Nicotinamide N-methyltransferase: At the crossroads between cellular metabolism and epigenetic regulation

Regulation of and challenges in targeting NAD+ metabolism

Nicotinamide adenine dinucleotide, in its oxidized (NAD+) and reduced (NADH) forms, is a reduction-oxidation (redox) co-factor and substrate for signalling enzymes that have essential roles in metabolism. The recognition that NAD+ levels fall in response to stress and can be readily replenished through supplementation has fostered great interest in the potential benefits of increasing or restoring NAD+ levels in humans to prevent or delay diseases and degenerative processes. However, much about the biology of NAD+ and related molecules remains poorly understood. In this Review, we discuss the current knowledge of NAD+ metabolism, including limitations of, assumptions about and unappreciated factors that might influence the success or contribute to risks of NAD+ supplementation. We highlight several ongoing controversies in the field, and discuss the role of the microbiome in modulating the availability of NAD+ precursors such as nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), the presence of multiple cellular compartments that have distinct pools of NAD+ and NADH, and non-canonical NAD+ and NADH degradation pathways. We conclude that a substantial investment in understanding the fundamental biology of NAD+, its detection and its metabolites in specific cells and cellular compartments is needed to support current translational efforts to safely boost NAD+ levels in humans.

Investigation on the mechanisms of scorpion venom in hepatocellular carcinoma model mice via untargeted metabolomics profiling

Metabolic reprogramming is frequently accompanied by hepatocellular carcinoma (HCC) progression. Disrupted metabolites act as potential biomarkers and drug therapeutic targets for HCC. Peptide extract of scorpion venom (PESV) induces cytotoxic anti-proliferative effects and apoptosis in tumors. However, the action mechanisms of PESV remain unknown. This study aimed to explore the serum metabolic profiles of tumor-bearing mouse model. We generated an orthotopic HCC xenograft mouse model by implanting H22 cells into the left hepatic lobe of male C57BL/6 mice. After surgery, the mice were assigned to two groups randomly: PESV (PESV-treated 40 mg/kg daily, i.g.; n = 6) and control (treated with the solvent equally for 14 d, n = 6) groups. Based on an untargeted metabolomics approach using ultra-high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry, differential metabolites were screened via univariate and multivariate data analyses. A total of 48 differential metabolites in negative ion mode and 63 in positive ion mode were identified in the serum samples. Furthermore, metabolic pathway analysis revealed that aminoacyl-tRNA biosynthesis, amino acid pathway, glutathione metabolism, protein transports, protein digestion and absorption, and cAMP signaling pathways play vital roles in PESV-induced inhibition of tumors. These findings highlight the distinct changes in the metabolic profiles of HCC-bearing mice after PESV treatment, suggesting the potential of the identified metabolic molecules as therapeutic targets for HCC.

Knockdown of nicotinamide N-methyltransferase ameliorates renal fibrosis caused by ischemia-reperfusion injury and remodels sphingosine metabolism

BACKGROUND

CKD currently affects 8.2% to 9.1% of the global population and the CKD mortality rate has increased during recent decades, making it necessary to identify new therapeutic targets. This study investigated the role of nicotinamide N-methyltransferase (NNMT) in renal fibrosis following ischemia-reperfusion injury (IRI), a key factor in chronic kidney disease (CKD) progression.

METHODS

We established a mouse model with a knockdown of NNMT to investigate the impact of this enzyme on renal fibrosis after unilateral IRI. We then utilized histology, immunohistochemistry, and metabolomic analyses to investigate fibrosis markers and sphingolipid metabolism in NNMT-deficient mice. We also utilized an Nnmt lentivirus interference vector or an Nnmt overexpression plasmid to transfect mouse kidney proximal tubule cells, stimulated these cells with TGF-β1, and then measured the pro-fibrotic response and the expression of the methylated and unmethylated forms of Sphk1.

RESULTS

The results demonstrated that reducing NNMT expression mitigated fibrosis, inflammation, and lipid deposition, potentially through the modulation of sphingolipid metabolism. Histology, immunohistochemistry, and metabolomic analyses provided evidence of decreased fibrosis and enhanced sphingolipid metabolism in NNMT-deficient mice. NNMT mediated the TGF-β1-induced pro-fibrotic response, knockdown of Nnmt decreased the level of unmethylated Sphk1 and increased the level of methylated Sphk1 in renal tubular epithelial cells.

CONCLUSIONS

Our findings suggest that NNMT functions in sphingolipid metabolism and has potential as a therapeutic target for CKD. Further research is needed to elucidate the mechanisms linking NNMT to sphingolipid metabolism and renal fibrosis.

Unfolding the complexity of epigenetics in male reproductive aging: a review of therapeutic implications

INTRODUCTION

Epigenetics studies gene expression changes influenced by environmental and lifestyle factors, linked to health conditions like reproductive aging. Male reproductive aging causes sperm decline, conceiving difficulties, and increased genetic abnormalities. Recent research focuses on epigenetics' role in male reproductive aging.

OBJECTIVES

This review explores epigenetics and male reproductive aging, focusing on sperm quality, environmental and lifestyle factors' impact, and potential health implications for offspring.

METHODS

An extensive search of the literature was performed applying multiple databases, such as PubMed and Google Scholar. The search phrases employed were: epigenetics, male reproductive ageing, sperm quality, sperm quantity, environmental influences, lifestyle factors, and offspring health. This review only included articles that were published in English and had undergone a peer-review process. The literature evaluation uncovered that epigenetic alterations have a substantial influence on the process of male reproductive ageing.

RESULT

Research has demonstrated that variations in the quality and quantity of sperm that occur with ageing are linked to adjustments in DNA methylation and histone. Moreover, there is evidence linking epigenetic alterations in sperm to environmental and lifestyle factors, including smoking, alcohol intake, and exposure to contaminants. These alterations can have enduring impacts on the well-being of descendants, since they can shape the activation of genes and potentially elevate the likelihood of genetic disorders. In conclusion, epigenetics significantly influences male reproductive aging, with sperm quality and quantity influenced by environmental and lifestyle factors.

CONCLUSION

This underscores the need for comprehensive approaches to managing male reproductive health, and underscores the importance of considering epigenetics in diagnosis and treatment.

Advances in the Synthesis and Physiological Metabolic Regulation of Nicotinamide Mononucleotide

Nicotinamide mononucleotide (NMN), the direct precursor of nicotinamide adenine dinucleotide (NAD+), is involved in the regulation of many physiological and metabolic reactions in the body. NMN can indirectly affect cellular metabolic pathways, DNA repair, and senescence, while also being essential for maintaining tissues and dynamic metabolic equilibria, promoting healthy aging. Therefore, NMN has found many applications in the food, pharmaceutical, and cosmetics industries. At present, NMN synthesis strategies mainly include chemical synthesis and biosynthesis. Despite its potential benefits, the commercial production of NMN by organic chemistry approaches faces environmental and safety problems. With the rapid development of synthetic biology, it has become possible to construct microbial cell factories to produce NMN in a cost-effective way. In this review, we summarize the chemical and biosynthetic strategies of NMN, offering an overview of the recent research progress on host selection, chassis cell optimization, mining of key enzymes, metabolic engineering, and adaptive fermentation strategies. In addition, we also review the advances in the role of NMN in aging, metabolic diseases, and neural function. This review provides comprehensive technical guidance for the efficient biosynthesis of NMN as well as a theoretical basis for its application in the fields of food, medicine, and cosmetics.

Changes in glucose metabolism, C-reactive protein, and liver enzymes following intake of NAD + precursor supplementation: a systematic review and meta-regression analysis

BACKGROUND

There are contradictory effects regarding the effect of NAD + precursor on glucose metabolism and liver enzymes. In order to obtain a better viewpoint from them, this study aimed to comprehensively investigate the effects of NAD + precursor supplementation on glucose metabolism, C-reactive protein (CRP), and liver enzymes.

METHODS

PubMed/MEDLINE, Web of Science, SCOPUS, and Embase databases were searched using standard keywords to identify all controlled trials investigating the glucose metabolism, CRP, and liver enzymes effects of NAD + precursor. Pooled weighted mean difference (WMD) and 95% confidence intervals (95% CI) were achieved by random-effects model analysis for the best estimation of outcomes.

