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

Advances of traditional Chinese medicine preclinical mechanisms and clinical studies on diabetic peripheral neuropathy

CONTEXT

Diabetic peripheral neuropathy (DPN) results in an enormous burden and reduces the quality of life for patients. Considering there is no specific drug for the management of DPN, traditional Chinese medicine (TCM) has increasingly drawn attention of clinicians and researchers around the world due to its characteristics of multiple targets, active components, and exemplary safety.

OBJECTIVE

To summarize the current status of TCM in the treatment of DPN and provide directions for novel drug development, the clinical effects and potential mechanisms of TCM used in treating DPN were comprehensively reviewed.

METHODS

Existing evidence on TCM interventions for DPN was screened from databases such as PubMed, the Cochrane Neuromuscular Disease Group Specialized Register (CENTRAL), and the Chinese National Knowledge Infrastructure Database (CNKI). The focus was on summarizing and analyzing representative preclinical and clinical TCM studies published before 2023.

RESULTS

This review identified the ameliorative effects of about 22 single herbal extracts, more than 30 herbal compound prescriptions, and four Chinese patent medicines on DPN in preclinical and clinical research. The latest advances in the mechanism highlight that TCM exerts its beneficial effects on DPN by inhibiting inflammation, oxidative stress and apoptosis, endoplasmic reticulum stress and improving mitochondrial function.

CONCLUSIONS

TCM has shown the power latent capacity in treating DPN. It is proposed that more large-scale and multi-center randomized controlled clinical trials and fundamental experiments should be conducted to further verify these findings.

Jinmaitong alleviates diabetic neuropathic pain by inhibiting JAK2/STAT3 signaling in microglia of diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Jinmaitong (JMT) is a prescription of Traditional Chinese Medicine that is composed of 12 crude drugs. It has been used in the treatment of diabetic neuropathic pain (DNP) for more than 30 years.

AIM OF STUDY

Microglia are thought to play an important role in neuropathic pain. This study aimed to evaluate the protective effect of JMT against DNP and to investigate the underlying mechanisms in which the microglia and JAK2/STAT3 signaling pathway were mainly involved.

MATERIALS AND METHODS

The chemical composition of JMT was analyzed using liquid chromatography tandem mass spectrometry. The diabetes model was constructed using 11 to 12-week-old male Zucker diabetic fatty (ZDF) rat (fa/fa). The model rats were divided into 5 groups and were given JMT at three dosages (11.6, 23.2, and 46.4 g/kg, respectively, calculated as the crude drug materials), JAK inhibitor AG490 (positive drug, 10 μg/day), and placebo (deionized water), respectively, for eight weeks (n = 6). Meanwhile, Zucker lean controls (fa/+) were given a placebo (n = 6). Body weight was tested weekly and blood glucose was monitored every 2 weeks. The mechanical allodynia and heat hyperalgesia were assessed using mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) tests. After treatment, the microglia activation marker Iba-1, CD11B, CD68, neuroinflammatory mediators, and mediators of the JAK2/STAT3 signaling pathway were compared between different groups. The mRNA and protein levels of target genes were assessed by quantitative real-time PCR and Western Blot, respectively.

RESULTS

We found that JMT significantly inhibited the overactivation of microglia in spinal cords, and suppressed neuroinflammation of DNP model rats, thereby ameliorating neurological dysfunction and injuries. Furthermore, these effects of JMT could be attributed to the inhibition of the JAK2/STAT3 signaling pathway.

CONCLUSIONS

Our findings suggested that JMT effectively ameliorated DNP by modulating microglia activation via inhibition of the JAK2/STAT3 signaling pathway. The present study provided a basis for further research on the therapeutic strategies of DNP.

Pyroptosis in Diabetic Peripheral Neuropathy and its Therapeutic Regulation

Pyroptosis is a pro-inflammatory form of cell death resulting from the activation of gasdermins (GSDMs) pore-forming proteins and the release of several pro-inflammatory factors. However, inflammasomes are the intracellular protein complexes that cleave gasdermin D (GSDMD), leading to the formation of robust cell membrane pores and the initiation of pyroptosis. Inflammasome activation and gasdermin-mediated membrane pore formation are the important intrinsic processes in the classical pyroptotic signaling pathway. Overactivation of the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome triggers pyroptosis and amplifies inflammation. Current evidence suggests that the overactivation of inflammasomes and pyroptosis may further induce the progression of cancers, nerve injury, inflammatory disorders and metabolic dysfunctions. Current evidence also indicates that pyroptosis-dependent cell death accelerates the progression of diabetes and its frequent consequences including diabetic peripheral neuropathy (DPN). Pyroptosis-mediated inflammatory reaction further exacerbates DPN-mediated CNS injury. Accumulating evidence shows that several molecular signaling mechanisms trigger pyroptosis in insulin-producing cells, further leading to the development of DPN. Numerous studies have suggested that certain natural compounds or drugs may possess promising pharmacological properties by modulating inflammasomes and pyroptosis, thereby offering potential preventive and practical therapeutic approaches for the treatment and management of DPN. This review elaborates on the underlying molecular mechanisms of pyroptosis and explores possible therapeutic strategies for regulating pyroptosis-regulated cell death in the pharmacological treatment of DPN.

