A prospective study of serum bile acid concentrations and colorectal cancer risk in post-menopausal women on the island of Guernsey

FXR agonists for colorectal and liver cancers, as a stand-alone or in combination therapy

Farnesoid X receptor (FXR, NR1H4) is generally considered as a tumor suppressor of colorectal and liver cancers. The interaction between FXR, bile acids (BAs) and gut microbiota is closely associated with an increased risk of colorectal and liver cancers. Increasing evidence shows that FXR agonists may be potential therapeutic agents for colorectal and liver cancers. However, FXR agonists alone do not produce the desired results due to the complicated pathogenesis and single therapeutic mechanism, which suggests that effective treatments will require a multimodal approach. Based on the principle of improvingefficacy andreducingside effects, combination therapy is currently receiving considerable attention. In this review, colorectal and liver cancers are grouped together to discuss the effects of FXR agonists alone or in combination for combating the two cancers. We hope that this review will provide a theoretical basis for the clinical application of novel FXR agonists or combination with FXR agonists against colorectal and liver cancers.

The role of farnesoid X receptor in metabolic diseases, and gastrointestinal and liver cancer

Farnesoid X receptor (FXR) is a ligand-activated transcription factor involved in the control of bile acid (BA) synthesis and enterohepatic circulation. FXR can influence glucose and lipid homeostasis. Hepatic FXR activation by obeticholic acid is currently used to treat primary biliary cholangitis. Late-stage clinical trials investigating the use of obeticholic acid in the treatment of nonalcoholic steatohepatitis are underway. Mouse models of metabolic disease have demonstrated that inhibition of intestinal FXR signalling reduces obesity, insulin resistance and fatty liver disease by modulation of hepatic and gut bacteria-mediated BA metabolism, and intestinal ceramide synthesis. FXR also has a role in the pathogenesis of gastrointestinal and liver cancers. Studies using tissue-specific and global Fxr-null mice have revealed that FXR acts as a suppressor of hepatocellular carcinoma, mainly through regulating BA homeostasis. Loss of whole-body FXR potentiates progression of spontaneous colorectal cancer, and obesity-induced BA imbalance promotes intestinal stem cell proliferation by suppressing intestinal FXR in Apc^min/+ mice. Owing to altered gut microbiota and FXR signalling, changes in overall BA levels and specific BA metabolites probably contribute to enterohepatic tumorigenesis. Modulating intestinal FXR signalling and altering BA metabolites are potential strategies for gastrointestinal and liver cancer prevention and treatment. In this Review, studies on the role of FXR in metabolic diseases and gastrointestinal and liver cancer are discussed, and the potential for development of targeted drugs are summarized.

Causal effects of gallstone disease on risk of gastrointestinal cancer in Chinese

BACKGROUND

Gallstone disease (GSD) is associated with a higher risk of gastrointestinal (GI) cancer. However, it is unclear whether the associations are causal.

METHODS

The prospective China Kadoorie Biobank (CKB) recorded 17,598 cases of GI cancer among 510,137 participants without cancer at baseline during 10 years of follow-up. Cox regression was used to estimate hazard ratios (HRs) for specific cancer by GSD status and duration. Mendelian randomisation was conducted to assess the genetic associations of GSD with specific cancer.

RESULTS

Overall 6% of participants had symptomatic GSD at baseline. Compared with those without GSD, individuals with symptomatic GSD had adjusted HRs of 1.13 (1.01-1.29) for colorectal, 2.01 (1.78-2.26) for liver, 3.70 (2.88-4.87) for gallbladder, 2.31 (1.78-3.07) for biliary tract, and 1.38 (1.18-1.74) for pancreatic cancer. Compared with participants without GSD, the risks of colorectal, liver, gallbladder, biliary tract, and pancreatic cancer were highest during 0 to <5 years following disease diagnosis. There was evidence of genetic associations of GSD with these cancers, with odds ratios per 1-SD genetic score of 1.08 (1.05-1.11) for colorectal, 1.22 (1.19-1.25) for liver, 1.56 (1.49-1.64) for gallbladder, 1.39 (1.31-1.46) for biliary tract, and 1.16 (1.10-1.22) for pancreatic cancer. When meta-analysing the genetic estimates in CKB and UK Biobank, there was evidence of causal associations of GSD with colon cancer, gallbladder and biliary tract cancer (GBTC), and total GI cancer (RR per 1-SD: 1.05 [0.99-1.11], 2.00 [1.91-2.09], and 1.09 [1.05-1.13]).

