Dietary fish oil regulates gene expression of cholesterol and bile acid transporters in mice

Aim: Fish oil rich in n‐3 polyunsaturated fatty acids is known to affect hepatic lipid metabolism. Several studies have demonstrated that fish oil may affect the bile acid metabolism as well as lipid metabolism, whereas only scarce data are available. The aim of this study was to investigate the effect of fish oil on the gene expression of the transporters and enzymes related to bile acid as well as lipid metabolism in the liver and small intestine. Methods: Seven‐week old male C57BL/6 mice were fed diets enriched in 10% soybean oil or 10% fish oil for 4 weeks. After 4 weeks, blood, liver and small intestine were obtained. Results: Hepatic mRNA expression of lipids (Abcg5/8, multidrug resistance gene product 2) and bile acids transporters (bile salt export pump, multidrug resistance associated protein 2 and 3, organic solute transporter α) was induced in fish oil‐fed mice. Hepatic Cyp8b1, Cyp27a1 and bile acid CoA : amino acid N‐acyltransferase were increased in fish oil‐fed mice compared with soybean‐oil fed mice. Besides, intestinal cholesterol (Abcg5/8) and bile acid transporters (multidrug resistance associated protein 2 and organic solute transporter α) were induced in fish oil‐fed mice. Conclusion: Fish oil induced the expression of cholesterol and bile acid transporters not only in liver but in intestine. The upregulation of Abcg5/g8 by fish oil is caused by an increase in cellular 27‐HOC through Cyp27a1 induction. The hepatic induction of bile acid synthesis through Cyp27a1 may upregulate expression of bile acid transporters in both organs.     

Method for quantitative assessment of transformation of non-micellar cholesterol carriers in model bile systems*

Aggregation and fusion of non-micellar particulate species, such as unilamellar vesicle and phospholipid lamellae, are believed to precede the nucleation of cholesterol crystals in bile. However, little is known about the time sequence relationship between transformation of non-micellar particles and the initial appearance of cholesterol crystals, as no adequate technique is available for assessing such transformations quantitatively. We have developed a novel method for quantitatively estimating vesicle transformation in supersaturated model bile systems, using a spectrophotometric technique to determine the time sequence relationship between such transformations and cholesterol crystal nucleation. We also investigated the potency of a given effector substance on this transformation. This method permits simultaneous quantitative determination of vesicle aggregation and of cholesterol crystal growth. Maximal vesicular aggregation as determined from turbidity, coincided with initiation of cholesterol crystal nucleation. The addition of divalent cations, Ca²⁺ and Mg²⁺, to the model bile solutions promoted vesicle aggregation and cholesterol crystal nucleation and growth. In contrast, apolipoproteins A-1 and A-2 retarded such processes. These data were highly reproducible and reliable. The method described is easy to perform, provides reproducible results and permits the determination of the potency of effector substances on vesicle transformation and on the nucleation of cholesterol crystals.     

急性冠脉综合征患者胆固醇、总胆汁酸及总胆红素检测的临床意义

目的探讨急性冠脉综合征（ACS）患者血清总胆固醇（TC）、总胆汁酸（TBA）及总胆红素（TBIL）的变化及临床意义。方法选取住院治疗的100例ACS患者为观察组,其中稳定型心绞痛（SA）39例,不稳定型心绞痛（UA）38例,急性心肌梗死（AMI）23例。同期健康体检者100例为对照组,检测两组血清总胆固醇（TC）、总胆汁酸（TBA）及总胆红素（TBIL）的水平,并做相关统计学分析。结果观察组的TC及TBA水平高于对照组,差异有统计学意义（P〈0.05）;且观察组的TC及TBA水平由SA、UA到AMI依次升高,差异有统计学意义（P〈0.05）;观察组的TBIL水平低于对照组,差异有统计学意义（P〈0.05）;观察组的TBIL水平由SA、UA到AMI依次减低,差异有统计学意义（P〈0.05）。结论 TC、TBA及TBIL联合检测对ACS的诊断及病情发展评价有重要的临床意义。     

