The molecular pathogenesis of diabetic encephalopathy (De), one of the serious complications of diabetes mellitus, is complex. In this study, we examined whether expression levels of SIrT1 and SIrT2 were the key for the development of brain dysfunctions and whether PARP-1 inhibitors could affect the expression of these proteins for prevention the development of De in rats with type 1 diabetes. after 10 weeks of the streptozotocin-induced diabetes mellitus (70 mg/kg), Wistar male rats were treated by i.p. injection with ParP-1 inhibitors, 1.5-isoquinolinediol (ISo) or nicotinamide (Nam) (3 or 100 mg/kg/daily i.p., respectively) for 2 weeks. The rats with blood glucose levels over 19.7 ± 2.1 mmol/l were taken into experiments. Western blots were performed to evaluate effects of PAPR-1 inhibitors on the levels of sirtuins, SIRT1 and SIRT2 expression. Diabetes induced significant reduction of SIRT1 expression and SIRT2 overexpression in brain nuclear extracts of diabetic rats compared to non-diabetic control. In brain, Nam attenuated SIrT2 overexpression in nuclear extracts of diabetic rats and slightly elevated SIRT1 expression, while ISO didn't affect expression of both sirtuins in diabetic rats. Furthermore, it was observed that in brain of diabetic rats, the ratio of free NaD/NaDh couples decreased 3.1-fold compared to non-diabetic control. The administration of ISo increased only slightly the ratio of free NaD/NaDh couples in the brain of diabetic rats while Nam increased this parameter 1.7-fold compared to diabetic rats. Therefore, we concluded that alterations in the expression of SIrT1 and SIrT2 in brain cell nuclei of diabetic rats can lead to the development of brain dysfunctions. one of the neuroprotective mechanisms of Nam action can also be realized through inhibition of SIrT2 expression in brain cell nuclei that down-regulate progression of diabetes-induced alterations and can be a therapeutic option for treatment of brain dysfunctions.

Objectives. The present study was designed to assess whether apoptosis-related genes as parp-1 and bax could be targets for treatment of diabetes mellitus and whether vitamin D may exert beneficial effects. Methods. Vitamin D3 treatment for 4 weeks, starting after 4 weeks of the diabetes duration. The expression of parp-1 and bax genes was estimated on mRNA levels using real time quantitative polymerase chain reaction. Results. After 8 weeks, diabetic rats had weight loss, while blood glucose was increased about 4.9-fold compared to control group. Vitamin D3 administration to diabetic animals had no effect on these parameters. It was found that total serum alkaline phosphatase activity was significantly elevated in diabetic rats as compared to control animals and was restored by vitamin D3. Diabetes was accompanied by reduction of nicotinamidadenindinucleotide, a substrate of poly-ADP-ribosylation, level by 31.7% as compared to control rats, which was not reversed in response to vitamin D3 treatment. In diabetic hearts, the mRNA expression level of parp-1 gene was 2.8-fold higher compared to control rats and partially decreased by vitamin D3 treatment. Less significant alterations were observed in diabetic hearts for the mRNA expression level of bax gene that was 2.0-fold higher compared to control animals and vitamin D3 normalized it. These results indicate that cardiomyocytes have a tendency to apoptosis. Conclusions. The findings suggest that investigated genes can be targets at the transcriptional level for vitamin D action that may be contributed to the improving metabolic/signaling pathways induced by diabetes mellitus.

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