Analysis of immunohistomorphological changes in the colonic mucosa in a high-saturated fat and high-cholesterol fed streptozotocin/nicotinamide diabetic rat model.

The mucosal surface of gastrointestinal tract is lined with epithelial cells that establish an effective barrier between the lumen and internal environment through intercellular junctions, preventing the passage of potentially harmful substances. The "intestinal barrier function" consist of a defensive system that prevent the passage of antigens, toxins, and microbial products, while maintains the correct development of the epithelial barrier, the immune system and the acquisition of tolerance toward dietary antigens and intestinal microbiota. Intestinal morphology changes subsequent to nutritional variations, stress, aging or diseases, which can also affect the composition of the microbiota, altering the homeostasis of the intestine. A growing body of evidence suggests that alterations in intestinal barrier function favor the development of exaggerated immune responses, leading to metabolic endotoxemia, which seems to be the origin of many chronic metabolic diseases such as type 2 diabetes mellitus (T2DM). Although the mechanisms are still unknown, the interaction between dietary patterns, gut microbiota, intestinal mucosa, and metabolic inflammation seems to be a key factor for the development of T2DM, among other diseases. This chapter details the different techniques that allow evaluating the morphological and molecular alterations that lead of the intestinal barrier dysfunction in a T2DM experimental model. To induce both diabetic metabolic disturbances and gut barrier disruption, Wistar rats were fed a high-saturated fat and high-cholesterol diet and received a single dose of streptozotocin/nicotinamide. This animal model may contribute to clarify the understanding of the role of intestinal barrier dysfunction on the late-stage T2DM etiology.

Prophylactic nicotinamide treatment protects from rotenone-induced neurodegeneration by increasing mitochondrial content and volume.

Leber's hereditary optic neuropathy (LHON) is driven by mtDNA mutations affecting Complex I presenting as progressive retinal ganglion cell dysfunction usually in the absence of extra-ophthalmic symptoms. There are no long-term neuroprotective agents for LHON. Oral nicotinamide provides a robust neuroprotective effect against mitochondrial and metabolic dysfunction in other retinal injuries. We explored the potential for nicotinamide to protect mitochondria in LHON by modelling the disease in mice through intravitreal injection of the Complex I inhibitor rotenone. Using MitoV mice expressing a mitochondrial-tagged YFP in retinal ganglion cells we assessed mitochondrial morphology through super-resolution imaging and digital reconstruction. Rotenone induced Complex I inhibition resulted in retinal ganglion cell wide mitochondrial loss and fragmentation. This was prevented by oral nicotinamide treatment. Mitochondrial ultrastructure was quantified by transition electron microscopy, demonstrating a loss of cristae density following rotenone injection, which was also prevented by nicotinamide treatment. These results demonstrate that nicotinamide protects mitochondria during Complex I dysfunction. Nicotinamide has the potential to be a useful treatment strategy for LHON to limit retinal ganglion cell degeneration.

Structural insights into Xanthomonas campestris pv. campestris NAD+ biosynthesis via the NAM salvage pathway.

Nicotinamide phosphoribosyltransferase (NAMPT) plays an important role in the biosynthesis of nicotinamide adenine dinucleotide (NAD+) via the nicotinamide (NAM) salvage pathway. While the structural biochemistry of eukaryote NAMPT has been well studied, the catalysis mechanism of prokaryote NAMPT at the molecular level remains largely unclear. Here, we demonstrated the NAMPT-mediated salvage pathway is functional in the Gram-negative phytopathogenic bacterium Xanthomonas campestris pv. campestris (Xcc) for the synthesis of NAD+, and the enzyme activity of NAMPT in this bacterium is significantly higher than that of human NAMPT in vitro. Our structural analyses of Xcc NAMPT, both in isolation and in complex with either the substrate NAM or the product nicotinamide mononucleotide (NMN), uncovered significant details of substrate recognition. Specifically, we revealed the presence of a NAM binding tunnel that connects the active site, and this tunnel is essential for both catalysis and inhibitor binding. We further demonstrated that NAM binding in the tunnel has a positive cooperative effect with NAM binding in the catalytic site. Additionally, we discovered that phosphorylation of the His residue at position 229 enhances the substrate binding affinity of Xcc NAMPT and is important for its catalytic activity. This work reveals the importance of NAMPT in bacterial NAD+ synthesis and provides insights into the substrate recognition and the catalytic mechanism of bacterial type II phosphoribosyltransferases.

