Journal of Chinese Pharmaceutical Sciences
http://www.jcps.ac.cn
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Panax notoginseng saponins protect against chronic ethanolinduced hepatic steatosis Renbo Ding, Jiaolin Bao, Yiwei Cao, Chengwei He, Yitao Wang, Jianbo Wan * State Key Laboratory of Quality Research in Chinese Medicine, Institute of Chinese Medical Sciences, University of Macau, Macao 999078, China
Abstract: Chronic alcohol consumption induces hepatic steatosis, the early stage of alcoholic liver disease (ALD). The aim of present study is to investigate the protective effect of Panax notoginseng saponins (PNS) against chronic ethanolinduced hepatic steatosis in vivo. Mice were pairfed a modified LieberDeCarli liquid diet containing alcohol or isocaloric maltose dextrin as control diet with or without PNS (200 mg/kg, BW) for 8 weeks. Animals supplemented with PNS were protected against hepatic lipid accumulation induced by chronic ethanol exposure. Accordingly, PNS could significantly decrease the elevation of plasma triglyceride, plasma enzyme activities, i.e. alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and hepatic TNFα and IL6 levels which were induced by chronic alcohol exposure. In addition, PNS markedly reduced the lipolysis of white adipose tissue (WAT) that stimulated by alcohol feeding through the inhibiting protein expression of phosphorylation of hormonesensitive lipase (pHSL), rather than total HSL. Furthermore, alcohol exposure also enhanced fatty acid uptake capacity in liver by elevated hepatic CD36 expression, which could attenuated by PNS treatment. These results demonstrate that PNS supplementation protects against chronic ethanolinduced hepatic steatosis, which is associated with ameliorating dysfunctional lipid metabolism of WAT and the reduced inflammatory cytokines. Our findings suggested that PNS might be potential to be developed as an effective agent for the treatment of chronic alcoholic steatosis. Keywords: Alcoholic fatty liver, Panax notoginseng saponins, Lipolysis, Inflammation CLC number: R96
Document code: A
Article ID: 1003–1057(2014)6–361–08
1. Introduction Longterm excess alcohol consumption leads to fatty liver (hepatic steatosis), characterized by lipid droplet accumulation (mainly triglycerides, or TG) in hepatocytes [1] . Fatty liver was initially assumed to be a benign and reversible condition [2] . An increasing number of evidence has demonstrated that fatty liver is a potentially pathologic condition that may progress to the advanced stage of alcoholic liver disease (ALD), such as hepatitis, cirrhosis and hepatic carcinoma [1–3] . Despite severe health impact of hepatic steatosis, there is still no effective approach to reverse the pathogenesis and progression of hepatic steatosis, except alcohol abstinence [4] . However, for alcoholdependent patients Received: 20140422, Revised: 20140506, Accepted: 20140510. Foundation items: Research Committee of the University of Macau (Grant No. MYRG123ICMS12 and MYRG111ICMS13) and from Macao Science and Technology Development Fund (Grant No. 010/2013/A1). * Corresponding author. Tel.: +8533974873, Fax: +85328841358, Email:
[email protected] http://dx.doi.org/10.5246/jcps.2014.06.049
and for patients with severe forms of ALD, drug therapy is urgently needed. Root of Panax notoginseng (Burk.) F. H. Chen, also called as Sanqi in Chinese, is a highlyvalued medicinal herbs that has been traditionally applied to clinic for preventive and therapeutic purposes, especially for cardiovascular diseases and hepatic diseases, either alone or in combination [5] . Panax notoginseng is contained in several famous Chinese traditional formula, such as ‘‘Pian Zi Huang’’ which is used for the treatment of several types of hepatitis. Dammarane triterpene saponins are generally considered to be the major bioactive constituents in P. notoginseng [5,6] . An increasing number of in vivo and in vitro studies have demonstrated that P. notoginseng and its saponins exerted extensively beneficial effects on several systems, including hematological [7] , immune system [8] , cardiovascular system [9] , central nervous [10] and endocrine system [11] . In the present study, the effects of PNS on chronic ethanolinduced hepatic steatosis and its molecular mechanisms were investigated.
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2. Materials and methods
2.4. Determination of hepatic lipid accumulation
2.1. Animals
Hepatic lipid accumulation was qualitatively examined by hepatic histology and quantitatively determined by a Triglyceride Quantification Kit. For hepatic histology, liver cryostat sections (8 µm) were fixed with 4% phosphatebuffered paraformaldehyde, stained with Oil red O (SigmaAldrich, St. Louis, MO) and counterstained with hematoxylin (SigmaAldrich) using a standard technique. The stained sections examined and recorded by Olympus CX31 light microscopy with CCD camera (Olympus Crop. Tokyo, Japan). For the quantification of hepatic triglyceride level, 50 mg of liver tissue was homogenized in 450 μL of chloroform–methanol solution (2:1, v/v). After extraction for 24 h at 4 ºC, samples were added 500 μL phosphatebuffered saline then centrifuged at 2000 r/min for 15 min. The organic layer was removed to new tubes and dried under nitrogen. The resulting pellet was dissolved in 100 μL phosphatebuffered saline containing 1% Triton X100 and the triglyceride contents were determined by using a Triglyceride Quanti fication Kit (Beijing BHKT Clinical Reagent Co., Ltd, Beijing, China) according to the manufacturer’s protocol [12,13] . The plasma triglyceride levels of mice were also examined using the same kit. The value of hepatic triglyceride content was normalized to tissue weight and expressed as mg/g of liver.
