ESPE Abstracts

Background: Patients with 21-hydroxylase deficiency (21OHD) require life-long glucocorticoid (GC) replacement and have high prevalence of metabolic disease. Our previous work using a zebrafish model of 21OHD (cyp21a2-/-) showed that cortisol-deficient adults were fertile and had normal external sex characteristics, however, they had large body size and increased subcutaneous and visceral fat deposition compared to wild-types. Unlike human 21OHD, they did not present hyperandrogenism. We analysed the liver transcriptome of cyp21a2-/- fish in order to better understand the role of cortisol in the developing metabolic phenotype and to gain insights into the mechanisms leading to metabolic disease in 21OHD.

Methods: We collected adult livers from an established GC-deficient zebrafish model (cyp21a2-/-) using 18 months old male and female wild-types and mutants (n=6 in each group). We conducted RNA extraction and paired-end sequencing, followed by transcriptomic analysis of differentially expressed genes (DEGs) and Gene Set Enrichment Analysis (GSEA).

Results: Regardless of genotype, females had significantly larger livers compared to males (weight to length ratio, P<0.001). Principal component analysis showed that sex had a higher impact on differential gene expression than GC-deficiency. There were 4195 DEGs between males and females in wild-type and 3889 in mutant fish, with 1946 DEGs shared between the two groups (independent of the mutation). For both wild-type and mutant fish, GSEA showed upregulation of ATP metabolism and small molecule catabolism in males compared to females, while translation and ribosome organisation were suppressed. Regarding the effects of GC-deficiency, in both males and females GSEA showed downregulation of oxidative phosphorylation and ATP metabolism and upregulation of ribosome organisation and translation in cyp21a2-/- compared to wild-type fish. However, wide dysregulations of lipid metabolic pathways were only found in mutant males, while in females the predominant feature was the upregulation of processes involved in organogenesis in cyp21a2-/- mutants compared to wild-types.

Conclusion: Our findings indicate that sex has higher impact than GC-deficiency on the regulation of metabolic processes in the adult zebrafish liver, energy homeostasis being significantly upregulated in males and reproduction and organogenesis in females. There were clear sex-depended effects of cortisol deficiency on the liver transcriptome, with a more marked impact on lipid metabolism in males. These findings suggest a complex interplay between GCs and sex hormones in the regulation of metabolism and energy homeostasis. They also highlight the benefit of using zebrafish lines of differentially impaired steroidogenesis for translational research in congenital adrenal hyperplasia.