Effect of honey and insulin treatment on oxidative stress and nerve conduction in an experimental model of diabetic neuropathy Wistar rats

The analgesic effects of insulin and its disorders in streptozotocin-induced short-term diabetes

Evidence suggests that insulin resistance plays an important role in developing diabetes complications. The association between insulin resistance and pain perception is less well understood. This study aimed to investigate the effects of peripheral insulin deficiency on pain pathways in the brain. Diabetes was induced in 60 male rats with streptozotocin (STZ). Insulin was injected into the left ventricle of the brain by intracerebroventricular (ICV) injection, then pain was induced by subcutaneous injection of 2.5% formalin. Samples were collected at 4 weeks after STZ injection. Dopamine (DA), serotonin, reactive oxygen species (ROS), and mitochondrial glutathione (mGSH) were measured by ELISA, and gene factors were assessed by RT-qPCR. In diabetic rats, the levels of DA, serotonin, and mGSH decreased in the nuclei of the thalamus, raphe magnus, and periaqueductal gray, and the levels of ROS increased. In addition, the levels of expression of the neuron-specific enolase and receptor for advanced glycation end genes increased, but the expression of glial fibrillary acidic protein expression was reduced. These results support the findings that insulin has an analgesic effect in non-diabetic rats, as demonstrated by the formalin test. ICV injection of insulin reduces pain sensation, but this was not observed in diabetic rats, which may be due to cell damage ameliorated by insulin.

Diabetic peripheral neuropathy: pathogenetic mechanisms and treatment

Diabetic peripheral neuropathy (DPN) refers to the development of peripheral nerve dysfunction in patients with diabetes when other causes are excluded. Diabetic distal symmetric polyneuropathy (DSPN) is the most representative form of DPN. As one of the most common complications of diabetes, its prevalence increases with the duration of diabetes. 10-15% of newly diagnosed T2DM patients have DSPN, and the prevalence can exceed 50% in patients with diabetes for more than 10 years. Bilateral limb pain, numbness, and paresthesia are the most common clinical manifestations in patients with DPN, and in severe cases, foot ulcers can occur, even leading to amputation. The etiology and pathogenesis of diabetic neuropathy are not yet completely clarified, but hyperglycemia, disorders of lipid metabolism, and abnormalities in insulin signaling pathways are currently considered to be the initiating factors for a range of pathophysiological changes in DPN. In the presence of abnormal metabolic factors, the normal structure and function of the entire peripheral nervous system are disrupted, including myelinated and unmyelinated nerve axons, perikaryon, neurovascular, and glial cells. In addition, abnormalities in the insulin signaling pathway will inhibit neural axon repair and promote apoptosis of damaged cells. Here, we will discuss recent advances in the study of DPN mechanisms, including oxidative stress pathways, mechanisms of microvascular damage, mechanisms of damage to insulin receptor signaling pathways, and other potential mechanisms associated with neuroinflammation, mitochondrial dysfunction, and cellular oxidative damage. Identifying the contributions from each pathway to neuropathy and the associations between them may help us to further explore more targeted screening and treatment interventions.

The Antinociceptive Effects of Combined Treatment With Atorvastatin and Vitamin C in the Chronic Constriction Injury Model of Rats

Introduction

Neuropathic pain (NP) is caused by damage to the somatosensory system. Nerve damage often results in chronic pain states, including hyperalgesia and allodynia. This study aims to evaluate the anti-nociceptive effects of atorvastatin, vitamin C, and their combination on various laboratory tests in an experimental model NP in rats.

Methods

To assess the analgesic effects of atorvastatin (5 and 10 mg/kg), vitamin C (500 mg/kg), and their co-administration on chronic constriction injury (CCI) was induced in rats. Behavioral tests, motor nerve conduction velocity (MNCV), pro-inflammatory cytokines, and oxidative markers were measured. Furthermore, histopathological examination was performed.

Results

In the present study, it was found that the CCI model can significantly cause hyperalgesia and allodynia on the 21st postoperative day. It was found that the co-administration of vitamin C and atorvastatin has attenuating effects on allodynia and hyperalgesia. Co-administration of vitamin C and atorvastatin also improved MNCV. In the treatment groups, the inflammatory reactions and oxidative markers decreased. Moreover, the co-administration of atorvastatin and vitamin C decreased the perineural inflammation around the sciatic nerve.

Conclusion

The results of this study showed that vitamin C potentiates the analgesic effects of atorvastatin in this model of experimental pain, and simultaneous consumption of these medications may be considered as effective therapeutics for NP. The protective properties of atorvastatin, and vitamin C, and their combination on the NP that were assessed can be regarded as a novelty for this study.

Highlights

The co-administration of atorvastatin and vitamin C significantly decreases inflammatory cytokines.The co-administration of atorvastatin and vitamin C significantly decreases stress oxidant markers.The co-administration of atorvastatin and vitamin C significantly attenuated nociceptive effects.

