Increased bile acid concentration in liver tissue with cholesterol gallstone disease

Bile acid metabolism and signaling in health and disease: molecular mechanisms and therapeutic targets

Bile acids, once considered mere dietary surfactants, now emerge as critical modulators of macronutrient (lipid, carbohydrate, protein) metabolism and the systemic pro-inflammatory/anti-inflammatory balance. Bile acid metabolism and signaling pathways play a crucial role in protecting against, or if aberrant, inducing cardiometabolic, inflammatory, and neoplastic conditions, strongly influencing health and disease. No curative treatment exists for any bile acid influenced disease, while the most promising and well-developed bile acid therapeutic was recently rejected by the FDA. Here, we provide a bottom-up approach on bile acids, mechanistically explaining their biochemistry, physiology, and pharmacology at canonical and non-canonical receptors. Using this mechanistic model of bile acids, we explain how abnormal bile acid physiology drives disease pathogenesis, emphasizing how ceramide synthesis may serve as a unifying pathogenic feature for cardiometabolic diseases. We provide an in-depth summary on pre-existing bile acid receptor modulators, explain their shortcomings, and propose solutions for how they may be remedied. Lastly, we rationalize novel targets for further translational drug discovery and provide future perspectives. Rather than dismissing bile acid therapeutics due to recent setbacks, we believe that there is immense clinical potential and a high likelihood for the future success of bile acid therapeutics.

Pathogenetic aspects of the development of cholelithiasis in patients with metabolic syndrome

Nowadays there is a steady tendency to increase the number of patients with gallstone disease and metabolic syndrome. Increasingly, gallstone disease is called a non-canonical cluster of metabolic syndrome, because the main components of metabolic syndrome are also modifiable risk factors for gallstone disease. This article discusses the pathogenetic parallels in the development of gallstone disease and metabolic syndrome - insulin resistance and hormones of adipose tissue, lipid metabolism disorders, immune factors and the cytokine system. There are described possible effects of cholecystectomy on metabolism in patients with metabolic syndrome.

Human-specific dual regulations of FXR-activation for reduction of fatty liver using in vitro cell culture model

Nuclear receptor farnesoid X receptor activation inhibits fatty acid synthesis through the liver X receptor-α-sterol regulatory element binding protein-1c pathway universally in animals, but also has human-specific crosstalk with the peroxisome proliferator-activated receptor-α. The effects of farnesoid X receptor-ligands on both the synthesis and degradation of fatty liver through nuclear receptor-related regulation were investigated in both human and murine hepatocytes. A fatty liver culture cell model was established using a synthetic liver X receptor-α-ligand (To901317) for both human and mouse non-neoplastic hepatocytes. The hepatocytes were exposed to natural or synthetic farnesoid X receptor-ligands (bile acids, GW4064, obeticholic acid) together with or after To901317. Cellular triglyceride accumulation was significantly inhibited by the farnesoid X receptor-ligands along with inhibition of lipogenic genes and up-regulation of farnesoid X receptor-target small heterodimer partner in both human and mouse cells. The accumulated triglyceride was significantly degraded by the farnesoid X receptor-ligands only in the human cells accompanied with the up-regulations of peroxisome proliferator-activated receptor-α and fatty acid β-oxidation. Farnesoid X receptor-ligands can be therapeutic agents for treating human fatty liver through dual effects on inhibition of lipogenesis and on enhancement of lipolysis.

