The potential role of FNDC5/irisin in various liver diseases: awakening the sleeping beauties

Exercise induced irisin mitigates hepatitis in anabolic-androgenic steroids treated rats via modulation of PGC-1-α/PPARγ/Nrf2 and NRF2/NF-κB/TLR4 signaling

Irisin, a myokine released during exercise, has been shown to exert protective effects against metabolic and inflammatory disorders. Its role in mitigating hepatic damage induced by anabolic-androgenic steroids (AAS) remains largely unexplored. This study was conducted to examine the effects of exercise on irisin level and its capability to prevent hepatotoxicity caused by anabolic androgenic steroids (AAS) in rat model. The fifty-two male rats were divided into four groups: control, AAS treated (15 mg/kg/day S.C/8 W), exercised, and exercised- AAS treated. The following procedures were carried out: liver function tests, serum irisin, tissue inflammatory and oxidative stress markers, macro and micromorphological evaluation, and the examination of nuclear factor erythroid 2-related factor 2 (Nrf2), peroxisome proliferator-activated receptor-gamma (PPARγ) and its coactivator-1α (PGC1α) by immunohistochemistry. The liver tissue's expression of nuclear factor kappa B (NF-κB), Toll-like receptor-4 (TLR4), and Nrf2 mRNA was also assessed. After administering AAS to animals, aerobic exercise was found to significantly improve liver function tests, inflammation, and oxidative stress, reduce liver weight, improve morphological and histological changes, and improve the hepatic injury score. Furthermore, there was a notable rise in serum irisin, hepatic PPARγ, PGC1α, and Nrf2 immune-expressions and Nrf2 mRNA expression, while NF-κB and TLR4 mRNA expressions were significantly decreased. In conclusion, the irisin/PGC1α/PPARγ/Nrf2 and Nrf2/NF-κB/TLR4 signaling pathways may be modulated by aerobic exercise, which also reduces the liver's oxidative stress and inflammatory reactions to AAS treatment.

Understanding the Role of Irisin in Longevity and Aging: A Narrative Review

Irisin is a protein resulting from a proteolytic cleavage of fibronectin type III domain-containing protein 5 (FND5). The ability of irisin to modulate adipocyte and control glucose metabolism in human metabolic diseases gave rise to the hypothesis that irisin could have a pivotal role in aging-related diseases. Although in animal models, increased levels of irisin have been positively associated with better health outcomes, in humans, its role remains controversial. To provide an overview of the main finding on irisin in older adults, a comprehensive search was performed through the MEDLINE-PubMed, Web of Science, Scopus, and Cochrane databases for studies conducted in older adults (≥60 years) published since 2012. After grouping and analyzing the articles based on diseases associated with older adults, the main conclusion of this narrative review is that the included studies did not yield consistent evidence regarding the association between irisin and health or disease in older adults. Further studies are necessary to clarify the effective role of this protein in promoting health and longevity.

Circulating irisin levels in patients with MAFLD: an updated systematic review and meta-analysis

Objective

Current research suggests that irisin is closely linked to the pathogenesis and progression of metabolic dysfunction-associated fatty liver disease (MAFLD). This systematic review and meta-analysis updates our previous meta-analysis and further explores the relevance between circulating irisin levels and MAFLD.

Methods

Nine databases (PubMed, EMBASE, Cochrane Library, CNKI, Wanfang, Weipu, CBM, Clinicaltrials.gov and gray literature) were retrieved as of 1st August, 2024. The standardized mean difference (SMD) and 95% confidence interval (CI) represent pooled effect size. We used the Newcastle-Ottawa Scale to evaluate the quality of articles and the certainty of evidence assessed by GRADE system. All statistical analyses were performed using RevMan 5.3 and Stata 12(Stata Corporation, yi TX).

Results

Fifteen case-control studies were included. Circulating irisin levels in the MAFLD group were markedly lower than those in the healthy group (SMD=-1.04 [-1.93, -0.14]). Subgroup analyses by race, age, severity and T2DM revealed that circulating irisin levels were lower in the MAFLD group compared to those in the healthy controls in the Asian population (SMD=-1.38 [-2.44, -0.31], P<0.05) and in those above 50 years old (SMD=-2.23 [-3.64, -0.81], P<0.05) and higher in the mild MAFLD groups than those in moderate to severe MAFLD groups (SMD = 11.68 [9.05, 14.31], P<0.05). And the circulating irisin levels in MAFLD patients with T2DM were significantly lower than those in healthy group (SMD = -2.90 [-4.49, -1.30]). ELISA kits from different companies also presented different relationships.

