Relationship of lipoprotein(a) with intimal medial thickness of the carotid artery in Type 2 diabetic patients in south India

Prevention of atherosclerotic cardiovascular disease in South Asians in the US: A clinical perspective from the National Lipid Association

It is now well recognized that South Asians living in the US (SAUS) have a higher prevalence of atherosclerotic cardiovascular disease (ASCVD) that begins earlier and is more aggressive than age-matched people of other ethnicities. SA ancestry is now recognized as a risk enhancer in the US cholesterol treatment guidelines. The pathophysiology of this is not fully understood but may relate to insulin resistance, genetic and dietary factors, lack of physical exercise, visceral adiposity and other, yet undiscovered biologic mechanisms. In this expert consensus document, we review the epidemiology of ASCVD in this population, enumerate the challenges faced in tackling this problem, provide strategies for early screening and education of the community and their healthcare providers, and offer practical prevention strategies and culturally-tailored dietary advice to lower the rates of ASCVD in this cohort.

Dyslipidemia and Cardiovascular Disease Prevention in South Asians: A Review and Discussion of Causes, Challenges and Management Strategies

BACKGROUND

South Asians are at a significantly increased risk of atherosclerotic cardiovascular disease (ASCVD). For a major portion of the South Asian population, the cardiovascular disease events occur at a relatively younger age, are associated with worse outcomes, and have potentially more severe socioeconomic implications compared to their western counterparts.

METHODS

The term "South Asian" typically constitutes individuals from India, Pakistan, Nepal, Bhutan, Bangladesh, Sri Lanka, and Maldives, including expatriates as well as their families from these countries. Based on this, South Asians form approximately 25% of the world's population, with a high ASCVD burden in this group. In this review, we discuss the pathophysiological factors underlying ASCVD in South Asians, the dyslipidemia types and management, and discuss approaches to improve the overall ASCVD prevention efforts in this large subset population of the world. Although the pathophysiological mechanisms underlying the excess risk of cardiovascular disease in South Asians are multifactorial, dyslipidemia is a primary risk factor for the incidence and prevalence of this disease. The traditional "South Asian" dyslipidemia pattern includes levels of low-density lipoprotein cholesterol (LDL-C) in the normal range with a high concentration of LDL particles, elevated triglycerides, low levels of high-density lipoprotein cholesterol (HDL-C) with dysfunctional HDL particles, and high levels of lipoprotein(a).

CONCLUSION

While combined efforts to study the expatriate South Asians in western countries have been able to identify South Asian specific dyslipidemias, causal associations and optimal management remain relatively less explored. Larger scale studies are needed to better quantify the relationship of each lipid parameter with ASCVD risk among South Asians as well as optimal lipid targets and management strategies to reduce morbidity and mortality in this high-risk group.

Lipids in South Asians: Epidemiology and Management

Purpose of Review

This review focuses on lipoprotein abnormalities in South Asians (SA) and addresses risk stratification and management strategies to lower atherosclerotic cardiovascular disease (ASCVD) in this high-risk population.

Recent Findings

South Asians (SAs) are the fastest growing ethnic group in the United States (U.S) and have an increased risk of premature coronary artery disease (CAD). While the etiology may be multifactorial, lipoprotein abnormalities play a key role. SAs have lower low-density lipoprotein cholesterol (LDL-C) compared with Whites and at any given LDL-C level, SA ethnicity poses a higher risk of myocardial infarction (MI) and coronary artery disease (CAD) compared with other non-Asian groups. SAs have lower high-density lipoprotein cholesterol (HDL-C) with smaller particle sizes of HDL-C compared with Whites. SAs also have higher triglycerides than Whites which is strongly related to the high prevalence of metabolic syndrome in SAs. Lipoprotein a (Lp(a)) levels are also higher in SAs compared with many other ethnic groups. This unique lipoprotein profile plays a vital role in the elevated ASCVD risk in SAs. Studies evaluating dietary patterns of SAs in the U.S show high consumption of carbohydrates and saturated fats.

Summary

SAs have a high-risk lipoprotein profile compared with other ethnicities. Lipid abnormalities play a central role in the pathogenesis of CAD in SAs. More studies are needed to understand the true impact of the various lipoproteins and their contribution to increasing ASCVD in SAs. Aggressive lowering of LDL-C in high-risk groups using medications, such as statins, and lifestyle modification including dietary changes is essential in overall CAD risk reduction.

