Gliadin antibodies in older population and neurological and psychiatric disorders.

OBJECTIVES: A variety of neurological and psychiatric disorders have recently been linked to coeliac disease and gluten sensitivity. We here explored whether persistently positive gliadin antibodies (AGA) and coeliac-type HLA increase the risk of gluten sensitivity-related neurological and psychiatric manifestations. The study was carried out in an older population who had consumed gluten for decades but who had no previous coeliac disease diagnosis. MATERIALS AND METHODS: The original study population comprised 4272 randomly selected older individuals, of whom 2089 had AGA and transglutaminase 2 antibodies (antiTG2) measured twice within a 3-year interval. Forty-nine persistently AGA-positive but antiTG2-negative subjects with coeliac-type HLA and 52 randomly selected persistently AGA- and antiTG2-negative age- and sex-matched controls were clinically examined for neurological disorders. The Psychological General Well-Being (PGWB) questionnaire, the SF-36 health survey questionnaire and the Depression Scale (DEPS) were employed to evaluate psychological well-being. The medical files of all the study subjects were analysed for previous illnesses. RESULTS: Persistently AGA-positive but antiTG2-negative older subjects carrying coeliac disease-type HLA did not evince significantly more neurological symptoms or diseases than AGA-negative control subjects (P = 0.682, P = 0.233). There were no statistically significant differences between AGA-positive and AGA-negative groups in psychological well-being and quality of life when measured by PGWB (P = 0.426), SF-36 questionnaires (P = 0.120) and DEPS (P = 0.683). CONCLUSIONS: At population level, persistent AGA positivity did not indicate gluten sensitivity-related neurological and psychiatric disorders.

4-Methylpyrazole decreases salivary acetaldehyde levels in aldh2-deficient subjects but not in subjects with normal aldh2.

BACKGROUND: Carcinogenic acetaldehyde is produced from ethanol locally in the upper digestive tract via alcohol dehydrogenases (ADHs) of oral microbes, mucosal cells, and salivary glands. Acetaldehyde is further oxidized into less harmful acetate mainly by the aldehyde dehydrogenase-2 (ALDH2) enzyme. ALDH2-deficiency increases salivary acetaldehyde levels and the risk for upper digestive tract cancer in heavy alcohol drinkers. 4-methylpyrazole (4-MP) is an ADH-inhibitor which could reduce the local production of acetaldehyde from ethanol in the saliva. METHODS: Five ALDH2-deficient subjects and six subjects with normal ALDH2 ingested a moderate dose of alcohol (0.4 g/kg of body weight), whereafter their salivary acetaldehyde levels, heart rate, skin temperature, and blood pressure were followed for up to four hours. Blood acetaldehyde and ethanol levels were determined at 60 min. The experiment was repeated after a week. Two hours before the second study day, the volunteers received 4-MP, 10-15 mg/kg of body weight orally. RESULTS: Total ethanol elimination rate decreased with 4-MP by 38-46% in all subjects. 4-MP also reduced blood acetaldehyde levels and suppressed the cardiocirculatory responses of the ALDH2-deficient volunteers. In addition, salivary acetaldehyde production in ALDH2-deficient subjects was significantly reduced when correlated with salivary ethanol levels. On the contrary, 4-MP did not have any effect on salivary or blood acetaldehyde levels in subjects with normal ALDH2. CONCLUSIONS: A single dose of 4-MP before ethanol ingestion reduces ethanol elimination rate, the flushing reaction, and both blood and salivary acetaldehyde levels in ALDH2-deficient subjects but not in subjects with the normal ALDH2 genotype. These results suggest that the role of oral mucosal and glandular ADHs in salivary acetaldehyde production is minimal and support earlier findings indicating that salivary acetaldehyde production is mainly of microbial origin in subjects with normal ALDH2.

Acetaldehyde production and other ADH-related characteristics of aerobic bacteria isolated from hypochlorhydric human stomach.

