Functional allele and genotype frequencies of CYP1A2, CYP2B6 and iNOS among mainland Chinese Tibetan, Mongolian, Uygur and Han populations.

Abstract

Cytochrome P450 1A2 (CYP1A2), CYP2B6 and inducible nitric oxide synthase (iNOS) are involved in the metabolism and action of many important therapeutic drugs, and genetic variants have been associated with interethnic differences in response to treatment, including chemotherapy. Eight hundred and forty-two unrelated Chinese healthy subjects (323 Tibetan, 134 Mongolian, 162 Uygur and 223 Han) were recruited for genotyping. Frequencies of CYP1A2 -163C>A, CYP2B6 516G>T and iNOS -954G>C were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods. The frequency of CYP1A2-163A was higher in Chinese Mongolian (0·698) than in Chinese Tibetan (0·633), Uygur (0·633) and Han populations (0·608, P < 0·05), respectively. The frequency of CYP1A2-163A in the Chinese population (total, 0·636) was intermediate between those reported in Caucasians (0·682, P < 0·05) and Africans (0·549, P < 0·01). The frequency of CYP2B6 516T in Chinese Uygur (0·287) was significantly higher than those in Chinese Tibetan (0·147, P < 0·01) and Mongolian (0·179, P < 0·01), respectively, but was similar to the frequency in Chinese Han (0·226). The frequencies of CYP2B6 516T were in the order of Africans (0·500) > Caucasians (0·286) > Chinese (0·200). The variant iNOS-954C was rare in Chinese Tibetan (0·005), Mongolian (0·004), Uygur (0·000) and Han (0·007), respectively, but showed higher frequencies in African ethnic groups. The frequencies of iNOS-954C were in the order of Africans (0·098) > Chinese (0·004) > Caucasians (0·000). This is the first report of the distribution frequencies of functional CYP1A2, CYP2B6 and iNOS genes among mainland Chinese Tibetan, Mongolian, Uygur and Han populations. These results should help inform studies of interethnic differences in disease susceptibility or drug responses.