Experimental Periodontitis Results in Prediabetes and Metabolic Alterations in Brain, Liver and Heart: Global Untargeted Metabolomic Analyses

Results from epidemiological studies suggest that there is an association between periodontitis and prediabetes, however, causality is not known. The results from our previous studies suggest that induction of periodontitis leads to hyperinsulinemia glucose intolerance and insulin resistance, all hallmarks of prediabetes. However, global effects of periodontitis on critical organs in terms of metabolic alterations are unknown. We determined the metabolic effects of periodontitis on brain, liver, heart and plasma resulting from Porphyromonas gingivalis induced periodontitis in mice. Periodontitis was induced by oral application of the periodontal pathogen, Porphyromonas gingivalis for 22 weeks. Global untargeted biochemical profiles in samples from these organs/plasma were determined by liquid and gas chromatography/mass spectrometry and compared between controls and animals with periodontitis. Oral application of Porphyromonas gingivalis induced chronic periodontitis and hallmarks of prediabetes. The results of sample analyses indicated a number of changes in metabolic readouts, including changes in metabolites related to glucose and arginine metabolism, inflammation and redox homeostasis. Changes in biochemicals suggested subtle systemic effects related to periodontal disease, with increases in markers of inflammation and oxidative stress most prominent in the liver. Signs of changes in redox homeostasis were also seen in the brain and heart. Elevated bile acids in liver were suggestive of increased biosynthesis, which may reflect changes in liver function. Interestingly, signs of decreasing glucose availability were seen in the brain. In all three organs and plasma, there was a significant increase in the microbiome-derived bioactive metabolite 4-ethylphenylsulfate sulfate in animals with periodontitis. The results of metabolic profiling suggest that periodontitis/bacterial products alter metabolomic signatures of brain, heart, liver, and plasma in the prediabetic state. These data provide scientific community valuable metabolic signatures that become the basis for understanding the impact of periodontitis on a systemic disease and potentially targets for therapeutic intervention.

The role of the gallbladder in humans

The basic function of the gallbladder in humans is one of protection. The accumulation of the primary bile acids (cholic acid and chenodeoxycholic acid) in the gallbladder reduces the formation of the secondary bile acids (deoxycholic acid and lithocholic acid), thus diminishing their concentration in the so-called gallbladder-independent enterohepatic circulation and protecting the liver, the stomach mucosa, the gallbladder, and the colon from their toxic hydrophobic effects. The presence or absence of the gallbladder in mammals is a determining factor in the synthesis of hydrophobic or hydrophilic bile acids. Because the gallbladder contracts 5-20 min after food is in the stomach and the "gastric chyme" moves from the stomach to the duodenum 1-3 h later, the function of the gallbladder bile in digestion may be insignificant. The aim of this article was to provide a detailed review of the role of the gallbladder and the mechanisms related to bile formation in humans.

Bile acid levels are increased in the liver of patients with steatohepatitis

BACKGROUND/AIMS

The pathogenesis of steatohepatitis remains largely unknown; however, bile acids may play a role as potential mediators of liver damage. The aim of this study was to characterize bile acid profiles in liver tissue of patients with steatohepatitis.

METHODS

Bile acid composition was determined by gas-liquid chromatography in liver tissue from patients with nonalcoholic steatohepatitis (NASH; n=15), patients with alcoholic steatohepatitis (ASH; n=14), and controls (n=8). Liver biopsies were graded for steatosis, inflammation, and fibrosis.

RESULTS

Bile acids were moderately increased in liver tissue of steatohepatitis patients compared with controls (P<0.05). Deoxycholic, chenodeoxycholic, and cholic acids were elevated by 92, 64, and 43%, respectively, in patients with steatohepatitis (P<0.05). Cholic acid was the prevailing bile acid in NASH patients and in controls. More hydrophobic bile acid species were elevated in ASH patients compared with controls (P<0.05). Significant correlations were found in NASH patients between hepatic chenodeoxycholic acid and fibrosis, and between cholic acid and trihydroxy/dihydroxy bile acids and inflammation (P<0.05). In patients with ASH, cholic acid and trihydroxy/dihydroxy bile acids were correlated with steatosis (P<0.01).

CONCLUSION

This study shows a distinct pattern of bile acids in the liver of patients with steatohepatitis. Further, the association between bile acids and histological liver injury suggests an association of specific bile acids and disease progression, possibly through bile acid-induced liver injury.

