The ACAT2 gene encodes a gatekeeper of intestinal cholesterol absorption that regulates cholesterolemia and gallstone disease.
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Animals↗
Biomedical subjects
F Nervi
Publications and source records attributed to F Nervi.
[Cancer of the gallbladder in Chile].
This issue of the Revista brings two articles relayed to gallbladder cancer (GC), a highly prevalent cancer among Chileans. The first papaer relates to therapy for Stage II NO GC. Authors from Universidad de la Frontera corroborate the bad results usually obatined with adjunct chemotheraphy and radiotheraphy, associated to a second operation. The second paper discusses the negative influences that the new Xth Edition of the International Classification of Diseases might have on GC control. This cancer appears now with a dramatic 100% decrease in mortality rate in the last 3 years, associated to a simultaneous increase of the digit related to biliary tract cancer of "undefined orgin", which in the great majority of cases truly corresponds to GC throughout the world. This involuntary bias could have a strong negative effect on health policy makers, because health resources will not be derived to perform more cholecystectomies needed to significantly decrease the number of gallbladders at risk. This is a major issue for the Chilean health system, since GC represents the first cause of deaths due to cancer among Chilean women.
Chile↗
Mitochondrial DNA polymorphisms in Chilean aboriginal populations: implications for the peopling of the southern cone of the continent.
The mitochondrial DNAs (mtDNAs) from individuals belonging to three Chilean tribes, the Mapuche, the Pehuenche, and the Yaghan, were studied both by RFLP analysis and D-loop (control region) sequencing. RFLP analysis showed that 3 individuals (1.3%) belonged to haplogroup A, 19 (8%) to haplogroup B, 102 (43%) to haplogroup C, and 113 (47.7%) to haplogroup D. Among the 73 individuals analyzed by D-loop sequencing, we observed 37 different haplotypes defined by 52 polymorphic sites. Joint analysis of data obtained by RFLP and sequencing methods demonstrated that, regardless of the method of analysis, the mtDNA haplotypes of these three contemporary South American aborigine groups clustered into four main haplogroups, in a way similar to those previously described for other Amerindians. These results further revealed the absence of haplogroup A in both the Mapuche and Yaghan as well as the absence of haplogroup B in the Yaghan. These results suggest that the people of Tierra del Fuego are related to tribes from south-central South America.
Base Sequence↗
Impaired biliary cholesterol secretion and decreased gallstone formation in apolipoprotein E-deficient mice fed a high-cholesterol diet.
BACKGROUND & AIMS: Because apolipoprotein E (apoE) is a key cholesterol transport molecule involved in the hepatic uptake of chylomicron cholesterol, it may play a critical role in controlling bile cholesterol elimination and cholesterol gallstone formation induced by dietary cholesterol. To test this hypothesis, we studied biliary lipid secretion and gallstone formation in apoE-deficient mice fed cholesterol-rich diets. METHODS: Bile lipid outputs and gallstone sequence events were analyzed in apoE-deficient mice fed a high-cholesterol diet or a lithogenic diet compared with control animals. RESULTS: A high-cholesterol diet increased biliary cholesterol secretion and gallbladder bile cholesterol concentration in wild-type mice; the increase in bile cholesterol secretion was significantly attenuated in apoE-deficient mice. ApoE knockout mice fed a high-cholesterol lithogenic diet had a markedly lower frequency of gallbladder bile cholesterol crystal and gallstone formation than wild-type mice, which was most likely a result of the decreased cholesterol saturation index found in gallbladder bile of apoE-deficient mice. CONCLUSIONS: These results show that apoE expression is an important factor for regulating both biliary secretion of diet-derived cholesterol as well as diet-induced cholesterol gallstone formation in mice.
Animals↗
Significance of biliary phospholipids for maintenance of the gastrointestinal mucosal barrier and hepatocellular integrity.
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Anti-Inflammatory Agents, Non-Steroidal↗
Sterol carrier protein 2 gene transfer changes lipid metabolism and enterohepatic sterol circulation in mice.
