Synaptic input changes to spinal cord motoneurons correlate with motor control impairments in a type 1 diabetes mellitus model

Angiotensin II Type 1 receptor blockade attenuates the neuropathological changes in the spinal cords of diabetic rats with modulation of nuclear factor erythroid 2-related factor 2/ heme oxygenase 1 system

Peripheral and central neuropathies frequently complicate worldwide diabetes. Compared to peripheral neuropathy, central neuropathy didn`t gain a major research interest. Angiotensin II is reported to be involved in diabetic neuropathic pain but its role in the central pathological changes in the spinal cord is not clear. Here, we study the role of Losartan; an Angiotensin II receptor 1 (AT1) antagonist in suppression of the diabetes-induced changes in the spinal cord. Three groups of rats were applied; a negative control group, a streptozotocin (STZ) diabetic group, and a group receiving STZ and Losartan. After two months, the pathological alteration in the spinal cord was investigated, and an immunohistochemical study was performed for neuronal, astrocytic, and microglial markers; nuclear protein (NeuN), Glial fibrillary acidic protein (GFAP), and Ionized calcium-binding adaptor molecule 1 (Iba1), respectively, and for an apoptosis marker; caspase-3, and the inflammatory marker; nuclear factor kappa B (NF-kB) signaling, heme oxygenase-1 (HO-1) and nuclear factor erythroid 2-related factor 2 (Nrf2); physiological antioxidant system. The results showed that Losartan caused recovery of spinal cord changes, by inhibiting the microglial and astrocytic activation, suppressing neuronal apoptosis and NF-kB expression with activation of Nrf2/HO-1 (P<0.0005). It is suggested, herein, that Losartan can suppress diabetes-induced glial activation, inflammation, neuronal apoptosis, and oxidative stress in the spinal cord; the mechanisms that may underlie the role of AT1 antagonism in suppressing diabetic neuropathic pain.

Suppression of neuronal apoptosis and glial activation with modulation of Nrf2/HO-1 and NF-kB signaling by curcumin in streptozotocin-induced diabetic spinal cord central neuropathy

Introduction

Diabetes is a global disease, commonly complicated by neuropathy. The spinal cord reacts to diabetes by neuronal apoptosis, microglial activation, and astrocytosis, with a disturbance in neuronal and glial Nuclear factor erythroid 2-related factor/Heme oxygenase-1 (Nrf2/HO-1) and Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) signaling. Curcumin, a bioactive natural substance, showed neuroprotective role in many diseases. However, its role in the treatment of the diabetic central neuropathy of spinal cord and the underlying mechanisms still need clarification. The present study tried to evaluate the role of curcumin in diabetes-induced central neuropathy of the spinal cord in rats.

Methods

Twenty rats were divided into three groups; group 1: a negative control group; group 2: received streptozotocin (STZ) to induce type I diabetes, and group 3: received STZ + Curcumin (150 mg/kg/day) for eight weeks. The spinal cords were examined for histopathological changes, and immunohistochemical staining for Glia fibrillary acidic protein (GFAP); an astrocyte marker, Ionized calcium-binding adaptor molecule 1 (Iba1), a microglial marker, neuronal nuclear protein (NeuN); a neuronal marker, caspase-3; an apoptosis marker, Nrf2/HO-1, NF-kB, and oxidative stress markers were assessed.

Results

Curcumin could improve spinal cord changes, suppress the expression of Iba1, GFAP, caspase-3, and NF-kB, and could increase the expression of NeuN and restore the Nrf2/HO-1 signaling.

Discussion

Curcumin could suppress diabetic spinal cord central neuropathy, glial activation, and neuronal apoptosis with the regulation of Nrf2/HO-1 and NF-kB signaling.

Does Diabetes Affect the Surgical Outcomes in Cases With Cervical Ossification of the Posterior Longitudinal Ligament? A Multicenter Study From Asia Pacific Spine Study Group

STUDY DESIGN

Retrospective multicenter study.

