The milk thistle extract silymarin, which is composed of multiple flavonolignans including the most active constituent silibinin (synonymous with silybin), is emerging as a treatment for a variety of diseases in human and veterinary patients.1 One of silibinin's proposed mechanisms of action is as an antioxidant that increases intracellular reduced glutathione content.2 It has recently been shown that oral administration of an SPC increases plasma silibinin concentrations in cats.a Because cats appear to be particularly susceptible to oxidative stress, administration of supplemental SPC may be a beneficial part of therapeutic regimens for a variety of diseases in this species. For example, cats with chronic liver disease have decreased concentrations of hepatic GSH.3
The production of reactive oxygen species by granulocytes (neutrophils and eosinophils) during an inflammatory reaction may contribute to the progression of disease.4 Conversely, oxidative stress and intracellular GSH content may regulate aspects of neutrophil function such as apoptosis.5 Neutrophil function appears decreased in several human diseases associated with oxidative stress, such as diabetes mellitus and renal failure, which are also common diseases in the feline population.6, 7
The purpose of the study reported here was to determine the effect of oral administration of an SPC on oxidative stress and granulocyte function in healthy cats. Phosphatidylcholine was used to increase the bioavailability of silibinin but may also have impacted the measured variables.
Glutathione peroxidase enzyme
Mean fluorescence intensity
Webb CB, Gustafson D, Twedt DC. Bioavailability following oral administration of a silibinin-phosphatidylcholine complex in cats (abstr), in Proceedings. Am Coll Vet Intern Med Forum 2008;22:812.
Cedar River Laboratories, Mason City, Iowa.
Nutramax Laboratories Inc, Edgewood, Md.
Siemens Healthcare Diagnostics, Deerfield, Ill.
Sigma-Aldrich, St Louis, Mo.
Invitrogen, Chicago, Ill.
DakoCytomation, Fort Collins, Colo.
SpectraAlign Beads, DakoCytomation, Fort Collins, Colo.
GraphPad, Prism Software, San Diego, Calif.
Randox Laboratories Ltd, Oceanside, Calif.
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