title: Metabolites of milk intake: a metabolomic approach in UK twins with findings replicated in two European cohorts.
abstract: OBJECTIVE
  Milk provides a significant source of calcium, protein, vitamins and other minerals to Western populations throughout life. Due to its widespread use, the metabolic and health impact of milk consumption warrants further investigation and biomarkers would aid epidemiological studies.
  
  
  METHODS
  Milk intake assessed by a validated food frequency questionnaire was analyzed against fasting blood metabolomic profiles from two metabolomic platforms in females from the TwinsUK cohort (n = 3559). The top metabolites were then replicated in two independent populations (EGCUT, n = 1109 and KORA, n = 1593), and the results from all cohorts were meta-analyzed.
  
  
  RESULTS
  Four metabolites were significantly associated with milk intake in the TwinsUK cohort after adjustment for multiple testing (P < 8.08 × 10-5) and covariates (BMI, age, batch effects, family relatedness and dietary covariates) and replicated in the independent cohorts. Among the metabolites identified, the carnitine metabolite trimethyl-N-aminovalerate (β = 0.012, SE = 0.002, P = 2.98 × 10-12) and the nucleotide uridine (β = 0.004, SE = 0.001, P = 9.86 × 10-6) were the strongest novel predictive biomarkers from the non-targeted platform. Notably, the association between trimethyl-N-aminovalerate and milk intake was significant in a group of MZ twins discordant for milk intake (β = 0.050, SE = 0.015, P = 7.53 × 10-4) and validated in the urine of 236 UK twins (β = 0.091, SE = 0.032, P = 0.004). Two metabolites from the targeted platform, hydroxysphingomyelin C14:1 (β = 0.034, SE = 0.005, P = 9.75 × 10-14) and diacylphosphatidylcholine C28:1 (β = 0.034, SE = 0.004, P = 4.53 × 10-16), were also replicated.
  
  
  CONCLUSIONS
  We identified and replicated in independent populations four novel biomarkers of milk intake: trimethyl-N-aminovalerate, uridine, hydroxysphingomyelin C14:1 and diacylphosphatidylcholine C28:1. Together, these metabolites have potential to objectively examine and refine milk-disease associations.
authors.affiliation: Department of Twin Research and Genetic Epidemiology, St Thomas Hospital, King's College London, London, SE1 7EH, UK. tess.pallister@kcl.ac.uk.
authors.forename: Tess
authors.initials: T
authors.lastname: Pallister
authors.affiliation: Estonian Genome Center, University of Tartu, Tartu, Estonia.
authors.forename: Toomas
authors.initials: T
authors.lastname: Haller
authors.affiliation: Institute of Epidemiology II, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764, Neuherberg, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Thorand
authors.affiliation: Institute of Genetic Epidemiology, Helmholtz Zentrum München - German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764, Neuherberg, Germany.|Research Unit of Molecular Epidemiology, Helmholtz Zentrum München, 85764, Neuherberg, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Altmaier
authors.affiliation: Department of Nutrition, Norwich Medical School, University of East Anglia, Norwich, UK.
authors.forename: Aedin
authors.initials: A
authors.lastname: Cassidy
authors.affiliation: Department of Twin Research and Genetic Epidemiology, St Thomas Hospital, King's College London, London, SE1 7EH, UK.
authors.forename: Tiphaine
authors.initials: T
authors.lastname: Martin
authors.affiliation: Department of Nutrition, Norwich Medical School, University of East Anglia, Norwich, UK.
authors.forename: Amy
authors.initials: A
authors.lastname: Jennings
authors.affiliation: Metabolon, Inc., Durham, NC, USA.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Mohney
authors.affiliation: Institute of Genetic Epidemiology, Helmholtz Zentrum München - German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764, Neuherberg, Germany.|Research Unit of Molecular Epidemiology, Helmholtz Zentrum München, 85764, Neuherberg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Gieger
authors.affiliation: Department of Nutrition, Norwich Medical School, University of East Anglia, Norwich, UK.
authors.forename: Alexander
authors.initials: A
authors.lastname: MacGregor
authors.affiliation: Institute of Bioinformatics and Systems Biology, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, 85764, Neuherberg, Germany.
authors.forename: Gabi
authors.initials: G
authors.lastname: Kastenmüller
authors.affiliation: Estonian Genome Center, University of Tartu, Tartu, Estonia.
authors.forename: Andres
authors.initials: A
authors.lastname: Metspalu
authors.affiliation: Department of Twin Research and Genetic Epidemiology, St Thomas Hospital, King's College London, London, SE1 7EH, UK.
authors.forename: Tim D
authors.initials: TD
authors.lastname: Spector
authors.affiliation: Department of Twin Research and Genetic Epidemiology, St Thomas Hospital, King's College London, London, SE1 7EH, UK. cristina.menni@kcl.ac.uk.
authors.forename: Cristina
authors.initials: C
authors.lastname: Menni
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D015415:Biomarkers / Q000032:analysis* / Q000097:blood / Q000652:urine; D015992:Body Mass Index; D015331:Cohort Studies; D004032:Diet; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage; D005260:Female; D006801:Humans; D008297:Male; D055442:Metabolome; D018977:Micronutrients / Q000008:administration & dosage; D008875:Middle Aged; D008892:Milk / Q000009:adverse effects*; D008954:Models, Biological; D015596:Nutrition Assessment; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D006113:United Kingdom; D014529:Uridine / Q000097:blood / Q000652:urine; D014631:Valerates / Q000032:analysis / Q000097:blood / Q000652:urine; D055815:Young Adult
chemical_list: D015415:Biomarkers; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D018977:Micronutrients; D014631:Valerates; C000627924:trimethyl-N-aminovalerate; D014529:Uridine
keywords: Biomarkers; Metabolomics; Milk; Nutrition; Twins