Advanced glycation end products (AGE) and diabetes: cause, effect, or both?

Low advanced Glycation end product diet improves the central obesity, insulin resistance and inflammatory profiles in Iranian patients with metabolic syndrome: a randomized clinical trial

The study aimed to investigate the effects of 8-weeks AGEs restricted diet on glycemic control as well as lipid profile, inflammatory and oxidative stress biomarkers and IR in overweight patients with Mets. In this randomized, controlled clinical trial 40 clients were randomly assigned to take either a low AGE (L-AGE) or a regular AGE (Reg-AGE) diet. Also, both groups were advised to follow an energy-restricted diet. At baseline and after 8-weeks of intervention, anthropometric parameters, dietary intake, plasma concentrations of malondialdehyde, carboxymethyllysine, TNF-α, hs-CRP and levels of serum glucose, lipid and insulin were assessed. AGEs restriction resulted in significant changes in mean differences levels of CML (p < 0.004), FBG (p < 0.01), HOMA-IR (p < 0.04), TNF-α (p < 0.01) and MDA (p < 0.02) in comparison to Reg-AGE. Moreover, weight (p < 0.0001) and WC (p < 0.001) significantly declined in the intervention group. Our results indicate that dAGEs restriction plus a low-calorie diet is superior to a low-calorie diet in amelioration of central obesity and IR at least partially through reduction of OS and inflammation in Mets subjects.

AGER1 downregulation associates with fibrosis in nonalcoholic steatohepatitis and type 2 diabetes

Type 2 diabetes is clinically associated with progressive necroinflammation and fibrosis in nonalcoholic steatohepatitis (NASH). Advanced glycation end-products (AGEs) accumulate during prolonged hyperglycemia, but the mechanistic pathways that lead to accelerated liver fibrosis have not been well defined. In this study, we show that the AGEs clearance receptor AGER1 was downregulated in patients with NASH and diabetes and in our NASH models, whereas the proinflammatory receptor RAGE was induced. These findings were associated with necroinflammatory, fibrogenic, and pro-oxidant activity via the NADPH oxidase 4. Inhibition of AGEs or RAGE deletion in hepatocytes in vivo reversed these effects. We demonstrate that dysregulation of NRF2 by neddylation of cullin 3 was linked to AGER1 downregulation and that induction of NRF2 using an adeno-associated virus-mediated approach in hepatocytes in vivo reversed AGER1 downregulation, lowered the level of AGEs, and improved proinflammatory and fibrogenic responses in mice on a high AGEs diet. In patients with NASH and diabetes or insulin resistance, low AGER1 levels were associated with hepatocyte ballooning degeneration and ductular reaction. Collectively, prolonged exposure to AGEs in the liver promotes an AGER1/RAGE imbalance and consequent redox, inflammatory, and fibrogenic activity in NASH.

Suicidal Erythrocyte Death in Metabolic Syndrome

Eryptosis is a coordinated, programmed cell death culminating with the disposal of cells without disruption of the cell membrane and the release of endocellular oxidative and pro-inflammatory milieu. While providing a convenient form of death for erythrocytes, dysregulated eryptosis may result in a series of detrimental and harmful pathological consequences highly related to the endothelial dysfunction (ED). Metabolic syndrome (MetS) is described as a cluster of cardiometabolic factors (hyperglycemia, dyslipidemia, hypertension and obesity) that increases the risk of cardiovascular complications such as those related to diabetes and atherosclerosis. In the light of the crucial role exerted by the eryptotic process in the ED, the focus of the present review is to report and discuss the involvement of eryptosis within MetS, where vascular complications are utterly relevant. Current knowledge on the mechanisms leading to eryptosis in MetS-related conditions (hyperglycemia, dyslipidemia, hypertension and obesity) will be analyzed. Moreover, clinical evidence supporting or proposing a role for eryptosis in the ED, associated to MetS cardiovascular complications, will be discussed.

High Plasmatic Levels of Advanced Glycation End Products are Associated with Metabolic Alterations and Insulin Resistance in Preeclamptic Women

Aims:

The purpose of this study was to investigate the association between plasmatic levels of advanced end glycation products (AGEs) and the metabolic profile in subjects diagnosed with preeclampsia, due to the known relation of these molecules with oxidative stress and inflammation, which in turn are related with PE pathogenesis.

Background:

It has been reported that increased levels of AGEs are observed in patients with preeclampsia as compared with healthy pregnant subjects, which was mainly associated with oxidative stress and inflammation. Besides, in women with preeclampsia, there are metabolic changes such as hyperinsulinemia, glucose intolerance, dyslipidemia, among others, that are associated with an exacerbated insulin resistance. Additionally, some parameters indicate the alteration of hepatic function, such as increased levels of liver enzymes. However, the relationship of levels of AGEs with altered lipidic, hepatic, and glucose metabolism parameters in preeclampsia has not been evaluated.

Objective:

To investigate the association between plasmatic levels of AGEs and hepatic, lipid, and metabolic profiles in women diagnosed with preeclampsia.

Methods:

Plasma levels of AGEs were determined by a competitive enzyme-linked immunosorbent assay (ELISA) in 15 patients diagnosed with preeclampsia and 28 normoevolutive pregnant subjects (control group). Hepatic (serum creatinine, gammaglutamyl transpeptidase, aspartate transaminase, alanine transaminase, uric acid, and lactate dehydrogenase), lipid (apolipoprotein A, apolipoprotein B, total cholesterol, triglycerides, low-density lipoproteins, and high-density lipoproteins), and metabolic variables (glucose, insulin, and insulin resistance) were assessed.

Results:

Plasmatic levels of AGEs were significantly higher in patients with preeclampsia as compared with the control. A positive correlation between circulating levels of AGEs and gamma-glutamyl transpeptidase, uric acid, glucose, insulin, and HOMA-IR levels was found in patients with preeclampsia. In conclusion, circulating levels of AGEs were higher in patients with preeclampsia than those observed in healthy pregnant subjects. Besides, variables of hepatic and metabolic profile, particularly those related to insulin resistance, were higher in preeclampsia as compared with healthy pregnant subjects. Interestingly, there is a positive correlation between AGEs levels and insulin resistance.

Conclusions:

Circulating levels of AGEs were higher in patients with preeclampsia than those observed in healthy pregnant subjects. Besides, hepatic and metabolic profiles, particularly those related to insulin resistance, were higher in preeclampsia as compared with healthy pregnant subjects. Interestingly, there is a positive correlation between AGEs levels and insulin resistance, suggesting that excessive glycation and an impaired metabolic profile contribute to the physiopathology of preeclampsia.

Dietary phenotype and advanced glycation end-products predict WTC-obstructive airways disease: a longitudinal observational study

BACKGROUND

Diet is a modifier of metabolic syndrome which in turn is associated with World Trade Center obstructive airways disease (WTC-OAD). We have designed this study to (1) assess the dietary phenotype (food types, physical activity, and dietary habits) of the Fire Department of New York (FDNY) WTC-Health Program (WTC-HP) cohort and (2) quantify the association of dietary quality and its advanced glycation end product (AGE) content with the development of WTC-OAD.

METHODS

WTC-OAD, defined as developing WTC-Lung Injury (WTC-LI; FEV1 < LLN) and/or airway hyperreactivity (AHR; positive methacholine and/or positive bronchodilator response). Rapid Eating and Activity Assessment for Participants-Short Version (REAP-S) deployed on 3/1/2018 in the WTC-HP annual monitoring assessment. Clinical and REAP-S data of consented subjects was extracted (7/17/2019). Diet quality [low-(15-19), moderate-(20-29), and high-(30-39)] and AGE content per REAP-S questionnaire were assessed for association with WTC-OAD. Regression models adjusted for smoking, hyperglycemia, hypertension, age on 9/11, WTC-exposure, BMI, and job description.

RESULTS

N = 9508 completed the annual questionnaire, while N = 4015 completed REAP-S and had spirometry. WTC-OAD developed in N = 921, while N = 3094 never developed WTC-OAD. Low- and moderate-dietary quality, eating more (processed meats, fried foods, sugary drinks), fewer (vegetables, whole-grains),and having a diet abundant in AGEs were significantly associated with WTC-OAD. Smoking was not a significant risk factor of WTC-OAD.

