Background: A significant side effect of type 2 diabetes mellitus is diabetic nephropathy (DN), which is typified by poor glucose homeostasis and insulin resistance in renal tissues. Thymoquinone (TQ), the active ingredient in Nigella sativa (NS), has been shown to have antioxidant and antidiabetic properties. However, nothing is known about their relative effects on renal glucose metabolism in hyperglycemic situations. The objective of this work was to examine and contrast the regulatory effects of NS and TQ on insulin signaling pathways and glucose transporter expression in NRK-52E renal epithelial cells grown in high-glucose environments. 
 
Methods: TQ (10 &micro;M) or NS extract (0.5 &micro;g/ml) were applied to NRK-52E cells after they were subjected to high glucose (246 mM). RT-qPCR was used to measure the mRNA expression levels of insulin signaling components (Ir, Irs1, Pi3k, Ampk, Gsk3&beta;) and glucose transporters (Glut1, Glut2, Glut3, Glut5, Sglt2). Western blot was used to measure the protein levels of Glut2, Glut3, Sglt2 and Irs1. The Duncan test (p&lt;0.05) and one-way ANOVA were used to determine statistical significance. 
 
Result: Ir, Irs1, Pi3k and Ampk levels were downregulated and Glut1, Glut2, Glut3 and Sglt2 expression was markedly elevated by high glucose exposure. These changes were reversed by TQ and NS therapy, with TQ having a stronger effect. TQ increased the levels of Irs1 and Pi3k while more successfully suppressing the expression of Sglt2 and Glut2. The transcriptional alterations were confirmed by Western blot results. TQ and NS improved insulin signaling pathways and modulated glucose transporter expression to protect renal cells. These results confirm that TQ and NS are safe to use as possible therapeutic agents to treat diabetic nephropathy. 
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Comparative Effects of Nigella sativa and Thymoquinone on Glucose Metabolism in a High Glucose-induced Renal Cell Line