DNA methylation

Abstract
DNA methylation is associated with excess cortisol and aldosterone. The DNA encoding aldosterone
synthase (CYP11B2) and 11β-hydroxylase (CYP11B1), which catalyzes the final step of cortisol
biosynthesis, is less methylated in aldosterone-producing adenomas (APA) and cortisol-producing
adenomas (CPA), respectively. Several studies have reported specific gene mutations in APA and
CPA, and some APAs also cause hypercortisolemia. The aim of this study was to clarify the
molecular mechanisms of cortisol co-production in APA using genetic and epigenetic analyses. We
evaluated 16 patients with APA between 2011 and 2018 at Kanazawa University Hospital (Ishikawa,
Japan). The diagnostic criteria for hypercortisolemia were based on the guideline from the Endocrine
Society. Gene mutation and DNA methylation analyses of the CYP11B2 and CYP11B1 promoters in
APA were performed. Of the 16 patients with APA, six also had hypercortisolemia. In the genetic
analysis, all six APAs with hypercortisolemia as well as eight of the 10 APAs without
hypercortisolemia had a KCNJ5 mutation. In the epigenetic analyses, the methylation status of the
CYP11B2 promoter was similar in the APAs with and without hypercortisolemia. However, in the
APAs with hypercortisolemia, the CYP11B1 promoter was significantly less methylated, especially at
two CpG sites near the Ad1/cAMP response element binding site within the CYP11B1 promoter. In
conclusion, the genetic analysis revealed no association between hypercortisolemia and the evaluated
gene mutations. However, the epigenetic analysis suggested that DNA methylation of the CYP11B1
promoter plays a role in concurrent hypercortisolemia and APA.