Establishment of an iPSC line (BCHNDi001-A) from a patient with nicotinamide nucleotide repair system deficiency caused by biallelic NAXD mutations.

NAD(P)HX dehydratase (NAXD) gene is one of the key enzymes encoding the nicotinamide nucleotide repair system, reportedly associated with Encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy, 2 (PEBEL2). Here, we generated an induced pluripotent stem cell (iPSC) line from the dermal fibroblasts (HDFs) of a PEBEL2 patient who carried biallelic mutations, c.101_102delTA(p.Thr35Phefs*63) and c.318C > G (p.Ile160Met) in NAXD. These iPSCs showed stable amplification in vitro, expressed pluripotent markers, and differentiated spontaneously into three germ layers, as well as NAXD mutations with normal karyotype.

Improvement of an enzymatic cascade synthesis of nicotinamide mononucleotide via protein engineering and reaction-process reinforcement.

Enzymatic synthesis of ß-nicotinamide mononucleotide (NMN) from D-ribose has garnered widespread attention due to its cheap material, the use of mild reaction conditions, and the ability to produce highly pure products with the desired optical properties. However, the overall NMN yield of this method is impeded by the low activity of rate-limiting enzymes. The ribose-phosphate diphosphokinase (PRS) and nicotinamide phosphoribosyltransferase (NAMPT), that control the rate of the reaction, were engineered to improve the reaction efficacy. The actives of mutants PRS-H150Q and NAMPT-Y15S were 334% and 57% higher than that of their corresponding wild-type enzymes, respectively. Furthermore, by adding pyrophosphatase, the byproduct pyrophosphate which can inhibit the activity of NAMPT was degraded, leading to a 6.72% increase in NMN yield. Following with reaction-process reinforcement, a high yield of 8.10 g L-1 NMN was obtained after 3 h of reaction, which was 56.86-fold higher than that of the stepwise reaction synthesis (0.14 g L-1 ), indicating that the in vitro enzymatic synthesis of NMN from D-ribose and niacinamide is an economical and feasible route.

Inhibitors of NAD+ Production in Cancer Treatment: State of the Art and Perspectives.

The addiction of tumors to elevated nicotinamide adenine dinucleotide (NAD+) levels is a hallmark of cancer metabolism. Obstructing NAD+ biosynthesis in tumors is a new and promising antineoplastic strategy. Inhibitors developed against nicotinamide phosphoribosyltransferase (NAMPT), the main enzyme in NAD+ production from nicotinamide, elicited robust anticancer activity in preclinical models but not in patients, implying that other NAD+-biosynthetic pathways are also active in tumors and provide sufficient NAD+ amounts despite NAMPT obstruction. Recent studies show that NAD+ biosynthesis through the so-called "Preiss-Handler (PH) pathway", which utilizes nicotinate as a precursor, actively operates in many tumors and accounts for tumor resistance to NAMPT inhibitors. The PH pathway consists of three sequential enzymatic steps that are catalyzed by nicotinate phosphoribosyltransferase (NAPRT), nicotinamide mononucleotide adenylyltransferases (NMNATs), and NAD+ synthetase (NADSYN1). Here, we focus on these enzymes as emerging targets in cancer drug discovery, summarizing their reported inhibitors and describing their current or potential exploitation as anticancer agents. Finally, we also focus on additional NAD+-producing enzymes acting in alternative NAD+-producing routes that could also be relevant in tumors and thus become viable targets for drug discovery.

