Sylvia Keller

Prevention of colitis-associated carcinogenesis in a mouse model by diet supplementation with ursodeoxycholic acid

Bile acids in the intestinal lumen contribute to the homeostatic regulation of proliferation and death of the colonic epithelial cells: Deoxycholic acid (DCA) appears to enhance and ursodeoxycholic acid (UDCA) to attenuate the process of chemically induced carcinogenesis. We studied the effects of UDCA on colitis‐related colorectal carcinogenesis. Three groups of 25 mice were given 0.7% dextran sulphate in drinking water for 7 days and pure water for 10 days and were fed a standard diet containing double iron concentration. In 2 groups, the diet was supplemented with 0.2% cholic acid (CA), the precursor of DCA, or with 0.4% UDCA. After 15 cycles, the histology, the expression of MUC2, β‐catenin, p27 and p16 and the fecal water concentration of DCA and UDCA were investigated. All animals showed colitis with similar severity and histologic as well as immunophenotypic alterations, resembling those of human colitis. Among the animals fed the nonsupplemented diet, 46% developed colorectal adenocarcinomas and 54% anal‐rectal squamous cell carcinomas. The prevalence of dysplasia and carcinomas did not change significantly in the animals given CA. Among the mice fed with UDCA, none developed adenocarcinomas and 20% squamous carcinomas. Dysplastic lesions were found in 88%, 67% and 40% of each group, respectively. The prevalence of dysplasia as well as of carcinoma showed an inverse relationship to the UDCA concentration in the fecal water. These data indicate that UDCA suppresses colitis‐associated carcinogenesis. This model is suitable for investigation of the mechanism of the anticarcinogenic effect of UDCA in vivo.

Effects of Chenodeoxycholic Acid on the Secretion of Gut Peptides and Fibroblast Growth Factors in Healthy Humans

CONTEXT Recent evidence suggests bile acids (BAs) are involved in the glycemic control via TGR5 activation with the subsequent release of gut peptides and farnesoid X receptor activation with ensuing release of fibroblast growth factors (FGFs). OBJECTIVE We hypothesized that intraduodenal infusions of chenodeoxycholic acid (CDCA) would stimulate FGF and gut peptide secretion, thereby positively influencing glucose homeostasis. DESIGN, SETTING, PARTICIPANTS, AND INTERVENTION This randomized, double-blind, placebo-controlled, crossover trial included 12 healthy volunteers who received intraduodenal infusions (2.0 mL/min for 180 minutes) of saline, CDCA (5 or 15 mmol/L), and a fatty acid (sodium oleate), either alone or with 5 mmol/L CDCA. After 60 minutes, an oral glucose tolerance test (oGTT) was performed. MAIN OUTCOME MEASURES Plasma levels of glucagon-like peptide-1 (GLP-1), peptide tyrosine tyrosine, cholecystokinin (CCK), total BAs, FGF19, FGF21, C-peptide, insulin, glucose, and glucagon were measured. RESULTS Within the first 60 minutes, high-concentration CDCA induced a small but significant increase in GLP-1 and CCK secretion (P = .016 and P =.011), whereas plasma C-peptide, insulin, and glucose were not affected. Attenuated C-peptide and insulin release was observed after the oGTT with 15 mmol/L CDCA (P = .013 and P =.011). Plasma BA and FGF19 levels significantly increased after CDCA administration (P = .001 and P < .001). CONCLUSIONS CDCA modulates GLP-1 and CCK secretion; the effect is small and does not influence glucose levels. The marked increase in plasma BAs and the attenuated insulin release after the oGTT indicate the role of BAs in glycemic control, independent of the incretin axis, and suggest involvement of farnesoid X receptor activation pathways.

