title: Deep subcutaneous adipose tissue lipid unsaturation associates with intramyocellular lipid content.
abstract: BACKGROUND
  Obese twins have lower saturated and higher long-chain polyunsaturated fatty acids (FA) in subcutaneous adipose tissue (SAT) compared to their lean monozygotic (MZ) co-twin. Whether this holds for metabolically distinct deep (DSAT) and superficial (SSAT) depots is unknown. Here we use non-invasive magnetic resonance spectroscopy (MRS) to measure the FA unsaturation in body mass index (BMI) discordant MZ twins in DSAT and SSAT and their relationship to ectopic fat content and body fat distribution. The main finding is further confirmed in an independent cohort using standardized measurement times.
  
  
  METHODS
  MRS and magnetic resonance imaging were used to measure DSAT and SSAT unsaturation and their relationship to intramyocellular lipids (IMCL), hepatocellular lipids (HCL) and the amount of subcutaneous (SAT) and visceral adipose tissue (VAT) in 16 pairs of healthy monozygotic twins (MZ) discordant for BMI. A second independent cohort of 12 healthy volunteers was used to measure DSAT unsaturation and IMCL with standardized measurement time. One volunteer also underwent repeated random measurements of DSAT unsaturation and IMCL.
  
  
  RESULTS
  In accordance with biopsy studies SSAT unsaturation was higher in the heavier twins (15.2±1.0% vs. 14.4±1.5%, P=0.024) and associated with SAT volume (R=0.672, P=0.001). DSAT unsaturation did not differ between twins (11.4±0.8 vs. 11.0±1.0, P=0.267) and associated inversely with IMCL content (R=-0.462, P=0.001). The inverse association between DSAT unsaturation and IMCL was also present in the participants of the second cohort (R=-0.641, P=0.025) and for the repeated sampling at random of one person (R=-0.765, P=0.027).
  
  
  CONCLUSIONS
  DSAT and SSAT FA unsaturation shows distinct associations with obesity and IMCL in MZ twins, reflecting compartment-specific metabolic activities. The FA unsaturation in the DSAT depot associates inversely with IMCL content, which raises the possibility of cross talk between the DSAT depot and the rapid turnover IMCL depot.
authors: Institute for Clinical Diabetology, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research, Heinrich Heine University, Düsseldorf, Germany; German Center for Diabetes Research (DZD), München-Neuherberg, Düsseldorf, Germany; HUS Medical Imaging Center, Radiology, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland. Electronic address: jesper.lundbom@ddz.uni-duesseldorf.de.
authors: Jesper
authors: J
authors: Lundbom
authors: Institute for Clinical Diabetology, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research, Heinrich Heine University, Düsseldorf, Germany; German Center for Diabetes Research (DZD), München-Neuherberg, Düsseldorf, Germany.
authors: Alessandra
authors: A
authors: Bierwagen
authors: Institute for Clinical Diabetology, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research, Heinrich Heine University, Düsseldorf, Germany; German Center for Diabetes Research (DZD), München-Neuherberg, Düsseldorf, Germany.
authors: Kálmán
authors: K
authors: Bodis
authors: Institute for Clinical Diabetology, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research, Heinrich Heine University, Düsseldorf, Germany; German Center for Diabetes Research (DZD), München-Neuherberg, Düsseldorf, Germany; Department of Endocrinology and Diabetology, Medical Faculty, Heinrich-Heine University, Düsseldorf, Germany.
authors: Julia
authors: J
authors: Szendrödi
authors: FIMM, Institute for Molecular Medicine, University of Helsinki, Helsinki 00014, Finland; Finnish Twin Cohort Study, Department of Public Health University of Helsinki, Helsinki 00014, Finland; National Institute for Health and Welfare, Department of Health, Helsinki 00271, Finland.
authors: Jaakko
authors: J
authors: Kaprio
authors: Obesity Research Unit, Research Programs Unit, Diabetes and Obesity, University of Helsinki, Helsinki 00014, Finland; Department of Psychiatry, Helsinki University Central Hospital, Helsinki, Finland.
authors: Aila
authors: A
authors: Rissanen
authors: HUS Medical Imaging Center, Radiology, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland.
authors: Nina
authors: N
authors: Lundbom
authors: Institute for Clinical Diabetology, German Diabetes Center (DDZ), Leibniz Center for Diabetes Research, Heinrich Heine University, Düsseldorf, Germany; German Center for Diabetes Research (DZD), München-Neuherberg, Düsseldorf, Germany; Department of Endocrinology and Diabetology, Medical Faculty, Heinrich-Heine University, Düsseldorf, Germany.
authors: Michael
authors: M
authors: Roden
authors: FIMM, Institute for Molecular Medicine, University of Helsinki, Helsinki 00014, Finland; Obesity Research Unit, Research Programs Unit, Diabetes and Obesity, University of Helsinki, Helsinki 00014, Finland; Endocrinology, Abdominal Center, Helsinki University Central Hospital and University of Helsinki, Helsinki 00290, Finland.
authors: Kirsi H
authors: KH
authors: Pietiläinen
mesh_terms: D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D005260:Female; D064368:Healthy Volunteers; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D050152:Intra-Abdominal Fat / Q000378:metabolism; D050356:Lipid Metabolism / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D032342:Muscle Cells / Q000378:metabolism*; D050151:Subcutaneous Fat / Q000378:metabolism*; D014430:Twins, Monozygotic
chemical_list: D005231:Fatty Acids, Unsaturated
keywords: Adipose tissue; Intramyocellular lipids; Magnetic resonance spectroscopy; Skeletal muscle; Unsaturation