Magnetic resonance imaging of the central nervous system in diabetic neuropathy

Diabetic Neuropathy Is Related to Rhinencephalon Degeneration in Adults With Type 1 Diabetes

Aims: We aimed to assess neurodegenerative changes in the rhinencephalon via magnetic resonance imaging (MRI) and relate it to olfactory function and diabetic peripheral neuropathy (DPN) in adults with type 1 diabetes (T1D). Materials and Methods: Individuals aged 18-65 with T1D duration over 10 years and control healthy subjects underwent olfactory assessment using Sniffin'Sticks and brain MRI to assess volumetric measurements of the olfactory bulbs and piriform cortex thickness. Results: 32 T1D (24 males) aged 43.5 years (IQR: 37.0-48), diabetes duration 24.5 years (IQR: 20.5-27.0), and A1C 7.95% (IQR: 7.4-8.4) were assessed. The control group consisted of 6 healthy adults (4 males) aged 41.0 years (IQR: 36.0-48.0). Significantly lower olfactory test results in TDI (threshold-differentiation-identification) (31.5 (IQR: 28.7-33.6) vs. 34.1 (IQR: 33.2-37.2), p = 0.02) were obtained in the T1D as compared to the controls. Summarized olfactory bulb (OB) volumes and thickness of the left pyriform cortex were significantly smaller in T1D than in controls (65.8 mm3 (IQR: 57.9-71.7) vs. 75.8 mm3 (IQR: 74.8-76.7); p = 0.0005 and 3.1 mm (IQR: 2.7-3.4) vs. 3.6 mm (IQR: 3.5-4.1); p =0.02). Patients with DPN had significantly smaller OB volumes than patients without DPN (58.1 mm3 (IQR: 54.0-70.9) vs. 69.8 mm3 (IQR: 65.0-72.2); p = 0.02). Tobacco smoking (β: -7.89; p = 0.013) and DPN (β:-7.02; p = 0.015) proved to be independent predictors of OB volume. Conclusions: In adults with a long history of T1D, olfactory function and structures are impaired. The presence of diabetic neuropathy and ongoing smoking addiction might be considered predictors of the degradation of rhinencephalon structures in people with T1D.

The role of gut microbiota in diabetic peripheral neuropathy rats with cognitive dysfunction

Introduction

Owing to advancements in non-invasive magnetic resonance imaging, many studies have repeatedly showed that diabetes affects the central nervous system in the presence of peripheral neuropathy, suggesting a common or interacting pathological mechanism for both complications.

Methods

We aimed to investigate the role of abnormal gut microbiota in rats with diabetic peripheral neuropathy (DPN) combined with cognitive dysfunction. Glucose-compliant rats with nerve conduction deficits were screened as a successful group of DPN rats. The DPN group was then divided into rats with combined cognitive impairment (CD) and rats with normal cognitive function (NCD) based on the results of the Novel object recognition test. Rat feces were then collected for 16S rRNA gene sequencing of the intestinal flora.

Results and Discussion

The results revealed that abnormalities in Firmicutes, Ruminococcaceae, Bacteroidia, and Actinobacteria-like microorganisms may induce DPN complicated by cognitive dysfunction.

Thalamic volumetric abnormalities in type 1 diabetes mellitus and 'peripheral' neuropathy

We hypothesized that thalamic volumes of patients with type 1 diabetes mellitus (DM) and nonpainful diabetic peripheral neuropathy (DPN) would be reduced relative to thalamic volumes of patients with type 1 DM and painful DPN. We calculated the standardized thalamic volumetric difference between these groups in a pilot sample to obtain a statistical power of 80% at a 5% significance level. Hence, we measured thalamic volumes from 15 patients with nonpainful DPN (10 women, mean age = 49 years, standard deviation [SD] = 11.5) and from 13 patients with painful DPN (8 women, mean age = 43 years, SD = 12.5) by using a manual segmentation approach. A volumetric difference of approximately 15% was found between the nonpainful (mean = 5072 mm³, SD = 528.1) and painful (mean = 5976 mm³, SD = 643.1) DPN groups (P < 0.001). Curiously, a volumetric difference between the left (mean = 5198 mm³, SD = 495.0) and the right (mean = 4946 mm³, SD = 590.6) thalamus was also found in patients with nonpainful DPN (P < 0.01), but not in patients with painful DPN (P = 0.97). Patients with nonpainful DPN have lower thalamic volumes than those with painful DPN, especially in the right thalamus.

