The Conversion of ENcapsulated GlucorAphanin, Gut Microbiota Phylogeny and gEnotype Study (ENGAGE) (ENGAGE)
The variation in extent of isothiocyanate (ITC) excretion in urine from a capsule delivered dose of glucoraphanin will correlate with differences in (a) the gut microbiota, and (b) the genotype of key polymorphic genes (GSTM1, GSTT1, and other as yet undetermined candidate genes).
Our study is a human dietary intervention in which participants will consume one capsule containing 100mg purified glucoraphanin from broccoli. The levels of glucoraphanin delivered by the capsule are similar to one to two portions of broccoli. As this is purified glucoraphanin there is no myrosinase enzyme present. All conversion of the glucoraphanin, contained within the capsule, to ITC will therefore occur by enzymes found in the gut microbiota.
The ability of the glucoraphanin in the capsule to be metabolised to ITCs by the gut microflora is unknown and will be assessed by measuring ITCs excreted in the urine. The ITCs will be quantified in urine using validated analytical methods.
It has been shown in human dietary intervention studies that the extent of conversion of glucosinolates varies greatly. In order to assess possible causative factors for variation in rate of glucoraphanin metabolism each participant will provide a faecal sample from which their faecal gut microbiota phylogeny will be analysed.
For a small number of participants a second faecal sample will be requested (a maximum of 3 participants). It is our aim to select one low, one medium and one high ITC excreter. Ideally the low and high excreters would be within the lowest and highest 5% excretion of ITC and the third participant would be as close to the mean ITC excretion as possible. The aim would be to culture the faecal microbiota over time with repeat dosing of glucoraphanin in order to select for microbiota that are able to metabolise glucoraphanin. It is known that the main hydrolysis product of glucoraphanin, sulforaphane, has a variety of benefits to human health, however there is no known clinical relevance to being a high, medium or low excreter of ITC.
For each participant a blood sample will also be requested in order that we can assess whether genotype affects the rate of ITC excretion in urine. The GSTM1 genotype and other, as yet, unidentified candidate genes of each participant will be determined. Whether the genotype affects the rate of ITC excretion either alone or in combination with the phylogenetic profile will be assessed.
|Study Design:||Intervention Model: Single Group Assignment
Masking: Open Label
Primary Purpose: Basic Science
|Official Title:||A Human Intervention Trial Investigating the Conversion of Encapsulated Glucoraphanin to Isothiocyanates; and the Potential Link Between the Extent of the Conversion to an Individual's Gut Microbiota Phylogeny and Genotype.|
- Urinary ITC concentration [ Time Frame: In 24h collections at (i) baseline and (ii) following glucoraphanin capsule administration. ]To measure urinary ITC by HP-LC and LC-MS using validated methods in urine collected during a dietary restriction period both before and after (24 hour urine collection) consumption of a 100mg glucoraphanin capsule.
- Faecal microbiota phylogenetic analysis [ Time Frame: At baseline ]To measure gut microbiota populations by faecal bacteria phylogenetic analysis.
- Genotype [ Time Frame: At baseline ]To determine the genotype of participants for key polymorphic genes by PCR on DNA extracted from blood.
|Study Start Date:||December 2012|
|Study Completion Date:||August 2016|
|Primary Completion Date:||December 2014 (Final data collection date for primary outcome measure)|
Experimental: dietary intervention
To measure the variation in extent of ITC excretion in urine from a capsule delivered dose of 100mg glucoraphanin
Dietary Supplement: 100mg glucoraphanin
The extent of ITC excretion in urine from a capsule delivered dose of glucoraphanin
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Please refer to this study by its ClinicalTrials.gov identifier: NCT01927666
|Institute Of Food Research|
|Norwich, Norfolk, United Kingdom, NR4 7UA|
|Principal Investigator:||Richard Mithen, PhD||Institute of Food Research|