Adipokines in Rheumatic diseases

Abstract

White adipose tissue (WAT) is recognized to be a multifactorial organ. It has a major endocrine function secreting several hormones, most notably leptin and adiponectin, together with a diverse range of other protein signals and factors. These adipose-derived peptides have been termed collectively “adipokines” participate in functions correlated with energy homeostasis and metabolism. Moreover, adipokines represent a new family of compounds that can be currently considered as key players of the complex network of soluble mediators involved in the pathophysiology of rheumatic diseases. Adipokines include classic pro-inflammatory proteins such as TNF-α and IL-6, both secreted by adipocytes, but synthesized also by immune cells infiltrating WAT, such as macrophages and others as leptin, adiponectin, resistin, visfatin. These pro-inflammatory adipokines appear to significantly contribute to the so-called “low grade inflammation” of obese subjects, a condition associated with increased risk of cancer, type 2 diabetes, cardiovascular complications, autoimmune and inflammatory diseases including rheumatic diseases such as rheumatoid arthritis (RA), osteoarthritis (OA) and systemic lupus (SLE) . Summary & Recommendations 060 These adipokines include: 1. Leptin Leptin is a hormone with pleiotropic actions. In fact, in addition to regulation of food intake, it also affects a variety of other physiological functions, including fertility, bone metabolism, inflammation, infection, immune responses and others. Recent evidence demonstrates an involvement of leptin in promoting the pathogenesis of different autoimmune and rheumatic diseases such as rheumatoid arthritis, multiple sclerosis and SLE. Several authors have demonstrated dependence between the risk of aggressive course of RA and leptin levels. It is increasingly evident that this hormone plays a key role in the OA pathophysiology. Leptin expression is much higher in osteoarthritic human cartilage than in normal cartilage, and there exists a strong correlation of synovial fluid leptin levels with body mass index (BMI) in people with severe osteoarthritis.