Cholesterol turnover, synthesis, and retention in hypercholesterolemic growing swine

Studies of the interaction of cholesterol absorption, excretion, synthesis, and retention were carried out with growing swine through the application of sterol and isotopic balance procedures to a non-steady state situation. The animals were fed either a low-fat commercial mash diet (MA), a commercial mash diet plus 2.4 g/day of crystalline cholesterol (MAC), or a high-fat milk diet containing 2.4 g/day cholesterol (MKC). [(14)C]Cholesterol and beta-[(3)H]sitosterol were used to measure fecal neutral steroid losses. Final plasma cholesterol levels averaged 91, 85, and 195 mg/100 ml for MA, MAC, and MKC animals, respectively. Total carcass dissection followed by cholesterol measurement revealed that accumulation of cholesterol in most body tissues was directly related to increase in body size in the rapidly growing swine. The only notable exceptions were plasma, liver, and bone with marrow of the MKC group, where cholesterol concentrations were significantly elevated. Absorption of cholesterol was significantly greater in animals fed MKC than MAC-fed swine (726 mg/day vs. 142 mg/day), whereas synthesis of cholesterol was significantly greater in MAC animals than in MKC animals (863 mg/day vs. 112 mg/day). Excretion of neutral and acid steroids into the intestine was not significantly different between MAC and MKC groups, but both classes of steroids were more efficiently reabsorbed in MKC animals. The overall differences between swine fed mash-cholesterol and those fed milk-cholesterol diets appear to result from more efficient absorption of both neutral and acid steroids in the milk-cholesterol group only partially compensated for by decreased cholesterol synthesis.