Advanced glycosylation end products in diabetic renal and vascular disease

Cinnamaldehyde ameliorates diabetes-induced biochemical impairments and AGEs macromolecules in a pre-clinical model of diabetic nephropathy

PURPOSE

Cinnamaldehyde, has various therapeutic potentials including glucose-lowering effect, and insulinotropic effect; however, its glycation inhibitory mechanism is not known yet. In this study, we explored the effects of cinnamaldehyde for its AGEs inhibitory mechanism in a streptozotocin-complete Freund's adjuvant (STZ-CFA) induced diabetic nephropathy (DN) rat model.

METHODS

Pre-clinical DN model was developed by the administration of multiple low doses of STZ-CFA in rats, mainly characterized by abnormal blood parameters and nephrotic damages. Diabetes-related systemic profile and histopathological hallmarks were evaluated using biochemical assays, microscopic imaging, immunoblot, and real-time PCR analyses, supported by cinnamaldehyde-albumin interaction assessed using STD-NMR and in silico site-directed interactions in the presence of glucose.

RESULTS

Cinnamaldehyde-treatment significantly reversed DN hallmarks, fasting blood glucose (FBG), serum insulin, glycated hemoglobin (HbA1c), urinary microalbumin, and creatinine contrasted to non-treated DN rats and aminoguanidine, a positive reference advanced glycation end products (AGEs) inhibitor. The pathological depositions of AGEs, receptor for advanced glycation end products (RAGE), and carboxymethyl lysine (CML), and transcriptional levels of AGE-RAGE targeted immunomodulatory factors (IL1β, TNF-α, NF-κB, TGF-β) were significantly improved in cinnamaldehyde treated rats as compared to aminoguanidine. Cinnamaldehyde post-treatment improved pancreatic pathology and systemic glycemic index (0.539 ± 0.01 vs. 0.040 ± 0.001, P < 0.001) in DN rats. Subsequently, in silico profiling of cinnamaldehyde defined the competitive binding inhibition with glucose in AGE and RAGE receptors that was further confirmed by in vitro STD-NMR analysis.

CONCLUSION

These findings suggest potential role of cinnamaldehyde in reversing STZ-induced diabetic nephropathic impairments; therefore, appears promising candidate for further pharmacological explorations towards diabetes-associated complications.

Mannan-Binding Lectin Is Associated with Inflammation and Kidney Damage in a Mouse Model of Type 2 Diabetes

Autoreactivity of the complement system may escalate the development of diabetic nephropathy. We used the BTBR OB mouse model of type 2 diabetes to investigate the role of the complement factor mannan-binding lectin (MBL) in diabetic nephropathy. Female BTBR OB mice (n = 30) and BTBR non-diabetic WT mice (n = 30) were included. Plasma samples (weeks 12 and 21) and urine samples (week 19) were analyzed for MBL, C3, C3-fragments, SAA3, and markers for renal function. Renal tissue sections were analyzed for fibrosis, inflammation, and complement deposition. The renal cortex was analyzed for gene expression (complement, inflammation, and fibrosis), and isolated glomerular cells were investigated for MBL protein. Human vascular endothelial cells cultured under normo- and hyperglycemic conditions were analyzed by flow cytometry. We found that the OB mice had elevated plasma and urine concentrations of MBL-C (p < 0.0001 and p < 0.001, respectively) and higher plasma C3 levels (p < 0.001) compared to WT mice. Renal cryosections from OB mice showed increased MBL-C and C4 deposition in the glomeruli and increased macrophage infiltration (p = 0.002). Isolated glomeruli revealed significantly higher MBL protein levels (p < 0.001) compared to the OB and WT mice, and no renal MBL expression was detected. We report that chronic inflammation plays an important role in the development of DN through the binding of MBL to hyperglycemia-exposed renal cells.

Progress and application of adipose-derived stem cells in the treatment of diabetes and its complications

Diabetes mellitus (DM) is a serious chronic metabolic disease that can lead to many serious complications, such as cardiovascular disease, retinopathy, neuropathy, and kidney disease. Once diagnosed with diabetes, patients need to take oral hypoglycemic drugs or use insulin to control blood sugar and slow down the progression of the disease. This has a significant impact on the daily life of patients, requiring constant monitoring of the side effects of medication. It also imposes a heavy financial burden on individuals, their families, and even society as a whole. Adipose-derived stem cells (ADSCs) have recently become an emerging therapeutic modality for DM and its complications. ADSCs can improve insulin sensitivity and enhance insulin secretion through various pathways, thereby alleviating diabetes and its complications. Additionally, ADSCs can promote tissue regeneration, inhibit inflammatory reactions, and reduce tissue damage and cell apoptosis. The potential mechanisms of ADSC therapy for DM and its complications are numerous, and its extensive regenerative and differentiation ability, as well as its role in regulating the immune system and metabolic function, make it a powerful tool in the treatment of DM. Although this technology is still in the early stages, many studies have already proven its safety and effectiveness, providing new treatment options for patients with DM or its complications. Although based on current research, ADSCs have achieved some results in animal experiments and clinical trials for the treatment of DM, further clinical trials are still needed before they can be applied in a clinical setting.

Recent progress in bone-repair strategies in diabetic conditions

Bone regeneration following trauma, tumor resection, infection, or congenital disease is challenging. Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia. It can result in complications affecting multiple systems including the musculoskeletal system. The increased number of diabetes-related fractures poses a great challenge to clinical specialties, particularly orthopedics and dentistry. Various pathological factors underlying DM may directly impair the process of bone regeneration, leading to delayed or even non-union of fractures. This review summarizes the mechanisms by which DM hampers bone regeneration, including immune abnormalities, inflammation, reactive oxygen species (ROS) accumulation, vascular system damage, insulin/insulin-like growth factor (IGF) deficiency, hyperglycemia, and the production of advanced glycation end products (AGEs). Based on published data, it also summarizes bone repair strategies in diabetic conditions, which include immune regulation, inhibition of inflammation, reduction of oxidative stress, promotion of angiogenesis, restoration of stem cell mobilization, and promotion of osteogenic differentiation, in addition to the challenges and future prospects of such approaches.

Fractures and dislocations of the foot and ankle in people with diabetes: a literature review

Diabetes (DM) increases fracture risk, and bone quality depends on type diabetes type, duration, and other comorbidities. Diabetes is associated with a 32% increased relative risk (RR) of total fractures and 24% increased RR of ankle fractures compared with patients without DM. Type 2 DM is associated with a 37% increased RR of foot fractures compared with patients without DM. The incidence of ankle fractures in the general population is 169/100,000 per year, while foot fractures occur less frequently, with an incidence of 142/100,000 per year. Biomechanical properties of bone are negatively impacted by stiff collagen, contributing to the increased risk of fragility fractures in patients with DM. Systemic elevation of proinflammatory cytokines, such as tumor necrosis factor-alpha (TNFα), interleukin-1β (IL-1β), and interleukin 6 (IL-6), impact bone healing in patients with DM. Fractures in patients with DM, can be associated with poorly regulated levels of RANKL (receptor activator of nuclear transcription factor kappa-b ligand) leading to prolonged osteoclastogenesis, and net bone resorption. One of the most salient factors in treating fractures and dislocations of the foot and ankle is to recognize the difference between patients with uncomplicated and complicated DM. Complicated diabetes is defined as 'end organ damage', and for the purposes of this review, includes patients with neuropathy, peripheral artery disease (PAD) and/or chronic renal disease. Uncomplicated diabetes is not associated with 'end organ damage'. Foot and ankle fractures in patients with complicated DM pose challenges, and surgery is associated with increased risks of impaired wound healing, delayed fracture healing, malunion, infection, surgical site infection, and revision surgery. While patients with uncomplicated DM can be treated like patients without DM, patients with complicated DM require close follow-up and robust fixation methods should be considered to withstand the anticipated prolonged healing period. The aims of this review are as follows: (1) to review pertinent aspects of DM bone physiology and fracture healing, (2) to review the recent literature on treatment of foot and ankle fractures in patients with complicated DM, and (3) to provide treatment protocols based on the recent published evidence.

