Nicotinamide Adenine Dinucleotide Salvage Pathway Research Articles

NAD deficiency contributes to progressive kidney disease in HIV nephropathy mice.

HIV disease remains prevalent in the USA and is particularly prevalent in sub-Saharan Africa. Recent investigations revealed that mitochondrial dysfunction in kidney contributes to HIV-associated nephropathy (HIVAN) in Tg26 transgenic mice. We hypothesized that nicotinamide adenine dinucleotide (NAD) deficiency contributes to energetic dysfunction and progressive tubular injury. We investigated metabolomic mechanisms of HIVAN tubulopathy. Tg26 and wild-type (WT) mice were treated with the farnesoid-X receptor (FXR) agonist INT-747 or nicotinamide riboside (NR) from 6 to 12 weeks of age. Multi-omic approaches were used to characterize kidney tissue transcriptomes and metabolomes. Treatment with INT-747 or NR ameliorated kidney tubular injury, as shown by serum creatinine, the tubular injury marker urinary neutrophil-associated lipocalin and tubular morphometry. Integrated analysis of metabolomic and transcriptomic measurements showed that NAD levels and production were globally downregulated in Tg26 mouse kidney, especially nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the NAD salvage pathway. Further, NAD-dependent deacetylase sirtuin3 activity and mitochondrial oxidative phosphorylation activity were lower in ex vivo proximal tubules from Tg26 mouse kidneys compared to those of WT mice. Restoration of NAD levels in kidney improved these abnormalities. These data suggest that NAD deficiency might be a treatable target for HIVAN.

Abstract 7217: Orthogonal targeting of NAD metabolism and ErbB2/ErbB3 signaling in pancreatic adenocarcinoma

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) is now the third leading cause for cancer related deaths in the US with a five-year survival of ~10% that has improved little over the past 20 years. Thus, there is a critical need to fully understand mechanisms of PDAC tumorigenesis in order to develop novel and effective therapies. Nicotinamide Adenine Dinucleotide (NAD), a critical co-factor and energy source required for cellular processes such as DNA repair and epigenetic regulation is frequently upregulated in PDAC. We recently reported a novel oncogenic axis connecting the NAD-dependent epigenetic regulator and oncogene C-terminal Binding Protein (CtBP) with the EGFR family growth factor receptors ErbB2/ErbB3 (ErbB2/3) in PDAC cells and tumors. Indeed, previous reports have shown ~30% of human PDAC tumors overexpress ErbB3, and our work has shown that PDAC tumor cell growth relies on maintenance of ErbB3 expression. Moreover, we show that the majority of PDAC cells with high levels of ErbB3 expression are uniquely sensitive to the ErbB2-targeted tyrosine kinase inhibitor lapatinib. In addition, we have recently shown that co-targeting NAD and CtBP with small molecule inhibitors is an effective and synergistic therapeutic strategy in PDAC model systems. Methods and Results: In the current study, we demonstrate NAD-dependent regulation of ErbB2/3 signaling in PDAC cells in vitro. Upon depletion of NAD using the NAD salvage pathway inhibitor GMX1778 in human PDAC cells, we observed a striking coordinate decrease in the levels of both ErbB2 and ErbB3. Furthermore, stable knockdown of the limiting enzyme of the complementing Preiss-Handler NAD synthetic pathway, Nicotinamide Adenine Phosphoribosyl Transferase, also resulted in robust downregulation of ErbB2/3 protein levels, suggesting a direct linkage in PDAC cells between the status of NAD metabolism and synthesis and activity of the key growth factor receptors ErbB2/3. Conclusions: Our findings highlight the novel connection between NAD and ErbB2/3 in PDAC. Furthermore, our data suggests combining chemical or biologic inhibitors of ErbB2/3 with an inhibitor of NAD synthesis may result in highly synergistic cytotoxic effects in PDAC cells and PDAC preclinical models. Such data could support the future development of a human PDAC clinical trial repurposing agents targeting NAD synthesis and ErbB2/3 that are already FDA-approved or currently in clinical testing. Citation Format: Kranthi Kumar Chougoni, Nari Kim, Martin M. Dcona, Diana T. Dcona, Gautam K. Malhotra, Steven R. Grossman. Orthogonal targeting of NAD metabolism and ErbB2/ErbB3 signaling in pancreatic adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7217.

