Malignant coronary artery disease in young Asian Indians: thoughts on pathogenesis, prevention, and therapy. Coronary Artery Disease in Asian Indians (CADI) Study

Possible ethnic differences in plasma homocysteine levels associated with coronary artery disease between south Asian and east Asian immigrants

BACKGROUND

Hyperhomocysteinemia has been identified as a risk factor for coronary artery disease (CAD). South Asians appear to have a high incidence of CAD, while East Asians have a very low incidence.

HYPOTHESIS

The present study was undertaken because the relative association of plasma homocysteine levels (PH) with CAD in South Asians (SA = Indian, Pakistani, Sri Lankan) and East Asians (EA = Chinese, Japanese) is not known.

METHODS

Fasting PH were drawn on all patients with CAD of SA (age 62.4+/-1.1 years, 72 men, 14 women) and EA (age 61.8+/-3.0 years, 13 men, 4 women) descent. These were compared with PH available from Caucasian (CA) patients (age 61.1+/-1.1 years, 89 men, 17 women) with CAD.

RESULTS

The PH in SA, EA, and CA patients were 11.0+/-0.5, 7.6+/-0.5, and 10.8+/-0.6 micromol/l, respectively (p<0.001 between EA and SA/CA). Percentages of SA, EA, and CA with elevated PH (> 12.0 micromol/l) were 33.7, 5.9, and 28.2%, respectively. There were no significant differences in the lipid subfractions between the SA and EA group. History of smoking was significantly higher in the EA (52.9 vs. 26.2%), while hypertension and diabetes mellitus had similar prevalences.

CONCLUSION

Significant differences in PH of SA versus EA patients with CAD exist. The relative contribution of homocysteine in the development of CAD appears to be less in EA immigrants. In contrast, the association between CAD and PH in SA immigrants appears to be similar to that of Caucasians.

Atheromatous plaque reflects serum total cholesterol levels: a comparative morphologic study of endarterectomy coronary atherosclerotic plaques removed from patients from the southern part of India and Caucasians from Ottawa, Canada

BACKGROUND

Natives of South India have a very high incidence of coronary artery disease, despite low calorie and fat intake.

HYPOTHESIS

This study was undertaken to determine whether morphologic features of atheromatous plaque reflect the serum total cholesterol.

METHODS

Fifty-three endarterectomy specimens from patients (mean age 47 +/- 9 years, mean cholesterol 203 +/- 47 mg/dl) obtained from one cardiac surgeon working in a single institution in South India were evaluated. Morphologic findings were compared with 40 endoarterectomy specimens obtained from age-matched Caucasians from Ottawa, Canada, with a reported mean cholesterol of 262 +/- 47 mg/dl. Morphometric measurements of the vessel size, percent stenosis, and the various components of the atherosclerotic plaque were determined by computerized planimetry.

RESULTS

The vessel size was smaller in the Indian than in the Canadian population (4.6 +/- 2.9 vs. 5.6 +/- 3.0 mm2, p = 0.07), the plaque area was less (4.3 +/- 2.3 vs. 5.3 +/- 2.8 mm2, p = 0.055) and the calculated percent stenosis was significantly less (93 vs. 96%, p = 0.028). Of all the parameters evaluated, only necrotic core in the Indian population (7.1 +/- 10.9% vs. Canadian 16.7 +/- 19.7%, p < 0.001) and proteoglycan deposition (7.9 +/- 11.2% vs. Canadian 3.7 +/- 5.3%, p < 0.023) were significantly different. Despite the Indians having low total cholesterol, there was greater diffuse double and triple-vessel disease and at a younger age than in the Caucasians.

CONCLUSIONS

From our data, it appears that the mechanism of development of atherosclerotic disease in the Indians may be different because they have smaller vessels, smaller necrotic core, and greater proteoglycan deposition. Other etiologies, especially those related to a high carbohydrate diet (which is typical for South Indians), should be considered.

The epidemiology of triglyceride as a coronary artery disease risk factor

Triglyceride (TG) has long been associated as a risk factor for coronary artery disease. A recent meta-analysis of various epidemiologic studies has confirmed this link. An important issue is to assess further the appropriate cutpoints to classify desirable TG because recent data indicate that levels < 200 mg/dl confer elevated risk. The dietary habits of present hunter-gatherer populations reveal the impact of a Westernized diet on both TG and cholesterol and suggest that a desirable TG is < 100 mg/dl. The epidemiologic and observational data in support of this concept are explored.

Atheroscerlotic heart disease in Bangladeshi immigrants: risk factors and angiographic findings

BACKGROUND

The prevalence of coronary artery disease (CAD) among Bangladeshis greatly exceeds that of Caucasians. Bangladeshis also suffer from premature onset, clinically aggressive and angiographically extensive disease. The role of conventional CAD risk factors (CCRFs) has been questioned. We therefore sought to determine if the CCRFs of Bangladeshis differed from non-Bangladeshis. We also sought to determine whether CAD was more extensive in Bangladeshis and if Bangladeshi ethnicity was independently predictive of extensive i.e., 3-vessel CAD at angiography.

METHODS

We reviewed the coronary angiograms and medical records of 75 Bangladeshis and 57 non-Bangladeshis presenting with myocardial infarction or angina pectoris.

