 3.41-14.90, P < 0.001).

CONCLUSIONS

TyG-WC is a novel and clinically effective marker for early identifying the risks of prediabetes and diabetes in FDRs of T2DM patients.

Examining the prevalence of metabolic syndrome among overweight/obese African-American breast cancer survivors vs. matched non-cancer controls

PURPOSE

Metabolic Syndrome (MetS) is more predominant in overweight, obese and minority populations. This study examined the prevalence of MetS in an exclusively African-American (AA) cohort of breast cancer (BC) survivors; an underrepresented group in previous studies demonstrating negative BC outcomes disparities for females with MetS.

METHODS

Using a case-control design, overweight/obese AA women with treated Stage I-IIIa BC were matched 1:1 on age, race, sex, and body mass index (BMI) category with non-cancer population controls (n = 444). Three of the following conditions were used to define MetS: HDL cholesterol <50 mg/dL (1.3 mmol/L), serum triglycerides ≥150 mg/dL (1.7 mmol/L), blood glucose ≥100 mg/dL (or on treatment), waist circumference ≥88 cm, or ≥130 mmHg systolic or ≥85 mmHg diastolic blood pressure (or on treatment). Matched-pairs analyses were conducted.

RESULTS

For BC cases, most women had self-reported Stage I (n = 76) or Stage II (n = 91) disease and were 6.9 (±5.2) years post-diagnosis. MetS was significantly lower in BC survivors vs. their non-cancer population controls (43.2 vs. 51.4 %, respectively; p < 0.05). The diagnosis of MetS did not differ by BMI stratification. A lower prevalence of ≥2 risk factors (80.2 vs. 85.6 %, p < 0.05) was observed for all cases vs.

CONTROLS

CONCLUSIONS

While MetS occurred less frequently in our BC cases vs. non-cancer controls, our estimates are nearly two times those reported in other BC survivors, suggesting important racial/ethnic differences.

IMPLICATIONS FOR CANCER SURVIVORS

The prognostic implications of MetS among AA BC survivors remain unknown and warrant further investigation.

Alterations in Hemoglobin and Serum 25-hydroxyvitamin D are Related Before and After Weight Loss Independent of African Admixture

African American (AA) and European American (EA) women often exhibit differences in hemoglobin (Hb) and 25-hydroxyvitamin D [25(OH)D], both of which can be altered by calorie restriction leading to weight loss. Given these known differences, it is of clinical interest to examine the potential for race-specific, adverse responses to weight loss. Sixty-four overweight (BMI 27-29.9 kg/m²), premenopausal women consumed a standardized, very-low calorie diet to reduce BMI < 25 kg/m2. Ancestry informative markers provided estimates of African admixture, an objective mean of expressing race. Blood sampling and anthropometric measures were performed at baseline and upon meeting target BMI. At baseline, in the overweight state, Hb (g/dL) (AA, 11.7 ± 0.9 vs. EA, 12.5 ± 0.8; p < .01) and 25(OH)D (nmol/L) (AA, 35.7 ± 12.9 vs. EA, 57.0 ± 20.0; p < .01) were lower in AAs. After weight loss, Hb decreased (AA, -0.5 ± 0.7 vs. EA, -0.4 ± 0.6; p = .48) to a similar extent among races. Conversely, 25(OH)D increased (AA, 43.4 ± 14.0 vs. EA 68.2 ± 24.3; p < .01) though the magnitude of change (Δ) was not different (AA, +7.8 ± 13.5 vs. EA, +11.2 ± 16.7; p = .37) between races. Multiple linear regression revealed a positive association between ΔHb and Δ25(OH)D (r = .386; p < .01) adjusted for African admixture, Δtestosterone, and Δbody fat%. Path analyses revealed a significant indirect effect of Δbody fat% on ΔHb through Δ25(OH)D, β =-0.023, CI [-0.06, -0.004]. Following 15% weight loss, participants with the largest increase in serum 25(OH)D exhibited the smallest decrease in Hb. Future research should clarify the optimal degree of calorie restriction to stimulate weight loss while mitigating the potential risk of anemia associated with dieting efforts.

The Visceral Adiposity Index in Comparison with Easily Measurable Anthropometric Markers Did Not Improve Prediction of Diabetes

OBJECTIVES

We evaluated the ability of the visceral adiposity index (VAI) compared to hypertriglyceridemic-waist (HTGW) phenotype, body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR) and waist-to-hip ratio (WHR) as a possible predictor of diabetes in a nondiabetic high-risk population.

METHODS

We analyzed 7-year follow-up data in nondiabetic first-degree relatives of consecutive patients 30 to 70 years of age with type 2 diabetes and with at least 1 follow-up examination (N=1720). The primary outcome was the diagnosis of type 2 diabetes based on repeated oral glucose tolerance tests. We examined the incidence of type 2 diabetes across quintiles of the VAI and plotted a receiver operating characteristic (ROC) curve to compare the abilities of predicting type 2 diabetes of the VAI, BMI, WC, WHR and WHtR.