Conclusions

There were significantly lower circulating irisin levels in the MAFLD group than in the healthy control group. Although these results differed from our previous results, there is no denying that circulating irisin levels are closely associated with the advancement of MAFLD.

Potential mechanisms of rheumatoid arthritis therapy: Focus on macrophage polarization

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease that affects multiple organs and systems in the human body, often leading to disability. Its pathogenesis is complex, and the long-term use of traditional anti-rheumatic drugs frequently results in severe toxic side effects. Therefore, the search for a safer and more effective antirheumatic drug is extremely important for the treatment of RA. As important immune cells in the body, macrophages are polarized. Under pathological conditions, macrophages undergo proliferation and are recruited to diseased tissues upon stimulation. In the local microenvironment, they polarize into different types of macrophages in response to specific factors and perform unique functions and roles. Previous studies have shown that there is a link between macrophage polarization and RA, indicating that certain active ingredients can ameliorate RA symptoms through macrophage polarization. Notably, Traditional Chinese medicine (TCM) monomer component and compounds demonstrate a particular advantage in this process. Building upon this insight, we reviewed and analyzed recent studies to offer valuable and meaningful insights and directions for the development and application of anti-rheumatic drugs.

FNDC5/Irisin Inhibits the Inflammatory Response and Mediates the Aerobic Exercise-Induced Improvement of Liver Injury after Myocardial Infarction

Myocardial infarction (MI) causes peripheral organ injury, in addition to cardiac dysfunction, including in the liver, which is known as cardiac hepatopathy. Aerobic exercise (AE) can effectively improve liver injury, although the mechanism and targets are currently not well established. Irisin, mainly produced by cleavage of the fibronectin type III domain-containing protein 5 (FNDC5), is a responsible for the beneficial effects of exercise training. In this study, we detected the effect of AE on MI-induced liver injury and explored the role of irisin alongside the benefits of AE. Wildtype and Fndc5 knockout mice were used to establish an MI model and subjected to AE intervention. Primary mouse hepatocytes were treated with lipopolysaccharide (LPS), rhirisin, and a phosphoinositide 3-kinase (PI3K) inhibitor. The results showed that AE significantly promoted M2 polarization of macrophages and improved MI-induced inflammation, upregulated endogenous irisin protein expression and activated the PI3K/ protein kinase B (Akt) signaling pathway in the liver of MI mice, while knockout of Fndc5 attenuated the beneficial effects of AE. Exogenous rhirisin significantly inhibited the LPS-induced inflammatory response, which was attenuated by the PI3K inhibitor. These results suggest that AE could effectively activate the FNDC5/irisin-PI3K/Akt signaling pathway, promote the polarization of M2 macrophages, and inhibit the inflammatory response of the liver after MI.

Irisin Is Related to Non-Alcoholic Fatty Liver Disease (NAFLD)

Irisin is a cytokine involved in many metabolic pathways occurring, among others, in muscles, adipose tissue and liver. Thus, fluctuations in irisin levels are suggested to be related to metabolic diseases. Therefore, the purpose of our study was to evaluate whether irisin may be associated with non-alcoholic fatty liver disease (NAFLD). A total of 138 patients (70/68 male/female, mean age 65.61 ± 10.44 years) were enrolled in the study. The patients were assigned to the NAFLD group (n = 72, including 46 patients with type 2 diabetes (T2DM]) and the group without NAFLD (n = 66, 31 patients with T2DM). NAFLD was diagnosed based on ultrasound examination, Hepatic Steatosis Index (HSI) and Fatty Liver Index. Baseline anthropometric, blood pressure and biochemical parameters were collected. The serum irisin level was determined using an ELISA test. We observed that NAFLD was associated with an increased concentration of irisin. Moreover, Spearman correlations and linear regression analysis revealed that irisin level correlates with some anthropometric and biochemical parameters such as body mass index, glycated hemoglobin, aspartic aminotransferase, creatinine and urea. Logistic regression analysis depicted that odds for NAFLD increase 1.17 times for each 1 μg/mL rise of irisin concentration. Finally, ROC analysis showed that the concentration of irisin possesses a discriminate capacity for NAFLD and optimal cut points concentration could be designed. The risk of NAFLD in the subgroup with irisin concentration above 3.235 μg/mL was 4.57 times higher than in patients with the lower concentration of irisin. To conclude, the obtained results suggest that irisin concentration is associated with some anthropometric and biochemical parameters and should be further investigated toward its usage as a diagnostic biomarker of NAFLD.