Modulating the Gut Microbiota and Metabolites with Traditional Chinese Medicines: An Emerging Therapy for Type 2 Diabetes Mellitus and Its Complications

Currently, an estimated 537 million individuals are affected by type 2 diabetes mellitus (T2DM), the occurrence of which is invariably associated with complications. Glucose-lowering therapy remains the main treatment for alleviating T2DM. However, conventional antidiabetic agents are fraught with numerous adverse effects, notably elevations in blood pressure and lipid levels. Recently, the use of traditional Chinese medicines (TCMs) and their constituents has emerged as a preferred management strategy aimed at curtailing the progression of diabetes and its associated complications with fewer adverse effects. Increasing evidence indicates that gut microbiome disturbances are involved in the development of T2DM and its complications. This regulation depends on various metabolites produced by gut microbes and their interactions with host organs. TCMs' interventions have demonstrated the ability to modulate the intestinal bacterial microbiota, thereby restoring host homeostasis and ameliorating metabolic disorders. This review delves into the alterations in the gut microbiota and metabolites in T2DM patients and how TCMs treatment regulates the gut microbiota, facilitating the management of T2DM and its complications. Additionally, we also discuss prospective avenues for research on natural products to advance diabetes therapy.

Research progress on the mechanism of TCM regulating intestinal microbiota in the treatment of DM mellitus

In recent years, with the improvement of people's living standards, the incidence of DM has increased year by year in China. DM is a common metabolic syndrome characterized by hyperglycemia caused by genetic, environmental and other factors. At the same time, long-term suffering from DM will also have an impact on the heart, blood vessels, eyes, kidneys and nerves, and associated serious diseases. The human body has a large and complex gut microbiota, which has a significant impact on the body's metabolism. Research shows that the occurrence and development of DM and its complications are closely related to intestinal microbiota. At present, western medicine generally treats DM with drugs. The hypoglycemic effect is fast and strong, but it can have a series of side effects on the human body. Compared with western medicine, Chinese medicine has its unique views and methods in treating DM. TCM can improve symptoms and treat complications by improving the imbalance of microbiota in patients with DM. Its characteristics of health, safety, and reliability are widely accepted by the general public. This article reviews the relationship between intestinal microbiota and DM, as well as the mechanism of TCM intervention in DM by regulating intestinal microbiota.

Targeted metabolomics reveals the aberrant energy status in diabetic peripheral neuropathy and the neuroprotective mechanism of traditional Chinese medicine JinMaiTong

Diabetic peripheral neuropathy (DPN) is a common and devastating complication of diabetes, for which effective therapies are currently lacking. Disturbed energy status plays a crucial role in DPN pathogenesis. However, the integrated profile of energy metabolism, especially the central carbohydrate metabolism, remains unclear in DPN. Here, we developed a metabolomics approach by targeting 56 metabolites using high-performance ion chromatography-tandem mass spectrometry (HPIC-MS/MS) to illustrate the integrative characteristics of central carbohydrate metabolism in patients with DPN and streptozotocin-induced DPN rats. Furthermore, JinMaiTong (JMT), a traditional Chinese medicine (TCM) formula, was found to be effective for DPN, improving the peripheral neurological function and alleviating the neuropathology of DPN rats even after demyelination and axonal degeneration. JMT ameliorated DPN by regulating the aberrant energy balance and mitochondrial functions, including excessive glycolysis restoration, tricarboxylic acid cycle improvement, and increased adenosine triphosphate (ATP) generation. Bioenergetic profile was aberrant in cultured rat Schwann cells under high-glucose conditions, which was remarkably corrected by JMT treatment. In-vivo and in-vitro studies revealed that these effects of JMT were mainly attributed to the activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK) and downstream peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α). Our results expand the therapeutic framework for DPN and suggest the integrative modulation of energy metabolism using TCMs, such as JMT, as an effective strategy for its treatment.

