Adiponectin, a protein secreted by adipose tissue, mimics insulin's metabolic effects. This study shows that adiponectin stimulates nitric oxide (NO) production in vascular endothelial cells, a key process in insulin-mediated glucose uptake and vasodilation. Using bovine aortic endothelial cells, researchers found that adiponectin increased NO production by about 3-fold, similar to the effect of lysophosphatidic acid (LPA). However, unlike LPA, adiponectin's effect on NO production was blocked by the PI3K inhibitor wortmannin, indicating a PI3K-dependent pathway. Phosphorylation of Akt at Ser473 and endothelial nitric oxide synthase (eNOS) at Ser1179 was observed in response to both adiponectin and insulin, and this was inhibited by wortmannin. Further experiments using dominant-inhibitory mutants of Akt and AMPK showed that AMPK, but not Akt, was involved in adiponectin-stimulated NO production. Specifically, AMPK-K45R significantly reduced adiponectin-induced eNOS phosphorylation at Ser1179, suggesting that AMPK plays a key role in this process. These findings indicate that adiponectin activates eNOS through a PI3K-dependent pathway involving AMPK, leading to increased NO production. This mechanism may contribute to adiponectin's metabolic and anti-atherogenic effects, potentially enhancing insulin's actions in vivo. The study highlights the importance of adiponectin in vascular function and its potential therapeutic implications in metabolic disorders such as diabetes.Adiponectin, a protein secreted by adipose tissue, mimics insulin's metabolic effects. This study shows that adiponectin stimulates nitric oxide (NO) production in vascular endothelial cells, a key process in insulin-mediated glucose uptake and vasodilation. Using bovine aortic endothelial cells, researchers found that adiponectin increased NO production by about 3-fold, similar to the effect of lysophosphatidic acid (LPA). However, unlike LPA, adiponectin's effect on NO production was blocked by the PI3K inhibitor wortmannin, indicating a PI3K-dependent pathway. Phosphorylation of Akt at Ser473 and endothelial nitric oxide synthase (eNOS) at Ser1179 was observed in response to both adiponectin and insulin, and this was inhibited by wortmannin. Further experiments using dominant-inhibitory mutants of Akt and AMPK showed that AMPK, but not Akt, was involved in adiponectin-stimulated NO production. Specifically, AMPK-K45R significantly reduced adiponectin-induced eNOS phosphorylation at Ser1179, suggesting that AMPK plays a key role in this process. These findings indicate that adiponectin activates eNOS through a PI3K-dependent pathway involving AMPK, leading to increased NO production. This mechanism may contribute to adiponectin's metabolic and anti-atherogenic effects, potentially enhancing insulin's actions in vivo. The study highlights the importance of adiponectin in vascular function and its potential therapeutic implications in metabolic disorders such as diabetes.