Interactions between Age-Related Type 2 Diabetes and the Small Intestine

The number of patients with type 2 diabetes is increasing worldwide. The mechanisms leading to type 2 diabetes and its complications is being researched; however, the pathological mechanisms of diabetes in the small intestine remain unclear. Therefore, we examined these pathological mechanisms in the small intestine using a mouse model of type 2 diabetes (KK-Ay/TaJcl) aged 10 and 50 weeks. The results showed that diabetes worsened with age in the mice with type 2 diabetes. In these mice, advanced glycation end products (AGEs) in the small intestine and mast cell expression increased, whereas diamine oxidase (DAO) decreased; increased tumor necrosis factor (TNF)-α and histamine levels in the plasma and small intestine were also detected. Additionally, the expression of zonula occludens (ZO)-1 and Claudin1 and cell adhesion molecules in the small intestine reduced. These results exacerbated with age. These findings indicate that type 2 diabetes causes AGE/mast cell/histamine and TNF-α signal transmission in the small intestine and decreases small intestinal wall cell adhesion molecules cause TNF-α and histamine to flow into the body, worsening the diabetic condition. In addition, this sequence of events is suggested to be strengthened in aged mice with type 2 diabetes, thus exacerbating the disease. These findings of this study may facilitate the elucidation of the pathological mechanisms of type 2 diabetes and its associated complications.

Deletion of Glyoxalase 1 exacerbates acetaminophen-induced hepatotoxicity in mice

Acetaminophen (APAP) overdose triggers a cascade of intracellular oxidative stress events culminating in acute liver injury. The clinically used antidote, N-acetylcysteine (NAC) has a narrow therapeutic window and early treatment is essential for satisfactory therapeutic outcome. For more versatile therapies that can be effective even at late-presentation, the intricacies of APAP-induced hepatotoxicity must be better understood. Accumulation of advanced glycation end-products (AGEs) and consequent activation of the receptor for AGEs (RAGE) are considered one of the key mechanistic features of APAP toxicity. Glyoxalase-1 (Glo-1) regulates AGE formation by limiting the levels of methylglyoxal (MEG). In this study, we studied the relevance of Glo-1 in APAP mediated activation of RAGE and downstream cell-death cascades. Constitutive Glo-1 knockout mice (GKO) and a cofactor of Glo-1, ψ-GSH, were employed as tools. Our findings show elevated oxidative stress, activation of RAGE and hepatocyte necrosis through steatosis in GKO mice treated with high-dose APAP compared to wild type controls. A unique feature of the hepatic necrosis in GKO mice is the appearance of microvesicular steatosis as a result of centrilobular necrosis, rather than inflammation seen in wild type. The GSH surrogate and general antioxidant, ψ-GSH alleviated APAP toxicity irrespective of Glo-1 status, suggesting that oxidative stress being the primary driver of APAP toxicity. Overall, exacerbation of APAP hepatotoxicity in GKO mice suggests the importance of this enzyme system in antioxidant defense against initial stages of APAP overdose.

Age-related changes in scalp biophysical parameters: A comparative analysis of the 20s and 50s age groups

BACKGROUND

Age-related changes in scalp parameters affect hair quality and scalp condition. However, detailed data on biophysical parameters of the scalp across age groups remain scarce. We aimed to investigate the differences in scalp parameters between individuals in their 20s and 50s and analyze their sex-specific variations.

MATERIALS AND METHODS

Two hundred participants (160 women and 40 men) were equally divided into 20s and 50s age groups. Biophysical parameters of the scalp, including elasticity, pH, trans-epidermal water loss (TEWL), sebum production, desquamation, firmness, redness, and yellowness, were measured in the vertex, occipital, and temporal regions. Hair density and thickness were measured in the temporal region. The accumulation of advanced glycation end products (AGEs) in the skin was noninvasively measured in a subset of 60 women.

RESULTS

Skin firmness and redness increased with age in women, whereas yellowness increased with age in both sexes. Sebum production and pH levels were significantly lower in the 50s age group than in the 20s age group, particularly in women. TEWL was lower in men in their 50s than in those in their 20s, particularly in the occipital region. A significant reduction in hair density was observed in the 50s age group in both sexes. AGE accumulation in the skin increased with age and was correlated with scalp skin yellowness.

CONCLUSION

Age-related changes in scalp parameters have important implications for hair health and scalp condition. These findings emphasize the importance of considering age and sex when developing hair care strategies.

Inter- and Intraindividual Differences in the Capacity of the Human Intestinal Microbiome in Fecal Slurries to Metabolize Fructoselysine and Carboxymethyllysine

The advanced glycation endproduct carboxymethyllysine and its precursor fructoselysine are present in heated, processed food products and are considered potentially hazardous for human health. Upon dietary exposure, they can be degraded by human colonic gut microbiota, reducing internal exposure. Pronounced interindividual and intraindividual differences in these metabolic degradations were found in anaerobic incubations with human fecal slurries in vitro. The average capacity to degrade fructoselysine was 27.7-fold higher than that for carboxymethyllysine, and degradation capacities for these two compounds were not correlated (R² = 0.08). Analysis of the bacterial composition revealed that interindividual differences outweighed intraindividual differences, and multiple genera were correlated with the individuals' carboxymethyllysine and fructoselysine degradation capacities (e.g., Akkermansia, Alistipes).

High Molecular Weight Fucoidan Restores Intestinal Integrity by Regulating Inflammation and Tight Junction Loss Induced by Methylglyoxal-Derived Hydroimidazolone-1

Fucoidan from brown seaweeds has several biological effects, including preserving intestinal integrity. To investigate the intestinal protective properties of high molecular weight fucoidan (HMWF) from Undaria pinnatifida on intestinal integrity dysfunction caused by methylglyoxal-derived hydroimidazolone-1 (MG-H1), one of the dietary advanced-glycation end products (dAGEs) in the human-colon carcinoma-cell line (Caco-2) cells and ICR mice. According to research, dAGEs may damage the intestinal barrier by increasing gut permeability. The findings of the study showed that HMWF + MG-H1 treatment reduced by 16.8% the amount of reactive oxygen species generated by MG-H1 treatment alone. Furthermore, HMWF + MGH-1 treatment reduced MG-H1-induced monolayer integrity disruption, as measured by alterations in transepithelial electrical resistance (135% vs. 75.5%) and fluorescein isothiocyanate incorporation (1.40 × 10^-6 cm/s vs. 3.80 cm/s). HMWF treatment prevented the MG-H1-induced expression of tight junction markers, including zonula occludens-1, occludin, and claudin-1 in Caco-2 cells and mouse colon tissues at the mRNA and protein level. Also, in Caco-2 and MG-H1-treated mice, HMWF plays an important role in preventing receptor for AGEs (RAGE)-mediated intestinal damage. In addition, HMWF inhibited the nuclear factor kappa B activation and its target genes leading to intestinal inflammation. These findings suggest that HMWF with price competitiveness could play an important role in preventing AGEs-induced intestinal barrier dysfunction.

