Administration of cholesterol-lowering statins to mice reduced the number of Borrelia burgdorferi
bacteria in the rodents and helped to prevent the spread of Lyme disease, a new study has suggested.
Tricia A. Van Laar, PhD, from the University of Texas at San Antonio, and colleagues, published the results of their study
in Microbes and Infection
“Using a mouse model of Lyme disease, we found that statins contribute to reducing bacterial burden and altering the murine immune response to favor clearance of spirochetes,” the authors write.
Lyme disease is the most commonly reported arthropod-borne disease in the United States, with more than 25,000 cases confirmed by the Centers for Disease Control and Prevention (CDC) in 2014. This systemic disease is caused by the bacterium Borrelia burgdorferi
and is transmitted to humans through the bite of infected Ixodes
Because most cases of Lyme disease involve ticks that bite humans after they have acquired the bacterium from other infected animals—known as reservoir hosts—it has been hypothesized that reducing the burden of borrelial infection in reservoir hosts will decrease the likelihood that ticks will become infected when they feed on reservoir hosts, thereby potentially reducing the chance of transmission of Lyme disease to humans.
Dr. Van Laar and colleagues therefore conducted a study to target Borrelia burgdorferi
through a key enzyme—3-hydroxy-3-methyl-glutaryl-coenzyme A reductase—which catalyzes a rate limiting step in the mevalonate pathway that plays an important role in the synthesis of essential components of the bacterium's cell wall, including cholesterol. The group had previously shown that the activity of this rate limiting enzyme could be inhibited using statins.
In the current study, the researchers infected mice with Borrelia burgdorferi
. Some of the mice received statins, while some did not. Two weeks after the mice were infected, the researchers examined different tissues in the body to look for differences in the numbers of bacteria that had spread to these areas. They found no significant difference in bacterial spread to tissues between statin-treated and untreated mice. However, they found a significant decrease in the numbers of bacteria in the skin, lymph node, and spleen of mice that received statin treatment. In addition, the reductions in bacterial burden in the lymph node and spleen were greater in mice treated with simvastatin, than in those treated with lovastatin; similarly, the reductions in bacterial burden in the skin were greater in mice treated with lovastatin.
According to the authors, “[i]t appears that statin treatment contributes to decreased bacterial burden in infected mice, which could be due to either direct interference with spirochetal growth or by limiting available cholesterol to the bacteria.” However, they also stress the possibility that changes in the animals’ immune response to the spirochetes could lead to increased bacterial clearance. “It is interesting to speculate that statins could potentially have a number of as yet uncharacterized primary or secondary anti-borrelial effects,” they note.
“These pharmacological properties can be further exploited to enhance bacterial clearance and/or reduce persistence in reservoir hosts to subsequently reduce the incidence of Lyme disease,” Dr. Van Laar and colleagues conclude.
Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.
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