Diabetic neuropathy and oxidative stress

Peripheral Neuropathy Associated with Higher Mortality in Population with Chronic Kidney Disease: National Health and Nutrition Examination Surveys

Introduction

Peripheral neuropathy (PN), one of the commonest neurological complications of chronic kidney disease (CKD), was associated with physical limitation. Studies showed that a decrease in physical capability in patients with CKD is related with an increased risk of mortality. The objective of our research was to directly explore the relationship between PN and risk of mortality in patients with CKD.

Method

1,836 participants with CKD and 6,036 participants without CKD, which were classified by PN based on monofilament examination in National Health and Nutrition Examination Survey (NHANES), were collected from the 1999 to 2004 National Health and Nutrition Examination Surveys. Multivariable Cox proportional hazard models were conducted to assess the relationships of PN and deaths in patients with CKD and non-CKD.

Results

During 14 years of a median follow-up from 1999 to 2015 and 2004 to 2015, 1,072 (58.4%) and 1,389 (23.0%) deaths were recorded in participants with CKD and without CKD, respectively. PN was related with increased all-cause mortality even after adjusting possible confounding factors in population with CKD (hazard ratio [HR] 1.34, 95% confidence interval [CI] 1.17-1.53) and without CKD (HR 1.27, 95% CI 1.12-1.43). And the adjusted HRs (95% CI) for cardiovascular mortality of the people with CKD and without CKD who suffered from PN were 1.42 (1.07, 1.90) and 1.23 (0.91, 1.67), respectively, versus those without PN.

Conclusion

PN was related with a higher risk of all-cause and cardiovascular death in people with CKD, which clinically suggests that the adverse prognostic impact of PN in the CKD population deserves attention and is an important target for intervention.

Bavachin ameliorates neuroinflammation and depressive-like behaviors in streptozotocin-induced diabetic mice through the inhibition of PKCδ

Depression and diabetes are closely linked; however, the pathogenesis of depression associated with diabetes is unclear, and there are no clinically effective antidepressant drugs for diabetic patients with depression. Bavachin is an important active ingredient in Fructus Psoraleae. In this study, we evaluated the anti-neuroinflammatory and antidepressant effects associated with diabetes and the molecular mechanisms of bavachin in a streptozotocin-induced diabetes mouse model. We found that bavachin clearly decreased streptozotocin (STZ)-induced depressive-like behaviors in mice. It was further found that bavachin significantly inhibited microglia activation and the phosphorylation level of PKCδ and inhibited the activation of the NF-κB pathway in vivo and in vitro. Knockdown of PKCδ with siRNA-PKCδ partially reversed the inhibitory effect of bavachin on the NF-κB pathway and the level of pro-inflammatory factors. We further found that PKCδ directly bound to bavachin based on molecular docking and pull-down assays. We also found that bavachin improved neuroinflammation-induced neuronal survival and functional impairment and that this effect may be related to activation of the ERK and Akt pathways mediated by the BDNF pathway. Taken together, these data suggested that bavachin, by targeting inhibition PKCδ to inhibit the NF-κB pathway, further reduced the inflammatory response and oxidative stress and subsequently improved diabetic neuronal survival and function and finally ameliorated diabetes-induced depressive-like behaviors in mice. For the first time, we found that bavachin is a potential agent for the treatment of diabetes-associated neuroinflammation and depression and that PKCδ is a potential target for the treatment of diabetes-associated neuroinflammation, including depression.

Rational design of a ratiometric fluorescent nanoprobe for real-time imaging of hydroxyl radical and its therapeutic evaluation of diabetes

Hydroxyl radical (•OH), one of the most reactive and deleterious substances in organisms, belongs to a class of reactive oxygen species (ROS), and it has been verified to play an essential role in numerous pathophysiological scenarios. However, due to its extremely high reactivity and short lifetime, the development of a reliable and robust method for tracking endogenous •OH remains an ongoing challenge. In this work, we presented the first ratiometric fluorescent nanoprobe NanoDCQ-3 for •OH sensing based on oxidative C-H abstraction of dihydroquinoline to quinoline. The study mainly focused on how to modulate the electronic effects to achieve an ideal ratiometric detection of •OH, as well as solving the inherent problem of hydrophilicity of the probe, so that it was more conducive to monitoring •OH in living organisms. The screened-out probe NanoDCQ-3 exhibited an exceptional ratiometric sensing capability, better biocompatibility, good cellular uptake, and appropriate in vivo retention, which has been reliably used for detecting exogenous •OH concentration fluctuation in living cells and zebrafish models. More importantly, NanoDCQ-3 facilitated visualization of •OH and evaluation of drug treatment efficacy in diabetic mice. These findings afforded a promising strategy for designing ratiometric fluorescent probes for •OH. NanoDCQ-3 emerged as a valuable tool for the detection of •OH in vivo and held potential for drug screening for inflammation-related diseases.

Neuropathic Pain in Aged People: An Unresolved Issue Open to Novel Drug Approaches, Focusing on Painful Diabetic Neuropathy

A majority of older patients suffer from neuropathic pain (NP) that significantly alters their daily activities and imposes a significant burden on health care. Multiple comorbidities and the risk of polypharmacy in the elderly make it challenging to determine the appropriate drug, dosage, and maintenance of therapy. Age-dependent processes play a contributing role in neuropathy given that diabetic neuropathy (DN) is the most common form of neuropathy. This narrative review is mainly focused on the drug treatment approach for neuropathy-associated pain in aged people including both drugs and dietary supplements, considering the latter as add-on mechanism-based treatments to increase the effectiveness of usual treatments by implementing their activity or activating other analgesic pathways. On one hand, the limited clinical studies assessing the effectiveness and the adverse effects of existing pain management options in this age segment of the population (> 65), on the other hand, the expanding global demographics of the elderly contribute to building up an unresolved pain management problem that needs the attention of healthcare providers, researchers, and health authorities as well as the expansion of the current therapeutic options.

Ferroptosis involves in Schwann cell death in diabetic peripheral neuropathy

Accumulating evidence shows that Schwann cells' (SCs) death caused by high glucose (HG) is involved in the pathological process of diabetic peripheral neuropathy (DPN). Ferroptosis is a novel form of regulatory cell death driven by iron-dependent lipid peroxidation. However, it is not clear whether ferroptosis is involved in the death process of SCs induced by HG. The expression of ferroptosis-related indicators in the serum of DPN patients was detected by ELISA. Subsequently, using cell counting kit‑8, western blot, real-time PCR, and Ki-67 staining, we investigated the effects of HG on the ferroptosis of SCs and initially explored the underlying mechanism. The results showed that the serum levels of glutathione peroxidase 4 (GPX4) and glutathione in patients with DPN decreased, while malondialdehyde levels increased significantly. Then, we observed that erastin and HG induced ferroptosis in SCs, resulting in the decrease in cell activity and the expression level of GPX4 and SLC7A11, which could be effectively reversed by the ferroptosis inhibitor Fer-1. Mechanistically, HG induced ferroptosis in SCs by inhibiting the NRF2 signaling pathway. Our results showed that ferroptosis was involved in the death process of SCs induced by HG. Inhibition of ferroptosis in SCs might create a new avenue for the treatment of DPN.

Is metformin neuroprotective against diabetes mellitus-induced neurodegeneration? An updated graphical review of molecular basis

Diabetes mellitus (DM) is a metabolic disease that activates several molecular pathways involved in neurodegenerative disorders. Metformin, an anti-hyperglycemic drug used for treating DM, has the potential to exert a significant neuroprotective role against the detrimental effects of DM. This review discusses recent clinical and laboratory studies investigating the neuroprotective properties of metformin against DM-induced neurodegeneration and the roles of various molecular pathways, including mitochondrial dysfunction, oxidative stress, inflammation, apoptosis, and its related cascades. A literature search was conducted from January 2000 to December 2022 using multiple databases including Web of Science, Wiley, Springer, PubMed, Elsevier Science Direct, Google Scholar, the Core Collection, Scopus, and the Cochrane Library to collect and evaluate peer-reviewed literature regarding the neuroprotective role of metformin against DM-induced neurodegenerative events. The literature search supports the conclusion that metformin is neuroprotective against DM-induced neuronal cell degeneration in both peripheral and central nervous systems, and this effect is likely mediated via modulation of oxidative stress, inflammation, and cell death pathways.

