GLP‑1R agonists ameliorate peripheral nerve dysfunction and inflammation via p38 MAPK/NF‑κB signaling pathways in streptozotocin‑induced diabetic rats

Effect of the glucagon-like peptide-1 receptor agonists on diabetic peripheral neuropathy: A meta-analysis

Previous researches found that glucagon-like peptide 1 receptor agonists (GLP-1RA) offer benefits beyond their anti-diabetic properties, including weight loss and cardiovascular disease prevention. However, the effects of GLP-1RA on diabetic peripheral neuropathy (DPN) remain unclear. This meta-analysis aims to assess the potential benefits of GLP-1RA treatment in DPN patients by evaluating peripheral neural function. Following the Cochrane Collaboration and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted a meta-analysis of the clinical trials investigating the impact of GLP-1RA treatment on peripheral neural function in patients with DPN. Outcomes were measured using electrophysiological tests, including nerve conduction velocity (NCV) and action potential amplitude. Our meta-analysis included six studies with 271 participants. Following GLP-1RA treatment, NCV significantly improved compared to the control group (MD 1.74; 95% CI 1.16 to 2.33; p < 0.001) and before treatment (MD 2.16; 95% CI 1.04 to 3.27; p < 0.001). Despite the improvement in NCV, blood glucose levels did not change significantly (MD -0.20 95% CI -0.87 to 0.46, p = 0.55) indicating that GLP-1RA enhances NCV through mechanisms other than glucose lowering. Nonetheless, as a result of the limited population studied, further research is needed to strengthen the reliability of these findings.

Dietary Zn proteinate with moderate chelation strength alleviates heat stress-induced intestinal barrier function damage by promoting expression of tight junction proteins via the A20/NF-κB p65/MMP-2 pathway in the jejunum of broilers

BACKGROUND

The aim of this study was to determine whether and how Zn proteinate with moderate chelation strength (Zn-Prot M) can alleviate heat stress (HS)-induced intestinal barrier function damage of broilers. A completely randomized design was used for comparatively testing the effects of Zn proteinate on HS and non-HS broilers. Under high temperature (HT), a 1 (Control, HT-CON) + 2 (Zn source) × 2 (added Zn level) factorial arrangement of treatments was used. The 2 added Zn sources were Zn-Prot M and Zn sulfate (ZnS), and the 2 added Zn levels were 30 and 60 mg/kg. Under normal temperature (NT), a CON group (NT-CON) and pair-fed group (NT-PF) were included.

RESULTS

The results showed that HS significantly reduced mRNA and protein expression levels of claudin-1, occludin, junctional adhesion molecule-A (JAMA), zonula occludens-1 (ZO-1) and zinc finger protein A20 (A20) in the jejunum, and HS also remarkably increased serum fluorescein isothiocyanate dextran (FITC-D), endotoxin and interleukin (IL)-1β contents, serum diamine oxidase (DAO) and matrix metalloproteinase (MMP)-2 activities, nuclear factor kappa-B (NF-κB) p65 mRNA expression level, and protein expression levels of NF-κB p65 and MMP-2 in the jejunum. However, dietary supplementation with Zn, especially organic Zn as Zn-Prot M at 60 mg/kg, significantly decreased serum FITC-D, endotoxin and IL-1β contents, serum DAO and MMP-2 activities, NF-κB p65 mRNA expression level, and protein expression levels of NF-κB p65 and MMP-2 in the jejunum of HS broilers, and notably promoted mRNA and protein expression levels of claudin-1, ZO-1 and A20.

CONCLUSIONS

Our results suggest that dietary Zn, especially 60 mg Zn/kg as Zn-Prot M, can alleviate HS-induced intestinal barrier function damage by promoting the expression of TJ proteins possibly via induction of A20-mediated suppression of the NF-κB p65/MMP-2 pathway in the jejunum of HS broilers.