CONCLUSIONS

GSD was associated with higher risks of several GI cancers, warranting future studies on the underlying mechanisms.

Identification of colorectal neoplasia by using serum bile acid profile

BACKGROUND

Colonoscopy is the gold standard for detecting earlier stages of CRC, although screening of patients is difficult because of invasiveness, low compliance and procedural health risks. Therefore, the need for new screening methods for CRC is rising. Previous studies have demonstrated the diagnostic ability of serum BAs; however, the results have been inconsistent. In this study, we conducted a comprehensive analysis of serum BAs from patients with CRC and verified their diagnostic ability to detect CRC.

METHODS

A total of 56 CRC patients (n = 14 each of stages I-IV), 59 patients with colonic adenoma and 60 healthy controls were included. Age and sex were matched for each group. Serum BA compositions were measured by LC-MS/MS and serum concentration of 30 types of BAs were analysed by discriminant analysis with multidimensional scaling method.

RESULTS

Free CA, 3epi-DCA&CDCA, 3-dehydro CA, GCA and TCA were extracted as principal component (PC) 1 and free 3-dehydroDCA as PC 2 by canonical discriminant function coefficients. The verification of discriminability using cross-validation method revealed that the correct classification rate was 66.3% for original data and 52.6% for cross-validation data.

CONCLUSIONS

A combined analysis using comprehensive serum BA concentration can be an efficient method for screening CRC.

Increased circulating total bile acid levels were associated with organ failure in patients with acute pancreatitis

Background

Recent studies have shown that bile acids (BAs) are closely related to metabolic and inflammatory diseases. Our study aimed to investigate whether circulating total bile acid (TBA) levels were associated with the severity of acute pancreatitis (AP).

Methods

We retrospectively collected data on patients diagnosed with AP in a tertiary center from 01 January 2014 to 31 December 2016. The highest TBA value during the first 1,2,3,5,7 days after admission was determined as D1, D2, D3, D5, D7 TBA_max. Patients were divided into the high TBA (HTBA) group and the normal TBA (NTBA) group according to whether the TBA_max was ≥10 μmol/L. The prognosis and complications, including death, organ failure (OF) and pancreatic necrosis, were compared between the two groups. Logistic regression analysis and receiving operating characteristic (ROC) curve were used to evaluate the relationship between circulating TBA and organ failure in AP patients.

Results

Through stratified analysis of each time period, we found that the incidence of OF in the HTBA group was significantly higher than that in the NTBA group, and the AP severity classification in the HTBA group was more serious than that in the NTBA group. In addition, according to the D7 TBA_max values, the pancreatic necrosis rate, percutaneous catheter drainage (PCD) rate and mortality in the HTBA group were higher than those in the NTBA group. Multivariate regression analysis showed that HTBA (odds ratio (OR), 4.894; P = 0.002) was an independent risk factor for AP complicated with OF, which was verified in the grouping based on D7 TBA_max. ROC analysis revealed that a circulating D7 TBA_max cutoff point of 6.450 umol/L had optimal predictive value for the development of OF in AP patients with an area under the curve of the ROC curve (AUCROC) of 0.777.

Conclusions

The increase of circulating TBA in early stage of AP is independently related to organ failure, which indicates the adverse prognosis of AP patients.

Prediagnostic Plasma Bile Acid Levels and Colon Cancer Risk: A Prospective Study

BACKGROUND

Bile acids have been proposed to promote colon carcinogenesis. However, there are limited prospective data on circulating bile acid levels and colon cancer risk in humans.

