Production of the gaseous signal molecule hydrogen sulfide in mouse tissues.

The gaseous molecule hydrogen sulfide (H(2)S) has been proposed as an endogenous signal molecule and neuromodulator in mammals. Using a newly developed method, we report here for the first time the ability of intact and living brain and colonic tissue in the mouse to generate and release H(2)S. This production occurs through the activity of two enzymes, cystathionine-gamma-lyase and cystathionine-beta-synthase. The quantitative expression of messenger RNA and protein localization for both enzymes are described in the liver, brain, and colon. Expression levels of the enzymes vary between tissues and are differentially distributed. The observation that, tissues that respond to exogenously applied H(2)S can endogenously generate the gas, strongly supports its role as an endogenous signal molecule.

A mixture of extracts of black and green teas and mulberry leaf did not reduce weight gain in rats fed a high-fat diet.

Tea extracts are used in many over-the-counter preparations claiming to promote weight loss. The rationale for this usage includes reports that green tea extract increases thermogenesis, and extracts of green and black tea and mulberry leaf inhibit the digestion/absorption of carbohydrate and fat. The investigators in this study tested the potential of increasing doses of a mixture of three extracts (50-percent black tea, 20-percent green tea, and 30-percent mulberry) to induce weight loss, steatorrhea, and blood lipid alterations in rats ingesting a high-fat diet, ad lib. The mixture was incorporated into chow in quantities of 0.5-, 3.0-, and 6.0 percent by weight; a control group received only chow. Food intake and weight were monitored daily, and quantitative fecal fat measurements were obtained weekly for four weeks. The 3.0- and 6.0-percent chows significantly increased fecal fat excretion to 15 percent of dietary fat intake (controls: 5 percent); however, no significant reduction in weight gain was observed. After four weeks of treatment, the 3.0- and 6.0-percent dosages were associated with significant reductions in serum triglycerides and increases in high-density lipoprotein (HDL) cholesterol. However, these chow concentrations were associated with significant increases in serum ALT, and the 6.0-percent chow markedly increased serum alkaline phosphatase. This study does not provide support for the utility of this combination of black tea, green tea, and mulberry extracts in weight-loss regimens and indicates that high doses of this extract combination may be hepatotoxic.

An extract of black, green, and mulberry teas causes malabsorption of carbohydrate but not of triacylglycerol in healthy volunteers.

BACKGROUND: In vitro studies suggest that extracts of black, green, and mulberry teas could interfere with carbohydrate and triacylglycerol absorption via their ability to inhibit alpha-amylase, alpha-glucosidase, sodium-glucose transporters, and pancreatic lipase. OBJECTIVE: We measured breath hydrogen and 13CO2 to investigate the ability of an extract of black, green, and mulberry tea leaves to induce malabsorption of carbohydrate and triacylglycerol in healthy volunteers. DESIGN: In a crossover design, healthy adult volunteers randomly ingested test meals with a placebo beverage or a preparation containing an extract of black (0.1 g), green (0.1 g), and mulberry (1.0 g) teas. One test meal contained 50 g carbohydrate as white rice, 10 g butter, and 0.2 g [13C]triolein, and the beverages contained 10 g sucrose. The calorie content of the second test meal consisted entirely of lipid (30 g olive oil and 0.2 g [13C]triolein). Breath-hydrogen and 13CO2 concentrations were assessed hourly for 8 h, and symptoms were rated on a linear scale. RESULTS: With the carbohydrate-containing meal, the tea extract resulted in a highly significant increase in breath-hydrogen concentrations, which indicated appreciable carbohydrate malabsorption. A comparison of hydrogen excretion after the carbohydrate-containing meal with that after the nonabsorbable disaccharide lactulose suggested that the tea extract induced malabsorption of 25% of the carbohydrate. The tea extract did not cause triacylglycerol malabsorption or any significant increase in symptoms. CONCLUSION: This study provides the basis for additional experiments to determine whether the tea extract has clinical utility for the treatment of obesity or diabetes.

Use of breath carbon monoxide to measure the influence of prosthetic heart valves on erythrocyte survival.

First-generation prosthetic heart valves commonly caused sufficient red blood cell (RBC) injury to induce hemolytic anemia. Although multiple studies have shown that new-generation valves are not associated with anemia, the extent to which these valves are injurious to RBCs is not known, because RBC survival not has not been measured in these subjects. Using a technique that uses breath carbon monoxide (CO) to quantify RBC turnover, this study measured RBC life span in 38 subjects with normally functioning, new-generation valves. Erythrocyte survival averaged 98.8 +/- 23 and 103 +/- 15 days, respectively, in 20 subjects with mechanical valves and 18 subjects with bioprosthetic valves (p >0.05). However, these life spans were significantly (p <0.01) less than those of healthy subjects (122 +/- 23 days) and a group of elderly subjects with osteoarthritis (128 +/- 26 days). The mean hemoglobin concentrations of the 2 groups of valve patients were within normal limits. In conclusion, new-generation heart valves commonly are associated with a small degree of hemolysis that is compensated for by increased RBC production.

