Intravenous but not intrathecal central nervous system-directed chemotherapy improves survival in patients with testicular diffuse large B-cell lymphoma

BACKGROUND

Testicular lymphoma is a rare malignancy affecting mainly elderly men, the majority representing diffuse large B-cell lymphoma (DLBCL). Its relapse rate is higher than that of nodal DLBCL, often affecting the central nervous system (CNS) with dismal prognosis.

PATIENTS AND METHODS

We searched for patients with testicular DLBCL (T-DLBCL) involvement from the pathology databases of Southern Finland University Hospitals and the Danish Lymphoma Registry. Clinical information was collected, and outcomes between treatment modalities were evaluated. Progression-free survival (PFS), disease-specific survival (DSS) and overall survival (OS) were assessed using Kaplan-Meier and Cox proportional hazards methods.

RESULTS

We identified 235 patients; of whom, 192 were treated with curative anthracycline-based chemotherapy. Full survival data were available for 189 patients. In univariate analysis, intravenous CNS-directed chemotherapy, and irradiation or orchiectomy of the contralateral testis translated into favourable PFS, DSS and OS, particularly among the elderly patients (each p ≤ 0.023). Intrathecal chemotherapy had no impact outcome. In multivariate analyses, the advantage of intravenous CNS-directed chemotherapy (hazard ration [HR] for OS, 0.419; 95% confidence interval [CI], 0.256-0.686; p = 0.001) and prophylactic treatment of contralateral testis (HR for OS, 0.514; 95% CI, 0.338-0.782; p = 0.002) was maintained. Rituximab improved survival only among high-risk patients (International Prognostic Index≥3, p = 0.019). The cumulative risk of CNS progression was 8.4% and did not differ between treatment modalities.

CONCLUSION

The results support the use of CNS-directed chemotherapy and prophylactic treatment of the contralateral testis in patients with T-DLBCL involvement. Survival benefit appears resulting from better control of systemic disease rather than prevention of CNS progression.

CD4⁺ and CD8⁺ regulatory T cells (Tregs) are elevated and display an active phenotype in patients with chronic HCV mono-infection and HIV/HCV co-infection

The aim of this study was to examine regulatory T cells (Tregs) in peripheral blood and liver tissue in patients with chronic hepatitis C virus (HCV) mono-infection and in patients with HIV/HCV co-infection. In a cross-sectional study were included 51 patients with chronic HCV infection, 24 patients with HIV/HCV co-infection and 24 healthy individuals. CD4⁺ and CD8⁺ Tregs were determined using flow cytometry. Fibrosis was examined by transient elastography. Inflammation, fibrosis and Tregs were determined in liver biopsies from 12 patients. Increased frequency of CD4⁺ and CD8⁺ Tregs was found in HIV/HCV co-infected patients [median: 6.4% (IQR: 5.7-6.9) and 1.0% (0.7-1.2), respectively] compared to HCV mono-infected patients [5.6% (4.2-6.3), P = 0.01 and 0.5% (0.3-0.7), P < 0.001, respectively]. Furthermore, HCV mono-infected patients had increased frequencies of Tregs compared with healthy controls (P < 0.05). However, no associations between the frequency of Tregs and fibrosis were found. Furthermore, characterization of CD4⁺ Tregs using CD45RA demonstrated a higher frequency of activated Tregs in both HCV mono-infected and HIV/HCV co-infected patients compared with healthy controls. Finally, number of intrahepatic Tregs was associated with both peripheral CD8⁺ Tregs and intrahepatic inflammation. In conclusion, HCV mono-infected patients and particularly HIV/HCV co-infected patients have increased the frequency of CD4⁺ and CD8⁺ Tregs compared with healthy controls. Furthermore, CD4⁺ Tregs in infected patients displayed an active phenotype. Tregs were not associated with fibrosis, but a positive correlation between intrahepatic Tregs and inflammation was found. Taken together, these results suggest a role for Tregs in the pathogenesis of chronic HCV infection.

