The Effect of Lactulose on Ammonia Production in a Faecal Incubation System

Abstract

Medical Research Society 33P UDCA + CDCA (both of which decrease the molar ratio of cholesterol in bile) increased from 41% before, to 50% and to 72% after 5 and 10 mg of UDCA day-1 kg-' body weight respectively. There were concomitant decreases in the propor tions of both cholic acid and its bacterial metabolite, deoxycholic acid but the proportion of lithocholate increased from 4-5% before to 9·0% during therapy. There were no changes in liver function or fasting serum lipids during treatment and no patient developed diarrhoea.These results (i) show that treatment of non-obese gallstone patients with only 5 mg of UDCA day -1 kg -1 body weight consistently produces unsaturated bile and, (ii) confirm that, in the short term, UDCA causes neither diarrhoea nor hypertransaminaseaemia. UDCA continues to offer a promising alternative to CDCA for the medical treatment of gallstones.

Ammonia production by intestinal bacteria: the effects of lactose, lactulose and glucose

“…LowpH is known to decrease ammonia production by pure cultures of enterobacteria and by mixtures of faecal organisms (Vince et al, 1973;Vince et al, 1978). The results presented in this study show that clostridia and gram-negative anaerobes also form less ammonia at low pH.…”

“…This is a particularly useful observation from the therapeutic point of view because lactulose, the synthetic disaccharide given to patients with hepatic encephalopathy to reduce the formation and absorption of ammonia, causes a marked decrease in caecal, and to a lesser extent faecal, pH (Agostini et al, 1972;Bown et al, 1974). These and earlier results suggest that intestinal bacteria are metabolically tolerant over a fairly widepH range, i.e., 5.5-7-0, but show a marked decrease in activity, as judged by ammonia release, when thepH falls to 5.0 or less (Vince et al, 1973;Vince et al, 1978). However this value is lower than the normal colonicpH of 5.5-7.6 (Bown et al, 1974) so that, in vivo, pH would not usually be a major factor limiting ammonia release.…”

“…These results help to explain the effect that lactulose and other fermentable substrates have in changing the balance of ammonia meta-bolism from net production to net utilisation in a faecal incubation system (Vince et al, 1978), for if bacterial uptake of ammonia continues normally and production falls, the net concentration of ammonia in the system will decrease accordingly.…”

“…The origin of colonic ammonia is uncertain; urea has been suggested as the main source (Wolpert, Phillips and Summerskill, 1971) but Vhce et al (1976) have shown that considerable amounts of ammonia, in excess of those normally found in faeces, were generated by bacteria from non-urea sources in an in-vitro faecal incubation system. Addition of fermentable substrate-lactulose, glucose, mannitol or sorbitol-to this system caused a decrease in the ammonia concentration (Vince, Killingley and Wrong, 1978). This decrease was independent of reduction in pH, which reduces ammonia formation by inhibiting deaminating enzymes Vince et al, 1973).…”

“…The combined effects of stimulation and inhibition of ammonia production from amino acids may explain partially why the reduction in ammonia formation observed in brain-heart infusion broth was sometimes considerably less than that seen with washed cells in the presence of single amino acids. However, the net effect of carbohydrate fermentation, both in a nutrient medium and in the faecal-incubation system, was to decrease the final ammonia concentration (Vince et al, 1978).…”