Relationship between GHb concentration and erythrocyte survival determined from breath carbon monoxide concentration.

OBJECTIVE: Subjects with decreased erythrocyte survival have an unusually low GHb percentage. The goal of this study was to determine whether hyperglycemia, as reflected by GHb percentage, is associated with decreased erythrocyte survival. RESEARCH DESIGN AND METHODS: Erythrocyte survival was quantitated in 23 subjects with type 2 diabetes, and these values were correlated with the subjects' GHb percentage. Erythrocyte survival was determined from the difference between the subjects' alveolar carbon monoxide (CO) concentration and atmospheric CO concentration. Reticulocyte counts were obtained in 16 subjects. RESULTS: Although the vast majority of the subjects had erythrocyte life spans that fell within the normal range (123 +/- 23 days), there was a highly significant inverse correlation (r = -0.66, P < 0.01) between life span and GHb percentage, with an average decline in life span of 6.9 days for each 1% rise in GHb. The reticulocyte count inversely correlated with erythrocyte life span (r = -0.77, P < 0.01). CONCLUSIONS: Hyperglycemia, as evidenced by high GHb percentage, is associated with an appreciable decrease in erythrocyte life span. Because GHb appears to be formed over the lifetime of the erythrocyte, this decreased erythrocyte survival suggests that high GHb percentages may systematically underestimate the true degree of hyperglycemia.

The effect of antibiotics and bismuth on fecal hydrogen sulfide and sulfate-reducing bacteria in the rat.

Colonic bacteria produce the highly toxic thiol, hydrogen sulfide. Despite speculation that this compound induces colonic mucosal injury, there is little information concerning manipulations that might reduce its production. We studied the effect of antibiotics and bismuth on the production of hydrogen sulfide in rats. Baseline fecal samples were analyzed for hydrogen sulfide concentration and release rate during incubation and numbers of sulfate-reducing bacteria. Groups of six rats received daily doses of ciprofloxacin, metronidazole, or sulfasalazine for one week, and feces were reanalyzed. Bismuth subnitrate was then added to the antibiotic regimens. While sulfide production and sulfate-reducing bacteria were resistant to treatment with ciprofloxacin or metronidazole, bismuth acted synergistically with ciprofloxacin to inhibit sulfate-reducing bacteria growth and to reduce sulfide production. Combination antibiotic-bismuth therapy could provide insights into the importance of sulfide and sulfate-reducing bacteria in both human and animal models of colitis and have clinical utility in the treatment of antibiotic-resistant enteric pathogens.

Stability of human methanogenic flora over 35 years and a review of insights obtained from breath methane measurements.

BACKGROUND & AIMS: Breath methane measurements reflect the in situ activity of the methanogenic colonic flora. Thirty-five years ago we found that 34% of healthy adult subjects were methane producers (breath methane level >1 ppm above atmospheric methane levels). The current study presents a new survey of breath methane levels designed to determine if the activity of the methanogenic flora has changed over the past 35 years. In addition, we review insights into the methanogenic flora that have resulted from breath methane measurements. METHODS: The end-alveolar breath methane concentrations of 212 healthy adults living in the Minneapolis area were determined via gas chromatography. The influence of sex, age, and bowel movement frequency on methane production was assessed. RESULTS: The findings that 36.4% of participants were methane producers, with a mean methane concentration in these producers of 16.6 ppm, are strikingly similar to the values of 33.6% and 15.2 ppm observed 35 years ago. Neither sex nor age showed a statistically significant relationship to methane production. There was a negative correlation between frequency of bowel movements and breath methane concentration in methane producers. CONCLUSIONS: The activity of the methanogenic flora of healthy adults remained remarkably stable over the past 35 years despite widespread antibiotic use and dietary changes. A literature review revealed that many associations have been shown between methane production and clinical states, but it remains to be determined if methanogens actively influence human physiology or are simply a marker of colonic function.

Use of breath carbon monoxide measurements to assess erythrocyte survival in subjects with chronic diseases.

Anemia is very common in patients with chronic diseases. To determine the role of increased red blood cell (RBC) turnover in such subjects, we estimated RBC survival in three groups of chronically ill patients using a simple technique in which RBC life span is estimated via measurements of breath carbon monoxide concentration. The study groups consisted of subjects with: (1) osteoarthritis, (2) rheumatoid arthritis, and (3) anemia who were hospitalized for treatment of a variety of chronic illnesses. None of the anemic subjects had evidence of hemorrhage, a deficiency state, or a marrow abnormality to account for their reduced hemoglobin concentration. Subjects with osteoarthritis had a mean RBC life span (127 +/- 25 days) that did not differ significantly from normal (122 +/- 23 days). In contrast, RBC life span was significantly reduced (P < 0.001) in both the rheumatoid arthritis subjects (90 +/- 15 days) and the anemic, hospitalized patients (87 +/- 33 days). The hemoglobin concentration of the rheumatoid patients was near normal (13.5 +/- 1.5 g/dl), indicating that the marrow was compensating for the reduced RBC life span, whereas no such compensation was apparent in the anemic, chronically ill subjects. We conclude that a modest (approximately 25%) reduction in RBC life span commonly occurs in patients with chronic disease, and this reduction becomes clinically relevant in subjects whose marrow cannot respond with increased RBC output.

