Increased platelet activation and fibrinogen in Asian Indians. Potential implications for coronary risk

Cardiovascular disease mortality in Asian Americans

BACKGROUND

Asian Americans are a rapidly growing racial/ethnic group in the United States. Our current understanding of Asian-American cardiovascular disease mortality patterns is distorted by the aggregation of distinct subgroups.

OBJECTIVES

The purpose of the study was to examine heart disease and stroke mortality rates in Asian-American subgroups to determine racial/ethnic differences in cardiovascular disease mortality within the United States.

METHODS

We examined heart disease and stroke mortality rates for the 6 largest Asian-American subgroups (Asian Indian, Chinese, Filipino, Japanese, Korean, and Vietnamese) from 2003 to 2010. U.S. death records were used to identify race/ethnicity and cause of death by International Classification of Diseases-10th revision coding. Using both U.S. Census data and death record data, standardized mortality ratios (SMRs), relative SMRs (rSMRs), and proportional mortality ratios were calculated for each sex and ethnic group relative to non-Hispanic whites (NHWs).

RESULTS

In this study, 10,442,034 death records were examined. Whereas NHW men and women had the highest overall mortality rates, Asian Indian men and women and Filipino men had greater proportionate mortality burden from ischemic heart disease. The proportionate mortality burden of hypertensive heart disease and cerebrovascular disease, especially hemorrhagic stroke, was higher in every Asian-American subgroup compared with NHWs.

CONCLUSIONS

The heterogeneity in cardiovascular disease mortality patterns among diverse Asian-American subgroups calls attention to the need for more research to help direct more specific treatment and prevention efforts, in particular with hypertension and stroke, to reduce health disparities for this growing population.

South Asian Ethnicity and Cardiovascular Risk

South Asians (SAs), in their countries or after migration, are at high risk of coronary artery disease (CAD) and mortality compared to other ethnic groups. It has been shown that >90% of CAD global risk could be attributed to 9 modifiable risk factors (RFs) worldwide. However, these conventional RFs may not fully explain this high risk of CAD among SAs. Therefore, attention has been directed toward nonconventional RFs. In this narrative review, we evaluate the conventional and emerging cardiovascular RFs characterizing SAs. These factors may explain the high morbidity and mortality among SAs. Further prospective studies are urgently needed to set algorithms for the optimal management of these RFs in high-risk populations like SAs.

Coagulation factors and antithrombin levels in young and elderly subjects in Pakistani population

Aging is associated with increased levels of coagulation factors and decrease in natural anticoagulant factors. This strongly supports that age-related hypercoagulable state occurs in elderly. This study aimed to measure the plasma levels of coagulation factors and anticoagulant levels in young and elderly to observe the effect of age on haemostatic system. Ninety healthy individuals, both men and women were divided into two groups on the basis of age. Group I included participants of less than 40 years of age, whereas, group II comprised of participants more than 60 years of age. Fibrinogen activity was assessed by using Clauss technique. Coagulation factor VII, and factor VIII activity by corresponding one stage assay based on prothrombin time and activated partial thromboplastin time. Antithrombin III was measured by the chromogenic method. Our results showed that significantly increased levels of fibrinogen (P = 0.001) were observed in the elderly population as compared to young. Higher fibrinogen levels in younger women than men and comparatively higher level than other races was observed in our local population. Increase in factor VII levels (P = 0.05) was also observed in the elderly group. This increase was statistically significant with age in women (P = 0.03). Factor VIII rose with age in both sexes (P = 0.001). Higher antithrombin activity was observed in the younger group whereas the older group demonstrated significantly lower antithrombin activity (P = 0.001). We conclude that considerable effects of age and sex are observed on coagulation factors and naturally occurring inhibitors.

