Bile acid transformation by the intestinal flora and cholesterol saturation in bile. Effects of Streptococcus faecium administration

Circulating neutrophil anti-pathogen dysfunction in cirrhosis

Neutrophils are the largest population of leucocytes and are among the first cells of the innate immune system to fight against intruding pathogens. In patients with cirrhosis, neutrophils exhibit altered functionality, including changes in phagocytic ability, bacterial killing, chemotaxis, degranulation, reactive oxygen species production and NET (neutrophil extracellular trap) formation. This results in their inability to mount an adequate antibacterial response and protect the individual from infection. Prognosis and survival in patients with cirrhosis are greatly influenced by the development of infectious complications. Multidrug-resistant bacterial infections in patients with cirrhosis are currently a growing problem worldwide; therefore, alternative methods for the prevention and treatment of bacterial infections in cirrhosis are urgently needed. The prevention and treatment of neutrophil dysfunction could be a potential way to protect patients from bacterial infections. However, the reasons for changes in neutrophil function in cirrhosis are still not completely understood, which limits the development of efficient therapeutic strategies. Both cellular and serum factors have been proposed to contribute to the functional impairment of neutrophils. Herein, we review the current knowledge on features and proposed causes of neutrophil dysfunction in cirrhosis, with a focus on current knowledge gaps and limitations, as well as opportunities for future investigations in this field.

The role of bile acids in carcinogenesis

Bile acids are soluble derivatives of cholesterol produced in the liver that subsequently undergo bacterial transformation yielding a diverse array of metabolites. The bulk of bile acid synthesis takes place in the liver yielding primary bile acids; however, other tissues have also the capacity to generate bile acids (e.g. ovaries). Hepatic bile acids are then transported to bile and are subsequently released into the intestines. In the large intestine, a fraction of primary bile acids is converted to secondary bile acids by gut bacteria. The majority of the intestinal bile acids undergo reuptake and return to the liver. A small fraction of secondary and primary bile acids remains in the circulation and exert receptor-mediated and pure chemical effects (e.g. acidic bile in oesophageal cancer) on cancer cells. In this review, we assess how changes to bile acid biosynthesis, bile acid flux and local bile acid concentration modulate the behavior of different cancers. Here, we present in-depth the involvement of bile acids in oesophageal, gastric, hepatocellular, pancreatic, colorectal, breast, prostate, ovarian cancer. Previous studies often used bile acids in supraphysiological concentration, sometimes in concentrations 1000 times higher than the highest reported tissue or serum concentrations likely eliciting unspecific effects, a practice that we advocate against in this review. Furthermore, we show that, although bile acids were classically considered as pro-carcinogenic agents (e.g. oesophageal cancer), the dogma that switch, as lower concentrations of bile acids that correspond to their serum or tissue reference concentration possess anticancer activity in a subset of cancers. Differences in the response of cancers to bile acids lie in the differential expression of bile acid receptors between cancers (e.g. FXR vs. TGR5). UDCA, a bile acid that is sold as a generic medication against cholestasis or biliary surge, and its conjugates were identified with almost purely anticancer features suggesting a possibility for drug repurposing. Taken together, bile acids were considered as tumor inducers or tumor promoter molecules; nevertheless, in certain cancers, like breast cancer, bile acids in their reference concentrations may act as tumor suppressors suggesting a Janus-faced nature of bile acids in carcinogenesis.

Cultivation and Genomic Characterization of the Bile Bacterial Species From Cholecystitis Patients

The microbes in human bile are closely related to gallbladder health and other potential disorders. Although the bile microbial community has been investigated by recent studies using amplicon or metagenomic sequencing technologies, the genomic information of the microbial species resident in bile is rarely reported. Herein, we isolated 138 bacterial colonies from the fresh bile specimens of four cholecystitis patients using a culturome approach and genomically characterized 35 non-redundant strains using whole-genome shotgun sequencing. The bile bacterial isolates spanned 3 classes, 6 orders, 10 families, and 14 genera, of which the members of Enterococcus, Escherichia-Shigella, Lysinibacillus, and Enterobacter frequently appeared. Genomic analysis identified three species, including Providencia sp. D135, Psychrobacter sp. D093, and Vibrio sp. D074, which are not represented in existing reference genome databases. Based on the genome data, the functional capacity between bile and gut isolates was compared. The bile strains encoded 5,488 KEGG orthologs, of which 4.9% were specific to the gut strains, including the enzymes involved in biofilm formation, two-component systems, and quorum-sensing pathways. A total of 472 antibiotic resistance genes (ARGs) were identified from the bile genomes including multidrug resistance proteins (42.6%), fluoroquinolone resistance proteins (12.3%), aminoglycoside resistance proteins (9.1%), and β-lactamase (7.2%). Moreover, in vitro experiments showed that some bile bacteria have the capabilities for bile salt deconjugation or biotransformation (of primary bile acids into secondary bile acids). Although the physiological or pathological significance of these bacteria needs further exploration, our works expanded knowledge about the genome, diversity, and function of human bile bacteria.