Accelerated AGEing: The Impact of Advanced Glycation End Products on the Prognosis of Chronic Kidney Disease

Advanced glycation end products (AGEs) are aging products. In chronic kidney disease (CKD), AGEs accumulate due to the increased production, reduced excretion, and the imbalance between oxidant/antioxidant capacities. CKD is therefore a model of aging. The aim of this review is to summarize the present knowledge of AGEs in CKD onset and progression, also focusing on CKD-related disorders (cardiovascular diseases, sarcopenia, and nutritional imbalance) and CKD mortality. The role of AGEs as etiopathogenetic molecules, as well as potential markers of disease progression and/or therapeutic targets, will be discussed.

The incidence of fractures at various sites in newly treated patients with type 2 diabetes mellitus

Purpose

In this descriptive study, we examined the incidence of fractures in patients with newly treated type 2 diabetes mellitus (T2D) compared to matched reference population.

Methods

Participants from the UK Clinical Practice research datalink (CPRD) GOLD (1987-2017), aged ≥30 years, with a T2D diagnosis code and a first prescription for a non-insulin anti-diabetic drug (n = 124,328) were included. Cases with T2D were matched by year of birth, sex and practice to a reference population (n = 124,328), the mean follow-up was 7.7 years. Crude fracture incidence rates (IRs) and incidence rate ratios (IRRs) were calculated. Analyses were stratified by fracture site and sex and additionally adjusted for BMI, smoking status, alcohol use and history of any fracture at index date.

Results

The IR of all fractures and major osteoporotic fractures was lower in T2D compared to the reference population (IRR 0.97; 95%CI 0.94-0.99). The IRs were lower for clavicle (IRR 0.67; 0.56-0.80), radius/ulna (IRR 0.81; 0.75-0.86) and vertebral fractures (0.83; 0.75-0.92) and higher for ankle (IRR 1.16; 95%CI 1.06-1.28), foot (1.11; 1.01-1.22), tibia/fibula (1.17; 1.03-1.32) and humerus fractures (1.11; 1.03-1.20). Differences in IRs at various fracture sites between T2D and the reference population were more pronounced in women than in men. In contrast, BMI adjusted IRs for all fractures (IRR 1.07; 1.04-1.10) and most individual fracture sites were significantly higher in T2D, especially in women.

Conclusion

The crude incidence of all fractures was marginally lower in patients with newly treated T2D compared to the matched reference population but differed according to fracture site, especially in women. BMI adjusted analyses resulted in higher incidence rates in T2D at almost all fracture sites compared to crude incidence rates and this was more pronounced in women than in men. This implies that BMI may have a protective impact on the crude incidence of fractures, especially in women with newly treated T2D.

Involvement of AGE and Its Receptors in the Pathogenesis of Hypertension in Elderly People and Its Treatment

Both systolic and diastolic blood pressures increase with age up to 50 to 60 years of age. After 60 years of age systolic pressure rises to 84 years of age but diastolic pressure remains stable or even decreases. In the oldest age group (85-99 years), the systolic blood pressure (SBP) is high and diastolic pressure (DBP) is the lowest. Seventy percent of people older than 65 years are hypertensive. This paper deals with the role of advanced glycation end products (AGE) and its cell receptor (RAGE) and soluble receptor (sRAGE) in the development of hypertension in the elderly population. Plasma/serum levels of AGE are higher in older people as compared with younger people. Serum levels of AGE are positively correlated with age, arterial stiffness, and hypertension. Low serum levels of sRAGE are associated with arterial stiffness and hypertension. Levels of sRAGE are negatively correlated with age and blood pressure. Levels of sRAGE are lower in patients with arterial stiffness and hypertension than patients with high levels of sRAGE. AGE could induce hypertension through numerous mechanisms including, cross-linking with collagen, reduction of nitric oxide, increased expression of endothelin-1, and transforming growth factor-β (TGF-β). Interaction of AGE with RAGE could produce hypertension through the generation of reactive oxygen species, increased sympathetic activity, activation of nuclear factor-kB, and increased expression of cytokines, cell adhesion molecules, and TGF- β. In conclusion, the AGE-RAGE axis could be involved in hypertension in elderly people. Treatment for hypertension in elderly people should be targeted at reduction of AGE levels in the body, prevention of AGE formation, degradation of AGE in vivo, downregulation of RAGE expression, blockade of AGE-RAGE interaction, upregulation of sRAGE expression, and use of antioxidants.

Evaluation of atherosclerosis-related biomarkers during perimenopause: A prospective cohort study in women with endometriosis

AIM

Endometriosis is linked to asymptomatic atherosclerosis and increases the risk of cardiovascular disease (CVD). Vascular function tests are used to assess atherosclerosis, an important indicator of CVD development. In this study, we aimed to evaluate atherosclerosis-related biomarkers, such as vascular function tests and laboratory data, in perimenopausal women with endometriosis.

METHODS

This prospective cohort study enrolled 207 women (≥40 years old) with endometriosis. Laboratory data, ankle brachial index (ABI), and cardio-ankle vascular index (CAVI) were evaluated.

RESULTS

The mean age, CAVI, and ABI of the participants at the initial examination were 45.02 years, 6.9 ± 0.6, and 1.07 ± 0.06, respectively. In multiple regression analysis, no factor was associated with CAVI, but ABI was significantly correlated with elevated total cholesterol (TC), low-density lipoprotein cholesterol, and estradiol (partial regression coefficient [β] = -0.00074, p = 0.017; β = -0.00075, p = 0.033; and β = -0.00022, p = 0.015, respectively). The annual rate of change in CAVI showed a positive correlation with TC and pentosidine and a negative correlation with history of hormone therapy. Neither correlation was strong. In a comparison of three groups classified by the annual rate of change in CAVI, the group with the severe change had a higher level of pentosidine. In adjusted multinomial logistic regression analysis, high pentosidine levels were a risk factor for increased rate of change in CAVI.

CONCLUSIONS

The association between CAVI and serum markers related to lipid metabolism and ovarian function was mild. Longitudinal analysis of CAVI showed an association with pentosidine, which may be helpful in assessing atherosclerosis risk in women with endometriosis during perimenopause.

Receptor of advanced glycation end product (RAGE) polymorphism and oxidative status in Hashimoto’s thyroiditis in Egyptian female patients: case control study

Background

Hashimoto's thyroiditis is the most widespread autoimmune illness targeting a specific organ. "Redox homeostasis" is achieved when the production of Reactive Oxygen Species and their elimination are in balance. Advanced glycation end products (AGEs) are formed when glucose and/or α-oxaloaldehydes react non-enzymatically with the amino groups of lipids, proteins, and DNA. Nowadays, many studies are concerned with AGEs, the polymorphisms of their receptors, and their association with increased risk of HT. However, few studies investigated the role of receptors of advanced glycation end product (RAGE) SNP in Egyptian females.

Objective

The goals of this investigation were to ascertain whether oxidative stress plasma malondialdehyde (MDA) and total antioxidant capacity (TAC) were associated with HT, in addition, to assess the association of RAGE polymorphisms (− 374 T > A and the − 429 T > C and Gly82Ser) with HT.

Subject and methods.

Our case–control study has 80 patients enrolled who have newly been diagnosed with HT and 80 age and sex-matched healthy female controls. Each participant underwent a thorough medical history, physical examination, and laboratory investigations, which included Genotyping of RAGE Gly82Ser, − 374 T > A and − 429 T > C using polymerase chain reaction-restriction fragment length polymorphisms (PCR–RFLP).

