Abstract
BACKGROUND: Major Depressive Disorder (MDD) is a heterogenous and etiologically complex disease often presenting with divergent appetitive phenotypes including Hyperphagic MDD (characterized by an increased appetite) and Hypophagic MDD (characterized by a decrease in appetite) which are closely related to comorbidities, including cardiometabolic disorders. Hyperphagia is associated with atypical depression, decreased stress-hormone signaling, a pro-inflammatory status, hypersomnia, and poorer clinical outcomes. Yet, our understanding of associated biological correlates of Hyperphagic and Hypophagic MDD remain fragmented. METHODS: We performed an exploratory study on peripheral blood RNA profiling using bulk RNAseq in unmedicated individuals with Hyperphagic and Hypophagic MDD (n = 7 and n = 13, respectively). RESULTS: At baseline, we discovered an increased expression of TADA2B in hyperphagic MDD with the significant enrichment of 72 gene ontology pathways mainly related to inflammation. In addition, we used the Maastricht Acute Stress Task to uncover stress-related transcriptomic profiles in Hyper- and Hypophagic MDD and discovered the upregulation of CCDC196 and the downregulation of SPATA33 in hyperphagic MDD. Gene ontology enrichment analysis after stress exposure showed pathways related to ribosomal activity. LIMITATIONS: The present findings are tempered primarily by the limited sample size, which requires independent replication of this exploratory study. However, stringent methods controlling for false positive findings mitigate the risk associated with sample size limitations. DISCUSSION: Limitations notwithstanding, findings suggest that hyper- and hypophagic MDD is associated with divergent RNA expression profiles in peripheral blood that are amplified by exposure to a controlled stress test. Our findings in a well-controlled study provide evidence for peripheral markers of a relevant endophenotype of MDD.