The therapeutic perspective of NAD+ precursors in age-related diseases.

Nicotinamide adenine dinucleotide (NAD+) is the fundamental molecule that performs numerous biological reactions and is crucial for maintaining cellular homeostasis. Studies have found that NAD+ decreases with age in certain tissues, and age-related NAD+ depletion affects physiological functions and contributes to various aging-related diseases. Supplementation of NAD+ precursor significantly elevates NAD+ levels in murine tissues, effectively mitigates metabolic syndrome, enhances cardiovascular health, protects against neurodegeneration, and boosts muscular strength. Despite the versatile therapeutic functions of NAD+ in animal studies, the efficacy of NAD+ precursors in clinical studies have been limited compared with that in the pre-clinical study. Clinical studies have demonstrated that NAD+ precursor treatment efficiently increases NAD+ levels in various tissues, though their clinical proficiency is insufficient to ameliorate the diseases. However, the latest studies regarding NAD+ precursors and their metabolism highlight the significant role of gut microbiota. The studies found that orally administered NAD+ intermediates interact with the gut microbiome. These findings provide compelling evidence for future trials to further explore the involvement of gut microbiota in NAD+ metabolism. Also, the reduced form of NAD+ precursor shows their potential to raise NAD+, though preclinical studies have yet to discover their efficacy. This review sheds light on NAD+ therapeutic efficiency in preclinical and clinical studies and the effect of the gut microbiota on NAD+ metabolism.

Improvement of transdermal absorption rate by nonthermal biocompatible atmospheric pressure plasma.

Nonthermal biocompatible plasma (NBP) is a promising option for improving medication absorption into the human skin. Currently, most plasma devices for cosmetics employ a floating-electrode plasma source for treating the skin. Human skin serves as the ground electrode in the floating-electrode plasma discharge, and discharge occurs between the skin and electrodes of the device. In this in vitro study, we aimed to evaluate the effect of NBP on the skin permeation of niacinamide. We have quantified the transdermal absorption rates of niacinamide in both untreated skin and skin treated with NBP for a duration of 10 s. The absorption of niacinamide for both without and with NBP treatment was observed until 12 h incubation time. Without plasma treatment, the human skin exhibited stable and low transdermal absorption of niacinamide up to 12 h. However, the NBP treatment significantly increased the transdermal absorption of niacinamide from 0.5 h to 6 h and continuously increased skin penetration over a duration of more than 12 h incubation period. The obtained results suggest that NBP-treated human skin showed a 60-fold higher penetration rate than non-treated skin. The increased penetration rate of niacinamide can be mainly attributed to plasmaporation subsequent to NBP treatment. The findings of this study demonstrate that NBP treatment results in remarkable skin permeability, making it a promising candidate for both cosmetic and pharmaceutical delivery applications.

Nicotinamide prevention in diabetes-induced alterations in the rat liver.

Objective. The study was performed to elucidate whether nicotinamide (NAm) can attenuate the diabetes-induced liver damage by correction of ammonia detoxifying function and disbalance of NAD-dependent processes in diabetic rats. Methods. After four weeks of streptozotocin-induced diabetes, Wistar male rats were treated for two weeks with or without NAm. Urea concentration, arginase, and glutamine synthetase activities, NAD+ levels, and NAD+/NADH ratio were measured in cytosolic liver extracts. Expression of parp-1 gene in the liver was estimated by quantitative polymerase chain reaction and PARP-1 cleavage evaluated by Western blotting. Results. Despite the blood plasma lipid peroxidation products in diabetic rats were increased by 60%, the activity of superoxide dismutase (SOD) was reduced. NAm attenuated the oxidative stress, but did not affect the enzyme activity in diabetic rats. In liver of the diabetic rats, urea concentration and arginase activity were significantly higher than in the controls. The glutamine synthetase activity was decreased. Decline in NAD+ level and cytosolic NAD+/NADH ratio in the liver of diabetic rats was observed. Western blot analysis demonstrated a significant up-regulation of PARP-1 expression accompanied by the enzyme cleavage in the diabetic rat liver. However, no correlation was seen between mRNA expression of parp-1 gene and PARP-1 protein in the liver of diabetic rats. NAm markedly attenuated PARP-1 cleavage induced by diabetes, but did not affect the parp-1 gene expression. Conclusions. NAm counteracts diabetes-induced impairments in the rat liver through improvement of its detoxifying function, partial restoration of oxidative stress, NAD+ level, normalization of redox state of free cytosolic NAD+/NADH-couples, and prevention of PARP-1 cleavage.

