title: Fasting ghrelin but not PYY(3-36) is associated with insulin-resistance independently of body weight in Wistar rats.
abstract: OBJECTIVE
  The objective of this study was to evaluate the association between insulin-resistance and fasting levels of ghrelin and PYY in Wistar rats.
  
  
  METHODS
  A total of 25 male Wistar rats, weighing 200-300 g, was included in this study. The animals were maintained in cages with a 12/12h light-dark cycle and fed standard chow and water ad libitum. After 12-h overnight fasting, ghrelin, PYY, insulin and glucose values were determined. Insulin resistance was assessed by means of the HOMA-IR, which was ranked and the median was used as a cut-off value to categorize insulin-resistance. HOMA-IR values equal and above 2.62 were considered insulin-resistant (IR) while values below 2.62 were considered insulin sensitive (IS). Differences between means were determined using the Student t-test. Multiple regression and Pearson's correlation test were used to evaluate the association between variables.
  
  
  RESULTS
  HOMA-IR median IQ range values for IS and IR groups were, respectively, 1.56 (0.89 - 2.16) vs. [4.06 (3.50 - 4.61); p < 0.001]. The IR group presented increased levels of fasting ghrelin, PYY and insulin respectively: [50.35 (25.99 - 74.71) pg/mL vs. 12.33 (8.77 - 15.89) pg/mL; p = 0.001]; [54.38 (37.50 - 71.26) pg/mL vs. 33.17 (22.34 - 43.99) pg/mL; p = 0.016]; [18.04 (14.48 - 21.60) uU/mL vs. 7.09 (4.83 - 9.35) uU/mL; p = 0.001]. Ghrelin, but not PYY, correlated linearly and positively with HOMA-IR: ghrelin vs. HOMA-IR (r = 0.52; p = 0.008), and PYY vs. HOMA-IR (r = 0.22; p = 0.200). This correlation was independent of body weight.
  
  
  CONCLUSIONS
  Fasting ghrelin and PYY serum levels are increased in lean, relatively insulin resistant Wistar rats, and this increase is independent of weight.
authors.affiliation: Faculdade de Medicina, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Luciana da Conceição
authors.initials: Lda C
authors.lastname: Antunes
authors.affiliation: Faculdade de Medicina, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Manoela Neves da
authors.initials: MN
authors.lastname: Jornada
authors.affiliation: Faculdade de Medicina, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Jessica Lorenzzi
authors.initials: JL
authors.lastname: Elkfury
authors.affiliation: Faculdade de Medicina, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Kelly Carraro
authors.initials: KC
authors.lastname: Foletto
authors.affiliation: Faculdade de Medicina, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Marcello Casaccia
authors.initials: MC
authors.lastname: Bertoluci
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight / Q000502:physiology*; D003430:Cross-Sectional Studies; D005215:Fasting / Q000378:metabolism*; D054439:Ghrelin / Q000097:blood / Q000378:metabolism*; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D010446:Peptide Fragments / Q000097:blood / Q000378:metabolism*; D019894:Peptide YY / Q000097:blood / Q000378:metabolism*; D017208:Rats, Wistar; D012044:Regression Analysis
chemical_list: D001786:Blood Glucose; D054439:Ghrelin; D007328:Insulin; D010446:Peptide Fragments; D019894:Peptide YY; C061785:peptide YY (3-36)