Acute Hypoglycemia Induces Painful Neuropathy and the Treatment of Coenzyme Q10

Excitatory and inhibitory neuronal signaling in inflammatory and diabetic neuropathic pain

Pain, although unpleasant, is an essential warning mechanism against injury and damage of the organism. An intricate network of specialised sensors and transmission systems contributes to reception, transmission and central sensitization of pain. Here, we briefly introduce some of the main aspects of pain signal transmission, including nociceptors and nociceptive signals, mechanisms of inflammatory and neuropathic pain, and the situation of diabetes-associated neuropathic pain. The role of glia-astrocytes, microglia, satellite glia cells-and their specific channels, transporters and signaling pathways is described. A focus is on the contribution of inhibitory synaptic signaling to nociception and a possible role of glycine receptors in glucose-mediated analgesia and treatment-induced diabetic neuropathy. Inhibitory receptors such as GABA_A- and glycine receptors are important contributors to nociceptive signaling; their contribution to altered pain sensation in diabetes may be of clinical relevance, and they could be promising therapeutic targets towards the development of novel analgesics.

Nutraceuticals: A Promising Approach Towards Diabetic Neuropathy

BACKGROUND

Various nutraceuticals from different sources have various beneficial actions and have been reported for many years. The important findings from the research conducted using various nutraceuticals exhibiting significant physiological and pharmacological activities have been summarized.

METHODS

An extensive investigation of literature was done using several worldwide electronic scientific databases like PUBMED, SCOPUS, Science Direct, Google Scholar, etc. The entire manuscript is available in the English language that is used for our various compounds of interest. These databases were thoroughly reviewed and summarized.

RESULTS

Nutraceuticals obtained from various sources play a vital role in the management of peripheral neuropathy associated with diabetes. Treatment with nutraceuticals has been beneficial as an alternative in preventing the progression. In particular, in vitro and in vivo studies have revealed that a variety of nutraceuticals have significant antioxidant and anti-inflammatory properties that may inhibit the early diabetes-driven molecular mechanisms that induce DPN.

CONCLUSION

Nutraceuticals obtained from different sources like a plant, an animal, and marine have been properly utilized for the safety of health. In our opinion, this review could be of great interest to clinicians, as it offers a complementary perspective on the management of DPN. Trials with a well-defined patient and symptom selection have shown robust pharmacological design as pivotal points to let these promising compounds become better accepted by the medical community.

Pleiotropic effects of anti-diabetic drugs: A comprehensive review

Diabetes mellitus characterized by hyperglycaemia presents an array of comorbidities such as cardiovascular and renal failure, dyslipidemia, and cognitive impairments. Populations above the age of 60 are in an urgent need of effective therapies to deal with the complications associated with diabetes mellitus. Widely used anti-diabetic drugs have good safety profiles and multiple reports indicate their pleiotropic effects in diabetic patients or models. This review has been written with the objective of identifying the widely-marketed anti-diabetic drugs which can be efficiently repurposed for the treatment of other diseases or disorders. It is an updated, comprehensive review, describing the protective role of various classes of anti-diabetic drugs in mitigating the macro and micro vascular complications of diabetes mellitus, and differentiating these drugs on the basis of their mode of action. Notably, metformin, the anti-diabetic drug most commonly explored for cancer therapy, has also exhibited some antimicrobial effects. Unlike class specific effects, few instances of drug specific effects in managing cardiovascular complications have also been reported. A major drawback is that the pleiotropic effects of anti-diabetic drugs have been mostly investigated only in diabetic patients. Thus, for effective repurposing, more clinical trials devoted to analyse the effects of anti-diabetic drugs in patients irrespective of their diabetic condition, are required.

Loganin prevents chronic constriction injury-provoked neuropathic pain by reducing TNF-α/IL-1β-mediated NF-κB activation and Schwann cell demyelination

BACKGROUND

Peripheral nerve injury can produce chronic and ultimately neuropathic pain. The chronic constriction injury (CCI) model has provided a deeper understanding of nociception and chronic pain. Loganin is a well-known herbal medicine with glucose-lowering action and neuroprotective activity.

PURPOSE

This study investigated the molecular mechanisms by which loganin reduced CCI-induced neuropathic pain.

METHODS

Sprague-Dawley rats were randomly divided into four groups: sham, sham+loganin, CCI and CCI+loganin. Loganin (1 or 5 mg/kg/day) was injected intraperitoneally once daily for 14 days, starting the day after CCI. For behavioral testing, mechanical and thermal responses were assessed before surgery and on d1, d3, d7 and d14 after surgery. Sciatic nerves (SNs) were collected to measure proinflammatory cytokines. Proximal and distal SNs were collected separately for Western blotting and immunofluorescence studies.

RESULTS

Thermal hyperalgesia and mechanical allodynia were reduced in the loganin-treated group as compared to the CCI group. Loganin (5 mg/kg/day) prevented CCI from inducing proinflammatory cytokines (TNF-α, IL-1β), inflammatory proteins (TNF-α, IL-1β, pNFκB, pIκB/IκB, iNOS) and receptor (TNFR1, IL-1R), adaptor protein (TRAF2) of TNF-α, and Schwann cell demyelination and axonal damage. Loganin also blocked IκB phosphorylation (p-IκB). Double immunofluorescent staining further demonstrated that pNFκB/pIκB protein was reduced by loganin in Schwann cells on d7 after CCI. In the distal stumps of injured SN, Schwann cell demyelination was correlated with pain behaviors in CCI rats.