OBJECTIVES

To evaluate the surgical outcomes of cervical ossification of the posterior longitudinal ligament (OPLL) in diabetes mellitus (DM) patients.

METHODS

Approximately 253 cervical OPLL patients who underwent surgical decompression with or without fixation were registered at 4 institutions in 3 Asian countries. They were followed up for at least 2 years. Demographics, imaging, and surgical information were collected, and cervical Japanese Orthopaedic Association (JOA) scores and the visual analog scale (VAS) for the neck were used for evaluation.

RESULTS

Forty-seven patients had DM, showing higher hypertension and cardiovascular disease prevalence. Although they presented worse preoperative JOA scores than non-DM patients (10.5 ± 3.1 vs. 11.8 ± 3.2; P = 0.01), the former showed comparable neurologic recovery at the final follow-up (13.9 ± 2.9 vs. 14.2 ± 2.6; P = 0.41). No correlation was noted between the hemoglobin A1c level in the DM group and the pre- and postoperative JOA scores. No significant difference was noted in VAS scores between the groups at pre- and postsurgery. Regarding perioperative complications, DM patients presented a higher C5 palsy frequency (14.9% vs. 5.8%; P = 0.04). A similar trend was observed when surgical procedure was limited to laminoplasty.

CONCLUSIONS

This is the first multicenter Asian study to evaluate the impact of DM on cervical OPLL patients. Surgical results were favorable even in DM cases, regardless of preoperative hemoglobin A1c levels or operative procedures. However, caution is warranted for the occurrence of C5 palsy after surgery.

Anti-hyperalgesic effects of photobiomodulation therapy (904 nm) on streptozotocin-induced diabetic neuropathy imply MAPK pathway and calcium dynamics modulation

Several recent studies have established the efficacy of photobiomodulation therapy (PBMT) in painful clinical conditions. Diabetic neuropathy (DN) can be related to activating mitogen-activated protein kinases (MAPK), such as p38, in the peripheral nerve. MAPK pathway is activated in response to extracellular stimuli, including interleukins TNF-α and IL-1β. We verified the pain relief potential of PBMT in streptozotocin (STZ)-induced diabetic neuropathic rats and its influence on the MAPK pathway regulation and calcium (Ca²⁺) dynamics. We then observed that PBMT applied to the L4-L5 dorsal root ganglion (DRG) region reduced the intensity of hyperalgesia, decreased TNF-α and IL-1β levels, and p38-MAPK mRNA expression in DRG of diabetic neuropathic rats. DN induced the activation of phosphorylated p38 (p-38) MAPK co-localized with TRPV1⁺ neurons; PBMT partially prevented p-38 activation. DN was related to an increase of p38-MAPK expression due to proinflammatory interleukins, and the PBMT (904 nm) treatment counteracted this condition. Also, the sensitization of DRG neurons by the hyperglycemic condition demonstrated during the Ca²⁺ dynamics was reduced by PBMT, contributing to its anti-hyperalgesic effects.

Diabetes Mellitus-Related Dysfunction of the Motor System

Although motor deficits in humans with diabetic neuropathy have been extensively researched, its effect on the motor system is thought to be lesser than that on the sensory system. Therefore, motor deficits are considered to be only due to sensory and muscle impairment. However, recent clinical and experimental studies have revealed that the brain and spinal cord, which are involved in the motor control of voluntary movement, are also affected by diabetes. This review focuses on the most important systems for voluntary motor control, mainly the cortico-muscular pathways, such as corticospinal tract and spinal motor neuron abnormalities. Specifically, axonal damage characterized by the proximodistal phenotype occurs in the corticospinal tract and motor neurons with long axons, and the transmission of motor commands from the brain to the muscles is impaired. These findings provide a new perspective to explain motor deficits in humans with diabetes. Finally, pharmacological and non-pharmacological treatment strategies for these disorders are presented.

