Role and Potential Mechanisms of Nicotinamide Mononucleotide in Aging

Senescent endothelial cell-derived Galectin 3 promotes silicosis through endothelial-fibroblast and endothelial-macrophage crosstalk

Silicosis is an occupational and irreversible interstitial lung disease, which is caused by the inhalation of respirable crystalline silica. Recent studies suggested that the senescence of endothelial cells is implicated in the pathogenesis of lung diseases. However, the role of senescent endothelial cells in silicosis remains poorly understood. By establishing multiple endothelial cell senescence models, and a silica-induced pulmonary fibrosis mouse model, we found that silica-induced endothelial cell senescence was accompanied by the increased expression of Galectin 3 (Gal3, gene name LGALS3). Mechanistically, silica-induced senescent cells synthesized a substantial amount of Gal3, which was subsequently released into the cellular microenvironment. Then, Gal3 directly binds to TGFBR1 on the cell membrane of lung fibroblasts and TLR4 on the macrophages, respectively. This cell communication facilitates the progression of silicosis by promoting fibroblast-myofibroblast transition (FMT) and NLRP3 inflammasome activation. Furthermore, Gal3 is regulated by the transcriptional regulatory factor CEBPB (CCAAT/ enhancer-binding protein beta) in senescent endothelial cells. In vivo, the administration of Lgals3 siRNA-loaded liposomes significantly ameliorated silica-induced pulmonary fibrosis. Collectively, our study demonstrated the critical role of endothelial cell senescence through the secretion of Gal3, which contributes to pulmonary fibrosis by promoting endothelial-fibroblast and endothelial-macrophage crosstalk.

Nicotinamide riboside and nicotinamide mononucleotide facilitate NAD+ synthesis via enterohepatic circulation

Decreased nicotinamide adenine dinucleotide (oxidized form) (NAD+) levels are reportedly associated with several aging-related disorders. Thus, supplementation with NAD+ precursors, such as nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR), exhibits beneficial effects against these disorders. However, the in vivo metabolic pathways of NMN and NR remain to be elucidated. In this study, we comprehensively analyzed the fate of orally and intravenously administered NMN and NR in mice using NAD+ metabolomics. We found that only a small portion of orally administered NMN and NR was directly absorbed from the small intestine and that most of them underwent gut microbiota-mediated deamidation and conversion to nicotinic acid (NA). Moreover, intravenously administered NMN and NR were rapidly degraded into nicotinamide and secreted to bile followed by deamidation to NA by gut microbiota. Thus, enterohepatic circulated NA is preferentially used in the liver. These findings showed that NMN and NR are indirectly converted to NAD+ via unexpected metabolic pathways.

Senescent alveolar type II epithelial cells-secreted GDF15 promotes silicosis progression via interfering intercellular communication

BACKGROUND

Silicosis is a chronic fibrotic pulmonary disease caused by consistent inhalation of respirable crystalline-free silica dust. The senescence of alveolar epithelial type II cells (ATII) is considered the initiation of pulmonary fibrosis. As a secreted protein, growth differentiation factor 15 (GDF15) was found intimately associated with the severity of lung diseases via senescence. Therefore, we speculate that GDF15 may involved in silica-induced pulmonary fibrosis.

METHODS

Co-culture was performed to observe the pro-fibrotic effect of GDF15, which is secreted from the silica-induced senescence ATII cells, on peripheral effector cells. We further explored GDF15-related signaling pathways via ChIP and IP assays. GDF15 siRNA lipid nanoparticles, anti-aging compound β-nicotinamide mononucleotide (NMN), and the Chinese traditional drug Bazibushen (BZBS) were used individually to intervene silicosis progress.

RESULTS

SiO2 and etoposide-stimulated MLE-12 cells showed senescence phenotype and secreted substantial GDF15, which is consistent with over-expressed GDF15 in lung tissues from silica-induced pulmonary fibrosis. The results further demonstrated that senescence ATII cells could facilitate co-cultured epithelial cell epithelial-mesenchymal transition (EMT) and fibroblast activation in a GDF15-dependent manner. Mechanistically, p53 regulates GDF15 transcription and secretion in senescence ATII cells. Moreover, secreted GFD15 performed its pro-fibrotic role by directly binding to TGF-βR via autocrine and paracrine manners. Also, lipid nanoparticles targeting GDF15 or cell senescence inhibitor NMN and BZBS showed efficient anti-fibrotic effects in vivo.