Indole-3-Propionic Acid Protects Against Heart Failure With Preserved Ejection Fraction.

Heart failure with preserved ejection fraction (HFpEF) is a common but poorly understood form of heart failure, characterized by impaired diastolic function. It is highly heterogeneous with multiple comorbidities, including obesity and diabetes, making human studies difficult. Metabolomic analyses in a mouse model of HFpEF showed that levels of indole-3-propionic acid (IPA), a metabolite produced by gut bacteria from tryptophan, were reduced in the plasma and heart tissue of HFpEF mice as compared with controls. We then examined the role of IPA in mouse models of HFpEF as well as 2 human HFpEF cohorts. The protective role and therapeutic effects of IPA were confirmed in mouse models of HFpEF using IPA dietary supplementation. IPA attenuated diastolic dysfunction, metabolic remodeling, oxidative stress, inflammation, gut microbiota dysbiosis, and intestinal epithelial barrier damage. In the heart, IPA suppressed the expression of NNMT (nicotinamide N-methyl transferase), restored nicotinamide, NAD+/NADH, and SIRT3 (sirtuin 3) levels. IPA mediates the protective effects on diastolic dysfunction, at least in part, by promoting the expression of SIRT3. SIRT3 regulation was mediated by IPA binding to the aryl hydrocarbon receptor, as Sirt3 knockdown diminished the effects of IPA on diastolic dysfunction in vivo. The role of the nicotinamide adenine dinucleotide circuit in HFpEF was further confirmed by nicotinamide supplementation, Nnmt knockdown, and Nnmt overexpression in vivo. IPA levels were significantly reduced in patients with HFpEF in 2 independent human cohorts, consistent with a protective function in humans, as well as mice. Our findings reveal that IPA protects against diastolic dysfunction in HFpEF by enhancing the nicotinamide adenine dinucleotide salvage pathway, suggesting the possibility of therapeutic management by either altering the gut microbiome composition or supplementing the diet with IPA.

Monosomy 7/del(7q) cause sensitivity to inhibitors of nicotinamide phosphoribosyltransferase in acute myeloid leukemia

AbstractMonosomy 7 and del(7q) (-7/-7q) are frequent chromosomal abnormalities detected in up to 10% of patients with acute myeloid leukemia (AML). Despite unfavorable treatment outcomes, no approved targeted therapies exist for patients with -7/-7q. Therefore, we aimed to identify novel vulnerabilities. Through an analysis of data from ex vivo drug screens of 114 primary AML samples, we discovered that -7/-7q AML cells are highly sensitive to the inhibition of nicotinamide phosphoribosyltransferase (NAMPT). NAMPT is the rate-limiting enzyme in the nicotinamide adenine dinucleotide salvage pathway. Mechanistically, the NAMPT gene is located at 7q22.3, and deletion of 1 copy due to -7/-7q results in NAMPT haploinsufficiency, leading to reduced expression and a therapeutically targetable vulnerability to the inhibition of NAMPT. Our results show that in -7/-7q AML, differentiated CD34+CD38+ myeloblasts are more sensitive to the inhibition of NAMPT than less differentiated CD34+CD38– myeloblasts. Furthermore, the combination of the BCL2 inhibitor venetoclax and the NAMPT inhibitor KPT-9274 resulted in the death of significantly more leukemic blasts in AML samples with -7/-7q than the NAMPT inhibitor alone. In conclusion, our findings demonstrate that AML with -7/-7q is highly sensitive to NAMPT inhibition, suggesting that NAMPT inhibitors have the potential to be an effective targeted therapy for patients with monosomy 7 or del(7q).

