Administration of metrnl delays the onset of diabetes in non-obese diabetic mice

Meteorin-like protein (Metrnl): a key exerkine in exercise-mediated cardiovascular health

CONTEXT

Cardiovascular diseases (CVDs) remain a leading global cause of mortality, necessitating non‑pharmacological interventions such as exercise. Meteorin‑like protein (Metrnl), an exercise‑induced myokine and adipokine, has emerged as a critical mediator of exercise‑mediated cardiovascular benefits, though its specific mechanisms and clinical implications remain underexplored.

OBJECTIVE

This review synthesizes current evidence on Metrnl's role as a key exerkine in cardiovascular health, focusing on its exercise‑induced regulatory mechanisms, tissue‑specific effects, and therapeutic potential for CVD management.

METHODS

A comprehensive analysis of preclinical and clinical studies was conducted, encompassing molecular, metabolic, and anti‑inflammatory pathways linked to Metrnl. Literature from PubMed, Scopus, and Web of Science was systematically reviewed to evaluate Metrnl's role in exercise‑mediated cardiovascular adaptations.

RESULTS

Exercise‑induced Metrnl enhances endothelial function, vascular remodeling, and metabolic regulation via AMPK, PPARγ, and KIT receptor signaling. It promotes glucose/lipid metabolism, angiogenesis, and anti‑inflammatory responses, reducing atherosclerotic risks and improving cardiac repair post‑infarction. Clinically, Metrnl levels correlate with CVD severity, acting as a biomarker for risk stratification. Acute exercise elevates Metrnl, while chronic training effects vary by modality and population. Paradoxically, elevated plasma Metrnl in acute cardiac events predicts adverse outcomes, whereas reduced levels in chronic conditions (e.g., diabetes, heart failure) reflect metabolic dysregulation.

DISCUSSION

Metrnl bridges exercise benefits to cardiovascular health through inter‑organ crosstalk, yet discrepancies exist in its chronic exercise‑mediated regulation. Its dual role as a protective mediator and stress‑responsive biomarker underscores context‑dependent interpretations. Unresolved questions include receptor specificity, tissue autonomy, and therapeutic delivery strategies.

CONCLUSION

Metrnl is a pivotal exerkine with promising diagnostic and therapeutic potential for CVDs. Translating its exercise‑mediated benefits into clinical applications requires further human trials to validate mechanisms and optimize interventions. Harnessing Metrnl could revolutionize strategies for CVD prevention and rehabilitation, leveraging exercise's molecular advantages.

METRNL mitigates oxidative stress and inflammatory drawbacks in ovalbumin/lipopolysaccharide-induced allergic airway diseases via the IKK/IκB/NF-κB signaling pathway

This study aimed to examine the potential impacts of METRNL as an antioxidant and anti-inflammatory through IκB kinase/inhibitor of nuclear factor-kappa B/nuclear factor-kappa-light-chain signaling pathway on many biomarkers and lung structure in rats with bronchial asthma induced by ovalbumin/lipopolysaccharide (OVA/LPS). Forty rats were randomly divided into four equal groups: control group, vehicle group, diseased (OVA/LPS) group OVA 2.5 ml/kg intratracheal installation/LPS 1.5 mg/kg intraperitoneally, and treated (OVA/LPS + METRNL) group, METRNL at a dose of 2 mg/rat/day IV. After 4 weeks, plasma and lung tissues were analyzed to assess oxidative stress inflammatory markers. Additionally, a histological assessment was conducted on lung tissues. Bronchial asthma was confirmed when increased levels of total serum IgE, total cell count, neutrophils, eosinophils, macrophages, and lymphocyte counts in the BAL fluid were observed. Moreover, OVA/LPS resulted in a reduction in levels of superoxide dismutase (SOD) while raising levels of malondialdehyde (MDA). Furthermore, it elevated concentrations of plasma inflammatory mediators, including tumor necrosis factor-alpha (TNF-alpha), interleukin 17 (IL-17), and transforming growth factor beta (TGF-β). The protective effects of METRNL were analyzed. The observed impacts are believed to result from the drug's anti-inflammatory and antioxidant properties and its action on the IKK/IκB/NF-κB signaling pathway. This investigation indicates that METRNL treatment positively improved rats' biochemical and histological aspects of OVA/LPS-induced airway allergic inflammation.