RESULTS

Bangladeshis were younger (56.1 vs. 62.4 years, p=.001), had a lower body-mass index (25.2 vs. 27.2 kg/m(2), p=.017) and were less likely to be current or recent smokers (40% vs. 58%, p=.041) than non-Bangladeshis. There were no statistically significant differences in the proportion of subjects in the 2 groups with respect to diabetes mellitus, dyslipidemia, hypertension or family history of CAD. Bangladeshis had twice the rate of 3-vessel CAD of non-Bangladeshis (53% vs. 26%, p=.002). Bangladeshi ethnicity was independently associated with >3X the likelihood of having 3-vessel CAD at angiography (p=.011).

CONCLUSIONS

This study demonstrated that the CCRF burden of Bangladeshis with CAD is not excessive compared to that of non-Bangladeshis and is therefore unlikely to account for the excessive CAD risk found in this cohort. We also conclude that Bangladeshis have more angiographically extensive CAD than non-Bangladeshis and that Bangladeshi ethnicity is independently predictive of 3-vessel disease.

Prevalence of ischemic heart disease among urban population of siliguri, west bengal

OBJECTIVES

To determine the prevalence of ischemic heart disease and the associated risk factors among the urban population of Siliguri.

MATERIALS AND METHODS

A cross-sectional survey of a random sample of the population aged >/=40 years old in the Municipal Corporation area of Siliguri. Study variables were age, sex, occupation, addiction, food habit, physical activity, body mass index, blood pressure, and electrocardiogram change.

RESULTS

Out of 250 individuals who took part in this study, 29 (11.6%) had ischemic heart disease (IHD) and 118 (47.2%) had hypertension. Males had a higher (13.5%) prevalence of IHD than females (9.4%). About 5% of the patients had asymptomatic IHD. IHD among the study population is significantly associated with hypertension and smoking.

Coronary artery diseases in South Asian immigrants: an update on high density lipoprotein role in disease prevention

Over the past several years, the overall prevalence and incidence of cardiovascular diseases (CVD) including coronary artery diseases (CAD) have declined in the United States (US) and in many developed countries. However, among South Asian in general and South Asian immigrants (SAIs) in particular, a disturbing trend toward high rates of CAD has been noted. This trend is associated with a high prevalence of conventional risk factors and metabolic syndrome in this population, yet these conventional risk factors may not account for the greater CAD risk among SAIs. A search for additional markers is warranted, to enable early detection and prevention of CAD in this high risk group. High density lipoprotein (HDL) is one of the predictor of CAD and is considered to be cardio-protective. However, some of the recent studies have shown that HDL is not only ineffective as an antioxidant but, paradoxically, appears to be pro-oxidant, and has been found to be associated with CAD. Such HDL is called dysfunctional HDL. We present here an overview CAD and CAD risk factors in general and dyslipidemias in particular in SAIs. In addition, the evolving theories on dysfunctional HDL and its impact on CAD are also briefly presented.

Waist circumference, metabolic syndrome and coronary artery disease in a Pakistani cohort

BACKGROUND

Metabolic syndrome (M-IRS) is common in Asians. This study investigated the relationship of two definitions of M-IRS to atherosclerosis in Indian Asians with suspected coronary arterial disease (CAD).

METHODS

400 patients with chest pain selected for the presence or absence of angiographic disease were recruited from a tertiary referral centre in Pakistan into a prospective case-control study. Patients were categorized by the National Cholesterol Education Program adult treatment panel 3 (NCEP) and International Diabetes Federation (IDF) definitions of the metabolic syndrome and the relationship of these to the presence of CAD and extent of atheroma burden was investigated.

RESULTS

M-IRS was present in 53% by IDF criteria and in 44% using the Asian criteria for NCEP. The 2 populations identified were only 69% concordant. No relationship existed between the presence of NCEP M-IRS and atheroma burden. In contrast, the presence of IDF M-IRS was associated with CAD (65 vs. 34%; RR=1.88; p<0.001) and angiographic disease burden (28 [0-224] vs. 0 (0-198); RR=1.83; p<0.001). This association persisted (beta=18.4; p<0.001) after correction for C-reactive protein (beta=8.67; p<0.001), lipoprotein (a) (beta=8.14; p=0.002), and estimated glomerular filtration rate (beta=-0.22; p=0.01). Differences in presumed underlying factors were found in the 2 populations identified by the definitions though both agreed on the separate weightings given to blood pressure and HDL-C/apolipoprotein A1.

CONCLUSIONS

The specific Asian IDF and NCEP definitions of M-IRS show limited concordance in Pakistanis. The IDF criteria in contrast to the NCEP criteria are associated with the presence of CAD even after allowing for other risk factors identified in this population.

Dyslipidemia in South Asian patients

South Asians around the globe have the highest rates of coronary artery disease (CAD). These rates are 50% to 300% higher than other populations, with a higher risk at younger ages. These high rates of CAD are accompanied by low or similar rates of major traditional risk factors. The prevalence of diabetes is three to six times higher among South Asians than Europeans, Americans, and other Asians but does not explain the "South Asian Paradox." A genetic predisposition to CAD, mediated by high levels of lipoprotein(a), markedly magnifies the adverse effects of traditional risk factors related to lifestyle and best explains the South Asian Paradox. Although the major modifiable risk factors do not fully explain the excess burden of CAD, they are doubly important and remain the foundation of preventive and therapeutic strategies in this population. A more aggressive approach to preventive therapy, especially dyslipidemia, at an earlier age and at a lower threshold is clearly warranted.

