Ethnic differences in the relationship between pericardial adipose tissue and coronary artery calcified plaque: African-American-diabetes heart study

Cardiometabolic predictors of high-risk CCTA phenotype in a diverse patient population

Introduction

Low-attenuation non-calcified plaque (LAP) burden and vascular inflammation by pericoronary adipose tissue (PCAT) measured from coronary CT angiography (CCTA) have shown to be predictors of cardiovascular outcomes. We aimed to investigate the relationships of cardiometabolic risk factors including lipoprotein(a) and epicardial adipose tissue (EAT) with CCTA high-risk imaging biomarkers, LAP and vascular inflammation.

Methods

The patient population consisted of consecutive patients who underwent CCTA for stable chest pain and had a complete cardiometabolic panel including lipoprotein(a). Plaque, PCAT and EAT were measured from CT using semiautomated software. Elevated LAP burden and PCAT attenuation were defined as ≥4% and ≥70.5 HU, respectively. The primary clinical end-point was a composite of myocardial infarction, revascularization or cardiovascular death.

Results

A total of 364 consecutive patients were included (median age 56 years, 64% female); the majority of patients were of Hispanic (60%), and the rest were of non-Hispanic Black (21%), non-Hispanic White (6%) and non-Hispanic Asian (4%) race/ethnicity. The prevalence of elevated LAP burden and PCAT attenuation was 31 and 18%, respectively, while only 8% had obstructive stenosis. There were significant differences in plaque characteristics among different racial/ethnic groups (p<0.001). Lipoprotein(a) correlated with LAP burden in Hispanic patients. Patients with elevated LAP were older, more likely to be have diabetes, hypertension, hyperlipidemia and smoke with higher CAC and EAT volume (all P<0.05). Patients with elevated LAP were more likely to develop the primary clinical outcome (p<0.001) but those with elevated PCAT were not (p=0.797).

Conclusion

The prevalence of LAP and PCAT attenuation were 31 and 18%, respectively. Lipoprotein(a) levels correlated with LAP burden in Hispanic patients. Age, male sex, hypertension and hyperlipidemia increased the odds of elevated LAP, which showed prognostic significance.

Racial Disparities in the Cardiac Computed Tomography Assessment of Coronary Artery Disease: Does Gender Matter

Coronary heart disease (CHD) represents a significant healthcare burden in terms of hospital resources, morbidity, and mortality. Primary prevention and early detection of risk factors for the development of CHD are pivotal to successful intervention programs and prognostication. Yet, there remains a paucity of evidence regarding differences in the assessment of these risk factors and the tools of assessment among different ethnicities. We conducted a narrative review to assess the utility of cardiac computed tomography, particularly coronary artery calcification (CAC), in different ethnicities. We also looked to see whether age, sex, comorbidities, and genetic background have peculiar influences on CAC. In this review, we highlight some of the pivotal studies regarding the question of CAC in relation to the development of CHD among different ethnicities. We identify several key trends in the literature showing that although African Americans have high rates of CHD, their risk of CAC may be relatively lower compared with other ethnicities. Similarly, South Asian patients may be at a high risk for adverse cardiac events due to elevated CAC. We also note that several studies are limited by small sample size and were based on 1 large cohort study. Future studies should include a large international prospective cohort to truly evaluate the effects of ethnicity on CAC and CHD risk. To appropriately apply CAC in the clinical practice, the variations in its scoring based on a subject's age, sex, comorbidity, and ethnicity should be addressed and interpreted beforehand.

Epicardial and visceral adipose tissue in relation to subclinical atherosclerosis in a Chinese population

Background

Body fatness is associated with risk of coronary heart disease and it has been postulated that epicardial adipose tissue (EAT) may have a particularly detrimental effect because of its localized toxic effects. We therefore aimed to examine the association between EAT and coronary artery calcification and compared this with associations for visceral adipose tissue (VAT) and other regional fat depots.

Methods

We conducted a cross-sectional study of 487 Chinese participants aged 50 years old and above, living in Singapore. Participants, free from known diabetes mellitus and coronary heart diseases, completed interviews, a health screening to evaluate obesity and cardiovascular disease risk factors, and computed tomography scans of the abdomen and coronary arteries. Associations between regional fat depots and subclinical atherosclerosis defined as CAC> = 100 were determined by multiple logistic regression analysis.