RESULTS

Forty-five articles with 9256 participants' were included in this article. The pooled findings showed that NAD + precursor supplementation had a significant increase in glucose (WMD: 2.17 mg/dL, 95% CI: 0.68, 3.66, P = 0.004) and HbA1c (WMD: 0.11, 95% CI: 0.06, 0.16, P < 0.001) as well as a significant decrease in CRP (WMD: -0.93 mg/l, 95% CI -1.47 to -0.40, P < 0.001) compared with control group, and was not statistically significant with respect to insulin and homeostasis model assessment of insulin resistance (HOMA-IR). However, we found no systemic changes in aspartate transaminase (AST), alanine transaminase (ALT), or alkaline phosphatase (ALP) levels after NAD + precursor supplementation. The results of the subgroup analysis showed that the intake of NAD + precursor during the intervention of more than 12 weeks caused a greater increase in the glucose level. Furthermore, Nicotinic acid supplementation (NA) causes a greater increase in glucose and HbA1c levels than nicotinamide (NE) supplementation.

CONCLUSIONS

Overall, these findings suggest that NAD + precursor supplementation might have an increase effect on glucose metabolism as well as a decrease in CRP.

Identification of 1-Methylnicotinamide as a specific biomarker for the progression of cirrhosis to hepatocellular carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) is a prevalent malignant tumor, often arising from hepatitis induced by the hepatitis B virus (HBV) in China. However, effective biomarkers for early diagnosis are lacking, leading to a 5-year overall survival rate of less than 20% among patients with advanced HCC. This study aims to identify serum biomarkers for early HCC diagnosis to enhance patient survival rates.

METHODS

We established an independent cohort comprising 27 healthy individuals, 13 patients with HBV-induced cirrhosis, 13 patients with hepatitis B-type HCC, and 8 patients who progressed from cirrhosis to hepatocellular carcinoma during follow-up. Serum metabolic abnormalities during the progression from cirrhosis to HCC were studied using untargeted metabolomics. Liquid chromatography-mass spectrometry-based metabolomics methods characterized the subjects' serum metabolic profiles. Partial least squares discriminant analysis (PLS-DA) was employed to elucidate metabolic profile changes during the progression from cirrhosis to HCC. Differentially expressed metabolites (DEMs) between cirrhosis and HCC groups were identified using the LIMMA package in the R language. Two machine learning algorithms, Least Absolute Shrinkage and Selection Operator (LASSO), and Random Forest Classifier (RF), were used to identify key metabolic biomarkers involved in the progression from cirrhosis to HCC. Key metabolic biomarkers were further validated using targeted metabolomics in a new independent validation cohort comprising 25 healthy individuals and 25 patients with early-stage hepatocellular carcinoma.

RESULTS

A total of 155 serum metabolites were identified, of which 21/54 metabolites exhibited significant changes in HCC patients compared with cirrhosis patients and healthy individuals, respectively. PLS-DA clustering results demonstrated a significant change trend in the serum metabolic profile of patients with HBV-induced cirrhosis during the progression to HCC. Utilizing LASSO regression and RF algorithms, we confirmed 10 key metabolic biomarkers. Notably, 1-Methylnicotinamide (1-MNAM) exhibited a persistent and significant decrease in healthy individuals, cirrhosis, and HCC patients. Moreover, 1-MNAM levels in developing patients were significantly higher during the cirrhosis stage than in the HCC stage. Targeted metabolomic validation in an external cohort further confirmed the good diagnostic performance of 1-MNAM in early HCC detection.

CONCLUSION

Our findings imply that 1-MNAM may be a specific biomarker for the progression of cirrhosis to HCC.

Overcoming Resistance to Standard-of-Care Therapies for Head and Neck Squamous Cell Carcinomas

Although there have been some advances during in recent decades, the treatment of head and neck squamous cell carcinoma (HNSCC) remains challenging. Resistance is a major issue for various treatments that are used, including both the conventional standards of care (radiotherapy and platinum-based chemotherapy) and the newer EGFR and checkpoint inhibitors. In fact, all the non-surgical treatments currently used for HNSCC are associated with intrinsic and/or acquired resistance. Herein, we explore the cellular mechanisms of resistance reported in HNSCC, including those related to epigenetic factors, DNA repair defects, and several signaling pathways. This article discusses these mechanisms and possible approaches that can be used to target different pathways to sensitize HNSCC to the existing treatments, obtain better responses to new agents, and ultimately improve the patient outcomes.

Nicotinamide N-methyltransferase (NNMT): a novel therapeutic target for metabolic syndrome

Metabolic syndrome (MetS) represents a constellation of metabolic abnormalities, typified by obesity, hypertension, hyperglycemia, and hyperlipidemia. It stems from intricate dysregulations in metabolic pathways governing energy and substrate metabolism. While comprehending the precise etiological mechanisms of MetS remains challenging, evidence underscores the pivotal roles of aberrations in lipid metabolism and insulin resistance (IR) in its pathogenesis. Notably, nicotinamide N-methyltransferase (NNMT) has recently surfaced as a promising therapeutic target for addressing MetS. Single nucleotide variants in the NNMT gene are significantly correlated with disturbances in energy metabolism, obesity, type 2 diabetes (T2D), hyperlipidemia, and hypertension. Elevated NNMT gene expression is notably observed in the liver and white adipose tissue (WAT) of individuals with diabetic mice, obesity, and rats afflicted with MetS. Knockdown of NNMT elicits heightened energy expenditure in adipose and hepatic tissues, mitigates lipid accumulation, and enhances insulin sensitivity. NNMT catalyzes the methylation of nicotinamide (NAM) using S-adenosyl-methionine (SAM) as the donor methyl group, resulting in the formation of S-adenosyl-l-homocysteine (SAH) and methylnicotinamide (MNAM). This enzymatic process results in the depletion of NAM, a precursor of nicotinamide adenine dinucleotide (NAD+), and the generation of SAH, a precursor of homocysteine (Hcy). Consequently, this cascade leads to reduced NAD+ levels and elevated Hcy levels, implicating NNMT in the pathogenesis of MetS. Moreover, experimental studies employing RNA interference (RNAi) strategies and small molecule inhibitors targeting NNMT have underscored its potential as a therapeutic target for preventing or treating MetS-related diseases. Nonetheless, the precise mechanistic underpinnings remain elusive, and as of yet, clinical trials focusing on NNMT have not been documented. Therefore, further investigations are warranted to elucidate the intricate roles of NNMT in MetS and to develop targeted therapeutic interventions.

Identification of nicotinamide N-methyltransferase as a promising therapeutic target for sarcopenia

Sarcopenia is a significant geriatric syndrome that involves the loss of skeletal muscle mass and strength. Due to its substantial endocrine role, the metabolic microenvironment of skeletal muscle undergoes changes with age. Examining the pathogenesis of sarcopenia through focusing on metabolic dysregulation could offer insights for developing more effective intervention strategies. In this study, we analyzed the transcriptomics data to identify specific genes involved in the regulation of metabolism in skeletal muscle during the development of sarcopenia. Three machine learning algorithms were employed to screen key target genes exhibiting strong correlations with metabolism, which were further validated using RNA-sequencing data and publicly accessible datasets. Among them, the metabolic enzyme nicotinamide N-methyltransferase (NNMT) was elevated in sarcopenia, and predicted sarcopenia with an area under the curve exceeding 0.7, suggesting it as a potential therapeutic target for sarcopenia. As expected, inhibition of NNMT improved the grip strength in aging mice and alleviated age-related decline in the mass index of the quadriceps femoris muscles and whole-body lean mass index. Additionally, the NNMTi treatment increased the levels of nicotinamide adenine dinucleotide (NAD+) content, as well as PGC1α and p-AMPK expression in the muscles of both the D-galactose-treated mouse model and naturally aging mouse model. Overall, this work demonstrates NNMT as a promising target for preventing age-related decline in muscle mass and strength.

Pan-cancer analysis combined with experiments predicts NNMT as a therapeutic target for human cancers

The identification of effective therapeutic targets plays a pivotal role in advancing cancer treatment outcomes. We employed a comprehensive pan-cancer analysis, complemented by experimental validation, to explore the potential of Nicotinamide N-methyltransferase (NNMT) as a promising therapeutic strategy for human cancers. By analyzing large-scale transcriptomic datasets across various cancer types, we consistently observed upregulated expression of NNMT. Furthermore, elevated NNMT expression correlated with inferior overall survival in multiple cancer cohorts, underscoring its significance as a prognostic biomarker. Additionally, we investigated the relationship between NNMT expression and the tumor immune microenvironment, which plays a crucial role in regulating anti-tumor immune responses. To confirm the malignant functions of NNMT in tumor cells, we conducted a series of cell-based experiments, revealing that NNMT promotes cancer cell proliferation and invasion, indicative of its oncogenic properties. The integration of computational analysis and experimental validation in our study firmly establishes NNMT as a potential therapeutic target for human cancers. Specifically, targeting NNMT holds promise for the development of innovative and effective cancer treatments. Further investigations into NNMT's role in cancer pathogenesis could potentially pave the way for groundbreaking advancements in cancer treatment.