RESULTS

The highest quintile of VAI compared with the lowest quintile was associated with type 2 diabetes in age- and gender-adjusted models (OR 2.45; 95% CI 1.56, 3.86). Those with the HTGW phenotype were 2.36 times (OR 2.36; 95% CI: 161, 3.44) more likely to develop type 2 diabetes than those with normal WCs and normal triglyceride levels. On ROC curve analysis, almost similar areas under the ROC were found for BMIs (60.9%; 95% CI: 57.1, 64.6); WC (61.0%, 95% CI 57.4, 64.5); WHtR (62.6%; 95% CI: 59.1, 66.2); WHR (55.7%; 95% CI 52.2, 59.3) and VAI (58.3%; 95% CI: 54.5, 62.1).

CONCLUSIONS

These data provide further evidence that VAI and HTGW are robust predictors of type 2 diabetes, but the predictive power was similar to that of BMI, WC, WHtR and WHR in our study population.

Cardiorespiratory Fitness and Light-Intensity Physical Activity Are Independently Associated with Reduced Cardiovascular Disease Risk in Urban Black South African Women: A Cross-Sectional Study

BACKGROUND

Low levels of physical activity, poor cardiorespiratory fitness, and a sedentary lifestyle have been associated with increased risk for cardiovascular disease (CVD) and type 2 diabetes (T2D). Few studies have examined their independent associations in an urban black sub-Saharan African population.

OBJECTIVES

To examine the independent associations of physical activity, cardiorespiratory fitness, and sedentary time on body composition and cardiometabolic risk factors for CVD and T2D in black South African women.

MATERIALS AND METHODS

A subsample (n = 76; 18-45 years) was recruited, as part of a cross-sectional study. Accelerometry, cardiorespiratory fitness, body composition, insulin sensitivity, serum lipids, and blood pressure were measured.

RESULTS

Light- but not moderate- to vigorous intensity physical activity was inversely associated with trunk fat mass (r = -0.25, P = 0.03). Sedentary time was associated with triglyceride (TG) (r = 0.36, P = 0.01) and TG/HDL-C (r = 0.34, P = 0.04), and these relationships were independent of body fat. Cardiorespiratory fitness was inversely associated with body fat % (r = -0.34, P = 0.02), central fat mass (r = -0.31, P = 0.03), visceral adipose tissue (VAT, r = -0.47, P < 0.01), and insulin resistance (HOMA-IR; r = -0.41, P = 0.01). The association between cardiorespiratory fitness and HOMA-IR was independent of body fat and physical activity, but not VAT. Cardiorespiratory fitness was inversely associated with sedentary time (r = -0.31, P = 0.03), but not with any of the physical activity variables (P > 0.05).

CONCLUSION

Both physical activity and cardiorespiratory fitness were associated with reduced total and central fat mass, VAT, and reduced cardiometabolic risk for CVD and T2D. Longitudinal studies are required to confirm whether the promotion of increasing light physical activity, while reducing sedentary time and increasing cardiorespiratory fitness, reduces the risk for obesity, CVD and T2D.

Specific characterization of regional storage fat in upper and lower limbs of young healthy adults

This study aimed to determine the specific characterization of regional storage fat in the upper limb as compared to the lower limb of young healthy adults. The regional storage fat and skeletal muscle in upper and lower limbs were obtained by magnetic resonance imaging (MRI) and multifrequency bioelectrical impedance analysis (BIA). For MRI measurements, images at the continuous anatomical cross-sectional areas of subcutaneous adipose tissue and skeletal muscle in the upper arm and thigh were selected for the analysis. Values measured by MRI were larger than those measured by BIA. MRI data showed that the percentage of fat was significantly higher in the upper arm compared to the thigh in both men and women. This study suggests that BIA results in a significantly different estimation of the whole body and limb composition when compared to MRI and that MRI is useful to determine regional specificities in the limb composition. From these quantified evaluation, we found significantly large amount of regional storage fat in upper limbs of young healthy adults, especially women.

Modulation of the lipidomic profile due to a lipid challenge and fitness level: a postprandial study

Background

The lipid composition of plasma is known to vary due to both phenotypic factors such as age, gender and BMI as well as with various diseases including cancer and neurological disorders. However, there is little investigation into the variation in the lipidome due to exercise and/ or metabolic challenges. The objectives of this present study were (i) To identify the glycerophospholipid, sphingolipids and ceramide changes in response to an oral lipid tolerance test (OLTT) in healthy adults and (ii) To identify the effect of aerobic fitness level on lipidomic profiles.

Methods

214 healthy adults aged 18–60 years were recruited as part of a metabolic challenge study. A sub-group of 40 volunteers were selected for lipidomic analysis based on their aerobic fitness level. Ceramides, glycerophospholipids and sphingomyelins were quantified in baseline fasting plasma samples as well as at 60, 120, 180, 240 and 300 min following a lipid challenge using high-throughput flow injection ESI-MS/MS.

