Ectopic Fat Depots and Coronary Artery Calcium in South Asians Compared With Other Racial/Ethnic Groups

Constructing a South Asian cardiovascular disease: a qualitative analysis on how researchers study cardiovascular disease in South Asians

BACKGROUND

Debates on the use of race in biomedical research have typically overlooked immigrant groups outside of the black-white racial dichotomy. Recent biomedical research on South Asians and cardiovascular disease provides an opportunity to understand how scientists define race and interpret racial health disparities from an underexamined perspective.

PURPOSE

To examine how researchers in the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study defined a South Asian population, and then compared health differences between South Asians and other populations.

METHODS

Qualitative content analysis was performed on eleven articles from August 2013 to January 2021 that directly compared the South Asian cohort in MASALA to four other groups. The MASALA study design article was also included in this analysis. Articles were analysed for how South Asians were defined, and for how health differences between South Asians and other populations were studied and discussed.

RESULTS

Researchers in MASALA were neither clear nor precise in defining South Asians as either an ancestral group or ethnic group. Their studies also prioritised investigating genetic and molecular causes of the cardiovascular health disparity between South Asians and other populations and failed to examine possible social factors.

CONCLUSIONS

These findings reflect a broader trend in biomedical research in which race and racial health disparities are poorly defined and studied, limiting scientists' understanding of the relationship between race and health. I propose methodologies to help researchers define populations and design studies without relying on biologically reductive assumptions.

Association Between Alcohol Consumption and Ectopic Fat in the Multi-Ethnic Study of Atherosclerosis

Background The relationship between alcohol consumption and ectopic fat distribution, both known factors for cardiovascular disease, remains understudied. Therefore, we aimed to examine the association between alcohol consumption and ectopic adiposity in adults at risk for cardiovascular disease. Methods and Results In this cross-sectional analysis, we categorized alcohol intake among participants in MESA (Multi-Ethnic Study of Atherosclerosis) as follows (drinks/day): <1 (light drinking), 1 to 2 (moderate drinking), >2 (heavy drinking), former drinking, and lifetime abstention. Binge drinking was defined as consuming ≥5 drinks on 1 occasion in the past month. Visceral, subcutaneous, and intermuscular fat area, pericardial fat volume, and hepatic fat attenuation were measured using noncontrast computed tomography. Using multivariable linear regression, we examined the associations between categories of alcohol consumption and natural log-transformed fat in ectopic depots. We included 6756 MESA participants (62.1±10.2 years; 47.2% women), of whom 6734 and 1934 had chest computed tomography (pericardial and hepatic fat) and abdominal computed tomography (subcutaneous, intermuscular, and visceral fat), respectively. In adjusted analysis, heavy drinking, relative to lifetime abstention, was associated with a higher (relative percent difference) pericardial 15.1 [95% CI, 7.1-27.7], hepatic 3.4 [95% CI, 0.1-6.8], visceral 2.5 [95% CI, -10.4 to 17.2], and intermuscular 5.2 [95% CI, -6.6 to 18.4] fat but lower subcutaneous fat -3.5 [95% CI, -15.5 to 10.2]). The associations between alcohol consumption and ectopic adiposity exhibited a J-shaped pattern. Binge drinking, relative to light-to-moderate drinking, was also associated with higher ectopic fat. Conclusions Alcohol consumption had a J-shaped association with ectopic adiposity. Both heavy alcohol intake and binge alcohol drinking were associated with higher ectopic fat.

Exploring the Diversity of Visceral, Subcutaneous and Perivascular Adipose Tissue in a Vascular Surgery Population

The prevalence of obesity has doubled, with a concomitant increase in cardiovascular disease. This study aimed to compare the characteristics of visceral, subcutaneous and peri-aortic adipose tissue determined with computed tomography (CT) scans and to correlate them with cardiovascular risk factors, anthropometric measures and medication. An observational and prospective study was conducted, and 177 subjects were included. Peri-aortic adipose tissue had the highest density, while the subcutaneous adipose tissue had the lowest. The density of subcutaneous adipose tissue differs from the density of visceral (p = 0.00) and peri-aortic adipose tissue (p = 0.00). Smokers/ex-smokers had a lower area (p = 0.00) and density (p = 0.02) of subcutaneous adipose tissue. Multiple linear regression analysis showed that sex was a predictor of subcutaneous adipose tissue area (β = -0.27, t = -3.12, p = 0.00) but smoking habits were not. After controlling for sex, we found that the association between smokers/ex-smokers and area of subcutaneous adipose tissue was lost, but the association with density persisted. Patients with hypertension had a higher visceral adipose tissue area, and this relationship was maintained even after adjusting for gender. Peri-aortic adipose tissue is similar to visceral and distinct from subcutaneous adipose tissue. Cardiovascular risk factors have different influences in distinct adipose compartments.

