Ethanol and lipids

The interaction of ethanol with lipid metabolism is complex. When ethanol is present, it becomes a preferred fuel for the liver and displaces fat as a source of energy. This favors fat accumulation. In addition, the altered redox state secondary to the oxidation of ethanol promotes lipogenesis, for instance, through enhanced formation of acylglycerols. The depressed oxidative capacity of the mitochondria injured by chronic alcohol feeding also contributes to the development of the fatty liver. Accumulation of fat acts as a stimulus for the secretion of lipoproteins and the development of hyperlipemia. Hyperlipemia may also be facilitated by the proliferation of the endoplasmic reticulum after chronic ethanol consumption and the associated increase of enzymes involved in the production of triglycerides and lipoproteins. The propensity to enhance lipoprotein secretion is offset, at least in part, by a decrease in microtubules and an impairment of the secretory capacity of the liver. The level of blood lipids depends on the balance between these two opposite changes: At the early stage of alcohol abuse, when liver damage is still small, hyperlipemia will prevail, whereas the opposite occurs with severe liver injury. When hyperlipemia occurs, it involves all lipoprotein classes, including high density lipoprotein (HDL). The latter have been suggested to be responsible for the lower incidence of coronary complications of moderate drinkers compared to teetotalers, but in fact, the subtype of HDL involved (HDL3) differs from the HDL2 subtype associated with protection.

Effects of ethanol intake on lipoprotein lipase activity in adipose tissue of fasting subjects

Ethanol (ca. 1 g/kg body weight) was given alone or together with glucose or lipid (mixed triglycerides) perorally to young, fasting subjects. The changes with time (0-6 hr) of lipoprotein lipase activity (LLA) in adipose tissue, plasma glycerol, triglyceride, insulin, blood glucose, and alcohol concentrations were followed. A maximal mean blood alcohol concentration of 0.09% (w/v) was obtained 1 hr after ingestion with no apparent intoxicating effects. Ethanol intake prevented the previously observed [Nilsson-Ehle, P., S. Carlström, and P. Belfrage, Scand, J. Clin. Lab. Invest. 35:373 (1975)] glucose-induced rapid elevation of adipose tissue LLA but had small effects on this enzymatic activity when given alone or together with lipid. Confirming results by others, ethanol intake decreased plasma glycerol concentration and increased plasma triglycerides, especially after intake of lipid. It is suggested that ethanol intake interferes with the normal carbohydrate-induced elevation of adipose tissue LLA after a mixed meal, thereby decreasing the removal capacity for circulating dietary lipid and causing enhanced and prolonged alimentary hyperlipemia.