Effect of sucrose diet on expression of apolipoprotein genes A-I, C-III and A-IV in rat liver

A sucrose-rich diet stimulates hepatic lipogenesis and induces net production of very low density lipoproteins in the liver. To study changes of hepatic apolipoprotein gene expression in response to such a diet, we measured the mRNA abundance of apolipoproteins A-I, C-III and A-IV in livers of rats fed a sucroserich diet or a control diet for 3 weeks. In livers of sucrose-fed rats, the abundance of cellular and nuclear apo A-IV mRNA increased to 185% ± 21% and 142% ± 22% of control values (P < 0.01), respectively. In sucrose-fed rats, the transcriptional activity of the apo A-IV gene, measured in a cell-free transcription system using isolated liver nuclei, increased to 144% ± 23% of control (P < 0.05). In contrast, this diet neither affected the abundance of cellular and nuclear apo A-1 and apo C-III mRNA nor the transcriptional activity of these genes in liver. These results are consistent with specialization of the regulatory elements of the genes coding for apolipoproteins A-I, C-I1I and A-IV. Alternatively, enhanced transcription of the apo A-IV gene may preclude increased synthesis of apo A-I and/or apo C-111 mRNA due to the close linkage of the three genes in the rat genome.