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Nicotinamide adenine dinucleotide biosynthesis promotes liver regeneration.

ABSTRACT: The regenerative capacity of the liver is essential for recovery from surgical resection or injuries induced by trauma or toxins. During liver regeneration, the concentration of nicotinamide adenine dinucleotide (NAD) falls, at least in part due to metabolic competition for precursors. To test whether NAD availability restricts the rate of liver regeneration, we supplied nicotinamide riboside (NR), an NAD precursor, in the drinking water of mice subjected to partial hepatectomy. NR increased DNA synthesis, mitotic index, and mass restoration in the regenerating livers. Intriguingly, NR also ameliorated the steatosis that normally accompanies liver regeneration. To distinguish the role of hepatocyte NAD levels from any systemic effects of NR, we generated mice overexpressing nicotinamide phosphoribosyltransferase, a rate-limiting enzyme for NAD synthesis, specifically in the liver. Nicotinamide phosphoribosyltransferase overexpressing mice were mildly hyperglycemic at baseline and, similar to mice treated with NR, exhibited enhanced liver regeneration and reduced steatosis following partial hepatectomy. Conversely, mice lacking nicotinamide phosphoribosyltransferase in hepatocytes exhibited impaired regenerative capacity that was completely rescued by administering NR.NAD availability is limiting during liver regeneration, and supplementation with precursors such as NR may be therapeutic in settings of acute liver injury. (Hepatology 2017;65:616-630).

SUBMITTER: Mukherjee S

PROVIDER: S-EPMC5258848 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Nicotinamide adenine dinucleotide biosynthesis promotes liver regeneration.

Mukherjee Sarmistha S Chellappa Karthikeyani K Moffitt Andrea A Ndungu Joan J Dellinger Ryan W RW Davis James G JG Agarwal Beamon B Baur Joseph A JA

Hepatology (Baltimore, Md.) 20161224 2

The regenerative capacity of the liver is essential for recovery from surgical resection or injuries induced by trauma or toxins. During liver regeneration, the concentration of nicotinamide adenine dinucleotide (NAD) falls, at least in part due to metabolic competition for precursors. To test whether NAD availability restricts the rate of liver regeneration, we supplied nicotinamide riboside (NR), an NAD precursor, in the drinking water of mice subjected to partial hepatectomy. NR increased DNA ...[more]

PMID: 27809334

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Project description:Nicotinamide adenine dinucleotide (NAD+) and related coenzymes play critical roles in liver function. Although hepatic alcohol metabolism depresses NAD+, current understanding of the NAD+ metabolome in alcohol-related liver disease (ArLD) is based on animal models. We used human liver samples to quantify the NAD+ metabolome in ArLD with samples obtained at the time of liver transplantation or resection at University Hospitals Birmingham National Health Service Foundation Trust. The severity of steatohepatitis in liver from patients with ArLD was assessed with standard liver function tests and histology. NAD-targeted quantitative metabolomic analysis of liver tissue was performed by liquid chromatography-tandem mass spectrometry. Seventy-two human liver specimens were analyzed, including 43 with ArLD. The NAD+ metabolome differed significantly between different types of liver disease (two-way analysis of variance [ANOVA], P = 0.001). ArLD liver tissue showed markedly depressed concentrations of NAD+ (432 μM vs. 616 μM in normal liver) and precursor molecules nicotinic acid and nicotinamide riboside. There was a significant overall difference in the NAD+ metabolome between ArLD samples with and without steatohepatitis (two-way ANOVA, P = 0.018). After correcting for multiple comparisons, a significant difference for individual components of the metabolome was observed for the concentration of NAD+ (mean, 462 μM vs. 322 μM; P < 0.01 in nonsevere vs. severe alcoholic steatohepatitis, respectively). NAD+ concentration was inversely related to serum bilirubin concentration (r 2 = -0.127; P = 0.04) and positively correlated with myeloperoxidase activity (r 2 = 0.31; P = 0.003). The concentration of NAD+ and its precursor molecules are significantly reduced in ArLD and are associated with disease activity. Conclusion: Liver samples from people with ArLD show depressed NAD+ and precursor levels as well as depressed myeloperoxidase activity.

Project description:AimsAccurate analysis of dinucleotide redox cofactors nicotinamide adenine dinucleotide phosphate reduced (NADPH), nicotinamide adenine dinucleotide phosphate (NADP+), nicotinamide adenine dinucleotide reduced (NADH), and nicotinamide adenine dinucleotide (NAD+) from biological samples is important to understanding cellular redox homeostasis. In this study, we aimed to develop a simple protocol for quenching metabolism and extracting NADPH that avoids interconversion among the reduced forms and the oxidized forms.ResultsWe compared seven different solvents for quenching and extraction of cultured mammalian cells and mouse tissues: a cold aqueous buffer commonly used in enzyme assays with and without detergent, hot aqueous buffer, and cold organic mixtures (80% methanol, buffered 75% acetonitrile, and acidic 40:40:20 acetonitrile:methanol:water with either 0.02 M or 0.1 M formic acid). Extracts were analyzed by liquid chromatography-mass spectrometry (LC-MS). To monitor the metabolite interconversion, cells were grown in 13C6-glucose medium, and unlabeled standards were spiked into the extraction solvents. Interconversion between the oxidized and reduced forms was substantial except for the enzyme assay buffer with detergent, 80% methanol and 40:40:20 acetonitrile:methanol:water, with the 0.1 M formic acid mix giving the least interconversion and best recoveries. Absolute NAD+, NADH, NADP+, and NADPH concentrations in cells and mouse tissues were measured with this approach.InnovationWe found that the interconversion between the reduced and oxidized forms during extraction is a major barrier to accurately measuring NADPH/NADP+ and NADH/NAD+ ratios. Such interconversion can be monitored by isotope labeling cells and spiking NAD(P)(H) standards.ConclusionExtraction with 40:40:20 acetonitrile:methanol:water with 0.1 M formic acid decreases interconversion and, therefore, is suitable for measurement of redox cofactor ratios using LC-MS. This solvent is also useful for general metabolomics. Samples should be neutralized immediately after extraction to avoid acid-catalyzed degradation. When LC-MS is not available and enzyme assays are accordingly used, inclusion of detergent in the aqueous extraction buffer reduces interconversion. Antioxid. Redox Signal. 28, 167-179.

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Nicotinamide adenine dinucleotide biosynthesis promotes liver regeneration.

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Nicotinamide adenine dinucleotide biosynthesis promotes liver regeneration.

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