Regulates insulin sensitivity and metabolic homeostasis. Inhibits the folate cycle, thereby reducing de novo purine biosynthesis which leads to the accumulation of the de novo purine synthesis intermediate 5-aminoimidazole-4-carboxamide (AICAR) and the activation of the metabolic regulator 5'-AMP-activated protein kinase (AMPK). Protects against age-dependent and diet-induced insulin resistance as well as diet-induced obesity.