Advanced glycosylation end products up-regulate connective tissue growth factor (insulin-like growth factor-binding protein-related protein 2) in human fibroblasts: a potential mechanism for expansion of extracellular matrix in diabetes mellitus

Molecular mechanisms linking type 2 diabetes mellitus and late-onset Alzheimer's disease: A systematic review and qualitative meta-analysis

Research evidence indicating common metabolic mechanisms through which type 2 diabetes mellitus (T2DM) increases risk of late-onset Alzheimer's dementia (LOAD) has accumulated over recent decades. The aim of this systematic review is to provide a comprehensive review of common mechanisms, which have hitherto been discussed in separate perspectives, and to assemble and evaluate candidate loci and epigenetic modifications contributing to polygenic risk linkages between T2DM and LOAD. For the systematic review on pathophysiological mechanisms, both human and animal studies up to December 2023 are included. For the qualitative meta-analysis of genomic bases, human association studies were examined; for epigenetic mechanisms, data from human studies and animal models were accepted. Papers describing pathophysiological studies were identified in databases, and further literature gathered from cited work. For genomic and epigenomic studies, literature mining was conducted by formalised search codes using Boolean operators in search engines, and augmented by GeneRif citations in Entrez Gene, and other sources (WikiGenes, etc.). For the systematic review of pathophysiological mechanisms, 923 publications were evaluated, and 138 gene loci extracted for testing candidate risk linkages. 3 57 publications were evaluated for genomic association and descriptions of epigenomic modifications. Overall accumulated results highlight insulin signalling, inflammation and inflammasome pathways, proteolysis, gluconeogenesis and glycolysis, glycosylation, lipoprotein metabolism and oxidation, cell cycle regulation or survival, autophagic-lysosomal pathways, and energy. Documented findings suggest interplay between brain insulin resistance, neuroinflammation, insult compensatory mechanisms, and peripheral metabolic dysregulation in T2DM and LOAD linkage. The results allow for more streamlined longitudinal studies of T2DM-LOAD risk linkages.

Cutaneous changes in diabetic patients: Primed for aberrant healing?

Cutaneous manifestations affect most patients with diabetes mellitus, clinically presenting with numerous dermatologic diseases from xerosis to diabetic foot ulcers (DFUs). Skin conditions not only impose a significantly impaired quality of life on individuals with diabetes but also predispose patients to further complications. Knowledge of cutaneous biology and the wound healing process under diabetic conditions is largely limited to animal models, and studies focusing on biology of the human condition of DFUs remain limited. In this review, we discuss the critical molecular, cellular, and structural changes to the skin in the hyperglycaemic and insulin-resistant environment of diabetes with a focus specifically on human-derived data. Elucidating the breadth of the cutaneous manifestations coupled with effective diabetes management is important for improving patient quality of life and averting future complications including wound healing disorders.

Regulation of CCN2 and Its Bioactivity by Advanced Glycation End Products

Advanced glycation end products (AGEs) have been implicated in the tissue fibrosis and extracellular matrix (ECM) expansion in organ complications of diabetes mellitus and in other diseases. CCN2, also known as cellular communication factor 2 and earlier as connective tissue growth factor, is a matrix-associated protein that acts as a pro-fibrotic cytokine to cause fibrosis in tissues in many diseases. We were the first to report that AGEs regulate CCN2, which itself can then affect ECM synthesis. In this chapter, we describe the methods of preparation of soluble AGEs and matrix-bound AGEs that can be used to study AGE effect on CCN2 and ECM expansion.

Incidence and risk factors associated with postoperative surgical site infection in younger adults with hip fractures: a case-control study

PURPOSE

Hip fracture is associated with high morbidity and mortality. The most common complication after hip fracture is surgical site infection (SSI). The goal was to investigate risks associated with SSI in young adults who underwent surgery for hip fractures.

METHODS

We conducted a case-control study enrolling 1243 patients from Jan 2015 to Dec 2019. This study investigated the multifaceted factors including demographics, lifestyles, comorbidities, surgical variables, and laboratory test results. Patients were divided into the case group (developed SSI) and control group (not developed SSI). Univariate analyses and multivariate logistic regression analyses were used to identify the risk factors independently associated with SSI.

RESULTS

A total of 25 patients including 16 (1.8%) in femoral neck fracture and nine (2.5%) in intertrochanteric fracture developed SSI post-operatively, with an accumulated incidence rate of 2.0%. Among them, four cases (1.6%) were deep SSI and 21 cases (98.4%) were superficial SSI. In most cases, Staphylococcus aureus caused the infections. Diabetes mellitus (OR 4.05, 95%CI: 1.08-15.23, P = 0.038), cerebrovascular disease (OR 3.71, 95%CI: 1.14-12.03, P = 0.029), heart disease (OR 6.23, 95%CI: 1.81-21.48, P = 0.004), and operative time (OR 1.01, 95%CI: 1.01-1.02, P = 0.002) in femoral neck fractures while ALP (> upper limit) (OR 33.39, 95%CI: 2.21-504.89, P = 0.011) and CK (> upper limit) (OR 40.97, 95%CI: 1.70-989.31, P = 0.022) in intertrochanteric fractures were found to be significantly associated with SSI.

CONCLUSION

Targeted pre-operative management, depending on the patients' fracture type and risk factors, should be developed to reduce post-operative SSI rates of younger adults with hip fracture.

Advanced Glycation End Products (AGEs) and Chronic Kidney Disease: Does the Modern Diet AGE the Kidney?

Since the 1980s, chronic kidney disease (CKD) affecting all ages has increased by almost 25%. This increase may be partially attributable to lifestyle changes and increased global consumption of a “western” diet, which is typically energy dense, low in fruits and vegetables, and high in animal protein and ultra-processed foods. These modern food trends have led to an increase in the consumption of advanced glycation end products (AGEs) in conjunction with increased metabolic dysfunction, obesity and diabetes, which facilitates production of endogenous AGEs within the body. When in excess, AGEs can be pathological via both receptor-mediated and non-receptor-mediated pathways. The kidney, as a major site for AGE clearance, is particularly vulnerable to AGE-mediated damage and increases in circulating AGEs align with risk of CKD and all-cause mortality. Furthermore, individuals with significant loss of renal function show increased AGE burden, particularly with uraemia, and there is some evidence that AGE lowering via diet or pharmacological inhibition may be beneficial for CKD. This review discusses the pathways that drive AGE formation and regulation within the body. This includes AGE receptor interactions and pathways of AGE-mediated pathology with a focus on the contribution of diet on endogenous AGE production and dietary AGE consumption to these processes. We then analyse the contribution of AGEs to kidney disease, the evidence for dietary AGEs and endogenously produced AGEs in driving pathogenesis in diabetic and non-diabetic kidney disease and the potential for AGE targeted therapies in kidney disease.

Fibrosis of the diabetic heart: Clinical significance, molecular mechanisms, and therapeutic opportunities

In patients with diabetes, myocardial fibrosis may contribute to the pathogenesis of heart failure and arrhythmogenesis, increasing ventricular stiffness and delaying conduction. Diabetic myocardial fibrosis involves effects of hyperglycemia, lipotoxicity and insulin resistance on cardiac fibroblasts, directly resulting in increased matrix secretion, and activation of paracrine signaling in cardiomyocytes, immune and vascular cells, that release fibroblast-activating mediators. Neurohumoral pathways, cytokines, growth factors, oxidative stress, advanced glycation end-products (AGEs), and matricellular proteins have been implicated in diabetic fibrosis; however, the molecular links between the metabolic perturbations and activation of a fibrogenic program remain poorly understood. Although existing therapies using glucose- and lipid-lowering agents and neurohumoral inhibition may act in part by attenuating myocardial collagen deposition, specific therapies targeting the fibrotic response are lacking. This review manuscript discusses the clinical significance, molecular mechanisms and cell biology of diabetic cardiac fibrosis and proposes therapeutic targets that may attenuate the fibrotic response, preventing heart failure progression.

