HPA axis dysregulation, NR3C1 polymorphisms and glucocorticoid receptor isoforms imbalance in metabolic syndrome.

Abstract

Metabolic syndrome (MetS) shares several similarities with hypercortisolism. To evaluate hypothalamic-pituitary-adrenal (HPA) axis sensitivity to dexamethasone (DEX), NR3C1 single nucleotide polymorphisms (SNPs), and expression of glucocorticoid receptor (GR) isoforms and cytokines in peripheral immune cells of MetS patients and controls. Prospective study with 40 MetS patients and 40 controls was conducted at the Ribeirão Preto Medical School University Hospital. Plasma and salivary cortisol were measured in basal conditions and after 0.25, 0.5, and 1mg of DEX given at 2300h. In addition, p.N363S (rs6195), p.ER22/23EK (rs6189-6190), and BclI (rs41423247) SNPs were evaluated by quantitative polymerase chain reaction allelic discrimination. Exons 3 to 9 and exon/intron boundaries of NR3C1 were sequenced. GR isoforms and cytokines (IL1B, IL2, IL4, IL6, IL8, IL10, IFNγ, TNFα) expression were assessed by quantitative polymerase chain reaction. Plasma and salivary cortisol (nmol/L) after 1-mg DEX were higher in MetS patients compared with controls (PF: 70.2±17.3 vs 37.9±2.6, P=.02, and SF: 4.9±1.7 vs 2.2±0.3, P<.0001). After all DEX doses, a lower number of MetS patients suppressed plasma and salivary cortisol compared with controls. The BclI genotypic frequencies (%) differed between patients (CC:56/CG:44) and controls (CC:50/CG:32.5/GG:17.5) (P=.03). The GRβ was overexpressed (fold=100.0; P=.002) and IL4 (fold=-265.0; P<.0001) was underexpressed in MetS. MetS patients exhibited decreased HPA sensitivity to glucocorticoid feedback. Moreover, the BclI polymorphism lower frequency, GRβ overexpression, and IL4 underexpression might underlie the molecular mechanism of glucocorticoid resistance in MetS. Thus, HPA axis dysregulation might contribute to MetS pathogenesis.