Tauroursodeoxycholic acid protects Schwann cells from high glucose-induced cytotoxicity by targeting NLRP3 to regulate cell migration and pyroptosis

Diabetic peripheral neuropathy (DPN) is the most prevalent complication of type 2 diabetes mellitus (T2DM), and it seriously affects the quality of life of patients. Tauroursodeoxycholic acid (TUDCA) is a bile acid that plays a protective role against various diseases. However, the function of TUDCA in DPN progression needs to be elucidated. Hence, this study clarified the action of TUDCA on DPN development and explored its mechanism of action. Fecal samples were collected from 50 patients with T2DM or DPN. Schwann cells induced by high levels were constructed to simulate an uncontrolled diabetic state. Cell viability and migration were measured using the CCK-8 and wound-healing assays, respectively. Reactive oxygen species and pyroptosis were detected using flow cytometry. Parabacteroides goldsteinii and Parabacteroides distasonis levels were decreased in the feces of patients with DPN. TUDCA enhanced the viability and migration ability of high glucose-stimulated Schwann cells. In addition, Schwann cell pyroptosis stimulated by high glucose levels was inhibited by TUDCA. Furthermore, the protective roles of TUDCA in cell viability, migration ability, and pyroptosis of Schwann cells stimulated by high glucose were suppressed by the overexpression of NLRP3. TUDCA enhanced cell viability and migration and suppressed pyroptosis in Schwann cells stimulated by high glucose levels by modulating NLRP3 expression. Thus, TUDCA may be a promising drug for DPN therapy.

Integrating plasma metabolomics and gut microbiome to reveal the mechanisms of Huangqi Guizhi Wuwu Decoction intervene diabetic peripheral neuropathy

ETHNOPHARMACOLOGICAL RELEVANCE

Huangqi Guizhi Wuwu Decoction (HGWD) is a classic traditional Chinese herbal formula from "Synopsis of Golden Chamber," which is used to treat blood stagnation and has been used for alleviating diabetic peripheral neuropathy (DPN) in the clinic. However, the mechanisms of HGWD intervention DPN are still to be discovered.

AIM OF THE STUDY

This study aims to explore the mechanism of HGWD intervention DPN by integrating plasma metabolomics and gut microbiome.

MATERIALS AND METHODS

BKS Cg-m+/+Leprdb/J (db/db) mice with DPN were at 16 weeks of age. The indices of DPN phenotypes in db/db mice, pathomorphology of the sciatic nerve, intraepithelial nerve fibers (IENF) of the foot pad, levels of blood lipids and oxidative stress, and inflammatory reaction were used to appraise the HGWD efficacy. Finally, the pharmacological mechanisms of HGWD intervening DPN were explored by metabolomics and 16S rRNA gene sequencing.

RESULTS

HGWD reversed DPN phenotypes in db/db mice, improved peripheral nerve structure, ameliorated the level of blood lipids and nerve growth factor in plasma, enhanced antioxidant capacity, and alleviated inflammatory responses. Plasma metabolomics disclosed that HGWD remarkably regulated the unusual levels of thirty-seven metabolites involved in sphingolipid metabolism, biosynthesis of unsaturated fatty acids, arachidonic acid metabolism, and amino acid biosynthesis pathways. The gut microbiome showed that nine bacteria were highly correlated with the efficacy of HGWD in DPN. Integrating analysis of microbiome and metabolomics demonstrated that the interaction of four bacteria with four metabolic pathways might be the significant mechanism of HGWD intervention in DPN.

CONCLUSIONS

The mediation of gut microbiota and plasma metabolism may be the potential mechanism of HGWD ameliorating DPN in db/db mice. The interaction of Lactobacillus, Alloprevotella, Bacteroides, and Desulfovibio with four metabolic pathways might be the critical mechanism for HGWD treating DPN.

Saikosaponin d (SSD) alleviates diabetic peripheral neuropathy by regulating the AQP1/RhoA/ROCK signaling in streptozotocin-induced diabetic rats

AIMS

Diabetic peripheral neuropathy (DPN) is one of the most important complications of diabetes with a poor prognosis. Saikosaponin d (SSD) is a triterpenoid saponin isolated from Radix Bupleuri that has multiple pharmacological activities. However, whether SSD affects DPN is unclarified.

METHODS

Sprague Dawley rats were treated with streptozotocin (STZ) and high-fat diet (HFD) to induce DPN, in the presence or absence of SSD, with or without transfection of lentivirus vectors carrying siRNA targeting aquaporin 1 (si-AQP1). The body weight, plasma glucose levels, mechanical and thermal hyperalgesia, and nerve conductive velocity (NCV) of rats were measured. Hematoxylin-Eosin staining was used for histopathological observation of sciatic nerves. RT-qPCR and western blotting were utilized for measuring expression levels of AQP1 and ras homolog family member A/Rho-associated protein kinase (RhoA/ROCK) signaling pathway-related markers in dorsal root ganglion (DRG) of rats.

