Alan Yean Yip Fong

Cytoprotective and Cytotoxic Effects of Rice Bran Extracts in Rat H9c2(2-1) Cardiomyocytes

This study was aimed at preliminarily assessing the cytoprotective and antioxidative effects of rice bran extracts (RBEs) from a Sarawak local rice variety (local name: “BJLN”) and a commercial rice variety, “MR219,” on oxidative stress in rat H9c2(2-1) cardiomyocytes. The cardiomyocytes were incubated with different concentrations of RBE and hydrogen peroxide (H2O2), respectively, to identify their respective IC50 values and safe dose ranges. Two nonlethal and close-to-IC50 doses of RBE were selected to evaluate their respective effects on H2O2 induced oxidative stress in cardiomyocytes. Both RBEs showed dose-dependent cytotoxicity effects on cardiomyocytes. H2O2 induction of cardiomyocytes pretreated with RBE further revealed the dose-dependent cytoprotective and antioxidative effects of RBE via an increase in IC50 values of H2O2. Preliminary analyses of induction effects of RBE and H2O2 on cellular antioxidant enzyme, catalase (CAT), also revealed their potential in regulating these activities and expression profile of related gene on oxidative stress in cardiomyocytes. Pretreated cardiomyocytes significantly upregulated the enzymatic activity and expression level of CAT under the exposure of H2O2 induced oxidative stress. This preliminary study has demonstrated the potential antioxidant effects of RBE in alleviating H2O2-mediated oxidative injuries via upregulation in enzymatic activities and expression levels of CAT.

Association of CYP2C19*2 polymorphism with clopidogrel response and 1-year major adverse cardiovascular events in a multiethnic population with drug-eluting stents

BACKGROUND Patients undergoing elective percutaneous coronary intervention (PCI) with drug-eluting stents (DES) who have impaired clopidogrel response, have a higher risk of subsequent major adverse cardiovascular events (MACE). AIM OF THE STUDY To establish the relationship between CYP2C19 genotype, clopidogrel responsiveness and 1-year MACE. MATERIALS & METHODS Aspirin/clopidogrel responses were assessed with Multiplate Analyzer and CYP2C19*2 allele by SpartanRx. RESULTS A total of 42.0% carried ≥1 CYP2C19*2 allele. Prevalences of aspirin and clopidogrel high on-treatment platelet reactivity (HPR; local cutoffs: 300 AU*min for aspirin and 600 AU*min for clopidogrel) were 11.5% and 19.8% respectively. In multivariate ana-lysis, clopidogrel HPR was found to be an independent predictor for 1-year MACE (adj HR: 3.48, p = 0.022 ). CONCLUSION Having clopidogrel HPR could be a potentially modifiable risk factor guided by phenotyping.

Increased serum levels of interleukin-6 and von Willenbrand Factor in early phase of acute coronary syndrome in a young and multiethnic Malaysian population

Objective Interleukin-6 (IL6; proinflammatory marker), von Willebrand Factor (vWF; endothelial dysfunction marker) and P-selectin (platelet activation marker), may play important roles in defining the pathogenesis of vulnerable plaques in acute coronary syndrome (ACS). This study aims to investigate the expression and relationship of these markers in early phases of ACS in a young and multiethnic Malaysian population. Design Peripheral whole blood mRNA, and serum levels of IL6, vWF and P-selectin were measured in 22 patients with ACS, and in 28 controls with angiographically significant coronary artery disease without previous ACS events. Venous blood from ACS patients was obtained within 1 h of hospital admission. Results No significant differences of IL6, vWF and P-selectin mRNA levels between ACS and controls were seen. ACS patients had significantly higher serum levels of IL6 and vWF (p<0.001), compared with controls. P-selectin correlated with IL6 (r=0.697, p=0.003) and vWF (r=0.497, p=0.05) at mRNA levels, indicating a possible association between these three indices of ACS pathogenesis. Conclusions Increased serum levels of IL6 and vWF suggest that inflammation and endothelial dysfunction may play a prominent role in the pathogenesis of the disease during the early phase of ACS.

