**4. Effects of probiotics on pancreatic digestive enzymes**

There is only limited research on the effects of probiotics on pancreatic digestive enzymes such as amylase, lipase, trypsin, chymotrypsin, although there are few publication related to effects of probiotics on mucosal digestive enzymes. The relation between microorganisms of intestinal tract and pancreatic enzymes has been investigated in some studies using germ-

The Impact of Probiotics on the Gastrointestinal Physiology 59

It has been observed that patients with lactose maldigestion had higher lactose tolerance when eating fermented dairy products such as yogurt and could easily digest them compared to milk. There are two mechanisms lying beneath this situation. First, βgalactosidase is released from bacteria in yogurt after digested by bile acids. Second, delaying gastric emptying and slowing intestinal transit times prolong the action of residual β-galactosidase in the small intestine and decrease the osmotic load of the lactose (Marteau et al., 2001). Ojetti et al. (2010) were investigated hydrogen breath excretion and gastrointestinal symptoms as indicators of lactose intolerance in patients. They have reported that hydrogen excretion decreased and clinical symptoms improved in the group given *Lactobacillus reuteri* compared to those of placebo group. De Vrese et al. (2001) tested whether live bacteria in the fermented or non-fermented milk product are a prerequisite for enhanced lactose cleavage by microbial β-galactosidase. They found that lactose digestion in lactose malabsorbers and gastrointestinal well-being can be significantly improved if a milk product contains active microbial β-galactosidase. The bacteria need not to be alive but intact cell walls are required to act as a mechanical protection of the enzyme during gastric

**5. The effect of probiotics on the absorptive function of the intestine** 

intestines, DRA is more expressed in colon than small intestines (Wang et al., 2002).

It has been determined that two carrier proteins play a role in the sodium absorption; "sodium hydrogen exchanger-2" (NHE-2) and NHE-3 which are the members of "solute carrier family-9" (SLC9) (Malakooti et al., 2011). While NHE-2 is expressed mostly in colon, NHE-3 is expressed mainly in ileum (Dudeja et al., 1996). The carrier proteins "down regulated in adenoma" (DRA) and putative anion transporter-1 (PAT-1) from SLC26 gene family have a role in chloride absorption. While PAT-1 is mainly expressed in small

Probiotics such as *Lactobacillus* are used as a treatment support in diseases especially characterized by fluid loss in children. It has been determined that probiotics reduce sodium chloride and fluid loss in these diseases (Raheja et al., 2010). Furthermore it has been reported that *Saccharomyces boulardii* increases chloride net absorption from jejunum and

To investigate the molecular mechanisms underlying the effects of probiotics on electrolyte and water absorption from intestinal tract, some *in vivo* and *in vitro* studies have been carried on. Human colon adenocarcinoma cell (Caco-2) has been used extensively as a model cell *in vitro* experiments subjected intestinal epithelium. Borthakur et al. (2008) reported that DRA activity increased in Caco-2 cells after short term *Lactobacillus acidophilus*  application and this will cause chloride absorption eventually. *Lactobacillus acidophilus* was reported to cause this effect by increasing DRA expression in apical membranes of epithelial cells. However, it has been determined that total DRA amount in the cell did not changed, only DRA expression on the surface increased and this effect was caused via phosphatidylinositol 3-kinase pathway. It has been also considered that some soluble substances secreted

Bacteria present in the intestines are consistently interacting with epithelial cells. Therefore, it has been determined that, while *Lactobacillus acidophilus* increase DRA mRNA expression

passage.

**5.1 Sodium and chloride absorptions** 

descending colon *in vitro* (Krammer & Karbash, 1993).

by *Lactobacillus acidophilus* revealed this effect*.* 

free animals. It has been indicated that the bacterial status altered preferentially the exocrine pancreatic function. The specific activities of amylase, trypsin and carboxypeptidase-A were lower in germ-free than in conventional rats (Lhoste et al., 1996). How microorganisms in digestive tract affect secretion of pancreatic enzymes has not been determined. However hormones which stimulate enzyme secretion in pancreas such as enteroglucagon, gastrin or pancreatic polypeptide have been reported to be lower in germ-free animals compared to conventional animals (Goodlad et al., 1989). Decreased pancreatic enzymes in germ-free animals may be explained by this report. Moreover the cecal micro flora may also affect the pancreas via its metabolites. In fact, SCFA can stimulate amylase release from the rat pancreas directly (Ohbo et al., 1996).

Matur et al. (2007) have been reported that chymotrypsin levels decreased but amylase, lipase and trypsin levels did not changed in pancreas of broiler chicks which were supplemented with *Enterrococcius facium* NCIMB10415. In addition, intestinal tract enzyme activities were reported to be lower in animals supplemented with probiotics than those of control animals in the same study. The researchers have suggested that the relevant probiotics may affect the biosynthesis of pancreatic enzymes or their secretion to small intestines, although the mechanism underlying this effect has not been fully elucidated yet.

Microorganisms in digestive tract may also affect digestive enzyme activities indirectly. Drouault et al. (2002) have reported that *Lactobacillus lactis* produces lipase and this lipase ameliorated steatorrhea in pigs fed on high lipid meal.