RESULTS

SSD increased the body weight, decreased plasma glucose levels, attenuated mechanical and thermal hyperalgesia, enhanced NCV and reduced proinflammatory cytokine levels in DPN rats. AQP1 displayed a high level in DPN rats and SSD treatment repressed the expression of AQP1. SSD enhanced the protective effect of AQP1 knockdown on the pathological changes of DPN. AQP1 depletion suppressed the activation of RhoA/ROCK signaling pathway in DPN rats.

CONCLUSION

SSD alleviates STZ/HFD-induced DPN in rats by inhibiting the AQP1/RhoA/ROCK signaling pathway.

Neuroprotective Effect of Ponicidin Alleviating the Diabetic Cognitive Impairment: Regulation of Gut Microbiota

Cognitive impairment is a major complication of diabetes mellitus, which is caused by constitutive hyperglycaemia. Ponicidin is a diterpenoid isolated from a Chinese traditional herb (Rabdosia rubescens) and demonstrates the various pharmacological effects. The goal of this study was to scrutinise the neuroprotective effect of ponicidin against diabetic nephropathy (DN) induced by streptozotocin (STZ). Intraperitoneal administration of STZ (55 mg/kg) was used for the induction of diabetes and rats were received oral administration of ponicidin (5, 10 and 15 mg/kg) until 28 days. The body weight, food intake, water intake and blood glucose level were assessed at regular time interval. Plasma insulin level, antioxidant, inflammatory cytokines, apoptosis marker and faecal gut microbiota compositions were estimated. DN-induced group rats revealed the augmented glucose level, water intake, food intake and reduced body weight. Ponicidin significantly (P < 0.001) repressed the glucose level and water food intake and improved the body weight and plasma insulin. Ponicidin significantly (P < 0.001) repressed the malonaldehyde (MDA) level and boosted the level of glutathione (GSH), glutathione reductase (GR) and superoxide dismutase (SOD) in the brain and serum level. Ponicidin significantly (P < 0.001) repressed the level of interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6) and enhanced the level of interleukin-4 (IL-4), interleukin-10 (IL-10) in the brain and serum level. DN group rats exhibited the enhanced relative abundance of Firmicutes, along with enhancing the Firmicutes/Bacteroidetes ratio and repressing the Bacteroidetes relative abundance. Ponicidin effectually restored the relative abundance of Allobaculum, Lactobacillus and Ruminococcus genera. Our findings clearly demonstrated that ponicidin has a neuroprotective effect against diabetic cognitive impairment through modulating the gut microbiome.

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.

Interactions between NSAIDs, opioids and the gut microbiota - Future perspectives in the management of inflammation and pain

The composition of intestinal microbiota is influenced by a number of factors, including medications, which may have a substantial impact on host physiology. Nonsteroidal anti-inflammatory drugs (NSAIDs) and opioid analgesics are among those widely used medications that have been shown to alter microbiota composition in both animals and humans. Although much effort has been devoted to identify microbiota signatures associated with these medications, much less is known about the underlying mechanisms. Mucosal inflammation, changes in intestinal motility, luminal pH and bile acid metabolism, or direct drug-induced inhibitory effect on bacterial growth are all potential contributors to NSAID- and opioid-induced dysbiosis, however, only a few studies have addressed directly these issues. In addition, there is a notable overlap between the microbiota signatures of these drugs and certain diseases in which they are used, such as spondyloarthritis (SpA), rheumatoid arthritis (RA) and neuropathic pain associated with type 2 diabetes (T2D). The aims of the present review are threefold. First, we aim to provide a comprehensive up-to-date summary on the bacterial alterations caused by NSAIDs and opioids. Second, we critically review the available data on the possible underlying mechanisms of dysbiosis. Third, we review the current knowledge on gut dysbiosis associated with SpA, RA and neuropathic pain in T2D, and highlight the similarities between them and those caused by NSAIDs and opioids. We posit that drug-induced dysbiosis may contribute to the persistence of these diseases, and may potentially limit the therapeutic effect of these medications by long-term use. In this context, we will review the available literature data on the effect of probiotic supplementation and fecal microbiota transplantation on the therapeutic efficacy of NSAIDs and opioids in these diseases.

