Gerda Dusel

Effect of Short-Chain Fatty Acids on the Human Colonic Mucosa in Vitro

Fermentable dietary fiber components are known to stimulate colonic crypt proliferation. As these compounds are rapidly degraded to short-chain fatty acids (SCFAs) by the anaerobic microflora, the hypothesis was tested that this trophic effect of fiber may be mediated by SCFAs. Biopsies were taken from normal cecal mucosa of 45 individuals during routine colonoscopy. They were incubated for 3 hours with sodium salts of SCFAs at physiological concentrations (three SCFAs = acetate 60 mmol/L + propionate 25 mmol/L + butyrate 10 mmol/L; acetate 60 mmol/L; propionate 25 mmol/L; butyrate 10 mmol/L) or equimolar NaCl (control). Cell proliferation was measured autoradiographically by subsequent pulse labeling with [3H]thymidine (1 hour). The labeling index (number of labeled cells divided by the total number of cells) was computed for the crypt as a whole and for five equal crypt compartments (compartment 1 = crypt base, compartment 5 = crypt surface). Cecal crypt proliferation was raised significantly in all incubation experiments with SCFAs. Butyrate (10 mmol/L, increase + 89%) and propionate (25 mmol/L, + 70%) were as effective in stimulating proliferation as the combination of three SCFAs (+103%), although the effect of acetate (+31%) was minor. Increasing the butyrate concentration to 25 mmol/L or 60 mmol/L did not result in a further increase of cell labeling. SCFAs stimulated proliferation in the basal three crypt compartments only. An expansion of the proliferative zone to compartments 4 and 5 was not observed. SCFAs, especially butyrate and propionate, are luminal trophic factors for the cecal epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of fish oil on rectal cell proliferation, mucosal fatty acids, and prostaglandin E2 release in healthy subjects

BACKGROUNDnExperimental studies have indicated dietary fish oil as a protective agent in colon carcinogenesis. Prostaglandins have been suggested to be involved in this process. In the present study, the effects of fish oil on rectal cell proliferation (i.e., intermediate biomarker of cancer risk), mucosal membrane fatty acids, and prostaglandin E2 (PGE2) release were investigated in 12 healthy volunteers.nnnMETHODSnIn addition to a controlled basal diet, the test subjects received either fish oil (4.4 g omega-3 fatty acids/day) or corn oil supplements for two 4-week periods in a double-blind, crossover trial. Rectal cell proliferation was determined by bromodeoxyuridine immunohistochemistry and ornithine decarboxylase activity. After 2-hour incubation with bromodeoxyuridine, PGE2 concentration in the incubation medium was measured by radioimmunoassay. Mucosal membrane fatty acids were analyzed by gas chromatography.nnnRESULTSnBromodeoxyuridine labeling index (9.2% vs. 10.9%; P < 0.05), ornithine decarboxylase activity (19.7 vs. 36.4 pmol.mg protein-1.h-1; P < 0.005), and PGE2 release from rectal biopsy specimens (435.5 vs. 671.5 pg/mg wet tissue; P < 0.05) were significantly lower during the fish oil than the corn oil period, whereas membrane fatty acids were not statistically different.nnnCONCLUSIONSnThe results support the hypothesis that dietary fish oil may protect against colon cancer.

Effect of free glutamine and alanyl-glutamine dipeptide on mucosal proliferation of the human ileum and colon

BACKGROUND/AIMSnGlutamine (Gln) is considered a trophic factor for small intestinal epithelia, which is important during severe illness. Its use in parenteral nutrition is precluded by its instability, a problem that may be overcome by use of the stable dipeptide L-alanyl-L-glutamine (Ala-Gln). The hypothesis was tested that Gln or Ala-Gln may stimulate cell proliferation not only in the ileum but also in the proximal and distal colon and, thus, may contribute to the gut barrier function.nnnMETHODSnBiopsy samples from the normal human ileum, proximal colon, and rectosigmoid were incubated for 4 hours with Gln (2 mmol/L), Ala-Gln (2 mmol/L), and saline (control). Cells in S phase were labeled with bromodeoxyuridine. In longitudinal crypt sections labeled and quiescent cells were counted.nnnRESULTSnGln as well as Ala-Gln stimulated crypt cell proliferation in the ileum, proximal colon, and rectosigmoid colon. In ileal specimens, labeling was greater in the entire crypt, whereas in both colonic regions, the trophic effect was confined to the basal crypt compartments.nnnCONCLUSIONSnGln and Ala-Gln have trophic effects not only in the ileum, but also in the proximal and distal colon. This could be important during parenteral nutrition when mucosal atrophy may weaken the gut barrier.

Antagonistic effects of sulfide and butyrate on proliferation of colonic mucosa: a potential role for these agents in the pathogenesis of ulcerative colitis.