Contact solvents for common bile duct stones. Study in an in vitro system

Abstract: Cholesterol and brown pigment stones found in the common bile duct are often radiolucent and therefore indistinguishable. The purpose of this study was to define contact solvent systems able to dissolve both stone types. The influence of mucolytic agents on in vitro pigment stone dissolution was first determined. It was shown that dithioerythritol induced more rapid dissolution than N-acetylcysteine. Alternating treatment with an aqueous alkaline solvent (pH=9.5), composed of sodium deoxycholate 50 mM, ethylenediaminetetraacetate 26 mM and dithioerythritol 50 mM, for 45 min, and an organic solvent methyl tert-butyl ether/dimethyl sulfoxide (90/10) for 15 min, was more effective for bilirubin, cholesterol, and fatty acid solubilization (p<0.01) than using these solvents separately. The dissolution of brown stones was nearly completed within 9 h and that of mixed cholesterol stones was obtained within 3 h. We conclude that the alternating treatment described is very effective for the rapid in vitro dissolution of the two major stone types present in the bile ducts, and deserves further assessment in vivo.     

非酒精性脂肪性肝病的靶向治疗研究进展

非酒精性脂肪性肝病（NAFLD）是最常见的进行性疾病,临床上目前尚无疗效确切的治疗药物。介绍了脂肪酸-胆酸偶合物（FABACs）和熊去氧胆酸-溶血磷脂酰乙醇胺偶合物（UDCA-LPE）两种新型的具有NAFLD防治作用的肝靶向药物的研究进展。FABACs通过调节脂代谢,特异性的降低高脂饲料所致NAFLD的肝脏脂肪升高,预防NAFLD的形成;而且对已形成的NAFLD也有治疗作用;Ⅱ期临床研究结果显示其起效快、安全性好。UDCA-LPE在降低NAFLD的肝脏脂肪的同时,能够抑制线粒体损伤和凋亡,促进肝细胞再生,对NAFLD发展过程中的相关炎症具有显著的抑制作用。因此,FABACs和UDCA-LPE对防治NAFLD具有良好的应用前景。     

Impaired absorption of cholesterol and bile acids in patients with an ileoanal anastomosis

Background—No data exist on cholesterolabsorption in patients with an ileoanal anastomosis (IAA).
Aims—To study cholesterol absorption and itseffects on cholesterol and bile acid metabolism in patients with an IAA.
Patients and methods—Cholesterol absorption, andserum, biliary, and faecal lipids were studied in 24 patients with anIAA and 20controls.
Results—Fractional cholesterol absorption wassignificantly lower in the patients (36% versus 47% in controls).Surprisingly, the calculated intestinal influx of endogenouscholesterol was reduced so that the absolute absorption of cholesterolwas decreased; elimination of cholesterol as faecal neutral steroidsremained normal. Thus, the slightly increased cholesterol synthesis was mainly due to increased faecal bile acid excretion, which, in turn, wasassociated with reduced absorption and biliary secretion of bile acids.Serum total and low density lipoprotein (LDL) cholesterol and LDLtriglycerides were lower in the patients. Molar percentage andsaturation index of biliary cholesterol were slightly higher inpatients with an IAA. Proportions of secondary bile acids in bile andfaeces were diminished, and faecal unidentified bile acids were higherin patients.
Conclusions—Cholesterol absorption issignificantly impaired in patients with an IAA, and is closely relatedto changes in serum and biliary lipids observed in these patients.

Keywords:cholesterol absorption; cholesterol synthesis; faecal bile acids; inflammatory bowel disease

     

肠道菌群和胆汁酸代谢对非酒精性脂肪性肝病发生发展的作用

随着肥胖及代谢综合征的流行,非酒精性脂肪性肝病的患病率逐年递增,在该病的发生和发展过程中,肠道菌群和胆汁酸代谢均发挥重要作用。讨论了肠道菌群和胆汁酸代谢之间的关系,重点强调了肠道菌群、胆汁酸和胆汁酸受体在非酒精性脂肪性肝病发生发展的过程中所起到的作用。     