Lidocaine Ameliorates Diabetic Peripheral Neuropathy in Streptozotocin-Induced Diabetic Rats through Modulating the c-Jun Signaling Pathway

As one of the common complications of diabetes mellitus (DM), Diabetic Peripheral Neuropathy (DPN) threatens human lives seriously. Emerging evidences have confirmed the protective effects of lidocaine on DPN. However, the possible role and underlying mechanisms of lidocaine in DPN have not been clarified. In this study, the potential role of lidocaine in DPN is explored, and the possible mechanisms are investigated. The rat DPN model is constructed through administration of streptozotocin (STZ, 60 mg/kg). All rats are randomly divided into four groups, including the control group, DPN group, lidocaine (3.78 mg/time) group, and lidocaine combined with the SP600125 (15 mg/kg) group. Mechanical threshold, thermal latency, and blood glucose of rats before and after treatment are detected, and Nerve Conduction Velocity (NCV) is assessed. Moreover, qRT-PCR and western blot assays are carried out to determine the expressions of the c-Jun signaling pathway. The experimental results demonstrate that lidocaine remarkably downregulates the mRNA and protein expressions of the c-Jun signaling pathway in serum and DRGs induced with DPN. Besides, lidocaine combined with SP600125 can obtain better effects than lidocaine alone. It is clearly evident that lidocaine has a certain therapeutic effect on DPN.

Analgesic and neuroprotective effects of Baimai Ointment on diabetic peripheral neuropathy

ETHNOPHARMACOLOGY RELEVANCE

Baimai (BM) ointment, a traditional Tibetan medicine, has been widely used to treat "white vein" disease, paralysis, hemiplegia and claudication caused by trauma, because of its great effects on muscle stretching and collateral activation. As one of the most terrible complications in diabetes patients, diabetes peripheral neuropathy (DPN) is mainly manifested as abnormal pain or numbness in extremities. However, whether BM ointment is a potential drug for DPN treatment is unclear.

AIMS OF THE STUDY

The aim of this study was to investigate the therapeutic effects of BM on DPN in a high-fat diet/low-dose of streptozotocin induced type 2 diabetes rat model and explore underlying mechanisms.

METHODS

The chemical components of BM were determined by high performance liquid chromatography (HPLC), and the possible targets and related pathways candidates involved in the effects of BM on DPN were predicted using network pharmacology methods. Next, the effects of different doses (1.5, 3.0 and 6.0 g/kg) of BM on physiological changes, pain behaviors, motor nerve conduction velocity (MNCV) in DPN rats were assessed and compared with placebo- and mecobalamine (Meco)-treated DPN controls. Then, the effects of BM on the expression of pain associated genes as well as the phosphorylation of PI3K/AKT and MAPKs pathways in DRG of DPN rats were examined.

RESULTS

Through HPLC analysis, curcumin was identified as one of the primary contents of BM. The information from network pharmacology indicated a series of target candidates for BM including IL6, IL10, TNF, CCL2, CXCL12, EGF, VEGFA, BDNF, TGFβ1 and TNF, as well as PI3K-AKT and MAPK signaling pathways. Topical treatment of BM significantly improved the hypersensitivity of mechanical and thermal pain, MNCV and the morphological changes and demyelination of sciatic nerve fibers, without affecting the body weight, serum metabolism or blood glucose. The up-regulated levels of neuropeptides Cgrp, Sst, Sp and chemokines Ccl2 and Ccl3 along with the abnormal expression of p-P38, p-ERK and p-AKT in the DRG of DPN rats were alleviated by BM application.

CONCLUSION

BM ointment has great activities in relieving pain hypersensitivity, neuroprotecting peripheral nerves damage caused by DPN, which may be related to the inhibition of related neuropeptide (Cgrp, Sst, Sp) and chemokine (Ccl2, Ccl3) expression and the regulation of PI3K/AKT and MAPKs signaling pathways in DRG.

Gut Microbiota: An Important Player in Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is one of the common metabolic diseases in the world. Due to the rise in morbidity and mortality, it has become a global health problem. To date, T2DM still cannot be cured, and its intervention measures mainly focus on glucose control as well as the prevention and treatment of related complications. Interestingly, the gut microbiota plays an important role in the development of metabolic diseases, especially T2DM. In this review, we introduce the characteristics of the gut microbiota in T2DM population, T2DM animal models, and diabetic complications. In addition, we describe the molecular mechanisms linking host and the gut microbiota in T2DM, including the host molecules that induce gut microbiota dysbiosis, immune and inflammatory responses, and gut microbial metabolites involved in pathogenesis. These findings suggest that we can treat T2DM and its complications by remodeling the gut microbiota through interventions such as drugs, probiotics, prebiotics, fecal microbiota transplantation (FMT) and diets.

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.