Activation of nicotinamide N-methyltrasferase and increased formation of 1-methylnicotinamide (MNA) in atherosclerosis

Lipopolysaccharide affects energy metabolism and elevates nicotinamide N-methyltransferase level in human aortic endothelial cells (HAEC)

This study aimed to investigate the putative role of nicotinamide N-methyltransferase in the metabolic response of human aortic endothelial cells. This enzyme catalyses S-adenosylmethionine-mediated methylation of nicotinamide to methylnicotinamide. This reaction is accompanied by the reduction of the intracellular nicotinamide and S-adenosylmethionine content. This may affect NAD⁺ synthesis and various processes of methylation, including epigenetic modifications of chromatin. Particularly high activity of nicotinamide N-methyltransferase is detected in liver, many neoplasms as well as in various cells in stressful conditions. The elevated nicotinamide N-methyltransferase content was also found in endothelial cells treated with statins. Although the exogenous methylnicotinamide has been postulated to induce a vasodilatory response, the specific metabolic role of nicotinamide N-methyltransferase in vascular endothelium is still unclear. Treatment of endothelial cells with bacterial lipopolysaccharide evokes several metabolic and functional consequences which built a multifaceted physiological response of endothelium to bacterial infection. Among the spectrum of biochemical changes substantially elevated protein level of nicotinamide N-methyltransferase was particularly intriguing. Here it has been shown that silencing of the nicotinamide N-methyltransferase gene influences several changes which are observed in cells treated with lipopolysaccharide. They include altered energy metabolism and rearrangement of the mitochondrial network. A complete explanation of the mechanisms behind the protective consequences of the nicotinamide N-methyltransferase deficiency in cells treated with lipopolysaccharide needs further investigation.

Therapeutic Potential of Emerging NAD+-Increasing Strategies for Cardiovascular Diseases

Cardiovascular diseases are the leading cause of death worldwide. Aging and/or metabolic stress directly impact the cardiovascular system. Over the last few years, the contributions of altered nicotinamide adenine dinucleotide (NAD+) metabolism to aging and other pathological conditions closely related to cardiovascular diseases have been intensively investigated. NAD+ bioavailability decreases with age and cardiometabolic conditions in several mammalian tissues. Compelling data suggest that declining tissue NAD+ is commonly related to mitochondrial dysfunction and might be considered as a therapeutic target. Thus, NAD+ replenishment by either genetic or natural dietary NAD+-increasing strategies has been recently demonstrated to be effective for improving the pathophysiology of cardiac and vascular health in different experimental models, as well as human health, to a lesser extent. Here, we review and discuss recent experimental evidence illustrating that increasing NAD+ bioavailability, particularly by the use of natural NAD+ precursors, may offer hope for new therapeutic strategies to prevent and treat cardiovascular diseases.

Nicotinamide N-Methyltransferase: An Emerging Protagonist in Cancer Macro(r)evolution

Nicotinamide N-methyltransferase (NNMT) has progressed from being considered merely a Phase II metabolic enzyme to one with a central role in cell function and energy metabolism. Over the last three decades, a significant body of evidence has accumulated which clearly demonstrates a central role for NNMT in cancer survival, metastasis, and drug resistance. In this review, we discuss the evidence supporting a role for NNMT in the progression of the cancer phenotype and how it achieves this by driving the activity of pro-oncogenic NAD+-consuming enzymes. We also describe how increased NNMT activity supports the Warburg effect and how it promotes oncogenic changes in gene expression. We discuss the regulation of NNMT activity in cancer cells by both post-translational modification of the enzyme and transcription factor binding to the NNMT gene, and describe for the first time three long non-coding RNAs which may play a role in the regulation of NNMT transcription. We complete the review by discussing the development of novel anti-cancer therapeutics which target NNMT and provide insight into how NNMT-based therapies may be best employed clinically.

The Utility of Nicotinamide N-Methyltransferase as a Potential Biomarker to Predict the Oncological Outcomes for Urological Cancers: An Update

Nicotinamide N-methyltransferase (NNMT) catalyzes the N-methylation reaction of nicotinamide, using S-adenosyl-L-methionine as the methyl donor. Enzyme overexpression has been described in many non-neoplastic diseases, as well as in a wide range of solid malignancies. This review aims to report and discuss evidence available in scientific literature, dealing with NNMT expression and the potential involvement in main urologic neoplasms, namely, renal, bladder and prostate cancers. Data illustrated in the cited studies clearly demonstrated NNMT upregulation (pathological vs. normal tissue) in association with these aforementioned tumors. In addition to this, enzyme levels were also found to correlate with key prognostic parameters and patient survival. Interestingly, NNMT overexpression also emerged in peripheral body fluids, such as blood and urine, thus leading to candidate the enzyme as promising biomarker for the early and non-invasive detection of these cancers. Examined results undoubtedly showed NNMT as having the capacity to promote cell proliferation, migration and invasiveness, as well as its potential participation in fundamental events highlighting cancer progression, metastasis and resistance to chemo- and radiotherapy. In the light of this evidence, it is reasonable to attribute to NNMT a promising role as a potential biomarker for the diagnosis and prognosis of urologic neoplasms, as well as a molecular target for effective anti-cancer treatment.