CONCLUSIONS

REAP-S was successfully implemented in the FDNY WTC-HP monitoring questionnaire and produced valuable dietary phenotyping. Our observational study has identified low dietary quality and AGE abundant dietary habits as risk factors for pulmonary disease in the context of WTC-exposure. Dietary phenotyping, not only focuses our metabolomic/biomarker profiling but also further informs future dietary interventions that may positively impact particulate matter associated lung disease.

Role of Glucose Metabolism and Mitochondrial Function in Diabetic Kidney Disease

PURPOSE OF REVIEW

Diabetic kidney disease (DKD) continues to be the primary cause of chronic kidney disease in the USA and around the world. The numbers of people with DKD also continue to rise despite current treatments. Certain newer hypoglycemic drugs offer a promise of slowing progression, but it remains to be seen how effective these will be over time. Thus, continued exploration of the mechanisms underlying the development and progression of DKD is essential in order to discover new treatments. Hyperglycemia is the main cause of the cellular damage seen in DKD. But, exactly how hyperglycemia leads to the activation of processes that are ultimately deleterious is incompletely understood.

RECENT FINDINGS

Studies primarily over the past 10 years have provided novel insights into the interplay of hyperglycemia, glucose metabolic pathways, mitochondrial function, and the potential importance of what has been called the Warburg effect on the development and progression of DKD. This review will provide a brief overview of glucose metabolism and the hypotheses concerning the pathogenesis of DKD and then discuss in more detail the supporting data that indicate a role for the interplay of glucose metabolic pathways and mitochondrial function.

Targeting adaptor protein SLP76 of RAGE as a therapeutic approach for lethal sepsis

Accumulating evidence shows that RAGE has an important function in the pathogenesis of sepsis. However, the mechanisms by which RAGE transduces signals to downstream kinase cascades during septic shock are not clear. Here, we identify SLP76 as a binding partner for the cytosolic tail of RAGE both in vitro and in vivo and demonstrate that SLP76 binds RAGE through its sterile α motif (SAM) to mediate downstream signaling. Genetic deficiency of RAGE or SLP76 reduces AGE-induced phosphorylation of p38 MAPK, ERK1/2 and IKKα/β, as well as cytokine release. Delivery of the SAM domain into macrophages via the TAT cell-penetrating peptide blocks proinflammatory cytokine production. Furthermore, administration of TAT-SAM attenuates inflammatory cytokine release and tissue damage in mice subjected to cecal ligation and puncture (CLP) and protects these mice from the lethality of sepsis. These findings reveal an important function for SLP76 in RAGE-mediated pro-inflammatory signaling and shed light on the development of SLP76-targeted therapeutics for sepsis.

Effectiveness of Early Advanced Glycation End Product Accumulation Testing in the Diagnosis of Diabetes: A Health Risk Factor Analysis Using the Body Mass Index as a Moderator

OBJECTIVE

To evaluate the value of non-invasive detection of advanced glycation end products (AGEs) in the early screening of type 2 diabetes mellitus (T2DM) in the community of China.

METHODS

From January 2018 to January 2019, a total of 912 patients with community health physical examination and no history of T2DM were selected, excluding the results of missing value > 5%. Finally, 906 samples were included in the study, with a response rate of 99.3%. Non-invasive diabetic detection technology was used to detect AGEs in the upper arm skin of all participants, AGE accumulations were classified as ≤P25, P25∼P50, P50∼P75, and >P75; HbA1c, insulin, C-peptide, total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), creatinine, urea, and other indicators were measured at the same time. Univariate analysis of variance was used to compare the differences in general data, biochemical indexes, skin AGE levels, and blood glucose among groups, and logistic regression analysis and latent category analysis were performed.

RESULTS

In univariate analysis, SBP, FBG, HbA1c, and age were correlated with higher AGE (p < 0.01); TG, TC, HDL, UA, and gender were not positively correlated with AGE (p < 0.01). After controlling for covariates (waist circumference, hip circumference), AGE accumulation was interacted with other variables. The results of latent category analysis (LCA) showed that the health risk factors (HRFs), including age, systolic blood pressure, HbA1c, FBG, triglyceride, total cholesterol, HDL-C, and uric acid, were divided as three groups, and AGE is divided into four categories according to the quartile method, which were low risk (≤P25), low to medium risk (P25∼P50), medium to high (P50∼P75), and high risk (>P75), respectively. The association between the quartile AGE and risk factors of the OR values was 1.09 (95% CI: 1.42, 2.86), 2.61 (95% CI: 1.11, 6.14), and 5.41 (95% CI: 2.42, 12.07), respectively. The moderation analysis using the PROCESS program was used to analyze whether BMI moderated the link between risk factors and AGE accumulation. There was also a significant three-way interaction among HRFs, BMI, and gender for AGE accumulation in the total sample (β = -0.30).

CONCLUSION

Non-invasive skin detection of AGEs has a certain application value for the assessment of T2DM risk and is related to a variety of risk factors.

Cirrhosis and insulin resistance: current knowledge, pathophysiological mechanisms, complications and potential treatments

End-stage chronic liver diseases are often associated with insulin resistance (IR) and diabetes mellitus (DM). Indeed, to quantify insulin sensitivity the euglycemic clamp technique was utilized, allowing the following to be stated: in small groups of patients, an IR in almost all cirrhotic patients can be observed, compared with a control group. Additionally, it has been demonstrated that IR in cirrhosis is linked to a decreased peripheral (muscle) glucose uptake rather than an increased liver glucose production. The homoeostasis model of IR (HOMA-IR) technique, devised only later, was then exploited to assess this same phenomenon in a larger sample population. The research established that even in patients with preserved liver function, cirrhosis is associated with significant alterations in glucose homoeostasis levels. The purpose of the present paper is to present the current research around the affiliation of cirrhosis and IR, discuss potential mechanisms explaining the association between cirrhosis and IR (i.e. endocrine perturbation, liver inflammation, altered muscle mass and composition, altered gut microbiota and permeability), complications that can arise as well as treatment options, through a critical review of the literature surrounding this subject. This research will also be investigating the beneficial impact, if there is any, of identifying and curing IR in patients with cirrhosis.

The Biological Activities and Therapeutic Potentials of Baicalein Extracted from Oroxylum indicum: A Systematic Review

In Southeast Asia, traditional medicine has a longestablished history and plays an important role in the health care system. Various traditional medicinal plants have been used to treat diseases since ancient times and much of this traditional knowledge remains preserved today. Oroxylum indicum (beko plant) is one of the medicinal herb plants that is widely distributed throughout Asia. It is a versatile plant and almost every part of the plant is reported to possess a wide range of pharmacological activities. Many of the important bioactivities of this medicinal plant is related to the most abundant bioactive constituent found in this plant-the baicalein. Nonetheless, there is still no systematic review to report and vindicate the biological activities and therapeutic potential of baicalein extracted from O. indicum to treat human diseases. In this review, we aimed to systematically present in vivo and in vitro studies searched from PubMed, ScienceDirect, Scopus and Google Scholar database up to 31 March 2020 based on keywords "Oroxylum indicum" and "baicalein". After an initial screening of titles and abstracts, followed by a full-text analysis and validation, 20 articles that fulfilled all the inclusion and exclusion criteria were included in this systematic review. The searched data comprehensively reported the biological activities and therapeutic potential of baicalein originating from the O. indicum plant for anti-cancer, antibacterial, anti-hyperglycemia, neurogenesis, cardioprotective, anti-adipogenesis, anti-inflammatory and wound healing effects. Nonetheless, we noticed that there was a scarcity of evidence on the efficacy of this natural active compound in human clinical studies. In conclusion, this systematic review article provides new insight into O. indicum and its active constituent baicalein as a prospective complementary therapy from the perspective of modern and scientific aspect. We indicate the potential of this natural product to be developed into more conscientious and judicious evidencebased medicine in the future. However, we also recommend more clinical research to confirm the efficacy and safety of baicalein as therapeutic medicine for patients.

