GDNF levels linked to mood state in bipolar disorder patients
MedWire News: Circulating levels of the glial cell-line derived neurotrophic factor (GDNF) are associated with mood state in patients with bipolar disorder (BD), research suggests.
"Growing evidence shows that BD is associated with abnormalities in neural circuits and synapses, as well in plastic processes," observe Izabela Guimaraes Barbosa (Universidade Federal de Minas Gerais, Belo Horizonte, Brazil) and team.
They add: "Neurotrophins play an important role in synaptic plasticity… [but] until now only a few studies have evaluated GDNF levels in BD patients, and it is still unclear whether GDNF levels are associated with BD and/or with different mood states."
The team therefore studied 70 BD patients, aged over 18 years, and 50 age- and gender-matched mentally healthy controls without a family history of psychiatric disorders. Of the BD patients, 35 were experiencing an episode of mania and 35 were euthymic, and all were medicated.
Blood samples were collected from all of the participants and assessed for GDNF levels using enzyme-linked immunosorbent assay.
Among the BD patients, the severity of manic and depressive symptoms was assessed using the Young Mania Rating Scale (YMRS) and the Hamilton Depression Rating Scale, respectively. Euthymia was defined by YMRS and HDRS scores of less than 7 for at least 4 weeks.
Overall, there was no significant difference in mean GDNF levels between BD patients and controls, at 55.78 and 39.78 pg/ml, respectively.
However, GDNF levels were significantly higher in euthymic than manic BD patients, at 76.74 versus 34.09 pg/ml. There was no significant difference in GDNF levels between manic BD patients and controls, although there was a tendency for reduced levels in patients.
In BD patients, GDNF levels were positively correlated with age and negatively correlated with YMRS scores. There was no association between GDNF levels and severity of depressive symptoms, duration of illness, or type of medication used.
The researchers note that there was no correlation between age and GDNF levels in controls.
Guimaraes Barbosa and team conclude in the journal Neuroscience Letters: "Our results provide evidence that peripheral levels of GDNF are related with different mood states in BD, reinforcing the involvement of neurotrophic factors in its physiopathology."
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By Mark Cowen