Results

Mixed model repeated measures analysis identified lipids which were significantly changing over the time course of the lipid challenge. Included in these lipids were lysophosphoethanolamines (LPE), phosphoethanolamines (PE), phosphoglycerides (PG) and ceramides (Cer). Five lipids (LPE a C18:2, LPE a C18:1, PE aa C36:2, PE aa C36:3 and N-C16:1-Cer) had a fold change > 1.5 at 120 min following the challenge and these lipids remained elevated. Furthermore, three of these lipids (LPE a C18:2, PE aa C36:2 and PE aa C36:3) were predictive of fasting and peak plasma TAG concentrations following the OLTT. Further analysis revealed that fitness level has a significant impact on the response to the OLTT: in particular significant differences between fitness groups were observed for phosphatidylcholines (PC), sphingomyelins (SM) and ceramides.

Conclusion

This study identified specific lipids which were modulated by an acute lipid challenge. Furthermore, it identified a series of lipids which were modulated by fitness level. Future lipidomic studies should take into account environmental factors such as diet and fitness level during biomarker discovery work.

Trial registration

Data, clinicaltrials.gov, NCT01172951

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-015-0062-x) contains supplementary material, which is available to authorized users.

Association between circulating endogenous androgens and insulin sensitivity changes with exercise training in midlife women

OBJECTIVE

Aging induces a shift in circulating hormones in women, accompanied by weight gain during the late reproductive, menopausal transition, and postmenopausal years. Exercise has been shown to counter weight gain; however, it might increase circulating androgens. A 6-month aerobic and resistance training exercise regimen was implemented to examine interrelationships between circulating sex hormones, body composition, aerobic capacity, insulin sensitivity, and insulin resistance.

METHODS

Twenty-eight women, aged 42 to 52 years, completed the 6-month intervention study. They were randomly assigned to either a control (CON; n = 10) group-and maintained their sedentary lifestyle-or an exercise intervention (EXE; n = 18) group. The exercise intervention consisted of combined aerobic and resistance workouts scheduled 6 days/week for 60 minutes/day. Body weight, composition, VO2 peak, plasma insulin, glucose, lipid profile, estradiol, testosterone, progesterone, dehydroepiandrosterone, and dehydroepiandrosterone sulfate (DHEAS) were measured at baseline and on month 6. Insulin sensitivity was estimated using the insulin sensitivity index and the quantitative insulin sensitivity check index, whereas insulin resistance was estimated using the homeostatic model for insulin resistance.

RESULTS

There was a trend toward increased DHEAS in both groups (P < 0.1), but not as a function of the intervention. Insulin sensitivity index increased in the EXE group compared with the CON group (P < 0.01). Multiple linear regression indicated that, at 6 months, DHEAS was a negative contributor to insulin sensitivity in the EXE group, but not in the CON group.

CONCLUSIONS

In midlife women, an increase in circulating DHEAS, such as that previously reported during the menopausal transition, is associated with higher insulin resistance, but exercise can mitigate this risk by improving insulin sensitivity, thereby countering the effects of DHEAS.

Ethnic differences in associations between fat deposition and incident diabetes and underlying mechanisms: the SABRE study

OBJECTIVE

To examine ethnic differences in ectopic fat and associations with incident diabetes.

METHODS

In a UK cohort study, 1338 Europeans, 838 South Asians, and 330 African Caribbeans living in London were aged 40-69 years at baseline. Baseline assessment included blood tests, anthropometry, and questionnaires. Anthropometry-based prediction equations estimated baseline visceral adipose tissue (VAT). Incident diabetes was ascertained from record review, self-report, or oral glucose tolerance testing.

RESULTS

South Asians had more and African Caribbeans less estimated VAT than Europeans. Both ethnic minorities had larger truncal skinfolds than Europeans. In men, adjustment for risk factors (BMI, smoking, systolic blood pressure, and HDL-cholesterol) markedly attenuated the association between estimated VAT and diabetes in Europeans (standardized subhazard ratios [95% CI]: from 1.74 [1.49, 2.03] to 1.16 [0.77, 1.76]) and African Caribbeans (1.72 [1.26, 2.35] to 1.44 [0.69, 3.02]) but not South Asians (1.60 [1.38, 1.86] to 1.90 [1.37, 2.64]). In women, attenuation was observed only for South Asians (1.80 [1.01, 3.23] to 1.07 [0.49, 2.31]). Associations between truncal skinfolds and diabetes appeared less affected by multivariable adjustment in South Asians and African Caribbeans than Europeans (1.24 [0.97, 1.57] and 1.28 [0.89, 1.82] versus 1.02 [0.77, 1.36] in men; 1.91 [1.03, 3.56] and 1.42 [0.86, 2.34] versus 1.23 [0.74, 2.05] in women).

