Ethanol modulates apolipoprotein B mRNA editing in the rat.
We have studied the rat ethanol-liquid diet model for chronic ethanol modulation of lipid homeostasis, apolipoprotein (apo) B production and apoB mRNA editing. Male Wistar rats were fed one of three diets: i) regular chow, ii) an isocaloric liquid diet, or iii) isocaloric ethanol-liquid diet where ethanol accounts for 35.5% of the total calories, for up to 40 days. There was no difference in body weight or liver/body weight ratio among the three groups of animals at the end of the feeding period. Hepatic and plasma triglycerides were elevated in the ethanol-treated animals only, correlated with an accumulation of lipid particles in the liver of these animals. By DNA excess hybridization, the steady state mRNA levels of apoB and apoB mRNA-editing protein relative to actin were not significantly altered. The proportion of edited apoB mRNA; i.e., apoB-48 mRNA/(apoB-48 + B-100) mRNA, increased in a time-dependent manner from approximately 50% to 100% in the ethanol-treated group. It remained unchanged in the chow- and liquid diet-fed animals. The proportion of apoB-48/apoB-100 protein synthesis was determined by [35S]methionine labeling followed by specific immunoprecipitation and SDS-polyacrylamide gel electrophoresis. The amount of newly synthesized apoB-48 increased from 30-50% to > 99% of the total apoB (apoB-48 + apoB-100). This increase in apoB-48 biosynthesis is reflected by an increase in circulating plasma apoB-48 from barely detectable to approximately 50% of total plasma apoB. Fractionation of plasma lipoproteins by fast protein liquid chromatography (FPLC) indicates that the ethanol-induced hypertriglyceridemia is completely accounted for by an increase in plasma very low density lipoprotein (VLDL). The proportion of apoB-48 as a percent of total apoB in the VLDL fraction increased from approximately 50% in controls to > 90% in ethanol-treated animals. Furthermore, there is a strong correlation between plasma triglyceride concentration and proportion of edited apoB-mRNA in the liver of ethanol-treated rats, but no direct correlation of the latter with intrahepatic triglyceride content. Ethanol-treated rats represent a new model for studying the regulation of apoB mRNA editing by dietary factors in vivo.
Lau
P P
PP
Department of Cell Biology, Baylor College of Medicine, Houston, TX 77030, USA.
Cahill
D J
DJ
Zhu
H J
HJ
Chan
L
L
D000818:Animals; D053283:Apolipoprotein B-48; D001055:Apolipoproteins B / Q000096:biosynthesis / Q000097:blood / Q000235:genetics*; D001483:Base Sequence; D001835:Body Weight / Q000187:drug effects; D004032:Diet; D004195:Disease Models, Animal; D000431:Ethanol / Q000494:pharmacology*; D006949:Hyperlipidemias / Q000139:chemically induced*; D008079:Lipoproteins, VLDL / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D017393:RNA Editing / Q000187:drug effects*; D012333:RNA, Messenger / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014280:Triglycerides / Q000378:metabolism
D053283:Apolipoprotein B-48; D001055:Apolipoproteins B; D008079:Lipoproteins, VLDL; D012333:RNA, Messenger; D014280:Triglycerides; D000431:Ethanol