Potential new treatment strategies for COVID-19: is there a role for bromhexine as add-on therapy?

Of huge importance now is to provide a fast, cost-effective, safe, and immediately available pharmaceutical solution to curb the rapid global spread of SARS-CoV-2. Recent publications on SARS-CoV-2 have brought attention to the possible benefit of chloroquine in the treatment of patients infected by SARS-CoV-2. Whether chloroquine can treat SARS-CoV-2 alone and also work as a prophylactic is doubtful. An effective prophylactic medication to prevent viral entry has to contain, at least, either a protease inhibitor or a competitive virus ACE2-binding inhibitor. Using bromhexine at a dosage that selectively inhibits TMPRSS2 and, in so doing, inhibits TMPRSS2-specific viral entry is likely to be effective against SARS-CoV-2. We propose the use of bromhexine as a prophylactic and treatment. We encourage the scientific community to assess bromhexine clinically as a prophylactic and curative treatment. If proven to be effective, this would allow a rapid, accessible, and cost-effective application worldwide.

Oncobiosis and Microbial Metabolite Signaling in Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma is one of the most lethal cancers in both men and women, with a median five-year survival of around 5%. Therefore, pancreatic adenocarcinoma represents an unmet medical need. Neoplastic diseases, such as pancreatic adenocarcinoma, often are associated with microbiome dysbiosis, termed oncobiosis. In pancreatic adenocarcinoma, the oral, duodenal, ductal, and fecal microbiome become dysbiotic. Furthermore, the pancreas frequently becomes colonized (by Helicobacter pylori and Malassezia, among others). The oncobiomes from long- and short-term survivors of pancreatic adenocarcinoma are different and transplantation of the microbiome from long-term survivors into animal models of pancreatic adenocarcinoma prolongs survival. The oncobiome in pancreatic adenocarcinoma modulates the inflammatory processes that drive carcinogenesis. In this review, we point out that bacterial metabolites (short chain fatty acids, secondary bile acids, polyamines, indole-derivatives, etc.) also have a role in the microbiome-driven pathogenesis of pancreatic adenocarcinoma. Finally, we show that bacterial metabolism and the bacterial metabolome is largely dysregulated in pancreatic adenocarcinoma. The pathogenic role of additional metabolites and metabolic pathways will be identified in the near future, widening the scope of this therapeutically and diagnostically exploitable pathogenic pathway in pancreatic adenocarcinoma.

Enterococcus faecium SF68 as a model for efficacy and safety evaluation of pharmaceutical probiotics

As normal inhabitants of diverse ecosystems, including the human gastrointestinal tract, the enterococci, and especially the two species Enterococcus faecalis and Enterococcus faecium, can be considered ubiquitous with regard to our natural environment. E. faecium has gained special importance thanks to beneficial strains marketed as probiotics, and because of its beneficial role in traditional fermented foods such as artisanal cheeses in some Southern European countries. Yet, following reports on the increasing association of some enterococcal strains with nosocomial infections such as endocarditis and bacteraemia, it became evident that strains from clinical origin are frequently highly resistant to ‘last-defence-line’ antibiotics such as the glycopeptide derivatives. For this reason enterococci have been classified in risk group 2 in the European Directive 93/88. With this paper it is intended to clarify the uncertain situation around the safety of the species E. faecium, also with referring to intra-species heterogeneity. In fact, well established scientific and surveillance data support the safety of some probiotic E. faecium strains for both human and animal applications. As a model, summarising yet extensive information is provided on the efficacy and safety of E. faecium SF68®, a pharmaceutical probiotic with a long history of safe use. We propose the approach presented in this review as a model for the evaluation of safety of probiotic strains of this species.