Perspectives on Stem Cell Therapy in Diabetic Neuropathic Pain

Diabetes mellitus-related morbidity and mortality are primarily caused by long-term complications such as retinopathy, nephropathy, cardiomyopathy, and neuropathy. Diabetic neuropathy (DN) involves the progressive degeneration of axons and nerve fibers due to chronic exposure to hyperglycemia. This metabolic disturbance leads to excessive activation of the glycolytic pathway, inducing oxidative stress and mitochondrial dysfunction, ultimately resulting in nerve damage. There is no specific treatment for painful DN, and new approaches should aim not only to relieve pain but also to prevent oxidative stress and reduce inflammation. Given that existing therapies for painful DN are not effective for diabetic patients, mesenchymal stromal cells (MSCs)-based therapy shows promise for providing immunomodulatory and paracrine regulatory functions. MSCs from various sources can improve neuronal dysfunction associated with DN. Transplantation of MSCs has led to a reduction in hyperalgesia and allodynia, along with the recovery of nerve function in diabetic rats. While the pathogenesis of diabetic neuropathic pain is complex, clinical trials have demonstrated the importance of MSCs in modulating the immune response in diabetic patients. MSCs reduce the levels of inflammatory factors and increase anti-inflammatory cytokines, thereby interfering with the progression of DM. Further investigation is necessary to ensure the safety and efficacy of MSCs in preventing or treating neuropathic pain in diabetic patients.

Glucagon-like peptide-1 receptor agonists for the management of diabetic peripheral neuropathy

Diabetes mellitus is a prevalent chronic disease characterized by hyperglycemia. Diabetic peripheral neuropathy (DPN) is one of the complications of diabetes mellitus and is caused by neuron injury induced by hyperglycemic circumstances. The incidence of DPN varies among different countries and regions, ranging from nearly 20% to over 70%. Patients with DPN may encounter symmetric pain or discomfort of the extremes, leading to reduced quality of life and even amputation. The pharmacological management for painful DPN mainly includes antidepressants due to their analgesic effects. Nevertheless, effective therapies to impact the pathogenesis and progression of DPN are lacking. Glucagon-like peptide-1 receptor (GLP-1R) agonists show efficacy in controlling blood glucose and serve as a treatment modality for diabetes mellitus. In recent years, evidence has been proposed that GLP-1R agonists exert neuroprotective effects through modulating inflammation, oxidative stress, and mitochondrial dysfunction. On the other hand, clinical evidence on the potential of GLP-1R agonists for treating DPN is still controversial and limited. This narrative review summarizes the preclinical and clinical studies investigating the capacity of GLP-1R agonists as therapeutic agents for DPN.

The alleviating effect and mechanism of GLP-1 on ulcerative colitis

Ulcerative Colitis (UC) is a major type of chronic inflammatory bowel disease of the colonic mucosa and exhibits progressive morbidity. The incidence and prevalence of UC is increasing worldwide. The global burden of UC, which can substantially reduce quality of life, is clearly increasing. These data highlight the need for research into prevention of UC and innovations in health-care systems to manage this complex and costly disease. Glucagon-like peptide-1 (GLP-1), a new antidiabetic drug, is used to treat Type 2 Diabetes Mellitus (T2DM). Accumulating evidence suggests that GLP-1 has additional roles other than glucose-lowering effects. Despite the abundance of GLP-1 research, studies in UC have been less consistent, especially body weight; for example, body weight, colon length, colon injury score, intestinal microbiota, remain to be studied further. To date, the molecular mechanism of the protective effect of GLP-1 on UC remains obscure. The effect of GLP-1 was studied by using a dextran sulfate sodium (DSS)-induced colitic mice and lipopolysaccharide (LPS) treated RAW264.7 cells (macrophage cell line) under in vivo and in vitro conditions, respectively. Our results indicate that GLP-1 significantly relieves ulcerative colitis as it represses the production of proinflammatory mediators. In addition, GLP-1 blocks the activation of the protein kinase B (AKT)/nuclear factor-κB (NF-κB), and mitogen-activated protein kinase (MAPK) signaling pathways. GLP-1 also alleviates DSS-induced injury to the intestinal mucosa and dysbiosis of gut microbiota. Altogether, GLP-1 has protection effect on ulcerative colitis. Thus, GLP-1 can be considered as a potential therapeutic candidate for the treatment of UC.

GLP-1 receptor agonist as a modulator of innate immunity

Glucagon-like peptide-1 (GLP-1) is a 30-amino acid hormone secreted by L cells in the distal ileum, colon, and pancreatic α cells, which participates in blood sugar regulation by promoting insulin release, reducing glucagon levels, delaying gastric emptying, increasing satiety, and reducing appetite. GLP-1 specifically binds to the glucagon-like peptide-1 receptor (GLP-1R) in the body, directly stimulating the secretion of insulin by pancreatic β-cells, promoting proliferation and differentiation, and inhibiting cell apoptosis, thereby exerting a glycemic lowering effect. The glycemic regulating effect of GLP-1 and its analogues has been well studied in human and murine models in the circumstance of many diseases. Recent studies found that GLP-1 is able to modulate innate immune response in a number of inflammatory diseases. In the present review, we summarize the research progression of GLP-1 and its analogues in immunomodulation and related signal pathways.

