Effects of Body Weight Reduction on Serum Irisin and Metabolic Parameters in Obese Subjects

BACKGROUND: Irisin is a myokine implicated in lipid and glucose metabolism. The objective of this study is to examine the effect of a body weight reduction on the serum irisin level and physical indicators in obese Japanese patients without diabetes. METHODS: The subjects were 22 patients (male/female, 5/17; age, 46.1±16.0 years; body mass index [BMI], 36.9±5.0 kg/m²) who completed a 6-month body weight reduction program at our clinic. The program included diet, exercise therapy and cognitive behavioral therapy. Blood parameters, body composition, exercise tolerance, homeostasis model assessment of insulin resistance (HOMA-IR), and serum irisin were determined before and after intervention, and relationships among changes in these data were examined. RESULTS: There were significant decreases in body weight and BMI after the intervention. Irisin before the intervention was significantly positively correlated with HOMA-IR (r=0.434, P<0.05). The mean irisin level showed no significant change after the intervention in all participants. However, improvements in % body fat, subcutaneous fat area, triglycerides, and fasting glucose were significantly greater in patients with an increase in irisin compared to those with a decrease in irisin after the intervention. Patients with an increase in irisin also had significantly lower fasting insulin (9.7±4.8 vs. 16.4±8.2, P<0.05) and HOMA-IR (2.2±1.1 vs. 3.7±1.6, P<0.05) after the intervention, compared to patients with a decrease in irisin. CONCLUSION: Body weight reduction did not alter irisin levels. However, irisin may play important roles in fat and glucose metabolism and insulin resistance, and the effects of body weight reduction on irisin kinetics may be a key for obesity treatment.

Cardiac Rehabilitation Increases Exercise Capacity with a Reduction of Oxidative Stress

BACKGROUND AND OBJECTIVES: Reactive oxygen species (ROS) mediate various signaling pathways that underlie vascular inflammation in atherogenesis and cardiovascular diseases. Cardiac rehabilitation (CR) has a variety of multiple beneficial effects, including anti-inflammatory effects. The purpose of the present study was to investigate the effects of CR on ROS in patients with cardiovascular diseases. SUBJECTS AND METHODS: The serum level of derivatives of reactive oxidative metabolites, an index of oxidative stress, was measured in 100 patients with cardiovascular diseases before, and, subsequently, 3 and 6 months after, CR. A biological antioxidant potential (BAP) test was applied to assess the antioxidant power of the serum. RESULTS: The resting reactive oxidative metabolite levels decreased 3-6 months after CR {pre: 351+/-97 Carratelli unit (CARR U), 3 months: 329+/-77 CARR U, 6 months: 325+/-63 CARR U, all p<0.01} with the increase of the percentage of the predicted values of VO2 peak and the percentage of the predicted values of VO2 at the anaerobic threshold (VO2 AT) and the decrease of the B-type natriuretic peptide (BNP). The BAP test and antioxidative/oxidative stress ratio increased 6 months after CR. The % changes of the antioxidative/oxidative stress ratio was positively correlated with the % changes of VO2 AT, and negatively correlated with the % changes of the BNP. CONCLUSION: These results suggest that intensive supervised CR significantly improved exercise capacity, which may be attributable to an adaptive response involving more efficient oxidative metabolites or the increased capacity of endogenous anti-oxidative systems in patients with cardiovascular diseases.