Cerebrospinal fluid irisin and lipoxin A4 are reduced in elderly Brazilian individuals with depression: Insight into shared mechanisms between depression and dementia

Introduction: Depression is frequent among older adults and is a risk factor for dementia. Identifying molecular links between depression and dementia is necessary to shed light on shared disease mechanisms. Reduced brain-derived neurotrophic factor (BDNF) and neuroinflammation are implicated in the pathophysiology of depression and dementia. The exercise-induced hormone, irisin, increases BDNF and improves cognition in animal models of Alzheimer's disease. Lipoxin A4 is a lipid mediator with anti-inflammatory activity. However, the roles of irisin and lipoxin A4 in depression remain to be determined.

Methods: In the present study, blood and CSF were collected from 61 elderly subjects, including individuals with and without cognitive impairment. Screening for symptoms of depression was performed using the 15-item Geriatric Depression Scale (GDS-15).

Results: CSF irisin and lipoxin A4 were positively correlated and reduced, along with a trend of BDNF reduction, in elderly individuals with depression, similar to previous observations in patients with dementia.

Discussion: Our findings provide novel insight into shared molecular signatures connecting depression and dementia.