Nursing & Health

Permanent URI for this collectionhttps://research.avondale.edu.au/handle/123456789/457

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    A Pilot Study Investigating Changes in the Human Plasma and Urine NAD+ Metabolome During a 6 Hour Intravenous Infusion of NAD+
    (2019-09-12) Watson, James; Broom, Susan; Bennett, James; Braidy, Nady; Mestayer, Richard; Berg, Jade; Grant, Ross

    Accumulating evidence suggests that active maintenance of optimal levels of the essential pyridine nucleotide, nicotinamide adenine dinucleotide (NAD+) is beneficial in conditions of either increased NAD+ turnover or inadequate synthesis, including Alzheimer’s disease and other neurodegenerative disorders and the aging process. While studies have documented the efficacy of some NAD+ precursors such as nicotinamide riboside (NR) in raising plasma NAD+, no data are currently available on the fate of directly infused NAD+ in a human cohort. This study, therefore, documented changes in plasma and urine levels of NAD+ and its metabolites during and after a 6 h 3 μmol/min NAD+ intravenous (IV) infusion. Surprisingly, no change in plasma (NAD+) or metabolites [nicotinamide, methylnicotinamide, adenosine phosphoribose ribose (ADPR) and nicotinamide mononucleotide (NMN)] were observed until after 2 h. Increased urinary excretion of methylnicotinamide and NAD+ were detected at 6 h, however, no significant rise in urinary nicotinamide was observed. This study revealed for the first time that: (i) at an infusion rate of 3 μmol/min NAD+ is rapidly and completely removed from the plasma for at least the first 2 h; (ii) the profile of metabolites is consistent with NAD+ glycohydrolase and NAD+ pyrophosphatase activity; and (iii) urinary excretion products arising from an NAD+ infusion include NAD+ itself and methyl nicotinamide (meNAM) but not NAM.

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    Kynurenine Pathway Metabolism and Neuroinflammatory Disease
    (2017-02-06) Grant, Ross; Braidy, Nady

    Immune-mediated activation of tryptophan (TRYP) catabolism via the kynurenine pathway (KP) is a consistent finding in all inflammatory disorders. Several studies by our group and others have examined the neurotoxic potential of neuroreactive TRYP metabolites, including quinolinic acid (QUIN) in neuroinflammatory neurological disorders, including Alzheimer’s disease (AD), multiple sclerosis, amylotropic lateral sclerosis (ALS), and AIDS related dementia complex (ADC). Our current work aims to determine whether there is any benefit to the affected individuals in enhancing the catabolism of TRYP via the KP during an immune response. Under physiological conditions, QUIN is metabolized to the essential pyridine nucleotide, nicotinamide adenine dinucleotide (NAD+ ), which represents an important metabolic cofactor and electron transporter. NAD+ also serves as a substrate for the DNA ‘nick sensor’ and putative nuclear repair enzyme, poly(ADP-ribose) polymerase (PARP). Free radical initiated DNA damage, PARP activation and NAD+ depletion may contribute to brain dysfunction and cell death in neuroinflammatory disease.

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    Application of Targeted Mass Spectrometry for the Quantification of Sirtuins in the Central Nervous System
    (2016-10-20) Sachdev, Perminder; Raftery, M; Teo, C; Smythe, George; Grant, Ross; Muenchhoff, J; Rowlands, B; Zhong, L; Braidy, Nady; Poljak, Anne; Jayasena, Tharusha

    Sirtuin proteins have a variety of intracellular targets, thereby regulating multiple biological pathways including neurodegeneration. However, relatively little is currently known about the role or expression of the 7 mammalian sirtuins in the central nervous system. Western blotting, PCR and ELISA are the main techniques currently used to measure sirtuin levels. To achieve sufficient sensitivity and selectivity in a multiplex-format, a targeted mass spectrometric assay was developed and validated for the quantification of all seven mammalian sirtuins (SIRT1-7). Quantification of all peptides was by multiple reaction monitoring (MRM) using three mass transitions per protein-specific peptide, two specific peptides for each sirtuin and a stable isotope labelled internal standard. The assay was applied to a variety of samples including cultured brain cells, mammalian brain tissue, CSF and plasma. All sirtuin peptides were detected in the human brain, with SIRT2 being the most abundant. Sirtuins were also detected in human CSF and plasma, and guinea pig and mouse tissues. In conclusion, we have successfully applied MRM mass spectrometry for the detection and quantification of sirtuin proteins in the central nervous system, paving the way for more quantitative and functional studies.

