Specific cytokine levels altered in BD patients

Jul 10 2012

By Mark Cowen

Levels of certain cytokines differ between bipolar disorder (BD) patients and mentally healthy individuals, as well as between manic and euthymic patients with the mood disorder, results from a systematic review and meta-analysis show.

The researchers found evidence for significant differences among these groups regarding levels of tumor necrosis factor (TNF)-α, soluble tumor necrosis factor receptor type 1 (sTNF-R1), and soluble interleukin-2 receptor (sIL-2R).

"This meta-analysis found some support for immune dysregulation in BD," comment Klaus Munkholm and colleagues from the University of Copenhagen in Denmark.

The team searched the literature and identified 13 published studies that evaluated levels of 15 different cytokines, cytokine receptors, or cytokine antagonists in a total of 556 manic bipolar disorder patients and 767 mentally healthy individuals.

The researchers note that "no studies evaluated cytokines, cytokine receptors or cytokine antagonists in a hypomanic or a mixed state and there were no follow-up studies of depressed patients."

Analysis of the pooled data revealed that levels of TNF-α were significantly higher in manic BD patients compared with controls, at a standardized mean difference (SMD) of 3.68, as were levels of sTNF-R1 (SMD=0.87) and sIL-2R (SMD=0.85).

Furthermore, levels of TNF-α and sTNF-R1 were significantly lower in euthymic compared with manic BD patients, at SMDs of −0.57 and −0.52, respectively.

Levels of sTNF-R1 levels were significantly elevated in euthymic patients compared with controls, at an SMD of 0.58, with no significant between-group differences regarding levels of other cytokines.

Writing in the Journal of Affective Disorders, Munkholm and team explain that "multiple lines of evidence indicate that BD is a systemic disease, with widespread biochemical alterations occurring in and beyond the central nervous system."

They conclude that the results from the current study "lend support to the theory of an activated immune response system in BD."

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