Fatigue and interleukin-6 - a multi-faceted relationship.

Many connective tissue diseases are characterized by fatigue, which is described in the literature as prostration, weakness, lassitude or asthenia. In many other diseases (autoimmune, neurologic or metabolic) fatigue impinges on daily activities and thus influences the quality of life. Different molecular backgrounds are involved in the development of fatigue. Not only does the immunosuppressive treatment of autoimmune diseases reduce fatigue, but also selective nutritional components may have an effect on secretion of cytokines which are responsible for development of the sensation of tiredness (e.g. secretion of interleukin-6). The beneficial influence of selected food components (such as polyunsaturated omega-3 fatty acids, nutritional antioxidants or adequate fat intake with the diet) on proinflammatory cytokine secretion has been demonstrated in many studies. In this review, the biochemical, neurological and nutritional aspects of fatigue in autoimmune diseases are underlined.