SATOSHI KUROSE

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: β = 0.635, R2 = 0.369, P < 0.01; women: β = 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.

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/m(2)) who reduced body weight by &gt;= 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 (beta=-0.280, R-2=0.068, P&lt;0.01). Conclusion: Improvement of insulin resistance in female obese patients requires maintenance of skeletal muscle mass.

【目的】心臓リハビリテーション(心リハ)による1メッツ(METs)以上の運動耐容能の改善が、急性冠症候群患者(ACS)の責任血管に残存する軽度冠動脈プラークの変化に及ぼす影響を検討した。【方法】ACSで緊急冠動脈インターベンションを行った男性41名を心リハ群21名と非心リハ群20名に分類した。心リハ群は週3回の標準的なプログラムを6ヵ月間継続し、心リハ群の内、1 METsを基準に改善群と不変群に分類した。非心リハ群は定期的な外来受診のみとした。入院時と6ヵ月後の冠動脈造影から定量的冠動脈解析を行い、ステント治療部位より遠位の10〜50%狭窄の部位を解析した。【結果】1 METs以上の改善群は33.3%であった。改善群のプラーク面積は減少傾向を認め、非心リハ群は有意に増加した。不変群のプラーク面積は有意な変化を認めなかった。改善群のΔ高感度C反応性蛋白は不変群より有意に低下した。【結論】ACS患者の1 METs以上の運動耐容能の増加は、軽度冠動脈プラークの進展抑制や安定化に関与する可能性が示唆された。(著者抄録)

スタティックストレッチングの施行が血管内皮と動脈スティフネスの及ぼす影響について検討した。対象は40歳以上で閉経前の、喫煙習慣のない健常女性11名(平均年齢47.4±3.0歳)を対象とした。介入期間は6ヵ月で、15分間のスタティックストレッチングを1日1回以上施行した。ストレッチングの部位は僧帽筋、前腕諸筋群、三角筋、上腕三頭筋に続き、上背部、大胸筋、広背筋ほか、ヒラメ筋、大腿四頭筋、ハムストリングス、脊柱起立筋下部など15部位が選択された。立位または臥位姿勢で15〜30秒間、少しきつい感覚を目安に施行した。その結果、1)スタティックストレッチングの施行率は82.8±15.5%で、介入後の対象者の体組成は腹囲のみに低い傾向がみられ、その他の項目には有意な変化は認められなかった。2)柔軟性の評価では長座体前屈、SLR(左右)、上背角度、腰部角度において介入前後で有意な変化が認められた。3)血管内皮機能の指標のRH-PAT indexは3ヵ月後、6ヵ月後ともに有意な改善が認められた。一方、動脈スティフネスの指標のbaPWVは3ヵ月後では有意差がみられなかったが、6ヵ月後には有意な改善が認められた。4)スタティックストレッチングは6ヵ月間の継続施行で柔軟性向上ほか、血管内皮機能と動脈スティフネスの良好な改善をもたらした。このことは抗動脈硬化の一助となるエクササイズと示唆された。

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 &gt;= 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 (Delta 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. (c) 2012 Asian Oceanian Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.