METHODS

Associations between prediagnostic plasma levels of 17 primary, secondary, and tertiary bile acid metabolites (conjugated and unconjugated) and colon cancer risk were evaluated in a nested case-control study within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Bile acid levels were quantified by tandem mass spectrometry in samples from 569 incident colon cancer cases and 569 matched controls. Multivariable logistic regression analyses were used to estimate odds ratios (ORs) for colon cancer risk across quartiles of bile acid concentrations.

RESULTS

Positive associations were observed between colon cancer risk and plasma levels of seven conjugated bile acid metabolites: the primary bile acids glycocholic acid (ORquartile 4 vs quartile 1= 2.22, 95% confidence interval [CI] = 1.52 to 3.26), taurocholic acid (OR = 1.78, 95% CI = 1.23 to 2.58), glycochenodeoxycholic acid (OR = 1.68, 95% CI = 1.13 to 2.48), taurochenodeoxycholic acid (OR = 1.62, 95% CI = 1.11 to 2.36), and glycohyocholic acid (OR = 1.65, 95% CI = 1.13 to 2.40), and the secondary bile acids glycodeoxycholic acid (OR = 1.68, 95% CI = 1.12 to 2.54) and taurodeoxycholic acid (OR = 1.54, 95% CI = 1.02 to 2.31). By contrast, unconjugated bile acids and tertiary bile acids were not associated with risk.

CONCLUSIONS

This prospective study showed that prediagnostic levels of certain conjugated primary and secondary bile acids were positively associated with risk of colon cancer. Our findings support experimental data to suggest that a high bile acid load is colon cancer promotive.

Gut microbiota and health: connecting actors across the metabolic system

Overweight-related metabolic diseases are an important threat to health in the Western world. Dietary habits are one of the main causative factors for metabolic syndrome, CVD and type 2 diabetes. The human gut microbiota is emerging as an important player in the interaction between diet and metabolic health. Gut microbial communities contribute to human metabolism through fermentation of dietary fibre and the result of intestinal saccharolytic fermentation is production of SCFA. Acetate, propionate and butyrate positively influence satiety, endocrine system, glucose homeostasis, adipogenesis, lipid oxidation, thermoregulation, hepatic gluconeogenesis, endothelial function and gut barrier integrity, and these mechanisms have all been linked to protection from type 2 diabetes, hypertension and cardiovascular health. The gut microbiota is also involved in bile acid metabolism and regulating their cell signalling potential, which has also been shown to modify pathways involved in metabolic health. Similarly, the gut microbiota renders recalcitrant plant polyphenols into biologically active small phenolic compounds which then act systemically to reduce metabolic disease risk. This review summarises how dietary patterns, specific foods and a healthy lifestyle may modulate metabolic health through the gut microbiota and their molecular cross-talk with the host.

A novel electrochemical biosensor for ultrasensitive detection of serum total bile acids based on enzymatic reaction combined with the double oxidation circular amplification strategy

Serum total bile acids (TBA) level is used as a sensitive and reliable index for hepatobiliary diseases in clinics. Herein, a novel electrochemical biosensor was fabricated using enzymatic reaction coupling with the double oxidation circular amplification strategy for the detection of human serum TBA. With the catalysis of 3α-hydroxysteroid dehydrogenase (3α-HSD), 3α-bile acids reacted specifically with nicotinamide adenine dinucleotide (NAD⁺). And then, the reduced nicotinamide adenine dinucleotide (NADH) was produced. After that, the NADH reacted with the electron mediator of tris(2,2'-bipyridine) ruthenium(Ⅲ) (Ru(bpy)₃³⁺), which was then transformed to Ru(bpy)₃²⁺. Ultimately, Ru(bpy)₃²⁺ was further oxidized to Ru(bpy)₃³⁺ under a certain voltage, which was detected by the chronoamperometry assay. The detection was performed using a disposable unmodified screen-printed carbon electrode (SPCE) without sample preparation. The proposed biosensor showed high sensitivity and accuracy with the linear range from 5.0 to 150.0 pmol/L in 10⁶-fold dilution serum. The established method had a good correlation with the enzymatic cycling method (r = 0.9372, P < 0.001, n = 72) commonly used in clinic. The electrochemical biosensor is simple, ultrasensitive and without sample pretreatment, showing great potential for point-of-care testing (POCT) of serum TBA in clinical samples. In addition, the biosensor is cost-effective with a small volume of samples, especially suitable for those who have difficulties in blood collection, such as infants, children and some small animals.