Plain Language Summary

Nerve damage causes the deposition of inflammatory factors and or oxidative stress at the site of injury, which in turn activates glial cells that are involved in increasing the inflammatory process by producing and releasing pro-inflammatory agents and oxidative stress. Among statins, atorvastatin is a drug to reduce inflammation, and its effectiveness has been recorded as an antioxidant effect. Vitamin C is known as a neuroprotective agent. Ascorbate inhibits the production of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in monocytes in high doses (20 mM) by inhibiting them. The rats were randomly divided into 7 groups of 10 animals as follows: 1: Sham-operated, 2: Chronic constriction injury (CCI), 3: CCI+vitamin C (500 mg/kg), 4: CCI+atorvastatin (5 mg/kg), 5: CCI+atorvastatin (10 mg/kg), 6: CCI+vitamin C (500 mg/kg)+atorvastatin (5 mg/kg), and 7: CCI+vitamin C (500 mg/kg)+atorvastatin (10 mg/kg). The results of the present study indicated that the anti-inflammatory, antioxidant, and neuroprotective properties of vitamin C and atorvastatin improved the effects of CCI in an empirical neuropathic in rats. Moreover, it was shown that the associated treatment with vitamin C and atorvastatin can reduce inflammatory factors, such as TNF-α and IL-6, and oxidative markers, such as glutathione peroxidase (GPx), superoxide dismutase (SOD), and malonaldehyde (MDA), while the nerve conduction velocity enhanced and inflammation decreased in histology studies in CCI rats.

Repeat intramuscular transplantation of human dental pulp stromal cells is more effective in sustaining Schwann cell survival and myelination for functional recovery after onset of diabetic neuropathy

BACKGROUND AIMS

Mesenchymal stromal cell (MSC) therapy for diabetic neuropathy (DN) has been extensively researched in vitro and in pre-clinical studies; however, the clinical scenario thus far has been disappointing. Temporary recovery, a common feature of these studies, indicates that either the retention of transplanted cells deteriorates with time or recovery of supportive endogenous cells, such as bone marrow-derived MSCs (BM-MSCs), does not occur, requiring further replenishment. In DN, BM-MSCs are recognized mediators of Schwann cell regeneration, and we have earlier shown that they suffer impairment in the pre-neuropathy stage. In this study, we attempted to further elucidate the mechanisms of functional recovery by focusing on changes occurring at the cellular level in the sciatic nerve, in conjunction with the biodistribution and movement patterns of the transplanted cells, to define the interval between doses.

METHOD & RESULTS

We found that two doses of 1 × 106 dental pulp stromal cells (DPSCs) transplanted intramuscularly at an interval of 4 weeks effectively improved nerve conduction velocity (NCV) and restored motor coordination through improving sciatic nerve architecture, Schwann cell survival and myelination. Despite very minimal recovery of endogenous BM-MSCs, a temporary restoration of NCV and motor function was achieved with the first dose of DPSC transplantation. However, this did not persist, and a repeat dose was needed to consolidate functional improvement and rehabilitate the sciatic nerve architecture.

CONCLUSION

Thus, repeat intramuscular transplantation of DPSCs is more effective for maintenance of Schwann cell survival and myelination for functional recovery after onset of DN.

Nox4 as a novel therapeutic target for diabetic vascular complications

Diabetic vascular complications can affect both microvascular and macrovascular. Diabetic microvascular complications, such as diabetic nephropathy, diabetic retinopathy, diabetic neuropathy, and diabetic cardiomyopathy, are believed to be caused by oxidative stress. The Nox family of NADPH oxidases is a significant source of reactive oxygen species and plays a crucial role in regulating redox signaling, particularly in response to high glucose and diabetes mellitus. This review aims to provide an overview of the current knowledge about the role of Nox4 and its regulatory mechanisms in diabetic microangiopathies. Especially, the latest novel advances in the upregulation of Nox4 that aggravate various cell types within diabetic kidney disease will be highlighted. Interestingly, this review also presents the mechanisms by which Nox4 regulates diabetic microangiopathy from novel perspectives such as epigenetics. Besides, we emphasize Nox4 as a therapeutic target for treating microvascular complications of diabetes and summarize drugs, inhibitors, and dietary components targeting Nox4 as important therapeutic measures in preventing and treating diabetic microangiopathy. Additionally, this review also sums up the evidence related to Nox4 and diabetic macroangiopathy.

Melatonin ameliorates serobiochemical alterations and restores the cardio-nephro diabetic vascular and cellular alterations in streptozotocin-induced diabetic rats