Impact of Dietary Advanced Glycation End Products on Female Reproduction: Review of Potential Mechanistic Pathways

Advanced glycation end products (AGEs), a heterogenous group of products formed by the reaction between protein and reducing sugars, can form endogenously due to non-enzymatic reactions or by exogenous sources such as diet where considerable increase in AGEs is observed due to the modification of food mainly by thermal processing. Recent studies have suggested that AGEs could impact, via inducing inflammation and oxidative stress, the reproductive health and fertility in both males and females. This review presents a summary of recently published data pertaining to the pathogenesis of dietary AGEs and their receptors as well as their potential impact on female reproductive health. More specifically, it will present data pertaining to dietary AGEs’ involvement in the mechanistic pathogenesis of polycystic ovary syndrome, ovarian dysfunction, as well as the AGEs’ effect perinatally on the female offspring reproduction. Understanding the mechanistic impact of dietary AGEs on female reproduction can help contribute to the development of targeted pharmacological therapies that will help curb rising female infertility.

Erectile Dysfunction in Individuals with Type 1 Diabetes is Associated with Long-term Metabolic Control and Diabetic Complications: A Cross-Sectional Study

Background  Erectile dysfunction (ED) affects approximately 38% of individuals with type 1 diabetes (T1DM). Skin autofluorescence (AF) reflects skin advanced glycation end product (AGE) deposits and is a marker of long-term glycemia control. Objective  The study investigates the relationship between ED and diabetes control in patients with T1DM. Methods  Adult patients with T1DM visiting the Diabetology Department were cross-sectionally investigated. Medical history, anthropometric features, and laboratory findings were collected. All individuals filled the International Index of Erectile Function (IIEF-5). IIEF-5 total score < 22 represented the presence of ED. AF was measured on the volar aspect of the forearm using AGE Reader. Insulin resistance (IR) was assessed by the estimated glucose disposal rate. Descriptive statistics and multivariate logistic regression analyses were performed. The adjusted covariates were general risk factors of ED. Results  Of a total of n  = 70 patients, n  = 30 (42.9%) suffered from ED. The presence of ED was associated with higher glycated hemoglobin level (OR, 95% CI; 1.62, 1.02-2.60; p  = 0.043), presence of at least one diabetic complication (3.49, 1.10-11.03; p  = 0.03), and skin AF (9.20, 1.60-52.94; p  = 0.01), but not with IR (0.78, 0.57-2.60; p  = 0.12). Skin AF values ≥ 2.2 indicates presence of ED with a sensitivity of 70.0% and a specificity of 77.5%. Area under the curve was equal to 0.72 (95% CI: 0.60-0.85). Conclusions  The presence of ED in individuals with T1DM is associated with HbA1c, the presence of at least one diabetic complication, and skin AF.

AGEs-Induced and Endoplasmic Reticulum Stress/Inflammation-Mediated Regulation of GLUT4 Expression and Atherogenesis in Diabetes Mellitus

In recent decades, complex and exquisite pathways involved in the endoplasmic reticulum (ER) and inflammatory stress responses have been demonstrated to participate in the development and progression of numerous diseases, among them diabetes mellitus (DM). In those pathways, several players participate in both, reflecting a complicated interplay between ER and inflammatory stress. In DM, ER and inflammatory stress are involved in both the pathogenesis of the loss of glycemic control and the development of degenerative complications. Furthermore, hyperglycemia increases the generation of advanced glycation end products (AGEs), which in turn refeed ER and inflammatory stress, contributing to worsening glycemic homeostasis and to accelerating the development of DM complications. In this review, we present the current knowledge regarding AGEs-induced and ER/inflammation-mediated regulation of the expression of GLUT4 (solute carrier family 2, facilitated glucose transporter member 4), as a marker of glycemic homeostasis and of cardiovascular disease (CVD) development/progression, as a leading cause of morbidity and mortality in DM.

Glyoxal-Lysine Dimer, an Advanced Glycation End Product, Induces Oxidative Damage and Inflammatory Response by Interacting with RAGE

The glyoxal-lysine dimer (GOLD), which is a glyoxal (GO)-derived advanced glycation end product (AGE), is produced by the glycation reaction. In this study, we evaluated the effect of GOLD on the oxidative damage and inflammatory response in SV40 MES 13 mesangial cells. GOLD significantly increased the linkage with the V-type immunoglobulin domain of RAGE, a specific receptor of AGE. We found that GOLD treatment increased RAGE expression and reactive oxygen species (ROS) production in mesangial cells. GOLD remarkably regulated the protein and mRNA expression of nuclear factor erythroid 2-related factor 2 (NRF2) and glyoxalase 1 (GLO1). In addition, mitochondrial deterioration and inflammation occurred via GOLD-induced oxidative stress in mesangial cells. GOLD regulated the mitogen-activated protein kinase (MAPK) and the release of proinflammatory cytokines associated with the inflammatory mechanism of mesangial cells. Furthermore, oxidative stress and inflammatory responses triggered by GOLD were suppressed through RAGE inhibition using RAGE siRNA. These results demonstrate that the interaction of GOLD and RAGE plays an important role in the function of mesangial cells.

Revealing Advanced Glycation End Products Associated Structural Changes in Serum Albumin

Structural alterations in proteins have a significant impact on their function and body physiology. Glycation via nonenzymatic forms of cross-linking leads to proteins' conformational changes, the macromolecule being recognized as a stable fibrillary structure, oligomerization, and becoming advanced glycation end products (AGEs). Protein that undergoes glycation-related modifications, namely, β-sheet enriched structural changes, are recognized as amyloid. In the current study, we characterized a single protein modified in vitro under physiological conditions to represent a protein glycation model. The glycation altered the helical conformation of serum albumin (SA) and promoted the formation of a β-sheet enriched with amyloid fibrils detected at multidimensional levels. The nanoscale resolution by spectroscopy in the presence of thioflavin-T (ThT) and 8-anilinonaphthalene-1-sulfonic acid (8-ANS) showed binding of the fibrils formed in the presence of glucose (GLU) and the carbonyl metabolites methylglyoxal (MGO) and glycolaldehyde (GAD). In the presence of MGO and GAD, the SA becomes insoluble aggregates, demonstrated by TEM microscopy and dynamic light scattering (DLS). The protein oligomerization was visualized when separated via SDS gel electrophoresis and mass photometry (MP) assays. Following the glycation, eventually, the material polymerized and became stiffer. The level of stiffness was analyzed by a rheometer that revealed a quick alteration under MGO and GAD. This is the first study to combine multiple spectroscopy assays, imaging, and rheology measurements of SA and to demonstrate a resolution on a nanoscale structural toward better resolution of the conformational changes of glycated SA, oligomerization, and protein aggregations under physiological conditions.

Methylglyoxal-Lysine Dimer, an Advanced Glycation End Product, Induces Inflammation via Interaction with RAGE in Mesangial Cells

INTRODUCTION

Advanced glycation end products (AGEs) and receptor of advanced glycation end products (RAGE) mediate renal function during diabetic and non-diabetic nephropathy development. Methylglyoxal-lysine dimer (MOLD), a typical toxic advanced glycation end product (TAGE), contributes to inflammatory responses during renal diseases. This study determines the effect of MOLD on inflammatory responses in mouse mesangial cells.