A South Asian Mediterranean-style diet is associated with favorable adiposity measures and lower diabetes risk: The MASALA cohort

OBJECTIVE

The Mediterranean diet is associated with lower risks for type 2 diabetes (T2D) and cardiovascular disease in certain populations, although data among diverse groups are limited. This study evaluated cross-sectional and prospective associations between a novel South Asian Mediterranean-style (SAM) diet and cardiometabolic risk among US South Asian individuals.

METHODS

The study included 891 participants at baseline in the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study. Culturally relevant foods were grouped into nine categories to construct the SAM score. The study examined associations of this score with cardiometabolic risk factors and incident T2D.

RESULTS

At baseline, higher adherence to the SAM diet was associated with lower glycated hemoglobin (-0.43% ± 0.15% per 1-unit increase in SAM score; p = 0.004) and lower pericardial fat volume (-1.22 ± 0.55 cm3 ; p = 0.03), as well as a lower likelihood of obesity (odds ratio [OR]: 0.88, 95% CI: 0.79-0.98) and fatty liver (OR: 0.82, 95% CI: 0.68-0.98). Over the follow-up (~5 years), 45 participants developed T2D; each 1-unit increase in SAM score was associated with a 25% lower odds of incident T2D (OR: 0.75, 95% CI: 0.59-0.95).

CONCLUSIONS

A greater intake of a SAM diet is associated with favorable adiposity measures and a lower likelihood of incident T2D.

Obesity and Cardiovascular Risk among South Asian Americans

Purpose of review

South Asian Americans experience higher cardiometabolic risk and disproportionately high rates of cardiovascular disease (CVD) compared to other racial and ethnic groups in the United States. The purpose of this review is to summarize recent evidence about the role of obesity in CVD risk in South Asian Americans and identify key evidence gaps and future directions for research and interventions for obesity in this group.

Recent findings

South Asian Americans are predisposed to abdominal obesity and have a higher distribution of visceral fat, intermuscular fat, and intrahepatic fat compared to adults of other race and ethnic groups. In this population, the risk for cardiometabolic disease appears to be elevated even at a normal body mass index. Social, cultural, religious, interpersonal, and environmental factors are related to obesity and obesity-related behaviors among South Asian Americans.

Summary

There is a relatively high prevalence of obesity in South Asian-origin populations in the United States, who have unique socio-cultural determinants of overweight and obesity. Future research should clarify why the risk for metabolic disease and CVD is elevated at normal BMI in the South Asian American population, and environmental and other structural factors that may influence obesity in this group. Interventions must be adapted to the social and cultural context of South Asian Americans to improve effectiveness and implementation.

Association between depressive symptoms and pericardial fat in healthy older men and women

Depressive symptoms are associated with increased risk for cardiovascular disease (CVD), and inflammation may contribute to this relationship. Pericardial fat, a highly metabolically active fat depot, is implicated in the pathogenesis of CVD, but its association with depressive symptoms is unclear. This study examined the cross-sectional and longitudinal association between depressive symptoms and pericardial fat over a three-year period. Participants were 543 healthy men and women (mean age = 62.9 years) without history or objective signs of coronary heart disease from the Whitehall II cohort. In men, depressive symptoms were positively associated with pericardial fat at baseline after adjustment for sociodemographics, waist to hip ratio and conventional cardiovascular risk factors. Inflammation, indexed by plasma interleukin 6 concentration, accounted for 17% of this association. Longitudinally, depressive symptoms did not predict pericardial fat three years later in men once baseline levels of pericardial fat were accounted for. No significant associations between depressive symptoms and pericardial fat were found in women. Overall, our findings suggest that greater pericardial fat might be a mechanism by which depressive symptoms are associated with increased risk for CVD in men, and inflammation may also lie on this pathway.

