Incubation of human fecal homogenates with ethanol (0.078 g m per dl) resulted in accumulation of increased quantities of higher alcohols and other unidentified metabolites when compared with homogenates incubated without ethanol. Studies in rats demonstrated nearly perfect equilibration between blood and colonic luminal ethanol suggesting that the colonic flora in alcoholics is chronically exposed to ethanol concentrations in the range used in the homogenate experiments. The higher alcohols produced by the homogenates were rapidly absorbed from the colon. We hypothesize that, when exposed to ethanol, the colonic flora produced toxic compounds which are absorbed and influence the body's response to ingested ethanol. Individual differences in this bacterial metabolism may account for the wide individual differences in susceptibility to ethanolrelated organ injury.Alcoholics vary in their susceptibility to ethanolrelated organ injury. For example, organ injury occurs in only a minority of heavy alcoholics and the damaged organ (e.g., liver, pancreas, nervous system, or heart) varies from patient to patient. A number of yet unproven hypotheses concerning individual differences in the metabolism of ethanol or its metabolic product, acetaldehyde, have been proposed to explain the differences in susceptibility to ethanol.The purpose of this report is to suggest another, apparently novel hypothesis which might help to explain some of the variable susceptibility to the ravages of ethanol-namely, that the metabolism of the colonic flora influences the host's response to ethanol.
MATERIALS AND METHODSThe influence of ethanol on the metabolism of colonic bacteria was studied by comparing the metabolic products produced by human feces when incubated in the presence or absence of ethanol. Freshly passed human feces were homogenized anaerobically in pH 7.4, 0.1 A4 PO, buffered saline (1 part feces3 parts buffer). Twentymilliliter aliquots of this homogenate were then anaerobically incubated at 37°C with or without the addition of pure ethanol (0.1% v/v or 0.078 gm per dl).Our initial gas chromatographic analyses of the volatiles produced during incubation showed a multiplicity of compounds in the ethanol-treated homogenate which were not present in the homogenate incubated without ethanol. To date, we have identified and quantitated the alcohols accumulating in homogenates of feces obtained from 20 healthy subjects. Two-milliliter aliquots of the homogenates were removed at 0, 3, 6, and 24 hr of incubation and analyzed by gas chromatography-mass spectroscopy as follows. Two grams of K&O3 (I) were added to 2 ml homogenate in a 30-ml sealed vial using isobutyl alcohol as an internal standard. The mixture was heated at 70°C for 30 min, and 5 ml of the gas space was then analyzed for alcohols by gas chromatographymass spectroscopy using a Hewlett-Packard, Model 5992-B. A 25-pm silica capillary column containing Carbowax (20 M ) was employed at an initial temperature of 10°C for 1 min and then programmed to increase at 10°C per min...