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Vitamin D-binding protein levels may help identify bipolar disorder in teens

Researchers identified increased blood levels of vitamin D-binding protein in adolescents with bipolar disorder compared with children without mood disorders, indicating higher levels of this protein may play a role in identifying the disorder.

“Childhood bipolar disorder can be very difficult to distinguish from other disorders, especially in youth with certain types of depression,” Barbara Gracious, MD, associate professor of clinical psychiatry and nutrition, Ohio State University, said in a press release. “Prompt diagnosis and appropriate treatment alleviates the suffering of the child and family and can potentially lessen the risk for suicide.”

In this pilot study, researchers examined the link between vitamin D and inflammatory markers in 36 teenagers with bipolar disorder and major depression forms of major mood disorders compared with those without mood disorders. They developed a screening immunoprecipitation-sequencing approach based on inflammatory brain glia maturation factor beta to detect possible mood disorder biomarkers. Using a cell-based reporter test for nuclear factor kappa-B activation, the investigators also analyzed the overall level of inflammation, and measured antibodies to oxidized LDL.

After quantifying vitamin D-binding protein levels in participants by western blot, Gracious and colleagues found that the levels in children with bipolar disorder were 136% higher than in those without major mood disorders (100%). For youth with major depression, the 121.1% increase in vitamin D-binding protein levels was not notably different from the other groups.

According to the authors, vitamin D-binding protein levels measured by western blot were not linked to levels measured by either monoclonal or polyclonal enzyme-linked immunosorbent assay (ELISA), suggesting ELISA antibodies do not detect all changes that occur in vitamin D-binding protein levels.

Furthermore, vitamin D-binding protein levels measured by monoclonal ELISA showed no association with vitamin D concentration in teens without mood disorders; however, among those with major depression — but not in those with bipolar disorder — vitamin D-binding protein levels detected by polyclonal ELISA were inversely related to vitamin D levels, according to the authors. This opposite trend may suggest a change in protein structure responsible for vitamin D transport in the major depression group compared with controls.

“Distinguishing [bipolar depression] from unipolar MDD early in the onset of illness can lead to more appropriately specific intervention, which has the potential to improve quality of life, reduce psychosocial morbidities, and recurrent mood episodes,” Gracious and colleagues wrote in Translational Psychiatry. “[Vitamin D-binding protein] holds promise as a diagnostic biomarker changing in response to all major factors contributing to pathogenesis of [bipolar disorder] and may shed light on [bipolar disorder] pathophysiologic mechanisms.” – by Savannah Demko

Disclosures: The authors report no relevant financial disclosures.