Deficiency of telomere-associated repressor activator protein 1 precipitates cardiac aging in mice via p53/PPARα signaling

Background: Telomere shortening and dysfunction may cause metabolic disorders, tissue damage and age-dependent pathologies. However, little is known about the association of telomere-associated protein Rap1 with mitochondrial energy metabolism and cardiac aging. Methods: Echocardiography was performed to detect cardiac structure and function in Rap1(+/+) and Rap1(-/-) mice at different ages (3 months, 12 months and 20 months). Telomere length, DNA damage, cardiac senescence and cardiomyocyte size were analyzed using the real-time PCR, Western blotting, senescence associated beta-galactosidase assay and wheat germ agglutinin staining, respectively. Western blotting was also used to determine the level of cardiac fatty acid metabolism related key enzymes in mouse and human myocardium. Chromatin immunoprecipitation assay was used to verify the direct link between p53 and PPAR alpha. The p53 inhibitor, Pifithrin-alpha and PPAR alpha activator WY14643 were utilized to identify the effects of Rap1/p53/PPAR alpha signaling pathway. Results: Telomere was shortened concomitant with extensive DNA damage in aged Rap1(-/-) mouse hearts, evidenced by reduced T/S ratios and increased nuclear gamma H2AX. Meanwhile, the aging-associated phenotypes were pronounced as reflected by altered mitochondrial ultrastructure, enhanced senescence, cardiac hypertrophy and dysfunction. Mechanistically, acetylated p53 and nuclear p53 was enhanced in the Rap1(-/-) mouse hearts, concomitant with reduced PPAR alpha. Importantly, p53 directly binds to the promoter of PPAR alpha in mouse hearts and suppresses the transcription of PPAR alpha. In addition, aged Rap1(-/-) mice exhibited reduced cardiac fatty acid metabolism. Pifithrin-alpha alleviated cardiac aging and enhanced fatty acid metabolism in the aged Rap1(-/-) mice. Activating PPAR alpha with WY14643 in primarily cultured Rap1(-/-) cardiomyocytes restored maximal oxygen consumption rates. Reduced Rap1 expression and impaired p53/PPAR alpha signaling also presented in aged human myocardium. Conclusion: In summary, Rap1 may link telomere biology to fatty acid metabolism and aging-related cardiac pathologies via modulating the p53/PPAR alpha signaling pathway, which could represent a therapeutic target in preventing/attenuating cardiac aging.

Automated summary

The study revealed that Rap1(-/-) mice exhibited signs of cardiac aging associated with telomere shortening and DNA damage, influencing cardiac fatty acid metabolism and aging-related phenotypes through modulation of the p53/PPAR alpha signaling pathway.