CaV3.1 channels facilitate calcium wave generation and myogenic tone development in mouse mesenteric arteries.

The arterial myogenic response to intraluminal pressure elicits constriction to maintain tissue perfusion. Smooth muscle [Ca2+] is a key determinant of constriction, tied to L-type (CaV1.2) Ca2+ channels. While important, other Ca2+ channels, particularly T-type could contribute to pressure regulation within defined voltage ranges. This study examined the role of one T-type Ca2+ channel (CaV3.1) using C57BL/6 wild type and CaV3.1-/- mice. Patch-clamp electrophysiology, pressure myography, blood pressure and Ca2+ imaging defined the CaV3.1-/- phenotype relative to C57BL/6. CaV3.1-/- mice had absent CaV3.1 expression and whole-cell current, coinciding with lower blood pressure and reduced mesenteric artery myogenic tone, particularly at lower pressures (20-60 mmHg) where membrane potential is hyperpolarized. This reduction coincided with diminished Ca2+ wave generation, asynchronous events of Ca2+ release from the sarcoplasmic reticulum, insensitive to L-type Ca2+ channel blockade (Nifedipine, 0.3 µM). Proximity ligation assay (PLA) confirmed IP3R1/CaV3.1 close physical association. IP3R blockade (2-APB, 50 µM or xestospongin C, 3 µM) in nifedipine-treated C57BL/6 arteries rendered a CaV3.1-/- contractile phenotype. Findings indicate that Ca2+ influx through CaV3.1 contributes to myogenic tone at hyperpolarized voltages through Ca2+-induced Ca2+ release tied to the sarcoplasmic reticulum. This study helps establish CaV3.1 as a potential therapeutic target to control blood pressure.

Binding Affinity Studies of Nicotinamide N-methyltransferase and Ligands by Saturation Transfer Difference NMR.

INTRODUCTION: Nicotinamide N-methyltransferase (NNMT) catalyzes the N-methylation of nicotinamide with S-adenosine-L-methionine (SAM) as the methyl donor. Abnormal expression of NNMT is associated with many diseases (such as multiple cancers and metabolic and liver diseases), making NNMT a potential therapeutic target. Limited studies concerning the enzymesubstrate/ inhibitor interactions could be found to fully understand the detailed reaction mechanism. METHODS: The binding affinity and ligand binding epitopes of nicotinamide or SAH for binding NNMT and its mutants were determined using saturated transfer difference (STD) nuclear magnetic resonance (NMR) techniques combined with site-directed mutagenesis. RESULTS: The average dissociation constant of WT NNMT with nicotinamide and S-adenosine homocysteine (SAH) was 5.5 ± 0.9 mM and 1.2 ± 0.3 mM, respectively, while the mutants Y20F and Y20G with nicotinamide were up to nearly 4 times and 20 times that of WT and with SAH nearly 2 times and 5 times that of WT. The data suggested that WT had the highest binding affinity for nicotinamide or SAH, followed by Y20F and Y20G, which was consistent with its catalytic activity. CONCLUSION: The binding affinity of nicotinamide and SAH to NNMT and its mutants were obtained by STD NMR in this study. It was found that nicotinamide and SAH bind to WT in a particular orientation, and Y20 is critical for their binding orientation and affinity to NNMT.