Dietary supplementation with flaxseed meal and oat hulls modulates intestinal histomorphometric characteristics, digesta- and mucosa-associated microbiota in pigs

The establishment of a healthy gastrointestinal milieu may not only offer an opportunity to reduce swine production costs but could also open the way for a lifetime of human health improvement. This study investigates the effects of feeding soluble fibre from flaxseed meal-containing diet (FM) and insoluble fibre from oat hulls-containing diet (OH) on histomorphological characteristics, digesta- and mucosa-associated microbiota and their associations with metabolites in pig intestines. In comparison with the control (CON) and OH diets, the consumption of FM increased (P < 0.001) the jejunal villi height (VH) and the ratio of VH to crypt depths. The PERMANOVA analyses showed distinct (P < 0.05) microbial communities in ileal digesta and mucosa, and caecal mucosa in CON and FM-diets fed pigs compared to the OH diet-fed pigs. The predicted functional metagenomes indicated that amino acids and butanoate metabolism, lysine degradation, bile acids biosynthesis, and apoptosis were selectively enhanced at more than 2.2 log-folds in intestinal microbiota of pigs fed the FM diet. Taken together, flaxseed meal and oat hulls supplementation in growing pigs’ diets altered the gastrointestinal development, as well as the composition and function of microbial communities, depending on the intestinal segment and physicochemical property of the dietary fibre source.

Foods as risk factors for colorectal adenomas: a case-control study in Burgundy (France)

Foods associated with precancerous colorectal adenoma, especially those associated with large adenomas, are poorly understood. We compared food intake in polyp-free controls (n = 427) with small adenoma (n = 154) or large adenoma (n = 208) cases in Burgundy (France). Logistic regression models controlled for age, gender, and energy. Consumption of lean meat was associated with a reduced risk of small adenomas [odds ratio (OR) for 4th vs. 1st quartile = 0.3, 95% confidence interval (CI) = 0.2-0.6] and large adenomas (OR = 0.4, 95% CI = 0.3-0.7) compared with controls. There was an increased risk with p t s and meat spread [OR = 2.1, 95% CI = 1.1-3.7 (small adenomas) and OR = 2.6, 95% CI = 1.5-4.4 (large adenomas)], bread [OR = 2.0, 95% CI = 1.1-3.6 (small adenomas) and OR = 2.2, 95% CI = 1.3-3.7 (large adenomas)], and pasta (OR = 1.7, 95% CI = 0.9-3.0 in small adenomas only). Animal fats were associated with an increased risk of large adenomas compared with small adenomas (OR = 2.4, 95% CI = 1.1-5.0), whereas yogurt intake was associated with a lower risk (OR for high vs. no intake = 0.5, 95% CI = 0.3-0.9). These findings suggest that some risk factors that have been found to be associated with cancer, such as refined cereal products and high-fat animal products, also influence early stages of colorectal carcinogenesis.

Bifidobacterium animalis strain DN-173 010 shortens the colonic transit time in healthy women: a double-blind, randomized, controlled study

BACKGROUND

A previous study has suggested that Bifidobacterium animalis DN-173 010 shortens the colonic transit time in women.

AIM

To confirm this effect and to determine whether modifications of the faecal bacterial mass and/or faecal secondary bile salts may be the explanation.

METHODS

A double-blind, cross-over study was performed. Thirty-six healthy women were studied in four consecutive 10-day periods. During periods 2 and 4, they ingested three 125 g cups per day of a fermented milk which was either a product containing B. animalis DN-173 010 or a control without bifidobacteria. Periods 1 and 3 were run-in and washout periods, respectively. The total and segmental colonic transit times were assessed using a pellet method. In 12 subjects, all stools were collected and analysed for pH, faecal weight, bacterial mass and bile acids.

RESULTS

The total and sigmoid transit times were significantly shorter during dosing with B. animalis compared to the control period. The other transit times, faecal weight, pH, bacterial mass and bile acids were not significantly affected.

CONCLUSIONS

B. animalis DN-173 010 shortens the colonic transit time in healthy women. This effect is not explained by modifications of the faecal bacterial mass or secondary bile acids.

Deoxycholic acid in gall bladder bile does not account for the shortened nucleation time in patients with cholesterol gall stones

The relations between the concentration of deoxycholic acid (DCA), the cholesterol saturation index, and the nucleation time in gall bladder bile were measured to determine the role of DCA in bile in the pathogenesis of cholesterol gall stone disease. Bile was obtained from patients with cholesterol gall stones (n = 30), subjects without gall stones (n = 35), and patients with pigment gall stones (n = 9). Three of 30 cholesterol gall stone patients and 10 of 35 gall stone free subjects were treated with antibiotics by mouth to decrease the concentration of bile DCA and determine the effect of DCA on biliary lithogenecity. Both the percentage and concentration of DCA in bile were similar in patients with and without cholesterol gall stones despite significant differences in their cholesterol saturation indices and nucleation times. Neither the percentage nor the concentration of DCA in bile correlated with either the cholesterol saturation index or the nucleation time. Analysis of subgroups with matching cholesterol saturation indices showed no correlation between the proportion of DCA in the bile and the cholesterol nucleation time. The proportion of DCA in bile was decreased by antibiotic treatment, but this had no effect on the cholesterol saturation index or nucleation time. These results suggest that DCA in bile is not responsible for biliary cholesterol saturation or cholesterol nucleation time.