A healthy plant-based diet is favorably associated with cardiometabolic risk factors among participants of South Asian ancestry

BACKGROUND

Plant-based diets are recommended for chronic disease prevention, yet there has been little focus on plant-based diet quality among participants of South Asian ancestry who consume a predominantly plant-based diet.

OBJECTIVES

We evaluated cross-sectional and prospective associations between plant-based diet quality and cardiometabolic risks among participants of South Asian ancestry who are living in the United States.

METHODS

We included 891 participants of South Asian ancestry who completed the baseline visit in the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study. The prospective analysis included 735 participants who completed exam 2 (∼5 years after baseline). The plant-based diet quality was assessed using 3 indices: an overall plant-based diet index (PDI) that summarizes the consumption of plant foods, a healthy PDI (hPDI) that measures consumption of healthy plant foods, and an unhealthy PDI (uPDI) that reflects consumption of less healthy plant foods.

RESULTS

At baseline, the PDI score was inversely associated with fasting glucose. We observed inverse associations between PDI and hPDI scores and HOMA-IR, LDL cholesterol, weight, and BMI (all P values < 0.05). Higher scores on the hPDI, but not PDI, were associated with lower glycated hemoglobin, higher adiponectin, a smaller visceral fat area, and a smaller pericardial fat volume. Each 5-unit higher hPDI score was associated with lower likelihoods of fatty liver (OR: 0.76; 95% CI: 0.64, 0.90) and obesity (OR: 0.88; 95% CI: 0.80, 0.97). There were no associations between uPDI scores and cardiometabolic risks. Prospectively, after covariate adjustment for baseline values, each 5-unit higher hPDI score was associated with an 18% lower risk of incident type 2 diabetes (OR: 0.82; 95% CI: 0.67, 1.00).

CONCLUSIONS

A higher intake of healthful plant-based foods was associated with a favorable cardiometabolic risk profile. Dietary recommendations to lower chronic disease risks among participants of South Asian ancestry should focus on the quality of plant-based foods.

Relationship of American Heart Association's Life Simple 7, Ectopic Fat, and Insulin Resistance in 5 Racial/Ethnic Groups

BACKGROUND

The inverse association between ideal cardiovascular health (CVH) as measured by the American Heart Association's Life Simple 7 (LS7) and cardiovascular disease (CVD) incidence is well documented. However, research exploring the association between CVH and specific risk factors for cardiometabolic disease is sparse in diverse cohorts.

METHODS

This study included 7717 participants from the Mediators of Atherosclerosis in South Asians Living in America and the Multi-Ethnic Study of Atherosclerosis cohorts. We assigned each LS7 component a 0, 1, and 2 and summed these scores to derive an overall CVH score. Visceral, subcutaneous, and intermuscular fat area, pericardial fat volume, and hepatic fat attenuation were measured using noncontrast computed tomography. Multivariable linear regression was used to examine associations between CVH categories and each log-transformed ectopic fat depot, as well as the homeostatic assessment for insulin resistance (HOMA-IR).

RESULTS

In adjusted analysis, compared to those with ideal CVH, participants with poor CVH demonstrated 63.4% (95% CI, 54.3-73.0) higher visceral fat area, 84.0% (95% CI, 76.5-92.1) higher pericardial fat volume, 61.6% (95% CI, 50.7-73.2) higher subcutaneous fat area, and 40.6% (95% CI, 30.2-52.0) higher intermuscular fat area, and 15.1% (95% CI, 13.1-17.2) higher hepatic fat (all Ps < 0.001). Also, poor CVH was associated with 148.2% (95% CI, 131.1-166.7) higher HOMA-IR. We also found significant heterogeneity in the strengths of association by race/ethnicity for each ectopic fat depot.

CONCLUSION

Poor and intermediate CVH, as defined by LS7 metrics, were associated with significantly higher measures of ectopic fat and insulin resistance among individuals from 5 racial/ethnic groups.