Nicotinamide riboside intervention alleviates hematopoietic system injury of ionizing radiation-induced premature aging mice.

Radiotherapy destroys cancer cells and inevitably harms normal human tissues, causing delayed effects of acute radiation exposure (DEARE) and accelerating the aging process in most survivors. However, effective methods for preventing premature aging induced by ionizing radiation are lacking. In this study, the premature aging mice of DEARE model was established after 6 Gy total body irradiation (TBI). Then the therapeutic effects and mechanism of nicotinamide riboside on the premature aging mice were evaluated. The results showed that 6 Gy TBI induced premature aging of the hematopoietic system in mice. Nicotinamide riboside treatment reversed aging spleen phenotypes by inhibiting cellular senescence and ameliorated serum metabolism profiles. Further results demonstrated that nicotinamide riboside supplementation alleviated the myeloid bias of hematopoietic stem cells and temporarily restored the regenerative capacity of hematopoietic stem cells probably by mitigating the reactive oxygen species activated GCN2/eIF2α/ATF4 signaling pathway. The results of this study firstly indicate that nicotinamide riboside shows potential as a DEARE therapeutic agent for radiation-exposed populations and patients who received radiotherapy.

A riboside hydrolase that salvages both nucleobases and nicotinamide in the auxotrophic parasite Trichomonas vaginalis.

Pathogenic parasites of the Trichomonas genus are causative agents of sexually transmitted diseases affecting millions of individuals worldwide and whose outcome may include stillbirths and enhanced cancer risks and susceptibility to HIV infection. Trichomonas vaginalis relies on imported purine and pyrimidine nucleosides and nucleobases for survival, since it lacks the enzymatic activities necessary for de novo biosynthesis. Here we show that T. vaginalis additionally lacks homologues of the bacterial or mammalian enzymes required for the synthesis of the nicotinamide ring, a crucial component in the redox cofactors NAD+ and NADP. Moreover, we show that a yet fully uncharacterized T. vaginalis protein homologous to bacterial and protozoan nucleoside hydrolases is active as a pyrimidine nucleosidase but shows the highest specificity toward the NAD+ metabolite nicotinamide riboside. Crystal structures of the trichomonal riboside hydrolase in different states reveals novel intermediates along the nucleoside hydrolase-catalyzed hydrolytic reaction, including an unexpected asymmetry in the homotetrameric assembly. The active site structure explains the broad specificity toward different ribosides and offers precise insights for the engineering of specific inhibitors that may simultaneously target different essential pathways in the parasite.

Effect of Exercise and Oral Niacinamide Mononucleotide on Improving Mitochondrial Autophagy in Alzheimer's Disease.

Oral niacinamide mononucleotide (NMN) and aerobic exercise have been shown to enhance niacinamide adenine dinucleotide (NAD+) in the body. NAD+ plays a critical role in the body and can directly and indirectly affect many key cellular functions, including metabolic pathways, DNA repair, chromatin remodeling, cell aging, and immune cell function. It is noteworthy that the level of NAD+ decreases gradually with increasing age. Decreased levels of NAD+ have been causally associated with a number of diseases associated with aging, including cognitive decline, cancer, metabolic diseases, sarcopenia, and frailty. Many diseases related to aging can be slowed down or even reversed by restoring NAD+ levels. For example, oral NMN or exercise to increase NAD+ levels in APP/PS1 mice have been proven to improve mitochondrial autophagy, but currently, there is no regimen combining oral NMN with exercise. This review summarizes recent studies on the effect of oral NMN on the enhancement of NAD+ in vivo and the improvements in mitochondrial autophagy abnormalities in AD through aerobic exercise, focusing on (1) how oral NMN improves the internal NAD+ level; (2) how exercise regulates the content of NAD+ in the body; (3) the relationship between exercise activation of NAD+ and AMPK; (4) how SIRT1 is regulated by NAD+ and AMPK and activates PGC-1α to mediate mitochondrial autophagy through changes in mitochondrial dynamics. By summarizing the results of the above four aspects, and combined with the synthesis of NAD+ in vivo, we can infer how exercise elevates the level of NAD+ in vivo to mediate mitochondrial autophagy, so as to propose a new hypothesis that exercise interferes with Alzheimer's disease (AD).