Discovery of Dual Function Agents That Exhibit Anticancer Activity via Catastrophic Nicotinamide Adenine Dinucleotide Depletion.

Nicotinamide adenine dinucleotide (NAD) is essentially involved in many biological processes of cancer cells, yet chemical intervention of NAD biosynthesis failed to obtain an optimal therapeutic benefit. We herein developed a new strategy to induce catastrophic NAD depletion by concurrently impairing NAD synthesis and promoting NAD consumption. We designed a series of new compounds that conjugate an inhibitor of nicotinamide phosphoribosyltransferase (NAMPT), a rate-limiting enzyme in the NAD salvage pathway, with a DNA-alkylating agent. Among them, compound 11b exhibited potent anticancer efficacy in cancer cell lines and mouse tumor models with intrinsic resistance to the parent compound FK866 or chlorambucil. Compound 11b caused catastrophic NAD depletion via a synergistic effect between the NAD salvage pathway blockade and DNA damage-triggered NAD consumption. Our findings suggest a new intervention strategy for causing catastrophic NAD depletion in cancer cells and provide basis for the development of new inhibitors targeting NAD metabolism.

A novel role for astrocytic fragmented mitochondria in regulating morphine addiction

Chronic morphine exposure causes the development of addictive behaviors, accompanied by an increase in neuroinflammation in the central nervous system. While previous researches have shown that astrocytes contribute to brain diseases, the role of astrocyte in morphine addiction through induced neuroinflammation remain unexplored. Here we show that morphine-induced inflammation requires the crosstalk among neuron, astrocyte, and microglia. Specifically, astrocytes respond to morphine-induced neuronal activation by increasing glycolytic metabolism. The dysregulation of glycolysis leads to an increased in the generation of mitochondrial reactive oxygen species and causes excessive mitochondrial fragmentation in astrocytes. These fragmented, dysfunctional mitochondria are consequently released into extracellular environment, leading to activation of microglia and release of inflammatory cytokines. We also found that blocking the nicotinamide adenine dinucleotide salvage pathway with FK866 could inhibit astrocytic glycolysis and restore the mitochondrial homeostasis and effectively attenuate neuroinflammatory responses. Importantly, FK866 reversed morphine-induced addictive behaviors in mice. In summary, our findings illustrate an essential role of astrocytic immunometabolism in morphine induced neural and behavioral plasticity, providing a novel insight into the interactions between neurons, astrocytes, and microglia in the brain affected by chronic morphine exposure.

Novel carbon skeletons activate human NicotinAMide Phosphoribosyl Transferase (NAMPT) enzyme in biochemical assay.

Nicotinamide adenine dinucleotide (NAD) is a central molecule in cellular metabolism that has been implicated in human health, the aging process, and an array of human diseases. NAD is well known as an electron storage molecule, cycling between NAD and the reduced NADH. In addition, NAD is cleaved into nicotinamide and Adenine diphosphate ribose by NAD-consuming enzymes such as sirtuins, PARPs and CD38. There are numerous pathways for the biosynthesis of NAD to maintain a baseline concentration and thus avoid cellular death. The NAD salvage pathway, a two-step process to regenerate NAD after cleavage, is the predominant pathway for humans. Nicotinamide PhosphribosylTransferase (NAMPT) is the rate-limiting enzyme within the salvage path. Exposure to pharmacological modulators of NAMPT has been reported to either deplete or increase NAD levels. This study used a curated set of virtual compounds coupled with biochemical assays to identify novel activators of NAMPT. Autodock Vina generated a ranking of the National Cancer Institute's Diversity Set III molecular library. The library contains a set of organic molecules with diverse functional groups and carbon skeletons that can be used to identify lead compounds. The target NAMPT surface encompassed a novel binding location that included the NAMPT dimerization plane, the openings to the two active site channels, and a portion of the known binding location for NAMPT substrate and product. Ranked molecules were evaluated in a biochemical assay using purified recombinant NAMPT enzyme. Two novel carbon skeletons were confirmed to stimulate NAMPT activity. Compound 20 (NSC9037) is a polyphenolic xanthene derivative in the fluorescein family, while compound 2 (NSC19803) is the polyphenolic myricitrin nature product. Micromolar quantities of compound 20 or compound 2 can double NAMPT's product formation. In addition, natural products that contain high concentrations of polyphenolic flavonoids, similar to myricitrin, also stimulate NAMPT activity. Confirmation of a novel binding site for these compounds will further our understanding of the cellular mechanism leading to NAD homeostasis and better human health outcomes.