Lower Extremity Nerve Conduction Abnormalities in Vietnamese Patients with Type 2 Diabetes: A Cross-Sectional Study on Peripheral Neuropathy and Its Correlation with Glycemic Control and Renal Function

Peripheral neuropathy is a common complication of type 2 diabetes mellitus (T2DM) that results in nerve conduction abnormalities. This study aimed to investigate the parameters of nerve conduction in lower extremities among T2DM patients in Vietnam. A cross-sectional study was conducted on 61 T2DM patients aged 18 years and older, diagnosed according to the American Diabetes Association’s criteria. Data on demographic characteristics, duration of diabetes, hypertension, dyslipidemia, neuropathy symptoms, and biochemical parameters were collected. Nerve conduction parameters were measured in the tibial and peroneal nerves, including peripheral motor potential time, response amplitude M, and motor conduction speed, as well as sensory conduction in the shallow nerve. The study found a high rate of peripheral neuropathy among T2DM patients in Vietnam, with decreased conduction rate, motor response amplitude, and nerve sensation. The incidence of nerve damage was highest in the right peroneal nerve and left peroneal nerve (86.7% for both), followed by the right tibial nerve and left tibial nerve (67.2% and 68.9%, respectively). No significant differences were found in the rate of nerve defects between different age groups, body mass index (BMI) groups, or groups with hypertension or dyslipidemia. However, a statistically significant association was found between the rate of clinical neurological abnormalities and the duration of diabetes (p < 0.05). Patients with poor glucose control and/or decreased renal function also had a higher incidence of nerve defects. The study highlights the high incidence of peripheral neuropathy among T2DM patients in Vietnam and the association between nerve conduction abnormalities and poor glucose control and/or decreased renal function. The findings underscore the importance of early diagnosis and management of neuropathy in T2DM patients to prevent serious complications.

Diabetic Peripheral Neuropathy Associated with Foot Ulcer: One of a Kind

Significance: Diabetic peripheral neuropathy (DPN) associated with a diabetic foot ulcer (DFU) is likely to be complicated with critical factors such as biofilm infection and compromised skin barrier function of the diabetic skin. Repaired skin with a history of biofilm infection is known to be compromised in barrier function. Loss of barrier function is also observed in the oxidative stress affected diabetic and aged skin. Recent Advances: Loss of barrier function makes the skin prone to biofilm infection and cellulitis, which contributes to chronic inflammation and vasculopathy. Hyperglycemia favors biofilm formation as glucose lowering led to reduction in biofilm development. While vasculopathy limits oxygen supply, the O2 cost of inflammation is high increasing hypoxia severity. Critical Issues: The host nervous system can be inhabited by bacteria. Because electrical impulses are a part of microbial physiology, polymicrobial colonization of the host's neural circuit is likely to influence transmission of action potential. The identification of perineural apatite in diabetic patients with peripheral neuropathy suggests bacterial involvement. DPN starts in both feet at the same time. Future Directions: Pair-matched studies of DPN in the foot affected with DFU (i.e., DFU-DPN) compared with DPN in the without ulcer, and intact skin barrier function, are likely to provide critical insight that would help inform effective care strategies. This review characterizes DFU-DPN from a translational science point of view presenting a new paradigm that recognizes the current literature in the context of factors that are unique to DFU-DPN.

The impact of oxidative stress-induced mitochondrial dysfunction on diabetic microvascular complications

Diabetes mellitus (DM) is a metabolic disease characterized by chronic hyperglycaemia, with absolute insulin deficiency or insulin resistance as the main cause, and causes damage to various target organs including the heart, kidney and neurovascular. In terms of the pathological and physiological mechanisms of DM, oxidative stress is one of the main mechanisms leading to DM and is an important link between DM and its complications. Oxidative stress is a pathological phenomenon resulting from an imbalance between the production of free radicals and the scavenging of antioxidant systems. The main site of reactive oxygen species (ROS) production is the mitochondria, which are also the main organelles damaged. In a chronic high glucose environment, impaired electron transport chain within the mitochondria leads to the production of ROS, prompts increased proton leakage and altered mitochondrial membrane potential (MMP), which in turn releases cytochrome c (cyt-c), leading to apoptosis. This subsequently leads to a vicious cycle of impaired clearance by the body's antioxidant system, impaired transcription and protein synthesis of mitochondrial DNA (mtDNA), which is responsible for encoding mitochondrial proteins, and impaired DNA repair systems, contributing to mitochondrial dysfunction. This paper reviews the dysfunction of mitochondria in the environment of high glucose induced oxidative stress in the DM model, and looks forward to providing a new treatment plan for oxidative stress based on mitochondrial dysfunction.

miRNA-130a-3p targets sphingosine-1-phosphate receptor 1 to activate the microglial and astrocytes and to promote neural injury under the high glucose condition

As a common complication of diabetes, diabetic pain neuropathy (DPN) is caused by neuron intrinsic and extrinsic factors. Neuron intrinsic factors include neuronal apoptosis and oxidative stress, while extrinsic factors are associated with glial activation. The present study was performed to reveal the functions of miR-130a-3p in apoptosis and oxidative stress of the high glucose (HG)-stimulated primary neurons as well as in the activation of microglial and astrocytes. Primary neurons, microglial, and astrocytes were isolated from newborn mice. Apoptosis was assessed by flow cytometry analysis and western blotting. Reactive oxygen species and glutathione levels were assessed to determine the oxidative stress. Markers of glial cells were detected by immunofluorescence staining. The results revealed that miR-130a-3p deficiency alleviated apoptosis and oxidative stress of HG-stimulated neurons as well as suppressed microglial and astrocyte activation. Moreover, sphingosine-1-phosphate receptor 1 (S1PR1) was found as a target downstream of miR-130a-3p. S1PR1 knockdown partially rescued the inhibitory effects of silenced miR-130a-3p on neuronal injury and glial activation. In conclusion, miR-130a-3p targets S1PR1 to activate the microglial and astrocytes and to promote apoptosis and oxidative stress of the HG-stimulated primary neurons. These findings may provide a novel insight into DPN treatment.

Effects of dietary inclusion of Bambara groundnut and sweet orange peels on streptozotocin/HFD type-2 induced diabetes mellitus complications and related biochemical parameters

The effects of dietary inclusion of Bambara groundnut and sweet orange peels composite bread on low-dose streptozotocin and high-fat diet (HFD)-induced type-2 diabetes mellitus (T2D) complications was evaluated in the present study. Male experimental rats-induced T2D were administered with acarbose (standard) and fed with Bambara groundnut and sweet orange peels composite bread for a period of 14 days while monitoring their blood glucose levels. More so, the activities of angiotensin-I-converting enzyme (ACE), serum aspartate aminotransferase, alkaline phosphatase, and alanine aminotransferase activities, as well as nitric oxide (NO), reactive oxygen species (ROS), albumin, total bilirubin, creatinine, urea, and uric acid serum concentrations were assayed for. Diabetic untreated rats showed disorders in ACE, AST, ALT, and ALP activities, and NO, ROS, glucose, albumin, bilirubin, creatinine, urea, uric acid levels, as well as lipid profiles. Interestingly, these disorders were significantly ameliorated in composite bread diet-fed rats in comparison to the diabetic untreated rats. Meanwhile, the presence of polyphenols in the Bambara groundnut and sweet orange peels composite bread diet could have aided the amelioration of these metabolic disorders after the 14th day of administration. Finally, it was proposed that the ability of Bambara groundnut-wheat and sweet orange peel composite bread to treat T2D and its complications makes it a more successful therapy than medications that just target one of the diseased states. PRACTICAL APPLICATIONS: Diabetes mellitus is a global and chronic disease that presently affects 536.6 million people alongside 1.5 million deaths directly attributed to it yearly. Several drug and medicinal agents have been employed for the management of diabetes but those drugs are mostly limited to the management of diabetes while the associated complications are most untreated, while drugs that can manage diabetes and its related complications mostly come at high prices. Therefore, there is an urgent need to evaluate legumes, such as Bambara groundnut, with proven therapeutic potential in the management of diabetes and its complications. However, the Bambara groundnut takes a long period to prepare for a meal, therefore including it in a ready-to-eat product will not only improve its acceptability but also add to economic improvement. Furthermore, adding a waste product, sweet orange peels, will both add flavor and source of additional antioxidant attributes.

