Nicotinamide N-methyltransferase Research Articles

Expression profile and prognostic value of NNMT in patients with pancreatic cancer

The elevation of Nicotinamide N-methyltransferase (NNMT) has been reported in pancreatic cancer tissues and cell lines, but its clinical and prognostic implications remain controversial. This study aimed at investigating the expression of NNMT in pancreatic benign and malignant tissues and the prognostic value of NNMT in pancreatic cancer. The expression of NNMT in tissue specimens of 28 chronic pancreatitis patients and 178 pancreatic cancer patients were assayed with immunohistochemistry on tissue microarray. The NNMT expression levels of pancreatic patients were correlated with their clinicopathological characteristics. The influences of NNMT expression and patients' clinicopathological characteristics on overall survival (OS) were analyzed. The percentage of NNMT high expression (NNMTh) in pancreatic cancer (55.6%) was significantly higher than those in chronic pancreatitis (21.4%) and paracancerous tissues (14.8%) (p < 0.001). NNMTh tends to significantly correlate with unfavorable clinicopathological features such as age > 60 years old (p = 0.014), tumor diameter > 4 cm (p < 0.001), TNM stage III or IV (p < 0.001) and poor tumor differentiation (p = 0.004). The median OS of patients with NNMTh and NNMTl were 7.0 months (95% CI: 5.275–8.725) and 11.5 months (95% CI: 9.759–13.241) respectively (p = 0.005). On multivariate analysis, NNMTl (hazards ratio [HR]: 0.399; 95% CI: 0.284–0.560; p < 0.001), absence of neurological involvement (HR: 0.651; 95% CI: 0.421–0.947; p = 0.041), TNM stage I or II (HR: 0.506; 95% CI: 0.299–0.719; p = 0.015) and well tumor differentiation (HR: 0.592; 95% CI: 0.319–0.894; p = 0.044) were significant favorable prognostic factors of OS. In conclusion, NNMT is upregulated in pancreatic cancer, correlates with unfavorable clinicopathological features and may serve as an independent prognosticator of patients' survival.

1-Methylnicotinamide ameliorates lipotoxicity-induced oxidative stress and cell death in kidney proximal tubular cells

Free fatty acid-bound albumin (FFA-albumin)-related oxidative stress is involved in the pathogenesis of proximal tubular cell (PTC) damage and subsequent renal dysfunction in patients with refractory proteinuria. Nicotinamide adenine dinucleotide (NAD) metabolism has recently been focused on as a novel therapeutic target for several modern diseases, including diabetes. This study was designed to identify a novel molecule in NAD metabolism to protect PTCs from lipotoxicity-related oxidative stress. Among 19 candidate enzymes involved in mammalian NAD metabolism, the mRNA expression level of nicotinamide n-methyltransferase (NNMT) was significantly increased in both the kidneys of FFA-albumin-overloaded mice and cultured PTCs stimulated with palmitate-albumin. Knockdown of NNMT exacerbated palmitate-albumin-induced cell death in cultured PTCs, whereas overexpression of NNMT inhibited it. Intracellular concentration of 1-Methylnicotinamide (1-MNA), a metabolite of NNMT, increased and decreased in cultured NNMT-overexpressing and -knockdown PTCs, respectively. Treatment with 1-MNA inhibited palmitate-albumin-induced mitochondrial reactive oxygen species generation and cell death in cultured PTCs. Furthermore, oral administration of 1-MNA ameliorated oxidative stress, apoptosis, necrosis, inflammation, and fibrosis in the kidneys of FFA-albumin-overloaded mice. In conclusion, NNMT-derived 1-MNA can reduce lipotoxicity-mediated oxidative stress and cell damage in PTCs. Supplementation of 1-MNA may have potential as a new therapy in patients with refractory proteinuria.

