[Deletion of CD36 gene ameliorates glucose metabolism abnormality induced by high-fat diet and promotes liver lipid accumulation].

This study aimed to investigate the effects and the underlying mechanism of CD36 gene on glucose and lipid metabolism disorder induced by high-fat diet in mice. Wild type (WT) mice and systemic CD36 knockout (CD36-/-) mice were fed with high-fat diet for 14 weeks (n = 12). Mice were intraperitoneally injected with glucose (1 g/kg) or insulin (5 units/kg) to perform glucose tolerance test (GTT) or insulin tolerance test (ITT). Liver lipid deposition was observed by HE staining, and the contents of total triglyceride (TG), free fatty acid (FFA), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the serum were determined by automatic biochemical analyzer. Real-time PCR and Western blot were used to detect insulin signaling pathways in liver and muscle tissues of mice. The mRNA levels of genes encoding phosphoenolpyruvate carboxykinase (PEPCK) in primary hepatocytes of mice were detected by real-time PCR, and glucose detection kit was used to detect gluconeogenesis. Co-immunoprecipitation (Co-IP) and ELISA were used to detect insulin receptor ß (IRß) tyrosine phosphorylation in mouse muscle. Real-time PCR and immunofluorescence staining (IF) were used to detect the expression and location of glucose transporter 4 (GLUT4) in muscle of mice. After high-fat diet feeding, serum FFA, TG, AST and ALT levels of CD36-/- mice were significantly higher than WT mice (P < 0.05). The appearance of CD36-/- mouse liver presented fatty degeneration, and HE staining results showed increased lipid accumulation in the liver, suggesting that CD36 knockout promoted the occurrence of fatty liver. However, CD36-/- mice showed decreased fasting glucose levels, increased glucose tolerance, and decreased insulin tolerance compared with WT mice (P < 0.05), suggesting that CD36 knockout protects against the abnormal glucose metabolism induced by high-fat diet. Compared with WT mice, there was no significant difference in insulin signaling pathway in CD36-/- mouse liver, and there were no significant differences in PEPCK expression and gluconeogenesis between the two groups of primary hepatocytes. In muscle tissue, Co-IP and ELISA experiments showed that the phosphorylation level of IRß tyrosine was significantly increased in CD36-/- mice compared with that in WT mice. Besides, the levels of p-AKT in CD36-/- mouse muscle were significantly increased (P < 0.05). At the same time, IF experiment indicated that GLUT4 localization in cell membrane was enhanced in the muscle of CD36-/- mice, indicating that insulin sensitivity and glucose utilization ability were enhanced in CD36-/- mouse muscle. The results suggested that deletion of CD36 gene increased lipid accumulation in liver of mice with high-fat diet, but had no significant effect on liver gluconeogenesis. CD36 deficiency improves the abnormal glucose metabolism in mice with high-fat diet mainly through improving insulin sensitivity of muscle tissue and promoting GLUT4-mediated glucose utilization.

[Lipopolysaccharide inhibits lipophagy in HepG2 cells via activating mTOR pathway].

