The effect ofGiardia lambliatrophozoites on lipolysisin vitro

Abstract

Infection withGiardia lambliaoften causes only minor mucosal changes to the small intestine yet frank fat malabsorption may still occur. Some evidence suggests abtext-abstract pancreatic exocrine function in subjects with giardiasis although the mechanism and significance of this is unclear. Studies were conductedin vitroto determine the effect ofG. lambliatrophozoites or culture filtrates from the organism on lipolysis of triglyceride by porcine pancreatic lipase. Live trophozoites significantly inhibited lipolysis. The degree of inhibition increased with longer duration of lipase exposure to trophozoites. Total amounts of enzyme inhibited were proportional to enzyme concentration, while the percentage inhibition was greatest at lowest concentration. At a lipase concentration of 1·7 i.u./ml, enzyme activity was reduced by 89·7% compared to controls after incubation for 4 h with trophozoites. The effect was abolished using killed, intact trophozoites. Culture filtrates ofG. lambliadid not inhibit lipolysis. Specificity of the effect was suggested by the failure of another flagellate protozoan,Trichomonas vaginalis, to inhibit lipase. In this assay system the inhibition of lipolysis was not dependent on the bile salt concentration present. The impact of this effectin vivoremains to be determined but it may contribute to fat malabsorption in giardiasis.