Predictors of antiviral treatment initiation in hepatitis C virus-infected patients: a Danish cohort study

Predictive factors for initiation of antiviral therapy in chronically infected hepatitis C virus (HCV) patients are not fully elucidated. The aim of this study was to determine predictive factors for initiation of treatment with standard or pegylated interferon either alone or combined with ribavirin. A Danish cohort of individuals chronically infected with HCV was used and observation time was calculated from the date of inclusion in the cohort to date of death, last clinical observation, 1 January 2007, or start of HCV antiviral treatment in treatment-naïve patients. Kaplan-Meier survival analysis was used to construct time to event curves. Cox regression was used to determine the incidence rate ratios as estimates of relative risk (RR) and 95% confidence intervals (CI). A total of 1780 patients were enrolled in the study. The cumulative chance of treatment initiation over 5 years was 33.0%. We found several strong predictors of treatment initiation: elevated alanine aminotransferase [>2 times upper limit (RR = 2.17, 95% CI 1.64-2.87), >3 times upper limit (RR = 3.64, 95% CI 2.75-4.81)], genotype 2 or 3 (RR = 1.86, 95% CI 1.49-2.31) and HIV co-infection (RR = 0.28, 95% CI 0.15-0.53). To our knowledge, this study is the first to estimate factors predicting initiation of antiviral treatment in patients with chronic HCV infection on a nationwide scale. We found that several of the factors predicting initiation of antiviral treatment correlate with factors known to predict a better response to treatment and factors known to increase the progression of liver disease.

Comparison of diarrhea induced by ingestion of fructooligosaccharide Idolax and disaccharide lactulose: role of osmolarity versus fermentation of malabsorbed carbohydrate

Whether carbohydrate malabsorption causes diarrhea probably depends on the balance between the osmotic force of the carbohydrate and the compensatory capacity of the colon to dispose of the carbohydrate by bacterial fermentation. The present study evaluated the specific role of the osmolarity by comparing the severity of diarrhea after ingestion of two nonabsorbable carbohydrates, the fructooligosaccharide Idolax and the disaccharide lactulose. Both carbohydrates are readily fermented by the colonic flora but differ in osmolarity, the osmotic force being twice as high for lactulose as for Idolax. Twelve subjects were given increasing doses (0, 20, 40, 80, 160 g/d) of Idolax and lactulose in a crossover design. Every dose level was administered for three days with intervals of one week. Stools were collected on the third day to determine 24-hr volume, concentrations of short-chain fatty acids, L- and D-lactate, residues of Idolax or lactulose, sodium, potassium, pH, osmolarity, and in vitro productions of organic acids. Measured by short-chain fatty acid and lactate formation in a fecal incubation system, the fermentation of Idolax and lactulose was identical and very rapid compared with a range of reference carbohydrates. A laxative effect of both Idolax and lactulose was demonstrated. The increment in fecal volume as a function of the dose administered was twice as high for lactulose (slope of the regression line = 7.3, r = 0.64, P< 10(-5)) as for Idolax (slope = 3.7, r = 0.51, P<10(-3)), i.e., isosmolar doses of lactulose and Idolax had the same effect on fecal volume. The variation in fecal volume was substantial (lactulose 80 g/day: 110-1360 g/day; Idolax 160 g/day: 130-1440 g/day). High responders had earlier and larger fecal excretions of the saccharide compared with low-responders. Fecal volume in carbohydrate-induced diarrhea is proportional to the osmotic force of the malabsorbed saccharide, even though all or the majority of the saccharide is degraded by colonic bacteria. The capacity to modify the diarrhea varies considerably from person to person and is associated with colonic saccharide disposal, whereas the variation in response to isosmolar amounts of different saccharides is small within the same individual.

Lactulose, disaccharides and colonic flora. Clinical consequences

Lactulose is one of the most frequently utilised agents in the treatment of constipation and hepatic encephalopathy because of its efficacy and good safety profile. The key to understanding the possible modes of action by which lactulose achieves its therapeutic effects in these disorders lies in certain pharmacological phenomena: (a) lactulose is a synthetic disaccharide that does not occur naturally; (b) there is no disaccharidase on the microvillus membrane of enterocytes in the human small intestine that hydrolyses lactulose; and (c) lactulose is not absorbed from the small intestine. Thus, the primary site of action is the colon in which lactulose is readily fermented by the colonic bacterial flora with the production of short-chain fatty acids and various gases. The purpose of this review is to focus on some pertinent basic aspects of the clinical pharmacology of lactulose and to discuss the possible mechanisms by which lactulose benefits patients with constipation and hepatic encephalopathy.

Oxidation of short and medium chain C2-C8 fatty acids in Sprague-Dawley rat colonocytes

BACKGROUND

The predominant colonic short chain fatty acids, acetate, propionate, and butyrate, are oxidised into CO2 in colonocytes from rat and humans in the preferred order of butyrate (C4) > propionate (C3) > acetate (C2)- hence butyrate is considered to be the principal oxidative substrate for colonocytes.

