title: Adipose tissue stearoyl-CoA desaturase 1 index is increased and linoleic acid is decreased in obesity-prone rats fed a high-fat diet.
abstract: BACKGROUND
  Fatty acid (FA) composition and desaturase indices are associated with obesity and related metabolic conditions. However, it is unclear to what extent desaturase activity in different lipid fractions contribute to obesity susceptibility. Our aim was to test whether desaturase activity and FA composition are linked to an obese phenotype in rats that are either obesity prone (OP) or resistant (OR) on a high-fat diet (HFD).
  
  
  METHODS
  Two groups of Sprague-Dawley rats were given ad libitum (AL-HFD) or calorically restricted (HFD-paired; pair fed to calories consumed by chow-fed rats) access to a HFD. The AL-HFD group was categorized into OP and OR sub-groups based on weight gain over 5 weeks. Five different lipid fractions were examined in OP and OR rats with regard to proportions of essential and very long-chain polyunsaturated FAs: linoleic acid (LA), alpha-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid and the stearoyl-CoA desaturase 1 (SCD-1) product 16:1n-7. FA ratios were used to estimate activities of the delta-5-desaturase (20:4n-6/20:3n-6), delta-6-desaturase (18:3n-6/18:2n-6), stearoyl-CoA desaturase 1 (SCD-1; 16:1n-7/16:0, SCD-16 and 18:1n-9/18:0, SCD-18), de novo lipogenesis (16:0/18:2n-6) and FA elongation (18:0/16:0). Fasting insulin, glucose, adiponectin and leptin concentrations were measured in plasma.
  
  
  RESULTS
  After AL-HFD access, OP rats had a significantly higher SCD-16 index and 16:1n-7 proportion, but a significantly lower LA proportion, in subcutaneous adipose tissue (SAT) triacylglycerols, as well as significantly higher insulin and leptin concentrations, compared with OR rats. No differences were found between the two phenotypes in liver (phospholipids; triacylglycerols) or plasma (cholesterol esters; phospholipids) lipid fractions or for plasma glucose or adiponectin concentrations. For the desaturase indices of the HFD-paired rats, the only significant differences compared with the OP or OR rats were higher SCD-16 and SCD-18 indices in SAT triacylglycerols in OP compared with HFD-paired rats.
  
  
  CONCLUSIONS
  The higher SCD-16 may reflect higher SCD-1 activity in SAT, which in combination with lower LA proportions may reflect higher insulin resistance and changes in SAT independent of other lipid fractions. Whether a lower SCD-16 index protects against diet-induced obesity is an interesting possibility that warrants further investigation.
authors.affiliation: Department of Neuroscience, Uppsala University, BMC, Uppsala, Sweden. jonathan.cedernaes@neuro.uu.se
authors.forename: Jonathan
authors.initials: J
authors.lastname: Cedernaes
authors.forename: Johan
authors.initials: J
authors.lastname: Alsiö
authors.forename: Ake
authors.initials: A
authors.lastname: Västermark
authors.forename: Ulf
authors.initials: U
authors.lastname: Risérus
authors.forename: Helgi B
authors.initials: HB
authors.lastname: Schiöth
mesh_terms: D052242:Adiponectin / Q000097:blood; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D031204:Caloric Restriction; D000090943:Delta-5 Fatty Acid Desaturase; D059305:Diet, High-Fat / Q000009:adverse effects; D004041:Dietary Fats / Q000378:metabolism*; D004281:Docosahexaenoic Acids / Q000378:metabolism; D015118:Eicosapentaenoic Acid / Q000378:metabolism; D044943:Fatty Acid Desaturases / Q000378:metabolism; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood; D019787:Linoleic Acid / Q000378:metabolism*; D050155:Lipogenesis; D008099:Liver / Q000378:metabolism* / Q000473:pathology; D008297:Male; D009765:Obesity / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013230:Stearoyl-CoA Desaturase / Q000378:metabolism*; D050151:Subcutaneous Fat / Q000378:metabolism* / Q000473:pathology; D014280:Triglycerides / Q000097:blood; D015430:Weight Gain; D017962:alpha-Linolenic Acid / Q000378:metabolism
chemical_list: D052242:Adiponectin; D001786:Blood Glucose; D000090943:Delta-5 Fatty Acid Desaturase; D004041:Dietary Fats; D007328:Insulin; D020738:Leptin; D014280:Triglycerides; D017962:alpha-Linolenic Acid; D004281:Docosahexaenoic Acids; D019787:Linoleic Acid; D015118:Eicosapentaenoic Acid; D044943:Fatty Acid Desaturases; D013230:Stearoyl-CoA Desaturase