Fermented Porcine Placenta and Its Dipeptides Modulate Cellular Senescence in Human Keratinocytes

Skin aging is primarily driven by oxidative stress, mitochondrial dysfunction, and cell cycle dysregulation. This study investigated the anti-senescence effects of fermented porcine placenta (FPP) and its dipeptides, leucine-glycine (LG) and proline-hydroxyproline (PH), in human epidermal keratinocytes (HEKs), using nicotinamide mononucleotide (NMN) as a reference for nicotinamide adenine dinucleotide (NAD⁺)-related pathways. FPP suppressed senescence-associated β-galactosidase (SA-β-gal) activity and Cyclin-dependent kinase inhibitor 2A (p16) expression while enhancing adenosine triphosphate (ATP) production and sirtuin 1 (SIRT1)-peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) signaling. LG and PH exhibited distinct actions: LG improved redox balance by increasing the NAD⁺/NADH ratio and NAD(P)H quinone oxidoreductase 1 (NQO1) activity, whereas PH modulated cell cycle regulators and upregulated sirtuin 3 (SIRT3) expression. Although both peptides contributed to FPP's effects, their combination did not fully replicate its overall activity, suggesting synergistic roles of multiple bioactive constituents. These findings highlight FPP as a multifactorial modulator of keratinocyte senescence, acting via mitochondrial and redox-related mechanisms.