Mechanistic efficacy assessment of selected novel methanimine derivatives against vincristine induced Neuropathy: In-vivo, Ex-vivo and In-silico correlates

Vincristine induced peripheral neuropathy (VIPN) is a serious untoward side effect suffered by cancer patients, which still lacks an adequate therapeutic approach. This study examined the alleviating potential of novel methanimine derivatives i.e. (E)-N-(4-nitrobenzylidene)-4-chloro-2-iodobenzamine (KB 9) and (E)-N-(2-methylbenzylidene)-4-chloro-2-iodobenzamine (KB 10) in VIPN. Vincristine was injected in BALB/c mice for 10 days to instigate nociceptive neuropathy. Dynamic and static allodynia, thermal (hot and cold) hyperalgesia were evaluated at 0, 5, 10 and 14 days using cotton brush, Von Frey filament application, hot plate test, acetone drop and cold water respectively. Tumour necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), lipid peroxide (LPO), glutathione-S-transferase (GST), catalase (CAT), superoxide dismutase (SOD) and reactive oxygen species (ROS) assays were performed to assess the efficacy of KB9 and KB10 against neuroinflammation and oxidative stress utilizing ELISA, immunohistochemistry and western blot analysis in brain and sciatic nerve tissues. Computational studies were executed to determine the stable binding conformation of both compounds with respect to COX-2 and NF-κB. Interestingly, both compounds substantially reduced protein expression related to neuroinflammation, oxidative stress (LPO, GST, SOD, CAT) and pain (NF-κB, COX-2, IL-1β and TNF-α). This molecular analysis suggested that the neuroprotective effect of KB9 and KB10 was mediated via regulation of inflammatory signaling pathways. Overall, this study demonstrated that KB9 and KB10 ameliorated vincristine induced neuropathy, through anti-inflammatory, anti-nociceptive and antioxidant mechanisms.

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

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

Crosstalk between Sirtuins and Nrf2: SIRT1 activators as emerging treatment for diabetic neuropathy

About 50% of the diabetic patients worldwide suffer from Diabetic peripheral neuropathy (DPN) which is characterized by chronic pain and loss of sensation, frequent foot ulcerations, and risk for amputation. Numerous factors like hyperglycemia, oxidative stress (OS), impaired glucose signaling, inflammatory responses, neuronal cell death are known to be the various mechanisms underlying DACD and DPN. Development of tolerance, insufficient and inadequate relief and potential toxicity of classical antinociceptives still remains a challenge in the clinical setting. Therefore, there is an emerging need for novel treatments which are both without any potential side effects as well as which focus more on the pathophysiological mechanisms underlying the disease. Also, sirtuins are known to deacetylate Nrf2 and contribute to its action of reducing ROS by generation of anti-oxidant enzymes. Therefore, targeting sirtuins could be a favourable therapeutic strategy to treat diabetic neuropathy by reducing ROS and thereby alleviating OS in DPN. In the present review, we outline the potential use of SIRT1 activators as therapeutic alternatives in treating DPN. We have tried to highlight how sirtuins are interlinked with Nrf2 and NF-κB and put forth how SIRT activators could serve as potential therapy for DPN.

Deoxy-sphingolipids, oxidative stress, and vitamin C correlate with qualitative and quantitative patterns of small fiber dysfunction and degeneration

ABSTRACT

Defined by dysfunction or degeneration of Aδ and C fibers, small fiber neuropathies (SFNs) entail a relevant health burden. In 50% of cases, the underlying cause cannot be identified or treated. In 100 individuals (70% female individuals; mean age: 44.8 years) with an idiopathic, skin biopsy-confirmed SFN, we characterized the symptomatic spectrum and measured markers of oxidative stress (vitamin C, selenium, and glutathione) and inflammation (transforming growth factor beta, tumor necrosis factor alpha), as well as neurotoxic 1-deoxy-sphingolipids. Neuropathic pain was the most abundant symptom (95%) and cause of daily life impairment (72%). Despite the common use of pain killers (64%), the painDETECT questionnaire revealed scores above 13 points in 80% of patients. In the quantitative sensory testing (QST), a dysfunction of Aδ fibers was observed in 70% and of C fibers in 44%, affecting the face, hands, or feet. Despite normal nerve conduction studies, QST revealed Aβ fiber involvement in 46% of patients' test areas. Despite absence of diabetes mellitus or mutations in SPTLC1 or SPTLC2 , plasma 1-deoxy-sphingolipids were significantly higher in the sensory loss patient cluster when compared with those in patients with thermal hyperalgesia ( P < 0.01) or those in the healthy category ( P < 0.1), correlating inversely with the intraepidermal nerve fiber density (1-deoxy-SA: P < 0.05, 1-deoxy-SO: P < 0.01). Patients with arterial hypertension, overweight (body mass index > 25 kg/m 2 ), or hyperlipidemia showed significantly lower L-serine (arterial hypertension: P < 0.01) and higher 1-deoxy-sphingolipid levels (arterial hypertension: P < 0.001, overweight: P < 0.001, hyperlipidemia: P < 0.01). Lower vitamin C levels correlated with functional Aβ involvement ( P < 0.05). Reduced glutathione was lower in patients with Aδ dysfunction ( P < 0.05). Idiopathic SFNs are heterogeneous. As a new pathomechanism, plasma 1-deoxy-sphingolipids might link the metabolic syndrome with small fiber degeneration.

Protective Role of Mitochondrial Uncoupling Proteins against Age-Related Oxidative Stress in Type 2 Diabetes Mellitus

The accumulation of oxidative damage to DNA and other biomolecules plays an important role in the etiology of aging and age-related diseases such as type 2 diabetes mellitus (T2D), atherosclerosis, and neurodegenerative disorders. Mitochondrial DNA (mtDNA) is especially sensitive to oxidative stress. Mitochondrial dysfunction resulting from the accumulation of mtDNA damage impairs normal cellular function and leads to a bioenergetic crisis that accelerates aging and associated diseases. Age-related mitochondrial dysfunction decreases ATP production, which directly affects insulin secretion by pancreatic beta cells and triggers the gradual development of the chronic metabolic dysfunction that characterizes T2D. At the same time, decreased glucose oxidation in skeletal muscle due to mitochondrial damage leads to prolonged postprandial blood glucose rise, which further worsens glucose homeostasis. ROS are not only highly reactive by-products of mitochondrial respiration capable of oxidizing DNA, proteins, and lipids but can also function as signaling and effector molecules in cell membranes mediating signal transduction and inflammation. Mitochondrial uncoupling proteins (UCPs) located in the inner mitochondrial membrane of various tissues can be activated by ROS to protect cells from mitochondrial damage. Mitochondrial UCPs facilitate the reflux of protons from the mitochondrial intermembrane space into the matrix, thereby dissipating the proton gradient required for oxidative phosphorylation. There are five known isoforms (UCP1-UCP5) of mitochondrial UCPs. UCP1 can indirectly reduce ROS formation by increasing glutathione levels, thermogenesis, and energy expenditure. In contrast, UCP2 and UCP3 regulate fatty acid metabolism and insulin secretion by beta cells and modulate insulin sensitivity. Understanding the functions of UCPs may play a critical role in developing pharmacological strategies to combat T2D. This review summarizes the current knowledge on the protective role of various UCP homologs against age-related oxidative stress in T2D.

Efficacy of vitamin and antioxidant supplements for treatment of diabetic peripheral neuropathy: systematic review and meta-analysis of randomized controlled trials

ABSTRACTThe results of treatment effect of vitamin or antioxidant intake on diabetic peripheral neuropathy (DPN) was inconsistent. Therefore, we performed a meta-analysis of randomized controlled trials (RCTs) to examine whether these supplements are effective in DPN treatment. We searched seven databases from inception to October 2021. All RCTs of DPN treatments with vitamin and antioxidant supplements were included. We performed sensitivity and subgroup analysis, and also tested for publication bias by the funnel plot and Egger's test. A total of 14 studies with 1384 patients were included in this systematic review. Three high-quality trials showed that vitamin and antioxidant supplements significantly increased sensory nerve conduction velocity (SNCV) of the sural nerve (MD = 2.66, 95%CI (0.60, 4.72), P < 0.05, I²= 0%). Seven studies (758 participants) suggested that these supplements might have improvement on motor nerve conduction velocity (MNCV) of the peroneal nerve in DPN patients with the random-effect model (MD = 0.60, 95%CI (0.28, 0.92), P < 0.05, I²= 65%). In four studies, these supplements could have improved on MNCV of the median nerve with the fixed-effect model (MD = 4.22, 95%CI (2.86, 5.57), P < 0.05, I²= 0%). However, ten studies (841 participants) have suggested that vitamin and antioxidant supplements have not decreased glycosylated haemoglobin (HbA1c). Vitamin and antioxidant supplements may improve the conduction velocity of nerves, including median, sural and peroneal nerves of patients with DPN. But these supplements have not decreased HbA1c in DPN patients. Several trials with a large sample size are needed to provide evidence support for clinical practice in the future.

