Jinmaitong decreases sciatic nerve DNA oxidative damage and apoptosis in a streptozotocin-induced diabetic rat model

The effects and potential mechanisms of essential metals on the associations of polycyclic aromatic hydrocarbons with blood cell-based inflammation markers

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are well-acknowledged pro-inflammatory chemicals, but their associations with blood cell-based inflammatory biomarkers need further investigation. Moreover, the effects and mechanisms of essential metals on PAH-related inflammation remain poorly understood.

OBJECTS

To elucidate the associations of PAHs on inflammatory biomarkers, as well as the effects and mechanisms of essential metals on these associations.

METHODS

A cross-sectional study was conducted on 1388 coke oven workers. We analyzed the modification effects of key essential metal(s) on PAHs-inflammatory biomarkers associations. To explore the possible mechanisms from an inflammation perspective, we performed a bioinformatic analysis on the genes of PAHs and essential metals obtained from the Comparative Toxicogenomics Database (CTD) and performed a mediation analysis.

RESULTS

We observed associations of PAHs and essential metals with lymphocyte-to-monocyte ratio (LMR) (P < 0.05). PAH mixtures were inversely associated with LMR (βQGC-index = -0.18, P < 0.001), with 1-hydroxypyrene (1-OH-Pyr) being the most prominent contributor (weight = 63.37%), whereas a positive association between essential metal mixtures and LMR was observed (βQGC-index = 0.14, P < 0.001), with tin being the most significant contributor (weight = 51.61%). An inverse association of 1-OH-Pyr with LMR was weakened by increased tin exposure (P < 0.05). The CTD database showed that PAHs and tin compounds co-regulated 22 inflammation-associated genes, but they regulated most genes in opposite directions. Further identified the involvement of oxidative stress and mediation analysis showed that the mediation effect of 8-hydroxydeoxyguanosine (8-OHdG) on 1-OH-Pyr-LMR association presented heterogeneity between low and high tin tertile groups (I2 = 37.84%).

CONCLUSION

1-OH-Pyr and tin were significantly associated with LMR. Modification effects indicated that the inverse association of 1-OH-Pyr with LMR was mitigated with an increase in tin. The mediation effect of 8-OHdG on the inverse association of 1-OH-Pyr with LMR may be partially dependent on tin.

Impact of gut-peripheral nervous system axis on the development of diabetic neuropathy

Diabetes is a chronic metabolic disease caused by a reduction in the production and/or action of insulin, with consequent development of hyperglycemia. Diabetic patients, especially those who develop neuropathy, presented dysbiosis, with an increase in the proportion of pathogenic bacteria and a decrease in the butyrate-producing bacteria. Due to this dysbiosis, diabetic patients presented a weakness of the intestinal permeability barrier and high bacterial product translocation to the bloodstream, in parallel to a high circulating levels of pro-inflammatory cytokines such as TNF-α. In this context, we propose here that dysbiosis-induced increased systemic levels of bacterial products, like lipopolysaccharide (LPS), leads to an increase in the production of pro-inflammatory cytokines, including TNF-α, by Schwann cells and spinal cord of diabetics, being crucial for the development of neuropathy.

Jinmaitong Alleviates Diabetic Neuropathic Pain Through Modulation of NLRP3 Inflammasome and Gasdermin D in Dorsal Root Ganglia of Diabetic Rats

