RESPONSE OF IMMATURE DIABETIC RAT BONE-LIGAMENT JUNCTIONS TO INSULIN AND EXERCISE

The mechanical and morphological characteristics of femur-medial colla teral ligament-tibia units and the histomorphometry of medial collater al ligament-tibial insertion were examined in female Sprague-Dawley ra ts with diabetes mellitus (type I, insulin-dependent diabetes). Diabet es was induced with the streptozotocin, a drug with toxic effects on i nsulin-producing islet cells in the pancreas. The groups studied inclu ded rats with untreated streptozotocin-induced diabetes mellitus (Diab etes), insulin-treated streptozotacin-induced diabetes (Diabetes-insul in), exercise with streptozotocin-induced diabetes (Diabetes-Exercise) , exercise with insulin-treated streptozotocin-induced diabetes (Diabe tes-Insulin-Exercise), and age-matched sedentary-control rats (Control ). Diabetes and Diabetes-Exercise groups had significantly lower body mass and higher blood glucose than Diabetes-Insulin, Diabetes-Insulin- Exercise, and Control groups, indicating that exercise alone did not: prevent growth retardation or improve blood glucose control in the str eptozotocin-induced diabetes. The strength of Diabetes femur-medial co llateral ligament-tibia units was significantly less than Control, but exercise (with or without insulin treatment) maintained the bone-liga ment-bone unit strength at a normal level. The load (per unit body mas s) of Diabetes-Exercise femur-medial collateral ligament-tibia unit wa s significantly greater than Control, Diabetes, and Diabetes-insulin g roups. The tensile stiffness (per unit body mass) of the femur-medial collateral ligament-tibia unit for the Diabetes-Exercise group was als o significantly greater than Control and Diabetes-insulin groups. The fibroblast-like cell density in medial collateral ligament at its tibi al-insertion site and medial collateral ligament insertion area was si gnificantly less in Diabetes rats. Diabetes mellitus can have deleteri ous effects on connective tissues, such as bone and ligament. Thus the bone-ligament junction becomes vulnerable. The results of this experi ment suggest, however, that exercise, with or without insulin treatmen t, can have a positive effect on the bone-ligament interface in the ra t with type I diabetes mellitus. Furthermore exercise (with insulin tr eatments) can mitigate growth retardation and many of the adverse effe cts of streptozotocin-induced diabetes on the structure and mechanical properties of immature bone-ligament junctions.