Diets causing taurine depletion in cats substantially elevate postprandial plasma cholecystokinin concentration

Excessive secretion of the intestinal hormone cholecystokinin (CCK) was postulated to cause diet-related taurine depletion in cats. To test this hypothesis, plasma CCK-like immunoreactivity (CCK-LI) was measured in cats given four diets, two purified and two canned, that contained similar concentrations of protein, fat, moisture and taurine but produced variable rates of taurine depletion. Plasma CCK-LI was measured by RIA with a tyrosine-sulfate specific, C-terminal anti-serum, validated for use in cat plasma. As indicated by measurements of taurine in whole blood and urine, a purified diet containing casein maintained body taurine, whereas the same diet containing soybean protein and a commercial canned diet preserved either by freezing or cooking depleted body taurine. Preprandial and peak postprandial plasma CCK-LI in cats given the casein-containing diet were 10.6 +/- 1.4 and 27.6 +/- 4.8 pmol/L, respectively, approximately two- to tenfold greater than those reported in humans. Integrated postprandial plasma CCK-LI was less for cats given the casein diet than cats given both forms of the canned diet; it tended to be lower in cats given the casein diet than in cats given the soy protein diet. A negative linear correlation was observed between apparent nitrogen digestibilities of the diets and integrated plasma CCK-LI. The results indicated that diets that cause taurine depletion have lower protein digestibilities and cause greater endocrine secretion of CCK than diets that maintain body taurine status.