Alteration of bile acid metabolism in two-thirds hepatectomized rat

Bile acid metabolism after two-thirds partial hepatectomy (PH) in rat was studied. Bile acid kinetics (i.e. synthesis rate and pool size) were determined by wash out method combined with gas liquid chromatography, and serum bile acids by gas liquid chromatography-mass spectrometry. Serum bile acid concentration was highest on the third day after PH, as the liver regeneration progressed but it gradually decreased with increasing cholic acid (CA)/chenodeoxycholic acid (CDCA), reflecting impaired hepatic uptake of bile acids and/or cholestasis during the early post-hepatectomy period. Predominance of CA in bile acid synthesis, pool, and biliary secretion was also found. On the third day after PH, liver weight recovered to 66% of the control value, but enhancement of bile acid synthesis was not observed. Consequently, pool size remained at 50% of control. On the seventh day, synthesis of bile acid, especially of CA, was enhanced and pool size and liver weight returned to 68 and 72% of the respective control values. Bile acid synthesis was returned to the control value on the fourteenth day with concomitant restoration of liver weight and bile acid pool size. These changes in bile acid kinetics parallel the events during hepatic regeneration after PH.     

Functional characterization of genetic variants in the apical sodium-dependent bile acid transporter (ASBT; SLC10A2)

Background and Aim: The major transporter responsible for bile acid uptake from the intestinal lumen is the apical sodium‐dependent bile acid transporter (ASBT, SLC10A2). Analysis of the SLC10A2 gene has identified a variety of sequence variants including coding region single nucleotide polymorphisms (SNPs) that may influence bile acid homeostasis/intestinal function. In this study, we systematically characterized the effect of coding SNPs on SLC10A2 protein expression and bile acid transport activity. Methods: Single nucleotide polymorphisms in SLC10A2 from genomic DNA of ethnically‐defined healthy individuals were identified using a polymerase chain reaction (PCR)‐based temperature gradient capillary electrophoresis (TGCE) system. A heterologous gene expression system was used to assess transport activity of SLC10A2 nonsynonymous variants and missense mutations. Total and cell surface protein expression of wild‐type and variant ASBT was assessed by Western blot analysis and immunofluorescence confocal microscopy. Expression of ASBT mRNA and protein was also measured in human intestinal samples. Results: The studies revealed two nonsynonymous SNPs, 292G>A and 431G>A, with partially impaired in vitro taurocholate transport. A novel variant, 790A>G, was also shown to exhibit near complete loss of taurocholate transport, similar to the previously identified ASBT missense mutations. Examination of ASBT protein expression revealed no significant differences in expression or trafficking to the cell surface among variants versus wild‐type ASBT. Analysis of ASBT mRNA and protein expression in human intestinal samples revealed modest intersubject variability. Conclusions: Genome sequencing and in vitro studies reveal the presence of multiple functionally relevant variants in SLC10A2 that may influence bile acid homeostasis and physiology.     

Technical aspects in the laparoscopic management of complicated common bile duct stones

The management of common bile duct (CBD) stones traditionally required open laparotomy and bile duct exploration. With the advent of endoscopic and laparoscopic technology in the latter half of last century, endoscopic retrograde cholangiopancreatography (ERCP) and laparoscopic cholecystectomy (LC) has become the mainstream treatment for CBD stones and gallstones in most medical centers around the world. However, in certain situations, ERCP cannot be feasible because of difficult cannulation and extraction. ERCP can also be associated with potential serious complications, in particular for complicated stones requiring repeated sessions and additional maneuvers. Since our first laparoscopic exploration of the CBD (LECBD) in 1995, we now adopt the routine practice of the laparoscopic approach in dealing with endoscopically irretrievable CBD stones. The aim of this article is to describe the technical details of this approach and to review the results from our series.     

