Berberine mitigates nonalcoholic hepatic steatosis by downregulating SIRT1-FoxO1-SREBP2 pathway for cholesterol synthesis / 中西医结合学报

OBJECTIVE@#To investigate effects of berberine (BBR) on cholesterol synthesis in HepG2 cells with free fatty acid (FFA)-induced steatosis and to explore the underlying mechanisms.@*METHODS@#A steatosis cell model was induced in HepG2 cell line fed with FFA (0.5 mmol/L, oleic acid:palmitic acid = 2:1), and then treated with three concentrations of BBR; cell viability was assessed with cell counting kit-8 assays. Lipid accumulation in cells was observed through oil red O staining and total cholesterol (TC) content was detected by TC assay. The effects of BBR on cholesterol synthesis mediators were assessed by Western blotting and quantitative polymerase chain reaction. In addition, both silent information regulator 1 (SIRT1) and forkhead box transcription factor O1 (FoxO1) inhibitors were employed for validation.@*RESULTS@#FFA-induced steatosis was successfully established in HepG2 cells. Lipid accumulation and TC content in BBR groups were significantly lower (P < 0.05, P < 0.01), associated with significantly higher mRNA and protein levels of SIRT1(P < 0.05, P < 0.01), significantly lower sterol regulatory element-binding protein 2 (SREBP2) and 3-hydroxy 3-methylglutaryl-CoA reductase levels (P < 0.05, P < 0.01), as well as higher Acetyl-FoxO1 protein level (P < 0.05, P < 0.01) compared to the FFA only group. Both SIRT1 inhibitor SIRT1-IN-1 and FoxO1 inhibitor AS1842856 blocked the BBR-mediated therapeutic effects. Immunofluorescence showed that the increased SIRT1 expression increased FoxO1 deacetylation, and promoted its nuclear translocation.@*CONCLUSION@#BBR can mitigate FFA-induced steatosis in HepG2 cells by activating SIRT1-FoxO1-SREBP2 signal pathway. BBR may emerge as a potential drug candidate for treating nonalcoholic hepatic steatosis.

Effect of Sulgidduk containing pine needle juice on lipid metabolism in high fat-cholesterol diet induced dyslipidemic rats / 한국영양학회지

PURPOSE: Dyslipidemia is a major risk factor for cardiovascular disease. Pine needles (Pinus densiflora seib et Zucc) are a traditional medicine used to treat dyslipidemia in clinical settings. This study examined the potential effects of sulgidduk, a Korean traditional rice cake containing pine needle juice to protect against dyslipidemia induced by a high-fat/sugidduk diet in a rat model. METHODS: Twenty one male Sprague-Dawley rats were divided randomly into three groups: normal control (NC), Sulgidduk diet (SD), Sulgidduk diet containing pine needle juice (PSD). The blood lipid levels, production of lipid peroxide in the plasma and liver, total cholesterol and triglyceride in the liver and feces, antioxidant enzyme activities in plasma and erythrocytes were measured to assess the effects of PSD on dyslipidemia. RESULTS: A high-fat/Sulgidduk diet induced dyslipidemia, which was characterized by significantly altered lipid profiles in the plasma and liver. The food intake was similar in the three groups, but weight gain and food efficiency ratio (FER) were reduced significantly in the PSD group compared to those in the SD group. The level of total cholesterol, LDL-cholesterol and TBARS in the plasma showed tendencies to decrease in the PSD group compared to those in the SD group. The levels of high-fat/Sulgidduk diet-induced sterol regulatory element-binding protein 2 (SREBP2) gene expression were reduced significantly in the PSD group. The supplementation of PSD reduced the hepatic triglyceride and total cholesterol levels significantly, and enhanced the fecal excretion of triglyceride and hepatic antioxidant enzyme activities compared to the SD group. CONCLUSION: These results suggest that the addition of 0.4% pine needle juice to Sulgidduk may be an alternative snack to control dyslipidemia.