Nicotinamide N-methyltransferase in endothelium protects against oxidant stress-induced endothelial injury

Nicotinamide N-methyltransferase (NNMT, EC 2.1.1.1.) plays an important role in the growth of many different tumours and is also involved in various non-neoplastic disorders. However, the presence and role of NNMT in the endothelium has yet to be specifically explored. Here, we characterized the functional activity of NNMT in the endothelium and tested whether NNMT regulates endothelial cell viability. NNMT in endothelial cells (HAEC, HMEC-1 and EA.hy926) was inhibited using two approaches: pharmacological inhibition of the enzyme by NNMT inhibitors (5-amino-1-methylquinoline - 5MQ and 6-methoxynicotinamide - JBSF-88) or by shRNA-mediated silencing. Functional inhibition of NNMT was confirmed by LC/MS/MS-based analysis of impaired MNA production. The effects of NNMT inhibition on cellular viability were analyzed in both the absence and presence of menadione. Our results revealed that all studied endothelial lines express relatively high levels of functionally active NNMT compared with cancer cells (MDA-MB-231). Although the aldehyde oxidase 1 enzyme was also expressed in the endothelium, the further metabolites of N1-methylnicotinamide (N1-methyl-2-pyridone-5-carboxamide and N1-methyl-4-pyridone-3-carboxamide) generated by this enzyme were not detected, suggesting that endothelial NNMT-derived MNA was not subsequently metabolized in the endothelium by aldehyde oxidase 1. Menadione induced a concentration-dependent decrease in endothelial viability as evidenced by a decrease in cell number that was associated with the upregulation of NNMT and SIRT1 expression in the nucleus in viable cells. The suppression of the NNMT activity either by NNMT inhibitors or shRNA-based silencing significantly decreased the endothelial cell viability in response to menadione. Furthermore, NNMT inhibition resulted in nuclear SIRT1 expression downregulation and upregulation of the phosphorylated form of SIRT1 on Ser47. In conclusion, our results suggest that the endothelial nuclear NNMT/SIRT1 pathway exerts a cytoprotective role that safeguards endothelial cell viability under oxidant stress insult.

A derivative of vitamin B3 applied several days after exposure reduces lethality of severely irradiated mice

Most, if not all, of the hitherto tested substances exert more or less pronounced pro-survival effects when applied before or immediately after the exposure to high doses of ionizing radiation. In the present study we demonstrate for the first time that 1-methyl nicotinamide (MNA), a derivative of vitamin B3, significantly (1.6 to 1.9 times) prolonged survival of BALB/c mice irradiated at LD30/30 (6.5 Gy), LD50/30 (7.0 Gy) or LD80/30 (7.5 Gy) of γ-rays when the MNA administration started as late as 7 days post irradiation. A slightly less efficient and only after the highest dose (7.5 Gy) of γ-rays was another vitamin B3 derivative, 1-methyl-3-acetylpyridine (1,3-MAP) (1.4-fold prolonged survival). These pro-survival effects did not seem to be mediated by stimulation of haematopoiesis, but might be related to anti-inflammatory and/or anti-thrombotic properties of the vitamin B3 derivatives. Our results show that MNA may represent a prototype of a radioremedial agent capable of mitigating the severity and/or progression of radiation-induced injuries when applied several hours or days after exposure to high doses of ionizing radiation.

Multi-omic signatures of atherogenic dyslipidaemia: pre-clinical target identification and validation in humans

BACKGROUND

Dyslipidaemia is a major risk factor for atherosclerosis and cardiovascular diseases. The molecular mechanisms that translate dyslipidaemia into atherogenesis and reliable markers of its progression are yet to be fully elucidated. To address this issue, we conducted a comprehensive metabolomic and proteomic analysis in an experimental model of dyslipidaemia and in patients with familial hypercholesterolemia (FH).

METHODS

Liquid chromatography/mass spectrometry (LC/MS) and immunoassays were used to find out blood alterations at metabolite and protein levels in dyslipidaemic ApoE^-/-/LDLR^-/- mice and in FH patients to evaluate their human relevance.

RESULTS

We identified 15 metabolites (inhibitors and substrates of nitric oxide synthase (NOS), low-molecular-weight antioxidants (glutamine, taurine), homocysteine, methionine, 1-methylnicotinamide, alanine and hydroxyproline) and 9 proteins (C-reactive protein, proprotein convertase subtilisin/kexin type 9, apolipoprotein C-III, soluble intercellular adhesion molecule-1, angiotensinogen, paraoxonase-1, fetuin-B, vitamin K-dependent protein S and biglycan) that differentiated FH patients from healthy controls. Most of these changes were consistently found in dyslipidaemic mice and were further amplified if mice were fed an atherogenic (Western or low-carbohydrate, high-protein) diet.

CONCLUSIONS

The alterations highlighted the involvement of an immune-inflammatory response system, oxidative stress, hyper-coagulation and impairment in the vascular function/regenerative capacity in response to dyslipidaemia that may also be directly engaged in development of atherosclerosis. Our study further identified potential biomarkers for an increased risk of atherosclerosis that may aid in clinical diagnosis or in the personalized treatment.

N1-Methylnicotinamide: An Anti-Ovarian Aging Hormetin?

Ovarian aging occurs due to the reduction of the quality and quantity of the oocytes, and is regulated by mitochondrial survival and apoptotic signals. Reactive Oxygen Species (ROS) are one of those signals considered detrimental to cellular homeostasis. Nowadays, ROS are regarded as a regulatory factor at low levels as it induces the stress resistance which in turn increases the longevity. It is believed that the main mechanism for the life-promoting role of the ROS mediated by the 5' Adenosine Monophosphate-activated Protein Kinase (AMPK). N1-Methylnicotinamide (MNAM) is well known for its anti-diabetic, anti-thrombotic, and anti-inflammatory activity. Aldehyde oxidase 1 (AOX1) is a detoxifying enzyme, which metabolizes the MNAM and produces two metabolites including N1-methyl-2-pyridone-5- carboxamide (2py) and N1-methyl-4-pyridone-3-carboxamide (4py). The activity of AOX1 enhances the production of ROS and improves the longevity. It has been reported that the MNAM could postpone the aging through the induction of low-level stress. It has been documented that the production of MNAM is significantly higher in the cumulus cells of the patients with Polycystic Ovary Syndrome (PCOS) and its administration on the rat model of PCOS has been shown to alleviate the hyperandrogenism and successfully activate the ovarian AMPK. Therefore, it can be hypothesized that the anti-ovarian aging effects of the MNAM are possibly based on the activation of AMPK through transient elevation of the ROS.