AIMS

To compare colonocyte oxidation of valerate (C5), hexanoate (C6), and octanoate (C8) with that of butyrate.

METHODS

Isolated rat colonocytes were incubated in the presence of a concentration range of 1-14C labelled C2-C8 fatty acids. Oxidation rates were obtained by quantifying the production of 14CO2, and Vmax (maximum velocity) and K(m) (Michaelis-Menten constant) were calculated by computer fitting of the data to a Michaelis-Menten plot.

RESULTS

The K(m) value of acetate (0.56 (SEM 0.02) mmol/l) was about fourfold higher than the K(m) of butyrate (0.13 (0.01) mmol/l), whereas the K(m) values of valerate (0.19 (0.01) mmol/l), hexanoate (0.19 (0.01) mmol/l), and octanoate (0.16 (0.01) mmol/l) were of the same order of magnitude as the K(m) of butyrate. Acetate did not influence butyrate oxidation, whereas butyrate strongly inhibited the oxidation of acetate. By contrast, valerate, hexanoate, and octanoate inhibited colonocyte oxidation of butyrate equally or more than the reverse inhibitory effect of butyrate on valerate, hexanoate, and octanoate oxidation. The maximum rates of ATP production were in the order of valerate > octanoate = hexanoate > butyrate > acetate (28.47 (0.70), 21.78 (0.75), 21.33 (0.78), 16.12 (0.49), 9.09 (0.34) (mumol/min/g) respectively).

CONCLUSIONS

Valerate, hexanoate, and octanoate seem to be excellent substrates for colonocyte oxidation, similar to butyrate. These results may influence the choice of fatty acid composition in enemas used for treatment of patients in whom deficient colonocyte oxidation is suspected-for example, patients with ulcerative colitis and diversion colitis.

Colonic production of butyrate in patients with previous colonic cancer during long-term treatment with dietary fibre (Plantago ovata seeds)

BACKGROUND

Butyrate has antineoplastic properties against colorectal cancer cells and is the preferred oxidative substrate for colonocytes. Like acetate and propionate (short-chain fatty acids; SCFAs), butyrate is produced by colonic fermentation of dietary fibre.

METHODS

Twenty patients resected for colorectal cancer were treated with 20 g/day of the fibre Plantago ovata seeds for 3 months, which increased the intake of fibre by 17.9 +/- 0.8 g/day, from basal levels of 19.2 +/- 1.7 g/day; 17 patients completed the study. Faecal samples were obtained on eight occasions, twice before treatment, and monthly three times during and three time after treatment.

RESULTS

One month of fibre therapy increased faecal concentrations of butyrate by 42 +/- 12% (from 13.2 +/- 1.2 to 19.3 +/- 3.0 mmol/l; P < 10(-4)), acetate by 25 +/- 6% (P < 10(-4)), propionate by 28 +/- 9% (P = 0.01), and total SCFAs by 25 +/- 6% (P < 10 (-4)). Concentrations were increased during the 3-month fibre treatment but reversed to pretreatment levels within 1 to 2 months after cessation of fibre supplementation. The relative concentration (ratio) of butyrate was not altered owing to a simultaneous increase in acetate and propionate. Faecal pH decreased initially but was normalized after 2 months of fibre supplements. Fibre therapy increased the 24-h productions of butyrate by 47 +/- 10% (P < 10(-4)) and acetate by 50 +/- 7% (P < 10(-4)) in 16.6% faecal homogenates with added P. ovata seeds (20mg/ml), but SCFA productions returned to pretreatment levels after discontinuation of additional fibre intakes.

CONCLUSIONS

Oral intake of P. ovata seeds adapted the colonic flora to increase the production of butyrate (and acetate) from this fibre and increased faecal concentrations of butyrate by 42% in patients resected for colonic cancer. The effects depended on continuity of treatment.

Trichinella infection and clinical disease

Trichinellosis is caused by ingestion of insufficiently cooked meat contaminated with infective larvae of Trichinella species. The clinical course is highly variable, ranging from no apparent infection to severe and even fatal disease. We report two illustrative cases of trichinellosis. Returning to Denmark a few days after having eaten roasted pork in the Republic of Serbia, a female patient suffered from severe vomiting, epigastric pain, diarrhoea, and later myalgia, arthralgia, generalized oedema, and prostration. A biopsy showed heavy infestation with Trichinella spiralis, 2000 larvae/g of muscle. Life-threatening cardiopulmonary, renal and central nervous system complications developed. The patient recovered after several months. Her husband, who also ate the pork, did not have clinical symptoms, but an increased eosinophil count and a single larva in a muscle biopsy confirmed infection. The epidemiology, clinical manifestations, diagnosis, treatment and prevention of trichinellosis are reviewed.

