Background: The newborn colon is devoid of microflora, in that bacterial colonization is established after birth. Short chain fatty acids, products of bacterial fermentation, are the major energy source for colonocytes. Because it is not known whether colonocytes in the newborn can metabolize butyrate, this was examined in newborn and infant rat colon.
Methods: Isolated colonocytes from rats of different perinatal ages were incubated with 14C-labeled butyrate or glucose in vitro. Complete oxidation was estimated by the production of 14C-labeled carbon dioxide, whereas intermediate metabolites were measured enzymatically.
Results: Oxidation of butyrate (in micromoles per hour per milligram of protein) was highest in newborns (5.83+/-1.76), declining to 1.32+/-0.28 at day 10 and to 0.34+/-0.04 in adult rats. Glucose oxidation was also highest at birth (0.39+/-0.23), with a minor increase at approximately day 20 (weaning period) before decreasing to adult levels (0.05+/-0). Butyrate oxidation was substantially higher than was glucose oxidation in all age groups. Production of metabolic intermediates paralleled substrate oxidation. Acetoacetate production was 4.35+/-2.68, 2.07+/-1.29, and 0.27+/-0.09 nmol/hr per milligram of protein in newborns, at postnatal day 10, and in adults, respectively. The corresponding values for beta-hydroxybutyrate were 3.62+/-3.35, 0.2+/-0.07, and 0.09+/-0.03 nmol/hr per milligram of protein; and L-lactate production was 0.54+/-0.52, 0.06+/-0.04, and 0.02+/-0 micromol/hr per milligram of protein respectively.
Conclusions: Neonatal rat colon epithelial cells resemble adult colonocytes in their preference for butyrate as a metabolic substrate, indicating a constitutive expression of this property.