Nicotinamide N-methyltransferase increases complex I activity in SH-SY5Y cells via sirtuin 3

Nicotinamide N-methyltransferase (NNMT, E.C. 2.1.1.1) N-methylates nicotinamide to 1-methylnicotinamide. We have previously shown that NNMT is significantly overexpressed in the brains of patients who have died of Parkinson's disease, and others have shown that NNMT is significantly overexpressed in a variety of diseases ranging from cancer to hepatic cirrhosis. In vitro overexpression has revealed many cytoprotective effects of NNMT, in particular increased complex I activity and ATP synthesis. Although this appears to be mediated by an increase in 1-methylnicotinamide production, the molecular mechanisms involved remain unclear. In the present study, we have investigated the role that sirtuins 1, 2 and 3, class III DNA deacetylase enzymes known to regulate mitochondrial energy production and cell cycle, have in mediating the effects of NNMT upon complex I activity. Expression of NNMT in SH-SY5Y human neuroblastoma cells, which have no endogenous expression of NNMT, significantly increased the expression of all three sirtuins. siRNA-mediated silencing of sirtuin 3 expression decreased complex I activity in NNMT-expressing SH-SY5Y cells to that observed in wild-type SH-SY5Y, and significantly reduced cellular ATP content also. These results demonstrate that sirtuin 3 is a key mediator of NNMT-induced complex I activity and ATP synthesis. These results further reinforce a central role for NNMT in the regulation of energy homeostasis and provide further mechanistic insight into the consequences of enhanced NNMT expression.

Nicotinamide N-methyltransferase regulates hepatic nutrient metabolism through Sirt1 protein stabilization.

Nicotinamide N-methyltransferase (Nnmt) methylates nicotinamide, a form of vitamin B3, to produce N1-methylnicotinamide (MNAM). Nnmt is an emerging metabolic regulator in adipocytes but its role in the liver, a tissue with the strongest Nnmt expression, is not known. In spite of its overall high expression, here we find that hepatic expression of Nnmt is highly variable and correlates with multiple metabolic parameters in mice and in humans. Further, we find that suppression of hepatic Nnmt expression in vivo alters glucose and cholesterol metabolism and that the metabolic effects of Nnmt in the liver are mediated by its product MNAM. Supplementation of high fat diet with MNAM decreases serum and liver cholesterol and liver triglycerides levels in mice. Mechanistically, increasing Nnmt expression or MNAM levels stabilizes sirtuin 1 protein, an effect, which is required for their metabolic benefits. In summary, we describe a novel regulatory pathway for vitamin B3 that could provide a new opportunity for metabolic disease therapy.

Human keratin 8 variants promote mouse acetaminophen hepatotoxicity coupled with c-jun amino-terminal kinase activation and protein adduct formation.

Keratins 8 and 18 (K8/K18) are the intermediate filaments proteins of simple-type digestive epithelia and provide important cytoprotective function. K8/K18 variants predispose humans to chronic liver disease progression and poor outcomes in acute acetaminophen (APAP)-related liver failure. Given that K8 G62C and R341H/R341C are common K8 variants in European and North American populations, we studied their biological significance using transgenic mice. Mice that overexpress the human K8 variants, R341H or R341C, were generated and used together with previously described mice that overexpress wild-type K8 or K8 G62C. Mice were injected with 600 mg/kg of APAP or underwent bile duct ligation (BDL). Livers were evaluated by microarray analysis, quantitative real-time polymerase chain reaction, immunoblotting, histological and immunological staining, and biochemical assays. Under basal conditions, the K8 G62C/R341H/R341C variant-expressing mice did not show an obvious liver phenotype or altered keratin filament distribution, whereas K8 G62C/R341C animals had aberrant disulphide cross-linked keratins. Animals carrying the K8 variants displayed limited gene expression changes, but had lower nicotinamide N-methyl transferase (NNMT) levels and were predisposed to APAP-induced hepatotoxicity. NNMT represents a novel K8/K18-associated protein that becomes up-regulated after K8/K18 transfection. The more pronounced liver damage was accompanied by increased and prolonged JNK activation; elevated APAP protein adducts; K8 hyperphosphorylation at S74/S432 with enhanced keratin solubility; and prominent pericentral keratin network disruption. No differences in APAP serum levels, glutathione, or adenosine triphosphate levels were noted. BDL resulted in similar liver injury and biliary fibrosis in all mouse genotypes. Expression of human K8 variants G62C, R341H, or R341C in mice predisposes to acute APAP hepatotoxicity, thereby providing direct evidence for the importance of these variants in human acute liver failure.

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

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. 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. 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. 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). 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.

