The MDR1 multidrug transporter represents one of the better characterized drug transporters that play an important role in protecting the body against xenobiotic insults. Single nucleotide polymorphisms (SNPs) and SNP haplotypes within this gene have been variously associated with differences in MDR1 expression/function, drug response as well as disease susceptibility. Nonetheless, the effect of polymorphisms at the MDR1 promoter region on its promoter activity remains less characterized. Through the examination of approximately 1.5 kilobases of MDR1 promoter region from five populations, including the Chinese, Malays, Indians, European Americans, and African Americans, we identified eight low-frequency SNPs, of which only two were polymorphic in at least four of the five populations examined. The other SNPs are mainly population-specific, the majority of which occur only in the African-American population. Recapitulation of the various combinations of SNP haplotypes in vitro in promoter-reporter assays revealed a few notable trends. The African and European American-specific haplotypes tended to result in enhanced MDR1 promoter activity only in the human embryonic kidney (HEK) 293 cell line. Haplotype GCTAACC, which occurs at variable frequencies in all the populations examined, with Asians having much lower frequencies (<2%) compared with the European Americans/African Americans (>4%), affected MDR1 promoter activity differently in different cell lines. Compared with the commonest haplotype, GCTA-ACC haplotype resulted in a significant decrease in MDR1 promoter activity in HeLa cells (P < 0.05) but a significant increase in the same promoter activity in HEK293 cells (P < 0.05). These results suggest that the MDR1 promoter region is largely invariant but that different haplotypes have differential effects on the MDR1 promoter activity in different cell lines.
OBJECTIVES: To compare the prevalence and correlates of cigarette smoking among East Asian college students.
METHODS: Data were collected from college students (N=16,558) in China, Hong Kong, Malaysia, Singapore, South Korea, and Taiwan (response rate: 78%).
RESULTS: Religion was independently associated with college students' smoking in China (adjusted odds ratio [AOR] = 1.82) and South Korea (AOR = 0.80). Being a heavy drinker and having a higher exposure to secondhand smoke were associated with higher smoking rates (Ps < .001).
CONCLUSIONS: The East Asian economies show a varied prevalence of college smoking but a similar pattern of relationship with its correlates.
Study site: 21 institutions in 6 East Asian economies: 3 colleges each from Hong Kong, Malaysia, Singapore, and South Korea; 4 colleges from Taiwan; and 5 colleges from China.
The MDR1 multidrug transporter plays a key role in determining drug bioavailability, and differences in drug response exist amongst different ethnic groups. Numerous studies have identified an association between the MDR1 single nucleotide polymorphism (SNP) exon 26 3435C>T and differences in MDR1 function. We performed a haplotype analysis of the MDR1 gene in three major ethnic groups (Chinese, Malays and Indians) by examining 10 intragenic SNPs. Four were polymorphic in all three ethnic groups: one occurring in the non-coding region and three occurring in coding exons. All three coding SNPs (exon 12 1236C>T, exon 21 2677G>T/A and exon 26 3435C>T) were present in high frequency in each ethnic group, and the derived haplotype profiles exhibited distinct differences between the groups. Fewer haplotypes were observed in the Malays (n = 6) compared to the Chinese (n = 10) and Indians (n = 9). Three major haplotypes (> 10% frequency) were observed in the Malays and Chinese; of these, two were observed in the Indians. Strong linkage disequilibrium (LD) was detected between the three SNPs in all three ethnic groups. The strongest LD was present in the Chinese, followed by Indians and Malays, with the corresponding LD blocks estimated to be approximately 80 kb, 60 kb and 40 kb, respectively. These data strongly support the hypothesis that strong LD between the neutral SNP exon 26 3435C>T and a nearby unobserved causal SNP underlies the observed associations between the neutral SNP and MDR1 functional differences. Furthermore, strong LD between exon 26 3435T and different unobserved causal SNPs in different study populations may provide a plausible explanation for conflicting reports associating the same exon 26 3435T allele with different MDR1 functional changes.
BACKGROUND: Little is known on the level of physical inactivity and its behavioral and cultural correlates among East Asian college students.
PURPOSE: The aim of this study is to examine and compare the level and behavioral and cultural correlates of physical inactivity among college students in Taiwan, Hong Kong, South Korea, Singapore, and Malaysia.
METHOD: Data were collected from a representative sample of college students (N = 12,137) in five East Asian economies during the 2008-2009 academic year. The stratified random sampling (stratum: geographic region) was used to select participating institutions. The overall response rate was 77%.
RESULTS: The percentage of physically inactive students was 7.2% for Singapore, 8.0% for Malaysia, 13.5% for Taiwan, 16.8% for Hong Kong, and 28.5% for South Korea. When gender, age, and body mass index were controlled, fruit and vegetable consumptions were significant correlates for physical inactivity across all the five economies. In Hong Kong, Korea, and Taiwan, those who engaged in binge drinking at least once during the past 2 weeks were less likely to be physically inactive than those who did not. Religion and military experience did not independently predict physical inactivity in any of the five economies.
CONCLUSION: Physical inactivity varies greatly across different economies in East Asia that are usually grouped together and considered a single homogeneous entity by some researchers. However, in terms of correlates of physical inactivity, findings of the current study indicate that the transversal value of physical activity might be transformed into a universal.