Nicotinamide Riboside and Phycocyanin Oligopeptides Affect Stress Susceptibility in Chronic Corticosterone-Exposed Rats

Nicotinamide riboside (NR) is an NAD+ precursor capable of regulating mammalian cellular metabolism. Phycocyanin oligopeptide (PC), a phytonutrient found in blue-green algae, has antioxidant and anti-inflammatory properties. This study explored the effects of NR, PC, and their combination on telomere length, inflammatory and antioxidant status in rats under chronic stressed conditions (CS). Forty-nine rats were allocated into seven groups: Control, chronic stress (CS), CS with NR (26.44 mg/kg), a low dose of 2.64 mg/kg of PC (PC-LD), or a high dose of 26.44 mg/kg PC (PC-HD), NR+PC-LD and NR+PC-HF. Rats were given daily corticosterone injections (40 mg/kg) to induce stressed conditions, or NR and PC were orally administered for 21 days. NR and PC supplementation, particularly NR plus PC, increased the serum antioxidant enzyme activities, hepatic nicotinamide adenine (NAD+) content, and telomere length (P<0.001 for all) compared with the CS group. The levels of serum malondialdehyde (MDA), liver interleukin-6 (IL-6), tumor necrosis factor α (TNF-α), IL-1β, and IL-8 were reduced under CS condition (P<0.001). In addition, CS decreased the levels of hepatic telomere-related proteins and sirtuin1 (SIRT1-3), while supplementation of NR and PC alone or in combination increased the levels of telomere-related proteins (e.g., POT1b, TRF1, and TRF2), and SIRT3, NAMPT P<0.05. In conclusion, NR and PC, especially their combination, can alleviate metabolic abnormalities by enhancing hepatic cytokines, SIRT3, NAMPT, and NAD+ levels in CS-exposed rats. More research is needed to elucidate further the potential health effects of the combination of NR and PC in humans.