title: Mammalian DNA δ15N exhibits 40‰ intramolecular variation and is unresponsive to dietary protein level.
abstract: We report the first high-precision characterization of molecular and intramolecular δ(15)N of nucleosides derived from mammalian DNA. The influence of dietary protein level on brain amino acids and deoxyribonucleosides was determined to investigate whether high protein turnover would alter amino acid (15)N or (13)C values. Pregnant guinea pig dams were fed control diets, or high or low levels of dietary protein throughout gestation, and all pups were fed control diets. The cerebellar DNA of offspring was extracted at 2 and 120 days of life, nucleosides isolated and δ(15)N and δ(13)C values characterized. Mean diet δ(15)N was 0.45 ± 0.33‰, compared with cerebellar whole tissue and DNA δ(15) N= +4.1 ± 0.7‰ and -4.5 ± 0.4‰, respectively. Cerebellar deoxythymidine (dT), deoxycytidine (dC), deoxyadenosine (dA), and deoxyguanosine (dG) δ(15)N were +1.4 ± 0.4, -2.1 ± 0.9, -7.2 ± 0.3, and -10.4 ± 0.5‰, respectively. There were no changes in amino acid or deoxyribonucleoside δ(15) N values due to dietary protein level. Using known metabolic relationships, we developed equations to calculate the intramolecular δ(15)N values originating from aspartate (asp) in purines (pur) or pyrimidines (pyr), glutamine (glu), and glycine (gly) to be δ(15)N(ASP-PUR), δ(15)N(ASP-PYR), δ(15) N(GLN), and δ(15) N(GLY) +11.9 ± 2.3‰, +7.0 ± 2.0‰, -9.1 ± 2.4‰, and -31.8 ± 8.9‰, respectively. A subset of twelve amino acids from food and brain had mean δ(15) N values of 4.3 ± 3.2‰ and 13.8 ± 3.1‰, respectively, and δ(15)N values for gly and asp were 12.6 ± 2.2‰ and 15.2 ± 0.8‰, respectively. A separate isotope tracer study detected no significant turnover of cerebellar DNA in the first six months of life. The large negative δ(15)N difference between gly and cerebellar purine N at the gly (7) position implies either that there is a major isotope effect during DNA synthesis, or that in utero gly has a different isotope ratio during rapid growth and metabolism from that in adult life. Our data show that cerebellar nucleoside intramolecular δ(15)N values vary over more than 40‰ and are not influenced by dietary protein level or age.
authors.affiliation: Cornell University, Division of Nutritional Sciences, Savage Hall, Ithaca, NY 14853, USA.
authors.forename: Maggie S
authors.initials: MS
authors.lastname: Strable
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Tschanz
authors.forename: Behzad
authors.initials: B
authors.lastname: Varamini
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Chikaraishi
authors.forename: Naohiko
authors.initials: N
authors.lastname: Ohkouchi
authors.forename: J Thomas
authors.initials: JT
authors.lastname: Brenna
mesh_terms: D000596:Amino Acids / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D000704:Analysis of Variance; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002531:Cerebellum / Q000737:chemistry / Q000378:metabolism; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000032:analysis; D005260:Female; D006168:Guinea Pigs; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008297:Male; D013058:Mass Spectrometry; D009587:Nitrogen Isotopes / Q000032:analysis*; D011247:Pregnancy; D011849:Radioactive Tracers
chemical_list: D000596:Amino Acids; D004044:Dietary Proteins; D009587:Nitrogen Isotopes; D011849:Radioactive Tracers; D004247:DNA
references.citation: Oecologia. 2006 Mar;147(2):212-22
references.pmid: 16328553
references.citation: Proc Natl Acad Sci U S A. 1997 Feb 18;94(4):1049-53
references.pmid: 11038597
references.citation: Plant Physiol. 1971 Mar;47(3):380-4
references.pmid: 16657626
references.citation: Proc Natl Acad Sci U S A. 1961 May 15;47:623-32
references.pmid: 13681011
references.citation: Cell. 2005 Jul 15;122(1):133-43
references.pmid: 16009139
references.citation: Am J Clin Nutr. 2000 May;71(5 Suppl):1344S-52S
references.pmid: 10799412
references.citation: Early Hum Dev. 1979 Mar;3(1):79-83
references.pmid: 118862
references.citation: Science. 1977 Jul 15;197(4300):261-3
references.pmid: 327543
references.citation: Free Radic Biol Med. 2006 Jun 1;40(11):1939-48
references.pmid: 16716895
references.citation: Proc Natl Acad Sci U S A. 2009 Aug 4;106(31):12580-6
references.pmid: 19617564
references.citation: Chem Res Toxicol. 2002 Mar;15(3):426-32
references.pmid: 11896691
references.citation: Nature. 2008 Jun 5;453(7196):783-7
references.pmid: 18454136
references.citation: Rapid Commun Mass Spectrom. 2001;15(15):1252-62
references.pmid: 11466780
references.citation: Anal Chem. 2005 Feb 15;77(4):1013-9
references.pmid: 15858980
references.citation: J Chromatogr A. 1997 Jan 3;757(1-2):307-10
references.pmid: 9025266
references.citation: Plant Physiol. 1961 Mar;36(2):133-8
references.pmid: 16655481
references.citation: Anal Chem. 2006 Apr 15;78(8):2752-7
references.pmid: 16615789
references.citation: Can J Biochem. 1966 Sep;44(9):1249-57
references.pmid: 6008218
references.citation: Nat Clin Pract Nephrol. 2006 Dec;2(12):700-7
references.pmid: 17124527
references.citation: Science. 1985 May 24;228(4702):1002-4
references.pmid: 4001927
references.citation: Appl Environ Microbiol. 1990 Jul;56(7):2012-20
references.pmid: 2389930
references.citation: Amino Acids. 2007 Nov;33(4):631-8
references.pmid: 17252306
references.citation: Anal Chem. 2005 Mar 15;77(6):1746-52
references.pmid: 15762581