Plastein reaction enhanced bile-acid binding capacity of soybean protein hydrolysates and whey protein hydrolysates

Plastein reaction is a modification reaction that can improve the functional properties of protein hydrolysate. The product of the reaction is a thixotropic aggregation of peptides. This study investigated the formation condition of soybean-whey plastein and bile acid binding capacity of plastein. Soy protein and whey protein were hydrolyzed by pepsin. The mixture (1:1, w/w) of two hydrolysates was modified by pepsin again. After the reaction, the decrease in free amino groups and the turbidity of the modified hydrolysate were measured to obtain appropriate reaction condition. Results showed that the concentration of hydrolysates 40% (w/v), enzyme ratio of 2.0 KU/g protein, pH 5.0, 37 °C, reaction time of 3.0 h respectively, were showed maximum changes in protein hydrolysates. Tricine SDS-PAGE analysis under denaturing conditions revealed that whey protein was more sensitive to pepsin and yielded different polypeptides (PPs) of molecular weight ranged from 3.5-17 kDa. However, a high molecular weight PP was completely hydrolyzed while PPs of 14.2-26 kDa were partially digested after pepsin treatment. Native page analysis further revealed the presence of a high-molecular weight PP in crude and purified plastein product. The bile acid binding capacity was improved by the plastein reaction. The amount of binding sodium deoxycholate, sodium taurocholate, and sodium cholate were 0.75, 2.0 and 1.87 μmol/100 mg respectively.

Implication of intestinal VDR deficiency in inflammatory bowel disease

BACKGROUND

To investigate the function of the intestinal Vdr gene in inflammatory bowel disease (IBD), in conjunction with the discovery of possible metabolic markers for IBD using intestine-specific Vdr knockout mice.

METHODS

Vdr(ΔIEpC) mice were generated, phenotyped and treated with a time-course of 3% dextran sulfate sodium (DSS) to induce colitis. Colitis was diagnosed by evaluating clinical symptoms and intestinal histopathology. Gene expression analysis was carried out. In addition, metabolic markers of IBD were explored by metabolomics.

RESULTS

Vdr(ΔIEpC) mice showed abnormal body size, colon structures and feces color. Calcium, collagen, and intestinal proliferation-related gene expression were all decreased, and serum alkaline phosphatase was highly increased. In the acute model which was treated with 3% DSS for six days, Vdr(ΔIEpC) mice showed a high score of IBD symptoms; enlarged mucosal layer and damaged muscularis layer. In the recovery experiment model, where mice were treated with 3% DSS for four days and water for three days, Vdr(ΔIEpC) mice showed a high score of IBD symptoms; severe damage of mucosal layer and increased expression of genes encoding proinflammatory cytokines. Feces metabolomics revealed decreased concentrations of taurine, taurocholic acid, taurodeoxycholic acid and cholic acid in Vdr(ΔIEpC) mice.

CONCLUSIONS

Disruption of the intestinal Vdr gene showed phenotypical changes that may exacerbate IBD. These results suggest that VDR may play an important role in IBD.

GENERAL SIGNIFICANCE

VDR function has been implicated in IBD. This is of value for understanding the etiology of IBD and for development of diagnostic biomarkers for IBD.