NAD+ Precursors and Intestinal Inflammation: Therapeutic Insights Involving Gut Microbiota.

The oxidized form of nicotinamide adenine dinucleotide (NAD+) is a critical metabolite for living cells. NAD+ may act either as a cofactor for many cellular reactions as well as a coenzyme for different NAD+-consuming enzymes involved in the physiological homeostasis of different organs and systems. In mammals, NAD+ is synthesized from either tryptophan or other vitamin B3 intermediates that act as NAD+ precursors. Recent research suggests that NAD+ precursors play a crucial role in maintaining the integrity of the gut barrier. Indeed, its deficiency has been associated with enhanced gut inflammation and leakage, and dysbiosis. Conversely, NAD+-increasing therapies may confer protection against intestinal inflammation in experimental conditions and human patients, with accumulating evidence indicating that such favorable effects could be, at least in part, mediated by concomitant changes in the composition of intestinal microbiota. However, the mechanisms by which NAD+-based treatments affect the microbiota are still poorly understood. In this context, we have focused specifically on the impact of NAD+ deficiency on intestinal inflammation and dysbiosis in animal and human models. We have further explored the relationship between NAD+ and improved host intestinal metabolism and immunity and the composition of microbiota in vivo. Overall, this comprehensive review aims to provide a new perspective on the effect of NAD+-increasing strategies on host intestinal physiology.

Defining NAD(P)(H) Catabolism.

Dietary vitamin B3 components, such as nicotinamide and nicotinic acid, are precursors to the ubiquitous redox cofactor nicotinamide adenine dinucleotide (NAD+). NAD+ levels are thought to decline with age and disease. While the drivers of this decline remain under intense investigation, strategies have emerged seeking to functionally maintain NAD+ levels through supplementation with NAD+ biosynthetic intermediates. These include marketed products, such as nicotinamide riboside (NR) and its phosphorylated form (NMN). More recent developments have shown that NRH (the reduced form of NR) and its phosphorylated form NMNH also increases NAD+ levels upon administration, although they initially generate NADH (the reduced form of NAD+). Other means to increase the combined levels of NAD+ and NADH, NAD(H), include the inhibition of NAD+-consuming enzymes or activation of biosynthetic pathways. Multiple studies have shown that supplementation with an NAD(H) precursor changes the profile of NAD(H) catabolism. Yet, the pharmacological significance of NAD(H) catabolites is rarely considered although the distribution and abundance of these catabolites differ depending on the NAD(H) precursor used, the species in which the study is conducted, and the tissues used for the quantification. Significantly, some of these metabolites have emerged as biomarkers in physiological disorders and might not be innocuous. Herein, we review the known and emerging catabolites of the NAD(H) metabolome and highlight their biochemical and physiological function as well as key chemical and biochemical reactions leading to their formation. Furthermore, we emphasize the need for analytical methods that inform on the full NAD(H) metabolome since the relative abundance of NAD(H) catabolites informs how NAD(H) precursors are used, recycled, and eliminated.

Elevation of NAD+ by nicotinamide riboside spares spinal cord tissue from injury and promotes locomotor recovery.