Liraglutide Attenuates Glucolipotoxicity-Induced RSC96 Schwann Cells’ Inflammation and Dysfunction

Diabetic neuropathy (DN) is a type of sensory nerve damage that can occur in patients with diabetes. Although the understanding of pathophysiology is incomplete, DN is often associated with structural and functional alterations of the affected neurons. Among all possible causes of nerve damage, Schwann cells (SCs) are thought to play a key role in repairing peripheral nerve injury, suggesting that functional deficits occurring in SCs may potentially exhibit their pathogenic roles in DN. Therefore, elucidating the mechanisms that underlie this pathology can be used to develop novel therapeutic targets. In this regard, glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have recently attracted great attention in ameliorating SCs’ dysfunction. However, the detailed mechanisms remain uncertain. In the present study, we investigated how GLP-1 RA Liraglutide protects against RSC96 SCs dysfunction through a diabetic condition mimicked by high glucose and high free fatty acid (FFA). Our results showed that high glucose and high FFAs reduced the viability of RSC96 SCs by up to 51%, whereas Liraglutide reduced oxidative stress by upregulating antioxidant enzymes, and thus protected cells from apoptosis. Liraglutide also inhibited NFκB-mediated inflammation, inducing SCs to switch from pro-inflammatory cytokine production to anti-inflammatory cytokine production. Moreover, Liraglutide upregulated the production of neurotrophic factors and myelination-related proteins, and these protective effects appear to be synergistically linked to insulin signaling. Taken together, our findings demonstrate that Liraglutide ameliorates diabetes-related SC dysfunction through the above-mentioned mechanisms, and suggest that modulating GLP-1 signaling in SCs may be a promising strategy against DN.

Glucagon-Like Peptide-1 Receptor Agonists as Potential Myelination-Inducible and Anti-Demyelinating Remedies

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) were developed as insulinotropic and anti-hyperglycemic agents for the treatment of type 2 diabetes, but their neurotrophic and neuroprotective activities have been receiving increasing attention. Myelin plays a key role in the functional maintenance of the central and peripheral nervous systems, and recent in vivo and in vitro studies have shed light on the beneficial effects of GLP-1RAs on the formation and protection of myelin. In this article, we describe the potential efficacy of GLP-1RAs for the induction of axonal regeneration and remyelination following nerve lesions and the prevention and alleviation of demyelinating disorders, particularly multiple sclerosis.

Huangqi Guizhi Wuwu Decoction can prevent and treat oxaliplatin-induced neuropathic pain by TNFα/IL-1β/IL-6/MAPK/NF-kB pathway

OBJECTIVE

This study explored the effects and mechanisms of Huangqi Guizhi Wuwu Decoction on chemotherapy-induced neuropathic pain (CINP).

METHODS

Bodyweight and related behavioral testing of the rat model were utilized to investigate the effects of Huangqi Guizhi Wuwu Decoction on CINP. ELISA was used to measure the levels of TNF-α, IL-1β, and IL-6, in the serum of chronic CINP rats. Immunohistochemistry and Western blot analysis were performed to detect the expression of MAPK pathway related-proteins namely ERK1/2, p38, and JNK, and the expression of downstream essential proteins such as c-Fos, CREB, and NF-κB.

RESULTS

Body weight and related behavioral testing of the rat model suggests that Huangqi Guizhi Wuwu Decoction can improve the slow weight gain of oxaliplatin-induced chronic CINP model rats and effectively prevent and treat oxaliplatin-induced regular CIPN rat model of hyperalgesia. It can also oppress the mechanical pain threshold, cold pain threshold, and heat pain threshold decreased. Furthermore, by ELISA, immunohistochemistry, and western blot analysis, we found that Huangqi Guizhi Wuwu Decoction can down-regulate the levels of TNF-α, IL-1β, and IL-6 in the serum of chronic CINP rats induced by oxaliplatin. It also suppresses the expression of MAPK pathway related-proteins ERK1/2, p38, and JNK. This results in a decrease in the expression of downstream essential proteins, c-Fos, CREB, and Nf-κB.

CONCLUSIONS

In conclusion, we found that Huangqi Guizhi Wuwu Decoction can combat nerve cell injury, reduce pain sensitization, and prevent and repair the damage of nerve cells in the oxaliplatin CINP model rats via TNFα/IL-1β/IL-6/MAPK/NF-kB pathway.

