Diet-induced and physiologically occurring hypercholesterolemias in the spontaneous hypothyroid European badger (Meles meles L.): a density gradient study of lipoprotein profile.

Abstract

As previously shown in this laboratory (Laplaud, P. M. et al. J. Lipid Res. 1980. 21: 724-738), the European badger is, with regard to its plasma lipid transport system, an original and complex animal of great potential interest to lipoprotein research. In an effort to study the response of this animal to cholesterol feeding, we gave a diet supplemented with 1% cholesterol to six male badgers (group H) during the late fall period when spontaneous hypercholesterolemia and hypothyroidism occur. Six more male animals of similar age received the standard diet (group C) and were simultaneously used as controls. Plasma lipids were measured using enzymatic methodologies, while the use of a recently described density gradient ultracentrifugation technique allowed detailed examination of lipoprotein composition and polyacrylamide gel electrophoresis of lipoproteins and tetramethylurea-soluble apoproteins in the fractions. The results suggest the superimposition, in H badgers, of the spontaneous and diet-induced hypercholesterolemias, maximum levels being reached in December in both C and H groups. While the two groups were very similar at the beginning of the experiment, highly significant differences (P < 0.01) were subsequently observed between C and H animals in plasma cholesterol and phospholipid concentrations. Density gradient ultracentrifugation provided evidence for the following diet-induced changes in lipoprotein profile: 1) a twofold increase in cholesteryl esters in particles of d < 1.006 g/ml; 2) the occurrence of large amounts of supplementary cholesterol-rich low density lipoproteins, mainly in the 1.019-1.027 g/ml region; 3) an increase in the 1.039-1.055 g/ml low density lipoproteins; and 4) a change in the ratio of the concentrations of high density lipoproteins of d 1.065-1.100 g/ml and d 1.100-1.162 g/ml, to the benefit of the former. Electrophoresis of the density gradient fractions revealed marked heterogeneity, especially in the low density part of the spectrum. Electrophoresis of the low molecular weight, tetramethylurea-soluble apoproteins failed to show marked differences between C and H badgers. However, chromatographic determination of the proportion of apoB in the protein moiety of the two main low density components showed that 1) it was consistently low, 2) its contribution to the higher density fraction (d 1.039-1.046 g/ml) was unaffected by the hypercholesterolemic diet (being about 25% in both C and H animals), and 3) its contribution to the lower density fraction (d 1.019-1.027 g/ml) decreased under the same nutritional conditions, representing about 20% in C as compared to about 10% in H badgers.-Laplaud, P. M., Beaubatie, and D. Maurel. Dietinduced and physiologically occurring hypercholesterolemias in the spontaneous hypothyroid European badger (Meles meles L.): a density gradient study of lipoprotein profile.