Gut microbiota, bacterial translocation, and interactions with diet : pathophysiological links between major depressive disorder and non-communicable medical comorbidities

Abstract

Background: Persistent low-grade immune-inflammatory processes, oxidative and nitrosative stress (O&NS), and hy- pothalamic-pituitary-adrenal axis activation are integral to the pathophysiology of major depressive disorder (MDD). The microbiome, intestinal compositional changes, and re-sultant bacterial translocation add a new element to the bi- directional interactions of the gut-brain axis; new evidence implicates these pathways in the patho-aetiology of MDD. In addition, abnormalities in the gut-brain axis are associated with several chronic non-communicable disorders, which frequently co-occur in individuals with MDD, including but not limited to irritable bowel syndrome (IBS), chronic fatigue syndrome (CFS), obesity, and type 2 diabetes mellitus (T2DM). Methods: We searched the PubMed/MEDLINE data- base up until May 1, 2016 for studies which investigated in- testinal dysbiosis and bacterial translocation (the ‘leaky gut’) in the pathophysiology of MDD and co-occurring somatic