Impact of a tailored exercise regimen on physical capacity and plasma proteome profile in post-COVID-19 condition

Abstract

Background: Individuals affected by the post-covid condition (PCC) show an increased fatigue and the so-called post-exertion malaise (PEM) that led health professionals to advise against exercise although accumulating evidence indicates the contrary. The goal of this study is to determine the impact of a closely monitored 8-week mixed exercise program on physical capacity, symptoms, fatigue, systemic oxidative stress and plasma proteomic profiles of PCC cases.

Methods: Twenty-five women and men with PCC were assigned sequentially to exercise (n = 15) and non-exercise (n = 10) groups. Individuals with no PCC served as a control group. The exercise program included cardiovascular and resistance exercises. Physical capacity, physical activity level and the presence of common PCC symptoms were measured before and after the intervention. Fatigue was measured the day following each exercise session. Plasma and PBMC samples were collected at the beginning and end of the training program. Glutathione and deoxyguanosine levels in PBMC and plasma proteomic profiles were evaluated.

Results: Bicep Curl (+15% vs 4%; p = 0.040) and Sit-to-Stand test (STS-30 (+31% vs +11%; p = 0.043)) showed improvement in the exercise group when compared to the non-exercise group. An interaction effect was also observed for the level of physical activity (p =0.007) with a positive effect of the program on their daily functioning and without any adverse effects on general or post-effort fatigue. After exercise, glutathione levels in PBMCs increased in women but remained unchanged in men. Discernable changes were observed in the plasma proteomics profile with certain proteins involved in inflammatory response decreasing in the exercise group.

Conclusions: Supervised exercise adapted to the level of fatigue and ability is safe and effective in PCC patients in improving their general physical capacity and wellbeing. Systemic molecular markers that accompany physical improvement can be monitored by analyzing plasma proteomics and markers of oxidative stress. Large-scale studies will help identify promising molecular markers to objectively monitor patient improvement.

Keywords: exercise; fatigue; long COVID; oxidative stress; physical activity; physical capacity; post COVID-19 condition; symptoms.

FIGURE 1

Schematic representation of the study design. PBMC, peripheral blood mononuclear cells; GSH, glutathione; 8-OHdG, 8-Hydroxy-2-Deoxyguanosine; LC-MS/MS, Liquid Chromatography tandem mass spectrometry; STS-30, sit-to-stand test; 6MWT, 6-min walk test; HGS, hand grip strength; TUG, Timed up and go test.

FIGURE 2

Evaluation of different exercise associated parameters at inclusion (pre-) and at the end of the study (post-) in the group that had physical training intervention (Exercise) or not (No-exercise). (A) STS-30-sit-to-stand test; (B) bicep curl; (C) 6MWT-6-min walk test; (D) Sit and reach; (E) HGS-hand grip strength; (F) Tug-Timed up and go test.

FIGURE 3

Fatigue score reported over time.

FIGURE 4

Proportion of T and B cell subsets in the peripheral blood samples at inclusion (pre-) and at the end of the study (post-) in the group that had physical training intervention (Exercise) or not (No-exercise). (A) Proportion of CD4⁺ and CD8⁺ cell subsets in T lymphocytes; (B) Proportion of naïve (IgD+), switched memory (SM, IgD-CD27⁺) and double negative (DN, IgD-CD27⁻) B cells subsets within CD19⁺ B cells. T and B cell response to spike protein at inclusion (pre-) and at the end of the study (post-) in the group that had physical training intervention (Exercise) or not (No-exercise). (C) PBMC were stimulated with pooled spike peptides and specific response was determined (AIM assay) in CD4⁺ and CD8⁺ T cell subsets. CD134+ (OX40) was used to identify spike-specific T cell responses. (D) PBMCs were labeled with D614G-RBD to label RBD-specific B cells in total, switched memory (SM) and double negative (DN) subsets. Statistical comparisons were carried out with the Wilcoxon test.

FIGURE 5

Total GSH levels in PBMCs isolated from exercise (E) and no-exercise (NE) PCC groups measured by enzymatic assay. (A) Paired analysis of pre- and post- GSH levels within exercise and no-exercise PCC groups. (B, C) Paired analysis of GSH levels among female (B) and male (C) PCC subjects within exercise (-E) and no-exercise (-NE) groups. Statistical comparisons were carried out with the Wilcoxon test. GSH, glutathione.

FIGURE 6

Concentration of 8-OHdG DNA in plasma samples measured by ELISA. (A) 8-OHdG DNA levels in PCC subjects before (Pre-E) and at the end (Post-E) of the exercise regimen compared to no-PCC controls. (B) 8-OHdG DNA concentration in no-exercise PCC subjects at the beginning (Pre-NE) and at the end (Post-NE) of the study period compared to no-PCC controls. (C) Paired analysis of pre- and post- 8-OHdG DNA levels within exercise and no-exercise PCC groups (D, E) Paired analysis of 8-OHdG DNA levels among female and male PCC subjects within exercise (-E) and no-exercise (-NE) groups. Statistical comparisons were carried out with Mann-Whitney’s test or the Wilcoxon test. 8-OHdG, 8-Hydroxy-2-Deoxyguanosine.

FIGURE 7

(A) Unsupervised clustering analysis showing segregation of the proteomic data of the PCC study groups. Most of the No-PCC controls cluster together (black). Most PCC samples collected at the beginning of the study cluster together at baseline (grey), whereas those who were subject to tailored exercise intervention clustered into a distinct group (green). (B) Principal component analysis (PCA).

FIGURE 8

Volcano plot comparing the plasma proteome of the post-exercise group with that of the pre-exercise group (A; Post-E versus Pre-E), and the corresponding data within the no-exercise groups (B; Post-NE versus Pre-NE). Proteins that are signicantly modulated (fold change of ± 0.5 and p-value of 0.05, indicated by dotted line) are labelled are indicated in red color. (C) cnet plot of pathways identified to be downregulated in the exercise group.