Spinal cord-wide structural disruption in type 2 diabetes rescued by exenatide "a glucagon-like peptide-1 analogue" via down-regulating inflammatory, oxidative stress and apoptotic signaling pathways

The mechanisms of spinal cord-wide structural and functional disruption in diabetic patients remain elusive. This study evaluated histopathological alterations of the spinal cord cytoarchitecture in T2DM model of rats and assessed the potential ameliorating effect of exenatide "a potent GLP-1 analogue". Thirty male rats were allocated into three groups; I (control), II (Diabetic): T2DM was induced by high fat diet for 8 weeks followed by a single I.P injection of STZ (25 mg/kg BW) and III (Diabetic/Exenatide): T2DM rats injected with exenatide (10 μg/Kg, S.C. twice daily for 2 weeks). Neurobehavioral sensory and motor tests were carried out and glycemic control biomarkers and indices of insulin resistance and sensitivity were measured. In addition, the spinal cord was processed for histological and immunohistochemical studies besides assessing its tissue homogenate levels of pro-inflammatory/anti-inflamatory cytokines and oxidant/antioxidant biomarkers. Moreover, RT-qPCR was performed to measure the expression of proapoptotic/antiapoptotic and neurotrophic genes. The diabetic rats exhibited thermal hyperalgesia, mechanical allodynia and decreased locomotor activity along with increased serum glucose, insulin, HbA1c, HOMA-IR while, quantitative insulin sensitivity check index (QUICKI) was decreased. Also, IL-1β NF-kB, MDA increased while IL-10, SOD activity and β-endorphin decreased in the spinal tissue. Up regulation of caspase-3 and down regulation of Bcl-2, nerve growth factor (NGF) and glial cell-derived neurotrophic (GDNF) in diabetic rats. Also, they exhibited histopathological changes and increased CD68 positive microglia and Bax immunoreactivity in the spinal cord. Subsequent to exenatide treatment, most biomolecular, structural and functional impairments of the spinal cord were restored in the diabetic rats. In conclusion, the neuro-modulating effect of exenatide against diabetic-induced spinal cord affection warrants the concern about its therapeutic relevance in confronting the devastating diabetic neuropathic complications.

Naturally Occurring Antioxidant Therapy in Alzheimer’s Disease

It is estimated that the prevalence rate of Alzheimer’s disease (AD) will double by the year 2040. Although currently available treatments help with symptom management, they do not prevent, delay the progression of, or cure the disease. Interestingly, a shared characteristic of AD and other neurodegenerative diseases and disorders is oxidative stress. Despite profound evidence supporting the role of oxidative stress in the pathogenesis and progression of AD, none of the currently available treatment options address oxidative stress. Recently, attention has been placed on the use of antioxidants to mitigate the effects of oxidative stress in the central nervous system. In preclinical studies utilizing cellular and animal models, natural antioxidants showed therapeutic promise when administered alone or in combination with other compounds. More recently, the concept of combination antioxidant therapy has been explored as a novel approach to preventing and treating neurodegenerative conditions that present with oxidative stress as a contributing factor. In this review, the relationship between oxidative stress and AD pathology and the neuroprotective role of natural antioxidants from natural sources are discussed. Additionally, the therapeutic potential of natural antioxidants as preventatives and/or treatment for AD is examined, with special attention paid to natural antioxidant combinations and conjugates that are currently being investigated in human clinical trials.

New horizons of biomaterials in treatment of nerve damage in diabetes mellitus: A translational prospective review

BACKGROUND

Peripheral nerve injury is a serious concern that leads to loss of neuronal communication that impairs the quality of life and, in adverse conditions, causes permanent disability. The limited availability of autografts with associated demerits shifts the paradigm of researchers to use biomaterials as an alternative treatment approach to recover nerve damage.

PURPOSE

The purpose of this study is to explore the role of biomaterials in translational treatment approaches in diabetic neuropathy.

STUDY DESIGN

The present study is a prospective review study.

METHODS

Published literature on the role of biomaterials in therapeutics was searched for.

RESULTS

Biomaterials can be implemented with desired characteristics to overcome the problem of nerve regeneration. Biomaterials can be further exploited in the treatment of nerve damage especially associated with PDN. These can be modified, customized, and engineered as scaffolds with the potential of mimicking the extracellular matrix of nerve tissue along with axonal regeneration. Due to their beneficial biological deeds, they can expedite tissue repair and serve as carriers of cellular and pharmacological treatments. Therefore, the emerging research area of biomaterials-mediated treatment of nerve damage provides opportunities to explore them as translational biomedical treatment approaches.

CONCLUSIONS

Pre-clinical and clinical trials in this direction are needed to establish the effective role of several biomaterials in the treatment of other human diseases.

Diagnostic Tools, Biomarkers, and Treatments in Diabetic polyneuropathy and Cardiovascular Autonomic Neuropathy

The various manifestations of diabetic neuropathy, including distal symmetric sensorimotor polyneuropathy (DSPN) and cardiovascular autonomic neuropathy (CAN), are among the most prevalent chronic complications of diabetes. Major clinical complications of diabetic neuropathies, such as neuropathic pain, chronic foot ulcers, and orthostatic hypotension, are associated with considerable morbidity, increased mortality, and diminished quality of life. Despite the substantial individual and socioeconomic burden, the strategies to diagnose and treat diabetic neuropathies remain insufficient. This review provides an overview of the current clinical aspects and recent advances in exploring local and systemic biomarkers of both DSPN and CAN assessed in human studies (such as biomarkers of inflammation and oxidative stress) for better understanding of the underlying pathophysiology and for improving early detection. Current therapeutic options for DSPN are (I) causal treatment, including lifestyle modification, optimal glycemic control, and multifactorial risk intervention, (II) pharmacotherapy derived from pathogenetic concepts, and (III) analgesic treatment against neuropathic pain. Recent advances in each category are discussed, including non-pharmacological approaches, such as electrical stimulation. Finally, the current therapeutic options for cardiovascular autonomic complications are provided. These insights should contribute to a broader understanding of the various manifestations of diabetic neuropathies from both the research and clinical perspectives.

Role of Vitamins in Neurodegenerative Diseases: A Review

BACKGROUND

Vitamins are the micronutrients required for boosting the immune system and managing any future infection. Vitamins are involved in neurogenesis, a defense mechanism working in neurons, metabolic reactions, neuronal survival, and neuronal transmission. Their deficiency leads to abnormal functions in the brain like oxidative stress, mitochondrial dysfunction, accumulation of proteins (synuclein, Aβ plaques), neurodegeneration, and excitotoxicity.

METHODS

In this review, we have compiled various reports collected from PubMed, Scholar Google, Research gate, and Science direct. The findings were evaluated, compiled, and represented in this manuscript.

CONCLUSION

The deficiency of vitamins in the body causes various neurological disorders like Alzheimer's disease, Parkinson's disease, Huntington's disease, and depression. We have discussed the role of vitamins in neurological disorders and the normal human body. Depression is linked to a deficiency of vitamin-C and vitamin B. In the case of Alzheimer's disease, there is a lack of vitamin-B1, B12, and vitamin-A, which results in Aβ-plaques. Similarly, in Parkinson's disease, vitamin-D deficiency leads to a decrease in the level of dopamine, and imbalance in vitamin D leads to accumulation of synuclein. In MS, Vitamin-C and Vitamin-D deficiency causes demyelination of neurons. In Huntington's disease, vitamin- C deficiency decreases the antioxidant level, enhances oxidative stress, and disrupts the glucose cycle. Vitamin B5 deficiency in Huntington's disease disrupts the synthesis of acetylcholine and hormones in the brain.

R, Patel B, Manne R, Patel DB. Preparation, Optimization and Evaluation of Chitosan-Based Avanafil Nanocomplex Utilizing Antioxidants for Enhanced Neuroprotective Effect on PC12 Cells

(1) Introduction: in recent decades, interdisciplinary research on the utilization of natural products as “active moiety carriers” was focused on due to their superior safety profile, biodegradability, biocompatibility and the ability for sustained or controlled release activity. The nano-based neuroprotective strategy is explored as an imperative treatment for diabetic neuropathy (DN). Avanafil (AV), that selectively inhibits the degradation of cGMP-specific phosphodiesterase, thereby increasing the levels of cGMP, makes a decisive mediator for cytoprotection. (2) Methods: AVnanocomplex formulations were prepared by a modified anti-solvent precipitation method and the method was optimized by Box–Behnken design. An optimized formulation was characterized and evaluated for various in vitro parameters; (3) results:based on the desirability approach, the formulation containing 2.176 g of chitosan, 7.984 g of zein and 90% v/v ethanol concentration can fulfill the prerequisites of optimum formulation (OB-AV-NC).OB-AV-NC was characterized and evaluated for various parameters. The neuroprotective mechanism of AV was evaluated by pretreatment of PC12 cells with plain AV, avanafil nanocomplex (NC) without antioxidants (AV-NC) and with antioxidants (α-Lipoic acid LP; Ellagic Acid EA), AV-LP-EA-Nanocomplex has also shown considerable attenuation in intracellular reactive oxygen species (ROS) and lipid peroxidation with a significant increase in the PC 12 viability under HG conditions in comparison to pure AV; (4) conclusion: the nanocomplex of AV prepared to utilize natural polymers and antioxidants aided for high solubility of AV and exhibited desired neuroprotective activity.This can be one of the promisingstrategy to translate the AV nanocomplex with safety and efficacy in treating DN.

