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

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