This study aimed to investigate the effect of lipopolysaccharide (LPS) on lipophagy in hepatocytes and the underlying mechanism. Human hepatoma cell line HepG2 was cultured in vitro, treated with 0.1 mmol/L palmitic acid (PA), and then divided into control group (0 µg/mL LPS), LPS group (10 µg/mL LPS), LPS+DMSO group and LPS+RAPA (rapamycin, 10 µmol/L) group. Lipid accumulation in hepatocytes was observed by oil red O staining. The autophagic flux of the cells was assessed using confocal laser scanning microscope after being transfected with autophagy double-labeled adenovirus (mRFP-GFP-LC3). The level of intracellular lipophagy was visualized by the colocalization of lipid droplets (BODIPY 493/503 staining) and lysosomes (lysosome marker, lysosomal associated membrane protein 1, LAMP1). The expression levels of mammalian target of rapamycin (mTOR), phosphorylated mTOR (p-mTOR), ribosome protein subunit 6 kinase 1 (S6K1), p-S6K1, LC3II/I and P62 protein were examined by Western blot. The results showed that the number of red lipid droplets stained with oil red O was significantly increased in LPS group compared with that in control group (P < 0.001). Moreover, in LPS group, the number of autophagosomes was increased, while the number of autophagolysosomes and the colocalization rate of LAMP1 and BODIPY were significantly decreased (P < 0.05). Meanwhile, the ratios of p-mTOR/mTOR and p-S6K1/S6K1, the ratio of LC3II/LC3I and the protein expression of P62 were significantly increased (P < 0.05) in LPS group. Furthermore, compared with LPS+DMSO group, RAPA treatment obviously reduced the number of lipid droplets and autophagosomes, and raised the number of autophagolysosomes and the colocalization rate of LAMP1 and BODIPY (P < 0.05). In conclusion, the results demonstrate that LPS inhibits lipophagy in HepG2 cells via activating mTOR signaling pathway, thereby aggravating intracellular lipid accumulation.

High-Fat Diet Induces Distinct Metabolic Response in Interleukin-6 and Tumor Necrosis Factor-α Knockout Mice.

Studies suggest interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) may be beneficial in obesity-related disorders with inconsistent results. This study was designed to investigate and compare their pathophysiological roles in lipid metabolism with gene knockout approach. Male wild-type (WT), IL-6 knockout (IL-6-/-), and TNF-α knockout (TNF-α-/-) mice were maintained on either a chow diet or a high-fat diet (HFD) for 12 weeks. Indices of lipid metabolism in blood, adipose, and liver were determined. Our data showed that IL-6-/- and TNF-α-/- mice were more pronounced in body weight gains, hypercholesterolemia, fasting and post-load hyperglycemia on a chow diet or a HFD compared with WT mice. In WT mice feeding on a HFD, lipolysis and glyceroneogenesis were enhanced, lipogenesis was inhibited in adipose tissue; lipogenesis was increased in liver tissue. IL-6-/- mice on a chow diet or a HFD showed similar metabolic phenotypes as WT mice on a HFD, since those mice had similar expression profiles of lipid-related genes in adipose tissue and liver. However, TNF-α-/- mice were different. Therefore, IL-6-/- and TNF-α-/- mice showed different hepatic triglyceride infiltration in response to different diets. Our study suggests that complete blockage of IL-6 and TNF-α is unbeneficial in obesity and obesity-related metabolic disorders in mice.

Pure Laparoscopic Liver Resection for Malignant Liver Tumor: Anatomic Resection Versus Nonanatomic Resection.

BACKGROUND: Laparoscopic liver resection (LLR) has been considered to be safe and feasible. However, few studies focused on the comparison between the anatomic and nonanatomic LLR. Therefore, the purpose of this study was to compare the perioperative factors and outcomes of the anatomic and nonanatomic LLR, especially the area of liver parenchymal transection and blood loss per unit area. METHODS: In this study, surgical and oncological data of patients underwent pure LLR procedures for malignant liver tumor were prospectively collected. Blood loss per unit area of liver parenchymal transection was measured and considered as an important parameter. All procedures were conducted by a single surgeon. RESULTS: During nearly 5 years, 84 patients with malignant liver tumor received a pure LLR procedure were included. Among them, 34 patients received anatomic LLR and 50 received nonanatomic LLR, respectively. Patients of the two groups were similar in terms of demographic features and tumor characteristics, despite the tumor size was significantly larger in the anatomic LLR group than that in the nonanatomic LLR group (4.77 ± 2.57 vs. 2.87 ± 2.10 cm, P = 0.001). Patients who underwent anatomic resection had longer operation time (364.09 ± 131.22 vs. 252.00 ± 135.21 min, P < 0.001) but less blood loss per unit area (7.85 ± 7.17 vs. 14.17 ± 10.43 ml/cm 2 , P = 0.018). Nonanatomic LLR was associated with more blood loss when the area of parenchymal transection was equal to the anatomic LLR. No mortality occurred during the hospital stay and 30 days after the operation. Moreover, there was no difference in the incidence of postoperative complications. The disease-free and overall survival rates showed no significant differences between the anatomic LLR and nonanatomic LLR groups. CONCLUSIONS: Both anatomic and nonanatomic pure LLR are safe and feasible. Measuring the area of parenchymal transection is a simple and effective method to estimate the outcomes of the liver resection surgery. Blood loss per unit area is an important parameter which is comparable between the anatomic LLR and nonanatomic LLR groups.