Methylglyoxal-derived hemoglobin advanced glycation end products induce apoptosis and oxidative stress in human umbilical vein endothelial cells

The presence of excess glucose promotes hemoglobin glycation via the biochemical modification of hemoglobin by dicarbonyl products. However, the precise effects of Hb-AGEs in human umbilical vein endothelial cells (HUVECs) are not known to date. Therefore, we investigated the tentative effects of Hb-AGEs in HUVECs. Initially, we used the AGE formation assay to examine the selectivity of MGO toward various proteins. Among all proteins, MGO-Hb-AGEs formation was higher compared to the formation of other dicarbonyl-mediated AGEs. Our next data demonstrated that treatment with 0.5 mg/mL of Hb-AGEs-4w significantly reduced cell viability in HUVECs. Further, we evaluated the role of MGO in conformational and structural changes in Hb. The results showed that Hb demonstrated a highly altered conformation upon incubation with MGO. Moreover, Hb-AGEs-4w treatment strongly increased ROS production, and decreased mitochondrial membrane potential in HUVECs, and moderately reduced the expression of phosphorylated forms of p-38 and JNK. We observed that Hb-AGEs-4w treatment increased the number of apoptotic cells and the Bax/Bcl-2 ratio and cleaved the nuclear enzyme PARP in HUVECs. Finally, Hb-AGEs also inhibited migration and proliferation of HUVECs, thus be physiologically significant in endothelial dysfunction. Taken together, our data suggest that Hb-AGEs may play a critical role in inducing vascular endothelial cell damage. Therefore, this study may provide a plausible explanation for the potential Hb-AGEs in human endothelial cell dysfunction of diabetic patients.

CCN2 (Cellular Communication Network factor 2) in the bone marrow microenvironment, normal and malignant hematopoiesis

CCN2, formerly termed Connective Tissue Growth Factor, is a protein belonging to the Cellular Communication Network (CCN)-family of secreted extracellular matrix-associated proteins. As a matricellular protein it is mainly considered to be active as a modifier of signaling activity of several different signaling pathways and as an orchestrator of their cross-talk. Furthermore, CCN2 and its fragments have been implicated in the regulation of a multitude of biological processes, including cell proliferation, differentiation, adhesion, migration, cell survival, apoptosis and the production of extracellular matrix products, as well as in more complex processes such as embryonic development, angiogenesis, chondrogenesis, osteogenesis, fibrosis, mechanotransduction and inflammation. Its function is complex and context dependent, depending on cell type, state of differentiation and microenvironmental context. CCN2 plays a role in many diseases, especially those associated with fibrosis, but has also been implicated in many different forms of cancer. In the bone marrow (BM), CCN2 is highly expressed in mesenchymal stem/stromal cells (MSCs). CCN2 is important for MSC function, supporting its proliferation, migration and differentiation. In addition, stromal CCN2 supports the maintenance and longtime survival of hematopoietic stem cells, and in the presence of interleukin 7, stimulates the differentiation of pro-B lymphocytes into pre-B lymphocytes. Overexpression of CCN2 is seen in the majority of B-acute lymphoblastic leukemias, especially in certain cytogenetic subgroups associated with poor outcome. In acute myeloid leukemia, CCN2 expression is increased in MSCs, which has been associated with leukemic engraftment in vivo. In this review, the complex function of CCN2 in the BM microenvironment and in normal as well as malignant hematopoiesis is discussed. In addition, an overview is given of data on the remaining CCN family members regarding normal and malignant hematopoiesis, having many similarities and some differences in their function.

Development and validation of risk prediction score for incisional surgical site infection after appendectomy

Surgical site infection (SSI) is a challenging and resource-consuming healthcare problem. Predicting the onset of SSI beforehand can help prevent or minimize its incidence. The present study aimed to determine the independent predictors of incisional SSI after open appendectomy using a multivariate analysis and to establish a predictive risk score of SSI after appendectomy. Records of eligible patients who underwent open appendectomy were reviewed. The characteristics and treatment outcomes of patients were collected and analyzed. Significant association between different variables and SSI after appendectomy was examined by univariate analysis. Then, variables with a significant association with SSI were entered into a multivariate binary logistic regression analysis to determine the significant independent predictors of SSI. The study included 343 patients (51.3% female). Incisional SSI was recorded in 44 (12.8%) patients. Univariate analysis revealed five parameters with a significant association with SSI, including BMI > 30 kg/m² (p < 0.0001), diabetes mellitus (DM) (p = 0.0001), total leukocyte count (p = 0.04), free intraperitoneal fluid (p < 0.0001), and perforated/gangrenous appendicitis (p < 0.0001). After identifying four significant independent predictors of incisional SSI by binary logistic regression analysis, a predictive risk score was developed. The independent predictors of SSI were DM (OR = 6.05, p = 0.005), free intraperitoneal fluid (OR = 6.94, p = 0.0001), obesity (OR = 8.94, p = 0.0001), and perforated/gangrenous appendicitis (OR = 24.64, p = 0.0001). Four independent predictors of incisional SSI after open appendectomy were found after multivariate analysis. A predictive risk score of SSI was developed and included obesity, DM, free intraperitoneal fluid, and perforated/gangrenous appendicitis as predictors of SSI.

Diabetic fibrosis

Diabetes-associated morbidity and mortality is predominantly due to complications of the disease that may cause debilitating conditions, such as heart and renal failure, hepatic insufficiency, retinopathy or peripheral neuropathy. Fibrosis, the excessive and inappropriate deposition of extracellular matrix in various tissues, is commonly found in patients with advanced type 1 or type 2 diabetes, and may contribute to organ dysfunction. Hyperglycemia, lipotoxic injury and insulin resistance activate a fibrotic response, not only through direct stimulation of matrix synthesis by fibroblasts, but also by promoting a fibrogenic phenotype in immune and vascular cells, and possibly also by triggering epithelial and endothelial cell conversion to a fibroblast-like phenotype. High glucose stimulates several fibrogenic pathways, triggering reactive oxygen species generation, stimulating neurohumoral responses, activating growth factor cascades (such as TGF-β/Smad3 and PDGFs), inducing pro-inflammatory cytokines and chemokines, generating advanced glycation end-products (AGEs) and stimulating the AGE-RAGE axis, and upregulating fibrogenic matricellular proteins. Although diabetes-activated fibrogenic signaling has common characteristics in various tissues, some organs, such as the heart, kidney and liver develop more pronounced and clinically significant fibrosis. This review manuscript summarizes current knowledge on the cellular and molecular pathways involved in diabetic fibrosis, discussing the fundamental links between metabolic perturbations and fibrogenic activation, the basis for organ-specific differences, and the promises and challenges of anti-fibrotic therapies for diabetic patients.

Inhibitors of Advanced Glycation End Product (AGE) Formation and Accumulation

A range of chemically different compounds are known to inhibit the formation and accumulation of advanced glycation end products (AGEs) or disrupt associated signalling pathways. There is evidence that some of these agents can provide end-organ protection in chronic diseases including diabetes. Whilst this group of therapeutics are structurally and functionally different and have a range of mechanisms of action, they ultimately reduce the deleterious actions and the tissue burden of advanced glycation end products. To date it remains unclear if this is due to the reduction in tissue AGE levels per se or the modulation of downstream signal pathways. Some of these agents either stimulate antioxidant defence or reduce the formation of reactive oxygen species (ROS), modify lipid profiles and inhibit inflammation. A number of existing treatments for glucose lowering, hypertension and hyperlipidaemia are also known to reduce AGE formation as a by-product of their action. Targeted AGE formation inhibitors or AGE cross-link breakers have been developed and have shown beneficial effects in animal models of diabetic complications as well as other chronic conditions. However, only a few of these agents have progressed to clinical development. The failure of clinical translation highlights the importance of further investigation of the advanced glycation pathway, the diverse actions of agents which interfere with AGE formation, cross-linking or AGE receptor activation and their effect on the development and progression of chronic diseases including diabetic complications. Advanced glycation end products (AGEs) are (1) proteins or lipids that become glycated as a result of exposure to sugars or (2) non-proteinaceous oxidised lipids. They are implicated in ageing and the development, or worsening, of many degenerative diseases, such as diabetes, atherosclerosis, chronic kidney and Alzheimer's disease. Several antihypertensive and antidiabetic agents and statins also indirectly lower AGEs. Direct AGE inhibitors currently investigated include pyridoxamine and epalrestat, the inhibition of the formation of reactive dicarbonyls such as methylglyoxal as an important precursor of AGEs via increased activation of the detoxifying enzyme Glo-1 and inhibitors of NOX-derived ROS to reduce the AGE/RAGE signalling.