Skeletal muscle growth to combat diabetes and obesity: the potential role of muscle-secreted factors

As the prevalence of obesity and metabolic disease continues to climb, the need for effective therapeutic interventions remains high. The growth of skeletal muscle (SkM) greatly influences systemic metabolism across the whole body, making this tissue an important therapeutic target to combat the rise of metabolic dysfunction. Transgenic rodent models of targeted SkM growth exhibit profound improvements in various remote tissues, including adipose tissue and the liver. It is currently unclear how selective stimulation of SkM growth alters the metabolism of distant tissues; however, evidence suggests that muscle-secreted factors may be involved. Here, we aim to provide basic biomedical researchers with a summary of the current knowledge regarding various muscle-secreted factors regulated by anabolic pathways and proteins in SkM, as well as their systemic metabolic effects, to implicate them in the whole-body metabolic effects of SkM growth. In this review, we also identify several knowledge gaps in this field, future directions of investigation, and implications for therapeutic interventions such as resistance exercise and pharmacology.

Low serum Metrnl levels are associated with increased risk of sarcopenia in the older adults

PURPOSE

Sarcopenia is a geriatric syndrome characterized by progressive loss of muscle mass and function. Meteorin-like (Metrnl) is a secretory protein that has protective effects on skeletal muscle injury. However, the association of Metrnl level with sarcopenia remains unclear.

METHODS

A total of 772 community-dwelling older adults (median age = 76 years), comprising 409 males and 363 females, from both urban and rural areas were enrolled. Serum Metrnl was measured by enzyme-linked immunosorbent assay. Appendicular skeletal muscle mass index (ASMI), grip strength, and gait speed were measured for the assessment of sarcopenia.

RESULTS

We found that serum Metrnl levels were lower in patients with sarcopenia [median (IQR) = 180.1 (151.3-220.3) pg/mL] than older adults without sarcopenia [211.9 (163.2-270.0) pg/mL, P < 0.001]. Receiver-operating characteristic curve analysis showed that the optimal cut-off value of serum Metrnl level that predicted sarcopenia was 197.2 pg/mL with a sensitivity of 59.2% and a specificity of 63.8% (AUC = 0.63, 95% CI = 0.59-0.67, P < 0.001). Multivariate logistic regression analyses showed that lower serum Metrnl level (< 197.2 pg/mL) was significantly associated with increased risk of sarcopenia (adjusted OR = 2.358, 2.36, 95% CI = 1.528-3.685, P < 0.001). Moreover, serum Metrnl concentration was positively correlated with the components of sarcopenia including ASMI (r = 0.135, P < 0.001), grip strength (r = 0.102, P = 0.005), and gait speed (r = 0.106, P = 0.003).

CONCLUSIONS

Taken together, our findings demonstrate that low serum Metrnl level is correlated with increased risk of sarcopenia in the older adults.

