CSF marker hints at bipolar pathogenesis
medwireNews: Levels of the cerebrospinal fluid (CSF) marker secretogranin (Sg)II are reduced in patients with bipolar I disorder, show study findings.
Moreover, in a cross-sectional analysis, SgII levels were negatively associated with increased severity of symptoms.
The findings “give important insight into the pathophysiology of bipolar disorder and suggest directions for future studies,” say lead researcher Joel Jakobsson (University of Gothenburg, Sweden) and colleagues in the Journal of Psychiatry and Neuroscience.
SgII is a component of dense-core secretory granules, which store and release neurotrophins, neuropeptides, and hormones, so reduced SgII levels may reflect a general reduction in activation of the regulated secretory pathway in the brain.
On the other hand, SgII forms part of secretoneurin, which reportedly has multiple effects that promote neuroprotection and plasticity.
“Thus, low SgII concentrations in patients with bipolar disorder might reflect decreased neuronal/synaptic plasticity and survival, which may in turn have impact on progressive brain changes and disease severity,” say Jakobsson et al. “Speculatively, defects in neurotrophin signalling might underlie progressive structural brain changes in patients with bipolar disorder.”
SgII levels were not significantly different in the CSF of 126 patients with bipolar disorder and 71 age- and gender-matched controls. However, they were significantly reduced in the 76 patients who had bipolar I disorder, relative to the controls, suggesting a link with disease severity. In support of this, SgII levels declined in line with increasing symptom severity on the Clinical Global Impression scale.
Another component of dense-core secretory granules, chromogranin B, was not associated with the presence or severity of bipolar disorder.
Previous research found that SgII levels were unaltered in patients with schizophrenia, so, “hypothetically, these contrasting findings might reflect a functional difference in the underlying pathogenesis of schizophrenia and bipolar disorder,” say the researchers.
However, they also note that, in their study, SgII levels were increased in patients with a previous episode of psychosis, implying that a shared pathogenesis could be masked by the presence of psychosis.
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Eleanor McDermid, Senior medwireNews Reporter