BACKGROUND & AIMS: Sterol carrier protein 2 (SCP-2) enhances sterol cycling and facilitates cholesterol translocation between intracellular organelles and plasma membrane in cultured cells, including hepatocytes. We examined the role of SCP-2 in hepatic cholesterol and lipid trafficking through the sinusoidal and canalicular secretory pathways of the liver in vivo. METHODS: Recombinant adenovirus-mediated SCP-2 gene transfer was used to obtain hepatic overexpression of SCP-2 in C57BL/6 mice. RESULTS: SCP-2 overexpression in the mouse liver resulted in an 8-fold increase of SCP-2 protein levels and determined various effects on lipid metabolism. It decreased high-density lipoprotein cholesterol and increased low-density lipoprotein (LDL) cholesterol concentrations. The expressions of hepatic LDL receptor, apolipoprotein (apo) A-I, apoB, and apoE were decreased. SCP-2 overexpression also increased hepatic cholesterol concentration, associated with decreased cholesterol neosynthesis. Increased biliary cholesterol and bile acid secretion, bile acid pool size, and intestinal cholesterol absorption were also observed. CONCLUSIONS: These results indicate that modulation of SCP-2 expression in the liver determines important modifications on lipoprotein metabolism, hepatic cholesterol synthesis and storage, biliary lipid secretion, bile acid metabolism, and intestinal cholesterol absorption.
Animals↗
Enrichment of canalicular membrane with cholesterol and sphingomyelin prevents bile salt-induced hepatic damage.
These studies were undertaken to characterize the role of plasma membrane cholesterol in canalicular secretory functions and hepatocyte integrity against intravenous taurocholate administration. Cholesterol and sphingomyelin concentrations and cholesterol/phospholipid ratios were significantly increased in canalicular membranes of diosgenin-fed rats, suggesting a more resistant structure against solubilization by taurocholate. During taurocholate infusion, control rats had significantly decreased bile flow, whereas diosgenin-fed animals maintained bile flow. Maximal cholesterol output increased by 176% in diosgenin-fed rats, suggesting an increased precursor pool of biliary cholesterol in these animals. Maximal phospholipid output only increased by 43% in diosgenin-fed rats, whereas bile salt output remained at control levels. The kinetics of glutamic oxalacetic transaminase, lactic dehydrogenase, and alkaline phosphatase activities in bile showed a significantly faster release in control than in diosgenin-fed rats. After 30 min of intravenous taurocholate infusion, necrotic hepatocytes were significantly increased in control animals. Preservation of bile secretory functions and hepatocellular cytoprotection by diosgenin against the intravenous infusion of toxic doses of taurocholate was associated with an increased concentration of cholesterol and sphingomyelin in the canalicular membrane. The increase of biliary cholesterol output induced by diosgenin was correlated to the enhanced concentration of cholesterol in the canalicular membrane.
Alkaline Phosphatase↗
Medical management of common bile duct stones.
Common bile duct stones are a common cause of morbidity and mortality in adults. An increasing number of surgical and medical therapies are available to manage them, with different success rates reported. The various medical treatment strategies were developed during the last decade, but these medical modalities should not be contemplated as a first-line alternative of treatment. A consensus from experts is that there is no primary indication to use solvents on common bile duct stones because they have a relatively high rate of adverse effects and their success is limited compared with lithotripsy. However, there is a subgroup of patients in whom invasive or surgical treatment is risky or may fail. In these patients stone dissolution by solvent may constitute a plausible therapeutic alternative or may help reduce the size of the stones sufficiently to facilitate subsequent endoscopic extraction. Solvents may also be indicated in settings where endoscopic techniques or lithotripsy are not available and the patient has a T-tube in the common bile duct. Even in this condition, however, it is probably quicker and more effective to refer the patient to a center with expertise and technologic support to practice stone removal.
Caprylates↗
Genetic epidemiology of cholesterol cholelithiasis among Chilean Hispanics, Amerindians, and Maoris.
BACKGROUND & AIMS: The etiology of cholesterol gallstones is multifactorial, with interactions of genes and the environment. The hypothesis that aborigine cholesterol lithogenic genes are widely spread among Chileans, a population with a high prevalence of gallstones, was tested. METHODS: Medical history and anthropometric measurements were obtained and abdominal ultrasonography was performed in 182 Mapuche Indians, 225 Maoris of Easter Island, and 1584 Hispanics. Blood groups, DNA, lipids, and glucose were analyzed. The Amerindian Admixture Index and mitochondrial DNA (mtDNA) assessed the ethnicity and degree of racial admixture. RESULTS: Amerindian Admixture Index was 0.8 in Mapuches and 0.4 in Hispanics. All Mapuches, 88% of Hispanics, but none of Maoris had Amerindian mtDNA haplotypes. Age- and sex-adjusted global prevalence of gallstone disease was higher in Mapuches (35%) than in Hispanics (27%) and Maoris (21%). Compared with Hispanics, the youngest group of Mapuches had the greatest corrected risk of gallstones: odds ratios of 6.0 in women and 2.3 in men. In contrast, the gallstone risk in Maoris was lower compared with Hispanics: odds ratios of 0.6 for women and 0.5 for men. CONCLUSIONS: Cholesterol lithogenic genes appear widely spread among Chilean Indians and Hispanics. They could determine the early formation of gallstones and explain the high prevalence of gallbladder diseases among some South American populations.