CYTOCHROME P450 2C19 POLYMORPHISM AND PLATELET AGGREGATION IN CLOPIDOGREL-TREATED PATIENTS AMONG MALAYSIAN MULTIETHNIC POPULATION

Objectives Cytochrome P450 2C19 (CYP2C19) *2 (681G>A; rs4244285) and CYP2C19*3 (636G>A; rs4986893) null alleles are responsible for the phenotypes of poor CYP2C19 enzyme function, hence adversely affecting the ability of clopidogrel to inhibit platelet aggregation. In recent years, a novel CYP2C19 gene variant, CYP2C19*17 (−3402C>T; rs11188072), has been identified and is associated with ultrarapid metabolism of CYP2C19 substrate. To date, there is limited data on CYP2C19 prevalence rates in a multiracial Malaysian population with coronary artery disease planned for percutaneous coronary intervention (PCI), and their impact on clopidogrel-mediated platelet aggregation (CPA). Therefore, the primary objective of this study was to assess the impact of CYP2C19 *2, *3 and *17 on CPA in patients planned for PCI. Methods From the 323 consecutive patients planned for PCI, 237 patients≥18 years of age, underwent either aspirin alone or both aspirin and clopidogrel therapy, were recruited from Sarawak General Hospital Heart Centre (Kota Samarahan, Malaysia). Venous blood samples were collected from each participant before their scheduled appointment for PCI. The CYP2C19*2, *3 and *17 were genotyped by PCR—restriction fragment linked polymorphism (PCR-RFLP) method. The antiplatelet effect of clopidogrel, as assessed by ADP-induced platelet aggregation, was measured by Multiplate impedance aggregometry. Results Of the 237 subjects (mean age 57.6±11.1), 77.6% were male and 22.4% were female. Ethnic group distribution was: Chinese 50.6% (n=120), Malay 21.1% (n=50), Iban 19.0% (n=45) and other races 9.3% (n=22) The allelic frequency of the CYP2C19 *1, *2, *3 and *17 were 63.0% (95% CI 62.1% to 59.0%), 29.0% (95% CI 28.7% to 29.3%), 6.0% (95% CI 5.9% to 6.1%) and 2% (95% CI 1.6% to 2.4%), respectively. Genotype determination revealed that 38.8% were extensive metabolisers (EM: *1/*1, *2/*17), 45.1% intermediate metabolisers (IM: *1/*2, *1/*3), 12.7% poor metabolisers (PM: *2/*2, *2/*3, *3/*3), 3.0% intermediate ultrarapid metaboliser (IUM: *1/*17) and 0.4% ultrarapid metaboliser (UM: *17/*17). The frequencies of the CYP2C19*2 variant allele and of the homozygous genotype were higher in Chinese descent individuals (35.8%; 12.5%) compared with other ethnic groups (p=0.010; p=0.022, respectively). Meanwhile, a similar proportion of CYP2C19*3 allele was observed in all ethnic groups (p=0.071). Overall, the PM genotypic prevalence rate was 15.0% in Chinese, 10.0% in Malays, 8.9% in Iban and 18.2% in other subjects (p=0.042). One Chinese subject shown to be homozygous *2 and heterozygous *17, hence resulting in a new combination of *2/*17. The predicted metabolic phenotype for this combination is unknown and we assume that the ultrarapid clopidogrel metabolism by *17 allele may be suppressed by loss-of-function *2 alleles, thus resulting in a functional metabolising enzyme phenotype. Hence, we grouped this individual as EM. Linkage disequilibrium analysis showed that the *17 were in different linkage disequilibrium with *2 and *3. Among the 118 subjects who underwent a similar double antiplatelet loading strategy (75 mg loading doses of aspirin for at least 2 days+75 mg loading doses of clopidogrel for at least 4 days), the prevalence rate of PM remains high within Chinese group (17.5%) compared to other ethnic groups (p=0.036). The CPA was observed to be higher in PM (333.6 aggregation unit×min (AU*min)), followed by IM (319.7 AU*min), EM (278.7 AU*min) and lowest in IUM (264.5 AU*min) (p>0.05). The *2 and *3 carriers also demonstrated higher platelet aggregation (310.6 AU*min) compared to *17 carriers (264.1 AU*min) (p=0.412). The absence of statistically significant differences between the different phenotypic groups could be attributed to the relatively small sample size. Nevertheless, there was a significant influence of CYP2C19 polymorphism on CPA in Chinese subjects only (p=0.032) even after adjustment for various cardiovascular risk factors. Conclusions The CYP2C19*2 is found at high frequency in Malaysians, especially in Chinese subjects, consistent to that found in other Asian populations of Chinese ethnic origin. Other CYP2C19 polymorphisms, particularly *17 were rare in the Malaysian population. However, carriers of *17 demonstrated better CPA compared to *2 and *3 carriers. Our findings indicate a broad inter-ethnic difference in CYP2C19 allelic frequencies. As both the presence of certain genotypes especially *2, and a lower CPA, have been shown to be associated with higher adverse cardiovascular event rates in patients prescribed clopidogrel, subsequent outcome studies in our multiethnic population are warranted.

