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

Olink Profiling of Aqueous Humor Identifies Novel Biomarkers for Wet Age-Related Macular Degeneration

Metabolic dysfunction is recognized as a contributing factor in the pathogenesis of wet age-related macular degeneration (wAMD). However, the specific metabolism-related proteins implicated in wAMD remain elusive. In this study, we assessed the expression profiles of 92 metabolism-related proteins in aqueous humor (AH) samples obtained from 44 wAMD patients and 44 cataract control patients. Our findings revealed significant alterations in the expression of 60 metabolism-related proteins between the two groups. Notably, ANGPTL7 and METRNL displayed promising diagnostic potential for wAMD, as evidenced by area under the curve values of 0.88 and 0.85, respectively. Subsequent validation studies confirmed the upregulation of ANGPTL7 and METRNL in the AH of wAMD patients and in choroidal neovascularization (CNV) models. Functional assays revealed that increased ANGPTL7 and METRNL played a pro-angiogenic role in endothelial biology by promoting endothelial cell proliferation, migration, tube formation, and spouting in vitro. Moreover, in vivo studies revealed the pro-angiogenic effects of ANGPTL7 and METRNL in CNV formation. In conclusion, our findings highlight the association between elevated ANGPTL7 and METRNL levels and wAMD, suggesting their potential as novel predictive and diagnostic biomarkers for this condition. These results underscore the significance of ANGPTL7 and METRNL in the context of wAMD pathogenesis and offer new avenues for future research and therapeutic interventions.

Organokines and liver enzymes in adolescent girls with polycystic ovary syndrome during randomized treatments

Introduction

Polycystic ovary syndrome (PCOS) is often associated with metabolic-associated fatty liver disease (MAFLD). MAFLD has been associated with altered hepatic function, systemic dysmetabolism, and abnormal circulating levels of signaling molecules called organokines. Here, we assessed the effects of two randomized treatments on a set of organokines in adolescent girls with PCOS and without obesity, and report the associations with circulating biomarkers of liver damage, which were assessed longitudinally in the aforementioned studies as safety markers.

Materials and methods

Liver enzymes [aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyl transferase (GGT)] were assessed as safety markers in previous randomized pilot studies comparing the effects of an oral contraceptive (OC) with those of a low-dose combination of spironolactone-pioglitazone-metformin (spiomet) for 1 year. As a post hoc endpoint, the organokines fibroblast growth factor-21 (FGF21), diazepam-binding protein-1 (DBI), and meteorin-like protein (METRNL) were assessed by ELISA after 6 months of OC (N = 26) or spiomet (N = 28). Auxological, endocrine-metabolic, body composition (using DXA), and abdominal fat partitioning (using MRI) were also evaluated. Healthy, age-matched adolescent girls (N = 17) served as controls.

Results

Circulating ALT and GGT levels increased during OC treatment and returned to baseline concentrations in the post-treatment phase; in contrast, spiomet treatment elicited no detectable changes in ALT and GGT concentrations. In relation to organokines after 6 months of treatment, (1) FGF21 levels were significantly higher in PCOS adolescents than in control girls; (2) DBI levels were lower in OC-treated girls than in controls and spiomet-treated girls; and (3) no differences were observed in METRNL concentrations between PCOS girls and controls. Serum ALT and GGT levels were directly correlated with circulating METRNL levels only in OC-treated girls (R = 0.449, P = 0.036 and R = 0.552, P = 0.004, respectively).

Conclusion

The on-treatment increase in ALT and GGT levels occurring only in OC-treated girls is associated with circulating METRNL levels, suggesting enhanced METRNL synthesis as a reaction to the hepatic changes elicited by OC treatment.

Clinical Trial Registration

https://doi.org, identifiers 10.1186/ISRCTN29234515, 10.1186/ISRCTN11062950.