CONCLUSIONS

Differences in overall truncal fat, as well as VAT, may contribute to the excess of diabetes in South Asian and African Caribbean groups, particularly for women.

Uncovering physiological mechanisms for health disparities in type 2 diabetes

Type 2 diabetes (T2D) prevalence in the United States is significantly higher in African Americans vs Whites. Yet, the physiological mechanisms contributing to this health disparity have been poorly described. To design effective strategies to reduce this disparity, there is a need to determine whether racial differences in diabetes prevalence are attributable to modifiable or non-modifiable factors. This review synthesizes and critically evaluates the potential physiological and genetic mechanisms that may contribute to the higher susceptibility of African Americans to T2D. These mechanisms include: 1) obesity and fat distribution; 2) metabolic flexibility; 3) muscle physiology; 4) energy expenditure and fitness; and 5) genetics. We focus on the clinical significance of findings and limitations of the recent literature.

Association between Appendicular Fat Mass and Metabolic Risk Factors

BACKGROUND

Different regional fat depots have different effects on lipid and glucose metabolism. The purpose of this study is to examine the relationship between body fat distribution as measured by dual-energy X-ray absorptiometry (DEXA) and metabolic risk factors and to disclose whether there is any difference between groups with and without metabolic syndrome (MS).

METHODS

A total of 292 participants (98 men, 194 women) over 19 years old underwent whole-body DEXA to evaluate body composition with respect to the whole body, leg, arm, and android regions. Anthropometry and blood tests for metabolic risks were measured.

RESULTS

One hundred and seven participants were diagnosed with MS. The MS group had significantly higher android fat (%) and had lower leg fat (%), arm fat (%), and appendicular (arms + legs) fat (%) than the non-MS group. Android fat (%) had a positive correlation with waist circumference (WC), systolic blood pressure (SBP), diastolic blood pressure (DBP), glucose, log insulin, hemoglobin A1c (HbA1c), triglyceride (TG), and low density lipoprotein cholesterol, and had a negative correlation with high density lipoprotein (HDL) cholesterol. Appendicular fat (%) had a negative correlation with WC, SBP, DBP, glucose, log insulin, HbA1c, and TG, and had a positive correlation with HDL cholesterol. The association of appendicular fat with metabolic risk was consistently observed in non-MS, but the association was not observed except for SBP, glucose and log insulin in MS.

CONCLUSION

In contrast with the adverse effects of android fat, appendicular fat distribution was associated with decreased risks of MS. The protective effect of appendicular fat against metabolic risk factors in non-MS was less characteristic in MS.

Low cardiorespiratory fitness in African Americans: a health disparity risk factor?

Low cardiorespiratory fitness (CRF) is a well-established risk factor for all-cause and cardiovascular disease mortality. African Americans have higher rates of cardiovascular disease compared with their Caucasian counterparts. However, the extent to which lower CRF levels contribute to the excess risk in African Americans has not been fully explored. The purpose of this review is to: (i) explore the literature evaluating the relationship between CRF and mortality specifically in African American populations; and (ii) critically evaluate the studies which have compared CRF between African American and Caucasians in epidemiological studies and clinical trials. We have further discussed several potential mechanisms that may contribute to the observation of lower CRF levels in African American compared with Caucasian adults, including potential racial differences in physical activity levels, muscle fiber type distribution, and hemoglobin levels. If lower CRF is generally present in African Americans compared with Caucasians, and is of a clinically meaningful difference, this may represent an important public health concern.

The application of visceral adiposity index in identifying type 2 diabetes risks based on a prospective cohort in China

Background

Visceral adiposity index (VAI), a novel sex-specific index for visceral fat measurement, has been proposed recently. We evaluate the efficacy of VAI in identifying diabetes risk in Chinese people, and compare the predictive ability between VAI and other body fatness indices, i.e., waist circumference (WC), body mass index (BMI) and waist- to- height ratio (WHtR).

Methods

Participants (n = 3,461) were recruited from an ongoing cohort study in Jiangsu Province, China. Hazard ratio (HR) and corresponding 95% confidence interval (CI) between diabetes risk and different body fatness indices were evaluated by Cox proportional hazard regression model. Receiver operating characteristic (ROC) curve and area under curve (AUC) were applied to compare the ability of identifying diabetes risk between VAI, WC, WHtR and BMI.

Results

A total number of 160 new diabetic cases occurred during the follow-up, with an incidence of 4.6%. Significant positive associations were observed for VAI with blood pressure, fasting plasma glucose, triglyceride, WC, BMI and WHtR. Moreover, increased VAI was observed to be associated with higher diabetes risk with a positive dose–response trend (p for trend < 0.001). As compared to individuals with the lowest VAI, those who had the highest VAI were at 2.55-fold risk of diabetes (95% CI: 1.58-4.11). The largest AUC was observed for VAI, following by WC, WHtR and BMI.

