Nardostachys jatamansi DC Extract Alleviates Insulin Resistance and Regulates Glucose Metabolism in C57BL/KsJ-db/db Mice Through the AMP-Activated Protein Kinase Signaling Pathway

This study investigated whether Nardostachys jatamansi DC extract (NJE) improved insulin sensitivity and suppressed hepatic glucose production in an animal model of type 2 diabetes. C57BL/KsJ-db/db mice were divided into three dietary groups: regular diet (control), NJE, and rosiglitazone. After 6 weeks of feeding, blood glucose, glycosylated hemoglobin, and plasma insulin levels were significantly lower in NJE than in diabetic control group mice. The oral glucose tolerance test also revealed a positive effect of NJE on increasing insulin sensitivity. The homeostatic index of insulin resistance was significantly lower in NJE than in diabetic control group mice. NJE markedly lowered the plasma lipid concentration compared to diabetic control group mice. In the skeletal muscle, the expression of phosphorylated AMP-activated protein kinase, pAkt substrate of 160kDa, and plasma membrane glucose transporter type 4 increased more in NJE compared to diabetic control group mice. NJE also decreased the expression of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase in the liver. These findings demonstrate that NJE alleviates hyperglycemia by improving insulin sensitivity and inhibiting gluconeogenesis in the liver.