Prevalence of common disease-associated variants in Asian Indians

Background

Asian Indians display a high prevalence of diseases linked to changes in diet and environment that have arisen as their lifestyle has become more westernized. Using 1200 genome-wide polymorphisms in 432 individuals from 15 Indian language groups, we have recently shown that: (i) Indians constitute a distinct population-genetic cluster, and (ii) despite the geographic and linguistic diversity of the groups they exhibit a relatively low level of genetic heterogeneity.

Results

We investigated the prevalence of common polymorphisms that have been associated with diseases, such as atherosclerosis (ALOX5), hypertension (CYP3A5, AGT, GNB3), diabetes (CAPN10, TCF7L2, PTPN22), prostate cancer (DG8S737, rs1447295), Hirschsprung disease (RET), and age-related macular degeneration (CFH, LOC387715). In addition, we examined polymorphisms associated with skin pigmentation (SLC24A5) and with the ability to taste phenylthiocarbamide (TAS2R38). All polymorphisms were studied in a cohort of 576 India-born Asian Indians sampled in the United States. This sample consisted of individuals whose mother tongue is one of 14 of the 22 "official" languages recognized in India as well as individuals whose mother tongue is Parsi, a cultural group that has resided in India for over 1000 years. Analysis of the data revealed that allele frequency differences between the different Indian language groups were small, and interestingly the variant alleles of ALOX5 g.8322G>A and g.50778G>A, and PTPN22 g.36677C>T were present only in a subset of the Indian language groups. Furthermore, a latitudinal cline was identified both for the allele frequencies of the SNPs associated with hypertension (CYP3A5, AGT, GNB3), as well as for those associated with the ability to taste phenylthiocarbamide (TAS2R38).

Conclusion

Although caution is warranted due to the fact that this US-sampled Indian cohort may not represent a random sample from India, our results will hopefully assist in the design of future studies that investigate the genetic causes of these diseases in India. Our results also support the inclusion of the Indian population in disease-related genetic studies, as it exhibits unique genotype as well as phenotype characteristics that may yield new insights into the underlying causes of common diseases that are not available in other populations.

Effect of combining viscous fibre with lovastatin on serum lipids in normal human subjects

OBJECTIVES

Soluble fibre supplements are recommended to reduce the levels of low-density lipoprotein cholesterol (LDL-C). Limited information exists on the interaction between fibre and hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins). The purpose of the present study was to evaluate the per se effect of psyllium (10 g/day) and lovastatin (20 mg/day) alone and in combination on serum lipids in normal human volunteers.

METHODS

In a 4-week open label, randomised, parallel study, subjects were randomised to receive 20 mg of lovastatin, 10 g of psyllium or 20 mg of lovastatin plus 10 g of psyllium in evening daily. Levels of total cholesterol (TC), LDL-C, high-density lipoprotein cholesterol (HDL-C), TC/LDL-C ratio, LDL-C/HDL-C ratio and triglycerides were determined after 1, 2, 3 and 4 weeks of treatment.

RESULTS

The study group comprised 36 adult, male subjects. All treatments were well tolerated, and after 4 weeks the mean LDL-C, TC and TG levels in the group receiving 20 mg of lovastatin plus 10 g of psyllium fell by 30.88%, 26.88% and 26.21% from baseline, compared with 24.78%, 19.55% and 32.88% in the group receiving 20 mg of lovastatin and 3.58%, 2.90% and 10.95% in the group receiving 10 g of psyllium respectively. Although additive effect was observed in the group receiving combination compared with group receiving lovastatin, the observed difference was not statistically significant. No significant changes from baseline in HDL-C levels occurred.

CONCLUSIONS

Psyllium soluble fibre should be considered as a safe and well-tolerated dietary supplement option to enhance cholesterol lowering.

Low levels of genetic divergence across geographically and linguistically diverse populations from India

Ongoing modernization in India has elevated the prevalence of many complex genetic diseases associated with a western lifestyle and diet to near-epidemic proportions. However, although India comprises more than one sixth of the world's human population, it has largely been omitted from genomic surveys that provide the backdrop for association studies of genetic disease. Here, by genotyping India-born individuals sampled in the United States, we carry out an extensive study of Indian genetic variation. We analyze 1,200 genome-wide polymorphisms in 432 individuals from 15 Indian populations. We find that populations from India, and populations from South Asia more generally, constitute one of the major human subgroups with increased similarity of genetic ancestry. However, only a relatively small amount of genetic differentiation exists among the Indian populations. Although caution is warranted due to the fact that United States–sampled Indian populations do not represent a random sample from India, these results suggest that the frequencies of many genetic variants are distinctive in India compared to other parts of the world and that the effects of population heterogeneity on the production of false positives in association studies may be smaller in Indians (and particularly in Indian-Americans) than might be expected for such a geographically and linguistically diverse subset of the human population.

Genomic studies of human genetic variation are useful for investigating human evolutionary history, as well as for designing strategies for identifying disease-related genes. Despite its large population and its increasing complex genetic disease burden as a result of modernization, India has been excluded from most of the largest genomic surveys.

The authors performed an extensive investigation of Indian genetic diversity and population relationships, sampling 15 groups of India-born immigrants to the United States and genotyping each individual at 1,200 genetic markers genome-wide. Populations from India, and groups from South Asia more generally, form a genetic cluster, so that individuals placed within this cluster are more genetically similar to each other than to individuals outside the cluster. However, the amount of genetic differentiation among Indian populations is relatively small. The authors conclude that genetic variation in India is distinctive with respect to the rest of the world, but that the level of genetic divergence is smaller in Indians than might be expected for such a geographically and linguistically diverse group.