Results

Chi-square revealed a significant association regarding the distribution of RAGE (− 374 T < C) genotypes TT and CC between patients and control (P = 0.04). Non-significant associations regarding the distribution of Gly82Ser genotypes Gly/Gly, Gly/Ser, Ser/Ser were found between patients and control (P = 0.5), and non-significant associations related to − 429 T > C gene polymorphism were revealed. In addition, patients with HT had higher MDA and lower TCA compared with controls.

Conclusion

The elevated MDA and decreased TAC as an antioxidant may be one of several risk factors associated with the prevalence of HT in individuals with the − 429 T > C RAGE mutation polymorphism that is associated with an increased risk of HT in Egyptian females.

Stem cell-derived and circulating exosomal microRNAs as new potential tools for diabetic nephropathy management

BACKGROUND

Despite major advances in the treatment of diabetic nephropathy (DN) in recent years, it remains the most common cause of end-stage renal disease. An early diagnosis and therapy may slow down the DN progression. Numerous potential biomarkers are currently being researched. Circulating levels of the kidney-released exosomes and biological molecules, which reflect the DN pathology including glomerular and tubular dysfunction as well as mesangial expansion and fibrosis, have shown the potential for predicting the occurrence and progression of DN. Moreover, many experimental therapies are currently being investigated, including stem cell therapy and medications targeting inflammatory, oxidant, or pro-fibrotic pathways activated during the DN progression. The therapeutic potential of stem cells is partly depending on their secretory capacity, particularly exosomal microRNAs (Exo-miRs). In recent years, a growing line of research has shown the participation of Exo-miRs in the pathophysiological processes of DN, which may provide effective therapeutic and biomarker tools for DN treatment.

METHODS

A systematic literature search was performed in MEDLINE, Scopus, and Google Scholar to collect published findings regarding therapeutic stem cell-derived Exo-miRs for DN treatment as well as circulating Exo-miRs as potential DN-associated biomarkers.

FINDINGS

Glomerular mesangial cells and podocytes are the most important culprits in the pathogenesis of DN and, thus, can be considered valuable therapeutic targets. Preclinical investigations have shown that stem cell-derived exosomes can exert beneficial effects in DN by transferring renoprotective miRs to the injured mesangial cells and podocytes. Of note, renoprotective Exo-miR-125a secreted by adipose-derived mesenchymal stem cells can improve the injured mesangial cells, while renoprotective Exo-miRs secreted by adipose-derived stem cells (Exo-miR-486 and Exo-miR-215-5p), human urine-derived stem cells (Exo-miR-16-5p), and bone marrow-derived mesenchymal stem cells (Exo-miR-let-7a) can improve the injured podocytes. On the other hand, clinical investigations have indicated that circulating Exo-miRs isolated from urine or serum hold great potential as promising biomarkers in DN.

AGEs and sRAGE Variations at Different Timepoints in Patients with Chronic Kidney Disease

Patients with chronic kidney disease (CKD) are affected by enhanced oxidative stress and chronic inflammation, and these factors may contribute to increase advanced glycation end-products (AGEs). In this study we quantified AGEs and soluble receptors for AGE (sRAGE) isoforms and evaluated the association between their variations and eGFR at baseline and after 12 months. We evaluated 64 patients. AGEs were quantified by fluorescence intensity using a fluorescence spectrophotometer, and sRAGE by ELISA. Median age was 81 years, male patients accounted for 70%, 63% were diabetic, and eGFR was 27 ± 10 mL/min/1.73 m². At follow up, sRAGE isoforms underwent a significant decrement (1679 [1393;2038] vs. 1442 [1117;2102], p < 0.0001), while AGEs/sRAGE ratios were increased (1.77 ± 0.92 vs. 2.24 ± 1.34, p = 0.004). Although AGEs and AGEs/sRAGE ratios were inversely related with eGFR, their basal values as well their variations did not show a significant association with eGFR changes. In a cohort of patients with a stable clinical condition at 1 year follow-up, AGEs/sRAGE was associated with renal function. The lack of association with eGFR suggests that other factors can influence its increase. In conclusion, AGEs/sRAGE can be an additional risk factor for CKD progression over a longer time, but its role as a prognostic tool needs further investigation.

Glycation and Glycosylation in Cardiovascular Remodeling: Focus on Advanced Glycation End Products and O-Linked Glycosylations as Glucose-Related Pathogenetic Factors and Disease Markers

Glycation and glycosylation are non-enzymatic and enzymatic reactions, respectively, of glucose, glucose metabolites, and other reducing sugars with different substrates, such as proteins, lipids, and nucleic acids. Increased availability of glucose is a recognized risk factor for the onset and progression of diabetes-mellitus-associated disorders, among which cardiovascular diseases have a great impact on patient mortality. Both advanced glycation end products, the result of non-enzymatic glycation of substrates, and O-linked-N-Acetylglucosaminylation, a glycosylation reaction that is controlled by O-N-AcetylGlucosamine (GlcNAc) transferase (OGT) and O-GlcNAcase (OGA), have been shown to play a role in cardiovascular remodeling. In this review, we aim (1) to summarize the most recent data regarding the role of glycation and O-linked-N-Acetylglucosaminylation as glucose-related pathogenetic factors and disease markers in cardiovascular remodeling, and (2) to discuss potential common mechanisms linking these pathways to the dysregulation and/or loss of function of different biomolecules involved in this field.

Osteoprotective Effects of ‘Anti-Diabetic’ Polyherbal Mixture in Type 1 Diabetic Rats

Bone loss leading to osteopenia and osteoporosis is a frequent secondary complication of diabetes. This study aimed to evaluate the value of a traditionally used ‘anti-diabetic’ polyherbal mixture as a possible remedy for the prevention of this complication. Diabetes was induced in Wistar female rats with a single intraperitoneal injection of alloxan monohydrate. The animals with blood glucose higher than 20 mmol/L for 14 consecutive days were considered diabetic. For the next 14 days, animals were treated with two concentrations of the polyherbal mixture (10 and 20 g of dry plant material/ kg). Bone histopathology was evaluated using the H&E and Masson’s trichrome staining. Alloxan-induced diabetes triggered bone histological changes characteristic for the development of osteopenia and osteoporosis and treatment with the polyherbal decoction restored these histopathological changes of the bones to the healthy animal level. At the same time, treatment with these tested doses has shown no adverse effects. These findings suggest that this mixture might be used as a remedy for the prevention of diabetic bone loss.

Relationship of low molecular weight fluorophore levels with clinical factors and fenofibrate effects in adults with type 2 diabetes

People with diabetes are at risk of chronic complications and novel biomarkers, such as Advanced glycation end-products (AGEs) may help stratify this risk. We assessed whether plasma low-molecular weight AGEs, also known as LMW-fluorophores (LMW-F), are associated with risk factors, predict complications, and are altered by fenofibrate in adults with type 2 diabetes. Plasma LMW-F were quantified at baseline, after six weeks fenofibrate, and one year post-randomisation to fenofibrate or placebo. LMW-F associations with existing and new composite vascular complications were determined, and effects of fenofibrate assessed. LMW-F correlated positively with age, glycated haemoglobin (HbA1c), pulse pressure, kidney dysfunction and inflammation; and negatively with urate, body mass index, oxidative stress and leptin, albeit weakly (r = 0.04–0.16, all p < 0.01). Independent determinants of LMW-F included smoking, diastolic blood pressure, prior cardiovascular disease or microvascular complications, Caucasian ethnicity, kidney function, HbA1c and diabetes duration (all p ≤ 0.01). Baseline LMW-F tertiles correlated with on-trial macrovascular and microvascular complications (trend p < 0.001) on univariate analyses only. Six weeks of fenofibrate increased LMW-F levels by 21% (p < 0.001). In conclusion, LMW-F levels correlate with many risk factors and chronic diabetes complications, and are increased with fenofibrate. LMW-F tertiles predict complications, but not independently of traditional risk factors.

