Viscoelastic behavior of small intestine in streptozotocin-induced diabetic rats

Diabetes is associated with remodeling of the morphology and elastic properties of the small intestine. This study aims to study remodeling of the viscoelastic (time-dependent) properties of the small intestine during experimental diabetes. Stress relaxation tests were performed on the duodenum, jejunum, and ileum in 10 nondiabetic and 28 streptozotocin (STZ) -induced diabetic rats. The rats were made diabetic by a single intraperitoneal injection of 50 mg/kg STZ. The diabetic rats were allocated into groups living four days or one, two, or four weeks after the induction of diabetes (N = 7 in each group). The mechanical test was performed using a machine that rapidly stretched the intestinal tube to 40% more than the resting length. The intestinal diameter and wall area were obtained from digitized images of the intestinal segments at no-load and zero-stress states. The stress (force per area) was computed and a reduced-stress relaxation function was applied. The log decay parameter C and the slow and fast time constants tau1 and tau2 were computed. STZ-induced diabetes was associated with a progressive increase in the wall thickness and wall cross-sectional area (P < 0.05). tau1 and tau2 increased and C decreased. The slope alpha became consistently less negative (P < 0.05), and the stress after 600-sec relaxation gradually increased during diabetes (P < 0.01). In conclusion, the viscoelastic behavior of the intestinal wall changed during the development of diabetes.