The potential role of dietary advanced glycation endproducts in the development of chronic non-infectious diseases: a narrative review

Increasing clinical and experimental evidence accumulated during the past few decades supports an important role for dietary advanced glycation endproducts (AGE) in the pathogenesis of many chronic non-infectious diseases, such as type 2 diabetes, CVD and others, that are reaching epidemic proportions in the Western world. Although AGE are compounds widely recognised as generated in excess in the body in diabetic patients, the potential importance of exogenous AGE, mostly of dietary origin, has been largely ignored in the general nutrition audience. In the present review we aim to describe dietary AGE, their mechanisms of formation and absorption into the body as well as their main mechanisms of action. We will present in detail current evidence of their potential role in the development of several chronic non-infectious clinical conditions, some general suggestions on how to restrict them in the diet and evidence regarding the potential benefits of lowering their consumption.

Non enzymatic covalent modification by glycolysis end product converts hemoglobin into its oxidative stress potency state

The effect of glycation by Pyruvic acid (PA) on the early and advanced conformational changes in Hemoglobin (Hb) was studied. Multi Spectroscopic measurement revealed that Hb undergoes structural conformational changes and unbound heme upon incubation with PA. These covalent modifications were followed by the reduction of heme centre and these reduction processes initiates its peroxidase-like activity. An extended PA glycation resulted in the appearance of advanced glycation end products fluorescence, with notable changes in compositions of secondary structure. The amyloidogenic state was confirmed by SEM, fluorescence microscope observation. This study reveals an insight to the role of pyruvic acid which increases the oxidative stress due to the heme reduction and diabetic complication.

The relationship between advanced glycation end products and gestational diabetes: A systematic review and meta-analysis

INTRODUCTION

Gestational Diabetes Mellitus (GDM) is a condition in which women without history of diabetes experience hyperglycemia during pregnancy, especially at the second and third trimesters. In women who have had GDM, an elevated body mass index (BMI) may have a substantial impact for persistent hyperglycemia in their lives after gestation. Beyond hyperglycemia, increased local oxidative stress directly promotes the formation of Advanced Glycation End-products (AGEs). Hence, this systematic review and meta-analysis was aimed to determine the relationship between the level of AGEs and/or related metabolic biomarkers with GDM.

METHODS

Literature search was carried out through visiting electronic databases, indexing services, and directories including PubMed/MEDLINE (Ovid®), EMBASE (Ovid®), google scholar and WorldCat to retrieve studies without time limit. Following screening and eligibility evaluation, relevant data were extracted from included studies and analyzed using Rev-Man 5.3 and STATA 15.0. Inverse variance method with random effects pooling model was used for the analysis of outcome measures at 95% confidence interval. Hedge's adjusted g statistics was applied to calculate the standardized mean difference (SMD) to consider the small sample bias. Besides, meta-regression, meta-influence, and publication bias analyses were conducted. The protocol has been registered on PROSPERO with ID: CRD42020173867.

RESULTS

A total of 16 original studies were included for the systematic review and meta-analysis. Compared with women with pregnant controls, the level of AGE was significantly higher in women with GDM (SMD [95% CI] = 2.26 [1.50‒3.02], Z = 5.83, P < 0.00001; I2 = 97%, P< 0.0001). The BMI was also significantly higher in women with GDM (SMD [95% CI] = 0.97 [0.33‒1.62], Z = 2.98, P = 0.003) compared to controls. Regarding specific and related metabolic biomarkers, there was higher level of HOMA-IR (SMD [95% CI] = 0.39 [0.22-0.55], Z = 4.65, P < 0.0001, after sensitivity analysis) and HbA1c (SMD [95% CI] = 0.58 [0.03‒1.12], Z = 2.07, P = 0.04, after sensitivity analysis) in gestational diabetic women. Subgroup analyses indicated that studies conducted in Asia and Europe, at third trimester of pregnancy and blood/plasma AGE samples showed a significant difference in AGE level among women with GDM compared to pregnant controls. What is more, meta-regression with the sample size (regression coefficient (Q) = -0.0092, P = 0.207) and year of publication (Q = 0.0035, P = 0.984) suggested that the covariates had no significant effect on the heterogeneity.

CONCLUSION

The study indicated that there was a strong relationship between AGE and GDM. Besides, the BMI and other specific biomarkers showed a significant difference between the two groups indicating the high risk of developing long-standing type 2 diabetes and its complications in gestational diabetic women. Early detection of these biomarkers may play a pivotal role in controlling postpartum diabetic complications.

Circulating antibodies against age-modified proteins in patients with coronary atherosclerosis

Advanced glycation endproducts (AGEs) are formed in a series of non-enzymatic reactions between reducing sugars and the amino groups of proteins and accumulate during aging, diabetes mellitus, chronic kidney disease and other chronic diseases. Accumulation of AGE-modifications alters protein structure and function, transforming these molecules into potential targets of the immune system, presumably triggering the production of autoantibodies against AGEs. In this study, we detected autoantibodies against AGE-modified proteins with ELISA in plasma samples of 91 patients with documented coronary artery disease (CAD), who underwent coronary artery bypass grafting (CABG) surgery. Patients with high levels of autoantibodies had a higher body mass index (BMI 28.6 vs 27.1 kg/m²; p = 0.046), were more likely to suffer from chronic obstructive pulmonary disease (COPD 30% vs 9.8%; p = 0.018), and more likely to need dialysis after the surgery (10% vs 0%; p = 0.037). Our findings show a weak link between the levels of autoantibodies against AGEs and diabetes mellitus (DM 44% vs 24.4%; p = 0.05). In a small subpopulation of patients, antibodies against native bovine serum albumin (BSA) were detected. A growing body of research explores the potential role of antibodies against AGE-modified proteins in pathogenesis of different chronic diseases; our data confirms the presence of AGE-autoantibodies in patients with CAD and that in parallel to the AGEs themselves, they may have a potential role in concomitant clinical conditions in patients undergoing CABG surgery. Further research is necessary to verify the molecular role of these antibodies in different pathological conditions.

RAGE Mediates Cholesterol Efflux Impairment in Macrophages Caused by Human Advanced Glycated Albumin

We addressed the involvement of the receptor for advanced glycation end products (RAGE) in the impairment of the cellular cholesterol efflux elicited by glycated albumin. Albumin was isolated from type 1 (DM1) and type 2 (DM2) diabetes mellitus (HbA1c > 9%) and non-DM subjects (C). Moreover, albumin was glycated in vitro (AGE-albumin). Macrophages from Ager null and wild-type (WT) mice, or THP-1 transfected with siRNA-AGER, were treated with C, DM1, DM2, non-glycated or AGE-albumin. The cholesterol efflux was reduced in WT cells exposed to DM1 or DM2 albumin as compared to C, and the intracellular lipid content was increased. These events were not observed in Ager null cells, in which the cholesterol efflux and lipid staining were, respectively, higher and lower when compared to WT cells. In WT, Ager, Nox4 and Nfkb1, mRNA increased and Scd1 and Abcg1 diminished after treatment with DM1 and DM2 albumin. In Ager null cells treated with DM-albumin, Nox4, Scd1 and Nfkb1 were reduced and Jak2 and Abcg1 increased. In AGER-silenced THP-1, NOX4 and SCD1 mRNA were reduced and JAK2 and ABCG1 were increased even after treatment with AGE or DM-albumin. RAGE mediates the deleterious effects of AGE-albumin in macrophage cholesterol efflux.

Advanced glycation end-products and advanced oxidation protein products levels are correlates of duration of type 2 diabetes

AIMS

Diabetes is associated with the excess formation of advanced glycation end-products (AGEs) and advanced oxidation protein products (AOPP), and low levels of ferric reducing ability of plasma (FRAP). However, the trend of oxidative and antioxidant markers levels according to diabetes duration is unclear.

MAIN METHODS

In a case-control study, 240 patients with diabetes and 100 healthy controls were enrolled. Patients were divided into four groups according to the duration of diabetes, including newly diagnosed, 1-5, 5-10, and 10-15 years. Serum AGEs, AOPP, and FRAP levels were compared among groups.

