Diabetes-induced Neuropathy Research Articles

Impact of L-Arginine on diabetes-induced neuropathy and myopathy: Roles of PAI-1, Irisin, oxidative stress, NF-κβ, autophagy and microRNA-29a

BackgroundT2DM is a chronic disorder with progressive neuromuscular alterations. L-arginine (ARG) is the most common semi-essential amino acid having several metabolic functions. Aimto investigate the impact of L-arginine in combating diabetic-induced neuromyopathy and its possible mechanisms. Materials & Methods24 rats were divided into CON, CON+ARG, DC, DC+ARG. Behavioral tests, Body weight (BW), fasting blood glucose (FBG), insulin, total antioxidant capacity (TAC), malondialdehyde (MDA), plasminogen activator inhibitor-1 (PAI-1), and irisin were done. Creatine kinase-MM (CK-MM), interleukin 4 (IL-4), interleukin 6 (IL-6), TAC, MDA, expression of microRNA-29a mRNA & light chain 3 protein were determined in muscle. Histological and NF-κβ immunohistochemical expression in muscle and nerve were assessed. ResultsARG supplementation to diabetic rats improved altered behavior, significantly increased BW, insulin, TAC, irisin and Il-4, decreased levels of glucose, microRNA-29a, NF-κβ and LC3 expression, PAI-1, CK-MM and restored the normal histological appearance. ConclusionsARG supplementation potently alleviated diabetic-induced neuromuscular alterations.

FNDC5/Irisin mitigates high glucose-induced neurotoxicity in HT22 cell via ferroptosis.

Diabetes-induced neuropathy represents a major etiology of dementia, highlighting an urgent need for the development of effective therapeutic interventions. In this study, we explored the role of fibronectin type III domain containing 5 (FNDC5)/Irisin in mitigating hyperglycemia-induced neurotoxicity in HT22 cells and investigated the underlying mechanisms. Our findings reveal that high glucose conditions are neurotoxic, leading to reduced viability of HT22 cells and increased apoptosis. Furthermore, the elevated expression of the intracellular ferroptosis marker Acyl-CoA Synthetase Long Chain Family Member 4 (ACSL4), along with increased levels of ferrous ions and malondialdehyde (MDA), suggests that high glucose conditions may induce ferroptosis in HT22 cells. FNDC5/Irisin treatment effectively mitigates high glucose-induced neurotoxicity and ferroptosis in HT22 cells. Mechanistically, FNDC5/Irisin enhances cellular antioxidant capacity, regulates ACSL4 expression, and improves intracellular redox status, thereby inhibiting ferroptosis and increasing HT22 cell survival under high-glucose conditions. These results highlight the neuroprotective potential of FNDC5/Irisin in high glucose environments, offering a promising avenue for developing treatments for diabetes-related neurodegenerative diseases.

Targeting Anti-Inflammatory Pathways to Treat Diabetes-Induced Neuropathy by 6-Hydroxyflavanone.

It is evident that inflammation and metabolic syndrome instigated by diabetes mellitus can precipitate diabetes-induced neuropathy (DIN) and pain. In order to find an effective therapeutic method for diabetes-related problems, a multi-target-directed ligand model was used. 6-Hydroxyflavanone (6-HF) carrying anti-inflammatory and anti-neuropathic pain potential due to its quadruplicate mechanisms, targeting cyclooxygenase-2 (COX-2), 5-lipoxygenase (5-LOX), and opioid and GABA-A receptors was investigated. The anti-inflammatory potential of the test drug was confirmed utilizing in silico, in vitro, and in vivo tests. A molecular simulation approach was utilized to observe the interaction of 6-HF with the inflammatory enzyme COX-2 as well as opioid and GABA-A receptors. The same was confirmed via in vitro COX-2 and 5-LOX inhibitory assays. In vivo tests were performed to analyze the thermal anti-nociception in the hot-plate analgesiometer and anti-inflammatory action in the carrageenan-induced paw edema model in rodents. The potential anti-nociceptive effect of 6-HF was evaluated in the DIN model in rats. The Naloxone and Pentylenetetrazole (PTZ) antagonists were used to confirm the underlying mechanism of 6-HF. The molecular modeling studies revealed a favorable interaction of 6-HF with the identified protein molecules. In vitro inhibitory studies revealed that 6-HF inhibited the COX-2 and 5-LOX enzymes significantly. The 6-HF at dosages of 15, 30, and 60 mg/kg substantially reduced heat nociception in a hot plate analgesiometer as well as carrageenan-induced paw edema in rodent models. The authors discovered that 6-HF had anti-nociception properties in a streptozotocin-induced diabetic neuropathy model. According to the findings of this study, 6-HF was demonstrated to diminish inflammation caused by diabetes as well as its anti-nociception effect in DIN.

