Vitamin B6 Dependence of One-Carbon Metabolism

NCT00877812 | Completed

• 1 other identifier: R01 D072398
• Study Type: interventional
• Target: 45
• Locations: 1 country
• Sites: 1

Brief Summary

Marginal vitamin B6 deficiency, which occurs commonly worldwide, leads to a cellular deficiency of the coenzyme pyridoxal phosphate (PLP). PLP is a coenzyme in several phases of one carbon (1C) metabolism, which is the array of reactions in which one carbon units are acquired and used in reactions including nucleotide synthesis, regeneration of methionine (Met) from homocysteine (Hcy), and methylation of many biological compounds. 1C metabolism is linked to the transsulfuration pathway in which Hcy undergoes PLP-dependent catabolism leading to cysteine, whose availability governs the formation of the antioxidant glutathione. Nutritional or genetic conditions that impair 1C metabolism are associated with elevation in plasma Hcy concentration and increased risk of vascular disease. It is believed that the metabolic effects of vitamin B6 deficiency will be most pronounced following protein intake when the vitamin B6-dependent pathways of amino acid metabolism experience the greatest substrate load. The human subjects protocols of this study consist of two distinct phases intended to extend our understanding of basic human 1C metabolism and the effects of marginal vitamin B6 deficiency under postprandial conditions. Phase 1 will investigate the effects of vitamin B6 nutrition on the PLP-dependent generation of 1C units by the glycine cleavage system and on the synthesis of glutathione. Phase 2 will investigate the dependence of methionine metabolism on vitamin B6 nutritional status, with particular emphasis on the recycling of Hcy to Met. Each phase of this study will involve 14 healthy, nutritionally adequate, young adults (7 male, 7 female) who will undergo metabolite profiling and kinetic analysis using intravenously infused stable isotopic tracers performed both before and after a \~4-week period of dietary vitamin B6 restriction. Subjects will be assigned to either Phase 1 or Phase 2, which will be identical in design except for the tracers and analytical methods used. We hypothesize that vitamin B6 deficiency will yield reduction in postprandial rates of homocysteine remethylation, generation of 1C units from glycine, and synthesis of glutathione. The results of this study will aid in assessing the consequences of nutritional and genetic variables affecting human metabolism and will further our understanding of the relationships between vitamin B6 nutrition and disease.

Conditions

Vitamin B6 Deficiency

Keywords

Vitamin B6; Vitamin B6 deficiency; Amino acids; pyridoxine

Outcome Measures

Primary Outcomes (2)

• Hypothesis Aim 1

  (a) Vitamin B6 deficiency will reduce the rate of glycine turnover and interconversion with serine and will reduce the generation of 1C units by the glycine cleavage system. (b) Vitamin B6 deficiency will yield a reduced in vivo rate of erythrocyte glutathione synthesis.

  One year

• Hypotheses Aim 2

  (a) Vitamin B6 deficiency will reduce the in vivo rate of generation of one-carbon units from serine and, thus, overall homocysteine remethylation. (b) In vivo rates of cysteine synthesis will be reduced in vitamin B6 deficiency. (c) Thymidylate synthesis from serine-derived one-carbon units will be reduced during vitamin B6 deficiency

  30 days

Secondary Outcomes (1)

• Hypotheses Aim 3

  30 days

Study Arms (2)

Arm 1 glycine and leucine infusion

EXPERIMENTAL

Determine in healthy, adequately pyridoxine nourished humans using a protocol based on amino acid glycine tracer methods: (a) the postprandial rates of in vivo glycine turnover, glycine-based generation of one-carbon units, thymidylate and purine synthesis, and the impact of vitamin B6 deficiency on the rates of these processes and (b) the effect of vitamin B6 deficiency on the postprandial rate of glutathione synthesis. 14 subjects will be chosen after screening is complete and will begin a B6 deficient diet for 30 days. At the beginning and end of the 30 days they will receive an infusion of leucine and glycine then they will begin the four week diet. At the end of four weeks the infusion will be repeated.

Dietary Supplement: Arm 1 glycine and leucine

Arm 2 Intervention of Serine and methionine infusion

EXPERIMENTAL

This arm will allow investigation of total Hcy remethylation and remethylation from serine-derived 1C units, kinetics of serine and the methionine cycle and kinetics of transsulfuration reactions. 14 healthy subjects will be selected and screened. Prior to starting a B6 deficient diet for four weeks an infusion of serine and methionine will commence. Following the first infusion the diet will begin and after four weeks another infusion will be done.

Dietary Supplement: Arm 2 Intervention of Serine and methionine infusion

Interventions

Arm 1 glycine and leucine DIETARY_SUPPLEMENT

Arm 1 glycine and leucine: A subset of 14 participants out of the total enrolled participants with an adequate nutritional status will undergo the tracer infusion of glycine and leucine amino acids protocol while an adequate vitamin pyridoxine, B6 status. After the first infusion each participant will then begin a diet low in vitamin B6 (\<0.5 mg/d) for 4 weeks to achieve marginal B6 status followed by a repeat of fasting blood sampling and tracer infusion protocol.