Silybin reduces obliterated retinal capillaries in experimental diabetic retinopathy in rats.

Silybin has been previously reported to possess anti-inflammatory properties, raising the possibility that it may reduce vascular damage in diabetic retinopathy. Present study was designed to investigate this potential effect of silybin and its underlying mechanisms in experimental diabetic retinopathy. Diabetes was induced with streptozotocin (STZ) plus high-fat diet in Sprague-Dawley rats, and silybin was administrated for 22 weeks after the induction of diabetes. Histochemical and immunofluorescence techniques were used to assess the obliterated retinal capillaries, leukostasis, and level of retinal intercellular adhesion molecule-1 (ICAM-1). Western blot was performed to quantitate the expression of retinal ICAM-1. Results showed that silybin treatment significantly prevented the development of obliterated retinal capillaries in diabetes, compared with vehicle treatment. In addition, leukostasis and level of the retinal ICAM-1 were found to decrease considerably in silybin-treated diabetic groups. In conclusion, these results indicate that silybin reduces obliterated retinal capillaries in experimental diabetes, and the recovered retinal vascular leukostasis and level of ICAM-1 at least partly contributes to the preventive effect of silybin.

[Effect of inflammatory stress on hepatic cholesterol accumulation and hepatic fibrosis in C57BL/6J mice].

OBJECTIVE: To investigate whether inflammatory stress exacerbates hepatic cholesterol accumulation and liver fibrosis using a C57BL/6J mouse model of chronic inflammation. METHODS: Twelve male C57BL/6J mice were given a high-fat diet (15.0% fat, 1.25% cholesterol, 0.5% cholic acid) and randomly assigned to the normal control group (n=6; subcutaneously injected with 0.5 mL of isotonic saline, every other day for 14 weeks) or the chronic inflammation model group (n=6; subcutaneously injected with of 0.5 mL of 10% casein, every other day for 14 weeks). At the end of week 14, the animals were sacrificed and blood was collected from the left ventricle for serological analysis of inflammatory markers and lipid profile, including serum amyloid A (SAA), interleukin-6 (IL-6), total cholesterol (TC) and free cholesterol (FC), low-density lipoprotein (LDL), and high-density lipoprotein (HDL)). Extracted liver tissues were divided for use in histological analysis (lipid accumulation and fibrosis evaluated by Oil Red O, Sirius red and Masson's trichrome staining) and quantitative fluorescence real-time PCR (to measure b-actin normalized expression of TNF-a MCP1, SREBP-2, LDLr, HMGCoA-r, ATF-6, GRP78, BMP-7, TGF-b, and collagens type I and type IV). Comparisons between groups were made by the two-samples t-test or Satterthwaite t-approximation test, collagen type I and type IV. RESULTS: Compared to the normal control group, the inflammation model group showed elevated serum IL-6 (12.55+/-4.75 vs. 32.41+/-7.42 pg/mL, P less than 0.01), reduced serum TC (14.82+/-1.56 vs. 10.62+/-0.48 mmol/L, P less than 0.01), up-regulated hepatic TNF-a mRNA expression (1.05+/-0.35 vs. 2.12+/-0.72, P less than 0.01), and elevated hepatic TC (12.10+/-2.57 vs. 23.21+/-8.75 mmol/L, P less than 0.05). In addition, the inflammation group showed abnormal lipid deposition, and increased and thickened reticular fibers. The livers of the inflammation group also showed up-regulated mRNA expression of SREBP-2 (normal control: 1.01+/-0.19 vs. 2.63+/-0.13, P less than 0.05), GRP78 (1.07+/-0.47 vs. 2.21+/-0.99, P less than 0.05), TGF-b (1.01+/-0.14 vs. 1.38+/-0.28, P less than 0.05), and collagen type I (1.02+/-0.27 vs. 1.71+/-0.51, P less than 0.05) and down-regulation of BMP-7 (1.01+/-0.15 vs. 0.55+/-0.25, P less than 0.01). CONCLUSION: Activation of the inflammatory system exacerbates hepatic cholesterol accumulation and hepatic fibrosis in C57BL/6J mice.