Role of Epigenetic Modulation in Neurodegenerative Diseases: Implications of Phytochemical Interventions

Epigenetics defines changes in cell function without involving alterations in DNA sequence. Neuroepigenetics bridges neuroscience and epigenetics by regulating gene expression in the nervous system and its impact on brain function. With the increase in research in recent years, it was observed that alterations in the gene expression did not always originate from changes in the genetic sequence, which has led to understanding the role of epigenetics in neurodegenerative diseases (NDDs) including Alzheimer's disease (AD) and Parkinson's disease (PD). Epigenetic alterations contribute to the aberrant expression of genes involved in neuroinflammation, protein aggregation, and neuronal death. Natural phytochemicals have shown promise as potential therapeutic agents against NDDs because of their antioxidant, anti-inflammatory, and neuroprotective effects in cellular and animal models. For instance, resveratrol (grapes), curcumin (turmeric), and epigallocatechin gallate (EGCG; green tea) exhibit neuroprotective effects through their influence on DNA methylation patterns, histone acetylation, and non-coding RNA expression profiles. Phytochemicals also aid in slowing disease progression, preserving neuronal function, and enhancing cognitive and motor abilities. The present review focuses on various epigenetic modifications involved in the pathology of NDDs, including AD and PD, gene expression regulation related to epigenetic alterations, and the role of specific polyphenols in influencing epigenetic modifications in AD and PD.

Diabetes Mellitus and Pregnancy: An Insight into the Effects on the Epigenome

Worldwide, diabetes mellitus represents a growing health problem. If it occurs during pregnancy, it can increase the risk of various abnormalities in early and advanced life stages of exposed individuals due to fetal programming occurring in utero. Studies have determined that maternal conditions interfere with the genotypes and phenotypes of offspring. Researchers are now uncovering the mechanisms by which epigenetic alterations caused by diabetes affect the expression of genes and, therefore, the development of various diseases. Among the numerous possible epigenetic changes in this regard, the most studied to date are DNA methylation and hydroxymethylation, as well as histone acetylation and methylation. This review article addresses critical findings in epigenetic studies involving diabetes mellitus, including variations reported in the expression of specific genes and their transgenerational effects.

Stem Cell Theory of Cancer: Clinical Implications for Cellular Metabolism and Anti-Cancer Metabolomics

Although Otto Warburg may be right about the role of glycolysis versus OXPHOS in cancer metabolism, it remains unclear whether an altered metabolism is causative or correlative and is the main driver or a mere passenger in the pathogenesis of cancer. Currently, most of our successful treatments are designed to eliminate non-cancer stem cells (non-CSCs) such as differentiated cancer cells. When the treatments also happen to control CSCs or the stem-ness niche, it is often unintended, unexpected, or undetected for lack of a pertinent theory about the origin of cancer that clarifies whether cancer is a metabolic, genetic, or stem cell disease. Perhaps cellular context matters. After all, metabolic activity may be different in different cell types and their respective microenvironments-whether it is in a normal progenitor stem cell vs. progeny differentiated cell and whether it is in a malignant CSC vs. non-CSC. In this perspective, we re-examine different types of cellular metabolism, e.g., glycolytic vs. mitochondrial, of glucose, glutamine, arginine, and fatty acids in CSCs and non-CSCs. We revisit the Warburg effect, an obesity epidemic, the aspartame story, and a ketogenic diet. We propose that a pertinent scientific theory about the origin of cancer and of cancer metabolism influences the direction of cancer research as well as the design of drug versus therapy development in cancer care.

Comparative Analysis of Two NNMT Bisubstrate Inhibitors through Chemoproteomic Studies: Uncovering the Role of Unconventional SAM Analogue Moiety for Improved Selectivity

Unconventional S-adenosyl-L-methionine (SAM) mimics with enhanced hydrophobicity are an adaptable building block to develop cell-potent inhibitors for SAM-dependent methyltransferases as targeted therapeutics. We recently discovered cell-potent bisubstrate inhibitors for nicotinamide N-methyltransferase (NNMT) by using an unconventional SAM mimic. To delve into the selectivity implications of the unconventional SAM mimic, we employed a chemoproteomic approach to assess two potent NNMT inhibitors LL320 (Ki, app = 6.8 nM) and II399 (containing an unconventional SAM mimic, Ki, app = 5.9 nM) within endogenous proteomes. Our work began with the rational design and synthesis of immobilized probes 1 and 2, utilizing LL320 and II399 as parent compounds. Systematic analysis of protein networks associated with these probes revealed a comprehensive landscape. Notably, NNMT emerged as the top-ranking hit, substantiating the high selectivity of both inhibitors. Meanwhile, we identified additional interacting proteins for LL320 (38) and II399 (17), showcasing the intricate selectivity profiles associated with these compounds. Subsequent experiments confirmed LL320's interactions with RNMT, DPH5, and SAHH, while II399 exhibited interactions with SHMT2 and MEPCE. Importantly, incorporating the unconventional SAM mimic in II399 led to improved selectivity compared to LL320. Our findings underscore the importance of selectivity profiling and validate the utilization of the unconventional SAM mimic as a viable strategy to create highly selective and cell-permeable inhibitors for SAM-dependent methyltransferases.

Anti-miR-873-5p improves alcohol-related liver disease by enhancing hepatic deacetylation via SIRT1

Background & Aims

Current therapies for the treatment of alcohol-related liver disease (ALD) have proven largely ineffective. Patients relapse and the disease progresses even after liver transplantation. Altered epigenetic mechanisms are characteristic of alcohol metabolism given excessive acetate and NAD depletion and play an important role in liver injury. In this regard, novel therapeutic approaches based on epigenetic modulators are increasingly proposed. MicroRNAs, epigenetic modulators acting at the post-transcriptional level, appear to be promising new targets for the treatment of ALD.

Methods

MiR-873-5p levels were measured in 23 liver tissue from Patients with ALD, and GNMT levels during ALD were confirmed using expression databases (transcriptome n = 62, proteome n = 68). High-resolution proteomics and metabolomics in mice following the Gao-binge model were used to investigate miR-873-5p expression in ALD. Hepatocytes exposed to 50 mM alcohol for 12 h were used to study toxicity. The effect of anti-miR-873-5p in the treatment outcomes of ALD was investigated.

Results

The analysis of human and preclinical ALD samples revealed increased expression of miR-873-5p in the liver. Interestingly, there was an inverse correlation with NNMT, suggesting a novel mechanism for NAD depletion and aberrant acetylation during ALD progression. High-resolution proteomics and metabolomics identified miR-873-5p as a key regulator of NAD metabolism and SIRT1 deacetylase activity. Anti-miR-873-5p reduced NNMT activity, fuelled the NAD salvage pathway, restored the acetylome, and modulated the levels of NF-κB and FXR, two known SIRT1 substrates, thereby protecting the liver from apoptotic and inflammatory processes, and improving bile acid homeostasis.

Conclusions

These data indicate that targeting miR-873-5p, a repressor of GNMT previously associated with NAFLD and acetaminophen-induced liver failure. is a novel and attractive approach to treating alcohol-induced hepatoxicity.

Impact and implications

The role of miR-873-5p has not been explicitly examined in the progression of ALD, a pathology with no therapeutic options. In this study, inhibiting miR-873-5p exerted hepatoprotective effects against ALD through rescued SIRT1 activity and consequently restored bile acid homeostasis and attenuated the inflammatory response. Targeting hepatic miR-873-5p may represent a novel therapeutic approach for the treatment of ALD.