It has been shown that feces of patients with ulcerative colitis uniformly contain sulfate reducing bacteria. Sulfide produced by these bacteria interferes with butyrate-dependent energy metabolism of cultured colonocytes and may be involved in the pathogenesis of ulcerative colitis. Mucosal biopsies from the sigmoid rectum of 10 patients (no caner, polyps, inflammatory bowel disease) were incubated with either NaCl, sodium hydrogen sulfide (1 mmol/L), a combination of both sodium hydrogen sulfide and butyrate (10 mmol/L), or butyrate. Mucosal proliferation was assessed by bromodeoxyuridine labeling of cells in S-phase. Compared to NaCl, sulfide increased the labeling of the entire crypt significantly, by 19% (p < 0.05). This effect was due to an expansion of the proliferative zone to the upper crypt (compartments 3–5), where the increase in proliferation was 54%. Sulfide-induced hyperproliferation was reversed when samples were coincubated with sulfide and butyrate. The study shows that sodium hydrogen sulfide induces mucosal hyperproliferation. Our data support a possible role of sulfide in the pathogenesis of UC and confirm the role of butyrate in the regulation of colonic proliferation and in the treatment of UC.

Cytokine-activated degradation of inhibitory κB protein α is inhibited by the short-chain fatty acid butyrate

Abstract. Butyrate, a short-chain fatty acid, is generated by anaerobic fermentation within the colon. Clinical trials suggest that short-chain fatty acids ameliorate inflammation in ulcerative colitis. Nuclear factor (NF) κB, an inducible transcription factor that is activated in inflamed colonic tissue, is sequestered to the cytoplasm by its inhibitory IκB proteins. The anti-inflammatory effects of butyrate are associated with an inhibition of NF-κB nuclear translocation. To investigate the mechanism of NF-κB inhibition we examined the effects of butyrate on IκBα. Human adenocarcinoma cells (SW480, SW620, and HeLa229) were treated with butyrate for up to 48xa0h followed by tumor necrosis factor (TNF) α stimulation. NF-κB was detected by immunofluorescence staining with an antibody against its p65 subunit. Levels of IκBα and phosphorylated IκBα were determined by western blot. Stimulation with TNFα resulted in rapid phosphorylation and degradation of IκBα followed by NF-κB nuclear translocation. Butyrate pretreatment successfully inhibited NF-κB activation. Pretreatment of adenocarcinoma cells with butyrate is associated with inhibition of TNFα-mediated phosphorylation and degradation of IκBα and effective blocking of NF-κB nuclear translocation. The anti-inflammatory effects of butyrate may at least in part be mediated by an inhibition of IκBα mediated activation of NF-κB.

histological changes in the colonic mucosa following irrigation with short-chain fatty acids

Objectives: Short‐chain fatty acids (SCFAs) derived from bacterial fermentation of complex carbohydrates are preferred luminal nutrients of the colonic mucosa. Starvation of colonocytes through lack or impaired metabolism of luminal SCFAs may be a cofactor in the pathogenesis of ulcerative colitis. Design: A detailed histological evaluation of colonic biopsy specimens was performed in patients with active distal ulcerative colitis who were treated with rectal enemas containing a mixture of SCFAs, n‐butyrate alone or saline placebo. Together with light microscopic parameters of mucosal inflammation, the pattern of crypt cell proliferation (proliferating cell nuclear antigen) and the mucosal activity of factor XIII were assessed. Results: Butyrate reduced the density of polymorphonuclear leucocytes in the lamina propria (4 weeks: P = 0.063; 8 weeks: P = 0.091); other inflammatory parameters remained unchanged. Both butyrate and the SCFA mixture reduced significantly the number of proliferating cells in the upper 40% of crypts. Tissue factor XIII activity in active ulcerative colitis was significantly lower than in mucosa from normal colons; however, it was not affected by SCFA or butyrate irrigation. Conclusion: SCFAs and butyrate have a more marked effect on crypt cell proliferation than on parameters of inflammation in patients with active ulcerative colitis.

MISSING ANTI-PROLIFERATIVE EFFECT OF FISH OIL ON RECTAL EPITHELIUM IN HEALTHY VOLUNTEERS CONSUMING A HIGH-FAT DIET: POTENTIAL ROLE OF THE N-3

Several studies have indicated dietary fish oil (FO) as a protective agent in colon carcinogenesis. Rectal cell proliferation as an intermediate biomarker of cancer risk was shown to be reduced by dietary FO in patients with adenomatous polyps and healthy subjects consuming a low-fat diet. Because the synthesis of prostaglandins (PG) which seem to be involved in this process is dependent on the ratio of n-3:n-6 fatty acids in the diet, the present study was designed to investigate whether this FO effect is also detectable in volunteers eating a high-fat diet (50% of energy) with a low n-3:n-6 ratio of 0.25. Twelve healthy volunteers received in addition to a controlled basal diet either FO (4.4 g n-3 fatty acids/day) or corn oil supplements (double-blind, crossover) for two 4-week periods. No significant differences between the two study periods were found for rectal cell proliferation as assessed by bromodeoxyuridine immunohistochemistry and ornithine decarboxylase activity, as well as for mucosal PGE2 release and mucosal membrane fatty acid composition. The results emphasize the importance of dietary n-3:n-6 ratio in determining the effects of FO on rectal cell proliferation.