Nicotinamide N-Methyltransferase: Genomic Connection to Disease

Single-nucleotide polymorphisms (SNPs) in and around the nicotinamide N-methyltransferase (NNMT) gene are associated with a range of cancers and other diseases and conditions. The data on these associations have been assembled, and their strength discussed. There is no evidence that the presence of either the major or minor base in any SNP affects the expression of nicotinamide N-methyltransferase. Nevertheless, suggestions have been put forward that some of these SNPs do affect NNMT expression and thus homocysteine metabolism. An alternative idea involving non-coding messenger RNAs (mRNAs) is suggested as a possible mechanism whereby health is influenced. It is postulated that these long, non-coding NNMT mRNAs may exert deleterious effects by interfering with the expression of other genes. Neither hypothesis, however, has experimental proof, and further work is necessary to elucidate NNMT genetic interactions.

Novel Propargyl-Linked Bisubstrate Analogues as Tight-Binding Inhibitors for Nicotinamide N-Methyltransferase

Nicotinamide N-methyltransferase (NNMT) catalyzes the methyl transfer from the cofactor S-adenosylmethionine to nicotinamide and other pyridine-containing compounds. NNMT is an important regulator for nicotinamide metabolism and methylation potential. Aberrant expression levels of NNMT have been implicated in cancer, metabolic, and neurodegenerative diseases, which makes NNMT a potential therapeutic target. Therefore, potent and selective NNMT inhibitors can serve as valuable tools to investigate the roles of NNMT in its mediated diseases. Here, we applied a rational strategy to design and synthesize the tight-binding bisubstrate inhibitor LL320 through a novel propargyl linker. LL320 demonstrates a Ki value of 1.6 ± 0.3 nM, which is the most potent inhibitor to date. The cocrystal structure of LL320 confirms its interaction with both the substrate and cofactor binding sites on NNMT. Importantly, this is the first example of using the propargyl linker to construct potent methyltransferase inhibitors, which will expand our understanding of the transition state of methyl transfer.

Niacin Protects against Butyrate-Induced Apoptosis in Rumen Epithelial Cells

The effects and underlying mechanisms of butyrate and butyrate+niacin on apoptosis in sheep rumen epithelial cells were investigated. Cells were exposed to butyrate (0-140 mM) for 6 h. A low concentration (20 mM) of butyrate increased cell viability and promoted growth whereas high concentrations (40-140 mM) inhibited proliferation. Cells were then cocultured with 120 mM butyrate and niacin (0-100 mM) for 6 h. Niacin addition attenuated butyrate-induced cellular damage and promoted proliferation at 20-80 mM; 40 mM presented the optimal effect. Higher concentrations (100 mM) of niacin resulted in low cell viability. Subsequent experiments confirmed that 120 mM butyrate increased intracellular reactive oxygen species (ROS) production and reduced the intracellular total antioxidant capacity (T-AOC) versus the untreated control. Compared with 120 mM butyrate, cotreatment with 40 mM niacin significantly reduced the intracellular ROS content and increased the intracellular T-AOC. Flow cytometry analysis revealed that 120 mM butyrate increased the proportion of apoptotic cells by 17.8% versus the untreated control, and 120 mM butyrate+40 mM niacin treatment reduced the proportion of apoptotic cells by 28.6% and 39.4% versus the untreated control and butyrate treatment, respectively. Treatment with 120 mM butyrate increased caspase-9 and p53 mRNA levels and decreased the expression of Bcl-2 and Bax, and the Bcl-2/Bax ratio versus the untreated control. Treatment with 120 mM butyrate+40 mM niacin downregulated the expression of caspase-3 and p53 and increased the expression of Bcl-2 and Bax versus butyrate treatment alone but had no effect on the Bcl-2/Bax ratio. Thus, high concentrations of butyrate may induce rumen epithelial cell apoptosis by increasing oxidative stress and inducing caspase-9 and p53 expression. Cotreatment with niacin regulates apoptosis-related gene expression by reducing intracellular ROS production and DNA damage and downregulating caspase-3 and p53 expressions to protect rumen epithelial cells against butyrate-induced apoptosis.

Comparison of Pulmonary and Systemic NO- and PGI2-Dependent Endothelial Function in Diabetic Mice

Diabetes increases the risk of pulmonary hypertension and is associated with alterations in pulmonary vascular function. Still, it is not clear whether alterations in the phenotype of pulmonary endothelium induced by diabetes are distinct, as compared to peripheral endothelium. In the present work, we characterized differences between diabetic complications in the lung and aorta in db/db mice with advanced diabetes. Male, 20-week-old db/db mice displayed increased HbA1c and glucose concentration compatible with advanced diabetes. Diabetic lungs had signs of mild fibrosis, and pulmonary endothelium displayed significantly ultrastructural changes. In the isolated, perfused lung from db/db mice, filtration coefficient (K_f,c) and contractile response to TXA₂ analogue were enhanced, while endothelial NO-dependent modulation of pulmonary response to hypoxic ventilation and cumulative production of NO₂⁻ were impaired, with no changes in immunostaining for eNOS expression. In turn, 6-keto-PGF_1α release from the isolated lung from db/db mice was increased, as well as immunostaining of thrombomodulin (CD141). In contrast to the lung, NO-dependent, acetylcholine-induced vasodilation, ionophore-stimulated NO₂⁻ generation, and production of 6-keto-PGF_1α were all impaired in aortic rings from db/db mice. Although eNOS immunostaining was not changed, that of CD141 was clearly lowered. Interestingly, diabetes-induced nitration of proteins in aorta was higher than that in the lungs. In summary, diabetes induced marked ultrastructural changes in pulmonary endothelium that were associated with the increased permeability of pulmonary microcirculation, impaired NO-dependent vascular function, with compensatory increase in PGI₂ production, and increased CD141 expression. In contrast, endothelial dysfunction in the aorta was featured by impaired NO-, PGI₂-dependent function and diminished CD141 expression.

