Effects of quercetin nanoemulsion on SIRT1 activation and mitochondrial biogenesis in the skeletal muscle of high-fat diet-fed mice.

Background/objectives: Quercetin (QT) is a plant flavonoid that offers health benefits owing to its various bioactive properties; however, as a hydrophobic substance, it has considerably low bioavailability. We previously demonstrated that QT nanoemulsion (QT+NE) formulated via oil-in-water nanoemulsification exhibited more effective cholesterol-lowering activity than ordinary QT in high cholesterol-fed rats. In this study, we investigated the effects of QT+NE on the regulation of skeletal muscle mitochondrial function in high-fat diet (HD)-fed mice.

Materials/methods: C57BL/6J mice were fed a normal chow diet (ND), HD (45% of calories from fat), or HD with 0.05% QT+NE or QT for 11 weeks. We analyzed sirtuin 1 (SIRT1) activation, mitochondrial changes, and the expression of genes involved in mitochondrial biogenesis in skeletal muscle.

Results: Body weight and body weight gain decreased in the QT+NE group compared with that in the HD group ( < 0.05), but not in the QT group. Epididymal adipose tissue weight decreased in both the QT and QT+NE groups ( < 0.05). Plasma lipid levels also improved in both the QT and QT+NE groups ( < 0.05). QT+NE intake upregulated the messenger RNA levels of SIRT1, peroxisome proliferator-activated receptor-γ coactivator 1-α, nuclear respiratory factor 1, and mitochondrial transcription factor A in skeletal muscle compared with HD intake alone ( < 0.05), whereas QT did not. In particular, SIRT1 activity was significantly increased in the QT+NE group compared with that in the QT group ( < 0.05). HD intake reduced mitochondrial DNA content compared with ND intake; nevertheless, QT+NE intake retained it ( < 0.05).

Conclusion: Collectively, our findings suggest that QT+NE may be beneficial in enhancing mitochondrial biogenesis in skeletal muscle of HD-fed mice, which may be associated with SIRT1 activation.