Metrnl as a secreted protein: Discovery and cardiovascular research

Secreted proteins have gained more and more attentions, since they can become therapeutic targets, drugs and biomarkers for prevention, diagnosis and treatment of disease and aging. In 2014, Metrnl (also named Meteorin-like, Cometin, Subfatin, Interleukin-39, Interleukin-41, Meteorin-β, and Metrn-β/Metrnβ), as a novel secreted protein released from a certain tissue, was reported by us and others. During the past decade, the number of articles on Metrnl has continued to increase. Different sources of Metrnl have been described with different functions, including Metrnl as an adipokine for insulin sensitization, a cardiokine against cardiac hypertrophy and dysfunction, an endothelium-derived factor against endothelial dysfunction and atherosclerosis, etc. Especially, we show that endothelial Metrnl is a major source for circulating Metrnl levels. Meanwhile, lots of clinical studies have investigated the relationship between blood Metrnl levels and metabolic, inflammatory and cardiovascular diseases. Metrnl appears a protective factor and a promising therapeutic target and/or drug against these diseases, given the relatively consistent conclusion from the preclinical studies. In addition to graphically demonstrating the role of Metrnl in various organs and diseases, this review will mainly describe the discovery of Metrnl, summarize the role of Metrnl in cardiovascular system that is a recently major progress in Metrnl research, and highlight several perspectives for future basic and translational research. Also, we suggest using one name Metrnl instead of other multiple names for the same protein.

Association of serum Metrnl levels and high-density lipoprotein cholesterol in patients with type 2 diabetes mellitus: a cross-sectional study

Purpose

Meteorin-like (Metrnl) is a novel adipokine which is highly expressed in adipose tissue and has a beneficial effect on glucose and lipid metabolism. High density lipoprotein cholesterol (HDL-C) is well recognized to be inversely associated with cardiovascular events. However, the relationship between serum Metrnl levels and HDL-C in the type 2 diabetes mellitus (T2DM) remains unclear. Therefore, the present study aimed to evaluate the association of serum Metrnl with HDL-C levels in T2DM.

Materials and Methods

Eighty participants with T2DM were included in this cross-sectional study. They were divided into two groups according to HDL-C levels: Group1 (lower HDL-C group): HDL-C < 1.04 mmol/L; Group2 (higher HDL-C group): HDL-C ≥ 1.04 mmol/L. Serum Metrnl levels were measured by enzyme-linked immunosorbent assay (ELISA).

Results

As compared with lower HDL-C levels groups, serum Metrnl levels were significantly higher in the group with higher HDL-C. Binary logistic regression analysis showed serum Metrnl levels were positively associated with HDL-C group after adjustment with sex, age, body mass index (BMI), mean arterial pressure (MAP), fasting blood glucose (FPG), triglyceride (TG). Furthermore, serum Metrnl levels were inversely correlated with insulin resistance index (HOMA-IR). HDL-C levels were lowest in the group with the lowest Metrnl levels group and remained positively associated with Metrnl after adjustment for sex, age, BMI, TG, and HOMA-IR by using multivariate logistic regression analysis.

Conclusion

Serum Metrnl levels were positively associated with HDL-C levels in patients with T2DM.This suggests that increasing serum Metrnl levels maybe a candidate for improving lipid metabolism and preventing cardiovascular events in T2DM.

Registry and the Registration No of the Study/Trial

The study was registered in the Chinese clinical trial registry (ChiCTR- 2100047148).

Investigation of serum Metrnl levels in pregnant women with gestational diabetes mellitus: a prospective non-interventional cohort study

OBJECTIVE

The objective of this study was to investigate serum Metrnl levels in pregnant women with gestational diabetes mellitus and compare them with pregnant women without gestational diabetes mellitus.

METHODS

The gestational diabetes mellitus group consisted of 87 pregnant women diagnosed with gestational diabetes mellitus, and the control group consisted of 93 healthy pregnant women without gestational diabetes mellitus. Serum Metrnl levels were determined by the enzyme-linked immunosorbent assay method.

RESULTS

The two groups were similar in terms of demographic features. The median serum Metrnl level was found to be 1.16 ng/mL in the gestational diabetes mellitus group, while it was determined as 2.2 ng/mL in the control group (p=0.001). The two groups were divided into two subgroups based on participants' body mass index, normal weight and overweight. The lowest median Metrnl level was detected in the normal weight gestational diabetes mellitus group, followed by the overweight gestational diabetes mellitus group, normal weight control group, and overweight control group (1.1, 1.2, 2, and 2.4 ng/mL, respectively). Receiver operating curve analysis was performed to determine the value of the serum Metrnl level in terms of predicting gestational diabetes mellitus. The area under the curve analysis of serum Metrnl for gestational diabetes mellitus estimation was 0.768 (p=0.000, 95%CI 0.698-0.839). The optimal cutoff value for serum Metrnl level was determined as 1.53 ng/mL with 69% sensitivity and 70% specificity.

