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.

Importance of Lean Muscle Maintenance to Improve Insulin Resistance by Body Weight Reduction in Female Patients with Obesity

BACKGROUND: It 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. METHODS: We 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. RESULTS: There 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). CONCLUSION: Improvement of insulin resistance in female obese patients requires maintenance of skeletal muscle mass.

Age-graded reductions in quadriceps muscle strength and peak aerobic capacity in COPD / Reduções graduadas por idade na força muscular do quadríceps e no pico de consumo de oxigênio na DPOC

BACKGROUND: Reductions in quadriceps strength and peak aerobic capacity (VO2) in patients with chronic obstructive pulmonary disease (COPD) have been studied in relatively small samples over a short period. Moreover, results were not corrected for confounding variables, such as lean muscle mass, gender, and gas transfer capacity of the lungs. OBJECTIVES: To compare quadriceps muscle strength and peak V.O2 in women and men while stratifying for age and gas transfer capacity. We then corrected for lower-limb lean muscle mass to see whether and to what extent the age-graded reduction remained evident. METHODS: Retrospectively, data of 374 women and 593 men with COPD were analyzed: lung function, current drug therapy, quadriceps strength, peak V.O2, lower-limb lean muscle mass, and gas transfer capacity. RESULTS: Quadriceps strength and peak V.O2 were lower in older women and men with a gas transfer capacity of <50% predicted, also after adjustment for lower-limb lean muscle mass. Moreover, quadriceps strength and peak V.O2 were lower in older women and men with a gas transfer capacity of <50% predicted, also after adjustment for lower-limb lean muscle mass. Moreover, quadriceps strength and peak V.O2 were related to age in COPD, particularly in women and men with a gas transfer capacity of >50% predicted. Yet, counter to our hypothesis, lower-limb lean muscle mass did not show an age-graded reduction and, in turn, could not account for the relationship of age with quadriceps strength and peak V.O2. CONCLUSIONS: It is apparent that there is an age-graded reduction in skeletal muscle function in patients with COPD. Therefore, prevention of an age-graded decline in quadriceps muscle strength and peak V.O2 may need to become an outcome of pulmonary rehabilitation of patients with COPD.

CONTEXTUALIZAÇÃO: As reduções da força do quadríceps e do pico de consumo de oxigênio (V.O2) em pacientes com doença pulmonar obstrutiva crônica (DPOC) são estudadas em amostras relativamente pequenas e por curto período de tempo. Além disso, os resultados não são corrigidos por variáveis confundidoras, como conteúdo de massa magra, gênero e capacidade de difusão pulmonar. OBJETIVOS: Comparar a força muscular do quadríceps e o pico de V.O2 em mulheres e homens estratificados por idade e capacidade de difusão pulmonar e, então, corrigir pela massa magra dos membros inferiores para verificar se e até que ponto a redução graduada por idade permaneceu evidente. MÉTODOS: Retrospectivamente, foram analisados dados de 374 mulheres e 593 homens com DPOC, referentes a: função pulmonar, tratamento medicamentoso, força do quadríceps, pico de V.O2, massa magra dos membros inferiores e capacidade de difusão pulmonar. RESULTADOS: A força muscular do quadríceps e o pico de V.O2 foram menores em idosos com capacidade de difusão pulmonar <50% do previsto, mesmo após correção pela massa magra dos membros inferiores. Além disso, a força do quadríceps e o pico de V.O2 correlacionaram-se com a idade, especialmente em homens e mulheres com capacidade de difusão >50% do previsto. No entanto, a massa magra dos membros inferiores não demonstrou redução graduada por idade e não justificou a relação da idade com a força do quadríceps e o pico de V.O2, contrariando a nossa hipótese. CONCLUSÕES: Aparentemente, há uma redução graduada por idade na função musculoesquelética em pacientes com DPOC. Portanto, a prevenção do declínio graduado por idade na força do quadríceps e no pico de V.O2 deveria ser um objetivo da reabilitação pulmonar em pacientes com DPOC.

Association of TNFRSF11B Polymorphism with Lean Muscle Mass in Population of Chinese Han / 中国康复理论与实践

@# Objective To investigate the association of the TNFRSF11B gene polymorphism and the lean muscle mass in population of Chinese Han living in Jinan. Methods Lean muscle mass of 419 volunteers were measured with dual energy X-ray absorptiometry. 8 tagging single nucleotide polymorphism (tSNP) of TNFRSF11B gene were genotyped. Results Lean muscle mass of whole body increased with the copy of the G allele of TNFRSF11B-rs2875845 and the T allele of TNFRSF11B-rs1485288 (P<0.05). Conclusion The G allele of rs2875845 and the T allele of rs1485288 in TNFRSF11B gene increase the level of the lean muscle mass in Chinese Han population.