Short-chain fatty acids in the human colon: relation to gastrointestinal health and disease

Fermentation, the process whereby anaerobic bacteria break down carbohydrates to short-chain (C2-C6) fatty acids (SCFAs), is an important function of the large bowel. SCFAs constitute approximately two-thirds of the colonic anion concentration (70-130 mmol/l), mainly as acetate, propionate, and butyrate. Gastroenterologists have, in spite of these facts, addressed this scientific field surprisingly late, in contrast to veterinarians, for whom the fermentative production of SCFAs has been acknowledged as a principal mechanism of intestinal digestion in plant-eating animals for decades. Interest in the effects of SCFA production on the human organism has been growing rapidly in the last 10 years, because gastrointestinal functions and beneficial effects are associated with these acids. SCFAs are of major importance in the understanding of the physiological function of dietary fibre and their possible role for colonic neoplasia. SCFA production and absorption are closely related to the nourishment of the colonic mucosa and sodium and water absorption, and mechanisms of diarrhoea. Patients with severe malabsorption compensate by the fermentation of otherwise osmotic active saccharides to SCFAs, which are readily absorbed and used as energy fuels in the organism. SCFA production from dietary carbohydrates is a mechanism whereby considerable amounts of calories can be salvaged in short-bowel patients with remaining colonic function if dietary treatment is adjusted. SCFA enemas are a new and promising treatment modality for patients with ulcerative colitis. The effect has been attributed to the oxidation of SCFAs in the colonocytes. An impressive number of papers have described the effects of butyrate on various cell functions, the significance of which is still unknown. Up until now, attention has been related especially to cancer prophylaxis and treatment. Diminished production of SCFAs appears to be involved in antibiotic-associated diarrhoea, diversion colitis, and possibly in pouchitis. The interaction between bacterial fermentation, ammonia metabolism, and bacterial growth and protein synthesis appears to be the main mechanism of action of lactulose treatment in hepatic coma. Pathological and extremely high rates of saccharide fermentation explain the severe deterioration in patients with D-lactate acidosis. Hence, this scientific field has come late to clinical working gastroenterologists, but as work is progressing the production of SCFAs in the large bowel becomes involved in several well-known intestinal disorders.

Kinetic studies on colonocyte metabolism of short chain fatty acids and glucose in ulcerative colitis

Short chain fatty acids (SCFAs) are potentially valuable as a topical therapy for distal ulcerative colitis. The mechanism of action is unknown but may involve improved intracellular energy production as previous evidence indicates that colonocyte oxidation of butyrate is impaired in ulcerative colitis. No information is, however, available on human mucosal metabolism of acetate and propionate in either health or disease or the Vmax and Km values of butyrate oxidation. The aim of the study was to assess the kinetic parameters, Vmax and Km, of the complete oxidation of short chain fatty acids and glucose by human colonocytes and to explore whether a metabolic abnormality could be confirmed in patients with ulcerative colitis. Colonocytes were isolated from surgical specimens obtained from 14 patients with ulcerative colitis and eight control subjects. Incubations were performed in the presence of a concentration range of 14C-labelled acetate, propionate butyrate, and glucose. Oxidation rates were obtained by quantifying the production of 14CO2. Vmax and Km were calculated by computer fitting of the data to a Michaelis-Menten plot. No significant differences were shown in either Vmax or Km values of any of the SCFAs or glucose comparing controls and patients with ulcerative colitis. Comparing the results obtained regarding the individual SCFAs, the most striking difference was the considerably lower Km value of butyrate. The apparent Vmax of acetate tended to be higher than Vmax of propionate and butyrate. Vmax of glucose oxidation was significantly lower compared with the Vmax values of SCFA oxidation. The study shows the ability of isolated human colonocytes to utilise each of the three major SCFAs, but does not support a pathogenic role for defective metabolism of butyrate in ulcerative colitis. The considerably lower Km of butyrate oxidation supports a specific role of butyrate as an energy source for the colonic mucosa in both health and ulcerative colitis.

Kinetic studies on the metabolism of short-chain fatty acids and glucose by isolated rat colonocytes

BACKGROUND/AIMS

Although the interest in colonic mucosal metabolism of short-chain fatty acids is steadily increasing, the kinetic parameters Vmax (maximum velocity) and Km (Michaelis constant) of the complete oxidation of these acids into CO2 by colonic epithelial cells have not previously been determined.

