Objective-To determine effects of purified and dry expanded (complex)
diets on intestinal structure and function in healthy cats and in a fe
line model of methotrexate-induced enteritis. Animals-19 adult specifi
c-pathogen-free cats. Procedure-Cats were randomized in groups to rece
ive a purified diet intragastrically or a complex diet orally to meet
their daily metabolizable energy requirements. After 21 days, cats rec
eived either methotrexate (MTX; 10 mg/kg of body weight, IV, n = 12) o
r saline solution IV (n = 7), and were anesthetized 72 hours later. Ce
liotomy was performed for aseptic removal of mesenteric lymph nodes, f
ull-thickness biopsy of the gastrointestinal tract, and collection of
aortic and portal venous blood samples for determination of arterioven
ous amino acid concentrations across the intestine. Results-MTX was as
sociated with severe enterotoxicosis in cats receiving the purified di
et, as manifested by diarrhea (4 of 6 cats) and vomiting (2 of 6 cats)
. One cat receiving the complex diet developed mild diarrhea, and none
of these cats vomited. The purified diet was associated with marked v
illus blunting in the proximal and distal portions of the duodenum and
increased bacterial translocation (3 of 6 cats), whereas none of the
cats in the complex diet group developed bacterial translocation after
MTX administration. For the cats given saline solution, bacterial tra
nslocation occurred in 1 of 4 cats receiving the complex diet versus 2
of 3 cats receiving the purified diet. Conclusions-Feeding of a compl
ex diet containing intact protein as the nitrogen source abrogated the
proximal small intestinal atrophy and bacterial translocation associa
ted with feeding an amino acid-based purified diet. Clinical Relevance
-Use of purified diets containing free amino acids as the only nitroge
n source cannot be endorsed in human and animal cancer patients receiv
ing systemic chemotherapy.