Microneedle-mediated delivery of Ziconotide-loaded liposomes fused with exosomes for analgesia.

Ziconotide (ZIC) is an N-type calcium channel antagonist for treating severe chronic pain that is intolerable, or responds poorly to the administration of other drugs, such as intrathecal morphine and systemic analgesics. As it can only work in the brain and cerebrospinal fluid, intrathecal injection is the only administration route for ZIC. In this study, borneol (BOR)-modified liposomes (LIPs) were fused with exosomes from mesenchymal stem cells (MSCs) and loaded with ZIC to prepare microneedles (MNs) to improve the efficiency of ZIC across the blood-brain barrier. To evaluate local analgesic effects of MNs, the sensitivity of behavioral pain to thermal and mechanical stimuli was tested in animal models of peripheral nerve injury, diabetes-induced neuropathy pain, chemotherapy-induced pain, and ultraviolet-B (UV-B) radiation-induced neurogenic inflammatory pain. BOR-modified LIPs loaded with ZIC were spherical or nearly spherical, with a particle size of about 95nm and a Zeta potential of -7.8mV. After fusion with MSC exosomes, the particle sizes of LIPs increased to 175nm, and their Zeta potential increased to -3.8mV. The nano-MNs constructed based on BOR-modified LIPs had good mechanical properties and could effectively penetrate the skin to release drugs. The results of analgesic experiments showed that ZIC had a significant analgesic effect in different pain models. In conclusion, the BOR-modified LIP membrane-fused exosome MNs constructed in this study for delivering ZIC provide a safe and effective administration for chronic pain treatment, as well as great potential for clinical application of ZIC.

Stem Cell Therapy in Diabetic Polyneuropathy: Recent Advancements and Future Directions

Diabetic polyneuropathy (DPN) is the most frequent, although neglected, complication of long-term diabetes. Nearly 30% of hospitalized and 20% of community-dwelling patients with diabetes suffer from DPN; the incidence rate is approximately 2% annually. To date, there has been no curable therapy for DPN. Under these circumstances, cell therapy may be a vital candidate for the treatment of DPN. The epidemiology, classification, and treatment options for DPN are disclosed in the current review. Cell-based therapies using bone marrow-derived cells, embryonic stem cells, pluripotent stem cells, endothelial progenitor cells, mesenchymal stem cells, or dental pulp stem cells are our primary concern, which may be a useful treatment option to ease or to stop the progression of DPN. The importance of cryotherapies for treating DPN has been observed in several studies. These findings may help for the future researchers to establish more focused, accurate, effective, alternative, and safe therapy to reduce DPN. Cell-based therapy might be a permanent solution in the treatment and management of diabetes-induced neuropathy.

Glial Cell Line-Derived Neurotrophic Factor Family Ligands, Players at the Interface of Neuroinflammation and Neuroprotection: Focus Onto the Glia.

Well-known effects of neurotrophic factors are related to supporting the survival and functioning of various neuronal populations in the body. However, these proteins seem to also play less well-documented roles in glial cells, thus, influencing neuroinflammation. This article summarizes available data on the effects of glial cell line derived neurotrophic factor (GDNF) family ligands (GFLs), proteins providing trophic support to dopaminergic, sensory, motor and many other neuronal populations, in non-neuronal cells contributing to the development and maintenance of neuropathic pain. The paper also contains our own limited data describing the effects of small molecules targeting GFL receptors on the expression of the satellite glial marker IBA1 in dorsal root ganglia of rats with surgery- and diabetes-induced neuropathy. In our experiments activation of GFLs receptors with either GFLs or small molecule agonists downregulated the expression of IBA1 in this tissue of experimental animals. While it can be a secondary effect due to a supportive role of GFLs in neuronal cells, growing body of evidence indicates that GFL receptors are expressed in glial and peripheral immune system cells. Thus, targeting GFL receptors with either proteins or small molecules may directly suppress the activation of glial and immune system cells and, therefore, reduce neuroinflammation. As neuroinflammation is considered to be an important contributor to the process of neurodegeneration these data further support research efforts to modulate the activity of GFL receptors in order to develop disease-modifying treatments for neurodegenerative disorders and neuropathic pain that target both neuronal and glial cells.

