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

Abstract

A purified pancreatic α-amylase inhibitor (α-AI) from white beans (Phaseolus vulgaris) was administered orally (100m/g body weight dissolved in 9g NaC/) for 22d to non-diabetic (ND) and type 2 diabetic (neonatal diabetes models n0-STZ and n5-STZ) male Wistar rats. Mean glycaemia (mmo/) declined from day 4 of the α-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 (m/) in the α-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 (/) 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 (/ 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 α-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, α-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.