Franz Volhard Clinical Research Center at Experimental and Clinical Research Center, Charité University Medical School and Max Delbrück Center for Molecular Medicine, Berlin, Germany.
Diabetes. 2010 Jul;59(7):1640-7. doi: 10.2337/db09-1200. Epub 2010 Mar 31.
Low cardiorespiratory fitness (CRF) predisposes one to cardiovascular disease and type 2 diabetes in part independently of body weight. Given the close relationship between intrahepatic lipid content (IHL) and insulin sensitivity, we hypothesized that the direct relationship between fitness and insulin sensitivity may be explained by IHL.
We included 138 overweight to obese, otherwise healthy subjects (aged 43.6 +/- 8.9 years, BMI 33.8 +/- 4 kg/m(2)). Body composition was estimated by bioimpedance analyses. Abdominal fat distribution, intramyocellular, and IHL were assessed by magnetic resonance spectroscopy and tomography. Incremental exercise testing was performed to estimate an individual's CRF. Insulin sensitivity was determined during an oral glucose tolerance test.
For all subjects, CRF was related to insulin sensitivity (r = 0.32, P < 0.05), IHL (r = -0.27, P < 0.05), and visceral (r = -0.25, P < 0.05) and total fat mass (r = -0.32, P < 0.05), but not to intramyocellular lipids (r = -0.08, NS). Insulin sensitivity correlated significantly with all fat depots. In multivariate regression analyses, independent predictors of insulin sensitivity were IHL, visceral fat, and fitness (r(2) = -0.43, P < 0.01, r(2) = -0.34, and r(2) = 0.29, P < 0.05, respectively). However, the positive correlation between fitness and insulin sensitivity was abolished after adjustment for IHL (r = 0.16, NS), whereas it remained significant when adjusted for visceral or total body fat. Further, when subjects were grouped into high versus low IHL, insulin sensitivity was higher in those subjects with low IHL, irrespective of fitness levels.
Our study suggests that the positive effect of increased CRF on insulin sensitivity in overweight to obese subjects may be mediated indirectly through IHL reduction.
低心肺功能适应性（CRF）可导致心血管疾病和 2 型糖尿病，部分原因独立于体重。鉴于肝内脂肪含量（IHL）与胰岛素敏感性之间的密切关系，我们假设适应性与胰岛素敏感性之间的直接关系可能通过 IHL 来解释。
我们纳入了 138 名超重或肥胖但健康的受试者（年龄 43.6±8.9 岁，BMI 33.8±4kg/m²）。通过生物阻抗分析估计身体成分。通过磁共振波谱和断层成像评估腹部脂肪分布、肌内和 IHL。进行递增运动测试以估计个体的 CRF。口服葡萄糖耐量试验期间测定胰岛素敏感性。
对于所有受试者，CRF 与胰岛素敏感性（r=0.32，P<0.05）、IHL（r=-0.27，P<0.05）、内脏（r=-0.25，P<0.05）和总脂肪量（r=-0.32，P<0.05）相关，但与肌内脂肪无关（r=-0.08，NS）。胰岛素敏感性与所有脂肪储量显著相关。多元回归分析显示，胰岛素敏感性的独立预测因子为 IHL、内脏脂肪和适应性（r²=-0.43，P<0.01，r²=-0.34，r²=0.29，P<0.05）。然而，在调整 IHL 后，适应性与胰岛素敏感性之间的正相关关系被消除（r=0.16，NS），而当调整内脏或总体脂肪时，这种相关性仍然显著。此外，当将受试者分为高 IHL 与低 IHL 组时，无论适应性水平如何，低 IHL 组的胰岛素敏感性均较高。
本研究表明，超重或肥胖受试者中 CRF 增加对胰岛素敏感性的积极影响可能通过 IHL 减少间接介导。