Genetics of Diabetic Retinopathy, a Leading Cause of Irreversible Blindness in the Industrialized World

Diabetic retinopathy (DR) is a chronic complication of diabetes and a leading cause of blindness in the industrialized world. Traditional risk factors, such as glycemic control and duration of diabetes, are unable to explain why some individuals remain protected while others progress to a more severe form of the disease. Differences are also observed in DR heritability as well as the response to anti-vascular endothelial growth factor (VEGF) treatment. This review discusses various aspects of genetics in DR to shed light on DR pathogenesis and treatment. First, we discuss the global burden of DR followed by a discussion on disease pathogenesis as well as the role genetics plays in the prevalence and progression of DR. Subsequently, we provide a review of studies related to DR’s genetic contribution, such as candidate gene studies, linkage studies, and genome-wide association studies (GWAS) as well as other clinical and meta-analysis studies that have identified putative candidate genes. With the advent of newer cutting-edge technologies, identifying the genetic components in DR has played an important role in understanding DR incidence, progression, and response to treatment, thereby developing newer therapeutic targets and therapies.

Sarcopenia in Chronic Kidney Disease: Focus on Advanced Glycation End Products as Mediators and Markers of Oxidative Stress

Sarcopenia is common in chronic kidney disease (CKD), and it is independently associated with morbidity and mortality. Advanced glycation end products (AGE) are mainly known as aging products. In CKD, AGE accumulate due to increased production and reduced kidney excretion. The imbalance between oxidant/antioxidant capacities in CKD patients is one of the main factors leading to AGE synthesis. AGE can, in turn, promote CKD progression and CKD-related complications by increasing reactive oxygen species generation, inducing inflammation, and promoting fibrosis. All these derangements can further increase AGE and uremic toxin accumulation and promote loss of muscle mass and function. Since the link between AGE and sarcopenia in CKD is far from being fully understood, we revised hereby the data supporting the potential contribution of AGE as mediators of oxidative stress in the pathogenesis of sarcopenia. Understanding how AGE and oxidative stress impact the onset of sarcopenia in CKD may help to identify new potential markers of disease progression and/or therapeutic targets.

Advanced Glycation End Products (AGE) and Soluble Forms of AGE Receptor: Emerging Role as Mortality Risk Factors in CKD

Advanced glycation end-products (AGE) can promote chronic kidney disease (CKD) progression and CKD-related morbidities. The soluble receptor for AGE (sRAGE) is a potential biomarker of inflammation and oxidative stress. Here, we explored the role of AGE, glycated albumin, sRAGE and its different forms, cRAGE and esRAGE, as prognostic factors for mortality in 111 advanced CKD patients. The median follow-up time was 39 months. AGE were quantified by fluorescence, sRAGE and its forms by ELISA. Malnutrition was screened by the Malnutrition Inflammation Score (MIS). The Cox proportional hazards regression model was used to assess the association of variables with all-cause mortality. Mean levels of sRAGE, esRAGE and cRAGE were 2318 ± 1224, 649 ± 454 and 1669 ± 901 pg/mL. The mean value of cRAGE/esRAGE was 2.82 ± 0.96. AGE were 3026 ± 766 AU and MIS 6.0 ± 4.7. eGFR correlated negatively with AGE, sRAGE, esRAGE and cRAGE, but not with cRAGE/esRAGE. Twenty-eight patients died. No difference was observed between diabetic and non-diabetic patients. Starting dialysis was not associated with enhanced risk of death. AGE, esRAGE and cRAGE/esRAGE were independently associated with all-cause mortality. AGE, esRAGE and cRAGE/esRAGE may help to stratify overall mortality risk. Implementing the clinical evaluation of CKD patients by quantifying these biomarkers can help to improve patient outcomes.

Association between combined treatment with SGLT2 inhibitors and metformin for type 2 diabetes mellitus on fracture risk: a meta-analysis of randomized controlled trials

This study analyzed the effects of combination therapy with sodium-glucose transporter-2 inhibitors (SGLT2is) and metformin on fracture risk. Summarizing available randomized controlled trials, we found that SGLT2is combined with metformin therapy did not influence fracture risk compared with metformin monotherapy or other comparators in patients with T2DM.

INTRODUCTION

No study is available evaluating the association between sodium-glucose transporter-2 inhibitors (SGLT2is) in combination with metformin use and fracture risk. Our study aimed to investigate the fracture risk of combination therapy with SGLT2is and metformin in patients with type 2 diabetes mellitus (T2DM).

METHODS

PubMed, Embase, ClinicalTrials.gov site, and the Cochrane Library databases were scrutinized for all eligible randomized controlled trials (RCTs). The summarized odds ratios (ORs) and their 95% confidence intervals (CI) were calculated using Review Manager 5.3 software.

RESULTS

A total of 25 RCTs involving 19,500 participants with T2DM were included in our studies. There were 88 fracture cases in the SGLT2is in combination with metformin therapy group and 79 in the control group. SGLT2is combined with metformin use did not influence fracture risk compared with metformin monotherapy or other comparators in patients with T2DM (OR = 0.97, 95% CI 0.71-1.32). After stratification by drug type, follow-up time, control regimen, and type of fracture, the upshots were still stable.

CONCLUSION

SGLT2is and metformin combination therapy did not influence fracture risk compared with metformin monotherapy or other comparators in patients with T2DM.

PROSPERO REGISTRATION NUMBER

CRD42020168435.

Molecular complexities underlying the vascular complications of diabetes mellitus - A comprehensive review

Diabetes is a chronic disease, characterized by hyperglycemia, which refers to the elevated levels of glucose in the blood, due to the inability of the body to produce or use insulin effectively. Chronic hyperglycemia levels lead to macrovascular and microvascular complications. The macrovascular complications consist of peripheral artery disease (PAD), cardiovascular diseases (CVD) and cerebrovascular diseases, while the microvascular complications comprise of diabetic microangiopathy, diabetic nephropathy, diabetic retinopathy and diabetic neuropathy. Vascular endothelial dysfunction plays a crucial role in mediating both macrovascular and microvascular complications under hyperglycemic conditions. In diabetic microvasculature, the intracellular hyperglycemia causes damage to the vascular endothelium through - (i) activation of four biochemical pathways, namely the Polyol pathway, protein kinase C (PKC) pathway, advanced glycation end products (AGE) pathway and hexosamine pathway, all of which commutes glucose and its intermediates leading to overproduction of reactive oxygen species, (ii) dysregulation of growth factors and cytokines, (iii) epigenetic changes which concern the changes in DNA as a response to intracellular changes, and (iv) abnormalities in non-coding RNAs, specifically microRNAs. This review will focus on gaining an understanding of the molecular complexities underlying the vascular complications in diabetes mellitus, to increase our understanding towards the development of new mechanistic therapeutic strategies to prevent or treat diabetes-induced vascular complications.

Glycation in Huntington's Disease: A Possible Modifier and Target for Intervention

Glycation is the non-enzymatic reaction between reactive dicarbonyls and amino groups, and gives rise to a variety of different reaction products known as advanced glycation end products (AGEs). Accumulation of AGEs on proteins is inevitable, and is associated with the aging process. Importantly, glycation is highly relevant in diabetic patients that experience periods of hyperglycemia. AGEs also play an important role in neurodegenerative diseases including Alzheimer’s (AD) and Parkinson’s disease (PD). Huntington’s disease (HD) is a hereditary neurodegenerative disease caused by an expansion of a CAG repeat in the huntingtin gene. The resulting expanded polyglutamine stretch in the huntingtin (HTT) protein induces its misfolding and aggregation, leading to neuronal dysfunction and death. HD patients exhibit chorea and psychiatric disturbances, along with abnormalities in glucose and energy homeostasis. Interestingly, an increased prevalence of diabetes mellitus has been reported in HD and in other CAG triplet repeat disorders. However, the mechanisms underlying the connection between glycation and HD progression remain unclear. In this review, we explore the possible connection between glycation and proteostasis imbalances in HD, and posit that it may contribute to disease progression, possibly by accelerating protein aggregation and deposition. Finally, we review therapeutic interventions that might be able to alleviate the negative impact of glycation in HD.

