Glycosylated Sulfonylurea (2DGs) Modulates Insulin ‐ dependent and Insulin ‐ independent Signaling Pathways via PI3K and P38 MAPK in L6 Skeletal Muscle Cell Line

Abstract

BackgroundMetformin and sulfonylureas are the most prescribed oral anti‐diabetic drugs globally. However, side effects like lactic acidosis, cardiovascular risks, hypoglycemia and weight gain limit their use in certain comorbidity cases. Metformin utilizes both insulin‐dependent and insulin‐independent sig naling pathways to modulate blood glucose levels in diabetic patients. Sulfonylureas increase insulin secretion from the pancreas and enhance glucose uptake by skeletal muscles through the PI3K signaling pathway. Glycosylated sulfonylurea (2DGs) is a modified analogue of sulfonylurea developed by integrating an aryl sulfonamide with a glucosamine moiety. Previous research on 2DGs has shown in vitro and in vivo antidiabetic, antioxidant, anti‐glycation activity and alleviation from kidney, liver, and cardiovascular diabetic‐related complications.ObjectiveThe current study focused on the evaluation of insulin signaling pathways of 2DGs in normal and insulin resistant L6 myotubes.MethodTo evaluate PI3K signaling, insulin resistance was induced in L6 myotubes using high glucose (25 mmol/l) and insulin (100 nmol/l) for 24 hours, followed by low glucose (5mmol/l) and no serum for 5 hours and insulin (100 nmol/l) for 30 mins. Treatment was done for 24 hours with tolbutamide and acetylated and deacetylated 2DGs at 5uM, 10uM. For p38 MAPK signaling, one group of L6 myotubes was incubated with SB203580 (p38 MAPK inhibitor) and second group was without SB203580. Both groups were treated with 2DGs similar as mentioned above. The treatment was left for 1 hour, after which DNA and protein extraction for quantitative PCR, ELISA, and Western blot experiment was done.ResultsThere was observed high expression of PIK3CA, SLC2A4 and MAPK14 gene in qPCR and upregulated phosphorylation of PI3K, GLUT 4 and p38 MAPK protein in acetylated and deacetylated treated groups compared to tolbutamide and non‐treated group. A positive Pearson correlation was observed between the PIK3CA, SLC2A4 and MAPK14 gene expressions and PI3K, GLUT 4 and p38 MAPK protein expressions respectively.ConclusionFinding indicates that 2DGs insulin signaling pathway seems to be through both insulin dependent via PI3K and insulin ‐ independent via p38 MAPK phosphorylation in insulin resistant and normal L6 myotubes respectively.