Assessing Colonic Folate Absorption & Metabolism

October 25, 2022 updated by: Deborah O'Connor, The Hospital for Sick Children

Factors Affecting Colonic Folate Absorption and Metabolism in Humans

Folate, a B-vitamin, is necessary in metabolic processes such as amino acid and nucleotide synthesis. Since folate cannot be synthesized by mammals, it must be consumed as foods and dietary supplements or generated by bacteria present in the colon. There are many known adverse health outcomes associated with folate deficiency in humans such as neural tube defects in newborns and colorectal cancer in adults. It has also been proposed that supra-physiological folate status can also be detrimental since it can lead to changes in immune function and the masking of vitamin B12 deficiency. It is generally believed that dietary sources of folate are primarily absorbed in the small intestine, however recent evidence suggests the colon may play a more significant role in the absorption of folate than previously understood. The aim of this study is to assess how folic acid supplementation influences colonic folate absorption and metabolism in humans. This will be accomplished by assessing the expression of two major folate transporters responsible for folate absorption in the colon. Participants will be randomized to receive multivitamins with either 0 or 400 µg folic acid during a 16-week randomized clinical trial in which blood and colonic tissue biopsies will be collected and analyzed. The total folate concentrations and expression of folate transporters in colonocytes will be measured to confirm levels and evaluate the impact of supplemental folic acid. The expression of two folate hydrolases responsible for converting naturally occurring folate to its bioavailable form will also be evaluated. This work will lead to a deeper understanding of colonic folate absorption and metabolism, resulting in more appropriate dietary and supplemental folate recommendations.

Study Overview

Status

Active, not recruiting

Conditions

Detailed Description

The vitamin folate is necessary for one-carbon metabolism in processes such as amino acid and nucleotide synthesis. As folate cannot be synthesized by mammals, it must be sourced from the diet and dietary supplements or generated by bacterial species present in the colon. There are a number of well-established adverse health outcomes associated with folate deficiency in humans, including congenital neural tube defects in newborns and colorectal cancer in adults. It has been proposed supra-physiological folate status can also be detrimental since it can lead to changes in immune function and the masking of vitamin B12 deficiency. It is generally believed that dietary sources of folate are primarily absorbed in the small intestine, however recent evidence from our team and others suggests that the colon may play a greater role in absorption of folate than previously understood. Specifically the amount of folate in the colon, much of it generated by the microbiome, can exceed dietary intakes of folate from natural sources. There are a number of gaps in knowledge regarding colonic folate absorption in humans. It is not known to what degree folate specific transporters such as proton coupled folate transporter (PCFT) and reduced folate carrier (RFC) are present in the colon of healthy humans. To date, the majority of studies conducted identifying the presence of RFC and PCFT in colonocytes have been performed using cell lines or tissue harvested from organ donors. To our knowledge, no study has investigated the mRNA and protein concentrations of both RFC and PCFT present in human colonic tissue retrieved as biopsies. It also remains to be determined if folate status influences RFC and PCFT expression at the level of the colon. Secondly, it remains unclear to what degree the two intestinal folate hydrolases, glutamate carboxypeptidase II (GCPII) and γ-glutamyl hydrolase (GGH) are present in colonic mucosa. To gain a more thorough understanding of the fundamental processes involved in folate absorption in the colon of humans, the following three objectives are proposed. The primary objective is to evaluate the impact of 0 and 400 µg supplemental folic acid on total folate concentrations within the colonic mucosa by measuring folate levels. The secondary objectives include evaluating the impact of 0 and 400 µg supplemental folic acid on the regulation of PCFT and RFC in the ileum and colon by assessing the expression of mRNA transcripts and proteins, and determining the degree to which GCPII and GGH are present in the lumen of the ileum and colon by quantifying enzyme activity and expression of mRNA transcripts and proteins. To accomplish this, a 16-week longitudinal open-labelled randomized clinical trial will be conducted. Recruitment and screening will require three separate steps comprised of an initial invitation to participate, followed by a telephone screening session to determine eligibility and finally a baseline in-person study visit prior to enrollment into the intervention phase of the study. Once enrolled, participants will be asked to follow a diet low in synthetic folic acid for the duration of the study. At enrollment, subjects will be randomized to receive a multivitamin supplement and either 0 or 400 µg folic acid. Follow-up study visits will take place at week 8 and week 16 where anthropometric measurements, blood and colonic tissue biopsies (Week 16 only) from the terminal ileum, cecum, ascending colon, and descending colon will be collected for analysis. 24-hour dietary recalls will be collected throughout the study to observe folate and caloric intake. Plasma, RBC folate levels, and colonic mucosa folate content will be determined via microbial assay. GCPII and GGH enzyme activity will be determined according to the Krumdieck and Baugh method with modification. PCFT and RFC expression will be determined via semi-quantitative real-time PCR and protein samples will be extracted in a Western Blot Analysis using RIPA lysis and extraction buffer. The proposed study will further our understanding of the fundamental processes of folate metabolism and absorption in the colon. Results from this study may help to establish the optimal intakes of dietary folate, meeting the requirements of humans, without the potential health risks related to over-exposure to folate.

