Abstract 336: Comparing Of In-vivo Carnosine Levels In Blood, Urine, And Muscle

Background: Dietary supplementation of carnosine, an endogenously produced antioxidant, can be potentially useful in decreasing oxidative stress in the vasculature. However, a safe and accurate measurement of in-vivo Carnosine levels has not been identified. Methods: We enrolled 28 healthy male (50%) and female participants. In-vivo levels of carnosine were measured in three distinct tissues in all 28 participants - urine, blood red blood cells (RBC), and muscle via proton magnetic resonance spectroscopy (1H-MRS). Generalized Linear Model with gamma-distribution and log-link was adjusted for age, sex, race, and diet. Coefficient of variance (CoV) was calculated for 1H-MRS repeat measurements: single location with multiple measurements and multiple locations with single measurements. Results: Univariate regression analysis showed a significant positive association between RBC and urinary carnosine levels (β=0.02; 95% CI: 0.004-0.03; P=0.01). The adjusted model also showed significant positive association between RBC and urinary carnosine levels (β=0.02; 95% CI: 0.002, 0.03; P=0.03). There was no association between 1H-MRS and RBC carnosine or urinary carnosine or carnosine conjugates in urine. The median CoV for multiple readings at single location were 8% and 1% for C2 and C4 peaks respectively, however 12% and 13% for C2 and C4 peaks respectively for single reading at multiple locations. Conclusions: Even though urine, blood (RBC), and muscle represent in-vivo tissues of the human body, the levels of carnosine pools in these different compartments are not in equilibrium with each other. 1H-MRS is highly sensitive to location of measurement. In-vivo levels of carnosine in urine and blood depot are in synchrony and should be used for large scale clinical and research studies like the NEAT clinical trial (NCT03314987), which studies the use of carnosine dietary supplementation to mitigate harmful cardiovascular effects of PM2.5 air pollution.