Project description:Background and Aims: We have shown in several controlled rat and human infection studies that dietary calcium improves intestinal resistance and strengthens the mucosal barrier. Reinforcement of gut barrier function is also relevant for inflammatory bowel disease (IBD). Therefore, we investigated the effect of supplemental calcium on spontaneous colitis development in HLA-B27 transgenic rats, an experimental animal model of IBD. Methods: HLA-B27 transgenic rats were fed a purified high-fat diet containing either a low or high calcium content (30 and 120 mmol CaHPO4/kg diet, respectively) for almost 7 weeks. Inert chromium ethylenediamine-tetraacetic acid (CrEDTA) was added to the diets to quantify intestinal permeability by measuring urinary CrEDTA excretion. Relative fecal dry-weight was determined to quantify diarrhea. Colonic inflammation was determined histologically, and by measuring mucosal interleukin-1M-NM-2. In addition, colonic mucosal gene expression of individual rats was analyzed, using whole genome microarrays. Interesting results were verified by Q-PCR. Results: The high-calcium diet significantly prevented the increase in intestinal permeability and diarrhea with time in HLA-B27 rats developing colitis as compared to the low-calcium group. The histological colitis score and mucosal interleukin-1M-NM-2 levels were lower in high-calcium fed rats. Supplemental calcium prevented the colitis-induced increase in the expression of extracellular matrix remodeling genes (e.g. matrix metalloproteinases, procollagens and fibronectin), which was confirmed by Q-PCR. Conclusions: Dietary calcium inhibits colitis development in HLA-B27 transgenic rats. Calcium prevents the colitis-related increase in intestinal permeability, diminishes diarrhea, and lowers the inflammatory response in the mucosa, resulting in less extracellular matrix breakdown. Keywords: nutritional intervention Female HLA-B27/M-NM-22-microglobulin transgenic rats on an inbred Fisher 344 background (n=8 in experimental group and n=9 in control group) (Taconic Farms, Inc, Germantown, NY), 8-10 weeks old and with a mean body weight of 128 g at the start of the experiment, were housed individually in metabolic cages. Animals were kept in a temperature- and humidity-controlled environment and in a 12-h light-dark cycle. Rats were fed a purified M-bM-^@M-^XhumanizedM-bM-^@M-^Y Western diet which contained in the control situation (per kg): 200 g acid casein, 326 g corn starch, 174 g glucose, 160 g palm oil, 40 g corn oil, 50 g cellulose and 5.16 g CaHPO4.2H2O (corresponding to 30 mmol calcium/kg diet; Sigma-Aldrich, St Louis, MO). Vitamins and minerals (other than calcium) were added to all diets according to the recommendations of the American Institute of Nutrition 1993.17 The experimental diet contained more calcium (120 mmol calcium/kg diet) at the expense of glucose. All samples were individually labelled and hybridized (Cy5). Equal amounts of Cy3 cRNA of all animals were pooled to serve as standard reference pool.

Project description:There is increased interest in the potential protective role of dietary Ca in the development of metabolic disorders related to the metabolic syndrome. Ca-induced intestinal precipitation of fatty acids and bile acids as well as systemic metabolic effects of Ca on adipose tissue is proposed to play a causal role. In this experiment, we have studied all these aspects to validate the suggested protective effect of Ca supplementation, independent of other dietary changes, on the development of diet-induced obesity and insulin resistance. In our diet intervention study, C57BL/6J mice were fed high-fat diets differing in Ca concentrations (50 v. 150 mmol/kg). Faecal excretion analyses showed an elevated precipitation of intestinal fatty acids (2·3-fold; P < 0·01) and bile acids (2-fold; P < 0·01) on the high-Ca diet. However, this only led to a slight reduction in fat absorption (from 98 to 95 %; P < 0·01), mainly in the distal small intestine as indicated by gene expression changes. We found no effect on body-weight gain. Lipolysis and lipogenesis-related parameters in adipose tissue also showed no significant changes on the high-Ca diet, indicating no systemic effects of dietary Ca on adiposity. Furthermore, early gene expression changes of intestinal signaling molecules predicted no protective effect of dietary Ca on the development of insulin resistance, which was confirmed by equal values for insulin sensitivity on both diets. Taken together, our data do not support the proposed protective effect of dietary Ca on the development of obesity and/or insulin resistance, despite a significant increase in fecal excretion of fatty acids and bile acids. Keywords: Diet intervention study Nine-week-old mice were fed a high fat purified diet with a low calcium concentration of 50mmol/kg (LCa diet) or a high calcium concentration of 150mmol/kg (HCa diet) for 8 weeks. Body weight was recorded weekly and after 7 weeks of diet intervention an oral glucose tolerance test was performed. For microarray analysis, after 2 weeks of diet intervention, 6 mice per diet group were anaesthetized with a mixture of isofluorane (1.5%), nitrous oxide (70%) and oxygen (30%) and the small intestines were excised. Adhering fat and pancreatic tissue were carefully removed. The small intestines were divided in three equal parts along the proximal to distal axis (SI 1, SI 2 and SI 3) and microarray analysis was performed on pooled mucosal scrapings.

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Dietary calcium and prebiotics modulate gut microbiome changes in rats

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