Purpose: Muscle mitochondria play a key role in regulating fatty acid and glucose metabolism. Dysfunction of muscle mitochondria is associated with metabolic diseases such as obesity and type 2 diabetes. Isorhamnetin (ISOR), also known as 3-O-methylquercetin, a quercetin metabolite, is a naturally occurring flavonoid in many plants. This study evaluated the effects of ISOR on the regulation of the mitochondrial function of C2C12 muscle cells. Methods: C2C12 muscle cells were differentiated for 5 days, and then treated in various concentrations of ISOR. Cytotoxicity was determined by assessing cell viability using the water-soluble tetrazolium salt-8 assay principle at different concentrations of ISOR and time points. Levels of the mitochondrial DNA (mtDNA) content and gene expression were measured by quantitative real-time polymerase chain reaction. The citrate synthase (CS) activity was quantified by the enzymatic method. Results: ISOR at a concentration of 10 μM did not show any cytotoxic effects. ISOR increased the mtDNA copy number in a time- or dose-dependent manner. The messenger RNA levels of genes involved in mitochondrial function, such as peroxisome proliferator-activated receptor-γ coactivator-1α, and uncoupling protein 3 were significantly stimulated by the ISOR treatment.The CS activity was also significantly increased in a time- or dose-dependent manner. Conclusion These results suggest that ISOR enhances the regulation of mitochondrial function, which was at least partially mediated via the stimulation of the mtDNA replication, mitochondrial gene expression, and CS activity in C2C12 muscle cells. Therefore, ISOR may be useful as a potential food ingredient to prevent metabolic diseases-associated muscle mitochondrial dysfunction.

Purpose: Muscle mitochondria play a key role in regulating fatty acid and glucose metabolism. Dysfunction of muscle mitochondria is associated with metabolic diseases such as obesity and type 2 diabetes. Isorhamnetin (ISOR), also known as 3-O-methylquercetin, a quercetin metabolite, is a naturally occurring flavonoid in many plants. This study evaluated the effects of ISOR on the regulation of the mitochondrial function of C2C12 muscle cells. Methods: C2C12 muscle cells were differentiated for 5 days, and then treated in various concentrations of ISOR. Cytotoxicity was determined by assessing cell viability using the water-soluble tetrazolium salt-8 assay principle at different concentrations of ISOR and time points. Levels of the mitochondrial DNA (mtDNA) content and gene expression were measured by quantitative real-time polymerase chain reaction. The citrate synthase (CS) activity was quantified by the enzymatic method. Results: ISOR at a concentration of 10 μM did not show any cytotoxic effects. ISOR increased the mtDNA copy number in a time- or dose-dependent manner. The messenger RNA levels of genes involved in mitochondrial function, such as peroxisome proliferator-activated receptor-γ coactivator-1α, and uncoupling protein 3 were significantly stimulated by the ISOR treatment.The CS activity was also significantly increased in a time- or dose-dependent manner. Conclusion These results suggest that ISOR enhances the regulation of mitochondrial function, which was at least partially mediated via the stimulation of the mtDNA replication, mitochondrial gene expression, and CS activity in C2C12 muscle cells. Therefore, ISOR may be useful as a potential food ingredient to prevent metabolic diseases-associated muscle mitochondrial dysfunction.

Purpose: Mulberry (Morus alba L.) fruit is widely grown in Asia and consumed as fresh fruit, jam, and juices. The fruit has beneficial health effects, including anti-diabetic, anti-tumor, and anti-obesity properties. However, the mechanisms by which mulberry fruit juice powder (MJ) regulates inflammatory microRNAs (miRs) are not yet known. This study investigated the effect of mulberry fruit juice powder on the regulation of inflammation and miR-132/143 during 3T3-L1 adipocyte differentiation. Methods: The 3T3-L1 cells were induced to differentiate for 2 days and then treated with various concentrations of MJ for 7 days. Cytotoxicity was determined by evaluating cell viability using a water-soluble tetrazolium salt-8 assay kit. Intracellular lipid accumulation was evaluated by oil-red O staining. The levels of the expression of genes involved in adipogenesis and inflammation, and miR-132/143 were measured by quantitative real-time polymerase chain reactions. Results: MJ showed no cytotoxic effect on 3T3-L1 adipocytes at concentrations below 100 ng/ mL. Intracellular lipid accumulation was reduced by MJ treatment at concentrations of 100 ng/mL. The messenger RNA (mRNA) levels of proliferator-activated receptor-γ, cytosinecytosine-adenosine-adenosine-thymidine/enhancer-binding protein-α, and adipocyte protein 2, which are involved in adipogenesis, were suppressed by MJ. A reduction was also seen in mRNA levels of genes related to the inflammatory response, such as tumor necrosis factor-α, interleukin-6, monocyte chemoattractant protein-1, and inducible nitric oxide synthase. The expression of the inflammatory miR-132 and miR-143 was also decreased by MJ. Conclusion These results suggest that MJ may suppress adipogenesis and inflammation through the regulation of miR-132/143 expression in 3T3-L1 adipocytes. Thus, MJ may be useful as a food agent that prevents obesity-associated inflammation.

