Adiposity in Depression or Depression in Adiposity? the Role of Immune-Inflammatory-Microbial Overlap

Abstract

Metabolic disorders, metabolic syndrome and non-alcoholic fatty liver disease, and depression are those of the most common and debilitating disorders worldwide that often coexist further increasing mortality risks. Although the exact mechanisms underlying this association are poorly known, several hypotheses have been proposed: antipsychotic medication and antidepressants use, diet and physical activity or any other lifestyle factors. However, the high co-occurrence rate of depression and metabolic disorders suggests a possible pathophysiological overlap. In this paper I review several raised mechanisms for this overlap which are the hypothalamic-pituitary-adrenal axis dysregulation, immune alterations with chronic inflammation, as well as oxidative stress. In my view, there is one common thread running through all the aforementioned areas of pathophysiology which is microbiota alteration. So far, several possible interventions in our microbiota have been introduced into clinical practice - dietary and other lifestyle changes, supplementation with prebiotics or probiotics, fecal microbiota transplantation – but with vague indications. A better characterization of the above associations may represent a critical step at phenotyping, and a more targeted approach to the treatment of both depressive and metabolic disorders. At the end of the paper, I give several practical applications for future studies.

Depressive symptoms and mortality‐findings from Helsinki birth cohort study

“…12,13 Some suggest HPA-axis overactivity to be related to melancholic depression and underactivity to non-melancholic depression. 14 These differences attempt to explain parts of the pathophysiology of depression and its subtypes, 13 but much still remains unknown.…”

“…On the other hand, hypothalamic–pituitary–adrenal (HPA) axis dysregulation has been associated with melancholic depression 12,13 . Some suggest HPA‐axis overactivity to be related to melancholic depression and underactivity to non‐melancholic depression 14 . These differences attempt to explain parts of the pathophysiology of depression and its subtypes, 13 but much still remains unknown.…”