The role of adipokines in osteoporosis management: a mini review

The prevalence of osteoporosis has been on the rise globally. With ageing populations, research has sought therapeutic solutions in novel areas. One such area is that of the adipokines. Current literature points to an important role for these chemical mediators in relation to bone metabolism. Well-established adipokines have been broadly reported upon. These include adiponectin and leptin. However, other novel adipokines such as visfatin, nesfatin-1, meteorin-like protein (Metrnl), apelin and lipocalin-2 are starting to be addressed pre-clinically and clinically. Adipokines hold pro-inflammatory and anti-inflammatory properties that influence the pathophysiology of various bone diseases. Omentin-1 and vaspin, two novel adipokines, share cardioprotective effects and play essential roles in bone metabolism. Studies have reported bone-protective effects of omentin-1, whilst others report negative associations between omentin-1 and bone mineral density. Lipocalin-2 is linked to poor bone microarchitecture in mice and is even suggested to mediate osteoporosis development from prolonged disuse. Nesfatin-1, an anorexigenic adipokine, has been known to preserve bone density. Animal studies have demonstrated that nesfatin-1 treatment limits bone loss and increases bone strength, suggesting exogenous use as a potential treatment for osteopenic disorders. Pre-clinical studies have shown adipokine apelin to have a role in bone metabolism, mediated by the enhancement of osteoblast genesis and the inhibition of programmed cell death. Although many investigations have reported conflicting findings, sufficient literature supports the notion that adipokines have a significant influence on the metabolism of bone. This review aims at highlighting the role of novel adipokines in osteoporosis while also discussing their potential for treating osteoporosis.

Causal relationship between glycemic traits and bone mineral density in different age groups and skeletal sites: a Mendelian randomization analysis

INTRODUCTION

Previous research has confirmed that patients with type 2 diabetes mellitus tend to have higher bone mineral density (BMD), but it is unknown whether this pattern holds true for individuals without diabetes. This Mendelian randomization (MR) study aims to investigate the potential causal relationship between various glycemic trait (including fasting glucose, fasting insulin, 2-h postprandial glucose, and glycated hemoglobin) and BMD in non-diabetic individuals. The investigation focuses on different age groups (15-30, 30-45, 45-60, and 60 + years) and various skeletal sites (forearm, lumbar spine, and hip).

MATERIALS AND METHODS

We utilized genome-wide association study data from large population-based cohorts to identify robust instrumental variables for each glycemic traits parameter. Our primary analysis employed the inverse-variance weighted method, with sensitivity analyses conducted using MR-Egger, weighted median, MR-PRESSO, and multivariable MR methods to assess the robustness and potential horizontal pleiotropy of the study results.

RESULTS

Fasting insulin showed a negative modulating relationship on both lumbar spine and forearm. However, these associations were only nominally significant. No significant causal association was observed between blood glucose traits and BMD across the different age groups. The direction of fasting insulin's causal effects on BMD showed inconsistency between genders, with potentially decreased BMD in women with high fasting insulin levels and an increasing trend in BMD in men.

CONCLUSIONS

In the non-diabetic population, currently available evidence does not support a causal relationship between glycemic traits and BMD. However, further investigation is warranted considering the observed gender differences.

AAV-Mediated nuclear localized PGC1α4 delivery in muscle ameliorates sarcopenia and aging-associated metabolic dysfunctions