Jinmaitong (JMT) is a compound prescription of traditional Chinese medicine that has been used to treat diabetic neuropathic pain (DNP) for many years. Here, we investigated the effects of JMT on the activation of NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome and pyroptosis in Dorsal root ganglia (DRG) of diabetic rats. Streptozotocin (STZ)-induced diabetic rats were gavaged with JMT (0.88 g/kg/d) or alpha-lipoic acid (ALA, positive control, 0.48 mmol/kg/d) for 12 weeks. Distilled water was administered as a vehicle control to both diabetic and non-affected control rats. Blood glucose levels and body weights were measured. Behavioral changes were tested with mechanical withdrawal threshold (MWT) and tail-flick latency (TFL) tests. Morphological injury associated with DRG was observed with hematoxylin and eosin (H&E) and Nissl’s staining. mRNA and protein levels of NLRP3 inflammasome components (NLRP3, ASC, caspase-1), downstream IL-1β and gasdermin D (GSDMD) were evaluated by immunohistochemistry, quantitative real time-PCR and western blot. The results showed that JMT had no effect on blood glucose levels and body weights, but significantly improved MWT and TFL behavior in diabetic rats, and attenuated morphological damage in the DRG tissues. Importantly, JMT decreased the mRNA and protein levels of components of NLRP3 inflammasome, including NLRP3, ASC and caspase-1. JMT also down-regulated the expression of IL-1β and GSDMD in the DRG of DNP rats. In addition, ALA treatment did not perform better than JMT. In conclusion, JMT effectively relieved DNP by decreasing NLRP3 inflammasome activation and pyroptosis, providing new evidence supporting JMT as an alternative treatment for DNP.

Jinmaitong ameliorates diabetic peripheral neuropathy in streptozotocin-induced diabetic rats by modulating gut microbiota and neuregulin 1

Jinmaitong (JMT), a compound prescription of traditional Chinese medicine, has long been used as a therapy for diabetic peripheral neuropathy (DPN). However, the neuroprotective mechanisms of JMT and its effect on gut microbiota remained unknown. Here, we examined the effects of JMT on behavior, pathomorphology and gut microbiota in streptozotocin (STZ)-induced DPN rats. Compared to distilled water administration, JMT reversed decreases in mechanical withdraw threshold and intraepidermal nerve fiber density, improved neurological morphology of sciatic nerves, increased serum neuregulin 1 (NRG1) level and contactin-associated protein (Caspr)-positive paranodes, and decreased amyloid precursor protein (APP) accumulation in DPN rats. More importantly, JMT enriched nine species of the gut microbiota of DPN rats, helping to prevent dysbiosis. Among these species, p_Actinobacteria, p_Proteobacteria and c_Actinobacteria were negatively correlated with DPN phenotypes and positively correlated with serum NRG1 level. These results indicate that JMT may exert a neuroprotective effect by modulating phenotype-associated gut microbiota and increasing serum NRG1 level in STZ-induced DPN rats. JMT may therefore be an effective complementary and alternative anti-DPN therapy.

Role of Pyroptosis in Diabetes and Its Therapeutic Implications

Pyroptosis is mainly considered as a new pro-inflammatory mediated-programmed cell death. In addition, pyroptosis is described by gasdermin-induced pore formation on the membrane, cell swelling and rapid lysis, and several pro-inflammatory mediators interleukin-1β (IL-1β) and interleukin-18 (IL-18) release. Extensive studies have shown that pyroptosis is commonly involved by activating the caspase-1-dependent canonical pathway and caspase-4/5/11-dependent non-canonical pathway. However, pyroptosis facilitates local inflammation and inflammatory responses. Current researches have reported that pyroptosis promotes the progression of several diabetic complications. Emerging studies have suggested that some potential molecules targeting the pyroptosis and inflammasome signaling pathways could be a novel therapeutic avenue for managing and treating diabetes and its complications in the near future. Our narrative review concisely describes the possible mechanism of pyroptosis and its progressive understanding of the development of diabetic complications.

Compound XiongShao Capsule ameliorates streptozotocin-induced diabetic peripheral neuropathy in rats via inhibiting apoptosis, oxidative - nitrosative stress and advanced glycation end products

ETHNOPHARMACOLOGICAL RELEVANCE

Compound XiongShao Capsule (CXSC), a traditional herb formula, has been approved for using to treat diabetic peripheral neuropathy (DPN) by the Shanghai Food and Drug Administration, with significant efficacy in clinic.

