Laxative effects of Salecan on normal and two models of experimental constipated mice

Zhou et al. BMC Gastroenterology 2013, 13:52 http://www.biomedcentral.com/1471-230X/13/52 RESEARCH ARTICLE Open Access Laxative effects of Salecan on normal and two models of experimental constipated mice Mengyi Zhou, Ping Jia, Jinping Chen, Aihui Xiu, Yue Zhao, Yibei Zhan, Peng Chen and Jianfa Zhang* Abstract Background: Constipation is one of the most common gastrointestinal complaints with a highly prevalent and often chronic functional gastrointestinal disorder affecting health-related quality of life. The aim of the present study was to evaluate the effects of Salecan on fecal output and small intestinal transit in normal and two models of drug-induced constipation mice. Methods: ICR mice were administrated intragastrically (i.g.) by gavage with 100, 200 and 300 mg/kg body weight (BW) of Salecan while the control mice were received saline. The constipated mice were induced by two types of drugs, loperamide (5 mg/kg BW, i.g.) and clonidine (200 μg/kg BW, i.g.), after Salecan treatment while the control mice were received saline. Number, weight and water content of feces were subsequently measured. Small intestinal transit was monitored by phenol red marker meal. Results: Salecan (300 mg/kg BW) significantly increased the number and weight of feces in normal mice. In two models of drug-induced constipation, Salecan dose-dependently restored the fecal number and fecal weight. The water content of feces was markedly affected by loperamide, but not by clonidine. Treatment with Salecan significantly raised the fecal water content in loperamide-induced constipation mice. Moreover, Salecan markedly stimulated the small intestinal transit in both loperamide- and clonidine-induced constipation model mice. Conclusions: These results suggest that Salecan has a potential to be used as a hydrophilic laxative for constipation. Keywords: Salecan, Constipation, Intestinal motility, Loperamide, Clonidine Background Constipation, defined as infrequent or difficult evacuation of feces [1], is a worldwide functional gastrointestinal disorder. A systematic review recorded prevalence rates in six different population groups from Asia ranging widely from 11.6% to 29.6% [2]. In general, constipation appears to be more common in the elderly, women, nonwhites, and persons in lower socio-economic and education classes [3]. Constipation also significantly impacts health-related quality of life in constipated people [4]. A primary mechanism for slow-transit constipation is a failure of peristalsis to move luminal contents through the colon results in more time for bacterial degradation of stool solids and more time for salt and water absorption, thus reducing stool frequency and stool weight dramatically [5]. Medical therapy for constipation contains traditional laxatives and agents. * Correspondence: Center for Molecular Metabolism, Nanjing University of Science & Technology, 200 Xiaolingwei Street, Nanjing 210094, China The former can induce defecation or modify stool consistency to make defecation easier, while the latter targets presumed defects in colonic neuromuscular function [5,6]. Although a common problem, the treatment of constipation has been far from satisfactory [7]. Beta-glucans, naturally occurring polysaccharides with poly-branched beta-(1→3)-D-glucans or beta-(1→6)-Dglucose side chains, are a major component of the bran of cereal plant and the cell wall of bacteria and fungi [8,9]. A number of studies demonstrate beta-glucans may be beneficial in gastrointestinal disease prevention and health promotion, including reduction of cholesterol absorption and bile acids excretion [10], fermentation by intestinal bacteria that yields short chain fatty acids [11], resistance to enteric bacterial and viral infections [12,13], stimulation autochthonous Lactobacillus populations in the colon [14], and prevention of colorectal cancer by effecting immune and cancer cells [15]. In addition, early observers suggest that a decreasing prevalence of constipation is © 2013 Zhou et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Zhou et al. BMC Gastroenterology 2013, 13:52 http://www.biomedcentral.com/1471-230X/13/52 associated with an increasing dietary fiber intake, depending on their ability to avoid digestion and absorption in small intestine and to escape bacterial metabolism in colon [16]. Cummings [17] has tabulated the efficacy of different fibers in terms of increased fecal weight per gram of administered fiber, including wheat bran, psyllium, cellulose, oats, corn, legumes, and pectin. Psyllium polysaccharide from Plantago ovate is approved by the FDA for its proven laxative effects as available fiber supplements [18,19]. Salecan, produced by Agrobacterium sp. ZX09, is a novel high molecular, water-soluble extracellular polysaccharide, and its structure is proven to consist of the following repeating unit:→3)-β-D-Glcp-(1→3)-[ β-D-Glcp-(1→3)-βD-Glcp-(1→3)]3-α-D-Glcp-(1→3)-α-D-Glcp-(1→ [20]. As a new beta-glucan with special molecular structure, its safety has been demonstrated in the acute and subchronic experiment [21]. Supplementation with Salecan reduced adiposity and improved glucose tolerance in high-fat dietfed mice through disturbing bile acid-promoted emulsification in intestine [22]. Its rheology study indicates that Salecan has a non-Newtonian viscosity behavior, and could be utilized in the food industry [23]. In the present study, we estimated the laxative effects of Salecan on fecal output and small intestinal transit in normal and two models of drug-induced constipation mice. Our results suggest that Salecan may be used as a hydrophilic laxative for constipation. Methods Salecan Salecan was prepared according to previous methods [20]. Briefly, Agrobacterium sp. ZX09 used in this study was isolated from a soil sample from the ocean coast of Shandong, China. Cultures were maintained on Htm agar containing NaH2PO4 (1 g) , KNO3 (3 g), CaCl2 (0.07 g), MgCl2 (0.2 g), FeSO4·7H2O (0.0125 g), MnSO4 (0.003 g), ZnCl2 (0.0075 g), sucrose (20 g), agar (9 g) and H2O (1000 ml), pH 7.2. A colony of the strain ZX09 was inoculated into a 250 ml flask containing 50 ml medium consisting of 2 % sucrose and mineral salt solution. The inoculated preparation was incubated at 28°C on a rotary shaker at 220 rpm for 24 h. A 0.5 ml portion was transferred to a 250 ml flask containing 50 ml fermentation medium. Fermentation was performed on a rotary shaker at 220 rpm for 48 h. The culture broth was diluted more than 3 times with de-ionized water and centrifuged at 12 000 × g for 30 min to separate cells from the supernatant. The supernatant was added to two volumes of 95 % ethanol. Productivity of Salecan was expressed in terms of the (...truncated)