Corrigendum to “Cytoprotective and Cytotoxic Effects of Rice Bran Extracts in Rat H9c2(2-1) Cardiomyocytes”

[This corrects the article DOI: 10.1155/2016/6943053.].

Prevalence of aspirin low responders in a multiethnic Asian cohort pretreated with aspirin and planned for elective percutaneous coronary intervention

Purpose: Aspirin low responsiveness or “aspirin resistance” has been reported with a prevalence rate of 5.5% to 60% depending on compliance, method, definition and study population. We aimed to assess the prevalence of aspirin responsiveness in a multiethnic Asian cohort planned for percutaneous coronary intervention (PCI). Methods: Of 323 patients screened, 237 patients receiving 75 mg aspirin daily for ≥2 days prior to angiography were recruited in Sarawak General Hospital (Malaysia) between 18/10/2010 and 14/3/2011 with prior written informed consent. Possible noncompliant patients were excluded. Platelet aggregation levels were analysed withmultiple electrode aggregometry (MEA) and expressed as AU*min. 157 patients who had MEA readings with correlation coefficient of ≥0.98 and difference from mean curve of <20% were included for analysis. Patients with MEA of ≥300 AU*min were classified as aspirin low responders. Results: 83.4% of patients were males with mean age of 56.7 years old. 54.1% of patients were Chinese, 23.6% Malays, 22.9% Ibans and 8.9% other ethnic minorities. Median (interquartile range) MEA was 141.0 (86.0) AU*min, 126.0 (74.0) AU*min and 153.0 (98.0) AU*min among Chinese, Malays and Ibans, respectively (p=0.129 Chinese vs. Malays, p=0.777 Chinese vs. Ibans, p=0.115 Malays vs. Ibans). Based on 300 AU*min as cut-off, 10 patients (6.4%) were aspirin low responders, with Ibans accounting for 50%, Chinese 40% and Malays 10%. Median (interquartile range) MEA of responders vs. low responders was 140.0 (78.8) AU*min vs. 439.5 (92.5) AU*min (p=0.001) among Chinese, 125.5 (73.0) AU*min vs. 844.0 (0) AU*min (p=0.092) among Malays and 131.0 (89.0) AU*min vs. 546.0 (174.0) AU*min (p<0.0001) among Ibans. Conclusion: There is a low prevalence of poor aspirin responders in our multiethnic Asian cohort. Aspirin low responsiveness rate was highest among the Iban and Chinese ethnic groups, suggesting a role of ethnicity on aspirin response.