Graeme P. Young

Effects of short chain fatty acids on a new human colon carcinoma cell line (LIM1215).

The effects of short chain fatty acids on a colon carcinoma cell line, LIM1215, have been studied. Of the four short chain fatty acids tested only butyrate at 1 mmol/l and 10 mmol/l and acetate at 10 mmol/l had significant effects on this cell line. The addition of butyrate to growth medium affected the growth rate and the production of alkaline phosphatase, dipeptidyl peptidase IV and carcinoembryonic antigen. Butyrate at a final concentration of 1 mmol/l increased the doubling time of the cells from 26 hours to 72 hours and decreased the cloning efficiency of the cells from 1.1% to 0.054%. Alkaline phosphatase concentrations increased rapidly in cells cultured in 1 mmol/l butyrate reaching peak levels after four days with alkaline phosphatase concentrations increasing more than six-fold. Levels of dipeptidyl peptidase IV and carcinoembryonic antigen were also increased after culture in butyrate containing medium. The number of alkaline phosphatase containing and dipeptidyl peptidase IV containing cells increased markedly in butyrate containing cultures. In contrast the number of mucus containing cells decreased in cultures grown in medium containing butyrate. This differentiating effect of butyrate on colon carcinoma cells may be relevant to the presence of butyrate in the colonic contents and the relationship between short chain fatty acids and fibre intake.

Antibiotic-associated colitis due to Clostridium difficile: Double-blind comparison of vancomycin with bacitracin*

A randomized double-blind study was carried out in patients with unresolving antibiotic-associated colitis due to Clostridium difficile, to compare the effect of bacitracin (80,000 U/day) with vancomycin (500 mg/day) on the resolution of symptoms, clearance of organism, and prevention of relapse. Forty-two patients with colitis, 9 of whom had a pseudomembrane, were randomized, 21 patients to each treatment group. The two groups were comparable in age, disease severity, and antibiotic exposure. For a 50% reduction in stool frequency the mean times (+/- SE) were 4.1 +/- 0.4 days for bacitracin and 4.2 +/- 0.4 days for vancomycin. Sixteen patients (76%) had symptom resolution after 7 days of treatment with bacitracin, compared with 18 patients (86%) given vancomycin. Patients who failed to respond were crossed over (blind) to the alternative antibiotic, but tended to be refractory to the alternative medication as well. Vancomycin-treated patients had negative toxin (83% vs. 53%, p = 0.04) and negative stool cultures (81% vs. 52%, p = 0.02) more frequently than did those patients given bacitracin. Similar numbers of patients in each group had symptomatic relapse during 1 mo of follow-up, but most of them relapsed yet again after blinded crossover therapy. Although bacitracin was significantly less effective than vancomycin in clearing C. difficile from the stools, both were of similar value in the control of symptoms in a group of patients with predominantly nonpseudomembranous colitis. In view of its low cost, bacitracin is a reasonable first-line alternative to vancomycin in the treatment of antibiotic-associated colitis.

Evaluation of new occult blood tests for detection of colorectal neoplasia

BACKGROUND Hemoccult II, the guaiac-based fecal occult blood test used in most colorectal cancer screening programs, has an unsatisfactory sensitivity for asymptomatic colorectal neoplasms. We evaluated the relative performance of four fecal occult blood tests, directed against various components of the hemoglobin molecule. METHODS All tests, Hemoccult II, HemoccultSENSA (a more sensitive guaiac test), HemeSelect (an immunochemical test specific for human hemoglobin), and HemoQuant (the heme-porphyrin assay), were performed by 107 patients with symptomatic colorectal cancer and 81 patients with predominantly asymptomatic adenoma. Hemoccult-SENSA and HemeSelect were performed by 1,355 screenees. RESULTS HemeSelect and Hemoccult-SENSA had significantly higher sensitivity for colorectal cancer (97% and 94%, respectively) than the other tests. HemeSelect had the highest sensitivity for adenomas; in 45 patients with large (> or = 10 mm) adenomas, sensitivity was 76% for HemeSelect, 60% for HemoccultSENSA, and 42% for both Hemoccult and HemoQuant. In the screenees, estimated specificity was 97.8% for HemeSelect and 96.1% for Hemoccult-SENSA. CONCLUSIONS HemeSelect and Hemoccult-SENSA have the highest levels of sensitivity for detection of colorectal neoplasia, but the immunochemical test HemeSelect provides the best combination of specificity and sensitivity.

