Performing Department
Small Animal Clinical Sciences
Non Technical Summary
Feline herpesvirus infection is extremely common in the domestic cat population, with essentially all cats exposed to the virus as kittens. More than 80% of cats develop neuronal latency of the virus and most experience periodic reactivation and shedding. Clinical signs include rhinosinusitis and keratoconjunctivitis, and the disease can be fatal in young kittens. L-lysine is commonly recommended as a supplement for cats exhibiting clinical signs consistent with herpesvirus infection, as there is evidence that it will decrease the severity of signs and shedding of the virus. Other reports have found little benefit from this supplement, but it remains commonly recommended as there are no reports of side effects.An inotropeis an agent that alters the force or energy of muscular contractions, including the heart muscle. Negatively inotropic agents weaken the force ofcontractions. Positively inotropic agents increase the strength of muscular contraction.The inotropic effect of l-lysine supplementation in cats hasnever been evaluated. The administration of positive inotropic agents to cats must be undertaken with some caution, as this species is commonly affected by hypertrophic cardiomyopathy. Frequently, this disease is accompanied by systolic anterior motion of the mitral valve, causing a dynamic obstruction to left ventricular outflow. There has been concern that administration of a positive inotrope to cats with hypertrophic cardiomyopathy might worsen the hypertrophy and exacerbate the outflow obstruction.We hypothesize that l-lysine will act as a positive inotrope when administered to healthy cats at 500mg PO twice daily.Significance: In the event that a positive inotropic effect is found, greater caution will be warranted for use of this supplement in cats, particularly cats with evidence of heart disease, and screening for underlying heart disease might be advisable before starting supplementation. In addition, if there is a positive inotropic effect, further studies investigating the use of l-lysine supplementation in cats with systolic dysfunction will be warranted. If there is no measurable effect in vivo, this will add to the evidence that l-lysine is a safe supplement for use in cats.
Animal Health Component
0%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
Our aim is to investigate the inotropic effect of l-lysine in cats when administered at the commonly prescribed dose of 500mg PO twice daily.
Project Methods
Experimental subjects: 12 healthy research cats owned by the University of Tennessee Small Animal Clinical Sciences department. Experimental design and data collection:Day 0: All 12 cats echoed. Blood drawn to assess cardiac troponin I and NT-proBNP levels. Blood pressure evaluated. Days 1-90: All 12 cats will receive l-lysine 500mg PO twice daily in a small amount of wet food and observed to eat it. A commercial supplement available in 500mg capsules will be used. A sample of the supplement will be submitted to Eurofins Laboratory for testing to verify l-lysine content prior to the start of the study. Day 90: All 12 cats echoed. Blood drawn to assess cardiac troponin I and BNP levels. Blood pressure evaluated. Day 180: If any cats show changes on Day 90 as compared with baseline (echocardiogram, cardiac troponin I, NT-proBNP), they will be re-evaluated 3 months after discontinuing l-lysine supplementation to assess whether the changes are reversible.Analytical procedures:Evaluation of systolic function, left ventricular geometry, and mitral valve motion will be assessed via standard echocardiographic M-mode evaluation of LVIDd, LVIDs, LVFWd, IVSd, FS%, and mitral valve motion. Aortic valve velocity will be evaluated to assess for outflow obstruction as well as tissue Doppler s' velocity to further evaluate systolic function. Mitral inflow interrogation and tissue Doppler e' and a' velocities will also be recorded to evaluate diastolic function. We will assess all of these measurements before and during l-lysine supplementation to determine whether there is a measureable positive inotropic effect of l-lysine supplementation.NT-proBNP is a hormone released from the ventricles in response to pressure and volume overload and neurohormonal stimuli. It has been shown to be of some value in diagnosing occult cardiomyopathy in cats, including cases of obstructive cardiomyopathy with or without hypertrophy. Cardiac troponin I (cTnI) is a sensitive and specific indicator of cardiomyocyte injury. We will measure both NT-proBNP and cTnI before and during l-lysine supplementation to determine whether there is evidence of ventricular overload or cardiomyocyte injury during l-lysine supplementation.If there are statistical changes in echocardiographic measurements or biomarker levels during l-lysine supplementation compared to baseline, those measurements will be repeated 3 months after discontinuing supplementation to demonstrate regression of changes with discontinuation of supplementation.Statistical analysis:Statistical analysis will be performed in conjunction with statistical support staff at the University of Tennessee College of Veterinary Medicine. A paired t-test will test for significant mean differences between groups.