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    Promoting NAD+ Metabolism: A new Target for Treating Degenerative Disease
    (2016-12-01) Braidy, Nady; Berg, Jade; Grant, Ross

    NAD+ is found in every cell of the body and is essential for life. It serves as a cofactor for dehydrogenase, reductase and hydroxylase enzymes where it facilitates electron transfer in major metabolic pathways such as glycolysis, the triacarboxylic acid (TCA) cycle, fatty acid synthesis and steroid hormone synthesis, enabling the conversion of the food we eat into the energy and chemical products the body needs. More recently it has been found that NAD+ is also required as a substrate by enzymes that regulate the expression of genes involved in cell viability and aging and in repair of damaged DNA. Through these reactions, NAD+ influences a variety of cell processes involved in cell health, including improving mitochondrial efficiency, enhancing cell viability, down-regulating inflammation, increasing the antioxidant capacity of cells and tissues, and activating the ‘longevity’ enzyme SIRT1. An increasing body of evidence indicates that enhancing NAD+ availability in the brain has the potential to moderate elements of the neurodegenerative disease processes associated with oxidative stress and aging, including Alzheimer’s disease. However there are difficulties associated with raising NAD+ levels using the classical pathway and vitamin B3 precursors nicotinic acid and nicotinamide. The recent discovery of two alternative naturally occurring B3 vitamins; nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) may resolve these problems. NR in particular has shown good efficacy in its ability to raise NAD+ levels under a variety of conditions. Directly boosting [NAD+] may present a new and exciting approach to preventing the natural decline in cellular energy and function as we age, particularly in the brain.

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    Molecular Targets of Tannic Acid in Alzheimer's Disease
    (2017-07-17) Grant, Ross; Sachdev, Permider; Mohammad Nabavi, Seyed; Jayasena, Tharusha; Poljak, Anne; Jugder, Bat-Erdene; Braidy, Nady

    Tannic acid (TA) is a naturally occurring plant-derived polyphenol found in several herbaceous and woody plants, including legumes, sorghum, beans, bananas, persimmons, raspberries, wines and a broad selection of teas. Clinically, TA has strong antioxidant/free radical scavenging, anti inflammatory, anti-viral/bacterial, and anti-carcinogenic properties. While the aetiology of Alzheimer’s disease (AD) remains unclear, this complex multifactorial neurodegenerative disorder remains the most common form of dementia, and is a growing public health concern worldwide. The neuroprotective effects of TA against AD have been shown in several in vitro and in vivo models of AD. Apart from its potent antioxidant and anti-inflammatory roles, evidence suggests that TA is also a natural inhibitor of β-secretase (BACE1) activity and protein expression. BACE1 is the primary enzyme responsible for the production and deposition of Aβ peptide. TA also destabilises neurotoxic amyloid beta (Aβ) fibrils in vitro. Apart from its effects on the Aβ cascade, TA can also inhibit the in vitro aggregation of tau peptide, a core component of intracellular neurofibrillary tangles (NFTs). This review summarizes the relevance of TA and TA-related vegetable extracts (tannins) in the pathogenesis of AD and its enzymatic targets. It also highlights the significance of TA as an important lead compound against AD.