Effects of cholecystectomy on the kinetics of primary and secondary bile acids

Removal of the gallbladder is thought to increase formation and pool size of secondary bile acids, mainly deoxycholic acid (DCA), by increased exposure of primary bile acids (cholic acid [CA], chenodeoxycholic acid [CDCA]) to bacterial dehydroxylation in the intestine. We have tested this hypothesis by simultaneous determination of pool size and turnover of DCA, CA, and CDCA in nine women before and at various intervals after removal of a functioning gallbladder. An isotope dilution technique using marker bile acids labeled with stable isotopes (2H4-DCA, 13C-CA, 13C-CDCA) was used. After cholecystectomy, concentration and output of bile acids relative to bilirubin increased (P less than 0.02) in fasting duodenal bile and cholesterol saturation decreased by 27% (P less than 0.05) consistent with enhanced enterohepatic cycling of bile acids. Three months after removal of the gallbladder bile acid kinetics were in a new steady state: pool size and turnover of CDCA were unchanged. Synthesis of CA, the precursor of DCA, was diminished by 37% (P = 0.05), probably resulting from feedback inhibition by continuous transhepatic flux of bile acids. The fraction of CA transferred after 7 alpha-dehydroxylation to the DCA pool increased from 46 +/- 16 to 66 +/- 32% (P less than 0.05). However, this enhanced transfer did not lead to increased input or size of the DCA pool, because synthesis of the precursor CA had decreased.

Intestinal transit, deoxycholic acid and the cholesterol saturation of bile--three inter-related factors

There is considerable evidence that the level of deoxycholic acid in the bile influences biliary cholesterol saturation. Deoxycholic acid is formed in the colon and absorbed slowly. Hence changes in colonic transit rate might influence biliary deoxycholic acid and the cholesterol saturation of bile. When 14 constipated subjects took standardised senna tablets for six weeks in a dose sufficient to lower mean whole gut transit time from 134 to 54 hours, deoxycholic acid as a proportion of biliary bile acids fell from 25.9 +/- 8.6 to 17.2 +/- 8.3% (p less than 0.0001) and deoxycholic acid pool measured by isotope dilution fell from 0.64 +/- 0.34 to 0.45 +/- 0.29 g (p less than 0.0001). In those subjects (n = 8) whose bile was initially supersaturated with cholesterol, the saturation index fell from 1.40 +/- 0.22 to 1.20 +/- 0.19 (p = 0.02). Conversely, when 12 normal volunteers took loperamide capsules sufficient to cause symptomatic constipation and to prolong mean transit-time from 48 to 103 hours, the deoxycholic acid pool increased from 0.40 +/- 0.24 to 0.57 +/- 0.17 g (p = 0.008). The percentage deoxycholic acid did not alter significantly, because the estimated total bile acid pool expanded (from 1.98 +/- 0.61 to 2.81 +/- 0.48 g; p less than 0.001), presumably because of loperamide slowing down small bowel transit. Despite this expansion of the bile acid pool, loperamide increased the cholesterol saturation index from 1.10 +/- 0.31 to 1.20 +/- 0.32 (p = 0.01). Changes in colonic transit rate alter the size of the deoxycholic acid pool and bile cholesterol saturation. These findings suggest that constipation or slow colonic transit might increase the chance of supersaturated bile and hence of gall stones.

Effect of Clostridium butyricum on the formation and dissolution of gallstones in experimental cholesterol cholelithiasis

The effect of oral administration of Clostridium butyricum Miyairi on the formation and dissolution of gallstones was examined in a mouse model of cholesterol cholelithiasis, in comparison with that of chenodeoxycholic acid (CDCA). A diet containing cholesterol and sodium cholate was used as a lithogenic diet. The feeding of the lithogenic diet containing 1.0 X 10(8) cells of this bacterium per g for five weeks prevented the formation of gallstones, resulted in lower values of the gallstone index, incidence and cholesterol content of gallstones than those of untreated group by 46, 43 and 46%, in order. Furthermore, after mice were maintained on the lithogenic diet for five weeks, subsequent bacterial treatment exhibited a marked gallstone dissolution effect. The feeding of 10(8) cells/g was effective for the prevention of gallstone formation and dissolution of gallstones, but that of 10(6) cells/g was not significantly effective. The gallstone index of the bacterium-treated group was lower than that of CDCA-treated group during the period of experiment, but there was no difference in the cholesterol content of gallstones between these two groups, which suggests a different mechanism of action of the bacterium from that of CDCA.