ABSTRACT
PURPOSE: Individual variability in the endogenous CYP3A metabolite 4ß-hydroxycholesterol (4ßOHC) is substantial, but to which extent this is determined by genetic and nongenetic factors remains unclear. The aim of the study was to evaluate the explanatory power of candidate genetic variants and key nongenetic factors on individual variability in 4ßOHC levels in a large naturalistic patient population. METHODS: We measured 4ßOHC concentration in serum samples from 655 patients and used multiple linear regression analysis to estimate the quantitative effects of CYP3A4*22, CYP3A5*3, and POR*28 variant alleles, comedication with CYP3A inducers, inhibitors and substrates, sex, and age on individual 4ßOHC levels. RESULTS: 4ßOHC concentration ranged >100-fold in the population, and the multiple linear regression model explained about one fourth of the variability (R 2 = 0.23). Only comedication with inducers or inhibitors, sex, and POR genotype were significantly associated with individual variability in 4ßOHC level. The estimated quantitative effects on 4ßOHC levels were greatest for inducer comedication (+>313%, P < 0.001), inhibitor comedication (-34%, P = 0.021), and female sex (+30%, P < 0.001), while only a modestly elevated 4ßOHC level was observed in carriers vs. noncarriers of POR*28 (+11%, P = 0.023). CONCLUSIONS: These findings suggest that the CYP3A4*22, CYP3A5*3, and POR*28 variant alleles are of limited importance for overall individual variability in 4ßOHC levels compared to nongenetic factors.