Understanding Metabolic Memory: A Tale of Two Studies

The results of the Diabetes Control and Complications Trial (DCCT) have given rise to much encouragement in the battle to stave off the complications of type 1 diabetes, showing dramatic declines in the development of severe retinopathy, nephropathy, and neuropathy in those treated intensively compared with conventional therapy. Particularly encouraging has been the continuing difference between the two groups despite both having similar HbA1c (∼8%) since the end of DCCT, when 96% of participants entered the observational Epidemiology of Diabetes Interventions and Complications (EDIC) study. This continuing relative benefit has been termed "metabolic memory," which implies altered metabolic regulation. Based on evidence from both the Epidemiology of Diabetes Complications (EDC) prospective cohort study of childhood-onset type 1 diabetes and DCCT/EDIC, we show that the metabolic memory effect can be largely explained by lower cumulative glycemic exposure in the intensive therapy group, and, on average, the development of complications increases with greater glycemic exposure, irrespective of whether this results from a high exposure for a short time or a lower exposure for a longer time. Thus, there is no need for a concept like "metabolic memory" to explain these observations. Potential mechanisms explaining the cumulative glycemic effect are also briefly discussed.

Glycation and Advanced Glycation End-Product Formation with Icodextrin and Dextrose

Objective

To review protein glycation and advanced glycation end-product formation with particular reference to its occurrence in the peritoneum following exposure to peritoneal dialysis fluid.

Data sources

Articles identified through searches on MEDLINE and BIDS and references cited therein.

Study selection

Studies on the interaction of amino groups with glucose, maltose and glucose polymers. Studies containing evidence of peritoneal advanced glycation end-product formation.

Data extraction

Studies evaluated as to whether they are in vivo, ex vivo or in vitro under non-physiological or physiological conditions.

Results

Protein glycation is slower with maltose and glucose polymers than with equimolar glucose. Advanced glycation end-product formation occurs with all three sugars, but to a greater extent after standard heat sterilization of dialysis fluid and to a lesser extent in heat sterilized fluids containing icodextrin rather than glucose. Glucose degradation products significantly contribute to protein-linked advanced glycation end-productlike fluorescence. Histology and immunohistochemistry demonstrate diabetiform changes and advanced glycation end-products in the peritoneal membrane following exposure to glucose-containing peritoneal dialysis fluids. Their presence is likely to be detrimental to peritoneal function and may contribute to loss of ultrafiltration.

Conclusions

Advanced glycation end-product formation is lower but still significant with heat sterilized peritoneal dialysis fluid containing icodextrin than with glucose. More research is needed to investigate the interaction of glucose degradation products and glucose polymers with proteins and the possible consequences of advanced glycation end-product formation on peritoneal function.

Glycation and HMG-CoA Reductase Inhibitors: Implication in Diabetes and Associated Complications

INTRODUCTION

Diabetes Mellitus (DM) acts as an absolute mediator of cardiovascular risk, prompting the prolonged occurrence, size and intricacy of atherosclerotic plaques via enhanced Advanced Glycation Endproducts (AGEs) formation. Moreover, hyperglycemia is associated with enhanced glyco-oxidized and oxidized Low-Density Lipoprotein (LDL) possessing greater atherogenicity and decreased the ability to regulate HMG-CoA reductase (HMG-R). Although aminoguanidine (AG) prevents the AGE-induced protein cross-linking due to its anti-glycation potential, it exerts several unusual pharmaco-toxicological effects thus restraining its desirable therapeutic effects. HMG-R inhibitors/ statins exhibit a variety of beneficial impacts in addition to the cholesterol-lowering effects.

OBJECTIVE

Inhibition of AGEs interaction with receptor for AGEs (RAGE) and glyco-oxidized-LDL by HMG-R inhibitors could decrease LDL uptake by LDL-receptor (LDL-R), regulate cholesterol synthesis via HMG-R, decrease oxidative and inflammatory stress to improve the diabetes-associated complications.

CONCLUSION

Current article appraises the pathological AGE-RAGE concerns in diabetes and its associated complications, mainly focusing on the phenomenon of both circulatory AGEs and those accumulating in tissues in diabetic nephropathy, diabetic neuropathy, and diabetic retinopathy, discussing the potential protective role of HMG-R inhibitors against diabetic complications.

A 10-Year Prospective Study of Bone Mineral Density and Bone Turnover in Males and Females With Type 1 Diabetes

CONTEXT

In a previous community-based, cross-sectional study, males with type 1 diabetes (T1D) had lower bone mineral density (BMD) than did matched people without diabetes but females with T1D had normal BMD.

OBJECTIVE

To determine whether BMD in the males continued to decline, the neutral effect of T1D on BMD in females persisted, and whether temporal BMD changes reflected changes in bone turnover markers.

DESIGN

Longitudinal observational study.

SETTING

Urban community.

PATIENTS

Forty-eight of the original 102 original cross-sectional study participants (20 males, 28 females) of mean age 42.0 years and median diabetes duration 14.6 years at baseline who were restudied a mean of 10.3 years later.

MAIN OUTCOME MEASURES

BMD at total hip, femoral neck, lumbar spine (L1 to L4), and distal forearm. Biochemical bone turnover markers.

RESULTS

After adjustment for age, body mass index (BMI), and renal function, there was no temporal change in BMD at the hip or forearm in the males (P ≥ 0.12), but lumbar spine BMD increased (P = 0.009). Females exhibited no statistically significant change in BMD in similar multivariable models that also included postmenopausal status, except a mild increase at the forearm (P = 0.046). Age- and sex-related changes in bone turnover markers paralleled those in general population studies.

CONCLUSIONS

There is a reduction in BMD in males with T1D that occurs early in the course of the disease but then stabilizes. BMD in females with T1D remains similar to that expected for age, BMI, and postmenopausal status.

The risks of sarcopenia, falls and fractures in patients with type 2 diabetes mellitus

Fracture risk in patients with type 2 diabetes mellitus (T2DM) is increased, and the mechanism is multifactorial. Recent research on T2DM-induced bone fragility shows that bone mineral density (BMD) is often normal or even slightly elevated. However, bone turnover may be decreased and bone material and microstructural properties are altered, especially when microvascular complications are present. Besides bone fragility, extra-skeletal factors leading to an increased propensity to experience falls may also contribute to the increased fracture risk in T2DM, such as peripheral neuropathy, retinopathy and diabetes medication (e.g. insulin use). One of the probable additional contributing factors to the increased fall and fracture risks in T2DM is sarcopenia, the age-related decline in skeletal muscle mass, quality and function. Although the association between sarcopenia, fall risk, and fracture risk has been studied in the general population, few studies have examined the association between T2DM and muscle tissue and the risks of falls and fractures. This narrative review provides an overview of the literature regarding the multifactorial mechanisms leading to increased fracture risk in patients with T2DM, with a focus on sarcopenia and falls.

Low bone turnover in premenopausal women with type 2 diabetes mellitus as an early process of diabetes-associated bone alterations: a cross-sectional study

BACKGROUND

Individuals with Diabetes Mellitus (DM) are at increased risk for fracture due to the decrease in bone strength and quality. Serum procollagen type I intact N-terminal (P1NP) and serum C-terminal cross-linking telopeptide of type I collagen (CTX) as markers of bone formation and resorption, respectively, have been reported to be decreased in T2DM. It remains unclear whether diabetes-associated alterations in the bone turnover of T2DM individuals are related to the longer duration of the disease or may occur earlier. Furthermore, previous studies on BTMs in T2DM individuals have mostly been done in postmenopausal women with T2DM, which might have masked the DM-induced alterations of bone turnover with concurrent estrogen deficiency. This study aims to assess the levels of serum P1NP and CTX as markers of bone turnover in premenopausal women with and without T2DM.

