Mattias Lorentzon

Genetic Variations in Sex Steroid-Related Genes as Predictors of Serum Estrogen Levels in Men

CONTEXT The risk of many conditions, including prostate cancer, breast cancer, and osteoporosis, is associated with serum levels of sex steroids. OBJECTIVE The aim of the study was to identify genetic variations in sex steroid-related genes that are associated with serum levels of estradiol (E2) and/or testosterone in men. DESIGN Genotyping of 604 single nucleotide polymorphisms in 50 sex steroid-related candidate genes was performed in the Gothenburg Osteoporosis and Obesity Determinants (GOOD) study (n = 1041 men; age, 18.9 +/- 0.6 yr). Replications of significant associations were performed in the Osteoporotic Fractures in Men (MrOS) Sweden study (n = 2568 men; age, 75.5 +/- 3.2 yr) and in the MrOS US study (n = 1922 men; age, 73.5 +/- 5.8 yr). Serum E2, testosterone, and estrone (E1) levels were analyzed using gas chromatography/mass spectrometry. RESULTS The screening in the GOOD cohort identified the single nucleotide polymorphism rs2470152 in intron 1 of the CYP19 gene, which codes for aromatase, responsible for the final step of the biosynthesis of E2 and E1, to be most significantly associated with serum E2 levels (P = 2 x 10(-6)). This association was confirmed both in the MrOS Sweden study (P = 9 x 10(-7)) and in the MrOS US study (P = 1 x 10(-4)). When analyzed in all subjects (n = 5531), rs2470152 was clearly associated with both E2 (P = 2 x 10(-14)) and E1 (P = 8 x 10(-19)) levels. In addition, this polymorphism was modestly associated with lumbar spine BMD (P < 0.01) and prevalent self-reported fractures (P < 0.05). CONCLUSIONS rs2470152 of the CYP19 gene is clearly associated with serum E2 and E1 levels in men.

OPG and RANK polymorphisms are both associated with cortical bone mineral density: Findings from a metaanalysis of the avon longitudinal study of parents and children and Gothenburg osteoporosis and obesity determinants cohorts

Context: Several single-nucleotide polymorphisms (SNPs) have been reliably associated with areal bone mineral density (aBMD) in genome-wide association studies of mostly older subjects. Objective: We aimed to test those SNPs for an association with peripheral quantitative computed tomography (pQCT) bone measures in two young cohorts. Design and Study Participants: We genotyped nine SNPs from the most promising aBMD candidates in a cohort of 15-yr-olds [in the Avon Longitudinal Study of Parents and Children (ALSPAC)] and carried out association analysis with several tibial pQCT measures to determine whether these candidates were important during adolescent growth and which particular skeletal parameters each of the candidates were acting upon. We also carried out a metaanalysis of the SNPs for association with cortical bone mineral density (BMDC) in ALSPAC and a similar male-only study (Gothenburg Osteoporosis and Obesity Determinants). Results: In the ALSPAC cohort, we found a significant association between RANK SNP (rs3018362) and BMDC but not any of the other pQCT bone measures. In the metaanalysis, we found the OPG SNP (rs4355801) and the RANK SNP (rs3018362) to be significantly associated with BMDC. We also found suggestive evidence of an association between the MARK3 SNP (rs2010281) and BMDC but with a direction of effect opposite to that previously reported. Conclusion: The association of genes from the RANK/RANKL/OPG pathway and BMDC provides new insight into how this system might affect the skeleton, confirming it to be associated with volumetric cortical bone density but observing no relationship with bone size.

Assessment of Gene-by-Sex Interaction Effect on Bone Mineral Density

Sexual dimorphism in various bone phenotypes, including bone mineral density (BMD), is widely observed; however, the extent to which genes explain these sex differences is unclear. To identify variants with different effects by sex, we examined gene‐by‐sex autosomal interactions genome‐wide, and performed expression quantitative trait loci (eQTL) analysis and bioinformatics network analysis. We conducted an autosomal genome‐wide meta‐analysis of gene‐by‐sex interaction on lumbar spine (LS) and femoral neck (FN) BMD in 25,353 individuals from 8 cohorts. In a second stage, we followed up the 12 top single‐nucleotide polymorphisms (SNPs; p < 1 × 10−5) in an additional set of 24,763 individuals. Gene‐by‐sex interaction and sex‐specific effects were examined in these 12 SNPs. We detected one novel genome‐wide significant interaction associated with LS‐BMD at the Chr3p26.1‐p25.1 locus, near the GRM7 gene (male effect = 0.02 and p = 3.0 × 10−5; female effect = −0.007 and p = 3.3 × 10−2), and 11 suggestive loci associated with either FN‐ or LS‐BMD in discovery cohorts. However, there was no evidence for genome‐wide significant (p < 5 × 10−8) gene‐by‐sex interaction in the joint analysis of discovery and replication cohorts. Despite the large collaborative effort, no genome‐wide significant evidence for gene‐by‐sex interaction was found to influence BMD variation in this screen of autosomal markers. If they exist, gene‐by‐sex interactions for BMD probably have weak effects, accounting for less than 0.08% of the variation in these traits per implicated SNP.