AIM OF THE STUDY

This study aimed to investigate the multidimensional pharmacological mechanisms and synergism of CXSC against DPN in rats.

METHODS

The quality analysis of CXSC was performed by high-performance liquid chromatography (HPLC) and thin-layer chromatography. Rats with DPNinduced by streptozotocin/high-fat diet for 4 weeks were treated with CXSC at three doses (1.2 g/kg, 0.36 g/kg, and 0.12 g/kg), or epalrestat (15 mg/kg) daily for 8 weeks continuously. During the treatment period, body weight, serum glucose levels, and nerve function, including nerve conduction velocity (NCV), and mechanical and thermal hyperalgesia were tested and assessed every 4 weeks. In the 13th week, the histopathological examination in the sciatic nerve was performed using a transmission electron microscope. The expression of apoptosis-related proteins of BAX, BCL2, and caspase-3 in the sciatic nerve was examined using hematoxylin and eosin staining. The serum levels of advanced glycation end products (AGEs), oxidative-nitrosative stress biomarkers of superoxide dismutase (SOD), and nitric oxide synthase (NOS) were measured using a rat-specific ELISA kit.

RESULTS

CXSC had no significant effect on body weight or serum glucose levels (P > 0.05), but it significantly improved mechanical hyperalgesia (F_5,36 = 18.24, P < 0.0001), thermal hyperalgesia (F_5,36 = 8.45, P < 0.0001), and NCV (motor NCV: F_5,36 = 7.644, P < 0.0001, sensory NCV: F_5,36 = 12.83, P < 0.0001). Besides, it maintained myelin and axonal structure integrity, downregulated the expression of apoptosis-related proteins in the sciatic nerve tissue, reduced AGEs and NOS levels, and enhanced antioxidant enzyme SOD activities in the serum.

CONCLUSION

CXSC exerted neuroprotective effects against rats with DPN through multidimensional pharmacological mechanisms including antiapoptotic activity in the sciatic nerve and downregulation of the level of serum NOS, SOD and AGEs.

Protective effect of quercetin on streptozotocin-induced diabetic peripheral neuropathy rats through modulating gut microbiota and reactive oxygen species level

OBJECTIVE

Diabetic peripheral neuropathy (DPN) is a prevalent complication of diabetes with no effective drug currently. As a powerful antioxidant, the flavonoid quercetin has been demonstrated to have potential neuroprotective and prebiotic capacity. But the mechanism of its neuroprotective function and the link to the gut microbiota remains to be elucidated.

METHODS

The neuroprotective effect of quercetin was evaluated on streptozotocin(STZ)-induced DPN rats through electrophysiology, behavioristic, and pathomorphology studies. Serum and urine reactive oxygen species (ROS) production levels and fecal gut microbiota compositions were detected, and the relationship between them was analyzed by Spearman's correlation.

RESULTS

Quercetin not only reversed the decreased mechanical withdraw thresholds and intraepidermal nerve fiber densities in DPN rats, but also improved neurological morphology of sciatic nerves, accompanied with up-regulated percentage of paranodes at paranodal junctions, and down-regulated amyloid precursor protein and ionized calcium-binding adaptor molecule 1 in DPN rats. More importantly, quercetin rescued gut dysbiosis in DPN rats by decreasing four potential pathogenic species and enriching two prebiotic species associated with DPN phenotypes and ROS production levels.

CONCLUSIONS

Quercetin exerts neuroprotective effect and modulates gut microbiota associated with DPN phenotypes and ROS production levels in STZ-induced DPN rats, suggesting the therapeutic application of quercetin for DPN prevention and treatment.

