Dramatic differences in lipoprotein composition among gray short-tailed opossums (Monodelphis domestica) fed a high cholesterol/saturated fat diet.

Lipoproteins of gray short-tailed opossums (Monodelphis domestica) were characterized to determine the basis of differences among individuals in response to a challenge diet enriched in saturated fat and cholesterol. Animals were selected from two phenotypic groups (high and low plasma cholesterol response to the challenge diet). Half of the animals in each group were fed basal diet (8.1% fat and 0.04% cholesterol by weight), and the remainder were fed challenge diet (17.7% fat and 0.61% cholesterol). The plasma cholesterol values of both groups fed the basal diet and of low responders fed the challenge diet were similar. In addition, both very-low-density and low-density lipoproteins (VLDL+LDLs) and high-density lipoproteins (HDLs) were similar among these groups in density and in lipid and apolipoprotein compositions. In contrast, the high responders fed the challenge diet showed a 7-fold increase in total plasma cholesterol, which was primarily a consequence of increases in the VLDL+LDL cholesterol component defined by heparin-Mn precipitation. Moreover, the VLDL+LDLs were more heterogeneous and were characterized by decreased densities. The VLDL+LDLs of the high-responding group had higher levels of apolipoprotein (apo) B and apoE than the other groups. Plasma apoB concentrations estimated by dot blotting techniques increased by 3-fold, and apoE by 44-fold in the high responding group. Understanding the factor(s) mediating responder phenotype in this new model species will expand our knowledge of the regulation of lipemic response to diet.