Effects of quercetin on the improvement of lipid metabolism through regulating hepatic AMPK and microRNA-21 in high cholesterol diet-fed mice / 한국영양학회지

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.

Inhibitory effect of water-soluble mulberry leaf extract on hepatic lipid accumulation in high-fat diet-fed rats via modulation of hepatic microRNA-221/222 expression and inflammation / 한국영양학회지

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.

Effects of mulberry fruit juice powder on inflammation and microRNA-132/143regulation in 3T3-L1 adipocytes / 한국영양학회지

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.

Effects of isorhamnetin on the regulation of mitochondrial function in C2C12 muscle cells / 한국영양학회지

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.

Effects of isorhamnetin on the regulation of mitochondrial function in C2C12 muscle cells / 한국영양학회지

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.

Dietary chitosan enhances hepatic CYP7A1 activity and reduces plasma and liver cholesterol concentrations in diet-induced hypercholesterolemia in rats

The present study was performed to elucidate the hypocholesterolemic action of chitosan on the diet-induced hypercholesterolemia in rats. Male Sprague-Dawley rats (n=24) were fed with chitosan-free diet (Control), diets containing 2% or 5% chitosan for 4 weeks. Hypercholesterolemia was induced by adding 1% cholesterol and 0.5% cholic acid to all diets. Body weight gain and food intake of rats did not differ among the groups. The chitosan treated groups showed significant improvement in the plasma concentration of total cholesterol and LDL-cholesterol compared to the control group (p<0.05). Also, the chitosan treated groups decreased the liver concentration of total lipid and total cholesterol compared to the control group (p<0.05). The activity of hepatic cholesterol 7alpha-hydroxylase (CYP7A1), the rate-limiting enzyme in the conversion of cholesterol to bile acids, was increased by 123% and 165% for the 2% or 5% chitosan diets, respectively. These findings suggest that enhancement of hepatic CYP7A1 activity may be a mechanism, which can partially account for the hypocholesterolemic effect of dietary chitosan in cholesterol metabolism.

Effects of Corn Peptide Consumption on Plasma Lipid Profiles in Cholesterol-Fed Rats

In this study, the effects of corn peptide consumption on plasma lipid profiles were investigated in high cholesterol dietfed rats. Male Sprague-Dawley rats (n = 21) were fed with corn peptide-free (control) diet, diets containing 2% or 5% corn peptide for 5 weeks. Hypercholesterolemia was induced by adding 1% cholesterol and 0.5% cholic acid to all diets. No difference was found in food intake and body weight gain among groups. The corn peptide treated groups showed significant improvement in the plasma level of HDL-cholesterol (p < 0.05) compared to the control group, while the plasma total cholesterol and LDL-cholesterol were not affected. 5% corn peptide supplemented diet reduced plasma level of triglycerides (p < 0.05). The atherogenic index was decreased in the corn peptide treated groups. These results suggest that consumption of corn peptide may lead to an amelioration of metabolic syndrome as well as a reduction of cardiovascular disease and hyperlipidemia through increasing the level of HDL-cholesterol, and decreasing the level of triglycerides in plasma.

Effects of Portulaca Oleracea L. Extract on Lipolysis and Hormone Sensitive Lipase (HSL) Gene Expression in 3T3-L1 Adipocytes

This study was performed to investigate the lipolytic effects of Portulaca oleracea L. extract in 3T3-L1 adipocytes. The Portulaca oleracea L. was extracted with extrusion method using twin-screw extruder under 58~60 rpm screw speed, 4~5 kg/hr feed rate, 140degrees C extrusion temperature. The lipolytic action of Portulaca oleracea L. extract was estimated by measuring the amount of glycerol and free fatty acids (FFA) released from 3T3-L1 adipocytes and by measuring the cellular lipid content in 3T3-L1 adipocytes. The hormone sensitive lipase (HSL) mRNA level was analyzed using quantitative real-time PCR. The Portulaca oleracea L. extract at 1 to 100 microgram/ml suppressed lipid accumulation. The release of glycerol and FFA into the medium, and the mRNA level of HSL were significantly increased by the addition of Portulaca oleracea L. extract at dose-dependent manner. In conclusion, the Portulaca oleracea L. extract was suggested to have the lipolytic effect through release of lipolytic products (FFA and glycerol) of triacylglyceride to the culture medium and suppression of lipid accumulation via up-regulation of HSL gene expression in 3T3-L1 adipocytes.