KEY FINDINGS

AGEs and AOPP were higher and FRAP was lower in patients with diabetes compared to healthy controls. Serum levels of AGEs increased progressively with increasing in diabetes duration. AGEs levels were 68.97 ± 7.28% in newly-diagnosed, 73.43 ± 12.96% in 1-5 years and 80.44 ± 13.84% in 10-15 years of diabetes duration (pairwise p-values <0.05). In linear regression analysis the correlation among AGEs, AOPP, FRAP, and diabetes duration remained significant after adjustment for age, BMI, HDL, HbA1c, waist circumference, microvascular complications, and coronary artery diseases. ROC analysis showed AGEs could predict the duration of diabetes when patients with 10-15 years duration of diabetes were compared to patients with 1-5 years duration of diabetes (AUC = 0.676, p-value = 0.003).

SIGNIFICANCE

Diabetes promotes AGEs, and AOPP production, independent of glycemic control and patients age. Serum levels of AGEs increase progressively with increasing duration of diabetes. AGEs may be helpful in estimating chronicity of diabetes.

Diabetic keratopathy: Insights and challenges

Ocular complications from diabetes mellitus are common. Diabetic keratopathy, the most frequent clinical condition affecting the human cornea, is a potentially sight-threatening condition caused mostly by epithelial disturbances that are of clinical and research attention because of their severity. Diabetic keratopathy exhibits several clinical manifestations, including persistent corneal epithelial erosion, superficial punctate keratopathy, delayed epithelial regeneration, and decreased corneal sensitivity, that may lead to compromised visual acuity or permanent vision loss. The limited amount of clinical studies makes it difficult to fully understand the pathobiology of diabetic keratopathy. Effective therapeutic approaches are elusive. We summarize the clinical manifestations of diabetic keratopathy and discuss available treatments and up-to-date research studies in an attempt to provide a thorough overview of the disorder.

Adverse Effects of Methylglyoxal on Transcriptome and Metabolic Changes in Visceral Adipose Tissue in a Prediabetic Rat Model

Excessive methylglyoxal (MG) production contributes to metabolic and vascular changes by increasing inflammatory processes, disturbing regulatory mechanisms and exacerbating tissue dysfunction. MG accumulation in adipocytes leads to structural and functional changes. We used transcriptome analysis to investigate the effect of MG on metabolic changes in the visceral adipose tissue of hereditary hypetriglyceridaemic rats, a non-obese model of metabolic syndrome. Compared to controls, 4-week intragastric MG administration impaired glucose tolerance (p < 0.05) and increased glycaemia (p < 0.01) and serum levels of MCP-1 and TNFα (p < 0.05), but had no effect on serum adiponectin or leptin. Adipose tissue insulin sensitivity and lipolysis were impaired (p < 0.05) in MG-treated rats. In addition, MG reduced the expression of transcription factor Nrf2 (p < 0.01), which controls antioxidant and lipogenic genes. Increased expression of Mcp-1 and TNFα (p < 0.05) together with activation of the SAPK/JNK signaling pathway can promote chronic inflammation in adipose tissue. Transcriptome network analysis revealed the over-representation of genes involved in insulin signaling (Irs1, Igf2, Ide), lipid metabolism (Nr1d1, Lpin1, Lrpap1) and angiogenesis (Dusp10, Tp53inp1).

Sulforaphane Inhibits MGO-AGE-Mediated Neuroinflammation by Suppressing NF-κB, MAPK, and AGE-RAGE Signaling Pathways in Microglial Cells

Advanced glycation end products (AGEs) are produced through the binding of glycated protein or lipid with sugar, and they are known to be involved in the pathogenesis of both age-dependent and independent neurological complications. Among dicarbonyl compounds, methylglyoxal (MGO), which is produced from glucose breakdown, is a key precursor of AGE formation and neurotoxicity. Several studies have shown the toxic effects of bovine serum albumin (BSA)-AGE (prepared with glucose, sucrose or fructose) both in in vitro and in vivo. In fact, MGO-derived AGEs (MGO-AGEs) are highly toxic to neurons and other cells of the central nervous system. Therefore, we aimed to investigate the role of MGO-AGEs in microglial activation, a key inflammatory event, or secondary brain damage in neuroinflammatory diseases. Interestingly, we found that sulforaphane (SFN) as a potential candidate to downregulate neuroinflammation induced by MGO-AGEs in BV2 microglial cells. SFN not only inhibited the formation of MGO-AGEs, but it did not show breaking activity on the MGO-mediated AGEs cross-links with protein, indicating that SFN could potentially trap MGO or inhibit toxic AGE damage. In addition, SFN significantly attenuated the production of neuroinflammatory mediators induced by MGO-AGEs in BV2 microglial cells. SFN also lowered the expression levels of AGE receptor (RAGE) in microglial cells, suggesting that SFN could downregulate MGO-AGE-mediated neurotoxicity at the receptor activation level. Altogether, our current study revealed that SFN might show neuropharmacological potential for downregulating MGO-AGEs-mediated neuronal complications thorough attenuating AGE formation and neuroinflammatory responses induced by MGO-AGEs in vitro.

Advanced glycation end products reduce macrophage-mediated killing of Staphylococcus aureus by ARL8 upregulation and inhibition of autolysosome formation

Staphylococcus aureus, a pathogen most frequently found in diabetic foot ulcer infection, was recently suggested as an intracellular pathogen. Autophagy in professional phagocytes like macrophages allows selective destruction of intracellular pathogens, and its dysfunction can increase the survival of internalized pathogens, causing infections to worsen and spread. Previous works have shown that S. aureus infections in diabetes appeared more severe and invasive, and coincided with the suppressed autophagy in dermal tissues of diabetic rat, but the exact mechanisms are unclear. Here, we demonstrated that accumulation of advanced glycation end products (AGEs) contributed to the diminished autophagy-mediated clearance of S. aureus in the macrophages differentiated from PMA-treated human monocytic cell line THP-1. Importantly, infected macrophages showed increased S. aureus containing autophagosome, but the subsequent fusion of S. aureus containing autophagosome and lysosome was suppressed in AGEs-pretreated cells, suggesting AGEs blocked the autophagic flux and enabled S. aureus survival and escape. At the molecular level, elevated lysosomal ARL8 expression in AGEs-treated macrophages was required for AGEs-mediated inhibition of autophagosome-lysosome fusion. Silencing ARL8 in AGEs-treated macrophages restored autophagic flux and increased S. aureus clearance. Our results therefore demonstrate a new mechanism, in which AGEs accelerate S. aureus immune evasion in macrophages by ARL8-dependent suppression of autophagosome-lysosome fusion and bactericidal capability.

Diabetes as a risk factor for periodontal disease-plausible mechanisms

The present narrative review examines the scientific evidence of the biological mechanisms that may link periodontitis and diabetes, as a source of comorbidity. Publications regarding periodontitis and diabetes, in human, animals, and in vitro were screened for their relevance. Periodontal microbiome studies indicate a possible association between altered glucose metabolism in prediabetes and diabetes and changes in the periodontal microbiome. Coinciding with this, hyperglycemia enhances expression of pathogen receptors, which enhance host response to the dysbiotic microbiome. Hyperglycemia also promotes pro-inflammatory response independently or via the advanced glycation end product/receptor for advanced glycation end product pathway. These processes excite cellular tissue destruction functions, which further enhance pro-inflammatory cytokines expression and alteration in the RANKL/osteoprotegerin ratio, promoting formation and activation of osteoclasts. The evidence supports the role of several pathogenic mechanisms in the path of true causal comorbidity between poorly controlled diabetes and periodontitis. However, further research is needed to better understand these mechanisms and to explore other mechanisms.