CONCLUSION

Serum Metrnl levels in pregnant women with gestational diabetes mellitus were found to be significantly lower than in pregnant women without gestational diabetes mellitus. The mechanisms underlying the decrease in serum Metrnl levels in gestational diabetes mellitus remain unclear for now, and future studies will reveal the role of Metrnl in the pathophysiology of gestational diabetes mellitus.

Homotherapy for heteropathy: Interleukin-41 and its biological functions

Interleukin-41 (IL-41) is a newly discovered cytokine, named Cometin, Subfatin, meteorin-like transcription (Metrnl), and so forth. It is widely expressed in animals and can exert its biological roles through autocrine and paracrine forms. It has functions such as anti-inflammatory, improving body metabolism, regulating immunity, regulating fat metabolism and participates in the process of autoimmune disease or inflammatory injury. It plays an important role in psoriasis, diabetes, Crohn's disease (CD), osteoarthritis, Kawasaki disease (KD), Graves' disease, autoimmune hepatitis, infertility, obesity, sepsis, cardiovascular diseases and respiratory diseases. This paper reviews the biological functions of IL-41, the relationship between IL-41 and diseases, the effects of IL-41 in the cytokine network and the possible signalling pathways. In order to explore the same target or the same drug for the treatment of different diseases from the perspective of homotherapy for heteropathy, cytokine strategies based on IL-41 have been put forward for the precise treatment of immune diseases and inflammatory diseases. It is worth noting that IL-41 related preparations for lung protection and smoking cessation are interesting research fields.

Metrnl: a promising biomarker and therapeutic target for cardiovascular and metabolic diseases

Modern human society is burdened with the pandemic of cardiovascular and metabolic diseases. Metrnl is a widely distributed secreted protein in the body, involved in regulating glucose and lipid metabolism and maintaining cardiovascular system homeostasis. In this review, we present the predictive and therapeutic roles of Metrnl in various cardiovascular and metabolic diseases, including atherosclerosis, ischemic heart disease, cardiac remodeling, heart failure, hypertension, chemotherapy-induced myocardial injury, diabetes mellitus, and obesity.

The Plasma Levels of Protein Adiponectin (AdipoQ) and Meteorin-Like (Metrnl) in Newly Diagnosed Type 2 Diabetes Mellitus

Purpose

This study aimed to measure the concentrations of the Adiponectin and Meteorin - Like (Metrnl) in newly diagnosed type 2 diabetes patients.

Patients and Methods

A comparative cross-sectional study contained two groups: Group 1 (86 newly diagnosed diabetes mellitus type 2 patients) and group 2 (71 healthy persons). The plasma concentrations of Adiponectin and Metrnl were measured by Enzyme Link Immunosorbent Assay (ELISA).

Results

The plasma level of Adiponectin of the newly diagnosed diabetes mellitus type 2 group and the healthy group were 1219.82 ng/mL (1132.43-2772.50) and 1187.25 ng/mL (1160.66-3807.50) respectively. The plasma level of Metrnl of two groups were 757.60 pg/mL (564.15-994.00) and 697.60 pg/mL (538.50-986.10) respectively. There were no significant difference between two groups. Metrnl had no correlation with glucose, HbA1c, lipid profile, BMI. Adiponectin had correlation with Metrnl and HDL-cholesterol. Adiponectin had no correlation to glucose, HbA1c, LDL-cholesterol, total cholesterol, triglyceride, BMI. People with the lower Adiponectin concentration had the higher risk of diabetes (OR=6.52; 95% CI: 2.43 -17.55).