Lipoprotein(a): An underrecognized genetic risk factor for malignant coronary artery disease in young Indians

Malignant coronary artery disease (CAD) refers to a severe and extensive atherosclerotic process involving multiple coronary arteries in young individuals (aged <45 years in men and <50 years in women) with a low or no burden of established risk factors. Indians, in general, develop acute myocardial infarction (AMI) about 10 years earlier; AMI rates are threefold to fivefold higher in young Indians than in other populations. Although established CAD risk factors have a predictive value, they do not fully account for the excessive burden of CAD in young Indians. Lipoprotein(a) (Lp(a)) is increasingly recognized as the strongest known genetic risk factor for premature CAD, with high levels observed in Indians with malignant CAD. High Lp(a) levels confer a twofold to threefold risk of CAD-a risk similar to that of established risk factors, including diabetes. South Asians have the second highest Lp(a) levels and the highest risk of AMI from the elevated levels, more than double the risk observed in people of European descent. Approximately 25% of Indians and other South Asians have elevated Lp(a) levels (≥50 mg/dl), rendering Lp(a) a risk factor of great importance, similar to or surpassing diabetes. Lp(a) measurement is ready for clinical use and should be an essential part of all CAD research in Indians.

South Asian Cardiovascular Disease & Cancer Risk: Genetics & Pathophysiology

South Asians (SAs) are at heightened risk for cardiovascular disease as compared to other ethnic groups, facing premature and more severe coronary artery disease, and decreased insulin sensitivity. This disease burden can only be partially explained by conventional risk factors, suggesting the need for a specific cardiovascular risk profile for SAs. Current research, as explored through a comprehensive literature review, suggests the existence of population specific genetic risk factors such as lipoprotein(a), as well as population specific gene modulating factors. This review catalogues the available research on cardiovascular disease and genetics, anthropometry, and pathophysiology, and cancer genetics among SAs, with a geographical focus on the U.S. A tailored risk profile will hinge upon population customized classification and treatment guidelines, informed by continued research.

Atherosclerotic Cardiovascular Disease in South Asians in the United States: Epidemiology, Risk Factors, and Treatments: A Scientific Statement From the American Heart Association

South Asians (from Bangladesh, Bhutan, India, the Maldives, Nepal, Pakistan, and Sri Lanka) make up one quarter of the world's population and are one of the fastest-growing ethnic groups in the United States. Although native South Asians share genetic and cultural risk factors with South Asians abroad, South Asians in the United States can differ in socioeconomic status, education, healthcare behaviors, attitudes, and health insurance, which can affect their risk and the treatment and outcomes of atherosclerotic cardiovascular disease (ASCVD). South Asians have higher proportional mortality rates from ASCVD compared with other Asian groups and non-Hispanic whites, in contrast to the finding that Asian Americans (Asian Indian, Chinese, Filipino, Japanese, Korean, and Vietnamese) aggregated as a group are at lower risk of ASCVD, largely because of the lower risk observed in East Asian populations. Literature relevant to South Asian populations regarding demographics and risk factors, health behaviors, and interventions, including physical activity, diet, medications, and community strategies, is summarized. The evidence to date is that the biology of ASCVD is complex but is no different in South Asians than in any other racial/ethnic group. A majority of the risk in South Asians can be explained by the increased prevalence of known risk factors, especially those related to insulin resistance, and no unique risk factors in this population have been found. This scientific statement focuses on how ASCVD risk factors affect the South Asian population in order to make recommendations for clinical strategies to reduce disease and for directions for future research to reduce ASCVD in this population.

Serum levels of Lp(a) are related to waist circumference in NAFLD patients with low prevalence of co-morbidities

BACKGROUND

Novel evidence suggests a relationship between circulating Lp(a) levels and the presence of cardiovascular events independently from the cardio-metabolic profile.

METHODS AND RESULTS

The purpose of this study was to investigate serum Lp(a) concentrations in relation to carotid intima-media thickness (IMT), anthropometric measures, lipid profile, assessment of insulin resistance, and other parameters conventionally used to predict CVD risk, in obese patients suffering from hepatic steatosis (HS), the well-known nonalcoholic fatty liver disease (NAFLD). Evidencing the key-points of this research, firstly, serum Lp(a) concentrations were not associated with carotid IMT in this selected population or, consequently, with early atherosclerosis, at least as evaluated by IMT. Secondly, carotid IMT was not predicted by HS severity, as evaluated by ultrasound. Finally, in the adjusted model, Lp(a) was positively predicted by waist circumference (WC) (β = 0.25, t = 2.3, p = 0.02) and negatively by central adiposity, assessed as visceral adipose tissue at US (β = -0.33, t = -3.0, p = 0.003).