Molecular Mechanisms of IL18 in Disease

Interleukin 18 (IL18) was originally identified as an inflammation-induced cytokine that is secreted by immune cells. An increasing number of studies have focused on its non-immunological functions, with demonstrated functions for IL18 in energy homeostasis and neural stability. IL18 is reportedly required for lipid metabolism in the liver and brown adipose tissue. Furthermore, IL18 (Il18) deficiency in mice leads to mitochondrial dysfunction in hippocampal cells, resulting in depressive-like symptoms and cognitive impairment. Microarray analyses of Il18-/- mice have revealed a set of genes with differential expression in liver, brown adipose tissue, and brain; however, the impact of IL18 deficiency in these tissues remains uncertain. In this review article, we discuss these genes, with a focus on their relationships with the phenotypic disease traits of Il18-/- mice.

Elucidating the role of nicotinamide N-methyltransferase-p53 axis in the progression of chronic kidney disease

Background

Chronic kidney disease (CKD) is a significant global health issue characterized by progressive loss of kidney function. Renal interstitial fibrosis (TIF) is a common feature of CKD, but current treatments are seldom effective in reversing TIF. Nicotinamide N-methyltransferase (NNMT) has been found to increase in kidneys with TIF, but its role in renal fibrosis is unclear.

Methods

Using mice with unilateral ureteral obstruction (UUO) and cultured renal interstitial fibroblast cells (NRK-49F) stimulated with transforming growth factor-β1 (TGF-β1), we investigated the function of NNMT in vivo and in vitro.

Results

We performed single-cell transcriptome sequencing (scRNA-seq) on the kidneys of mice and found that NNMT increased mainly in fibroblasts of UUO mice compared to sham mice. Additionally, NNMT was positively correlated with the expression of renal fibrosis-related genes after UUO injury. Knocking down NNMT expression reduced fibroblast activation and was accompanied by an increase in DNA methylation of p53 and a decrease in its phosphorylation.

Conclusions

Our findings suggest that chronic kidney injury leads to an accumulation of NNMT, which might decrease p53 methylation, and increase the expression and activity of p53. We propose that NNMT promotes fibroblast activation and renal fibrosis, making NNMT a novel target for preventing and treating renal fibrosis.

Nicotinamide N -methyltransferase promotes M2 macrophage polarization by IL6 and MDSC conversion by GM-CSF in gallbladder carcinoma

BACKGROUND AND AIMS

Nicotinamide N -methyltransferase (NNMT), an enzyme responsible for the methylation of nicotinamide, is involved in many metabolic pathways in adipose tissue and the liver. However, the role of NNMT in editing the tumor immune microenvironment is not well understood.

APPROACH AND RESULTS

Here, we identified that NNMT can promote IL6 and granulocyte-macrophage colony-stimulating factor (GM-CSF) expression by decreasing the tri-methyl-histone H3 levels on the promoters of IL6 and CSF2 (encoding GM-CSF) and CCAAT/Enhancer Binding Protein, an essential transcription factor for IL6 expression, thus promoting differentiation of macrophages into M2 type tumor-associated macrophages and generation of myeloid-derived suppressor cells from peripheral blood mononuclear cells. Treatment of xenografted tumor models overexpressing NNMT gallbladder carcinoma (GBC) cells with the NNMT inhibitor JBSNF-000088 resulted in compromised tumor development and decreased expression levels of IL6, GM-CSF, tumor-associated macrophage marker CD206, and myeloid-derived suppressor cell marker CD33 but increased expression levels of CD8. In addition, elevated expression of NNMT in tumors of patients with GBC was correlated with increased expression levels of CD206 and CD33 but with decreased levels of CD8 and survival of patients.

CONCLUSIONS

These data highlight the critical role of NNMT in GBC progression. Inhibition of NNMT by JBSNF-000088 is a potential molecular target for GBC immunotherapy.

p16High senescence restricts cellular plasticity during somatic cell reprogramming

Despite advances in four-factor (4F)-induced reprogramming (4FR) in vitro and in vivo, how 4FR interconnects with senescence remains largely under investigated. Here, using genetic and chemical approaches to manipulate senescent cells, we show that removal of p16High cells resulted in the 4FR of somatic cells into totipotent-like stem cells. These cells expressed markers of both pluripotency and the two-cell embryonic state, readily formed implantation-competent blastoids and, following morula aggregation, contributed to embryonic and extraembryonic lineages. We identified senescence-dependent regulation of nicotinamide N-methyltransferase as a key mechanism controlling the S-adenosyl-L-methionine levels during 4FR that was required for expression of the two-cell genes and acquisition of an extraembryonic potential. Importantly, a partial 4F epigenetic reprogramming in old mice was able to reverse several markers of liver aging only in conjunction with the depletion of p16High cells. Our results show that the presence of p16High senescent cells limits cell plasticity, whereas their depletion can promote a totipotent-like state and histopathological tissue rejuvenation during 4F reprogramming.

Nicotinamide N-methyltransferase sustains a core epigenetic program that promotes metastatic colonization in breast cancer

Metastatic colonization of distant organs accounts for over 90% of deaths related to solid cancers, yet the molecular determinants of metastasis remain poorly understood. Here, we unveil a mechanism of colonization in the aggressive basal-like subtype of breast cancer that is driven by the NAD+ metabolic enzyme nicotinamide N-methyltransferase (NNMT). We demonstrate that NNMT imprints a basal genetic program into cancer cells, enhancing their plasticity. In line, NNMT expression is associated with poor clinical outcomes in patients with breast cancer. Accordingly, ablation of NNMT dramatically suppresses metastasis formation in pre-clinical mouse models. Mechanistically, NNMT depletion results in a methyl overflow that increases histone H3K9 trimethylation (H3K9me3) and DNA methylation at the promoters of PR/SET Domain-5 (PRDM5) and extracellular matrix-related genes. PRDM5 emerged in this study as a pro-metastatic gene acting via induction of cancer-cell intrinsic transcription of collagens. Depletion of PRDM5 in tumor cells decreases COL1A1 deposition and impairs metastatic colonization of the lungs. These findings reveal a critical activity of the NNMT-PRDM5-COL1A1 axis for cancer cell plasticity and metastasis in basal-like breast cancer.

Recent Advances in the Management of Clear Cell Renal Cell Carcinoma: Novel Biomarkers and Targeted Therapies

Renal cell carcinoma (RCC) belongs to a heterogenous cancer group arising from renal tubular epithelial cells. Among RCC subtypes, clear cell renal cell carcinoma (ccRCC) is the most common variant, characterized by high aggressiveness, invasiveness and metastatic potential, features that lead to poor prognosis and high mortality rate. In addition, diagnosis of kidney cancer is incidental in the majority of cases, and this results in a late diagnosis, when the stage of the disease is advanced and the tumor has already metastasized. Furthermore, ccRCC treatment is complicated by its strong resistance to chemo- and radiotherapy. Therefore, there is active ongoing research focused on identifying novel biomarkers which could be useful for assessing a better prognosis, as well as new molecules which could be used for targeted therapy. In this light, several novel targeted therapies have been shown to be effective in prolonging the overall survival of ccRCC patients. Thus, the aim of this review is to analyze the actual state-of-the-art on ccRCC diagnosis, prognosis and therapeutic options, while also reporting the recent advances in novel biomarker discoveries, which could be exploited for a better prognosis or for targeted therapy.

NAD+ Metabolism and Immune Regulation: New Approaches to Inflammatory Bowel Disease Therapies

Inflammatory bowel disease (IBD), which includes Crohn's disease (CD) and ulcerative colitis (UC), is a multifactorial systemic inflammatory immune response. Nicotinamide adenine dinucleotide (NAD⁺) is a co-enzyme involved in cell signaling and energy metabolism. Calcium homeostasis, gene transcription, DNA repair, and cell communication involve NAD⁺ and its degradation products. There is a growing recognition of the intricate relationship between inflammatory diseases and NAD⁺ metabolism. In the case of IBD, the maintenance of intestinal homeostasis relies on a delicate balance between NAD⁺ biosynthesis and consumption. Consequently, therapeutics designed to target the NAD⁺ pathway are promising for the management of IBD. This review discusses the metabolic and immunoregulatory processes of NAD⁺ in IBD to examine the molecular biology and pathophysiology of the immune regulation of IBD and to provide evidence and theoretical support for the clinical use of NAD⁺ in IBD.