Imbalanced learning: Improving classification of diabetic neuropathy from magnetic resonance imaging

One of the fundamental challenges when dealing with medical imaging datasets is class imbalance. Class imbalance happens where an instance in the class of interest is relatively low, when compared to the rest of the data. This study aims to apply oversampling strategies in an attempt to balance the classes and improve classification performance. We evaluated four different classifiers from k-nearest neighbors (k-NN), support vector machine (SVM), multilayer perceptron (MLP) and decision trees (DT) with 73 oversampling strategies. In this work, we used imbalanced learning oversampling techniques to improve classification in datasets that are distinctively sparser and clustered. This work reports the best oversampling and classifier combinations and concludes that the usage of oversampling methods always outperforms no oversampling strategies hence improving the classification results.

Sensorimotor and pain-related alterations of the gray matter and white matter in Type 2 diabetic patients with peripheral neuropathy

Although diabetic peripheral neuropathy (DPN) has long been considered a disease of the peripheral nervous system, recent neuroimaging studies have shown that alterations in the central nervous system may play a crucial role in its pathogenesis. Here, we used surface‐based morphometry (SBM) and tract‐based spatial statistics (TBSS) to investigate gray matter (GM) and white matter (WM) differences between patients with DPN (n = 67, 44 painless and 23 painful) and healthy controls (HCs; n = 88). Compared with HCs, patients with DPN exhibited GM abnormalities in the pre‐ and postcentral gyrus and in several deep GM nuclei (caudate, putamen, medial pallidum, thalamus, and ventral nuclear). They also exhibited altered WM tracts (corticospinal tract, spinothalamic tract, and thalamocortical projecting fibers). These findings suggest impaired motor and somatosensory pathways in DPN. Further, patients with DPN (particularly painful DPN) exhibited morphological differences in the cingulate, insula, prefrontal cortex, and thalamus, as well as impaired WM integrity in periaqueductal WM and internal and external capsules. This suggests pain‐perception/modulation pathways are altered in painful DPN. Intermodal correlation analyses found that the morphological indices of the brain regions identified by the SBM analysis were significantly correlated with the fractional anisotropy of brain regions identified by the TBSS analysis, suggesting that the GM and WM alterations were tightly coupled. Overall, our study showed sensorimotor and pain‐related GM and WM alterations in patients with DPN, which might be involved in the development of DPN.

Type 1 diabetes-associated cognitive impairment and diabetic peripheral neuropathy in Chinese adults: results from a prospective cross-sectional study

BACKGROUND

To compare neurocognitive functioning of Type 1 diabetic mellitus (T1DM) and healthy adults, and explore risk factors of cognitive dysfunction of T1DM patients, especially the association between cognitive impairment and diabetic peripheral neuropathy (DPN).

METHODS

Seventy T1DM (age: 32.17 ± 9.57 yr., duration: 8.99 ± 7.02 yr) patients and 48 healthy volunteers were included. All subjects received evaluation of MMSE and MoCA scales. Cognitive function of T1DM patients was evaluated in different cognitive domains. Risk factors affecting cognitive function were further explored.

