Pigment gallstone formation in the cholesterol-fed guinea pig

Area of Science:

• Gastroenterology
• Animal Models
• Biliary Lithiasis

Background:

• Dietary cholesterol significantly impacts gallstone formation.
• Guinea pigs are a relevant model for studying gallstone pathogenesis.
• Understanding gallstone composition is crucial for therapeutic strategies.

Purpose of the Study:

• To investigate the effects of a cholesterol-supplemented diet on gallstone formation in Hartley guinea pigs.
• To characterize the composition and properties of diet-induced gallstones.
• To assess associated physiological changes, including liver and bile parameters.

Main Methods:

• Hartley guinea pigs were fed either a 0.5% cholesterol-supplemented diet or a trace cholesterol diet.
• Gallstone formation was monitored over 6 and 12 weeks.
• Gallstones were analyzed for composition (solubility, thin-layer chromatography).
• Bile lithogenic index, hematocrit, and gallbladder volume were measured.

Main Results:

• Cholesterol-supplemented diet led to significant gallstone formation (17/23 at 6 weeks, 11/11 at 12 weeks) compared to controls (2/44).
• Gallstones were primarily calcium bilirubinate aggregates, soluble in sodium hydroxide.
• Cholesterol-fed animals exhibited hypercholesterolemia, fatty liver, increased gallbladder volume, and hemolytic anemia (lower hematocrit).
• Bile lithogenic index was low in both groups, with no cholesterol crystals found.

Conclusions:

• Dietary cholesterol induces gallstone formation in guinea pigs, characterized by calcium bilirubinate crystals.
• The mechanism involves factors beyond bile cholesterol saturation, potentially related to altered bile composition or gallbladder function.
• Cholesterol feeding also induces hemolytic anemia and affects gallbladder physiology in this model.