Mechanism for lowering blood ammonia levels by lactitol

Combination of polydextrose and lactitol affects microbial ecosystem and immune responses in rat gastrointestinal tract

The effects of various dietary fibres on gut health have been studied extensively but their combined effects are scarcely documented. In the present study the effects of 2 % (w/w) polydextrose (PDX), 2 % (w/w) disaccharide lactitol, or 2 % (w/w) PDX+2 % (w/w) lactitol on gut microflora, microbial metabolism and gut immune responses were investigated in rats. Both PDX and lactitol alone had an effect on many of the studied parameters, but their combination had stronger than additive effects in some parameters. The PDX+lactitol combination altered the microbial community structure as seen by a culture-independent method, percentage guanine+cytosine (%G+C) profiling, increasing the areas of %G+C 35–39 (P<0·0001) and %G+C 45–49 (P=0·0002), and decreasing %G+C 65–74 (P<0·0003). These changes were also reflected in the microbial metabolism so that the production of biogenic amines and branched volatile fatty acids was significantly reduced, by 12 (P=0·03) and 50 % (P=0·002), respectively, indicating a shift from putrefactive towards saccharolytic metabolism. PDX increased the secretion of IgA in the caecum (P=0·007). Secretion of IgA increased even more, almost ten-fold, with the combination of PDX+lactitol (P<0·0001) when compared with the control group. Lactitol increased the production of butyrate by caecal microbes by two- to three-fold when compared with the PDX or control group (P<0·0001). Butyrate is a preferred energy source for mucosal cells; thus a boost in the availability of energy for immune cells may have still added to the synergistic effects of PDX and lactitol on immune cells. It is noteworthy that improvement in the IgA secretion occurred without signs of mucosal inflammation.

Effect of lactitol on blood ammonia response to oral glutamine challenge in cirrhotic patients: evidence for an effect of nonabsorbable disaccharides on small intestine ammonia generation

OBJECTIVE

Nonabsorbable disaccharides are widely used to decrease blood ammonia concentration. Their principal mode of action is the modification of pH and bacterial flora in the colon. The aim of the present study was to test the hypothesis that these drugs may also reduce small intestine ammonia generation.

METHODS

Eight male cirrhotics without overt hepatic encephalopathy received 20 g of glutamine in 100 ml of water. Venous samples for whole blood ammonia were taken before, 30 and 60 min after the load. Immediately after the last blood sample the patients were submitted to the following psychometric tests: number connection test, Posner's attention test, and Sternberg paradigm. After the first glutamine load, patients were started on lactitol (initial dose 20 g, three times a day). Once two bowel movements/day were obtained and maintained for at least 5 days, oral glutamine challenge and psychometric tests were repeated.

RESULTS

Ammonia increased significantly after the glutamine load (from 83 +/- 13 to 164 +/- 30 microg/dl at 30 min and 210 +/- 29 microg/dl at 60 min; mean +/- SE; p = 0.006 analysis of variance) but not after glutamine load after lactitol treatment (from 77 +/- 17 to 111 +/- 21 microg/dl and 142 +/- 24 microg/dl; p = not significant). The peak increment (127 +/- 24 vs 65 +/- 18 microg/dl; p = 0.008) of ammonia elevation was significantly smaller during lactitol administration. The patients' psychometric performance after the glutamine load did not differ significantly after lactitol treatment.

CONCLUSIONS

Lactitol reduces the elevation in blood ammonia that follows oral glutamine challenge. Because enterally administered glutamine is efficiently absorbed in the jejunum and, in part, metabolized to ammonia we suggest that lactitol affects small intestine ammonia generation probably by shortening the residence time of intestinal contents.