Fenofibrate Differently Affects the Heart's Morphology and Metabolism in Young and Old Rats.

Fenofibrate (FF), a lipid-lowering drug, may decrease the risk of cardiovascular diseases in some pathological settings, yet data on its cardiac effects in physiological aging is scarce. To determine FF and age effects on the heart's morphology and expression of metabolism-related genes, we treated young and old male rats for 30 days with 0.1% or 0.5% FF. FF did not affect serum activities of LDH and creatine kinase in both age groups. Upon FF treatment the structure of the heart muscle did not change in young rats; however, 0.5% FF increased the abundance of collagen fibers in old rats, and lipid accumulation in cardiomyocytes in young and old animals. FF increased immunoreactivity of the hypertrophy marker NPPA that was more pronounced in old than in young rats, while VEGFB immunoreactivity did not change. FF upregulated phospho-AMPK and PGC1α protein levels only in the cardiac muscle of old rats, while in both age groups it mildly increased the expression of selected fatty acid oxidation genes. We conclude that the cardiac muscle response to FF is dose-dependent and influenced by age. The observed negative impact of high-dose FF in the hearts of aged rats underscores the importance of dose optimization in the elderly.