Chemoprevention of colorectal cancer with ursodeoxycholic acid: pro

Colorectal cancer is the third and second most common cancer among men and women, respectively, in France. Interest in the chemoprevention of colorectal cancer has increased over the last two decades. Experimental data strongly suggest that ursodeoxycholic acid (UDCA) may have chemopreventative actions in colorectal cancer. UDCA is able to inhibit tumor development in azoxymethane and in dextran-related colitis models. In high-risk populations such as subjects with previous colorectal adenoma removal or inflammatory bowel disease, five out of 10 published studies suggested beneficial effects with UDCA on colonic carcinogenesis. In the azoxymethane model, UDCA inhibited tumor development by counteracting the tumor-promoting effects of secondary bile acids such as deoxycholic acid (DCA). The opposing effects of UDCA and DCA on lipid raft composition may be central to their effects on colonic tumorigenesis. Differential effects of DCA and UDCA on growth factor and inflammatory signals involved in colorectal carcinogenesis, such as epidermal growth factor receptor (EGFR) signaling and COX-2 expression, very likely mediate their opposing effects on colonic tumor promotion and tumor inhibition, respectively.

Role of bacteria in oncogenesis

Although scientific knowledge in viral oncology has exploded in the 20th century, the role of bacteria as mediators of oncogenesis has been less well elucidated. Understanding bacterial carcinogenesis has become increasingly important as a possible means of cancer prevention. This review summarizes clinical, epidemiological, and experimental evidence as well as possible mechanisms of bacterial induction of or protection from malignancy.

Ursodeoxycholic acid and chemoprevention of colorectal cancer

Colorectal cancer is respectively the third and second most common cancer among men and women in France. Interest in chemoprevention for colorectal cancer has increased over the last two decades. Beside non-steroidal anti-inflammatory drugs, ursodeoxycholic acid (UDCA) may have chemopreventive action in colorectal cancer with a likely better tolerance. In high-risk populations such as patients with inflammatory bowel disease or prior colorectal adenoma or carcinoma, retrospective and prospective studies have suggested a beneficial effect of UDCA. In azoxymethane model, UDCA inhibits tumor development by countering the tumor-promoting effects of secondary bile acids, such as deoxycholic acid (DCA). The opposing effects of UDCA and DCA on lipid raft composition may be central to their effects on colonic tumorigenesis. Differential effects of DCA and UDCA on growth factor and inflammatory signals involved in colorectal carcinogenesis, such as epidermal growth factor receptors (EGFR) signaling and Cox-2 expression, likely mediate their opposing effects on colonic tumor promotion and tumor inhibition, respectively.

Steam cooking significantly improves in vitro bile acid binding of collard greens, kale, mustard greens, broccoli, green bell pepper, and cabbage

Bile acid binding capacity has been related to the cholesterol-lowering potential of foods and food fractions. Lowered recirculation of bile acids results in utilization of cholesterol to synthesize bile acid and reduced fat absorption. Secondary bile acids have been associated with increased risk of cancer. Bile acid binding potential has been related to lowering the risk of heart disease and that of cancer. Previously, we have reported bile acid binding by several uncooked vegetables. However, most vegetables are consumed after cooking. How cooking would influence in vitro bile acid binding of various vegetables was investigated using a mixture of bile acids secreted in human bile under physiological conditions. Eight replicate incubations were conducted for each treatment simulating gastric and intestinal digestion, which included a substrate only, a bile acid mixture only, and 6 with substrate and bile acid mixture. Cholestyramine (a cholesterol-lowering, bile acid binding drug) was the positive control treatment and cellulose was the negative control. Relative to cholestyramine, in vitro bile acid binding on dry matter basis was for the collard greens, kale, and mustard greens, 13%; broccoli, 10%; Brussels sprouts and spinach, 8%; green bell pepper, 7%; and cabbage, 5%. These results point to the significantly different (P < or = .05) health-promoting potential of collard greens = kale = mustard greens > broccoli > Brussels sprouts = spinach = green bell pepper > cabbage as indicated by their bile acid binding on dry matter basis. Steam cooking significantly improved the in vitro bile acid binding of collard greens, kale, mustard greens, broccoli, green bell pepper, and cabbage compared with previously observed bile acid binding values for these vegetables raw (uncooked). Inclusion of steam-cooked collard greens, kale, mustard greens, broccoli, green bell pepper, and cabbage in our daily diet as health-promoting vegetables should be emphasized. These green/leafy vegetables, when consumed regularly after steam cooking, would lower the risk of cardiovascular disease and cancer, advance human nutrition research, and improve public health.

