A Role for Taurine in Food Sensitivities in Fish

Abstract

As the aquaculture industry expands to feed an ever-growing world population, it seeks to develop more low-cost, environmentally sustainable feed ingredients. Fish meal replacement by plant sources of protein, including those derived from soybeans, wheat, and peas may have unintended effects. Certain fish species have reacted poorly to particular ingredients, including components of soy and pea protein. We present here evidence for potential negative health effects, including possible inflammation, elicited by wheat gluten incorporation into the feed of Cobia (Rachycentron canadum). European sea bass (Dicentrarchus labrax), on the contrary, seem to well tolerate this ingredient. We sought to evaluate the ability of taurine, a known immunomodulator, to alleviate inflammation in cases of adverse effects caused by particular plant ingredients in feed. We saw evidence for this in the cobia study, and though our study did not induce any inflammation in sea bass, we detected dramatically increased levels of taurine levels in the plasma of fish consuming a diet containing 4% wheat gluten. In another study, supplemental taurine in European sea bass shifted spectral sensitivity to a longer wavelength, though there were no apparent anatomical differences in the retina between the un-supplemented and supplemented groups. We observed changes to the microbiome induced by dietary wheat gluten, and in a separate study, taurine. Wheat gluten addition to the diet greatly increased the number of predominant orders represented in the intestinal microbiota. Taurine caused less of a shift, but interestingly, the predominant orders were very uniform throughout the sections of the intestines of the taurine-fed fish. In two different studies, we attempted to characterize a dietary taurine-dependent zebrafish that was incapable of endogenous taurine synthesis. However, both of our potential strains turned out to be producing a wild-type CSAD (cysteine sulfinic acid decarboxylase) protein even in the presence of early termination codons in the csad gene. We also observed the expression of two smaller sizes of CSAD, ~53 and ~55 kDa, in addition to the previously described ~59 kDa protein. The two smaller sizes appear to be produced early in development and are not detectable by 3.5 weeks post-fertilization.