CYP3A5*3 and *6 single nucleotide polymorphisms in three distinct Asian populations

Objective: To determine the frequencies of two functional single nucleotide polymorphisms, CYP3A5*3 and CYP3A5*6, in the CYP3A5 gene in three distinct Asian ethnic groups, namely, the Chinese, Malays and Indians. Methods: Single nucleotide polymorphism analyses of CYP3A5*1, *3 and *6 were performed in 296 healthy subjects (108 Chinese, 98 Malays and 90 Indians) using the polymerase chain reaction-restriction fragment length polymorphism method. Results: The *1 allele frequency was 25% in Chinese compared with 40% in Malays and Indians (P = 0.001). The *3 allele frequency was also higher in the Chinese population, being 76% versus 60% in the Malays and Indians (P = 0.001). The Malays and Indians also had allele frequencies significantly different from Caucasian, Japanese and African-American populations (each P less than or equal to 0.001) previously published in the literature. The *6 allele was not detected in any the three Asian ethnic groups analysed. Conclusion: These results seem to suggest that genetic polymorphisms in CYP3A5 in Asians, in particular Malays and Indians but also Chinese although to a lesser extent, may be an important genetic contributor to interindividual as well as interethnic differences in clearance of CYP3A substrates.