Adult↗
Cholesterol saturation, not proteins or cholecystitis, is critical for crystal formation in human gallbladder bile.
BACKGROUND & AIMS: Biliary proteins are promoters of cholesterol crystallization in artificial model bile. However, their pathogenic importance for cholesterol precipitation in native gallbladder bile (GB) is uncertain. The aim of this study was to evaluate the significance of biliary lipids and proteins on cholesterol crystal detection time (ChCDT) of GB in patients with gallstones. METHODS: ChCDT and concentrations of lipids, albumin, mucins, aminopeptidase N, alpha1-acid glycoprotein, haptoglobin, and immunoglobulins (Igs) were measured in GB of 92 patients, 52 of whom had cholesterol gallstones. RESULTS: ChCDT was markedly reduced in gallstone patients. Compared with patients without gallstones, they had a significant increase in cholesterol saturation and total protein, albumin, mucin, and IgG biliary concentrations. In univariate analysis, ChCDT of GB was significantly correlated with cholesterol saturation and total lipid, protein, Ig, aminopeptidase N, and alpha1-acid glycoprotein concentrations. However, stepwise logistic regression analysis showed that only cholesterol saturation independently correlated to ChCDT. Gallbladder inflammation correlated with the concentration of Igs, but subtraction of IgG from GB did not modify the ChCDT. CONCLUSIONS: Biliary cholesterol transport and saturation, but not proteins, appear critical for the cholesterol crystallization abnormality observed in native bile from patients with gallstones.
Bile↗
Uptake of dodecanedioic acid by isolated rat liver.
The uptake of dodecanedioic acid (C12); a dicarboxylic acid with 12 carbon atoms, was studied in the isolated perfused rat liver. Fifty mumol of C12 were injected as a bolus into the perfusing liver solution. The concentration of C12 in perfusate samples taken over 2 h from the beginning of the experiments were analyzed by high performance liquid chromatography. An in vitro experimental session was performed to determine the binding curve of C12 to defatted bovine serum albumin. These data were then used to compute the perfusate C12 free fraction. The number of binding sites on the albumin molecule was equal to 4.29 +/- 0.21 (S.E.), while the affinity constant was 6.33 +/- 0.87 x 10(3). M-1. Experimental values of perfusate C12 concentration versus time were individually plotted and fitted to a monoexponential decay for each liver perfused. The predicted C12 concentration at time zero averaged 0.354 +/- 0.0375 mumol/ml. Prom this value the apparent volume of distribution of C12 was obtained and corresponded to 153.02 +/- 14.56 ml. The disappearance rate constant from the perfusate was 0.0278 +/- 0.0030 min-1. The C12 half life was 26.6 +/- 2.3 min. The mean hepatic clearance from the perfusate was 4.08 +/- 0.38 ml/min. In conclusion, C12 is quickly taken up by the liver so that in about 100 min it was completely cleared from the perfusate.
Animals↗
[Occult gallbladder disease or microlithiasis in patients with acute pancreatitis: a frequent clinical event].
BACKGROUND: Patients with acute pancreatitis (AP) and a normal gallbladder by standard echographic evaluation may have "occult" gallbladder disease or microlithiasis with recurrent episodes of AP. AIM: To conduct a prospective evaluation of patients with the diagnosis of non-biliary AP in order to detect "occult" gallbladder disease and to compare its clinical presentation with that of biliary AP. PATIENTS AND METHODS: Patients admitted with the diagnosis of AP to a clinical hospital were included in the study. According to an abdominal ultrasound study, patients were classified as having or not cholelithiasis. A duodenal biliary drainage was performed in 15 patients with AP and without gallbladder stones. RESULTS: Patients without cholelithiasis had recurrent AP more often than patients with biliary AP (53 and 3.3% respectively). Excessive alcohol ingestion did not rule out the possibility of biliary etiology. In 6 patients, the analysis of duodenal bile showed cholesterol crystals, and cholecystectomy confirmed the existence of gallbladder disease in 5. All of them remained asymptomatic during a follow-up period of four years. One patient refused surgery, with subsequent development of gallstones and recurrent episodes of AP. In other 4 patients, gallbladder disease was confirmed by percutaneous gallbladder puncture or during cholecystectomy. No recurrence of AP were observed during the follow-up CONCLUSIONS: Microlithiasis or "occult" gallbladder disease accounts for at least 67% of the original "non-biliary" AP. Duodenal bile analysis is a useful and necessary technique for the evaluation of patients with "non-biliary" acute pancreatitis. Careful clinical and echographic follow-up of this subgroup of patients with AP is mandatory.