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    Differential Expression of Sirtuins in the Aging rat Brain
    (2015-05-08) Guillemin, Gilles J.; Sachdev, Perminder; Smythe, George; Chan-Ling, Tailoi; Mansour, Hussein; Jayasena, Tharusha; Grant, Ross; Poljak, Anne; Braidy, Nady

    Although there are seven mammalian sirtuins (SIRT1-7), little is known about their expression in the aging brain. To characterize the change(s) in mRNA and protein expression of SIRT1-7 and their associated proteins in the brain of “physiologically” aged Wistar rats. We tested mRNA and protein expression levels of rat SIRT1-7, and the levels of associated proteins in the brain using RT-PCR and western blotting. Our data shows that SIRT1 expression increases with age, concurrently with increased acetylated p53 levels in all brain regions investigated. SIRT2 and FOXO3a protein levels increased only in the occipital lobe. SIRT3-5 expression declined significantly in the hippocampus and frontal lobe, associated with increases in superoxide and fatty acid oxidation levels, and acetylated CPS-1 protein expression, and a reduction in MnSOD level. While SIRT6 expression declines significantly with age acetylated H3K9 protein expression is increased throughout the brain. SIRT7 and Pol I protein expression increased in the frontal lobe. This study identifies previously unknown roles for sirtuins in regulating cellular homeostasis and healthy aging.

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    Resveratrol as a Potential Therapeutic Candidate for the Treatment and Management of Alzheimer's Disease
    (2016-04-28) Grant, Ross; Sachdev, Perminder; Mohammad Nabavi, Seyed; Mansour, Hussein; Jayasena, Tharusha; Poljak, Anne; Jugder, Bat-Erdene; Braidy, Nady

    Resveratrol (3,4',5-trihydroxystilbene) is a naturally occurring phytochemical present in red wine, grapes, berries, chocolate and peanuts. Clinically, resveratrol has exhibited significant antioxidant, anti-inflammatory, anti-viral, and anti-cancer properties. Although resveratrol was first isolated in 1940, it was not until the last decade that it was recognised for its potential therapeutic role in reducing the risk of neurodegeneration, and Alzheimer's disease (AD) in particular. AD is the primary cause of progressive dementia. Resveratrol has demonstrated neuroprotective effects in several in vitro and in vivo models of AD. Apart from its potent antioxidant and anti-inflammatory roles, evidence suggests that resveratrol also facilitates non-amyloidogenic breakdown of the amyloid precursor protein (APP), and promotes removal of neurotoxic amyloid beta (Aβ) peptides, a critical step in preventing and slowing down AD pathology. Resveratrol also reduces damage to neuronal cells via a variety of additional mechanisms, most notably is the activation of NAD+-dependent histone deacetylases enzymes, termed sirtuins. However in spite of the considerable advances in clarifying the mechanism of action of resveratrol, it is unlikely to be effective as monotherapy in AD due to its poor bioavailability, biotransformation, and requisite synergism with other dietary factors. This review summarizes the relevance of resveratrol in the pathophysiology of AD. It also highlights why resveratrol alone may not be an effective single therapy, and how resveratrol coupled to other compounds might yet prove an effective therapy with multiple targets.

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    Nicotinamide Adenine Dinucleotide and its Related Precursors for the Treatment of Alzheimer's Disease
    (2018-03-01) Sachdev, Perminder; Grant, Ross; Braidy, Nady

    Purpose of review The current review discusses the biology and metabolism of the essential pyridine nucleotide nicotinamide adenine dinucleotide (NAD+) in the central nervous system. We also review recent work suggesting important neuroprotective effects that may be associated with the promotion of NAD+ levels through NAD+ precursors against Alzheimer's disease.

    Recent findings Perturbations in the physiological homoeostatic state of the brain during the ageing process can lead to impaired cellular function, and ultimately leads to loss of brain integrity and accelerates cognitive and memory decline. Increased oxidative stress has been shown to impair normal cellular bioenergetics and enhance the depletion of the essential nucleotides NAD+ and ATP. NAD+ and its precursors have been shown to improve cellular homoeostasis based on association with dietary requirements, and treatment and management of several inflammatory and metabolic diseases in vivo. Cellular NAD+ pools have been shown to be reduced in the ageing brain, and treatment with NAD+ precursors has been hypothesized to restore these levels and attenuate disruption in cellular bioenergetics.

    Summary NAD+ and its precursors may represent an important therapeutic strategy to maintain optimal cellular homoeostatic functions in the brain. NAD+ precursors are available in a variety of foods and may be translated to the clinic in the form of supplements.

