miR-125a-5p in astrocytes attenuates peripheral neuropathy in type 2 diabetic mice through targeting TRAF6

Effects of Pain Relief Through Minimal Exercise Intervention in a Rat Model of Neuropathic Pain

We aimed to minimize the frequency of exercise intervention and test the efficacy of pain relief. We also investigated the mechanism of neuropathic pain to determine the best frequency of pain relief for neuropathic pain. The chronic constriction injury (CCI) rat model was randomly divided into three groups: exercise (Ex), No-Ex, and normal. The treadmill exercise intervention was administered, and the 50% withdrawal threshold was assessed using the Von Frey Test. Ionized calcium-binding adaptor molecule 1 (IBA1), glial fibrillary acidic protein (GFAP), brain-derived neurotrophic factor (BDNF), C-C chemokine receptor type 2 (CCR2), and tumor necrosis factor receptor-associated factor 6 (TRAF6) activation was determined through immunohistochemistry. In the brain, we examined the increased expression of β-endorphin/met-enkephalin in the gray matter of the midbrain aqueduct. Co-expression of CCR2, IBA1, and Neu-N was observed in the spinal cord dorsal horn by immunofluorescence staining. The 50% pain response threshold was significantly lower in the Ex group than in the No-Ex group at five weeks post-CCI, indicating a high analgesic effect. In the dorsal horn of the spinal cord, IBA1 and GFAP were significantly decreased in the Ex group than in the No-Ex group at five weeks post-CCI. However, no significant difference in activation of BDNF, CCR2, and TRAF6 was observed. In the midbrain, the Ex group showed a significant increase compared to the No-Ex group. In summary, our results suggest that in minimal-exercise intervention, neuropathic pain relief is achieved by activation of the descending pain inhibitory system in the midbrain.

Glial cell alterations in diabetes-induced neurodegeneration

Type 2 diabetes mellitus is a global epidemic that due to its increasing prevalence worldwide will likely become the most common debilitating health condition. Even if diabetes is primarily a metabolic disorder, it is now well established that key aspects of the pathogenesis of diabetes are associated with nervous system alterations, including deleterious chronic inflammation of neural tissues, referred here as neuroinflammation, along with different detrimental glial cell responses to stress conditions and neurodegenerative features. Moreover, diabetes resembles accelerated aging, further increasing the risk of developing age-linked neurodegenerative disorders. As such, the most common and disabling diabetic comorbidities, namely diabetic retinopathy, peripheral neuropathy, and cognitive decline, are intimately associated with neurodegeneration. As described in aging and other neurological disorders, glial cell alterations such as microglial, astrocyte, and Müller cell increased reactivity and dysfunctionality, myelin loss and Schwann cell alterations have been broadly described in diabetes in both human and animal models, where they are key contributors to chronic noxious inflammation of neural tissues within the PNS and CNS. In this review, we aim to describe in-depth the common and unique aspects underlying glial cell changes observed across the three main diabetic complications, with the goal of uncovering shared glial cells alterations and common pathological mechanisms that will enable the discovery of potential targets to limit neuroinflammation and prevent neurodegeneration in all three diabetic complications. Diabetes and its complications are already a public health concern due to its rapidly increasing incidence, and thus its health and economic impact. Hence, understanding the key role that glial cells play in the pathogenesis underlying peripheral neuropathy, retinopathy, and cognitive decline in diabetes will provide us with novel therapeutic approaches to tackle diabetic-associated neurodegeneration.

[Production and internalization of extracellular vesicules in normal and under conditions of hyperglycemia and insulin resistance]

Extracellular vesicles (EVs) are spherical structures of cell membrane origin, ranging in the size from 40 nm to 5000 nm. They are involved in the horizontal transfer of many proteins and microRNAs. The mechanisms EV internalization include clathrin-dependent endocytosis, caveolin-dependent endocytosis, raft-mediated endocytosis, and macropinocytosis. Type 2 diabetes mellitus (T2DM) is a common group of metabolic disorders in adults; the incidence and prevalence increase in parallel with the obesity epidemic. Since adipose tissue plays a crucial role in the development of insulin resistance, EVs secreted by adipose tissue can be a kind of information transmitter in this process. EVs of adipocytic origin are predominantly absorbed by tissue macrophages, adipocytes themselves, hepatocytes, and skeletal muscles. This contributes to the M1 polarization of macrophages, a decrease in glucose uptake by hepatocytes and myocytes due to the transfer of functionally active microRNAs by these EVs, which affect carbohydrate and lipid metabolism. Patients with T2DM and impaired glucose tolerance have significantly higher levels of CD235a-positive (erythrocyte) EVs, as well as a tendency to increase CD68-positive (leukocyte) and CD62p-positive (platelets/endothelial cells) EVs. The levels of CD31+/CD146-positive BB (endothelial cells) were comparable between diabetic and euglycemic patients. EVs from diabetic patients were preferably internalized by monocytes (mainly classical and intermediate monocyte fractions and to a lesser extent by non-classical monocyte fractions) and B cells compared to euglycemic patients. Internalization of EVs from patients with T2DM by monocytes leads to decreased apoptosis, changes in differentiation, and suppression of reactions controlling oxidative stress in monocytes. Thus, insulin resistance increases secretion of EVs, which are preferentially internalized by monocytes and influence their function. EVs are considered as sources of promising clinical markers of insulin resistance, complications of diabetes mellitus (endothelial dysfunction, retinopathy, nephropathy, neuropathy), and markers of EVs can also be used to monitor the effectiveness of therapy for these complications.