PRDX4 and age: Both C248 and NMN increased mitochondrial morphology and quantity, mitochondrial membrane potential (<i>p</i> < 0.01), ATP production (<i>p</i> < 0.01), and mitochondrial DNA (mtDNA) copy number (<i>p</i> < 0.01).<h4>Conclusion</h4>This study reveals that the small molecular C248, a bioactive peptide of PRDX4, is a new candidate molecule for intervening in LC senescence and confirms that mitochondrial protection is a key strategy for improving age-related testicular dysfunction.