Spinal cord injury (SCI)-induced tissue damage spreads to neighboring spared cells in the hours, days, and weeks following injury, leading to exacerbation of tissue damage and functional deficits. Among the biochemical changes is the rapid reduction of cellular nicotinamide adenine dinucleotide (NAD+), an essential coenzyme for energy metabolism and an essential cofactor for non-redox NAD+-dependent enzymes with critical functions in sensing and repairing damaged tissue. NAD+ depletion propagates tissue damage. Augmenting NAD+ by exogenous application of NAD+, its synthesizing enzymes, or its cellular precursors mitigates tissue damage. Nicotinamide riboside (NR) is considered to be one of the most promising NAD+ precursors for clinical application due to its ability to safely and effectively boost cellular NAD+ synthesis in rats and humans. Moreover, various preclinical studies have demonstrated that NR can provide tissue protection. Despite these promising findings, little is known about the potential benefits of NR in the context of SCI. In the current study, we tested whether NR administration could effectively increase NAD+ levels in the injured spinal cord and whether this augmentation of NAD+ would promote spinal cord tissue protection and ultimately lead to improvements in locomotor function. Our findings indicate that administering NR (500 mg/kg) intraperitoneally from four days before to two weeks after a mid-thoracic contusion-SCI injury, effectively doubles NAD+ levels in the spinal cord of Long-Evans rats. Moreover, NR administration plays a protective role in preserving spinal cord tissue post-injury, particularly in neurons and axons, as evident from the observed gray and white matter sparing. Additionally, it enhances motor function, as evaluated through the BBB subscore and missteps on the horizontal ladderwalk. Collectively, these findings demonstrate that administering NR, a precursor of NAD+, increases NAD+ within the injured spinal cord and effectively mitigates the tissue damage and functional decline that occurs following SCI.

Identification of structural determinants of nicotinamide phosphoribosyl transferase (NAMPT) activity and substrate selectivity.

NAD homeostasis in mammals requires the salvage of nicotinamide (Nam), which is cleaved from NAD+ by sirtuins, PARPs, and other NAD+-dependent signaling enzymes. Nam phosphoribosyltransferase (NAMPT) catalyzes the rate-limiting step in vitamin B3 salvage, whereby Nam reacts with phosphoribosyl pyrophosphate (PRPP) to form nicotinamide mononucleotide. NAMPT has a high affinity towards Nam, which is further enhanced by autophosphorylation of His247. The mechanism of this enhancement has remained unknown. Here, we present high-resolution crystal structures and biochemical data that provide reasoning for the increased affinity of the phosphorylated NAMPT for its substrate. Structural and kinetic analyses suggest a mechanism that includes Mg2+ coordination by phospho-His247, such that PRPP is stabilized in a position highly favorable for catalysis. Under these conditions, nicotinic acid (NA) can serve as a substrate. Moreover, we demonstrate that a stretch of 10 amino acids, present only in NAMPTs from deuterostomes, facilitates conformational plasticity and stabilizes the chemically unstable phosphorylation of His247. Thereby the apparent substrate affinity is considerably enhanced compared to prokaryotic NAMPTs. Collectively, our study provides a structural basis for the important function of NAMPT to recycle Nam into NAD biosynthesis with high affinity.

Nicotinamide supplementation alters plasma lipidomic profiles of peripartal dairy cows.

Fatty liver syndrome, a common health problem in dairy cows, occurs during the transition from pregnancy to lactation. If the energy supplied to the cow's body cannot meet its needs, a negative energy balance ensues, and the direct response is fat mobilization. Nicotinamide (NAM) has been reported to reduce the nonesterified fatty acid concentration of postpartum plasma. To study the biochemical adaptations underlying this physiologic dysregulation, 12 dairy cows were sequentially assigned to a NAM (45 g/day) treatment or control group. Blood samples were collected on day (D) 1 and D21 relative to parturition. Changes to the plasma lipid metabolism of dairy cows in the two groups were compared using lipidomics. There were significant increases in plasma sphingomyelins d18:1/18:0, d18:1/23:0, d18:1/24:1, d18:1/24:0, and d18:0/24:0 in the NAM group on D1 relative to parturition. In addition, fatty acids 18:2, 18:1, 18:0, 16:1, and 16:0 were obviously decreased on D21 relative to calving. This research has provided insights into how NAM supplementation improves lipid metabolism in perinatal dairy cows.