Interleukin-1β influences functional regeneration following nerve injury in mice through nuclear factor-κB signaling pathway

This study focuses on investigating the role of interleukin-1β (IL-1β) in functional regeneration following nerve injury in mice. A microarray-based mRNA profiling study was used to analyze the expression level of IL-1β in peripheral nerve regeneration. Quantitative real-time polymerase chain reaction and Western blot were applied to assess the IL-1β expressions of C57BL/6J-crush and C57BL/6J-crush+IL-1β mice at different post-injury time-points after the standard sciatic nerve crush injury. The outcomes of nerve regeneration were evaluated by behavioral tests. IL-1β was found to be up-regulated in peripheral nerve regeneration and significantly raised on the 3rd day and returned to normal levels on the 14th day after nerve injury. Compared with C57BL/6J-crush+IL-1β mice, the nerve regeneration of C57BL/6J-crush mice was worse after nerve crush injury. IL-1β increased mechanical sensitivity and stimulated amplitude. IL-1β could benefit the recovery of sciatic nerve crush injury by facilitating nerve regeneration.

Carnosic acid protects non-alcoholic fatty liver-induced dopaminergic neuron injury in rats

Non-alcoholic fatty liver disease (NAFLD) has been reported to induce cognitive impairments of hippocampus and may influence central nervous system. In the present study, we investigated whether carnosic acid (CA) ameliorates dopaminergic neuron injury in a rat model of NAFLD. In order to induce NAFLD, rats were fed with high-fat diet (HFD) for 10 weeks. We found that continued CA administration reduced lipid accumulation marked by decreases in alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglyceride (TG), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) levels, and an increase in high-density lipoprotein cholesterol (HDL-C) level in the serum. H&E staining revealed that feeding CA reduced lipid droplets accumulation, and alleviated oxidative stress by increasing in superoxide dismutase (SOD) level and decreasing in malondialdehyde (MDA) level in the liver. In addition, by measuring several parameters of gait analysis, we demonstrated that CA treatment ameliorated behavioral impairments, as evidenced by decreased duration and maximum variation, accompanied by increased average speed and cadence. Furthermore, CA treated-animals displayed an increase in the contents of dopamine (DA) and its metabolites 3,4-dihydroxyphenylacelic acid (DOPAC) and elevated the expressions of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra (SN) as well as the TH protein in the striatum. Together, these findings suggest that CA may be an effective agent in protecting rats from NAFLD-induced dopaminergic neuron injury.

Synaptic input changes to spinal cord motoneurons correlate with motor control impairments in a type 1 diabetes mellitus model

INTRODUCTION

Hyperglycemia is the main cause of diabetic complications, contributing to a widespread degeneration of the nervous system. Nevertheless, the main focus has been the sensory neurons because of neuropathic pain, while the impairments associated with the spinal cord and motor deficits, mostly of those initiated at early stages of the disease, have been poorly investigated. In this way, the present study used the nonobese diabetic mouse model to evaluate the microenvironment around motoneurons at ventral horn of the spinal cord, following prolonged hyperglycemia.

METHODS

Adult female mice were divided into two groups: spontaneously diabetic (n = 33) and nondiabetic (n = 26). Mice were considered hyperglycemic when blood glucose surpassed 400 mg/dL. Following 2 weeks from that stage, part of the animals was euthanized and the lumbar intumescences were obtained and processed for immunohistochemistry and transmission electron microscopy. For immunohistochemistry, the antibodies used for integrated density of pixels quantification were anti-synaptophysin, anti-GFAP, and anti-Iba1. The functional analysis was monitored with the walking track test (CatWalk system) during 4 weeks.

RESULTS

The results revealed significant motor impairment in diabetic animals in comparison to the control group. Such loss of motor control correlated with a significant reduction in presynaptic terminals apposed to the motoneurons. Nevertheless, there were no significant changes in glial reaction in the spinal cord.

CONCLUSION

Overall, the results herein revealed central nervous system changes at early stages of the disease that may in turn contribute to the motor deficit. Such changes open a new window of investigation in early stages of diabetes to better comprehend motor impairment as a long-term complication of the disease.