Methyl donor deficiency affects small-intestinal differentiation and barrier function in rats

Dietary methyl donors and their genetic determinants are associated with Crohn's disease risk. We investigated whether a methyl-deficient diet (MDD) may affect development and functions of the small intestine in rat pups from dams subjected to the MDD during gestation and lactation. At 1 month before pregnancy, adult females were fed with either a standard food or a diet without vitamin B-12, folate and choline. A global wall hypotrophy was observed in the distal small bowel (MDD animals 0.30mm v. controls 0.58 mm; P<0.001) with increased crypt apoptosis (3.37 v. 0.4 %; P<0.001), loss of enterocyte differentiation in the villus and a reduction in intestinal alkaline phosphatase production. Cleaved caspase-3 immunostaining (MDD animals 3.37% v. controls 0.4%, P<0.001) and the Apostain labelling index showed increased crypt apoptosis (3.5 v. 1.4 %; P=0.018). Decreased proliferation was observed in crypts of the proximal small bowel with a reduced number of minichromosome maintenance 6 (MDD animals 52.83% v. controls 83.17 %; P=0.048) and proliferating cell nuclear antigen-positive cells (46.25 v. 59%; P=0.05). This lack of enterocyte differentiation in the distal small bowel was associated with an impaired expression of beta-catenin and a decreased beta-catenin-E-cadherin interaction. The MDD affected the intestinal barrier in the proximal small bowel by decreasing Paneth cell number after immunostaining for lysosyme (MDD animals 8.66% v. controls 21.66 %) and by reducing goblet cell number and mucus production after immunostaining for mucin-2 (crypts 8.66 v. 15.33%; villus 7 v. 17%). The MDD has dual effects on the small intestine by producing dramatic effects on enterocyte differentiation and barrier function in rats.