Therapeutic Potentials of Scavenger Receptor CD36 Mediated Innate Immune Responses Against Infectious and Non-Infectious Diseases

CD36 is a multifunctional glycoprotein, expressed in different types of cells and known to play a significant role in the pathophysiology of the host. The structural studies revealed that the scavenger receptor consists of short cytosolic domains, two transmembrane domains, and a large ectodomain. The ectodomain serves as a receptor for a diverse number of endogenous and exogenous ligands. The CD36-specific ligands are involved in regulating the immune response during infectious and non-infectious diseases in the host. The role of CD36 in regulating the innate immune response during Pneumonia, Tuberculosis, Malaria, Leishmaniasis, HIV, and Sepsis in a ligand- mediated fashion. Apart from infectious diseases, it is also considered to be involved in metabolic disorders such as Atherosclerosis, Alzheimer's, cancer, and Diabetes. The ligand binding to scavenger receptor modulates the CD36 down-stream innate immune response, and it can be exploited to design suitable immuno-modulators. Hence, the current review focused on the role of the CD36 in innate immune response and therapeutic potentials of novel heterocyclic compounds as CD36 ligands during infectious and non-infectious diseases.

The association of non-invasive skin autofluorescence measurements with cardiovascular and all-cause mortality in hemodialysis patients: a meta-analysis

BACKGROUND

This systematic review and meta-analysis were aimed to study the association of tissue accumulation of advanced glycation end products (AGEs) measured as skin autofluorescence (SAF) with cardiovascular disease (CVD), cardiovascular mortality (CVM) and all-cause mortality (ACM) in hemodialysis (HD) patients.

METHODS

All major databases were searched for relevant studies reporting SAF in dialysis patients. Data for meta-analyses were extracted in the form of odds ratios (OR) and/or hazard ratios (HR) and the pooled overall outcomes were computed for the association of SAF with CVD, CVM, ACM in HD patients using either fixed or random effects meta-analysis based on the between-study heterogeneity. The sensitivity and meta-regression analyses were performed.

RESULTS

We included nine studies in this meta-analysis. The SAF levels were associated with higher risk for cardiovascular morbidity (pooled OR = 2.59, Z = 2.30, P = 0.02), cardiovascular (pooled HR = 3.03, Z = 3.13, P = 0.002) and overall mortalities (pooled HR = 2.23, Z = 6.30, P < 0.001) in HD patients.

CONCLUSION

In HD patients, the novel and non-invasive measurement of tissue AGEs as SAF levels could be useful for risk estimating the cardiovascular and all-cause mortalities.

Advanced Glycation End Products Enhance Biofilm Formation by Promoting Extracellular DNA Release Through sigB Upregulation in Staphylococcus aureus

Bacterial biofilms do serious harm to the diabetic foot ulcer (DFU) because they play a crucial role in infection invasion and spread. Staphylococcus aureus, the predominant Gram-positive bacteria in diabetic foot infection (DFI), is often associated with colonization and biofilm formation. Through biofilm formation tests in vitro, we observed that S. aureus bacteria isolated from DFU wounds were more prone to form biofilms than those from non-diabetic patients, while there was no difference in blood sugar between the biofilm (+) diabetics (DB+) and biofilm (-) diabetics (DB-). Furthermore, we found that advanced glycation end products (AGEs) promoted the biofilm formation of S. aureus in clinical isolates and laboratory strains in vitro, including a methicillin-resistant strain. Analysis of biofilm components demonstrated that the biofilms formed mainly by increasing extracellular DNA (eDNA) release; remarkably, the S. aureus global regulator sigB was upregulated, and its downstream factor lrgA was downregulated after AGE treatments. Mechanism studies using a sigB-deleted mutant (Newman-ΔsigB) confirmed that AGEs decreased expression of lrgA via induction of sigB, which is responsible for eDNA release and is a required component for S. aureus biofilm development. In conclusion, the present study suggests that AGEs promote S. aureus biofilm formation via an eDNA-dependent pathway by regulating sigB. The data generated by this study will provide experimental proof and theoretical support to improve DFU infection healing.

Higher skin autofluorescence detection using AGE-Reader™ technology as a measure of increased tissue accumulation of advanced glycation end products in dialysis patients with diabetes: a meta-analysis

This meta-analysis was conducted to compare skin autofluorescence (SAF) levels as a measure of advanced glycation end products (AGEs) accumulation between diabetic and non-diabetic dialysis patients. Relevant studies were identified primarily by searching PubMed/MEDLINE and other online databases and manual searching of cross-references. Random-effects model was used to obtain standardized mean differences (SMD) as a summary statistic. Heterogeneity was tested with meta-regression and sub-group analyses. Publication bias and robustness of this meta-analysis were tested using funnel plot and sensitivity analyses. A total of 11 reports comparing SAF between diabetic and non-diabetic dialysis patients were finally included in this meta-analysis. Dialysis patients with diabetes showed significantly higher circulatory SAF levels than their non-diabetic counterparts (SMD = 0.39; P < 0.0001). The difference was more evident in hemodialysis modality (SMD = 0.40; P < 0.0001). A one-study leave-out sensitivity analysis validated the robustness of this meta-analysis. The presence of diabetes in dialysis patients is associated with increased AGEs accumulation reflected through SAF measurements using a novel and non-invasive AGE-Reader™ technology. Our findings are in support of considering anti-AGE therapeutic strategies in addition to standard glycemic management in dialysis patients with diabetes.

Reduction in Circulating Advanced Glycation End Products by Mediterranean Diet Is Associated with Increased Likelihood of Type 2 Diabetes Remission in Patients with Coronary Heart Disease: From the Cordioprev Study

SCOPE

It is hypothesized that decreased advanced glycation end products (AGEs) levels could affect type 2 diabetes mellitus (T2DM) remission in newly diagnosed patients through the consumption of two healthy diets.

METHODS AND RESULTS

Patients from CORDIOPREV study, all with previous cardiovascular events, with T2DM at the beginning of the study are included. Patients are randomized to a Mediterranean or a low-fat diet for five years. No different diabetes remission rates are found among diets. Serum methylglioxal (MG) and carboximethyllysine (CML), levels dietary AGE, as well as gene expression of AGER1 and RAGE are measured. Serum MG decreases only after the consumption of the Mediterranean diet. Moreover, a COX regression analysis shows that each SD decrease in the MG, occurring after the Mediterranean diet, increases the probability of T2DM remission with HR:2.56(1.02-6.25) and p = 0.046 and each SD increase in disposition index at baseline increases the probability of remission with HR:1.94(1.32-2.87) and p = 0.001.

CONCLUSIONS

It is demonstrated that the reduction of serum AGEs levels and the modulation of its metabolism, occurring after the consumption of a Mediterranean diet, might be involved in the molecular mechanism underlying the T2DM remission of newly diagnosed patients with coronary heart disease.

ε2 allele and ε2-involved genotypes (ε2/ε2, ε2/ε3, and ε2/ε4) may confer the association of APOE genetic polymorphism with risks of nephropathy in type 2 diabetes: a meta-analysis

Background

Diabetic nephropathy (DN) contributes to end-stage renal failure. Microvascular injury resulted from reactive oxygen species is implicated in the pathogenesis of DN. Genetic polymorphism of Apolipoprotein E (APOE) influences the antioxidative properties of the protein. The relationship of APOE polymorphism with the risks of nephropathy in type 2 diabetes (T2DN) remains elusive.

Methods

An up-to-date meta-analysis was conducted on the basis of studies selected from PubMed, WanFang database, Embase, Vip database, Web of Science, Scopus, and CNKI database.

Results

A total of 33 studies conferring 3266 cases and 3259 controls were selected on the basis of criteria of inclusion and exclusion in this meta-analysis. For APOE alleles, the pooled odds ratio (OR) of ε2 vs. ε3 was 1.89 (95% confidence intervals [95% CI]: 1.49–2.38, P < 0.0001). With regard to APOE genotypes, ε2/ε2, ε2/ε3, and ε2/ε4 increased the risk of T2DN (ε2/ε2 vs. ε3/ε3: OR = 2.32, 95% CI: 1.52–3.56, P = 0.0001; ε2/ε3 vs. ε3/ε3: OR = 1.97, 95% CI: 1.50–2.59, P<0.0001; ε2/ε4 vs. ε3/ε3: OR = 1.69, 95% CI: 1.18–2.44, P = 0.0046).

Conclusions

This meta-analysis found that the APOE ε2 allele and the ε2-involved genotypes (ε2/ε2, ε2/ε3, and ε2/ε4) are the risk factors of T2DN.