CONCLUSIONS

Our results elucidate that senescence ATII cell-secreted GDF15 plays a vital role in promoting silicosis by influencing surrounding cells, and provides scientific clues for the selection of potential therapeutic drugs for silicosis.

Long-Term Administration of Nicotinamide Mononucleotide Mitigates High-Fat-Diet-Induced Physiological Decline in Aging Mice

BACKGROUND

Nicotinamide adenine dinucleotide (NAD+) levels decline with age, and boosting it can improve multi-organ functions and lifespan.

OBJECTIVES

Nicotinamide mononucleotide (NMN) is a natural NAD+ precursor with the ability to enhance NAD+ biosynthesis. Numerous studies have shown that a high-fat diet (HFD) can accelerate the process of aging and many diseases. We hypothesized that long-term administration of NMN could exert protective effects on adipose, muscle, and kidney tissues in mice on an HFD act by affecting the autophagic pathway.

METHODS

Mice at 14 mo of age were fed an HFD, and NMN was added to their drinking water at a dose of 400 mg/kg for 7 mo. The locomotor ability of the mice was assessed by behavioral experiments such as grip test, wire hang test, rotarod, and beam-walking test. At the end of the behavioral experiments, the pathological changes of each peripheral organ and the expression of autophagy-related proteins, as well as the markers of the senescence and inflammaging were analyzed by pathological staining, immunohistochemical staining, and western blotting, respectively.

RESULTS

We found that NMN supplementation increased NAD+ levels and ultimately attenuated age- and diet-related physiological decline in mice. NMN inhibited HFD-induced obesity, promoted physical activity, improved glucose and lipid metabolism, improved skeletal muscle function and renal damage, as well as mitigated the senescence and inflammaging as demonstrated by p16, interleukin 1β, and tumor necrosis factor α levels. In addition, the present study further emphasizes the potential mechanisms underlying the bidirectional relationship between NAD+ and autophagy. We detected changes in autophagy levels in various tissue organs, and NMN may play a protective role by inhibiting excessive autophagy induced by HFD.

CONCLUSIONS

Our findings demonstrated that NMN administration attenuated HFD-induced metabolic disorders and physiological decline in aging mice.

β-Nicotinamide Mononucleotide Reduces Oxidative Stress and Improves Steroidogenesis in Granulosa Cells Associated with Sheep Prolificacy via Activating AMPK Pathway

Oxidative stress is a significant factor in the death of granulosa cells (GCs), leading to follicular atresia and consequently limiting the number of dominant follicles that can mature and ovulate within each follicular wave. Follicular fluid contains a diverse array of metabolites that play crucial roles in regulating GCs' proliferation and oocyte maturation, which are essential for follicle development and female fertility. However, the mechanisms behind metabolite heterogeneity and its effects on GCs' function remain poorly understood. Here, we identified elevated nicotinamide levels in the follicular fluid of high-prolificacy sheep, correlated with oxidative stress in GCs, by an integrated analysis. In vitro experiments demonstrated that supplementation with β-nicotinamide mononucleotide (NMN) significantly increased the levels of nicotinamide adenine dinucleotide (NAD+) and adenosine triphosphate (ATP) in GCs. NMN treatment effectively reduced Lipopolysaccharide (LPS)-induced apoptosis and mitigated mitochondrial dysfunction, while also decreasing the production of reactive oxygen species (ROS), thereby enhancing the activity of the antioxidant defense system. Importantly, NMN treatment improved the impairments in steroid hormone levels induced by LPS. Mechanistically, the protective effects of NMN against GCs function were mediated via the AMPK/mTOR pathway. Collectively, our findings elucidate the metabolic characteristics associated with sheep prolificacy and demonstrate that NMN effectively protects GCs from LPS-induced dysfunction and enhances ovarian responsiveness via the AMPK/mTOR pathway. These findings also position NMN as a potential novel metabolic biomarker in enhancing ovarian function.

