Background Meteorin-like (Metrnl) is a novel adipomyokine that may improve glucose tolerance and affect insulin resistance. This study aimed to investigate the association between serum levels of Metrnl with blood glucose status and to its association with insulin resistance. Material/Methods The study included 160 subjects with normal glucose tolerance (NGT) (n=40), impaired fasting glucose (IFG) (n=40), impaired glucose tolerance (IGT) (n=40), and newly diagnosed type 2 diabetes mellitus (T2DM) (n=40). An enzyme-linked immunosorbent assay (ELISA) was used to measure the serum levels of Metrnl. Partial correlation analysis was used to analyze the relationship between serum levels of Metrnl and metabolic parameters. Multiple logistic regression analysis was performed to identify the association between serum levels of Metrnl with the risk of diabetes. Results Serum levels of Metrnl was highest in patients with T2DM and significantly increased in patients with prediabetes compared with individuals with NGT. After adjusting for age, gender, and body mass index (BMI), serum Metrnl level was significantly correlated with lipid profile, glucose profile, and insulin resistance. Multiple logistic regression analysis showed that Metrnl significantly increased the risk of T2DM (OR=1.727; P=0.008) before adjusting for the homeostatic model assessment of insulin resistance (HOMA-IR). When further adjusted for HOMA-IR, Metrnl was no longer associated with an increased OR for T2DM (OR=1.491; P=0.066), while the HOMA-IR significantly increased the risk of T2DM (OR=1.935; P=0.008). Conclusions Serum levels of Metrnl were significantly increased in patients with T2DM and may increase the risk of T2DM independent of insulin resistance.

Diabetes mellitus (DM) patients experience memory and cognitive deficits. The mechanisms underlying this dysfunction in the brain of DM patients are not fully understood, and therefore, no optimized therapeutic strategy has been established so far. The aim of the present study was to assess whether irisin was able to improve memory and cognitive performance in a streptozotocin-induced diabetic mouse model. A diabetic mouse model was established and behavioral tests were performed. We also set up primary cultures for mechanism studies. Western blots and EMSA were used for molecular studies. Significant impairment of cognition and memory was observed in these DM mice, which could be effectively prevented by irisin cotreatment. We also found upregulated levels of GFAP protein, reduced synaptic protein expression, and increased levels of interleukin-1β (IL-1β) and interleukin-6 (IL-6) in the brains; however, irisin significantly attenuated these cellular responses. Meanwhile, our results demonstrated that irisin inhibited the activation of P38, STAT3, and NFκB proteins of DM mice. Furthermore, our results suggested that irisin might regulate the function of P38, STAT3, and NFκB in hippocampal tissues of DM mice. Collectively, irisin inhibited neuroinflammation in STZ-induced DM mice by inhibiting cytokine release and improving their cognitive function. Our findings revealed the mechanism of irisin’s anti-inflammatory effect in the CNS.

The depression incidence is much higher in patients with diabetes mellitus (DM), and the majority of these cases remain under-diagnosed. Type 1 diabetes mellitus (T1D) is now widely thought to be an organ-specific autoimmune disease. As a chronic autoimmune condition, T1D is characterized by T cell-mediated selective loss of insulin-producing β-cells. The age of onset of T1D is earlier than T2D, and T1D patients have an increased vulnerability to depression due to its diagnosis and treatment burden occurring in a period when the individuals are young. The literature has suggested that inflammatory cytokines play a wide role in both diseases. In this review, the mechanisms behind the initiation and propagation of the autoimmune response in T1D and depression are analyzed, and the contribution of cytokines to both conditions is discussed. This review outlines the immunological mechanism of T1D and depression, with a particular emphasis on the role of tumor necrosis factor-α (TNF-α), IL-1β, and interferon-γ (IFN-γ) cytokines and their signaling pathways. The purpose of this review is to highlight the possible pathways of the cytokines shared by these two diseases via deciphering their cytokine cascades. They may provide a basic groundwork for future study of the possible mechanism that links these two diseases and to develop new compounds that target the same pathway but can conquer two diseases.