Activation of IL-1 signaling pathway in Schwann cells during diabetic neuropathy

Conserved Transcriptional Signatures in Human and Murine Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) is one of the most common complications of diabetes. In this study, we employed a systems biology approach to identify DPN-related transcriptional pathways conserved across human and various murine models. Eight microarray datasets on peripheral nerve samples from murine models of type 1 (streptozotocin-treated) and type 2 (db/db and ob/ob) diabetes of various ages and human subjects with non-progressive and progressive DPN were collected. Differentially expressed genes (DEGs) were identified between non-diabetic and diabetic samples in murine models, and non-progressive and progressive human samples using a unified analysis pipeline. A transcriptional network for each DEG set was constructed based on literature-derived gene-gene interaction information. Seven pairwise human-vs-murine comparisons using a network-comparison program resulted in shared sub-networks including 46 to 396 genes, which were further merged into a single network of 688 genes. Pathway and centrality analyses revealed highly connected genes and pathways including LXR/RXR activation, adipogenesis, glucocorticoid receptor signalling, and multiple cytokine and chemokine pathways. Our systems biology approach identified highly conserved pathways across human and murine models that are likely to play a role in DPN pathogenesis and provide new possible mechanism-based targets for DPN therapy.

Chronic hyperglycemia mediated physiological alteration and metabolic distortion leads to organ dysfunction, infection, cancer progression and other pathophysiological consequences: An update on glucose toxicity

Chronic exposure of glucose rich environment creates several physiological and pathophysiological changes. There are several pathways by which hyperglycemia exacerbate its toxic effect on cells, tissues and organ systems. Hyperglycemia can induce oxidative stress, upsurge polyol pathway, activate protein kinase C (PKC), enhance hexosamine biosynthetic pathway (HBP), promote the formation of advanced glycation end-products (AGEs) and finally alters gene expressions. Prolonged hyperglycemic condition leads to severe diabetic condition by damaging the pancreatic β-cell and inducing insulin resistance. Numerous complications have been associated with diabetes, thus it has become a major health issue in the 21st century and has received serious attention. Dysregulation in the cardiovascular and reproductive systems along with nephropathy, retinopathy, neuropathy, diabetic foot ulcer may arise in the advanced stages of diabetes. High glucose level also encourages proliferation of cancer cells, development of osteoarthritis and potentiates a suitable environment for infections. This review culminates how elevated glucose level carries out its toxicity in cells, metabolic distortion along with organ dysfunction and elucidates the complications associated with chronic hyperglycemia.

Association Between Tumor Necrosis Factor-α and Diabetic Peripheral Neuropathy in Patients with Type 2 Diabetes: a Meta-Analysis

Tumor necrosis factor-α (TNF-α) is a cell signaling protein involved in systemic inflammation, and is also an important cytokine in the acute phase reaction. Several studies suggested a possible association between TNF-α and diabetic peripheral neuropathy (DPN) in type 2 diabetic patients, but no accurate conclusion was available. A systematic review and meta-analysis of observational studies was performed to comprehensively assess the association between serum TNF-α levels and DPN in type 2 diabetic patients. We searched Pubmed, Web of Science, Embase, and China Biology Medicine (CMB) databases for eligible studies. Study-specific data were combined using meta-analysis. Fourteen studies were finally included into the meta-analysis, which involved a total of 2650 participants. Meta-analysis showed that there were obviously increased serum TNF-α levels in DPN patients compared with type 2 diabetic patients without DPN (standard mean difference [SMD] = 1.203, 95 % CI 0.795-1.611, P < 0.001). There were also obviously increased levels of serum TNF-α in diabetic patients with DPN when compared with healthy controls (SMD = 2.364, 95 % CI 1.333-3.394, P < 0.001). In addition, there were increased serum TNF-α levels in painful DPN patients compared with painless DPN patients (SMD = 0.964, 95 % CI 0.237-1.690, P = 0.009). High level of serum TNF-α was significantly associated with increased risk of DPN in patients with type 2 diabetes (odds ratio [OR] = 2.594, 95 % CI 1.182-5.500, P = 0.017). Increased serum levels of TNF-α was not associated with increased risk of painful DPN in patients with type 2 diabetes (OR = 2.486, 95 % CI 0.672-9.193, P = 0.172). Sensitivity analysis showed that there was no obvious change in the pooled estimates when omitting single study by turns. Type 2 diabetic patients with peripheral neuropathy have obviously increased serum TNF-α levels than type 2 diabetic patients without peripheral neuropathy and healthy controls, and high level of serum TNF-α may be associated with increased risk of peripheral neuropathy independently. Further prospective cohort studies are needed to assess the association between TNF-α and DPN.