METHODS

This cross-sectional study involves 41 premenopausal women with T2DM, and 40 premenopausal women without DM. Sampling was done consecutively. P1NP and CTX measurement was done using the electrochemi-luminescence immunoassay (ECLIA) method. Other data collected include levels of HbA1C, ALT, creatinine, eGFR and lipid profile.

RESULTS

Median (interquartile range) P1NP in T2DM is 29.9 ng/ml (24.7-41.8 ng/ml), while in non-DM is 37.3 ng/ml, (30.8-47.3 ng/ml; p = 0.007). Median (interquartile range) CTX in T2DM is 0.161 ng/ml (0.106-0.227 ng/ml), while in non-DM is 0.202 ng/ml (0.166-0.271 ng/ml; p = 0.0035). Levels of P1NP and CTX in the T2DM group did not correlate with the duration of disease, age, BMI or the levels of HbA1C.

CONCLUSIONS

Premenopausal women with T2DM indeed have lower bone turnover when compared with non-DM controls. This significantly lower bone turnover process starts relatively early in the premenopausal age, independent of the duration of DM. Gaining understanding of the early pathophysiology of altered bone turnover may be key in developing preventive strategies for diabetoporosis.

Bone Metabolism and Fracture Risk in Diabetes Mellitus

Individuals with Type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) are at increased risk for fragility fractures. Bone mineral density (BMD) is decreased in T1DM but often normal or even elevated in T2DM when compared with age-matched non-DM populations. However, bone turnover is decreased in both T1DM and T2DM. The pathophysiologic mechanisms leading to bone fragility is multifactorial, and potentially leads to reduced bone formation, altered bone microstructure and decreased bone strength. Interestingly, different antidiabetic treatments may influence fracture risk due to effects on glycemic control, triggering of hypoglycemic events or osteoblastogenesis.

Fenofibrate decreases the bone quality by down regulating Runx2 in high-fat-diet induced Type 2 diabetes mellitus mouse model

Background

This study is to investigate the effect of fenofibrate on the bone quality of Type 2 diabetes mellitus (T2DM) mouse model.

Methods

T2DM mouse model was induced by high-fat-diet, and the mice were treated with fenofibrate (100 mg/kg) (DIO-FENO) or PBS (DIO-PBS) for 4 weeks. The bone microstructure and biomechanical properties of femora were analyzed by micro-CT and 3-Point bending test. The protein expression was detected by immunohistochemical staining and Western blot. The cell apoptosis was evaluated by TUNEL staining. The Bcl2, caspase 3, and osteoblast marker genes were detected by RT-qPCR.

Results

The biomechanical properties of bones from DIO-FENO group were significantly lower than those in the control and DIO-PBS groups. Besides, the trabecular number was lower than those of the other groups, though the cortical porosity was decreased compared with that of DIO-PBS group because of the increase of apoptotic cells. The expression of osteocalcin and collagen I were decreased after treatment with fenofibrate in T2DM mice. Moreover, the cell viability was decreased after treated with different concentrations of fenofibrate, and the expression of Runx2 decreased after treated with high dose of fenofibrate.

Conclusion

Fenofibrate decreases the bone quality of T2DM mice through decreasing the expression of collagen I and osteocalcin, which may be resulted from the down regulation of Runx2 expression.

Potential Role of Serum and Urinary Biomarkers in Diagnosis and Prognosis of Diabetic Nephropathy

PURPOSE OF REVIEW

Diabetic nephropathy (DN) is a progressive kidney disease caused by alterations in kidney architecture and function, and constitutes one of the leading causes of end-stage renal disease (ESRD). The purpose of this review is to summarize the state of the art of the DN-biomarker field with a focus on the new strategies that enhance the sensitivity of biomarkers to predict patients who will develop DN or are at risk of progressing to ESRD.

OBJECTIVE

In this review, we provide a description of the pathophysiology of DN and propose a panel of novel putative biomarkers associated with DN pathophysiology that have been increasingly investigated for diagnosis, to predict disease progression or to provide efficient personal treatment.

METHODS

We performed a review of the literature with PubMed and Google Scholar to collect baseline data about the pathophysiology of DN and biomarkers associated. We focused our research on new and emerging biomarkers of DN.

KEY FINDINGS

In this review, we summarized the critical signaling pathways and biological processes involved in DN and highlighted the pathogenic mediators of this disease. We next proposed a large review of the major advances that have been made in identifying new biomarkers which are more sensitive and reliable compared with currently used biomarkers. This includes information about emergent biomarkers such as functional noncoding RNAs, microRNAs, long noncoding RNAs, exosomes, and microparticles.

LIMITATIONS

Despite intensive strategies and constant investigation, no current single treatment has been able to reverse or at least mitigate the progression of DN, or reduce the morbidity and mortality associated with this disease. Major difficulties probably come from the renal disease being heterogeneous among the patients.

IMPLICATIONS

Expanding the proteomics screening, including oxidative stress and inflammatory markers, along with metabolomics approaches may further improve the prognostic value and help in identifying the patients with diabetes who are at high risk of developing kidney diseases.

Mechanisms of diabetes mellitus-induced bone fragility

The risk of fragility fractures is increased in patients with either type 1 diabetes mellitus (T1DM) or type 2 diabetes mellitus (T2DM). Although BMD is decreased in T1DM, BMD in T2DM is often normal or even slightly elevated compared with an age-matched control population. However, in both T1DM and T2DM, bone turnover is decreased and the bone material properties and microstructure of bone are altered; the latter particularly so when microvascular complications are present. The pathophysiological mechanisms underlying bone fragility in diabetes mellitus are complex, and include hyperglycaemia, oxidative stress and the accumulation of advanced glycation endproducts that compromise collagen properties, increase marrow adiposity, release inflammatory factors and adipokines from visceral fat, and potentially alter the function of osteocytes. Additional factors including treatment-induced hypoglycaemia, certain antidiabetic medications with a direct effect on bone and mineral metabolism (such as thiazolidinediones), as well as an increased propensity for falls, all contribute to the increased fracture risk in patients with diabetes mellitus.

Do Advanced Glycation End Products and Its Receptor Play a Role in Pathophysiology of Hypertension?

There is a close relationship between arterial stiffness and blood pressure. The studies suggest that the advanced glycation end products (AGEs) and its cell receptor (RAGE) are involved in the arterial stiffness in two ways: changes in arterial structure and vascular function. Plasma levels of AGEs and expression of RAGE are elevated, while the levels of soluble RAGE (sRAGE) and endogenous secretory RAGE (esRAGE) are lowered in patients with hypertension (HTN). There is a positive correlation between plasma levels of AGEs and arterial stiffness, and an inverse association between arterial stiffness/HTN, and serum levels of sRAGE and esRAGE. Various measures can reduce the levels of AGEs and expression of RAGE, and elevate sRAGE. Arterial stiffness and blood pressure could be reduced by lowering the serum levels of AGEs, and increasing the levels of sRAGE. Levels of AGEs can be lowered by reducing the consumption of AGE-rich diet, short duration of cooking in moist heat at low temperature, and cessation of cigarette smoking. Drugs such as aminoguanidine, vitamins, angiotensin-converting enzyme (ACE) inhibitors, angiotensin-II receptor blockers, statins, and metformin inhibit AGE formation. Alagebrium, an AGE breakers reduces levels of AGEs. Clinical trials with some drugs tend to reduce stiffness. Systemic administration of sRAGE has beneficial effect in animal studies. In conclusion, AGE-RAGE axis is involved in arterial stiffness and HTN. The studies suggest that inhibition of AGEs formation, reduction of AGE consumption, blockade of AGE-RAGE interaction, suppression of RAGE expression, and exogenous administration of sRAGE may be novel therapeutic strategies for treatment of arterial stiffness and HTN.