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    Role of Nicotinamide Adenine Dinucleotide and Related Precursors as Therapeutic Targets for Age-Related Degenerative Diseases: Rationale, Biochemistry, Pharmacokinetics, and Outcomes
    (2019-01-10) Sachdev, Perminder; Grant, Ross; Jayasena, Tharusha; Poljak, Anne; Khorshidi, Fatemeh; Clement, James; Berg, Jade; Braidy, Nady

    Significance: Nicotinamide adenine dinucleotide (NAD+) is an essential pyridine nucleotide that serves as an essential cofactor and substrate for a number of critical cellular processes involved in oxidative phosphorylation and ATP production, DNA repair, epigenetically modulated gene expression, intracellular calcium signaling, and immunological functions. NAD+ depletion may occur in response to either excessive DNA damage due to free radical or ultraviolet attack, resulting in significant poly(ADP-ribose) polymerase (PARP) activation and a high turnover and subsequent depletion of NAD+, and/or chronic immune activation and inflammatory cytokine production resulting in accelerated CD38 activity and decline in NAD+ levels. Recent studies have shown that enhancing NAD+ levels can profoundly reduce oxidative cell damage in catabolic tissue, including the brain. Therefore, promotion of intracellular NAD+ anabolism represents a promising therapeutic strategy for age-associated degenerative diseases in general, and is essential to the effective realization of multiple benefits of healthy sirtuin activity. The kynurenine pathway represents the de novo NAD+ synthesis pathway in mammalian cells. NAD+ can also be produced by the NAD+ salvage pathway.

    Recent Advances: In this review, we describe and discuss recent insights regarding the efficacy and benefits of the NAD+ precursors, nicotinamide (NAM), nicotinic acid (NA), nicotinamide riboside (NR), and nicotinamide mononucleotide (NMN), in attenuating NAD+ decline in degenerative disease states and physiological aging.

    Critical Issues: Results obtained in recent years have shown that NAD+ precursors can play important protective roles in several diseases. However, in some cases, these precursors may vary in their ability to enhance NAD+ synthesis via their location in the NAD+ anabolic pathway. Increased synthesis of NAD+ promotes protective cell responses, further demonstrating that NAD+ is a regulatory molecule associated with several biochemical pathways.

    Future Directions: In the next few years, the refinement of personalized therapy for the use of NAD+ precursors and improved detection methodologies allowing the administration of specific NAD+ precursors in the context of patients' NAD+ levels will lead to a better understanding of the therapeutic role of NAD+ precursors in human diseases.

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    Characterisation of the Kynurenine Pathway in Skin‐Derived Fibroblasts and Keratinocytes
    (2015-06-01) Braidy, Nady; Guillemin, Gilles J.; Lovejoy, David; Bustamente, Sonia; Grant, Ross; Sheipouri, Diba

    Acute UVB exposure triggers inflammation leading to the induction of indoleamine 2,3 dioxygenase (IDO1), one of the first enzymes in the kynurenine pathway (KP) for tryptophan degradation. However, limited studies have been undertaken to determine the catabolism of tryptophan within the skin. The aim of this study was two fold: (1) to establish if the administration of the proinflammatory cytokine interferon‐gamma (IFN‐γ) and/or UVB radiation elicits differential KP expression patterns in human fibroblast and keratinocytes; and (2) to evaluate the effect of KP metabolites on intracellular nicotinamide adenine dinucleotide (NAD+) levels, and cell viability. Primary cultures of human fibroblasts and keratinocytes were used to examine expression of the KP at the mRNA level using qPCR, and at the protein level using immunocytochemistry. Cellular responses to KP metabolites were assessed by examining extracellular lactate dehydrogenase (LDH) activity and intracellular NAD+ levels. Major downstream KP metabolites were analyzed using GC/MS and HPLC. Our data shows that the KP is fully expressed both in human fibroblasts and keratinocytes. Exposure to UVB radiation and/or IFN‐γ causes significant changes in the expression pattern of downstream KP metabolites and enzymes. Exposure to various concentrations of KP metabolites showed marked differences in cell viability and intracellular NAD+ production, providing support for involvement of the KP in the de novo synthesis of NAD+ in the skin. This new information will have a significant impact on our understanding of the pathogenesis of UV related skin damage and the diagnosis of KP related disease states.