Circulating irisin level in chronic kidney disease patients: a systematic review and meta-analysis

Irisin Is a Potential Novel Biomarker and Therapeutic Target Against Kidney Diseases

Kidney diseases, characterized by renal dysfunction, are the leading causes of death worldwide. It is crucial to prevent and treat kidney diseases to reduce their associated morbidity and mortality. Moderate physical exercise has been recognized to be advantageous for kidney health. Irisin is an exercise-induced myokine that was identified in 2012. It plays an important role in energy and bone metabolism, oxidative stress reduction, anti-inflammatory processes, cell death inhibition, and cardiovascular protection. However, the relationship between irisin and kidney diseases have not been fully elucidated. This review explores the role of irisin as a biomarker for kidney disease diagnosis and its associated complications, as well as the mechanisms through which it participates in various cell death pathways, such as apoptosis, autophagy, pyroptosis, and ferroptosis. Furthermore, irisin secretion levels were discussed to provide a basis for kidney disease prevention and treatment avenues, as well as therapeutic guidance for developing new and promising intervention strategies. Clinical Trial Registration: None.

Translational research on cognitive impairment in chronic kidney disease

Cognitive decline is common in patients with acute or chronic kidney disease. Several areas of brain function can be affected, including short- and long-term memory, attention and inhibitory control, sleep, mood, eating control and motor function. Cognitive decline in kidney disease shares risk factors with cognitive dysfunction in people without kidney disease, such as diabetes, high blood pressure, sedentary lifestyle and unhealthy diet. However, additional kidney-specific risk factors may contribute, such as uremic toxins, electrolyte imbalances, chronic inflammation, acid-base disorders or endocrine dysregulation. Traditional and kidney-specific risk factors may interact to cause damage to the blood-brain barrier, induce vascular damage in the brain and cause neurotoxicity or neuroinflammation. Here, we discuss recent insights into the pathomechanisms of cognitive decline from animal models and novel avenues for prevention and therapy. We focus on a several areas that influence cognition: blood-brain barrier disruption, the role of skeletal muscle, physical activity and the endocrine factor irisin, and the emerging therapeutic role of sodium-glucose cotransporter 2 (SGLT2) inhibitors and glucagon-like peptide 1 (GLP-1) receptor agonists. Taken together, these studies demonstrate the importance of animal models in providing a mechanistic understanding of this complex condition and their potential to explain the mechanisms of novel therapies.

The kidney-skeletal muscle-heart axis in chronic kidney disease: implications for myokines

Myokines are signalling moieties released by the skeletal muscle in response to acute and/or chronic exercise, which exert their beneficial or detrimental effects through paracrine and/or autocrine pathways on the skeletal muscle and through endocrine pathways in many other organs (e.g. the heart). Interestingly, alterations in myokines have been described in patients with heart failure (HF) that are associated with adverse structural and functional left ventricular remodelling and poor cardiac outcomes. Recent experimental and clinical studies have shown that the muscle regulation of a number of myokines is altered in chronic kidney disease (CKD) thus representing a new molecular aspect of the pathophysiology of skeletal myopathy present in patients with CKD. Muscle dysregulation of myokines may contribute to a number of disorders in non-dialysis and dialysis patients with CKD, including the high risk of developing HF. This possibility would translate into a range of new diagnostic and therapeutic options. In fact, the measurement of circulating myokines opens their possible usefulness as biomarkers to personalize exercise training and pharmacological therapies for the prevention and treatment of HF in patients with CKD and skeletal myopathy. This review will analyse information on some myokines that target the heart and are altered at the level of skeletal muscle and circulation in patients with CKD.

Irisin promotes intestinal epithelial cell proliferation via Wnt/β-catenin and focal adhesion kinase signaling pathways

The regeneration of epithelia is crucial for maintaining intestinal homeostasis. Irisin is an exercise-induced hormone originally found to be secreted by skeletal muscles, thereby regulating energy metabolism. Recent studies have revealed that irisin protected against gut inflammation. However, the direct effects of irisin on the intestinal epithelial cells remain to be elucidated. In this study, mouse intestinal organoids were used to assess the effects of irisin on the proliferation of the intestinal epithelial cells. At a concentration of 100 ng/mL irisin significantly increased the growth of the intestinal organoids and upregulated the Wnt/β-catenin and focal adhesion kinase (FAK) signaling pathway genes. Notably, a FAK inhibitor 14 blocked the effects of irisin on the proliferation of the intestinal epithelial cells by inhibiting FAK phosphorylation, as well as the expressions of Wnt target genes. Furthermore, irisin (100 ng/mL) improved the recovery of the intestinal organoids from cellular damages caused by TNF-α, and markedly increased the expression of Wnt target genes in the intestinal epithelial cells. Taken together, irisin activates Wnt/β-catenin and FAK signaling pathways in the intestinal epithelial cells, thereby promoting intestinal epithelial self-renewal under normal homeostatic conditions and intestinal epithelial regeneration upon damages.

