Exogenous glucocorticoid dose impacts circulating microRNA expression in patients with adrenal insufficiency due to 21-hydroxylase deficiency

Introduction Patients with adrenal insufficiency due to 21-hydroxylase deficiency (21-OHD) are often exposed to supraphysiologic doses of glucocorticoids (GCs), which can augment metabolic dysfunction by altering glucose, lipid and protein metabolism. Exogenous GCs also fail to mimic the natural circadian rhythm of cortisol secretion. MicroRNAs (miRNAs) are important regulators of gene expression involved in various biological and pathological processes. GCs can regulate miRNAs and in turn miRNAs can modulate GC receptor (GR) activity influencing GR-mediated activity. In this pilot study, we examine the effects of exogenous GCs on circulating miRNA levels in patients with adrenal insufficiency due to classic 21-OHD. Patients/methods Blood samples were collected from 37 patients with classic 21-OHD. Comprehensive miRNA-seq transcriptomic profiling was performed followed by functional enrichment analysis. Patients on different GC types (short- vs. long-acting) and on different GC doses (physiologic, moderate, or high dose;<12 mg/m 2 /day, 12-18 mg/m 2 /day, >18 mg/m 2 /day hydrocortisone equivalents (HCe), respectively) were compared. Results Seven miRNAs (hsa-miR-320a, hsa-miR-122, hsa-let-7b, hsa-let-7i, hsa-miR-4747, hsa-miR3591, hsa-miR-4732) were differentially expressed in patients receiving high-dose GC therapy compared to those receiving physiologic doses ( P < 0.05). Expression of all 7 miRNAs was negatively correlated with GC dose ( P ≤ 0.03). Gene ontology enrichment and KEGG pathway analyses of sequencing results found that the differentially expressed miRNAs were involved in cell cycle progression and proliferation, insulin signaling, metabolic dysfunction, circadian rhythm, and GR signaling. Furthermore, MIENTURNET integrative pathway and network analyses of miRNAs identified 470 target genes, many of which play a role in insulin sensitivity, lipid metabolism, gluconeogenesis, oxidative stress and/or tumor metabolism. Conversely, no differences were observed in miRNA profiles between patients who were on short-acting compared to long-acting GCs. Conclusions In patients with CAH, daily GC dose > 18 mg/m 2 /day HCe impacts the expression of miRNAs that are known to be associated with GCs and their biological effects. The identification of a distinct circulating miRNA signature associated with supraphysiologic GC exposure in patients with CAH suggests that miRNAs could emerge as a valuable non-invasive biomarker for detecting GC excess and monitoring treatment.