Results

Epicardial adipose tissue (EAT) was highly correlated with visceral adipose tissue (VAT) (Pearson r = 0.72) and trunk fat mass (r = 0.66). The age and sex-adjusted odd ratio (OR) (in 1-SD increase) of subclinical atherosclerosis was 1.28 (1.01–1.61) for EAT and 1.40 (1.04–1.88) for VAT. These associations were weaker and non-significant after adjusting for markers of dyslipidemia and hyperglycemia. Total body fat, subcutaneous abdominal fat, and leg, arm and trunk fat mass were not significantly associated with atherosclerosis.

Conclusion

VAT and EAT showed similar associations with coronary artery calcification and the associations could be mediated by traditional risk factors in this ethnic Chinese population.

Adiposity is inversely associated with hippocampal volume in African Americans and European Americans with diabetes

AIMS

To assess associations between body mass index (BMI), waist circumference (WC), and computed tomography-determined volumes of pericardial, visceral, and subcutaneous adipose tissue with magnetic resonance imaging-(MRI) based cerebral structure and cognitive performance in individuals with type 2 diabetes (T2D).

METHODS

This study was performed in 348 African Americans (AAs) and 256 European Americans (EAs) with T2D. Associations between adiposity measures with cerebral volumes of white matter (WMV), gray matter (GMV), white matter lesions, hippocampal GMV, and hippocampal WMV, cognitive performance and depression were examined using marginal models incorporating generalized estimating equations. All models were adjusted for age, sex, education, smoking, HbA1c, hypertension, statins, cardiovascular disease, MRI scanner (MRI outcomes only), and time between scans; some neuroimaging measures were additionally adjusted for intracranial volume.

RESULTS

Participants were 59.9% female with mean (SD) age 57.7(9.3)years, diabetes duration 9.6(6.8)years, and HbA1c 7.8(1.9)%. In AAs, inverse associations were detected between hippocampal GMV and both BMI (β [95% CI]-0.18 [-0.30, -0.07], P=0.0018) and WC (-0.23 [-0.35, -0.12], P=0.0001). In the full bi-ethnic sample, inverse associations were detected between hippocampal WMV and WC (P≤0.0001). Positive relationships were observed between BMI (P=0.0007) and WC (P<0.0001) with depression in EAs.

CONCLUSIONS

In patients with T2D, adiposity is inversely associated with hippocampal gray and white matter volumes.

Relationships between measures of adiposity with subclinical atherosclerosis in patients with type 2 diabetes

OBJECTIVE

Assess cross-sectional relationships between body mass index (BMI), waist circumference (WC), pericardial (PAT), visceral (VAT), and subcutaneous adipose tissue (SAT) volumes with calcified plaque (CP) in African Americans (AAs) and European Americans (EAs) with type 2 diabetes.

METHODS

Computed tomography measured PAT, VAT, SAT, and CP in coronary arteries (CAC), carotid arteries, and aorta. Generalized estimating equations models were fitted to test for associations between adiposity and CP, stratified by ethnicity while accounting for familial correlations.

RESULTS

AAs (N = 753) vs. EAs (N = 562) had significantly lower PAT and VAT, despite equal or higher BMI. In multivariable models adjusting for age, gender, education, HbA1c, statins, smoking, cardiovascular disease, hypertension, nephropathy, and C-reactive protein, PAT positively associated with presence of CAC in AAs (P < 0.001), not EAs (P = 0.68; ethnicity interaction P < 0.01). Inverse associations were detected between SAT and severity of aorta CP (P < 0.01) in AAs and between BMI, WC, and SAT with severity of aorta CP in all participants.

CONCLUSIONS

Ethnic- and gender-specific differences in BMI, WC, PAT, SAT, and VAT were present in AAs and EAs with diabetes. Only PAT was positively associated with CAC in AAs; paradoxical inverse associations were seen between several other adiposity measures and subclinical cardiovascular disease.