Pathogenesis, diagnosis and clinical management of diabetic sensorimotor peripheral neuropathy

Diabetic sensorimotor peripheral neuropathy (DSPN) is a serious complication of diabetes mellitus and is associated with increased mortality, lower-limb amputations and distressing painful neuropathic symptoms (painful DSPN). Our understanding of the pathophysiology of the disease has largely been derived from animal models, which have identified key potential mechanisms. However, effective therapies in preclinical models have not translated into clinical trials and we have no universally accepted disease-modifying treatments. Moreover, the condition is generally diagnosed late when irreversible nerve damage has already taken place. Innovative point-of-care devices have great potential to enable the early diagnosis of DSPN when the condition might be more amenable to treatment. The management of painful DSPN remains less than optimal; however, studies suggest that a mechanism-based approach might offer an enhanced benefit in certain pain phenotypes. The management of patients with DSPN involves the control of individualized cardiometabolic targets, a multidisciplinary approach aimed at the prevention and management of foot complications, and the timely diagnosis and management of neuropathic pain. Here, we discuss the latest advances in the mechanisms of DSPN and painful DSPN, originating both from the periphery and the central nervous system, as well as the emerging diagnostics and treatments.

Genetic and Epigenomic Modifiers of Diabetic Neuropathy

Diabetic neuropathy (DN), the most common chronic and progressive complication of diabetes mellitus (DM), strongly affects patients’ quality of life. DN could be present as peripheral, autonomous or, clinically also relevant, uremic neuropathy. The etiopathogenesis of DN is multifactorial, and genetic components play a role both in its occurrence and clinical course. A number of gene polymorphisms in candidate genes have been assessed as susceptibility factors for DN, and most of them are linked to mechanisms such as reactive oxygen species production, neurovascular impairments and modified protein glycosylation, as well as immunomodulation and inflammation. Different epigenomic mechanisms such as DNA methylation, histone modifications and non-coding RNA action have been studied in DN, which also underline the importance of “metabolic memory” in DN appearance and progression. In this review, we summarize most of the relevant data in the field of genetics and epigenomics of DN, hoping they will become significant for diagnosis, therapy and prevention of DN.

Upconversion-based nanosystems for fluorescence sensing of pH and H2O2

Hydrogen peroxide (H₂O₂), a key reactive oxygen species, plays an important role in living organisms, industrial and environmental fields. Here, a non-contact upconversion nanosystem based on the excitation energy attenuation (EEA) effect and a conventional upconversion nanosystem based on the joint effect of EEA and fluorescence resonance energy transfer (FRET) are designed for the fluorescence sensing of H₂O₂. We show that the upconversion luminescence (UCL) is quenched by MoO_3-x nanosheets (NSs) in both systems due to the strong absorbance of MoO_3-x NSs in the visible and near-infrared regions. The recovery in UCL emissions upon addition of H₂O₂ enables quantitative monitoring of H₂O₂. Benefiting from the non-contact method, hydrophobic OA-NaYF₄:Yb,Er can be used as the luminophore directly and ultrahigh quenching efficiency (99.8%) is obtained. Moreover, the non-contact method exhibits high sensitivity toward H₂O₂ with a detection limit of 0.63 μM, which is lower than that determined by simple spectrophotometry (0.75 μM) and conventional upconversion-based nanocomposites (9.61 μM). As an added benefit, the same strategy can be applied to the sensing of pH, showing a broad pH-responsive property over a range of 2.6 to 8.2. The successful preparation of different upconversion-based nanosystems for H₂O₂ sensing using the same material as the quencher provides a new design strategy for fluorescence sensing of other analytes.

Leptin improves the in vitro development of preimplantation rabbit embryos under oxidative stress of cryopreservation

Vitrification is an economically effective method for embryo cryopreservation in human and livestock animals; however, it carries the risk of damage by the exposure to severe oxidative stress. The present study was conducted to evaluate the effect of leptin at different levels on the in vitro development of fresh and vitrified preimplantation embryos in a rabbit model. Normal embryos at morulae stage were randomly cultured for 2 h with 0, 10, 20 or 100 ng/mL of leptin, then were cultured for further 48 h as freshly or after vitrification. Thereafter, developed blastocysts form the best leptin level in fresh and vitrified embryos along with their controls were allocated to analyze the pro-oxidant (malondialdehyde, MDA; nitric oxide, NO), antioxidant (total antioxidant capacity, TAC; superoxide dismutase, SOD; glutathione peroxidase, GPx), apoptotic (Bcl-2 associated X protein, BAX; heat shock 60kD protein member 1, HSP60; tumor necrosis factor alpha, TNFα) and developmental (sex determining region Y box protein 2, SOX2; Nanog homeobox protein, NANOG; Octamer-binding protein 4, OCT4) biomarkers. Results indicate that expanding and hatching rates of embryos were significantly higher at 20 ng/mL leptin than the other levels, while vitrification had an independent suppression effect on the in vitro development rates. The MDA and NO were significantly higher, while TAC, SOD and GPx were significantly lower in the vitrified than fresh embryos. In contrast, leptin treatment significantly decreased the pro-oxidant biomarkers and increased the antioxidant biomarkers in both fresh and vitrified embryos. Vitrification significantly increased the antiapoptotic biomarkers, and decreased the developmental biomarkers in embryos. In contrast, leptin decreased the BAX and TNFα, increased the HSP60, and moreover, ameliorated the reduction of developmental biomarkers in the vitrified embryos. These results conclude that leptin could be used as antiapoptotic and antioxidant promotor to support the in vitro embryonic development, particularly under oxidative stress emerged from cryopreservation programs.

The role and therapeutic potential of Hsp90, Hsp70, and smaller heat shock proteins in peripheral and central neuropathies

Heat shock proteins (Hsps) are molecular chaperones that also play important roles in the activation of the heat shock response (HSR). The HSR is an evolutionary conserved and protective mechanism that is used to counter abnormal physiological conditions, stressors, and disease states, such as those exemplified in cancer and/or neurodegeneration. In normal cells, heat shock factor-1 (HSF-1), the transcription factor that regulates the HSR, remains in a dormant multiprotein complex that is formed upon association with chaperones (Hsp90, Hsp70, etc.), co-chaperones, and client proteins. However, under cellular stress, HSF-1 dissociates from Hsp90 and induces the transcriptional upregulation of Hsp70 to afford protection against the encountered cellular stress. As a consequence of both peripheral and central neuropathies, cellular stress occurs and results in the accumulation of unfolded and/or misfolded proteins, which can be counterbalanced by activation of the HSR. Since Hsp90 is the primary regulator of the HSR, modulation of Hsp90 by small molecules represents an attractive therapeutic approach against both peripheral and central neuropathies.

Electroacupuncture Alleviates Diabetic Peripheral Neuropathy by Regulating Glycolipid-Related GLO/AGEs/RAGE Axis

Diabetic peripheral neuropathy (DPN) is one of the most common complications of diabetes mellitus (DM) and affects over one-third of all patients. Neuropathic pain and nerve dysfunction induced by DM is related to the increase of advanced glycation end products (AGEs) produced by reactive dicarbonyl compounds in a hyperglycemia environment. AGEs induce the expression of pro-inflammatory cytokines via the main receptor (RAGE), which has been documented to play a crucial role in the pathogenesis of diabetic peripheral neuropathy. Electroacupuncture (EA) has been reported to have a positive effect on paralgesia caused by various diseases, but the mechanism is unclear. In this study, we used high-fat-fed low-dose streptozotocin-induced rats as a model of type 2 diabetes (T2DM). Persistent metabolic disorder led to mechanical and thermal hyperalgesia, as well as intraepidermal nerve fiber density reduction and nerve demyelination. EA improved neurological hyperalgesia, decreased the pro-inflammatory cytokines, reduced the generation of AGEs and RAGE, and regulated the glyoxalase system in the EA group. Taken together, our study suggested that EA plays a role in the treatment of T2DM-induced DPN, and is probably related to the regulation of metabolism and the secondary influence on the GLO/AGE/RAGE axis.

Alizarin-based molecular probes for the detection of hydrogen peroxide and peroxynitrite

Phenol fluorophores are a large family of fluorophores, which have attracted more and more attention in the design of probes.