METHODS AND RESULTS

The murine mesangial cell line SV40 MES 13 is used to assess nuclear factor-kappa B (NF-κB) expression, reactive oxygen species (ROS) production, and mitochondria labeling. The interaction model between RAGE and MOLD is also determined. MOLD treatment of mesangial cells markedly increases RAGE expression and the linkage with V-type Ig domain of RAGE. MOLD induces ROS production and mitochondrial dysfunction. MOLD activates phosphatidylinositol 3-kinase-protein kinase B (PI3KB) and NF-κB signaling pathways. It is confirmed that these changes are reversed when ROS is suppressed. These effects may be regulated through mitogen-activated protein kinases and pro-inflammatory cytokines in circulatory inflammation responses.

CONCLUSION

MOLD plays a major role in nephropathy via ROS production and mitochondrial dysfunction through direct association with RAGE. Further, the NF-kB and PI3K/AKT signaling pathways triggered by ROS mediate the inflammatory response to exacerbate MOLD-induced damages in inflammation-related diabetic and non-diabetic renal diseases.

The Role of Protein Adduction in Toxic Neuropathies of Exogenous and Endogenous Origin

The peripheral (axonal) neuropathy associated with repeated exposure to aliphatic and aromatic solvents that form protein-reactive γ-diketones shares some clinical and neuropathological features with certain metabolic neuropathies, including type-II diabetic neuropathy and uremic neuropathy, and with the largely sub-clinical nerve damage associated with old age. These conditions may be linked by metabolites that adduct and cross-link neuroproteins required for the maintenance of axonal transport and nerve fiber integrity in the peripheral and central nervous system.

Skin autofluorescence predicts cancer in subjects with type 2 diabetes

INTRODUCTION

Subjects with type 2 diabetes have an excess risk of cancer. The potential role of advanced glycation end products (AGEs) accumulated during long-term hyperglycemia in cancer development has been suggested by biological studies but clinical data are missing. AGEs can be estimated by measuring the skin autofluorescence. We searched whether the skin autofluorescence could predict new cancers in persons with type 2 diabetes.

RESEARCH DESIGN AND METHODS

From 2009 to 2015, we measured the skin autofluorescence of 413 subjects hospitalized for uncontrolled or complicated type 2 diabetes, without any history of cancer. The participants were followed for at least 1 year and the occurrences of new cancers were compared according to their initial skin autofluorescences.

RESULTS

The participants were mainly men (57.9%), with poorly controlled (HbA1c 72±14 mmol/mol or 8.7%±1.8%) and/or complicated type 2 diabetes. Their median skin autofluorescence was 2.6 (2.2-3.0) arbitrary units. Forty-five new cancer cases (10.9%) were registered during 4.8±2.3 years of follow-up: 75.6% of these subjects had skin autofluorescence higher than the median (χ²: p=0.001). By Cox regression analysis adjusted for age, gender, body mass index, history of smoking and renal parameters, skin autofluorescence >2.6 predicted a 2.57-fold higher risk of cancer (95% CI 1.28 to 5.19, p=0.008). This association remained significant after excluding the eight cancers that occurred in the 4 years after inclusion (OR 2.95, 95% CI 1.36 to 6.38, p=0.006). As a continuous variable, skin autofluorescence was also related to new cancers (OR 1.05, 95% CI 1.01 to 1.10, p=0.045).

CONCLUSIONS

Skin autofluorescence, a potential marker of glycemic memory, predicts the occurrence of cancer in subjects with type 2 diabetes. This relation provides a new clinical argument for the role of AGEs in cancer. Their estimation by measuring the skin autofluorescence may help select subjects with diabetes in cancer screening programs.

Low Soluble Receptor for Advanced Glycation End Products Precedes and Predicts Cardiometabolic Events in Women With Rheumatoid Arthritis

Background: Cardiovascular disease (CVD) causes premature mortality in rheumatoid arthritis (RA). Levels of soluble (s)RAGE change with aging, hypertension and hypercholesterolemia. We assessed whether sRAGE was associated with increased risk of CVD in RA patients.

Methods: Serum sRAGE was measured in 184 female RA patients and analyzed with respect to CVD risk estimated by the Framingham algorithm (eCVR), metabolic profile and inflammation. Levels of sRAGE in 13 patients with known cardio-metabolic morbidity defined the cut-off for low sRAGE. Prospective 5-year follow-up of new CV and metabolic events was completed.

Results: Low sRAGE was significantly associated with previous history and with new imminent cardiometabolic events in the prospective follow-up of RA patients. In both cases, low sRAGE reflected higher estimation of CVR in those patients. Low sRAGE was attributed to adverse metabolic parameters including high fasting plasma glucose and body fat content rather than inflammation. The association of sRAGE and poor metabolic profile was prominent in patients younger than 50 years.

Conclusions: This study points at low sRAGE as a marker of metabolic failure developed during chronic inflammation. It highlights the importance for monitoring metabolic health in female RA patients for timely prevention of CVD.

Trial registration:ClinicalTrials.gov with ID NCT03449589. Registered 28, February 2018.

Plasma Concentration of Advanced Glycation End-Products From Wild Canids and Domestic Dogs Does Not Change With Age or Across Body Masses

Dogs provide a physiological paradox: In domestic dogs, small breeds live longer lives than large breed dogs. Comparatively, a wild canid can be a similar size than many large breed dogs and outlive their domestic cousin. We have previously shown that oxidative stress patterns between domestic and wild canids differ, so that wild canids invest in a robust antioxidant system across their lives; whereas domestic dogs tend to accumulate lipid damage with age. There is a close association between oxidative stress and the production of a carbohydrate based-damage, Advanced Glycation End-products (AGEs). AGEs can bind to their receptor (RAGE), which can lead to increases in reactive oxygen species (ROS) production, and decreases in antioxidant capacity. Here, I used plasma from wild and domestic canids to address whether blood plasma AGE-BSA concentration associated with body mass and age in domestic dogs; And whether AGE-BSA concentration patterns in blood plasma from wild canids are similar to those found in domestic dogs. I found no correlation between circulating AGE-BSA concentration and body size or age in either domestic dogs and wild canids. These data suggest that AGEs formation may be a conserved trait across the evolution of domesticated dogs from wild ancestors, in opposition to oxidative stress patterns between these two groups. And, that, in domestic dogs, lipid metabolism, rather than carbohydrate metabolism, may be upregulated to yield the previously found differences in circulating lipid damage across lifespan and body sizes.

Activation of Notch1 signaling in podocytes by glucose-derived AGEs contributes to proteinuria

INTRODUCTION

Advanced glycation end-products (AGEs) are implicated in the pathogenesis of diabetic nephropathy (DN). Previous studies have shown that AGEs contribute to glomerulosclerosis and proteinuria. Podocytes, terminally differentiated epithelial cells of the glomerulus and the critical component of the glomerular filtration barrier, express the receptor for AGEs (RAGE). Podocytes are susceptible to severe injury during DN. In this study, we investigated the mechanism by which AGEs contribute to podocyte injury.

RESEARCH DESIGN AND METHODS

Glucose-derived AGEs were prepared in vitro. Reactivation of Notch signaling was examined in AGE-treated human podocytes (in vitro) and glomeruli from AGE-injected mice (in vivo) by quantitative reverse transcription-PCR, western blot analysis, ELISA and immunohistochemical staining. Further, the effects of AGEs on epithelial to mesenchymal transition (EMT) of podocytes and expression of fibrotic markers were evaluated.