RESULTS

Three patients with educational level ≤ 6-year were excluded from final analysis. Scores of both MMSE (28.4 ± 1.7 vs. 29.1 ± 1.0, P = 0.005) and MoCA scales (25.9 ± 2.7 vs.27.1 ± 2.4, P = 0.017) in T1DM group were lower than that in control group. For MMSE scale, scores of orientation (9.60 ± 0.79 vs.9.87 ± 0.39, P < 0.001) and language function (8.56 ± 0.65 vs.8.83 ± 0.38, P < 0.001) in T1DM groups were lower than that in control group. For MoCA scale, scores of attention and concentration (2.30 ± 0.74 vs.2.57 ± 0.58, P < 0.001), visuospatial/executive function (4.32 ± 0.91 vs.4.64 ± 0.63, P < 0.001), memory (2.96 ± 1.50 vs.3.66 ± 1.28, P < 0.001), language function (5.71 ± 0.69 vs.5.87 ± 0.39, P = 0.007), and abstraction (1.55 ± 0.68 vs.1.82 ± 0.42, P < 0.001) were lower in T1DM group than that in control group. Logistic regression showed age, fasting C peptide, educational level and nerve conduction velocity (NCV) were associated with cognitive dysfunction diagnosed by MoCA scores for the patients with type 1 diabetes.

CONCLUSIONS

T1DM adults had mild to moderate cognitive impairment, mainly presenting as dysfunctions of attention and concentration, visuospatial/executive, language, and abstraction. In addition to age, fasting C peptide level, and educational level, DPN, as a diabetic complication, was identified to be associated with cognitive impairments.

Declining Skeletal Muscle Function in Diabetic Peripheral Neuropathy

PURPOSE

The present review highlights current concepts regarding the effects of diabetic peripheral neuropathy (DPN) in skeletal muscle. It discusses the lack of effective pharmacologic treatments and the role of physical exercise intervention in limb protection and symptom reversal. It also highlights the importance of magnetic resonance imaging (MRI) techniques in providing a mechanistic understanding of the disease and helping develop targeted treatments.

METHODS

This review provides a comprehensive reporting on the effects of DPN in the skeletal muscle of patients with diabetes. It also provides an update on the most recent trials of exercise intervention targeting DPN pathology. Lastly, we report on emerging MRI techniques that have shown promise in providing a mechanistic understanding of DPN and can help improve the design and implementation of clinical trials in the future.

FINDINGS

Impairments in lower limb muscles reduce functional capacity and contribute to altered gait, increased fall risk, and impaired balance in patients with DPN. This finding is an important concern for patients with DPN because their falls are likely to be injurious and lead to bone fractures, poorly healing wounds, and chronic infections that may require amputation. Preliminary studies have shown that moderate-intensity exercise programs are well tolerated by patients with DPN. They can improve their cardiorespiratory function and partially reverse some of the symptoms of DPN. MRI has the potential to bring new mechanistic insights into the effects of DPN as well as to objectively measure small changes in DPN pathology as a result of intervention.

IMPLICATIONS

Noninvasive exercise intervention is particularly valuable in DPN because of its safety, low cost, and potential to augment pharmacologic interventions. As we gain a better mechanistic understanding of the disease, more targeted and effective interventions can be designed.

Pain modulation from the brain during diabetic neuropathy: Uncovering the role of the rostroventromedial medulla