Current and Emerging Pharmacotherapeutic Interventions for the Treatment of Peripheral Nerve Disorders

Peripheral nerve disorders are caused by a range of different aetiologies. The range of causes include metabolic conditions such as diabetes, obesity and chronic kidney disease. Diabetic neuropathy may be associated with severe weakness and the loss of sensation, leading to gangrene and amputation in advanced cases. Recent studies have indicated a high prevalence of neuropathy in patients with chronic kidney disease, also known as uraemic neuropathy. Immune-mediated neuropathies including Guillain-Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy may cause significant physical disability. As survival rates continue to improve in cancer, the prevalence of treatment complications, such as chemotherapy-induced peripheral neuropathy, has also increased in treated patients and survivors. Notably, peripheral neuropathy associated with these conditions may be chronic and long-lasting, drastically affecting the quality of life of affected individuals, and leading to a large socioeconomic burden. This review article explores some of the major emerging clinical and experimental therapeutic agents that have been investigated for the treatment of peripheral neuropathy due to metabolic, toxic and immune aetiologies.

Effects of Glucagon-Like Peptide-1 Receptor Agonist Exendin-4 on the Reinstatement of Cocaine-Mediated Conditioned Place Preference in Mice

A high percentage of relapse to compulsive cocaine-taking and cocaine-seeking behaviors following abstinence constitutes a major obstacle to the clinical treatment of cocaine addiction. Thus, there is a substantial need to develop effective pharmacotherapies for the prevention of cocaine relapse. The reinstatement paradigm is known as the most commonly used animal model to study relapse in abstinent human addicts. The primary aim of this study is to investigate the potential effects of systemic administration of glucagon-like peptide-1 receptor agonist (GLP-1RA) exendin-4 (Ex4) on the cocaine- and stress-triggered reinstatement of cocaine-induced conditioned place preference (CPP) in male C57BL/6J mice. The biased CPP paradigm was induced by alternating administration of saline and cocaine (20 mg/kg), followed by extinction training and then reinstatement by either a cocaine prime (10 mg/kg) or exposure to swimming on the reinstatement test day. To examine the effects of Ex4 on the reinstatement, Ex4 was systemically administered 1 h after the daily extinction session. Additionally, we also explored the associated molecular basis of the behavioral effects of Ex4. The expression of nuclear factor κβ (NF-κβ) in the nucleus accumbens (NAc) was detected using Western blotting. As a result, all animals that were treated with cocaine during the conditioning period successfully acquired CPP, and their CPP response was extinguished after 8 extinction sessions. Furthermore, the animals that were exposed to cocaine or swimming on the reinstatement day showed a significant reinstatement of CPP. Interestingly, systemic pretreatment with Ex4 was sufficient to attenuate cocaine- and stress-primed reinstatement of cocaine-induced CPP. Additionally, the expression of NF-κβ, which was upregulated by cocaine, was normalized by Ex4 in the cocaine-experienced mice. Altogether, our study reveals the novel effect of Ex4 on the reinstatement of cocaine-induced CPP and suggests that GLP-1R agonists appear to be highly promising drugs in the treatment of cocaine use disorder.

Semaglutide attenuates seizure severity and ameliorates cognitive dysfunction by blocking the NLR family pyrin domain containing 3 inflammasome in pentylenetetrazole‑kindled mice

Epilepsy comorbidities and anti-epileptic drugs (AEDs) are currently the main limitations of epilepsy treatment. Semaglutide is a glucagon like peptide-1 analogue that has entered the market as a new once-weekly drug for type II diabetes. The aim of the present study was to investigate the functions of semaglutide in epilepsy and inflammation models, in order to investigate its potential mechanism. In vitro, an inflammation model was established using lipopolysaccharide (LPS) and nigericin stimulation in BV2 cells. In vivo, chronic epilepsy model mice were generated using a pentylenetetrazole (PTZ) kindling method. BV2 cell proliferation was assessed using the Cell Counting Kit-8. The effects of semaglutide on NLR family pyrin domain containing 3 (NLRP3) inflammasome activation and inflammatory cytokine secretion were determined using western blotting (WB) and ELISA. A lactate dehydrogenase (LDH) assay kit was used to detect the effect of semaglutide on LDH release. Electrocorticography and the modified Racine scale were used to assess seizure severity. Cognitive function was evaluated with behavioral assessment. Morphological changes in the hippocampus were observed with Nissl staining. Double immunofluorescence staining for NeuN and Iba-1, WB and immunofluorescence analysis of apoptosis-related proteins were used to evaluate neuronal apoptosis. The NLRP3 inflammasome was assessed by reverse transcription-quantitative PCR, WB and immunofluorescence staining, and inflammatory cytokine release was evaluated by WB analysis in the hippocampus of C57/BL6J model mouse. Semaglutide attenuated the LPS- and nigericin-induced inflammatory response and LDH release by blocking NLRP3 inflammasome activation in BV2 cells. Moreover, semaglutide decreased seizure severity, alleviated hippocampal neuronal apoptosis, ameliorated cognitive dysfunction, blocked NLRP3 inflammasome activation and decreased inflammatory cytokine secretion in PTZ-kindled mice. These results indicated that semaglutide reduced seizure severity, exerted neuroprotective effects and ameliorated cognitive dysfunction, possibly via inhibition of NLRP3 inflammasome activation and inflammatory cytokine secretion. Semaglutide may therefore be a novel, promising adjuvant therapeutic for epilepsy and its associated comorbidities.

