title: Replicatively senescent human fibroblasts reveal a distinct intracellular metabolic profile with alterations in NAD+ and nicotinamide metabolism.
abstract: Cellular senescence occurs by proliferative exhaustion (PEsen) or following multiple cellular stresses but had not previously been subject to detailed metabolomic analysis. Therefore, we compared PEsen fibroblasts with proliferating and transiently growth arrested controls using a combination of different mass spectroscopy techniques. PEsen cells showed many specific alterations in both the NAD+ de novo and salvage pathways including striking accumulations of nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) in the amidated salvage pathway despite no increase in nicotinamide phosphoribosyl transferase or in the NR transport protein, CD73. Extracellular nicotinate was depleted and metabolites of the deamidated salvage pathway were reduced but intracellular NAD+ and nicotinamide were nevertheless maintained. However, sirtuin 1 was downregulated and so the accumulation of NMN and NR was best explained by reduced flux through the amidated arm of the NAD+ salvage pathway due to reduced sirtuin activity. PEsen cells also showed evidence of increased redox homeostasis and upregulated pathways used to generate energy and cellular membranes; these included nucleotide catabolism, membrane lipid breakdown and increased creatine metabolism. Thus PEsen cells upregulate several different pathways to sustain their survival which may serve as pharmacological targets for the elimination of senescent cells in age-related disease.
authors.affiliation: Centre for Clinical &Diagnostic Oral Sciences, Institute of Dentistry, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Turner Street, London, E1 2AD, UK.
authors.forename: Emma L
authors.initials: EL
authors.lastname: James
authors.affiliation: Centre for Clinical &Diagnostic Oral Sciences, Institute of Dentistry, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Turner Street, London, E1 2AD, UK.
authors.forename: James A E
authors.initials: JA
authors.lastname: Lane
authors.affiliation: Metabolon, Inc. 617 Davis Drive, Suite 400, Durham, NC, 27713, USA.
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Michalek
authors.affiliation: Metabolon, Inc. 617 Davis Drive, Suite 400, Durham, NC, 27713, USA.
authors.forename: Edward D
authors.initials: ED
authors.lastname: Karoly
authors.affiliation: Centre for Clinical &Diagnostic Oral Sciences, Institute of Dentistry, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, Turner Street, London, E1 2AD, UK.
authors.forename: E Kenneth
authors.initials: EK
authors.lastname: Parkinson
mesh_terms: D002453:Cell Cycle; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence; D016000:Cluster Analysis; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism*; D006706:Homeostasis; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism*; D055442:Metabolome; D055432:Metabolomics; D008954:Models, Biological; D009243:NAD / Q000378:metabolism*; D009536:Niacinamide / Q000378:metabolism*; D010084:Oxidation-Reduction; D025341:Principal Component Analysis; D014364:Tryptophan / Q000378:metabolism
chemical_list: D009243:NAD; D009536:Niacinamide; D014364:Tryptophan