Nicotinamide N-methyltransferase (NNMT) regulates the glucocorticoid signaling pathway during the early phase of adipogenesis

Obesity is associated with adipose tissue dysfunction through the differentiation and expansion of pre-adipocytes to adipocytes (hyperplasia) and/or increases in size of pre-existing adipocytes (hypertrophy). A cascade of transcriptional events coordinates the differentiation of pre-adipocytes into fully differentiated adipocytes; the process of adipogenesis. Although nicotinamide N-methyltransferase (NNMT) has been associated with obesity, how NNMT is regulated during adipogenesis, and the underlying regulatory mechanisms, remain undefined. In present study we used genetic and pharmacological approaches to elucidate the molecular signals driving NNMT activation and its role during adipogenesis. Firstly, we demonstrated that during the early phase of adipocyte differentiation NNMT is transactivated by CCAAT/Enhancer Binding Protein beta (CEBPB) in response to glucocorticoid (GC) induction. We found that Nnmt knockout, using CRISPR/Cas9 approach, impaired terminal adipogenesis by influencing the timing of cellular commitment and cell cycle exit during mitotic clonal expansion, as demonstrated by cell cycle analysis and RNA sequencing experiments. Biochemical and computational methods showed that a novel small molecule, called CC-410, stably binds to and highly specifically inhibits NNMT. CC-410 was, therefore, used to modulate protein activity during pre-adipocyte differentiation stages, demonstrating that, in line with the genetic approach, chemical inhibition of NNMT at the early stages of adipogenesis impairs terminal differentiation by deregulating the GC network. These congruent results conclusively demonstrate that NNMT is a key component of the GC-CEBP axis during the early stages of adipogenesis and could be a potential therapeutic target for both early-onset obesity and glucocorticoid-induced obesity.

Notch and Wnt Signaling Modulation to Enhance DPSC Stemness and Therapeutic Potential

The Dental Pulp of permanent human teeth is home to stem cells with remarkable multilineage differentiation ability: human Dental Pulp Stem Cells (DPSCs). These cells display a very notorious expression of pluripotency core factors, and the ability to give rise to mature cell lineages belonging to the three embryonic layers. For these reasons, several researchers in the field have long considered human DPSCs as pluripotent-like cells. Notably, some signaling pathways such as Notch and Wnt contribute to maintaining the stemness of these cells through a complex network involving metabolic and epigenetic regulatory mechanisms. The use of recombinant proteins and selective pharmacological modulators of Notch and Wnt pathways, together with serum-free media and appropriate scaffolds that allow the maintenance of the non-differentiated state of hDPSC cultures could be an interesting approach to optimize the potency of these stem cells, without a need for genetic modification. In this review, we describe and integrate findings that shed light on the mechanisms responsible for stemness maintenance of hDPSCs, and how these are regulated by Notch/Wnt activation, drawing some interesting parallelisms with pluripotent stem cells. We summarize previous work on the stem cell field that includes interactions between epigenetics, metabolic regulations, and pluripotency core factor expression in hDPSCs and other stem cell types.

Amino acid metabolic reprogramming in tumor metastatic colonization

Metastasis is considered as the major cause of cancer death. Cancer cells can be released from primary tumors into the circulation and then colonize in distant organs. How cancer cells acquire the ability to colonize in distant organs has always been the focus of tumor biology. To enable survival and growth in the new environment, metastases commonly reprogram their metabolic states and therefore display different metabolic properties and preferences compared with the primary lesions. For different microenvironments in various colonization sites, cancer cells must transfer to specific metabolic states to colonize in different distant organs, which provides the possibility of evaluating metastasis tendency by tumor metabolic states. Amino acids provide crucial precursors for many biosynthesis and play an essential role in cancer metastasis. Evidence has proved the hyperactivation of several amino acid biosynthetic pathways in metastatic cancer cells, including glutamine, serine, glycine, branched chain amino acids (BCAAs), proline, and asparagine metabolism. The reprogramming of amino acid metabolism can orchestrate energy supply, redox homeostasis, and other metabolism-associated pathways during cancer metastasis. Here, we review the role and function of amino acid metabolic reprogramming in cancer cells colonizing in common metastatic organs, including lung, liver, brain, peritoneum, and bone. In addition, we summarize the current biomarker identification and drug development of cancer metastasis under the amino acid metabolism reprogramming, and discuss the possibility and prospect of targeting organ-specific metastasis for cancer treatment.

A Case Study of Dysfunctional Nicotinamide Metabolism in a 20-Year-Old Male

We present a case study of a 20-year-old male with an unknown neurodegenerative disease who was referred to the Undiagnosed Diseases Network Vanderbilt Medical Center site. A previous metabolic panel showed that the patient had a critical deficiency in nicotinamide intermediates that are generated during the biosynthesis of NAD(H). We followed up on these findings by evaluating the patient's ability to metabolize nicotinamide. We performed a global metabolic profiling analysis of plasma samples that were collected: (1) under normal fed conditions (baseline), (2) after the patient had fasted, and (3) after he was challenged with a 500 mg nasogastric tube bolus of nicotinamide following the fast. Our findings showed that the patient's nicotinamide N-methyltransferase (NNMT), a key enzyme in NAD(H) biosynthesis and methionine metabolism, was not functional under normal fed or fasting conditions but was restored in response to the nicotinamide challenge. Altered levels of metabolites situated downstream of NNMT and in neighboring biochemical pathways provided further evidence of a baseline defect in NNMT activity. To date, this is the only report of a critical defect in NNMT activity manifesting in adulthood and leading to neurodegenerative disease. Altogether, this study serves as an important reference in the rare disease literature and also demonstrates the utility of metabolomics as a diagnostic tool for uncharacterized metabolic diseases.

Identification of an energy metabolism-related six-gene signature for distinguishing and forecasting the prognosis of low-grade gliomas

Background

Low-grade gliomas (LGG) account for 20-25% of all gliomas. In this study, we assessed whether metabolic status was correlated with clinical outcomes in LGG patients using data from The Cancer Genome Atlas (TCGA).

Methods

LGG patient data were collected from TCGA, and the Molecular Signature Database was used to extract gene sets related to energy metabolism. After performing a consensus-clustering algorithm, the LGG patients were divided into four clusters. We then compared the tumor prognosis, function, immune cell infiltration, checkpoint proteins, chemo-resistance, and cancer stem cells (CSC) between the two groups with the greatest prognostic difference. Using least absolute shrinkage and selection operator (LASSO) analysis, an energy metabolism-related signature was further developed.

Results

Energy metabolism-related signatures were applied to identify four clusters (C1, C2, C3, and C4) using a consensus-clustering algorithm. C1 LGG patients were more related to the synapse and had higher CSC scores, more chemo-resistance, and a better prognosis. C4 LGG was observed to have more immune-related pathways and better immunity. We then identified six energy metabolism-related genes (PYGL, HS3ST3B, NNMT, FMOD, CHST6, and B3GNT7) that can accurately predict LGG prognosis not only as a whole but also based on the independent predictions of each of these six genes.

Conclusions

The energy metabolism-related subtypes of LGG were identified, which were strongly related to the immune microenvironment, immune checkpoint proteins, CSCs, chemo-resistance, prognosis, and LGG advancement. A signature of genes involved in energy metabolism could help to distinguish and predict the prognosis of LGG patients, and a promising method to discover patients that may benefit from LGG therapy.

NNMT Is an Immune-Related Prognostic Biomarker That Modulates the Tumor Microenvironment in Pan-Cancer

Emerging evidence has revealed the significant roles of nicotinamide n-methyltransferase (NNMT) in cancer initiation, development, and progression; however, a pan-cancer analysis of NNMT has not been conducted. In this study, we first thoroughly investigated the expression and prognostic significance of NNMT and the relationship between NNMT and the tumor microenvironment using bioinformatic analysis. NNMT was significantly increased and associated with poor prognosis in many common cancers. NNMT expression correlated with the infiltration levels of cancer-associated fibroblasts and macrophages in pan-cancer. Function enrichment analysis discovered that NNMT related to cancer-promoting and immune pathways in various common cancers, such as colon adenocarcinoma, head and neck squamous cell carcinoma, ovarian serous cystadenocarcinoma, and stomach adenocarcinoma. NNMT expression was positively correlated with tumor-associated macrophages (TAMs), especially M2-like TAMs. The results suggest that NNMT might be a new biomarker for immune infiltration and poor prognosis in cancers, providing new direction on therapeutics of cancers.