Conclusions

VAI is positively associated with the risk of diabetes. Compared to other indices for body fatness measurements, VAI is a better and convenience surrogate marker for visceral adipose measurement and could be used in identifying the risk of diabetes in large-scale epidemiologic studies.

Effects of age and aerobic fitness on myocardial lipid content

BACKGROUND

Aging and sedentary lifestyles lead to cardiac atrophy, ventricular stiffening, and impaired diastolic function. Both conditions are marked by increased adiposity, which can lead to ectopic fat deposition in nonadipocyte tissues including the myocardium. The effect of excess intramyocardial fat on cardiac function in nonobese individuals is unknown.

METHODS AND RESULTS

Cardiac lipid content was measured by magnetic resonance spectroscopy in 153 healthy nonobese subjects with varying fitness levels quantified by peak oxygen uptake during treadmill exercise. Cardiac function (echo) and left ventricular (LV) filling pressures (right heart catheterization) were measured under varying preloads. LV stiffness was calculated from a curve fit of the diastolic portion of the pressure-volume curve. The strongest clinical predictors of lipid content were body mass index (β=+0.03; 95% confidence interval, 0.001-0.06) and peak oxygen uptake (β=-0.02; 95% confidence interval, -0.03 to -0.009; R(2)=0.14; P<0.001). Subjects in the highest quintile had smaller LV end-diastolic volumes (68±13 versus 58±12 mL/m(2); P<0.01) and decreased peak early mitral annular and increased peak late mitral inflow velocities. There were no differences in LV stiffness, but a leftward shift in the pressure-volume curve suggested a less distensible ventricle with increasing myocardial lipid levels. After adjusting for age, fitness, and body mass index, echocardiographic and morphometric differences among groups were attenuated and no longer significant.

CONCLUSIONS

Body mass index and fitness levels are the strongest predictors of myocardial lipid content in nonobese humans. Cardiac lipid content is associated with decreased ventricular distensibility, and it may provide a causal mechanism linking changes in LV function related to age and fitness.

Fat-free mass and fasting glucose values in patients with and without statin therapy assigned to age groups between <60 and >75 years

OBJECTIVE

The aging-associated changes in body composition result in an increased cardiometabolic risk. A tremendous reduction of cardiovascular morbidity and mortality can be obtained by statin therapy. Statins are well tolerated, with myopathy as the most serious negative side effect. Some recently published studies indicate that the incidence of type 2 diabetes might be increased during intensified statin therapy. The aim of our study was to investigate whether statin therapy has an influence on the aging-associated changes in fat-free mass (FFM).

METHODS

A total of 3,280 persons attending a medical outdoor center between January 2005 and July 2011 were assigned to 3 age groups from <60 to >75 years. Clinical data, body mass index (BMI), and body composition were evaluated in the different age groups in patients with and without statin therapy. To analyze the impact of statin use on FFM, we regressed a patient's FFM on an interaction term between statin use and age and other control variables.

RESULTS

Aging was associated with a decrease in BMI and FFM, while fat mass continuously increased up to the age of >75 years. This was paralleled by a continuous increase in fasting glucose levels in patients with and without statin therapy. The loss of FFM between the age group <60 years and >75 years was more pronounced in statin-treated patients (10.88%) than in non-statin users (8.47%). Creatine phosphokinase values revealed a decrease of 7.77 U/l between the age groups <60 and >75 years in non-statin users and of 14.75 U/l in statin users. Statistical analysis indicated that the effect of statin therapy on FFM is more pronounced in younger than in older patients.

CONCLUSIONS

Patients under statin therapy seem to be more vulnerable to the aging-associated lowering of FFM. Diagnostic procedures and interventions to prevent a loss of muscle mass might be of particular advantage in elderly patients under statin therapy.

Increased vitamin D is associated with decline of naïve, but accumulation of effector, CD8 T cells during early aging

Given the protective roles of 25-hydroxyvitamin D (25[OH]D or vitamin D) in musculoskeletal health and the potential beneficial effects of vitamin D supplementation in reducing the risk of various chronic diseases, intensive repletion of vitamin D has been widely advocated. Of note, CD8 T cells have the highest levels of the vitamin D receptor compared with other major immune cells. The effects of vitamin D on CD8 T cells during aging, however, remain unclear. This study determined the relationship between vitamin D levels and CD8 T-cell status in 34 healthy female subjects (all >60 years old). The CD8 T cell phenotype was defined by the surface expression of CD28 and CD95. The low-25(OH)D serum groups (≤30 ng/ml) had higher percentages of CD28⁺CD95^-CD8⁺ (naïve) T cells and lower percentages of CD28⁺CD95⁺CD8⁺ (effector) T cells. By contrast, subjects with high levels of 25(OH)D had very low percentages of naïve CD8 T cells but very high percentages of effector CD8 T cells. There was a significant inverse correlation between 25(OH)D levels and the frequency of naïve CD8 T cells. The results show that higher levels of vitamin D are correlated with decreased frequencies of naïve CD8 T cells during early aging, suggesting that higher levels of 25(OH)D accelerate CD8 T-cell senescence. These results warrant the further evaluation of the effects of vitamin D supplementation in immune aging.