Human mass balance, metabolite profile and identification of metabolic enzymes of [14C]ASP015K, a novel oral janus kinase inhibitor

1. The human mass balance of 14C-labelled ASP015K ([14C]ASP015K), an orally bioavailable Janus kinase (JAK) inhibitor, was characterized in six healthy male subjects after a single oral dose of [14C]ASP015K (100 mg, 3.7 MBq) in solution. [14C]ASP015K was rapidly absorbed with tmax of 1.6 and 1.8 h for ASP015K and total radioactivity in plasma, respectively. Mean recovery in urine and feces amounted to 36.8% and 56.6% of the administered dose, respectively. The main components of radioactivity in plasma and urine were ASP015K and M2 (5′-O-sulfo ASP015K). In feces, ASP015K and M4 (7-N-methyl ASP015K) were the main components.2. In vitro study of ASP015K metabolism showed that the major isozyme contributing to the formation of M2 was human sulfotransferase (SULT) 2A1 and of M4 was nicotinamide N-methyltransferase (NNMT).3. The in vitro intrinsic clearance (CLint_in vitro) of M4 formation from ASP015K in human liver cytosol (HLC) was 11-fold higher than that of M2. The competitive inhibitory effect of nicotinamide on M4 formation in the human liver was considered the reason for high CLint_in vitro of M4 formation, while each metabolic pathway made a near equal contribution to the in vivo elimination of ASP015K. ASP015K was cleared by multiple mechanisms.

Differential involvement of IL-6 in the early and late phase of 1-methylnicotinamide (MNA) release in Concanavalin A-induced hepatitis

Exogenous 1-methylnicotinamide (MNA) displays anti-inflammatory activity. The aim of this work was to characterize the profile of release of endogenous MNA during the initiation and progression of murine hepatitis induced by Concanavalin A (ConA). In particular we aimed to clarify the role of interleukin-6 (IL-6) as well as the energy state of hepatocytes in MNA release in early and late phases of ConA-induced hepatitis in mice. Hepatitis was induced by ConA in IL-6(+/+) and IL-6(-/-) mice, and various parameters of liver inflammation and injury, as well as the energy state of hepatocytes, were analysed in relation to MNA release. The decrease in ATP/ADP and NADH/NAD ratios, cytokine release (IL-6, IFN-ɤ), acute phase response (e.g. haptoglobin) and liver injury (alanine aminotransaminase, ALT) were all blunted in ConA-induced hepatitis in IL-6(-/-) mice as compared to IL-6(+/+) mice. The release of MNA in response to Con A was also significantly blunted in IL-6(-/-) mice as compared to IL-6(+/+) mice in the early stage of ConA-induced hepatitis. In turn, nicotinamide N-methyltransferase (NNMT) and aldehyde oxidase (AO) activities were blunted in the liver and MNA plasma concentration was elevated to similar degree in the late stage after Concanavalin A in IL-6(+/+) and IL-6(-/-) mice. In conclusion, we demonstrated that in ConA-induced hepatitis, early, but not late MNA release was IL-6-dependent. Our results suggest that in the initiation and early hepatitis, MNA release is linked to the energy deficit/impaired redox status in hepatocytes, while in a later phase, MNA release is rather linked to the systemic inflammation.

Loss of the RNA polymerase III repressor MAF1 confers obesity resistance.

MAF1 is a global repressor of RNA polymerase III transcription that regulates the expression of highly abundant noncoding RNAs in response to nutrient availability and cellular stress. Thus, MAF1 function is thought to be important for metabolic economy. Here we show that a whole-body knockout of Maf1 in mice confers resistance to diet-induced obesity and nonalcoholic fatty liver disease by reducing food intake and increasing metabolic inefficiency. Energy expenditure in Maf1(-/-) mice is increased by several mechanisms. Precursor tRNA synthesis was increased in multiple tissues without significant effects on mature tRNA levels, implying increased turnover in a futile tRNA cycle. Elevated futile cycling of hepatic lipids was also observed. Metabolite profiling of the liver and skeletal muscle revealed elevated levels of many amino acids and spermidine, which links the induction of autophagy in Maf1(-/-) mice with their extended life span. The increase in spermidine was accompanied by reduced levels of nicotinamide N-methyltransferase, which promotes polyamine synthesis, enables nicotinamide salvage to regenerate NAD(+), and is associated with obesity resistance. Consistent with this, NAD(+) levels were increased in muscle. The importance of MAF1 for metabolic economy reveals the potential for MAF1 modulators to protect against obesity and its harmful consequences.