GPX8 regulates clear cell renal cell carcinoma tumorigenesis through promoting lipogenesis by NNMT

BACKGROUND

Clear cell renal cell carcinoma (ccRCC), with its hallmark phenotype of high cytosolic lipid content, is considered a metabolic cancer. Despite the implication of this lipid-rich phenotype in ccRCC tumorigenesis, the roles and regulators of de novo lipid synthesis (DNL) in ccRCC remain largely unexplained.

METHODS

Our bioinformatic screening focused on ccRCC-lipid phenotypes identified glutathione peroxidase 8 (GPX8), as a clinically relevant upstream regulator of DNL. GPX8 genetic silencing was performed with CRISPR-Cas9 or shRNA in ccRCC cell lines to dissect its roles. Untargeted metabolomics, RNA-seq analyses, and other biochemical assays (e.g., lipid droplets staining, fatty acid uptake, cell proliferation, xenograft, etc.) were carried out to investigate the GPX8's involvement in lipid metabolism and tumorigenesis in ccRCC. The lipid metabolic function of GPX8 and its downstream were also measured by isotope-tracing-based DNL flux measurement.

RESULTS

GPX8 knockout or downregulation substantially reduced lipid droplet levels (independent of lipid uptake), fatty acid de novo synthesis, triglyceride esterification in vitro, and tumor growth in vivo. The downstream regulator was identified as nicotinamide N-methyltransferase (NNMT): its knockdown phenocopied, and its expression rescued, GPX8 silencing both in vitro and in vivo. Mechanically, GPX8 regulated NNMT via IL6-STAT3 signaling, and blocking this axis suppressed ccRCC survival by activating AMPK. Notably, neither the GPX8-NNMT axis nor the DNL flux was affected by the von Hippel Lindau (VHL) status, the conventional regulator of ccRCC high lipid content.

CONCLUSIONS

Taken together, our findings unravel the roles of the VHL-independent GPX8-NNMT axis in ccRCC lipid metabolism as related to the phenotypes and growth of ccRCC, which may be targeted for therapeutic purposes.

NAD+ Homeostasis and NAD+-Consuming Enzymes: Implications for Vascular Health

Nicotinamide adenine dinucleotide (NAD+) is a ubiquitous metabolite that takes part in many key redox reactions. NAD+ biosynthesis and NAD+-consuming enzymes have been attracting markedly increasing interest since they have been demonstrated to be involved in several crucial biological pathways, impacting genes transcription, cellular signaling, and cell cycle regulation. As a consequence, many pathological conditions are associated with an impairment of intracellular NAD+ levels, directly or indirectly, which include cardiovascular diseases, obesity, neurodegenerative diseases, cancer, and aging. In this review, we describe the general pathways involved in the NAD+ biosynthesis starting from the different precursors, analyzing the actual state-of-art of the administration of NAD+ precursors or blocking NAD+-dependent enzymes as strategies to increase the intracellular NAD+ levels or to counteract the decline in NAD+ levels associated with ageing. Subsequently, we focus on the disease-related and age-related alterations of NAD+ homeostasis and NAD+-dependent enzymes in endothelium and the consequent vascular dysfunction, which significantly contributes to a wide group of pathological disorders.

Metabolomics study of ribavirin in the treatment of orthotopic lung cancer based on UPLC-Q-TOF/MS

Ribavirin is a common antiviral drug, especially for patients with hepatitis C. Our recent studies demonstrated that ribavirin showed anti-tumor activity in colorectal cancer and hepatocellular carcinoma, but its effects on lung cancer remains unclear. This study aimed to evaluate the anti-tumor activity of ribavirin against lung cancer and elucidate the underlying mechanism. We established orthotopic mouse model of lung cancer (LLC and GLC-82) and employed an ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS)-based metabolomics approach. We found that ribavirin significantly inhibited the proliferation and colony formation of lung cancer cells. Tumor sizes of orthotopic lung cancer in ribavirin-treated groups were also significantly lower than those in control groups. Metabolomics analysis revealed that ribavirin mainly affected 5 metabolic pathways in orthotopic lung tumor models, taurine and hypotaurine metabolism, nicotinate and nicotinamide metabolism, linoleic acid metabolism, arginine biosynthesis and arachidonic acid metabolism. Furthermore, we identified 5 upregulated metabolites including β-nicotinamide adenine dinucleotide (NAD⁺), nicotinamide (NAM), taurine, ornithine and citrulline, and 7 downregulated metabolites including 1-methylnicotinamide (MNAM), S-adenosyl-l-homocysteine (SAH), N1-Methyl-2-pyridone-5-carboxamide (2PY), homocysteine (Hcy), linoleic acid, arachidonic acid (AA) and argininosuccinic acid in ribavirin-treated groups. These results provide new insight into the anti-tumor mechanism of ribavirin for lung cancer.

Chromatin and Cancer: Implications of Disrupted Chromatin Organization in Tumorigenesis and Its Diversification

A hallmark of cancers is uncontrolled cell proliferation, frequently associated with an underlying imbalance in gene expression. This transcriptional dysregulation observed in cancers is multifaceted and involves chromosomal rearrangements, chimeric transcription factors, or altered epigenetic marks. Traditionally, chromatin dysregulation in cancers has been considered a downstream effect of driver mutations. However, here we present a broader perspective on the alteration of chromatin organization in the establishment, diversification, and therapeutic resistance of cancers. We hypothesize that the chromatin organization controls the accessibility of the transcriptional machinery to regulate gene expression in cancerous cells and preserves the structural integrity of the nucleus by regulating nuclear volume. Disruption of this large-scale chromatin in proliferating cancerous cells in conventional chemotherapies induces DNA damage and provides a positive feedback loop for chromatin rearrangements and tumor diversification. Consequently, the surviving cells from these chemotherapies become tolerant to higher doses of the therapeutic reagents, which are significantly toxic to normal cells. Furthermore, the disorganization of chromatin induced by these therapies accentuates nuclear fragility, thereby increasing the invasive potential of these tumors. Therefore, we believe that understanding the changes in chromatin organization in cancerous cells is expected to deliver more effective pharmacological interventions with minimal effects on non-cancerous cells.

Effects of the SLC38A2-mTOR Pathway Involved in Regulating the Different Compositions of Dietary Essential Amino Acids-Lysine and Methionine on Growth and Muscle Quality in Rabbits

In recent years, ensuring food security has been an important challenge for the world. It is important to make good use of China’s domestic local feed resources to provide safe, stable, efficient, and high-quality rabbit meat products for China and the world. Lysine and methionine are the two most limiting essential amino acids in the rabbit diet. However, little is known about the rational composition of lysine and methionine in rabbit diets and the mechanisms that affect growth and development. Accordingly, in this study, we sought to address this knowledge gap by examining the effects of different compositions of lysine and methionine in rabbit diets. Subsequently, the growth status, nitrogen metabolism, blood biochemical indexes, muscle development, muscle quality, and the growth of satellite cells were evaluated in the animals. The results showed that diets containing 0.80% Lys and 0.40% Met improved average daily weight gain, feed conversion, nitrogen use efficiency, and muscle quality in the rabbits (p < 0.05). Additionally, it altered the amino acid transport potential in muscle by upregulating the expression of the SLC7A10 gene (p < 0.05). Meanwhile, the cell viability and the rate of division and migration of SCs in the 0.80% Lys/0.40 % Met composition group were increased (p < 0.05). SLC38A2 and P−mTOR protein expression was upregulated in the 0.80% lysine/0.40% methionine composition group (p < 0.05). In conclusion, 0.80% Lys/0.40% Met was the most suitable lysine and methionine composition in all tested diets. SLC38A2 acted as an amino acid sensor upstream of mTOR and was involved in the 0.80% Lys/0.40% Met regulation of muscle growth and development, thus implicating the mTOR signaling pathway in these processes.

Novel tricyclic small molecule inhibitors of Nicotinamide N-methyltransferase for the treatment of metabolic disorders

Nicotinamide N-methyltransferase (NNMT) is a metabolic regulator that catalyzes the methylation of nicotinamide (Nam) using the co-factor S-adenosyl-L-methionine to form 1-methyl-nicotinamide (MNA). Overexpression of NNMT and the presence of the active metabolite MNA is associated with a number of diseases including metabolic disorders. We conducted a high-throughput screening campaign that led to the identification of a tricyclic core as a potential NNMT small molecule inhibitor series. Elaborate medicinal chemistry efforts were undertaken and hundreds of analogs were synthesized to understand the structure activity relationship and structure property relationship of this tricyclic series. A lead molecule, JBSNF-000028, was identified that inhibits human and mouse NNMT activity, reduces MNA levels in mouse plasma, liver and adipose tissue, and drives insulin sensitization, glucose modulation and body weight reduction in a diet-induced obese mouse model of diabetes. The co-crystal structure showed that JBSNF-000028 binds below a hairpin structural motif at the nicotinamide pocket and stacks between Tyr-204 (from Hairpin) and Leu-164 (from central domain). JBSNF-000028 was inactive against a broad panel of targets related to metabolism and safety. Interestingly, the improvement in glucose tolerance upon treatment with JBSNF-000028 was also observed in NNMT knockout mice with diet-induced obesity, pointing towards the glucose-normalizing effect that may go beyond NNMT inhibition. JBSNF-000028 can be a potential therapeutic option for metabolic disorders and developmental studies are warranted.