N1-methylnicotinamide (MNAM) as a guardian of cardiovascular system

Atherosclerosis is identified as the formation of atherosclerotic plaques, which could initiate the formation of a blood clot in which its growth to coronary artery can lead to a heart attack. N-methyltransferase (NNMT) is an enzyme that converts the NAM (nicotinamide) to its methylated form, N1-methylnicotinamide (MNAM). Higher levels of MNAM have been reported in cases with coronary artery disease (CAD). Further, MNAM increases endothelial prostacyclin (PGI2) and nitric oxide (NO) and thereby causes vasorelaxation. The vasoprotective, anti-inflammatory and anti-thrombotic roles of MNAM have been well documented; however, the exact underlying mechanisms remain to be clarified. Due to potential role of MNAM in the formation of lipid droplets (LDs), it might exert its function in coordination with lipids, and their targets. In this study, we summarized the roles of MNAM in cardiovascular system and highlighted its possible mode of actions.

Covalent inhibitors of nicotinamide N-methyltransferase (NNMT) provide evidence for target engagement challenges in situ

Nicotinamide N-methyltransferase (NNMT) catalyzes the N-methylation of nicotinamide using S-adenosyl-L-methionine (SAM) as a methyl donor and, through doing so, can modulate cellular methylation potential to impact diverse epigenetic processes. NNMT has been implicated in a range of diseases, including cancer and metabolic disorders. Potent, selective, and cell-active inhibitors would constitute valuable probes to study the biological functions and therapeutic potential of NNMT. We previously reported the discovery of electrophilic small molecules that inhibit NNMT by reacting with an active-site cysteine residue in the SAM-binding pocket. Here, we have used activity-based protein profiling (ABPP)-guided medicinal chemistry to optimize the potency and selectivity of NNMT inhibitors, culminating in the discovery of multiple alpha-chloroacetamide (αCA) compounds with sub-µM IC₅₀ values in vitro and excellent proteomic selectivity in cell lysates. However, these compounds showed much weaker inhibition of NNMT in cells, a feature that was not shared by off-targets of the αCAs. Our results show the potential for developing potent and selective covalent inhibitors of NNMT, but also highlight challenges that may be faced in targeting this enzyme in cellular systems.

Nicotinamide N-methyltransferase: potential involvement in cutaneous malignant melanoma

Nicotinamide N-methyltransferase (NNMT) is an enzyme that catalyzes the N-methylation of nicotinamide and pyridine compounds, participating in xenobiotic and drug metabolism. Data on literature have evidenced a possible role of NNMT in many solid cancers, but no data are currently available in cutaneous melanoma. Recent important advances have been achieved in the treatment of advanced melanoma with targeted therapy and immunotherapy. However, the identification of biomarkers that can be used for the detection of early stage disease as well as for monitoring the therapeutic response during treatment is of utmost importance. The aim of this study was to study the possible role of NNMT in melanoma. In the present study, we carried out immunohistochemical analyses to evaluate the expression of the enzyme NNMT in 34 melanomas and 34 nevi. Moreover, we explored the relationship between NNMT levels and the prognostic parameters of patients with melanoma. The results obtained showed significantly (P<0.0001) higher NNMT expression in melanoma compared with that detected in nevi. In addition, a significant (P<0.05) inverse relationship was found between enzyme levels and Breslow thickness, Clark level, the presence/number of mitoses, and ulceration. Taken together, these data seem to suggest that NNMT could represent a molecular biomarker for melanoma, thus highlighting its potential for both diagnosis and prognosis of this neoplasm.

Clinical performance and utility of a NNMT-based urine test for bladder cancer

Background:

Bladder cancer (BC) represents the most common neoplasm of the urinary tract. Although cystoscopy and urine cytology represent the gold standard methods to monitor BC, both procedures have limitations. Therefore, the identification of reliable biomarkers for early and noninvasive detection of BC is urgently required.

Methods:

In this study, we analyzed nicotinamide N-methyltransferase (NNMT) expression in urine samples from 55 BC patients and 107 controls, using real-time polymerase chain reaction (PCR). Receiver operating characteristic (ROC) analysis was used to identify the best cutoff value to discriminate BC patients from healthy donors, and to evaluate the diagnostic accuracy of a urine-based NNMT test.

Results:

The results demonstrated that urinary NNMT expression was significantly (p<0.05) higher in BC patients. Moreover, a significant (p<0.05) inverse correlation was found between NNMT expression and histological grade. The ROC analysis revealed that a ΔCq of 13.3 was the best cutoff value, since it was associated with the highest combination of sensitivity and specificity. Moreover, the area under the curve (AUC) value was 0.913 (p<0.05), indicating the excellent diagnostic accuracy of a urine-based NNMT test.

Conclusions:

Our data indicate that NNMT is a promising biomarker that could be used to support the early and noninvasive diagnosis of BC.