Obesity-related non-communicable diseases: South Asians vs White Caucasians

South Asians are at higher risk than White Caucasians for the development of obesity and obesity-related non-communicable diseases (OR-NCDs), including insulin resistance, the metabolic syndrome, type 2 diabetes mellitus (T2DM) and coronary heart disease (CHD). Rapid nutrition and lifestyle transitions have contributed to acceleration of OR-NCDs in South Asians. Differences in determinants and associated factors for OR-NCDs between South Asians and White Caucasians include body phenotype (high body fat, high truncal, subcutaneous and intra-abdominal fat, and low muscle mass), biochemical parameters (hyperinsulinemia, hyperglycemia, dyslipidemia, hyperleptinemia, low levels of adiponectin and high levels of C-reactive protein), procoagulant state and endothelial dysfunction. Higher prevalence, earlier onset and increased complications of T2DM and CHD are often seen at lower levels of body mass index (BMI) and waist circumference (WC) in South Asians than White Caucasians. In view of these data, lower cut-offs for obesity and abdominal obesity have been advocated for Asian Indians (BMI; overweight >23 to 24.9 kg m(-2) and obesity ≥ 25 kg m(-2); and WC; men ≥ 90 cm and women ≥ 80 cm, respectively). Imbalanced nutrition, physical inactivity, perinatal adverse events and genetic differences are also important contributory factors. Other differences between South Asians and White Caucasians include lower disease awareness and health-seeking behavior, delayed diagnosis due to atypical presentation and language barriers, and religious and sociocultural factors. All these factors result in poorer prevention, less aggressive therapy, poorer response to medical and surgical interventions, and higher morbidity and mortality in the former. Finally, differences in response to pharmacological agents may exist between South Asians and White Caucasians, although these have been inadequately studied. In view of these data, prevention and management strategies should be more aggressive for South Asians for more positive health outcomes. Finally, lower cut-offs of obesity and abdominal obesity for South Asians are expected to help physicians in better and more effective prevention of OR-NCDs.

Soluble, platelet-bound, and total P-selectin as indices of platelet activation in congestive heart failure

BACKGROUND

Many complications associated with congestive heart failure (CHF) have a thrombosis-related aetiology. Platelets play an important role in thrombogenesis, but it is not clear whether circulating platelets actively participate in thrombosis-related complications associated with CHF.

OBJECTIVE

To determine whether soluble P-selectin, platelet surface P-selectin, and total platelet P-selectin as indices of platelet activation in CHF patients-compared to 'disease controls' and 'healthy controls'-and to assess their prognostic value in CHF.

METHODS

We measured soluble P-selectin (sP-sel, by enzyme-linked immunosorbent assay, ELISA), total platelet P-selectin (pP-sel, by a novel 'platelet lysate' assay), platelet surface P-selectin (CD62P%G) and platelet surface CD63 (CD63%G) expression by flow cytometry-in 108 patients with stable congestive heart failure (all with left ventricular ejection fraction (LVEF) <50%). Levels were compared with 50 healthy controls and 70 'disease controls' (patients with coronary artery disease with normal left ventricular systolic function).

RESULTS

CHF patients and disease controls had higher sP-sel, CD62P%G and CD63%G than healthy controls. There were no significant correlations between sP-sel, pP-sel, CD62P%G and CD63%G with ejection fraction (all P>0.05). There were no differences in these markers when ischaemic and non-ischaemic aetiologies of CHF were compared. After a median follow-up of 490 days (range 340-535), there were 7 deaths, 15 hospitalizations for worsening heart failure, 1 for cardiac resynchronization therapy, 4 for revascularizations, 4 for myocardial infarctions, and 1 stroke. None of the platelet markers were predictive of the composite end-point at follow-up.

CONCLUSIONS

Patients with stable CHF exhibit evidence of abnormal platelet activation, despite usage of antiplatelet agents. These abnormalities did not determine prognosis and were broadly similar to those seen in 'disease controls' indicating that platelet abnormalities in CHF may simply be related to associated comorbidities.

Vascular risk factors in South Asians

South Asians originate from the Indian sub-continent (India, Pakistan, Bangladesh, Sri Lanka and Nepal) and represent one fifth of the world's population. Several studies suggested that South Asians have an increased risk of developing coronary heart disease (CHD) when compared with European populations. We review the role of traditional and emerging risk factors in the increased CHD risk in South Asians. The high prevalence of insulin resistance and type 2 diabetes mellitus in South Asians may be a major cause for their elevated vascular risk. However, other established and emerging risk factors are also overrepresented in South Asians. Large-scale prospective studies could determine the relative contribution of established and emerging vascular risk factors in South Asians. There is an urgent need for trials in South Asians that will evaluate clinical outcomes following treatment of these risk factors.