Vitamin D and rosuvastatin obliterate peripheral neuropathy in a type-2 diabetes model through modulating Notch1, Wnt-10α, TGF-β and NRF-1 crosstalk

AimsVitamin D and rosuvastatin are well-known drugs that mediate beneficial effects in treating type-2 diabetes (T2D) complications; however, their anti-neuropathic potential is debatable. Hence, our study investigates their neurotherapeutic potential and the possible underlying mechanisms using a T2D-associated neuropathy rat model. Main methodsDiabetic peripheral neuropathy (DPN) was induced with 8 weeks of administration of a high fat fructose diet followed by a single i.p. injection of streptozotocin (35 mg/kg). Six weeks later, DPN developed and rats were divided into five groups; viz., control, untreated DPN, DPN treated with vitamin D (cholecalciferol, 3500 IU/kg/week), DPN treated with rosuvastatin (10 mg/kg/day), or DPN treated with combination vitamin D and rosuvastatin. We determined their anti-neuropathic effects on small nerves (tail flick test); large nerves (electrophysiological and histological examination); neuronal inflammation (TNF-α and IL-18); apoptosis (caspase-3 activity and Bcl-2); mitochondrial function (NRF-1, TFAM, mtDNA, and ATP); and NICD1, Wnt-10α/β-catenin, and TGF-β/Smad-7 pathways. Key findingsTwo-month treatment with vitamin D and/or rosuvastatin regenerated neuronal function and architecture and abated neuronal inflammation and apoptosis. This was verified by the inhibition of the neuronal content of TNF-α, IL-18, and caspase-3 activity, while augmenting Bcl-2 content in the sciatic nerve. These treatments inhibited the protein expressions of NICD1, Wnt-10α, β-catenin, and TGF-β; increased the sciatic nerve content of Smad-7; and enhanced mitochondrial biogenesis and function. SignificanceVitamin D and/or rosuvastatin alleviated diabetes-induced neuropathy by suppressing Notch1 and Wnt-10α/β-catenin; modulating TGF-β/Smad-7 signaling pathways; and enhancing mitochondrial function, which lessened neuronal degeneration, demyelination, and fibrosis.

Clavulanic Acid Attenuating Effect on the Diabetic Neuropathic Pain in Rats.

Diabetic neuropathy is one of the most common complications of diabetes mellitus. Excess glutamate release and oxidative stress are hypothesized to be involved in the pathophysiology of diabetes-induced neuropathy. This study was designed to investigate the effect of clavulanic acid (CLAV), a competitive beta-lactamase inhibitor, on the streptozocin (STZ)-induced neuropathic pain and possible mechanisms in the spinal cord of rats. Male Wistar rats were divided into naive group; control group which got a single dose of STZ (50mg/kg, i.p.), as a model of diabetic neuropathic pain; prophylactic groups: animals received CLAV (10, 20 and 40mg/kg, i.p.) 1 week after STZ for 10 days; and therapeutic group: animals received 20mg/kg CLAV, 21 days after STZ for 10 days. Study of pain behaviors was started on days 0, 7, 14, 21, 28, 35 and 42 after STZ. The expression of the glutamate transport 1 (GLT1), genes of oxidative stress including inducible nitric oxide synthase (iNOS), proinflammatory cytokine, tumor necrosis factor alpha (TNF-α), as well as genes involved in the apoptosis including bcl2, bcl2-associated x (bax) were measured in the spinal cord tissue by Real Time PCR, on day 42. On day 21 post injection of STZ, diabetic animals showed significant mechanical allodynia, cold allodynia and thermal hyperalgesia. CLAV in all doses of 10, 20 and 40mg/kg reduced symptoms of allodynia and hyperalgesia, in both prophylactic and therapeutic regimens. While iNOS, TNF-α, bax/bcl2 were found significantly overexpressed in spinal cord of diabetic animals, their expression in animals received CLAV had been reduced. In contrast, GLT1 that had decreased in the spinal cord of diabetic animals, significantly increased in those received CLAV. CLAV was found a promising candidate for reliving neuropathic pain in diabetes mellitus. Such beneficial effect of CLAV could be, in part, attributed to the increased expression of GLT 1, inhibition of nitrosative stress, anti-inflammation, and inhibition of some apoptotic mediators followed by administration into diabetic animals.