RESULTS

Using human podocytes and a mouse model, we demonstrated that AGEs activate Notch1 signaling in podocytes and provoke EMT. Inhibition of RAGE and Notch1 by FPS-ZM1 (N-Benzyl-4-chloro-N-cyclohexylbenzamide) and DAPT (N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenyl glycine t-butylester), respectively, abrogates AGE-induced Notch activation and EMT. Inhibition of RAGE and Notch1 prevents AGE-induced glomerular fibrosis, thickening of the glomerular basement membrane, foot process effacement, and proteinuria. Furthermore, kidney biopsy sections from people with DN revealed the accumulation of AGEs in the glomerulus with elevated RAGE expression and activated Notch signaling.

CONCLUSION

The data suggest that AGEs activate Notch signaling in the glomerular podocytes. Pharmacological inhibition of Notch signaling by DAPT ameliorates AGE-induced podocytopathy and fibrosis. Our observations suggest that AGE-induced Notch reactivation in mature podocytes could be a novel mechanism in glomerular disease and thus could represent a novel therapeutic target.

Can advanced glycation end-products and their receptors be affected by weight loss? A systematic review

Advanced glycation end products (AGEs) have been implicated in the pathogenesis of most chronic diseases. Therefore, identification of treatments that can attenuate the effects of these compounds and prevent cardiometabolic complications is of extreme public health interest. Recently, body weight management interventions showed positive results on reducing serum AGE concentrations. Moreover, the soluble receptor for advanced glycation end products (sRAGE) is considered to be a novel biomarker to identify patients with obesity most likely to benefit from weight management interventions. This systematic review aimed to critically analyze papers evaluating the effects of weight loss on serum AGEs and its receptors in adults with excess body weight. MEDLINE, Cochrane, Scopus, and Lilacs databases were searched. Three studies evaluating the response of AGEs to energy-restricted diets and six assessing sRAGE as the primary outcome were included. Energy-restricted diets and bariatric surgery reduced serum AGE concentrations, but effects on endogenous secretory RAGE (esRAGE) and sRAGE concentrations are conflicting. These results may be associated with mechanisms related to changes in dietary intake and limiting endogenous AGE formation. Therefore, the role of energy-restricted diets and bariatric surgery on lowering serum AGE concentrations, as well as its effects on AGEs receptors, deserves further investigation.

Effect of reducing dietary advanced glycation end products on obesity-associated complications: a systematic review

CONTEXT

Consumption of dietary advanced glycation end products (AGEs) is associated with oxidative stress, inflammation, and other chronic conditions commonly associated with obesity.

OBJECTIVE

To analyze the effects of dietary AGEs on complications associated with obesity.

DATA SOURCES

This systematic review was conducted and reported according to PRISMA guidelines. The PubMed, Cochrane, and Scopus databases were searched, using the terms "advanced glycation end products," "overweight," and "obesity." The last search was performed in October 2018.

DATA EXTRACTION

Six studies that evaluated the effects of low-AGE and high-AGE diets were included in the review. The duration of the studies ranged from 1 day to 12 weeks. A comparison of all the compiled data was conducted by the authors.

DATA ANALYSIS

Circulating and urinary AGE markers, besides soluble receptor for AGEs, were considered as the primary outcomes. The secondary outcomes were cardiometabolic, inflammatory, glycemic, anthropometric, and renal markers.

CONCLUSIONS

AGE-RAGE interactions can activate the NF-κB (nuclear factor kappa B) signaling pathway and inhibit the PI3K-AKT pathway in adipocytes, which may explain their association with chronic diseases. This interaction can be considered as a novel explanation for the pathogenesis of obesity. AGEs can also be used as a biomarker for monitoring responses to dietary interventions in overweight and obese people.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42018082745.

Androgens Increase Accumulation of Advanced Glycation End Products in Granulosa Cells by Activating ER Stress in PCOS

Polycystic ovary syndrome (PCOS) is associated with hyperandrogenism, and we previously found that androgens activate endoplasmic reticulum (ER) stress in granulosa cells from patients with PCOS. In addition, recent studies demonstrated the accumulation of advanced glycation end products (AGEs) in granulosa cells from PCOS patients, which contribute to the pathology. Therefore, we hypothesized that androgens upregulate the receptor for AGEs (RAGE) expression in granulosa cells by activating ER stress, thereby increasing the accumulation of AGEs in these cells and contributing to the pathology. In the present study, we show that testosterone increases RAGE expression and AGE accumulation in cultured human granulosa-lutein cells (GLCs), and this is reduced by pretreatment with tauroursodeoxycholic acid (TUDCA), an ER stress inhibitor in clinical use. Knockdown of the transcription factor C/EBP homologous protein (CHOP), an unfolded protein response factor activated by ER stress, inhibits testosterone-induced RAGE expression and AGE accumulation. The expression of RAGE and the accumulation of AGEs are upregulated in granulosa cells from PCOS patients and dehydroepiandrosterone-induced PCOS mice. Administration of the RAGE inhibitor FPS-ZM1 or TUDCA to PCOS mice reduces RAGE expression and AGE accumulation in granulosa cells, improves their estrous cycle, and reduces the number of atretic antral follicles. In summary, our findings indicate that hyperandrogenism in PCOS increases the expression of RAGE and accumulation of AGEs in the ovary by activating ER stress, and that targeting the AGE-RAGE system, either by using a RAGE inhibitor or a clinically available ER stress inhibitor, may represent a novel approach to PCOS therapy.

The Function of PPARγ/AMPK/SIRT-1 Pathway in Inflammatory Response of Human Articular Chondrocytes Stimulated by Advanced Glycation End Products

Accumulation of advanced glycation end products (AGEs) in the articular cartilage is a major risk factor for osteoarthritis (OA). To determine the mechanistic basis of AGE action in OA, we treated human articular chondrocytes with AGEs, and found that they not only up-regulated the pro-inflammatory cytokines interleukin (IL)-1β and tumor necrosis factor (TNF)-α, but also inhibited AMP-activated protein kinase (AMPK) phosphorylation and decreased sirtuin 1 (SIRT-1) levels in a concentration- and time-dependent manner. Pioglitazone, a peroxisome proliferator-activated receptor-γ (PPARγ) agonist restored the inhibited AMPK and SIRT-1 by AGEs. Pre-treatment of the cells with the agonists or antagonists of AMPK and SIRT-1 respectively abolished and augmented the inflammatory state induced by AGEs. Furthermore, AMPK agonist also restored the levels of SIRT-1 in the AGE-stimulated chondrocytes. Our findings indicate AGEs induce an inflammatory response in human articular chondrocytes via the PPARγ/AMPK/SIRT-1 pathway, which is therefore a potential target in OA therapy.

Effect of Glyoxal Modification on a Critical Arginine Residue (Arg-31α) of Hemoglobin: Physiological Implications of Advanced Glycated end Product an in vitro Study

BACKGROUND

Non-enzymatic protein glycation is involved in structure and stability changes that impair protein functionality, resulting in several human diseases, such as diabetes and amyloidotic neuropathies (Alzheimer's disease, Parkinson's disease and Andrade's syndrome). Glyoxal, an endogenous reactive oxoaldehyde, increases in diabetes and reacts with several proteins to form advanced glycation end products through Maillard-like reaction.