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.

NAD+ Precursors: A Questionable Redundancy

The last decade has seen a strong proliferation of therapeutic strategies for the treatment of metabolic and age-related diseases based on increasing cellular NAD⁺ bioavailability. Among them, the dietary supplementation with NAD⁺ precursors—classically known as vitamin B3—has received most of the attention. Multiple molecules can act as NAD⁺ precursors through independent biosynthetic routes. Interestingly, eukaryote organisms have conserved a remarkable ability to utilize all of these different molecules, even if some of them are scarcely found in nature. Here, we discuss the possibility that the conservation of all of these biosynthetic pathways through evolution occurred because the different NAD⁺ precursors might serve specialized purposes.

Nicotinamide N-Methyltransferase inhibits HBV replication by suppressing NR5A1 expression invitro

Chronic hepatitis B virus (HBV) infection can lead to fibrosis, liver cirrhosis, and primary hepatocellular carcinoma. Investigating host factors that regulate HBV replication helps to identify antiviral targets. In the current study, we identified Nicotinamide N-Methyltransferase gene (NNMT) as a novel factor that regulates HBV transcription. NNMT is up-regulated at both the mRNA and protein levels in HepG2.2.15 cells compared to HepG2 cells. Overexpression of NNMT reduces HBV replication in several cell models, while knockdown of NNMT enhances HBV DNA levels. Mechanistically, NNMT suppresses HBV DNA replication by inhibiting HBV RNA transcription. The region required for the inhibitory effect of NNMT was narrowed to nt 1672-1708 in enhancer II by luciferase assays. On the other hand, ChIP assays and EMSA results showed that NNMT does not bind to this region substantially, either directly or indirectly. Next, a collection of hepatic nuclear receptor transcription factors was screened to determine whether they were affected by NNMT overexpression. NR5A1, a positive regulator of HBV replication, decreased significantly after NNMT overexpression. Collectively, the findings of this study shed light on the regulation of HBV transcription.

NMR Metabolomics Assessment of Osteogenic Differentiation of Adipose-Tissue-Derived Mesenchymal Stem Cells

This Article presents, for the first time to our knowledge, an untargeted nuclear magnetic resonance (NMR) metabolomic characterization of the polar intracellular metabolic adaptations of human adipose-derived mesenchymal stem cells during osteogenic differentiation. The use of mesenchymal stem cells (MSCs) for bone regeneration is a promising alternative to conventional bone grafts, and untargeted metabolomics may unveil novel metabolic information on the osteogenic differentiation of MSCs, allowing their behavior to be understood and monitored/guided toward effective therapies. Our results unveiled statistically relevant changes in the levels of just over 30 identified metabolites, illustrating a highly dynamic process with significant variations throughout the whole 21-day period of osteogenic differentiation, mainly involving amino acid metabolism and protein synthesis; energy metabolism and the roles of glycolysis, the tricarboxylic acid cycle, and oxidative phosphorylation; cell membrane metabolism; nucleotide metabolism (including the specific involvement of O-glycosylation intermediates and NAD⁺); and metabolic players in protective antioxidative mechanisms (such as glutathione and specific amino acids). Different metabolic stages are proposed and are supported by putative biochemical explanations for the metabolite changes observed. This work lays the groundwork for the use of untargeted NMR metabolomics to find potential metabolic markers of osteogenic differentiation efficacy.

Metabolomic Profiling Reveals That 5-Hydroxylysine and 1-Methylnicotinamide Are Metabolic Indicators of Keloid Severity

Background: Keloid is a skin fibroproliferative disease with unknown pathogenesis. Metabolomics provides a new perspective for revealing biomarkers related to metabolites and their metabolic mechanisms. Method: Metabolomics and transcriptomics were used for data analysis. Quality control of the data was performed to standardize the data. Principal component analysis (PCA), PLS-DA, OPLS-DA, univariate analysis, CIBERSORT, neural network model, and machine learning correlation analysis were used to calculate differential metabolites. The molecular mechanisms of characteristic metabolites and differentially expressed genes were identified through enrichment analysis and topological analysis. Result: Compared with normal tissue, lipids have a tendency to decrease in keloids, while peptides have a tendency to increase in keloids. Significantly different metabolites between the two groups were identified by random forest analysis, including 1-methylnicotinamide, 4-hydroxyproline, 5-hydroxylysine, and l-prolinamide. The metabolic pathways which play important roles in the pathogenesis of keloids included arachidonic acid metabolism and d-arginine and d-ornithine metabolism. Metabolomic profiling reveals that 5-hydroxylysine and 1-methylnicotinamide are metabolic indicators of keloid severity. The high-risk early warning index for 5-hydroxylysine is 4 × 10⁸-6.3×10⁸ (p = 0.0008), and the high-risk predictive index for 1-methylnicotinamide is 0.95 × 10⁷-1.6×10⁷ (p = 0.0022). Conclusion: This study was the first to reveal the metabolome profile and transcriptome of keloids. Differential metabolites and metabolic pathways were calculated by machine learning. Metabolomic profiling reveals that 5-hydroxylysine and 1-methylnicotinamide may be metabolic indicators of keloid severity.

A network pharmacology-based approach to explore mechanism of action of medicinal herbs for alopecia treatment

Hair loss is one of the most common skin problems experienced by more than half of the world's population. In East Asia, medicinal herbs have been used widely in clinical practice to treat hair loss. Recent studies, including systematic literature reviews, indicate that medicinal herbs may demonstrate potential effects for hair loss treatment. In a previous study, we identified medical herbs used frequently for alopecia treatment. Herein, we explored the potential novel therapeutic mechanisms of 20 vital medicinal herbs for alopecia treatment that could distinguish them from known mechanisms of conventional drugs using network pharmacology analysis methods. We determined the herb-ingredient–target protein networks and ingredient-associated protein (gene)-associated pathway networks and calculated the weighted degree centrality to define the strength of the connections. Data showed that 20 vital medicinal herbs could exert therapeutic effects on alopecia mainly mediated via regulation of various target genes and proteins, including acetylcholinesterase (AChE), phospholipase A2 (PLA2) subtypes, ecto-5-nucleotidase (NTE5), folate receptor (FR), nicotinamide N-methyltransferase (NNMT), and quinolinate phosphoribosyltransferase (QPRT). Findings regarding target genes/proteins and pathways of medicinal herbs associated with alopecia treatment offer insights for further research to better understand the pathogenesis and therapeutic mechanism of medicinal herbs for alopecia treatment with traditional herbal medicine.

Tumor stromal nicotinamide N-methyltransferase overexpression as a prognostic biomarker for poor clinical outcome in early-stage colorectal cancer

In a quest for prognostic biomarkers in early-stage colorectal cancer, we investigated NNMT (nicotinamide N-methyltransferase) in large cohorts of patients. Immunohistochemical examination of 679 patients illustrates that NNMT protein is predominantly expressed in the cancer stroma at varying levels, and about 20% of cancer tissues overexpress NNMT when compared to levels observed in normal colorectal mucosa. Clinical correlation analyses of 572 patients with early-stage cancers reveal that NNMT protein overexpression is significantly associated with shorter overall and disease-free survival, but no such correlation is found in late-stage colorectal cancer. Analyses of TCGA and CPTAC colorectal cancer cohorts show that NNMT mRNA expression is positively correlated with protein levels, is significantly higher in CIMP-high or MSI subtypes than in CIMP-low or MSS subtypes, and is positively correlated with its paralog INMT but not with its interaction partners such as PNMT, ADK, APP, ATF6, BMF, BRD4, CDC37, or CRYZ. In early-stage cancers, NNMT expression is higher in BRAF-mutated than in BRAF wild type tumors but is not affected by KRAS or PIK3CA mutation status. As a cancer stromal protein with important roles in metabolism and cancer epigenetics, NNMT is emerging as a promising biomarker for risk stratification of early-stage cancers.

