NAD Abstracts 1

© 2011

NAD+ metabolism in health and disease

            (Belenky, Bogan et al. 2007) Download

Nicotinamide adenine dinucleotide (NAD(+)) is both a coenzyme for hydride-transfer enzymes and a substrate for NAD(+)-consuming enzymes, which include ADP-ribose transferases, poly(ADP-ribose) polymerases, cADP-ribose synthases and sirtuins. Recent results establish protective roles for NAD(+) that might be applicable therapeutically to prevent neurodegenerative conditions and to fight Candida glabrata infection. In addition, the contribution that NAD(+) metabolism makes to lifespan extension in model systems indicates that therapies to boost NAD(+) might promote some of the beneficial effects of calorie restriction. Nicotinamide riboside, the recently discovered nucleoside precursor of NAD(+) in eukaryotic systems, might have advantages as a therapy to elevate NAD(+) without inhibiting sirtuins, which is associated with high-dose nicotinamide, or incurring the unpleasant side-effects of high-dose nicotinic acid.

Therapeutic effects of oral NADH on the symptoms of patients with chronic fatigue syndrome

            (Forsyth, Preuss et al. 1999) Download

BACKGROUND: Chronic fatigue syndrome (CFS) is a disorder of unknown etiology, consisting of prolonged, debilitating fatigue, and a multitude of symptoms including neurocognitive dysfunction, flu-like symptoms, myalgia, weakness, arthralgia, low-grade fever, sore throat, headache, sleep disturbances, and swelling and tenderness of lymph nodes. No effective treatment for CFS is known. OBJECTIVE: The purpose of the study was to evaluate the efficacy of the reduced form of nicotinamide adenine dinucleotide (NADH) i.e., ENADA the stabilized oral absorbable form, in a randomized, double-blind, placebo-controlled crossover study in patients with CFS. Nicotinamide adenine dinucleotide is known to trigger energy production through ATP generation which may form the basis of its potential effects. METHODS: Twenty-six eligible patients who fulfilled the Center for Disease Control and Prevention criteria for CFS completed the study. Medical history, physical examination, laboratory studies, and questionnaire were obtained at baseline, 4, 8, and 12 weeks. Subjects were randomly assigned to receive either 10 mg of NADH or placebo for a 4-week period. Following a 4-week washout period, subjects were crossed to the alternate regimen for a final 4-week period. RESULTS: No severe adverse effects were observed related to the study drug. Within this cohort of 26 patients, 8 of 26 (31%) responded favorably to NADH in contrast to 2 of 26 (8%) to placebo. Based upon these encouraging results we have decided to conduct an open-label study in a larger cohort of patients. CONCLUSION: Collectively, the results of this pilot study indicate that NADH may be a valuable adjunctive therapy in the management of the chronic fatigue syndrome and suggest that further clinical trials be performed to establish its efficacy in this clinically perplexing disorder.

Nampt: linking NAD biology, metabolism and cancer

            (Garten, Petzold et al. 2009) Download

Nicotinamide phosphoribosyltransferase (Nampt) converts nicotinamide to nicotinamide mononucleotide (NMN), a key nicotinamide adenine dinucleotide (NAD) intermediate. Previously identified as a cytokine pre-B-cell colony-enhancing factor and controversially claimed as an insulin-mimetic hormone visfatin, Nampt has recently drawn much attention in several fields, including NAD biology, metabolism and inflammation. As a NAD biosynthetic enzyme, Nampt regulates the activity of NAD-consuming enzymes such as sirtuins and influences a variety of metabolic and stress responses. Nampt also plays an important part in regulating insulin secretion in pancreatic beta-cells. Nampt seems to have another function as an immunomodulatory cytokine and, therefore, has a role in inflammation. This review summarizes these various functional aspects of Nampt and discusses its potential roles in diseases, including type 2 diabetes and cancer.

Elevation of cellular NAD levels by nicotinic acid and involvement of nicotinic acid phosphoribosyltransferase in human cells