18F-Labeled dihydromethidine: positron emission tomography radiotracer for imaging of reactive oxygen species in intact brain

Dihydromethidine (DHM) labeled with 18F at the para position of the peripheral benzene ring was designed as a positron emission tomography (PET) radiotracer for non-invasive imaging of reactive oxygen species (ROS). This compound readily crosses the blood-brain barrier and is oxidized by ROS, and the oxidation product is retained intracellularly. PET imaging of ROS-producing rat brain microinfused with sodium nitroprusside identified specific brain regions with high ROS concentrations. This tracer should be useful for studies of the pathophysiological roles of ROS, and in the diagnosis of neurodegenerative diseases.

Emerging Roles of microRNAs as Biomarkers and Therapeutic Targets for Diabetic Neuropathy

Diabetic neuropathy (DN) is the most prevalent chronic complication of diabetes mellitus. The exact pathophysiological mechanisms of DN are unclear; however, communication network dysfunction among axons, Schwann cells, and the microvascular endothelium likely play an important role in the development of DN. Mounting evidence suggests that microRNAs (miRNAs) act as messengers that facilitate intercellular communication and may contribute to the pathogenesis of DN. Deregulation of miRNAs is among the initial molecular alterations observed in diabetics. As such, miRNAs hold promise as biomarkers and therapeutic targets. In preclinical studies, miRNA-based treatment of DN has shown evidence of therapeutic potential. But this therapy has been hampered by miRNA instability, targeting specificity, and potential toxicities. Recent findings reveal that when packaged within extracellular vesicles, miRNAs are resistant to degradation, and their delivery efficiency and therapeutic potential is markedly enhanced. Here, we review the latest research progress on the roles of miRNAs as biomarkers and as potential clinical therapeutic targets in DN. We also discuss the promise of exosomal miRNAs as therapeutics and provide recommendations for future research on miRNA-based medicine.

NADPH Oxidase Inhibition: Preclinical and Clinical Studies in Diabetic Complications

Significance: Oxidative stress plays a critical role in the development and progression of serious micro- and macrovascular complications of diabetes. Nicotinamide adenine dinucleotide phosphate oxidase (NOX)-derived reactive oxygen species (ROS) significantly contribute to oxidative stress-associated inflammatory pathways that lead to tissue damage of different organs, including the kidneys, retina, brain, nerves, and the cardiovascular system. Recent Advances: Preclinical studies, including genetic-modified mouse models or cell culture models, have revealed the role of specific NOX isoforms in different diabetic complications, and suggested them as a promising target for the treatment of these diseases. Critical Issues: In this review, we provide an overview of the role of ROS and oxidative stress in macrovascular complications, such as stroke, myocardial infarction, coronary artery disease, and peripheral vascular disease that are all mainly driven by atherosclerosis, as well as microvascular complications, such as diabetic retinopathy, nephropathy, and neuropathy. We summarize conducted genetic deletion studies of different Nox isoforms as well as pharmacological intervention studies using NOX inhibitors in the context of preclinical as well as clinical research on diabetic complications. Future Directions: We outline the isoforms that are most promising for future clinical trials in the context of micro- and macrovascular complications of diabetes.

Plasma sphingosine 1-phosphate concentrations and cardiovascular autonomic neuropathy in individuals with type 2 diabetes

The aim of this study was to test the hypothesis that plasma sphingosine 1-phosphate (S1P) levels are associated with the risk of cardiovascular autonomic neuropathy (CAN) in type 2 diabetes patients. This cross-sectional study included 287 individuals with type 2 diabetes. CAN was evaluated using cardiovascular reflex tests. Logistic regression analyses were conducted to assess the relationship between plasma S1P levels and CAN. Plasma S1P concentrations were significantly lower in individuals with CAN than in those without CAN. There was a significant interaction between plasma S1P levels and sex with respect to CAN (p for interaction = 0.003). When stratified by sex, the association between plasma S1P levels and CAN exhibited a sex difference; in multivariable analysis, plasma S1P levels were significantly associated with CAN in women (odds ratio per standard deviation increase in the log-transformed value, 0.40; 95% confidence interval, 0.23–0.70, p = 0.001). However, there was no significant association between plasma S1P and CAN in men. Plasma S1P concentrations were inversely associated with CAN only in women with type 2 diabetes.

Glucose time in range and peripheral neuropathy in type 2 diabetes mellitus and chronic kidney disease

​OBJECTIVE: Compared with hemoglobin A1c (HbA1c), continuous glucose monitoring (CGM) may better capture risk of diabetes complications in patients with chronic kidney disease (CKD), including diabetic peripheral neuropathy (DPN). We hypothesized that glucose time in range (TIR), measured by CGM, is associated with DPN symptoms among participants with type 2 diabetes mellitus (type 2 DM) and moderate-to-severe CKD. ​RESEARCH DESIGN AND METHODS: We enrolled 105 people with type 2 DM treated with insulin or sulfonylurea, 81 participants with CKD (estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m²) and 24 matched control participants with eGFR ≥60 mL/min/1.73 m². Each participant wore a CGM for two 6-day periods. Calculated glycemic measures included TIR (glucose 70-180 mg/dL) and glucose management indicator (GMI). DPN symptoms were assessed using the Michigan Neuropathy Screening Instrument (MNSI) questionnaire, with a positive MNSI score defined as ≥2 symptoms. ​RESULTS: Participants with CKD had a mean age of 68 years, diabetes duration 20 years, eGFR 38 mL/min/1.73 m² and HbA1c 7.8%, 61 mmol/mol. Sixty-two participants reported ≥2 DPN symptoms, 51 (63%) with CKD and 11 (46%) controls. Less TIR and higher GMI were associated with higher risk of MNSI questionnaire score ≥2 (OR 1.25 (95% CI 1.02 to 1.52) per 10% lower TIR, and OR 1.79 (95% CI 1.05 to 3.04) per 1% higher GMI, adjusting for age, gender and race). Similar results were observed when analyses were restricted to participants with CKD. In contrast, there was no significant association of HbA1c with DPN symptoms. ​CONCLUSIONS: Symptoms of DPN were common among participants with long-standing type 2 DM and CKD. Lower TIR and higher GMI were associated with DPN symptoms.

Almond-supplemented diet improves sexual functions beyond Phosphodiesterase-5 inhibition in diabetic male rats

Hyperglycemia, an important feature of diabetes, can cause oxidative stress, which is associated with varieties of diabetic complications including erectile dysfunction. Therefore, this study sought to investigate the effect of almond-supplemented diet on some biochemical indices relevant to erection in diabetic male rats. Forty-two male rats were divided into two groups: A (n = 6) and B (n = 36). Diabetes was induced in Group B via injection of a single dose of STZ (50 mg/kg) intraperitoneally and confirmed 72 h after induction. Diabetic rats (blood glucose ≥250 mg/dL) were subsequently divided into six groups (n = 6). Fourteen days after confirmation of diabetes, rats were fed with diets containing almond drupe and seeds (10 and 20% inclusion) for fourteen days. The effects of the diets on blood glucose, sexual behavior, sexual hormones, phosphodiesterase-5 activity, nitric oxide, H₂S, and AGEs levels were evaluated. Significant increase in blood glucose level, phosphodiesterase-5 activity, and glycated hemoglobin was observed in diabetic rats. Furthermore, diabetes caused a significant decrease in nitric oxide, H₂S, sexual hormones (testosterone, follicle-stimulating hormone and luteinizing hormone) levels, and sexual behavioral indices. However, treatment with diets supplemented with almond drupe and seeds significantly reversed these effects in diabetic rats. Findings in this study revealed that almond-supplemented diets enhance some important biomarkers relevant to erection in diabetic rats. Thus, dietary inclusion of almond (drupe and seeds) could serve as a cheap and readily available nutraceutical in the management of erectile dysfunction associated with diabetes.

Biomarkers of response to alpha-lipoic acid ± palmitoiletanolamide treatment in patients with diabetes and symptoms of peripheral neuropathy

PURPOSE

To evaluate the effect of oral alpha-lipoic acid (ALA) ± palmitoyl-ethanolamide (PEA) on neuropathic symptoms in patients with diabetic peripheral neuropathy (DPN) and to identify factors related to the efficacy of the treatment.

METHODS

This is a retrospective observational pilot study evaluating 49 patients with diabetes and positive Neuropathy Symptoms Score (NSS). Clinical and biochemical variables, including NSS, were compared between untreated patients and patients treated with oral 600 mg/day ALA ± 600 mg/day PEA at baseline (first occurrence of NSS ≥ 3) and at least 2 months after baseline. Number of days between treatment initiation and symptoms' relief and related factors were also investigated.