Advanced glycation end products mediated cellular and molecular events in the pathology of diabetic nephropathy

Diabetic nephropathy (DN) is a major cause of morbidity and mortality in diabetic patients and a leading cause of end-stage renal disease (ESRD). Degenerative changes such as glomerular hypertrophy, hyperfiltration, widening of basement membranes, tubulointerstitial fibrosis, glomerulosclerosis and podocytopathy manifest in various degrees of proteinuria in DN. One of the key mechanisms implicated in the pathogenesis of DN is non-enzymatic glycation (NEG). NEG is the irreversible attachment of reducing sugars onto free amino groups of proteins by a series of events, which include the formation of Schiff’s base and an Amadori product to yield advanced glycation end products (AGEs). AGE modification of client proteins from the extracellular matrix induces crosslinking, which is often associated with thickening of the basement membrane. AGEs activate several intracellular signaling cascades upon interaction with receptor for AGEs (RAGE), which manifest in aberrant cellular responses such as inflammation, apoptosis and autophagy, whereas other receptors such as AGE-R1, AGE-R3 and scavenger receptors also bind to AGEs and ensue endocytosis and degradation of AGEs. Elevated levels of both serum and tissue AGEs are associated with adverse renal outcome. Increased evidence supports that attenuation of AGE formation and/or inhibition of RAGE activation manifest(s) in improving renal function. This review provides insights of NEG, discusses the cellular and molecular events triggered by AGEs, which manifest in the pathogenesis of DN including renal fibrosis, podocyte epithelial-mesenchymal transition and activation of renin-angiotensin system. Therapies designed to target AGEs, such as inhibitors of AGEs formation and crosslink breakers, are discussed.

Structural, biological and biophysical properties of glycated and glycoxidized phosphatidylethanolamines

Glycation and glycoxidation of proteins and peptides have been intensively studied and are considered as reliable diagnostic biomarkers of hyperglycemia and early stages of type II diabetes. However, glucose can also react with primary amino groups present in other cellular components, such as aminophospholipids (aminoPLs). Although it is proposed that glycated aminoPLs can induce many cellular responses and contribute to the development and progression of diabetes, the routes of their formation and their biological roles are only partially revealed. The same is true for the influence of glucose-derived modifications on the biophysical properties of PLs. Here we studied structural, signaling, and biophysical properties of glycated and glycoxidized phosphatidylethanolamines (PEs). By combining high resolution mass spectrometry and nuclear magnetic resonance spectroscopy it was possible to deduce the structures of several intermediates indicating an oxidative cleavage of the Amadori product yielding glycoxidized PEs including advanced glycation end products, such as carboxyethyl- and carboxymethyl-ethanolamines. The pro-oxidative role of glycated PEs was demonstrated and further associated with several cellular responses including activation of NFκB signaling pathways. Label free proteomics indicated significant alterations in proteins regulating cellular metabolisms. Finally, the biophysical properties of PL membranes changed significantly upon PE glycation, such as melting temperature (Tm), membrane surface charge, and ion transport across the phospholipid bilayer.

HDL in diabetic nephropathy has less effect in endothelial repairing than diabetes without complications

Background

Diabetic nephropathy has a high cardiovascular risk with a low-level HDL(high density lipoprotein) in epidemiologic studies. Glycated HDL in diabetes can diminish the capacity to stimulate endothelial cell migration, but the mechanism has not been adequately explored in diabetic nephropathy. We performed this study to find out whether HDL in diabetic nephropathy is more dysfunctional than HDL in diabetes without complications.

Methods

Endothelial cells were treated with N-HDL (normal), D-HDL (T2DM[type 2 diabetes mellitus] without complications), DN-HDL (T2DM nephropathy), N-apoA-I (normal apoA-I), and G-apoA-I (glycated apoA-I in vitro). Cell migration capacity was measured with wound-healing and transwell migration assay in vitro and electric carotid injury model in vivo. Protein glycation levels were measured with nanoLC-MS/MS. PI3K expression and Akt phosphorylation were analyzed by western blot.

Results

In wound-healing assay, DN-HDL showed a 17.12 % decrease compared with D-HDL (p < 0.05). DN-HDL showed a 29.85 % decrease in comparison with D-HDL (p < 0.001) in transwell assay. In the electric carotid injury model, D-HDL and DN-HDL impaired the re-endothelialization capacity; DN-HDL was less effective than D-HDL. Meanwhile, DN-HDL was found to have a significantly higher protein glycation level than D-HDL (p < 0.001). PI3K expression and Akt phosphorylation were reduced significantly in DN-HDL in comparison with D-HDL and N-HDL.

Conclusions

We found that HDL from diabetic nephropathy has a higher level of glycation and induced less cell migration in vitro and in vivo compared with that from diabetes without nephropathy. This finding suggests that diabetic nephropathy has higher levels of glycated HDL and partially explains why patients with DN have a higher risk of cardiovascular disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12944-016-0246-z) contains supplementary material, which is available to authorized users.

Interrelationship of elevated serum Advanced Glycation End-product levels and malnutrition (Subjective Global Assessment) scores with the severity of retinopathy in type II diabetes

BACKGROUND AND AIMS

Hyperglycemia in diabetes causes endogenous formation of Advanced Glycation End-products (AGEs) which accumulate in various body parts including retina causing diabetic retinopathy. AGEs also originate from exogenous dietary sources contributing to the body's AGE pool. Currently, curing of diabetic retinopathy is mainly focused on medication, surgical or laser interventions and not much emphasis is given on preventing or halting its occurrence or advancement to more severe stages, nutritionally. Planning a 'low glycemic index-low AGE' diet therapy for diabetic subjects can reduce endogenous and exogenous origin AGEs in the body and help in controlling retinopathy. Sound and accurate assessment of nutritional status is a crucial step for planning a therapeutic diet for this condition. As this aspect has not gained sufficient attention till now we are assessing the association of serum Advanced Glycation End-product (AGE) levels with the severity of diabetic retinopathy and for the first time estimating the nutritional status of subjects with this eye disorder for long term patient care.

METHODS

This was a tertiary care centre-based, case-control study involving sixty three consecutive cases with diabetes divided as 21 cases with diabetes but no retinopathy, 21 cases with non proliferative diabetic retinopathy (NPDR), 21 cases with proliferative diabetic retinopathy (PDR) along with 21 healthy controls. Serum AGE levels of all the cases and controls were evaluated by Enzyme Linked Immuno Sorbent Assay (ELISA) and nutritional status was assessed by anthropometric measurements and SGA scores.

RESULTS

Serum AGE levels were found significantly elevated in PDR group when compared with no retinopathy (p < 0.05) and control (p < 0.001) group. Control group was also significantly different from (p < 0.05) from NPDR group. Increase in SGA scores was statistically significant amongst the four study groups though other indices of nutritional status showed no definite trend with the increasing severity of retinopathy.

CONCLUSION

Our study shows that serum AGE levels are potential risk markers of diabetic retinopathy and SGA can be used as a regular tool for the assessment of nutritional status of diabetic retinopathy subjects which will help planning a 'low glycemic index-low AGE' therapeutic diet for halting this morbidity.

Skin autofluorescence is associated with carotid intima-media thickness, diabetic microangiopathy, and long-lasting metabolic control in type 1 diabetic patients. Results from Poznan Prospective Study

AIMS

Our aim was to assess the association between skin autofluorescence (AF) related to advanced glycation end products (AGEs) accumulation and long-term metabolic control, microvascular complications and carotid intima-media thickness (IMT) in an observational cohort of type 1 diabetes (DM1).