            (Hara, Yamada et al. 2007) Download

NAD plays critical roles in various biological processes through the function of SIRT1. Although classical studies in mammals showed that nicotinic acid (NA) is a better precursor than nicotinamide (Nam) in elevating tissue NAD levels, molecular details of NAD synthesis from NA remain largely unknown. We here identified NA phosphoribosyltransferase (NAPRT) in humans and provided direct evidence of tight link between NAPRT and the increase in cellular NAD levels. The enzyme was abundantly expressed in the small intestine, liver, and kidney in mice and mediated [(14)C]NAD synthesis from [(14)C]NA in human cells. In cells expressing endogenous NAPRT, the addition of NA but not Nam almost doubled cellular NAD contents and decreased cytotoxicity by H(2)O(2). Both effects were reversed by knockdown of NAPRT expression. These results indicate that NAPRT is essential for NA to increase cellular NAD levels and, thus, to prevent oxidative stress of the cells. Kinetic analyses revealed that NAPRT, but not Nam phosphoribosyltransferase (NamPRT, also known as pre-B-cell colony-enhancing factor or visfatin), is insensitive to the physiological concentration of NAD. Together, we conclude that NA elevates cellular NAD levels through NAPRT function and, thus, protects the cells against stress, partly due to lack of feedback inhibition of NAPRT but not NamPRT by NAD. The ability of NA to increase cellular NAD contents may account for some of the clinically observed effects of the vitamin and further implies a novel application of the vitamin to treat diseases such as those associated with the depletion of cellular NAD pools.

Protecting axonal degeneration by increasing nicotinamide adenine dinucleotide levels in experimental autoimmune encephalomyelitis models

            (Kaneko, Wang et al. 2006) Download

Axonal damage is a major morphological alteration in the CNS of patients with multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). However, the underlying mechanism for the axonal damage associated with MS/EAE and its contribution to the clinical symptoms remain unclear. The expression of a fusion protein, named "Wallerian degeneration slow" (Wld(S)), can protect axons from degeneration, likely through a beta-nicotinamide adenine dinucleotide (NAD)-dependent mechanism. In this study, we find that, when induced with EAE, Wld(S) mice showed a modest attenuation of behavioral deficits and axon loss, suggesting that EAE-associated axon damage may occur by a mechanism similar to Wallerian degeneration. Furthermore, nicotinamide (NAm), an NAD biosynthesis precursor, profoundly prevents the degeneration of demyelinated axons and improves the behavioral deficits in EAE models. Finally, we demonstrate that delayed NAm treatment is also beneficial to EAE models, pointing to the therapeutic potential of NAm as a protective agent for EAE and perhaps MS patients.

Niacin status, NAD distribution and ADP-ribose metabolism

            (Kirkland 2009) Download

Dietary niacin deficiency, and pharmacological excesses of nicotinic acid or nicotinamide, have dramatic effects on cellular NAD pools, ADP-ribose metabolism, tissue function and health. ADP-ribose metabolism is providing new targets for pharmacological intervention, and it is important to consider how the supply of vitamin B3 may directly influence ADP-ribosylation reactions, or create interactions with other drugs designed to influence these pathways. In addition to its redox roles, NAD+ is used as a substrate for mono-, poly- and cyclic ADP-ribose formation. During niacin deficiency, not all of these processes can be maintained, and dramatic changes in tissue function and clinical condition take place. Conversely, these reactions may be differentially enhanced by pharmacological intakes of vitamin B3, and potentially by changing expression of specific NAD generating enzymes. A wide range of metabolic changes can take place following pharmacological supplementation of nicotinic acid or nicotinamide. As niacin status decreases towards a deficient state, the function of other types of pharmaceutical agents may be modified, including those that target ADP-ribosylation reactions, apoptosis and inflammation. This article will explore what is known and yet to be learned about the response of tissues, cells and subcellular compartments to excessive and limiting supplies of niacin, and will discuss the etiology of the resulting pathologies.

Enzymology of mammalian NAD metabolism in health and disease

            (Magni, Orsomando et al. 2008) Download

Mounting evidence attests to the paramount importance of the non-redox NAD functions. Indeed, NAD homeostasis is related to the free radicals-mediated production of reactive oxygen species responsible for irreversible cellular damage in infectious disease, diabetes, inflammatory syndromes, neurodegeneration and cancer. Because the cellular redox status depends on both the absolute concentration of pyridine dinucleotides and their respective ratios of oxidized and reduced forms (i.e., NAD/NADH and NADP/NADPH), it is conceivable that an altered regulation of the synthesis and degradation of NAD impairs the cell redox state and likely contributes to the mechanisms underlying the pathogenesis of the above mentioned diseases. Taking into account the recent appearance in the literature of comprehensive reviews covering different aspects of the significance of NAD metabolism, with particular attention to the enzymes involved in NAD cleavage, this monograph includes the most recent results on NAD biosynthesis in mammals and humans. Due to recent findings on nicotinamide riboside as a nutrient, its inclusion under "niacins" is proposed. Here, the enzymes involved in the de novo and reutilization pathways are overviewed.