Lipid Pentad Index: A novel bioindex for evaluation of lipid risk factors for atherosclerosis in young adolescents and children of premature coronary artery disease patients in India

OBJECTIVE

To evaluate the role of non-conventional lipid risk factors like Lipoprotein(a) [Lp(a)], Apolipoprotein A-I (Apo A-I) and Apolipoprotein B-100 (Apo B-100) and other conventional lipid profile parameters in children and adolescents of premature coronary artery disease (CAD) patients in India; and thereby explain the highest occurrence of premature CAD in this population.

METHODS

Forty-five children and adolescents of premature CAD patients (cases, mean age 12.08+/-3.71 years) and forty-five age and sex matched children and adolescents of healthy parents without any history or clinical evidence suggestive of CAD were studied (controls, mean age 12.14+/-3.91 years).

RESULTS

We found a significant increase in mean levels of Lp(a), Apo B-100, Total cholesterol (TC), Low Density Lipoprotein-Cholesterol (LDL-C) and Triglyceride (TG) in cases than controls. In contrast, Apo A-I and High Density Lipoprotein-Cholesterol (HDL-C) values decreased. Lipid Tetrad Index (LTI) and Atherogenic Index in Indian children and adolescents were also calculated. Kolmogorov D statistic and cumulative probability plot suggest that the new Lipid Pentad Index (LPI) defined by us is able to discriminate case and control populations more precisely than the existing LTI and Atherogenic Index.

CONCLUSIONS

The new proposed LPI appears to be a better indicator of lipid risk factors in children and adolescents of premature CAD patients from India, than the prior LTI and Atherogenic Index.

Myocardial infarction in young adults

Although myocardial infarction (MI) mainly occurs in patients older than 45, young men or women can suffer MI. Fortunately, its incidence is not common in patients younger than 45 years. However, the disease carries a significant morbidity, psychological effects, and financial constraints for the person and the family when it occurs at a young age. The causes of MI among patients aged less than 45 can be divided into four groups: (1) atheromatous coronary artery disease; (2) non-atheromatous coronary artery disease; (2) hyper-coagulable states; (4) MI related to substance misuse. There is a considerable overlap between all the groups. This article reviews the literature and highlights the practical issues involved in the management of young adults with MI.

Coronary artery diameter as a risk factor for acute coronary syndromes in Asian-Indians

Asian-Indians have high rates of coronary artery disease (CAD), which also occurs at an earlier age, with 50% of all heart attacks occurring in patients <55 years old and 25% in those <40 years old. Previous studies have cited structural factors in Asian-Indians, specifically smaller coronary arteries, as the cause of increased CAD in this population. We found that Asian-Indian patients have smaller coronary arteries, with a statistically significant difference in the mean diameter even after correction for body surface area.

High-density lipoprotein subclass distribution in individuals of Asian Indian descent: the National Asian Indian Heart Disease Project

Individuals of Asian Indian descent have significantly higher cardiovascular event rates as compared with other ethnic groups. The authors investigated the prevalence of metabolic disorders linked to coronary artery disease in an Asian Indian male population compared with non-Asian Indian males. Standard lipid measurements did not discriminate between groups, and the Asian Indian group exhibited less of the high coronary artery disease risk small low-density lipoprotein trait. Despite less of the small low-density lipoprotein trait in the Asian Indian group and no difference in high-density lipoprotein cholesterol, the Asian Indian group had a significantly higher prevalence (p < 0.0002) of low high-density lipoprotein 2b, implying impaired reverse cholesterol transport. This observation remained significant in the subgroup of patients with high-density lipoprotein cholesterol over 40 mg/dL, a region felt not to reflect impaired reverse cholesterol transport. Low high-density lipoprotein 2b combined with the higher lipoprotein(a) in the Asian Indian group may help explain the high prevalence of coronary artery disease in this ethnic population.

Plasma lipoprotein concentrations in ethnic populations

There is a complex interplay between genetic and environmental factors that influences the expression of plasma lipoprotein levels. It is therefore not surprising that differences in lipid levels have been reported between ethnic groups. There are conflicting data on racial and ethnic variations in lipids, and also limited data on the relationship between lipoprotein levels and coronary heart disease risk in specific populations. This review summarizes available data on ethnic variations in plasma lipoproteins and the potential impact on coronary morbidity and mortality.

Cardiovascular stress responses among Asian Indian and European American women and men

Asian Indians have approximately 3 times the rate of coronary artery disease as do age-matched European Americans, but the increased risk cannot be explained by the presence of known physiological and behavioral risk factors. One previous study suggested that Asian Indians have diminished vasoactive responses to isoproterenol, but no published study has examined responses to psychological stressors. The purpose of this study was to test the hypothesis that the vasomotor response to stress, as indexed by hemodynamic measures, would be exaggerated in Asian Indian men and women, relative to European American individuals. Thirty-seven Asian Indian and 43 European American men and women were tested in a standard reactivity protocol, whereas heart rate, blood pressure, and cardiac impedance measures were assessed. Asian Indian men and women had significantly smaller changes in systolic blood pressure and mean arterial pressure during the stressors, relative to European American men and women. Asian Indian women, but not men, had significantly smaller diastolic blood pressure and total peripheral-resistance index changes to the stressors, relative to the other 3 groups. These data are in contrast to our expectation of decreased tendency of Asian Indians to vasodilate during psychological stress but do suggest that sex and Asian Indian ethnicity interact to influence vascular reactivity to stressors.

