Scientific Abstract
Proposal No. IBD-0227R
Principal Investigator: James M. Mullin, Ph.D.
Applicant Organization: Lankenau Institute for Medical Research (Wynnewood, Pennsylvania, U.S.A.)
Project Title: Improvement in gastrointestinal barrier function and morbidity by restriction of sulfur-containing amino acids in Crohn's disease patients
Period of Award: October 1, 2008 - June 30, 2010
Sulfur-containing amino acid (SCAA)-restricted diet alters tight junction (TJ) structure and composition, decreases TJ permeability and thereby enhances epithelial barrier function. This is one of very few known modalities capable of causing improved barrier function, in contrast to a growing list of frequently pathogenic agents capable of causing TJ leak [1]. It is noteworthy that restriction of dietary SCAAs, like the better known regimen of caloric restriction, has been documented to significantly increase lifespan and offset age-related morbidity in a variety of animal models [2-61]. In this proposal, we hypothesize that specifically methionine restriction will induce improved barrier function at the TJ level across gastrointestinal epithelial tissues of Crohn's disease (CD) patients and thereby improve their gastrointestinal physiology and overall quality of life. The effects of methionine restriction on epithelial barrier function and tight junctions have never before been addressed, nor has methionine restriction ever been tested in IBD. As in the cell culture studies reported herein, we hypothesize that this improvement will be related to diet-induced alteration of gastrointestinal TJ claudin composition resulting in a subsequent decrease in TJ leak [improvement of barrier function]. This proposal is predicated upon aberrant epithelial barrier function being a causal or at least contributory component in CD, the case for which goes back at least 25 years [7-12]. These compromises of the gastrointestinal barrier in IBD were later traced to alterations of specific tight junctional claudin proteins [13, 14].
We propose recruiting CD patients with mild-moderate (active) disease for a four week trial of a diet that will decrease methionine to 40% of normal dietary intake. This diet is meat and fish free and is low in dairy and legumes. All other essential amino acids will be maintained at normal levels by a nutrient supplement (Hominex-2 [Abbott Labs]), which will also bring minerals/vitamins and total calories up to normal daily intake. A triple sugar (mannitol/lactulose/sucralose) permeability test (to observe small and large bowel permeability) [I 5, 16] will be performed before the diet is begun, within three days of ending the diet, and four weeks after normal eating is resumed. A Crohn's Disease Activity Index (CDAI) will be administered at the same times. Plasma and intracellular (RBC) methionine, cysteine and taurine levels will be monitored throughout, as will erythrocyte sedimentation rate, CRP, ESRICRP ratio, and homocysteine. TJ proteins in uroepithelia (recovered from urine samples) will be assayed at those three times by PAGE and Western immunoblots for occludin and eight claudins. Our goal is to achieve evidence that this very health-beneficial diet will alter TJ permeability in the gut, thereby improving barrier function and alleviating transmucosal injury and resultant clinical symptoms in a CD population.
We propose recruiting CD patients with mild-moderate (active) disease for a four week trial of a diet that will decrease methionine to 40% of normal dietary intake. This diet is meat and fish free and is low in dairy and legumes. All other essential amino acids will be maintained at normal levels by a nutrient supplement (Hominex-2 [Abbott Labs]), which will also bring minerals/vitamins and total calories up to normal daily intake. A triple sugar (mannitol/lactulose/sucralose) permeability test (to observe small and large bowel permeability) [I 5, 16] will be performed before the diet is begun, within three days of ending the diet, and four weeks after normal eating is resumed. A Crohn's Disease Activity Index (CDAI) will be administered at the same times. Plasma and intracellular (RBC) methionine, cysteine and taurine levels will be monitored throughout, as will erythrocyte sedimentation rate, CRP, ESRICRP ratio, and homocysteine. TJ proteins in uroepithelia (recovered from urine samples) will be assayed at those three times by PAGE and Western immunoblots for occludin and eight claudins. Our goal is to achieve evidence that this very health-beneficial diet will alter TJ permeability in the gut, thereby improving barrier function and alleviating transmucosal injury and resultant clinical symptoms in a CD population.