Nicotinamide Supplementation Attenuates Renal Interstitial Fibrosis via Boosting the Activity of Sirtuins

Abstract

<b><i>Background:</i></b> Progressive tubulointerstitial fibrosis (TIF) is the final common pathway leading to ESRD. There is an urgent need to develop effective approaches slowing the progression of TIF. Previous studies showed that systemic supplementation of nicotinamide (NAM) increases renal NAD<sup>+</sup> and reverses ischemic-reperfusion induced acute renal injury. However, the role and mechanism of NAM in TIF has been unclear. <b><i>Methods:</i></b> In vivo, we injected NAM (0.25 mg/g) 3 days before unilateral ureter obstruction (UUO) till day 7 post-operation. In vitro, mouse primary proximal tubular epithelial cells (PTCs), rat renal NRK-49F cells, and human renal proximal tubular epithelial cell (HK-2) were pretreated with the indicated concentration of NAM 1 h before incubation with transform growth factor-β1 (TGF-β1) or aristolochic acid (AA) for 24 or 48 h. To evaluate the role of sirtuins (SIRTs), PTCs were pretreated with EX527 or resveratrol 30 min before incubation with NAM and TGF-β1. <b><i>Results:</i></b> In the present study, we demonstrated that NAM supplementation prevented UUO-induced TIF, and AA-induced renal injury. NAM also decreased the expression of pro-fibrotic proteins and pro-inflammatory cytokines (IL-6 and TNF-α) and attenuated interstitial inflammation. In vitro experiment showed that, NAM inhibited AA-induced G2/M arrest of HK-2 cells by downregulating the expression of cyclin G1, a target gene of p53. In addition, NAM inhibited TGF-β1-induced fibroblast proliferation and activation shown as downregulated expression of collagen I, fibronectin, PCNA, cyclin D1, IL-6, and TNF-α. NAM decreased the acetylation of Smad3 and p53. EX527, an inhibitor of SIRT1, reversed the effect of NAM on TGF-β1-induced matrix protein production. However, resveratrol, a SIRT1 activator, did not further boost the protective effect of NAM on reducing matrix protein production. <b><i>Conclusions:</i></b> Taken together, these data indicate that NAM supplementation could inhibit TIF at least partially by boosting the activity of sirtuins.

The significance of NAD + metabolites and nicotinamide N-methyltransferase in chronic kidney disease

“…We have previously reported that NMN administration improves albuminuria in diabetic nephropathy 32 . Additionally, NAM administration improves renal fibrosis 33 , 34 . Taken together, decreased NAD + and precursors for NAD + synthesis in CKD could contribute to CKD progression.…”

“…Administrating NAD + precursors and methionine to augment this effect might provide a more robust explanation of the underlying mechanism. As for NAD + precursors, it has been reported that NAM administration improves renal fibrosis 33 , 34 . On the other hand, methionine has been reported to increase renal tubular damage 53 , and methionine administration does not always increase SAM/SAH 54 .…”

Endogenous metabolism in endothelial and immune cells generates most of the tissue vitamin B3 (nicotinamide)

“…For instance, NAM treatment was shown to (1) inhibit cytokine responses (IL-1β, IL-6, IL-8, TNFα) to endotoxin in whole human blood ( Ungerstedt et al., 2003 ), (2) to diminish the IFN-γ-induced expression of adhesion proteins such as intercellular adhesion molecule-1 (ICAM-1) on thyroid and endothelial cells, which presumably reduces lymphocyte homing to inflammatory sites ( Hiromatsu et al., 1992 , 1993 ), and (iii) to inhibit cytokine-induced MHC class II antigens on pancreatic cells ( Yamada et al., 1990 ). Administration of NAM in vivo attenuated cytokine induction in ischemia/reperfusion-induced lung injury in rats ( Su et al., 2007 ); alleviated the progression of kidney disease in mouse models by reducing inflammation and fibrosis ( Kumakura et al., 2021 ; Zhen et al., 2021 ); and reduced high-fat diet-induced steatosis and inflammation in mice ( Mitchell et al., 2018 ). However, these studies did not investigate whether NAM has a direct effect as an anti-inflammatory molecule.…”

Nicotinamide and acute kidney injury

“…NAM (250 mg/kg i.p. 3 days before UUO and continuing to Day 7) also reduced fibrosis and Neutrophil gelatinase-associated lipocalin (NGAL) levels in mice at Day 7 [ 32 ]. Moreover, in murine aristolochic acid nephropathy NAM (500 mg/kg, i.p.…”

“…Moreover, in murine aristolochic acid nephropathy NAM (500 mg/kg, i.p. 1 day before and continuously up to Day 14) reduced tubular injury and cytokine expression on Day 15, but this effect was weaker than in the UUO model [ 32 ]. Drinking NAM (0.3, 0.6 or 1.2% NAM) from Day 0 until the end of study (6 weeks) improved kidney function and decreased tubular injury and inflammation in murine adenine-induced CKD.…”