ABSTRACT
Both D-aspartic acid (DAA) and nitrate have received considerable attention in recent years. Vitamin D3 is also considered important for overall physical health and has been associated with elevated blood testosterone. The present study evaluated the impact of a DAA-nitrate-vitamin D3 containing dietary supplement on anaerobic exercise performance, blood testosterone and nitrate/nitrite in men. Methods: 24 resistance-trained men (mean age: 23 years) were assigned to ingest a DAA-nitrate-vitamin D3 supplement or a placebo for 28 days. Exercise performance (upper body muscle power, force, and endurance; Wingate cycle sprints), in addition to blood total and free testosterone and nitrate/nitrite was measured before and after 14 and 28 days of supplementation. Results: No increase in total or free testosterone was noted at either measurement time (p>0.05), with values remaining stable or decreasing slightly following intake of the supplement. Nitrate/nitrite was increased significantly following intake of the supplement (p<0.05), from 19.1±2.1 µmol∙L-1 (pre) to 70.0±12.4 µmol∙L-1 at 14 days and 68.6±7.7 µmol∙L-1 at 28 days. Despite this increase in nitrate/nitrite, no performance variable was impacted in a statistically significant manner by supplementation (p>0.05). However, the cumulative number of repetitions performed during a five-set bench press challenge was 11.3% higher after 28 days of supplementation, as compared to 3.6% higher for placebo. Conclusion: Twenty-eight days of treatment with a DAA-nitrate-vitamin D3 supplement increases blood nitrate/nitrite and can moderately improve repetitive bench press performance. However, this supplement does not result in an increase in total or free testosterone or any other performance measure.
ABSTRACT
Background: The topic of postprandial oxidative stress continues to receive considerable attention, with elevations in oxidative stress biomarkers associated with human disease (e.g., insulin resistance, atherosclerosis). The predictable rise in serum triglyceride (TAG) following high fat meal ingestion is strongly correlated to the increase in circulating oxidative stress biomarkers. Our intent with the present study was two-fold: 1) To further characterize the postprandial response to high fat feeding and 2) to develop regression models that could be used to predict the oxidative stress response to high fat feeding. Methods: 154 men and women reported to the lab in the morning hours following an overnight fast and consumed a high fat liquid meal. Blood samples were collected before meal ingestion and at 2 and 4 hours following meal ingestion. Samples were analyzed for TAG and oxidative stress biomarkers (hydrogen peroxide [H2O2], malondialdehyde [MDA], advanced oxidation protein products [AOPP]). Simple linear regression analyses were used for model development to predict the oxidative stress response to feeding. In addition, biochemical variables were analyzed using an analysis of variance (ANOVA) to present response to feeding data across time. Results: In all of the regression models, TAG explained a significant portion of the outcome variables (H2O2, MDA, and AOPP) and predictor models were created for each variable. In addition, values for TAG and all oxidative stress biomarkers increased following meal ingestion. A time effect was noted where all values were higher post meal ingestion as compared to pre meal for all biochemical variables (p<0.05). Conclusion: Obtaining serum TAG values in response to a high fat meal challenge may provide investigators with the ability to predict postprandial oxidative stress using regression equations.
ABSTRACT
Background: ELISA procedures are widely available and used for the measurement of saliva and blood (serum and plasma) testosterone. Suggestions for strong correlations between these two fluids have been made but differences in assay format, as well as in the collection procedures, storage, and processing of samples can influence results. Methods: The present study compared saliva and serum free testosterone concentrations in 20 healthy men (31.0±11.0 years; mean ± SD) using ELISA procedures. Men provided both a saliva and blood sample on the same day in the morning hours following an overnight fast. Special care was taken in the collection, storage, and processing of samples. Following complete thawing and mixing of samples, both fluids were analyzed in duplicate using commercially available ELISA kits, both prior to and following centrifugation. Results: Saliva testosterone values were 440.6±238.2 pg·mL-1 and 348.8±210.0 pg·mL-1 without and with centrifugation, respectively. Serum testosterone values were 9.0±4.2 pg·mL-1 and 8.3±3.7 pg·mL-1 without and with centrifugation, respectively. Conclusion: If utilizing ELISA procedures, saliva and serum testosterone values cannot be used interchangeably, at least when utilizing the ELISA procedures employed in the present study. This is evidenced by the approximate 10-100 times higher testosterone concentration in saliva as compared to serum. Moreover, processing samples via centrifugation leads to a significant (~23%) loss in testosterone in saliva, with a much smaller loss (~7%) in serum. Investigators and clinicians should take note of these findings if planning to measure saliva or serum testosterone using ELISA procedures.