Also known as: amino acids, B6, leucine, methionine, deficieny

Arm 1 glycine and leucine infusion

Arm 2 Intervention of Serine and methionine infusion DIETARY_SUPPLEMENT

Arm 2 Intervention of Serine and methionine infusion: A subset of 14 participants out of the total enrolled participants. Received an adequate nutritional status will undergo the tracer infusion of methionine and serine amino acids protocol while in adequate vitamin pyridoxine, B6 status. After the first infusion each subject will then begin a diet low in vitamin B6 (\<0.5 mg/d) for 4 weeks to achieve marginal B6 status followed by repeat of fasting blood sampling and tracer infusion protocol.

Also known as: B6 deficiency, methionine, serine

Arm 2 Intervention of Serine and methionine infusion

Eligibility Criteria

• Age: 20 Years - 40 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• years of age
• adequate vitamin B6 levels
• not pregnant

You may not qualify if:

• abnormal labs
• pregnancy
• on medications

Sponsors & Collaborators

• University of Florida: lead
• National Institutes of Health (NIH): collaborator

Study Sites (1)

University of Florida

Gainesville, Florida, 32611, United States

Location

Related Publications (7)

• Lamers Y, Williamson J, Gilbert LR, Stacpoole PW, Gregory JF 3rd. Glycine turnover and decarboxylation rate quantified in healthy men and women using primed, constant infusions of [1,2-(13)C2]glycine and [(2)H3]leucine. J Nutr. 2007 Dec;137(12):2647-52. doi: 10.1093/jn/137.12.2647.

  PMID: 18029478 RESULT

• Lamers Y, Coats B, Ralat M, Quinlivan EP, Stacpoole PW, Gregory JF 3rd. Moderate vitamin B-6 restriction does not alter postprandial methionine cycle rates of remethylation, transmethylation, and total transsulfuration but increases the fractional synthesis rate of cystathionine in healthy young men and women. J Nutr. 2011 May;141(5):835-42. doi: 10.3945/jn.110.134197. Epub 2011 Mar 23.

  PMID: 21430249 RESULT

• Lamers Y, O'Rourke B, Gilbert LR, Keeling C, Matthews DE, Stacpoole PW, Gregory JF 3rd. Vitamin B-6 restriction tends to reduce the red blood cell glutathione synthesis rate without affecting red blood cell or plasma glutathione concentrations in healthy men and women. Am J Clin Nutr. 2009 Aug;90(2):336-43. doi: 10.3945/ajcn.2009.27747. Epub 2009 Jun 10.

  PMID: 19515736 RESULT

• Lamers Y, Williamson J, Ralat M, Quinlivan EP, Gilbert LR, Keeling C, Stevens RD, Newgard CB, Ueland PM, Meyer K, Fredriksen A, Stacpoole PW, Gregory JF 3rd. Moderate dietary vitamin B-6 restriction raises plasma glycine and cystathionine concentrations while minimally affecting the rates of glycine turnover and glycine cleavage in healthy men and women. J Nutr. 2009 Mar;139(3):452-60. doi: 10.3945/jn.108.099184. Epub 2009 Jan 21.

  PMID: 19158217 RESULT

• DeRatt BN, Ralat MA, Gregory JF. Short-Term Vitamin B-6 Restriction Does Not Affect Plasma Concentrations of Hydrogen Sulfide Biomarkers Lanthionine and Homolanthionine in Healthy Men and Women. J Nutr. 2015 Apr 1;146(4):714-719. doi: 10.3945/jn.115.227819.

  PMID: 26962179 DERIVED

• Gregory JF, DeRatt BN, Rios-Avila L, Ralat M, Stacpoole PW. Vitamin B6 nutritional status and cellular availability of pyridoxal 5'-phosphate govern the function of the transsulfuration pathway's canonical reactions and hydrogen sulfide production via side reactions. Biochimie. 2016 Jul;126:21-6. doi: 10.1016/j.biochi.2015.12.020. Epub 2016 Jan 4.

  PMID: 26765812 DERIVED

• Rios-Avila L, Coats B, Chi YY, Midttun O, Ueland PM, Stacpoole PW, Gregory JF 3rd. Metabolite profile analysis reveals association of vitamin B-6 with metabolites related to one-carbon metabolism and tryptophan catabolism but not with biomarkers of inflammation in oral contraceptive users and reveals the effects of oral contraceptives on these processes. J Nutr. 2015 Jan;145(1):87-95. doi: 10.3945/jn.114.201095. Epub 2014 Nov 19.

  PMID: 25527663 DERIVED

MeSH Terms

Conditions

Vitamin B 6 Deficiency

Interventions

Leucine; Amino Acids; Methionine; Serine

Condition Hierarchy (Ancestors)

Vitamin B Deficiency; Avitaminosis; Deficiency Diseases; Malnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases

Intervention Hierarchy (Ancestors)

Amino Acids, Branched-Chain; Amino Acids, Peptides, and Proteins; Amino Acids, Essential; Amino Acids, Sulfur; Sulfur Compounds; Organic Chemicals; Amino Acids, Neutral

Study Officials

• Jesse F Gregory, PhD

  University of Florida

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NON RANDOMIZED
• Masking: NONE
• Purpose: DIAGNOSTIC
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: April 1, 2009
• First Posted: April 8, 2009
• Study Start: January 1, 2008
• Primary Completion: September 1, 2010
• Study Completion: September 1, 2010
• Last Updated: March 27, 2013

Record last verified: 2013-03

Locations

US (1)