Brain FNDC5/Irisin Expression in Patients and Mouse Models of Major Depression
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Bibliographic record
Abstract
Abstract Major depressive disorder (MDD) is a major cause of disability in adults. MDD is both a comorbidity and a risk factor for Alzheimer’s disease (AD), and regular physical exercise has been associated with reduced incidence and severity of MDD and AD. Irisin is an exercise-induced myokine derived from proteolytic processing of fibronectin type III domain-containing protein 5 (FNDC5). FNDC5/irisin is reduced in the brains of AD patients and mouse models. However, whether brain FNDC5/irisin expression is altered in depression remains elusive. Here, we investigate changes in fndc5 expression in postmortem brain tissue from MDD individuals and mouse models of depression. We found decreased fndc5 expression in the MDD prefrontal cortex, both with and without psychotic traits. We further demonstrate that the induction of depressive-like behavior in male mice by lipopolysaccharide decreased fndc5 expression in the frontal cortex, but not in the hippocampus. Conversely, chronic corticosterone administration increased fndc5 expression in the frontal cortex, but not in the hippocampus. Social isolation in mice did not result in altered fndc5 expression in either frontal cortex or hippocampus. Finally, fluoxetine, but not other antidepressants, increased fndc5 gene expression in the mouse frontal cortex. Results indicate a region-specific modulation of fndc5 in depressive-like behavior and by antidepressant in mice. Our finding of decreased prefrontal cortex fndc5 expression in MDD individuals differs from results in mice, highlighting the importance of carefully interpreting observations in mice. The reduction in fndc5 mRNA suggests that decreased central FNDC5/irisin could comprise a shared pathologic mechanism between MDD and AD.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it