Orosomucoid: a promising biomarker for the assessment of exercise-induced fatigue triggered by basic combat training

Establishing the minimal important difference of the visual analog scale for assessing exercise-induced fatigue

BACKGROUND

Exercise-induced fatigue is a physiological state characterized by performance decline. The Visual Analog Scale (VAS) is one of the most commonly used subjective methods for evaluating exercise-induced fatigue. However, there is a limited interpretation of how much a change in this method indicates a fatigue status that matters to the exercise performance due to the lack of a well-established minimal important difference (MID).

METHODS

This study is a secondary analysis of data from three trials. We analyzed individual participant data before and after exercise-induced fatigue. Anchor-based methods were used to determine the MID of the VAS for fatigue, using Countermovement Jump (CMJ) height as an anchor. Specifically, the MID was calculated using mean change, receiver operating characteristic (ROC) curve analysis, and linear regression methods.

RESULTS

Data from 71 participants (80.28% male, 22.85 ± 2.51 years), corresponding to 230 person-time measurements, were included in this analysis. The CMJ height fulfilled the requirements to be used as an anchor. MIDs for mean change, ROC curve, and linear regression analysis were 48.51, 44.13, and 43.08, respectively. The Youden's Index indicated that the MID calculated by the mean change method was the most relevant and reliable in distinguishing between fatigued and non-fatigued states.

CONCLUSIONS

This study establishes a MID (48.51) for interpreting changes in VAS scores. Future research utilizing VAS to assess exercise-induced fatigue should not only consider statistical differences but also examine whether the changes meet the MID threshold to interpret the actual impact of interventions.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (ChiCTR), Registration Number: ChiCTR2500095599 (Retrospectively registered; registration date: 09/01/2025).

Alpha 1-acid glycoprotein is upregulated in severe COVID-19 patients and decreases neutrophil NETs in SARS-CoV-2 infection

Orosomucoid, or alpha-1 acid glycoprotein (AGP), is a major acute-phase protein expressed in response to systemic injury and inflammation. AGP has been described as an inhibitor of neutrophil migration on sepsis, particularly its immunomodulation effects. AGP's biological functions in coronavirus disease 2019 (COVID-19) are not understood. We sought to investigate the role of AGP in severe COVID-19 infection patients and neutrophils infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Epidemiological data, AGP levels, and other laboratory parameters were measured in blood samples from 56 subjects hospitalized in the ICU with SARS-CoV-2 infection. To evaluate the role of AGP in NETosis in neutrophils, blood samples from health patients were collected, and neutrophils were separated and infected with SARS-CoV-2. Those neutrophils were treated with AGP or vehicle, and NETosis was analyzed by flow cytometry. AGP was upregulated in severe COVID-19 patients (p<0.05). AGP level was positively correlated with IL-6 and C-reactive protein (respectively, p=0.005, p=0.002) and negatively correlated with lactate (p=0.004). AGP treatment downregulated early and late NETosis (respectively, 35.7% and 43.5%) in neutrophils infected with SARS-CoV-2 and up-regulated IL-6 supernatant culture expression (p<0.0001). Our data showed increased AGP in COVID-19 infection and contributed to NETosis regulation and increased IL-6 production, possibly related to the Cytokine storm in COVID-19.

Cystatin-c May Indicate Subclinical Renal Involvement, While Orosomucoid Is Associated with Fatigue in Patients with Long-COVID Syndrome

Long-COVID syndrome is associated with high healthcare costs, but its pathophysiology is not yet fully understood. Inflammation, renal impairment or disturbance of the NO system emerge as potential pathogenetic factors. We aimed to investigate the relationship between symptoms of long-COVID syndrome and serum levels of cystatin-c (CYSC), orosomucoid (ORM), l-arginine, symmetric dimethylarginine (SDMA) and asymmetric dimethylarginine (ADMA). A total of 114 patients suffering from long-COVID syndrome were included in this observational cohort study. We found that serum CYSC was independently associated with the anti-spike immunoglobulin (S-Ig) serum level (OR: 5.377, 95% CI: 1.822-12.361; p = 0.02), while serum ORM (OR: 9.670 (95% CI: 1.34-9.93; p = 0.025) independently predicted fatigue in patients with long-COVID syndrome, both measured at baseline visit. Additionally, the serum CYSC concentrations measured at the baseline visit showed a positive correlation with the serum SDMA levels. The severity of abdominal and muscle pain indicated by patients at the baseline visit showed a negative correlation with the serum level of L-arginine. In summary, serum CYSC may indicate subclinical renal impairment, while serum ORM is associated with fatigue in long-COVID syndrome. The potential role of l-arginine in alleviating pain requires further studies.