C57BL/6 male mice, weighting 20–25 g, were obtained from Laboratory Animal Services Centre, The Chinese University of Hong Kong (Hong Kong, China). Mice were maintained on individually ventilated cage (IVC) system in a temperature and humiditycontrolled room ((22.5±0.5) °C, (50±5)% humidity) with a 12 h light dark cycle, and allowed free access to food and water. The animal studies were approved by Animal Ethics Committee, Institute of Chinese Medical Sciences, University of Macau (Approval No. AEC13002). 2.2. Liquid diet and PNS preparation Due to the tendency of animals given ethanol to reduce their solid food consumption, animals were fed with liquid diet. Liquid diets were based on the LieberDeCarli formulation and purchased from Trophic Animal Feed Hightech Co. Ltd. (Nantong, China). The LieberDeCarli ethanolcontaining diet consisted of 35% of total energy as fat, 18% as protein, 11% as carbohydrate, and 36% as ethanol. In the LieberDeCarli control diet, ethanol was replaced as isocaloric maltose dextrin. PNS was purchased from International Laboratory Inc. (San Francisco, CA) with the labeled purity of over 95%. PNS was dissolved in LieberDeCarli ethanol containing liquid diet. All the liquid diets are freshly prepared for the experiment. 2.3. Establishment of alcoholic fatty liver model After 7 d acclimation to liquid diet, all mice (eight week old) were randomly divided into three groups, e.g. control group, ethanol group and PNS treatment groups (200 mg/kg, BW). Each group contains 6 mice. Mice in either ethanol group or PNS treatment group were fed LieberDeCarli ethanolcontaining liquid diets with or without PNS supplement progressively. Specifically, ethanol was introduced at 12% of total energy in the diet for 2 d, 24% of total energy for the subsequent 2 d, and 36% of total energy thereafter. The control group animals were received the LieberDeCarli control liquid diet. After 8 weeks feeding, all mice were euthanized, and plasma, liver and epididymal fat were collected. The portion of tissues from the same lobe of liver in each mouse was embedded in OCT (Frozen tissue matrix) for histological analysis.
2.5. Plasma measure of hepatotoxicity Plasma biochemical markers, including alanine aminotransferase (ALT) and aspartate amino transferase (AST), are often used to indicate liver damage [14] . To examine the effect of PNS on ethanolinduced hepato toxicity, ALT and AST activities in the plasma were determined using commercial spectro photometric kits (Nanjing Jiancheng Bioengineering Institute, Nanjing, China) following the manufacturer’s protocol. 2.6. Assessment of adipose tissue lipolysis Lipolysis of epididymal adipose tissue was measured as free fatty acid released into the culture medium ex vivo at the different time points. Briefly, adipose tissue explants were washed in culture plates with prewarmed Dulbecco’s PBS containing 100 U/mL penicillin and 100 μg/mL streptomycin. After removing possible connective tissue and blood vessels, 30 mg of epididymal adipose tissue was transferred to 12well plates, cut into small pieces, and cultured in 2 mL Dulbecco’s
Ding, R.B. et al. / J. Chin. Pharm. Sci. 2014, 23 (6), 361–368
modified Eagle’s medium (DMEM) supplemented with Lglutamine (2 mM), penicillin (50 U/mL), strep tomycin (50 μg/mL), and 2% fatty acidfree bovine serum albumin. Free fatty acids released into the culture medium at the time points of 0, 1, 2 and 3 were determined by Fatty Acid Quantification Kit (Biovision, Milpitas, CA) according to its manufacturer's instructions [15,16] . Plasma free fatty acid was also measured using the same kit. 2.7. Measurement of hepatic cytokines Hepatic cytokines, including TNFα and IL6, were measured in 50 mg of liver tissue that had been homogenized in 450 μL PBS containing 0.5% Triton X100 and 1% protease inhibitors. After centrifugation at 12 000 g for 10 min, the levels of TNFα and IL6 in the supernatant were examined using Mouse TNFα ELISA MAX™ Standard kit and Mouse IL6 ELISA MAX™ Standard kit (BioLegend Inc., San Diego, CA), respectively, according to the manufacturer’s instructions [17] . The values were normalized to total protein, and expressed as pg/mg of protein.
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a polyvinylidene fluoride membrane and blocked with 5% nonfat dry milk in Trisbuffered saline with 0.1% Tween20. Then, the membrane was immunoblotted with primary antibody against HSL, PhosphoHSL, and GAPDH (Cell Signaling Technology, Inc., Danvers, MA) at 4 ºC for overnight. After washing, the membranes were incubated with antirabbit IgG (Cell Signaling Technology) at room temperature for 1 h, the bands were visualized using Amersham ECL Select Western Blotting Detection Reagent (GE Healthcare BioSciences., Piscataway, NJ) under a BioRad ChemiDoc™ XRS System (BioRad Laboratories, Hercules, CA). 2.10. Statistical analysis All values are expressed as mean±SD. Student’s ttest was used for betweengroup comparison using GraphPad Prism 5.0 software, and differences between groups were considered significant at P