Intrathecal Injection of SIRT1-modified Human Mesenchymal Stem Cells Alleviates Neuropathic Pain in Rat.

Accumulating evidence has elucidated that human mesenchymal stem cells (hMSCs) exert profound analgesic effects on numerous animal models of neuropathic pain, including drug-induced peripheral nerves, diabetes-induced neuropathy, and chronic constriction injury. We aimed to address whether forcing expression of sirtuin 1 (SIRT1) can enhance the efficacy of hMSCs on alleviation of pain sensation. A rat model of chronic constriction injury (CCI) mimicking peripheral nerve injury was incorporated in the study. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) testing were used to measure pain-related behavior. Our results demonstrated that SIRT1 was decreased post-CCI surgery. Compared to hMSCs-control implantation, the hMSCs-SIRT1 (hMSCs overexpressing SIRT1) implantation exhibited superior effects on reducing pro-inflammatory cytokine levels in serum and spinal dorsal horn, while ameliorating neuropathic pain in CCI rat. Engineering hMSCs such as overexpressing SIRT1 may serve as a promising strategy for the treatment of patients with neuropathic pain.

Gongronema latifolium Benth. leaf extract attenuates diabetes-induced neuropathy via inhibition of cognitive, oxidative stress and inflammatory response.

Gongronema latifolium (G. latifolium) Benth. leaves are traditionally used to treat diabetes mellitus (DM) and other diseases in Nigeria and West Africa. This study was performed to evaluate the neuroprotective effect of aqueous extract of G. latifolium leaf against DM. Antidiabetic activity of G. latifolium extracts (6.36, 12.72 and 25.44 mg kg-1 , i.p.) was determined in alloxan-induced diabetic rats. Fasting blood glucose level and oxidative stress markers catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), malondialdehyde (MDA), and nitric oxide (NO) levels were measured. Cognitive biomarkers acetylcholinesterase (AChE), butyrylcholinesterase (BChE), dopamine (DOPA), serotonin, epinephrine and norepinephrine and cyclooxygenase (COX-2) were measured in the brain of controls and of G. latifolium-treated diabetic rats. Administration of G. latifolium leaf extract to diabetic rats significantly restored the alterations in the levels of fasting blood glucose (FBG). The MDA and NO levels were significantly reduced with an improvement in CAT, SOD, and GPx activity in the kidneys and brains of diabetic rats treated with G. latifolium. Gongronema latifolium also significantly decreased the levels of AChE, BChE, DOPA, serotonin, epinephrine, and nor-epinephrine in diabetic rats. G. latifolium effectively ameliorated COX-2 in diabetic rats. This study showed that leaf extract of G. latifolium improved antioxidant defense against oxidative stress. It displays a neuroprotective effect resulting in the modulation of brain neurotransmitters, which could be considered as a promising treatment therapy. © 2020 Society of Chemical Industry.

Exercise and insulin-like growth factor1 supplementation improve angiogenesis and angiogenic cytokines in a rat model of diabetes-induced neuropathy.