Serum N1-Methylnicotinamide is Associated With Coronary Artery Disease in Chinese Patients

Background

We previously reported that serum N¹‐methylnicotinamide (me‐Nam), an indicator of nicotinamide N‐methyltransferase activity, is associated with obesity and diabetes mellitus in Chinese patients. However, whether nicotinamide N‐methyltransferase plays a role in human coronary artery disease (CAD) remains to be elucidated. We aim to investigate the associations of serum me‐Nam with CAD in Chinese patients.

Methods and Results

Serum me‐NAM was measured by liquid chromatography‐mass spectrometry in patients with (n=230) or without (n=103) CAD as defined by coronary angiography. The severity of CAD was expressed by number of diseased coronary arteries. Serum me‐Nam was higher (7.65 ng/mL versus 4.95 ng/mL, P<0.001) in patients with CAD than in those without. Serum me‐Nam was positively correlated with high‐sensitivity C‐reactive protein and negatively correlated with high‐density lipoprotein before and after adjustment for potential confounding variables (P≤0.002). In multivariable logistic regression analyses, compared with those in the lowest tertile of serum me‐NAM levels, patients in the top tertile had the highest risks for CAD (odds ratio, 4.21; 95% CI, 1.97–8.97 [P<0.001]). After adjustment for potential confounding variables, serum me‐NAM was also increased from 0‐ to 3‐vessel disease (P for trend=0.01).

Conclusions

Serum me‐Nam is strongly associated with presence and severity of CAD, suggesting nicotinamide N‐methyltransferase as a potential target for treating atherosclerosis in humans.

Copper oxide nanoparticle toxicity profiling using untargeted metabolomics

BACKGROUND

The rapidly increasing number of engineered nanoparticles (NPs), and products containing NPs, raises concerns for human exposure and safety. With this increasing, and ever changing, catalogue of NPs it is becoming more difficult to adequately assess the toxic potential of new materials in a timely fashion. It is therefore important to develop methods which can provide high-throughput screening of biological responses. The use of omics technologies, including metabolomics, can play a vital role in this process by providing relatively fast, comprehensive, and cost-effective assessment of cellular responses. These techniques thus provide the opportunity to identify specific toxicity pathways and to generate hypotheses on how to reduce or abolish toxicity.

RESULTS

We have used untargeted metabolome analysis to determine differentially expressed metabolites in human lung epithelial cells (A549) exposed to copper oxide nanoparticles (CuO NPs). Toxicity hypotheses were then generated based on the affected pathways, and critically tested using more conventional biochemical and cellular assays. CuO NPs induced regulation of metabolites involved in oxidative stress, hypertonic stress, and apoptosis. The involvement of oxidative stress was clarified more easily than apoptosis, which involved control experiments to confirm specific metabolites that could be used as standard markers for apoptosis; based on this we tentatively propose methylnicotinamide as a generic metabolic marker for apoptosis.

CONCLUSIONS

Our findings are well aligned with the current literature on CuO NP toxicity. We thus believe that untargeted metabolomics profiling is a suitable tool for NP toxicity screening and hypothesis generation.

Activation of the nicotinamide N-methyltransferase (NNMT)-1-methylnicotinamide (MNA) pathway in pulmonary hypertension

Background

Pulmonary arterial hypertension (PAH) is associated with inflammatory response but it is unknown whether it is associated with alterations in NNMT activity and MNA plasma concentration. Here we examined changes in NNMT-MNA pathway in PAH in rats and humans.

Methods

PAH in rats was induced by a single subcutaneous injection of MCT (60 mg/kg). Changes in NNMT activity in the lungs and liver (assessed as the rate of conversion of nicotinamide (NA) to MNA), changes in plasma concentration of MNA and its metabolites (analyzed by LC/MS) were analyzed in relation to PAH progression. PAH was characterized by right ventricular hypertrophy (gross morphology), cardiac dysfunction (by MRI), lung histopathology, lung ultrastructure, and ET-1 concentration in plasma. NO-dependent and PGI₂-dependent function in isolated lungs was analyzed. In naive patients with idiopathic pulmonary hypertension (IPAH) characterized by hemodynamic and biochemical parameters MNA and its metabolites in plasma were also measured.

Results

MCT-injected rats developed hypertrophy and functional impairment of the right ventricle, hypertrophy of the pulmonary arteries, endothelial ultrastructural defects and a progressive increase in ET-1 plasma concentration—findings all consistent with PAH development. In isolated lung, NO-dependent regulation of hypoxic pulmonary vasoconstriction was impaired, while PGI₂ production (6-keto-PGF_1α) was increased. NNMT activity increased progressively in the liver and in the lungs following MCT injection, and NNMT response was associated with an increase in MNA and 6-keto-PGF_1α concentration in plasma. In IPAH patients plasma concentration of MNA was elevated as compared with healthy controls.

Conclusions

Progression of pulmonary hypertension is associated with the activation of the NNMT-MNA pathway in rats and humans. Given the vasoprotective activity of exogenous MNA, which was previously ascribed to PGI₂ release, the activation of the endogenous NNMT-MNA pathway may play a compensatory role in PAH.

Urinary N-methylnicotinamide and β-aminoisobutyric acid predict catch-up growth in undernourished Brazilian children

Enteric infections, enteropathy and undernutrition in early childhood are preventable risk factors for child deaths, impaired neurodevelopment, and later life metabolic diseases. However, the mechanisms linking these exposures and outcomes remain to be elucidated, as do biomarkers for identifying children at risk. By examining the urinary metabolic phenotypes of nourished and undernourished children participating in a case-control study in Semi-Arid Brazil, we identified key differences with potential relevance to mechanisms, biomarkers and outcomes. Undernutrition was found to perturb several biochemical pathways, including choline and tryptophan metabolism, while also increasing the proteolytic activity of the gut microbiome. Furthermore, a metabolic adaptation was observed in the undernourished children to reduce energy expenditure, reflected by increased N-methylnicotinamide and reduced β-aminoisobutyric acid excretion. Interestingly, accelerated catch-up growth was observed in those undernourished children displaying a more robust metabolic adaptation several months earlier. Hence, urinary N-methylnicotinamide and β-aminoisobutyric acid represent promising biomarkers for predicting short-term growth outcomes in undernourished children and for identifying children destined for further growth shortfalls. These findings have important implications for understanding contributors to long-term sequelae of early undernutrition, including cognitive, growth, and metabolic functions.