A Metabolic Insight Into the Neuroprotective Effect of Jin-Mai-Tong (JMT) Decoction on Diabetic Rats With Peripheral Neuropathy Using Untargeted Metabolomics Strategy

Jin-Mai-Tong (JMT) decoction is a traditional Chinese compound prescription for treating diabetic peripheral neuropathy (DPN). The aim of this study is to investigate the neuroprotective effect of JMT decoction on diabetic rats with peripheral neuropathy and to elucidate the potential mechanism based on a metabolomics approach. Sprague-Dawley (SD) rats were randomly divided into four groups: control group, Streptozotocin (STZ) induced model group, JMT low dose (JMT-L) treated group and JMT high dose (JMT-H) treated group. After 12 weeks of treatment, behavioral changes, small fiber loss, and histopathological damages of sciatic nerves were estimated. Serum samples were collected for untargeted metabolomics analysis based on UPLC/QTOF-MS and multivariate statistics. As a result, JMT treatment at two dosages (13.9 and 27.8 g/kg⋅d) evidently improved the mechanical pain threshold (P < 0.05), increased the intraepidermal nerve fiber density (IENFD) and subepidermal nerve fiber density (SNFD) (P < 0.05), and renovated the demyelination and axonal atrophy of sciatic nerves on DPN rats. Furthermore, metabolomics study revealed that the serum metabolic profiles altered significantly among the control group and the STZ-induced model group. A total of 21 metabolites were identified as potential biomarkers related to the therapeutic effect of JMT decoction. Among them, 16 biomarkers were found in both JMT-H and JMT-L treated groups, while the five others were specific to JMT-H group. These metabolites mainly involved in lipid metabolism, tricarboxylic acid (TCA) cycle, amino acid metabolism, and so on. Besides, correlation analysis indicated that both mechanical pain threshold and distal nerve fiber density were negatively correlated with the serum levels of metabolites from lipid metabolism and TCA cycle. In conclusion, the results demonstrated that JMT decoction has an obvious protective effect against DPN, which could be mediated via ameliorating the metabolic disorders in diabetic rats with peripheral neuropathy.

Factors associated with diabetic polyneuropathy-related sensory symptoms and signs in patients with polyneuropathy: A cross-sectional Japanese study (JDDM 52) using a non-linear model

AIMS/INTRODUCTION

To assess the prevalence of diabetic polyneuropathy (DPN)-related sensory symptoms/signs and associated factors in patients with polyneuropathy, considering non-linear effects for numerical variables.

MATERIALS AND METHODS

A cross-sectional survey of patients with type 2 diabetes mellitus from 17 primary care clinics across Japan was carried out. DPN and DPN-related sensory symptoms/signs were diagnosed according to the Diabetic Neuropathy Study Group in Japan criteria.

RESULTS

Of the 9,914 patients with type 2 diabetes mellitus in this study, 2,745 had DPN and 1,689 had DPN-related sensory symptoms/signs (61.5% of patients with DPN). There were significant correlations between DPN-related sensory symptoms/signs and smoking status (odds ratio 2.04 for current and 1.64 for former; P < 0.001 and P = 0.002, respectively), sex (odds ratio 0.56 for male/female; P < 0.001) and alcohol consumption (odds ratio 2.02 for former/never; P = 0.004). Based on the non-linear logistic regression model, significant correlations were observed between the presence of DPN-related sensory symptoms/signs and higher systolic blood pressure (SBP), longer diabetes duration, and decreasing age. The logarithm of odds for SBP increased until reaching approximately 130 mmHg, then it plateaued.

CONCLUSIONS

Some modifiable factors assessed in the large survey database might be associated with DPN-related sensory symptoms/signs, namely smoking, alcohol consumption and SBP. Maintaining SBP <130 mmHg was associated with lower odds of DPN-related sensory symptoms/signs in patients with DPN.

