Ethanol-Induced Inhibition of Human Intestinal Enzyme Activities: Reversal by Folic Acid

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The effects of ethyl alcohol on intestinal enzyme activities were studied in 10 normal volunteer subjects consuming either a constant, synthetic diet containing 100 gg of folic acid per day, or an ad libitum mixed diet. During the constant diet, ethanol (15 ml four times a day) caused a 36 to 45% decrease in the activities of the glycolytic enzymes, hexokinase, fructose-l-phosphate aldolase, fructose-1, 6-diphosphate aldolase, and a 58% decrease in the activity of the gluconeogenetic enzyme fructose-l, 6-diphosphatase. Conversely, the ethanol caused a 33% increase in the activity of pyruvate kinase. Folate given with the ethanol reversed the inhibitory action of ethanol by causing a 44% increase in fructose-l-phosphate aldolase, 42% in fructose-1, 6-diphosphate aldolase, and 45% in hexokinase, and no change in fructose-1, 6-diphosphatase activity. A synergistic effect occurred with pyruvate kinase which showed a maximum (2.8-fold) increase in activity when both folate and ethanol were given. Folic acid alone caused a 1.6- to 2-fold increase in all the enzymes. Mean plasma and red blood cell folate levels were 1.7 and 116 ng per ml, respectively, at the beginning of the study, and increased to 34.3 and 196 ng per ml, respectively, after folate treatment. Ethanol treatment did not interfere with the absorption of folate when large doses of 15 mg per day were administered, and at no time during the study did folate levels decrease below control values. With the ad libitum mixed diet, changes in enzyme activities with ethanol and folate were qualitatively similar to those seen during the constant synthetic diet. The effect of ethanol and folic acid on intestinal enzyme activities demonstrates how ethanol and folic acid may interact by affecting mutually susceptible enzymes.