Association between albuminuria, atherosclerotic plaques, elevated pulse wave velocity, age, risk category and prognosis in apparently healthy individuals

METHOD

Two thousand and fifty-nine healthy individuals aged 41, 51, 61 and 71 years examined in 1993, were divided in age, SCORE and Framingham risk score (FRS) groups. Subclinical vascular damage (SVD) was defined as carotid-femoral pulse wave velocity (cfPWV) at least 12 m/s, carotid atherosclerotic plaques or albuminuria defined as urine albumin/creatinine ratio at least 90th percentile of 0.73/1.06 mg/mmol men/women. In 2006, the composite endpoint (CEP) of cardiovascular death, nonfatal myocardial infarction, nonfatal stroke and hospitalization for ischemic heart disease was recorded (n = 229).

RESULTS

With increasing age, SCORE or FRS risk group, prevalence of cfPWV at least 12 m/s (5.2, 14.5, 35.3, 53.5% or 4.4, 15.6, 50.9, 66.1% or 4.0, 9.5, 32.1, 56.1%), atherosclerotic plaque (4.0, 19.0, 35.3, 53.5% or 3.5, 16.8, 43.7, 55.9%, or 6.6, 7.6, 9.8, 20.0%) and albuminuria (7.9, 8.7, 11.4, 20.6% or 7.9, 8.2, 16.6, 19.5% or 6.6, 7.6, 9.8, 20.0%) increased, all P < 0.001.CEP was associated with albuminuria in individuals aged 61 or 71 years, with moderate or very high SCORE or intermediate or high FRS (all P < 0.05), with atherosclerotic plaques in individuals aged 41, 51 or 61 years, with moderate SCORE or with high-intermediate or high FRS (all P < 0.01), and with cfPWV at least 12 m/s in individuals aged 51 years (P < 0.001) or high FRS (P < 0.05). Presence of at least one SVD was significantly associated with an increased risk in individuals aged 51 [hazard ratio 2.7 (1.6-4.8)] and 61 years [hazard ratio 2.7 (1.5-4.7)], moderate [hazard ratio 2.4 (1.6-3.7)] or high SCORE risk group [hazard ratio 2.3 (1.2-4.7)] and low-intermediate [hazard ratio 3.3 (1.5-7.0)], high-intermediate [hazard ratio 2.3 (1.5-3.5)] and high FRS risk group [hazard ratio 2.0 (1.4-3.0)].

CONCLUSION

SVD and especially atherosclerotic plaques or urine albumin/creatinine ratio (UACR) at least 0.73/1.06 mg/mmol (men/women) added prognostic information in individuals aged 51 or 61 years or with moderate or intermediate risk.

Pericardial adipose tissue and coronary artery calcification in the Multi-ethnic Study of Atherosclerosis (MESA)

OBJECTIVE

To examine the relationship of pericardial adipose tissue (PAT) with coronary artery calcification in the Multi-Ethnic Study of Atherosclerosis.

DESIGN AND METHODS

The baseline cohort comprised 6,814 Caucasian (38%), African-American (28%), Chinese American (12%), and Hispanic (22%) adults aged 45-84, without known clinical cardiovascular disease. Cardiac CT was used to measure PAT (cm(3) ) and calcification (Agatston score). We examined cross-sectional associations of PAT with the presence (score >0) and severity (continuous score if >0) of calcification using prevalence ratio (PR) (n = 6,672) and linear regression (n = 3,362), respectively. Main models were adjusted for age, age(2) , gender, race/ethnicity, field site, smoking, physical activity, alcohol, and education.

RESULTS

PAT volume (adjusted for age, height, weight, and site) was greatest in Chinese males, whereas Black males had less PAT than all but Black females. PAT was associated with presence [PR per standard deviation (SD): 1.06 (95% CI: 1.04, 1.08)] and severity [difference in log Agatston score per SD: 0.15 (0.09, 0.21)] of calcification, but neither association varied by race/ethnicity. Adjustment for generalized adiposity attenuated but did not eliminate the associations. With further adjustment for traditional risk factors and inflammatory markers, only the association with severity remained statistically significant [PR: 1.02 (1.00, 1.04); difference: 0.10 (0.03, 0.17)]. Heterogeneity by sex was observed for the presence of calcification (PR in men: 1.04; in women: 1.08; P for interaction <0.0001).

