The relationship between changes in serum myostatin and adiponectin levels in patients with obesity undergoing a weight loss program.

BACKGROUND: An effective strategy for weight loss in patients who are overweight or obese is to reduce body fat mass while maintaining skeletal muscle mass. Adiponectin and myostatin are affected through changes in body composition due to weight loss, and examining their dynamics may contribute to strategies for maintaining skeletal muscle mass through weight loss. We aimed to examine the relationships among myostatin, adiponectin, and body composition, depending on the extent of weight loss, in patients with obesity undergoing a weight loss program. METHODS: We examined 66 patients with obesity (age: 46.8 ± 14.0 years, body mass index: 34.3 [31.0-38.4] kg/m2) attending a hospital weight loss program. We categorized the patients into two groups, namely an L group (those with a weight reduction of < 5% from baseline) and an M group (those with a weight reduction of > 5% from baseline). All patients underwent blood tests and were assessed for body composition, insulin resistance, adipocytokine and myokine levels, exercise tolerance, and muscle strength at baseline and post-intervention. RESULTS: Serum myostatin and adiponectin levels increased post-intervention in both groups. Body weight and %fat decreased, and the rate of lean body mass (%LBM) increased in both groups. Exercise capacity and muscle strength improved in the M group only. Change in (⊿) myostatin correlated with ⊿%fat, ⊿%LBM, and ⊿adiponectin. ⊿adiponectin (ß = - 0.262, p = 0.035) was an independent predictor of ⊿myostatin. CONCLUSIONS: Myostatin and adiponectin might cross-talk and regulate changes in skeletal muscle and fat mass with or without successful weight loss. These findings indicate that evaluating serum myostatin and adiponectin levels in clinical practice could be used to predict the effects of weight loss and help prevent skeletal muscle mass loss.

Relationships between serum irisin levels and metabolic parameters in Japanese patients with obesity.

BACKGROUND/PURPOSE: Irisin 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. METHODS: The 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. RESULTS: In 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: ß = 0.635, R2 = 0.369, P < 0.01; women: ß = 0.385, R2 = 0.129, P < 0.01). CONCLUSION: The 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.

Improvement in endothelial function by lifestyle modification focused on exercise training is associated with insulin resistance in obese patients.

A new method to evaluate endothelial function, namely, reactive hyperemia peripheral arterial tonometry (RH-PAT), has been developed. RH-PAT is an index of endothelial function, indicating initial atherosclerotic lesions. The present study aimed to investigate the effect of lifestyle modification with a focus on exercise training on RH-PAT in obese patients. We studied 43 obese patients (body mass index ≥ 30). RH-PAT was measured, and the RH-PAT index was calculated as a ratio of the digital pulse volume during reactive hyperemia divided by that at baseline. Further, we assessed body composition, arterial stiffness, insulin resistance, adipocytokine levels, and exercise tolerance. The exercise program consisted of 30 min on a cycle ergometer or treadmill, 3 times per week for 6 months. Training intensity was adjusted to the anaerobic threshold. Significant improvements were observed in the RH-PAT index following exercise training. We noted a significant reduction in weight, body fat percentage, and leptin values, and a significant increase in adiponectin levels and exercise tolerance. An abnormal baseline RH-PAT index was observed in 24 patients (55.8%); however, the improvement rate was higher in these patients than in patients with normal RH-PAT index values. Stepwise multiple regression analysis revealed that changes in insulin resistance (Δ”HOMA-IR) were independently correlated with changes in the RH-PAT index. Our results indicate that lifestyle modification with a focus on exercise training improved the RH-PAT index in obese patients. Patients with abnormal RH-PAT index values before lifestyle modification with exercise training demonstrated a high rate of improvement following exercise. Further, our results suggest that insulin resistance was the only independent factor influencing improvement in endothelial function.