Effect of an aqueous extract of Phaseolus vulgaris on the properties of tail tendon collagen of rats with streptozotocin-induced diabetes

Changes in the structural and functional properties of collagen caused by advanced glycation might be of importance for the etiology of late complications in diabetes. The present study was undertaken to investigate the influence of oral administration of aqueous pod extract (200 mg/kg body weight) of Phaseolus vulgaris, an indigenous plant used in Ayurvedic Medicine in India, on collagen content and characteristics in the tail tendon of streptozotocin-diabetic rats. In diabetic rats, collagen content (117.01 ± 6.84 mg/100 mg tissue) as well as its degree of cross-linking was increased, as shown by increased extent of glycation (21.70 ± 0.90 μg glucose/mg collagen), collagen-linked fluorescence (52.8 ± 3.0 AU/μmol hydroxyproline), shrinkage temperature (71.50 ± 2.50°C) and decreased acid (1.878 ± 0.062 mg hydroxyproline/100 mg tissue) and pepsin solubility (1.77 ± 0.080 mg hydroxyproline/100 mg tissue). The α/β ratio of acid- (1.69) and pepsin-soluble (2.00) collagen was significantly decreased in streptozotocin-diabetic rats. Administration of P. vulgaris for 45 days to streptozotocin-diabetic rats significantly reduced the accumulation and cross-linking of collagen. The effect of P. vulgaris was compared with that of glibenclamide, a reference drug administered to streptozotocin-diabetic rats at the dose of 600 μg/kg body weight for 45 days by gavage. The effects of P. vulgaris (collagen content, 64.18 ± 1.97; extent of glycation, 12.00 ± 0.53; collagen-linked fluorescence, 33.6 ± 1.9; shrinkage temperature, 57.0 ± 1.0; extent of cross-linking - acid-soluble collagen, 2.572 ± 0.080, and pepsin-soluble collagen, 2.28 ± 0.112) were comparable with those of glibenclamide (collagen content, 71.5 ± 2.04; extent of glycation, 13.00 ± 0.60; collagen-linked fluorescence, 38.9 ± 2.0; shrinkage temperature, 59.0 ± 1.5; extent of cross-linking - acid-soluble collagen, 2.463 ± 0.078, and pepsin-soluble collagen, 2.17 ± 0.104). In conclusion, administration of P. vulgaris pods had a positive influence on the content of collagen and its properties in streptozotocin-diabetic rats.