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Title: Reactivation of Peroxisome Proliferator-activated Receptor Alpha in Spontaneously Hypertensive Rat: Age-associated Paradoxical Effect on the Heart
Authors: Purushothaman, Sreeja
Sathik, M. B. Mohamed
Nair, R. Renuka
Keywords: Experimental Medicine
Issue Date: 2011
Abstract: Prevention of left ventricular hypertrophy remains a challenge in the prevention of hypertension-induced adverse cardiac remodeling. Cardiac hypertrophy is associated with a shift in energy metabolism from predominantly fatty acid to glucose with a corresponding reduction in the expression of fatty acid oxidation enzyme genes. Although initially adaptive, the metabolic switch seems to be detrimental in the long run. This study was taken up with the objective of examining whether the stimulation of fatty acid oxidation by the activation of peroxisome proliferator-activated receptor alpha PPAR alpha), a key regulator of fatty acid metabolism, can prevent cardiac hypertrophy. Fenofibrate was used as the PPAR alpha agonist. Spontaneously hypertensive rats (SHRs) in the initial stages of hypertrophy (2 months) and those with established hypertrophy (6 months) were treated with fenofibrate (100 for 60 days). Cluster of differentiation 36 (CD36)-responsible for myocardial fatty acid uptake, carnitine palmitoyl transferase 1 beta-a mitochondrial transporter protein and medium chain acyl-Co-A dehydrogenase-a key enzyme in beta oxidation of fatty acids were selected as indicators of fatty acid metabolism. Hypertrophy was apparent at 2 months and metabolic shift at 4 months of age in SHRs. The treatment prevented cardiac remodeling in young animals but aggravated hypertrophy in older animals. Hypertrophy showed a positive association with malondialdehyde levels and cardiac NF-kappa B gene expression, signifying the role of oxidative stress in the mediation of hypertrophy. Expression of carnitine palmitoyl transferase 1 beta and medium chain acyl-Co-A dehydrogenase was upregulated on treatment. However, CD36 showed an age-dependent variation on treatment, with no change in expression in young rats and downregulation in older animals. It is inferred that the stimulation of PPAR alpha before the initiation of metabolic remodeling may prevent cardiac hypertrophy, but reactivation after the metabolic adaptation aggravates hypertrophy. Whether the down-regulation of CD36 is mediated by decreased substrate availability remains to be explored. Age-dependent paradoxical effect on the heart in response to fenofibrate, used as a lipid-lowering drug, can have therapeutic implications.
Appears in Collections:Journal Articles

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