BACKGROUND: Acetaldehyde is a known local carcinogen in the digestive tract in humans. Bacterial overgrowth in the hypochlorhydric stomach enhances production of acetaldehyde from ethanol in vivo after alcohol ingestion. Therefore, microbially produced acetaldehyde may be a potential risk factor for alcohol-related gastric and cardiac cancers. This study was aimed to investigate which bacterial species and/or groups are responsible for acetaldehyde formation in the hypochlorhydric human stomach and to characterize their alcohol dehydrogenase (ADH) enzymes. METHODS: After 7 days of treatment with 30 mg of lansoprazole twice a day, a gastroscopy was performed on eight volunteers to obtain hypochlorhydric gastric juice. Samples were cultured and bacteria were isolated and identified; thereafter, their acetaldehyde production capacity was measured gas chromatographically by incubating intact bacterial suspensions with ethanol at 37 degrees C. Cytosolic ADH activities, Km values, and protein concentration were determined spectrophotometrically. RESULTS: Acetaldehyde production of the isolated bacterial strains (n = 51) varied from less than 1 to 13,690 nmol of acetaldehyde/10(9) colony-forming units/hr. ADH activity of the strains that produced more than 100 nmol of acetaldehyde/10(9) colony-forming units/hr (n = 23) varied from 3.9 to 1253 nmol of nicotinamide adenine dinucleotide per minute per milligram of protein, and Km values for ethanol ranged from 0.65 to 116 mM and from 0.5 to 3.1 M (high Km). There was a statistically significant correlation (r = 0.64, p < 0.001) between ADH activity and acetaldehyde production from ethanol in the tested strains. The most potent acetaldehyde producers were Neisseria and Rothia species and Streptococcus salivarius, whereas nearly all Stomatococcus, Staphylococcus, and other Streptococcus species had a very low capacity to produce acetaldehyde. CONCLUSIONS: This study demonstrated that certain bacterial species or groups that originate from the oral cavity are responsible for the bulk of acetaldehyde production in the hypochlorhydric stomach. These findings provide new information with the respect to the local production of carcinogenic acetaldehyde in the upper digestive tract of achlorhydric human subjects.

Poor dental status increases acetaldehyde production from ethanol in saliva: a possible link to increased oral cancer risk among heavy drinkers.

Epidemiological data support evidence that poor dental status increases oral cavity cancer risk especially among heavy alcohol consumers, but the causality of this finding is unclear. The enzymatic conversion of ethanol by the physiological oral microflora may lead to an accumulation of the highly carcinogenic intermediate acetaldehyde. This study was conducted to evaluate the role of dental status on the microbial production of acetaldehyde from ethanol in saliva. The microbial acetaldehyde production from ethanol was related to the dental score in 132 volunteers. After adjustment for smoking, alcohol consumption, age and gender, poor dental status was shown to lead to an approximately twofold increase in salivary acetaldehyde production from ethanol (P=0.02). Our results could be an important factor underlying the role of poor dental hygiene and status in oral cancer risk associated with ethanol drinking.

Hypochlorhydria induced by a proton pump inhibitor leads to intragastric microbial production of acetaldehyde from ethanol.

BACKGROUND: Acetaldehyde, produced locally in the digestive tract, has recently been shown to be carcinogenic in humans. AIM: To examine the effect of iatrogenic hypochlorhydria on intragastric acetaldehyde production from ethanol after a moderate dose of alcohol, and to relate the findings to the changes in gastric flora. METHODS: Eight male volunteers ingested ethanol 0.6 g/kg b.w. The pH, acetaldehyde level and microbial counts of the gastric juice were then determined. The experiment was repeated after 7 days of lansoprazole 30 mg b.d. RESULTS: The mean (+/- S.E.M.) pH of the gastric juice was 1.3 +/- 0.06 and 6.1 +/- 0.5 (P < 0.001) before and after lansoprazole, respectively. This was associated with a marked overgrowth of gastric aerobic and anaerobic bacteria (P < 0. 001), by a 2.5-fold (P=0.003) increase in gastric juice acetaldehyde level after ethanol ingestion, and with a positive correlation (r=0. 90, P < 0.001) between gastric juice acetaldehyde concentration and the count of aerobic bacteria. CONCLUSIONS: Treatment with proton pump inhibitors leads to hypochlorhydria, which associates with intragastric overgrowth of aerobic bacteria and microbially-mediated acetaldehyde production from ethanol. Since acetaldehyde is a local carcinogen in the concentrations found in this study, long-term use of gastric acid secretory inhibitors is a potential risk-factor for gastric and cardiac cancers.