METHODS

Isolated rat colonocytes were incubated in the presence of a concentration range of 14C-labeled acetate, propionate, butyrate, and glucose. Oxidation rates were obtained by quantifying the production of 14CO2. Vmax and Km were calculated by computer-fitting of the data to a Michaelis-Menten plot.

RESULTS

The apparent Vmax values were similar comparing acetate, propionate, and butyrate (1.114 +/- 0.061, 0.991 +/- 0.072, and 1.007 +/- 0.070 mumol/min.g, respectively), but significantly lower for glucose (0.339 +/- 0.022 mumol/min.g). The corresponding Km values were all different and in the order of butyrate (0.184 +/- 0.017 mmol/L) < propionate (0.339 +/- 0.025 mmol/L) < acetate (0.487 +/- 0.019 mmol/L) < glucose (0.777 +/- 0.051 mmol/L). In substrate competition experiments, butyrate caused a strong noncompetitive inhibition of acetate oxidation and a mixed type of inhibition of propionate oxidation. Propionate inhibited the oxidation of acetate noncompetitively and that of butyrate competitively. Acetate only slightly inhibited the oxidation of propionate and butyrate.

CONCLUSIONS

Colonic epithelial cells seem to utilize short-chain fatty acids in a preferential order of butyrate > propionate > acetate. Oxidation of propionate or acetate, however, may provide the energy needed for cellular functions if the metabolism of butyrate is impaired or the luminal supply is limited.

Short-chain fatty acids, lactate, and ammonia in ileorectal and ileal pouch contents: a model of cecal fermentation

Fecal concentrations of total short-chain fatty acids were normal in 16 patients with ileorectal anastomoses (mean +/- SEM, 99.7 +/- 10.3 mmol/L) and 28 patients with ileal pouch-anal anastomoses (138.8 +/- 8.5 mmol/L) and did not differ from those in 14 healthy noncolectomized controls (130.7 +/- 12.6 mmol/L). Acetate:propionate:butyrate:isobutyrate+valerate+isovalerate ratios were similar in the ileorectum (71:12:12:5%) and in the colorectum (66:14:13:7%) of healthy noncolectomized controls, whereas the concentration of acetate was increased at the expense of the polypeptide-derived isobutyrate, valerate, and isovalerate in the ileal pouch (77:12:11:1%). Ammonia was accordingly significantly diminished in ileal pouch contents (28.8 +/- 3.2 mmol/L vs 45.2 +/- 4.1 mmol/L in controls) in contrast to concentrations in ileorectal contents (36.2 +/- 5.3 mmol/L). Concentrations of lactate were normal and low. Twenty-four-hour productions of total short-chain fatty acids in 16.6% fecal homogenates from both groups of patients were normal. Addition of saccharides (eg, glucose, starch, pectin, ispaghula husk) increased the production of acetate, propionate, and butyrate and decreased the production of ammonia and isobutyrate, valerate, and isovalerate, which was increased in homogenates with albumin added. This pattern of substrate fermentation was similar in homogenates from ileal pouch, ileorectum, and control colorectum. In conclusion, the concentrations of short-chain fatty acids, lactate, and ammonia indicate that ileorectal fermentation resembles normal colorectal fermentation in noncolectomized healthy individuals, whereas the fermentation in ileal pouch contents seems to be more carbohydrate predominated.(ABSTRACT TRUNCATED AT 250 WORDS)

Short-chain fatty acids in pouch contents from patients with and without pouchitis after ileal pouch-anal anastomosis

Fecal concentrations of short-chain fatty acids were markedly reduced in 6 patients with pouchitis (mean +/- SE, 56.2 +/- 13.3 mmol/L) compared with 28 patients without pouchitis (139.0 +/- 8.5 mmol/L; P less than 10(-3)). The ratios of acetate to propionate to butyrate were not changed (pouchitis, 75:12:11%; normal pouches, 76:12:11%), i.e., all acids were equally reduced. The 24-hour production of total short-chain fatty acids in 16.6% fecal homogenates from patients with pouchitis was decreased (17.5 +/- 5.3 mmol/L) compared with patients without pouchitis (33.3 +/- 3.4 mmol/L; P less than 0.05), which could be overcome by the addition of saccharides to the homogenates. Pouch excretions of saccharides were similar in the two groups, but dilution occurred during pouchitis because of the increased outputs. Concentrations and productions of short-chain fatty acids correlated with pouch concentrations and excretions of sodium and saccharides. L-Lactate was elevated in pouchitis outputs, but differences in stool culture counts, mucosal histology, fecal concentration, assimilation or production of ammonia, nitrogen excretion, pH, and osmolality were not found. Pouchitis is characterized by decreased fecal concentrations and productions of short-chain fatty acids possibly caused by low pouch concentrations of fermentable saccharides.