Activation of renin-angiotensin system is involved in dyslipidemia-mediated renal injuries in apolipoprotein E knockout mice and HK-2 cells.

BACKGROUND: Dyslipidemia and activation of renin-angiotensin system (RAS) contribute to the progression of chronic kidney disease (CKD). This study investigated possible synergistic effects of intrarenal RAS activation with hyperlipidemia in renal injuries. METHODS: Apolipoprotein knockout mice were fed with normal chow diet (control) or high fat diet (HF group) for eight weeks. Human proximal tubular epithelial cell line (HK-2) was treated without (control) or with cholesterol (30 µg/ml) plus 25-hydroxycholesterol (1 µg/ml) (lipid group) for 24 hours. The plasma lipid profile and RAS components were determined by clinical biochemistry assay and radiommunoassay, respectively. Collagen deposition in kidneys was evaluated by Masson-staining. The gene and protein expressions of molecules involved in RAS components and biomarkers of epithelial mesenchymal transition (EMT) were examined by real-time PCR, immunochemical staining, and Western blot. RESULTS: The mice fed with high-fat diet showed significant hyperlipidemia with collagen deposition in renal tubular interstitium compared to controls. The plasma levels of renin, angiotensin I, and angiotensin II were no difference in two groups. However, the kidneys of HF group showed up-regulated RAS components, which were positively associated with increased plasma levels of triglyceride, total cholesterol, and LDL. These effects were further confirmed by in vitro studies. Lipid loading induced HK-2 cells underwent EMT, which was closely associated with the increased expressions of intracellular RAS components. CONCLUSIONS: Local RAS activation was involved in hyperlipidemia-mediated renal injuries, suggesting that there are synergistic effects resulting from RAS activation with hyperlipidemia that accelerates the progression of CKD.

[Effect of RNAi-mediated silencing of SREBP2 gene on inflammatory cytokine-induced cholesterol accumulation in HepG2 cells].

OBJECTIVE: To investigate the effect of RNA interference (RNAi)-mediated silencing of the SREBP2 on inflammatory cytokine-induced cholesterol accumulation in HepG2 cells. METHODS: Short-hairpin (sh)RNA targeting SREBP2 or negative control (NC) shRNA were transfected into HepG2 cells by a liposomal method. G418-selective culturing was used to obtain the SREBP2 shRNA HepG2 and NC shRNA HepG2 cell lines. The two cell lines were cultured in serum-free medium and left untreated (control) or treated with TNF-a (20 ng/ml), low-density lipoprotein (LDL) loading (100 mug/ml), or a combination LDL plus TNF-a treatment. Lipid accumulation was evaluated by oil red O (ORO) staining. Intracellular cholesterol level was measured by enzymatic assay. The mRNA and protein levels of SREBP2 and its downstream target genes, LDL receptor (LDLr), and HMGCoA reductase, were measured by real-time PCR and Western blotting, respectively. RESULTS: SREBP2 shRNA HepG2 and NC shRNA HepG2 stable cell lines were successfully established. ORO staining and cholesterol quantitative analysis showed that LDL loading significantly increased intracellular cholesterol and that expression of SREBP2 further exacerbated the inflammatory cytokine-induced lipid accumulation, as seen in NC shRNA HepG2 cells. LDL loading of NC shRNA HepG2 decreased the gene and protein expressions of SREBP2, LDLr, and HMGCoA reductase, but the suppressive effect was overridden by inflammatory cytokine. SREBP2 shRNA HepG2 cells showed lower levels of cholesterol accumulation under LDL loading and inflammatory stress conditions. Moreover, the mRNA and protein levels of SREBP2, LDLr, and HMGCoA reductase were much lower than in NC shRNA HepG2 cells under the same conditions. CONCLUSION: Inflammatory cytokine exacerbated cholesterol accumulation in HepG2 via disrupting SREBP2. RNAi-mediated inhibition of SREBP2 expression significantly ameliorated the cholesterol accumulation induced by inflammatory cytokine.