Hypercholesterolemia in rats with hepatomas: increased oxysterols accelerate efflux but do not inhibit biosynthesis of cholesterol

Hypercholesterolemia is an important paraneoplastic syndrome in patients with hepatoma, but the nature of this defect has not yet been identified. We investigated the molecular mechanisms of hypercholesterolemia in a hepatoma-bearing rat model. Buffalo rats were implanted in both flanks with Morris hepatoma 7777 (McA-RH7777) cells. After 4 weeks, tumor weight was 5.5+/-1.7 g, and serum cholesterol level increased from 60+/-2 to 90+/-2 mg/dL. Protein and mRNA expression of the ATP-binding cassette transporters A1 and G1 (ABCA1 and ABCG1) was markedly higher in tumors than in livers. These increases were associated with activation of liver X receptor alpha (LXRalpha) as a result of the increased tissue oxysterol concentrations. The accumulation of oxysterols in the hepatomas appeared to be caused mainly by the upregulation of cholesterol biosynthesis, despite the increased tissue sterol concentrations. Overexpression of the sterol regulatory element-binding protein (SREBP) processing system relative to sterol concentration contributed to the resistance to sterols in this tumor. In addition, bile acid biosynthesis was inhibited despite the reduced expression of the small heterodimer partner (SHP) and activated LXRalpha, which also appeared to contribute to the accumulation of oxysterols followed by the acceleration of cholesterol efflux. In conclusion, hypercholesterolemia in McA-RH7777 hepatoma-bearing rats was caused by increased cholesterol efflux from tumors as a result of activation of LXRalpha. Overexpression of the SREBP processing system contributed to the activation of LXRalpha by maintaining high oxysterol levels in tissue.

Disrupted coordinate regulation of farnesoid X receptor target genes in a patient with cerebrotendinous xanthomatosis

Cerebrotendinous xanthomatosis (CTX), sterol 27-hydroxylase (CYP27A1) deficiency, is associated with markedly reduced chenodeoxycholic acid (CDCA), the most powerful activating ligand for farnesoid X receptor (FXR). We investigated the effects of reduced CDCA on FXR target genes in humans. Liver specimens from an untreated CTX patient and 10 control subjects were studied. In the patient, hepatic CDCA concentration was markedly reduced but the bile alcohol level exceeded CDCA levels in control subjects (73.5 vs. 37.8 +/- 6.2 nmol/g liver). Cholesterol 7alpha-hydroxylase (CYP7A1) and Na+/taurocholate-cotransporting polypeptide (NTCP) were upregulated 84- and 8-fold, respectively. However, small heterodimer partner (SHP) and bile salt export pump were normally expressed. Marked CYP7A1 induction with normal SHP expression was not explained by the regulation of liver X receptor alpha (LXRalpha) or pregnane X receptor. However, another nuclear receptor, hepatocyte nuclear factor 4alpha (HNF4alpha), was induced 2.9-fold in CTX, which was associated with enhanced mRNA levels of HNF4alpha target genes, CYP7A1, 7alpha-hydroxy-4-cholesten-3-one 12alpha-hydroxylase, CYP27A1, and NTCP. In conclusion, the coordinate regulation of FXR target genes was lost in CTX. The mechanism of the disruption may be explained by a normally stimulated FXR pathway attributable to markedly increased bile alcohols with activation of HNF4alpha caused by reduced bile acids in CTX liver.

Prospective evaluation of intestinal homing memory T cells in ulcerative colitis

BACKGROUND

Intestinal homing (beta7+) memory T cells reflect the mucosal environment in which they were primed. We hypothesized that prospective assessment of cytokine production by intestinal homing (beta7+) memory T cells in ulcerative colitis patients followed from remission to early relapse may elucidate shifts in cytokine production relevant to the mucosal environment associated with the early phase of inflammation.