Shortening of telomere length by metabolic factors in diabetes: protective effects of fenofibrate

People with diabetes mellitus have shorter telomeres compared with non-diabetic subjects. The aim of this study was to investigate an in-vitro model of telomere shortening under diabetes metabolic conditions. The mechanisms of the accelerated telomere length attrition and the potential telomere protective action of fenofibrate with related cellular mechanisms were also examined. Human dermal fibroblasts were passaged and cultured in normal (5.5 mM) or high (25 mM) D-glucose, across 7 days with hydrogen peroxide (H₂O₂), glucosamine (GA), or glycated albumin (AGEs-BSA). Relative telomere length (RTL) was determined by qPCR. The expression of shelterin complex members which regulate telomere stability were measured by qRT-PCR and Western immunoblot. Culture in high glucose decreased RTL compared with normal glucose: H₂O₂ and GA lowered the RTL after 7 days (each P < 0.05 vs untreated control), whereas AGEs-BSA had no effect compared with control-BSA. At day 7 the mRNA levels of most shelterin complex members, were induced by H₂O₂ and to a lesser extent by GA. Trf1 and Trf2 protein were induced by H₂O_2. Co-treatment with fenofibrate (100 μM) significantly attenuated the reduction in RTL caused by H₂O₂ and GA and prevented Trf induction by H₂O₂. However knockdown of Trf1 and Trf2 expression using specific siRNA did not prevent H₂O₂ effects to lower RTL, thus implicating factors other than these Trfs alone in the fenofibrate protection against the H₂O₂ induction of RTL lowering. These in vitro findings demonstrate that diabetic conditions can induce telomere shortening and that fenofibrate has protective effects on telomere attrition, through as yet undefined mechanisms.

Incidence and risk of surgical site infection after adult femoral neck fractures treated by surgery: A retrospective case-control study

Surgical site infections (SSI) are devastating complications after surgery for femoral neck fractures. There are a lot of literature have shown a strong association between diabetic patients and SSI. This study aimed to identify diabetes as an independent risk factor of SSI, focusing on femoral neck fractures, and to investigate the other potential risk factors for SSI.We retrospectively collected data from patients who underwent surgery for femoral neck fractures through the medical record management system at a single level 1 hospital between January 2015 and June 2016. Demographic and clinical patient factors and characteristics of SSI were recorded. The case group was defined as patients with SSI and the control group was defined as patients without SSI. Univariate and multivariate analyses were performed to determine the risk factors for SSI.Data were provided for 692 patients, among whom 26 had SSI, representing an incidence rate of 3.67%. In the SSI group, 24 (3.47%) patients had superficial infection and 2 (0.29%) had deep infection. On multivariate analysis, diabetes (P < .001) was determined an independent risk factor of SSI, so were surgery performed between May and September (P = .04), body mass index (P = .031), corticosteroid therapy (P = .003), anemia (P = .041), and low preoperative hemoglobin levels.Our results suggest that clinicians should recognize patients with these factors, particularly diabetes. And taking management optimally in the preoperative period will prevent the SSI after femoral neck fracture.

Connective Tissue Growth Factor and Renal Fibrosis

CCN2, also known as connective tissue growth factor (CTGF), is one of important members of the CCN family. Generally, CTGF expresses at low levels in normal adult kidney, while increases significantly in various kidney diseases, playing an important role in the development of glomerular and tubulointerstitial fibrosis in progressive kidney diseases. CTGF is involved in cell proliferation, migration, and differentiation and can promote the progression of fibrosis directly or act as a downstream factor of transforming growth factor β (TGF-β). CTGF also regulates the expression and activity of TGF-β and bone morphogenetic protein (BMP), thereby playing an important role in the process of kidney repair. In patients with chronic kidney disease, elevated plasma CTGF is an independent risk factor for progression to end-stage renal disease and is closely related to glomerular filtration rate. Therefore, CTGF may be a potential biological marker of kidney fibrosis, but more clinical studies are needed to confirm this view. This section briefly describes the role and molecular mechanisms of CTGF in renal fibrosis and also discusses the potential value of targeting CCN2 for the treatment of renal fibrosis.

The effect of diabetes on perioperative complications following spinal surgery: a meta-analysis

Background

Degenerative spinal diseases and diabetes mellitus (DM) have increasingly become a social and economic burden. The effect of DM on spinal surgery complications reported by previous studies remains controversial.

Methods

We searched MEDLINE, Cochrane CENTRAL, ScienceDirect, EMBASE, and Google Scholar to identify studies reporting the relationship between DM and spinal surgery complications. Two independent reviewers performed independent data abstraction. The I2 statistic was used to assess heterogeneity. A fixed-effects or random-effects model was used for the meta-analysis.

Results

Twenty-four studies met the inclusion criteria. Surgical site infection and the incidence of deep venous thrombosis after spinal surgery were significantly higher in patients with than in patients without diabetes, and the length of hospital stay was significantly longer in patients with diabetes (P<0.05). No significant differences were observed in the risk of reoperation, blood loss, and operation time between patients with and those without diabetes (P.0.05).

Conclusion

Patients with diabetes have a higher risk when undergoing spinal surgery than patients without diabetes. Diabetes increases the risks of postoperative mortality, surgical site infection, deep venous thrombosis, and a prolonged hospitalization time after spinal surgery.

α‑lipoic acid can greatly alleviate the toxic effect of AGES on SH‑SY5Y cells

The aim of the study was to explore the influence of α‑lipoic acid (α‑LA) on the cytotoxicity of advanced glycation end‑products (AGEs) against SH‑SY5Y cells. AGE‑bovine serum albumin (BSA) was incubated in vitro using SH‑SY5Y cells as a target model, and the control group was set. Cells were exposed to AGE‑BSA, and α‑LA was selectively added to the cells. Cell growth and death was determined by the MTT assay, which measures cellular metabolic rate, lactate dehydrogenase (LDH) leakage rate and cellular axonal length. Immunocytochemistry was employed to detect the expression of β‑amyloid (Aβ) protein in cells, and mRNA expression of amyloid precursor protein (APP) and the receptor for AGE (RAGE) were assayed by PT‑PCR. The metabolism of MTT was clearly increased, the rate of LDH leakage was significantly decreased, and axonal length was significantly increased in cells treated with α‑LA (0.1 g/l) as compared to untreated cells. Furthermore, the expression levels of Aβ protein were also decreased. In addition, α‑LA (0.1 g/l) markedly inhibited the expression of RAGE mRNA, and did not influence APP mRNA expression as compared the control group. α‑LA (0.1 g/l) was effective at dampening the cytotoxicity of AGE‑BSA, a preliminary observation that confirms the ability of α‑LA to significantly alleviate the cytotoxicity of AGEs against SH‑SY5Y cells.