Aging-related nicotinamide adenine dinucleotide oxidase response to dietary supplementation: the French paradox revisited

            (Morre, Morre et al. 2010) Download

Aging-related cell-surface NADH oxidase (arNOX)-specific activities increase with age between age 30 and ages 50-65. The protein is shed and circulates. Activity correlates with a number of aging-related disorders including low-density lipoprotein (LDL) oxidation as a precondition to atherosclerosis as well as oxidation of collagen and elastin as a major contributor to skin aging. arNOX inhibitors formulated for sustained release are capable of maintaining circulating arNOX at low levels with regular use as food supplements formulated with natural compounds. Among the best sources are certain culinary seasonings, all of which are ingredients used extensively in the French kitchen. Their regular use may contribute to an understanding of the nutritional basis for the French Paradox.

Converting NADH to NAD+ by nicotinamide nucleotide transhydrogenase as a novel strategy against mitochondrial pathologies during aging

            (Olgun 2009) Download

Mitochondrial DNA defects are involved supposedly via free radicals in many pathologies including aging and cancer. But, interestingly, free radical production was not found increased in prematurely aging mice having higher mutation rate in mtDNA. Therefore, some other mechanisms like the increase of mitochondrial NADH/NAD(+) and ubiquinol/ubiquinone ratios, can be in action in respiratory chain defects. NADH/NAD(+) ratio can be normalized by the activation or overexpression of nicotinamide nucleotide transhydrogenase (NNT), a mitochondrial enzyme catalyzing the following very important reaction: NADH + NADP(+ )<--> NADPH + NAD(+). The products NAD(+) and NADPH are required in many critical biological processes, e.g., NAD(+) is used by histone deacetylase Sir2 which regulates longevity in different species. NADPH is used in a number of biosynthesis reactions (e.g., reduced glutathione synthesis), and processes like apoptosis. Increased ubiquinol/ubiquinone ratio interferes the function of dihydroorotate dehydrogenase, the only mitochondrial enzyme involved in ubiquinone mediated de novo pyrimidine synthesis. Uridine and its prodrug triacetyluridine are used to compensate pyrimidine deficiency but their bioavailability is limited. Therefore, the normalization of the ubiquinol/ubiquinone ratio can be accomplished by allotopic expression of alternative oxidase, a mitochondrial ubiquinol oxidase which converts ubiquinol to ubiquinone.

The importance of NAD in multiple sclerosis

            (Penberthy and Tsunoda 2009) Download

The etiology of multiple sclerosis (MS) is unknown but it manifests as a chronic inflammatory demyelinating disease in the central nervous system (CNS). During chronic CNS inflammation, nicotinamide adenine dinucleotide (NAD) concentrations are altered by (T helper) Th1-derived cytokines through the coordinated induction of both indoleamine 2,3-dioxygenase (IDO) and the ADP cyclase CD38 in pathogenic microglia and lymphocytes. While IDO activation may keep auto-reactive T cells in check, hyper-activation of IDO can leave neuronal CNS cells starving for extracellular sources of NAD. Existing data indicate that glia may serve critical functions as an essential supplier of NAD to neurons during times of stress. Administration of pharmacological doses of non-tryptophan NAD precursors ameliorates pathogenesis in animal models of MS. Animal models of MS involve artificially stimulated autoimmune attack of myelin by experimental autoimmune encephalomyelitis (EAE) or by viral-mediated demyelination using Thieler's murine encephalomyelitis virus (TMEV). The Wld(S) mouse dramatically resists razor axotomy mediated axonal degeneration. This resistance is due to increased efficiency of NAD biosynthesis that delays stress-induced depletion of axonal NAD and ATP. Although the Wld(S) genotype protects against EAE pathogenesis, TMEV-mediated pathogenesis is exacerbated. In this review, we contrast the role of NAD in EAE versus TMEV demyelinating pathogenesis to increase our understanding of the pharmacotherapeutic potential of NAD signal transduction pathways. We speculate on the importance of increased SIRT1 activity in both PARP-1 inhibition and the potentially integral role of neuronal CD200 interactions through glial CD200R with induction of IDO in MS pathogenesis. A comprehensive review of immunomodulatory control of NAD biosynthesis and degradation in MS pathogenesis is presented. Distinctive pharmacological approaches designed for NAD-complementation or targeting NAD-centric proteins (SIRT1, SIRT2, PARP-1, GPR109a, and CD38) are outlined towards determining which approach may work best in the context of clinical application.