Assessment of brain-derived neurotrophic factor and irisin concentration in children with chronic kidney disease: a pilot study

Patients suffering from chronic kidney disease (CKD) are particularly placed at risk of multiorgan complications. One of them is malnutrition, which adds up to a higher mortality factor among them. This study was designed to determine the usefulness of brain-derived neurotrophic factor (BDNF) and irisin assays in the assessment of CKD development. The study group included 28 children with CKD at stages 2-5 treated conservatively. The outcome of our study revealed decreased serum BDNF and irisin levels in CKD patients, whereas urine concentrations were increased for BDNF and decreased for irisin, comparing to healthy controls. There was a positive correlation between anthropometric measures and urine BDNF concentration, as well as anthropometric measures and both serum and urine irisin levels in the study group, however no dependence of the tested markers on the stage of CKD was observed. In recent years, a role of myokines was described as vital for maintaining metabolic homeostasis therefore we suspect a potential role of these multifaceted markers in detecting malnutrition in CKD children.

Chronic kidney disease combined with metabolic syndrome is a non-negligible risk factor

Metabolic syndrome (MetS) is a group of conditions characterized by hypertension (HTN), hyperglycaemia or insulin resistance (IR), hyperlipidaemia, and abdominal obesity. MetS is associated with a high incidence of cardiovascular events and mortality and is an independent risk factor for chronic kidney disease (CKD). MetS can cause CKD or accelerate the progression of kidney disease. Recent studies have found that MetS and kidney disease have a cause-and-effect relationship. Patients with CKD, those undergoing kidney transplantation, or kidney donors have a significantly higher risk of developing MetS than normal people. The present study reviewed the possible mechanisms of MetS in patients with CKD, including the disorders of glucose and fat metabolism after kidney injury, IR, HTN and the administration of glucocorticoid and calcineurin inhibitors. In addition, this study reviewed the effect of MetS in patients with CKD on important target organs such as the kidney, heart, brain and blood vessels, and the treatment and prevention of CKD combined with MetS. The study aims to provide strategies for the diagnosis, treatment and prevention of CKD in patients with MetS.

Increased Circulating Irisin Levels in Kidney Transplant Patients: Is There a Connection with Glycaemic Control?

Irisin is a myokine with potential effects on glucose metabolism and the development of diabetes in humans. We analysed irisin serum levels (ISL) in 47 patients without diabetes before and 1, 2, 3, 4 and 5 weeks after kidney transplantation (KTx). All measurements of irisin before KTx levels were lower than 25 ng/mL (median 8.4 ng/mL). We found an outstanding increase in ISL measured after KTx, reaching more than 1000 times in 44% of patients (HIL-high irisin level group). The increase appeared at the first measurement (one week after KTx). Factors connected to the large growth of ISL were, i.e., BMI > 30 (p = 0.04) and subsequent KTx-second and third (p < 0.001). The global mean blood glucose level during the first two weeks after KTx was significantly lower in the HIL group (p = 0.002), the same as the day-by-day analysed mean fasting and postprandial serum glucose in the first days after KTx. In 12 months of observation, diabetes requiring insulin therapy occurred in the HIL group at a rate of 19%, while in the rest of the patients, the rate was 27%, p = 0.526. Irisin levels increase significantly in some patients after kidney transplantation, accompanied by lower blood glucose levels in the early post-transplant period. Whether an increase in irisin levels results in better glycaemic control remains questionable and requires further research, as well as the relationship between irisin levels and the occurrence of PTDM.

The role of irisin in kidney diseases

Irisin is a hormone that is produced mainly by skeletal muscles in response to exercise. It has been found to have a close correlation with obesity and diabetes mellitus for its energy expenditure and metabolic properties. Recent research has revealed that irisin also possesses anti-inflammatory, anti-oxidative and anti-apoptotic properties, which make it associated with major chronic diseases, such as chronic kidney disease (CKD), liver diseases, osteoporosis, atherosclerosis and Alzheimer s disease. The identification of irisin has not only opened up new possibilities for monitoring metabolic and non-metabolic diseases but also presents a promising therapeutic target due to its multiple biological functions. Studies have shown that circulating irisin levels are lower in CKD patients than in non-CKD patients and decrease with increasing CKD stage. Furthermore, irisin also plays a role in many CKD-related complications like protein energy wasting (PEW), cardiovascular disease (CVD) and chronic kidney disease-mineral and bone disorder (CKD-MBD). In this review, we present the current knowledge on the role of irisin in kidney diseases and their complications.

Serum irisin levels and osteoporosis in patients with advanced chronic kidney disease and renal transplant recipients

AIM

To elucidate the association of serum irisin levels with bone mineral density (BMD) and calcium-phosphorus metabolism parameters in chronic kidney disease (CKD) patients and renal transplant recipients (RTRs).