Systems-level analysis of transcriptome reorganization during liver regeneration

Tissue homeostasis and regeneration depend on the reversible transitions between quiescence (G0) and proliferation. The liver has a remarkable capacity to regenerate after injury or resection by cell growth and...

Connections between metabolism and epigenetic modifications in cancer

How cells sense and respond to environmental changes is still a key question. It has been identified that cellular metabolism is an important modifier of various epigenetic modifications, such as DNA methylation, histone methylation and acetylation and RNA N6-methyladenosine (m6A) methylation. This closely links the environmental nutrient availability to the maintenance of chromatin structure and gene expression, and is crucial to regulate cellular homeostasis, cell growth and differentiation. Cancer metabolic reprogramming and epigenetic alterations are widely observed, and facilitate cancer development and progression. In cancer cells, oncogenic signaling-driven metabolic reprogramming modifies the epigenetic landscape via changes in the key metabolite levels. In this review, we briefly summarized the current evidence that the abundance of key metabolites, such as S-adenosyl methionine (SAM), acetyl-CoA, α-ketoglutarate (α-KG), 2-hydroxyglutarate (2-HG), uridine diphospho-N-acetylglucosamine (UDP-GlcNAc) and lactate, affected by metabolic reprogramming plays an important role in dynamically regulating epigenetic modifications in cancer. An improved understanding of the roles of metabolic reprogramming in epigenetic regulation can contribute to uncover the underlying mechanisms of metabolic reprogramming in cancer development and identify the potential targets for cancer therapies.

Long non-coding RNA XIST promotes osteoporosis by inhibiting the differentiation of bone marrow mesenchymal stem cell by sponging miR-29b-3p that suppresses nicotinamide N-methyltransferase

Bone formation is important in the development of osteoporosis (OP). X–inactive specific transcript (XIST), a lncRNA, is involved in this process; however, mode of its action is not known. We compared the serum levels of XIST and miR-29b-3p among the patients with and without OP. In rat bone marrow mesenchymal stem cells (BMSCs), during osteogenic differentiation, XIST expression was detected first, followed by overexpression or suppression of miR-29b-3p and NNMT. Expression of osteogenic genes, ALP (electrochemical alkaline phosphatase) and RUNX2 (Runt-related transcription factor 2) were detected by RT-qPCR and western blots, and the calcium nodules in BMSCs were detected by staining. The relationships of XIST, miR-29b-3p, and NNMT were characterized by dual-luciferase reporter assay. Serum XIST was significantly upregulated in patients of OP. XIST downregulated the ALP and Runx2 levels and inhibited calcium nodules, whereas low expression of XIST reversed these events. MiR-29b-3p was inhibited by XIST sponge and lowered the levels of ALP, Runx2, and calcium nodules. NNMT was negatively regulated by miR-29b-3p, promoting the osteogenic differentiation of BMSCs. In conclusion, XIST is highly expressed in OP, and regulates NNMT by sponging miR-29b-3p to suppress the osteogenic differentiation of BMSCs.

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 (NNMT) upregulation via the mTORC1-ATF4 pathway activation contributes to palmitate-induced lipotoxicity in hepatocytes

Defined as the dysfunction and/or cell death caused by toxic lipids accumulation in hepatocytes, hepatic lipotoxicity plays a pathological role in non-alcoholic fatty liver disease. The cellular and molecular mechanisms underlying lipotoxicity remain to be elucidated. In this study, using AML12 cells, a non-transformed murine hepatocyte cell line, exposed to palmitate (a 16-C saturated fatty acid) as an experimental model, we investigated the role and mechanisms of nicotinamide N-methyltransferase (NNMT), a methyltransferase catalyzing nicotinamide methylation and degradation, in hepatic lipotoxicity. We initially identified activating transcription factor 4 (ATF4) as a major transcription factor for hepatic NNMT expression. Here, we demonstrated that palmitate upregulates NNMT expression via activating ATF4 in a mechanistic target of rapamycin complex 1 (mTORC1)-dependent mechanism in that mTORC1 inhibition by both Torin1 and rapamycin attenuated ATF4 activation and NNMT upregulation. We further demonstrated that the mTORC1-dependent ATF4 activation is an integral signaling event of unfolded protein response (UPR) as both ATF4 activation and NNMT upregulation by tunicamycin, a well-documented endoplasmic reticulum (ER) stress inducer, are blunted when hepatocytes were pretreated with Torin1. Importantly, our data uncovered that NNMT upregulation contributes to palmitate-induced hepatotoxicity as NNMT inhibition, via either pharmacological (NNMT inhibitors) or genetic approach (siRNA transfection), provided protection against palmitate lipotoxicity. Our further mechanistic exploration identified protein kinase A (PKA) activation to contribute, at least, partially to the protective effect of NNMT inhibition against lipotoxicity. Collectively, our data demonstrated that NNMT upregulation by the mTORC1-ATF4 pathway activation contributes to the development of lipotoxicity in hepatocytes.

The dynamic broad epigenetic (H3K4me3, H3K27ac) domain as a mark of essential genes

Transcriptionally active chromatin is marked by tri-methylation of histone H3 at lysine 4 (H3K4me3) located after first exons and around transcription start sites. This epigenetic mark is typically restricted to narrow regions at the 5`end of the gene body, though a small subset of genes have a broad H3K4me3 domain which extensively covers the coding region. Although most studies focus on the H3K4me3 mark, the broad H3K4me3 domain is associated with a plethora of histone modifications (e.g., H3 acetylated at K27) and is therein termed broad epigenetic domain. Genes marked with the broad epigenetic domain are involved in cell identity and essential cell functions and have clinical potential as biomarkers for patient stratification. Reducing expression of genes with the broad epigenetic domain may increase the metastatic potential of cancer cells. Enhancers and super-enhancers interact with the broad epigenetic domain marked genes forming a hub of interactions involving nucleosome-depleted regions. Together, the regulatory elements coalesce with transcription factors, chromatin modifying/remodeling enzymes, coactivators, and the Mediator and/or Integrator complex into a transcription factory which may be analogous to a liquid–liquid phase-separated condensate. The broad epigenetic domain has a dynamic chromatin structure which supports frequent transcription bursts. In this review, we present the current knowledge of broad epigenetic domains.

Interaction between Metformin, Folate and Vitamin B12 and the Potential Impact on Fetal Growth and Long-Term Metabolic Health in Diabetic Pregnancies

Metformin is the first-line treatment for many people with type 2 diabetes mellitus (T2DM) and gestational diabetes mellitus (GDM) to maintain glycaemic control. Recent evidence suggests metformin can cross the placenta during pregnancy, thereby exposing the fetus to high concentrations of metformin and potentially restricting placental and fetal growth. Offspring exposed to metformin during gestation are at increased risk of being born small for gestational age (SGA) and show signs of ‘catch up’ growth and obesity during childhood which increases their risk of future cardiometabolic diseases. The mechanisms by which metformin impacts on the fetal growth and long-term health of the offspring remain to be established. Metformin is associated with maternal vitamin B₁₂ deficiency and antifolate like activity. Vitamin B₁₂ and folate balance is vital for one carbon metabolism, which is essential for DNA methylation and purine/pyrimidine synthesis of nucleic acids. Folate:vitamin B₁₂ imbalance induced by metformin may lead to genomic instability and aberrant gene expression, thus promoting fetal programming. Mitochondrial aerobic respiration may also be affected, thereby inhibiting placental and fetal growth, and suppressing mammalian target of rapamycin (mTOR) activity for cellular nutrient transport. Vitamin supplementation, before or during metformin treatment in pregnancy, could be a promising strategy to improve maternal vitamin B₁₂ and folate levels and reduce the incidence of SGA births and childhood obesity. Heterogeneous diagnostic and screening criteria for GDM and the transient nature of nutrient biomarkers have led to inconsistencies in clinical study designs to investigate the effects of metformin on folate:vitamin B₁₂ balance and child development. As rates of diabetes in pregnancy continue to escalate, more women are likely to be prescribed metformin; thus, it is of paramount importance to improve our understanding of metformin’s transgenerational effects to develop prophylactic strategies for the prevention of adverse fetal outcomes.