Effectiveness of devices purported to reduce flatus odor.

OBJECTIVE: A variety of charcoal-containing devices are purported to minimize problems with odoriferous rectal gas; however, the evidence supporting the efficacy of these products is virtually all anecdotal. We objectively evaluated the ability of these devices to adsorb two malodorous, sulfide gases (hydrogen sulfide and methylmercaptan) instilled at the anus. METHODS: Via a tube, 100 ml of nitrogen containing 40 ppm of sulfide gases and 0.5% H(2) was instilled at the anus of six healthy volunteers who wore gas impermeable Mylar pantaloons over their garments. Since H(2) is not adsorbed by charcoal, the fraction of the sulfide gases removed could be determined from the concentration ratio of sulfide gas: H(2) in the pantaloon space relative to the ratio in instilled gas. RESULTS: Measurements with no device in place showed that subjects' garments removed 22.0 +/- 5.3% of the sulfide gases, and results obtained with each device were corrected for this removal. The only product that adsorbed virtually all of the sulfide gases was briefs constructed from an activated carbon fiber fabric. Pads worn inside the underwear removed 55-77% of the sulfide gases. Most cushions were relatively ineffective, adsorbing about 20% of the gases. CONCLUSIONS: The ability of charcoal-containing devices to adsorb odoriferous rectal gases is limited by incomplete exposure of the activated carbon to the gases. Briefs made from carbon fiber are highly effective; pads are less effective, removing 55-77% of the odor; cushions are relatively ineffective.

Association between fecal hydrogen sulfide production and pouchitis.

PURPOSE: The beneficial effect of antibiotics in pouchitis suggests that an unidentified fecal bacterial product causes this condition. A candidate compound is hydrogen sulfide, a highly toxic gas produced by certain fecal bacteria, which causes tissue injury in experimental models. We investigated hydrogen sulfide release and sulfate-reducing bacterial counts in pouch contents to determine whether hydrogen sulfide production correlates with pouchitis. METHODS: During incubation at 37 degrees C, the production of hydrogen sulfide, methylmercaptan, carbon dioxide, and hydrogen were studied using fresh fecal specimens obtained from 50 patients with ileoanal pouches constructed after total proctocolectomy for ulcerative colitis (n = 45) or for familial adenomatous polyposis (n = 5). Patients with ulcerative colitis were divided into five groups: a) no history of pouchitis (pouch for at least 2 years; n = 8); b) past episode(s) of pouchitis but no active disease for the previous year (n = 9); c) pouchitis in the past year but presently inactive (n = 9); d) ongoing antibiotic treatment (metronidazole or ciprofloxacin) for pouchitis (n = 11); e) currently suffering from pouchitis (n = 8). RESULTS: Release of hydrogen sulfide when pouchitis was active (6.06 +/- 1.03 micromol g(-1) 4 h(-1)) or had occurred in the past year (4.71 +/- 0.41 pmol g(-1) 4 h(-1)) was significantly higher (P < 0.05) than when pouchitis had never occurred (1.71 +/- 0.43 micromol g(-1) 4 h(-1)) or had been inactive in the past year (2.62 +/- 0.49 micromol g(-1) 4 h(-1)). Antibiotic therapy was associated with very low hydrogen sulfide release (0.68 +/- 0.29 micromol g(-1) 4 h(-1)). Pouch contents from familial adenomatous polyposis patients produced significantly less hydrogen sulfide (0.75 +/- 0.09 micromol g(-1) 4 h(-1)) than did any group of nonantibiotic-treated ulcerative colitis patients. Sulfate-reducing bacterial counts in active pouchitis (9.5 +/- 0.5 log10/g) were significantly higher than in those who never experienced pouchitis (7.38 +/- 0.32 log10/g), and these counts fell dramatically with antibiotic treatment. No statistically significant differences in carbon dioxide and hydrogen were observed among the groups not receiving antibiotics. CONCLUSIONS: Pouch contents of patients with ongoing pouchitis or an episode within the previous year released significantly more hydrogen sulfide than did the contents of patients who never had an attack of pouchitis and those with longstanding inactive disease. The response to therapy with metronidazole or ciprofloxacin was associated with marked reductions in hydrogen sulfide release and sulfate-reducing bacteria. These results provide a rationale for additional studies to determine whether the high sulfide production is a cause or effect of pouchitis. The lower hydrogen sulfide production by pouch contents of familial adenomatous polyposis vs. patients with ulcerative colitis suggests a fundamental difference in gut sulfide metabolism that could have implications for the etiology of ulcerative colitis as well as the pouchitis of patients with ulcerative colitis.