Mechanistic Causes of Reduced Cardiorespiratory Fitness in Type 2 Diabetes

Type 2 diabetes (T2D) has been rising in prevalence in the United States and worldwide over the past few decades and contributes to significant morbidity and premature mortality, primarily due to cardiovascular disease (CVD). Cardiorespiratory fitness (CRF) is a modifiable cardiovascular (CV) risk factor in the general population and in people with T2D. Young people and adults with T2D have reduced CRF when compared with their peers without T2D who are similarly active and of similar body mass index. Furthermore, the impairment in CRF conferred by T2D is greater in women than in men. Various factors may contribute to this abnormality in people with T2D, including insulin resistance and mitochondrial, vascular, and cardiac dysfunction. As proof of concept that understanding the mediators of impaired CRF in T2D can inform intervention, we previously demonstrated that an insulin sensitizer improved CRF in adults with T2D. This review focuses on how contributing factors influence CRF and why they may be compromised in T2D. Functional exercise capacity is a measure of interrelated systems biology; as such, the contribution of derangement in each of these factors to T2D-mediated impairment in CRF is complex and varied. Therefore, successful approaches to improve CRF in T2D should be multifaceted and individually designed. The current status of this research and future directions are outlined.

Antidiabetic Effects of Flavan-3-ols and Their Microbial Metabolites

Diet is one of the pillars in the prevention and management of diabetes mellitus. Particularly, eating patterns characterized by a high consumption of foods such as fruits or vegetables and beverages such as coffee and tea could influence the development and progression of type 2 diabetes. Flavonoids, whose intake has been inversely associated with numerous negative health outcomes in the last few years, are a common constituent of these food items. Therefore, they could contribute to the observed positive effects of certain dietary habits in individuals with type 2 diabetes. Of all the different flavonoid subclasses, flavan-3-ols are consumed the most in the European region. However, a large proportion of the ingested flavan-3-ols is not absorbed. Therefore, the flavan-3-ols enter the large intestine where they become available to the colonic bacteria and are metabolized by the microbiota. For this reason, in addition to the parent compounds, the colonic metabolites of flavan-3-ols could take part in the prevention and management of diabetes. The aim of this review is to present the available literature on the effect of both the parent flavan-3-ol compounds found in different food sources as well as the specific microbial metabolites of diabetes in order to better understand their potential role in the prevention and treatment of the disease.

Vitamin B6 and Diabetes: Relationship and Molecular Mechanisms

Vitamin B6 is a cofactor for approximately 150 reactions that regulate the metabolism of glucose, lipids, amino acids, DNA, and neurotransmitters. In addition, it plays the role of antioxidant by counteracting the formation of reactive oxygen species (ROS) and advanced glycation end-products (AGEs). Epidemiological and experimental studies indicated an evident inverse association between vitamin B6 levels and diabetes, as well as a clear protective effect of vitamin B6 on diabetic complications. Interestingly, by exploring the mechanisms that govern the relationship between this vitamin and diabetes, vitamin B6 can be considered both a cause and effect of diabetes. This review aims to report the main evidence concerning the role of vitamin B6 in diabetes and to examine the underlying molecular and cellular mechanisms. In addition, the relationship between vitamin B6, genome integrity, and diabetes is examined. The protective role of this vitamin against diabetes and cancer is discussed.

The inefficacy of donepezil on glycated-AChE inhibition: Binding affinity, complex stability and mechanism

Donepezil (DPZ) is a well-known drug for Alzheimer's disease that inhibits acetylcholinesterase activity (AChE). In the present study, the inhibitory effect of DPZ on non-enzymatic glycated-AChE (GLY-AChE) was studied by different experimental and simulation techniques. The initial investigation revealed that glycation process could reduce AChE activity approximately 60% in the pure enzyme and 38% in the extracted crude AChE from neural cells cultured in the presence of high glucose (HG) concentration. It is suggested that glycation of lysine residues on the structure of AChE could change the conformation of the active site (Trp-86 and His-447) in a way that the orientation of acetylcholine interrupted. The further studies indicated that DPZ is although a strong inhibitor for the native enzyme, it is not able to affect the GLY-AChE activity. The K_D values of AChE-DPZ and GLY-AChE-DPZ complexes were estimated to be 1.88 × 10^-9 and 2.10 × 10^-6, respectively. The stability assessment showed that AChE-DPZ complex is more stable than the glycated complex. Our results indicate that, glycation process could impact on the conformation of the residues involved in the DPZ binding cavity on α-helix domain. Therefore, DPZ is not able to bind its specific cavity to induce its inhibitory effects on GLY-AChE.

Cardiac tissue remodeling in healthy aging: the road to pathology

This review aims to highlight the normal physiological remodeling that occurs in healthy aging hearts, including changes that occur in contractility, conduction, valve function, large and small coronary vessels, and the extracellular matrix. These "normal" age-related changes serve as the foundation that supports decreased plasticity and limited ability for tissue remodeling during pathophysiological states such as myocardial ischemia and heart failure. This review will identify populations at greater risk for poor tissue remodeling in advanced age along with present and future therapeutic strategies that may ameliorate dysfunctional tissue remodeling in aging hearts.

Thiamine pyrophosphate improved vascular complications of diabetes in rats with type 2 diabetes by reducing glycation, oxidative stress, and inflammation markers

Background: Thiamine deficiency contributes to hyperglycemia and diabetes complications. Thus, in this study, the effect of thiamine pyrophosphate (TPP) on the in vivo and in vitro formation of glycation, oxidative stress, and inflammatory markers (the main contributors of vascular diabetes complications) was examined in type 2 diabetes rat model.

Methods: Type 2 diabetes was induced in rats with a combination of streptozotocin and nicotinamide (55+200 mg/kg). Two groups of rats, healthy and diabetic, were treated with 0.1% TPP in drinking water daily for 3 months and the 2 others received water only. The glucose, insulin, early to end glycation products, the activity of glyoxalase system, lipid profile, LDL oxidation markers, inflammatory markers, creatinine in the serum, and proteinuria in the urine of all rats were determined. Moreover, albumin and LDL were incubated with glucose in the presence and absence of TPP, and the samples were investigated for glycation and oxidation products. Different variables in all 4 groups were compared with multiple analysis of variance (MANOVA-Tukey) test using SPSS version 16. Significance level was set at p<0.05.

Results: TPP decreased the formation of diverse glycation and oxidation products in both in vivo (glycated LDL= 144.50±3.48 and oxidized LDL= 54.08±2.67 μmol/l) and in vitro (glycated LDL= 107.00±2.82 and oxidized LDL= 50.83±1.22 μmol/l). In addition, the vitamin reduced fasting blood sugar (9.23±0.29), insulin resistance (9.10±0.50), tumor necrosis factor-α (285.43±15.97), interleukin-6 (257.65±13.06), and improved the lipid profile, the activity of Glo system (Glo-I= 31.65±1.06 and Glo-II= 27.01±0.90 U/mL) and renal function in the diabetic rat (p<0.001).

Conclusion: TPP decreased the major risk factors for diabetic complications and corrected the alternations of glucose and lipid metabolism in type 2 diabetic rats; thus, it is recommended for diabetes treatment.

Association between the tissue accumulation of advanced glycation end products and exercise capacity in cardiac rehabilitation patients

Background

Advanced glycation end products (AGEs) are associated with aging, diabetes mellitus (DM), and other chronic diseases. Recently, the accumulation of AGEs can be evaluated by skin autofluorescence (SAF). However, the relationship between SAF levels and exercise capacity in patients with cardiovascular disease (CVD) remains unclear. This study aimed to investigate the association between the tissue accumulation of AGEs and clinical characteristics, including exercise capacity, in patients with CVD.

Methods

We enrolled 319 consecutive CVD patients aged ≥40 years who underwent early phase II cardiac rehabilitation (CR) at our university hospital between November 2015 and September 2017. Patient background, clinical data, and the accumulation of AGEs assessed by SAF were recorded at the beginning of CR. Characteristics were compared between two patient groups divided according to the median SAF level (High SAF and Low SAF).

