Background: The several studies reported that the diabetic conditions induce apoptosis in various organs such as brain and testis. Recent studies have shown that the diabetes conditions can trigger male infertility and neurodegenerative diseases. Also, it is increasingly evident that there is a close relationship between diabetes, cell death, Alzheimer disease and infertility. Toll like receptors (TLRs) are the main components of innate immune system. TLRs are involved in cell death and inflammation in diabetic condition. It is clear that TLRs especially TLR4 is up regulated in diabetic mice. This study designed to define the effect of insulin treatment on mRNA expression of TLR4and cell density in the brain hippocampal tissue and testis of diabetic rats in after induction of diabetes type 1.Methods: Diabetes type 1 was induced in rat by single injection of streptozotocin(STZ) with dose 55 mg/kg. To assessment the direct effect of hyperglycemia on target gene expressions and morphological analysis, insulin treatment was done to reduce the blood glucose. Hippocampal and testicular tissue damage and expression of the TLR4 in various times after diabetes type 1 induction were assessed in control, diabetic and diabetic insulin treated rats.In order to histological analysis, after certain periods, the animals were killed; their hippocampi and tests were removed, and fixed in formaldehyde (37%). The fixed samples were then embedded in paraffin and sectioned (4 μm thick) on gelatin precoated slides. They were further deparaffinized, stained with Hematoxylin-Eosin (H&E) and DAPI, and observed under the microscope to evaluation the cell density of hippocampi and tests tissues section in specified times. Also, expression levels of TLR4 quantified by qPCR and statistically analyzed by one way ANOVA method. Results: The results showed differential pattern expression among different groups of treated (diabetic and diabetic-insulin treated) and control rats. Hyperglycemia condition after diabetes type 1 induction increased expression of TLR4 and cell density reduction in diabetic groups. The insulin treatment decreased the expression of TLR4 in diabetes-insulin treated group. Also, testicular and hippocampi cell density were improved after insulin treatment. Conclusion: Insummary,the results suggesting that hyperglycemia following diabetes play an important role in initiation innate immunity and cell death, and insulin treatment can reduce the expression of TLR4 and increased cell density in diabetic tests and hippocampi tissues.

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