Affinity-based protein profiling-driven discovery of myricanol as a Nampt activator

Herein, we synthesized an affinity-based probe of myricanol (pMY) with a photo-affinity cross-linker to initiate a bioconjugation reaction, which was applied for target identification in live C2C12 myotubes. Pull-down of biotinylated pMY coupled with mass spectroscopy and Western blotting revealed that pMY can bind with nicotinamide phosphoribosyltransferase (Nampt), a rate-limiting enzyme in the nicotinamide adenine dinucleotide salvage pathway. Cellular thermal shift assay, drug affinity responsive target stability assay and recombinant protein labeling further validated the direct interaction between myricanol and Nampt. Myricanol did not affect the protein expression of Nampt, but enhanced its activity. Knock-down of Nampt totally abolished the promoting effect of myricanol on insulin-stimulated glucose uptake in C2C12 myotubes. Taken together, myricanol sensitizes insulin action in myotubes through binding with and activating Nampt.

NAD salvage pathway machinery expression in normal and glaucomatous retina and optic nerve

Glaucoma is the leading cause of irreversible blindness and is a major health and economic burden. Current treatments do not address the neurodegenerative component of glaucoma. In animal models of glaucoma, the capacity to maintain retinal nicotinamide adenine dinucleotide (NAD) pools declines early during disease pathogenesis. Treatment with nicotinamide, an NAD precursor through the NAD salvage pathway, robustly protects against neurodegeneration in a number of glaucoma models and improves vision in existing glaucoma patients. However, it remains unknown in humans what retinal cell types are able to process nicotinamide to NAD and how these are affected in glaucoma. To address this, we utilized publicly available RNA-sequencing data (bulk, single cell, and single nucleus) and antibody labelling in highly preserved enucleated human eyes to identify expression of NAD synthesizing enzyme machinery. This identifies that the neural retina favors expression of the NAD salvage pathway, and that retinal ganglion cells are particularly enriched for these enzymes. NMNAT2, a key terminal enzyme in the salvage pathway, is predominantly expressed in retinal ganglion cell relevant layers of the retina and declines in glaucoma. These findings suggest that human retinal ganglion cells can directly utilize nicotinamide and could maintain a capacity to do so in glaucoma, showing promise for ongoing clinical trials.

Discovery of small-molecule activators of nicotinamide phosphoribosyltransferase (NAMPT) and their preclinical neuroprotective activity.

The decline of nicotinamide adenine dinucleotide (NAD) occurs in a variety of human pathologies including neurodegeneration. NAD-boosting agents can provide neuroprotective benefits. Here, we report the discovery and development of a class of potent activators (NATs) of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the NAD salvage pathway. We obtained the crystal structure of NAMPT in complex with the NAT, which defined the allosteric action of NAT near the enzyme active site. The optimization of NAT further revealed the critical role of K189 residue in boosting NAMPT activity. NATs effectively increased intracellular levels of NAD and induced subsequent metabolic and transcriptional reprogramming. Importantly, NATs exhibited strong neuroprotective efficacy in a mouse model of chemotherapy-induced peripheral neuropathy (CIPN) without any overt toxicity. These findings demonstrate the potential of NATs in the treatment of neurodegenerative diseases or conditions associated with NAD level decline.