Insulin sensitivity is associated with thigh adipose tissue distribution in healthy postmenopausal women

OBJECTIVE

Evidence suggests intermuscular adipose tissue (IMAT) may be linked to insulin resistance, whereas thigh subcutaneous adipose tissue (SAT) may be related favorably with indices of metabolic health. However, whether adipose tissue depots of the thigh are differentially related to insulin sensitivity independent of total adiposity and other adipose tissue depots has not been determined. The objective of this study was to identify independent associations of the subcompartments of adipose tissue of the thigh with insulin sensitivity among 97 healthy early postmenopausal women.

MATERIALS AND METHODS

Computed tomography (CT) scans of the mid-thigh were used to assess Thigh-SAT, Thigh perimuscular adipose tissue (PMAT), and Thigh-IMAT. CT scans at the L4-L5 intervertebral space were used to assess intra-abdominal adipose tissue (IAAT) and Abdominal-SAT. Total body fat was measured by dual-energy X-ray absorptiometry (DXA). The insulin sensitivity index (S(I)) was assessed by using a frequently sampled intravenous glucose tolerance test with minimal model analysis.

RESULTS

Results indicated S(I) was positively associated with Thigh-SAT independent of total fat mass and other adipose tissue compartments. Among all women combined, S(I) was inversely associated with Thigh-IMAT independent of total fat mass. However, the relationship between S(I) and Thigh-IMAT was independent of IAAT only among women with high levels of Thigh-IMAT and IAAT.

CONCLUSIONS

This is the first study to demonstrate independent, opposing relationships of Thigh-SAT and Thigh-IMAT with insulin sensitivity in healthy postmenopausal women. Further research is needed to determine if these associations are causal in nature.

Differences between adiposity indicators for predicting all-cause mortality in a representative sample of United States non-elderly adults

BACKGROUND

Adiposity predicts health outcomes, but this relationship could depend on population characteristics and adiposity indicator employed. In a representative sample of 11,437 US adults (National Health and Nutrition Examination Survey, 1988-1994, ages 18-64) we estimated associations with all-cause mortality for body mass index (BMI) and four abdominal adiposity indicators (waist circumference [WC], waist-to-height ratio [WHtR], waist-to-hip ratio [WHR], and waist-to-thigh ratio [WTR]). In a fasting subsample we considered the lipid accumulation product (LAP; [WC enlargement*triglycerides]).

METHODS AND FINDINGS

For each adiposity indicator we estimated linear and categorical mortality risks using sex-specific, proportional-hazards models adjusted for age, black ancestry, tobacco exposure, and socioeconomic position. There were 1,081 deaths through 2006. Using linear models we found little difference among indicators (adjusted hazard ratios [aHRs] per SD increase 1.2-1.4 for men, 1.3-1.5 for women). Using categorical models, men in adiposity midrange (quartiles 2+3; compared to quartile 1) were not at significantly increased risk (aHRs<1.1) unless assessed by WTR (aHR 1.4 [95%CI 1.0-1.9]). Women in adiposity midrange, however, tended toward elevated risk (aHRs 1.2-1.5), except for black women assessed by BMI, WC or WHtR (aHRs 0.7-0.8). Men or women in adiposity quartile 4 (compared to midrange) were generally at risk (aHRs>1.1), especially black men assessed by WTR (aHR 1.9 [1.4-2.6]) and black women by LAP (aHR 2.2 [1.4-3.5]). Quartile 4 of WC or WHtR carried no significant risk for diabetic persons (aHRs 0.7-1.1), but elevated risks for those without diabetes (aHRs>1.5). For both sexes, quartile 4 of LAP carried increased risks for tobacco-exposed persons (aHRs>1.6) but not for non-exposed (aHRs<1.0).

CONCLUSIONS

Predictions of mortality risk associated with top-quartile adiposity vary with the indicator used, sex, ancestry, and other characteristics. Interpretations of adiposity should consider how variation in the physiology and expandability of regional adipose-tissue depots impacts health.

Individualised aerobic and resistance exercise training improves cardiorespiratory fitness and reduces cardiovascular risk in patients with rheumatoid arthritis

BACKGROUND AND OBJECTIVES

Low cardiorespiratory fitness (CRF) is a significant predictor of cardiovascular disease (CVD), and interventions aiming at increasing CRF are known to reduce CVD risk. The effects of such interventions on CVD risk have not been studied in patients with rheumatoid arthritis (RA).

METHODS

40 age, gender, body mass index (BMI) and disease duration matched RA patients were allocated to either an exercise (receiving 6 months individualised aerobic and resistance high intensity exercise intervention, three times per week), or control (receiving advice on exercise benefits and lifestyle changes) arm. Participants were assessed at baseline, 3 and 6 months for aerobic capacity (VO2max), individual CVD risk factors (blood pressure, lipids, insulin resistance, body composition), 10-year CVD event probability and RA characteristics (C-reactive protein (CRP), Disease Activity Score 28 (DAS28) and Health Assessment Questionnaire (HAQ)).

