title: Feeding butter with elevated content of trans-10, cis-12 conjugated linoleic acid to obese-prone rats impairs glucose and insulin tolerance.
abstract: BACKGROUND
  We recently demonstrated that feeding a natural CLAt10,c12-enriched butter to lean female rats resulted in small, but significant increases in fasting glucose and insulin concentrations, and impaired insulin tolerance. Our goal was to extend these findings by utilizing the diabetes-prone female fatty Zucker rat. Rats were fed custom diets containing 45 % kcal of fat derived from control and CLAt10,c12-enriched butter for 8 weeks.
  
  
  METHODS
  CLA t10,c12-enriched butter was prepared from milk collected from cows fed a high fermentable carbohydrate diet to create subacute rumen acidosis (SARA); control (non-SARA) butter was collected from cows fed a low grain diet. Female fatty Zucker rats (10 weeks old) were randomly assigned to one of four diet treatments: i) low fat (10 % kcal), ii) 45 % kcal lard, iii) 45 % kcal SARA butter, or iv) 45 % kcal non-SARA butter. A low fat fed lean Zucker group was used as a control group. After 8 weeks, i) glucose and insulin tolerance tests, ii) insulin signaling in muscle, adipose and liver, and iii) metabolic caging measurements were performed.
  
  
  RESULTS
  Glucose and insulin tolerance were significantly impaired in all fatty Zucker groups, but to the greatest extent in the LARD and SARA conditions. Insulin signaling (AKT phosphorylation) was impaired in muscle, visceral (perigonadal) adipose tissue and liver in fatty Zucker rats, but was generally similar across dietary groups. Physical activity, oxygen consumption, food intake and weight gain were also similar amongst the various fatty Zucker groups.
  
  
  CONCLUSIONS
  Increasing the consumption of a food naturally enriched with CLAt10,c12 significantly worsens glucose and insulin tolerance in a diabetes-prone rodent model. This outcome is not explained by changes in tissue insulin signaling, physical activity, energy expenditure, food intake or body mass.
authors.affiliation: Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, N1G2W1, Canada.
authors.forename: Melissa
authors.initials: M
authors.lastname: Hamilton
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, N1G2W1, Canada.
authors.forename: Loren E
authors.initials: LE
authors.lastname: Hopkins
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, N1G2W1, Canada.
authors.forename: Ousama
authors.initials: O
authors.lastname: AlZahal
authors.affiliation: Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, N1G2W1, Canada.
authors.forename: Tara L
authors.initials: TL
authors.lastname: MacDonald
authors.affiliation: Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, N1G2W1, Canada.
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Cervone
authors.affiliation: Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, N1G2W1, Canada.
authors.forename: David C
authors.initials: DC
authors.lastname: Wright
authors.affiliation: Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, N1G2W1, Canada.
authors.forename: Brian W
authors.initials: BW
authors.lastname: McBride
authors.affiliation: Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, N1G2W1, Canada. ddyck@uoguelph.ca.
authors.forename: David J
authors.initials: DJ
authors.lastname: Dyck
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D002079:Butter / Q000009:adverse effects; D059305:Diet, High-Fat / Q000009:adverse effects*; D004435:Eating / Q000502:physiology; D005260:Female; D005951:Glucose Tolerance Test; D007328:Insulin / Q000378:metabolism; D007333:Insulin Resistance; D050152:Intra-Abdominal Fat / Q000187:drug effects / Q000378:metabolism; D044243:Linoleic Acids, Conjugated / Q000008:administration & dosage / Q000009:adverse effects*; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D009765:Obesity / Q000209:etiology / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D051381:Rats; D011924:Rats, Zucker; D015430:Weight Gain / Q000502:physiology
chemical_list: D001786:Blood Glucose; D007328:Insulin; D044243:Linoleic Acids, Conjugated; D002079:Butter