title: Tongue fat infiltration in obese versus lean Zucker rats.
abstract: OBJECTIVE
  Obesity is the most important risk factor for obstructive sleep apnea (OSA), and the effects of obesity may be mediated by tongue fat. Our objective was to examine the effects of obesity on upper airway structures in obese (OBZ) and non-obese (NBZ) Zucker rats.
  
  
  METHODS
  Animal study.
  
  
  METHODS
  Academic Medical Center.
  
  
  METHODS
  OBZ (638.2 ± 39 g; 14.9 ± 1.1 w) and age-matched NBZ Zucker (442.6 ± 37 g, 15.1 ± 1.5 w) rats.
  
  
  METHODS
  TONGUE FAT AND VOLUME AND WERE ASSESSED USING: in vivo magnetic resonance spectroscopy (MRS), magnetic resonance imaging including Dixon imaging for tongue fat volume, ex vivo biochemistry (fat quantification; triglyceride (mg)/tissue (g), and histology (Oil Red O stain).
  
  
  RESULTS
  MRS: overall OBZ tongue fat/water ratio was 2.9 times greater than NBZ (P < 0.002) with the anterior OBZ tongue up to 3.3 times greater than NBZ (P < 0.002). Biochemistry: Triglyceride (TG) in the tongue was 4.4 times greater in OBZ versus NBZ (P < 0.0006). TG was greater in OBZ tongue (3.57 ± 1.7 mg/g) than OBZ masseter muscle (0.28 ± 0.1; P < 0.0001) but tongue and masseter TG were not different in NBZ rats (0.82 ± 0.3 versus 0.28 ± 0.1 mg/g, P = 0.67). Dixon fat volume was significantly increased in OBZ (56 ± 15 mm3) versus NBZ (34 ± 5 mm3, P < 0.004). Histology demonstrated a greater degree of intracellular muscle fat and extramuscular fat infiltration in OBZ versus NBZ rats.
  
  
  CONCLUSIONS
  Genetically obese rats had a large degree of fat infiltration in the tongue compared to both skeletal muscle and tongue tissues of the non-obese age-matched littermates. The significant fat increase and sequestration in the obese tongue may play a role in altered tongue neuromuscular function, tongue stiffness or metabolic function.
authors.affiliation: Center for Sleep and Circadian Neurobiology ; Division of Sleep Medicine.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Brennick
authors.affiliation: Department of Radiology.
authors.forename: James
authors.initials: J
authors.lastname: Delikatny
authors.affiliation: Center for Sleep and Circadian Neurobiology ; Division of Sleep Medicine.
authors.forename: Allan I
authors.initials: AI
authors.lastname: Pack
authors.affiliation: Department of Radiology.
authors.forename: Stephen
authors.initials: S
authors.lastname: Pickup
authors.affiliation: Center for Sleep and Circadian Neurobiology.
authors.forename: Sarika
authors.initials: S
authors.lastname: Shinde
authors.affiliation: Center for Sleep and Circadian Neurobiology.
authors.forename: Jing-Xu
authors.initials: JX
authors.lastname: Zhu
authors.affiliation: Center for Sleep and Circadian Neurobiology.
authors.forename: Ivana
authors.initials: I
authors.lastname: Roscoe
authors.affiliation: Center for Sleep and Circadian Neurobiology.
authors.forename: David Y
authors.initials: DY
authors.lastname: Kim
authors.affiliation: Philadephia Research and Education Foundation, Philadelphia, PA ; Division of Infectious Disease, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
authors.forename: Laurence U
authors.initials: LU
authors.lastname: Buxbaum
authors.affiliation: Biomedical Statistical Consulting, Maple Shade, NJ.
authors.forename: Jacqueline R
authors.initials: JR
authors.lastname: Cater
authors.affiliation: Center for Sleep and Circadian Neurobiology ; Division of Sleep Medicine.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Schwab
mesh_terms: D000273:Adipose Tissue / Q000503:physiopathology*; D050154:Adiposity; D000818:Animals; D016022:Case-Control Studies; D008055:Lipids / Q000032:analysis; D008297:Male; D008406:Masseter Muscle / Q000033:anatomy & histology / Q000502:physiology; D009765:Obesity / Q000150:complications* / Q000503:physiopathology*; D051381:Rats; D011924:Rats, Zucker; D012137:Respiratory System / Q000503:physiopathology; D020181:Sleep Apnea, Obstructive / Q000150:complications* / Q000503:physiopathology*; D013851:Thinness; D014059:Tongue / Q000033:anatomy & histology / Q000737:chemistry / Q000503:physiopathology*; D014867:Water / Q000032:analysis
chemical_list: D008055:Lipids; D014867:Water
keywords: Dixon imaging; MRI; Zucker rats; obesity; obstructive sleep apnea; spectroscopy; tongue; upper airway