Intermuscular adipose tissue in Type 2 diabetes mellitus: Non-invasive quantitative imaging and clinical implications

Intermuscular adipose tissue (IMAT) is an ectopic fat depot found beneath the fascia and within the muscles. IMAT modulates muscle insulin sensitivity and triggers local and systemic chronic low-grade inflammation by producing cytokines and chemokines, which underlie the pathogenesis of Type 2 diabetes mellitus (T2DM). Imaging techniques have been increasingly used to non-invasively quantify IMAT in patients with diabetes in research and healthcare settings. In this study, we systematically reviewed the cell of origin and definition of IMAT, and the use of quantitative and functional imaging technology pertinent to the etiology, risk factors, lifestyle modification, and therapeutic treatment of diabetes. The purpose of this article is to provide important insight into the current understanding of IMAT and future prospects of targeting IMAT for T2DM control.

Ectopic fat deposition in populations of black African ancestry: A systematic review and meta-analysis

AIMS

In populations of black African ancestry (BA), a paradox exists whereby lower visceral adipose tissue is found despite their high risk for type 2 diabetes (T2D). This systematic review investigates ethnic differences in other ectopic fat depots (intrahepatic lipid: IHL; intramyocellular lipid: IMCL and intrapancreatic lipid; IPL) to help contextualise their potential contribution to T2D risk.

METHODS

A systematic literature search was performed in December 2020 to identify studies reporting at least one ectopic fat comparison between BA and one/more other ethnicity. For IHL, a meta-analysis was carried out with studies considered comparable based on the method of measurement.

RESULTS

Twenty-eight studies were included (IHL: n = 20; IMCL: n = 8; IPL: n = 4). Meta-analysis of 11 studies investigating IHL revealed that it was lower in BA populations vs pooled ethnic comparators (MD -1.35%, 95% CI -1.55 to -1.16, I2 = 85%, P < 0.00001), white European ancestry (MD -0.94%, 95% CI -1.17 to -0.70, I2 = 79%, P < 0.00001), Hispanic ancestry (MD -2.06%, 95% CI -2.49 to -1.63, I2 = 81%, P < 0.00001) and South Asian ancestry comparators (MD -1.92%, 95% CI -3.26 to -0.57, I2 = 78%, P = 0.005). However, heterogeneity was high in all analyses. Most studies found no significant differences in IMCL between BA and WE. Few studies investigated IPL, however, indicated that IPL is lower in BA compared to WE and HIS.

CONCLUSION

The discordance between ectopic fat and greater risk for T2D in BA populations raises questions around its contribution to T2D pathophysiology in BA.

Coronary artery disease in East and South Asians: differences observed on cardiac CT

Epidemiological studies have observed East Asians (EAs) are significantly less likely to develop or die from coronary artery disease (CAD) compared with Caucasians. Conversely South Asians (SAs) develop CAD at higher rate and earlier age. Recently, a range of features derived from cardiac CT have been identified which may further characterise ethnic differences in CAD. Emerging data suggest EAs exhibit less coronary calcification and high-risk, non-calcified plaque compared with Caucasians on CT, with no difference in luminal stenosis. In contrast, SAs exhibit similar to higher coronary calcification and luminal stenosis, smaller luminal dimensions and more high-risk, non-calcified plaque than Caucasians. Beyond demonstrating ethnic differences in CAD, cardiac CT may enhance and individualise cardiovascular risk stratification in EAs and SAs. While data thus far in EAs have demonstrated calcium score and CT-derived luminal stenosis may incrementally predict cardiovascular risk beyond traditional risk scores, there remains a paucity of data assessing its use in SAs. Future studies may clarify the prognostic value of cardiac CT in SAs and investigate how this modality may guide preventative therapy and coronary intervention of CAD in EAs and SAs.

Association of Epicardial Fat Volume With the Extent of Coronary Atherosclerosis and Cardiovascular Adverse Events in Asymptomatic Patients With Diabetes

