Abstract
Walnuts contain a complex array of natural compounds and phytochemicals that exhibit a wide range of health benefits, including protection against inflammation and colon cancer. In this study, we assess the effects of dietary supplementation with walnuts on colonic mucosal injury induced in mice by the ulcerogenic agent, dextran sodium sulfate (DSS). C57Bl/6J mice were started on the Total Western Diet supplemented with freshly-ground whole walnuts (0, 3.5, 7 and 14% g/kg) 2 weeks prior to a 5-day DSS treatment and walnut diets were continued throughout the entire experimental period. Mice were examined at 2 days or 10 days after withdrawal of DSS. In a separate study, a discovery-based metabolite profiling analysis using liquid chromatography tandem mass spectrometry (LC-MS/MS) was performed on fecal samples and colonic mucosa following two weeks of walnut supplementation. Dietary walnut supplementation showed significant effects in the 10-day post-DSS recovery-phase study, in which the extent of ulceration was significantly reduced (7.5% vs. 0.3%, p < 0.05) with 14% walnuts. In the metabolite-profiling analysis, walnuts caused a significant increase in several polyunsaturated fatty acids (PUFAs), including docosahexaenoic acid (DHA) and 9-oxo-10(E),12(E)-octadecadienoic acid (9-oxoODA), as well as kynurenic acid. In colon tissue samples, walnuts caused a significant increase in the levels of S-adenosylhomocysteine (SAH) and betaine, important components of fatty acid β-oxidation. These metabolite changes may contribute in part to the observed protection against DSS-induced inflammatory tissue injury.
Highlights
Dietary supplementation with nuts has shown a variety of health benefits
We examined the effects of walnut supplementation on the extent of colonic injury during the acute phase of dextran sodium sulfate (DSS)-induced colitis
This study has shown that dietary supplementation of walnuts has the ability to protect mice against DSS-induced experimental colitis
Summary
Dietary supplementation with nuts has shown a variety of health benefits. Walnuts (Juglans regia) contain the highest levels of the omega-3 fatty acid, namely alpha-linoleic acid (ALA), with the most favorable ratio of omega-3:omega-6 fatty acids (1:4.2) [1]. Walnuts contain a large number of phytochemicals, including phenolic antioxidants, and high levels of nutrients with beneficial properties to guard against a variety of diseases, including heart disease, diabetes, neurological disorders, inflammation and cancer [1,2,3]. Walnuts are a rich source of fiber (up to 6.4%), which has been shown to support the maintenance of disease remission in patients suffering from inflammatory bowel disease (IBD) [4]. IBD, encompassing both Crohn’s disease (CD) and ulcerative colitis (UC), are chronic intestinal inflammatory disorders of largely unknown etiology [5]. As recently reviewed [7], diet clearly plays
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