Macrophage Migration Inhibitory Factor in Major Depressive Disorder: A Multilevel Pilot Study

Area of Science:

• Neuroscience
• Immunology
• Genetics

Background:

• Macrophage migration inhibitory factor (MIF) is a debated inflammatory marker in major depressive disorder (MDD).
• Conflicting results exist regarding MIF's role (anti- or pro-depressive) in MDD.
• Previous research has not comprehensively investigated MIF at genetic, expression, and protein levels in MDD.

Purpose of the Study:

• To investigate the potential of MIF as a risk factor and biomarker for diagnosing, monitoring, or predicting the course of MDD.
• To examine MIF at genetic, expression, and protein levels in patients with current or remitted MDD compared to healthy controls.
• To explore the influence of sex and prior medication on MIF's role in MDD.

Main Methods:

• Genotyping of three MIF polymorphisms in 267 participants (66 currently depressed, 63 depressed without prior medication, 39 remitted, 61 controls).
• Analysis of peripheral MIF expression and serum levels in patient subgroups and controls.
• Assessment of depression severity using self-evaluation and clinician rating scales, with repeated measures after three weeks of therapy for currently depressed patients.

Main Results:

• Absence of minor allele homozygous individuals in female MDD patients suggests a potential protective genetic effect, not observed in males.
• No significant group differences in overall MIF protein or expression levels.
• MIF protein levels decreased during treatment, but neither protein nor expression levels correlated with changes in depression severity.
• MIF levels showed potential predictive value for depression course in specific subgroups.

Conclusions:

• The study suggests a possible genetic influence of MIF in female MDD patients but does not support its use as a robust biomarker for MDD diagnosis or monitoring.
• The predictive potential of MIF warrants further investigation, considering confounding factors like sex and prior medication.
• This research is the first to explore MIF across genetic, expression, and protein levels in depression, highlighting the need for nuanced interpretation.