Grifola frondosa (Maitake) extract activates PPARδ and improves glucose intolerance in high-fat diet-induced obese mice.

Grifola frondosa is a mushroom that has anti-obesity effects, but the detailed mechanism is poorly understood. In this study, we found that lipid soluble extracts derived from G. frondosa (GFE) had peroxisome proliferator-activated receptor δ (PPARδ) agonist activity, inducing the expression of PPARδ-target genes in vitro. Furthermore, administration of GFE to high-fat diet-induced obese mice lowered the total blood cholesterol levels, upregulated the expression of PPARδ-target genes in skeletal muscles and improved glucose intolerance. Additionally, analyses of C2C12 myotubes revealed that GFE restored glucose uptake, which was inhibited by sodium palmitate, to normal levels. Unexpectedly, such acceleration was not abolished by a PPARδ antagonist. These results suggest that G. frondosa is a novel functional food that may prevent life-style related diseases like obesity and diabetes, and that these beneficial effects are likely to be mediated through the activation of PPARδ and a PPARδ-independent insulin signaling pathway.