OBJECTIVE

Human hemoglobin, the most abundant protein in blood cells is subjected to nonenzymatic modification by reactive oxoaldehydes in diabetic condition. In the present study, the effect of a low concentration of glyoxal (5 μM) on hemoglobin (10 μM) has been investigated following a period of 30 days incubation in vitro.

METHODS

Different techniques, mostly biophysical and spectroscopic (e.g. circular dichroism, differential scanning calorimetric study, dynamic light scattering, mass spectrometry, etc.) were used to study glyoxal-induced changes of hemoglobin.

RESULTS

Glyoxal-treated hemoglobin exhibits decreased absorbance around 280 nm, decreased fluorescence and reduced surface hydrophobicity compared to normal hemoglobin. Glyoxal treatment enhances the stability of hemoglobin and lowers its susceptibility to thermal aggregation compared to control hemoglobin as seen by different studies. Finally, peptide mass fingerprinting study showed glyoxal to modify an arginine residue of α-chain of hemoglobin (Arg-31α) to hydroimidazolone.

CONCLUSION

Increased level of glyoxal in diabetes mellitus as well as its high reactivity may cause modifications of the heme protein. Thus, considering the significance of glyoxal-induced protein modification under physiological conditions, the observation appears clinically relevant in terms of understanding hydroimidazolone-mediated protein modification under in vivo conditions.

Molecular and Cellular Bases of Immunosenescence, Inflammation, and Cardiovascular Complications Mimicking "Inflammaging" in Patients with Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an archetype of systemic autoimmune disease, characterized by the presence of diverse autoantibodies and chronic inflammation. There are multiple factors involved in lupus pathogenesis, including genetic/epigenetic predisposition, sexual hormone imbalance, environmental stimulants, mental/psychological stresses, and undefined events. Recently, many authors noted that "inflammaging", consisting of immunosenescence and inflammation, is a common feature in aging people and patients with SLE. It is conceivable that chronic oxidative stresses originating from mitochondrial dysfunction, defective bioenergetics, abnormal immunometabolism, and premature telomere erosion may accelerate immune cell senescence in patients with SLE. The mitochondrial dysfunctions in SLE have been extensively investigated in recent years. The molecular basis of normoglycemic metabolic syndrome has been found to be relevant to the production of advanced glycosylated and nitrosative end products. Besides, immunosenescence, autoimmunity, endothelial cell damage, and decreased tissue regeneration could be the results of premature telomere erosion in patients with SLE. Herein, the molecular and cellular bases of inflammaging and cardiovascular complications in SLE patients will be extensively reviewed from the aspects of mitochondrial dysfunctions, abnormal bioenergetics/immunometabolism, and telomere/telomerase disequilibrium.

Advanced Glycation End Products (AGEs), Receptor for AGEs, Diabetes, and Bone: Review of the Literature

Diabetes compromises bone cell metabolism and function, resulting in increased risk of fragility fracture. Advanced glycation end products (AGEs) interact with the receptor for AGEs (RAGE) and can make a meaningful contribution to bone cell metabolism and/or alter function. Searches in PubMed using the key words "advanced glycation end-product," "RAGE," "sRAGE," "bone," and "diabetes" were made to explain some of the clinical outcomes of diabetes in bone metabolism through the AGE-RAGE signaling pathway. All published clinical studies were included in tables. The AGE-RAGE signaling pathway participates in diabetic complications, including diabetic osteopathy. Some clinical results in diabetic patients, such as reduced bone density, suppressed bone turnover markers, and bone quality impairment, could be potentially due to AGE-RAGE signaling consequences. However, the AGE-RAGE signaling pathway has some helpful roles in the bone, including an increase in osteogenic function. Soluble RAGE (sRAGE), as a ligand decoy, may increase in either conditions of RAGE production or destruction, and then it cannot always reflect the AGE-RAGE signaling. Recombinant sRAGE can block the AGE-RAGE signaling pathway but is associated with some limitations, such as accessibility to AGEs, an increase in other RAGE ligands, and a long half-life (24 hours), which is associated with losing the beneficial effect of AGE/RAGE. As a result, sRAGE is not a helpful marker to assess activity of the RAGE signaling pathway. The recombinant sRAGE cannot be translated into clinical practice due to its limitations.

Adipose-derived Stem Cells Attenuates Diabetic Osteoarthritis via Inhibition of Glycation-mediated Inflammatory Cascade

Diabetes mellitus (DM) is well-known to exert complications such as retinopathy, cardiomyopathy and neuropathy. However, in recent years, an elevated osteoarthritis (OA) complaints among diabetics have been observed, portending the risk of diabetic OA. Since formation of advanced glycation end products (AGE) is believed to be the etiology of various diseases under hyperglycemic conditions, we firstly established that streptozotocin-induced DM could potentiate the development of OA in C57BL/6J mouse model, and further explored the intra-articularly administered adipose-derived stem cell (ADSC) therapy focusing on underlying AGE-associated mechanism. Our results demonstrated that hyperglycemic mice exhibited OA-like structural impairments including a proteoglycan loss and articular cartilage fibrillations in knee joint. Highly expressed levels of carboxymethyl lysine (CML), an AGE and their receptors (RAGE), which are hallmarks of hyperglycemic microenvironment were manifested. The elevated oxidative stress in diabetic OA knee-joint was revealed through increased levels of malondialdehyde (MDA). Further, oxidative stress-activated nuclear factor kappa B (NF-κB), the marker of proinflammatory signalling pathway was also accrued; and levels of matrix metalloproteinase-1 and 13 were upregulated. However, ADSC treatment attenuated all OA-like changes by 4 weeks, and dampened levels of CML, RAGE, MDA, NF-κB, MMP-1 and 13. These results suggest that during repair and regeneration, ADSCs inhibited glycation-mediated inflammatory cascade and rejuvenated cartilaginous tissue, thereby promoting knee-joint integrity in diabetic milieu.

Dietary Genistein Inhibits Methylglyoxal-Induced Advanced Glycation End Product Formation in Mice Fed a High-Fat Diet

BACKGROUND

Methylglyoxal (MGO), an important precursor of advanced glycation end products (AGEs), circulates at high concentrations in diabetic patients' blood and plays an important role in the pathogenesis of diabetes and other chronic diseases.

OBJECTIVES

The aim of this study was to determine whether dietary genistein can prevent indicators of metabolic syndrome (MetS) induced by a very-high-fat (VHF) diet or a high-fat (HF) diet plus exogenous MGO, and the accumulation of MGO and AGEs in mice.

METHODS

Male, 6-wk-old C57BL/6J mice (n = 15) were fed a low-fat (LF) diet (10% fat energy) or a VHF diet (60% fat energy) alone or including 0.25% genistein (VHF-G) for 16 wk in study 1. In study 2, 75 similar mice were fed the LF diet (LF) or the HF diet alone (HF) or in combination with up to 0.2% MGO in water (HFM) and 0.067% (HFM-GL) or 0.2% (HFM-GH) dietary genistein for 18 wk. Anthropometric and metabolic data were obtained in both studies to determine the effects of MGO and genistein on variables indicative of MetS.