Results

The High SAF group was significantly older and exhibited a higher prevalence of DM than the Low SAF group. The sex ratio did not differ between the two groups. AGE levels showed significant negative correlations with peak oxygen uptake and ventilator efficiency (both P <  0.0001). Exercise capacity was significantly lower in the high SAF group than in the low SAF group, regardless of the presence or absence of DM (P <  0.05). A multivariate logistic regression analysis showed that SAF level was an independent factor associated with reduced exercise capacity (odds ratio 2.10; 95% confidence interval 1.13–4.05; P = 0.02).

Conclusion

High levels of tissue accumulated AGEs, as assessed by SAF, were significantly and independently associated with reduced exercise capacity. These data suggest that measuring the tissue accumulation of AGEs may be useful in patients who have undergone CR, irrespective of whether they have DM.

The Role of Dietary Advanced Glycation End Products in Metabolic Dysfunction

Advanced glycation end products (AGEs) are a heterogeneous group of molecules produced, non-enzymatically, from the interaction between reducing sugars and the free amino groups of proteins, nucleic acids, and lipids. AGEs are formed as a normal consequence of metabolism but can also be absorbed from the diet. They have been widely implicated in the complications of diabetes affecting cardiovascular health, the nervous system, eyes, and kidneys. Increased levels of AGEs are also detrimental to metabolic health and may contribute to the metabolic abnormalities induced by the Western diet, which is high in processed foods and represents a significant source of AGEs. While increased AGE levels are a consequence of diabetic hyperglycaemia, AGEs themselves activate signaling pathways, which compromise insulin signaling and pancreatic β-cell function, thus, contributing to the development of type 2 diabetes mellitus (T2DM). Furthermore, AGEs may also contribute to the obesogenic effects of the Western diet by promoting hypothalamic inflammation and disrupting the central control of energy balance. Here, the role of dietary AGEs in metabolic dysfunction is reviewed with a focus on the mechanisms underpinning their detrimental role in insulin resistance, pancreatic β-cell dysfunction, hypothalamic control of energy balance, and the pathogenesis of T2DM and obesity.

N ε-(carboxymethyl)lysine formation from the Maillard reaction of casein and different reducing sugars

Dietary advanced glycation end products (AGEs) are involved in the pathogenesis of diabetic complications, atherosclerosis, and kidney disease. Formation of N ^ε-(carboxymethyl)lysine (CML), a well-known AGEs, was evaluated from the reaction of casein from bovine milk with different reducing sugars (glucose, tagatose, and xylose) at various sugar concentrations and heating temperatures (75 and 120 °C) used in food processing to determine the best sweetener to be used in dairy products. The concentration of CML was measured using an enzyme-linked immunosorbent assay. Additionally, SDS-PAGE was carried out to observe the changes in the molecular weight of casein. The results reveal that tagatose leads to a lower CML concentration at 75 °C than glucose or xylose, whereas no significant differences are observed at 120 °C. We conclude that it would be more appropriate to use tagatose rather than glucose or xylose as a sweetener, considering the AGEs contents in heat-treated dairy products.

Receptor for advanced glycation end products modulates oxidative stress and mitochondrial function in the soleus muscle of mice fed a high-fat diet

Accumulation of advanced glycation end products (AGEs) and activation of the receptor for AGEs (RAGE) are implicated in the progression of pathologies associated with aging, chronic inflammation, diabetes, and cellular stress. RAGE activation is also implicated in cardiovascular complications of type 2 diabetes, such as nephropathy, retinopathy, accelerated vascular diseases, and cardiomyopathy. Studies investigating the effects of AGE/RAGE axis activation on skeletal muscle oxidative stress and metabolism are more limited. We tested whether a high-fat diet (HFD) would alter circulating AGE concentration, skeletal muscle AGE accumulation, and oxidative stress in wild-type and RAGE-deficient mice. The physiological significance of AGE/RAGE axis activation in HFD-fed mice was evaluated in terms of exercise tolerance and mitochondrial respiratory chain complex activity. HFD elicited adiposity, abnormal fat distribution, and oral glucose intolerance. HFD also induced accumulation of N^ε-carboxymethyl-l-lysine, increased protein carbonyl levels, and impaired respiratory chain complex activity in soleus muscle. Ablation of RAGE had no effects on weight gain and oral glucose tolerance in HFD-fed mice. Peak aerobic capacity and mitochondrial cytochrome-c oxidase activity were restored in HFD-fed RAGE^-/- mice. We concluded that RAGE signaling plays an important role in skeletal muscle homeostasis of mice under metabolic stress. Novelty HFD in mice induces accumulation of AGEs, oxidative stress, and mitochondrial dysfunction in the soleus muscle. RAGE, the multi-ligand receptor for AGEs, modulates oxidative stress and mitochondrial electron transport chain function in the soleus muscle of HFD-fed mice.

Proteomic characterization of obesity-related nephropathy

Background

Nephropathy related to obesity lacks a pathophysiological understanding and definite diagnostic pathways by biomarkers.

Methods

In this study we investigated the association between urinary peptides and body mass index (BMI) and renal function in proteome data sets from 4015 individuals.

Results

A total of 365 urinary peptides were identified to be significantly associated with BMI. The majority of these peptides were collagen fragments. In addition, most of the peptides also demonstrated a significant concordant association with estimated glomerular filtration rate (eGFR) in the investigated cohort, with the presence of diabetes exhibiting no significant association. A new classifier was developed, based on 150 urinary peptides, that enabled the distinction of non-obese subjects with preserved kidney function from obese, non-diabetic subjects with eGFR >45 mL/min/1.73 m² in an independent cohort, with an area under the curve of 0.93.

Conclusions

On a molecular level, the data strongly suggest a link between obesity and fibrosis, which may be a major cause of obesity-related nephropathy.

Measures of lung function and their relationship with advanced glycation end-products

BACKGROUND

Advanced glycation end-products (AGEs) have been implicated in the pathophysiology of chronic obstructive pulmonary disease (COPD). However, the association between AGE accumulation in the skin measured by skin autofluorescence (SAF) and lung function in healthy subjects has not been explored in detail. We use a population-based study of 50-64-year-olds to assess spirometry, diffusing capacity of the lung for carbon monoxide (D LCO) and impulse oscillometry (IOS) in relation to SAF.

METHODS

Participants with information on SAF, lung function and potential confounding variables were included from the Swedish Cardiopulmonary Bioimage Study (SCAPIS) cohort (spirometry, n=4111; D LCO, n=3889; IOS, n=3970). Linear regression was used to assess changes in lung function (as measured by spirometry (forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC), D LCO and IOS (resistance measured at 5 (R 5) and 20 Hz (R 20), R 5-R 20, area of reactance, reactance measured at 5 Hz (X- 5), and resonant frequency)) by a 1-sd increase in SAF.

RESULTS

FEV1, FVC and D LCO were significantly and inversely associated with SAF after adjustment for potential confounding factors (per 1-sd increase in SAF: FEV1 -0.03 L (95% CI -0.04- -0.02 L), p<0.001; FVC -0.03 L (95% CI -0.05- -0.02 L), p<0.001; D LCO -0.07 mmol·min-1·kPa-1 (95% CI -0.11- -0.03 mmol·min-1·kPa-1), p<0.001). This association was also found in nonsmokers and in non-COPD subjects. Pulmonary reactance (X 5) but not pulmonary resistance (R 5, R 20 and R 5-R 20) was significantly associated with SAF (per 1-sd increase in SAF: X 5 -0.001 kPa·L-1·s (95% CI -0.003-0.00 kPa·L-1·s), p=0.042), which was mirrored in non-COPD patients but not in current nonsmokers.

CONCLUSIONS

AGE accumulation, as measured by SAF, is significantly associated with lung function decrements indicative of changes in the lung parenchyma.