Murine gamma herpes virus 68 infection promotes fatty liver formation and hepatic insulin resistance in C57BL/6J mice.

PURPOSE: Murine gamma herpes virus 68 (MHV68) is a naturally occurring mouse pathogen that is homologous to Epstein-Barr virus. This study was designed to determine the correlation between MHV68 infection and lipid accumulation and insulin resistance in livers of C57BL/6J mice, and to explore the underlying mechanisms. METHODS: C57BL/6J mice fed a high fat diet were randomly assigned to receive either MHV68 or phosphate buffered saline treatment. Insulin sensitivities were evaluated by glucose tolerance tests. Serum was analyzed for lipids and cytokines. Liver was taken for histology and lipid analysis. Quantitative RT-PCR and western blotting were used to measure expression of hepatic mammalian target of rapamycin (mTOR), ribosomal S6 kinase 1 (S6K1), insulin receptor substrate-1 (IRS-1), sterol regulatory element binding protein-1 (SREBP1), fatty acid synthase (FAS), and acetyl CoA carboxylase (ACC). RESULTS: MHV68 infection promoted fatty liver, hypertriglyceridemia, insulin resistance, and hyperinsulinemia in association with elevated inflammatory cytokines. In the livers of MHV68-infected C57BL/6J mice, SREBP1, FAS, ACC levels were increased. MHV68 infection also inhibited total IRS-1 expression and increased serine phosphorylation levels of IRS-1, which is parallel to the over activation of mTOR signaling pathway. Sirolimus, a specific inhibitor of mTOR pathway, inhibited MHV68-induced hepatic expression of serine p-IRS-1, increased total IRS-1 levels and improved MHV68-induced hepatic insulin resistance. CONCLUSION: In C57BL/6J mice, MHV68 infection promotes fatty liver formation and hepatic insulin resistance, which can be ameliorated by sirolimus.

[Effect of HBV on the expression of SREBP in the hepatocyte of chronic hepatitis B patients combined with hepatic fatty change].