Differences in body mass index and waist: hip ratios in North Indian rural and urban populations

Overweight could be a major factor in determining the increasing rates of coronary heart disease in the Indian population, by its influence on blood pressure, diabetes and insulin resistance. We studied the prevalence of overweight in north Indian urban and rural population samples. The urban sample population (n = 3050) was selected using a multistage sampling with stratification for geographical zone and the type of residential colony and cluster sampling of urban blocks in each stratum. The rural sample (n = 2487) was selected by random sampling of villages stratified for population size followed by coverage of all eligible persons in the village. All participating individuals were 35-64 years of age. Women constituted 52.2% (n = 1594) and 57% (n= 1417) of urban and rural samples, respectively. The study reveals that overweight is widely prevalent in the adult urban Delhi population, whereas underweight is a significant problem in the rural population. This was noted across all the age groups in both men and women. We estimated 'comprehensive coronary risk estimates' based on the New Zealand Heart foundation guidelines and noted that the proportion of high and very high risk subjects increased in a continuous manner even within the 'normal' ranges of BMI. This difference in prevalence in the urban population could represent the demographic transition in the Indian population.

Cardiovascular diseases in the developing countries: dimensions, determinants, dynamics and directions for public health action

The global burden of disease due to cardiovascular diseases (CVDs) is escalating, principally due to a sharp rise in the developing countries which are experiencing rapid health transition. Contributory causes include: demographic shifts with altered population age profiles; lifestyle changes due to recent urbanisation, delayed industrialisation and overpowering globalisation; probable effects of foetal undernutrition on adult susceptibility to vascular disease and possible gene-environment interactions influencing ethnic diversity. Altered diets and diminished physical activity are critical factors contributing to the acceleration of CVD epidemics, along with tobacco use. The pace of health transition, however, varies across developing regions with consequent variations in the relative burdens of the dominant CVDs. A comprehensive public health response must integrate policies and programmes that effectively impact on the multiple determinants of these diseases and provide protection over the life span through primordial, primary and secondary prevention. Populations as well as individuals at risk must be protected through initiatives that espouse and enable nutrition-based preventive strategies to protect and promote cardiovascular health. An empowered community, an enlightened policy and an energetic coalition of health professionals must ensure that development is not accompanied by distorted nutrition and disordered health.

Prevalence of the APOC3 promoter polymorphisms T-455C and C-482T in Asian-Indians

Potential mechanisms accounting for the high cardiovascular death rates observed in Asian-Indians are dyslipidemia and insulin resistance. Polymorphisms in the APOC3 promoter (-455 T/C and -482 C/T) were frequently encountered in young Asian-Indians and they correlated with reduced concentrations of apolipoprotein A-I.

Primordial prevention of coronary heart disease in India: challenges and opportunities

Demographic shifts, lifestyle changes, and adverse effects of childhood nutrition portend an epidemic of coronary heart disease in the Indian subcontinent, which is currently experiencing health transition. Indian susceptibility includes atherogenic blood lipid levels and a metabolic complex of central obesity, glucose intolerance, hyperinsulinemia, and dyslipidemia due to insulin resistance. These characteristics are demonstrated dramatically in urban Indians and in Indian migrants to the west. Prime targets for effective strategies of primordial prevention include children and families in lower socio-economic classes now in transition. There is the greatest urgency in India for medical, political, and social action to prevent high risk in the first place, combating the tobacco trade, enlisting food and agriculture agencies, and promoting physical activity in the population. An empowered community with an enlightened policy can prevent the threatened epidemic.

Increased prevalence of smaller and denser LDL particles in Asian Indians

There is increasing evidence to believe that Asian Indians are at an increased risk of coronary heart disease (CHD), which cannot be attributed to the common risk factors. Individuals with small, dense LDL phenotype are also known to be at increased risk of CHD. Our objective was to examine whether the prevalence of smaller and denser LDL particles is increased in Asian Indians. Thirty-nine Asian Indians (22 men and 17 women), aged 25 to 45 years, were matched with 39 whites for age and gender. Cholesterol profiles of lipoprotein classes and LDL subclasses were measured using the Vertical Auto Profile-II (VAP-II) and LDL-VAP-II methods, respectively. Six LDL subclasses (LDL1 to LDL6) have been identified using the LDL-VAP-II, with LDL1 and LDL6, respectively, being the most and least buoyant subclasses. The prevalence of small, dense LDL type (subjects with major LDL subclass 5 or 6) was significantly higher in Asian Indians compared with white subjects (44% versus 21%; P<0.05). The relative position of the major LDL density peak (LDL-Rf) on 0 to 1 scale in LDL-VAP-II density gradient was also significantly decreased in Asian Indians (0.462+/-0.076 versus 0. 505+/-0.086; P<0.02), suggesting an increased LDL density. Furthermore, this increased prevalence of small, dense LDL type appears to be due to the increased triglycerides (TG) (r for LDL-Rf versus TG=0.681, P<0.001), with fasting insulin being one of the important determinants of TG (r for TG versus fasting insulin=0.572, P<0.001). In addition, fasting insulin was significantly increased in Asian Indians with small, dense LDL type compared with other Asian Indians, suggesting a significant role of insulin resistance in increasing the prevalence of small, dense LDL type. We conclude that the increased prevalence of small, dense LDL observed in Asian Indians might contribute to their increased CHD risk.