High salivary acetaldehyde after a moderate dose of alcohol in ALDH2-deficient subjects: strong evidence for the local carcinogenic action of acetaldehyde.

BACKGROUND: Due to a point mutation, aldehyde dehydrogenase-2 (ALDH2) isoenzyme is deficient in 30% to 50% of Asians. Among Asian ALDH2-deficient heavy drinkers, the risk for digestive tract cancers is markedly increased (odds ratio 3.4-54.2). The reason for this is unknown but could be due to the local carcinogenic action of acetaldehyde. METHODS: Salivary and blood acetaldehyde levels were determined in 20 healthy Asians after a moderate dose of alcohol (0.5 g/kg of body weight). Salivary acetaldehyde production capacity from ethanol in vitro was measured also. ALDH2 genotype of the Asians was determined from isolated leukocyte-deoxyribonucleic acid by polymerase chain reaction/restriction fragment length polymorphism method. Acetaldehyde content of parotid gland saliva was measured in three ALDH2-deficient Asians and three White subjects with normal ALDH2 after the same dose of ethanol. RESULTS: Seven of the Asians were heterozygous for the mutant ALDH2*2 allele (flushers). They had two to three times higher salivary acetaldehyde levels than the Asians (n = 13) with normal ALDH2 throughout the follow-up period of 240 min (p < 0.001). Only in the flushers did the parotid gland contribute to salivary acetaldehyde production. The in vitro capacity of saliva to produce acetaldehyde from ethanol was equal in both groups. The flushers' blood acetaldehyde levels were only one ninth of the levels in saliva. CONCLUSIONS: By using this human "knockout model" for deficient acetaldehyde removal, we found that in addition to oral microflora, acetaldehyde in saliva may also originate from the oxidation of ethanol in the parotid gland. When combined with earlier epidemiological data, these results offer a strong evidence for the local carcinogenic action of acetaldehyde in humans.

Metronidazole increases intracolonic but not peripheral blood acetaldehyde in chronic ethanol-treated rats.

BACKGROUND: Metronidazole leads to the overgrowth of aerobic flora in the large intestine by reducing the number of anaerobes. According to our previous studies, this shift may increase intracolonic bacterial acetaldehyde formation if ethanol is present. Metronidazole is also reported to cause disulfiram-like effects after alcohol intake, although the mechanism behind this is obscure. Therefore, the aim was to study the effect of long-term metronidazole and alcohol treatment on intracolonic acetaldehyde levels and to explore the possible role of intestinal bacteria in the metronidazole related disulfiram-like reaction. METHODS: A total of 32 rats were divided into four groups: controls (n = 6), controls receiving metronidazole (n = 6), ethanol group (n = 10), and ethanol and metronidazole group (n = 10). All rats were pair-fed with the liquid diet for 6-weeks, whereafter blood and intracolonic acetaldehyde levels and liver and colonic mucosal alcohol (ADH) and aldehyde dehydrogenase (ALDH) activities were analyzed. RESULTS: The rats receiving ethanol and metronidazole had five times higher intracolonic acetaldehyde levels than the rats receiving only ethanol (431.4 +/- 163.5 microM vs. 84.7 +/- 14.4 microM,p = 0.0035). In contrast, blood acetaldehyde levels were equal. Cecal cultures showed the increased growth of Enterobacteriaceae in the metronidazole groups. Metronidazole had no inhibitory effect on hepatic or colonic mucosal ADH and ALDH activities. CONCLUSIONS: The increase in intracolonic acetaldehyde after metronidazole treatment is probably due to the replacement of intestinal anaerobes by ADH-containing aerobes. Unlike disulfiram, metronidazole neither inhibits liver ALDH nor increases blood acetaldehyde. Thus, our findings suggested that the mechanism behind metronidazole related disulfiram-like reaction might be located in the gut flora instead of the liver.

Increased salivary acetaldehyde levels in heavy drinkers and smokers: a microbiological approach to oral cavity cancer.