Conclusion

Adiponectin and Metrnl were not significantly different in newly diagnosed type 2 diabetes and healthy people. The lower concentration of Adiponectin might increase the risk of type 2 diabetes.

Meteorin-like Protein and Asprosin Levels in Children and Adolescents with Obesity and Their Relationship with Insulin Resistance and Metabolic Syndrome

OBJECTIVE

Two newly discovered adipokines, including Meteorin-like protein (Metrnl) and asprosin, have been implicated in glucose and insulin metabolism. This study aimed to investigate the associations of these adipokines with obesity in children and adolescents.

METHODS

This study was performed on 35 normal-weight children and 35 children with obesity. Anthropometric and biochemical parameters were determined. Serum concentrations of Metrnl, asprosin, and insulin were measured using enzyme-linked immunosorbent assay.

RESULTS

Metrnl level was significantly lower in obese children than normal-weight children. Additionally, Metrnl was negatively correlated with body mass index (BMI), insulin, waist-to-hip ratio, and homeostatic model assessment of insulin resistance (HOMA-IR). Our results also revealed that circulating asprosin levels were significantly increased in obese children compared to the control subjects and were positively correlated with BMI, insulin, HOMA-IR, cholesterol, and LDL-C.

CONCLUSION

Obesity is accompanied by significant alterations in Metrnl and asprosin and therefore these adipokines, especially Metrnl, are suggested as new promising therapeutic targets for obesity and its associated metabolic imbalances.

Meteorin-like/Metrnl, a novel secreted protein implicated in inflammation, immunology, and metabolism: A comprehensive review of preclinical and clinical studies

Meteorin-like, also known as Metrnl, Meteorin-β, Subfatin, and Cometin, is a novel secreted protein exerting pleiotropic effects on inflammation, immunology, and metabolism. Earlier research on this hormone focused on regulating energy expenditure and glucose homeostasis. Consequently, several studies attempted to characterize the molecule mechanism of Metrnl in glucose metabolism and obesity-related disorders but reported contradictory clinical results. Recent studies gradually noticed its multiple protective functions in inflammatory immune regulations and cardiometabolic diseases, such as inducing macrophage activation, angiogenesis, tissue remodeling, bone formation, and preventing dyslipidemias. A comprehensive understanding of this novel protein is essential to identify its significance as a potential therapeutic drug or a biomarker of certain diseases. In this review, we present the current knowledge on the physiology of Metrnl and its roles in inflammation, immunology, and metabolism, including animal/cell interventional preclinical studies and human clinical studies. We also describe controversies regarding the data of circulation Metrnl in different disease states to determine its clinical application better.

Endothelial METRNL determines circulating METRNL level and maintains endothelial function against atherosclerosis

METRNL is a recently identified secreted protein with emerging functions. This study is to find major cellular source of circulating METRNL and to determine METRNL novel function. Here, we show METRNL is abundant in human and mouse vascular endothelium and released by endothelial cells using endoplasmic reticulum-Golgi apparatus pathway. By creating endothelial cell-specific Metrnl knockout mice, combined with bone marrow transplantation to produce bone marrow-specific deletion of Metrnl, we demonstrate that most of circulating METRNL (approximately 75%) originates from the endothelial cells. Both endothelial and circulating METRNL decrease in atherosclerosis mice and patients. By generating endothelial cell-specific Metrnl knockout in apolipoprotein E-deficient mice, combined with bone marrow-specific deletion of Metrnl in apolipoprotein E-deficient mice, we further demonstrate that endothelial METRNL deficiency accelerates atherosclerosis. Mechanically, endothelial METRNL deficiency causes vascular endothelial dysfunction including vasodilation impairment via reducing eNOS phosphorylation at Ser1177 and inflammation activation via enhancing NFκB pathway, which promotes the susceptibility of atherosclerosis. Exogenous METRNL rescues METRNL deficiency induced endothelial dysfunction. These findings reveal that METRNL is a new endothelial substance not only determining the circulating METRNL level but also regulating endothelial function for vascular health and disease. METRNL is a therapeutic target against endothelial dysfunction and atherosclerosis.