Serum lipoprotein(A) profiles in a Singaporean population

Lipoprotein(a) [Lp(a)] is formed when apolipoprotein(a) is linked to low density lipoprotein (LDL)-cholesterol via a single disulfide bond. It is an independent risk factor for myocardial infarction and raised concentrations are associated with an increased risk of developing coronary artery disease. Singapore has a multi-racial population of 77% Chinese, 14% Malays and 7% Indians. Studies have shown that the Indians have significantly higher standardised mortality ratios (SMR) compared to the Chinese and the Malays. We measured serum Lp(a) concentrations in 803 healthy individuals recruited from the Multiphasic Health Screening Programme, using the Macra Lp(a) sandwich enzyme immunoassay kit (Strategics Diagnostics, Delaware, USA). Lp(a) concentrations were skewed in all three groups. Our population mean was 9.0 mg/dl, with 50th, 75th and 95th percentile values of 10.2, 19.8 and 43.1 mg/dl, respectively, which are lower than values reported from Caucasian populations (15.0, 29.0 and 60.0 mg/dl, respectively). Males had lower Lp(a) concentrations than females (P < 0.05). The Indian group had significantly higher concentrations (median 12.3 mg/dl) compared to their Chinese (median 9.6 mg/dl) and Malay (median 8.4 mg/dl) counterparts (P < 0.05). This could partly account for the higher SMR seen in the Indian population in Singapore. As serum Lp(a) concentrations are method- and population-dependent, we recommend that laboratories determine their own reference ranges by their method to avoid misclassification of the coronary heart disease (CHD) risk of patients.

Clinical and angiographic features in patients under 35 years with a first Q wave acute myocardial infarction

Sixty patients less than 35 years with a first Q wave acute myocardial infarction were prospectively studied to evaluate their features, risk factors and evidence of any viral infection. Typical chest pain was present in 98.3% with Q waves and ST segment elevation in all. None had hypotension or cardiogenic shock. Smoking was the most common risk factor (81.7%). Mean total cholesterol was 5.74 (+/-1.42) mmol/l. History of a viral illness was present in 28.3%, severe emotional stress in 21.7% and exhausting physical activity in 18.3%. Mean left ventricular diastolic and end systolic volumes were increased (90.11+/-22.5 ml/m2) and (46.62+/-20.46 ml/m2), respectively. The ejection fraction was depressed (49.71+/-1.6%). Triple vessel disease was seen only in 6.8 and 26.7% had insignificant or no coronary artery disease. Left anterior descending artery was most frequently involved (66%). None had left main involvement. Coronary ectasia was present in 11.7%, intracoronary thrombus in 28.3% and 40% had collaterals. Patients with no significant disease had no diabetes, a smaller number had a raised total cholesterol or smoked and had a lower ejection fraction. Patients from the Indian subcontinent who had fewer conventional risk factors, had more severe disease than those from the Arab world suggesting that other etiological factors need investigation.

Cardiovascular disease risk factors in 2 distinct ethnic groups: Indian and Pakistani compared with American premenopausal women

BACKGROUND

Although people from the Indian subcontinent have high rates of cardiovascular disease (CVD), studies of such in Indian and Pakistani women living in the United States are lacking.

OBJECTIVE

This study accounted for variability in serum lipid (total cholesterol and triacylglycerol) and lipoprotein [LDL cholesterol, lipoprotein(a), and HDL cholesterol] concentrations in Indian and Pakistani compared with American premenopausal women in the United States. Body composition, regional fat distribution, dietary intake, and energy expenditure were compared between groups.

DESIGN

The 2 groups were 47 Indian and Pakistani and 47 American women. Health was assessed via medical history, physical activity, body composition (via anthropometry and dual-energy X-ray absorptiometry), dietary intake (via 7-d food records), and serum lipids.

RESULTS

Serum total cholesterol, triacylglycerol, LDL cholesterol, lipoprotein(a), the ratio of total to HDL cholesterol, and the ratio of LDL to HDL cholesterol were greater (P <0.03), whereas HDL-cholesterol values were lower (P = 0.011) in Indians and Pakistanis than in Americans. Multiple regression analysis indicated that approximately 18% of the variance in total cholesterol (P = 0.0010) and LDL cholesterol (P = 0.0009) was accounted for by ethnicity, energy expenditure, and the ratio of the sum of central to the sum of peripheral skinfold thicknesses. Ethnicity, sum of central skinfold thicknesses, ratio of polyunsaturated to saturated fat, and monounsaturated fat intake accounted for approximately 43% of the variance in triacylglycerol concentration (P < 0.0001). Monounsaturated fat, percentage body fat, and alcohol intake accounted for approximately 26% of variance in HDL cholesterol. Ethnicity contributed approximately 22% of the 25% overall variance in lipoprotein(a).

CONCLUSIONS

Results suggest that these Indian and Pakistani women are at higher CVD risk than their American counterparts, but that increasing their physical activity is likely to decrease overall and regional adiposity, thereby improving their serum lipid profiles.