RESULTS

Thirty subjects were treated with ALA ± PEA and 19 subjects did not receive any specific treatment for neuropathy symptoms. Follow-up visits occurred after 98 ± 46 days. NSS significantly decreased in patients treated with ALA ± PEA (5.4 ± 1.3 at baseline vs. 1.7 ± 2.4 at follow-up, p < 0.001), but not in untreated patients (p = 0.164). Subjects treated with ALA ± PEA reported a mean time from treatment initiation to symptoms' relief of 18.4 ± 9.0 days. The number of days of treatment needed for symptoms' relief was inversely related to HDL-cholesterol levels (r = -0.503, p = 0.010) and to eGFR (r = -0.428, p = 0.033), whereas there was no significant relationship between time to symptoms' relief and age, HbA1c, lipid profile and the severity of symptoms at baseline.

CONCLUSIONS

This study documents that oral administration of ALA ± PEA helps in controlling neuropathy symptoms in diabetes. Moreover, our data show that higher HDL-c levels and better renal function are associated to a faster therapeutic effect, suggesting them as biomarkers of response to therapy with ALA ± PEA.

Protective Effects of Specneuzhenide on Renal Injury in Rats with Diabetic Nephropathy

Background

We aim to investigate the protective effects and potential mechanisms in specneuzhenide (SPE) on renal injury in rats with diabetic nephropathy (DN).

Results

SPE could inhibit the decrease of body weight compared with the model group (P<0.05), and trigger improvement in the renal index (P<0.05). High dose and low dose SPE could trigger a significant decrease in serum IL1β, IL-6 and TNF-α compared with the model group (P<0.05). SPE could attenuate the glomerular lesions in DN rats. SPE induced up-regulation of podocin and CD2AP (P<0.05).

Conclusion

SPE showed protective effects on renal injury through attenuating the pathological injury and urine protein. This process may be closely related to the modulation of CD2AP and podocin expression.

Association of monocyte-to-high density lipoprotein-cholesterol ratio with peripheral neuropathy in patients with Type II diabetes mellitus

Aim: We assessed the association of monocyte count to high-density lipoprotein cholesterol ratio (MHR) with diabetic peripheral neuropathy (DPN) and its role as a marker for identification of high-risk patients for DPN. Methods: A total of 180 patients with Type II diabetes mellitus (T2DM) were enrolled in the study. MHR, erythrocyte sedimentation rate and serum CRP along with other tests for T2DM and DPN were measured. Results: Duration of T2DM (p = 0.013), insulin use (p = 0.006) and serum CRP levels (p = 0.008) were significantly higher in patients with DPN. MHR was similar between groups (p = 0.447). Duration of diabetes (OR: 1.048; p = 0.038) and the serum CRP levels (OR: 1.073; p = 0.026) were found as independent predictors for the presence of DPN, however, MHR was not. Conclusion: Higher MHR indicates an enhanced inflammation and oxidative stress which was not found to be associated with the presence of DPN.

A Doubly-Quenched Fluorescent Probe for Low-Background Detection of Mitochondrial H2O2

Hydrogen peroxide (H₂O₂) is an important product of oxygen metabolism and plays a crucial role in regulating a variety of cellular functions. Fluorescent probes have made a great contribution to our understanding of the biological role of endogenous H₂O₂. However, fluorescent probes for H₂O₂ featuring aryl boronates can suffer from moderate turn-on fluorescence responses. Strategies that can reduce the background fluorescence of these boronate-masked probes would significantly improve the sensitivity of endogenous H₂O₂ detection. In this work, we propose a general and reliable double-quenching concept for the design of fluorescent probes with low background fluorescence. A new fluorescent probe was developed for the detection of endogenous H₂O₂ in mitochondria of live cancer cells. This probe exploits a boronate-driven lactam formation and an eliminable quenching moiety simultaneously (i.e., the double-quenching effect) to reduce the background fluorescence, which ultimately results in the achievement of a >50-fold fluorescence turn-on. A linear concentration range of response between 1 and 60 μM and a detection limit of 0.025 μM can be obtained. This study not only presents a highly sensitive fluorescent probe for the detection of H₂O₂ but also provides a new concept for the design of fluorescent probes with a previously unachievable fluorescence off-on response ratio for other types of ROS and many other biologically relevant analytes.

Relationship between Serum Asymmetric Dimethylarginine Level and Microvascular Complications in Diabetes Mellitus: A Meta-Analysis

Objective

The purpose of the meta-analysis was to evaluate the relationship between serum asymmetric dimethylarginine (ADMA) level and microvascular complications in diabetes mellitus (DM) including diabetic retinopathy (DR), diabetic neuropathy (DN), and diabetic nephropathy.

Methods

Studies were comprehensively identified by searching Web of Science, Embase, and PubMed databases up to August 30, 2018. The meta-analysis was carried out to compare the difference of serum ADMA concentrations of DR, DN, and diabetic nephropathy patients with healthy controls. The Newcastle-Ottawa Scale and the Agency for Healthcare Research and Quality were applied to assess the methodological quality. Chi-squared Q test and I² statistics were applied to evaluate statistical heterogeneity. Subgroup analyses were conducted and publication bias was assessed by Egger's test.

Result

Ten studies were finally entered in the meta-analysis. Statistically significant heterogeneity was observed across these studies (I ² = 77.0%, p < 0.001). Compared with DM without microvascular complications, circulating level of ADMA was significantly higher in DM with microvascular complications (all p < 0.05). Sensitivity analysis suggested that the results of this meta-analysis were shown to be stable. There was no significant publication bias (P=0.823).

Conclusion

Elevated ADMA levels correlate with diabetic microangiopathies such as DR and diabetic nephropathy. ADMA may play an important role in the pathobiology of microvascular complications of diabetes.

Emerging Biomarkers, Tools, and Treatments for Diabetic Polyneuropathy

Diabetic neuropathy, with its major clinical sequels, notably neuropathic pain, foot ulcers, and autonomic dysfunction, is associated with substantial morbidity, increased risk of mortality, and reduced quality of life. Despite its major clinical impact, diabetic neuropathy remains underdiagnosed and undertreated. Moreover, the evidence supporting a benefit for causal treatment is weak at least in patients with type 2 diabetes, and current pharmacotherapy is largely limited to symptomatic treatment options. Thus, a better understanding of the underlying pathophysiology is mandatory for translation into new diagnostic and treatment approaches. Improved knowledge about pathogenic pathways implicated in the development of diabetic neuropathy could lead to novel diagnostic techniques that have the potential of improving the early detection of neuropathy in diabetes and prediabetes to eventually embark on new treatment strategies. In this review, we first provide an overview on the current clinical aspects and illustrate the pathogenetic concepts of (pre)diabetic neuropathy. We then describe the biomarkers emerging from these concepts and novel diagnostic tools and appraise their utility in the early detection and prediction of predominantly distal sensorimotor polyneuropathy. Finally, we discuss the evidence for and limitations of the current and novel therapy options with particular emphasis on lifestyle modification and pathogenesis-derived treatment approaches. Altogether, recent years have brought forth a multitude of emerging biomarkers reflecting different pathogenic pathways such as oxidative stress and inflammation and diagnostic tools for an early detection and prediction of (pre)diabetic neuropathy. Ultimately, these insights should culminate in improving our therapeutic armamentarium against this common and debilitating or even life-threatening condition.

Neurons and Microglia; A Sickly-Sweet Duo in Diabetic Pain Neuropathy

Diabetes is a common condition characterized by persistent hyperglycemia. High blood sugar primarily affects cells that have a limited capacity to regulate their glucose intake. These cells include capillary endothelial cells in the retina, mesangial cells in the renal glomerulus, Schwann cells, and neurons of the peripheral and central nervous systems. As a result, hyperglycemia leads to largely intractable complications such as retinopathy, nephropathy, hypertension, and neuropathy. Diabetic pain neuropathy is a complex and multifactorial disease that has been associated with poor glycemic control, longer diabetes duration, hypertension, advanced age, smoking status, hypoinsulinemia, and dyslipidemia. While many of the driving factors involved in diabetic pain are still being investigated, they can be broadly classified as either neuron -intrinsic or -extrinsic. In neurons, hyperglycemia impairs the polyol pathway, leading to an overproduction of reactive oxygen species and reactive nitrogen species, an enhanced formation of advanced glycation end products, and a disruption in Na⁺/K⁺ ATPase pump function. In terms of the extrinsic pathway, hyperglycemia leads to the generation of both overactive microglia and microangiopathy. The former incites a feed-forward inflammatory loop that hypersensitizes nociceptor neurons, as observed at the onset of diabetic pain neuropathy. The latter reduces neurons' access to oxygen, glucose and nutrients, prompting reductions in nociceptor terminal expression and losses in sensation, as observed in the later stages of diabetic pain neuropathy. Overall, microglia can be seen as potent and long-lasting amplifiers of nociceptor neuron activity, and may therefore constitute a potential therapeutic target in the treatment of diabetic pain neuropathy.