Purpose: Quercetin is a polyphenolic flavonoid abundant in many fruits and vegetables. It has potential health-beneficial properties, such as antioxidant, anti-obesity, anti-cancer, anti-diabetic and anti-inflammatory effects. The purpose of this study was to investigate whether the lipid metabolism improvement effect of quercetin affected the regulation of AMP-activated protein kinase (AMPK) activity and microRNA (miR)-21 expression in the liver of mice fed a high-cholesterol diet. Methods: Male C57BL/6J mice were fed with normal diet, quercetin-free diet and diets containing 0.05% or 0.1% quercetin for six weeks. Hypercholesterolemia was induced by adding 1% cholesterol and 0.5% cholic acid to all diets. Serum and liver triglyceride (TG), and total cholesterol (TC) concentrations were analyzed using a commercial enzymatic colorimetric kit.AMPK activity was quantified using an AMPK kinase assay kit. The levels of miR-21 and genes involved in lipid metabolism were measured by real-time quantitative polymerase chain reaction. Results: Supplementation of quercetin reduced serum and hepatic TG and TC levels without changing body weight and food intake. Dietary quercetin significantly inhibited the mRNA levels of hepatic sterol-regulatory element binding protein-1c, acetyl-CoA carboxylase 1 and fatty acid synthesis, which are involved in hepatic lipogenesis. Dietary quercetin enhanced AMPK activity and suppressed miR-21 expression, promoting hepatic lipid accumulation. Conclusion These results suggest that the lipid-lowering effect of quercetin on the serum and liver of mice may be partially mediated by the regulation of lipogenic gene expression, AMPK activity and miR-21 expression in the liver of mice fed a high-cholesterol diet.

Purpose: This study investigated the effects of water-soluble mulberry leaf extract (ME) on hepatic lipid accumulation in high-fat diet-fed rats via the regulation of hepatic microRNA (miR)-221/222 and inflammation. Methods: Male Sprague-Dawley rats (4 weeks old) were randomly divided into 3 groups (n = 7 each) and fed with 10 kcal% low-fat diet (LF), 45 kcal% high-fat diet (HF), or HF + 0.8% ME for 14 weeks. Lipid profiles and cytokine levels of the liver and serum were measured using commercial enzymatic colorimetric and enzyme-linked immunosorbent assay, respectively.The messenger RNA (mRNA) and miR levels in liver tissue were assayed by real-time quantitative reverse-transcription polymerase chain reaction. Results: Supplementation of ME reduces body weight and improves the liver and serum lipid profiles as compared to the HF group. The mRNA levels of hepatic peroxisome proliferatoractivated receptor-gamma, sterol regulatory element binding protein-1c, fatty acid synthase, and fatty acid translocase, which are genes involved in lipid metabolism, were significantly downregulated in the ME group compared to the HF group. In contrast, the mRNA level of hepatic carnitine palmitoyl transferase-1 (involved in fatty acid oxidation) was upregulated by ME supplementation. Furthermore, administration of ME significantly downregulated the mRNA levels of inflammatory mediators such as hepatic tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), monocyte chemoattractant protein-1, and inducible nitric oxide synthase. The serum levels of TNF-α, IL-6, and nitric oxide were also significantly reduced in ME group compared to the HF group. Expression of hepatic miR-221 and miR-222, which increase in the inflammatory state of the liver, were also significantly inhibited in the ME group compared to the HF group. Conclusion These results indicate that ME has the potential to improve hepatic lipid accumulation in high-fat diet-fed rats via modulation of inflammatory mediators and hepatic miR-221/222 expressions.

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 cholesterollowering 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 (P < 0.05), but not in the QT group. Epididymal adipose tissue weight decreased in both the QT and QT+NE groups (P < 0.05). Plasma lipid levels also improved in both the QT and QT+NE groups (P < 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 (P < 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 (P < 0.05).HD intake reduced mitochondrial DNA content compared with ND intake; nevertheless, QT+NE intake retained it (P < 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.

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 cholesterollowering 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 (P < 0.05), but not in the QT group. Epididymal adipose tissue weight decreased in both the QT and QT+NE groups (P < 0.05). Plasma lipid levels also improved in both the QT and QT+NE groups (P < 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 (P < 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 (P < 0.05).HD intake reduced mitochondrial DNA content compared with ND intake; nevertheless, QT+NE intake retained it (P < 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.

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 cholesterollowering 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 (P < 0.05), but not in the QT group. Epididymal adipose tissue weight decreased in both the QT and QT+NE groups (P < 0.05). Plasma lipid levels also improved in both the QT and QT+NE groups (P < 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 (P < 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 (P < 0.05).HD intake reduced mitochondrial DNA content compared with ND intake; nevertheless, QT+NE intake retained it (P < 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.

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 cholesterollowering 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 (P < 0.05), but not in the QT group. Epididymal adipose tissue weight decreased in both the QT and QT+NE groups (P < 0.05). Plasma lipid levels also improved in both the QT and QT+NE groups (P < 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 (P < 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 (P < 0.05).HD intake reduced mitochondrial DNA content compared with ND intake; nevertheless, QT+NE intake retained it (P < 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.

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 cholesterollowering 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 (P < 0.05), but not in the QT group. Epididymal adipose tissue weight decreased in both the QT and QT+NE groups (P < 0.05). Plasma lipid levels also improved in both the QT and QT+NE groups (P < 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 (P < 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 (P < 0.05).HD intake reduced mitochondrial DNA content compared with ND intake; nevertheless, QT+NE intake retained it (P < 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.