To investigate the effect of HBV on the expression of Sterol regulatory element binding proteins( SREBP ) in the hepatocyte of patients with chronic hepatitis B (CHB) combined with hepatic fatty change. 55 cases diagnosed as CHB combined with hepatic fatty change in our department were selected and liver biopsies were carried out. The patients were dividied into 3 groups, group A: HBV DNA is less than or equal to 1000 copies/ml(15 cases), group B: 1000 copies/ml less than HBV DNA less than 100000 copies/ml (18 cases) and group C: HBV DNA is more than or equal to 100000 copies/ml (22 cases). 10 patients with HBV DNA in less than or equal to 1000 copies/ml after antiviral therapy with Nucleoside analogues were seen as group C1 (before treatment) and group C2 (after treatment) respectively; 12 patients with HBV DNA is more than or equal to 100000 copies/ml after antiviral therapy were classified as group C3 (before treatment) and group C4 (after treatment). Lipid droplets in the hepatic tissue were observed with oil red staining. Real time PCR were performed to detect the expressions of SREBP-1c and SREBP-2 mRNA in the liver. The protein expressions of SREBP-1c and SREBP-2 were detected with immunohistochemistry staining. Statistic data were analysed with SPSS11.5 software. (1) Red integrated optical densities (IOD) reflected by lipid drops in group A, B and C are 1004.27+/-218.63, 1937.01+/-401.47 and 4133.79+/-389.28 respectively, the degree of oil red O in each group was different (F = 385.69, P is less than to 0.01), which is increased as HBV DNA load increasing; Red IOD in group C1, C2 and C3, C4 are 4020.84+/-326.64, 1012.02+/-244.89, 4189.18+/-329.21 and 4121.76+/-304.09 respectively. Compared with group C1, the degree of oil red O in group C2 is decreased and the difference is statistically significant (t = 22.55, P is less than to 0.01); However, the difference of the degree of oil red O between group C4 and C3 is not statistically significant. (2) Compared with group A, the expressions of SREBP-1c mRNA in group B and C are raised by 1.218+/-0.130 and 1.798+/-0.118 times respectively, among group A, B, C, the expressions of SREBP-1c mRNA are statistically significant different ( F = 297.47, P is less than to 0.01). The expressions of SREBP-2 mRNA in group B and C are decreased by 0.956+/-0.118 and 0.972+/-0.153 times as compared to group A. However, the difference of SREBP-2 mRNA expression among the 3 groups is not statistically significant ( F = 0.568, P is more than to 0.05). Compared with group C1, SREBP-1c mRNA in group C2 is decreased by 0.714+/-0.081 folds (t=11.224, P is less than to 0.01), while SREBP-2 mRNA in group C2 is raised by1.034+/-0.155 times(t=0.692, P is more than to 0.05). SREBP-1c mRNA and SREBP-2 mRNA in group C4 are raised by 1.012+/-0.206 times and decreased by 0.998+/-0.183 times as compared to group C3 without difference found (t=0.196 or 0.031, P is more than to 0.05). (3) the expressions of SREBP-1c protein in group A, B and C are 36257.21+/-5709.79, 50413.47+/-4989.28 and 71025.83+/-6047.13 respectively, and the difference is statistically significant among the 3 groups (F = 178.26, P is less than to 0.01); the expressions of SREBP-2 protein in group A, B and C are 32913.52+/-3951.21, 32625.91+/-4025.06 and 34173.44+/-5316.25 respectively, but the difference is not statistically significant among the 3 groups ( F = 0.562, P is more than to 0.05), SREBP-1c protein levels in group C1, C2, C3, C4 are 69832.16+/-4941.36, 48735.47+/-5471.41, 70871.69+/-5083.14 and 68913.32+/-5343.22 respectively, the difference of SREBP-1c protein levels between group C1 and C2 is statistically significant (t=10.260, P is less than to 0.01); while the difference between group C3 and group C4 is not statistically significant(t=1.558, P is more than to 0.05). The expressions of SREBP-2 protein in group C1, C2, C3 and C4 are 33 980.21+/-4081.80, 34011.50+/-3859.27, 33610.12+/-4761.10 and 32915.66+/-5023.61 respectively, the difference of SREBP-2 protein levels in group C1 and group C2 is not statistically significant (t=0.038, P is more than to 0.05) and same result exists between group C3 and group C4 (t=0.459, P is more than to 0.05). HBV DNA may participate in the hepatic steatosis formation through interfering with the SREBP-1c expression.

[Inflammation enhances the accumulation of lipid in ApoE/SRA/CD36 KO mice liver].

