Ahmed S. Elokda

Norepinephrine and Cardiovascular Responses to Maximal Exercise in Parkinson's Disease On and Off Medication

The aim of this experiment is to understand how Parkinsons disease (PD) medication affects the autonomic responses of individuals during an acute exercise stress test. Fourteen people with PD and fifteen healthy individuals age‐matched between 50 and 80 years performed a modified Bruce protocol. Subjects with PD performed the test once off medication (PD‐off) and then 1 week later on medication (PD‐on). Heart rate (HR), blood pressure (BP), VO2, and norepinephrine (NE) levels were taken at rest and at peak exercise. At peak exercise HR, BP, and NE values for the PD‐on and PD‐off group were all significantly lower than healthy controls, regardless of whether subjects were on their medication. Autonomic abnormalities during exercise in this population appear to be disease manifested and not impactedby medications used to treat PD. We can assume, both on and off medication, this population will show markedly lower BP, HR, and NE responses.

Effects of a maximal graded exercise test on glutathione as a marker of acute oxidative stress.

PURPOSE Strenuous exercise in animal studies has been shown to cause acute oxidative stress due to the generation of oxygen-centered free radicals reflected in lower levels of glutathione (GSH), higher levels of glutathione disulfide (GSSG), and a drop in GSH:GSSG ratios, the maintenance of which is crucial for a variety of cell functions. Human studies on this topic are limited. The purpose of this study was to investigate the effects of a maximal graded exercise test GXTmax (modified Bruce protocol) on GSH as a marker of acute oxidative stress, and whether full recovery will occur at 60 minutes postexercise. METHODS Eighty sedentary subjects were used as a sample of convenience. Venous blood samples for GSH and GSSG were collected directly before, immediately after, and 60 minutes post-GXTmax. Repeated-measures analysis of variance and Bonferroni adjusted t tests (post-GXTmax) versus resting, and 60 minutes recovery versus resting) were used for data analysis. RESULTS As an acute response to maximal exercise, the GSH levels dropped significantly from a resting baseline value of 1025.75 microM to an immediate post-GXTmax value of 893.30 microM (pooled SE = 7.17 microM). The GSSG levels significantly increased from 2.24 microM to 3.15 microM (pooled SE = 0.03 microM). The GSH:GSSG ratio levels significantly dropped from baseline 462.12 to 276.40 postexercise (pooled SE = 5.98). The blood GSH, GSSG, and GSH:GSSG ratio levels showed no significant difference at 60 minutes post-GXTmax when compared with resting values, indicating full recovery. CONCLUSION The current results indicated that in sedentary individuals, a maximal treadmill GXT is an effective technique for inducing acute oxidative stress as evidenced by GSH system responses, with full return to resting baseline levels within 60 minutes of recovery. The potential for using this model in assessing oxidative stress responses to cardiac and pulmonary rehabilitation is of clinical interest, with a need for further investigation.

Effects of Exercise and B Vitamins on Homocysteine and Glutathione in Parkinson’s Disease: A Randomized Trial

Background: Individuals with Parkinson’s disease (PD) have decreased glutathione levels and elevated homocysteine levels. These substances are considered markers of health, and an inverse relationship has been suggested through the transsulfuration pathway. This experiment tested the effects of exercise and B vitamin supplementation on homocysteine and glutathione levels, and if a relationship was present between these two markers in those with PD. Secondary aims included examining the impact of the interventions on aerobic efficiency and strength. Methods: Thirty-six subjects were randomly assigned to 4 groups. The Vit group received vitamins B6, B12 and folic acid daily for 6 weeks. The Ex group received aerobic and strength training twice weekly for 6 weeks. The Vit + Ex group received both interventions. A control group received no intervention. Subjects were tested prior to and after intervention on the following measures: glutathione and homocysteine levels, strength measures and oxygen consumption. Results: Subjects who received 6 weeks of B vitamin supplementation had lowered homocysteine levels. Subjects who received 6 weeks of exercise training had increased glutathione levels, strength and aerobic capacity. The combination of vitamin and exercise did not yield greater changes than the separate intervention. The control subjects did not change on any measures. Conclusion: Positive results were realized with each intervention; however, the expected relationship between glutathione and homocysteine was not found in this sample of subjects with PD. Homocysteine and glutathione levels can be improved independently in individuals with PD with exercise or vitamins B6, B12 and folic acid supplementation.

Relationship of resting B-type natriuretic peptide level to cardiac work and total physical work capacity in heart failure patients.

PURPOSE Plasma B-type natriuretic peptide (BNP) levels obtained at rest have been previously shown to be correlated with the global functional capacity measures of peak oxygen uptake (&OV0312;O2peak) and the minute ventilation/carbon dioxide (VE/&OV0312;CO2) slope. The purpose of this study was to assess the relationship of the plasma BNP level to the rate-pressure product (RPP) as an indicator of central or cardiac work capacity. METHODS Twenty-two subjects (12 men), mean age 57 ± 12 years, diagnosed with heart failure (8 ischemic/14 nonischemic) were recruited. All subjects were stable on optimal medical therapy for at least 1 month. Blood samples for BNP level analysis were obtained at rest. Subjects underwent a symptom-limited treadmill exercise test using a ramping protocol while &OV0312;O2, heart rate (HR), and blood pressure (BP) were monitored. Correlation analyses were conducted to assess the relationship of BNP level to RPP level, &OV0312;O2peak, VE/&OV0312;CO2 slope, end-tidal CO2 pressure (PETCO2), and left ventricular ejection fraction (LVEF). RESULTS Resting BNP levels were significantly correlated with RPP levels (r = −0.69). The BNP level and the RPP level were correlated with &OV0312;O2peak (r = −0.63 and r = 0.66, respectively) and VE/&OV0312;CO2 slope (r = 0.53 and r = −0.54, respectively). The RPP level but not the BNP level was correlated with PETCO2 (r = 0.57). Neither BNP nor RPP levels were well correlated with LVEF (r = −0.26 and r = 0.14, respectively). DISCUSSION The results of this study suggest that resting plasma BNP level may be a useful clinical measure for evaluating both global functional capacity and myocardial specific work capacity in individuals with heart failure.