Nicotinamide phosphoribosyltransferase (Nampt) of hybrid crucian carp protects intestinal barrier and enhances host immune defense against bacterial infection

Nicotinamide phosphoribosyltransferase (Nampt) can act extracellularly as a mediator of inflammation or intracellularly as a rate-limiting enzyme, regulating nicotinamide adenine dinucleotide (NAD) biosynthesis in the NAD salvage pathway. Nampt exerts important immunological functions during infection in mammals. However, the in vivo function of fish Nampt in immune regulation and inflammation is essentially unknown. With an aim to elucidate the antimicrobial mechanism of Nampt in fish, we in this study examined the function of Nampt from hybrid crucian carp. Hybrid crucian carp Nampt (WR-Nampt) possesses the conserved nicotinamide phosphoribosyltransferase domain and shows high similarity to that of mammalian Nampt. WR-Nampt is expressed in multiple tissues and is upregulated by bacterial infection. Overexpression of WR-Nampt significantly increased the number of goblet cells of distal intestine. In addition, WR-Nampt induced significant inductions in the expression of the antimicrobial molecules (IL-22, Hepcidin-1, LEAP-2 and MUC2) and tight junctions (ZO-1 and Occludin). Consistent with this, fish administered with WR-Nampt significantly alleviated the intestinal permeability and apoptosis, thereby enhancing host's resistance against bacterial infection. Together these results revealed the potential effect of WR-Nampt in intestinal barrier and immune defense against bacterial infection.

Overexpression of nicotinamidase 3 (NIC3) gene and the exogenous application of nicotinic acid (NA) enhance drought tolerance and increase biomass in Arabidopsis.

Overexpressing Nicotinamidase 3 gene, and the exogenous application of its metabolite nicotinic acid (NA), enhance drought stress tolerance and increase biomass in Arabidopsis thaliana. With progressive global climatic changes, plant productivity is threatened severely by drought stress. Deciphering the molecular mechanisms regarding genes responsible for balancing plant growth and stress amelioration could imply multiple possibilities for future sustainable goals. Nicotinamide adenine dinucleotide (NAD) biosynthesis and recycling/ distribution is a crucial feature for plant growth. The current study focuses on the functional characterization ofnicotinamidase 3(NIC3) gene, which is involved in the biochemical conversion of nicotinamide (NAM) to nicotinic acid (NA) in the salvage pathway of NAD biosynthesis. Our data show that overexpression of NIC3geneenhances drought stress tolerance and increases plant growth. NIC3-OX plants accumulated more NA as compared to WT plants. Moreover, the upregulation of several genes related to plant growth/stress tolerance indicates that regulating the NAD salvage pathway could significantly enhance plant growth and drought stress tolerance. The exogenous application of nicotinic acid (NA) showed a similar phenotype as the effect of overexpressing NIC3gene. In short, we contemplated the role of NIC3gene and NA application in drought stress tolerance and plant growth. Our results would be helpful in engineering plants with enhanced drought stress tolerance and increased growth potential.

Depleting adenine to prime for apoptosis

Cancer Triple-negative breast cancer (TNBC) is difficult to treat. Daniels et al. identified a metabolic vulnerability in TNBC patient cells and cell lines that may create a therapeutic opportunity for patients. The authors searched for metabolism-perturbing small-molecule compounds that sensitized TNBC lines to apoptosis induced by BH3 mimetics that block anti-apoptotic proteins. They found that inhibition of the rate-limiting enzyme of the nicotinamide adenine dinucleotide salvage pathway, specifically the loss of adenine downstream of inhibition, primed TNBC cells for apoptotic death. Sci. Signal. 14 , eabc7405 (2021).