OBJECTIVE: To investigate if inflammatory stress enhances liver lipid accumulation via SREBPs mediated dysregulation of low density protein receptor (LDLr) expression in apolipoprotein E, scavenger receptors class A and CD36 triple knockout (ApoE/SRA/CD36 KO) mice. METHODS: 16 Male ApoE/SRA/CD36 KO mice were subcutaneously injected with 0.5 ml 10% casein or PBS. The mice were fed a Western diet (Harlan, TD88137) containing 21% fat and 0.15% of cholesterol for 14 weeks. Animals were sacrificed and blood samples were collected. The serum amyloid A (SAA), IL-6, total cholesterol (TC), LDL and high density protein (HDL) were assayed. The lipid accumulation in liver was evaluated by Oil Red O staining. The mRNA and protein expression of SREBP-2, SREBPs cleavage activating protein (SCAP) and LDLr were analyzed by Real-Time Polymerase Chain Reaction (RT-PCR) and immunohistochemistry staining. RESULTS: Blood levels of SAA [(26.60+/-3.24) ng/ml vs (14.35+/-1.73) ng/ml, P < 0.01] and IL-6 [(36.37+/-2.20) pg/ml vs (18.02+/-4.87) pg/ml, P < 0.01] were higher, while TC [(7.72+/-1.70) mmol/L vs (13.23+/-3.61)mmol/L, P less than 0.01], LDL-cholesterol [(2.94+/-0.44) mmol/L vs (9.28+/-3.66) mmol/L, P less than 0.01] and HDL cholesterol [(2.24+/-0.63) mmol/L vs (4.13+/-0.42) mmol/L, P less than 0.01] were lower in inflamed mice compared to controls. ORO staining showed that lipid accumulation in the liver was more extensive in inflamed group despite lower blood lipid levels. Meanwhile, Real Time PCR data showed inflammation induced the expression of LDLr (4.56 fold), SCAP (3.14 fold) and SREBP-2 (14.72 fold) in liver. Immunohistochemical staining also indicated increased proteins expression in the liver, which was consistent with mRNA data. CONCLUSIONS: Inflammation causes lipid accumulation in liver via disrupting SREBP-2 and LDLr expression.

Mechanisms of dysregulation of low-density lipoprotein receptor expression in HepG2 cells induced by inflammatory cytokines.

BACKGROUND: Low-density lipoprotein (LDL) receptor is normally regulated via a feedback system that is dependent on intracellular cholesterol levels. We have demonstrated that cytokines disrupt cholesterol-mediated LDL receptor feedback regulation causing intracellular accumulation of unmodified LDL in peripheral cells. Liver is the central organ for lipid homeostasis. The aim of this study was to investigate the regulation of cholesterol exogenous uptake via LDL receptor and its underlying mechanisms in human hepatic cell line (HepG2) cells under physiological and inflammatory conditions. METHODS: Intracellular total cholesterol (TC), free cholesterol (FC) and cholesterol ester (CE) were measured by an enzymic assay. Oil Red O staining was used to visualize lipid droplet accumulation in cells. Total cellular RNA was isolated from cells for detecting LDL receptor, sterol regulatory element binding protein (SREBP)-2 and SREBP cleavage-activating protein (SCAP) mRNA levels using real-time quantitative PCR. LDL receptor and SREBP-2 protein expression were examined by Western blotting. Confocal microscopy was used to investigate the translocation of SCAP-SREBP complex from the endoplasmic reticulum (ER) to the Golgi by dual staining with anti-human SCAP and anti-Golgin antibodies. RESULTS: LDL loading increased intracellular cholesterol level, thereby reduced LDL receptor mRNA and protein expression in HepG2 cells under physiological conditions. However, interleukin 1 beta (IL-1 beta) further increased intracellular cholesterol level in the presence of LDL by increasing both LDL receptor mRNA and protein expression in HepG2. LDL also reduced the SREBP and SCAP mRNA level under physiological conditions. Exposure to IL-1 beta caused over-expression of SREBP-2 and also disrupted normal distribution of SCAP-SREBP complex in HepG2 by enhancing translocation of SCAP-SREBP from the ER to the Golgi despite a high concentration of LDL in the culture medium. CONCLUSIONS: IL-1 beta disrupts cholesterol-mediated LDL receptor feedback regulation by enhancing SCAP-SREBP complex translocation from the ER to the Golgi, thereby increasing SREBP-2 mediated LDL receptor expression even in the presence of high concentration of LDL. This results in LDL cholesterol accumulation in hepatic cells via LDL receptor pathway under inflammatory stress.