RESULTS

There were no differences between groups at baseline in any of the assessed variables. VO2max (p=0.001), blood pressure (systolic: p<0.001; diastolic: p=0.003), triglycerides (p=0.030), high density lipoprotein (HDL; p=0.042), total cholesterol:HDL ratio (p=0.005), BMI (p=0.001), body fat (p=0.026), 10-year CVD event probability (p=0.012), CRP (p=0.042), DAS28 (p=0.008) and HAQ (p=0.003) were all significantly improved in the exercise versus the control group. The change in VO2max was the strongest predictor for the observed improvements in all of the assessed CVD risk factors and disease characteristics.

CONCLUSIONS

Individualised aerobic and resistance exercise intervention can lead to significantly improved CRF, individual CVD risk factors, composite CVD risk, and disease activity and severity in RA patients.

Leg fat might be more protective than arm fat in relation to lipid profile

PURPOSE

The objective of this study was to determine the independent relationships of trunk fat, leg fat and arm fat to cardiovascular (CVD) risk factors, after controlling for relevant confounders such as fat mass index, cardiorespiratory fitness and objectively measured physical activity.

METHODS

This is a cross-sectional study involving 683 university students, aged 18-30 years. Total and regional body fat distribution was measured using dual-energy X-ray absorptiometry. The associations of trunk, leg and arm fat with CVD risk factors (triglycerides-TG-, high-density lipoprotein cholesterol-HDL-c-, TG/HDL-c ratio, HOMA(IR), mean arterial pressure, C-reactive protein) were examined using regression linear models, controlling for age, sex, fat mass index [total body fat(kg)/height(m(2))], maximal oxygen consumption and physical activity by accelerometer.

RESULTS

After controlling for fat mass index, and other confounders, higher levels of trunk fat were found to be associated with a poorer lipid profile, while higher levels of leg fat were found to be associated with a better lipid profile. We did not find any association between arm fat and lipid profile after controlling for total fatness and other confounders. Neither trunk, leg or arm fat was found to be related to insulin resistance, blood pressure or inflammation markers.

CONCLUSIONS

Our data suggest that the region where fat is accumulated might have a differential effect on lipid profile: trunk fat has an adverse effect, leg fat has a protective effect, and arm fat has no effect. The differences observed between upper- and lower-body peripheral fat depots should be further explored.

Preferential fat deposition in subcutaneous versus visceral depots is associated with insulin sensitivity

BACKGROUND

Studies on the relationship between regional fat and insulin resistance yield mixed results. Our objective was to determine whether regional fat distribution, independent of obesity, is associated with insulin resistance.

DESIGN

Subjects included 115 healthy, overweight/moderately obese adults with body mass index (BMI) 25-36.9 kg/m(2) who met predetermined criteria for being insulin resistant (IR) or insulin sensitive (IS) based on the modified insulin suppression test. Computerized tomography was used to quantify visceral adipose tissue (VAT), sc adipose tissue (SAT), and thigh adipose tissue. Fat mass in each depot was compared according to IR/IS group, adjusting for BMI and sex.

RESULTS

Despite nearly identical mean BMI in the IR vs. IS groups, VAT and %VAT were significantly higher in the IR group, whereas SAT, %SAT, and thigh sc fat were significantly lower. In logistic regression analysis, each sd increase in VAT increased the odds of being IR by 80%, whereas each increase in SAT decreased the odds by 48%; each increase in thigh fat decreased the odds by 59% and retained significance after adjusting for other depots. When grouped by VAT tertile, IS vs. IR individuals had significantly more SAT. There was no statistically significant interaction between sex and these relationships.

CONCLUSION

These data demonstrate that after adjustment for BMI and VAT mass, sc abdominal and thigh fat are protective for insulin resistance, whereas VAT, after adjustment for SAT and BMI, has the opposite effect. Whether causal in nature or a marker of underlying pathology, these results clarify that regional distribution of fat-favoring sc depots is associated with lower risk for insulin resistance.

Body composition and coronary heart disease mortality--an obesity or a lean paradox?

OBJECTIVE

To determine the combined effects of body mass index (BMI) and body fat (BF) on prognosis in coronary heart disease (CHD) to better understand the obesity paradox.

PATIENTS AND METHODS

We studied 581 patients with CHD between January 1, 2000, and July 31, 2005, who were divided into low (<25) and high BMI (≥25), as well as low (≤25% men and ≤35% women) and high BF (>25% in men and >35% in women). Four groups were analyzed by total mortality during the 3-year follow-up by National Death Index: low BF/low BMI (n=119), high BF/low BMI (n=26), low BF/high BMI (n=125), and high BF/high BMI (n=311).