Silymarin Ameliorates Diabetes-Induced Proangiogenic Response in Brain Endothelial Cells through a GSK-3β Inhibition-Induced Reduction of VEGF Release

Diabetes mellitus (DM) is a major risk factor for cardiovascular disease. Additionally, it was found to induce a dysfunctional angiogenic response in the brain that was attributed to oxidative stress. Milk thistle seed extract (silymarin) has potent antioxidant properties, though its potential use in ameliorating diabetes-induced aberrant brain angiogenesis is unknown. Glycogen synthase kinase-3β is a regulator of angiogenesis that is upregulated by diabetes. Its involvement in diabetes-induced angiogenesis is unknown. To evaluate the potential of silymarin to ameliorate diabetes-induced aberrant angiogenesis, human brain endothelial cells (HBEC-5i) were treated with 50 μg/mL advanced glycation end (AGE) products in the presence or absence of silymarin (50, 100 μM). The angiogenic potential of HBEC-5i was evaluated in terms of migration and in vitro tube formation capacities. The involvement of GSK-3β was also evaluated. AGE significantly increased the migration and tube formation rates of HBEC-5i by about onefold (p = 0.0001). Silymarin reduced AGE-induced migration in a dose-dependent manner where 50 μM reduced migration by about 50%, whereas the 100 μM completely inhibited AGE-induced migration. Similarly, silymarin 50 μg/mL blunted AGE-induced tube formation (p = 0.001). This effect was mediated through a GSK-3β-dependent inhibition of VEGF release. In conclusion, silymarin inhibits AGE-induced aberrant angiogenesis in a GSK-3β-mediated inhibition of VEGF release.

Protein Kinase C as Regulator of Vascular Smooth Muscle Function and Potential Target in Vascular Disorders

Vascular smooth muscle (VSM) plays an important role in maintaining vascular tone. In addition to Ca2+-dependent myosin light chain (MLC) phosphorylation, protein kinase C (PKC) is a major regulator of VSM function. PKC is a family of conventional Ca2+-dependent α, β, and γ, novel Ca2+-independent δ, ɛ, θ, and η, and atypical ξ, and ι/λ isoforms. Inactive PKC is mainly cytosolic, and upon activation it undergoes phosphorylation, maturation, and translocation to the surface membrane, the nucleus, endoplasmic reticulum, and other cell organelles; a process facilitated by scaffold proteins such as RACKs. Activated PKC phosphorylates different substrates including ion channels, pumps, and nuclear proteins. PKC also phosphorylates CPI-17 leading to inhibition of MLC phosphatase, increased MLC phosphorylation, and enhanced VSM contraction. PKC could also initiate a cascade of protein kinases leading to phosphorylation of the actin-binding proteins calponin and caldesmon, increased actin-myosin interaction, and VSM contraction. Increased PKC activity has been associated with vascular disorders including ischemia-reperfusion injury, coronary artery disease, hypertension, and diabetic vasculopathy. PKC inhibitors could test the role of PKC in different systems and could reduce PKC hyperactivity in vascular disorders. First-generation PKC inhibitors such as staurosporine and chelerythrine are not very specific. Isoform-specific PKC inhibitors such as ruboxistaurin have been tested in clinical trials. Target delivery of PKC pseudosubstrate inhibitory peptides and PKC siRNA may be useful in localized vascular disease. Further studies of PKC and its role in VSM should help design isoform-specific PKC modulators that are experimentally potent and clinically safe to target PKC in vascular disease.

Diabetes mellitus in patients with cirrhosis: clinical implications and management

Disorders of glucose metabolism, namely glucose intolerance and diabetes, are frequent in patients with chronic liver diseases. In patients with cirrhosis, diabetes can be either a classical type 2 diabetes mellitus or the so-called hepatogenous diabetes, i.e. a consequence of liver insufficiency and portal hypertension. This review article provides an overview of the possible pathophysiological mechanisms explaining diabetes in patients with cirrhosis. Cirrhosis is associated with portosystemic shunts as well as reduced hepatic mass, which can both impair insulin clearance by the liver, contributing to peripheral insulin resistance through insulin receptors down-regulation. Moreover, cirrhosis is associated with increased levels of advanced-glycation-end products and hypoxia-inducible-factors, which may play a role in the development of diabetes. This review also focuses on the clinical implications of diabetes in patients with cirrhosis. First, diabetes is an independent factor for poor prognosis in patients with cirrhosis. Specifically, diabetes is associated with the occurrence of major complications of cirrhosis, including ascites and renal dysfunction, hepatic encephalopathy and bacterial infections. Diabetes is also associated with an increased risk of hepatocellular carcinoma in patients with chronic liver diseases. Last, the management of patients with concurrent diabetes and liver disease is also addressed. Recent findings suggest a beneficial impact of metformin in patients with chronic liver diseases. Insulin is often required in patients with advanced cirrhosis. However, the favourable impact of controlling diabetes in patients with cirrhosis has not been demonstrated yet.

Diabetes mellitus is associated with increased risk of surgical site infections: A meta-analysis of prospective cohort studies

BACKGROUND AND OBJECTIVE

Observational studies have suggested an association between diabetes mellitus and the risk of surgical site infections (SSIs), but the results remain inconclusive. We conducted a meta-analysis of prospective cohort studies to elucidate the relationship between diabetes mellitus and SSIs.

METHODS

We searched PubMed, Embase, and Web of Science databases and reviewed the reference lists of the retrieved articles to identify relevant studies. Associations were tested in subgroups representing different patient characteristics and study quality criteria. The random-effect model was used to calculate the overall relative risk (RR).

RESULTS

Fourteen prospective cohort studies (N = 91,094 participants) were included in this meta-analysis, and the pooled crude RR was 2.02 (95% confidence interval, 1.68-2.43) with significant between-study heterogeneity observed (I(2) = 56.50%). Significant association was also detected after we derived adjusted RRs for studies not reporting the adjusted RRs and calculated the combined adjusted RR of the 14 studies (RR, 1.69; 95% confidence interval, 1.33-2.13). Results were consistent and statistically significant in all subgroups. Stratified analyses found the number of confounders adjusted for, sample size, and method of diabetes case ascertainment might be the potential sources of heterogeneity. Sensitivity analysis further demonstrated the robustness of the result.

CONCLUSIONS

This meta-analysis suggests diabetes mellitus is significantly associated with increased risk of SSIs. Future studies are encouraged to reveal the mechanisms underlying this association.

The role of CTGF in diabetic retinopathy

Connective tissue growth factor (CTGF, CCN2) contributes to fibrotic responses in diabetic retinopathy, both before clinical manifestations occur in the pre-clinical stage of diabetic retinopathy (PCDR) and in proliferative diabetic retinopathy (PDR), the late clinical stage of the disease. CTGF is a secreted protein that modulates the actions of many growth factors and extracellular matrix (ECM) proteins, leading to tissue reorganization, such as ECM formation and remodeling, basal lamina (BL) thickening, pericyte apoptosis, angiogenesis, wound healing and fibrosis. In PCDR, CTGF contributes to thickening of the retinal capillary BL and is involved in loss of pericytes. In this stage, CTGF expression is induced by advanced glycation end products, and by growth factors such as vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-β. In PDR, the switch from neovascularization to a fibrotic phase - the angio-fibrotic switch - in PDR is driven by CTGF, in a critical balance with vascular endothelial growth factor (VEGF). We discuss here the roles of CTGF in the pathogenesis of DR in relation to ECM remodeling and wound healing mechanisms, and explore whether CTGF may be a potential novel therapeutic target in the clinical management of early as well as late stages of DR.

Histopathologic changes in the cochlea associated with diabetes mellitus--a review

BACKGROUND

The pathologic changes that occur as a result of diabetic microangiopathy have been well described for the kidneys and the eyes. Although many studies suggest an association between diabetes mellitus and hearing loss, the pathologic changes in the cochlea in association with the diabetic state remain to be clarified.

AIM/OBJECTIVE

The aim of this review is to determine the effects of diabetes mellitus on cochlear morphology.

METHOD

A comprehensive search for relevant articles was carried out on electronic databases of Ovid Medline, Ovid Medline in Process, PubMed, Ovid Embase,or Biosis Preview, The Cochrane Library, ISI Web of Science, and Scopus. Articles published in English between 1940 and June 2010 were eligible to be reviewed. Using predefined inclusion criteria, published articles on histologic changes occurring in the cochlea due to diabetes mellitus were selected and reviewed, and their findings were synthesized.

