Background: The hallmark of type 2 diabetes is the dysfunction of pancreatic β cells and insulin resistance. Beta cell dysfunction plays a significant role in the pathogenesis, during the development of type 2 diabetes due to oxidative stress. Therefore the aim of our work is to determine the antioxidant property of Gelam honey, on the stress induced insulin signalling pathways in the β cells, of the pancreatic hamster cells (HIT-T15) cultured in vitro.
Methods: Phenolic extracts from a local Malaysian species of Gelam honey (Melaluca spp.), was prepared using the standard extraction methods. HIT-T15 cells were cultured in 5% CO2 and then pre-incubated with Gelam honey extracts (20, 40, 60 and 80µg/ml) as well as quercetin (20, 40, 60 and 80µM), prior to stimulation by 20 and 50mM of glucose. The cell lysate were collected to determine the effect of honey extracts and quercetin on the stress activated MAPK phosphorylation , NF-kB phosphorylation, and IRS-1 serine phosphorylation causing insulin resistance and the Akt phosphorylation, causing increase in insulin content by using western blot method.
Results: HIT-T15 cells cultured under hyperglycemic conditions demonstrated insulin resistance with a significant increase in the levels of MAPK, NF-kB, IRS-1 serine phosphorylation (ser307) and a significant decrease in insulin content by reducing the expression of Akt (ser473). Pretreatment with quercetin and Gelam honey extract improved insulin resistance and insulin content by reducing the expression of phosphorylated MAPK, NF-kB, and IRS-1 (ser307) and increasing the expression of phosphorylated Akt significantly.
Conclusion: Our data provide evidence that Gelam honey has protective effects against hyperglycemia induced oxidative stress activated signaling pathways by improving insulin content and insulin resistance.