INS and diabetes mellitus: STZ selectively destroys pancreatic insulin-secreting β cells causing diabetes similar to type 2 diabetes in humans according to [23], and induction of diabetes with STZ was associated with the characteristic loss of body weight due to increased muscle wasting and loss of tissue proteins because protein and fat are broken down to provide energy instead of blood glucose [47]; therefore, the body weight in the STZ-induced diabetic rats (diabetic controls) in the present study decreased significantly.