NAD+ depletion by type I interferon signaling sensitizes pancreatic cancer cells to NAMPT inhibition

Emerging evidence suggests that intratumoral interferon (IFN) signaling can trigger targetable vulnerabilities. A hallmark of pancreatic ductal adenocarcinoma (PDAC) is its extensively reprogrammed metabolic network, in which nicotinamide adenine dinucleotide (NAD) and its reduced form, NADH, are critical cofactors. Here, we show that IFN signaling, present in a subset of PDAC tumors, substantially lowers NAD(H) levels through up-regulating the expression of NAD-consuming enzymes PARP9, PARP10, and PARP14. Their individual contributions to this mechanism in PDAC have not been previously delineated. Nicotinamide phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme in the NAD salvage pathway, a dominant source of NAD in cancer cells. We found that IFN-induced NAD consumption increased dependence upon NAMPT for its role in recycling NAM to salvage NAD pools, thus sensitizing PDAC cells to pharmacologic NAMPT inhibition. Their combination decreased PDAC cell proliferation and invasion in vitro and suppressed orthotopic tumor growth and liver metastases in vivo.

Abstract 6045: Interferon signaling induces NAD(H) consumption via PARP9/10/14 and sensitizes pancreatic cancer cells to NAMPT inhibition

Abstract Interferons (IFNs) are critical cytokines which, in the tumor microenvironment, have the potential to trigger targetable vulnerabilities. Pancreatic ductal adenocarcinoma (PDAC) has an extensively reprogrammed metabolic network in which nicotinamide adenine dinucleotide (NAD) is required as a co-factor for critical cell processes. NAMPT is the rate-limiting enzyme in the NAD salvage pathway, which is the dominant source of NAD in cancer cells. Findings from clinical trials with NAMPT inhibitors (NAMPTi) suggest the need to identify patient subsets that are highly sensitive to NAD depletion. An NAD assay was used to profile the effect of type I IFN signaling and NAMPTi on NAD levels in a panel of 12 human PDAC models. The effect of this NAD reduction was profiled in vitro with cell proliferation and mitochondrial respiration assays, Incucyte cell imaging, and flow cytometry for DNA damage (pH2A.X assay) and apoptosis (Annexin V assay). After confirmation of the synergy between IFN signaling and NAMPTi, a high throughput screen was performed to identify drugs that are potentiated by reduced NAD levels. Inhibition of PDAC proliferation and induction of DNA damage and apoptosis with the combination treatment was validated in vitro using the same assays previously described. In vivo studies were then performed with orthotopic tumor models (with Luciferase labeling for bioluminescence imaging) and patient-derived xenograft (PDX) models. We found that IFN signaling, present in a subset of PDAC tumors, substantially lowered NAD(H) levels through upregulating the expression of NAD consuming enzymes PARP9, PARP10, and PARP14. IFN and NAMPTi collaboratively reduced NAD levels in PDAC cells, inhibited PDAC cell proliferation and invasion in vitro, and suppressed orthotopic PDAC tumor growth and liver metastasis in vivo. We then identified clinical oncology drugs more potent in PDAC cells with lower NAD levels induced by IFN and NAMPTi, which included DNA-damaging compounds Gemcitabine (GEM) and Paclitaxel (PTX). Mechanistically, the NAD-dependent PARP family members are critical in DNA repair. Their activity can be monitored by measuring PAR abundance, which was substantially reduced by IFNβ and NAMPTi with and without the GEM/PTX combination. NAD(H) reduction and GEM/PTX collaboratively enhanced phosphorylation of CHEK2, a marker of DNA damage response, and triggered PDAC cell apoptosis. All of these findings were rescued by nicotinamide riboside (NR) supplementation (which bypasses the need for rate-limiting NAMPT in NAD synthesis), validating that these findings were due to the effect of on-target NAD(H) reduction. Our findings predict that using PARP9/10/14 as biomarkers will allow the identification of PDAC patients whose tumors have relatively low NAD(H) levels, which we hypothesize would render them vulnerable to combination therapies with NAMPTi and DNA damaging agents. Citation Format: Alexandra M. Moore, Lei Zhou, Shili Xu, Timothy R. Donahue. Interferon signaling induces NAD(H) consumption via PARP9/10/14 and sensitizes pancreatic cancer cells to NAMPT inhibition [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6045.