Different Fibers Have Different Regional Effects on Luminal Contents of Rat Colon

The purpose of this study was to compare the effects of two highly fermentable fibers (oat brain and guar gum) with those of a less fermentable fiber (wheat bran) on the luminal environment of the large bowel. Rats were fed one of four diets containing either low fiber (2%), a highly fermented fiber (guar, 10%, or oat bran, 10%), or a medium fermented fiber (wheat bran, 10%). Short-chain fatty acids and pH showed a falling gradient along the large bowel with the low fiber, guar, and oat bran diets. However, wheat bran maintained total short-chain fatty acid levels in fresh feces at three times the levels seen with the other diets; both fecal butyrate concentrations and pH were maintained at cecal values in the distal large bowel. Thus, dietary fibers have differing effects on different regions of the luminal environment depending on their fermentability; it appears that slowly fermented fibers have a greater influence on the distal environment. Because butyrate is implicated as having an antitumor action, the variable effects of dietary fiber on tumorigenesis might be accounted for by its ability to influence distal large bowel butyrate concentrations.

Contrasting effects of butyrate on the expression of phenotypic markers of differentiation in neoplastic and non-neoplastic colonic epithelial cells in vitro

The in vitro effect of butyrate on expression of differentiation markers in colonic epithelial cells was assessed in the colon cancer cell line, LIM1215 and in epithelial cells isolated from a surgically resected histologically normal colon. Markers used to assess cell differentiation were: net glycoprotein synthesis ([3H]‐glucosamine uptake) expressed relative to net protein synthesis ([14C]‐leucine uptake), and the expression of the brush border glycoproteins (alkaline phosphatase and carcino‐embryonic antigen) in cell homogenates calculated relative to cellular protein content. In response to 24 h exposure to 1 mmol/L butyrate, all markers significantly increased in LIM1215 cells whereas they all significantly decreased in isolated colonic epithelial cells under identical culture conditions. Similar effects were seen at butyrate concentrations of up to 4 mmol/L. Butyrate suppressed proliferation of LIM1215 cells but had no consistent effect on [3H]‐thymidine uptake by, or DNA content of, normal epithelial cells. Additional experiments found no evidence of a toxic effect of butyrate at those concentrations nor of an alteration of cell responsiveness to butyrate due to the isolation process itself. In contrast to its differentiative effect on neoplastic cells, butyrate reduces the expression of phenotypic markers of differentiation in vitro in colonic epithelial cells from non‐neoplastic mucosa.

A controlled trial of cisapride in anorexia nervosa.

To determine the efficacy of cisapride, 10 mg three times daily, in improving gastric emptying, reducing distress during meals, and facilitating weight gain in anorexia nervosa, we conducted an 8-week, randomized, double-blind, placebo-controlled trial on 29 inpatients. Measures included scintigraphic gastric emptying studies at 0, 2, 4, and 8 weeks; subjective distress during meals measured by visual analogue scales; self-rating of degree of global improvement in symptoms associated with eating at end of study; and weight measured weekly. Gastric emptying improved significantly but equally in both groups over the study period. Yet subjective measures were better in the cisapride group; they rated themselves as more hungry (p = .02) and more improved on the global measure of change in symptoms (p = .02). Even so, the cisapride group did not gain more weight. The correlation between gastric emptying and weight gain was modest (r = .30; p = .11), and between gastric emptying and the subjective measures, virtually absent.

A comparative study of the influence of differing barley brans on DMH-induced intestinal tumours in male Sprague-Dawley rats.

The influence of barley brans on the incidence and burden of intestinal tumours in rats induced by 1,2‐dimethylhydrazine (DMH) was studied in a 7 month feeding experiment. The basic diet was American Institute of Nutrition (AIN) 76 modified by adjustment to 20% fat and 40% starch; brans were added so as to supply 5% dietary fibre. The barley brans studied were commercial barley bran (BB1; 13.0% dietary fibre) from the aleurone/subaleurone layer, outerlayer barley bran (BB2) including the germ (25.5% dietary fibre) and spent barley grain bran (SBG; a by‐product of the brewery and including the hull; 47.7% dietary fibre). They were compared with wheat bran (WB; 44% dietary fibre) and cellulose (or control; 98% dietary fibre). Commercial barley bran and wheat bran were most effective in reducing tumour incidence and burden. The incidence of tumours fell significantly from 70% (BB2) and 50% (SBG) to 10% (BB1) and 20% (WB) and tumour burden and tumour mass index (TMI) were also reduced by similar orders of magnitude. There were significantly higher short chain fatty acid (SCFA) concentrations in WB‐ and BBl‐fed rat faecal pellets relative to cellulose‐ and BB2‐fed rat faeces; butyrate, in particular, was affected. Regression analysis of butyrate against tumour incidence showed a trend (r=‐0.898; P=0.055), but the concentration of butyrate alone could not account for the reduction in tumour incidence observed. In a second experiment, when two brans (BB1 and SBG) were introduced after DMH dosing, there were higher incidences and burdens of tumours, indicating that protection by such brans was not as effective under these circumstances. Commercially available barley bran and wheat bran appear to significantly reduce tumour incidence and burden in this model relative to other brans, influencing both the initiatory as well as promotional stages of chemically induced carcinogenesis.

