Effect of genistein, a natural soy isoflavone, on pancreatic β-cells of streptozotocin-induced diabetic rats: Histological and immunohistochemical study

Diabetes mellitus is one of the oldest disorders that is rapidly emerging as a global health problem. Soy genistein is a legume that has numerous health benefits. This work aimed to study the effect of different doses of genistein on histological, immunohistochemical and morphometrical changes in β-cells of streptozotocin (STZ)-induced diabetic rats and to correlate these effects with plasma glucose and insulin levels. Fifty adult male rats were divided into five equal groups. Group I served as a control. Group II received genistein. Group III comprised STZ-induced diabetic rats. Group IV diabetic animals treated with low dosage genistein. Group V diabetic animals treated with high dosage genistein. Genistein was given for 4 weeks after STZ injection. Rats were sacrificed and pancreatic specimens were taken for light and electron microscopic examination. Blood samples were collected for detection of serum glucose and insulin levels. After diabetic induction, the islets appeared shrunken with cytoplasmic vacuolation of their cells and negative insulin immunoreaction. Ultrastructurally, β-cells showed darkly stained nuclei with marked loss of granules. Morphometrically, significant loss of β-cells was detected. The serum insulin level was decreased with elevation in the serum glucose. High-dose but not low-dose genistein improved the morphology of islets with increased insulin immunoreaction. Genistein also significantly decreased β-cells loss and improved glucose and insulin levels. In conclusion, genistein has a protective effect on pancreatic β-cells damage, possesses the ability to regenerate β-cells and improves serum levels of insulin and glucose in STZ-induced diabetic rats in a dosage-dependent manner.