Epicardial adipose tissue has a paracrine effect, enhancing coronary artery atherosclerotic plaque development. This study evaluated epicardial fat volume (EFV), adipokines, coronary atherosclerosis, and adverse cardiovascular events in a cohort of asymptomatic patients with type 2 diabetes mellitus (T2DM). Epicardial fat volume was calculated using data from computed tomography coronary angiograms. Adipokines and inflammatory cytokines were also assayed and correlated with EFV. Epicardial fat volume was also assessed as a predictor of coronary artery calcium (CAC) score, number of coronary artery plaques, and significant plaque (>50% luminal stenosis). Data from the EFV analysis were available for 221 (85.7%) participants. Median EFV was 97.4 cm³, mean body mass index was 28.1 kg/m², and mean duration of T2DM was 13 years. Statistically significant, but weak, correlations were observed between several adipokines, inflammatory cytokines, and EFV. Epicardial fat volume was a significant univariate (P = .01), but not multivariate, predictor of the number of coronary plaques, but not of CAC score or significant plaque. After a mean follow-up of 22.8 months, 12 adverse cardiovascular events were reported, exclusively in participants with EFV >97.4 cm³. Epicardial fat volume has limited utility as a marker of coronary artery plaque in patients with T2DM and is weakly correlated with adipokine expression.

Intermuscular Fat Content in Young Chinese Men With Newly Diagnosed Type 2 Diabetes: Based on MR mDIXON-Quant Quantitative Technique

OBJECTIVE

Skeletal muscle fat content is one of the important contributors to insulin resistance (IR), but its diagnostic value remains unknown, especially in the Chinese population. Therefore, we aimed to analyze differences in skeletal muscle fat content and various functional MRI parameters between diabetic patients and control subjects to evaluate the early indicators of diabetes. In addition, we aimed to investigate the associations among skeletal muscle fat content, magnetic resonance parameters of skeletal muscle function and IR in type 2 diabetic patients and control subjects.

METHODS

We enrolled 12 patients (age:29-38 years, BMI: 25-28 kg/m²) who were newly diagnosed with type 2 diabetes (intravenous plasma glucose concentration≥11.1mmol/l or fasting blood glucose concentration≥7.0mmol/l) together with 12 control subjects as the control group (age: 26-33 years, BMI: 21-28 kg/m²). Fasting blood samples were collected for the measurement of glucose, insulin, 2-hour postprandial blood glucose (PBG2h), and glycated hemoglobin (HbAlc). The magnetic resonance scan of the lower extremity and abdomen was performed, which can evaluate visceral fat content as well as skeletal muscle metabolism and function through transverse relaxation times (T2), fraction anisotropy (FA) and apparent diffusion coefficient (ADC) values.

RESULTS

We found a significant difference in intermuscular fat (IMAT) between the diabetes group and the control group (p<0.05), the ratio of IMAT in thigh muscles of diabetes group was higher than that of control group. In the entire cohort, IMAT was positively correlated with HOMA-IR, HbAlc, T2, and FA, and the T2 value was correlated with HOMA-IR, PBG2h and HbAlc (p<0.05). There were also significant differences in T2 and FA values between the diabetes group and the control group (p<0.05). According to the ROC, assuming 8.85% of IMAT as the cutoff value, the sensitivity and specificity of IMAT were 100% and 83.3%, respectively. Assuming 39.25ms as the cutoff value, the sensitivity and specificity of T2 value were 66.7% and 91.7%, respectively. All the statistical analyses were adjusted for age, BMI and visceral fat content.

CONCLUSION

Deposition of IMAT in skeletal muscles seems to be an important determinant for IR in type 2 diabetes. The skeletal muscle IMAT value greater than 8.85% and the T2 value greater than 39.25ms are suggestive of IR.

Genetic and Environmental Factors Contributing to Visceral Adiposity in Asian Populations

Obesity-associated metabolic illnesses are increasing at an alarming rate in Asian countries. A common feature observed in the Asian population is a higher incidence of abdominal obesity-the "skinny-fat" Asian syndrome. In this review, we critically evaluate the relative roles of genetics and environmental factors on fat distribution in Asian populations. While there is an upward trend in obesity among most Asian countries, it appears particularly conspicuous in Malaysia. We propose a novel theory, the Malaysian gene-environment multiplier hypothesis, which explains how ancestral variations in feast-and-famine cycles contribute to inherited genetic predispositions that, when acted on by modern-day stressors-most notably, urbanization, westernization, lifestyle changes, dietary transitions, cultural pressures, and stress-contribute to increased visceral adiposity in Asian populations. At present, the major determinants contributing to visceral adiposity in Asians are far from conclusive, but we seek to highlight critical areas for further research.

Incidence and Progression of Coronary Artery Calcium in South Asians Compared With 4 Race/Ethnic Groups

Background

South Asians have a relatively high prevalence of coronary artery calcium (CAC) compared with other race/ethnic groups. We determined CAC incidence and progression among South Asians, and compared them with 4 race/ethnic groups.