Catheter Sepsis during Parenteral Nutrition: The Safety of Long-Term OpSite Dressings

A prospective controlled study of the safety of various catheter dressing protocols was carried out in 168 patients receiving parenteral nutrition via an infraclavicular central venous catheter. Four protocols were compared: 36 patients received gauze dressings changed three times per week; 31 received OpSite dressings changed every 7th day (OpS-7), 32 received OpSite changed every 10th day (OpS-10), and 69 received OpSite changed twice weekly (OpS-ICU). Mean duration of parenteral nutrition was approximately 2 weeks and all groups were well matched except that OpS-ICU patients suffered more frequently from an acute illness. Catheter-related sepsis was identified by clinical signs of systemic sepsis, positive peripheral venous blood and catheter-tip cultures and/or defervescence of fever after catheter removal. Catheter-related sepsis rates were low in all groups: 1/36 for Gauze, 0/31 for OpS-7, 1/32 for OpS-10, and 2/69 for OpS-ICU. Septicemia attributable to causes apart from catheter sepsis occurred in two, two, three, and four patients, respectively. Bacterial colonization of skin beneath OpSite was no more common in the OpS-10 than in the other groups. Signs of inflammation at catheter insertion sites were common in all groups but did not relate closely to skin colonization. OpSite can be safely applied to central venous catheters inserted under strict aseptic conditions, even in patients with open septic drainage. Dressings can be left in place for 7 days with a margin of safety lasting to 10 days, thus saving on cost of materials and nursing time.

Colonic epithelium is diffusely abnormal in ulcerative colitis and colorectal cancer.

The hypothesis that the colonic epithelium is diffusely abnormal in ulcerative colitis was examined by comparing disease related responses in expression of markers of differentiation by colonic crypt cells to culture with and without butyrate. Cells were isolated from patients with normal colon (15), cancer (24), ulcerative colitis (19), or Crohns disease (16). Alkaline phosphatase activities were measured in cell homogenates and the rate of glycoprotein synthesis assessed at the end of 24 hours of culture and expressed relative to the rate of protein synthesis as the G:P ratio. Alkaline phosphatase activities, but not G:P ratios, differed across the groups before and after 24 hour culture (p < 0.05), activities being lowest in the cancer group and highest in inflammatory bowel disease groups. Butyrate (1 mM) suppressed alkaline phosphatase activities in the cancer group by mean (SEM) of 17 (4) (p = 0.006) compared with no change in the other groups. Butyrate suppressed G:P ratios only in the cancer (6 (3)%, p = 0.03) and ulcerative colitis groups (5 (3)%, p = 0.04) and the changes in both were different (p < 0.05) from those in normal cells (increase of 10 (7)%). Changes in ulcerative colitis were different from those in Crohns disease (p = 0.029). Responses were independent of the presence or absence of mucosal inflammation. These data confirm the diffuse nature of epithelial abnormalities in colorectal cancer. In ulcerative colitis, a different pattern of abnormality occurs, supporting the notion that the epithelium is also diffusely abnormal independent of mucosal inflammation.

Haem in the gut. I. Fate of haemoproteins and the absorption of haem

Haem (FeII‐protoporphyrin‐IX) is presented to the gut lumen as haemoproteins derived from exogenous (dietary) and endogenous (mucosal cell desquamation and bleeding) sources. Haemoproteins such as haemoglobin, myoglobin and catalase undergo hydrolysis by luminal proteases to release the haem. Released haem is maintained in a soluble form in the gut lumen by the products of haemoprotein digestion. Chelators of elemental iron do not bind haem‐iron and so haem‐iron is better absorbed than elemental iron. Haem‐iron does not exchange with luminal elemental iron. Mucosal uptake of haem is limited. Less than 10% binds to the brush border of the villus cell. Although the mechanisms by which haem binds to the brush border and is transported to the intracellular environment are poorly understood, it is known that some haem is transferred to secondary lysosomes where the porphyrin ring is split to release iron and form bilirubin. Depending upon the composition of the diet, the iron released from haem within the villus cell can be the major physiological source of iron. In iron‐deficiency in humans, absorption of haem‐iron can increase threefold whereas absorption of elemental‐iron can increase tenfold. These observations indicate that haem‐iron and elemental‐iron are absorbed via different mechanisms which are subject to different regulation. For haem‐iron to be absorbed, the haem itself must be taken up by the mucosa.