Study Type

Interventional

Enrollment (Anticipated)

24

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

    • Ontario
      • Toronto, Ontario, Canada, M5B 1W8
        • St. Michael's Hospital

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 75 years (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

Inclusion Criteria:

  1. Males >18 years old and <75 years old;
  2. Females who are pre-menopausal that have had a hysterectomy or tubal ligation, post-menopausal (at least 1 year) and <75 years old;
  3. Describe themselves as generally healthy.
  4. Recommended to have a colonoscopy examination by their Doctor

Exclusion Criteria:

  1. They have a history of gastrointestinal disease (such as Crohn's disease, ulcerative colitis, celiac disease) and/ or gastrointestinal cancers;
  2. They have had a previous colon resection;
  3. They are regularly using medications that may affect gastrointestinal pH or folate metabolism (e.g. proton pump inhibitors, phenytoin, phenobarbital, primidone, or have used oral antibiotics within the last 2 weeks);
  4. On a regular basis they consume >2 alcoholic drinks/day for women or >3/day for men;
  5. They are currently smokers;
  6. They are folic acid supplement users or have used folic acid supplements or multivitamins containing folic acid in the last 4 months;
  7. They have a bleeding disorder (such as hemophilia)
  8. They are unlikely able to discontinue anti-coagulant therapy prior to colonoscopy

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Active Comparator: Folic Acid supplementation
Participants receive an adult multivitamin supplement along with a folic acid supplement
Participants receive a 400 microgram Folic Acid supplement
Participants will receive an adult multivitamin supplement
Placebo Comparator: No supplementation
Participants only receive an adult multivitamin supplement
Participants will receive an adult multivitamin supplement

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Colonic folate levels
Time Frame: 4 months
Evaluate the impact of 0 and 400 µg supplemental folic acid on total folate concentrations within the colonic mucosa by measuring folate levels
4 months

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
PCFT
Time Frame: 4 months
Evaluate the impact of 0 and 400 µg supplemental folic acid on the regulation of PCFT in the ileum and colon by assessing the expression of mRNA transcripts and proteins
4 months
RFC
Time Frame: 4 months
Evaluate the impact of 0 and 400 µg supplemental folic acid on the regulation of RFC in the ileum and colon by assessing the expression of mRNA transcripts and proteins
4 months
GCPII
Time Frame: 4 months
Determine the degree to which GCPII is present in the lumen of the ileum and colon by quantifying enzyme activity and expression of mRNA transcripts and proteins
4 months
GGH
Time Frame: 4 months
Determine the degree to which GGH is present in the lumen of the ileum and colon by quantifying enzyme activity and expression of mRNA transcripts and proteins
4 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

December 17, 2018

Primary Completion (Anticipated)

October 15, 2023

Study Completion (Anticipated)

October 15, 2023

Study Registration Dates

First Submitted

January 8, 2018

First Submitted That Met QC Criteria

January 29, 2018

First Posted (Actual)

February 5, 2018

Study Record Updates

Last Update Posted (Actual)

October 26, 2022

Last Update Submitted That Met QC Criteria

October 25, 2022

Last Verified

October 1, 2022

More Information

Terms related to this study

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

No

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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