Methods and Results

Data from the MASALA (Mediators of Atherosclerosis in South Asians Living in America) study were used to calculate CAC incidence and progression rates and any CAC change. Data from the MESA (Multi‐Ethnic Study of Atherosclerosis) were used to compare the CAC incidence and progression rates. A total of 698 South Asians had repeat CAC measurements after 4.8±0.8 years. Among those with no CAC at baseline, the age‐adjusted CAC incidence was 8.8% (95% CI, 6.8–10.8%) in men and 3.6% (2.5–4.8%) in women. The median annual CAC progression was 26 (interquartile range, 11–62) for men and 13 (interquartile range, 4–34) for women. Compared with MESA, age‐adjusted CAC incidence was similar in South Asian men compared with white, black, and Latino men, but significantly higher than Chinese men (11.1% versus 5.7%, P=0.008). After adjusting for age, diabetes mellitus, hypertension, and statin medication use, Chinese, black, and Latino men had significantly less CAC change compared with South Asian men, but there were no differences between South Asian and white men. There was no difference in CAC incidence or progression between South Asian women and women in MESA.

Conclusions

South Asian men had greater CAC change than Chinese, black, and Latino men but similar change to that of whites after adjusting for traditional risk factors.

Ethnic Disparities in Adiposity: Focus on Non-alcoholic Fatty Liver Disease, Visceral, and Generalized Obesity

PURPOSE OF REVIEW

Excessive adiposity has become a public health problem worldwide, contributing to the rise in obesity-related diseases and associated morbidity and mortality. This review details the relative significance of race/ethnicity as it pertains to adiposity and non-alcoholic fatty liver disease (NAFLD).

RECENT FINDINGS

Fat distribution remains a more reliable measure of adiposity than anthropometric measures, with visceral adipose tissue (VAT) associated with increased risk of cardiometabolic disease. While obesity is the most common risk factor for NAFLD, the racial/ethnic prevalence of obesity does not completely parallel NAFLD risk. Combating racial/ethnic disparities in obesity requires understanding differential risk among various groups. Hispanics are disproportionally impacted by NAFLD and have high rates of obesity, VAT, and insulin resistance (IR). This contrasts with Blacks, who have high prevalence of obesity and IR, accompanied by a paradoxically favorable lipid profile and low prevalence of VAT and NAFLD. Many features of adiposity and NAFLD are mediated by genetic and environmental factors, the latter being modifiable and the focus of interventions.

Body Composition and Diabetes Risk in South Asians: Findings From the MASALA and MESA Studies

OBJECTIVE

South Asians have a higher prevalence of type 2 diabetes compared with other race/ethnic groups. Body composition is associated with the risk for type 2 diabetes. Differences in body composition between South Asians and other race/ethnic groups are one hypothesized mechanism to explain the disproportionate prevalence of type 2 diabetes in this population.

RESEARCH DESIGN AND METHODS

This study used data from the Mediators of Atherosclerosis in South Asians Living in America (MASALA) and the Multi-Ethnic Study of Atherosclerosis (MESA) cohorts to determine whether body composition mediated the elevated prevalence of impaired fasting glucose and type 2 diabetes in South Asians. Participants (n = 2,615) with complete body composition data were included. Ordinal logistic regression models were calculated to determine the odds for glycemic impairment in South Asians compared with the MESA cohort.

RESULTS

In multivariate models, South Asians had a significantly higher prevalence of glycemic impairment and type 2 diabetes compared with all four race/ethnic groups included in the MESA (P < 0.001 for all). In unadjusted and multivariate adjusted models, South Asians had higher odds for impaired fasting glucose and type 2 diabetes compared with all other race/ethnic groups (P < 0.001 for all). The addition of body composition measures did not significantly mitigate this relationship.

CONCLUSIONS

We did not identify strong evidence that accounting for body composition explains differences in the risk for type 2 diabetes. Future prospective studies of the MESA and MASALA cohorts are needed to understand how adipose tissue impacts the risk for type 2 diabetes and how to best assess this risk.