What is the central question of this study? Do changes in levels of angiogenesis-related mediators [vascular endothelial growth factor-A (VEGF-A), thrombospondin-1 (TSP-1) and nuclear factor-κB (NF-κB)] in the sciatic nerve mediate diabetic neuropathy in the streptozotocin-induced type1 diabetic male rat? Can exercise and insulin-like growth factor1 (IGF-I) treatment improve the diabetes-related decrease in angiogenesis in sciatic nerve in these animals? What is the main finding and its importance? Levels of VEGF-A, TSP-1 and NF-κB change in the sciatic nerve of diabetic rats and might mediate diabetic neuropathy. Treatment with IGF-I and exercise could increase angiogenesis in the diabetic rats by increasing VEGF-A and decreasing TSP-1 and NF-κB expression in the sciatic nerve. Diabetic neuropathy is a severe complication of diabetes that affects 40-50% of diabetic people in the world. The aim of this study was to characterize alterations in angiogenesis and related molecular mediators in the sciatic nerve in diabetic conditions alone or in diabetes in combination withexercise and/or administration of insulin-like growth factor1 (IGF-I). Forty male Wistar rats were assigned into one of five groups, namely control, diabetes, diabetes+exercise, diabetes+IGF-I and diabetes+exercise+IGF-I. Type1 diabetes was induced by i.p. injection of streptozotocin (60mgkg-1 ). After 30 days of treatment with exercise or IGF-I alone or in combination, diabetic neuropathy was evaluated with a hotplate, glycated haemoglobin was measured, angiogenesis was determined by immunostaining for PECAM-1/CD31, and expressions of vascular endothelial growth factor-A (VEGF-A), thrombospondin-1 (TSP-1) and nuclear factor-κB (NF-κB) were determined by enzyme-linked immunosorbent assay.After 4weeks, the diabetes group showed a significant decrease in capillary density and VEGF-A levels, but a significant increasein glycated haemoglobin in blood, TSP-1 and NF-κB levels in the sciatic nerve compared with the control group, and these effects were ameliorated by exercise and IGF-I. However, simultaneous treatment of diabetic rats with IGF-I and exercise did not have any synergistic effects. These findings indicate that diabetes-induced neuropathy may be associated, in part, with decreasedangiogenesis mediated by overproduction of TSP-1 and NF-κB, in addition to reduced production of VEGF-A. The findings also showed that exercise and IGF-I can reduce neuropathy, followed by increased angiogenesis, by changes in TSP-1, NF-κB and VEGF-A production levels.

In Vitro and In Vivo Effects of Flavonoids on Peripheral Neuropathic Pain.

Neuropathic pain is a common symptom and is associated with an impaired quality of life. It is caused by the lesion or disease of the somatosensory system. Neuropathic pain syndromes can be subdivided into two categories: central and peripheral neuropathic pain. The present review highlights the peripheral neuropathic models, including spared nerve injury, spinal nerve ligation, partial sciatic nerve injury, diabetes-induced neuropathy, chemotherapy-induced neuropathy, chronic constriction injury, and related conditions. The drugs which are currently used to attenuate peripheral neuropathy, such as antidepressants, anticonvulsants, baclofen, and clonidine, are associated with adverse side effects. These negative side effects necessitate the investigation of alternative therapeutics for treating neuropathic pain conditions. Flavonoids have been reported to alleviate neuropathic pain in murine models. The present review elucidates that several flavonoids attenuate different peripheral neuropathic pain conditions at behavioral, electrophysiological, biochemical and molecular biological levels in different murine models. Therefore, the flavonoids hold future promise and can be effectively used in treating or mitigating peripheral neuropathic conditions. Thus, future studies should focus on the structure-activity relationships among different categories of flavonoids and develop therapeutic products that enhance their antineuropathic effects.

Study of 18β Glycyrrhetinic Acid for the Prevention of Progression of Diabetes Induced Neuropathy in Laboratory Animals

Diabetes is a metabolic disease that is associated with oxidative stress and the dysfunction of mitochondria. Long-term diabetes may cause different associated complications. One of the most common complications of diabetes mellitus is neuropathy. The present study aimed to investigate the possible neuroprotective effects of 18β glycyrrhetinic acid (GA), the metabolite of glycyrrhizic acid, which is the main active component commonly used in traditional Chinese medicine on oxidative damage and the sciatic nerve of diabetesinduced neuropathy in laboratory animals. Diabetes was induced in male Wistar rats (200–260 g) by injecting a single dose of nicotinamide (110 mg/kg, intraperitoneally) and streptozotocin (STZ) (55 mg/kg, intraperitoneally). The rats were divided into six groups. Pregabalin (10 mg/kg, p.o.) and 18β GA (50, 100, and 200 mg/kg, p.o.) were administered daily after four weeks of nicotinamide-STZ injection to the rats of groups III to VI respectively for four weeks. Various behavioral (heat and mechanical hyperalgesia, allodynia, etc.), hemodynamic and biochemical parameters were investigated, and the histological examination of the sciatic nerve was carried out. In the present study, the 18β GA (100 and 200 mg/kg) significantly (p is less than 0.01, p is less than 0.001) increased in the tail withdrawal latency and increased in paw withdrawal threshold, and increased in systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure. Furthermore, 18β GA (100 and 200 mg/kg) significantly (p is less than 0.01, p is less than 0.001) restored altered blood glucose level, total protein, antioxidant status, and histological abnormalities. Pregabalin (10 mg/kg) showed a maximum protective effect, but a low dose of 18β GA (50 mg/kg) was not enough to show the protective activity in diabetic rats. In most of the tests, non-significant differences were observed between the control and 18β GA 200 mg/kg groups. Moreover, 18β GA lowers the inflammation and demyelination in sciatic nerves. Beyond its antioxidant role possessed neuroprotective effect via modulation of endogenous enzymes in nicotinamide-STZ induced diabetic in rats.

