Effect of germfree state on the capacities of isolated rat colonocytes to metabolize n-butyrate, glucose, and glutamine.
OBJECTIVE
Among substrates available to the colonic mucosa, n-butyrate from bacterial origin represents a major fuel. The present work investigated possible modifications of energy substrate metabolism in colonocytes isolated from germfree rats.


METHODS
Colonocytes isolated from germfree vs. conventional rats were incubated (30 minutes at 37 degrees C) in the presence of 14C-labeled n-butyrate (10 mmol/L), glucose (5 mmol/L), or glutamine (5 mmol/L). 14CO2 and metabolites generated were measured. Possible regulatory steps were also investigated.


RESULTS
Glucose use rate was 25% lower in germfree rat colonocytes due to a reduced glycolytic capacity in these cells. Differences in 6-phosphofructo-1-kinase activity could account for this decrease. In contrast, glutamine use rate was 45% higher, and this was correlated with a higher maximum velocity of glutaminase in these cells. Nevertheless, the capacities to oxidize glucose and glutamine remained unchanged. Although the capacity to use n-butyrate was maintained in colonocytes of germfree rats, the ketogenic capacity was lower, whereas the capacity to oxidize n-butyrate was higher. The mitochondrial 3-hydroxy-3-methylglutaryl-coenzyme A synthase protein was identified in the colonic mucosa. Moreover, the messenger RNA and amount of protein were 75% lower in the germfree state.


CONCLUSIONS
The absence of an intestinal microflora induces specific changes in the metabolic capacities of colonocytes.
D000818:Animals; D002087:Butyrates / Q000378:metabolism*; D002478:Cells, Cultured; D003106:Colon / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D005856:Germ-Free Life; D005947:Glucose / Q000378:metabolism*; D005972:Glutaminase / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism*; D006904:Hydroxymethylglutaryl-CoA Synthase / Q000235:genetics / Q000378:metabolism; D007413:Intestinal Mucosa / Q000201:enzymology; D008297:Male; D008928:Mitochondria / Q000201:enzymology; D010084:Oxidation-Reduction; D010732:Phosphofructokinase-1 / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344
D002087:Butyrates; D012333:RNA, Messenger; D005973:Glutamine; D006904:Hydroxymethylglutaryl-CoA Synthase; D010732:Phosphofructokinase-1; D005972:Glutaminase; D005947:Glucose