Effects of meteorin-like hormone on endocrine function of hypothalamo-hypophysial system and peripheral uncoupling proteins in rats

BACKGROUND

Meteorin-like hormone (Metrnl) is a peptide secreted from the adipose tissue and modulates the whole-body energy metabolism. Metrnl release into the circulation is influenced by obesity, cold exposure, and exercise. Thyroid hormones also exert many of their effects on metabolism through uncoupling proteins (UCPs). This study aimed to determine effect of Metrnl on hypothalamo-hypophysier-thyroid axis and energy metabolism and reveal the possible involvement of UCPs in this process.

METHODS AND RESULTS

Fourty male Sprague-Dawley rats were divided into 4 groups with 10 animals in each group: control, sham, 10 and 100 nM Metrnl. Hypothalamus, muscle, white adipose tissue (WAT) and brown adipose tissue (BAT) samples were collected to detect thyrotropin-releasing hormone (TRH), and UCP1 and UCP3 protein levels by western blot analysis. Serum thyroid-stimulating hormone (TSH), triiodothyronine (T3) and thyroxine (T4) hormone levels were determined by enzyme-linked immunosorbent assay. Central infusion of Metrnl caused significant increase in serum TSH, T3 and T4 levels compared to control (p < 0.05). After Metrnl treatment, there were significant increases in TRH in hypothalamus tissue, UCP1 in WAT and BAT; and UCP3 protein in the muscle tissue (p < 0.05).

CONCLUSIONS

The findings that Metrnl induced increases in the peripheral UCPs and hypothalamus-pituitary-thyroid axis hormones implicate a role for this hormone in body energy homeostasis through UCP-mediated mechanisms.

Exercise Inhibits NLRP3 Inflammasome Activation in Obese Mice via the Anti-Inflammatory Effect of Meteorin-like

Obesity is associated with chronic low-grade inflammation. The benefits of exercise are partly attributed to its anti-inflammatory effect, but whether exercise can regulate NLRP3 inflammasome activation in obese adipose tissue remains unknown. Meteorin-like (METRNL), a recently discovered myokine, has been implicated in mediating the effect of exercise on metabolism. Herein, we examined the effect of exercise and METRNL on NLRP3 inflammasome activation. High-fat diet (HFD)-induced obese mice were subjected to treadmill exercise for 8 weeks. A subgroup of HFD mice was switched to normal chow with the exercise intervention. Exercise and diet attenuated weight gain, fat accumulation, and insulin resistance in obese mice. In addition, exercise downregulated gene and protein levels of inflammasome markers, including NLRP3 and caspase-1, in adipose tissue. In isolated bone marrow-derived macrophages, activation of NLRP3 inflammasome was suppressed in the exercise group, as confirmed by the downregulation of IL-1β and IL-18. Exercise significantly enhanced the expression of METRNL in various muscle depots, and further in vitro analysis revealed that recombinant METRNL treatment inhibited IL-1β secretion in macrophages. In conclusion, exercise exerts its anti-inflammatory action by suppressing adipose tissue NLRP3 inflammasome, and this is, in part, associated with METRNL induction in muscle and its anti-inflammatory effects in macrophages.

Meteorin-Like Protein (Metrnl) in Obesity, during Weight Loss and in Adipocyte Differentiation