Potential involvement of nicotinamide N-methyltransferase in the pathogenesis of metabolic syndrome.

Metabolic syndrome is a complex disorder characterized by the presence of insulin resistance (IR), type 2 diabetes mellitus (T2DM), impaired glucose tolerance (IGT), or impaired fasting glucose (IFG), plus at least two of the following conditions--hypertension, hyperlipidemia, obesity, and microalbuminuria. Metabolic syndrome exposes patients to a greater risk of developing cardiovascular disease (CVD) and is often associated with elevated levels of homocysteine (Hcy). In the current work, we analyzed the expression of nicotinamide N-methyltransferase (NNMT). Because NNMT is involved in Hcy metabolism and participates in the regulation of the cellular and plasma levels of this compound, we explored the role played by the enzyme in metabolic syndrome. Real-time PCR, immunohistochemistry, western blot analysis, and catalytic activity assay were performed to evaluate NNMT expression levels in adipose tissue from 10 Wistar Ottawa Karlsburg W (WOKW) rats, which are an animal model for metabolic syndrome, and from 10 Dark Agouti (DA) rats as the disease-resistant control strain. NNMT mRNA, protein, and activity levels were significantly higher in adipose tissue obtained from WOKW rats compared with those observed in adipose tissue of DA rats. Data reported in this study represent the first evidence supporting the hypothesis that NNMT could play an important role in the pathogenesis of metabolic syndrome and could have a potential for the development of a targeted therapy.

Identification and Characterization of Cancer Stem Cells from Head and Neck Squamous Cell Carcinoma Cell Lines

Background/Aims: Head and neck squamous cell carcinoma (HNSCC) ranks sixth worldwide for tumor-related mortality. A subpopulation of tumor cells, termed cancer stem cells (CSCs), has the ability to support cancer growth. Therefore, profiling CSC-enriched populations could be a reliable tool to study cancer biology. Methods: We performed phenotypic characterization of 7 HNSCC cell lines and evaluated the presence of CSCs. CSCs from Hep-2 cell line and HNSCC primary cultures were enriched through sphere formation and sphere-forming cells have been characterized both in vitro and in vivo. In addition, we investigated the expression levels of Nicotinamide N-methyltransferase (NNMT), an enzyme overexpressed in several malignancies. Results: CSC markers were markedly expressed in Hep-2 cell line, which was found to be highly tumorigenic. CSC-enriched populations displayed increased expression of CSC markers and a strong capability to form tumors in vivo. We also found an overexpression of CSC markers in tumor formed by CSC-enriched populations. Interestingly, NNMT levels were significantly higher in CSC-enriched populations compared with parental cells. Conclusion: Our study provides an useful procedure for CSC identification and enrichment in HNSCC. Moreover, results obtained seem to suggest that CSCs may represent a promising target for an anticancer therapy.

Association of MTHFR A1298C polymorphism with conotruncal heart disease.

Congenital heart diseases are common congenital anomalies with 1% prevalence worldwide and are associated with significant childhood morbidity and mortality. Among a wide range of aetiologically heterogeneous conditions, conotruncal anomalies account for approximately one-third of all congenital heart defects. The aetiology of conotruncal heart diseases is complex, with both environmental and genetic causes. Hyperhomocysteinaemia, which is often accompanied by the defects of folic acid metabolism, is known to cause conotruncal heart anomalies. In this study, we have evaluated three polymorphisms in the following two hyperhomocysteinaemia-related genes: methylenetetrahydrofolate reductase (MTHFR C677T and A1298C) and nicotinamide N-methyl transferase (NNMT rs694539) in 79 children with conotruncal heart disease and 99 children without conotruncal heart disease. Genotype distribution of the MTHFR A1298C polymorphism showed a statistically significant difference between the two groups. In the case group, AC and CC genotypes were higher than the control group (p<0.05). We have found that MTHFR A1298C polymorphism is associated with conotruncal heart disease; C allele (p=0.028), AC (OR[95% CI]=2.48[1.24-4.95], p=0.010), CC (OR[95% CI]=3.01[1.16-7.83], p=0.023), and AC+CC (OR[95% CI]=2.60[1.36-4.99], p=0.004) genotypes are more frequent in the patient group. Genotype distributions of the MTHFR C677T and NNMT rs694539 polymorphisms were similar in the two groups when evaluated separately and also according to the dominant genetic model (p>0.05). Our results suggest that MTHFR 1298C allele is a risk factor for conotruncal heart disease.