Differential association between biomarkers of subclinical inflammation and painful polyneuropathy: results from the KORA F4 study

OBJECTIVE

Inflammatory processes have been implicated in the pathogenesis of painful neuropathy in rodents, but the relationship between inflammatory biomarkers and painful distal sensorimotor polyneuropathy (DSPN) has not been assessed in population-based studies. Therefore, we investigated whether circulating levels of seven pro- and anti-inflammatory immune mediators were associated with painful DSPN in older individuals in a large population-based study.

RESEARCH DESIGN AND METHODS

The study population consisted of individuals with painless (n = 337) and painful DSPN (n = 54) from a source population (n = 1,047) of men and women aged 61-82 years who participated in the German KORA F4 survey (2006-2008). We measured circulating levels of seven immune mediators and assessed their associations with the presence of painful DSPN using multiple logistic regression models.

RESULTS

After adjustment for age and sex, we found positive associations between serum concentrations of the cytokine interleukin (IL)-6 and the soluble intercellular adhesion molecule (sICAM)-1 and painful DSPN (P = 0.004 and P = 0.005, respectively), whereas no associations were observed for C-reactive protein, IL-18, tumor necrosis factor-α, adiponectin, and IL-1 receptor antagonist (IL-1RA, P = 0.07-0.38). Associations between IL-6 and sICAM-1 and painful DSPN remained significant after additional adjustment for waist circumference, height, hypertension, cholesterol, smoking, alcohol intake, physical activity, history of myocardial infarction and/or stroke, presence of other neurological conditions, and use of nonsteroidal anti-inflammatory drugs (P = 0.005 and P = 0.016, respectively).

CONCLUSIONS

Painful DSPN is linked to systemic subclinical and vascular inflammation in the older population independent of anthropometric, lifestyle, and metabolic confounders.

Mechanisms of diabetic complications

It is increasingly apparent that not only is a cure for the current worldwide diabetes epidemic required, but also for its major complications, affecting both small and large blood vessels. These complications occur in the majority of individuals with both type 1 and type 2 diabetes. Among the most prevalent microvascular complications are kidney disease, blindness, and amputations, with current therapies only slowing disease progression. Impaired kidney function, exhibited as a reduced glomerular filtration rate, is also a major risk factor for macrovascular complications, such as heart attacks and strokes. There have been a large number of new therapies tested in clinical trials for diabetic complications, with, in general, rather disappointing results. Indeed, it remains to be fully defined as to which pathways in diabetic complications are essentially protective rather than pathological, in terms of their effects on the underlying disease process. Furthermore, seemingly independent pathways are also showing significant interactions with each other to exacerbate pathology. Interestingly, some of these pathways may not only play key roles in complications but also in the development of diabetes per se. This review aims to comprehensively discuss the well validated, as well as putative mechanisms involved in the development of diabetic complications. In addition, new fields of research, which warrant further investigation as potential therapeutic targets of the future, will be highlighted.

The effects of thalidomide and minocycline on taxol-induced hyperalgesia in rats

Chemotherapy-induced pain is the most common treatment-limiting complication encountered by cancer patients receiving taxane-, vinca alkaloid- or platin-based chemotherapy. Several lines of evidence indicate that activation of pro-inflammatory cascades involving the release of cytokines including tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1beta) and interleukin-6 (IL-6) as well as various growth factors are key events in the pathogenesis of many types of nerve-injury related pain. Similar mechanisms might also be involved in the etiology of chemotherapy-induced pain. Thalidomide and minocycline have profound immunomodulatory actions in addition to their originally intended pharmacological actions. These compounds were evaluated here for effects in preventing the development of taxol-induced mechanical and thermal hyperalgesia in rats. Thalidomide (50.0 mg/kg) reduced taxol-induced mechanical allodynia and hyperalgesia whereas minocycline (20.0 mg/kg) reduced taxol-induced mechanical hyperalgesia and allodynia as well as taxol-induced thermal hyperalgesia. These results suggest that immunomodulatory agents may provide a treatment option for the protection or reversal of chemotherapy-related pain.