RESULTS

Changes were observed in the basement membrane of the capillaries of the stria vascularis and in the basilar membrane, which was remarkably thickened, giving rise to diabetic microangiopathy. Loss of spiral ganglion neurons, organ of Corti cells, and atrophic changes in the stria vascularis were varied and infrequent.

CONCLUSION

There seems to be variable vulnerability of different cochlear cell types to the DM state. Further studies are required to determine the factors responsible for the differences in the histopathologic observations of cochlear tissues.

The pathogenesis of Achilles tendinopathy: a systematic review

Achilles tendinopathy is a degenerative, not an inflammatory, condition. It is prevalent in athletes involved in running sports. A systematic literature review on Achilles tendon tendinopathy has been performed according to the intrinsic (age, sex, body weight, tendon temperature, systemic diseases, muscle strength, flexibility, previous injuries and anatomical variants, genetic predisposition and blood supply) and extrinsic risk factors (drugs and overuse), which can cause tendon suffering and degeneration. Different theories have been found: Neurogenic, Angiogenic, Impingement and "Iceberg" Hypotheses. Multiple databases were utilized for articles published between 1964 and 2013. The different hypothesis were analyzed, differently considering those concerning the pathogenesis of tendinopathy and those concerning the etiology of complaints in patients. This review of the literature demonstrates the heterogeneity of Achilles tendinopathy pathogenesis. Various risk factors have been identified and have shown an interaction between them such as genes, age, circulating and local cytokine production, sex, biomechanics and body composition.

The impact of 1,25-dihydroxyvitamin D3 on the expression of connective tissue growth factor and transforming growth factor-β1 in the myocardium of rats with diabetes

AIMS

To define whether 1,25-dihydroxyvitamin D3 (1,25-(OH)2 D3) can protect against myocardial fibrosis and to investigate its impact on the expression of connective tissue growth factor (CTGF) and transforming growth factor-β1 (TGF-β1) in the myocardium of rats with diabetes.

METHODS

Male Sprague-Dawley rats were divided into normal (control), 1,25-(OH)2 D3 therapy, and diabetes groups. In the diabetes and 1,25-(OH)2 D3 therapy groups, type 2 diabetes models were established using a high-fat, high-sugar diet and streptozotocin. Rats in the 1,25-(OH)2 D3 therapy group were also treated with 1,25-(OH)2 D3. After 6 weeks, the body weight, cardiac weight, cardiac weight index, plasma glucose, lactic dehydrogenase (LDH) and creatine kinase (CK) were measured; morphological changes in the myocardium were observed using microscopy following hematoxylin-eosin and Masson staining. CTGF and TGF-β1 expressions in the myocardium were detected using immunohistochemistry staining and reverse transcription polymerase chain reaction.

RESULTS

The body and cardiac weights of the rats in the diabetes and 1,25-(OH)2 D3 group were lower, but the cardiac weight index, plasma glucose, LDH and CK were higher compared with the control group (P<0.05). The body weight and plasma glucose, LDH and CK were decreased in 1,25-(OH)2 D3 group compared with the diabetes group (P<0.05). Pathological changes in the 1,25-(OH)2 D3 group were milder than the diabetes group. CTGF and TGF-β1 expression in the diabetes and 1,25-(OH)2 D3 groups were increased significantly, but in the 1,25-(OH)2 D3 group were significantly lower than diabetes group at the mRNA level.

CONCLUSION

1,25-(OH)2 D3 had a partially protective effect on myocardial fibrosis of diabetic rats, which might inhibit CTGF and TGF-β1 expression in the myocardial tissues.

Haptoglobin genotype-dependent differences in macrophage lysosomal oxidative injury

The major function of the Haptoglobin (Hp) protein is to control trafficking of extracorpuscular hemoglobin (Hb) thru the macrophage CD163 receptor with degradation of the Hb in the lysosome. There is a common copy number polymorphism in the Hp gene (Hp 2 allele) that has been associated with a severalfold increased incidence of atherothrombosis in multiple longitudinal studies. Increased plaque oxidation and apoptotic markers have been observed in Hp 2-2 atherosclerotic plaques, but the mechanism responsible for this finding has not been determined. We proposed that the increased oxidative injury in Hp 2-2 plaques is due to an impaired processing of Hp 2-2-Hb complexes within macrophage lysosomes, thereby resulting in redox active iron accumulation, lysosomal membrane oxidative injury, and macrophage apoptosis. We sought to test this hypothesis in vitro using purified Hp-Hb complex and cells genetically manipulated to express CD163. CD163-mediated endocytosis and lysosomal degradation of Hp-Hb were decreased for Hp 2-2-Hb complexes. Confocal microscopy using lysotropic pH indicator dyes demonstrated that uptake of Hp 2-2-Hb complexes disrupted the lysosomal pH gradient. Cellular fractionation studies of lysosomes isolated from macrophages incubated with Hp 2-2-Hb complexes demonstrated increased lysosomal membrane oxidation and a loss of lysosomal membrane integrity leading to lysosomal enzyme leakage into the cytoplasm. Additionally, markers of apoptosis, DNA fragmentation, and active caspase 3 were increased in macrophages that had endocytosed Hp 2-2-Hb complexes. These data provide novel mechanistic insights into how the Hp genotype regulates lysosomal oxidative stress within macrophages after receptor-mediated endocytosis of Hb.

High preoperative hemoglobin A1c is a risk factor for surgical site infection after posterior thoracic and lumbar spinal instrumentation surgery

BACKGROUND

Diabetes mellitus (DM) is reported to be a risk factor for surgical site infection (SSI), which is a serious complication after spinal surgery. The effect of DM on SSI after instrumented spinal surgery remains to be clarified. The aim was to elucidate perioperative risk factors for infection at the surgical site after posterior thoracic and lumbar spinal arthrodesis with instrumentation in patients with DM.

METHODS

Consecutive patients who underwent posterior instrumented thoracic and lumbar spinal arthrodesis during the years 2005-2011, who could be followed for at least 1 year after surgery, were included. These included 36 patients with DM (19 males and 17 females; mean age 64.3 years). The patients' medical records were retrospectively reviewed to determine the SSI rate. The characteristics of the DM patients were examined in detail, including the levels of serum glucose and HbA1c, which indicate the level of diabetes control.

RESULTS

Patients with DM had a higher rate of SSI (6 of 36 patients, 16.7 %) than patients without DM (10 of 309 patients, 3.2 %). Although the perioperative serum glucose level did not differ between DM patients that did or did not develop SSI, the preoperative HbA1c value was significantly higher in the patients who developed SSI (7.6 %) than in those who did not (6.9 %). SSI developed in 0.0 % of the patients with controlled diabetes (HbA1c <7.0 %) and in 35.3 % of the patients with uncontrolled diabetes (HbA1c ≥7.0 %).

CONCLUSIONS

DM patients whose blood glucose levels were poorly controlled before surgery were at high risk for SSI. To prevent SSI in DM patients, we recommend lowering the HbA1c to <7.0 % before performing surgery.

Advanced glycation end products and diabetic complications

During long standing hyperglycaemic state in diabetes mellitus, glucose forms covalent adducts with the plasma proteins through a non-enzymatic process known as glycation. Protein glycation and formation of advanced glycation end products (AGEs) play an important role in the pathogenesis of diabetic complications like retinopathy, nephropathy, neuropathy, cardiomyopathy along with some other diseases such as rheumatoid arthritis, osteoporosis and aging. Glycation of proteins interferes with their normal functions by disrupting molecular conformation, altering enzymatic activity, and interfering with receptor functioning. AGEs form intra- and extracellular cross linking not only with proteins, but with some other endogenous key molecules including lipids and nucleic acids to contribute in the development of diabetic complications. Recent studies suggest that AGEs interact with plasma membrane localized receptors for AGEs (RAGE) to alter intracellular signaling, gene expression, release of pro-inflammatory molecules and free radicals. The present review discusses the glycation of plasma proteins such as albumin, fibrinogen, globulins and collagen to form different types of AGEs. Furthermore, the role of AGEs in the pathogenesis of diabetic complications including retinopathy, cataract, neuropathy, nephropathy and cardiomyopathy is also discussed.