Teneligliptin Exerts Antinociceptive Effects in Rat Model of Partial Sciatic Nerve Transection Induced Neuropathic Pain

Neuropathic pain (NP), is a chronic pain resulting from nerve injury, with limited treatment options. Teneligliptin (TEN) is a dipeptidyl peptidase-4 inhibitor (DPP-4i) approved to treat type 2 diabetes. DPP-4is prevent the degradation of the incretin hormone glucagon-like peptide 1 (GLP-1) and prolong its circulation. Apart from glycemic control, GLP-1 is known to have antinociceptive and anti-inflammatory effects. Herein, we investigated the antinociceptive properties of TEN on acute pain, and partial sciatic nerve transection (PSNT)-induced NP in Wistar rats. Seven days post PSNT, allodynia and hyperalgesia were confirmed as NP, and intrathecal (i.t) catheters were implanted and connected to an osmotic pump for the vehicle (1 μL/h) or TEN (5 μg/1 μL/h) or TEN (5 μg) + GLP-1R antagonist Exendin-3 (9–39) amide (EXE) 0.1 μg/1 μL/h infusion. The tail-flick response, mechanical allodynia, and thermal hyperalgesia were measured for 7 more days. On day 14, the dorsal horn was harvested and used for Western blotting and immunofluorescence assays. The results showed that TEN had mild antinociceptive effects against acute pain but remarkable analgesic effects against NP. Furthermore, co-infusion of GLP-1R antagonist EXE with TEN partially reversed allodynia but not tail-flick latency. Immunofluorescence examination of the spinal cord revealed that TEN decreased the immunoreactivity of glial fibrillary acidic protein (GFAP). Taken together, our findings suggest that TEN is efficient in attenuation of PSNT-induced NP. Hence, the pleiotropic effects of TEN open a new avenue for NP management.

Effects of Incretin-Related Diabetes Drugs on Bone Formation and Bone Resorption

Patients with type 2 diabetes have an increased risk of fracture compared to the general population. Glucose absorption is accelerated by incretin hormones, which induce insulin secretion from the pancreas. The level of the incretin hormone, glucagon-like peptide-1 (GLP-1), shows an immediate postprandial increase, and the circulating level of intact GLP-1 is reduced rapidly by dipeptidyl peptidase-4 (DPP-4)-mediated inactivation. Therefore, GLP-1 receptor agonists and DPP-4 inhibitors are effective in the treatment of type 2 diabetes. However, these incretin-related diabetic agents have been reported to affect bone metabolism, including bone formation and resorption. These agents enhance the expression of bone markers, and have been applied to improve bone quality and bone density. In addition, they have been reported to suppress chronic inflammation and reduce the levels of inflammatory cytokine expression. Previously, we reported that these incretin-related agents inhibited both the expression of inflammatory cytokines and inflammation-induced bone resorption. This review presents an overview of current knowledge regarding the effects of incretin-related diabetes drugs on osteoblast differentiation and bone formation as well as osteoclast differentiation and bone resorption. The mechanisms by which incretin-related diabetes drugs regulate bone formation and bone resorption are also discussed.

