Search for new genetic markers for type 1 diabetes

Abstract

This study aims to identify certain early pancreatic beta cell’s dysregulations responsible for type 1 diabetes development and to evaluate certain biological effects of curcumin and nicotinamide that may be effective in the management of type 1 diabetes. Initially, β-cell disorders were studied using streptozotocin-treated NIT-1 cells as an experimental model. Streptozotocin significantly induced the death of both β-cells and mice-isolated pancreatic islets. Streptozotocine-treated NIT- 1cells showed a set of disorders including an up-regulation of three genes expression related to ER- stress (ATF4, NF-ĸB1, and CHOP), and a state of oxidative stress which was observed as a decrease in GSH level and an increase in ROS accumulation, MDA level, and the activities of XO and SOD. Secondly, the potential beneficial effects of curcumin and nicotinamide on pancreatic beta-cells (NIT-1 cell line) and pancreatic islets (isolated from mice) were evaluated. Nicotinamide was non- toxic to both islets and NIT-1 cells, while curcumin showed a minor insignificant toxicity to NIT-1 cells .Curcumin and nicotinamide significantly enhanced insulin secretion in pancreatic islets. Curcumin significantly reduced insulin secretion in β-cells, whereas nicotinamide slightly increased this secretion. Both molecules significantly protected β-cells against the STZ-induced death and STZ-induced ROS accumulation. Curcumin at low dose (30µg/ml) exerted an antioxidant effect in β- cell as reflected by high level of GSH and low levels of MDA and SOD, while at high dose (60µg/ml), it induced oxidative stress. The antioxidant activity of nicotinamide was confirmed in vitro by evaluating its effect on xanthine oxydase activity. Nicotinamide showed remarquable and dose-dependent inhibition of XO activity. The possible side effects of these molecules on pancreatic β-cell was also verified by assessing their impact on the expression of NF-ĸB1, ATF4, and CHOP genes. Both molecules at high dose (60µg/ml) increased the expression of these genes. Bioinformatic study showed the interaction of curcumin with a set of proteins involved in apoptosis, oxidative stress, and inflammation.The immuno-modulatory activity of curcumin and nicotinamide on human neutrophil was also assessed. Curcumin significantly decreased neutrophil viability, elastase activity, and myeloperoxidase activity in a dose-dependent manner, while nicotinamide showed no immunomodulatory effects on these parameters. Curcumin's potential as a HNE and MPO inhibitor was confirmed through computational studies, including molecular docking analysis, DFT calculations, and MEP analysis, which revealed its high affinity with HNE and MPO enzyme active sites and provide informations on the electronic, energetic, and elecroteostatic characteristics of curcumin.