CONCLUSION

Our findings indicate that loganin improves CCI-induced neuroinflammation and pain behavior by downregulating TNF-α/IL-1β-dependent NF-κB activation.

Modulation of Glycine Receptor-Mediated Pain Signaling in vitro and in vivo by Glucose

The inhibitory glycine receptor (GlyR) plays an important role in rapid synaptic inhibition in mammalian spinal cord, brainstem, higher brain centers, and is involved in transmission of nociceptive signals. Glucose and related mono- and disaccharides potentiate currents mediated by recombinant α1, α1-β, and α3 GlyRs. Here, we confirmed the specific potentiation of α3 GlyR signaling by glucose through: (i) patch-clamp electrophysiology on recombinant receptors; and (ii) by verifying in vitro data in a mouse model in vivo. Mice were intraperitoneally (IP) injected with glucose (2 g/kg) or vehicle, and then challenged with sublethal doses of strychnine (0.2 mg/kg and 0.5 mg/kg). Pain-related behavior was assessed using two established models: (i) touch sensitivity tests using von Frey filaments; and (ii) hotplate assay. We observed a reduction of pain sensitivity in glucose-treated mice relative to vehicle-treated control mice. Injection of strychnine resulted in an increased sensitivity to tactile and heat stimuli, which was reversed in the presence of glucose. Analgesic effects of glucose were more pronounced in von Frey experiments, consistent with the established use of this model for neuropathic pain. Overall, glucose showed mild analgesic effects and was able to compensate for strychnine-induced allodynia in mice. Since the action of strychnine is specific for GlyR, these experiments show for the first time an in vivo potentiation of GlyR activity by glucose and suggest a molecular mechanism for glucose-mediated analgesia.

Significant Changes in Metabolic Profiles after Intervention with Selenium and Coenzyme Q10 in an Elderly Population

Selenium and coenzyme Q₁₀ (SeQ₁₀) are important for normal cellular function. Low selenium intake leads to increased cardiovascular mortality. Intervention with these substances with healthy elderly persons over a period of four years in a double-blind, randomised placebo-controlled prospective study showed reduced cardiovascular mortality, increased cardiac function, and a lower level of NT-proBNP. Therefore, we wanted to evaluate changes in biochemical pathways as a result of the intervention with SeQ₁₀ using metabolic profiling. From a population of 443 healthy elderly individuals that were given 200 µg selenium and 200 mg coenzyme Q₁₀, or placebo daily for four years, we selected nine males on active intervention and nine males on placebo for metabolic profiling in the main study. To confirm the results, two validation studies (study 1 n = 60 males, study 2 n = 37 males) were conducted. Principal component analyses were used on clinical and demographic data to select representative sets of samples for analysis and to divide the samples into batches for analysis. Gas chromatography time-of-flight mass spectrometry-based metabolomics was applied. The metabolite data were evaluated using univariate and multivariate approaches, mainly T-tests and orthogonal projections to latent structures (OPLS) analyses. Out of 95 identified metabolites, 19 were significantly decreased due to the intervention after 18 months of intervention. Significant changes could be seen in the pentose phosphate, the mevalonate, the beta-oxidation and the xanthine oxidase pathways. The intervention also resulted in changes in the urea cycle, and increases in the levels of the precursors to neurotransmitters of the brain. This adds information to previous published results reporting decreased oxidative stress and inflammation. This is the first-time metabolic profiling has been applied to elucidate the mechanisms behind an intervention with SeQ₁₀. The study is small and should be regarded as hypothesis-generating; however, the results are interesting and, therefore, further research in the area is needed. This study was registered at Clinicaltrials.gov, with the identifier NCT01443780.

Nerve conduction study of the association between glycemic variability and diabetes neuropathy

BACKGROUND

It remains unclear whether glycemic variability is related to diabetes microvascular disease, especially diabetes peripheral neuropathy (DPN). We investigated the association between glycemic variability and DPN with type 1 or 2 diabetes.

METHODS

Forty patients (23 males and 17 females; aged 34-79 years) underwent continuous glucose monitoring (CGM) and a nerve conduction study (NCS). Glycemic variability was estimated by mean amplitude of glycemic excursions (MAGE) in CGM. DPN was quantitatively evaluated by NCS in the median, tibial, sural and medial plantar nerves.

RESULTS

MAGE had a significantly positive correlation with disease duration and low-density lipoprotein cholesterol level (r = 0.462, p = 0.003; and r = 0.40, p = 0.011, respectively), and a significantly negative correlation with BMI and medial plantar compound nerve action potential amplitude (r = - 0.39, p = 0.012; and r = - 0.32, p = 0.042, respectively). Multivariate linear regression analysis with adjustment for clinical background showed that MAGE (β = - 0.49, p= 0.007) was independently associated with a higher risk of medial plantar neuropathy.

CONCLUSIONS

Glycemic variability may be an independent risk factor for DPN.