Background:Impaired stress resilience and a dysfunctional hypothalamic-pituitary-adrenal (HPA) axis are suggested to play key roles in the pathophysiology of illness progression in bipolar disorder (BD), but the mechanisms leading to this dysfunction have never been elucidated. This study aimed to examine HPA axis activity and underlying molecular mechanisms in patients with BD and unaffected siblings of BD patients.Methods:Twenty-four euthymic patients with BD, 18 siblings of BD patients, and 26 healthy controls were recruited for this study. All subjects underwent a dexamethasone suppression test followed by analyses associated with the HPA axis and the glucocorticoid receptor (GR).Results:Patients with BD, particularly those at a late stage of illness, presented increased salivary post-dexamethasone cortisol levels when compared to controls (p = 0.015). Accordingly, these patients presented reduced ex vivo GR responsiveness (p = 0.008) and increased basal protein levels of FK506-binding protein 51 (FKBP51, p = 0.012), a co-chaperone known to desensitize GR, in peripheral blood mononuclear cells. Moreover, BD patients presented increased methylation at the FK506-binding protein 5 (FKBP5) gene. BD siblings presented significantly lower FKBP51 protein levels than BD patients, even though no differences were found in FKBP5 basal mRNA levels.Conclusions:Our data suggest that the epigenetic modulation of the FKBP5 gene, along with increased FKBP51 levels, is associated with the GR hyporesponsiveness seen in BD patients. Our findings are consistent with the notion that unaffected first-degree relatives of BD patients share biological factors that influence the disorder, and that such changes are more pronounced in the late stages of the illness.

Background:Growing evidence supports the existence of neurobiological trait abnormalities in individuals at genetic risk for bipolar disorder. The aim of this study was to examine potential differences in brain-derived neurotrophic factor, cytokines, oxidative stress, and telomere length markers between patients with bipolar disorder, their siblings, and healthy controls.Methods:Thirty-six patients with bipolar disorder type I, 39 siblings, and 44 healthy controls were assessed. Serum levels of brain-derived neurotrophic factor, interleukin-6, interleukin-10, tumor necrosis factor-α, C-C motif chemokine 11, C-C motif chemokine 24, and 3-nitrotyrosine were measured, as were the activities of glutathione peroxidase, glutathione reductase, and glutathione S-transferase. Telomere length (T/S ratio) was measured using quantitative polymerase chain reaction.Results:Telomere length was different between the 3 groups (P = .041) with both patients and siblings showing a shorter T/S ratio compared with healthy controls. Patients showed increased levels of interleukin-6 (P = .005) and interleukin-10 (P = .002) compared with controls as well as increased levels of interleukin-6 (p = 0.014) and CCL24 (P = .016) compared with their siblings. C-C motif chemokine 11 levels were increased in siblings compared with controls (P = .015), and a similar tendency was found in patients compared with controls (P = .045). Glutathione peroxidase activity was decreased in patients compared with controls (P = .006) and siblings (P = .025). No differences were found for the other markers.Conclusions:The present results suggest that unaffected siblings may present accelerated aging features. These neurobiological findings may be considered as endophenotypic traits. Further prospective studies are warranted.