Colonic fermentation of ispaghula, wheat bran, glucose, and albumin to short-chain fatty acids and ammonia evaluated in vitro in 50 subjects

The production of short-chain fatty acids and ammonia was measured in 16.6% fecal homogenates from 50 subjects incubated at 37 degrees C for 6 and 24 hours. All 50 homogenates produced ammonia and short-chain fatty acids of any chain length (C2-C5). Incubation for 24 hours with dietary fiber (ispaghula husk or wheat bran), albumin, or glucose (10 mg/mL) increased the short-chain fatty acid production (43.6 +/- 2.8, 45.4 +/- 2.0, 60.3 +/- 3.2, and 65.8 +/- 3.1 mmol/L, respectively) compared with controls (21.4 +/- 1.3 mmol/L). The degradation of different substrates was associated with the production of different amounts of ammonia and short-chain fatty acids. Ispaghula, wheat bran, albumin, and glucose were fermented to acetate (> 2 mmol/L; 24-hour incubations) in 86%, 96%, 98%, and 98% of the homogenates, to propionate in 80%, 76%, 100%, and 68%, and to butyrate in 32%, 94%, 88%, and 54% of the homogenates, respectively. Isobutyrate, valerate, and isovalerate were produced from albumin in all (100%) of the homogenates, but only in 2 to 4% of the homogenates incubated with ispaghula or glucose. Ammonia was always (100%) produced after the addition of albumin and always (98%) consumed (assimilated) when glucose was fermented. Surgery (sigmoid or right- or left-sided colonic resection) did not change the pattern of ammonia and short-chain fatty acid production from these substrates. This study suggests that the different colonic flora from a large number of subjects share general biochemical characteristics, which metabolize different substrates to specific patterns of ammonia and short-chain fatty acids.

The colon in carbohydrate malabsorption: short-chain fatty acids, pH, and osmotic diarrhoea

Short-chain (C2-C6) fatty acids (SCFA) are the major anions in colonic contents and the result of anaerobic fermentation of mainly saccharides. The effects and regulation of saccharide fermentation were studied in vitro and in vivo. In vitro faecal incubation was used to study the effects of lactose, glucose, and galactose and of pH on SCFA formation. Changing the pH to below 5 or above 11 abolished SCFA formation in the faecal incubates; in the pH 5-9 interval SCFA production was high, with only minor pH dependence. Adding glucose, galactose, or lactose to the incubation system increased SCFA production, but at high saccharide concentrations (100-300 mmol/l) SCFA formation was inhibited by the pH change. In vivo disaccharide malabsorption with increasing doses of lactulose caused a decrease in faecal pH to less than 5, values inhibitory to fermentation, before the appearance of carbohydrate in faeces. In 6 of 12 volunteers diarrhoea occurred suddenly and was caused by malabsorbed non-fermented carbohydrate. The six other volunteers had a gradual increase in faecal output with lactulose dose and developed diarrhoea before the appearance of saccharide in faeces. The intake of lactulose tolerated before diarrhoea ensued varied between individuals, with the majority having diarrhoea of more than 11/day at 160 g lactulose per day. At this dose SCFA absorption was estimated to be in the range 550 to 1150 mmol/day.

Longitudinal study of influence of Helicobacter pylori on current risk of duodenal ulcer relapse. The Hvidovre Ulcer Project Group

Seventy-four patients with duodenal ulcer were followed up longitudinally for 2 years after initial ulcer healing. Endoscopy including biopsy of the antral mucosa was performed every 3rd month and whenever clinical symptoms of relapse occurred. The presence of Helicobacter pylori in the biopsy specimens was scored as 0 (none), 1 (sporadic occurrence), 2 (clusters), and 3 (numerous bacteria found diffusely in the mucus layer). The incidence rates of ulcer relapse per patient-month, grouped in accordance with these scores, were (with 95% confidence intervals) 0.073 (0.048-0.111), 0.083 (0.052-0.133), 0.123 (0.096-0.157), and 0.069 (0.041-0.116), respectively. No significant differences in incidence rates across H. pylori scores were observed when taking into account the observation period after healing of the first ulcer, number of ulcer recurrence (1st, 2nd, 3rd), sex, age, smoking habits, peak acid output, time of healing of the preceding ulcer, treatment of the present ulcer (cimetidine, antacids, or no treatment), or type and degree of gastritis. Thus, although H. pylori is prevalent in patients with duodenal ulcer disease, the present study indicates that H. pylori does not have a substantial note in the precipitation of active duodenal ulcer.