Platelet and leukocyte activation, atherosclerosis and inflammation in European and South Asian men

BACKGROUND

Increased platelet activation occurs in ischemic heart disease (IHD), but increased platelet activation is also seen in cerebrovascular atherosclerosis and peripheral artery disease. It is not clear therefore whether platelet activation is an indicator of IHD or a marker of generalized atherosclerosis and inflammation. South Asian subjects are at high risk of IHD, but little is known regarding differences in platelet and leukocyte function between European and South Asian subjects.

METHODS

Fifty-four male subjects (age 49-79 years) had coronary artery calcification measured by multislice computed tomography (CT), aortic atherosclerosis assessed by measurement of carotid-femoral pulse wave velocity (aortic PWV), and femoral and carotid atherosclerosis measured by B-mode ultrasound. Platelet and leukocyte activation was assessed by flow cytometry of platelet-monocyte complexes (PMC), platelet expression of PAC-1 binding site and CD62P, and expression of L-selectin on leukocytes.

RESULTS

Elevated circulating PMC correlated significantly with elevated aortic PWV and PMC were higher in subjects with femoral plaques. In contrast PMC did not differ by increasing coronary artery calcification category or presence of carotid plaques. Higher numbers of PMC were independently related to elevated levels of C-reactive protein (CRP), higher aortic PWV, hypertension and smoking in a multivariate model. Markers of platelet and leukocyte activation did not differ significantly by ethnicity.

CONCLUSIONS

Increased PMC are related to the extent of aortic and femoral atherosclerosis rather than coronary or carotid atherosclerosis. The association between elevated CRP and increased PMC suggests that inflammation in relation to generalized atherosclerosis may play an important role in PMC activation.

Platelet reactivity among Asian Indians and Caucasians

Asian Indians are reported to have higher mortality and morbidity from coronary artery disease (CAD) than other ethnic groups. This variation in events cannot be explained only by differences in conventional risk factors. Platelet activation is an important factor in the pathogenesis of CAD, however, there are limited data concerning platelet reactivity in Asian Indians. Therefore, we aimed to examine platelet reactivity in healthy Asian Indians vs. Caucasians. Thirty-five healthy, nonsmoking Asian Indians (mean age 30.1 +/- 3.6 years, 31.4% women) were matched for age and sex with 35 healthy, nonsmoking Caucasians (mean age 30.8 +/- 5 years, 31.4% women). Platelet reactivity was evaluated by measuring platelet aggregation, platelet leukocyte aggregates (PLA) formation in response to a 6-mer thrombin receptor agonist peptide (TRAP) at a final concentration of 40 microM and flow cytometry determined P-selectin expression induced by ADP, TRAP and arachidonic acid (AA). In addition, P-Selectin glycoprotein ligand-1 (PSGL-1) density on leukocytes was measured. There were no differences in platelet aggregation, basal PLA or PSGL-1 density on leukocytes between the two groups. AA-stimulated P-selectin expression was significantly higher in Asian Indians than in Caucasians (6.1 +/- 0.51 vs. 4.2 +/- 0.41 MFI, P < 0.02). After stimulation with TRAP, platelets from Asian Indians had increased PLA formation compared with Caucasians (41.6 +/- 2.9% vs. 31.4 +/- 2.7%, P < 0.02). AA induced P-selectin expression and TRAP stimulated PLA formation is increased in Asian Indians compared with Caucasians. These differences indicate an increase in measures of platelet reactivity among Asian Indians and may help elucidate the reported disparity in cardiovascular disease rates between the two ethnic groups.

Coronary heart disease mortality for six ethnic groups in California, 1990–2000

PURPOSE

To investigate ethnic variations in coronary heart disease death in California, the authors examined total and CHD-specific mortality among non-Hispanic white (white), Hispanic, non-Hispanic black (black), Chinese, Japanese, and Asian Indian Americans. Deaths were identified in the California Mortality Database and population information was derived from the 1990 and 2000 censuses.

METHODS

Age-standardized death rates per 100,000 population were calculated for ages 25 to 84 years from 1990 to 2000. Proportional mortality ratios (PMRs) for each sex and age group were calculated by dividing the proportion of deaths due to CHD in each ethnic group by the proportion of deaths due to CHD in the total population.

