Alcohol Produces Dose-Dependent Antiatherogenic and Atherogenic Plasma Lipoprotein Responses

Abstract

Abstract

A comprehensive assessment of lipoprotein compositional/metabolic response to incremental caloric ethanol (EtOH) doses ranging from low to moderate to high was undertaken using male squirrel monkeys. Control monkeys were maintained on a chemically defined, isocaloric liquid diet, while experimental primates were fed increasing doses of alcohol (6, 12, 18, 24, 30, and 36% of energy) substituted isocalorically for carbohydrate at 3-month intervals. Liver function tests and plasma triglyceride were normal for all animals. Plasma cholesterol showed a transient increase at the 12% caloric dose that was attributed solely to an increase in high density lipoprotein (HDL). A more pronounced increase in plasma sterol, beginning at 24% and continuing to 36% EtOH, was the result of increments in both HDL and low density lipoprotein (LDL) cholesterol, although the contribution by the latter was substantial primarily at the 36% dose. Plasma apolipoprotein elevations (HDL apolipoprotein A-1, LDL apolipoprotein B) generally accompanied the lipoprotein lipid increases, although the first atherogenic response for LDL became manifest as a significant increase in apolipoprotein B at 18% EtOH calories. Postheparin plasma lipoprotein lipase was not affected by dietary alcohol, whereas hepatic triglyceride lipase activity showed significant increases at higher (24 and 36%) EtOH doses. Plasma lecithin-cholesterol acyltransferase activity was normal at the 6 and 12% EtOH doses, but exhibited a significant reduction beginning at 18% and continuing to 36% EtOH. Alterations in these key lipoprotein regulatory enzymes may represent the underlying metabolic basis for the observed changes in lipoprotein levels and our earlier findings of HDL₂/HDL₃ subtraction modifications. Results from our study indicate that in squirrel monkeys, moderate (12%) EtOH caloric intake favors an antiatherogenic lipoprotein profile (↑HDL, normal LDL levels, and lecithin-cholesterol acyltransferase activity), whereas higher doses (24–36%) produce both coronary-protective (↑HDL) and atherogenic (↑LDL) responses. Moreover, the 18% EtOH level represents an important transition dose which signals early adverse alterations in lipoprotein composition (↑apolipoprotein B) and metabolism (↓lecithin-cholesterol acyltransferase).