MAJOR DEPRESSIVE DISORDER, TYPE 2 DIABETES MELLITUS AND INFLAMMATION

Inflammation may play a key role in the pathogenesis of both depression and type 2 diabetes. However, elevated levels of circulating IL-6 are an independent predictor of type 2 diabetes and are thought to occur with the development of insulin resistance and β-cell dysfunction. There is no evidence linking IL-6 to β-cell dysfunction and eventual β-cell apoptosis. Elevated levels of IL-6 are always associated with increased hypothalamic-pituitary-adrenal (HPA) activity in depression. This increases cortisol, which then triggers TDO and reduces the availability of tryptophan for the production of melatonin, NAS and serotonin. Therefore, IL-6 contributes to the regulation of important biological pathways that underlie stress and the subsequent depression that results from stress.