Acute Disease↗
Modulation of intrahepatic cholesterol trafficking: evidence by in vivo antisense treatment for the involvement of sterol carrier protein-2 in newly synthesized cholesterol transport into rat bile.
Biliary cholesterol represents one of the two major excretory pathways for sterol elimination from the body and plays a central role in cholesterol gallstone formation. Biliary cholesterol originates from a precursor pool of preformed and newly synthesized free cholesterol. Although it has been suggested that newly synthesized and preformed biliary cholesterol are secreted by independent pathways, the specific cellular and molecular mechanisms are unknown. We used male Wistar rats to study the time-course of the appearance of newly synthesized cholesterol, phosphatidylcholine and protein into bile. The specific role of sterol carrier protein-2 (SCP-2) in the transport of newly synthesized biliary cholesterol was evaluated by an in vivo antisense oligonucleotide approach. In contrast to [14C]phosphatidylcholine and [35S]proteins, the time-course of [14C]cholesterol appearance into bile was rapid, and microtubule- and Golgi-independent. In vivo SCP-2 antisense treatment reduced and delayed the appearance of biliary [14C]cholesterol. Furthermore, hepatic SCP-2 expression increased more than 3-fold over control values in rats that had been treated with diosgenin to increase biliary secretion of newly synthesized cholesterol. These results suggest that SCP-2 is necessary for the rapid transport of newly synthesized cholesterol into bile and that hepatocytes can induce SCP-2 expression according to the rate of biliary secretion of newly synthesized cholesterol.
Animals↗
Fibrates induce mdr2 gene expression and biliary phospholipid secretion in the mouse.
Disruption of the murine mdr2 gene leads to the complete absence of biliary phospholipids. We tested the hypothesis that the increase in biliary phospholipid output induced by fibrates is mediated via induction of the hepatic mdr2 gene and its encoded product, the P-glucoprotein canalicular flippase. Increased levels of mdr2 mRNA were observed in the liver of mice treated with different fibrates: ciprofibrate, 660+/-155% (as compared with control group); clofibrate, 611+/-77%; bezafibrate, 410+/-47%; fenofibrate, 310+/-52%; gemfibrozil, 190+/-25% (P <0.05 compared with control group). Induction of expression of the mdr gene family was specific to the mdr2 gene. Two- to three-fold increases in P-glycoprotein immunodetection were evident on the canalicular plasma-membrane domain of clofibrate- and ciprofibrate-treated mice. Biliary phospholipid output increased from 4.2+/-1.2 nmol/min per g of liver in the control group to 8.5+/-0.6, 7.1+/-2.9 and 5.8+/-2.5 in ciprofibrate-, clofibrate- and bezafibrate-treated mice respectively (P <0.05 compared with control group). Moreover, a significant correlation between biliary phospholipid output and the relative levels of mdr2 mRNA was found (r=0.86; P <0.05). In treated animals, bile flow as well as cholesterol and bile acid outputs remained unchanged. Our findings constitute the first evidence that pharmacological modulation of biliary lipid secretion mediated by fibrates can be related to the overexpression of a specific liver gene product, the mdr2 P-glycoprotein, and are consistent with the hypothesis that the mdr2 P-glycoprotein isoform plays a crucial role in the secretion of biliary phospholipid.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
Sterol carrier protein-2 is involved in cholesterol transfer from the endoplasmic reticulum to the plasma membrane in human fibroblasts.