Genetic polymorphism of cholesterol 7alpha-hydroxylase (CYP7A1) and colorectal adenomas: Self Defense Forces Health Study

Bile acids have long been implicated in colorectal carcinogenesis, but epidemiological evidence is limited. Cholesterol 7alpha-hydroxylase (CYP7A1) is the rate-limiting enzyme producing bile acids from cholesterol. A recent case-control study showed a decreased risk of proximal colon cancer associated with the CC genotype of the CYP7A1 A-203C polymorphism. The present study examined the relationship between the CYP7A1 A-203C polymorphism and colorectal adenoma, which is a well-established precursor lesion of colorectal cancer. The study subjects comprised 446 cases of colorectal adenomas and 914 controls of normal total colonoscopy among men receiving a preretirement health examination at two hospitals of the Self Defense Forces (SDF). The CYP7A1 genotype was determined by the polymerase chain reaction-restriction fragment length polymorphism method. Statistical adjustment was made for age, hospital, rank in the SDF, smoking, alcohol use, body mass index, physical activity and parental history of colorectal cancer. The CYP7A1 polymorphism was not measurably related to the overall risk of colorectal adenomas. However, the CC genotype was associated with a decreased risk of proximal colon adenomas, but not of distal colon and rectal adenomas. Adjusted odds ratios of proximal colon adenomas (95% confidence intervals) for the AC and CC genotype versus AA genotype were 0.82 (0.54-1.24) and 0.56 (0.34-0.95), respectively. The findings add to evidence for the role of bile acids in colorectal carcinogenesis. The CC genotype of the CYP7A1 A-203C polymorphism probably renders lower activity of the enzyme synthesizing bile acids.

Genetic polymorphism in cytochrome P450 7A1 and risk of colorectal cancer: the Fukuoka Colorectal Cancer Study

Bile acids have long been implicated in the etiology of colorectal cancer, but epidemiologic evidence remains elusive. Cholesterol 7alpha-hydroxylase (CYP7A1) is the rate-limiting enzyme in the synthesis of bile acids from cholesterol in the liver, and thus may be an important determinant of bile acid production. We examined the association between the CYP7A1 A-203C polymorphism and colorectal cancer. The CYP7A1 A-203C polymorphism was determined by the PCR-RFLP method in 685 incident cases of colorectal cancer and 778 controls randomly selected from a community in the Fukuoka area, Japan. The CC genotype was slightly less frequent in the case group, and the adjusted odds ratio for the CC versus AA genotype was 0.88 (95% confidence interval, 0.65-1.20). In the analysis by subsite of the colorectum, a decreased risk associated with the CYP7A1 CC genotype was observed for proximal colon cancer, but not for either distal colon or rectal cancer. The adjusted odds ratios (95% confidence intervals) of proximal colon cancer for the CC genotype were 0.63 (0.36-1.10) compared with the AA genotype, and 0.59 (0.37-0.96) compared with the AA and AC genotypes combined. A decreased risk of proximal colon cancer in relation to the CC genotype of CYP7A1 A-203C, which probably renders less activity of the enzyme converting cholesterol to bile acids, is new evidence for the role of bile acids in colorectal carcinogenesis.

Serum bile acids and risk factors for colorectal cancer

The ratio of deoxycholic acid to chenodeoxycholic acid in the serum of 62 men was inversely related to body mass index and to saturated fat intake after adjustment for body mass index, smoking, and age conversely, this ratio was associated positively with the intake of fibre from grains.