Meteorin-like protein (Metrnl) is an adipo-myokine with pleiotropic effects in adipose tissue (AT). Its systemic regulation in obesity and under weight loss is unclear. Circulating Metrnl concentrations were analyzed by ELISA in severely obese patients undergoing bariatric surgery (BS) or low calorie diet (LCD). Metrnl mRNA expression was analyzed in human and murine tissues and cell lines by quantitative real-time PCR. About 312 morbidly obese individuals underwent BS (n = 181; BMI 53.4 + 6.8 kg/m²) or LCD (n = 131; BMI 43.5 + 6.7 kg/m²). Serum samples were obtained at baseline and 3, 6, and 12 months after intervention. AT specimen from subcutaneous and visceral adipose tissue were resected during BS. Serum Metrnl levels were lower in type 2 diabetic patients and negatively correlated with HbA1c. In BS and LCD patients, Metrnl concentrations significantly increased after 3 months and returned to baseline levels after 12 months. There was no gender-specific effect. Metrnl mRNA expression did not differ between visceral and subcutaneous AT in n = 130 patients. In contrast, Metrnl gene expression in mice was highest in intra-abdominal AT followed by subcutaneous, peri-renal, and brown AT. In the murine 3T3-L1 cell line, Metrnl expression was high in pre-adipocytes and mature adipocytes with a transient downregulation during adipocyte differentiation. Metrnl expression remained unaffected upon treatment with glucose, insulin, fatty acids, bile acids, and incretins. Polyunsaturated omega-3 and omega-6 fatty acids downregulated Metrnl expression. Systemic Metrnl is transiently upregulated during massive weight loss and gene expression in adipocytes is differentially regulated.

Meteorin-Like Ameliorates β Cell Function by Inhibiting β Cell Apoptosis of and Promoting β Cell Proliferation via Activating the WNT/β-Catenin Pathway

Meteorin-like (Metrnl) is a newly discovered myokine. Plasma Metrnl is decreased in subjects with newly diagnosed type 2 diabetes (T2D) and correlated with insulin resistance. This study aims to determine the effects of Metrnl on the apoptosis and proliferation of β cell. Mouse insulinoma MIN6 cells were divided into six groups: normal control, low glucose, high glucose, Vehicle, Metrnl, and Dickkopf 1 (DKK1) groups. MIN6 cells in Metrnl group were transfected with recombinant pCDH-Metrnl vector. WNT/β-catenin pathway was inhibited using DKK1. Then the apoptosis of MIN6 cells was detected using flow cytometry and TUNEL labeling. Immunofluorescence of Ki67 or Edu-594 was used to determine the β cell proliferation. db/db mice were confirmed as T2D group. Lentivirus-Metrnl was injected from the caudal vein of db/db mice once every two weeks for two times. High glucose induced the apoptosis of MIN6 cells and elevated expression of caspase 3. In addition, high glucose resulted in reduced β cell proliferation, cell viability, insulin secretion as well as decreased expression of β-catenin and TCF4. Metrnl ameliorated the above effects of high glucose. And the protecting role of Metrnl was inhibited by DKK1. T2D mice showed higher body weight and blood glucose compared with the controls. The β cell apoptosis was increased while the β cell proliferation and WNT/β-catenin pathway were inhibited in T2D mice. Metrnl treatment partly reversed the above changes in T2D mice. Metrnl ameliorates β cell function by inhibiting β cell apoptosis of and promoting β cell proliferation via activating the WNT/β-catenin pathway.

Myokine-mediated exercise effects: the role of myokine meteorin-like hormone (Metrnl)

Meterorin-like hormone (Metrnl), as a novel secreted factor, has been shown to be involved in physiological and pathophysiological processes. The behaviour of Metrnl in metabolic conditions like type 2 diabetes is conflicting. Metrnl-mediated (treatment with Metrnl) auto/paracrine actions in skeletal muscle are glucose uptake, fat oxidation and muscle regeneration. Exercise-induced Metrnl actions are increased fat oxidation in both skeletal muscle and adipose tissue, the control of inflammation in adipose tissue (metainflammation), and the regulation of muscle regeneration. Based on the current knowledge, Metrnl as a myokine can establish the muscle-fat crosstalk; however, the ability of Metrnl as a myokine to create other crosstalks remains unclear yet. Additionally, given the considerable anti-inflammatory roles of Metrnl in muscle regeneration, it could be a potential therapeutic candidate for muscle-related inflammatory diseases and ageing skeletal muscle which need to be addressed in the future studies.