Endocrine Abstracts

JOINT2385

Background: It is known that conditions causing cortisol deficiency, such as congenital adrenal hyperplasia, lead to systemic dysregulations that are associated to the development of co-morbidities. We wanted to test to what degree dysregulations caused by cortisol deficiency are corrected by a physiological dose of hydrocortisone (HC) treatment in a 21-hydroxylase deficient zebrafish model (cyp21a2-/-).

Methods: We used wild-type (WT) and cyp21a2-/- zebrafish larvae, comparing between four groups: WT untreated, cyp21a2-/- untreated, WT treated and cyp21a2-/- treated on day 4 post-fertilisation with hydrocortisone 10µM solution for 24 hours. Following RNA sequencing, transcriptomic analysis including differential gene expression (DGE), and Gene Set Enrichment Analysis (GSEA) was performed.

Results: DGE and principal component analysis showed that 50% of the variance related to hydrocortisone treatment, and 16% to genotype. HC treatment in WT led to 3153 differentially expressed genes (DEG). GSEA showed that in WT larvae, HC caused the suppression of multiple biological processes pertaining to innate and adaptive immunity. ATP synthesis, provision of energy precursors, lipid and protein metabolism were among the most upregulated processes. In untreated cyp21a2-/- mutants there were 1096 DEG compared to WT, while in treated mutants only 334 DEG compared to treated WT. In untreated cyp21a2-/-, the majority of downregulated biological processes pertained to ribosomal biosynthesis and mitochondrion organisation, and the most upregulated ones to the mitotic cell cycle. In treated mutants, the dysregulation of ribosomal biosynthesis was no longer present, however, there was downregulation of the cell cycle processes which had been upregulated in untreated mutants. Treated cyp21a2-/- mutants shared 185 significantly supressed biological processes with treated WT, of which the majority related to the immune response. There were 195 processes upregulated following HC treatment in both mutants and WT, including ATP synthesis, fatty acid beta-oxidation and several other metabolic processes. However, 89 processes were upregulated by HC only in cyp21a2-/-, of which only 9 had been downregulated in untreated mutants, the remaining 79 representing additional dysregulations and including metabolic processes such as lipid synthesis, localisation and transport.

Conclusion: HC treatment administered in zebrafish larvae restored only some of the biological dysregulations caused by cortisol deficiency. However, it also overcorrected processes and resulted in additional dysregulations. Interestingly, HC treatment caused the upregulation of several lipid metabolic processes only in the cortisol deficient zebrafish. Translated to human cortisol deficiency, these findings highlight the challenge of adequate glucocorticoid replacement and the need for further research aimed at optimising treatment.