The role of KEAP1 in Nrf2 regulation in response to chronic exercise training

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Kerry James Martin (Creator)
The University of North Carolina at Greensboro (UNCG )
Web Site:
Allan H. Goldfarb

Abstract: Aerobic exercise training is a beneficial stress that causes physiological changes to adapt to many different forms of stress. Oxidative stress is a form of stress that is classified by the production and imbalance of harmful radicals, termed reactive oxygen and nitrogen species (RONS). Cells within the body can produce antioxidants to act as a defense against these dangerous molecules and potential future RONS. An imbalance in antioxidant production to oxidative stress can lead to cell dysfunction or cell death, which may lead to diseased states. A normal response to an increase in RONS leads to activation of a transcription factor, nuclear erythroid 2-related factor 2 (Nrf2), which signals the production of antioxidants. As such, Nrf2 has emerged as the ‘master regulator’ of antioxidant production. However, Kelch-like ECH Associated Protein 1 (KEAP1) is the protein that is responsible for Nrf2 regulation and activation. While this pathway has been implicated as a major role in redox homeostasis, much remains unknown about its response to exercise. Therefore, the purpose of this study was to evaluate the changes that occur in the KEAP1/Nrf2/Antioxidant pathway to exercise training. In order to assess these changes, mice (C57BL/6) were assigned to two groups: 1) underwent an 8-week exercise training program (n = 14) and 2) were sedentary control (n = 9). The exercise training program consisted of treadmill running 5 days per week initially for 45 minutes to 1 hour and progressed each week by adding duration, speed, and incline, ending at approximately 65% VO2max intensity. Seventy-two hours after the last session, mice were sacrificed; quadriceps, gastrocnemius, and soleus hindlimb muscles were harvested and stored for biochemical analysis. Multiplexed fluorescent western blot analysis was used to quantify KEAP1, nuclear Nrf2, cytosolic Nrf2, SOD1, and HO1 protein levels; the latter two proteins are related to controlling RONS. Because multivariate assumptions were violated and power was low, univariate repeated-measures ANOVAs were used to assess the differences between sedentary and exercise groups, along with potential differences between muscles. Simple main effects illustrated significant differences between exercise groups in the gastrocnemius (F = 4.438, p = 0.047), soleus (F = 6.082, p = 0.022), and deep quadriceps (F = 10.756, p = 0.004). SOD1, KEAP1, and cytosolic Nrf2 fraction all approached significance for a main effect of exercise between groups (p = 0.062, p =0.111, p = 0.104, respectively). Additionally, HO1 and SOD1 each demonstrated a significant effect of muscle (p < 0.001, each). The Nrf2/KEAP1 (both cytosolic and total ratios) did not differ between muscle groups or between exercise groups and did not significantly predict antioxidant level production. It appears that exercise training, according to this protocol, increases nuclear translocation in a muscle-dependent fashion. Future studies should address complications with the current study, particularly low power from low sample size, as well as genetic regulations explaining control between Nrf2 activation and down-stream antioxidant production.

Additional Information

Language: English
Date: 2021
Antioxidants, Cell Signaling, Exercise, Nrf2, Oxidative Stress, Redox
Aerobic exercises $x Physiological aspects
Cellular signal transduction
Oxidative stress

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