Hostility is associated with increased platelet activation in coronary heart disease

OBJECTIVE

To determine whether Potential for Hostility is related to platelet activation (PA) among patients with coronary heart disease (CHD) and healthy controls. Increased PA has been associated with adverse secondary events after myocardial infarction or coronary angioplasty.

METHODS

We tested 32 CHD patients and 23 healthy men and women, aged 45 to 73 years, for PA by using whole blood flow cytometry. PA was measured in blood exiting a bleeding time wound (wound-induced platelet activation) and also in venous blood stimulated in vitro with collagen. Monoclonal antibodies were used to test for fibrinogen receptor activation and fibrinogen receptor binding. All subjects refrained from taking aspirin for at least 14 days before testing; CHD patients stopped nitrates and calcium channel blockers for 24 hours, while continuing to take lipid-lowering medications. Potential for Hostility was assessed, using the Type A Structured Interview.

RESULTS

Among the CHD patients only, all four of the wound-induced fibrinogen receptor activation indicators (activation and binding) were related to hostility; the relationships were significant for receptor activation at 2 minutes, and for receptor binding at 1 minute (r values = .46, p values = .02). Subjects on lipid-lowering medications had lower PA for most measures. Healthy subjects had higher wound-induced fibrinogen receptor activation at 2 minutes and fibrinogen receptor activation in vitro than the CHD patients (p = .04), but after statistical adjustment for lipid-lowering medications, there were no significant differences between the patients and controls.

CONCLUSIONS

PA was related to hostility among CHD patients, consistent with previous studies indicating a relationship between PA and psychological factors among CHD patients. However, PA was not increased in nonsmoking, nondepressed CHD patients relative to controls.

Effect of garlic (Allium sativum) on blood lipids, blood sugar, fibrinogen and fibrinolytic activity in patients with coronary artery disease

Thirty patients with coronary artery disease (CAD) were administered garlic (study group) while another 30 patients received the placebo (control group). Various risk parameters were determined at 1.5 and 3 months of garlic administration. Garlic, administered in a daily dose of 2 x 2 capsules (each capsule containing ethyl acetate extract from 1 g peeled and crushed raw garlic), reduced significantly total serum cholesterol and triglycerides, and increased significantly HDL-cholesterol and fibrinolytic activity. There was no effect on the fibrinogen and glucose levels. In vitro effects of the garlic oil on platelet aggregation (PAg) and eicosanoid metabolism were examined; it inhibited PAg induced by several platelet agonists, and also platelet thromboxane formation. Two important paraffinic polysulphides - diallyl disulphide (DADS) and diallyl trisulphide (DATS) - derived from garlic and are usual constituents of garlic oil, showed antiplatelet activity, and also inhibited platelet thromboxane formation. In this respect DATS was more potent than DADS. The nature of inhibition of PAg by DATS was found to be reversible.

Apolipoprotein screening in Australian children: feasibility and the effect of age, sex, and ethnicity

OBJECTIVE

(i) To evaluate the feasibility of detecting adverse lipid profiles in schoolchildren by measuring capillary dried blood spot apolipoprotein levels, and (ii) to assess the effect of age, sex and ethnicity on apolipoprotein levels.

DESIGN

We measured capillary dried blood spot apolipoproteins B and A-I (apo B and apo A-I); assessed levels in relation to age, sex and ethnicity; and recalled children with elevated levels for a full lipid profile measurement.

PARTICIPANTS AND SETTING

6992 children (3501 boys and 3491 girls), aged 5-13 years, from schools in eastern Sydney, 1991-1995.

MAIN OUTCOME MEASURES

Capillary blood levels of apolipoproteins B and A-I, and serum total cholesterol level.

RESULTS

Of the 6951 children who provided an adequate fingerprick blood sample, we recalled 1465 children (21.1%) (640 boys [43.7%] and 825 girls [56.3%]) with elevated apo B levels and/or apo B:apo A-I ratios for further testing, either by us or by their family doctor (overall estimated compliance rate up to 70%). Among the 458 children who returned to us, there was a 90% positive predictive value for a total cholesterol level of over 4.5 mmol/L in those with both elevated apo B levels and high apo B:apo A-I ratios. Girls had higher apo B levels and apo B:apo A-I ratios than boys (P < 0.00001 for both), and in both sexes there was a trend downwards for apo B and upwards for apo B:apo A-I ratio over the age range tested, but levels were relatively stable between the ages of 6 and 10 years. Indian children (1.5% of the screened population) had the highest apo B levels, followed by white children (71.1%); Asian children (9.2%) had the lowest (P < 0.00001 compared with Indian and white children).

CONCLUSIONS

The high positive predictive value of capillary blood apolipoprotein levels for an adverse lipid profile in children suggests that measuring apolipoprotein levels by this method is a useful initial approach to cardiovascular risk assessment.

Central obesity, insulin resistance, syndrome X, lipoprotein(a), and cardiovascular risk in Indians, Malays, and Chinese in Singapore

STUDY OBJECTIVE

To examine the hypothesis that the higher rates of coronary heart disease (CHD) in Indians (South Asians) compared with Malays and Chinese is at least partly explained by central obesity, insulin resistance, and syndrome X (including possible components).

DESIGN

Cross sectional study of the general population.

SETTING

Singapore.

PARTICIPANTS

Random sample of 961 men and women (Indians, Malays, and Chinese) aged 30 to 69 years.

