title: Early cardiac changes in a rat model of prediabetes: brain natriuretic peptide overexpression seems to be the best marker.
abstract: BACKGROUND
  Diabetic cardiomyopathy (DCM) is defined as structural and functional changes in the myocardium due to metabolic and cellular abnormalities induced by diabetes mellitus (DM). The impact of prediabetic conditions on the cardiac tissue remains to be elucidated. The goal of this study was to elucidate whether cardiac dysfunction is already present in a state of prediabetes, in the presence of insulin resistance, and to unravel the underlying mechanisms, in a rat model without obesity and hypertension as confounding factors.
  
  
  METHODS
  Two groups of 16-week-old Wistar rats were tested during a 9 week protocol: high sucrose (HSu) diet group (n = 7) - rats receiving 35% of sucrose in drinking water vs the vehicle control group (n = 7). The animal model was characterized in terms of body weight (BW) and the glycemic, insulinemic and lipidic profiles. The following parameters were assessed to evaluate possible early cardiac alterations and underlying mechanisms: blood pressure, heart rate, heart and left ventricle (LV) trophism indexes, as well as the serum and tissue protein and/or the mRNA expression of markers for fibrosis, hypertrophy, proliferation, apoptosis, angiogenesis, endothelial function, inflammation and oxidative stress.
  
  
  RESULTS
  The HSu-treated rats presented normal fasting plasma glucose (FPG) but impaired glucose tolerance (IGT), accompanied by hyperinsulinemia and insulin resistance (P < 0.01), confirming this rat model as prediabetic. Furthermore, although hypertriglyceridemia (P < 0.05) was observed, obesity and hypertension were absent. Regarding the impact of the HSu diet on the cardiac tissue, our results indicated that 9 weeks of treatment might be associated with initial cardiac changes, as suggested by the increased LV weight/BW ratio (P < 0.01) and a remarkable brain natriuretic peptide (BNP) mRNA overexpression (P < 0.01), together with a marked trend for an upregulation of other important mediators of fibrosis, hypertrophy, angiogenesis and endothelial lesions, as well as oxidative stress. The inflammatory and apoptotic markers measured were unchanged.
  
  
  CONCLUSIONS
  This animal model of prediabetes/insulin resistance could be an important tool to evaluate the early cardiac impact of dysmetabolism (hyperinsulinemia and impaired glucose tolerance with fasting normoglycemia), without confounding factors such as obesity and hypertension. Left ventricle hypertrophy is already present and brain natriuretic peptide seems to be the best early marker for this condition.
authors.affiliation: Laboratory of Pharmacology and Experimental Therapeutics, IBILI, Faculty of Medicine, University of Coimbra, Coimbra, Portugal.
authors.forename: Sara
authors.initials: S
authors.lastname: Nunes
authors.forename: Edna
authors.initials: E
authors.lastname: Soares
authors.forename: João
authors.initials: J
authors.lastname: Fernandes
authors.forename: Sofia
authors.initials: S
authors.lastname: Viana
authors.forename: Eugénia
authors.initials: E
authors.lastname: Carvalho
authors.forename: Frederico C
authors.initials: FC
authors.lastname: Pereira
authors.forename: Flávio
authors.initials: F
authors.lastname: Reis
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000097:blood / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism*; D004195:Disease Models, Animal; D042241:Early Diagnosis; D005786:Gene Expression Regulation; D017379:Hypertrophy, Left Ventricular / Q000097:blood / Q000175:diagnosis / Q000378:metabolism*; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D020097:Natriuretic Peptide, Brain / Q000096:biosynthesis* / Q000097:blood; D011236:Prediabetic State / Q000097:blood / Q000175:diagnosis / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D020097:Natriuretic Peptide, Brain