High-fat Diet-induced Obesity Induces Peripheral Neuropathy During Impaired Cutaneous Wound Healing

Type-II diabetes is a societal epidemic that is associated with obesity and metabolic disease often resulting from poor diet and reduced physical activity. Two major complications associated with type-II diabetes are peripheral neuropathy which leads to a loss of sensation and chronic pain as well as poor wound healing, which can progress to ulceration and ultimately amputation. Since clinical trials for the treatment of these chronic conditions have only fostered limited success we examined the possibility that the nervous system and wound repair are linked. The PURPOSE of this study was to investigate the potential that the peripheral nervous system is a necessary regulator for normal wound repair and that diabetes-induced neuropathy is in part, causative of impaired wound healing. METHODS: We administered a 6 mm skin punch biopsy wound to high-fat diet (HFD, 10 weeks of feeding with 60% of energy from fat content, n=9) and control (10% of energy via fat content, n=9) fed mice. RESULTS: A diabetic phenotype was confirmed in HFD mice as evidenced by elevated body weight (Control mean weight=32.4g, HFD mean weight=40.7g) and impaired glucose tolerance (p < 0.05) in response to an intraperitoneal glucose tolerance test. Following skin injury, HFD mice demonstrated an impaired wound healing rate as evidenced by a larger wound diameter and area (p < 0.05) at days 2-9 while hematoxylin, and eosin staining of tissue-cross sections revealed larger wound widths and a poorly formed dermis in HFD mice in comparison to controls at day 9. Immunohistochemical analysis demonstrated that poor wound healing was coincident with a reduction of S100ß+ cutaneous Schwann cells within and around the healing dermis. Ongoing analysis includes the examination of additional markers of cutaneous neuropathy using immunohistochemistry to quantify total nerve axons (UCHL-1+ cells), growing/regenerating axons (Gap43+ cells) and markers of activated/dedifferentiated Schwann cells (p75NTR+,Sox2+ cells) as well as testing the efficacy of Schwann cell transplantation to rescue HDF-induced neuropathy and wound healing deficits. CONCLUSION: Collectively, these experiments will give insight into the mechanisms underpinning two major complications associated with type-II diabetes that could be further explored to develop novel therapeutics.

Increased ATP and ADO Overflow From Sympathetic Nerve Endings and Mesentery Endothelial Cells Plus Reduced Nitric Oxide Are Involved in Diabetic Neurovascular Dysfunction.

Since the mechanism of human diabetic peripheral neuropathy and vascular disease in type 1 diabetes mellitus remains unknown, we assessed whether sympathetic transmitter overflow is altered by this disease and associated to vascular dysfunction. Diabetes was induced by streptozotocin (STZ)-treatment and compared to vehicle-treated rats. Aliquots of the ex vivo perfused rat arterial mesenteric preparation, denuded of the endothelial layer, were collected to quantify analytically sympathetic nerve co-transmitters overflow secreted by the isolated mesenteries of both groups of rats. Noradrenaline (NA), neuropeptide tyrosine (NPY), and ATP/metabolites were detected before, during, and after electrical field stimulation (EFS, 20 Hz) of the nerve terminals surrounding the mesenteric artery. NA overflow was comparable in both groups; however, basal or EFS-secreted ir-NPY was 26% reduced (p < 0.05) in diabetics. Basal and EFS-evoked ATP and adenosine (ADO) overflow to the arterial mesentery perfusate increased twofold and was longer lasting in diabetics; purine tissue content was 37.8% increased (p < 0.05) in the mesenteries from STZ-treated group of rats. Perfusion of the arterial mesentery vascular territory with 100 μM ATP, 100 nM 2-MeSADP, or 1 μM UTP elicited vasodilator responses of the same magnitude in controls or diabetics, but the increase in luminally accessible NO was 60–70% lower in diabetics (p < 0.05). Moreover, the concentration–response curve elicited by two NO donors was displaced downwards (p < 0.01) in diabetic rats. Parallel studies using primary cultures of endothelial cells from the arterial mesentery vasculature revealed that mechanical stimulation induced a rise in extracellular nucleotides, which in the cells from diabetic rats was larger and longer-lasting when comparing the extracellular release of ATP and ADO values to those of vehicle-treated controls. A 5 min challenge with purinergic agonists elicited a cell media NO rise, which was reduced in the endothelial cells from diabetic rats. Present findings provide neurochemical support for the diabetes-induced neuropathy and show that mesenteric endothelial cells alterations in response to mechanical stimulation are compatible with the endothelial dysfunction related to vascular disease progress.