Hypolipidemic effect of powder of Panax notoginseng and its mechanism / 中草药

Objective: To investigate the hypolipidemic effects of powder of Panax notoginseng (PPN) and explore its possible mechanism. Methods: Hyperlipidemic rats model was established, and orally given three dosages of PPN for 8 weeks. The levels of serum ALT, AST, TC, TG, and LDL-C were detected. The pathological changes of liver tissues were observed by H&E staining. Gene expressions of hepatic low density lipoprotein receptor (LDLR), SIRT1, and LXR-α were measured with RT-PCR analysis. Protein expression of SREBP-2 and SCAP was determined by Western blotting. Results: Three dosages of PPN significantly decreased serum ALT, AST, TC, TG, and LDL-C levels. Histological data indicated that PPN notably reduced liver injury and hepatic steatosis in hyperlipidemic rats. In molecular study, mRNA expression of hepatic LDLR and SIRT1 was up-regulated and LXR-α gene expression was down-regulated in PPN treated rats. Additionally, PPN significantly reduced protein expression of SREBP-2 and SCAP. Conclusion: The positive effect of PPN on hyperlipidemic rats may be related to the inhibition of cholesterol synthesis of PPN through the up-regulation of SIRT1 and down-regulation of LXR-α and SCAP/SREBP-2 signaling pathway. Additionally, PPN could up-regulate hepatic LDLR mRNA expression and improve uptake of LDL-C in circulation.

Effects of ingredients of Korean brown rice cookies on attenuation of cholesterol level and oxidative stress in high-fat diet-fed mice

BACKGROUND/OBJECTIVES: Owing to health concerns related to the consumption of traditional snacks high in sugars and fats, much effort has been made to develop functional snacks with low calorie content. In this study, a new recipe for Korean rice cookie, dasik, was developed and its antioxidative, lipid-lowering, and anti-inflammatory effects and related mechanisms were elucidated. The effects were compared with those of traditional rice cake dasik (RCD), the lipid-lowering effect of which is greater than that of traditional western-style cookies. MATERIALS/METHODS: Ginseng-added brown rice dasik (GBRD) was prepared with brown rice flour, fructooligosaccharide, red ginseng extract, and propolis. Mice were grouped (n = 7 per group) into those fed a normal AIN-76 diet, a high-fat diet (HFD), and HFD supplemented with RCD or GBRD. Dasik in the HFD accounted for 7% of the total calories. The lipid, reactive oxygen species, and peroxynitrite levels, and degree of lipid peroxidation in the plasma or liver were determined. The expression levels of proteins involved in lipid metabolism and inflammation, and those of antioxidant enzymes were determined by western blot analysis. RESULTS: The plasma and hepatic total cholesterol concentrations in the GBRD group were significantly decreased via downregulation of sterol regulatory element-binding protein-2 and 3-hydroxy-3-methylglutaryl-CoA reductase (P < 0.05). The hepatic peroxynitrite level was significantly lower, whereas glutathione was higher, in the GBRD group than in the RCD group. Among the antioxidant enzymes, catalase (CAT) and glutathione peroxidase (GPx) were significantly upregulated in the GBRD group (P < 0.05). In addition, nuclear factor-kappaB (NF-κB) expression in the GBRD group was significantly lower than that in the RCD group. CONCLUSIONS: GBRD decreases the plasma and hepatic cholesterol levels by downregulating cholesterol synthesis. This new dasik recipe also improves the antioxidative and anti-inflammatory status in HFD-fed mice via CAT and GPx upregulation and NF-κB downregulation. These effects were significantly higher than those of RCD.

Niacin accelerates LDL-C uptake in HepG2 cells via downregulation of PCSK9 / 中国药理学通报

Aim To explore the effects of niacin on LDL-C uptake and metabolism in HepG2 cells,and to clarify the functions of niacin in lipid-lowering and slo-wing the atherosclerosis process,thus to provide a sci-entific basis for niacin as a lipid-lowering drug in clini-cal development.Methods Oil red O staining was used to observe HepG2 cells after lipid uptake.Enzy-matic method was used to determine the content of in-tracellular free cholesterol (FC)and total cholesterol (TC).The LDLR levels on the surface of cell mem-brane were detected by immunofluorescence flow cy-tometer.The mRNA and protein expressions of LDLR, SREBP2 and PCSK9 were analyzed by qPCR and Western blot.Results The results of oil red O staining showed that the rate of oil red O-positive cells and the number of red lipid droplets were significantly in-creased in niacin group than control group.Niacin sig-nificantly increased the levels of TC and FC in HepG2 cells(P <0.05 ).What’s more,niacin significantly upregulated the expression of LDLR and significantly downregulated the protein expression of PCSK9,while it had no effect on the expression of SREBP2.Conclu-sion Niacin accelerates LDL-C uptake probably via downregulating the expression of PCSK9 and reducing the degradation of LDLR protein in HepG2 cells.