No evidence for cognitive improvement from oral nicotinamide adenine dinucleotide (NADH) in dementia

            (Rainer, Kraxberger et al. 2000) Download

Reduced nicotinamide adenine dinucleotide (NADH) is advertised as an over-the-counter product or dietary supplement to treat Alzheimer's disease. We performed a 3-month open-label study with oral 10 mg/day NADH with 25 patients with mild to moderate dementia of the Alzheimer, vascular, and fronto-temporal types in addition to their current cholinomimetic drug medication. In 19 patients who completed the study, we found no evidence for any cognitive effect as defined by established psychometric tests. We conclude that NADH is unlikely to achieve cognitive improvements in an extent reported earlier, and present theoretical arguments against an effectiveness of this compound in dementia disorders.

Nampt/PBEF/Visfatin regulates insulin secretion in beta cells as a systemic NAD biosynthetic enzyme

            (Revollo, Korner et al. 2007) Download

Intracellular nicotinamide phosphoribosyltransferase (iNampt) is an essential enzyme in the NAD biosynthetic pathway. An extracellular form of this protein (eNampt) has been reported to act as a cytokine named PBEF or an insulin-mimetic hormone named visfatin, but its physiological relevance remains controversial. Here we show that eNampt does not exert insulin-mimetic effects in vitro or in vivo but rather exhibits robust NAD biosynthetic activity. Haplodeficiency and chemical inhibition of Nampt cause defects in NAD biosynthesis and glucose-stimulated insulin secretion in pancreatic islets in vivo and in vitro. These defects are corrected by administration of nicotinamide mononucleotide (NMN), a product of the Nampt reaction. A high concentration of NMN is present in mouse plasma, and plasma eNampt and NMN levels are reduced in Nampt heterozygous females. Our results demonstrate that Nampt-mediated systemic NAD biosynthesis is critical for beta cell function, suggesting a vital framework for the regulation of glucose homeostasis.

NAD+ and vitamin B3: from metabolism to therapies

            (Sauve 2008) Download

The role of NAD(+) metabolism in health and disease is of increased interest as the use of niacin (nicotinic acid) has emerged as a major therapy for treatment of hyperlipidemias and with the recognition that nicotinamide can protect tissues and NAD(+) metabolism in a variety of disease states, including ischemia/reperfusion. In addition, a growing body of evidence supports the view that NAD(+) metabolism regulates important biological effects, including lifespan. NAD(+) exerts potent effects through the poly(ADP-ribose) polymerases, mono-ADP-ribosyltransferases, and the recently characterized sirtuin enzymes. These enzymes catalyze protein modifications, such as ADP-ribosylation and deacetylation, leading to changes in protein function. These enzymes regulate apoptosis, DNA repair, stress resistance, metabolism, and endocrine signaling, suggesting that these enzymes and/or NAD(+) metabolism could be targeted for therapeutic benefit. This review considers current knowledge of NAD(+) metabolism in humans and microbes, including new insights into mechanisms that regulate NAD(+) biosynthetic pathways, current use of nicotinamide and nicotinic acid as pharmacological agents, and opportunities for drug design that are directed at modulation of NAD(+) biosynthesis for treatment of human disorders and infections.

Ethanol enhances hepatitis C virus replication through lipid metabolism and elevated NADH/NAD+

            (Seronello, Ito et al. 2010) Download

Ethanol has been suggested to elevate HCV titer in patients and to increase HCV RNA in replicon cells, suggesting that HCV replication is increased in the presence and absence of the complete viral replication cycle, but the mechanisms remain unclear. In this study, we use Huh7 human hepatoma cells that naturally express comparable levels of CYP2E1 as human liver to demonstrate that ethanol, at subtoxic and physiologically relevant concentrations, enhances complete HCV replication. The viral RNA genome replication is affected for both genotypes 2a and 1b. Acetaldehyde, a major product of ethanol metabolism, likewise enhances HCV replication at physiological concentrations. The potentiation of HCV replication by ethanol is suppressed by inhibiting CYP2E1 or aldehyde dehydrogenase and requires an elevated NADH/NAD(+) ratio. In addition, acetate, isopropyl alcohol, and concentrations of acetone that occur in diabetics enhance HCV replication with corresponding increases in the NADH/NAD(+). Furthermore, inhibiting the host mevalonate pathway with lovastatin or fluvastatin and fatty acid synthesis with 5-(tetradecyloxy)-2-furoic acid or cerulenin significantly attenuates the enhancement of HCV replication by ethanol, acetaldehyde, acetone, as well as acetate, whereas inhibiting beta-oxidation with beta-mercaptopropionic acid increases HCV replication. Ethanol, acetaldehyde, acetone, and acetate increase the total intracellular cholesterol content, which is attenuated with lovastatin. In contrast, both endogenous and exogenous ROS suppress the replication of HCV genotype 2a, as previously shown with genotype 1b. Conclusion: Therefore, lipid metabolism and alteration of cellular NADH/NAD(+) ratio are likely to play a critical role in the potentiation of HCV replication by ethanol rather than oxidative stress.

