BDNF not linked to executive function in BD patients
MedWire News: Executive function is not associated with levels of brain-derived neurotrophic factor (BDNF) in patients with bipolar disorder (BD), study results suggest.
Writing in the Journal of Affective Disorders, Izabela Guimarães Barbosa (Universidade Federal de Minas Gerais, Belo Horizonte, Brazil) and colleagues explain: "There is a growing body of evidence suggesting that BD patients demonstrate cognitive impairment and a compromise of memory, attention, and executive function."
They add that "BDNF and proinflammatory molecules are important contributors to the pathophysiology of BD, and imbalance in peripheral levels of these molecules may be implicated in the cognitive decline observed in BD patients."
To investigate, the team studied 25 euthymic patients with the mood disorder and 25 age-, gender-, and education-matched mentally healthy individuals (controls).
The participants were assessed for executive functioning using the Frontal Assessment Battery (FAB). This is a brief examination that evaluates neurocognitive processes related to the frontal lobes, and includes six subtests for conceptualization, mental flexibility, motor programming, sensitivity of interference, inhibitory control, and environmental autonomy. Scores range from 0 (worst) to 3 (best) for each subtest, and total FAB score is the sum of these subtest scores.
Blood samples were also collected from the participants and assessed for levels of BDNF, tumor necrosis factor (TNF)-α, and its soluble receptors sTNFR1 and sTNFR2 using enzyme-linked immunosorbent assay.
The researchers found that BD patients had significantly poorer mean total FAB scores than controls, at 12.80 versus 14.92, with particularly poorer sensitivity to interference and inhibitory control subtest scores, at 2.40 versus 2.84 and 1.00 versus 1.76, respectively.
BD patients also had significantly higher BDNF levels than controls, but the two groups did not differ significantly regarding mean levels of TNF-α, sTNFR1, or sTNFR2.
In BD patients, TNF-α levels positively correlated with FAB inhibitory control scores, while in controls, sTNFR2 levels negatively correlated with FAB motor programing scores. There were no significant correlations between executive function and levels of BDNF or sTNFR1 in either group.
Plasma levels of BDNF, TNF-α, sTNFR1, and sTNFR2 did not differ in BD patients according to medication use, psychiatric comorbidities, substance dependence, and previous episodes of depression or psychosis, the researchers note.
Barbosa et al conclude: "Impaired executive functioning in stable BD patients was not associated with BDNF plasma levels, but it could be associated with a pro-inflammatory state, at least in specific cognitive measures related to inhibitory control."
They add: "The inclusion of larger samples and more comprehensive neurocognitive batteries would allow for further testing of this hypothesis."
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By Mark Cowen