METHODS

This is a cross-sectional study involving CKD patients and RTRs. Healthy volunteers served as controls. Age, gender, and dialysis vintage were recorded. Serum irisin, creatinine, glucose, calcium, albumin, 25(OH) vitamin D, ferritin, C-reactive protein, A1C, and lipid profile were studied in all participants. Estimated glomerular filtration rate (eGFR), corrected calcium, and body mass index (BMI) were calculated.

RESULTS

Overall, 49 patients (23 hemodialysis, 26 RTRs) and 25 control subjects were included. In hemodialysis (HD) group, 8 patients (34.8%) had osteoporosis, and 12 patients (52.2%) had osteopenia. In RTR group, 3 patients (11.5%) had osteoporosis, while 15 patients (57.7%) had osteopenia. Among controls, one had osteoporosis, and 7 had osteopenia. There was no significant difference between HD and RTRs; however, osteoporosis rate was significantly lower in control subjects. BMD measurements (femur and lumbar T- and Z-scores) were comparable between HD and RTR groups. Control group DEXA values were similar to RTRs; however, they were significantly higher compared to HD group. 25(OH) vitamin D levels were comparable between the HD and RTR groups, and these were significantly lower compared to values of the control group. Mean serum irisin level was 426.6 ± 191.2 pg/mL in hemodialysis group, 342.6 ± 174.8 in the RTR group, and 208.0 ± 186.1 in controls. Serum irisin levels were similar in RTR and HD groups, but their values were significantly higher compared to controls. When we compared serum irisin levels between patients with and without osteoporosis in the whole cohort and hemodialysis and RTR groups, there was no difference. Serum irisin was positively correlated with lumbar T-score both in hemodialysis and RTR groups.

CONCLUSION

Our study is the first in the literature revealing the positive correlation of serum irisin level with femur T-score in RTRs. Serum irisin level was also positively correlated with femur T-scores in hemodialysis patients.

Serum irisin level is higher in peritoneal dialysis than in hemodialysis

BACKGROUND

Previous studies have proved that irisin is related to the development of chronic kidney disease. In this study, we aimed to compare serum irisin level in patients treated with peritoneal dialysis (PD) and hemodialysis (HD).

METHODS

Two hundred and fifty-two dialysis patients (146 PD patients and 106 HD patients) were included in the study. Levels of serum irisin and other parameters were compared between the two groups' patients.

RESULTS

There were higher serum irisin levels in PD patients than those in HD patients [113.10 (106.15 ~ 119.15) ng/ml vs. 45.72(21.67 ~ 79.71) ng/ml, P < 0.001]. Moreover, body fat mass, percent body fat, serum calcium, high-density lipoprotein, low-density lipoprotein, carbon dioxide combining power (CO₂CP) and residual renal function were higher in patients on PD than that in those on HD, whereas levels of lean body mass, systolic blood pressure, albumin, serum uric acid, potassium, and phosphorus（It should be "were" replace are) are higher in HD patients in comparison to PD patients. Dialysis modality (PD/HD), serum CO₂CP level, lean body mass, and percent body fat independently positively correlated with natural logarithm of irisin (lnirisin) by multivariate linear regression analysis.

CONCLUSIONS

In this study, we prove that serum irisin level is significantly higher in patients treated with peritoneal dialysis than that with hemodialysis. As well as, increasing skeletal muscle mass and fat body percent, and correcting metabolic acidosis may increase serum irisin levels.

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.

Circulating Irisin Levels in Patients with Chronic Plaque Psoriasis

Irisin is an adipo-myokine, mainly synthetized in skeletal muscles and adipose tissues, that is involved in multiple processes. Only a few studies have evaluated serum irisin in psoriatic patients. This study aims to analyze serum irisin levels in patients with chronic plaque psoriasis, to compare them with values in controls, and to assess whether concentration of circulating irisin correlates with the severity of psoriasis, calculated by means of Psoriasis Area and Severity Index (PASI). We enrolled 46 patients with chronic plaque psoriasis; the control group included 46 sex- and age-matched subjects without any skin or systemic diseases. Serum irisin levels were measured by competitive enzyme linked immunosorbent assay. Our results showed a non-significant increase in serum irisin concentration in psoriatic patients compared to controls. A negative non-linear correlation between PASI and irisin levels was detected in psoriatic patients. Indeed, dividing patients according to psoriasis severity, the negative association between irisin and PASI was stronger in patients with mild psoriasis than in patients with higher PASI scores. Several control variables we tested showed no significant impact on serum irisin. However, erythrocyte sedimentation rate in the normal range was associated with significantly higher irisin levels in psoriatic patients. In conclusion, although irisin levels were not significantly different between controls and psoriatic patients, irisin was found to be negatively associated with psoriasis severity, especially in subjects with low PASI scores; however, further studies are needed to clarify the role of irisin in subjects with psoriasis.