glycogen and Fascioliasis

It is generally accepted that free-living stages of parasitic helminths are dependent on aerobic degradation of endogenous energy sources for their energy generation. This concept, however, is not the result of extensive experimental evidence, but originated mainly intuitively as oxygen is widely available in their habitat and these stages generally have a small size. Schistosoma mansoni, the sole parasitic helminth whose energy metabolism has been studied throughout its life-cycle indeed has aerobically functioning free-living stages. However, large differences exist in energy metabolism between adult stages of distinct parasitic helminths, and caution should be taken in predicting that all free-living stages of all parasitic helminths have the same, aerobic energy metabolism. Hence, this report studied the energy metabolism of Fasciola hepatica miracidia and demonstrated that F. hepatica miracidia are also dependent on aerobic degradation of their endogenous glycogen stores by glycolysis and on Krebs cycle activity for energy generation. However, in contrast to S. mansoni, F. hepatica miracidia cannot function anaerobically, as inhibition of the respiratory chain blocked motility and carbohydrate degradation, and finally resulted in death of the miracidia. Therefore, this report demonstrated that differences exist between miracidia of distinct species, in pre-adaptation of their energy metabolism to the occasional hypoxic conditions within their next host.

Topics: Animals; Carbohydrate Metabolism; Energy Metabolism; Fasciola hepatica; Fascioliasis; Glycogen; Life Cycle Stages; Liver; Oxygen Consumption; Sheep; Sheep Diseases

Infection of rats with the liver fluke, Fasciola hepatica, impaired the responses of the perfused liver to calcium uptake and glucose release induced by the synergistic action of glucagon and vasopressin. Treatment of infected rats with dexamethasone prevented the impairment of each of these two responses.

Topics: Animals; Calcium; Dexamethasone; Drug Synergism; Fasciola hepatica; Fascioliasis; Glucagon; Glucose; Glycogen; Liver; Male; Perfusion; Rats; Rats, Inbred Strains; Vasopressins

Sheep infected with adult Fasciola hepatica were drenched with rafoxanide. At 4, 8, 16 and 24 h after drenching the sheep were killed and the flukes removed, washed and rapidly frozen in liquid nitrogen. The content of key metabolites in the fermentation pathway were determined and compared with those in control F. hepatica, whose hosts were not treated with rafoxanide. Rafoxanide decreased glycogen, malate, NADH and ATP levels. The level of other metabolites in the pathway increased for the first 8-16 h after rafoxanide treatment. The marked decrease in ATP and glycogen, and the increase in total [NAD+]/[NADH] and [oxaloacetate]/[malate], together with the changed content of other metabolites, led to the conclusion that the mode of action of rafoxanide against F. hepatica in vivo is by uncoupling oxidative phosphorylation.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Fasciola hepatica; Fascioliasis; Fermentation; Glycogen; NAD; NADP; Rafoxanide; Salicylamides; Sheep; Sheep Diseases

Topics: Adenosine Triphosphate; Animals; Energy Metabolism; Fasciola hepatica; Fascioliasis; Fructosephosphates; Glucosephosphates; Glycogen; Rafoxanide; Salicylamides; Sheep; Sheep Diseases