The cellular mechanism of cholesterol transport from the endoplasmic reticulum to the plasma membrane is currently unknown. To assess the possibility that sterol carrier protein-2 (SCP-2) is involved in this transport, we studied the time course of newly synthesized cholesterol incorporation in the plasma membrane of normal and SCP-2-deficient (Zellweger syndrome) human fibroblasts. Cholesterol transfer was rapid, cytoskeleton-independent, and Golgi-independent in normal cells, but it was slower, cytoskeleton-dependent, and Golgi-dependent in SCP-2-deficient cells. After SCP-2 antisense oligonucleotides treatment of normal fibroblasts, the rapid transport was reduced by 81% with a simultaneous increase of the slower one. These results suggest that in normal fibroblasts the major fraction of newly synthesized cholesterol is transported to the plasma membrane by a SCP-2-dependent mechanism. In contrast, in SCP-2-deficient cells, newly synthesized cholesterol leaves the endoplasmic reticulum by a cytoskeleton/Golgi-dependent mechanism.
Base Sequence↗
Apolipoprotein E polymorphism in patients with acute pancreatitis.
We have shown that patients with previous acute pancreatitis (AP) may have an abnormal catabolism of chylomicron remnants (CMR). Because apoprotein E (Apo E) genetic polymorphism has an important influence on CMR clearance, we compared frequency distribution of Apo E phenotypes in 52 patients with AP, 109 patients with gallstones, and 110 control subjects. Apo E phenotypes were detected by isoelectric focusing and immunoblotting. After adjusting for differences in age and gender, fasting triglyceride level was comparable between the study groups. The frequency distribution of Apo E phenotypes was not different between the three study groups and it was in Hardy-Weinberg equilibrium. The gene frequency for Apo E2 was 0.212, 0.273, and 0.243 in AP, gallstone, and control group, respectively. For Apo E3 it was 0.701, 0.627, and 0.674, and for Apo E4 0.090, 0.100, and 0.083 in the same groups, respectively. Differences were not statistically significant (chi 2). In conclusion, the abnormal catabolism of CMR in patients with AP is not attributable to Apo E polymorphism. An alternative explanation may be sought in the activity of the recently identified hepatocytic Apo E receptor [LDL-related receptor protein (LRP)].
Acute Disease↗
Cholesterol crystallization-promoting activity of aminopeptidase-N isolated from the vesicular carrier of biliary lipids.
Different hydrophobic glycoproteins are associated to native biliary vesicles, which are the major carrier of biliary cholesterol. Some of these proteins promote cholesterol crystallization, a key step in cholesterol gallstone formation. This study was specifically conducted to identify the 130 kDa biliary vesicle-associated glycoprotein and to determine its in vitro effect on the cholesterol crystal formation time. The 130 kDa vesicular glycoprotein was identified as aminopeptidase-N by amino acid sequencing and specific enzymatic assay. Polyclonal antibodies raised against aminopeptidase-N allowed us to determine its concentration in human hepatic bile, which varied from 17.3 to 57.6 micrograms/ml. Aminopeptidase-N showed a concentration-dependent cholesterol crystallization activity when it was added to supersaturated model bile at a concentration range usually found in native bile. Because of this promoting effect on in vitro cholesterol crystal formation, we suggest that biliary aminopeptidase-N may play a critical role in the pathogenesis of cholesterol gallstone disease.
Amino Acid Sequence↗
Isolation and partial characterization of cholesterol pronucleating hydrophobic glycoproteins associated to native biliary vesicles.
Cholesterol is transported both in unilamellar phosphatidylcholine vesicles and in bile salts-mixed micelles in native bile. The vesicular carrier of biliary lipids apparently has a well defined protein profile with a potent cholesterol crystallization-promoting activity. This study was conducted to identify and further characterize these vesicular proteins and to test the effect of isolated vesicular proteins on the cholesterol crystal formation in supersaturated model bile. The results confirmed that proteins are a constant component of highly purified biliary vesicles both in hepatic and gallbladder bile. Immunoglobulins (IgA, IgG and IgM) and albumin are associated to the purified hepatic biliary vesicles. Furthermore, four different hydrophobic glycoproteins with a molecular mass of 130, 114, 86, and 62-67 kDa were isolated. These glycoproteins showed no reactivity with anti-human whole serum or anti-immunoglobulin antibodies, suggesting that these proteins are biliary-specific. Isolated 130, 114 and 62-67 kDa vesicular glycoproteins significantly decreased the cholesterol nucleation time in artificial model bile. We concluded that some, but not all, vesicular-bound hydrophobic glycoproteins have cholesterol pronucleating activity and they may be involved in the pathogenesis of cholesterol gallstone disease.
Bile↗