White bean amylase inhibitor administered orally reduces glycaemia in type 2 diabetic rats

A purified pancreatic alpha-amylase inhibitor (alpha-AI) from white beans (Phaseolus vulgaris) was administered orally (100 mg/kg body weight dissolved in 9 g NaCl/l) for 22 d to non-diabetic (ND) and type 2 diabetic (neonatal diabetes models n0-STZ and n5-STZ) male Wistar rats. Mean glycaemia (mmol/l) declined from day 4 of the alpha-AI administration in ND rats (5.48 (sem 0.08) v. 4.39 (sem 0.13); P<0.05), n0-STZ diabetic rats (7.94 (sem 0.42) v. 5.56 (sem 0.32); P<0.01) and n5-STZ diabetic rats (17.34 (sem 2.58) v. 11.93 (sem 1.96)), until the end of treatment: ND (5.22 (sem 0.21) v. 3.97 (sem 0.06); P<0.01); n0-STZ (8.10 (sem 0.19) v. 5.21 (sem 0.30); P<0.01); and n5-STZ (16.36 (sem 2.14) v. 7.69 (sem 1.34); P<0.01). There was a decrease in water intake (ml/d) in the alpha-AI-treated diabetic rats: n0-STZ (30 (sem 0.10) v. 22 (sem 1.50); P<0.01) and n5-STZ (76 (sem 5.04) v. 57 (sem 4.85); P<0.01). Food intake (g/d) decreased in all three groups: ND (23 (sem 0.31) v. 20 (sem 0.03); P<0.05); n0-STZ (22 (sem 0.55) v. 16 (sem 0.98); P<0.01); and n5-STZ (31 (sem 0.58) v. 23 (sem 1.20); P<0.01). The enterocyte sucrase and maltase activities (U/g proteins) were high (P<0.01) in the untreated diabetic rats, n0-STZ (45 (sem 4) and 152 (sem 10), respectively) and n5-STZ (67 (sem 12) and 151 (sem 10), respectively) with respect to the ND rats (24 (sem 2) and 74 (sem 10), respectively). After alpha-AI treatment, enzyme activities declined in both diabetic rats, n0-STZ (21 (sem 2) and 85 (sem 11); P<0.01) and n5-STZ (28 (sem 7) and 75 (sem 19); P<0.05), to values close to those in the ND rats. In conclusion, alpha-AI significantly reduced glycaemia in both the ND and diabetic animals and reduced the intake of food and water, and normalized the elevated disaccharidase levels of the diabetic rats.