Serum N(1)-Methylnicotinamide Is Associated With Obesity and Diabetes in Chinese

CONTEXT

Nicotinamide N-methyltransferase (NNMT) is a novel histone methylation modulator that regulates energy metabolism, and NNMT knockdown prevents diet-induced obesity in mice. However, whether NNMT plays a role in human obesity and type 2 diabetes (T2DM) remains to be elucidated.

OBJECTIVE

NNMT catalyzes methylation of nicotinamide to generate N(1)-methylnicotinamide (me-NAM). We aimed to investigate the associations of serum me-NAM with obesity and T2DM in Chinese.

DESIGN, SETTING, AND PARTICIPANTS

The study subjects (n = 1160) were recruited from Dali, a city of Yunnan Province, in southwest China. Anthropometric phenotypes, fasting glucose, and serum lipids were measured. Serum me-NAM was measured by liquid chromatography-mass spectrometry.

RESULTS

Serum me-NAM was positively correlated with body mass index and waist circumference and negatively with high-density lipoprotein (P ≤ .03). The correlations remained highly significant in the multivariate adjusted correlation analyses. In men (n = 691), positive correlations between me-NAM and fasting glucose, low-density lipoprotein, liver function, and serum creatinine levels were also observed in both simple and multivariate adjusted correlation analyses. In multiple logistic regression analyses, elevated serum me-NAM was associated with higher risks for overweight/obesity (odds ratios, 2.36 and 5.78; 95% confidence intervals, 1.10-5.08 and 1.78-18.76 for men and women, respectively; P ≤ .03) and diabetes (odds ratios, 1.56 and 1.86; 95% confidence intervals, 1.10-2.22 and 1.05-3.31 for men and women, respectively; P ≤ .03).

CONCLUSIONS

This first large-scale population study shows that me-NAM, as an indicator of NNMT activity, is strongly associated with obesity and diabetes, supporting NNMT as a potential target for treating obesity and diabetes in humans.

Extracellular nucleotide catabolism in aortoiliac bifurcation of atherosclerotic ApoE/LDLr double knock out mice

Atherosclerosis is a consequence of diverse pathologies that could be affected by signaling mediated by nucleotides and their metabolites. Concentration of specific nucleotide derivatives in the proximity of purinergic receptors is controlled by extracellular enzymes such as ecto-nucleoside triphopsphate diphosphohydrolase (eNTPD), ecto-5'-nucleotidase (e5NT), and ecto-adenosine deaminase (eADA). To estimate changes in metabolism of extracellular nucleotides in the atherosclerotic vessel wall, aortoiliac bifurcation of ApoE/LDLr (-/-) mice was perfused with solution containing adenosine-5'-triphosphate (ATP), adenosine-5'-monophosphate (AMP) or adenosine. Formation of the product of eNTPD, e5NT or eADA was measured by high performance liquid chromatography (HPLC). The most significant difference between ApoE/LDLr (-/-) and wild-type mice was several times higher rate of conversion of adenosine to inosine catalyzed by eADA activity. This highlights potential decrease in intravascular adenosine concentration in atherosclerosis.

Nicotinamide N-methyltransferase is overexpressed in prostate cancer and correlates with prolonged progression-free and overall survival times

Nicotinamide N -methyltransferase (NNMT) has been identified to be associated with tumorigenesis and the malignant transformation of numerous types of cancer. The aim of the present study was to explore the expression and prognostic significance of NNMT in prostate cancer (PCa). Immunohistochemical NNMT expression was examined in 26 cases of benign prostate hyperplasia (BPH), 18 cases of high-grade prostatic intraepithelial neoplasia (HGPIN) and 120 cases of PCa. While rarely expressed in BPH (8/26 cases; 30.8%), NNMT was found to be significantly upregulated in HGPIN (15/18 cases; 83.3%) and PCa (77/120 cases; 64.2%). Clinicopathological analysis revealed that NNMT expression was negatively correlated with Gleason score (P<0.001). Furthermore, Kaplan-Meier survival curves revealed that high NNMT expression was associated with prolonged progression-free survival (PFS) and overall survival (OS) times in patients with advanced PCa. Multivariate analysis showed that NNMT was an independent prognostic marker of PFS and OS in patients with advanced PCa. The results of the present study suggested that NNMT may contribute to the development of PCa and may potentially be a favorable prognostic marker for the survival of patients with advanced PCa.

Upregulation of tissue and urinary nicotinamide N-methyltransferase in bladder cancer: potential for the development of a urine-based diagnostic test

Carcinoma of the bladder is one of the most common urologic malignancies occurring worldwide. Diagnosis and monitoring of bladder urothelial carcinoma (UC) are based on cystoscopy and urinary cytology. However, these diagnostic methods still have some limitations, mainly related to invasive nature and lack of sensitivity. New reliable and non-invasive biomarkers for bladder cancer detection are therefore required. To explore the involvement of enzymes of drug metabolism in bladder cancer, in the present study, we analyzed the gene expression profiles of tumor and normal looking tissues obtained from the same patient by cDNA macroarray. The enzyme nicotinamide N-methyltransferase (NNMT) was identified as a highly expressed gene in bladder cancer. RT-PCR, Real-Time PCR, Western blot analysis, and catalytic activity assay, performed on a large cohort of patients with bladder UC, confirmed NNMT upregulation. NNMT mRNA and protein levels were also determined in urine specimens obtained from patients with bladder UC and healthy subjects. We found that NNMT expression levels were significantly higher in patients with bladder tumor compared to controls that showed very low or undetectable amounts of NNMT transcript and protein. Our results indicate that a marked NNMT increase is a peculiar feature of bladder UC and suggest the potential suitability of urine NNMT expression levels determination for early and non-invasive diagnosis of bladder cancer.