Bacteria Boost Mammalian Host NAD Metabolism by Engaging the Deamidated Biosynthesis Pathway

Nicotinamide adenine dinucleotide (NAD), a cofactor for hundreds of metabolic reactions in all cell types, plays an essential role in metabolism, DNA repair, and aging. However, how NAD metabolism is impacted by the environment remains unclear. Here, we report an unexpected trans-kingdom cooperation between bacteria and mammalian cells wherein bacteria contribute to host NAD biosynthesis. Bacteria confer resistance to inhibitors of NAMPT, the rate-limiting enzyme in the amidated NAD salvage pathway, in cancer cells and xenograft tumors. Mechanistically, a microbial nicotinamidase (PncA) that converts nicotinamide to nicotinic acid, a precursor in the alternative deamidated NAD salvage pathway, is necessary and sufficient for this protective effect. Using stable isotope tracing and microbiota-depleted mice, we demonstrate that this bacteria-mediated deamidation contributes substantially to the NAD-boosting effect of oral nicotinamide and nicotinamide riboside supplementation in several tissues. Collectively, our findings reveal an important role of bacteria-enabled deamidated pathway in host NAD metabolism.

Targeting NAD immunometabolism limits severe graft-versus-host disease and has potent antileukemic activity.

Acute graft-versus-host disease (aGVHD) and tumor relapse remain major complications after allogeneic hematopoietic stem cell transplantation. Alloreactive T cells and cancer cells share a similar metabolic phenotype to meet the bioenergetic demands necessary for cellular proliferation and effector functions. Nicotinamide adenine dinucleotide (NAD) is an essential co-factor in energy metabolism and is constantly replenished by nicotinamide phosphoribosyl-transferase (Nampt), the rate-limiting enzyme in the NAD salvage pathway. Here we show, that Nampt blockage strongly ameliorates aGVHD and limits leukemic expansion. Nampt was highly elevated in serum of patients with gastrointestinal GVHD and was particularly abundant in human and mouse intestinal T cells. Therapeutic application of the Nampt small-molecule inhibitor, Fk866, strongly attenuated experimental GVHD and caused NAD depletion in T-cell subsets, which displayed differential susceptibility to NAD shortage. Fk866 robustly inhibited expansion of alloreactive but not memory T cells and promoted FoxP3-mediated lineage stability in regulatory T cells. Furthermore, Fk866 strongly reduced the tumor burden in mouse leukemia and graft-versus-leukemia models. Ex vivo studies using lymphocytes from GVHD patients demonstrated potent antiproliferative properties of Fk866, suggesting potential clinical utility. Thus, targeting NAD immunometabolism represents a novel approach to selectively inhibit alloreactive T cells during aGVHD with additional antileukemic efficacy.

Suppression of nicotinamide phosphoribosyltransferase expression by miR-154 reduces the viability of breast cancer cells and increases their susceptibility to doxorubicin

