Serum high-density lipoprotein particles of alcohol-fed rats are deficient in apolipoprotein E.

Effects of chronic ethanol consumption on serum lipoproteins have been studied in the rat. The serum levels of triglycerides, cholesterol, phospholipids and apolipoproteins AI and AIV increased significantly after 1 week of ethanol feeding, and they remained elevated up to 7 weeks of alcohol drinking. By contrast, serum total apolipoprotein E decreased or, sometimes, did not change. Very-low-density lipoprotein cholesterol, triglycerides and very-low-density lipoprotein apolipoprotein E of the alcohol-fed rats increased in parallel and were about 2- to 2.5-fold over the controls. Whereas high-density lipoprotein cholesterol, phospholipids, apolipoprotein AI and AIV increased 1.2-fold by chronic alcohol feeding, the level of high-density lipoprotein apolipoprotein E decreased to 70% of that of the control rats. The rates of secretion of apolipoprotein AI, E and AIV into the culture medium by hepatocytes isolated from ethanol-fed rats were 1.8-, 1.3- and 1.1-fold higher than those from control rats. These data indicate that (i) chronic ethanol feeding increases very-low-density lipoprotein and high-density lipoprotein in the rat; (ii) serum high-density lipoprotein particles of the ethanol-fed rats are deficient in apolipoprotein E, and (iii) chronic ethanol feeding increases hepatic secretion of apolipoprotein AI, E and AIV. Since the steady-state serum level of apolipoprotein E decreases or remains unchanged in the presence of increased hepatic apolipoprotein E secretion, this imbalance suggests that alcohol feeding either accelerates the rate of degradation of serum apolipoprotein E or suppresses apolipoprotein E synthesis by nonhepatic tissues.