Effect of Calorie Restriction on Doxorubicin Induced Cardiac Dysfunction

1. Effect of Calorie Restriction on Doxorubicin Induced Cardiac Dysfunction Celina Lucero and Genysie Van Duren Stephanie Greufe and Reid Hayward Abstract Doxorubicin (DOX) is one of the most potent, deadly, and effective chemotherapies in existence. However it has severe adverse effects leading to cardiomyopathy in the patients receiving it. Calorie restriction (CR) is the only proven non-genetic way of extending a person’s life. It is a means of reducing energy intake while not causing malnutrition. Purpose: The purpose of this experiment was to see if combining doxorubicin with calorie restriction would lessen the adverse effects caused by DOX. Methods: Sprague-Dawley rats were used in this experiment. The animals were randomly assigned to one of four groups AL+SAL, AL+DOX, CR+SAL and CR+DOX. The DOX was given in dosages equivalent to a patient receiving DOX in a hospital and the CR was 60% of the food that the AL animals were eating. Echocardiographs were used to monitor cardiac function. Results: The data from the echoes shows minor differences between the four groups. The DOX groups seemed to have slightly less dysfunction compared to that of the CR groups, however the data in total is inconclusive. Discussion The rat’s body weight during the experiment in all four groups usual decreased, except for the AL.SAL rats which fluctuated. The CR groups weights, decreased more than the AL group rats. This makes sense since the CR groups had less food intake compared to the AL groups. The CR+DOX group did not lose as much weight as the CR+SAL group though. Similar research, however, has found a significant decrease in body weight with the treatment of DOX (Hayward 2007). The current research which has shown no changes in body weight due to the DOX is likely due to the lower cumulative dose of DOX (7.5mg/kg compared to 15-20 mg/kg). There were no significant differences found in the left ventricle thickness measurements, however in Dr. Hayward’s study he found that DOX will normally cause a noticeable thinning in the LV walls and increase in LVD. There were minor differences seen, but not as profound as the previous study’s. This again may be because of the time constraint which prohibited the rats from being exposed longer to the DOX with larger cumulative doses. There were significant findings in the Vcfa, CR.DOX was significantly lower than the AL.DOX group. This is good evidence that the CR treatment some of the rats were receiving was indeed reducing the cardiotoxicity of the DOX. The rest of the calculated variables did not show significant differences statistically. There were no significant differences found in the Doppler’s variables either.Therat has been a reliable method of experimentation. Only two of the rats died, both of them being rats that were injected with DOX, and they died while giving them sedatives for the echoes. Other than those to there were no more fatalities among the other rats. Results Body Mass. The body mass of the four groups fluctuated during the 4 weeks. The AL group’s weights remained similar during the 4 weeks. While both CR group’s body weighs remained lower; DOX appeared to have no effect on body weights. No significant differences were detected. Echocardiographs. M-mode.To keep track of the rat’s cardiac function, echoes were taken weekly beginning at week 2. There were no significant differences found in SWs, SWd, PWs, PWd, LVDs, and LVDd. The Vcfa was significantly decreased (p<.05) in CR.DOX compared to AL.DOX. No significant differences were seen in the LVmass, RWT, FS, and MPI. Echocardiographs. Doppler. There were no significant differences in Vmax(M), Vmax (A), ET, HRI, IVRT, and IVCT. Remember that the significant differences are based on statistics, not necessarily by their standard appearance of initial observations. Introduction Doxorubicin (DOX) is one of the most effective and potent chemotherapies in use today. DOX is used to treat various types of cancers. DOX works by being injected into the bloodstream, enters the cancer cell, and causes damage through apoptosis. DOX’s benefits are countered once it enters the heart, where it does damage to the cardiac tissue, through apoptosis and oxidative stress, leading to dysfunction. Calorie restriction (CR) is where ones calorie intake is decreased while not causing any malnutrition. CR has been proven to prolong lifespan. CR has been shown to decrease disease via decreased oxidative stress. This research attempts to prove that CR may be able to reduce DOX’s cardiotoxicity. Hypothesis Calorie restriction will help reduce the build up of Doxorubicin in the heart which in turn will decrease the chance of cardiac dysfunction. Methods/Materials Fourteen 10 week old Sprague-Dawley rats were randomly assigned to one of four groups, AL+SAL, AL+DOX, CR+SAL, and CR+DOX. First 14 days of the experiment, AL animals were given free access to food, while CR animals received 60 % of the AL intake. Beginning on week 2 and continuing to week 4 animals received weekly injections of 2.5 mg/kg of DOX for a cumulative dose of 7.5 mg/kg of DOX. In addition, weekly echocardiograms were used to access cardio functions. See timeline below. Figure 4. The average of the fractional shortening (FS) over the four week trials. The black bar is the standard error. The x-axis represents the four test groups. Figure 2. Shows the average body mass of the four groups of rats. The x-axis represents the four test groups. The black bar is the standard error. References Hayward, R. (2007). Doxorubicin Cardiotoxicity in the Rat: An In Vivo Characterization. Journal of the     American Association for Laboratory Animal Science, 20-32. KatashiOkoshi*, L. S. (2002). Food restriction-induced myocardial dysfunction. Nutrition Research,         1353–1364. Figure 3. The comparison of the correct velocity of circumferential shortening (Vcfa) in cardio at week four. The black bar is a result of the standard error. The x-axis represents the four test groups while the y-axis represents the Vcfa in mm. Acknowledgments Lori Ball FSI director Krystal Meisel technical help Stephanie Gruefe mentor Reed Hayword mentor’s adviser Frank and Gloria Walsh Genysie’s sponsor Suncore foundation Celina’s sponsor Xcel energy Genysie’s project sponsor Kinder Morgan foundation Celina’s project sponsor Figure 5. the upper image is the left ventricle in M-mode. The lower image is the inflow and outflow through left ventricle in Doppler. Figure 1. Research timeline.