title: Senescent human fibroblasts show increased glycolysis and redox homeostasis with extracellular metabolomes that overlap with those of irreparable DNA damage, aging, and disease.
abstract: Cellular senescence can modulate various pathologies and is associated with irreparable DNA double-strand breaks (IrrDSBs). Extracellular senescence metabolomes (ESMs) were generated from fibroblasts rendered senescent by proliferative exhaustion (PEsen) or 20 Gy of γ rays (IrrDSBsen) and compared with those of young proliferating cells, confluent cells, quiescent cells, and cells exposed to repairable levels of DNA damage to identify novel noninvasive markers of senescent cells. ESMs of PEsen and IrrDSBsen overlapped and showed increased levels of citrate, molecules involved in oxidative stress, a sterol, monohydroxylipids, tryptophan metabolism, phospholipid, and nucleotide catabolism, as well as reduced levels of dipeptides containing branched chain amino acids. The ESM overlaps with the aging and disease body fluid metabolomes, supporting their utility in the noninvasive detection of human senescent cells in vivo and by implication the detection of a variety of human pathologies. Intracellular metabolites of senescent cells showed a relative increase in glycolysis, gluconeogenesis, the pentose-phosphate pathway, and, consistent with this, pyruvate dehydrogenase kinase transcripts. In contrast, tricarboxylic acid cycle enzyme transcript levels were unchanged and their metabolites were depleted. These results are surprising because glycolysis antagonizes senescence entry but are consistent with established senescent cells entering a state of low oxidative stress.
authors.forename: Emma L
authors.initials: EL
authors.lastname: James
authors.affiliation: ‡Metabolon, Inc., 617 Davis Drive, Suite 400, Durham, North Carolina 27713, United States.
authors.forename: Ryan D
authors.initials: RD
authors.lastname: Michalek
authors.forename: Gayani N
authors.initials: GN
authors.lastname: Pitiyage
authors.forename: Alice M
authors.initials: AM
authors.lastname: de Castro
authors.affiliation: ‡Metabolon, Inc., 617 Davis Drive, Suite 400, Durham, North Carolina 27713, United States.
authors.forename: Katie S
authors.initials: KS
authors.lastname: Vignola
authors.affiliation: ‡Metabolon, Inc., 617 Davis Drive, Suite 400, Durham, North Carolina 27713, United States.
authors.forename: Janice
authors.initials: J
authors.lastname: Jones
authors.affiliation: ‡Metabolon, Inc., 617 Davis Drive, Suite 400, Durham, North Carolina 27713, United States.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Mohney
authors.affiliation: ‡Metabolon, Inc., 617 Davis Drive, Suite 400, Durham, North Carolina 27713, United States.
authors.forename: Edward D
authors.initials: ED
authors.lastname: Karoly
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Prime
authors.forename: Eric Kenneth
authors.initials: EK
authors.lastname: Parkinson
mesh_terms: D000375:Aging / Q000502:physiology; D018929:Cell Culture Techniques; D016922:Cellular Senescence / Q000502:physiology*; D004249:DNA Damage / Q000502:physiology; D005347:Fibroblasts / Q000502:physiology* / Q000528:radiation effects; D005720:Gamma Rays; D005943:Gluconeogenesis / Q000502:physiology; D006019:Glycolysis / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D013058:Mass Spectrometry; D055442:Metabolome / Q000235:genetics*; D008954:Models, Biological; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology; D016133:Polymerase Chain Reaction; D018709:Statistics, Nonparametric
keywords: DNA damage; aging; citrate; energy; extracellular; metabolome; redox homeostasis; senescence