University of South Australia scientists say their blood test can pinpoint levels of a specific protein in the brain linked to mood disorders, providing a “potential new biomarker” for depression and bipolar disorder.
The researchers say links between low levels of mature brain-derived neurotrophic factor (mBDNF) and depression are well known but, until now, it hasn’t been possible to distinguish between the three forms of the BDNF protein in blood samples.
The mature form promotes the growth of neurons and protects the brain, but the other two forms bind to different receptors, causing nerve damage and inflammation.
UniSA Professor Xin-Fu Zhou said their test kit, unlike others, could precisely distinguish between these proteins.
“We need to identify in what conditions this bad guy is abnormally expressed and whether we have any way to suppress this bad guy,” he told InDaily.
“From a therapeutic point of view, from a diagnostic point of view, we can use it to assess the patients and their conditions, what happens, what is their response to the treatment.”
Zhou said there was strong evidence to suggest that psychological stress decreases mBDNF and a lack of mBDNF causes depression.
The research, in collaboration with the University of Adelaide and Kunming Medical University in China, has been published in a new paper in the Journal of Psychiatric Research led by UniSA PhD student Liying Lin.
The researchers said that in a study of 215 people in China – including 90 patients with clinical depression and 15 with bipolar disorder – clear links were found with low levels of mBDNF in the patients’ blood.
The more severe the depression, the lower the mBDNF level.
They also found that mature BDNF levels were lower in patients not on antidepressants than those on the medication.
The researchers say serum mBDNF levels below a certain level could be used as a “cut off point” to diagnose depression and bipolar disorder.
“This could be an objective biomarker in addition to a clinical assessment by a doctor,” Zhou said.
“Growing evidence indicates that inflammation in brain cells is linked with depressive behaviours and proBDNF seems to activate the immune system.
“Therefore, we must separate it from mature BDNF to get an accurate reading.
“Interestingly, our recent studies in animals showed that proBDNF injected in both the brain and muscle can directly trigger depressive behaviours.”
Zhou said the next step was to examine whether imbalances between pro BDNF and mature BDNF could be restored in electric convulsive therapy.
“Mood disorders affect millions of people worldwide, however, about one third of people with depression and bipolar disorder are resistant to antidepressants or alternative therapies,” Zhou said.
“The reasons are not understood but it could have something to do with the imbalances between the different forms of BDNF, which we hope to investigate next.”
Zhou said the new test kit had an accuracy rate of 80-83 per cent.
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