Butyrate and glucose metabolism by colonocytes in experimental colitis in mice

Abstract

Background/aims: Impaired colonocyte metabolism of butyrate has been implicated in the aetiopathogenesis of ulcerative colitis. Colonocyte butyrate metabolism was investigated in experimental colitis in mice.

Methods: Colitis was induced in Swiss outbred white mice by oral administration of 4% dextran sulphate sodium (DSS). Colonocytes isolated from colitic and normal control mice were incubated with [(14)C]butyrate or glucose, and production of (14)CO(2), as well as of intermediate metabolites (acetoacetate, beta-hydroxybutyrate and lactate), was measured. The effect of different substrate concentrations on oxidation was also examined.

Results: Butyrate oxidation (micromol/h per mg protein; mean (SEM)) was significantly reduced in DSS colitis, values on day 7 of DSS administration being 0.177 (0.007) compared with 0.406 (0.035) for control animals (p<0.001). Glucose oxidation (micromol/h per mg protein; mean (SEM)) on day 7 of DSS administration was significantly higher than in controls (0.06 (0.006) v 0.027 (0.004), p<0.001). Production of beta-hydroxybutyrate was decreased and production of lactate increased in DSS colitis compared with controls. Increasing butyrate concentration from 10 to 80 mM enhanced oxidation in DSS colitis (0.036 (0.002) to 0.285 (0.040), p<0.001), although it continued to remain lower than in controls. Surface and crypt epithelial cells showed similar ratios of butyrate to glucose oxidation. When 1 mM DSS was added to normal colonocytes in vitro, it did not alter butyrate oxidation. The initial histological lesion of DSS administration was very patchy and involved crypt cells. Abnormal butyrate oxidation became apparent only after six days of DSS administration, at which time histological abnormalities were more widespread.

Conclusions: Colonocyte metabolism of butyrate, but not of glucose, is impaired in DSS colitis, and may be important in pathophysiology. Histological abnormalities preceded measurable defects in butyrate oxidation.

Figure 1

Effect of substrate concentration on butyrate and glucose oxidation (measured as CO₂ production) by colonocytes. Shown here are the absolute number of substrate molecules oxidised. DSS, colonocytes from mice subjected to two cycles of feeding with dextran sulphate sodium; controls, colonocytes obtained from pair fed mice maintained on normal feed. Values are mean (SEM) from four experiments. ***Significantly different from respective controls (Student's t test, p<0.001).

Figure 2

Effect of 1 mM dextran sulphate sodium (DSS), added in vitro, on CO₂ production by colonocytes using either 10 mM butyrate or 10 mM glucose as substrate. Values are mean (SEM) from four experiments. **p<0.01 compared with controls (paired t test).

Figure 3

Light micrographs of normal mouse colon before and during sequential isolation of surface and crypt cells. (A) At the start of colonocyte isolation; (B) after isolation of surface cells; (C) after isolation of crypt cells. Haematoxylin and eosin stain; original magnification × 40.

Figure 4

Butyrate and glucose oxidation (measured as CO₂ production) by surface and crypt colonocytes isolated from normal mice. Values represent the mean (SEM) from four experiments. **p<0.01 compared with surface cells (paired t test).