Jinmaitong, a Traditional Chinese Compound Prescription, Ameliorates the Streptozocin-Induced Diabetic Peripheral Neuropathy Rats by Increasing Sciatic Nerve IGF-1 and IGF-1R Expression

Jinmaitong (JMT) is a Traditional Chinese Compound Prescription for the treatment of diabetic peripheral neuropathy (DPN). This study aims to investigate the effect of JMT on the insulin-like growth factor 1 (IGF-1) and the insulin like growth factor 1 receptor (IGF-1R) expression in sciatic nerves of diabetic rats. Firstly, the chemical profile of JMT was characterized by UPLC/Q-TOF-MS analysis. A total of 72 compounds were putatively identified. Secondly, streptozotocin (STZ)-induced diabetic rats were treated with neurotropin (NTP, 2.67 NU/kg/day) or JMT at low-dosage (0.4375 g/kg/day), medium-dosage (0.875 g/kg/day), and high-dosage (1.75 g/kg/day) for continuous 16 weeks. Blood glucose and body weight were detected every 4 weeks during the experiment. The mechanical pain and morphological change on sciatic nerves were detected by pain measurement instrument and microscopy. The IGF-1 level in serum and tissues were measured though ELISA and immunohistochemistry. The mRNA and protein expressions of IGF-1, IGF-1R, peripheral myelin protein zero (P0), and peripheral myelin protein 22 (PMP22) in the tissues were measured by qRT-PCR and western blot. As a result, JMT had no significant effect on body weight, but reduced the fasting blood glucose levels of diabetic rats. Besides, the pathological morphology, mechanical pain thresholds, serum level and tissue expression of IGF-1, mRNA, and protein levels of IGF-1R, P0, and PMP22 were significantly improved in JMT group at middle dosage. In conclusion, JMT could ameliorate the behavioristics and morphology changes in DPN rats by promoting IGF-1 and IGF-1R gene and protein expressions in sciatic nerves, as well as regulating the peripheral nerve remyelination genes P0 and PMP22 expressions, which provides scientific evidence for the clinical application of JMT in DPN patients.

Jinmaitong Ameliorates Diabetic Peripheral Neuropathy Through Suppressing TXNIP/NLRP3 Inflammasome Activation In The Streptozotocin-Induced Diabetic Rat Model

BACKGROUND

Jinmaitong (JMT) has been used to prevent and treat diabetic peripheral neuropathy (DPN) for decades. The present study aimed to elucidate the effects of JMT on thioredoxin-interacting protein (TXNIP) and Nod-like receptor protein 3 (NLRP3) inflammasome activation in the streptozotocin (STZ)-induced rat model.

METHODS

The diabetic rat model was induced by a single intraperitoneal injection of 55 mg/kg STZ. The rats were divided into 3 groups (n = 8-10 per group): diabetic control, JMT (0.876 g/kg/d), and alpha-lipoic acid (ALA; 100 mg/kg/d). Body weight and blood glucose levels were monitored every 4 weeks for 12 weeks. Mechanical allodynia and myelin sheath injury of sciatic nerves (SNs) were assessed using the mechanical withdrawal threshold (MWT) test and Luxol fast blue staining. Serum T-superoxide dismutase (T-SOD), malondialdehyde (MDA), and catalase (CAT) levels were measured using commercially available kits. TXNIP/NLRP3 inflammasome proteins, including TXNIP, NLRP3, pro-caspase-1, and cleaved -caspase-1, and the downstream protein interleukin (IL)-1β, were measured using immunohistochemistry and Western blot. Gasdermin D (GSDMDC1) protein expression was analyzed using Western blot, and serum IL-1β and IL-18 levels were detected using ELISA.

RESULTS

JMT did not significantly affect body weight or level of fasting blood glucose but improved mechanical allodynia and myelin sheath injury of SNs at 12 weeks following treatment. Moreover, JMT increased serum levels of the anti-oxidative enzymes CAT and T-SOD, and decreased MDA levels. Both JMT and ALA decreased expression of TXNIP, NLRP3, and cleaved-caspase-1 protein. JMT and ALA also decreased IL-1β, IL-18, and GSDMDC1 protein expression.

CONCLUSION

The current study demonstrated that TXNIP/NLRP3 inflammasome activation is involved in the molecular mechanisms underlying JMT's protective effects in the STZ-induced diabetic rat model, which provides novel evidence to support the future clinical use of JMT.