High-Level Production of Nicotinamide Mononucleotide by Engineered Escherichia Coli

Nicotinamide mononucleotide (NMN), a key precursor of NAD+, is a promising nutraceutical due to its excellent efficacy in alleviating aging and disease. The bioproduction of NMN faces challenges related to incomplete metabolic engineering and insufficient metabolic flux. Here, we constructed an NMN synthesis pathway in Escherichia coli BW25113 by deleting the competitive pathway genes and introducing three heterologous genes encoding the key enzymes nicotinamide phosphoribosyltransferase (NAMPT), phosphoribosyl pyrophosphate synthetase and an NMN transporter. Next, the identification of a highly active NAMPT and optimization of gene expression markedly increased the conversion of NAM to NMN, with a titer of 3503.85 mg/L in shake flasks. Furthermore, by facilitating the coutilization of glucose and xylose, more metabolic flux was diverted toward PRPP biosynthesis, resulting in an NMN titer of 15.66 g/L through whole-cell catalysis and 46.66 g/L in a 2-L bioreactor. This represents the highest NMN yield reported to date, exhibiting great potential for initiating sustainable industrial production of NMN.

Improved Physical Performance Parameters in Patients Taking Nicotinamide Mononucleotide (NMN): A Systematic Review of Randomized Control Trials

Nicotinamide adenine dinucleotide (NAD+) is essential in the proper function of many essential cellular processes in the human body. The purpose of this review is to investigate the effect of nicotinamide mononucleotide (NMN), a NAD+ precursor, on physical performance and evaluate the safety profile of supplementation. A systematic review search criteria following the guidelines from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) was performed in four databases for randomized controlled trials on NMN supplementation. Study variables included title, author, publication date, study year, number of patients, dosage, mean age, mean follow-up time, pre- and post-intervention reported outcomes, and rates of complications. Ten studies, including 437 patients, with a mean age of 58.0 years (35.1 to 81.1 years) and a mean follow-up time of 9.6 weeks (4 to 12 weeks) were included in this study. NMN dosages ranged from 150 to 1200 mg/day. Mean pre-intervention grip strength (two studies) and skeletal mass index (two studies) were 29.9 kilograms (kg) (range: 21.4-40.1 kg) and 7.4 kg/m2 (range: 6.9-7.65 kg/m2), respectively. Mean post-intervention grip strength and skeletal mass index were 30.5 kg (range: 21.7-41.9 kg) and 7.4 kg/m2 (6.8-7.64 kg/m2), respectively. There were no serious adverse effects observed. Moreover, of the reported side effects, they were determined to be independent of NMN supplementation. Therefore, patients taking NMN supplementation demonstrated non-significantly improved physical performance parameters. NMN is well tolerated with no serious adverse effects observed.

β-Nicotinamide mononucleotide supplementation prolongs the lifespan of prematurely aged mice and protects colon function in ageing mice

Ageing is defined as the degeneration of physiological functions in numerous tissues and organs of an organism, which occurs with age. As we age, the gut undergoes a series of changes and weaknesses that may contribute to overall ageing. Emerging evidence suggests that β-nicotinamide mononucleotide (NMN) plays a role in regulating intestinal function, but there is still a lack of literature on its role in maintaining the colon health of ageing mice. In our research, Zmpste24-/- mice proved that NMN prolonged their life span and delayed senescence. This study was designed to investigate the effects of long-term intervention on regulating colon function in ageing mice. Our results indicated that NMN improved the pathology of intestinal epithelial cells and intestinal permeability by upregulating the expression of intestinal tight junction proteins and the number of goblet cells, increasing the release of anti-inflammatory factors, and increasing beneficial intestinal bacteria. NMN increased the expression of the proteins SIRT1, NMNAT2, and NMNAT3 and decreased the expression of the protein P53. It also regulated the activity of ISCs by increasing Wnt/β-catenin and Lgr5. Our findings also revealed that NMN caused a significant increase in the relative abundance of Akkermansia muciniphila and Bifidobacterium pseudolongum and notable differences in metabolic pathways related to choline metabolism in cancer. In summary, NMN supplementation can delay frailty in old age, aid healthy ageing, and delay gut ageing.