Role of nicotinamide N-methyltransferase in non-small cell lung cancer: in vitro effect of shRNA-mediated gene silencing on tumourigenicity

Lung cancer is the second most commonly diagnosed neoplasm, and represents the leading cause of tumour death worldwide. As patients are often diagnosed at a late stage, current therapeutic strategies have limited effectiveness and the prognosis remains poor. Successful treatment depends on early diagnosis and knowledge concerning molecular mechanisms underlying lung carcinogenesis. In the present study, we focused on nicotinamide N-methyltransferase (NNMT), which is overexpressed in several malignancies. First, we analysed NNMT expression in a cohort of 36 patients with non-small cell lung cancer (NSCLC) by immunohistochemistry. Subsequently, we examined NNMT expression levels in the human lung cancer cell line A549 by Real-Time PCR, Western blot and catalytic activity assay, and evaluated the effect of NNMT knockdown on cell proliferation and anchorage-independent cell growth by MTT and soft agar colony formation assays, respectively. NSCLC displayed higher NNMT expression levels compared to both tumour-adjacent and surrounding tissue. Moreover, shRNA-mediated gene silencing of NNMT led to a significant inhibition of cell proliferation and colony formation ability on soft agar. Our results show that the downregulation of NNMT significantly reduced in vitro tumorigenicity of A549 cells and suggest that NNMT could represent an interesting molecular target for lung cancer therapy.

Nicotinamide N-methyltransferase enhances the capacity of tumorigenesis associated with the promotion of cell cycle progression in human colorectal cancer cells

Nicotinamide N-methyltransferase (NNMT), an enzyme involved in the biotransformation and detoxification of many drugs and xenobiotic compounds, has been found to be overexpressed in several malignancies, including colorectal cancer. However, the biological function of NNMT and the related mechanisms in colorectal cancer have not been elucidated. In the present study, we investigated the effects of NNMT on tumorigenesis by overexpressing NNMT in the human colorectal cancer cells line SW480 which lacks constitutive NNMT expression, and downregulating NNMT expression in HT-29 cells, which exhibit high endogenous expression of NNMT. We found that NNMT significantly accelerates cell proliferation, enhances colony formation in vitro and tumorigenicity in mice; it also inhibits apoptosis, promotes cell cycle progression, increases ATP and 1-methylnicotinamide level and decreases ROS level. We also showed that 1-methylnicotinamide accelerates cell growth, inhibits apoptosis, promotes cell cycle progression, attenuates ROS production and increases ATP level. Our results indicate that NNMT enhances the capacity of tumorigenesis associated with the inhibition of cell apoptosis and the promotion of cell cycle progression in human colorectal cancer cells and the 1-methylnicotinamide increased by NNMT mediates the cellular effects of NNMT in cells. NNMT may play a vital role in energy balance and ROS induction.

N-methylnicotinamide and nicotinamide N-methyltransferase are associated with microRNA-1291-altered pancreatic carcinoma cell metabolome and suppressed tumorigenesis.

The cell metabolome comprises abundant information that may be predictive of cell functions in response to epigenetic or genetic changes at different stages of cell proliferation and metastasis. An unbiased ultra-performance liquid chromatography-mass spectrometry-based metabolomics study revealed a significantly altered metabolome for human pancreatic carcinoma PANC-1 cells with gain-of-function non-coding microRNA-1291 (miR-1291), which led to a lower migration and invasion capacity as well as suppressed tumorigenesis in a xenograft tumor mouse model. A number of metabolites, including N-methylnicotinamide, involved in nicotinamide metabolism, and l-carnitine, isobutyryl-carnitine and isovaleryl-carnitine, involved in fatty acid metabolism, were elevated in miR-1291-expressing PANC-1. Notably, N-methylnicotinamide was elevated to the greatest extent, and this was associated with a sharp increase in nicotinamide N-methyltransferase (NNMT) mRNA level in miR-1291-expressing PANC-1 cells. In addition, expression of NNMT mRNA was inversely correlated with pancreatic tumor size in the xenograft mouse model. These results indicate that miR-1291-altered PANC-1 cell function is associated with the increase in N-methylnicotinamide level and NNMT expression, and in turn NNMT may be indicative of the extent of pancreatic carcinogenesis.

