Study On Salecan In Regulation Of Intestinal Physiology And Pathology

β-glucans are natural products, polymers of glucose that are ubiquitously found in the cell walls of fungi and plants as well as in bacterial products. More attention has been focused on β-(1,3)-D-glucans due to their unique and various biological activities, including body weight regulation, cholesterol-lowering effect, immune modulation, and antioxidant and antitumor activities. Salecan is a novel β-(1,3)-D-glucan that was obtained by our group recently, and it consists of the following repeating unit:→3)-β-D-Glcp-(1→3)-[β-D-Glcp-(1→3)-β-D-Glcp-(1→3)]3-α-D-Glcp-(1→3)-a-D-Glcp-(1→. Previous studies have demonstrated that salecan has excellent toxicological profile and rheological properties. And salecan also has multiple biological activities, including regulation of the postprandial rise in blood glucose, inhibition of pancreatic a-amylase-catalysed digestion of starch, and attenuation of acute liver injury induced by ethanol or carbon tetrachloride. The above facts suggest that salecan has a great potential for application in industries such as food and feed. The gut is an obvious target for the development of functional foods, acting as it does as the interface between diet and the metabolic events which sustain life. Thus, to developing its applications as a new functional food ingredient, it is necessary and meaningful to evaluate the effects of salecan in intestine.Using a mouse model fed with a western-type high-fat diet, which contains21%fat and0.15%cholesterol, we found that supplementation with3%or6%salecan improved high-fat diet-induced physiological changes. Mice fed with a high-fat diet supplemented with6%salecan had significantly lower body weight gain, percentage of body fat mass, parametrial white adipose tissue weight, plasma triglyceride (TG), total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C), and hepatic TG and TC (11.17%,53.12%,57.89%,30.74%,27.99%,43.50%,52.47%and44.03%, respectively, compared with those fed a high-fat diet). Daily food intake data revealed that supplementation with3%or6%salecan caused an obvious reduction of dietary food intake (22.31%and35.29%, respectively, compared with the high-fat diet-fed mice). Besides, salecan markedly elevated fecal TG in a dose-dependent manner that compared the high-fat diet-fed mice, fecal TG was increased1.31-fold in mice fed with a high-fat diet supplemented with3%salecan and0.46-fold in mice fed with a high-fat diet supplemented with6%salecan. These results indicate that salecan impacts intestinal fat absorption and reduces fat accumulation by controlling food intake and increasing fecal fat excretion. These findings suggest that salecan may represent a potential strategy against the high-fat diet-induced obesity.The study of the physical characteristics of salecan revealed that the viscosity of salecan solution at2%concentration was9500mPa-s, and salecan could hold9.7times its own weight of water, which meant that it had a good water holding capacity. The results from an in vivo study showed that a single gavage dose of salecan (300mg/kg) significantly increased the number and weight of8-h feces in normal mice without causing diarrhea (32.97%and26.83%, respectively). In both5mg/kg loperamide-and200μg/kg clonidine-induced constipation model mice,salecan dose-dependently promoted defecation in drug-induced constipated mice as evidenced by the increased fecal number and fecal weight (5.00-and16.33-fold, respectively, by300mg/kg salecan in loperamide-induced constipation model mice, and124.89%and79.17%, respectively, by300mg/kg salecan in clonidine-induced constipation model mice). The water content of feces was markedly affected by loperamide, but not by clonidine. Treatment with300mg/kg salecan significantly raised the fecal water content by10.39%in loperamide-induced constipated mice. Moreover, salecan had no ameliorating effects on gastric emptying, but markedly stimulated small intestinal transit in these two constipation models. In loperamide-and clonidine-induced constipation model mice, salecan at a dose of300mg/kg obviously increased small intestinal transit by88.29%and108.51%, respectively. The above results suggest that salecan stimulates intestinal peristalsis and promotes defecation due to its water holding capacity and swelling force, and has the potential to be used as a new, safe, effective and inexpensive hydrophilic laxative for constipation.After4weeks of treatment of3week-old mice with either8%cellulose or8%salecan, the following significant differences from the cellulose-treated mice were found in the salecan-treated mice:increased body weight gain by22.98%, greater mass of cecum and cecal contents by77.78%and45.56%, respectively, and higher butyrate concentrations in the cecal and colonic contents by132.84%and179.74%, respectively. As reflected using PCR-DGGE profiles, salecan changed the composition of the cecal microbial community in mice. qPCR confirmed that the populations of Lactobacillus and Bifidobacterium were increased3.12-and6.18-fold, respectively, in the cecal contents of mice consuming salecan. The above results suggest that the dietary incorporation of salecan, by increasing beneficial microbiota and providing SCFAs, may be beneficial in improving gastrointestinal health, and have relevance to the use of salecan as a dietary supplement for human consumption.Male mice were fed a diet containing0,4%or8%salecan for26days, and4%dextran sulphate sodium (DSS) was administered to induce ulcerative colitis (UC) during the last5 days of the experimental period. The results revealed that the dietary incorporation of salecan attenuated the severity of DSS colitis in a dose-dependent manner. A diet containing8%salecan lowered the disease activity index (52.38%), increased erythrocytes, hemoglobin and haematocrit (67.65%,66.80%and61.51%, respectively), decreased the DSS-induced colon shortening (17.15%), attenuated the degree of crypt distortion, goblet cells loss and colonic inflammation, and inhibited the increase in myeloperoxidase activity (46.94%). Further, qPCR analysis reflected that a diet containing4%or8%salecan inhibited the increase in the mRNA levels of colonic TNF-a by28.59%and56.36%, respectively, and up-regulated the mRNA levels of Dectin-1by1.49-and3.18-fold, respectively. These results suggest that the contribution of salecan to the reduction of colonic damage and inflammation in mice with DSS-induced colitis is associated with the down-regulation of TNF-a mRNA levels, which may derive from its ability to increase Dectin-1mRNA levels, and salecan holds promise as a new, effective and inexpensive nutritional supplement in the management of inflammatory bowel disease.In conclusion, salecan exhibits beneficial effects on the regulation of intestinal physiology and pathology. And our results have relevance to the application of salecan in food and feed industries.