Effects of Polygonatum sibiricum rhizome ethanol extract in high-fat diet-fed mice.

CONTEXT: The rhizome of Polygonatum sibiricum Redoute (Liliaceae) has long been used to treat diabetes-associated complications. However, the pharmacological mechanism of P. sibiricum on metabolic disorders is not clear. OBJECTIVE: This study investigates the effect of an ethanol extract of P. sibiricum rhizomes (designated ID1216) on obesity conditions including weight loss in high-fat (HF) diet-fed mice and explores the potential underlying mechanisms. METHODS: To identify the metabolic impact of the P. sibiricum rhizome extract, HF diet-fed mice were administered ID1216 orally at doses of 250 and 1000 mg/kg/d for 10 weeks, and various factors related to metabolic syndrome were analyzed. We also examined the effects of ID1216 on the expression of genes involved in adipogenesis and lipolysis in 3T3-L1 cells, as well as genes associated with energy homeostasis in C2C12 myocytes. RESULTS: ID1216 administration led to significant decreases in body weight gain (37.5%), lipid accumulation in adipose tissues (52.8%), and the levels of plasma triglycerides (26.4%) and free fatty acids (28.1%) at a dose of 250 mg/kg/d, compared with the vehicle-treated group, as well as improved insulin resistance. In addition, ID1216 was found to regulate the expression of genes related to adipogenesis and fatty acid oxidation in 3T3-L1 cells and enhance the expression of genes that modulate energy homeostasis in C2C12 myocytes. CONCLUSIONS: ID1216 may be a promising therapeutic agent for improving obesity conditions through the sirtuin-1 and peroxisome proliferator-activated receptor γ coactivator-1α pathway.

Signaling mechanisms of sphingosine 1-phosphate-induced ERK1/2 activation in cultured feline esophageal smooth muscle cells.

Sphingosine 1-phosphate (S1P) is a bioactive lipid, stored and released from activated platelets, macrophages, and other mammalian cells. We previously reported that S1P induces esophageal smooth muscle contraction in freshly isolated intact cells. Here, we measured S1P-induced ERK1/2 activation and upstream signaling in cultured feline esophageal smooth muscle cells. Activation of ERK1/2 by S1P peaked at 5 min, was sustained up to 30 min, and was blocked by PTX. In contrast, S1P did not activate p38 MAPK or JNK. PTX inhibited S1P-induced ERK1/2 activation. We then used phospholipase inhibitors, DEDA for PLA(2), U73122 for PLC, and rhoCMB for PLD, to determine that ERK1/2 activation was downstream of PLC activation. The PKC inhibitors, GF109203X and chelerythrine, also suppressed ERK1/2 activation. Whereas the PTK inhibitor, genistein, partially inhibited ERK1/2 activation, the EGFR tyrosine kinase inhibitor, tyrphostin 51, had no effect. Taken together, S1P-induced ERK1/2 activation in cultured ESMCs requires a PTX-sensitive G protein, stimulation of the PLC pathway, and subsequent activation of the PKC and PTK pathways.