A 3-month static stretching intervention was found to improve vascular endothelial function, and an additional 3-month intervention also improved arterial stiffness. However, these effects were reversed by detraining.

SummaryBackground/PurposeIrisin is a skeletal muscle myokine that causes the brown coloration of white fat, promotes fat burning, inhibits weight gain and may be useful for treatment of obesity. Irisin is also related to glucose/lipid metabolism and may prevent onset of diabetes, but a consensus on irisin secretion has not been reached. The purpose of this study was to determine the relationships between serum irisin levels and physical factors in untreated Japanese men and women with obesity.MethodsThe subjects were 66 untreated patients with obesity (body mass index ≥30 kg m−2) who visited our obesity clinic. The subjects included 19 men and 47 women with a mean age of 45.7 ± 13.4 years, mean body weight of 93.8 ± 17.6 kg, and mean body mass index of 36.5 ± 4.7 kg m−2. At the initial visit, blood sampling was performed, body composition was evaluated using dual energy X‐ray absorptiometry, and exercise tolerance was determined in a cardiopulmonary exercise test. Homeostasis model of assessment – insulin resistance (HOMA‐IR), an index of insulin resistance, and the serum level of irisin were measured.ResultsIn men, serum irisin was positively correlated with fasting blood glucose (r = 0.491, P < 0.05), immunoreactive insulin (r = 0.536, P < 0.05), HOMA‐IR (r = 0.635, P < 0.01), body weight (r = 0.491, P < 0.05), lean body mass of the trunk (r = 0.579, P < 0.05) and whole lean body mass (r = 0.489, P < 0.05). In women, serum irisin was positively correlated with immunoreactive insulin (r = 0.502, P < 0.01) and HOMA‐IR (r = 0.385, P < 0.01). In both sexes, HOMA‐IR was an independent variable associated with obesity (men: β = 0.635, R2 = 0.369, P < 0.01; women: β = 0.385, R2 = 0.129, P < 0.01).ConclusionThe serum level of irisin was positively correlated with HOMA‐IR in Japanese patients with obesity of both sexes. This suggests that compensatory enhancement of irisin secretion may occur in response to insulin resistance.

BackgroundIt has recently been suggested that skeletal muscle has an important role in insulin resistance in obesity, in addition to exercise tolerance and the fat index. The aim of this study was to identify body composition factors that contribute to improvement of insulin resistance in female patients with obesity who reduce body weight.MethodsWe studied 92 female obese patients (age 40.9±10.4 years, body mass index 33.2±4.6 kg/m2) who reduced body weight by ≥5% after an intervention program including diet, exercise therapy, and cognitive behavioral therapy. Before and after the intervention, body composition was evaluated by dual-energy X-ray absorptiometry to examine changes in skeletal muscle mass. Homeostasis model assessment of insulin resistance (HOMA-IR) was measured as an index of insulin resistance. Cardiopulmonary exercise was also performed by all patients.ResultsThere were significant improvements in body weight (–10.3%±4.5%), exercise tolerance (anaerobic threshold oxygen uptake 9.1%±18.4%, peak oxygen uptake 11.0%±14.2%), and HOMA-IR (–20.2%±38.3%). Regarding body composition, there were significant decreases in total body fat (–19.3%±9.6%), total fat-free mass (–2.7%±4.3%), and % body fat (–10.1%±7.5%), whereas % skeletal muscle significantly increased (8.9%±7.2%). In stepwise multiple linear regression analysis with change in HOMA-IR as the dependent variable, the change in % skeletal muscle was identified as an independent predictor (β=–0.280, R2=0.068, P<0.01).ConclusionImprovement of insulin resistance in female obese patients requires maintenance of skeletal muscle mass.

BackgroundIrisin 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.MethodsThe 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.ResultsThere 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.ConclusionBody 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.

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