C57Bl/6 N mice on a western diet display reduced intestinal and hepatic cholesterol levels despite a plasma hypercholesterolemia

BackgroundSmall intestine and liver greatly contribute to whole body lipid, cholesterol and phospholipid metabolism but to which extent cholesterol and phospholipid handling in these tissues is affected by high fat Western-style obesogenic diets remains to be determined.MethodsWe therefore measured cholesterol and phospholipid concentration in intestine and liver and quantified fecal neutral sterol and bile acid excretion in C57Bl/6 N mice fed for 12 weeks either a cholesterol-free high carbohydrate control diet or a high fat Western diet containing 0.03% (w/w) cholesterol. To identify the underlying mechanisms of dietary adaptations in intestine and liver, changes in gene expression were assessed by microarray and qPCR profiling, respectively.ResultsMice on Western diet showed increased plasma cholesterol levels, associated with the higher dietary cholesterol supply, yet, significantly reduced cholesterol levels were found in intestine and liver. Transcript profiling revealed evidence that expression of numerous genes involved in cholesterol synthesis and uptake via LDL, but also in phospholipid metabolism, underwent compensatory regulations in both tissues. Alterations in glycerophospholipid metabolism were confirmed at the metabolite level by phospolipid profiling via mass spectrometry.ConclusionsOur findings suggest that intestine and liver react to a high dietary fat intake by an activation of de novo cholesterol synthesis and other cholesterol-saving mechanisms, as well as with major changes in phospholipid metabolism, to accommodate to the fat load.

Intestinal steroid profiles and microbiota composition in colitic mice

Reduced gut microbiota diversity in conjunction with a bloom of few bacterial species is a common feature in inflammatory bowel disease (IBD) patients. However, the environmental changes caused by inflammation and their possible impact on the microbiota are largely unknown. Since IBD is associated with an impaired intestinal steroid metabolism, we hypothesized that changes in intestinal steroid and particularly bile acid (BA) concentrations affect microbial communities. We used Interleukin-10 deficient (IL-10-/-) mice as a model for chronic gut inflammation. Healthy wild-type mice served as controls. In these animals, intestinal steroid concentrations and gut microbial diversity were analyzed at 24 weeks of age. The IL 10-/- mice developed moderate inflammation in cecum and colon and colorectal tumor formation was observed in 55 % of the animals. Compared to the healthy conditions, gut inflammation was associated with higher intestinal cholesterol and cholic acid concentrations and a reduced microbial diversity. The latter was accompanied by a proliferation of Robinsoniella peoriensis, Clostridium innocuum, Escherichia coli, and Enterococcus gallinarum. All these species proved to be highly bile acid resistant. We concluded that chronic colitis in IL-10-/- mice is associated with changes in intestinal steroid profiles. These changes may be due to alterations in gut microbiota composition or vice versa. Whether the bacterial sterol and bile acid metabolism is implicated in colitis and colorectal carcinoma etiology remains to be clarified.

Dietary crystalline common-, micro-, nanoscale and emulsified nanoscale sitosterol reduce equally the cholesterol pool in guinea pigs, but varying nanosystems result in different sterol concentrations in serosal jejunum

UNLABELLED Due to hypocholesterolemic effects, sitosterol is used in functional foods and nanoscale dispersions. To investigate the influence of dietary sitosterol on sterol concentrations in Dunkin Hartley guinea pigs, seven groups consisting of eight animals each were fed either a basal diet (BD), a high-cholesterol diet (HC) or a high-cholesterol diet supplemented with crystalline commonscale (CCS), microscale (CMS, low-dosed: CMLS), nanoscale (CNS) or emulsified nanoscale (ENS) sitosterol. When compared to HC group, all sitosterol formulations decreased liver cholesterol concentrations. No differences in cholesterol or sitosterol concentration were found in plasma and liver between CCS, CMS, CNS, and ENS groups. Apparent cholesterol digestibility decreased by increasing crystalline microscale sitosterol doses. Despite a lower sitosterol intake, ENS group had higher serosal sitosterol concentrations in jejunum than CNS group. To elucidate an impact of the sitosterol nanosystem on gut tissues further studies are necessary. FROM THE CLINICAL EDITOR In this study, the use of sitosterols in a rat model led to contradicting conclusions regarding their ability to reduce cholesterol levels efficiently in guinea pigs, suggesting that more preclinical data is needed before this method could become applicable to human studies.