CYP3A7, expressed in the human fetal liver and normally silenced after birth, plays a major role in the 16alpha-hydroxylation of dehydroepiandrosterone (DHEA), DHEA sulfate (DHEAS), and estrone. Due to a replacement of part of the CYP3A7 promoter with a sequence identical with the same region in the CYP3A4 promoter (referred to as CYP3A7*1C), some individuals still express a variant of the CYP3A7 gene later in life.
The objective of this study was to examine the effect of the CYP3A7*1C polymorphism on serum steroid hormone levels.
Two population-based cohort studies were performed. Study group 1 consisted of 208 subjects randomly selected from the Rotterdam Study, and study group 2 consisted of 345 elderly independently living men.
Serum DHEA(S), androstenedione, estradiol, estrone, and testosterone levels were the main outcome measures.
In study groups 1 and 2, heterozygous CYP3A7*1C carriers had almost 50% lower DHEAS levels compared with homozygous carriers of the reference allele [study group 1, 1.74 +/- 0.25 vs. 3.33 +/- 0.15 micromol/liter (P = 0.02); study group 2, 2.09 +/- 0.08 vs. 1.08 +/- 0.12 micromol/liter (P < 0.001)]. No differences in circulating DHEA, androstenedione, estradiol, or testosterone levels were found. However, in study group 2, serum estrone levels were lower in heterozygous CYP3A7*1C carriers compared with homozygous carriers of the reference allele (0.11 +/- 0.002 vs. 0.08 +/- 0.006 nmol/liter; P < 0.001).
The CYP3A7*1C polymorphism causes the persistence of enzymatic activity of CYP3A7 during adult life, resulting in lower circulating DHEAS and estrone levels.
"The diminished effects in models 3 and 4 might be a consequence of the adjustment for precursor hormones with a circadian rhythm, as p-values remain similar in a model without the precursor hormone . As was previously put forward , a short half-life of DHEA and thus a high metabolic clearance rate  can explain the fact that no differences were found for mean DHEA levels among genotypes . Since there are strong correlations between DHEA, DHEAS and androstenedione  these might explain the significant difference observed for CYP3A7 genotypes. "
[Show abstract][Hide abstract] ABSTRACT: To study if polymorphisms in genes encoding for CYP3A enzymes, that play a role in steroid hormone metabolism, affect steroid hormone serum levels and prostate cancer incidence or mortality.
3048 male participants of The Rotterdam Study were included. Prostate cancer cases and non-cases were studied for differences in baseline hormone levels with Student's t-test. General linear models were performed on different random subsets of hormone levels to study associations with genotype. Cox' proportional hazard models were used to study prostate cancer incidence and mortality among genotypes.
Both DHEAS sulphate as free-testosterone were significantly increased at baseline in males who developed a prostate cancer within the study period. CYP3A4 G-allele carriage was associated with lower levels of estrone sulphate (p=0.005) and higher levels of estradiol (p=0.04) compared to non-carriers. CYP3A5 A-allele carriage was associated with increased levels of estrone sulphate (p=0.02). CYP3A7 G-allele carriage was associated with the highest number of significant differences in steroid hormone levels. Carriers of the allele resulting in continued enzyme expression during adulthood had decreased levels of dehydroepiandrosterone (DHEA) sulphate (p=0.05), androstenedione (p=0.006), estrone (p=0.0001) and estrone sulphate (p=0.003) compared to mean levels of these hormones in homozygous wild type carriers. CYP3A43 genotype was not associated with any of the studied hormone levels. However, carriers of the CYP3A43 G-allele showed a significant 5-fold increase in mortality among early onset diagnosed prostate cancers.
Increased levels of free testosterone and DHEA sulphate were associated with prostate cancer incidence along the study period. Primarily the amount of CYP3A7 expression seemed to affect steroid hormone levels. Nevertheless, testosterone, a precursor of the prostate growth and differentiation stimulating dehydrotestosterone, was not influenced by CYP3A genotype. In line with this, no significant associations were observed for CYP3A genotypes and prostate cancer incidence.
[Show abstract][Hide abstract] ABSTRACT: The overall goal was to develop individualized dosing guidelines for the sedatives propofol and midazolam in infants and in critically ill patients, on the basis of population pharmacokinetic-pharmacodynamic (PK-PD) modeling. Both under- and oversedation significantly and adversely affects patient outcome. Due to the high intra- and interindividual variability in dose requirements dosing is complicated. In this thesis the interindividual variability in response has been examined by covariate analysis. In this analysis the effects of bodyweight, cardiac function, severity of illness and liver blood flow and the unexplained interindividual variability have been characterized. It was shown that infants require higher doses of propofol because of differences in pharmacokinetics rather than pharmacodynamics. When comparing the results of the PK-PD model of propofol and midazolam in infants, propofol is preferred over midazolam because of the lower interindividual variability in pharmacodynamics compared to midazolam. In critically ill patients severity of the illness was found to be a major determinant of the level of sedation, with lower propofol dosing requirements with increasing severity of illness. The PK-PD models can be used as a basis for individualized dosing of propofol and midazolam, which is essential for optimizing the quality of sedation in clinical practice and will improve patients’ outcome.
[Show abstract][Hide abstract] ABSTRACT: Previous studies have reported that glucose tolerance can be improved by short-term altitude living and activity. However, not all literature agrees that insulin sensitivity is increased at altitude. The present study investigated the effect of a 25-day mountaineering activity on glucose tolerance and its relation to serum levels of dehydroepiandrosterone-sulfate (DHEA-S) and tumor necrosis factor-alpha (TNF-alpha) in 12 male subjects. On day 3 at altitude, we found that serum DHEAS was reduced in the subjects with initially greater DHEA-S value, whereas the subjects with initially lower DHEA-S remained unchanged. To further elucidate the role of DHEA-S in acclimatization to mountaineering activity, all subjects were then divided into lower and upper halves according to their sea-level DHEA-S concentrations: low DHEA-S (n = 6) and high DHEA-S groups (n = 6). Glucose tolerance, insulin level, and the normal physiologic responses to altitude exposure, including hematocrit, hemoglobin, erythropoietin (EPO), and cortisol were measured. We found that glucose and insulin concentrations on an oral glucose tolerance test were significantly lowered by the mountaineering activity only in the high DHEA-S group. Similarly, hematocrit and hemoglobin concentration in altitude were increased only in the high DHEA-S group. In contrast, the low DHEA-S subjects exhibited an EPO value at sea level and altitude greater than the high DHEA-S group, suggesting an EPO resistance. The findings of the study imply that DHEA-S is essential for physiologic acclimatization to mountaineering challenge.
High Altitude Medicine & Biology 02/2006; 7(3):228-36. DOI:10.1089/ham.2006.7.228 · 1.28 Impact Factor
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