1 Facultad de Ciencias Naturales, Universidad Autónoma de Querétaro, México; 2 Laboratorio de Mecanismos de Defensa de Plantas. CINVESTAV-Irapuato, México.
Our working group has previously determined that a lectin fraction (LF) of Tepary bean (Phaseolus acutifolius) seeds presents cytotoxic effects on colon cancer cells by apoptosis induction, as well as in vivo inhibition of early colon tumorigenesis by intragastric administration. The LF does not exhibit toxicity however; it affects body weight gain and food intake. The Tepary bean seeds also contain a Bowman-Birk protease inhibitor (PI) that decreases the in vitro invasion ability and increases cell adhesion. Due to those properties, lectins and PI from Tepary bean are considered potential tools for cancer treatment however, both type of proteins present antinutritional effects, so the present study evaluated the effect of subchronic administration of LF and a lectin-IP combination (LIP-60) from Tepary bean on nitrogen absorption, protein digestibility and bowel villi morphology. Six week-old Sprague Dawley male rats were treated daily with LF (50 mg/kg) or LIP-60 (100 mg/kg) by intragastric cannula for 30 days. The fecal nitrogen excretion increased 3-7% for the LF administered group while the LIP-60 group showed 4-13%. The ileal nitrogen showed the largest increase at 20 days with 37% for the LF administered group and 52% for LIP-60 group. Urine showed the largest increase at 10 days with 57% and 79% for LF and LIP-60, respectively. The percentage of ileal protein digestibility decreased between 3-6% for both treatments, while total protein digestibility decreased from 1-9% for LF group and 1-14% for LIP-60 group, suggesting a direct effect of the IP. Bowel villi atrophy was observed, which can directly be related to the decrease in body weight gain observed mainly for LF treated group. Future studies will deepen over the effects provoked on intestinal health and integrity.