The antioxidant and prooxidant impacts of varying levels of alpha-lipoic acid on biomarkers of myoglobin oxidation in vitro

Abstract EN

R-alpha-lipoic acid (R-ALA) has been known to protect protein oxidation and lessen the pathogenesis of oxidative- related multiple diseases; however, its dosing remains unresolved.

This study aimed to examine whether in vitro R-ALA varying levels would have antioxidant or prooxidant impacts on biomarkers of myoglobin oxidation in terms of carbonyls and free thiols for myoglobin upon long-term incubation.

Myoglobin (1mg/mL) was cotreated with 6 different concentrations of R-ALA: 50 μM, 100 μM, 500 μM, 1mM, 2mM and 4mM for 30 days at pH 6.6 and temperature 37 °C.

Myoglobin oxidative modifications as protein carbonyls and its oxidative defence as free thiols were determined by standard procedures.

Thirty-day coincubation of native myoglobin with R-ALA at 500 μM, 1mM, 2mM, and 4mM significantly (p<0.05) elevated carbonyls (2.51±0.19; 2.59±0.22; 2.71±0.32 and 2.79±0.39 nM/ mg protein respectively) compared to their levels in native control myoglobin (1.67±0.43 nM/ mg protein) and significantly (p<0.05) decreased free thiols (4.60±0.36; 4.49±0.46; 4.38±0.28 and 4.07±0.39 nM/ mg protein respectively) against their levels in native control myoglobin (5.71±0.62 nM/ mg protein).

Conversely, coincubation of myoglobin with 50μM and 100μM R-ALA reduced carbonyls (1.02±0.29 and 0.9±0.19 nM/ mg protein respectively) compared to the control levels (1.67±0.43 nM/ mg protein) and elevated free thiols (6.1±0.28 and 6.83±0.28 nM/ mg protein respectively) against control levels (5.71±0.62 nM/ mg protein) levels; 100μM elicited significant (p<0.05) differences, but 50μM did not.

Findings indicate that high levels of R-ALA (0.5- 4mM) provoked myoglobin oxidative damage while moderate level (50-100μM) protected protein upon any spontaneous oxidative damage during long-term coincubation.

Thus, R-ALA concentrations, which set the balance between R-ALA pro- and antioxidants, dictate the primary impacts of R-ALA on myoglobin redox status.

Additional in vivo investigations are needed to assess the therapeutic insights of current findings.