Stefan Norbert, Kantartzis Konstantinos, Machann Jürgen, Schick Fritz, Thamer Claus, Rittig Kilian, Balletshofer Bernd, Machicao Fausto, Fritsche Andreas, Häring Hans-Ulrich
Department of Internal Medicine IV, University of Tübingen, D-72076 Tübingen, Germany.
Arch Intern Med. 2008 Aug 11;168(15):1609-16. doi: 10.1001/archinte.168.15.1609.
Obesity represents a risk factor for insulin resistance, type 2 diabetes mellitus, and atherosclerosis. In addition, for any given amount of total body fat, an excess of visceral fat or fat accumulation in the liver and skeletal muscle augments the risk. Conversely, even in obesity, a metabolically benign fat distribution phenotype may exist.
In 314 subjects, we measured total body, visceral, and subcutaneous fat with magnetic resonance (MR) tomography and fat in the liver and skeletal muscle with proton MR spectroscopy. Insulin sensitivity was estimated from oral glucose tolerance test results. Subjects were divided into 4 groups: normal weight (body mass index [BMI] [calculated as weight in kilograms divided by height in meters squared], < 25.0), overweight (BMI, 25.0-29.9), obese-insulin sensitive (IS) (BMI, > or = 30.0 and placement in the upper quartile of insulin sensitivity), and obese-insulin resistant (IR) (BMI, > or = 30.0 and placement in the lower 3 quartiles of insulin sensitivity).
Total body and visceral fat were higher in the overweight and obese groups compared with the normal-weight group (P < .05); however, no differences were observed between the obese groups. In contrast, ectopic fat in skeletal muscle (P < .001) and particularly the liver (4.3% +/- 0.6% vs 9.5% +/- 0.8%) and the intima-media thickness of the common carotid artery (0.54 +/- 0.02 vs 0.59 +/- 0.01 mm) were lower and insulin sensitivity was higher (17.4 +/- 0.9 vs 7.3 +/- 0.3 arbitrary units) in the obese-IS vs the obese-IR group (P < .05). Unexpectedly, the obese-IS group had almost identical insulin sensitivity and the intima-media thickness was not statistically different compared with the normal-weight group (18.2 +/- 0.9 AU and 0.51 +/- 0.02 mm, respectively).
A metabolically benign obesity that is not accompanied by insulin resistance and early atherosclerosis exists in humans. Furthermore, ectopic fat in the liver may be more important than visceral fat in the determination of such a beneficial phenotype in obesity.
肥胖是胰岛素抵抗、2型糖尿病和动脉粥样硬化的危险因素。此外，对于任何给定的全身脂肪量，内脏脂肪过多或肝脏和骨骼肌中的脂肪堆积会增加风险。相反，即使在肥胖人群中，也可能存在代谢良性的脂肪分布表型。
在314名受试者中，我们用磁共振断层扫描测量了全身、内脏和皮下脂肪，并用质子磁共振波谱测量了肝脏和骨骼肌中的脂肪。根据口服葡萄糖耐量试验结果评估胰岛素敏感性。受试者分为4组：正常体重（体重指数[BMI][按千克体重除以身高米的平方计算]，<25.0）、超重（BMI，25.0 - 29.9）、肥胖-胰岛素敏感（IS）（BMI，≥30.0且胰岛素敏感性处于上四分位数）和肥胖-胰岛素抵抗（IR）（BMI，≥30.0且胰岛素敏感性处于下三个四分位数）。
与正常体重组相比，超重和肥胖组的全身和内脏脂肪更高（P <.05）；然而，肥胖组之间未观察到差异。相比之下，肥胖-IS组与肥胖-IR组相比，骨骼肌中的异位脂肪（P <.001），特别是肝脏中的异位脂肪（4.3%±0.6%对9.5%±0.8%）和颈总动脉内膜中层厚度（0.54±0.02对0.59±0.01毫米）更低，胰岛素敏感性更高（17.4±0.9对7.3±0.3任意单位）（P <.05）。出乎意料的是，肥胖-IS组的胰岛素敏感性与正常体重组几乎相同，内膜中层厚度在统计学上无差异（分别为18.2±0.9 AU和0.51±0.02毫米）。
人类中存在一种不伴有胰岛素抵抗和早期动脉粥样硬化的代谢良性肥胖。此外，在确定肥胖中的这种有益表型时，肝脏中的异位脂肪可能比内脏脂肪更重要。