RESULTS

Body weight gain, fat deposits, dyslipidemia, hyperglycemia, and fatty liver were ameliorated by dietary genistein in both studies. The plasma MGO concentration in VHF-G mice was 52% lower than that in VHF mice. Moreover, the AGE concentrations in plasma, liver, and kidney of VHF-G mice were 73%, 52%, and 49%, respectively, lower than in the VHF group (study 1). Similarly, the concentrations of plasma MGO and AGE in plasma, liver, and kidney of HFM-GH mice were 33.5%, 49%, 69%, and 54% lower than in HFM mice (study 2). Genistein inhibited AGE formation by trapping MGO to form adducts and upregulating the expressions of glyoxalase I and II and aldose reductase in liver and kidney to detoxify MGO in both studies.

CONCLUSIONS

Our data demonstrate for the first time that genistein significantly lowers MGO and AGE concentrations in 2 mouse MetS models via multiple pathways.

Age-dependent Changes in Plasma Amino Acids Contribute to Alterations in Glycoxidation Products

BACKGROUND

Glycative stress is involved in the pathogenesis of various degenerative disorders. This study sought to determine the effect of age-related changes in amino acids on serum levels of pentosidine and carboxymethyl-lysine (CML) in healthy individuals.

METHODS

The subjects were 78 healthy individuals categorized into three age groups. The ages of the groups were as follows: 26 young adults (20-30 y, 25.2±3.03), 26 middle-aged adults (35-50 y, 39.46±6.97) and 26 older adults (60 y or older, 69.80±10.01). Serum levels of pentosidine and CML were measured by ELISA and levels of plasma amino acids were determined using HPLC.

RESULTS

Serum levels of pentosidine and CML in the youngest group were higher than in the oldest group (p=0.026, 0.029, respectively). There was a positive correlation between the serum levels of pentosidine and CML and the levels of plasmaTyrosine (p=0.032, r=0.211 and p=0.037, r=0.224), Valine (p=0.037, r=0.224 and p=0.021, r=0.247) and Isoleucine (p=0.041, r=0.203 and p=0.021, r=0.247), respectively. Serum levels of pentosidine and CML may be modulated by the plasma levels of selected amino acids.

CONCLUSIONS

Better understanding of the role of these selective amino acids might provide new perception of how glycation pathways may be altered and pave the way for new therapeutic principles.

Glycation Damage: A Possible Hub for Major Pathophysiological Disorders and Aging

Glycation is both a physiological and pathological process which mainly affects proteins, nucleic acids and lipids. Exogenous and endogenous glycation produces deleterious reactions that take place principally in the extracellular matrix environment or within the cell cytosol and organelles. Advanced glycation end product (AGE) formation begins by the non-enzymatic glycation of free amino groups by sugars and aldehydes which leads to a succession of rearrangements of intermediate compounds and ultimately to irreversibly bound products known as AGEs. Epigenetic factors, oxidative stress, UV and nutrition are important causes of the accumulation of chemically and structurally different AGEs with various biological reactivities. Cross-linked proteins, deriving from the glycation process, present both an altered structure and function. Nucleotides and lipids are particularly vulnerable targets which can in turn favor DNA mutation or a decrease in cell membrane integrity and associated biological pathways respectively. In mitochondria, the consequences of glycation can alter bioenergy production. Under physiological conditions, anti-glycation defenses are sufficient, with proteasomes preventing accumulation of glycated proteins, while lipid turnover clears glycated products and nucleotide excision repair removes glycated nucleotides. If this does not occur, glycation damage accumulates, and pathologies may develop. Glycation-induced biological products are known to be mainly associated with aging, neurodegenerative disorders, diabetes and its complications, atherosclerosis, renal failure, immunological changes, retinopathy, skin photoaging, osteoporosis, and progression of some tumors.

Vascular legacy beyond blood pressure control: benefits of perindopril/indapamide combination in hypertensive patients with diabetes

OBJECTIVES

Much of the chronic care of patients with type 2 diabetes mellitus and hypertension involves the prevention of diabetic complications. Renin-angiotensin system inhibitors are recommended as first-line therapies because of their nephroprotective properties. Their combination with metabolically neutral diuretics is recommended to reduce blood pressure, morbidity and mortality. Our objective was to review the mechanisms by which the combination of the angiotensin-converting enzyme inhibitor, perindopril, and metabolically neutral thiazide-like diuretic, indapamide, targets the pathways involved in microvascular and macrovascular diabetic complications.

METHODS

For this narrative review, extensive literature searches were performed using PubMed/Medline. Articles published in English describing clinical trials and mechanism of action studies that were relevant to the treatment of patients with perindopril and/or indapamide were included.

RESULTS

Perindopril/indapamide treatment has been shown to reduce blood pressure and to have significant beneficial effects on arterial distensibility, kidney structure and function, and endothelial function. Recent data also suggests that perindopril may reduce the deleterious accumulation of advanced glycation end products in diabetic tissue. In the Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation diabetes trial, perindopril/indapamide treatment significantly reduced the relative risk of microvascular and macrovascular events by 9%, cardiovascular mortality by 18%, and all-cause mortality by 14%. Interestingly, 6 years after the end of the double-blind period, follow-up data showed that the beneficial effects on mortality continued to be significant even though differences in blood pressure and glycated hemoglobin levels had not been significant for several years. Together this data suggests that treatment with perindopril/indapamide has microvascular and macrovascular effects that extend beyond blood pressure lowering and that this treatment might confer a long-lasting beneficial vascular legacy.

CONCLUSION

Moving forward, understanding the pathophysiological bases of the effects that extend beyond those of blood pressure control will help us differentiate between anti-hypertensive choices.

Maternal serum advanced glycation end products level as an early marker for predicting preterm labor/PPROM: a prospective preliminary study

OBJECTIVE

To evaluate the value of maternal serum advanced glycation end products (AGEs) level at 11-13 weeks' gestation for the prediction of preterm labor and or preterm premature rupture of membranes (PPROM).

MATERIALS AND METHODS

This prospective cross-sectional study is performed in a university-affiliated hospital between February and April 2016. The participants of this study are low-risk pregnant women. Blood samples for maternal AGEs level were collected in the first trimester of pregnancy and all women completed their antenatal follow-up and delivered in our center. During the follow-up 21 women developed preterm labor/PPROM. The first trimester maternal AGEs levels of preterm labor/PPROM cases were compared with uncomplicated cases (n = 25) matched for age-parity and BMI. The predictive value of AGEs levels for preterm labor/PPROM was also assessed.

RESULTS

First-trimester AGEs levels were significantly higher in cases complicated with preterm labor/PPROM (1832 (415-6682) versus 1276 (466-6445) ng/L, p = .001 and 1722 (804-6682) versus 1343 (466-6445) ng/L, p = .025). According to receiver-operating characteristic curve analysis, the calculated cut off value of AGEs was 1538 ng/L with the sensitivity 91.7%, specificity 73.8%; and the negative and positive predictive values were 91.6% and 29.5%, respectively.

CONCLUSIONS

For the prediction of preterm labor/PPROM, the relatively high AGEs levels in the first trimester might be a useful marker.