Diabetic neuropathy has a profound impact in the quality of life of patients who frequently complain of pain. The mechanisms underlying diabetic neuropathic pain (DNP) are no longer ascribed only to damage of peripheral nerves. The effects of diabetes at the central nervous system are currently considered causes of DPN. Management of DNP may be achieved by antidepressants that act on serotonin (5-HT) uptake, namely specific serotonin reuptake inhibitors. The rostroventromedial medulla (RVM) is a key pain control center involved in descending pain modulation at the spinal cord through local release of 5-HT and plays a peculiar role in the balance of bidirectional control (i.e. inhibitory and facilitatory) from the brain to the spinal cord. This review discusses recently uncovered neurobiological mechanisms that mediate nociceptive modulation from the RVM during diabetes installation. In early phases of the disease, facilitation of pain modulation from the RVM prevails through a triplet of mechanisms which include increase in serotonin expression at the RVM and consequent rise of serotonin levels at the spinal cord and upregulation of local facilitatory 5HT3 receptors, enhancement of spontaneous activity of facilitatory RVM neurons and up-regulation of the expression of transient receptor potential vanilloid type 1 (TRPV1) receptor. With the progression of diabetes the alterations in the RVM increase dramatically, with oxidative stress and neuronal death associated to microglia-mediated inflammation. In a manner similar to other central areas, like the thalamus, the RVM is likely to be a "pain generator/amplifier" during diabetes, accounting to increase DNP. Early interventions in DNP prevention using strategies that simultaneously tackle the exacerbation of 5-HT3 spinal receptors and of microglial RVM activity, namely those that increase the levels of anti-inflammatory cytokines, should be considered in the future of DNP treatment.

Insights into the pathogenesis and treatment of painful diabetic neuropathy

Painful diabetic distal symmetrical polyneuropathy (painful DPN) is a puzzle with two important missing pieces: Firstly we still do not understand why only some patients with neuropathy experience painful symptoms; Secondly we still do not have a complete understanding of how nociception generated in the peripheral nervous system is processed by the central nervous system (CNS). Available treatments offer only symptom relief and there is currently no effective treatment based on arresting or reversing the progression of disease. Therefore the management of painful DPN remains less than optimal because the complex pathophysiology of nociception and pain perception in health and disease is incompletely understood. Studies of the peripheral nervous system are investigating the molecular processes involved in signal transduction that have the potential to be interrupted or modified to ease pain. Magnetic resonance imaging techniques are helping to elucidate central pain processing pathways and describe the translation of nociception to pain. Combining the knowledge from these two streams of enquiry we will soon be able to predict accurately who will develop painful DPN, how we can halt or reverse the condition, or who will respond to symptomatic treatments. Future developments in the treatment of painful DPN will be underpinned by decoding the peripheral and central mechanisms of pain. Research is focusing on these areas of enquiry in the hope that answers will lead to effective treatments to alleviate pain and reverse pathology for those suffering from painful DPN.

Vitamin D for the treatment of painful diabetic neuropathy

OBJECTIVE

To assess the effect of high-dose vitamin D in patients with painful diabetic neuropathy.

METHODS

A single intramuscular dose of 600 000 IU vitamin D was administered, and the effects on metabolic parameters and neuropathic pain assessed over 20 weeks.

RESULTS

143 participants with predominantly type 2 diabetes, aged 52.31±11.48 years, with a Douleur Neuropathique 4 (DN4) score (3.0±1.8), total McGill pain score (21.2±14.9), and Short Form McGill Pain Questionnaire (SFMPQ) score (2.1±0.9), were enrolled. The baseline 25-hydroxyvitamin D (25(OH)D) level was 31.7±23.3 ng/mL and 58 (40.5%) patients showed evidence of vitamin D deficiency (25(OH)D<20 ng/mL). Intramuscular administration of vitamin D resulted in a significant increase in 25(OH)D (46.2±10.2 ng/mL, p<0.0001) and a reduction in positive symptoms on the DN4 (p<0.0001), total pain score (p<0.0001), and SFMPQ (p<0.0001).

CONCLUSIONS

Treatment with a single intramuscular dose of 600 000 IU of vitamin D in patients with painful diabetic neuropathy is associated with a significant decrease in the symptoms of painful diabetic neuropathy.

TRIAL REGISTRATION NUMBER

BIDE-12/2014.

Understanding and treating painful diabetic neuropathy: time for a paradigm shift

The pathogenesis of diabetic neuropathy (DN) continues to be unclear and as a result, progress in developing effective therapies has been disappointing. In particular, there is only limited understanding of why some patients suffer severe chronic pain, whilst others have painless symptoms. Assessment of the peripheral nerves frequently shows no differences between painful and painless DN. There is growing evidence that the nerve damage in DN is more generalized, including the central nervous system, and these central changes are key to the development and persistence of pain in DN. The advent of new radiological techniques provides us with non-invasive modalities to study central pathophysiological processes in greater detail. These insights are increasingly leading to the recognition that painful DN is a complex and heterogeneous disorder, which requires a multimodal approach to treatment.