Selective and Sensitive Sensing of Hydrogen Peroxide by a Boronic Acid Functionalized Metal-Organic Framework and Its Application in Live-Cell Imaging

A new boronic acid functionalized Zr(IV) metal-organic framework having the capability of sensing H₂O₂ in live cells is reported. The Zr-MOF bears a UiO-66 structure and contains 2-boronobenzene-1,4-dicarboxylic acid (BDC-B(OH)₂) as a framework linker. The activated Zr-UiO-66-B(OH)₂ compound (called 1') is highly selective for the fluorogenic detection of H₂O₂ in HEPES buffer at pH 7.4, even in the presence of interfering ROS (ROS = reactive oxygen species) and other biologically relevant analytes. The fluorescent probe was found to display extraordinary sensitivity for H₂O₂ (detection limit 0.015 μM) in HEPES buffer, which represents a lower value in comparison to those of the MOF probes documented so far for sensing H₂O₂ using other analytical methods. Taking advantage of its high selectivity and sensitivity for H₂O₂ in HEPES buffer, the probe was successfully employed for the imaging of intracellular H₂O₂. Imaging studies with MDAMB-231 cells revealed the emergence of bright blue fluorescence after loading with probe 1' and subsequent treatment with H₂O₂ solution.

The leptin receptor mutation of the obese Zucker rat causes sciatic nerve demyelination with a centripetal pattern defect

Young male Zucker rats with a leptin receptor mutation are obese, have a non-insulin-dependent diabetes mellitus (NIDDM), and other endocrinopathies. Tibial branches of the sciatic nerve reveal a progressive demyelination that progresses out of the Schwann cells (SCs) where electron-contrast deposits are accumulated while the minor lines or intermembranous SC contacts display exaggerated spacings. Cajal bands contain diversely contrasted vesicles adjacent to the abaxonal myelin layer with blemishes; they appear dispatched centripetally out of many narrow electron densities, regularly spaced around the myelin annulus. These anomalies widen and yield into sectors across the stacked myelin layers. Throughout the worse degradations, the adaxonal membrane remains along the axonal neuroplasm. This peripheral neuropathy with irresponsive leptin cannot modulate hypothalamic-pituitary-adrenal axis and SC neurosteroids, thus exacerbates NIDDM condition. Additionally, the ultrastructure of the progressive myelin alterations may have unraveled a peculiar, centripetal mode of trafficking maintenance of the peripheral nervous system myelin, while some adhesive glycoproteins remain between myelin layers, somewhat hindering the axon mutilation. Heading title: Peripheral neuropathy and myelin.

The pectin-insulin patch application prevents the onset of peripheral neuropathy-like symptoms in streptozotocin-induced diabetic rats

Peripheral neuropathic condition is amongst the classical symptoms of progressed diabetes. An intensive glycemic control with insulin injections has been shown to delay the onset and the progression of this condition in diabetes. In this study, we investigated the effect of pectin-insulin patch application on peripheral neuropathic symptoms in streptozotocin-induced diabetic rats. Pectin-insulin patches (20.0, 40.8, and 82.9 μg/kg) were daily applied thrice in streptozotocin-induced diabetic rats for 45 days. The diabetic animals sham treated with insulin-free patch served as negative control, while diabetic animals receiving subcutaneous insulin served as positive controls. The locomotor activity, gripping strength, and thermal perception were assessed at day 36, day 40, and day 44, respectively. On the 45th day, the animals were sacrificed, after which the plasma insulin, nitric oxide, C-reactive protein, tumor necrosis factor alpha, and malondialdehyde were measured. The patch application attenuated hyperglycemia with an improvement in the locomotor activity, thermal perception, and gripping strength in diabetic animals. Furthermore, the application of the patch augmented plasma nitric oxide while attenuating plasma malondialdehyde and tumor necrosis factor alpha. The application of pectin-insulin patch delays the onset of peripheral neuropathic-like symptoms in diabetic animals.

Nanoceria ameliorates doxorubicin induced cardiotoxicity: Possible mitigation via reduction of oxidative stress and inflammation

Doxorubicin (DOX) is one of the most commonly used anticancer drugs but its use has been limited due to constraints of cardiotoxic side effects. The precise mechanism underlying cardiotoxicity is not yet fully understood but oxidative stress has been found to be a primary mechanism behind this. In addition, DOX induced cardiotoxicity also shows involvement of proinflammatory cytokines such as IL-6 and TNF-α. Since oxidative stress plays major role in DOX induced cardiotoxicity, different antioxidants have been tried to prevent cardiotoxicity of DOX. Nanoparticles have risen up as a promising material with a wide variety of actions, and cerium oxide nanoparticles or nanoceria (NC) is one of such kind with great antioxidant potential. NC has emerged as a promising antioxidant in different pathological conditions. The present study was aimed to investigate possible protective effects of NC in DOX induced cardiotoxicity. Cardiotoxicity was induced in Swiss mice by DOX administration through i.p. route at a dose level of 15 mg/kg in two divided doses on alternate days. In our study, NC was found to mitigate cardiotoxic potential of DOX and prevented weight loss. NC restored the levels of cardiac injury markers lactate dehydrogenase (LDH) and creatinine kinase MB (CK-MB). Moreover, NC reduced malondialdehyde (MDA) levels and increased endogenous antioxidants such as reduced glutathione (GSH) and catalase levels. In addition, NC decreased proinflammatory cytokine levels and also prevented the alteration in normal structure of heart samples. Our study showed protective effects of NC in DOX induced cardiotoxicity which can become a potential therapeutic intervention against DOX induced cardiotoxicity.

The Effects of Hesperidin and Quercetin on Serum Tumor Necrosis Factor-Alpha and Interleukin-6 Levels in Streptozotocin-induced Diabetes Model

Background:

Diabetes mellitus (DM) is a metabolic disorder that occurs as a result of absolute or relative insufficiency of insulin release and/or insulin effect due to impairment of carbohydrate, fat and protein metabolism, and it is characterized by hyperglycemia and leads to various complications.

Objective:

In this study, it was aimed to investigate the effects of hesperidin (HP) and quercetin, which are natural flavonoids, on serum malondialdehyde (MDA), glutathione (GSH), tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6) levels in rats with streptozotocin (STZ)-induced diabetes.

Materials and Methods:

The experimental animals were divided into four groups, each group comprising ten rats designated as follows: Group 1 served as control rats (C); Group 2 served as diabetic rats (DM); Group 3 served as diabetic rats administered HP (DM + HP) (100 mg/kg b. w.); and Group 4 served as diabetic rats administered quercetin (DM + Q) (100 mg/kg b. w.).

Results:

Serum MDA and GSH levels were significantly higher in STZ-induced DM group than control group (P < 0.05). In DM + HP and DM + Q groups, MDA levels were significantly decreased compared to DM groups (P < 0.05), but there was no significant difference GSH levels between DM, DM + HP, and DM + Q groups (P > 0.05). TNF-α levels in STZ-induced DM group were significantly decreased compared to control group (P < 0.05), and groups of DM + HP and DM + Q had higher serum TNF-α levels than STZ-induced DM group (P < 0.05). In STZ-induced DM group, serum IL-6 levels were decreased compared to control group (P < 0.05).

Conclusion:

As a result, in this study, we determined that HP and quercetin may play an effective role in regulating insulin metabolism metabolism in diabetes. However, considering the incompatibility of various results in the literature as well as our own results, we think that the actual role of cytokines in the pathogenesis of diabetes is one of the issues that need to be clarified in further studies.

SUMMARY

Hesperidin (HP) and quercetin reduced the insulin, total cholesterol, triglyceride, low-density lipoprotein cholesterol, and malondialdehyde (MDA) serum levels and raised the glutathione (GSH) levels compared to diabetes mellitus (DM) group

SZT-induced DM increased the MDA serum levels and decreased the GSH levels compared to control group

HP and quercetin-treated rats showed higher interleukin-6 and tumor necrosis factor alpha cytokine levels than DM group

HP and quercetin may play an effective role in regulating insulin metabolism in diabetes.

Abbreviations used: DM: Diabetes mellitus, MDA: Malondialdehyde, GSH: Glutathione; IL-6: Interleukin-6, TNF-α: Tumor necrosis factor alpha, HP: Hesperidin, Q; Quercetin, STZ: Streptozotocin, TC: Total cholesterol, TG: Triglyceride, HDL-C: High density lipoprotein cholesterol, LDL-C: Low density lipoprotein cholesterol, VLDL-C: Very-low-density lipoprotein cholesterol.