The Ameliorative Effects of a Tocotrienol-Rich Fraction on the AGE-RAGE Axis and Hypertension in High-Fat-Diet-Fed Rats with Metabolic Syndrome

The clinical value of tocotrienols is increasingly appreciated because of the unique therapeutic effects that are not shared by tocopherols. However, their effect on metabolic syndrome is not well-established. This study aimed to investigate the effects of a tocotrienol-rich fraction (TRF) from palm oil in high-fat-diet-treated rats. Male, post-weaning Sprague Dawley rats were provided high-fat (60% kcal) diet for eight weeks followed by a TRF (60 mg/kg) treatment for another four weeks. Physical, metabolic, and histological changes were compared to those on control and high-fat diets respectively. High-fat feeding for eight weeks induced all hallmarks of metabolic syndrome. The TRF reversed systolic and diastolic hypertension, hypercholesterolemia, hepatic steatosis, impaired antioxidant defense, and myeloperoxidase hyperactivity triggered by the high-fat diet. It also conferred an inhibitory effect on protein glycation to reduce glycated hemoglobin A1c and advanced glycation end products (AGE). This was accompanied by the suppression of the receptor for advanced glycation end product (RAGE) expression in the liver. The treatment effects on visceral adiposity, glycemic control, triglyceride level, as well as peroxisome proliferator-activated receptor α and γ expression were negligible. To conclude, treatment with a TRF exhibited protective effects on the cardiovascular and liver health in addition to the amelioration of plasma redox imbalance and AGE-RAGE activation. Further investigation as a therapy for metabolic syndrome is therefore worthwhile.

High dietary advanced glycation end products are associated with poorer spatial learning and accelerated Aβ deposition in an Alzheimer mouse model

There is growing evidence of the involvement of advanced glycation end products (AGEs) in the pathogenesis of neurodegenerative processes including Alzheimer's disease (AD) and their function as a seed for the aggregation of Aβ, a hallmark feature of AD. AGEs are formed endogenously and exogenously during heating and irradiation of foods. We here examined the effect of a diet high in AGEs in the context of an irradiated diet on memory, insoluble Aβ₄₂, AGEs levels in hippocampus, on expression of the receptor for AGEs (RAGE), and on oxidative stress in the vasculature. We found that AD‐like model mice on high‐AGE diet due to irradiation had significantly poorer memory, higher hippocampal levels of insoluble Aβ₄₂ and AGEs as well as higher levels of oxidative stress on vascular walls, compared to littermates fed an isocaloric diet. These differences were not due to weight gain. The data were further supported by the overexpression of RAGE, which binds to Aβ₄₂ and regulates its transport across the blood–brain barrier, suggesting a mediating pathway. Because exposure to AGEs can be diminished, these insights provide an important simple noninvasive potential therapeutic strategy for alleviating a major lifestyle‐linked disease epidemic.

Atherosclerosis and the Hypercholesterolemic AGE-RAGE Axis

Background Interaction of advanced glycation end products (AGE) with the receptor for advanced glycation end products (RAGE) has been implicated in the pathogenesis of atherosclerosis. Soluble receptors for advanced glycation end products (sRAGE) act as a decoy for AGE by competing with RAGE and suppressing developing atherosclerosis. Hypercholesterolemia and the oxidative stress are known factors involved in atherosclerosis. High-density lipoprotein cholesterol (HDL-C) is known to exert a protective effect against the development of atherosclerosis. We hypothesize that hypercholesterolemia-induced atherosclerosis may be mediated through the AGE-RAGE axis. Objectives Two objectives to be determined are: (1) if hypercholesterolemia is positively correlated with serum AGE, AGE/sRAGE, and malondialdehyde (MDA: a marker for oxidative stress) and (2) if the protective effect of HDL-C is positively associated with serum sRAGE and negatively correlated with the levels of AGE and AGE/sRAGE. Methods Measurement of serum lipid levels from 100 patients allowed the separation into two groups (hypercholesterolemic and normocholesterolemic). Measurements of serum levels of AGE, sRAGE, and MDA were performed. Results Serum levels of sRAGE were lower, while the levels of AGE and AGE/sRAGE were higher in hypercholesterolemic subjects as compared with normocholesterolemic subjects. sRAGE levels are positively correlated with HDL, while they are negatively correlated with low-density lipoprotein, triglycerides, total cholesterol, and MDA in hypercholesterolemic subjects. Conclusions Hypercholesterolemia is positively correlated with serum AGE, AGE/sRAGE, and MDA. The effect of HDL-C may be due to increases in sRAGE and decreases in the levels of AGE and AGE/sRAGE. Hypercholesterolemia-induced atherosclerosis may be mediated through the AGE-RAGE axis; however, more research must be conducted.

[Protein carbonylation - reasons, effects and determination]

Disorder of cellular metabolic homeostasis resulting in the enhanced level of reactive oxygen species, glucose or reactive carbonyl compounds (products of lipid, glucose and amino acids oxidation) causes modifications of cellular components, particularly proteins. As a result of polypeptide chain direct oxidative modifications, carbonyl groups are formed. Reactions of polypeptides with glucose resulting in advanced glycation end products (AGE) generation and reaction with lipid peroxidation products giving advanced lipoxidation end products (ALE) and mechanisms of the above products generation are described. Since accumulation of modified proteins in cells can lead to the development of different diseases including diabetes and its associated diseases as well as neurodegenerative diseases their identification as well as quantitative determination is very important. Obtained data are used in diagnosis and in pharmacotherapy. However, variety of products and a wide range of their concentration in biological samples, cause that different analytic techniques must be used for their analysis. In this review, methods for their determination, with particular emphasis on proteomic approach using state of the art analytical techniques are shown.

Uremic Toxicity of Advanced Glycation End Products in CKD

Advanced glycation end products (AGEs), a heterogeneous group of compounds formed by nonenzymatic glycation reactions between reducing sugars and amino acids, lipids, or DNA, are formed not only in the presence of hyperglycemia, but also in diseases associated with high levels of oxidative stress, such as CKD. In chronic renal failure, higher circulating AGE levels result from increased formation and decreased renal clearance. Interactions between AGEs and their receptors, including advanced glycation end product-specific receptor (RAGE), trigger various intracellular events, such as oxidative stress and inflammation, leading to cardiovascular complications. Although patients with CKD have a higher burden of cardiovascular disease, the relationship between AGEs and cardiovascular disease in patients with CKD is not fully characterized. In this paper, we review the various deleterious effects of AGEs in CKD that lead to cardiovascular complications and the role of these AGEs in diabetic nephropathy. We also discuss potential pharmacologic approaches to circumvent these deleterious effects by reducing exogenous and endogenous sources of AGEs, increasing the breakdown of existing AGEs, or inhibiting AGE-induced inflammation. Finally, we speculate on preventive and therapeutic strategies that focus on the AGE-RAGE axis to prevent vascular complications in patients with CKD.