Effects of SIRT1 gene knock-out via activation of SREBP2 protein-mediated PI3K/AKT signaling on osteoarthritis in mice / 华中科技大学学报（医学）（英德文版）

This study investigated the effects of SIRT1 gene knock-out on osteoarthritis in mice, and the possible roles of SREBP2 protein and the PI3K/AKT signaling pathway in the effects. Mice were randomly divided into a normal group and a SIRT1 gene knock-out group (6 mice in each group). In these groups, one side of the knee anterior cruciate ligament was traversed, and the ipsilateral medial meniscus was cut to establish an osteoarthritis model of knee joint. The countralateral synovial bursa was cut out, serving as controls. The knee joint specimens were then divided into four groups: SIRT1control group (group A, n=6); SIRT1osteoarthritis group (group B, n=6); SIRT1control group (group C, n=6); SIRT1osteoarthritis group (group D, n=6). HE staining, Masson staining, Safranin O-Fast Green staining and Van Gieson staining were used to observe the morphological changes in the articular cartilage of the knee. Immunohistochemical staining was employed to detect the expression of SIRT1, SREBP2, VEGF, AKT, HMGCR and type II collagen proteins. SA-β-gal staining was utilized to evaluate chondrocyte aging. The results showed clear knee joint cartilage destruction and degeneration in the SIRT1osteoarthritis group. The tidal line was twisted and displaced anteriorly. Type II collagen was destroyed and distributed unevenly. Compared with the SIRT1osteoarthritis group and SIRT1control group, SIRT1 protein expression was not obviously changed in the SIRT1osteoarthritis group (P>0.05), while the expression levels of the SREBP2, VEGF and HMGCR proteins were significantly increased (P<0.05) and the levels of AKT and type II collagen proteins were significantly decreased (P<0.05). SIRT1 gene knock-out may aggravate cartilage degeneration in osteoarthritis by activating the SREBP2 protein-mediated PI3K/AKT signalling pathway, suggesting that SIRT1 gene may play a protective role against osteoarthritis.

Role of leptin on the expression of low density lipoprotein receptor.

Background & objectives: Leptin resistance oriented hyperleptinaemia is a common problem in obese subjects in association with hypercholesterolaemia. The most common target for hypercholesterolaemia is impaired low density lipoprotein receptor (LDLR). This study was carried out to investigate whether any alteration in LDLR expression could explain the occurrence of hypercholesterolaemia in the event of hyperleptinaemia. Methods: Expression of LDLR and SREBP2 (sterol regulatory element binding protein 2) were examined in HepG2 cells by RT-PCR and Western blotting. JAK2 inhibitor II was used to verify the effect of JAK-STAT (Janus Kinase-Signal Transducer and Activator of Transcription) pathway (common mediator for cytokine signaling). Co-localization of LDLR and insulin receptor (IR) was examined by confocal microscopy. Results: Leptin was found to reduce the expression of LDLR and its transcription factor SREBP2. On the other hand, a weak signal for stimulation of LDLR by leptin was noted to be mediated by JAK2 pathway. But the joint effect of the two signaling pathways kept LDLR only in depressed mode in presence of leptin. Confocal microscopy showed that LDLR made an intensively co-localized complex with insulin receptor in presence of leptin. Interpretation & conclusions: Our results show that though leptin stimulates LDLR expression very weakly through JAK-STAT signaling pathway, it mainly imposes inhibition on LDLR expression by inhibiting transcription factor SREBP2. The inter-association between LDLR and IR may be a reason to render LDLR functionally inactive in presence of leptin.

Biomarkers of hyperlipidemia cholesterol metabolism in hamster / 中国药理学通报

Aim To establish the hyperlipidemic model and ex-plore the mechanism of hypercholesterolemia in hamster. Meth-ods Hamsters were randomly divided into the control and model groups. The hamsters in the control group were fed with the standard chow and the model group were fed with the high fat di-et. Serum lipids and CYP7A1 activity were detected by enzymat-ic method. The molecular mechanism of cholesterol metabolism was investigated by real-time PCR. Results In comparison with the control group, the concentrations of serum TC, LDL-C, TG and hepatic TC, TG were significantly increased in the model group. The mechanism research showed that in hamsters fed with the high fat diet, the CYP7A1 activity and the mRNA expres-sions of hepatic LDL-R, SREBP-2, CYP7A1, LXRαwere down-regulated, the expression of hepatic FXR was up-regulated. Conclusion The hyperlipidemic model could be developed in hamsters fed with the high fat diet for 4 weeks. LDL-R, SREBP-2, CYP7A1, FXR and LXRαare the biomarkers of hypercholes-terolemia, and also the targets of hypolipidemic drugs.