RNA-mediated gene silencing of nicotinamide N-methyltransferase is associated with decreased tumorigenicity in human oral carcinoma cells

Oral squamous cell carcinoma (OSCC) is the most common type of oral cancer. Despite progress in the treatment of OSCC, overall survival has not improved substantially in the last three decades. Therefore, identification of reliable biomarkers becomes essential to develop effective anti-cancer therapy. In this study, we focused on the enzyme Nicotinamide N-methyltransferase (NNMT), which plays a fundamental role in the biotransformation of many xenobiotics. Although several tumors have been associated with abnormal NNMT expression, its role in cancer cell metabolism remains largely unknown. In this report, 7 human oral cancer cell lines were examined for NNMT expression by Real-Time PCR, Western blot and HPLC-based catalytic assay. Subsequently, we evaluated the in vitro effect of shRNA-mediated silencing of NNMT on cell proliferation. In vivo tumorigenicity of oral cancer cells with stable knockdown of NNMT was assayed by using xenograft models. High expression levels of NNMT were found in PE/CA PJ-15 cells, in keeping with the results of Western blot and catalytic activity assay. PE/CA PJ-15 cell line was stably transfected with shRNA plasmids against NNMT and analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and soft agar Assays. Transfected and control cells were injected into athymic mice in order to evaluate the effect of NNMT silencing on tumor growth. NNMT downregulation resulted in decreased cell proliferation and colony formation ability on soft agar. In athymic mice, NNMT silencing induced a marked reduction in tumour volume. Our results show that the downregulation of NNMT expression in human oral carcinoma cells significantly inhibits cell growth in vitro and tumorigenicity in vivo. All these experimental data seem to suggest that NNMT plays a critical role in the proliferation and tumorigenic capacity of oral cancer cells, and its inhibition could represent a potential molecular approach to the treatment of oral carcinoma.

Nicotinamide N-methyltransferase overexpression is associated with Akt phosphorylation and indicates worse prognosis in patients with nasopharyngeal carcinoma

Nicotinamide N-methyltransferase (NNMT) is overexpressed in many human cancers and is associated with poor prognosis. Akt (also known as protein kinase B) is an evolutionarily conserved serine/threonine kinase, serving as a downstream effector of the phosphatidylinositol 3-kinase signaling pathway. NNMT was first identified as a differentially upregulated gene in nasopharyngeal cancer tissues through data mining from published transcriptomic databases. Since no prior study has attempted to evaluate the clinical significance of NNMT or phosphorylated Akt (pAkt) expression in nasopharyngeal cancer, this study explores their expression in a large cohort of patients with nasopharyngeal cancer. The study included 124 nasopharyngeal cancer patients who were free of distant metastasis at initial diagnosis. Pathological slides were reviewed and clinical findings collected. We evaluated the expression of NNMT and pAkt immunohistochemically, stratified them into two groups (high and low expression) and examined the correlation with disease-specific survival (DSS), metastasis-free survival (MeFS), local recurrence-free survival (LRFS), and various clinicopathological factors. NNMT expression was significantly positively associated with pAkt expression. The high expression of both markers was significantly associated with an increment of tumor stage (p = 0.006 and p = 0.006, respectively). High expression of NNMT correlated significantly with a more aggressive clinical course and a significantly shorter DSS. Furthermore, NNMT expression and pAkt expression were strongly predictive of MeFS (p = 0.008; p = 0.0063) and LRFS (p = 0.005; p = 0.0125). In multivariate analysis, high expression of NNMT remained as a robust prognosticator for both end points evaluated. It independently portended inferior DSS (p = 0.02, HR = 1.976) and worse MeFS (p = 0.029, HR = 2.022) after tumor stage (p = 0.033, HR = 2.150; p = 0.028, HR = 2.942, for DSS and LRFS, respectively). We found NNMT positively correlated with pAkt expression and was independent adverse prognosticators of patient survival. NNMT therefore has potential utility as an indicator for prognosis, predicting treatment response to chemotherapy or radiation therapy, and even as a therapeutic target in the future.

Assessment of gene expression profiles in peripheral occlusive arterial disease

BACKGROUND

Molecular events responsible for the onset and progression of peripheral occlusive arterial disease (POAD) are incompletely understood. Gene expression profiling may point out relevant features of the disease.

METHODS

Tissue samples were collected as operatory waste from a total of 36 patients with (n = 18) and without (n = 18) POAD. The tissues were histologically evaluated, and the patients with POAD were classified according to Leriche-Fontaine (LF) classification: 11% with stage IIB, 22% with stage III, and 67% with stage IV. Total RNA was isolated from all samples and hybridized onto Agilent 4×44K Oligo microarray slides. The bioinformatic analysis identified genes differentially expressed between control and pathologic tissues. Ten genes with a fold change ≥ 2 (1 with a fold change ≥ 1.8) were selected for quantitative polymerase chain reaction validation (GPC3, CFD, GDF10, ITLN1, TSPAN8, MMP28, NNMT, SERPINA5, LUM, and FDXR). C-reactive protein (CRP) was assessed with a specific assay, while nicotinamide N-methyltransferase (NNMT) was evaluated in the patient serum by enzyme-linked immunosorbent assay.