Fecal ammonia in patients with adenomatous polyps and cancer of the colon

The correlation between high intakes of protein and high incidence of human colonic cancer is unexplained. Appreciable amounts of ammonia are generated in the large bowel through bacterial degradation of proteins and peptides, and experimental studies indicate that ammonia may select for neoplastic growth. Fecal concentrations of ammonia did not differ among 17 patients with former colonic adenomas [40.6 +/- 4.5 (SE) mM], 17 patients with former colonic cancer (51.4 +/- 3.9 mM), and 16 healthy controls (46.4 +/- 6.1 mM). By use of an in vitro fecal incubation system, possible alterations in bacterial fermentation and formation of ammonia were investigated. Fecal suspensions were incubated for 6 and 24 hours with and without addition of fermentable substrates (ispaghula husk, wheat bran, albumin, and glucose; 10 mg/ml). The in vitro production of ammonia in unsupplemented fecal homogenates from both groups of patients was comparable with the production found in homogenates from healthy controls, and the response to fermentable substrates was similar in all three groups. Addition of albumin caused a marked increase in the production of ammonia, and addition of glucose increased bacterial assimilation of ammonia considerably. These well-known characteristics of bacterial metabolism of ammonia apparently did not differ between healthy individuals and patients investigated more than three months after colonoscopic polypectomy or colonic cancer resection.

Fermentation to short-chain fatty acids and lactate in human faecal batch cultures. Intra- and inter-individual variations versus variations caused by changes in fermented saccharides

The fermentation to short-chain fatty acids, lactate, and ammonia from several non-starch polysaccharides, glucose, and albumin was investigated in 16.6% faecal homogenates. Increasing concentrations (0-30 mg/ml) of glucose, wheat bran, pectin, ispaghula, cellulose, or albumin incubated for 24 h in homogenates pooled from three individuals increased short-chain fatty acid production linearly. Amounts and ratios of short-chain fatty acids formed were highly dependent on the type of substrate fermented. Fermentable saccharides increased ammonia assimilation, in contrast to the metabolic inert cellulose. Nine faecal homogenates sampled from three individuals at three occasions were incubated for 6 and 24 h. The production of total short-chain fatty acids, acetate, propionate, and butyrate and the accumulation of D- and L-lactate changed considerably in relation to the type of substrate added (cellulose, ispaghula, wheat bran, pectin, gum arabic, and glucose; p less than 10(-4)-10(-7). In contrast, there were no significant (p greater than 0.05) differences in organic acid formation between the nine homogenates, and the intra- and inter-individual variations were of the same magnitude. Variations in fermentation, when measured as organic acid formation, were therefore related to the type of substrate fermented rather than the individual tested.

Colonic fermentation to short-chain fatty acids is decreased in antibiotic-associated diarrhea

To elucidate the pathogenesis of antibiotic-associated diarrhea, colonic carbohydrate fermentation was investigated in three groups of subjects--a group of controls, a group of patients with antibiotic-associated diarrhea, and a group of patients receiving antibiotic therapy without diarrhea. Compared with controls, the colonic fermentation was markedly impaired in patients with antibiotic-associated diarrhea reflected by both very low concentrations (22.1 vs. 59.5 mmol/L; P less than 0.01) and production rates of short-chain fatty acids. In the group of patients without diarrhea, the effect on the colonic fermentation was dependent on the antibiotic administered. Penicillin and pivampicillin PO did not reduce the concentrations (69.9 and 66.7 mmol/L, respectively) or production rates. Dicloxacillin, erythromycin, and combined IV treatment with ampicillin, netilmicin, and metronidazole reduced both concentrations (27.1, 38.2, and 18.8 mmol/L; P less than 0.01) and production rates of short-chain fatty acids to levels seen in patients with diarrhea. L-Lactate and D-lactate concentrations were normal in all patients (less than 5 mmol/L), but lactate production was reduced in the patients who had reduced production of short-chain fatty acids, including patients with diarrhea. Thus, antibiotic-associated diarrhea was always related to reduced fecal concentrations and production rates of short-chain fatty acids and production rates of lactate. These results suggest that the antibiotic-associated diarrhea might be secondary to impaired colonic fermentation in otherwise disposed subjects, resulting in accumulation of luminal carbohydrate and/or decreased short-chain fatty acid-stimulated sodium and water absorption.

