4β-Hydroxywithanolide E isolated from Physalis pruinosa calyx decreases inflammatory responses by inhibiting the NF-κB signaling in diabetic mouse adipose tissue

BACKGROUND: Chronic inflammation in adipose tissue together with obesity induces insulin resistance. Inhibitors of chronic inflammation in adipose tissue can be a potent candidate for the treatment of diabetes; however, only a few compounds have been discovered so far. The objective of this study was to find a novel inhibitor that can suppress the inflammatory response in adipose tissue and to elucidate the intracellular signaling mechanisms of the compound. METHODS: To find the active compounds, we established an assay system to evaluate the inhibition of induced MCP-1 production in adipocyte/macrophage coculture in a plant extract library. The active compound was isolated by performing high-performance liquid chromatography (HPLC) and was determined as 4 beta-hydroxywithanolide E (4 beta HWE) by nuclear magnetic resonance (NMR) and mass spectroscopy (MS) spectral analyses. The effect of 4 beta HWE on inflammation in adipose tissue was assessed with adipocyte culture and db/db mice. RESULTS: During the screening process, Physalis pruinosa calyx extract was found to inhibit production of MCP-1 in coculture strongly. 4 beta HWE belongs to the withanolide family of compounds, and it has the strongest MCP-1 production inhibitory effect and lowest toxicity than any other withanolides in coculture. Its anti-inflammatory effect was partially dependent on the attenuation of NF-kappa B signaling in adipocyte. Moreover, in vivo experiments showed that the oral administration of 4 beta HWE to db/db mice resulted in the inhibition of macrophage invasion and cytokine expression in adipose tissue after 2 weeks of treatment; improved the plasma adiponectin, non-esterified fatty acids and MCP-1 concentrations; and increased glucose tolerance after 3 to 4 weeks of treatment. CONCLUSIONS: These results suggest that 4 beta HWE has anti-inflammatory effect via inhibition of NF-kappa B activation in adipocyte. Moreover, the attenuation of inflammation in adipocyte has an effect on the inhibition of macrophage accumulation in obese adipose tissue. Consequently, 4 beta HWE improves impaired glucose tolerance. Thus, 4 beta HWE is a useful natural anti-inflammatory compound to attenuate progression of diabetes and obesity.