The Development and Progression of Mechanical Allodynia in UC, Davis Type 2 Diabetic Rats

Type 2 diabetes (T2DM) is a metabolic disorder that can lead to many neuropathic complications such as mechanical allodynia, which is perceived pain caused by a normally non‐painful stimulus. T2DM is also associated with exaggerated pressor and cardioaccelerator responses to skeletal muscle contraction, namely the exercise pressor reflex. The mechanisms by which diabetes elicits these effects are not fully understood; however, both mechanical allodynia and the exercise pressor reflex are evoked by thin‐fiber afferent activity. The purpose of this study was to utilize noninvasive techniques to monitor the development and progression of diabetes‐induced neuropathy in thin‐fiber afferents. We used male UC Davis T2DM (n=9) rats from the age of 4 to 7 months to model the progression of T2DM. We took monthly measurements of blood glucose, HbA1c, and body weight. We also measured changes in mechanical sensitivity using von Frey filaments. Filaments were applied to the L5 dermatome on the plantar side of the left and right hind paws, between the footpads; the lowest force eliciting an abrupt paw withdrawal was measured and averaged between paws. We found that blood glucose (4mo: 255±28 mg/dl, 5mo: 366±50 mg/dl, 6mo: 417±58 mg/dl, 7mo: 453±49 mg/dl) and HbA1c (4mo: 5.7±0.2%, 5mo: 6.6±0.4%, 6mo: 9.3±1.2%, 7mo: 10.3±1.2%) were above the diabetic threshold (300 mg/dl, 6.5%) at 5, 6, and 7 months of age; they were significantly higher at 6 and 7 months, compared to 4 months, p&lt;0.05. Body weight was significantly higher at 5, 6, and 7 months compared to 4 months (4mo: 525±4g, 5mo: 609±3g, 6mo: 620±21g, 7mo: 610±31g; p&lt;0.05). Sensitivity to von Frey filaments was significantly greater, indicating mechanical allodynia, at 6 and 7 months compared to 4 months (4mo: 29±3.2 g, 5mo: 26.3±4.5 g, 6mo: 14.1±3.3 g, 7mo: 9.7±1.7 g; p&lt;0.05). We conclude that mechanical allodynia progresses in severity as the rats develop and progress with T2DM. Moreover, these observations may provide insight to diabetes‐induced changes in thin‐fiber dependent reflexes, such as the exercise pressor reflex.Support or Funding InformationN/AThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Nerve conduction study in neurologically asymptomatic diabetic patients and correlation with glycosylated hemoglobin and duration of diabetes

Background: Diabetes-induced neuropathy is one of the most challenging complications of diabetes mellitus (DM). Large number of patients has subclinical neuropathy at the time of detection of diabetes. Nerve conduction studies (NCS) remain the most reliable, accurate, and sensitive measure of peripheral nerve function. The study of F waves is particularly useful for the diagnosis of peripheral neuropathy. Aims and Objectives: The present study was conducted to study various nerve conduction parameters in neurologically asymptomatic diabetic patients with an attempt to evaluate their value in the early detection of subclinical diabetic neuropathy and to find out if any correlation exists. Materials and Methods: This case–control study was carried out on 44 neurologically asymptomatic established patients of Type II DM of both sexes, aged 40–60 years attending the medicine outpatient department (OPD). NCS parameters of various nerves were studied. Blood sugar and glycosylated hemoglobin (HbA1c) were determined. Results: A longer latency, smaller amplitude and slower conduction velocity were found in all the nerves. Persistence was found to be lower and F-wave minimum latency prolonged amongst the cases. Sensory and motor NCS were found to be inferior in those with higher HbA1c. Latency, amplitude, and Nerve conduction velocity (NCV) of sural nerve showed deterioration with the duration of diabetes. All parameters of median, ulnar and common peroneal nerves showed deterioration with the duration of diabetes with the exception of NCV in common peroneal nerve and persistence in median nerve. Conclusions: NCS parameters are valuable for identification and future prediction of diabetic peripheral neuropath.