METHODS

Twelve patients with frequently relapsing ulcerative colitis (> or = 2 relapses in the previous 12 months) were recruited in remission and followed prospectively until relapse. Antibody labeling of whole blood and flow cytometry were used to identify beta7+ cells and beta7- populations within CD3+CD45RA- leukocytes. Production of cytokines (IFN-gamma, TNF-alpha, IL-2, IL-10, TGF-beta, and IL-4) was determined by intracellular labeling.

RESULTS

Early relapse of ulcerative colitis was associated with a shift of T cells from the naive to the memory T cell pool, and further the ratio of beta7+:beta7- memory T cells was significantly reduced at relapse (p < 0.01). A greater proportion of intestinal homing beta7+ memory T cells produced IL-4 (p < 0.02) and TNF-alpha (p < 0.05) at disease relapse compared with remission. Non-intestinal homing beta7- memory T cells also showed a tendency toward an increased production of TH1 and TH2 cytokines.

CONCLUSIONS

The earliest phase of intestinal inflammation in ulcerative colitis patients is associated with an increase in both TH1 (TNF-alpha and TH2 (IL-4) cytokines by intestinal homing beta7+ memory T cells. These data support the principles of targeting lymphocyte trafficking as therapies in ulcerative colitis.

Differential expression of CCR5 and CRTH2 on infiltrated cells in colonic mucosa of patients with ulcerative colitis

BACKGROUND AND AIM

The pathogenesis of ulcerative colitis (UC) is unclear, but abnormal infiltration of T lymphocytes in the colonic mucosa has been implicated in the mucosal tissue damage. The abnormal cytokine production because of a T helper (h)1/Th2 imbalance may play an important role in continuing inflammation in the colonic mucosa. In the present study, the expression of chemokine receptor 5 (CCR5) as a Th1 marker and a chemoattractant receptor-homologs molecule expressed on Th2 cells (CRTH2) were investigated in order to analyze impaired Th1/Th2 responses in the colonic mucosa of UC patients.

METHODS

Tissue samples were obtained by colonic biopsies from patients with UC or colonic polyps, with informed consent. Immunohistochemical analysis was performed on periodate, lysine-paraformaldehyde-fixed serial cryostat sections using the labeled streptavidin biotin method. Monoclonal antibodies against CD4, CCR5 or CRTH2 were used as primary antibodies. The number of cells expressing CD4, CCR5 or CRTH2 per unit area was calculated by using an image analyzer.

RESULTS

In the patients with UC, the numbers of CD4- and CCR5-positive cells were significantly increased in inflamed mucosa, and appeared to be correlated with the disease activity. The infiltration of CRTH2-positive cells was predominantly observed in the mildly inflamed or the margin of inflamed mucosa of UC patients.

CONCLUSION

There is a possibility that Th1 responses significantly occur in colonic mucosa with severe inflammation, while Th2 responses mainly occur with mild inflammation in UC patients. The Th1/Th2 imbalance in colonic mucosa may be related to the disease progression of UC.

Selective inhibition of CYP27A1 and of chenodeoxycholic acid synthesis in cholestatic hamster liver

The aim of this study was to explore the regulation of serum cholic acid (CA)/chenodeoxycholic acid (CDCA) ratio in cholestatic hamster induced by ligation of the common bile duct for 48 h. The serum concentration of total bile acids and CA/CDCA ratio were significantly elevated, and the serum proportion of unconjugated bile acids to total bile acids was reduced in the cholestatic hamster similar to that in patients with obstructive jaundice. The hepatic CA/CDCA ratio increased from 3.6 to 11.0 (P<0.05) along with a 2.9-fold elevation in CA concentration (P<0.05) while the CDCA level remained unchanged. The hepatic mRNA and protein level as well as microsomal activity of the cholesterol 7alpha-hydroxylase, 7alpha-hydroxy-4-cholesten-3-one 12alpha-hydroxylase and 5beta-cholestane-3alpha,7alpha,12alpha-triol 25-hydroxylase were not significantly affected in cholestatic hamsters. In contrast, the mitochondrial activity and enzyme mass of the sterol 27-hydroxylase were significantly reduced, while its mRNA levels remained normal in bile duct-ligated hamster. In conclusion, bile acid biosynthetic pathway via mitochondrial sterol 27-hydroxylase was preferentially inhibited in bile duct-ligated hamsters. The suppression of CYP27A1 is, at least in part, responsible for the relative decreased production of CDCA and increased CA/CDCA ratio in the liver, bile and serum of cholestatic hamsters.

