title: The use of magnetic resonance imaging to characterize abnormal body composition phenotypes in youth with Prader-Willi syndrome.
abstract: 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.
authors.affiliation: 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.
authors.forename: Camila E
authors.initials: CE
authors.lastname: Orsso
authors.affiliation: Department of Pediatrics, University of Alberta, 11405-87 Avenue, Edmonton, AB, Canada T6G 2R3.
authors.forename: Michelle
authors.initials: M
authors.lastname: Mackenzie
authors.affiliation: Department of Exercise Science, Concordia University, 7141 Sherbrooke Street West, Office SP-165.06, Montreal, QB, Canada H4B1R6.
authors.forename: Angela S
authors.initials: AS
authors.lastname: Alberga
authors.affiliation: Department of Medicine, 1-116 Li Ka Shing Centre for Health Research Innovation, University of Alberta, Edmonton, AB, Canada T6G 2E1.
authors.forename: Arya M
authors.initials: AM
authors.lastname: Sharma
authors.affiliation: Department of Pediatrics, University of Alberta, 11405-87 Avenue, Edmonton, AB, Canada T6G 2R3.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Richer
authors.affiliation: Department of Kinesiology, California State University, Fullerton, 800 N. State College Blvd, CA 92834, USA.
authors.forename: Daniela A
authors.initials: DA
authors.lastname: Rubin
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, 4-002 Li Ka Shing Centre, Edmonton, AB, Canada T6G 2E1.
authors.forename: Carla M
authors.initials: CM
authors.lastname: Prado
authors.affiliation: Department of Pediatrics, University of Alberta, 11405-87 Avenue, Edmonton, AB, Canada T6G 2R3. Electronic address: haqq@ualberta.ca.
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Haqq
mesh_terms: D050153:Abdominal Fat / Q000378:metabolism; D000293:Adolescent; D000367:Age Factors; D000886:Anthropometry; D001823:Body Composition; D050218:Body Fat Distribution; D015992:Body Mass Index; D002648:Child; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D010641:Phenotype; D011218:Prader-Willi Syndrome / Q000378:metabolism*; D012737:Sex Factors
keywords: Adipose tissue distribution; Body composition; Magnetic resonance imaging; Prader–Willi syndrome; Skeletal muscle