In vitro studies on the effects of Saccharomyces boulardii and Bacillus cereus var. toyoi on nutrient transport in pig jejunum

The probiotics Saccharomyces boulardii and Bacillus cereus var. toyoi are nonpathogenic microbes which have been shown to affect certain functions of the mucosal barrier in pig jejunum such as electrogenic ion transport capacity and paracellular permeability. The present studies were performed to investigate potential effects of the probiotics on jejunal nutrient transport such as sodium-dependent glucose transport or proton-dependent dipeptide transport. For this purpose the in vitro Ussing-chamber technique was applied in order to examine net electrogenic ion flux rates (short circuit currents, I-sc) across isolated intact jejunal epithelia in the absence and presence of either 10 mmol/l glucose (mucosal side) or two-fold application of 5 mmol/l glycyl-L-sarcosine or glycyl-L-glutamine to the mucosal bathing solution. Brush border membrane vesicles (BBMV) were prepared in order to characterize kinetic parameters (V-max, K-m) of Na-dependent glucose transport. Intestinal tissues were obtained from growing pigs in a weight range between 23 and 33 kg. All animals were fed twice daily and received 0.8-0.9 kg/day of a standard diet. After a 9- to 10-day adaptation period the diets for treated animals were either supplemented for 8 days with 1.7 x 10(7) colony-forming units (CFU)/g feed of S. boulardii or for 3 weeks with 10(6) CFU/g feed B. cereus var, toyoi. Under basal conditions I-sc values were not affected by different treatment protocols (controls: 0.74+/-0.04 mu eq/cm(2) per h, n=9; S. boulardii: 0.74 +/- 0.12 mu eq/cm(2) per h, n = 7; B. cereus 0.68 +/- 0.09 mu eq/cm(2) per h, n= 5). Irrespective of dietary treatment, the addition of glucose resulted in significant increases of I-sc indicating substantial onset of electrogenic net Na/glucose cotransport. Maximal I-sc values occurred within 30 min and reached 2.79 +/- 0.41 mu eq/cm(2) per h in control epithelia. This was significantly lower than found in S. botilnrdii (4.47 +/- 0.43 mu eq/cm(2) per h, p < 0.05) and B. cereus var. toyoi tissues (4.45 +/- 0.31 mu eq/cm(2) per h, p < 0.05). G(t) values were 22.4 +/- 1.3 mS/cm(2) in control animals and were significantly lower as shown in S. boulardii (p < 0.01) and B. cereus var. toyoi (p < 0.01)-treated animals (28.4 +/- 1.3 and 29.9 + 0 8 mS/cm(2), respectively). V-max values of Na-dependent glucose uptake into BBMV differed significantly between controls (0.64 +/- 0.08 nmol/mg protein per 10 s; n=5), S. boulardii (0.89 +/- 0.06 nmol/mg protein per 10 s; n = 5, p < 0.05) and B. cereus var. toyoi preparations (1.08 +/- 0.05 nmol/mg protein per 10s; n=3, p < 0.01). K-m values were not significantly affected (control: 0.31 +/- 0.04 mmol/l, S. boulardii: 0.29 +/- 0.05 mmol/l, B. cereus var, toyoi: 0.21 +/- 0.01 mmol/l). Irrespective of dietary treatment, application of the dipeptide model substances glycyl-L-sarcosine or glycyl-L-glutamine resulted in significant increases of I-sc indicating marked stimulation of electrogenic net H+/dipeptide cotransport. Highest I-sc responses occurred in B. cereus var. toyoi preparations and lowest were found in control tissues. However, these differences were not significant. G(t) values were not affected by different dietary treatments. The results clearly demonstrate that oral administration of either S. boulardii or B. cereus var. toyoi stimulates Na-dependent glucose absorption in pig jejunum.