METHODS

The analysis included 77 patients with DM1 (28 women and 49 men) aged 38 (IQR: 34-41), diabetes duration 15 (14-17), participating in Poznan Prospective Study (PoProStu). Skin AF was measured with AGE Reader (DiagnOptics).

RESULTS

We found 50% of any microvascular complication; 37% of retinopathy, 37% of diabetic kidney disease and 22% of distal symmetrical neuropathy. Median carotid IMT was 0.57 (0.52-0.67) mm and skin AF 2.2 (IQR: 1.9-2.6). We found positive correlation between skin AF and patients' age (r=0.31, p=0.006), mean HbA1c from the observation time (r=0.35, p=0.001) and IMT (r=0.39, p<0.001). In multivariate logistic regression presence of microvascular complications was independently associated with skin AF: for retinopathy (OR 3.49; 95% CI: 1.08-11.28, p=0.03), for diabetic kidney disease (OR 3.62; 95% CI: 1.16-11.28, p=0.02), for neuropathy (OR 5.01; 95% CI: 1.21-20.77, p=0.02) and for any microangiopathy (OR 3.13; 95% CI: 1.06-9.18, p=0.03).

CONCLUSION

Skin AF is a reliable marker of past glycemic control of diabetes. Increased accumulation of AGEs is related to the presence of diabetic microangiopathy as well as subclinical macroangiopathy in patients with type 1.

Antidiabetic effect of green rooibos (Aspalathus linearis) extract in cultured cells and type 2 diabetic model KK-A(y) mice

Previous studies have demonstrated antidiabetic effects for rooibos (Aspalathus linearis) and aspalathin (ASP), one of its main polyphenols. Rooibos, an endemic plant of South Africa, is well-known for its use as herbal tea. Green ('unfermented') rooibos has been shown to contain more ASP than 'fermented' rooibos tea, currently the major product. In the present study, we investigated the antidiabetic effect of green rooibos extract (GRE) through studies on glucose uptake in L6 myotubes and on pancreatic β-cell protective ability from reactive oxygen species (ROS) in RIN-5F cells. Its in vivo effect was also examined using obese diabetic KK-A(y) mice. GRE increased glucose uptake under insulin absent condition and induced phosphorylation of 5'-adenosine monophosphate-activated protein kinase (AMPK) in L6 myotubes as previously demonstrated for ASP. In addition to AMPK, GRE also promoted phosphorylation of Akt, another promoter of glucose transporter 4 (GLUT4) translocation, in L6 myotubes unlike ASP, suggesting an involvement of GRE component(s) other than ASP in Akt phosphorylation. Promotion of GLUT4 translocation to the plasma membrane by GRE in L6 myotubes was demonstrated by Western blotting analysis. GRE suppressed the advanced glycation end products (AGEs)-induced increase in ROS levels in RIN-5F pancreatic β-cells. Subchronic feeding with GRE suppressed the increase in fasting blood glucose levels in type 2 diabetic model KK-A(y) mice. These in vitro and in vivo results strongly suggest that GRE has antidiabetic potential through multiple modes of action.

Emerging role of advanced glycation-end products (AGEs) in the pathobiology of eye diseases

Advanced glycation end products (AGEs) have been implicated in vision loss associated with macula degeneration, cataract formation, diabetic retinopathy and glaucoma. This pathogenic potential is mainly attributed to their accumulation in ocular tissues where they mediate aberrant crosslinking of extracellular matrix proteins and disruption of endothelial junctional complexes that affects cell permeability, mediates angiogenesis and breakdown of the inner blood-retinal barrier. Furthermore, AGEs severely affect cellular metabolism by disrupting ATP production, enhancing oxidative stress and modulating gene expression of anti-angiogenic and anti-inflammatory genes. Elucidation of AGE-induced mechanisms of action in different eye compartments will help in the understanding of the complex cellular and molecular processes associated with eye diseases. Several pharmaceutical agents with anti-glycating and anti-oxidant properties as well as AGE crosslink 'breakers' have been currently applied to eye diseases. The role of diet and the beneficial effects of certain nutriceuticals provide an alternative way to manage chronic visual disorders that affect the quality of life of millions of people.

Chronic spontaneous urticaria is characterized by lower serum advanced glycation end-products

Background. Chronic spontaneous urticaria (CSU) is associated with activation of acute phase response. On the other hand, it is known that systemic inflammation may lead to increased formation of advanced glycation end-products (AGEs), associated with pathogenesis of various diseases. Aim. We aim to test whether chronic inflammation manifested by activated acute phase response may provide a mechanism for increased serum AGEs concentration in CSU. Methods. Concentrations of AGEs were measured spectrofluorimetrically in serum of CSU patients and the healthy subjects. Results. Serum AGEs and albumin concentrations in CSU patients were significantly lower as compared with the healthy subjects. Serum CRP concentration was significantly higher in patients with CSU than in the controls. Significant positive correlation was observed between AGEs and albumin concentrations in the subjects. Conclusions. CSU is not associated with increased circulating AGEs concentrations, despite the enhanced systemic inflammatory response. Paradoxical decrease of serum AGEs concentrations is probably a reflection of lower concentration of “negative acute phase proteins” such as albumin.

Advanced glycation end products and diabetic retinopathy

Studies have established hyperglycemia as the most important factor in the progress of vascular complications. Formation of advanced glycation end products (AGEs) correlates with glycemic control. The AGE hypothesis proposes that hyperglycemia contributes to the pathogenesis of diabetic complications including retinopathy. However, their role in diabetic retinopathy remains largely unknown. This review discusses the chemistry of AGEs formation and their patho-biochemistry particularly in relation to diabetic retinopathy. AGEs exert deleterious effects by acting directly to induce cross-linking of long-lived proteins to promote vascular stiffness, altering vascular structure and function and interacting with receptor for AGE, to induce intracellular signaling leading to enhanced oxidative stress and elaboration of key proinflammatory and prosclerotic cytokines. Novel anti-AGE strategies are being developed hoping that in next few years, some of these promising therapies will be successfully evaluated in clinical context aiming to reduce the major economical and medical burden caused by diabetic retinopathy.

Proteomics and systems biology for understanding diabetic nephropathy

Like many diseases, diabetic nephropathy is defined in a histopathological context and studied using reductionist approaches that attempt to ameliorate structural changes. Novel technologies in mass spectrometry-based proteomics have the ability to provide a deeper understanding of the disease beyond classical histopathology, redefine the characteristics of the disease state, and identify novel approaches to reduce renal failure. The goal is to translate these new definitions into improved patient outcomes through diagnostic, prognostic, and therapeutic tools. Here, we review progress made in studying the proteomics of diabetic nephropathy and provide an introduction to the informatics tools used in the analysis of systems biology data, while pointing out statistical issues for consideration. Novel bioinformatics methods may increase biomarker identification, and other tools, including selective reaction monitoring, may hasten clinical validation.

V, Patócs A, Lichthammer A, Veresné Bálint M, Rácz K, Reismann P. The role of methylglyoxal metabolism in type-2 diabetes and its complications

Transient or chronic hyperglycaemia increases the formation of intracellular reactive oxygen species and aldehydes. The accumulation of reactive aldehydes is implicated in the development of diabetic complications. Methylglyoxal, a glucose dependent α-dicarbonyl might be the most important reactive aldehyde in diabetes and its complications. Diabetes was the first disease in which evidence emerged for the increased formation of methylglyoxal in the cells and in the serum. Methylglyoxal has a toxic effect on insulin secretion from pancreatic beta-cells, and on modifications of proteins and nucleic acids. Moreover, methylglyoxal is one of the major precursors of advanced glycation end-products. The glyoxalase enzyme system that exists in all mammalian cells is catalyzing the detoxification of methylglyoxal. This review summarizes the methylglyoxal metabolism in normoglycaemic and hyperglycamic conditions and the role of methylglyoxal in the development of late diabetic microvascular complications. Orv. Hetil., 2012, 153, 574–585.