Dietary thiaminase impairs cardiac function and increases heart size in lake trout (Salvelinus namaycush)

The consumption of invasive, high-thiaminase prey fishes can cause thiamine deficiency, which has been hypothesized to be a major barrier for lake trout (Salvelinus namaycush Walbaum in Artedi, 1792) restoration in the Great Lakes. In fishes, an understudied aspect of thiamine deficiency is its effect on cardiac function, despite evidence of this effect in mammals. Here, parr of two strains of lake trout (Seneca and Slate) were raised on either a control or high-thiaminase diet for nine months. We then measured cardiac function and morphology, particularly as it relates to the ability of the heart to meet oxygen demands at warmer water temperatures. The thiaminase diet was associated with significant heart enlargement and reduced cardiac performance at high temperatures. These effects were observed in both strains, but were more pronounced in Slate strain fish. Our data suggest that dietary thiaminase impairs cardiac function in fishes, and that these impairments may become increasingly important as water temperatures increase through climate change.