Serum levels of short-chain fatty acids in cirrhosis and hepatic coma

Short-chain fatty acids cause reversible coma in animals and may contribute to the pathogenesis of the hepatic coma in humans. The concentrations of short-chain fatty acids in peripheral venous blood were significantly elevated in 15 patients with hepatic encephalopathy caused by cirrhosis (362 +/- 83 mumol/L; mean +/- S.E.M.) compared with 17 cirrhotic patients without encephalopathy (178 +/- 57 mumol/L) and 11 normal individuals (60 +/- 8 mumol/L). However, no correlation between the depth of coma and the level of short-chain fatty acids was found after repetitive measurements in the coma group. Compared with normal individuals, all short-chain fatty acids, except valerate, were elevated in patients with hepatic encephalopathy, whereas only the concentrations of isobutyrate and isovalerate were significantly elevated in cirrhotic patients without encephalopathy. The concentrations of short-chain fatty acids in 21 nonencephalopathic cirrhotic patients who underwent catheterization were equally distributed in the aorta (187 +/- 56 mumol/L), the hepatic vein (212 +/- 75 mumol/L), the azygos vein (140 +/- 37 mumol/L) and the renal vein (135 +/- 43 mumol/L) compared with peripheral venous blood (178 +/- 57 mumol/L). This study does not support the idea that short-chain fatty acids are of major importance in the pathogenesis of hepatic coma in patients with cirrhosis.

Colonic fermentation of dietary fibre to short chain fatty acids in patients with adenomatous polyps and colonic cancer

Short chain (C2-C6) fatty acids are produced in the colon through bacterial fermentation of mainly dietary fibre. Butyrate (C4) possesses antineoplastic effects on human colon carcinoma cells, and epidemiological studies indicate that high fibre diets may reduce the incidence of colorectal cancer. The role of dietary fibre during colorectal carcinogenesis might therefore be related to its fermentation to butyrate. Faecal concentrations of total short chain fatty acids and concentrations and ratios of the individual C2-C6 fatty acids did not differ between 16 healthy controls, 17 patients with colonic adenomas, and 17 patients with colonic cancer. Comparison of the molar production velocities (mmol/l.hour) of total and individual short chain fatty acids from glucose, ispagula, wheat bran, and albumin in six and 24 hour faecal incubations showed no differences. The ratio of butyrate production to total short chain fatty acid production from fibre, however, was reduced in patients with colonic cancer and adenomas compared with healthy controls (ispagula, six hours: 6.4, 7.6, and 11.5% respectively, p = 0.005 and 24 hour: 9.1, 9.9, and 15.4%, p = 0.002; wheat bran, six hours: 9.9, 10.2, and 14.7% respectively, p = 0.06 and 24 hours: 15.1, 16.8, and 21.0%, p = 0.01). It may be that the low ratios of colonic butyrate formation combined with low fibre diets increase the risk of colonic neoplasia.

The degradation of amino acids, proteins, and blood to short-chain fatty acids in colon is prevented by lactulose

Short-chain (C2-C5) fatty acids account for 60%-70% of the anions in the colon. Acetate (C2) is nontoxic in contrast to C(3)4-C5 fatty acids (propionate, butyrate, isobutyrate, valerate, and isovalerate), which induce coma in animals and may be important in the pathogenesis of hepatic coma in humans. An in-vitro fecal incubation system was used to map out short-chain fatty acid production in the presence of lactulose, amino acids, albumin, or blood. Albumin and blood increased production of all C2-C5 fatty acids. In contrast, lactulose was converted to acetate only and increased fecal acidity. The degradation of amino acids, albumin, and blood to short-chain fatty acids was completely inhibited by 10-25 mM lactulose. This was caused mainly by the acidifying effect of lactulose. pH-independent inhibition of blood and amino acid degradation to short-chain fatty acids required concentrations of lactulose exceeding 50-100 mM. Thus, the effect of lactulose in the treatment of hepatic coma may be related to its rapid fermentation into organic acids at rates exceeding colonic buffering capacity. This probably reduces formation of toxic fatty acids and ammonia from amino acids, polypeptides, and blood in the colon.