Potential Roles of Stevia rebaudiana Bertoni in Abrogating Insulin Resistance and Diabetes: A Review
Figure 2
The disruptions in the insulin-signalling pathway in an insulin-resistant state caused by elevated actions of TNF-α and FFA. IRS1 is no longer phosphorylated on its tyrosine residues but on serine residues, resulting in nonfunctional, inhibitory proteins. TNF-α also influences increased gene expressions of TNF-α but decreases PPARγ and GLUT4 expressions, resulting in lower levels of GLUT4 proteins. Glucose uptake is reduced, leading to hyperglycemia and hyperinsulinemia. IR: insulin receptor; Y: tyrosine; S: serine; ATP: adenosine triphosphate; ADP: adenosine diphosphate; IRS1: insulin receptor substrate 1; PI3K: phosphoinositide kinase 3; PIP2: phosphatidylinositol 4,5-bisphosphate; TNF-α: tumour necrosis factor α; FFA: free fatty acid; IKK: a type of serine kinase; ROS: reactive oxygen species; PPARγ: peroxisome proliferator activator-receptor γ; GLUT4: glucose transporter 4.