Melatonin possesses a wide range of pharmacological activities, including antidiabetic properties. Diabetes mellitus (DM) induces several physiopathological changes in body organs, which could be observed lately after systemic failure. In the current study, we aimed to investigate the serobiochemical changes and the histopathological picture in the diabetic heart and the kidney early before chronic complications and highlight the association between hyperglycemia, glomerular alterations, and cardiovascular changes. In addition, the role of melatonin in the treatment of cardio-nephro diabetic vascular and cellular adverse changes in streptozotocin-induced diabetic rats was also studied. A total of 40 mature Wistar albino rats were distributed into five groups; (1) control untreated rats, (2) diabetic mellitus untreated (DM) rats, in which DM was induced by the injection of streptozotocin (STZ), (3) control melatonin-treated (MLT), (4) melatonin-treated diabetic (DM + MLT) rats, in which melatonin was injected (10 mg/kg/day, i.p.) for 4 weeks, and (5) insulin-treated diabetic (DM + INS) rats. The serum biochemical analysis of diabetic STZ rats showed a significant (P < 0.05) increase in the concentrations of blood glucose, total oxidative capacity (TOC), CK-MB, endothelin-1, myoglobin, H-FABP, ALT, AST, urea, and creatinine as compared to control rats. In contrast, there was a significant (P < 0.05) decrease in serum concentration of insulin, total antioxidative capacity (TAC), total nitric oxide (TNO), and total protein level in DM rats vs. the control rats. Significant improvement in the serobiochemical parameters was noticed in both (DM + MLT) and (DM + INS) groups as compared with (DM) rats. The histological examination of the DM group revealed a disorder of myofibers, cardiomyocyte nuclei, and an increase in connective tissue deposits in between cardiac tissues. Severe congestion and dilation of blood capillaries between cardiac muscle fibers were also observed. The nephropathic changes in DM rats revealed various deteriorations in glomeruli and renal tubular cells of the same group. In addition, vascular alterations in the arcuate artery at the corticomedullary junction and interstitial congestion take place. Melatonin administration repaired all these histopathological alterations to near-control levels. The study concluded that melatonin could be an effective therapeutic molecule for restoring serobiochemical and tissue histopathological alterations during diabetes mellitus.

The role of dietary antioxidants in type 2 diabetes and neurodegenerative disorders: An assessment of the benefit profile

Healthy diet is vital to cellular health. The human body succumbs to numerous diseases which afflict severe economic and psychological burdens on the patient and family. Oxidative stress is a possible crucial regulator of various pathologies, including type 2 diabetes and neurodegenerative diseases. It generates reactive oxygen species (ROS) that trigger the dysregulation of essential cellular functions, ultimately affecting cellular health and homeostasis. However, lower levels of ROS can be advantageous and are implicated in a variety of signaling pathways. Due to this dichotomy, the terms oxidative "eustress," which refers to a good oxidative event, and "distress," which can be hazardous, have developed. ROS affects multiple signaling pathways, leading to compromised insulin secretion, insulin resistance, and β-cell dysfunction in diabetes. ROS is also associated with increased mitochondrial dysfunction and neuroinflammation, aggravating neurodegenerative conditions in the body, particularly with age. Treatment includes drugs/therapies often associated with dependence, side effects including non-selectivity, and possible toxicity, particularly in the long run. It is imperative to explore alternative medicines as an adjunct therapy, utilizing natural remedies/resources to avoid all the possible harms. Antioxidants are vital components of our body that fight disease by reducing oxidative stress or nullifying the excess toxic free radicals produced under various pathological conditions. In this review, we focus on the antioxidant effects of components of dietary foods such as tea, coffee, wine, oils, and honey and the role and mechanism of action of these antioxidants in alleviating type 2 diabetes and neurodegenerative disorders. We aim to provide information about possible alternatives to drug treatments used alone or combined to reduce drug intake and encourage the consumption of natural ingredients at doses adequate to promote health and combat pathologies while reducing unwanted risks and side effects.

Association Between Serum Albumin Levels and Diabetic Peripheral Neuropathy Among Patients with Type 2 Diabetes: Effect Modification of Body Mass Index

BACKGROUND

The role of serum albumin in the risk of diabetic peripheral neuropathy (DPN) remains unclear. This study aimed to explore the relationship between serum albumin level and DPN, and to examine any possible effect modifiers among patients with type 2 diabetes mellitus.

METHODS

This cross-sectional study was conducted in Jiangxi, China, from May 2012 to December 2014. Serum albumin levels were determined in 523 subjects, and the association between serum albumin level and DPN was evaluated using linear regression models (odds ratio [OR] and corresponding 95% confidence interval [CI]).

RESULTS

There was a significant inverse association between serum albumin level (per 1 g/L increment, OR 0.95 [95% CI 0.92-0.98]) and the risk of DPN. Accordingly, when serum albumin was assessed as quartiles, a significantly lower risk of DPN was found in participants in quartile 4 (OR 0.49 [95% CI 0.25-0.95]), compared with those in quartile 1. Consistently, higher albumin levels (≥35 g/L) were associated with decreased odds for DPN (OR 0.36 [95% CI 0.17-0.74]) compared with lower levels. Furthermore, the albumin-DPN association was significantly stronger in patients with a relatively high body mass index (BMI; ≥24 kg/m²; OR 0.91 [95% CI 0.85-0.98]) than in those with a low BMI (<24 kg/m²; OR 0.99 [95% CI 0.94-1.04]; P for interaction = 0.042).

CONCLUSION

These data suggest that serum albumin level could be a novel risk factor for DPN among patients with type 2 diabetes and relatively high BMI (>24 kg/m²).