Orsso Camila E, Mackenzie Michelle, Alberga Angela S, Sharma Arya M, Richer Lawrence, Rubin Daniela A, Prado Carla M, Haqq Andrea M
Department of Agricultural, Food and Nutritional Science, University of Alberta, 4-002 Li Ka Shing Centre, Edmonton, AB, Canada T6G 2E1; Department of Pediatrics, University of Alberta, 11405-87 Avenue, Edmonton, AB, Canada T6G 2R3.
Department of Pediatrics, University of Alberta, 11405-87 Avenue, Edmonton, AB, Canada T6G 2R3.
Metabolism. 2017 Apr;69:67-75. doi: 10.1016/j.metabol.2017.01.020. Epub 2017 Jan 16.
Magnetic resonance imaging (MRI) provides detailed assessment of body composition compartments. No studies have employed state-of-the-art MRI methods to accurately examine abdominal adipose tissue (AT) and skeletal muscle in youth with Prader-Willi syndrome (PWS). Therefore, this study aimed to describe AT distribution and skeletal muscle in the abdominal region of youth with PWS using MRI.
Anthropometric measures and whole-abdominal T1-weighted MRI were performed in sixteen (5 males and 11 females) youth diagnosed with PWS, and seventeen (10 males and 7 females) youth who did not have PWS (controls). Volume of subcutaneous, visceral, intermuscular, and total AT, and skeletal muscle in the abdominal region were quantified using a semiautomatic procedure. Results were summarized using median and interquartile range (IQR, 25th-75th), and ANCOVA test was used (with age and sex as covariates) to examine differences in body composition compartments between PWS and control group.
PWS group had similar age (10.5, 6.6-13.9 vs. 12.8, 10.0-14.4years; P=0.14) and BMI z-score (0.5, 0.2-1.3 vs. 0.2, -0.3 to 1.0; P=0.33) when compared with controls. Significant differences were observed in absolute volumes of total AT (PWS: 4.1, 2.0-6.6L; control: 2.9, 2.0-4.5L; P=0.01), subcutaneous AT (PWS: 2.8, 1.4-4.8L; control: 1.8, 1.1-3.2L; P=0.01), and intermuscular AT (PWS: 0.3, 0.1-0.4L; control: 0.3, 0.2-0.3L; P<0.005). Visceral AT/subcutaneous AT was lower in PWS (0.4, 0.3-0.5) compared to controls (0.5, 0.4-0.6), P=0.01. In addition, skeletal muscle volume was lower in PWS (1.5, 1.0-2.6L) compared to controls (3.1, 1.6-3.9L), P=0.03. Ratios of abdominal AT compartments to skeletal muscle were all higher in PWS compared to controls (all P<0.005).
PWS youth have greater abdominal adiposity, particularly subcutaneous AT and intermuscular AT, and lower volume of skeletal muscle compared to controls. The decreased ratio of visceral AT/subcutaneous AT in youth with PWS suggests an improved metabolic profile for the level of adiposity present; however, elevated ratios of AT to skeletal muscle suggest a sarcopenic obesity-like phenotype, which could lead to worse health outcomes.
磁共振成像（MRI）可对身体成分各部分进行详细评估。尚无研究采用先进的MRI方法准确检查普拉德-威利综合征（PWS）青少年的腹部脂肪组织（AT）和骨骼肌。因此，本研究旨在使用MRI描述PWS青少年腹部区域的AT分布和骨骼肌情况。
对16名（5名男性和11名女性）诊断为PWS的青少年以及17名（10名男性和7名女性）无PWS的青少年（对照组）进行人体测量和全腹部T1加权MRI检查。采用半自动程序对腹部区域的皮下、内脏、肌间和总AT以及骨骼肌体积进行量化。结果采用中位数和四分位数间距（IQR，第25至75百分位数）进行总结，并使用协方差分析（以年龄和性别作为协变量）来检验PWS组和对照组之间身体成分各部分的差异。
与对照组相比，PWS组的年龄（10.5岁，6.6 - 13.9岁 vs. 12.8岁，10.0 - 14.4岁；P = 0.14）和BMI z评分（0.5，0.2 - 1.3 vs. 0.2， - 0.3至1.0；P = 0.33）相似。在总AT（PWS组：4.1L，2.0 - 6.6L；对照组：2.9L，2.0 - 4.5L；P = 0.01）、皮下AT（PWS组：2.8L，1.4 - 4.8L；对照组：1.8L，1.1 - 3.2L；P = 0.01）和肌间AT（PWS组：0.3L，0.1 - 0.4L；对照组：0.3L，0.2 - 0.3L；P < 0.005）的绝对体积上观察到显著差异。与对照组（0.5，0.4 - 0.6）相比，PWS组的内脏AT/皮下AT较低（0.4，0.3 - 0.5），P = 0.01。此外，与对照组（3.1L，1.6 - 3.9L）相比，PWS组的骨骼肌体积较低（1.5L，1.0 - 2.6L），P = 0.03。与对照组相比，PWS组腹部AT各部分与骨骼肌的比值均更高（所有P < 0.005）。
与对照组相比，PWS青少年腹部肥胖更严重，尤其是皮下AT和肌间AT，且骨骼肌体积更低。PWS青少年内脏AT/皮下AT比值降低表明，就当前肥胖水平而言，其代谢状况有所改善；然而，AT与骨骼肌的比值升高表明存在类似肌肉减少性肥胖的表型，这可能导致更差的健康结局。