CONCLUSION

Serum Lp(a) values may not play a direct role in increasing IMT, albeit associated with WC.

Review: Diabetes and cardiac disease in South Asians

South Asians have a higher prevalence of diabetes, coronary heart disease and cardiovascular death. Their predisposition to insulin resistance partly explains this excess risk. After immigration, the adoption of a western diet allied to increased sedentary behaviour leads to weight gain, hypertension and hyperlipidaemia, factors which in turn combine to amplify the chances of getting heart disease. Further contributory factors are increased sub-clinical inflammation, increased thrombogenic tendency and higher serum homocysteine levels. South Asians with diabetes might do as well as White people with respect to intensive glycaemic and blood pressure control. However, there is little evidence for measures to reduce cardiovascular risk as South Asians have not been included as a subgroup in most large trials. Future prospective studies, including studies on the prevention of diabetes and cardiovascular disease in this high-risk population, are therefore urgently required.

Lipoprotein(a) and SYNTAX Score Association with Severity of Coronary Artery Atherosclerosis in North India

OBJECTIVES

This cross-sectional study investigated the association of lipoprotein(a) [Lp(a)] levels as an atherosclerosis predictor and their relationship to the severity of coronary artery disease (CAD).

METHODS

360 consecutive patients at Sanjay Gandhi Postgraduate Institute of Medical Sciences and King George's Medical University hospitals, Lucknow, North India, with chest pains, CAD symptoms and on lipid-lowering therapy were enrolled between June 2009 and October 2011. Before coronary artery angiography (CAG), a fasting blood sample was assessed for lipid and Lp(a) levels. The synergy between percutaneous coronary intervention with taxus and cardiac surgery (SYNTAX) score was calculated according to the CAG results. Patients were divided into 3 groups based on CAD severity and SYNTAX scores.

RESULTS

Angiography revealed CAD in 270 patients. Lp(a) levels were higher in CAD compared to non-CAD patients (48.7 ± 23.8 mg/dl versus 18.9 ± 11.1 mg/dl [P <0.0001]). The levels of Lp(a) were lower in single than in double and triple vessels (39.3 ± 18.4 mg/dl versus 58.0 ± 23.0 mg/dl, and 69.2 ± 24.1 mg/dl, [P <0.05]). Lp(a) levels were significantly higher in severe CAD with SYNTAX score >30 (88.0±24.0 mg/dl). Lp(a) levels correlated significantly with SYNTAX scores (r = 0.70, P <0.0001).

CONCLUSION

In this study, Lp(a) levels were positively associated with a patient's SYNTAX score in diseased vessels. Furthermore, an elevated Lp(a) level was a causal, independent risk factor of CAD. Lowering Lp(a) levels would reduce CAD in primary and secondary prevention settings. There is an urgent need to define more precisely which patients to treat and which to target for earlier interventions.

Carotid Intima-Media Thickness in Asymptomatic Subjects With Low Lipoprotein(a) Levels

Background

Elevated and extreme circulating levels of lipoprotein(a) (Lp(a)) are considered to be an atherosclerotic risk factor, although additional studies on the low levels of Lp(a) are necessary to provide confirmation. The carotid intima-media thickness (CIMT) is known as a surrogate index of atherosclerosis. The aim of the present study was to investigate the correlation between the serum Lp(a) and CIMT in asymptomatic subjects with a relatively low Lp(a) level.

Methods

The study included 65 asymptomatic female Japanese subjects (mean age: 60 years) with a serum Lp(a) level < 30 mg/dL. Clinical data including the serum Lp(a) and CIMT were measured, and their correlations were examined.

Results

The median Lp(a) level was 18.6 mg/dL and the mean CIMT level was 0.8 mm. There was a significant and inverse correlation between the CIMT and Lp(a) (r = - 0.24, P ≤ 0.05), in addition to a significant and positive correlation between the CIMT and subject age and systolic blood pressure. A stepwise multiple linear regression analysis identified the Lp(a) to be correlated independently, significantly and inversely with the CIMT.

Conclusions

The Lp(a) levels were inversely correlated with the CIMT in this population, suggesting that subjects with a low Lp(a) level may have a predisposition to carotid atherosclerosis. This finding was preliminary and should be investigated further in larger studies and in additional settings.