MAIN RESULTS

Fasting serum insulin concentration was correlated directly and strongly with body mass index (BMI), waist-hip ratio (WHR), and abdominal diameter. The fasting insulin concentration was correlated inversely with HDL cholesterol and directly with the fasting triglyceride concentration, blood pressures, plasminogen activator inhibitor 1 (PAI-1), and tissue plasminogen activator (tPA), but it was not correlated with LDL cholesterol, apolipoproteins B and A1, lipoprotein(a), (Lp(a)), fibrinogen, factor VIIc, or prothrombin fragment (F)1 + 2. This indicates that the former but not the latter are part of syndrome X. While Malays had the highest BMI, Indians had a higher WHR (men 0.93 and women 0.84) than Malays (men 0.91 and women 0.82) and Chinese (men 0.91 and women 0.82). In addition, Indians had higher fasting insulin values and more glucose intolerance than Malays and Chinese. Indians had lower HDL cholesterol, and higher PAI-1, tPA, and Lp(a), but not higher LDL cholesterol, fasting triglyceride, blood pressures, fibrinogen, factor VIIc, or prothrombin F1 + 2.

CONCLUSIONS

Indians are more prone than Malays or Chinese to central obesity with insulin resistance and glucose intolerance and there are no apparent environmental reasons for this in Singapore. As a consequence, Indians develop some but not all of the features of syndrome X. They also have higher Lp(a) values. All this puts Indians at increased risk of atherosclerosis and thrombosis and must be at least part of the explanation for their higher rates of CHD.

Correlation of lipoprotein (a) to angiographically defined coronary artery disease in Indians

Lipoprotein (a) [Lp(a)] levels have been correlated with angiographically defined coronary artery disease (CAD). Pattern of Lp(a) distribution in various racial groups is different. To study this relationship in Indian patients, plasma levels of Lp(a) and other lipid values were assessed in 101 patients undergoing coronary arteriography. Lp(a) concentration was higher in CAD group (n = 77) compared to normal coronary artery group (n = 24) (26.83 +/- 22.09 mg/dl vs. 15.07 +/- 14.61 mg/dl, P < 0.05). Lp(a) values had graded association with CAD. In Lp(a) quartile of < 5 mg/dl, 66.7% patients had CAD; in Lp(a) quartile of 5-25 mg/dl, 69.0% had CAD; Lp(a) quartile of 26-75 mg/dl, 87.5% had CAD; and in Lp(a) quartile of > or = 76 mg/dl, all patients had CAD. High density lipoprotein (HDL) cholesterol was higher in the normal coronary artery group as compared to CAD group (45.25 +/- 8.26 mg/dl vs. 41.83 +/- 16.47 mg/dl; NS). In HDL quartile of < 35 mg/l, 88.9% patients had angiographically defined CAD. Plasma values of total cholesterol, triglycerides (TG), apolipoprotein-A1 (Apo-A1), apolipoprotein-B (Apo-B), low density lipoprotein (LDL) cholesterol, LDL/HDL cholesterol ratio and Apo A1/B ratio were not significantly different in the groups with normal coronary arteries and CAD. Our results indicate that the measurement of Lp(a) provides a better marker for predicting the presence of angiographically defined CAD as compared to traditional measures.

Comparison of plasma lipid and lipoprotein profiles in hypertensive black versus white men. Department of Veterans Affairs Cooperative Study Group on Antihypertensive Agents

An abnormal plasma lipid and lipoprotein profile is an independent and strong predictor of mortality and morbidity from coronary artery disease (CAD). We report on plasma lipid and lipoprotein profiles with respect to race, age, obesity, blood pressure (BP), smoking, and drinking history in 1,292 male veterans with a diastolic BP of 95 to 109 mm Hg while off antihypertensive medications. Blacks had 24% (p <0.001) lower triglycerides than whites. In contrast, the following parameters were higher in blacks than in whites by the indicated percentages: high-density lipoprotein (HDL) cholesterol, 16% (p <0.001); HDL2 cholesterol, 36% (p <0.001); apolipoprotein (Apo) A1, 8% (p <0.001); HDL/low-density lipoprotein (LDL), 18% (p = 0.018); HDL2/LDL, 36% (p = 0.031); HDL2/HDL3, 21% (p <0.001); and Apo A1/Apo B, 15% (p <0.001). Triglycerides were unchanged up to age 60, but were lower by 24% (p <0.001) in those aged > or = 70. Apo A1 levels were higher (p <0.001), whereas LDL cholesterol was lower (p <0.008) in moderate alcohol consumers versus abstainers. Triglycerides were higher (p <0.001), whereas HDL, HDL2 cholesterol, and Apo A1 were lower (p <0.001) with increasing obesity. Moderate alcohol consumption had a strong favorable effect on HDL, HDL2, and HDL3 cholesterol among subjects of normal weight, but this effect was diminished in obese subjects. Total and LDL cholesterol were higher by 6.4% (p = 0.001) and 9.4% (p <0.003), respectively, whereas HDL cholesterol remained unchanged in those with diastolic BP of 105 to 109 mm Hg versus those with diastolic BP of 95 to 99 mm Hg. We conclude that hypertensive black men have lipid and lipoprotein profiles indicative of less CAD risk than white men. Chronic moderate alcohol consumption correlates with a favorable plasma lipid and lipoprotein profile in normal, but not obese, men. Obesity is associated with an adverse plasma lipid and lipoprotein profile. Thus, race, alcohol intake, and obesity may be important modifiers of CAD in untreated hypertensive men.