The pathogenetic mechanisms behind alcohol-associated carcinogenesis in the upper digestive tract remain unclear, as alcohol is not carcinogenic. However, there is increasing evidence that a major part of the tumour-promoting action of alcohol might be mediated via its first, toxic and carcinogenic metabolite acetaldehyde. Acetaldehyde is produced from ethanol in the epithelia by mucosal alcohol dehydrogenases, but much higher levels derive from microbial oxidation of ethanol by the oral microflora. In this study we investigated factors that might alter the composition and quantities of the oral microflora and, consequently, influence microbial acetaldehyde production. Information about dental health, smoking habits, alcohol consumption and other factors was obtained by a questionnaire from 326 volunteers with varying social backgrounds and health status, e.g. oral cavity malignancy. Paraffin-induced saliva was collected and the microbial production of acetaldehyde from ethanol was measured. Smoking and heavy drinking were the strongest factors increasing microbial acetaldehyde production. Whether poor dental status may alter local acetaldehyde production from ethanol remained unanswered. Bacterial analysis revealed that mainly gram-positive aerobic bacteria and yeasts were associated with higher acetaldehyde production. Increased local microbial salivary acetaldehyde production due to ethanol among smokers and heavy drinkers could be a biological explanation for the observed synergistic carcinogenic action of alcohol and smoking on upper gastrointestinal tract cancer. It offers a new microbiological approach to ethanol-associated carcinogenesis at these anatomic sites.

Microbially produced acetaldehyde from ethanol may increase the risk of colon cancer via folate deficiency.

High alcohol and low folate intake are independent risk factors for colorectal cancer. Acetaldehyde has been postulated to be a factor responsible for ethanol-associated carcinogenesis. High levels of acetaldehyde accumulate in the large intestine via the microbial oxidation of alcohol. Acetaldehyde degrades folate in vitro. Thus, it is possible that high intracolonic acetaldehyde levels break down folate in the colon. Our aim was to test the effect of high alcohol and acetaldehyde concentrations in the gut on systemic and local intestinal folate levels in rats. Twenty rats received 3 g/kg of ethanol twice a day for 2 weeks with or without concomitant ciprofloxacin administration. Twenty control rats received saline with or without ciprofloxacin. All rats were fed a diet with normal folate content. Alcohol treatment led to very high intracolonic acetaldehyde levels (387 +/- 185 microM), which were markedly decreased by concomitant ciprofloxacin treatment (21 +/- 4 microM). Erythrocyte, serum and small intestinal folate levels were unaffected by alcohol treatment. Alcohol administration decreased significantly colonic mucosal folate levels by 48%, and this effect was prevented by ciprofloxacin. We conclude that alcohol administration for 2 weeks leads to local folate deficiency of colonic mucosa in rats, most probably via the degradation of folate by the high levels of acetaldehyde microbially produced from ethanol. Our findings offer a unique explanation for the increased risk of colonic cancer associated with alcohol intake and folate deficiency.

Role of yeasts in the salivary acetaldehyde production from ethanol among risk groups for ethanol-associated oral cavity cancer.

BACKGROUND: Acetaldehyde, the first metabolite of alcohol, has been proposed to be the carcinogenic substance behind ethanol-related oral cancers. High levels of acetaldehyde are formed from ethanol in saliva by the oral flora, but so far the role of certain microbial species responsible for this phenomenon is not known. Yeasts are common commensals of the oral cavity that have alcohol-oxidizing enzymes, thus providing a potential source of acetaldehyde from ethanol. The aim of this study was to examine the contribution of oral yeasts to the production of ethanol-derived acetaldehyde in the oral cavity. METHODS: Fifty-five saliva samples were divided into two groups, high and low, based on the in vitro salivary acetaldehyde production capacity from ethanol. Yeasts were isolated and identified from these samples, and their acetaldehyde production capacity was determined gas chromatographically by incubating intact cells with ethanol at the physiological pH of 7.4. RESULTS: Yeast colonization was found in 78% of the high acetaldehyde-producing salivas, compared with 47% in the low acetaldehyde-producing salivas (p = 0.026). Among carriers, the density of yeasts was higher in the high than in low acetaldehyde producers (p = 0.025). Candida albicans was the main species isolated (88% of all oral isolates). Moreover, C. albicans strains isolated from the high acetaldehyde-producing salivas formed significantly higher acetaldehyde levels from ethanol than C. albicans strains from low-acetaldehyde-producing salivas (73.1 nmol ach/10e6 colony-forming units vs. 43.2 nmol ach/10e6 colony-forming units, p = 0.035). CONCLUSIONS: This study shows that some C. albicans strains have a marked capacity to produce toxic and carcinogenic acetaldehyde from ethanol in vitro. Because the in vitro production of salivary acetaldehyde has been previously shown to correlate with in vivo acetaldehyde production, our finding could be an important microbial pathogenetic factor underlying cancer of the oral cavity associated with ethanol drinking.

