The Effect of Elevated Protein Intake on DNA Damage in Older People: Comparative Secondary Analysis of Two Randomized Controlled Trials

Abstract

A high protein intake at old age is important for muscle protein synthesis, however, this could also trigger protein oxidation with the potential risk for DNA damage. The aim of this study was to investigate whether an increased protein intake at recommended level or well above would affect DNA damage or change levels of reduced (GSH) and oxidised glutathione (GSSG) in community-dwelling elderly subjects. These analyses were performed in two randomized intervention studies, in Austria and in New Zealand. In both randomized control trials, the mean protein intake was increased with whole foods, in the New Zealand study (n = 29 males, 74.2 ± 3.6 years) to 1.7 g/kg body weight/d (10 weeks intervention; p < 0.001)) in the Austrian study (n = 119 males and females, 72.9 ± 4.8 years) to 1.54 g/kg body weight/d (6 weeks intervention; p < 0.001)). In both studies, single and double strand breaks and as formamidopyrimidine—DNA glycosylase-sensitive sites were investigated in peripheral blood mononuclear cells or whole blood. Further, resistance to H2O2 induced DNA damage, GSH, GSSG and CRP were measured. Increased dietary protein intake did not impact on DNA damage markers and GSH/GSSG levels. A seasonal-based time effect (p < 0.05), which led to a decrease in DNA damage and GSH was observed in the Austrian study. Therefore, increasing the protein intake to more than 20% of the total energy intake in community-dwelling seniors in Austria and New Zealand did not increase measures of DNA damage, change glutathione status or elevate plasma CRP.

Effect of Repeated Bolus and Continuous Glucose Infusion on DNA Damage and Oxidative Stress Biomarkers in Healthy Male Volunteers

“…The determination of UCB as well as that of the antioxidative potential by FRAP are methods for the indirect determination of oxidative stress. The measured markers for this study have been used in numerous human studies for this purpose and are suitable to assess short-and long-term changes in the body [15,30,31]. We revealed a significant time effect for all measured DNA damage and oxidative stress markers, with the exception of FRAP, which showed only a tendency, over the period of the nine measured blood sampling points within 48 h. However, there was no significant difference between the two groups, continuous and bolus.…”

Age-related influence on DNA damage, proteomic inflammatory markers and oxidative stress in hospitalized COVID-19 patients compared to healthy controls

“…DNA damage in whole blood was assessed with the Comet assay, a method for visualizing DNA damage in single cells. The protocol was performed as already described by Draxler et al [ 36 ]. 10 μl of whole blood samples were mixed with 200 μL 1%-agarose solution and 5 μL of the mixture were spotted onto 12 spot microscopy slides.…”