RESULTS

During the 3-year follow-up, mortality was highest in the low BF/low BMI group (11%), which was significantly (P<.001) higher than that in the other 3 groups (3.9%, 3.2%, and 2.6%, respectively); using the high BF/high BMI group as a reference, the low BF/low BMI group had a 4.24-fold increase in mortality (confidence interval [CI], 1.76-10.23; P=.001). In multivariate logistic regression for mortality, when entered individually, both high BMI (odds ratio [OR], 0.79; CI, 0.69-0.90) and high BF (OR, 0.89; CI, 0.82-0.95) as continuous variables were independent predictors of better survival, whereas low BMI (OR, 3.60; CI, 1.37-9.47) and low BF (OR, 3.52; CI, 1.34-9.23) as categorical variables were independent predictors of higher mortality.

CONCLUSION

Although both low BF and low BMI are independent predictors of mortality in patients with CHD, only patients with combined low BF/low BMI appear to be at particularly high risk of mortality during follow-up. Studies are needed to determine optimal body composition in the secondary prevention of CHD.

Age-related changes in insulin sensitivity and β-cell function among European-American and African-American women

Type 2 diabetes (T2D) is more prevalent among African-American (AA) than European-American (EA) women for reasons that are unknown. Ethnic differences in physiological processes related to insulin sensitivity (S(I)) and secretion, and age-related changes in these processes, may play a role. The purpose of this study was to identify ethnicity- and age-related differences in S(I) and β-cell responsivity among AA and EA females, and to determine whether these differences are independent of body composition and fat distribution. Healthy, normoglycemic females aged 7-12 years (n = 62), 18-32 years (n = 57), and 40-70 years (n = 49) were recruited for entry into this study. Following an overnight fast, S(I), intravenous glucose tolerance (Kg), acute C-peptide secretion (X0), and basal, first-phase, second-phase, and total β-cell responsivity to glucose (PhiB, Phi1, Phi2, and Phi(TOT), respectively) were measured by an intravenous glucose tolerance test. Total % body fat was assessed by dual-energy X-ray absorptiometry, and intra-abdominal adiposity (IAAT) by computed tomography. Main effects of age group and ethnicity were measured with analysis of covariance, adjusting for % fat, IAAT, and S(I) as indicated. AA had lower S(I), and higher Kg, X0, Phi1, and Phi(TOT) (P < 0.05), which remained after adjustment for % fat and IAAT. Greater X0, Phi1, and Phi(TOT) among AA were independent of S(I). Advancing age was associated with greater Phi2 among both EA and AA. To conclude, inherent ethnic differences in β-cell function exist independently of adiposity and S(I). Future research should examine whether ethnic differences in β-cell physiology contribute to disparities in T2D risk.

Age Related Shift in Visceral Fat

Fat distribution, especially increased visceral fat, may be as important as overall obesity in increasing risk of heart disease, type 2 diabetes and certain cancers. Risk of disease, as well as visceral fat, increases dramatically with age. Cross-sectional data suggests that increased risk of disease may be largely prevented if the age related increase in visceral fat does not occur. The objective of this short review is to present data that shows visceral fat increasing over 200% in men and 400% in women between the 3rd and 7th decades, show that a combination of weight gain, loss of muscle, and a shift from peripheral to central fat patterning contributes to this increase, and identify hormones that may be responsible for the shift. Finally, the review will show how participation in exercise can slow the age related shift in visceral fat.

Differences emerge in visceral adipose tissue accumulation after selection for innate cardiovascular fitness

Cardiorespiratory fitness (CRF) has been reported to be inversely associated with visceral adipose tissue (VAT) accumulation, independent of body weight. However, the confounding effect of physical activity on the association between CRF and VAT remains inadequately addressed. On the basis of maximal oxygen uptake (VO(2 max)), 143 sedentary, overweight women were dichotomized into high-fit (HF) and low-fit (LF) groups. Body composition and VAT were measured using dual-energy X-ray absorptiometry and computed tomography, respectively, and activity-related energy expenditure (AEE) was calculated using the doubly labeled water technique. No differences were observed between HF and LF for body mass index (HF 28.2 ± 1.3; LF 28.3 ± 1.31 kg m(-2)), total body weight (HF 77.5 ± 6.8; LF 77.9 ± 7.3 kg), total fat mass (HF 33.5 ± 5.1; LF 33.9 ± 4.4 kg) or AEE (HF 439.9 ± 375.4; LF 517.9 ± 298.7 kcal day(-1)). Significant differences in visceral adiposity (HF 68.5 ± 30.4; LF 91.2 ± 31.8 cm(2); P<0.001) and insulin sensitivity (HF 5.1 ± 1.8; LF 3.1 ± 2.4 S(I) × 10(-4) min(-1) μIU(-1) ml(-1); P<0.01) were observed between the HF and LF groups, independent of age, race and AEE. This study affirms previous findings that CRF is an important determinant of the accumulation of VAT, and this relationship is independent of physical activity.