Advanced glycation end products and diabetic complications

During long standing hyperglycaemic state in diabetes mellitus, glucose forms covalent adducts with the plasma proteins through a non-enzymatic process known as glycation. Protein glycation and formation of advanced glycation end products (AGEs) play an important role in the pathogenesis of diabetic complications like retinopathy, nephropathy, neuropathy, cardiomyopathy along with some other diseases such as rheumatoid arthritis, osteoporosis and aging. Glycation of proteins interferes with their normal functions by disrupting molecular conformation, altering enzymatic activity, and interfering with receptor functioning. AGEs form intra- and extracellular cross linking not only with proteins, but with some other endogenous key molecules including lipids and nucleic acids to contribute in the development of diabetic complications. Recent studies suggest that AGEs interact with plasma membrane localized receptors for AGEs (RAGE) to alter intracellular signaling, gene expression, release of pro-inflammatory molecules and free radicals. The present review discusses the glycation of plasma proteins such as albumin, fibrinogen, globulins and collagen to form different types of AGEs. Furthermore, the role of AGEs in the pathogenesis of diabetic complications including retinopathy, cataract, neuropathy, nephropathy and cardiomyopathy is also discussed.

Connective tissue growth factor is involved in structural retinal vascular changes in long-term experimental diabetes

Early retinal vascular changes in the development of diabetic retinopathy (DR) include capillary basal lamina (BL) thickening, pericyte loss and the development of acellular capillaries. Expression of the CCN (connective tissue growth factor/cysteine-rich 61/nephroblastoma overexpressed) family member CCN2 or connective tissue growth factor (CTGF), a potent inducer of the expression of BL components, is upregulated early in diabetes. Diabetic mice lacking one functional CTGF allele (CTGF⁺/⁻) do not show this BL thickening. As early events in DR may be interrelated, we hypothesized that CTGF plays a role in the pathological changes of retinal capillaries other than BL thickening. We studied the effects of long-term (6-8 months) streptozotocin-induced diabetes on retinal capillary BL thickness, numbers of pericytes and the development of acellular capillaries in wild type and CTGF⁺/⁻ mice. Our results show that an absence of BL thickening of retinal capillaries in long-term diabetic CTGF⁺/⁻ mice is associated with reduced pericyte dropout and reduced formation of acellular capillaries. We conclude that CTGF is involved in structural retinal vascular changes in diabetic rodents. Inhibition of CTGF in the eye may therefore be protective against the development of DR.

Cysteine-rich protein 61 (CCN1) and connective tissue growth factor (CCN2) at the crosshairs of ocular neovascular and fibrovascular disease therapy

The vasculature forms a highly branched network investing every organ of vertebrate organisms. The retinal circulation, in particular, is supported by a central retinal artery branching into superficial arteries, which dive into the retina to form a dense network of capillaries in the deeper retinal layers. The function of the retina is highly dependent on the integrity and proper functioning of its vascular network and numerous ocular diseases including diabetic retinopathy, age-related macular degeneration and retinopathy of prematurity are caused by vascular abnormalities culminating in total and sometimes irreversible loss of vision. CCN1 and CCN2 are inducible extracellular matrix (ECM) proteins which play a major role in normal and aberrant formation of blood vessels as their expression is associated with developmental and pathological angiogenesis. Both CCN1 and CCN2 achieve disparate cell-type and context-dependent activities through modulation of the angiogenic and synthetic phenotype of vascular and mesenchymal cells respectively. At the molecular level, CCN1 and CCN2 may control capillary growth and vascular cell differentiation by altering the composition or function of the constitutive ECM proteins, potentiating or interfering with the activity of various ligands and/or their receptors, physically interfering with the ECM-cell surface interconnections, and/or reprogramming gene expression driving cells toward new phenotypes. As such, these proteins emerged as important prognostic markers and potential therapeutic targets in neovascular and fibrovascular diseases of the eye. The purpose of this review is to highlight our current knowledge and understanding of the most recent data linking CCN1 and CCN2 signaling to ocular neovascularization bolstering the potential value of targeting these proteins in a therapeutic context.

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.

Imbalance of angiogenesis in diabetic complications: the mechanisms

Type 2 diabetes mellitus is a complex disease and a chronic health-care problem. Nowadays, because of alteration of lifestyle such as lack of exercise, intake of high fat diet subsequently obesity and aging population, the prevalence of diabetes mellitus is increasing quickly in around the world. The international diabetes federation estimated in 2008, that 246 million adults in worldwide suffered from diabetes mellitus and the prevalence of disease is expected to reach to 380 million by 2025. Although, mainly in management of diabetes focused on hyperglycemia, however, it is documented that abnormalities of angiogenesis may contribute in the pathogenesis of diabetes complications. Angiogenesis is the generation of new blood vessels from pre-existing ones. Normal angiogenesis depends on the intricate balance between angiogenic factors (such as VEGF, FGF₂, TGF-β, angiopoietins) and angiostatic factors (angiostatin, endostatin, thrombospondins). Vascular abnormalities in different tissues including retina and kidney can play a role in pathogenesis of micro-vascular complications of diabetes; also vascular impairment contributes in macrovascular complications e.g., diabetic neuropathy and impaired formation of coronary collaterals. Therefore, identifying of different mechanisms of the diabetic complications can give us an opportunity to prevent and/or treat the following complications and improves quality of life for patients and society. In this review, we studied the mechanisms of angiogenesis in micro-vascular and macro-vascular complications of diabetes mellitus.

Aberrant angiogenesis: The gateway to diabetic complications

Diabetes Mellitus is a metabolic cum vascular syndrome with resultant abnormalities in both micro- and macrovasculature. The adverse long-term effects of diabetes mellitus have been described to involve many organ systems. Apart from hyperglycemia, abnormalities of angiogenesis may cause or contribute toward many of the clinical manifestations of diabetes. These are implicated in the pathogenesis of vascular abnormalities of the retina, kidneys, and fetus, impaired wound healing, increased risk of rejection of transplanted organs, and impaired formation of coronary collaterals. A perplexing feature of the aberrant angiogenesis is that excessive and insufficient angiogenesis can occur in different organs in the same individual. The current article hereby reviews the molecular mechanisms including abnormalities in growth factors, cytokines, and metabolic derangements, clinical implications, and therapeutic options of dealing with abnormal angiogenesis in diabetes.

Connective tissue growth factor regulates retinal neovascularization through p53 protein-dependent transactivation of the matrix metalloproteinase (MMP)-2 gene

BACKGROUND

The role of connective tissue growth factor (CTGF/CCN2) in pathological angiogenesis in the retina is unknown.

RESULTS

CTGF/CCN2 stimulates retinal neovascularization through transactivation of p53 target genes such as matrix metalloproteinase (MMP)-2.

CONCLUSION

CTGF/CCN2 effects on abnormal vessel formation in the retina are mediated by p53 and MMP-2.

