Relationships between transit time in man and in vitro fermentation of dietary fiber by fecal bacteria.
OBJECTIVE
To assess the effects of drug-induced changes in mean transit time (MTT) on the activity of human fecal flora in vitro.


METHODS
The activity of fecal flora was estimated by the ability of a fecal inoculum to ferment a substrate (beet fiber) in vitro in a batch system for 24 h. The inoculum was collected from 8 healthy volunteers studied during three 3-week randomized periods, who received a controlled diet alone (control period) or the same diet with either cisapride or loperamide. Cisapride and loperamide were adjusted in order to halve and double MTT measured during the control period. At the end of each period, the percentage disappearance of the initial added substrate and the concentration and the profile of short-chain fatty acids (SCFAs), were determined.


RESULTS
In the control period, the pH of the inoculum and SCFA concentration were inversely related to MTT (P=0.0001). Individual SCFA production was also significantly related to MTT (P<0.01). Cisapride-reduced transit time was associated with a significant rise in the concentrations of total SCFAs (P<0.05), propionic and butyric acids (P<0.05) and the percentage substrate disappearance (P<0.05). Inverse relations were observed during the loperamide period. Moreover, MTT was inversely related to the percentage substrate disappearance (P<0.001), SCFA production (P<0.001) and butyrate production (P<0.0005).


CONCLUSIONS
Changes in MTT alter bacterial activity and modify the bacterial pathways affecting the proportion of individual SCFAs. European Journal of Clinical Nutrition (2000) 54, 603-609
Oufir
L E
LE
Centre de Recherche en Nutrition Humaine CRI-INSERM 9508, Hospital Hotel-Dieu, Nantes, France.
Barry
J L
JL
Flourié
B
B
Cherbut
C
C
Cloarec
D
D
Bornet
F
F
Galmiche
J P
JP
D000328:Adult; D001421:Bacteria, Anaerobic / Q000378:metabolism*; D020117:Cisapride / Q000378:metabolism / Q000494:pharmacology; D003106:Colon / Q000382:microbiology; D004032:Diet; D004043:Dietary Fiber / Q000378:metabolism*; D005232:Fatty Acids, Volatile / Q000032:analysis / Q000378:metabolism; D005243:Feces / Q000382:microbiology*; D005260:Female; D005285:Fermentation / Q000502:physiology; D005765:Gastrointestinal Agents / Q000494:pharmacology; D005772:Gastrointestinal Transit / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D008139:Loperamide / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D008697:Methane / Q000378:metabolism
D004043:Dietary Fiber; D005232:Fatty Acids, Volatile; D005765:Gastrointestinal Agents; D008139:Loperamide; D008697:Methane; D020117:Cisapride