RESULTS

A multiple regression analysis showed that the level of CRP in the serum is correlated with the POAD LF stages (r(2) = 0.22, P = 0.046) and that serum NNMT is higher in IV LF POAD patients (P = 0.005). The mRNA gene expression of LUM is correlated with the LF stage (r(2) = 0.45, P = 0.009), and the mRNA level of ITLN1 is correlated with the ankle-brachial index (r(2) = 0.42, P = 0.008).

CONCLUSIONS

Our analysis shows that NNMT, ITLN1, LUM, CFD, and TSPAN8 in combination with other known markers, such as CRP, could be evaluated as a panel of biomarkers of POAD.

Novel avenues of drug discovery and biomarkers for diabetes mellitus

Globally, developed nations spend a significant amount of their resources on health care initiatives that poorly translate into increased population life expectancy. As an example, the United States devotes 16% of its gross domestic product to health care, the highest level in the world, but falls behind other nations that enjoy greater individual life expectancy. These observations point to the need for pioneering avenues of drug discovery to increase life span with controlled costs. In particular, innovative drug development for metabolic disorders such as diabetes mellitus becomes increasingly critical given that the number of diabetic people will increase exponentially over the next 20 years. This article discusses the elucidation and targeting of novel cellular pathways that are intimately tied to oxidative stress in diabetes mellitus for new treatment strategies. Pathways that involve wingless, β-nicotinamide adenine dinucleotide (NAD(+)) precursors, and cytokines govern complex biological pathways that determine both cell survival and longevity during diabetes mellitus and its complications. Furthermore, the role of these entities as biomarkers for disease can further enhance their utility irrespective of their treatment potential. Greater understanding of the intricacies of these unique cellular mechanisms will shape future drug discovery for diabetes mellitus to provide focused clinical care with limited or absent long-term complications.

Inhibiting Proliferation in KB Cancer Cells by RNA Interference-Mediated Knockdown of Nicotinamide N-Methyltransferase Expression

The enzyme Nicotinamide N-methyltransferase (NNMT) catalyzes the methylation of nicotinamide and other pyridines, playing a pivotal role in the biotransformation and detoxification of many drugs and xenobiotic compounds. Several tumours have been associated with abnormal NNMT expression, however its role in tumour development remains largely unknown. In this study we investigated expression levels of Nicotinamide N-methyltransferase in a cancer cell line and we evaluated the effect of shRNA-mediated silencing of NNMT on cell proliferation. Cancer cells were examined for NNMT expression by semiquantitative RT-PCR and Western blot analysis. A HPLC-based catalytic assay was performed to assess enzyme activity. Cells were transfected with four shRNA plasmids against NNMT and control cells were treated with transfection reagent only (mock). The efficiency of gene silencing was detected by Real-Time PCR and Western blot analysis. MTT cell proliferation assay and the soft agar colony formation assay were then applied to investigate the functional changes in cancerous cell. NNMT mRNA was detected in cancer cells, showing a very high expression level. In keeping with the results of RT-PCR analysis, the protein level and NNMT enzyme activity were particularly high in KB cells. ShRNA vectors targeted against NNMT efficiently suppressed gene expression, showing inhibition observed at both the mRNA and protein levels. Down-regulation of NNMT significantly inhibited cell proliferation and decreased colony formation ability on soft agar. The present data support the hypothesis that the enzyme plays a role in tumour expansion and its inhibition could represent a possible molecular approach to the treatment of cancer.

Diabetes mellitus: channeling care through cellular discovery

Diabetes mellitus (DM) impacts a significant portion of the world's population and care for this disorder places an economic burden on the gross domestic product for any particular country. Furthermore, both Type 1 and Type 2 DM are becoming increasingly prevalent and there is increased incidence of impaired glucose tolerance in the young. The complications of DM are protean and can involve multiple systems throughout the body that are susceptible to the detrimental effects of oxidative stress and apoptotic cell injury. For these reasons, innovative strategies are necessary for the implementation of new treatments for DM that are generated through the further understanding of cellular pathways that govern the pathological consequences of DM. In particular, both the precursor for the coenzyme beta-nicotinamide adenine dinucleotide (NAD(+)), nicotinamide, and the growth factor erythropoietin offer novel platforms for drug discovery that involve cellular metabolic homeostasis and inflammatory cell control. Interestingly, these agents and their tightly associated pathways that consist of cell cycle regulation, protein kinase B, forkhead transcription factors, and Wnt signaling also function in a broader sense as biomarkers for disease onset and progression.

The vitamin nicotinamide: translating nutrition into clinical care

Nicotinamide, the amide form of vitamin B(3) (niacin), is changed to its mononucleotide compound with the enzyme nicotinic acide/nicotinamide adenylyltransferase, and participates in the cellular energy metabolism that directly impacts normal physiology. However, nicotinamide also influences oxidative stress and modulates multiple pathways tied to both cellular survival and death. During disorders that include immune system dysfunction, diabetes, and aging-related diseases, nicotinamide is a robust cytoprotectant that blocks cellular inflammatory cell activation, early apoptotic phosphatidylserine exposure, and late nuclear DNA degradation. Nicotinamide relies upon unique cellular pathways that involve forkhead transcription factors, sirtuins, protein kinase B (Akt), Bad, caspases, and poly (ADP-ribose) polymerase that may offer a fine line with determining cellular longevity, cell survival, and unwanted cancer progression. If one is cognizant of the these considerations, it becomes evident that nicotinamide holds great potential for multiple disease entities, but the development of new therapeutic strategies rests heavily upon the elucidation of the novel cellular pathways that nicotinamide closely governs.