Effective fraction from Simiao Wan prevents hepatic insulin resistant by inhibition of lipolysis via AMPK activation.

Simiao Wan (SMW) is a traditional Chinese formula, including Atractylodis Rhizoma, Achyranthis Bidentatae Radix, Phellodendri Chinensis Cortex and Coicis Semen at the ratio of 1:1:2:2. It can be used to the treatment of diabetes. However, its bioactive compounds and underlying mechanism are unclear. This study aimed to screen the antilipolytic fraction from SMW and investigate its therapeutic mechanisms on hepatic insulin resistance. Different fractions of SMW were prepared by membrane separation combined with macroporous resin and their antilipolytic activities were screened in fasted mice. The effects of 60% ethanol elution (ESMW) on lipolysis were investigated in 3T3-L1 adipocytes stimulated by palmitic acid (PA) and high fat diet (HFD)-fed mice. In our study, ESMW is the bioactive fraction responsible for the antilipolytic activity of SMW and 13 compounds were characterized from ESMW by UHPLC-QTOF-MS/MS. ESMW suppressed protein kinase A (PKA)-hormone-sensitive lipase (HSL) related lipolysis and increased AMP-activated protein kinase (AMPK) phosphorylation in PA challenged 3T3-L1 adipocytes. AMPKα knockdown abolished the inhibitory effects of ESMW on IL-6 and HSL pSer-660, revealing that the antilipolytic and anti-inflammatory activities of ESMW are AMPK dependent. Furthermore, ESMW ameliorated insulin resistance and suppressed lipolysis in HFD-fed mice. It inhibited diacylglycerol accumulation in the liver and inhibited hepatic gluconeogenesis. Conditional medium collected from ESMW-treated 3T3-L1 cells ameliorated insulin action on hepatic gluconeogenesis in liver cells, demonstrating the antilipolytic activity contributed to ESMW beneficial effects on hepatic glucose production. In conclusion, ESMW, as the antilipolytic fraction of SMW, inhibited PKA-HSL related lipolysis by activating AMPK, thus inhibiting diacylglycerol (DAG) accumulation in the liver and thereby improving insulin resistance and hepatic gluconeogenesis.
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