Ciprofloxacin decreases the rate of ethanol elimination in humans.

BACKGROUND: Extrahepatic ethanol metabolism is postulated to take place via microbial oxidation in the colon, mediated by aerobic and facultative anaerobic bacteria. AIMS: To evaluate the role of microbial ethanol oxidation in the total elimination rate of ethanol in humans by reducing gut flora with ciprofloxacin. METHODS: Ethanol was administered intravenously at the beginning and end of a one week period to eight male volunteers. Between ethanol doses volunteers received 750 mg ciprofloxacin twice daily. RESULTS: A highly significant (p=0.001) reduction in the ethanol elimination rate (EER) was detected after ciprofloxacin medication. Mean (SEM) EER was 107.0 (5.3) and 96.9 (4.8) mg/kg/h before and after ciprofloxacin, respectively. Faecal Enterobacteriaceae and Enterococcus sp. were totally absent after medication, and faecal acetaldehyde production capacity was significantly (p<0.05) decreased from 0.91 (0.15) to 0.39 (0.08) nmol/min/mg protein. Mean faecal alcohol dehydrogenase (ADH) activity was significantly (p<0. 05) decreased after medication, but ciprofloxacin did not inhibit human hepatic ADH activity in vitro. CONCLUSIONS: Ciprofloxacin treatment decreased the ethanol elimination rate by 9.4%, with a concomitant decrease in intestinal aerobic and facultative anaerobic bacteria, faecal ADH activity, and acetaldehyde production. As ciprofloxacin has no effect on liver blood flow, hepatic ADH activity, or cytochrome CYP2E1 activity, these effects are probably caused by the reduction in intestinal flora.

Role of catalase in in vitro acetaldehyde formation by human colonic contents.

Ingested ethanol is transported to the colon via blood circulation, and intracolonic ethanol levels are equal to those of the blood ethanol levels. In the large intestine, ethanol is oxidized by colonic bacteria, and this can lead to extraordinarily high acetaldehyde levels that might be responsible, in part, for ethanol-associated carcinogenicity and gastrointestinal symptoms. It is believed that bacterial acetaldehyde formation is mediated via microbial alcohol dehydrogenases (ADHs). However, almost all cytochrome-containing aerobic and facultative anaerobic bacteria possess catalase activity, and catalase can, in the presence of hydrogen peroxide (H2O2), use several alcohols (e.g., ethanol) as substrates and convert them to their corresponding aldehydes. In this study we demonstrate acetaldehyde production from ethanol in vitro by colonic contents in a reaction catalyzed by both bacterial ADH and catalase. The amount of acetaldehyde produced by the human colonic contents was proportional to the ethanol concentration, the amount of colonic contents, and the length of incubation time, even in the absence of added nicotinamide adenine dinucleotide or H2O2. The catalase inhibitors sodium azide and 3-amino-1,2,4-triazole (3-AT) markedly reduced the amount of acetaldehyde produced from 22 mM ethanol in a concentration dependent manner compared with the control samples (0.1 mM sodium azide to 73% and 10 mM 3-AT to 67% of control). H2O2 generating system [beta-D(+)-glucose + glucose oxidase] and nicotinamide adenine dinucleotide induced acetaldehyde formation up to 6- and 5-fold, respectively, and together these increased acetaldehyde formation up to 11-fold. The mean supernatant catalase activity was 0.53+/-0.1 micromol/min/mg protein after the addition of 10 mM H2O2, and there was a significant (p < 0.05) correlation between catalase activity and acetaldehyde production after the addition of the hydrogen peroxide generating system. Our results demonstrate that colonic contents possess catalase activity, which probably is of bacterial origin, and indicate that in addition to ADH, part of the acetaldehyde produced in the large intestine during ethanol metabolism can be catalase dependent.