CONCLUSION

PAT was associated with the presence and severity of coronary artery calcification in this cohort, but neither association varied by race/ethnicity.

An ACACB variant implicated in diabetic nephropathy associates with body mass index and gene expression in obese subjects

Acetyl coenzyme A carboxylase B gene (ACACB) single nucleotide polymorphism (SNP) rs2268388 is reproducibly associated with type 2 diabetes (T2DM)-associated nephropathy (DN). ACACB knock-out mice are also protected from obesity. This study assessed relationships between rs2268388, body mass index (BMI) and gene expression in multiple populations, with and without T2DM. Among subjects without T2DM, rs2268388 DN risk allele (T) associated with higher BMI in Pima Indian children (n = 2021; p-additive = 0.029) and African Americans (AAs) (n = 177; p-additive = 0.05), with a trend in European Americans (EAs) (n = 512; p-additive = 0.09), but not Germans (n = 858; p-additive = 0.765). Association with BMI was seen in a meta-analysis including all non-T2DM subjects (n = 3568; p-additive = 0.02). Among subjects with T2DM, rs2268388 was not associated with BMI in Japanese (n = 2912) or EAs (n = 1149); however, the T allele associated with higher BMI in the subset with BMI≥30 kg/m(2) (n = 568 EAs; p-additive = 0.049, n = 196 Japanese; p-additive = 0.049). Association with BMI was strengthened in a T2DM meta-analysis that included an additional 756 AAs (p-additive = 0.080) and 48 Hong Kong Chinese (p-additive = 0.81) with BMI≥30 kg/m(2) (n = 1575; p-additive = 0.0033). The effect of rs2268388 on gene expression revealed that the T risk allele associated with higher ACACB messenger levels in adipose tissue (41 EAs and 20 AAs with BMI>30 kg/m(2); p-additive = 0.018) and ACACB protein levels in the liver tissue (mixed model p-additive = 0.03, in 25 EA bariatric surgery patients with BMI>30 kg/m(2) for 75 exams). The T allele also associated with higher hepatic triglyceride levels. These data support a role for ACACB in obesity and potential roles for altered lipid metabolism in susceptibility to DN.

Mapping body fat distribution: a key step towards the identification of the vulnerable patient?

Although excess body fat is a significant health hazard, estimation of body fat content with the body mass index may not adequately reflect the amount of atherogenic adipose tissue (AT), i.e. visceral and ectopic fat. As opposed to subcutaneous AT that supposedly acts as a metabolic sink buffering excess dietary energy, visceral or intra-abdominal AT depots respond to several external stimuli that trigger lipolysis and secretion of free fatty acids (FFAs). Reaching the liver, FFAs accumulate in the liver and, over time, promote a chronic condition known as non-alcoholic fatty liver disease (NAFLD). The liver of the typical NAFLD patient secretes large amounts of very-low-density lipoproteins, the lipid content of which may accumulate in additional organs (skeletal muscle, heart, and pancreas). Here, we review the evidence emerging from functional and population studies that point towards an important role of ectopic fat accumulation in the pathophysiology of type 2 diabetes and cardiovascular disease. We conclude that although patients with impaired glycemic control or type 2 diabetes are at increased cardiovascular disease (CVD) risk, estimating cardiovascular risk goes wellbeyond the assessment of glycemic control and traditional CVD risk factors, and the estimation of visceral/ectopic fat deposition via readily available imaging techniquesshould be considered.