Biliary lipid composition in idiopathic bile acid malabsorption

Background—Chronic diarrhoea is the clinicalhallmark of patients presenting with idiopathic bile acidmalabsorption. Its pathogenesis is unknown; colonic water secretion canbe induced by dihydroxy bile acids, but it is not known whetherenrichment of the bile acid pool with these bile acids occurs in suchpatients. Furthermore, bile acid malabsorption is known to affectbiliary lipid composition, but no information is available for theidiopathic type.
Aims—To verify: (a) whetherdiarrhoea in patients with idiopathic bile acid malabsorption isassociated with enrichment of the bile acid pool with dihydroxy bileacids; and (b) whether supersaturation with cholesterol ofduodenal bile occurs in such patients as a result of chronic bile acid depletion.
Patients—Thirteen patients with idiopathic bileacid malabsorption diagnosed according to abnormal ⁷⁵SeHCATtest and absence of other organic diseases, and 23 control subjects.
Methods—Bile rich duodenal fluid was collectedduring intravenous ceruletide infusion in the fasting state. Biliarylipids were analysed by enzymatic assays and bile acids by highperformance liquid chromatography.
Results—Patients with idiopathic bile acidmalabsorption had a cholesterol saturation index similar to controls.Bile acid composition showed only a decrease in percentage cholic acid(29(2)% versus 36 (2)%; p<0.05); the dihydroxy:trihydroxy bile acid ratio was similar to controls.
Conclusions—Patients with idiopathic bile acidmalabsorption do not have an increased risk of forming cholesterolgallstones. The mechanism of diarrhoea does not seem to depend on anenrichment of the bile acid pool with dihydroxy bile acids.

Keywords:primary bile acid malabsorption; bile acids; diarrhoea; ⁷⁵SeHCAT; biliary lipids; cholesterol saturationindex

     

Measurement of apolipoprotein A1 in cholesterol gallstones and gallbladder bile of patients with gallstones

Biliary apolipoprotein A1 in bile inhibits the nucleation of cholesterol crystals from bile supersaturated with cholesterol. In the present study, using an enzyme-linked immunosorbent assay of apolipoprotein Al, we determined the content of apolipoprotein Al in cholesterol gallstones and samples of gallbladder bile collected simultaneously from 23 patients during cholecystectomy. Protein content in cholesterol gallstones ranged from 50 to 5700 g/g, with median, quartile, and three quartile values being 250, 111, and 740; apolipoprotein A1 content ranged from 9 to 9000 ng/g (200, 41, 647). The gallbladder bile samples contained protein at concentrations of 0.4-9.0 mg/ml (2.0, 1.1, 3.2), while apolipoprotein A1 was present at concentrations of 2.0-136.0 g/ml (30.0, 10.0, 90.0). A notable finding was that the A1/total protein (TP) values for gallbladder bile, which ranged from 0.13% to 6.80% (1.62, 0.89, 3.34), were several times higher than those determined for gallstone samples, which ranged from 0.01% to 1.2%, 2% (0.06, 0.02, 0.25). The results of sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the protein profile in cholesterol gallstones was similar to that in gallbladder bile. It was concluded that: (1) the protein contained in gallstones may originate from bile, (2) the content of apolipoprotein A1 in cholesterol gallstones is only a trace amount, compared with that in gallbladder bile, and (3) biliary apolipoprotein A1 may be retained in a soluble phase in gallbladder bile, with minimal precipitation onto the surfaces of gallstones.     

Effects of long term hydrophilic bile acid therapy on in vitro contraction of gallbladder muscle strips in patients with cholesterol gallstones

AIM:To evaluate ursodeoxycholic acid (UDCA) therapy on the in vitro contraction of gallbladder smooth muscle strips from cholesterol gallstone patients. METHODS:The contraction forces of gallbladder smooth muscle strips from 28 patients with cholesterol gallstones treated with UDCA were compared with contraction forces from 14 untreated patients. The strips were stimulated with increasing concentrations of cholecystokinin-8 (CCK-8). RESULTS:Although the contraction forces that developed in response to CCK-8 were higher in strips from specimens of UDCA treated patients compared to untreated patients,longer treatment periods (6-wk) caused more contraction responses than the short treatment period of 3-wk (F = 19.297,1.85 ± 0.22 g vs 1.70 ± 0.10 g,P < 0.01). Contraction forces developed with maximal stimulation with KCl in the 6-wk treatment group were also higher than contraction forces in the untreated group (F = 4.274,3.77 ± 0.45 g vs 3.30 ± 0.30 g,P < 0.05). CONCLUSION:Six-week UDCA treatment caused an increase in contractions of muscle strips from patients with cholesterol gallstones when compared to shorter treatment administration or controls. We suggest that extending UDCA treatment periods may cause more effective contractions in the gallbladder,and thereby increase the rate of response to treatment.