Metformin is an oral antidiabetic drug that is widely used in the treatment of type 2 diabetes mellitus. It belongs to the class of drugs called biguanides and primarily works by decreasing the production of glucose in the liver and increasing the sensitivity of muscle cells to insulin. This results in improved glucose uptake and utilization by the cells, ultimately leading to better glycemic control.Metformin interacts with several biochemical pathways to exert its therapeutic effects:1. AMP-activated protein kinase AMPK activation: Metformin activates AMPK, an enzyme that plays a crucial role in cellular energy homeostasis. Activation of AMPK leads to the inhibition of gluconeogenesis glucose production in the liver and increased glucose uptake in the skeletal muscles. This reduces the overall blood glucose levels in the body.2. Inhibition of mitochondrial respiratory chain complex 1: Metformin inhibits the activity of complex 1 in the mitochondrial respiratory chain, leading to a decrease in ATP production. This results in an increase in the cellular AMP/ATP ratio, which further activates AMPK. The inhibition of complex 1 also leads to reduced hepatic gluconeogenesis.3. Inhibition of glucagon-induced cyclic AMP cAMP production: Metformin suppresses the production of cAMP in response to glucagon, a hormone that increases blood glucose levels. This inhibition reduces the activation of protein kinase A PKA , which in turn decreases the expression of genes involved in gluconeogenesis and glycogenolysis breakdown of glycogen to glucose .4. Insulin sensitization: Metformin improves insulin sensitivity in peripheral tissues, such as skeletal muscle and adipose tissue, by enhancing insulin-stimulated glucose uptake and utilization. This is achieved through the activation of AMPK and the subsequent translocation of glucose transporter 4 GLUT4 to the cell membrane.5. Decreased intestinal glucose absorption: Metformin has been shown to reduce the absorption of glucose in the intestine, which contributes to its overall glucose-lowering effect.In summary, metformin works in treating type 2 diabetes by targeting multiple biochemical pathways that contribute to glucose homeostasis. Its primary mechanisms of action include the activation of AMPK, inhibition of mitochondrial respiratory chain complex 1, suppression of glucagon-induced cAMP production, insulin sensitization, and decreased intestinal glucose absorption. These actions collectively lead to reduced hepatic glucose production, increased glucose uptake and utilization by peripheral tissues, and improved glycemic control.