Effect of race and genetics on vitamin D metabolism, bone and vascular health

The pathophysiology of chronic kidney disease-mineral and bone disorder accounts for an inverse relationship between bone mineralization and vascular calcification in progressive nephropathy. Inverse associations between bone mineral density (BMD) and calcified atherosclerotic plaque are also observed in individuals of European and African ancestry without nephropathy, suggesting a mechanistic link between these processes that is independent of kidney disease. Despite lower dietary calcium intake and serum 25-hydroxyvitamin D (25(OH)D) concentrations, African Americans have higher BMD and develop osteoporosis less frequently than do European Americans. Moreover, despite having more risk factors for cardiovascular disease, African Americans have a lower incidence and severity of calcified atherosclerotic plaque formation than do European Americans. Strikingly, evidence is now revealing that serum 25(OH)D and/or 1,25 dihydroxyvitamin D levels associate positively with atherosclerosis but negatively with BMD in African Americans; by contrast, vitamin D levels associate negatively with atherosclerosis and positively with BMD in individuals of European ancestry. Biologic phenomena, therefore, seem to contribute to population-specific differences in vitamin D metabolism, bone and vascular health. Genetic and mechanistic approaches used to explore these differences should further our understanding of bone-blood vessel relationships and explain how African ancestry protects from osteoporosis and calcified atherosclerotic plaque, provided that access of African Americans to health care is equivalent to individuals of European ethnic origin. Ultimately, in our opinion, a new mechanistic understanding of the relationships between bone mineralization and vascular calcification will produce novel approaches for disease prevention in aging populations.

Cerebral white matter hyperintensity in African Americans and European Americans with type 2 diabetes

Previous studies involving inner city populations detected higher cerebral white matter hyperintensity (WMH) scores in African Americans (AAs) compared with European Americans (EAs). This finding might be attributable to the higher prevalence of cardiovascular disease (CVD) risk factors and poorer access to healthcare in AAs. Despite racial differences in CVD risk factor profiles, AAs have paradoxically lower levels of subclinical CVD. We hypothesized that AAs with diabetes and good access to healthcare would have comparable or lower levels of WMH as EAs. Racial differences in the distribution of WMH were analyzed in 46 AAs and 156 EAs with type 2 diabetes enrolled in the Diabetes Heart Study (DHS)-Mind, and replicated in a sample of 113 AAs and 61 EAs patients who had clinically indicated cerebral magnetic resonance imaging. Wilcoxon 2-sample tests and linear models were used to compare the distribution of WMH in AAs and EAs and to test for association between WMH and race. The unadjusted mean WMH score from the Diabetes Heart Study-Mind was 1.9 in AAs and 2.3 in EAs (P = .3244). Among those with clinically indicated magnetic resonance imaging, the mean WMH score was 2.9 in AAs and 3.9 in EAs (P = .0503). Adjustment for age and sex produced no statistically significant differences in WMH score between AAs and EAs. These independent datasets reveal comparable WMH scores in AAs and EAs, suggesting that disparities in access to healthcare and environmental exposures likely underlie the previously reported excess burden of WMH in AAs.

[Identification and quantification of fat compartments with CT and MRI and their importance]

In addition to being overweight, as defined by the BMI, the distribution, composition and biological activity of adipose tissue are key elements in the cardiovascular risk stratification of patients. Several non-invasive techniques have been developed to quantify local fat depots, whereby computed tomography (CT) and magnetic resonance imaging (MRI) are the most important. In general adipose tissue is subdivided into subcutaneous and visceral compartments and although both are associated with cardiovascular risk factors and disease, visceral fat has on average a stronger association and a clearly higher biological activity independent of traditional risk factors. This maybe explained by the higher endocrine activity and secretion of pro-inflammatory cytokines by visceral fat. Especially pericardial adipose tissue, a local visceral fat depot surrounding the coronary arteries, is associated with the presence, extent and severity of coronary artery disease. However, several other local fat depots have been identified and associations with various diseases have been established. This article gives an overview over the current methods for the identification and quantification of local fat depots and summarizes the hypothesized and known associations. Furthermore, it gives an overview of the potential significance of individual local fat depots for cardiovascular risk stratification.