Hyperglycemia-induced oxidative stress induces apoptosis by inhibiting PI3-kinase/Akt and ERK1/2 MAPK mediated signaling pathway causing downregulation of 8-oxoG-DNA glycosylase levels in glial cells

Glial cells are very important for normal brain function and alterations in their activity due to hyperglycemia, could contribute to diabetes-related cognitive dysfunction. Oxidative insults often cause rapid changes in almost all cells including glial cells. However, pathophysiologic mechanisms that lead to diabetic complications are not completely elucidated. Therefore, we examined whether elevated glucose levels directly or indirectly disrupt antioxidant defense mechanisms causing alterations in signaling pathways, cell cycle dysregulation, and reactive oxygen/nitrogen species-mediated apoptosis in glial cells. Findings of this study demonstrated that exposure of glial cells to high glucose markedly induces cellular and molecular injuries, as evidenced by elevated levels of reactive oxygen/nitrogen species, biomolecules damage, cell cycle dysregulation, decrease in antioxidant enzymes, and decrease in cell viability. Pretreatment of cells with N-acetyl-L-cysteine reduced high glucose-induced cytotoxicity by increasing the levels of antioxidant enzymes, and decreasing the number of apoptotic cells. Further, at molecular level high glucose treatment resulted in a significant increase in phosphorylation of Akt, MAPKs, tuberin, down regulation of 8-oxoG-DNA glycosylase and increase in 8-hydroxydeoxyguanosine accumulations. Pretreatment of cells with N-acetyl-L-cysteine, phosphatidylinositol3-kinase/Akt and ERK1/2 inhibitors completely abolished the apoptotic effects of high glucose. Moreover, N-acetyl-L-cysteine significantly inhibited reactive oxygen/nitrogen species generation, elevated antioxidants levels, inhibited Akt, ERK1/2, tuberin phosphorylation, decreased 8-hydroxydeoxyguanosine accumulation and upregulated 8-oxoG-DNA glycosylase expression. Our results demonstrate that high glucose induces apoptosis and inhibits proliferation of glial cells, which may be mediated by the phosphorylation of tuberin, down regulation of 8-oxoG-DNA glycosylase and 8-hydroxydeoxyguanosine accumulation via activation of Akt and ERK1/2MAPK pathways.

Rectal sensitivity in diabetes patients with symptoms of gastroparesis

In a clinical setting, diabetic autonomic complications (cardiac, gastrointestinal, urogenital, etc.) are often handled as separate entities. We investigated rectal sensitivity to heat, mechanical distension, and electrical stimulations in 20 patients with diabetes and symptoms of gastroparesis, to evaluate the extent of visceral neuronal damage. Furthermore, to evaluate the relation between the nervous structures we examined gastric emptying and cardiac autonomic function with the hypothesis being an association between these. We found that 60% of patients had delayed gastric empting. Rectal hyposensitivity was a general finding as they tolerated 67% higher thermal, 42% more mechanical, and 33% higher electrical current intensity compared to healthy controls. In patients, most heart rate variability parameters were reduced; they reported significantly more gastrointestinal symptoms and a reduced quality of life in all SF-36 domains. Shortened RR interval correlated with reduced rectal temperature sensitivity, and gastric retention rate was negatively associated with symptoms of nausea and vomiting. To conclude, in these patients with signs and symptoms of diabetic gastroparesis, rectal sensitivity was reduced, and heart rate variability was impaired. Thus, we suggest regarding diabetic autonomic neuropathy as a diffuse disorder. Symptoms of widespread autonomic dysfunction and sensory disorders should be expected and treated in these patients.