Review for 10.1186/s12876-025-04052-1 (2025)

Title: Irisin prevents liver injury during exhausting physical activity by suppressing ferroptosis
via Nrf2/GPX4 signaling
Version: 1 Date: 24 Feb 2025
Reviewer:  Ayoub Saeidi
Reviewer's report:
Introduction:
The introduction is well-written but could benefit from some improvements. Below are two key
issues:
1. Overgeneralization of the Impact of Moderate Exercise: The introduction starts by
emphasizing the benefits of moderate exhaustive exercise, including boosting the immune
system, slowing aging, and reducing the risk of diabetes. However, the term "moderate
exhaustive exercise" is a bit contradictory, as "exhaustive" typically refers to high-intensity or
prolonged exercise. Moderate exercise, on the other hand, is usually less intense and sustainable
over a longer period. Clarifying the distinction between moderate and exhaustive exercise would
strengthen the accuracy of the claims.
2. Lack of Clear Hypothesis or Research Question: While the introduction provides a solid
background on the relevance of liver damage from intense physical activity, it doesn't clearly
state the specific research question or hypothesis. The transition into the introduction of irisin
and ferroptosis is a bit abrupt. A clearer statement of the research gap, or the question that this
study aims to answer, would help the reader understand the study's direction. For instance, you
could highlight why the relationship between irisin and exercise-induced liver damage remains
underexplored.
Method:
1. Lack of Detail on Ethical Considerations and Sample Size Calculation: The method mentions
that animal experiments were approved by the Ethics Committee, but it does not provide
sufficient detail on the ethical guidelines followed (e.g., any measures taken to minimize animal
suffering) or how the sample size was determined. Including the rationale behind the sample
size, such as power analysis or references to similar studies, is crucial to ensure that the study
is appropriately powered and that the number of animals used is justified to avoid unnecessary
use of animals.
2. Ambiguity in the EE Model and Exercise Protocol: The exercise exhaustion (EE) model,
particularly the treadmill running protocol, is described vaguely. The exact nature of "strenuous
running" and the intensity increments are unclear. The description of "engaging in daily uphill
running on a treadmill set at a 10° incline" combined with increasing the velocity is somewhat
confusing, as it doesn’t explain how this was maintained over time, and how long the total
duration of exercise was each day. Additionally, the use of electric shock to induce fatigue
raises ethical concerns, and the manuscript should provide further justification for its use, as
well as detailed information on how this was ethically managed. The method lacks clarity on
how exhaustion and fatigue were precisely quantified.
Discussion:
1. Ambiguity in Molecular and Conceptual Mechanisms: The text mentions that irisin exerts
its protective effects through the Nrf2/GPX4 pathway, but there is no clear explanation of
the molecular processes or interactions involved. To enhance understanding, it is important to
provide a more detailed explanation of how irisin activates this pathway and which specific
proteins and enzymes are involved. Additionally, describing the exact relationship between this
pathway, oxidative stress reduction, and ferroptosis in liver tissue would further solidify the
scientific credibility of the paper.
2. Lack of Discussion on Gender and Individual Differences: The study was conducted on
mice, but there is no mention of potential gender or individual physiological differences in the
response to irisin and high-intensity exercise. Are there significant differences between male and
female mice or between different ages or health conditions in their response to irisin or exercise?
Including such information could deepen the findings and clarify the limitations of the study.
3. Need for Further Discussion on Long-term Effects and Dosage of Irisin: The article mentions
that different doses of irisin have varying effects, but there is no discussion on the long-term
effects or safety of high doses of irisin in mice. This raises the question of whether prolonged
use of irisin as a therapeutic intervention could result in unforeseen side effects. It would be
beneficial to examine the effects of various irisin doses on different markers of liver damage in
more detail to make more reliable conclusions.
Please refer to the following articles in the introduction and discussion:
# High-intensity Interval Training Improves Lipocalin-2 and Omentin-1 Levels in Men with
Obesity
# Intensity Dependent Effects of Interval Resistance Training on Myokines and Cardiovascular
Risk Factors in Males With Obesity
# Differential Effects of Exercise Programs on Neuregulin 4, Body Composition and
Cardiometabolic Risk Factors in Men With Obesity
# Effects of Exercise Training on Bone Health Parameters in Individuals With Obesity: A
Systematic Review and Meta-Analysis
#Astaxanthin Supplemented with High-Intensity Functional Training Decreases Adipokines
Levels and Cardiovascular Risk Factors in Men with Obesity