Influence of unsaturated high-fat diet in the lipid energy metabolism regulation and in the cardiac dysfunction in rats with supravalvar aortic stenosis

Author(s)

Loreta Casquel de Tomasi

• Document type: Doctoral Thesis
• Institution: Universidade Estadual Paulista (Unesp)
• Defense date: 2017-02-17
• Advisor: Antônio Carlos Cicogna

Abstract

Introduction: Although controversial, in general, data from literature show that in experimental models with ventricular dysfunction and preserved ejection fraction, the carbohydrates and fatty acids metabolism is normal. At the stage of reduced ejection capacity, with or without heart failure, there is a switch for fetal programming, increased glucose utilization, and decrease in fatty acid oxidation due to downregulation of proteins involved in lipids uptake and oxidation. There are no studies that evaluated the effects of high-fat diet on energy metabolism and cardiac function after the establishment of ventricular hypertrophy with isolated diastolic dysfunction. Objective: To test the hypothesis that increased unsaturated fatty acid supply, from a high-fat diet, attenuate the downregulation of lipid metabolism and the impairment of cardiac function in rats with left ventricular hypertrophy and diastolic dysfunction by stimulating genes and proteins involved in the regulation of lipid energy metabolism. Methods: Male Wistar rats (80g) underwent aortic stenosis (AS) or Sham surgery. After 6 weeks, rats received either normolipid diet (N, 17% calories from fat) or high-fat diet (H, 40% calories from fat) for 12 weeks yielding 4 groups: Sham-N (n=13), AS-N (n=11), Sham-H (n=12), AS-H (n=14). Cardiac structure and function was assessed by echocardiography at 6 and 18 weeks after surgery. Cardiac lipid energy metabolism was analyzed by gene and protein expression of PPARα, PGC1α, FAT/CD36, CPT1β, MCAD, the activity of beta-hydroxy-acyl CoA dehydrogenase (OHADH) and TAG content. We analysed the activities of hexokinase (HK) and phosphofructokinase (PFK), involved in the glycolytic pathway, and citrate synthase (CS), from Krebs cycle. The protein expression of lactate dehydrogenase (LDH), pyruvate dehydrogenase (PDH) and the metabolic sensors, total AMPK, AMPK phosphorylated on threonine 172 and SIRT1 were also evaluated, as well as the intracellular AMP/ATP and NAD+ /NADH ratios. Results: In the 6th week, prior to dietary treatment, the AS animals had left ventricular hypertrophy, diastolic dysfunction and improved systolic function. In the 18th week, AS animals kept diastolic dysfunction and improved systolic function, that is, there was no worsening of cardiac performance. There was no difference in cardiac structure and function between the AS-N and AS-H groups. There was a decrease in the expression of genes related to lipid uptake and oxidation (CD36, CPT1β, MCAD) in the AS groups compared to the Sham, and there was no difference between the AS groups. The activity of hexokinase and phosphofructokinase was higher in AS compared to Sham, and was similar between AS-N and AS-H. The activity of OHADH was not different between AS-N and Sham-N and also did not differ between AS-N and AS-H. TAG content was reduced in AS-N vs Sham-N and was not different between AS groups. Expression of the proteins PGC1α, PPARα, CPT1β, MCAD, LDH, PDH, the sensors SIRT1, AMPK, pAMPK Thr172, and the NAD+ /NADH ratio were not different among the four groups. Conclusion: In contrast to our hypothesis, during the progression of cardiac remodeling, animals with aortic stenosis showed partial alterations in myocardial lipid metabolism and did not present worsening of cardiac function. The high-unsaturated fat diet had no effect on the metabolic process and cardiac function of these animals. The mechanisms in which the high-fat diet was unable to stimulate PPARα in animals with aortic stenosis is unknown. (AU)

• FAPESP's process: 12/19679-0 - Influence of unsaturated high-fat diet in the lipid energy metabolism regulation and in the cardiac dysfunction in rats with supravalvar aortic stenosis
• Grantee: Loreta Casquel de Tomasi
• Support Opportunities: Scholarships in Brazil - Doctorate