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Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

Dietary Ascophyllum nodosum Increases Urinary Excretion of Tricarboxylic Acid Cycle Intermediates in Male Sprague-Dawley Rats^1–3,

⁴ National Research Council of Canada, Institute for Marine Biosciences, Halifax, NS, Canada B3H 3Z1 and ⁵ Department of Family and Nutritional Sciences, University of Prince Edward Island, Charlottetown, PE, Canada C1A 4P3

We used a ¹H NMR-based metabonomics approach to examine the physiological effects of the seaweed Ascophyllum nodosum in a mammalian model, assess the dosage level required to elicit a response in the urinary profile, and identify potential toxic effects. Male Sprague-Dawley rats (n = 6/group) were fed a control or 5, 10, or 15% freeze-dried, ground A. nodosum diet for 4 wk. Urine samples were collected 3 times daily (0–4, 4–8, and 8–24 h) prior to feeding experimental diets and, at the end of the study, were profiled using ¹H NMR spectroscopy. Food intake, weight gain, and serum enzyme (alanine transaminase and aspartate transaminase) levels indicated that seaweed diets were well tolerated. The spectral data and principal component analysis (PCA) revealed that rats fed 5, 10, and 15% seaweed diets had increased urinary excretion of citrate, 2-oxoglutarate, succinate, trimethylamine (TMA), TMA-N-oxide, and malonate and decreased excretion of taurine, creatinine, and acetate compared with the controls. In addition, mannitol was detected in the 8- to 24-h urine samples from seaweed-fed rats. Metabolic responses related to ingestion of seaweed polyphenolics and fiber were not observed in the spectral profiles. Increased seaweed concentration in the diet did not increase the magnitude of the rats' response as detected by ¹H NMR. Visual analysis and PCA of the spectral data for serum samples collected at the end of the study did not show diet-related clustering. The lack of toxicity at 15% seaweed incorporation allows the use of this concentration in future A. nodosum intervention studies.

^* To whom correspondence should be addressed. E-mail: shawna.mackinnon{at}nrc-cnrc.gc.ca.

Manuscript received 30 March 2009. Initial review completed 27 April 2009. Revision accepted 24 May 2009.

Published online 17 June 2009.