The role of acetaldehyde in the actions of alcohol (update 2000)

BACKGROUND

Recent advances in the field of acetaldehyde (AcH) research have raised the need for a comprehensive review on the role of AcH in the actions of alcohol. This update is an attempt to summarize the available AcH research.

METHODS

The descriptive part of this article covers not only recent research but also the development of the field. Special emphasis is placed on mechanistic analyses, new hypotheses, and conclusions.

RESULTS

Elevated AcH during alcohol intoxication causes alcohol sensitivity, which involves vasodilation associated with increased skin temperature, subjective feelings of hotness and facial flushing, increased heart and respiration rate, lowered blood pressure, sensation of dry mouth or throat associated with bronchoconstriction and allergy reactions, nausea and headache, and also reinforcing reactions like euphoria. These effects seem to involve catecholamine, opiate peptide, prostaglandin, histamine, and/or kinin mechanisms. The contribution of AcH to the pathological consequences of chronic alcohol intake is well established for different forms of cancer in the digestive tract and the upper airways. AcH seems to play a role in the etiology of liver cirrhosis. AcH may have a role in other pathological developments, which include brain damage, cardiomyopathy, pancreatitis, and fetal alcohol syndrome. AcH creates both unpleasant aversive reactions that protect against excessive alcohol drinking and euphoric sensations that may reinforce alcohol drinking. The protective effect of AcH may be used in future treatments that involve gene therapy with or without liver transplantation.

CONCLUSIONS

AcH plays a role in most of the actions of alcohol. The individual variability in these AcH-mediated actions will depend on the genetic polymorphism, not only for the alcohol and AcH-metabolizing enzymes but also for the target sites for AcH actions. The subtle balance between aversive and reinforcing, protecting and promoting factors will determine the overall behavioral and pathological developments.

Intrahepatic cholestasis of pregnancy

Intrahepatic cholestasis of pregnancy is one of the primary disorders of the liver that adversely affects maternal well-being and fetal outcome. Early identification of this condition, careful interdisciplinary monitoring, and prompt delivery at fetal maturity can improve outcomes in the mother and child. Although the cause is unclear, IHCP probably arises from a genetic predisposition for increased sensitivity to estrogens and progestogens and altered membrane composition and expression of bile ducts, hepatocytes, and canalicular transport systems. As a result, the elevations in maternal levels of bile acids and their molar ratios seen in healthy pregnancy rise further in IHCP patients. Also, as the normal fetal-to-maternal transfer of bile acids across the trophoblast is impaired, the excess bile acids with abnormal profiles accumulate and are toxic to the fetus. The management of IHCP is dictated by the increased risks of fetal distress, spontaneous preterm delivery, and sudden death, as well as by alleviating pruritus in the mother. These risks to the fetus rise progressively to delivery, regardless of serum levels of bile acids and ALT. Close monitoring of these markers is essential but does not prevent sudden fetal distress and death. Provision should be made to induce labor as soon as fetal lung maturity has been established. Ursodeoxycholic acid is the only therapy that has proven effective, albeit in small studies, in alleviating pruritus and restoring towards normal the abnormal profiles of bile acids and sulfated steroids in serum and other body fluids. Ursodeoxycholic acid seems to have no obvious adverse effects on the fetus, but experience is insufficient to draw conclusions regarding teratogenicity and prevention of adverse outcomes.