Evaluation of Therapeutic Effectiveness of Prescribed Medications in Patients with Type 2 Diabetes Mellitus: Findings from a Tertiary Care Hospital, Lahore, Pakistan.

Aim:The present study was aimed to highlight the current prescribing pattern of oral hypoglycemia in type 2 diabetes mellitus and to evaluate the therapeutic effectiveness of these therapeutic categories in achieving target glycemic control.Methods:This is a prospective, cross-sectional, observational study of 6 months’ duration conducted in a tertiary care hospital of Lahore, Pakistan.Results:The current research recruited 145 patients presented in diabetes management center of a tertiary care hospital in Lahore, Pakistan. Mean age of the participants was 50.2 (± 8.5) years. Out of the 145 patients, 63% were females and 37% were males. Most patients were diagnosed to have diabetes within the past 5 years. Diabetes-induced neuropathy was the most common complication (71.7%) among the patients. A large proportion of these patients (70.3%) were also suffering from other comorbidities among which the most common one is hypertension. The average number of prescribed medications was 1.31. Metformin was prescribed to a majority of patients (64%) as monotherapy while 28.96% received combination therapy. Mean glycated hemoglobin (HBA1c) before and after 3 months of treatment was 8.5 (± 2.3) and 8.04 (± 2.1), respectively. Inferential statistics show a strong association between HBA1c and life style modifications and adherence to medication therapy (P = 0.05). However, the correlation between HBA1c and Morisky score and duration of disease was inverse and weak (P = 0.6, 0.4). The t-test values show a small difference between HBA1c values before and after 3 months (t = 0.440 and 0.466, respectively).Conclusion:Optimization of medication regimen and continuous patient education regarding life style modification and adherence to medication therapy are necessitated to bring HBA1c values near to target.

Oxidative, metabolic, and apoptotic responses of Schwann cells to high glucose levels.

The specific response of murine Schwann cells IMS32 to acute and chronic hyperglycemia conditions was evaluated. The pathophysiological alterations were studied to deepening the role of Schwann cells in diabetes-related neurotoxicity and to assess a model to screen new protective molecules. IMS32 were incubated with 30 and 56 mM glucose for 48 h and 7 and 14 days, and markers of oxidative stress, apoptosis, and polyol pathway were evaluated. High glucose induced O(2) -production and lipid peroxidation at all time point whereas Caspase 3 activity was induced only after 14 days. Aldose reductase activity and expression were significantly increased after 48 h and 14 days, respectively. Our results describe the response of Schwann cells to high glucose conditions and suggest the use of IMS32 for the screening of protective molecules in diabetes-induced neuropathy.

Dopamine Deficiency Contributes to Early Visual Dysfunction in a Rodent Model of Type 1 Diabetes

Dopamine (DA) functions as an essential neuromodulator in the brain and retina such that disruptions in the dopaminergic system are associated with common neurologic disorders such as Parkinson's disease. Although a reduction in DA content has been observed in diabetes, its effects in the development of diabetes-induced neuropathy remains unknown. Because the retina is rich in DA and has a well known diabetes-induced pathology (diabetic retinopathy or DR), this study was designed to examine the role of retinal DA deficiency in early visual defects in DR. Using rodent models of type 1 diabetes mellitus, we investigated whether diabetes caused a reduction in retinal DA content in both rats and mice and determined whether restoring DA levels or activating specific DA receptor pathways could improve visual function (evaluated with optokinetic tracking response) of diabetic mice, potentially via improvement of retinal function (assessed with electroretinography). We found that diabetes significantly reduced DA levels by 4 weeks in rats and by 5 weeks in mice, coincident with the initial detection of visual deficits. Treatment with l-DOPA, a DA precursor, improved overall retinal and visual functions in diabetic mice and acute treatment with DA D1 or D4 receptor agonists improved spatial frequency threshold or contrast sensitivity, respectively. Together, our results indicate that retinal DA deficiency is an underlying mechanism for early, diabetes-induced visual dysfunction and suggest that therapies targeting the retinal dopaminergic system may be beneficial in early-stage DR.