Fibroblast growth factor 21 facilitates peripheral nerve regeneration through suppressing oxidative damage and autophagic cell death

Seeking for effective drugs which are beneficial to facilitating axonal regrowth and elongation after peripheral nerve injury (PNI) has gained extensive attention. Fibroblast growth factor 21 (FGF21) is a metabolic factor that regulates blood glucose and lipid homeostasis. However, there is little concern for the potential protective effect of FGF21 on nerve regeneration after PNI and revealing related molecular mechanisms. Here, we firstly found that exogenous FGF21 administration remarkably promoted functional and morphologic recovery in a rat model of sciatic crush injury, manifesting as persistently improved motor and sensory function, enhanced axonal remyelination and regrowth and accelerated Schwann cells (SCs) proliferation. Furthermore, local FGF21 application attenuated the excessive activation of oxidative stress, which was accompanied with the activation of nuclear factor erythroid‐2‐related factor 2 (Nrf‐2) transcription and extracellular regulated protein kinases (ERK) phosphorylation. We detected FGF21 also suppressed autophagic cell death in SCs. Additionally, treatment with the ERK inhibitor U0126 or autophagy inhibitor 3‐MA partially abolishes anti‐oxidant effect and reduces SCs death. Taken together, these results indicated that the role of FGF21 in remyelination and nerve regeneration after PNI was probably related to inhibit the excessive activation of ERK/Nrf‐2 signalling‐regulated oxidative stress and autophagy‐induced cell death. Overall, our work suggests that FGF21 administration may provide a new therapy for PNI.

Strategies and Research Progress of Chinese Medicine in Prevention and Treatment of Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) seriously affects the quality of life in patients with type 2 diabetes mellitus. This paper reviews the role of Chinese medicine in the main treatment goal of DPN, including protecting pancreatic β-cells, in the use of antioxidation therapy to delay disease progression, and in the endpoint of neural repair and regeneration. We propose that protecting the body from injury caused by high glucose and oxidative stress, and promoting repair and regeneration of nerves should be the research direction for the prevention and treatment of DPN.

Inhibition of the TRPM2 and TRPV1 Channels through Hypericum perforatum in Sciatic Nerve Injury-induced Rats Demonstrates their Key Role in Apoptosis and Mitochondrial Oxidative Stress of Sciatic Nerve and Dorsal Root Ganglion

Sciatic nerve injury (SNI) results in neuropathic pain, which is characterized by the excessive Ca²⁺ entry, reactive oxygen species (ROS) and apoptosis processes although involvement of antioxidant Hypericum perforatum (HP) through TRPM2 and TRPV1 activation has not been clarified on the processes in SNI-induced rat, yet. We investigated the protective property of HP on the processes in the sciatic nerve and dorsal root ganglion neuron (DRGN) of SNI-induced rats. The rats were divided into five groups as control, sham, sham+HP, SNI, and SNI+HP. The HP groups received 30 mg/kg HP for 4 weeks after SNI induction. TRPM2 and TRPV1 channels were activated in the neurons by ADP-ribose or cumene peroxide and capsaicin, respectively. The SNI-induced TRPM2 and TRPV1 currents and intracellular free Ca²⁺ and ROS concentrations were reduced by HP, N-(p-amylcinnamoyl) anthranilic acid (ACA), and capsazepine (CapZ). SNI-induced increase in apoptosis and mitochondrial depolarization in sciatic nerve and DRGN of SNI group were decreased by HP, ACA, and CapZ treatments. PARP-1, caspase 3 and 9 expressions in the sciatic nerve, DRGN, skin, and musculus piriformis of SNI group were also attenuated by HP treatment. In conclusion, increase of mitochondrial ROS, apoptosis, and Ca²⁺ entry through inhibition of TRPM2 and TRPV1 in the sciatic nerve and DRGN neurons were decreased by HP treatment. The results may be relevant to the etiology and treatment of SNI by HP.