TNF and diabetes mellitus: The anti-inflammatory effect of metformin against diabetes and gamma irradiation as indicated by reduced CD68 expression was in accordance with Han et al. [15] who proved that metformin inhibited the pro-inflammatory cytokines, such as IL-1 and TNF-α, in the pancreatic tissues of STZ induced diabetic mice that may partially explained the amelioration of the histopathological changes due to diabetes.