Sarcopenia is characterized of muscle mass loss and functional decline in elder individuals which severely affects human physical activity, metabolic homeostasis, and life quality. Physical exercise is considered effective in combating muscle atrophy and sarcopenia, yet it is not feasible to elders with limited mobility. PGC-1α4, a short isoform of PGC-1α, is strongly induced in muscle under resistance training, and promotes muscle hypertrophy. In the present study, we showed that the transcriptional levels and nuclear localization of PGC1α4 was reduced during aging, accompanied with muscle dystrophic morphology, and gene programs. We thus designed NLS-PGC1α4 and ectopically express it in myotubes to enhance PGC1α4 levels and maintain its location in nucleus. Indeed, NLS-PGC1α4 overexpression increased muscle sizes in myotubes. In addition, by utilizing AAV-NLS-PGC1α4 delivery into gastrocnemius muscle, we found that it could improve sarcopenia with grip strength, muscle weights, fiber size and molecular phenotypes, and alleviate age-associated adiposity, insulin resistance and hepatic steatosis, accompanied with altered gene signatures. Mechanistically, we demonstrated that NLS-PGC-1α4 improved insulin signaling and enhanced glucose uptake in skeletal muscle. Besides, via RNA-seq analysis, we identified myokines IGF1 and METRNL as potential targets of NLS-PGC-1α4 that possibly mediate the improvement of muscle and adipose tissue functionality and systemic energy metabolism in aged mice. Moreover, we found a negative correlation between PGC1α4 and age in human skeletal muscle. Together, our results revealed that NLS-PGC1α4 overexpression improves muscle physiology and systematic energy homeostasis during aging and suggested it as a potent therapeutic strategy against sarcopenia and aging-associated metabolic diseases.

The Role of Meteorin-Like Peptide and Asprosin in Colon Carcinoma

INTRODUCTION

 Colon cancer is one of the most frequent gastrointestinal system cancers on a global scale. Common colonoscopy tests have reduced the incidence of colorectal cancer (CRC). Although nutrition, microorganisms, and their metabolites are related to colon cancer, the exact mechanism of CRC is still not clear. For this reason, it is of great importance to elucidate the molecular mechanisms of colon oncogenesis.

METHODS

This study was conducted retrospectively with samples obtained from the laboratory of Firat University Faculty of Medicine, Department of Pathology. A total of 30 patient samples were used. The control group consisted of healthy colon tissues from the same patients, and the other group consisted of colon carcinoma tissues from the same patients. Tissue samples of both groups were evaluated immunohistochemically with meteorin-like (METRNL) peptide and Asprosin.

RESULTS

The immunoreactivity of METRNL was found to be lower in colon carcinoma tissues than in healthy colon tissues (0.2 ± 0.06 and 0.08 ± 0.03, respectively). Asprosin immunoreactivity was found to be higher in colon carcinoma tissues than in healthy colon tissues (0.4 ± 0.07 and 1.08 ± 0.15, respectively).

CONCLUSION

As a result of this study, it was observed that there was a significant difference between healthy colon tissue and colon carcinoma tissue in terms of METRNL and Asprosin expression. Both proteins might be involved in the molecular mechanism of colon carcinoma. This situation is important in terms of diagnosis.

Potential clinical value of serum interleukin-41 levels in patients with acute gout

BACKGROUND

Gout is a common metabolic rheumatic disease, and there have been no reports on the serum levels of interleukin (IL)-41 in gout patients. The purpose of this study was to therefore determine the expression of IL-41 in the serum of gout patients.

METHODS

Eighty-one participants were enrolled in this study, including 34 patients with acute gout, 27 gout patients in remission, and 20 healthy controls (HCs). Baseline data were obtained through interviews and laboratory parameters were acquired via blood sample testing. We measured serum IL-41 concentrations with an enzyme-linked immunosorbent assay, and executed Spearman's correlation analysis to investigate the correlation between IL-41 and other parameters, and the diagnostic value for IL-41 was demonstrated using a receiver operating characteristic curve. Multivariate analysis was conducted by adopting logistic regression.

RESULTS

Serum IL-41 concentrations in acute-gout patients were higher than those in HCs and there was no significant difference in serum IL-41 levels between remission gout patients and HCs. In addition, IL-41 was positively correlated with white blood cell count, erythrocyte sedimentation rate, and C-reactive protein and serum amyloid A concentrations, while it was negatively correlated with triglyceride levels. IL-41 showed good diagnostic value for gout, and the combination of IL-41 and uric acid produced a superior diagnostic value. We also noted that IL-41 was an independent risk factor for acute gout.

CONCLUSIONS

This study revealed that serum IL-41 was elevated in patients with acute gout, and suggests that IL-41 may constitute a novel diagnostic marker for acute gout.