Comparative aspects of cholesterol metabolism and lecithin:cholesterol acyltransferase activity in dogs and cats
Little research has focused on the relationship between lecithin:cholesterol acyltransferase (LCAT) activity and cholesterol metabolism in dogs and cats. To study weight loss and cholesterol metabolism in dogs, four experimental weight-loss diets were fed to 12 obese female beagles for 8 wk in a partial crossover design (n = 6). High- (HGI) or low-glycemic index (LGI) starch and diacylglycerol or triacylglycerol oil were combined to compose diets with similar fatty acid (FA) profiles. Body weight was measured weekly. Fasted blood samples were drawn at wk1, wk4, and wk8 to measure plasma total (TC), unesterified (UC), and esterified cholesterol (EC) concentrations, LCAT activity, and FA composition of the phospholipid (PL) and EC fractions. All groups lost weight. UC increased from wk1 to wk4 (p < 0.05). LCAT activity increased from wk1 to wk4 and remained elevated at wk8 (p < 0.05). Plasma PL FA profiles reflected the diets fed with few diet or time effects. Plasma EC FA profiles reflected the specificity of LCAT for linoleic acid (LA) with minimal diet or time effects. We conclude that weight reduction in dogs occurs in conjunction with increased LCAT activity and altered plasma cholesterol fractions but not changes in plasma PL or EC FA profiles. To measure the activity and demonstrate the FA specificity of LCAT in felines fed varying types of fat, 29 female cats were fed diets enriched with high-oleic sunflower (n = 9), menhaden fish (n = 10), or safflower (n = 10) oil (8g oil/100g kibble) for 4 wk. Fasted blood samples were drawn at d0, d14, and d28 for determination of the blood parameters mentioned previously. LCAT and TC showed no time or diet effects. UC decreased at d28 compared to d0 and d14, while EC increased at d28 compared to d0 and d14 (all p < 0.05). Plasma EC FA profiles reflected the specificity of LCAT for LA with many diet and time effects but contained no docosahexanoic acid (DHA). We conclude that feline LCAT has no measurable affinity for DHA, but both feline and canine LCAT demonstrated specificity for LA regardless of diet fed.