BackgroundNicotinamide phosphoribosyltransferase (NAMPT) enzyme acts as the major enzyme in the nicotinamide adenine dinucleotide (NAD) synthesis salvage pathway. Deregulation of NAD could be associated with progression of several cancers such as breast cancer. Here, the consequence of NAMPT inhibition by miR-154 was investigated on breast cancer cells.MethodsMDA-MB-231 and MCF-7 cancer cell lines were transfected with the mimic and inhibitors of miR-154-5p and their corresponding negative controls. Consequently, levels of NAMPT and NAD were assayed employing qRT-PCR, Western blotting and enzymatic method, respectively. Subsequently, flow cytometry and colorimetric methods were performed to evaluate apoptosis and cell viability. Bioinformatics analyses as well as luciferase assay were done to investigate whether the 3′-UTR of NAMPT is directly targeted by miR-154.ResultsAccording to the obtained results, NAMPT was recognized as a target for binding of miR-154 and the levels of this miRNA was inversely associated with both mRNA and protein levels of NAMPT in breast cancer cell lines. Functionally, miR-154 inhibited the NAD salvage pathway leading to a remarkable decrease in cell viability and increased rate of cell death. When breast cancer cells were simultaneously treated with doxorubicin and miR-154 mimic, cell viability was considerably reduced compared to treatment with doxorubicin alone in both cell lines.ConclusionsIt was concluded that the inhibition of NAD production by miR-154 might be introduced as an appropriate therapeutic approach in order to improve breast cancer outcome either alone or in combination with other conventional chemotherapeutic agents.

Reconstitution of Organismal Liver Clock Function Requires Light

Recently Koronowski et al. (Cell, 2019) showed that reconstitution of the liver circadian clock in otherwise genetically arrhythmic mice revives the daily program of the nicotinamide adenine dinucleotide salvage pathway and glycogenesis in vivo. This liver-autonomous metabolic cycling cannot be sustained under constant darkness, revealing the importance of the daily light cycle to restore liver function.

Nicotinamide Riboside, an NAD + Precursor, Reduces Hepatic Stellate Cell Activation and Attenuates Liver Fibrosis in a Diet-induced Mouse Model of Liver Fibrosis (OR24-06-19)

ObjectivesThere is limited pharmacological treatment for liver fibrosis, which can result from chronic liver injury. In this study, we investigated the effect of nicotinamide riboside (NR), a nicotinamide adenine dinucleotide (NAD) precursor, on the development of liver fibrosis in a diet-induced mouse model of liver fibrosis in vivo and in hepatic stellate cells (HSCs) in vitro. MethodsMale C57BL/6 J mice were randomly assigned to three groups: a low-fat control (LF; 6% fat by wt), a high-fat/high-sucrose/high-cholesterol control (HF; 35%/34%/2.0% by wt, n = 13) or a HF diet supplemented with NR at 400 mg/kg/day (HF-NR, n = 14) for 20 weeks. Features of liver fibrosis were assessed by molecular, histological, and biochemical analyses to determine the effect of NR. Metabolic rates, energy expenditure and physical activity were measured using indirect calorimetry. Primary mouse and human HSCs, the primary extracellular matrix-producing cell-type in the liver, were used to determine the anti-fibrogenic effects of NR in vitro. ResultsHF-NR group had reduced body weight gain, which was attributable to increased energy expenditure. NR supplementation did not affect serum alanine aminotransferase levels and markers of steatosis and inflammation in the liver. However, liver trichrome and picrosirius red staining and total collagen quantification showed significant reductions of collagen by NR. Consistently, hepatic collagen 1a1 mRNA and protein were significantly reduced in the HF-NR group. Liver NAD levels were significantly reduced by HF, but was increased by NR supplementation. RNA-Seq analysis of NAD metabolism genes in quiescent and activated HSCs indicated that NAD levels might be reduced in activated HSCs due to repression of NAD salvage pathway, which regenerates NAD from nicotinamide. Indeed, treatment of primary human and mouse HSCs with NR significantly reduced their activation in vitro. ConclusionsNR supplementation prevented the development of liver fibrosis in a diet-induced mouse model of liver fibrosis independent of hepatic steatosis and inflammation. The data suggest that NR may directly reduce HSC activation to exert its anti-fibrotic effect. NR may be developed as a potential preventative for human liver fibrosis. Funding SourcesThe NIH, USDA Multistate Hatch, and USDA Hatch.