Antidiabetic Medicinal Plants and Their Mechanisms of Action

Diabetes is one of the prominent metabolic disorders nowadays. It is associated with many complications, including polyuria, weight loss, polydipsia, polyphagia, blurred vision, retinopathy, neuropathy, and nephropathy. Ongoing research has advanced on the mechanisms accompanying the prevention and treatment of diabetes, and the vast majority of research papers in the field of drug design and pharmacokinetics concentrate on the mechanisms through which the homeostasis of serum glucose is achieved. Several organs are fundamental in the process of regulating blood glucose levels, namely, the pancreas, liver, muscles, and adipose tissues. On the one hand, pancreatic β-islets are responsible for insulin production. As such, some drugs are focused to augment the islet size, cell size and number, or insulin secretion levels. On the other hand, the liver is the most crucial organ to sense fluctuations in blood glucose concentration and respond via buffering mechanisms accordingly. Furthermore, muscle and adipose tissues play concomitant roles to withdraw extra glucose from the bloodstream. Several key enzymes (e.g., phosphofructokinase, phosphorylase, glucose-6-phosphatase, etc.), transporters (GLUT2, GLUT4, etc.), as well as cell surface receptors (IRS, TM7, and others) in the hepatic, muscular, and adipose tissues are major targets for antidiabetic drugs. Global control of blood glucose levels can be via insulin-dependent protein kinase B (PKB) or insulin-independent AMP-activated protein kinase (AMPK) signaling cascades. Additionally, several drugs target to soothe the cell damage associated with hyperglycemia. In this respect, antioxidants have invaluable effects that should not be ignored. Moreover, the simple routes for glycemic control are via the inhibition of glucose digestion and absorption. In this chapter, strategies to treat diabetes are discussed, with an emphasis on the phytochemical drugs used in the Middle East and their mechanisms of action.