Inversely regulated immune-related processes mediate anxiety-obesity links in zebrafish

Anxiety disorders often associate with metabolic impairments, but the underlying developmental and molecular mechanisms are yet unknown. To seek RNAs that may link anxiety and obesity, we subjected RNA from zebrafish larvae of a caffeine-induced anxiety model and a high fat diet (HFD)-induced obesity model to RNA-sequencing. We found differentially expressed genes in the larval anxiety and obesity models, including long noncoding RNAs and transfer fragment RNAs. Surprisingly, they were inversely regulated and comprised overrepresentation of immune system pathways, e.g., interleukin signaling and inflammation. Similarly, inverse regulation persisted in adulthood, but with different overrepresented immune system processes, e.g., T cell activation, leukocyte cell-cell adhesion and antigen processing and presentation. Furthermore, unlike the known link in adult zebrafish, obesity in zebrafish larvae was not accompanied by anxiety-like behavior. These results may reflect an antagonistic pleiotropic phenomenon involving re-adjusted modulation of the anxiety-metabolic links with the immune system. Furthermore, the HFD potential to normalize the anxiety-upregulated immune-related genes may explain previously reported protective roles of high fat diet in rodent anxiety and Alzheimers disease models.