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.

Nicotinamide N-methyltransferase is a novel regulator of energy metabolism in adipose tissue

Nicotinamide N-methyltransferase is a novel regulator of energy metabolism in adipose tissue

Biguanide therapy for diabetes and cancer &amp; a novel methyltransferase that regulates energy expenditure and adiposity and is elevated in many cancers

Compounds containing guanidine-related molecules have been used since medieval times to relieve symptoms of diabetes mellitus. Guanidine itself was too toxic but two linked guanidine rings (biguanides) were useful and generally safer. For 20 years, phenformin was used before adverse effects led to removal from the US and European markets. Metformin continues to be widely prescribed for diabetes treatment and is associated with improved survival compared to other diabetes drugs. With the current interest in using the more potent phenformin for cancer therapy, it is timely to review the risks, benefits, and potential contraindications. The adipose cell is as an endocrine organ in addition to its role in energy storage. Adipocytes secrete hormones, cytokines and other factors that influence energy balance, glucose homeostasis, insulin sensitivity and vascular biology. In humans with obesity and type 2 diabetes, expression of the Glut4 glucose transporter is down-regulated selectively in adipocytes resulting in systemic insulin resistance. Knocking out Glut4 selectively in adipocytes in mice increases the risk of diabetes while adipose-specific Glut4 overexpression confers enhanced glucose tolerance in spite of increased adiposity. To understand how adipocytes regulate glucose homeostasis and insulin sensitivity, we performed DNA microarray analysis of adipose tissue from mice with adipose-specific knockdown or overexpression of Glut4. The most highly reciprocally regulated gene is nicotinamide N-methyltransferase (Nnmt). NNMT methylates nicotinamide (vitamin B3) using S-adenosylmethionine (SAM) as a methyl donor. Nicotinamide is a precursor for NAD+, an important cofactor linking cellular redox states with energy metabolism. NNMT expression is increased in adipose tissue and liver of obese and diabetic mice. Furthermore, NNMT knockdown in adipose tissue and liver using anti-sense oligonucleotides in mice on a high fat diet, protects against diet-induced obesity by augmenting cellular energy expenditure. This involves a novel mechanism which could provide new strategies for prevention and treatment of obesity and type 2 diabetes. Since NNMT is also elevated in many cancers, NNMT knockdown could be beneficial for cancer prevention and/or treatment.

Nicotinamide N-methyltransferase (NNMT)

Nicotinamide N-methyltransferase (NNMT)

Metabolomics reveals 1‐methylnicotinamide and nicotinamide N‐methyltransferase as crucial biomarkers in microRNA‐1291‐altered pancreatic carcinoma cell metabolism (1147.1)

Our recent studies have demonstrated that microRNA miR‐1291 may play an important role in the regulation of tumorigenesis of pancreatic cancer cells. To understand the underlying mechanisms, we employed a LC/MS‐based metabolomics approach to determine the impact of miR‐1291 on pancreatic carcinoma cell metabolism. Our data showed that the miR‐1291 stably transfected and control PANC‐1 cells are readily segregated based upon their metabolomic profiles. A number of significantly altered cellular metabolites were identified, including 1‐methylnicotinamide (MNA), taurine, L‐carnitine, isobutyryl‐carnitine, isovaleryl‐carnitine and hydroxybutyryl‐carnitine. Among them, MNA was altered to the greatest extent, and the increase in cellular MNA was associated with a sharply elevated expression of nicotinamide N‐methyltransferase (NNMT). In addition, NNMT mRNA expression was inversely related to the size of PANC‐1 derived xenograft tumors. Our results suggest that MNA and NNMT are possible biomarkers in miR‐1291‐altered pancreatic carcinoma cell metabolism. The findings may help identify key metabolic pathways in PANC‐1 cells perturbed by miR‐1291 and understand their involvement in pancreatic tumorigenesis.