RESULTS

Blacks had the highest all-cause age-standardized death rates among men (1614) and women (1014). Blacks had the highest CHD death rates among men (272) and women (190). PMRs for CHD were highest in Asian Indian men (161) and women (144), reflective of the higher percentage of CHD deaths compared with all cause deaths in this group. All sex-ethnic groups showed a decline in all cause and CHD mortality compared with the period between 1985 and 1990, except Asian Indian women, who experienced a 16% increase in all cause mortality and 5% increase in CHD mortality.

CONCLUSIONS

There is considerable heterogeneity in CHD mortality among ethnic subgroups, and additional research is needed to guide treatment and prevention efforts. Blacks and Asian Indians in California are identified as particularly high risk populations.

Increased fibrinogen, von Willebrand factor and tissue plasminogen activator levels in insulin resistant South Asian patients with ischaemic stroke

The aim of this study was to determine differences in atherothrombotic risk factors in South Asian subjects with a history of ischaemic stroke and South Asian subjects free from personal and family history of clinically detectable stroke. Eighty South Asian patients with ischaemic stroke (confirmed on cranial computerised scan) and 80 South Asian controls with similar age and gender distributions were recruited at random. The frequency of hypertension (P=<0.0001), myocardial infarction (P=0.003) and diabetes mellitus (<0.0001) were significantly higher in stroke patients. Stroke patients had lower high-density lipoprotein cholesterol (0.95 vs. 1.1 mmol/l, P=<0.0001), higher plasma glucose (8.1 vs. 6.6 mmol/l, P=0.01) and trendwise higher HBA(1C) (6.4 vs. 6.0%, P=0.09). There was no difference in insulin levels but insulin resistance was significantly higher in stroke patients (3.75 vs. 2.66, P=0.01). Stroke patients showed elevated levels of fibrinogen (3.78 vs. 3.41 mg/dl, P=0.02), von Willebrand factor (1.78 vs. 1.50 IU/ml, P=0.006) and tissue plasminogen activator (12.8 vs. 11.3 ng/ml, P=0.04), but the differences did not persist after adjustment for glucose, triglycerides, HDL, WHR, and BMI. Higher levels of fibrinogen, von Willebrand factor and t-PA in South Asian stroke patients disappeared after adjustment for features of insulin resistance syndrome but persisted after adjustment for presence of diabetes, confirming that these changes are essentially dependant on features of insulin resistance syndrome. A prospective study would be required to elucidate the role of thrombotic risk factors in South Asians with ischaemic stroke.

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.

Increased serotonin receptor density and platelet GPIIb/IIIa activation among smokers

This study sought to determine whether depressive symptoms and/or platelet serotonin receptor (5HT2A) density are associated with increased platelet activation (PA) found among smokers. Flow cytometric detection of PA was used to study 36 smokers and 16 nonsmokers, aged 18 to 48 years. Subjects were tested at baseline and after either smoking 2 cigarettes (smokers) or a similar resting interval (nonsmokers). Assessment of PA included both platelet secretion and fibrinogen receptor (GPIIb/IIIa) binding. Platelet 5HT2A receptor binding and saturation were tested using [3H]LSD, and depressive symptoms were measured using the Beck Depression Inventory. Platelet 5HT2A receptor density was increased among smokers versus nonsmokers (82.7+/-67.7 versus 40.0+/-20.2 fmol/mg protein; P<0.005), and there was a dose-dependent relationship between receptor density and packs/d among smokers. Baseline wound-induced GPIIb/IIIa binding at 1 minute and GPIIb/IIIa binding in response to collagen stimulation in vitro was increased among smokers (P<0.05); there were no changes in PA among smokers after smoking, and platelet secretion was not elevated among smokers. Depressive symptoms were associated with 5HT2A receptor density among nonsmokers (P<0.005), but no such relationship was evident among smokers; PA was unrelated to 5HT2A receptor density in either group. The findings indicate that smoking is associated with increased platelet serotonin receptor density and with increased GPIIb/IIIa receptor binding, although these 2 factors are not related to each other or to depressive symptoms among smokers. Serotonergic dysfunction may be an important factor in the development of cardiovascular disease among smokers.

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.