Genetic variants of SLCO1B7 are of relevance for the transport function of OATP1B3-1B7

The family of Organic Anion Transporting Polypeptides are known to facilitate the transmembrane transport. OATP1B3-1B7 is a novel member of the OATP1B-subfamily, and is encoded by SLCO1B3-SLCO1B7 readthrough deriving from the genes SLCO1B3 and SLCO1B7 on chromosome 12. The resulting protein is expressed in the smooth endoplasmatic reticulum of hepatocytes, is functional, and transports dehydroepiandrosterone-sulfate (DHEAS). In the gene area encoding for the 1B7-part of the protein, there are coding polymorphisms. It was the aim of this study to test the frequency and the impact of these genetic variants on transport activity. The minor allele frequency (MAF) of the coding polymorphisms was determined in a cohort of 192 individuals. DHEAS transport function was determined by applying the vTF-7 based heterologous expression system using plasmids encoding for OATP1B3-1B7 or the respective variants. The genetic variants 641 T (MAF 0.021), 1073 G (MAF 0.169) and 1775 A (MAF 0.013) significantly reduced DHEAS accumulation in cells transfected with OATP1B3-1B7, albeit without significantly influencing expression of the transporter as determined by Western blot analysis and immunofluorescence after heterologous expression. Genotyping revealed complete linkage of the variants 884A, 1073 G and 1501C. Presence of the haplotype abolished the DHEAS-transport function of OATP1B3-1B7. Naturally and frequently occurring genetic variants located within the gene region of SLCO1B7 encoding for the 1B7-part of OATP1B3-1B7 influence the in vitro function of this member of the OATP1B-family. With their functional characterisation, we provide the basis for pharmacogenetic studies, which may help to understand the in vivo relevance of this transporter.

Changes in Adrenal Androgens During Puberty Suppression and Gender-Affirming Hormone Treatment in Adolescents With Gender Dysphoria

INTRODUCTION

Gender-affirming hormone treatment is known to affect adrenal androgen levels in adult individuals with gender dysphoria (GD). This may be clinically relevant because the adrenal gland plays a critical role in many different metabolic processes.

AIM

This study aims to assess the effects of gonadotropin-releasing hormone analogs (GnRHa) treatment and gender-affirming hormone treatment on adrenal androgen levels in adolescents with GD.

METHODS

In this prospective study, dehydroepiandrosterone-sulfate (DHEAS) and androstenedione values were measured every 6 months during 2 years of GnRHa treatment only, and 2 years of GnRHa combined with gender-affirming hormone treatment (estradiol or testosterone) in 73 transgirls and 54 transboys. To determine trends in adrenal androgen levels a linear mixed model was used to approximate androgen levels.

MAIN OUTCOME MEASURES

DHEAS and androstenedione levels were the main outcome measures.

RESULTS

DHEAS levels rose in transboys during GnRHa treatment, which may represent the normal increase during adolescence. In transgirls no change in DHEAS levels during GnRHa treatment was found. Gender-affirming hormone treatment did not affect DHEAS levels in either sex. In transboys androstenedione levels decreased during the first year of GnRHa treatment, which may reflect reduced ovarian androstenedione synthesis, and rose during the first year of gender-affirming hormone treatment, possibly due to conversion of administered testosterone. In transgirls androstenedione levels did not change during either GnRHa or gender-affirming hormone treatment.

CLINICAL IMPLICATIONS

No deleterious effects of treatment on adrenal androgen levels were found during approximately 4 years of follow-up.

STRENGTHS & LIMITATIONS

This is one of the largest cohort of adolescents with GD, treated using a uniform protocol, with standardized follow-up. The lack of a control group is a limitation.

CONCLUSION

The changes in androstenedione levels during GnRHa and gender-affirming hormone treatment in transboys may not be of adrenal origin. The absence of changes in androstenedione levels in transgirls or DHEAS levels in either sex during gender-affirming hormone treatment suggests that gender-affirming hormone treatment does not significantly affect adrenal androgen production. Schagen SEE, Lustenhouwer P, Cohen-Kettenis PT, et al. Changes in Adrenal Androgens During Puberty Suppression and Gender-Affirming Hormone Treatment in Adolescents With Gender Dysphoria. J Sex Med 2018;15:1357-1363.