Effects of Deoxycholic Acid and Butyrate on Mucosal Prostaglandin E2 Release and Cell Proliferation in the Human Sigmoid Colon

BACKGROUNDnA high-fat, low-fiber diet resulting in increased excretion of fecal secondary bile acids is regarded as a major risk factor for colon cancer. Incubation of human colonic biopsies with the secondary bile acid deoxycholic acid (DCA) leads to hyperproliferation with expansion of the proliferative zone, ie, a biomarker of increased cancer risk. Antiproliferative effects on various colon cancer cell lines, however, were reported for butyrate (BUT), a fermentation product of dietary fiber.nnnMETHODSnIn the following in vitro study we incubated biopsies from the normal sigmoid colon of 12 patients (age 55.8 +/- 3.6 years) with 5 microM DCA or a combination of 5 microM DCA plus 10 mM BUT (DCA/BUT) and determined epithelial proliferation by bromodeoxyuridine immunohistochemistry. As a possible mediator for the DCA effects on colonic cell proliferation, mucosal prostaglandin E2 (PGE2) release into the incubation medium was measured by 125I-PGE2 radioimmunoassay.nnnRESULTSnIncubation with DCA alone revealed a significantly higher labeling index for the whole crypt (.17 vs .11, p < .01) and for the upper 40% of the crypt (.05 vs .01, p < .01) compared with DCA/BUT. Mucosal PGE2 release during DCA/BUT incubation showed a trend toward lower values compared with DCA incubation (357.07 vs 434.29 pg/mg per hour; p = .07).nnnCONCLUSIONnThe results indicate a normalization of DCA-induced hyperproliferation of colonic epithelium by butyrate that is not clearly mediated by PGE2. Considering that nutrition affects the luminal concentrations of DCA and butyrate, our findings may have implications for colonic carcinogenesis.

Effects of isomalt consumption on gastrointestinal and metabolic parameters in healthy volunteers

The polyol isomalt (Palatinit) is a well established sugar replacer. The impact of regular isomalt consumption on metabolism and parameters of gut function in nineteen healthy volunteers was examined in a randomised, double-blind, cross-over trial with two 4-week test periods. Volunteers received 30 g isomalt or 30 g sucrose daily as part of a controlled diet. In addition to clinical standard diagnostics, biomarkers and parameters currently discussed as risk factors for CHD, diabetes or obesity were analysed. Urine and stool Ca and phosphate excretions were measured. In addition, mean transit time, defecation frequency, stool consistency and weight were determined. Consumption of test products was affirmed by the urinary excretion of mannitol. Blood lipids were comparable in both phases, especially in volunteers with hyperlipidaemia, apart from lower apo A-1 (P=0.03) for all subjects. Remnant-like particles, oxidised LDL, NEFA, fructosamine and leptin were comparable and not influenced by isomalt. Ca and phosphate homeostasis was not affected. Stool frequency was moderately increased in the isomalt phase (P=0.006) without changes in stool consistency and stool water. This suggests that isomalt is well tolerated and that consumption of isomalt does not impair metabolic function or induce hypercalciuria. In addition, the study data indicate that isomalt could be useful in improving bowel function.

Effects of fish oil on fecal bacterial enzymes and steroid excretion in healthy volunteers: implications for colon cancer prevention.

Diet-induced changes in fecal excretion of secondary bile acids, certain neutral sterols, and bacterial enzyme activities are known to play a role in colon cancer development. Dietary fish oil (FO) has been implicated as a protective agent in colon carcinogenesis. In the present study, the effects of FO and corn oil (CO) on these fecal parameters were investigated in 24 healthy volunteers consuming a low- or a high-fat diet (30% or 50% of energy derived from fat). After four weeks of FO or CO supplementation (4.4 g of n-3 fatty acids/day), no significant differences were noted for fecal activities of beta-glucuronidase, beta-glucosidase, and sulfatase, nor was fecal bile acid excretion significantly affected by FO or CO consumption. However, daily excretion of the putative colon carcinogen 4-cholesten-3-one was significantly lower in the FO than in the CO period during low- and high-fat experiments. This may be another biochemical mechanism by which FO exerts its protective effect on colon cancer development.