Chemistry Reference
In-Depth Information
3.2.2.3 Epithelial Cell Growth and Differentiation
Possibly, the most important role of SCFAs on colonic physiology is their trophic
effect on the intestinal epithelium. The rate of production of crypt cells is reduced
in the colon of rats bred in germ-free environments, and their crypts contain fewer
cells than do those of rats colonized by conventional flora, suggesting that intralu-
minal bacteria affect cell proliferation in the colon (Guarner and Malagelada, 2003).
Differentiation of epithelial cells is greatly affected by interaction with resident
microorganisms. All three major SCFAs stimulate epithelial cell proliferation and
differentiation in the large and small bowel
in vivo.
However, among the SCFAs
produced by fermentation, butyrate has specific biological activities in the colon.
Butyrate stimulates proliferation and differentiation in normal epithelial cell lines
and has the opposite effects in transformed cell
in vitro
. Moreover, butyrate pro-
motes reversion of cells from neoplastic to nonneoplastic phenotypes (Guarner and
Malagelada, 2003). In pig also, FOS has been shown to stimulate SCFA production:
a test diet containing FOS (10 percent)
ad libitum
for 10 days led to a significant
increase in the concentration of SCFA, especially for
n
-butyrate (Tsukahara et al.,
2003). sc-FOS, which presents a high level of butyrate production during bacterial
fermentation (Tsukahara et al., 2003), thus may modulate cell proliferation in a ben-
eficial manner.
3.2.2.4 Immunity
The intestinal mucosa is the main interface between the immune system and the
external environment. Thus, it is not surprising that gut-associated lymphoid tissues
contain the largest pool of immunocompetent cells in the human body. The colonic
microflora, especially bifidobacteria, has been reported to exert a high influence on
the immune system of the host, such as mitogenic or adjuvant activities, promotion of
macrophages, stimulation of antibody production, and antitumor effects (Salminen
et al., 1998; Bornet
et al., 2002).
In children, a controlled study showed that a preparation of cereals containing
a mixture of inulin and FOS (0.2 g/kg of body weight) increased vaccinal immuno-
globulin G (IgG) levels 10 weeks after immunization of the infant against measles
(Firmansyah
et al., 2001). The level of positive reaction with adequate IgG response
was 96 percent in children receiving the prebiotic compared with 88 percent in the
control infants. There was no difference in the levels of antimeasles IgM. A recent
study (Bakker-Zierikzee
et al., 2006) also demonstrated a significant increase in
fecal secretory IgA in infants who received a formula enriched with a mix of GOS
and FOS (0.6 g/100 mL) compared to a standard group. This mix of prebiotics, which
stimulates bifidobacteria and leads to a fermentation profile close to the one found in
breastfed children, was often studied and appeared as beneficial for infants (Moro
et
al., 2003; Boehm
et al., 2004; Decsi
et al., 2005; Knol
et al., 2005).
Atopic diseases, such as atopic eczema, allergic rhinitis, and asthma, are increas-
ing in Western societies, demanding rapid comprehension and prevention. Several