Body fat, metabolic syndrome and hyperglycemia in South Asians

The prevalence of overweight and obesity is escalating in South Asian countries. South Asians display higher total and abdominal obesity at a lower BMI when compared to Whites. Consequently, metabolic dysfunction leading to metabolic syndrome (MetS) and type 2 diabetes mellitus (T2DM) will account for a majority of the health burden of these countries. In this review, we discuss those factors that contribute to MetS and T2DM in South Asians when compared to whites, focusing on adiposity. Abdominal obesity is the single-most important risk factor for MetS and its predisposition to T2DM. Excessive ectopic fat deposition in the liver (non-alcoholic fatty liver disease) has been linked to insulin resistance in Asian Indians, while the effects of ectopic fat accumulation in pancreas and skeletal muscle need more investigation. South Asians also have lower skeletal muscle mass than Whites, and this may contribute to their higher risk T2DM. Lifestyle factors contributing to MetS and T2DM in South Asians include inadequate physical activity and high intakes of refined carbohydrates and saturated fats. These are reflective of the recent but rapid economic transition and urbanization of the South Asian region. There is need to further the research into genetic determinants of dysmetabolism as well as gene x environment interactions. Collectively, MetS and T2DM have multi-factorial antecedents in South Asians and efforts to combat it through low-cost and socio-culturally appropriate lifestyle interventions need to be supported.

South Asians: why are they at a higher risk for cardiovascular disease?

PURPOSE OF REVIEW

We comment on the high prevalence of cardiovascular disease (CVD) in South Asians (SA). The effect of various risk factors, for example biochemical, genetic, lifestyle, socioeconomic factors and psychosocial stress on CVD risk is discussed.

RECENT FINDINGS

'Prediabetes' is common in SA, but its relationship with coronary artery disease (CAD) is not significant unlike for the white population. At the same time, 'prediabetes' in SA is associated with an increased risk for cerebrovascular disease (CeVD). The differentiating factor could be the high lipids in Europeans and their relationship to CAD. Likewise, higher diastolic blood pressure in SA may explain the risk of CeVD. Small, dense, low-density lipoprotein (LDL), low high-density lipoprotein-cholesterol (HDL-C) concentration and high triglycerides may contribute to atherosclerosis. Thrombotic factors such as increased levels of plasminogen activator inhibitor, fibrinogen, lipoprotein (a) and homocysteine have been shown to be associated with increased CVD. Impaired cerebrovascular autoregulation and sympathovagal activity, increased arterial stiffness and endothelial dysfunction may increase CVD risk further. In addition, environmental and dietary factors may exaggerate the unfavourable cardiovascular profile through genetic factors.

SUMMARY

The implications of the findings suggest comprehensive screening of SA for CVD. Cultural differences should be considered while designing prevention strategies specifically targeting barriers for uptake of preventive service.

The impact of fat distribution on subclinical coronary atherosclerosis in middle-aged Chinese adults

BACKGROUND

The relationship between obesity and cardiovascular disease (CVD) depends not only on the amount of body fat but also on its distribution, which has not been fully investigated in Chinese populations. We aimed to compare measures of fat accumulation in associations with subclinical coronary atherosclerosis in middle-aged Chinese adults.

METHODS

A total of 548 participants aged 40-60years without previous history or clinical symptoms of CVD were randomly selected to undergo abdominal computed tomography (CT) scanning and coronary CT angiography for the evaluation of subcutaneous and visceral fat accumulation and coronary atherosclerosis, respectively. γ-glutamyltranspeptidase (GGT) was used as a surrogate indicator of liver fat accumulation.

RESULTS

Measures of obesity such as body-mass index (BMI), waist circumference, visceral fat areas, and GGT levels, but not subcutaneous fat areas increased substantially across groups of participants without coronary stenosis, with <50% stenosis, and with significant (≥50%) stenosis after adjustment for age and sex. The multivariable multinomial logistic regression analysis showed that most obesity indicators such as BMI, waist circumference, visceral fat areas, and GGT levels were significantly associated with risks of having <50% coronary stenosis after adjustment for conventional cardiovascular risk factors. However, only GGT levels were significantly associated with risks of having significant (≥50%) coronary stenosis after adjustment. In addition, no significant associations were found between measures of fat accumulation and coronary calcification.

CONCLUSIONS

Liver fat accumulation might be more important in the association with subclinical coronary atherosclerosis compared with general and abdominal fat accumulation.