A paradigm shift is currently taking place in the etiopathogenesis of neuropsychiatric disorders as immunometabolism is replacing the earlier neurotransmitter model. According to the new concept, cellular bioenergetics drives information processing in the central nervous system; therefore, neuropathology is conceptualized as a direct consequence of impaired metabolism. Along the same lines, endoplasmic reticulum stress and gut barrier dysfunction are emerging as novel targets in schizophrenia and affective disorders, linking immune responses to cellular distress. Furthermore, microglia, the brain’s innate immune cells, acquire energy through oxidative phosphorylation, while in the resting state, and glycolysis upon activation, contributing to lactate accumulation and reduced brain pH. The same metabolic signature characterizes neuropsychiatric disorders as the central nervous system derives adenosine triphosphate from aerobic glycolysis, upregulating lactate and generating an acidic environment. Although known for over three decades, the link between dysmetabolism and neuropathology was poorly defined until the discovery of brain-resident innate lymphoid cells, including natural killer cells, and lactylation of histone and nonhistone proteins. In this perspective article, we examine three anti-inflammatory microglial systems relevant for neuropsychiatry: lactate, oxytocin, and the aryl hydrocarbon receptor. We also discuss potential interventions for restoring microglial homeostasis.

Gut microbes are immunologically tolerated in the gastrointestinal tract but trigger aggressive immune responses upon translocation across the gut barrier. Although oral tolerance, a physiological process that dampens immune responses to food proteins and commensal microbiota, remains poorly defined, significant progress was made during and after the Human Immunodeficiency Virus epidemic in the 1980s and the discovery of regulatory T cells in 1995. Additional insight was gained after the discoveries of innate lymphoid cells in 2008 and the functional elucidation of mucosal mast cells. Prior to the historical discovery of human pathogens, the etiologies of most human diseases were considered unknown. The same was true about many genetic disorders prior to the Human Genome Project. Here, we hypothesize that many of the remaining idiopathic conditions, including autoimmune, fibroproliferative, and neuropsychiatric diseases as well as some cancers, can be considered microbial translocation disorders triggered by the host immune responses to extraintestinal gut microbes and/or their constituent parts. In addition to microbial translocation, we also discuss potential interventions for intestinal barrier rehabilitation, including antibodies against tumor necrosis factor-like ligand 1A and membrane lipid replacement supplements.