Metabolism of L-sorbose in the rat and the effect of the intestinal microflora on its utilization both in the rat and in the human

Prebiotic potential of L-sorbose and xylitol in promoting the growth and metabolic activity of specific butyrate-producing bacteria in human fecal culture

Dietary low-digestible carbohydrates (LDCs) affect gut microbial metabolism, including the production of short-chain fatty acids. The ability of various LDCs to promote butyrate production was evaluated in in vitro human fecal cultures. Fecal suspensions from five healthy males were anaerobically incubated with various LDCs. L-Sorbose and xylitol markedly promoted butyrate formation in cultures. Bacterial 16S rRNA gene-based denaturing gradient gel electrophoresis analyses of these fecal cultures revealed a marked increase in the abundance of bacteria closely related to the species Anaerostipes hadrus or A. caccae or both, during enhanced butyrate formation from L-sorbose or xylitol. By using an agar plate culture, two strains of A. hadrus that produced butyrate from each substrate were isolated from the feces of two donors. Furthermore, of 12 species of representative colonic butyrate producers, only A. hadrus and A. caccae demonstrated augmented butyrate production from L-sorbose or xylitol. These findings suggest that L-sorbose and xylitol cause prebiotic stimulation of the growth and metabolic activity of Anaerostipes spp. in the human colon.

Bacterial adaptation in patients with short bowel and colon in continuity

BACKGROUND & AIMS

Long-term carbohydrate malabsorption in patients with short bowel and colon in continuity (SBC) could result in a more efficient fermentation. The bacterial fermentation capacity in patients with SBC was assessed.

METHODS

Eleven fasting patients with SBC ingested 60 g lactulose with 10 g polyethylene glycol. Stool specimens were analyzed. Patients were compared with 8 normal subjects who ingested 60 g lactulose on two occasions, separated by 8 days during which 20 g lactulose was taken twice daily. Moreover, the daily amount of bacteria excreted in stools was measured in 6 patients with SBC and 6 normal subjects.

RESULTS

Despite fast transit time, patients fermented more lactulose and hexoses and had a higher activity of beta-galactosidase in stools than nonadapted normal subjects (P < 0.01); these parameters were roughly similar in patients and adapted normal subjects. The fecal output of short-chain fatty acids was significantly lower in patients than in nonadapted normal subjects (P < 0.03). Patients excreted a significantly greater amount of bacteria in stools than normal subjects (P < 0.05).

CONCLUSIONS

In patients with SBC, the capacity of bacterial flora to ferment lactulose and fecal bacterial mass is spontaneously increased, suggesting that hyperfermentation may affect other carbohydrates. Moreover, hyperfermentation is associated with efficient removal of extra short-chain fatty acids from fecal water.

Metabolism of maltitol by conventional rats and mice and germ-free mice, and comparative digestibility between maltitol and sorbitol in germ-free mice

The metabolism of maltitol (4-alpha-D-glucosylsorbitol) was assessed in fasting conventional (C) rats, C mice and germ-free (GF) mice, using [U-14C]maltitol. The radiorespirometric patterns of 14CO2 collected for 48 h after the administration of labelled maltitol were characterized by a constant rate of 14CO2 production lasting 4 h for both C rats and mice. The pattern for the GF mice showed a peak at the second hour followed immediately by a slow decrease. The percentage recovery of 14CO2 was significantly lower for the GF mice (59%) compared with C animals (72-74%). Urine, faeces and intestinal contents after 48 h totalled 19% of the administered radioactivity in the C rats and mice and 39% in the GF mice. The digestibility of maltitol and the absorption of sorbitol in GF mice was also assessed. The caecum and small intestine of GF mice, 3 h after administration of equimolar quantities of maltitol (140 mg/kg body-weight) or sorbitol (70 mg/kg body-weight), contained 39 and 51% of the ingested dose respectively, present mostly in the caecum as sorbitol. The alpha-glucosidase (maltase) (EC3.2.1.20) activity of the small intestine was appreciably higher (1.5-1.7 times) in the GF mice than in the C mice. These results suggest that the enzymic activities in the small intestine of mice and rats are sufficient to hydrolyse maltitol extensively. Consequently, the slow absorption of sorbitol seems to be an important factor limiting the overall assimilation of maltitol in the small intestine.

Lower fat deposition and energy utilization of growing rats fed diets containing sorbose

1. Growing rats were fed diets containing graded levels (0, 100, 200 and 300 g/kg diet) of sorbose for 6 weeks. Protein, fat and energy deposition were determined by carcass analysis. 2. The values for growth, serum insulin level, digestible energy (DE), metabolizable energy (ME) and fat and energy deposition declined with the increment of dietary sorbose. 3. The efficiency of protein utilization (protein retained/protein consumed) was hardly affected by dietary sorbose. The DE and ME of sorbose per se was calculated as 14.09 and 12.35 kJ/g respectively. The efficiency of energy utilization (energy retained/ME intake) decreased with the increase of dietary sorbose, although sorbose had an ME. 4. The relative weights of gastro-intestinal tract and liver were positively associated with dietary sorbose level, although the reverse was true for the amount of stomach content, being heavier with higher dietary sorbose. 5. It is suggested that dietary sorbose, as a sweetener as well as a bulky agent, seems to be a suitable sugar for the obese and diabetic with special reference to lower body fat and energy deposition without reducing protein utilization.