title: Effect of the type of dietary fat on biliary lipid composition and bile lithogenicity in humans with cholesterol gallstone disease.
abstract: OBJECTIVE
  The effect of the type of dietary fat on bile lipids and lithogenicity is unclear. This study compared the effects of two dietary oils that differed in fatty acid profile on biliary lipid composition in humans.
  
  
  METHODS
  Female patients who had cholesterol gallstones and were scheduled for elective cholecystectomy were studied. For 30 d before surgery, subjects were kept on diets that contained olive oil (olive oil group, n = 9) or sunflower oil (sunflower oil group, n = 9) as the main source of fat. Gallbladder bile and stones were sampled at surgery. After cholecystectomy, duodenal samples were collected by nasoduodenal intubation during fasting and after administration of mixed liquid meals that included the corresponding dietary oil. Duodenal and gallbladder bile samples were analyzed for cholesterol, phospholipids, and total bile acids by established methods. Individual bile acid conjugates in gallbladder bile were measured by high-performance liquid chromatography. Gallstones were analyzed by semiquantitative polarizing light microscopy.
  
  
  RESULTS
  Despite marked differences in the absolute concentration of biliary lipids and total lipid content, manipulation of dietary fat ingestion did not influence the cholesterol saturation or the profile of individual bile acids in gallbladder bile obtained from patients who had gallstones. All but one subject had mixed cholesterol stones. A cholesterol saturation index of hepatic bile in fasted cholecystectomized patients was similar in both dietary groups and indicative of supersaturation. In response to the test meal, the cholesterol saturation index decreased significantly in patients given the olive oil diet, reaching values lower than one at 120 min postprandially. In contrast, hepatic bile secreted by patients who consumed sunflower oil appeared supersaturated (cholesterol saturation index >1.5) throughout the experiment.
  
  
  CONCLUSIONS
  Our results suggest that the type of dietary fat habitually consumed can influence bile composition in humans. In gallbladder, this influence was noted in the presence of more concentrated bile in the olive oil group. However, this was not translated into a modification of cholesterol saturation, which is likely due to the fact that cholesterol gallstones were present by the time the dietary intervention started. The finding that a typical postprandial variation in hepatic bile lithogenicity occurred only in olive oil patients was revealing. While keeping in mind the methodologic limitations of this part of the study, some gastrointestinal and metabolic mechanisms for this effect are discussed.
authors.affiliation: Institute of Nutrition and Food Technology, Department of Physiology, University of Granada, Granada, Spain. mdyago@ugr.es
authors.forename: María Dolores
authors.initials: MD
authors.lastname: Yago
authors.forename: Victoria
authors.initials: V
authors.lastname: González
authors.forename: Pilar
authors.initials: P
authors.lastname: Serrano
authors.forename: Rafael
authors.initials: R
authors.lastname: Calpena
authors.forename: María Alba
authors.initials: MA
authors.lastname: Martínez
authors.forename: Emilio
authors.initials: E
authors.lastname: Martínez-Victoria
authors.forename: Mariano
authors.initials: M
authors.lastname: Mañas
mesh_terms: D000328:Adult; D001646:Bile / Q000187:drug effects / Q000378:metabolism*; D001647:Bile Acids and Salts / Q000378:metabolism; D001659:Biliary Tract / Q000187:drug effects* / Q000378:metabolism; D002769:Cholelithiasis / Q000378:metabolism* / Q000601:surgery; D002784:Cholesterol / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004041:Dietary Fats / Q000494:pharmacology*; D005260:Female; D042882:Gallstones / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism; D008859:Microscopy, Polarization / Q000379:methods; D008875:Middle Aged; D000069463:Olive Oil; D010938:Plant Oils / Q000494:pharmacology; D011184:Postoperative Period; D011300:Preoperative Care / Q000379:methods; D000074242:Sunflower Oil; D013997:Time Factors
chemical_list: D001647:Bile Acids and Salts; D004041:Dietary Fats; D000069463:Olive Oil; D010938:Plant Oils; D000074242:Sunflower Oil; D002784:Cholesterol