SIGNIFICANCE

CTGF/CCN2 and its downstream effectors are potential targets in the development of new antiangiogenic treatments. Pathological angiogenesis in the retina is driven by dysregulation of hypoxia-driven stimuli that coordinate physiological vessel growth. How the various components of the neovascularization signaling network are integrated to yield pathological changes has not been defined. Connective tissue growth factor (CTGF/CCN2) is an inducible matricellular protein that plays a major role in fibroproliferative disorders. Here, we show that CTGF/CCN2 was dynamically expressed in the developing murine retinal vasculature and was abnormally increased and localized within neovascular tufts in the mouse eye with oxygen-induced retinopathy. Consistent with its propitious vascular localization, ectopic expression of the CTGF/CCN2 gene further accelerated neovascularization, whereas lentivirus-mediated loss-of-function or -expression of CTGF/CCN2 harnessed ischemia-induced neovessel outgrowth in oxygen-induced retinopathy mice. The neovascular effects of CTGF/CCN2 were mediated, at least in part, through increased expression and activity of matrix metalloproteinase (MMP)-2, which drives vascular remodeling through degradation of matrix and non matrix proteins, migration and invasion of endothelial cells, and formation of new vascular patterns. In cultured cells, CTGF/CCN2 activated the MMP-2 promoter through increased expression and tethering of the p53 transcription factor to a highly conserved p53-binding sequence within the MMP-2 promoter. Concordantly, the neovascular effects of CTGF/CCN2 were suppressed by p53 inhibition that culminated in reduced enrichment of the MMP-2 promoter with p53 and decreased MMP-2 gene expression. Our data identified new gene targets and downstream effectors of CTGF/CCN2 and provided the rational basis for targeting the p53 pathway to curtail the effects of CTGF/CCN2 on neovessel formation associated with ischemic retinopathy.

Low-density lipoprotein induced expression of connective tissue growth factor via transactivation of sphingosine 1-phosphate receptors in mesangial cells

The pro-fibrotic connective tissue growth factor (CTGF) has been linked to the development and progression of diabetic vascular and renal disease. We recently reported that low-density lipoproteins (LDL) induced expression of CTGF in aortic endothelial cells. However, the molecular mechanisms are not fully defined. Here, we have studied the mechanism by which LDL regulates CTGF expression in renal mesangial cells. In these cells, treatment with pertussis toxin abolished LDL-stimulated activation of ERK1/2 and c-Jun N-terminal kinase (JNK), indicating the involvement of heterotrimeric G proteins in LDL signaling. Treatment with LDL promoted activation and translocation of endogenous sphingosine kinase 1 (SK1) from the cytosol to the plasma membrane concomitant with production of sphingosine-1-phosphate (S1P). Pretreating cells with SK inhibitor, dimethylsphinogsine or down-regulation of SK1 and SK2 revealed that LDL-dependent activation of ERK1/2 and JNK is mediated by SK1. Using a green fluorescent protein-tagged S1P₁ receptor as a biological sensor for the generation of physiologically relevant S1P levels, we found that LDL induced S1P receptor activation. Pretreating cells with S1P₁/S1P₃ receptor antagonist VPC23019 significantly inhibited activation of ERK1/2 and JNK by LDL, suggesting that LDL elicits G protein-dependent activation of ERK1/2 and JNK by stimulating SK1-dependent transactivation of S1P receptors. Furthermore, S1P stimulation induced expression of CTGF in a dose-dependent manner that was markedly inhibited by blocking the ERK1/2 and JNK signaling pathways. LDL-induced CTGF expression was pertussis toxin sensitive and inhibited by dimethylsphinogsine down-regulation of SK1 and VPC23019 treatment. Our data suggest that SK1-dependent S1P receptor transactivation is upstream of ERK1/2 and JNK and that all three steps are required for LDL-regulated expression of CTGF in mesangial cells.

CCN-2 is up-regulated by and mediates effects of matrix bound advanced glycated end-products in human renal mesangial cells

CCN-2, also known as connective tissue growth factor (CCN-2/CTGF) is a cysteine rich, extracellular matrix protein that acts as a pro-fibrotic cytokine in tissues in many diseases, including in diabetic nephropathy. We have published that soluble advanced glycation end products (AGEs), that are present in increased amounts in diabetes, induce CCN-2. However in vivo AGEs are known to be heavily tissue bound and whether matrix bound AGEs regulate CCN-2 has not been investigated. In this study we determined in human renal mesangial cells if CCN-2 is induced by matrix associated AGEs and if CCN-2 may then secondarily mediate effects of matrix AGEs on extracellular matrix expansion. Data generated show that CCN-2 mRNA and protein expression are induced by matrix bound AGEs, and in contrast, this was not the case for TGF-β1 mRNA regulation. Using CCN-2 adenoviral anti-sense it was found that CCN-2 mediated the up-regulation of fibronectin and the tissue inhibitor of matrix metalloproteinase, TIMP-1, that was caused by matrix bound AGEs. In conclusion, CCN-2 is induced by non-enzymatically glycated matrix and it mediates downstream fibronectin and TIMP-1 increases, thus through this mechanism potentially contributing to ECM accumulation in the renal glomerulus in diabetes.

What is the role of the receptor for advanced glycation end products-ligand axis in liver injury?

Multiligand receptor for advanced glycation end products (RAGE) is expressed in a wide variety of tissues, including the liver. Interactions with its ligands lead to cellular activation and thus prolonged inflammation and apoptosis. RAGE also exists in a soluble, truncated isoform called soluble RAGE, which has the same ligand-binding specificity as membrane-RAGE; acting as decoy, it can contribute to the removal/neutralization of circulating ligands and the resultant reduction of signaling pathway activation. Experimental and clinical studies have highlighted the idea that the RAGE-ligand axis is involved in the development of liver fibrosis, inflammation, and regeneration after a massive injury and in the setting of liver transplantation. The involvement of the RAGE-ligand axis in vascular disease, diabetes, cancer, and neurodegeneration is well established, but it still needs to be clarified in the setting of liver diseases. We present a review of the recent literature on this receptor in surgical and clinical settings involving the liver, and we highlight the open issues and possible directions of future research.

RAGE biology, atherosclerosis and diabetes

Diabetes is characterized by accelerated atherosclerosis with widely distributed vascular lesions. An important mechanism by which hyperglycaemia contributes to vascular injury is through the extensive intracellular and extracellular formation of AGEs (advanced glycation end products). AGEs represent a heterogeneous group of proteins, lipids and nucleic acids, irreversibly cross-linked with reducing sugars. AGEs are implicated in the atherosclerotic process, either directly or via receptor-mediated mechanisms, the most extensively studied receptor being RAGE (receptor for AGEs). The AGE–RAGE interaction alters cellular signalling, promotes gene expression and enhances the release of pro-inflammatory molecules. It elicits the generation of oxidative stress in numerous cell types. The importance of the AGE–RAGE interaction and downstream pathways leading to injurious effects as a result of chronic hyperglycaemia in the development, progression and instability of diabetic atherosclerotic lesions has been amply demonstrated in animal studies. Moreover, the deleterious link of AGEs with diabetic vascular complications has been suggested in many human studies. In the present review, our current understanding of their role as an important mediator of vascular injury through the various stages of atherosclerosis in diabetes will be reviewed and critically assessed.

Mastering a mediator: blockade of CCN-2 shows early promise in human diabetic kidney disease

In diabetes complications, CCN-2 (known originally as CTGF) has been implicated in diabetic nephropathy both as a marker and a mediator of disease. This commentary addresses CCN-2 in diabetic nephropathy, in the context of the recent publication of the first human study to inhibit CCN-2 bioactivity in diabetic kidney disease.

Vascular basement membrane thickening in diabetic retinopathy

Vascular basement membrane (BM) thickening is a fundamental structural alteration of small blood vessels in diabetes. Over two decades of research has established hyperglycemia as the primary causal factor mediating this alteration. Various high glucose-induced mechanisms have been investigated and excess synthesis of BM components has been identified as a major contributing factor to BM thickening. Although BM thickening has been long hailed as the histological hallmark of diabetic microangiopathy, the consequences of BM thickening on the functionality of target organs of diabetes remain elusive even today. This review presents an overview of our current understanding of the BM structure and function, and focuses on how capillary BM thickening develops, its effect on retinal vascular function, and potential strategies for preventing the development of BM thickening in diabetic retinopathy.

