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Georgia Veterinary Scholar Program

Georgia Veterinary Scholar

Faculty Mentor

Kathy Guthrie
University of Georgia
Class of 2007

Dr. Duncan Ferguson

 

Screening for Potential Goitrogenic Effects of Phenolic Compounds in Cat Food Using a Model Iodide Organification System

 

Hyperthyroidism is the most frequently diagnosed endocrine disorder in cats, with one in 300 cats developing the disorder. The most common symptoms of feline hyperthyroidism are weight loss, polyphagia, unkempt haircoat, polyuria/polydipsia, vomiting, hyperactivity, and increased fecal volume. Between 97-99% of cats with hyperthyroidism have autonomous functional adenomas of the thyroid. Seventy percent have bilateral adenomas. Because there is no isthmus connecting the two lobes of the thyroid in the feline, the bilateral nature in the majority of cases is significant, indicating that a major factor of developing hyperthyroidism could be nutritional or environmental.

In unpublished work from our laboratory, several anti-oxidant compounds found in commercial cat food were identified as having potential goitrogenic effects in an in vitro iodide organification assay. These compounds include butylated hydroxyanisole (BHA), with its metabolite, tert-butyl hydroquinone (TBHQ), and ethoxyquin (EQ). Furthermore, several studies have identified isoflavones, present in commercial pet foods that use soy beans as a protein source, as influencing serum thyroid hormone levels. Eating canned food has been associated with a higher risk of developing feline hyperthyroidism. Bisphenol-A (BPA) is a plasticizing compound used to line the inside of the metal cans containing pet food and will be evaluated for its ability to influence iodination.

Our laboratory developed an in vitro procedure for iodide organification based on research conducted by Taurog that will be used to screen for anti-thyroid effects of suspect goitrogens. The in vitro assay is composed of a lactoperoxidase-glucose oxidase system which simulates the enzymatic activity of thyroid peroxidase and FAD-dependent acyl coA β oxidase systems which generate hydrogen peroxidase. Bovine serum albumin (BSA) serves as a substitute for feline thyroglobulin. It has been shown that this assay very closely mimics the in vivo organification of iodide.

 

 

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