The research findings – published in the Journal of Leukocyte Biology – suggest that polyphenols found in apple peel can suppress activation of immune T cell activation in a model of colitis. The study reported to be first to demonstrate such a role for T cells in polyphenol-mediated protection against an autoimmune disease.
The authors of the study suggested that the results could lead to new therapies for people with disorders related to bowel inflammation, including ulcerative colitis, Crohn's disease and colitis-associated colorectal cancer.
“Collectively, these results show that oral administration of APP protects against experimental colitis and diminishes proinflammatory cytokine expression via T cells,” wrote the research authors, led by Dr. David Pascual from the Department of Immunology and Infectious Diseases at Montana State University, USA.
Dr. John Wherry, deputy editor of the Journal of Leukocyte Biology added that the research suggests another reason why "an apple a day keeps the doctor away”:
"It appears that the old adage rings true in more ways than one," he said.
"In addition to the obvious health benefits of the nutrients and fibre in fruits and vegetables, this study indicates that even something as relatively common as the apple contains other healthy ingredients that can have serious therapeutic value," said Wherry.
Pascual and his team chemically induced a model of colitis – using dextran sulfate sodium (DSS) in mice. The researchers then gave a placebo to one group of mice, whilst the other group was given an oral dose of apple polyphenols. The results revealed that mice treated orally with apple polyphenols were protected from colitis.
They said that oral, but not peritoneal, administration of the apple peel polyphenols (APP) during colitis induction significantly protected the mice against disease: “as evidenced by the lack of weight loss, colonic inflammation, and shortening of the colon.”
In addition, the team reported that treated mice had fewer activated T cells in the colon.
They added that in mice lacking T cells, the apple polyphenols were unable to protect against colitis or suppress pro-inflammatory cytokine expression – indicating a mechanism of protection against colitis via the suppression of T cell activation or recruitment.
Pascual noted that many people with colitis use some form of dietary supplement or natural remedy to complement conventional therapies:
“But most of the information on the health effects of complementary medicine remains anecdotal. Also, little is known about exactly how these therapies work, if they work at all," he explained.
"Our results show that a natural product found in apple peels can suppress colonic inflammation by antagonizing inflammatory T cells to enhance resistance against autoimmune disease," affirmed Pascual.
Source: Journal of Leukocyte Biology
Volume 90, Number 6, Pages 1043-1054, doi: 10.1189/jlb.0311168
“Apple polyphenols require T cells to ameliorate dextran sulfate sodium-induced colitis and dampen proinflammatory cytokine expression”
Authors: J.A. Skyberg, A. Robison, S. Golden, M.F. Rollins, et al