A novel primate model of delayed wound healing in diabetes: dysregulation of connective tissue growth factor

AIMS/HYPOTHESIS

Chronic non-healing wounds are a common complication of diabetes. Prolonged inflammation and decreased matrix accumulation may contribute. Connective tissue growth factor (CTGF) is induced during normal wound healing, but its regulation in diabetic wounds is unknown. We developed a primate model for the study of in vivo wound healing in baboons with long diabetes duration.

METHODS

Drum implants were placed subcutaneously into thighs of diabetic and non-diabetic control baboons. After 2 and 4 weeks the skin incision sites were removed for measurement of breaking strength and epithelial thickness. Drum implants were removed for analysis of granulation tissue and inflammatory cells, CTGF and tissue inhibitor of matrix metalloproteinase (TIMP-1). Degradation of added CTGF by wound fluid was also examined.

RESULTS

Healed incision site skin was stiffer (less elastic) in diabetic baboons and epithelial remodelling was slower compared with controls. Granulation tissue from diabetic baboons was reduced at 2 and 4 weeks, with increased vessel lumen areas at 4 weeks. Macrophages were reduced while neutrophils persisted in diabetic tissue. In diabetic wound tissue at 4 weeks there was less CTGF induced, as shown by immunohistochemistry, compared with controls. In contrast, immunoreactive fragments of CTGF were significantly increased in whole tissue lysate in diabetic baboons, suggesting that CTGF is redistributed in diabetes from granulation tissue into wound fluid. When recombinant human CTGF was co-incubated with wound fluid, increased CTGF degradation products were observed in both control and diabetic samples.

CONCLUSIONS/INTERPRETATION

This baboon model of wound healing reflects the abnormal microenvironment seen in human diabetic wounds and provides insights into the dysregulation of CTGF in diabetic wounds.

Regulation of pro-inflammatory and pro-fibrotic factors by CCN2/CTGF in H9c2 cardiomyocytes

Connective tissue growth factor (CTGF), also known as CCN2, is implicated in fibrosis through both extracellular matrix (ECM) induction and inhibition of ECM degradation. The role of CTGF in inflammation in cardiomyocytes is unknown. In some mesenchymal cell systems, CTGF mediates effects through TGF-beta or tyrosine kinase cell surface receptor, TrkA, signalling. In this study, cellular mechanisms by which CTGF regulates pathways involved in fibrosis and inflammation were explored. Murine H9c2 cardiomyocytes were treated with recombinant human (rh)CTGF and ECM formation gene expression: fibronectin, collagen type -I and -III and ECM degradation genes: TIMP-1, TIMP-2 and PAI-1 were found to be induced. CTGF treatment also increased pro-inflammatory cytokines TNF-alpha, IL-6, MCP-1 and IL-8. CTGF upregulated TGF-beta1 mRNA and rapidly induced phosphorylation of TrkA. The CTGF-induced pro-fibrotic and pro-inflammatory effects were blocked by anti-TGF-beta neutralizing antibody and Alk 5 inhibitor (SB431542). A specific blocker of TrkA activation, k252a, also abrogated CTGF-induced effects on fibrosis and gene expresison of MCP-1 and IL-8, but not TNF-alpha or IL-6. Collectively, this data implicates CTGF in effects on pro-fibrotic genes and pro-inflammatory genes via TGF-beta pathway signalling and partly through TrkA.

Role of the receptor for advanced glycation end products in hepatic fibrosis

AIM: To study the role of advanced glycation end products (AGE) and their specific receptor (RAGE) in the pathogenesis of liver fibrogenesis.

METHODS: In vitro RAGE expression and extracellular matrix-related gene expression in both rat and human hepatic stellate cells (HSC) were measured after stimulation with the two RAGE ligands, advanced glycation end product-bovine serum albumin (AGE-BSA) and N^ε-(carboxymethyl) lysine (CML)-BSA, or with tumor necrosis factor-α (TNF-α). In vivo RAGE expression was examined in models of hepatic fibrosis induced by bile duct ligation or thioacetamide. The effects of AGE-BSA and CML-BSA on HSC proliferation, signal transduction and profibrogenic gene expression were studied in vitro.

RESULTS: In hepatic fibrosis, RAGE expression was enhanced in activated HSC, and also in endothelial cells, inflammatory cells and activated bile duct epithelia. HSC expressed RAGE which was upregulated after stimulation with AGE-BSA, CML-BSA, and TNF-α. RAGE stimulation with AGE-BSA and CML-BSA did not alter HSC proliferation, apoptosis, fibrogenic signal transduction and fibrosis- or fibrolysis-related gene expression, except for marginal upregulation of procollagen α1(I) mRNA by AGE-BSA.

CONCLUSION: Despite upregulation of RAGE in activated HSC, RAGE stimulation by AGE does not alter their fibrogenic activation. Therefore, RAGE does not contribute directly to hepatic fibrogenesis.

Adverse effects of high glucose and free fatty acid on cardiomyocytes are mediated by connective tissue growth factor

Diabetic cardiomyopathy is characterized by interstitial fibrosis and cardiomyocyte hypertrophy and apoptosis. Also known as CCN2, connective tissue growth factor (CTGF) is implicated in the fibrosis; however, whether it contributes to cardiomyocytes changes and adverse effects of high glucose and lipids on these cells remains unknown. Hearts from streptozotocin-induced diabetic rats had elevated CTGF and changes of pathological myocardial hypertrophy, fibrosis, and cardiomyocyte apoptosis. Rat H9c2 cardiomyocytes were then treated with recombinant human (rh)CTGF, high glucose, or the saturated free fatty acid palmitate. Each reagent induced cell hypertrophy, as indicated by the ratio of total protein to cell number, cell size, and gene expression of cardiac hypertrophy marker genes atrial natriuretic peptide (ANP), and α-skeletal actin. Each treatment also caused apoptosis measured by increased caspase3/7 activity, apoptotic cells by transferase-mediated dUTP nick end labeling (TUNEL) assay, and lower viable cell number. Further studies showed CTGF mRNA was rapidly induced by high glucose and palmitate in H9c2 cells and in mouse neonatal cardiomyocyte primary cultures. small interfering RNA against CTGF blocked the high glucose and palmitate induction of hypertrophy and apoptosis. In addition, these CTGF effects were through the tyrosine kinase A (TrkA) receptor with tyrosine kinase activity, which has previously been implicated in CTGF signaling: TrkA was phosphorylated by CTGF, and a specific TrkA blocker abrogated CTGF-induced effects on hypertrophy and apoptosis. For the first time in any system, fatty acid is newly identified as a regulator of CTGF, and this work implicates autocrine CTGF as a mediator of adverse effects of high glucose and fatty acids in cardiomyocytes.

Pathogenesis of tendinopathies: inflammation or degeneration?

The intrinsic pathogenetic mechanisms of tendinopathies are largely unknown and whether inflammation or degeneration has the prominent role is still a matter of debate. Assuming that there is a continuum from physiology to pathology, overuse may be considered as the initial disease factor; in this context, microruptures of tendon fibers occur and several molecules are expressed, some of which promote the healing process, while others, including inflammatory cytokines, act as disease mediators. Neural in-growth that accompanies the neovessels explains the occurrence of pain and triggers neurogenic-mediated inflammation. It is conceivable that inflammation and degeneration are not mutually exclusive, but work together in the pathogenesis of tendinopathies.

Feasibility of using magnetic resonance elastography to study the effect of aging on shear modulus of skeletal muscle

A common complication associated with aging is the stiffening of skeletal muscles. The purpose of this study was to determine the ability of magnetic resonance elastography (MRE) to study this phenomenon in vivo. Twenty female subjects were included in the study with an age range of 50 to 70 years. Shear modulus was calculated for the tibialis anterior of each subject. There was not a significant relationship between age and shear modulus. However, three subjects had abnormally high values and were among the oldest subjects tested. There was a significant relationship between age and tissue stiffness homogeneity. More research is needed to determine whether the changes seen here are reflective of increased tissue cross-linking or related to reduced muscle quality. However, MRE shows promise as a tool to study aging-related muscle stiffness changes or to evaluate treatments to counteract these changes.