The role of IL-10 in inflammatory bowel disease: "of mice and men"

Inflammatory bowel disease (IBD) is a generic term typically used to describe a group of idiopathic inflammatory intestinal conditions in humans that are generally divided into Crohn's disease and ulcerative colitis. Although the etiology of these diseases remains unknown, a number of rodent models of IBD have recently been identified, all sharing the concept that the development of chronic intestinal inflammation occurs as a consequence of alterations in the immune system that lead to a failure of normal immunoregulation in the intestine. On the basis of these models, it has been hypothesized that the development of IBD in humans may be related to a dysregulated immune response to normal flora in the gut. Immunodeficient scid mice injected with CD4+ CD45RB(high) T cells and mice deficient in interleukin (IL)-10 (IL-10-/-) are among the rodent models of IBD. In both models, there is inflammation and evidence of a Th1-like response in the large intestine, characterized by CD4+ T-cell and macrophage infiltrates, and elevated levels of interferon-gamma. Because IL-10 is an immunomodulatory cytokine that is capable of controlling Th1-like responses, the role of IL-10 was investigated in these models. IL-10 was shown to be important in regulating the development of intestinal inflammation in both models. These results provided key data that supported initiation of clinical trials evaluating the efficacy of IL-10 in patients with IBD.

Hepatic and serum bile acid compositions in patients with biliary atresia: a microanalysis using gas chromatography-mass spectrometry with negative ion chemical ionization detection

Hepatic and serum bile acids in five patients with biliary atresia were preoperatively determined by microanalysis using gas chromatography-mass spectrometry with negative ion chemical ionization detection. The hepatic content of total bile acids was markedly elevated (3079+/-711 nmol/g protein), most of which were primary bile acids. Accumulation of unconjugated bile acids (2.93% to 4.62% of the total) was observed in the liver tissue of these patients, although only trace amounts were detected in their sera. The ratio of glycine-conjugated to taurine-conjugated bile acids was 0.44+/-0.18 in liver tissue and 0.79+/-0.52 in serum and these values were significantly lower than those of controls. This study has shown that the composition of bile acids in serum does not reflect that in liver tissue faithfully. The accumulation of these hydrophobic bile acids may contribute to initiating or exacerbating liver injury in infants with cholestatic liver diseases.

Accumulation of 7 alpha-hydroxycholesterol in liver tissue of patients with cholesterol gallstones

Patients with cholesterol gallstones have a reduced pool of bile acids. This study was undertaken to clarify the mechanism by which bile acid biosynthesis does not increase to supranormal levels to cause a reexpansion of the pool. We investigated the first two steps of the bile acid biosynthesis pathway by assaying the activities of cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme in this pathway, and 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase, and by measuring the concentrations of 7 alpha-hydroxycholesterol and 7 alpha-hydroxy-4-cholesten-3-one in liver specimens from ten patients with cholesterol gallstones and ten gallstone-free controls. In the patients with gallstones, cholesterol 7 alpha-hydroxylase activity, 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase activity, and hepatic 7 alpha-hydroxy-4-cholesten-3-one concentration did not significantly different from levels in controls, but hepatic 7 alpha-hydroxycholesterol concentration was more than twofold that of controls (12.9 +/- 2.6 vs 5.3 +/- 1.2 nmol/g liver, P < 0.01). The concentration of 7 alpha-hydroxycholesterol positively correlated with the ratio of cholesterol 7 alpha-hydroxylase activity to 3 beta-hydroxy-delta 5-C27-steroid dehydrogenase/isomerase activity (r = 0.93; P < 0.005) in the gallstone-free controls. In contrast, this correlation disappeared in the patients with gallstones. These results suggest a derangement of the normal 7 alpha-hydroxycholesterol metabolism in the patients with gallstones. The reason for the accumulation of 7 alpha-hydroxycholesterol remains unclear; however, it is possible that, in patients with cholesterol gallstone, the accumulated 7 alpha-hydroxycholesterol causes inappropriate suppression of cholesterol 7 alpha-hydroxylase activity by product inhibition.