Luminal short-chain fatty acids and postresection intestinal adaptation.

BACKGROUND

Short-chain fatty acids (SCFAs) reportedly have a trophic effect on the small intestine. However, it is unclear if this is a local or primarily systemic effect. Loss of the ileocolonic junction (ICJ) may result in increased SCFAs and bacteria in the small intestine from colonic reflux. Our aim was to evaluate the effect of bypass of the ICJ on intestinal SCFA content and postresection adaptation.

METHODS

Thirty dogs were studied: transection control (TC, n = 10), distal resection of 50% intestine (DR, n = 10), and distal resection with bypass of ICJ (DRBP, n = 10). Animals were killed at 4 and 12 weeks. Luminal SCFAs and bacteria and adaptation of the small intestine were evaluated.

RESULTS

Caloric intake was significantly less in the two resected groups (67 +/- 3 DR and 63 +/- 3, DRBP vs 78 +/- 5 kcal/kg/d TC, p < .05). Body weight and albumin levels were decreased at 12 weeks but were similar between the resected groups (81% +/- 3% and 74% +/- 6% initial and 1.9 +/- 0.1 and 2.1 +/- 0.2 g/dL, DR and DRBP, respectively). Steatorrhea was present for 12 weeks after resection and was greater after DRBP (14.2% +/- 3.8% vs 8.6% +/- 1.9% at 4 weeks and 13.6% +/- 2.5% vs 6.7% +/- 0.6% at 12 weeks, p < .05). Bypassed animals had elevated intraluminal SCFA content (3126 +/- 1094 vs 1791 +/- 538 DR and 1600 +/- 446 micrograms/mL TC, p < .05) and anaerobic bacterial counts (100% vs 50% and 44%, respectively). Tissue inflammation and myeloperoxidase activity were similar. Small intestinal length (174 +/- 10 and 180 +/- 10 cm) and circumference (5.2 +/- 0.4 and 5.2 +/- 0.3 cm) increased to a similar extent in both resected groups at 12 weeks. Thickness of mucosa (1939 +/- 162 vs 1662 +/- 162 microns) and muscle (865 +/- 45 vs 978 +/- 79 microns) layers were similar after DR and DRBP.

CONCLUSIONS

(1) Bypass of the ICJ after distal resection results in increased growth of anaerobic bacteria and luminal SCFA and is associated with more marked steatorrhea. (2) Bypass of the ICJ does not influence structural adaptation of the small intestine. (3) These findings do not support a local trophic effect for SCFA.