Vitamin B3, the nicotinamide adenine dinucleotides and aging

            (Xu and Sauve 2010) Download

Organism aging is a process of time and maturation culminating in senescence and death. The molecular details that define and determine aging have been intensely investigated. It has become appreciated that the process is partly an accumulation of random yet inevitable changes, but it can be strongly affected by genes that alter lifespan. In this review, we consider how NAD(+) metabolism plays important roles in the random patterns of aging, and also in the more programmatic aspects. The derivatives of NAD(+), such as reduced and oxidized forms of NAD(P)(+), play important roles in maintaining and regulating cellular redox state, Ca(2+) stores, DNA damage and repair, stress responses, cell cycle timing and lipid and energy metabolism. NAD(+) is also a substrate for signaling enzymes like the sirtuins and poly-ADP-ribosylpolymerases, members of a broad family of protein deacetylases and ADP-ribosyltransferases that regulate fundamental cellular processes such as transcription, recombination, cell division, proliferation, genome maintenance, apoptosis, stress resistance and senescence. NAD(+)-dependent enzymes are increasingly appreciated to regulate the timing of changes that lead to aging phenotypes. We consider how metabolism, specifically connected with Vitamin B3 and the nicotinamide adenine dinucleotides and their derivatives, occupies a central place in the aging processes of mammals.


References

Belenky, P., K. L. Bogan, et al. (2007). "NAD+ metabolism in health and disease." Trends Biochem Sci 32(1): 12-9.

Forsyth, L. M., H. G. Preuss, et al. (1999). "Therapeutic effects of oral NADH on the symptoms of patients with chronic fatigue syndrome." Ann Allergy Asthma Immunol 82(2): 185-91.

Garten, A., S. Petzold, et al. (2009). "Nampt: linking NAD biology, metabolism and cancer." Trends Endocrinol Metab 20(3): 130-8.

Hara, N., K. Yamada, et al. (2007). "Elevation of cellular NAD levels by nicotinic acid and involvement of nicotinic acid phosphoribosyltransferase in human cells." J Biol Chem 282(34): 24574-82.

Kaneko, S., J. Wang, et al. (2006). "Protecting axonal degeneration by increasing nicotinamide adenine dinucleotide levels in experimental autoimmune encephalomyelitis models." J Neurosci 26(38): 9794-804.

Kirkland, J. B. (2009). "Niacin status, NAD distribution and ADP-ribose metabolism." Curr Pharm Des 15(1): 3-11.

Magni, G., G. Orsomando, et al. (2008). "Enzymology of mammalian NAD metabolism in health and disease." Front Biosci 13: 6135-54.

Morre, D. J., D. M. Morre, et al. (2010). "Aging-related nicotinamide adenine dinucleotide oxidase response to dietary supplementation: the French paradox revisited." Rejuvenation Res 13(2-3): 159-61.

Olgun, A. (2009). "Converting NADH to NAD+ by nicotinamide nucleotide transhydrogenase as a novel strategy against mitochondrial pathologies during aging." Biogerontology 10(4): 531-4.

Penberthy, W. T. and I. Tsunoda (2009). "The importance of NAD in multiple sclerosis." Curr Pharm Des 15(1): 64-99.

Rainer, M., E. Kraxberger, et al. (2000). "No evidence for cognitive improvement from oral nicotinamide adenine dinucleotide (NADH) in dementia." J Neural Transm 107(12): 1475-81.

Revollo, J. R., A. Korner, et al. (2007). "Nampt/PBEF/Visfatin regulates insulin secretion in beta cells as a systemic NAD biosynthetic enzyme." Cell Metab 6(5): 363-75.

Sauve, A. A. (2008). "NAD+ and vitamin B3: from metabolism to therapies." J Pharmacol Exp Ther 324(3): 883-93.

Seronello, S., C. Ito, et al. (2010). "Ethanol enhances hepatitis C virus replication through lipid metabolism and elevated NADH/NAD+." J Biol Chem 285(2): 845-54.

Xu, P. and A. A. Sauve (2010). "Vitamin B3, the nicotinamide adenine dinucleotides and aging." Mech Ageing Dev 131(4): 287-98.