Keywords

Lp(a); Carotid artery; IMT; Atherosclerosis

Carotid intimal-medial thickness is not increased in women with previous gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is known to increase the risk of cardiovascular diseases. Measuring the carotid artery intimal-medial thickness (CIMT) is a non-invasive technique used to evaluate early atherosclerosis and to predict future cardiovascular diseases. We examined the association between CIMT and cardiovascular risk factors in young Korean women with previous GDM.

METHODS

One hundred one women with previous GDM and 19 women who had normal pregnancies (NP) were recruited between 1999 and 2002. At one year postpartum, CIMT was measured using high-resolution B-mode ultrasonography, and oral glucose tolerance tests were performed. Fasting glucose, glycated hemoglobin A1c (HbA1c), insulin levels and lipid profiles were also measured. CIMTs in the GDM and NP groups were compared, and the associations between CIMT and cardiovascular risk factors were analyzed in the GDM group.

RESULTS

CIMT results of the GDM group were not significantly different from those of the NP group (GDM, 0.435±0.054 mm; NP, 0.460±0.046 mm; P=0.069). In the GDM group, a higher HbA1c was associated with an increase in CIMT after age adjustment (P=0.011). CIMT results in the group with HbA1c >6.0% were higher than those of the normal HbA1c (HbA1c ≤6.0%) (P=0.010). Nine of the patients who are type 2 diabetes mellitus converters within one year postpartum but showed no significant difference in CIMT results compared to NP group.

CONCLUSION

Higher HbA1c is associated with an increase in CIMT in women with previous GDM. However, CIMT at one year postpartum was not increased in these women compared to that in NP women.

Epidemiology of cardiovascular disease in type 2 diabetes: the Indian scenario

Noncommunicable diseases, of which coronary artery disease (CAD) and diabetes top the list, have overtaken communicable diseases with respect to overall mortality, even in developing countries like India. High prevalence rates of diabetes and CAD are seen not only in affluent migrant Indians, but also in those living within the subcontinent. Indeed the epidemic of diabetes and CAD is now spreading to the middle- and lower-income groups in India. The risk for CAD is two to four times higher in diabetic subjects, and in Indians, CAD occurs prematurely, i.e., one to two decades earlier than in the West. Thus there is an urgent need for studies on CAD in diabetic and nondiabetic subjects in India. The Chennai Urban Population Study, a population-based study in Chennai, in South India, showed a prevalence of CAD of 11%, which is 10 times more than what it was in 1970. Clustering of risk factors for CAD such as hyperglycemia, central body obesity, dyslipidemia, and hypertension tends to occur, and interplay of these risk factors could explain the enhanced CAD risk in Indians. Additionally, low-grade inflammation and a possible inherent genetic susceptibility are other contributing factors. Preventive measures such as lifestyle modification with healthy diet, adequate physical activity, and decrease in stress could help prevent the twin epidemics of diabetes and CAD.

High-density lipoprotein-cholesterol and risk of stroke and carotid atherosclerosis: a systematic review

BACKGROUND AND PURPOSE

Epidemiological studies have found no relationship between total cholesterol and stroke risk, but little attention has been paid to high-density lipoprotein-cholesterol (HDL-C).

METHODS

We performed a systematic PubMed literature search for epidemiological studies that examined the association between HDL-C level and stroke or carotid intima-media thickness (IMT).

RESULTS

We identified 18 studies on the relationship between HDL-C and stroke risk and 37 on HDL-C and carotid IMT. Eight of ten prospective cohort studies (n=238,739) and three of eight case-control studies (n=3604 cases, 8220 controls) supported an association between elevated HDL-C level and decreased risk of stroke. Prospective cohort studies reporting on relative risk per unit increase in HDL-C showed an 11-15% decreased stroke risk per 10-mg/dl increase in HDL-C. Of 37 studies on carotid IMT, 31 reported cross-sectional, one longitudinal, and five both cross-sectional and longitudinal associations between HDL-C level and carotid IMT. Of 36 cross-sectional studies (n=51,288), 20 showed an inverse association between HDL-C level and carotid IMT. Of six longitudinal studies (n=20,065), three showed no association, one showed a weak association in a subgroup of white women and two showed a significant inverse relationship between HDL-C level and carotid IMT. Pooled estimates could not be calculated because of the variation in study designs and analysis.

CONCLUSIONS

The weight of evidence in the literature supports an inverse association between HDL-C level and stroke or carotid atherosclerosis, but more data are needed to firmly establish this protective effect.

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.