Insulin-producing cells from mesenchymal stromal cells: Protection against cognitive impairment in diabetic rats depends upon implant site

Diabetes mellitus (DM) is a serious public health problem and can cause long-term damage to the brain, resulting in cognitive impairment in these patients. Insulin therapy for type 1 DM (DM1) can achieve overall blood glucose control, but glycemic variations can occur during injection intervals, which may contribute to some complications. Among the additional therapies available for DM1 treatment is the implantation of insulin-producing cells (IPCs) to attenuate hyperglycemia and even reverse diabetes. Here, we studied the strategy of implanting IPCs obtained from mesenchymal stromal cells (MSCs) from adipose tissue, comparing two different IPC implant sites, subcapsular renal (SR) and subcutaneous (SC), to investigate their putative protection against hippocampal damage, induced by STZ, in a rat DM1 model. Both implants improved hyperglycemia and reduced the serum content of advanced-glycated end products in diabetic rats, but serum insulin was not observed in the SC group. The SC-implanted group demonstrated ameliorated cognitive impairment (evaluated by novel object recognition) and modulation of hippocampal astroglial reactivity (evaluated by S100B and GFAP). Using GFP+ cell implants, the survival of cells at the implant sites was confirmed, as well as their migration to the pancreas and hippocampus. The presence of undifferentiated MSCs in our IPC preparation may explain the peripheral reduction in AGEs and subsequent cognitive impairment recovery, mediated by autophagic depuration and immunomodulation at the hippocampus, respectively. Together, these data reinforce the importance of MSCs for use in neuroprotective strategies, and highlight the logistic importance of the subcutaneous route for their administration.

Leukotriene Pathway Activation Associates with Poor Glycemic Control and with Cardiovascular Autonomic Neuropathy in Type 1 Diabetes

Background and Aims

Since hyperglycemia promotes inflammation by different pathways and inflammation participates in the development of chronic diabetes complications, we investigated the association between the leukotriene (LT) pathway and microvascular diabetes complications.

Methods and Results

Quantitative polymerase chain reaction was employed to quantify the expression of ALOX5 (encodes 5-lipoxygenase), LTB4R (encodes one of the LTB4 receptors), and MYD88 in peripheral blood mononuclear cells from 164 type 1 diabetes (T1D) individuals presenting or not diabetes kidney disease, retinopathy, peripheral neuropathy, and cardiovascular autonomic neuropathy (CAN); 26 nondiabetic subjects were included as controls. LTB4 plasmatic concentrations were also evaluated. The expression of LTB4R was significantly higher in T1D individuals than in controls. T1D individuals with microvascular complications presented lower MYD88 mRNA expression when compared to those without microvascular complications. Higher LTB4 concentrations were found in individuals with CAN versus without CAN. The observation of two distinct subgroups of T1D individuals in the correlation analyses motivated us to evaluate the characteristics of each one of these groups separately. The group presenting higher expression of ALOX5 and of LTB4R also presented higher values of HbA₁C, of fructosamine, and of plasmatic LTB4.

Conclusion

In the diabetes setting, the LT pathway is not only activated by hyperglycemia but is also modulated by the status of the autonomic nervous system.

Advanced Glycation End Products (AGEs): Biochemistry, Signaling, Analytical Methods, and Epigenetic Effects

The advanced glycation end products (AGEs) are organic molecules formed in any living organisms with a great variety of structural and functional properties. They are considered organic markers of the glycation process. Due to their great heterogeneity, there is no specific test for their operational measurement. In this review, we have updated the most common chromatographic, colorimetric, spectroscopic, mass spectrometric, and serological methods, typically used for the determination of AGEs in biological samples. We have described their signaling and signal transduction mechanisms and cell epigenetic effects. Although mass spectrometric analysis is not widespread in the detection of AGEs at the clinical level, this technique is highly promising for the early diagnosis and therapeutics of diseases caused by AGEs. Protocols are available for high-resolution mass spectrometry of glycated proteins although they are characterized by complex machine management. Simpler procedures are available although much less precise than mass spectrometry. Among them, immunochemical tests are very common since they are able to detect AGEs in a simple and immediate way. In these years, new methodologies have been developed using an in vivo novel and noninvasive spectroscopic methods. These methods are based on the measurement of autofluorescence of AGEs. Another method consists of detecting AGEs in the human skin to detect chronic exposure, without the inconvenience of invasive methods. The aim of this review is to compare the different approaches of measuring AGEs at a clinical perspective due to their strict association with oxidative stress and inflammation.

Development of a novel Maillard reaction-based time-temperature indicator for monitoring the fluorescent AGE content in reheated foods

Dietary advanced glycation end products (AGEs) are formed via the Maillard reaction in foods, especially in reheated foods, and can cause chronic diseases. In this study, a series of Maillard reaction-based time-temperature indicators (TTIs: TTI-1, TTI-2, and TTI-3) were developed with lysine and xylose for monitoring the dynamic formation of fluorescent AGEs in reheated foods. The discoloration kinetics of Maillard reaction-based TTIs and the dynamics of fluorescent AGE formation were explored. Formulas were derived to illustrate the relationship of the color change in the TTIs with time and temperature. The activation energies (E a values) for generating the TTIs were 96.17, 87.98, and 83.55 kJ mol-1, respectively. TTI-1 was the optimal indicator for instant soy milk powder because it showed the lowest activation energy difference in this study. The results show that this series of Maillard reaction-based TTIs can be used to monitor the AGE contents in various reheated foods.

Vitreous and Vision Degrading Myodesopsia

Macromolecules comprise only 2% of vitreous, yet are responsible for its gel state, transparency, and physiologic function(s) within the eye. Myopia and aging alter collagen and hyaluronan association causing concurrent gel liquefaction and fibrous degeneration. The resulting vitreous opacities and collapse of the vitreous body during posterior vitreous detachment are the most common causes for the visual phenomenon of vitreous floaters. Previously considered innocuous, the vitreous opacities that cause floaters sometimes impact vision by profoundly degrading contrast sensitivity function and impairing quality-of-life. While many people adapt to vitreous floaters, clinically significant cases can be diagnosed with Vision Degrading Myodesopsia based upon echographic assessment of vitreous structure and by measuring contrast sensitivity function. Perhaps due to the ubiquity of floaters, the medical profession has to date largely ignored the plight of those with Vision Degrading Myodesopsia. Improved diagnostics will enable better disease staging and more accurate identification of severe cases that merit therapy. YAG laser treatments may occasionally be slightly effective, but vitrectomy is currently the definitive cure. Future developments will usher in more informative diagnostic approaches as well as safer and more effective therapeutic strategies. Improved laser treatments, new pharmacotherapies, and possibly non-invasive optical corrections are exciting new approaches to pursue. Ultimately, enhanced understanding of the underlying pathogenesis of Vision Degrading Myodesopsia should result in prevention, the ultimate goal of modern Medicine.

Clinicoradiographic markers of peri-implantitis in cigarette-smokers and never-smokers with type 2 diabetes mellitus at 7-years follow-up

BACKGROUND

It is hypothesized that in the long-term, (a) peri-implant inflammatory variables (plaque index [PI], bleeding on probing [BOP], probing depth (PD) and crestal bone loss [CBL]) are worse in cigarette-smokers (CS) and patients with type-2 diabetes mellitus (T2DM) than never-smokers (NS) without T2DM. The aim of the present 7-year follow-up clinical observational study was to assess the survival of dental implant in CS and NS with T2DM.

METHODS

Study participants were divided into four groups based on glycemic status and self-reported cigarette-smoking habit: a) CS with T2DM; b) CS without T2DM; c) NS with T2DM; and d) NS without T2DM. Demographic information was collected using a questionnaire and hemoglobin A1c (HbA1c) levels were measured. Peri-implant PI, BOP, PD, and CBL were measured. Sample-size was estimated was statistical analysis was done using analysis of variance. P <0.01 was considered significant.

RESULTS

In total, 101 male patients were included. There was no significant contrast in age among the groups. Every partaker in the study groups had one dental implant placed in posterior maxilla or mandible. The mean HbA1c levels were significantly higher among CS (P <0.01) and NS (P <0.01) with T2DM than individuals without T2DM. Peri-implant PI (P <0.01), PD (P <0.01), and CBL (P <0.01) were significantly higher among CS and NS with T2DM and CS without T2DM than NS without T2DM. Peri-implant BOP was significantly higher among CS and NS with T2DM than CS and NS without T2DM (P <0.01).

CONCLUSIONS

Peri-implant inflammatory variables were worse among CS and NS with T2DM than NS without T2DM. A state of chronic hyperglycemia seems to be a stronger mediator of inflammation than cigarette smoking in patients with T2DM.