Alcohol as a nutrient: interactions between ethanol and carbohydrate

This study examined metabolic interactions between two nutrients--ethanol and carbohydrate. Both nutrients are metabolized by a common pathway to fatty acids from acetyl-coenzyme A by lipogenic enzymes. The effects of ethanol and carbohydrate on the induction of lipogenic enzymes in livers of rats were examined using two types of base diets differing in carbohydrate and lipid content and using isocaloric substitutions of ethanol, carbohydrate, and fat. Three nonlipogenic enzymes were used for comparison. Isocaloric substitution of both fat and carbohydrate for ethanol was necessary to show the specific effects of alcohol on the activity of lipogenic or nonlipogenic enzymes. Carbohydrate, and not ethanol, induced lipogenic enzymes. Ethanol specifically reduced the activity of lactate dehydrogenase and malic enzyme, but did not affect those of alcohol dehydrogenase or glycerol 3-phosphate dehydrogenase. Ethanol interacted with carbohydrate to increase the activity of ATP citrate lyase. In addition, we studied the effects of ethanol and different kinds of carbohydrates on the growth of rats and on the morphology of their livers and intestines. Ethanol significantly decreased growth characteristics (weight gain, growth rate, and caloric efficiency). Fructose, either as a monosaccharide or in sucrose, decreased this alcohol effect. Sucrose was better than glucose in lowering lipid accumulation in livers of rats. Fragility of intestinal villi was found with an alcohol, low carbohydrate diet, but was not present in alcohol diets with a higher level of carbohydrate. In contrast to carbohydrate, ethanol lacked some characteristics of a nutrient, namely, it did not induce some enzymes involved in its metabolism and did not promote optimum growth.