Relationships between calcified atherosclerotic plaque and bone mineral density in African Americans with type 2 diabetes

Inverse relationships have been reported between bone mineral density (BMD) and calcified atherosclerotic plaque (CP). This suggests these processes may be related. We examined relationships between BMD and CP in 753 African Americans with type 2 diabetes from 664 families, accounting for the effects of modifiable cardiovascular disease (CVD) risk factors. Association analyses were performed using generalized estimating equations (GEEs) to assess cross-sectional relationships between computed tomography-determined measures of thoracic and lumbar vertebral volumetric BMD (vBMD) and CP in the coronary and carotid arteries and infrarenal aorta. Significant inverse associations were seen between thoracic and lumbar vBMD and CP in all three vascular beds in unadjusted analyses. A fully adjusted model accounting for age, sex, body mass index, systolic blood pressure, low-density lipoprotein cholesterol, C-reactive protein, hemoglobin A(1c), smoking, and hormone-replacement therapy revealed significant inverse associations between thoracic vBMD and CP in coronary and carotid arteries and aorta, whereas lumbar vBMD was associated with CP in coronary artery and aorta. Inverse associations exist between vertebral BMD and calcified atherosclerotic plaque in African-American men and women with type 2 diabetes. This relationship was independent of conventional CVD risk factors and supports the hypothesis that bone metabolism and atherosclerotic plaque mineralization are related processes.

Association of PNPLA3 SNP rs738409 with liver density in African Americans with type 2 diabetes mellitus

AIM

Non-alcoholic fatty liver disease (NAFLD) is commonly diagnosed in patients with obesity and type 2 diabetes mellitus (T2DM), and has been associated with the single nucleotide polymorphism (SNP) rs738409 in the PNPLA3 gene. This association remains to be investigated in African Americans with T2DM, a group at lower risk for hepatic steatosis relative to European Americans with T2DM.

METHODS

We examined 422 African Americans with T2DM (40.3% male; age: 56.4±9.6 years; Body Mass Index: 35.2±8.2 kg/m(2)), all with measures of liver density reflecting hepatic fat content on abdominal computed tomography, and blood glucose and lipid profiles. Associations between rs738409 and phenotypes of interest were determined using SOLAR, assuming an additive model of inheritance with covariates age, sex, BMI and use of lipid-lowering medications.

RESULTS

Mean±SD liver density was 55.4±10.2 Hounsfield Units. SNP rs738409 in PNPLA3 was significantly associated with liver density (P=0.0075) and hepatic steatosis (P=0.0350), but not with blood glucose, HbA(1c), total cholesterol, triglycerides, high-density or low-density lipoprotein levels or liver function tests (P=0.15-0.96).

CONCLUSION

These findings provide evidence that the PNPLA3 SNP rs738409 contributes to risk for increased liver fat content in African Americans with T2DM, an effect that appears to be independent from serum lipids. Although African Americans are less susceptible to fatty liver than European Americans, PNPLA3 appears to be a risk locus for hepatic steatosis in diabetic African Americans.

Review of the Diabetes Heart Study (DHS) family of studies: a comprehensively examined sample for genetic and epidemiological studies of type 2 diabetes and its complications

The Diabetes Heart Study (DHS) is a genetic and epidemiological study of 1,443 European American and African American participants from 564 families with multiple cases of type 2 diabetes. Initially, participants were comprehensively examined for measures of subclinical cardiovascular disease (CVD) including computed tomography measurement of vascular calcified plaque, ultrasound imaging of carotid artery wall thickness, and electrocardiographic intervals. Subsequent studies have investigated the relationship between bone mineral density and vascular calcification, measures of adiposity, and biomarkers. Ongoing studies are carrying out an extensive evaluation of cerebrovascular disease using magnetic resonance imaging and cognitive assessment. A second, parallel study, the African American DHS, has expanded the sample of African Americans to investigate marked racial differences in subclinical CVD between European Americans and African Americans. Studies in development will evaluate the impact of social stress during the lifecourse on CVD risk, and the prevalence of gastroparesis in this diabetes enriched sample. In addition, the ongoing high mortality rate in DHS participants provides novel insights into the increased risks for type 2 diabetes affected individuals. A comprehensive genetic analysis of the sample is underway using the genome-wide association study (GWAS) approach. Data from this GWAS survey will complement prior family-based linkage data in the analysis of genetic contributors to the wide range of traits in the sample. To our knowledge the DHS family of studies has created the most comprehensively examined sample of individuals with type 2 diabetes yet available, and represents a unique resource for the study people with type 2 diabetes. The aim of this review is to provide a collective overview of the major results from the DHS family of studies, and relate them to the larger body of biomedical investigations of diabetes and its complications.