Establishment and assessment of two methods for quantitative detection of serum duck hepatitis B virus DNA.

AIM: To establish and assess the methods for quantitative detection of serum duck hepatitis B virus (DHBV) DNA by quantitative membrane hybridization using DHBV DNA probe labeled directly with alkaline phosphatase and fluorescence quantitative PCR (qPCR). METHODS: Probes of DHBV DNA labeled directly with alkaline phosphatase and chemiluminescent substrate CDP-star were used in this assay. DHBV DNA was detected by autoradiography, and then scanned by DNA dot-blot. In addition, three primers derived from DHBV DNA S gene were designed. Semi-nested primer was labeled by AmpliSensor. Standard curve of the positive standards of DHBV DNA was established after asymmetric preamplification, semi-nested amplification and on-line detection. Results from 100 samples detected separately by alkaline phosphatase direct-labeled DHBV DNA probe with dot-blot hybridization and digoxigenin-labeled DHBV DNA probe hybridization. Seventy samples of duck serum were tested by fluorescent qPCR and digoxigenin-labeled DHBV DNA probe in dot-blot hybridization assay and the correlation of results was analysed. RESULTS: Sensitivity of alkaline phosphatase direct-labeled DHBV DNA probe was 10 pg. The coincidence was 100% compared with digoxigenin-labeled DHBV DNA probe assay. After 30 cycles, amplification products showed two bands of about 180 bp and 70 bp by 20 g/L agarose gel electrophoresis. Concentration of amplification products was in direct proportion to the initial concentration of positive standards. The detection index was in direct proportion to the quantity of amplification products accumulated in the current cycle. The initial concentration of positive standards was in inverse proportion to the number of cycles needed for enough quantities of amplification products. Correlation coefficient of the results was (0.97, P<0.01) between fluorescent qPCR and dot-blot hybridization. CONCLUSION: Alkaline phosphatase direct-labeled DHBV DNA probe in dot-blot hybridization and fluorescent qPCR can be used as valuable means to quantify DHBV DNA in serum.

Assessment of a method for detecting serum HBV DNA with HBV DNA probe labelled directly by alkaline phosphatase.

OBJECTIVE: To assess a sensitive and specific technique for detecting serum HBV DNA with an HBV DNA probe labelled directly by alkaline phosphatase (AlkPhos Direc probe). METHODS: AlkPhos Direc probe was prepared with purified HBV DNA labelled directly by alkaline phosphatase. The probe and chemiluminescent substrate CDP-star for AP were used in hybridization assay. HBV DNA was detected by autoradiography on a film. The results of 80 samples were compared between the chemiluminescent dot blot hybridization assay with the AlkPhos Direc probe and another assay with the digoxigenin-labelled HBV DNA probe. The correlation of seventy-sample results of fluorescent quantitative HBV DNA PCR assay and dot blot hybridization assay with the AlkPhos Direc probe was analysed. RESULTS: The sensitivity of the AlkPhos Direc probe was 10 pg at least. The coincidence of the AlkPhos Direc probe was 100% compared with that of the digoxigenin-labelled HBV DNA probe. A correlation coefficient of HBV DNA quantitative results between fluorescent quantitative HBV DNA PCR assay and dot blot hybridization assay with the AlkPhos Direc probe was 0.98 (P<0.01). CONCLUSIONS: The method detecting HBV DNA in serum with the HBV DNA AlkPhos Direc probe is sensitive and specific. The results of the two assays with the AlkPhos Direc probe or with the digoxigenin-labelled HBV DNA probe are completely coincident. The correlation of HBV DNA quantitative results between fluorescent QPCR assay and dot blot hybridization assay with the AlkPhos Direc probe is satisfactory.