Deciphering the Neuroprotective Role of Glucagon-like Peptide-1 Agonists in Diabetic Neuropathy: Current Perspective and Future Directions

Diabetic neuropathy is referred to as a subsequential and debilitating complication belonging to type 1 and type 2 diabetes mellitus. It is a heterogeneous group of disorders with a particularly complex pathophysiology and also includes multiple forms, ranging from normal discomfort to death. The evaluation of diabetic neuropathy is associated with hyperglycemic responses, resulting in an alteration in various metabolic pathways, including protein kinase C pathway, polyol pathway and hexosamine pathway in Schwann and glial cells of neurons. The essential source of neuronal destruction is analogous to these respective metabolic pathways, thus identified as potential therapeutic targets. These pathways regulating therapeutic medications may be used for diabetic neuropathy, however, only target specific drugs could have partial therapeutic activity. Various antidiabetic medications have been approved and marketed, which possess the therapeutic ability to control hyperglycemia and ameliorate the prevalence of diabetic neuropathy. Among all antidiabetic medications, incretin therapy, including Glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors, are the most favorable medications for the management of diabetes mellitus and associated peripheral neuropathic complications. Besides enhancing glucose-evoked insulin release from pancreatic β-cells, these therapeutic agents also play a vital role to facilitate neurite outgrowth and nerve conduction velocity in dorsal root ganglion. Furthermore, incretin therapy also activates cAMP and ERK signalling pathways, resulting in nerve regeneration and repairing. These effects are evidently supported by a series of preclinical data and investigations associated with these medications. However, the literature lacks adequate clinical trial outcomes related to these novel antidiabetic medications. The manuscript emphasizes the pathogenesis, current pharmacological approaches and vivid description of preclinical and clinical data for the effective management of diabetic neuropathy.

Gene Expression Profiling of the Sciatic Nerve in Streptozotocin-Induced Diabetic Rats with Peripheral Neuropathy

AIMS

To investigate the candidate biomarkers and molecular mechanisms involved in the early phase of experimental diabetic peripheral neuropathy (DPN).

METHODS

Diabetes in Sprague-Dawley rats was induced with streptozotocin (STZ) treatment, followed with neurological tests and histological examinations to assess the neuropathic symptoms of DPN. Microarray was performed on the sciatic nerve tissues from control rats and DPN rats at then6th week after diabetes induction, and differentially expressed genes (DEGs) between them were identified and applied for further bioinformatic analyses.

RESULTS

Experimental DPN rats were successfully constructed, presenting significantly decreased withdrawal threshold and motor nerve conduction velocity, and typical histological changes in the sciatic nerve. 597 DEGs (186 up- and 411 downregulated) were identified in DPN rats. DEGs from the 3 most highly connected clusters in the protein-protein interaction network were enriched for biological processes or pathways such as "cell division," "cell cycle," "protein phosphorylation," "chemokine signaling pathway," "neuropeptide signaling pathway," "response to drug," "cellular response to insulin stimulus," "PPAR signaling pathway," and "glycerophospholipid metabolism." Thirteen genes were identified as the hub DEGs in the PPI network. Eleven transcriptional factors (TFs) targeting 9 of the 13 hub DEGs were predicted.

CONCLUSIONS

The present study identified a pool of candidate biomarkers such as Cdk1, C3, Mapk12, Agt, Adipoq, Cxcl2, and Mmp9 and molecular mechanisms which may be involved in the early phase of experimental DPN. The findings provide clues for exploring new strategies for the early diagnosis and treatment of DPN.

Neuroprotective effects of melatonin on erectile dysfunction in streptozotocin-induced diabetic rats

PURPOSE

To explore the neuroprotective effects and its possible mechanisms of melatonin (MT) on erectile dysfunction in streptozotocin-induced diabetic rats.

METHODS

Twenty-eight Sprague-Dawley rats received intraperitoneal injection of streptozotocin and 8 weeks later, the determined diabetic rats randomly got intraperitoneal injection of phosphate buffer solution (PBS) or MT. Another 12 normal rats received PBS treatment. Four weeks later, intracavernous pressure, mean arterial pressure, pathological changes in penis, and major pelvic ganglion (MPG) were measured. Malondialdehyde, superoxide dismutase, p38 and p-p38 levels in penis were detected.

RESULTS

Diabetic rats showed significant decreases of erectile function accompanied with serious neuropathy in dorsal penile nerve (DPN) and MPG, meanwhile collagen deposition, oxidative stress, and p-p38 levels in penis were elevated. Melatonin treatment partially but significantly improved the erectile function, ameliorated neuropathy in DPN and MPG, and decreased collagen deposition, oxidative stress, and p-p38 levels in diabetic rats.

CONCLUSIONS

Melatonin treatment helps improve erectile function and ameliorate neuropathy and fibrosis in diabetic rats. These may be associated with reductions in oxidative stress, p38MAPK signaling pathway, and neuropathy.