Effects of Exercise-related Irisin on Inflammation and Pain in Individuals With Osteoarthritis

Osteoarthritis, which is seen with a frequency of approximately 10% in men over the age of 60 and approximately 18% in women, ranks first among the diseases related to the joint. Many factors such as age, gender, obesity, physical activity, trauma, and genetic factors are involved in the etiology of the disease. In osteoarthritis, intra-articular production and destruction events can occur simultaneously, so it is a dynamic process. Among the joints in the lower and upper extremities, osteoarthritis is most common in the knee joint. Various approaches are used in the treatment, including drug therapy, hyaluronic acid injection, use of glucosamine and chondritis sulfate, exercises, physiotherapy applications, and diet applications for weight loss to reduce pain and increase physical function.

The most important indicator of osteoarthritis is cartilage destruction. In general, the main factor that initiates cartilage damage is the abnormal mechanical forces that the joint is exposed to. It is thought that the most important factors in the pathogenesis of cartilage damage are chondrocytes, which are sensitive to mechanical loading. Chondrocytes additionally have the ability to produce and respond to inflammatory mediators. Chondrocytes secrete catabolic enzymes such as nitric oxide synthetase and cyclooxygenase, matrix metalloproteinases (MMP), disintegrin-metalloproteinase containing thrombospondin 1 domain (ADAMTS 4 and 5) and proinflammatory cytokines. is considered. In addition, prostaglandin E 2 (PGE 2) and nitric oxide (NO) have been described as effective mediators of inflammation and cartilage destruction. Proinflammatory cytokines [for example, interleukin-1 (IL-1), interleukin-6 (IL-6) and tumor necrosis factor-a (TNFα)] cyclooxygenase-2 (COX-2) and nitric oxide synthase (NOS), particularly NOS induces the expression of the inducible isoform (iNOS). COX-2 and iNOS are responsible for the increase in PGE 2 and NO levels, which play an important role in inflammation and pain. Therefore, it can be predicted that the severity of OA will be related to local prostanoid levels and/or other proinflammatory messengers.

Physiotherapy and rehabilitation is one of the important treatment options in OA. Generally, range of motion exercises, strengthening exercises and endurance exercises are applied to patients. An exercise program can be as effective as an NSAID in reducing pain. Decreased quadriceps muscle strength is a finding seen in patients with symptomatic knee OA. In addition, aerobic exercise has the potential to improve cardiovascular fitness, many of the comorbidities often associated with OA, such as diabetes, hypertension, and obesity.

In humans, increased levels of physical activity are generally associated with reduced concentrations of circulating proinflammatory mediators such as C-reactive protein and tumor necrosis factor a (TNFα). Interleukin-6 (IL-6), which is proinflammatory under certain conditions, is released at high levels from exercising muscles and has been shown to exert anti-inflammatory effects on TNFα and endotoxin-induced inflammation.

Irisin is an exercise-induced myokine that has attracted the attention of the scientific community for its potential thermogenic effect. It has been found that the release of irisin is stimulated by exercise in people who exercise for a certain period of time. However, studies on the effect of irisin on inflammatory and pain in individuals with OA have not been found in the literature. Because OA is a major public health problem, a less costly population-based approach is desirable. Therefore, the aim of this study was to investigate the effects of exercise-related irisin on inflammation and pain in patients with OA who underwent exercise.