Stability of Individual Maillard Reaction Products in the Presence of the Human Colonic Microbiota

Maillard reaction products (MRPs) are taken up in substantial amounts with the daily diet, but the majority are not transported across the intestinal epithelium. The aim of this study was to obtain first insights into the stability of dietary MRPs in the presence of the intestinal microbiota. Four individual MRPs, namely, N-ε-fructosyllysine (FL), N-ε-carboxymethyllysine (CML), pyrraline (PYR), and maltosine (MAL), were anaerobically incubated with fecal suspensions from eight human volunteers at 37 °C for up to 72 h. The stability of the MRPs was measured by HPLC with UV and MS/MS detections. The Amadori product FL could no longer be detected after 4 h of incubation. Marked interindividual differences were observed for CML metabolism: Depending on the individual, at least 40.7 ± 1.5% of CML was degraded after 24 h of incubation, and the subjects could thus be tentatively grouped into fast and slow metabolizers of this compound. PYR was degraded by 20.3 ± 4.4% during 24 h by all subjects. The concentration of MAL was not significantly lowered in the presence of fecal suspensions. In no case could metabolites be identified and quantified by different mass spectrometric techniques. This is the first study showing that the human colonic microbiota is able to degrade selected glycated amino acids and possibly use them as a source of energy, carbon, and/or nitrogen.

Glycated serum albumin stimulates expression of endothelial cell specific molecule-1 in human umbilical vein endothelial cells: Implication in diabetes mediated endothelial dysfunction

Pro-inflammatory conditions induced by products of protein glycation in diabetes substantially enhance the risk of endothelial dysfunction and related vascular complications. Endothelial cell specific molecule-1 (ESM-1) or endocan has been demonstrated as a potential biomarker in cancer and sepsis. Its role in diabetes-induced pathologies remains unknown. The expression of ESM-1 gene is under cytokine regulation, indicating its role in endothelium-dependent pathological disorders. In this study, we investigated the effect of advanced glycated human serum albumin (AGE-HSA) on the production of ESM-1. We show that AGE-HSA exerts a modulating role on the expression of ESM-1 in human umbilical vein endothelial cells. It up-regulates expression of ESM-1 protein in a dose-dependent manner which correlates with its messenger RNA (mRNA) transcription. RAGE and galectin-3, both AGE receptors, show antagonistic action on its expression. While gene silencing of RAGE has down-regulatory effect, that of galectin-3 has up-regulatory effect on AGE-induced expression of ESM-1. Inhibition of MAPKKK and JNK pathways did not alter the expression. In contrast, phosphatidylinositol 3 kinase (PI3K) inhibition significantly up-regulated ESM-1 expression. In conclusion, these results suggest that AGE-induced activation of human umbilical vein endothelial cells promotes formation of endocan which is an endothelial dysfunction marker and may be related to vascular disease in diabetes.

Oxidative stress markers are increased in patients with mastocytosis

BACKGROUND

Mastocytosis is characterized by clonal proliferation of mast cells limited to the skin (cutaneous mastocytosis: CM and mastocytosis in the skin: MIS) and/or involving internal organs (systemic mastocytosis: SM). Oxidative stress occurring in various inflammatory and neoplastic disorders causes molecular damage with the production of advanced oxidation protein products (AOPPs) and advanced glycation end products (AGEs). We evaluated these markers of oxidative stress in patients with CM/MIS and SM and correlated their levels with the presence of symptoms related to mast cell activation.

METHODS

Serum levels of AOPPs and AGEs in 34 patients with mastocytosis (23 CM/MIS and 11 SM) and 27 healthy controls were measured by spectrofluorimetric and spectrophotometric methods. Serum tryptase levels were measured by immunofluorescence.

RESULTS

Serum AOPPs, but not AGEs, were significantly higher in patients with mastocytosis as compared to healthy controls. While serum tryptase levels were higher in patients with SM as compared to those with CM/MIS, there was no difference in AOPP and AGE concentrations between these two groups of patients. Patients with recurrent mediator-related symptoms had lower AOPPs and AGEs as compared to patients without symptoms. AOPPs and AGEs were inversely correlated with the severity of symptoms, and in patients with symptoms, AOPPs correlated with tryptase levels.

DISCUSSION

Our data show that mastocytosis is associated with a state of increased oxidative stress that, in patients with mediator-related symptoms, correlates with mast cell burden as assessed by tryptase. Patients with symptoms presumably have an adaptive response resulting in lower blood levels of AOPPs and AGEs.

Effects of sevelamer carbonate on advanced glycation end products and antioxidant/pro-oxidant status in patients with diabetic kidney disease

BACKGROUND AND OBJECTIVES

The primary goals were to re-examine whether sevelamer carbonate (SC) reduces advanced glycation end products (AGEs) (methylglyoxal and carboxymethyllysine [CML]), increases antioxidant defenses, reduces pro-oxidants, and improves hemoglobin A1c (HbA1c) in patients with type 2 diabetes mellitus (T2DM) and diabetic kidney disease (DKD). Secondary goals examined albuminuria, age, race, sex, and metformin prescription.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This two-center, randomized, intention-to-treat, open-label study evaluated 117 patients with T2DM (HbA1c >6.5%) and stages 2-4 DKD (urinary albumin/creatinine ratio ≥200 mg/g) treated with SC (1600 mg) or calcium carbonate (1200 mg), three times a day, without changing medications or diet. Statistical analyses used linear mixed models adjusted for randomization levels. Preselected subgroup analyses of sex, race, age, and metformin were conducted.

RESULTS

SC lowered serum methylglyoxal (95% confidence interval [CI], -0.72 to -0.29; P<0.001), serum CML (95% CI, -5.08 to -1.35; P≤0.001), and intracellular CML (95% CI, -1.63 to -0.28; P=0.01). SC increased anti-inflammatory defenses, including nuclear factor like-2 (95% CI, 0.58 to 1.29; P=0.001), AGE receptor 1 (95% CI, 0.23 to 0.96; P=0.001), NAD-dependent deacetylase sirtuin-1 (95% CI, 0.20 to 0.86; P=0.002), and estrogen receptor α (95% CI, 1.38 to 2.73; P ≤0.001). SC also decreased proinflammatory factors such as TNF receptor 1 (95% CI, -1.56 to -0.72; P≤0.001) and the receptor for AGEs (95% CI, -0.58 to 1.53; P≤0.001). There were no differences in HbA1c, GFR, or albuminuria in the overall group. Subanalyses showed that SC lowered HbA1c in women (95% CI, -1.71 to -0.27; P=0.01, interaction P=0.002), and reduced albuminuria in those aged <65 years (95% CI, -1.15 to -0.07; P=0.03, interaction P=0.02) and non-Caucasians (95% CI, -1.11 to -0.22; P=0.003, interaction P≤0.001), whereas albuminuria increased after SC and calcium carbonate in Caucasians.

CONCLUSIONS

SC reduced circulating and cellular AGEs, increased antioxidants, and decreased pro-oxidants, but did not change HbA1c or the albumin/creatinine ratio overall in patients with T2DM and DKD. Because subanalyses revealed that SC may reduce HbA1c and albuminuria in some patients with T2DM with DKD, further studies may be warranted.

Ginseng improves cognitive deficit via the RAGE/NF-κB pathway in advanced glycation end product-induced rats

BACKGROUND

Ginseng, the root of Panax ginseng (PG), is used widely as a herbal medicine to prevent and treat various diseases. Panax ginseng has pharmacological effects on neurodegenerative diseases such as Alzheimer's disease (AD). The present study evaluated the neuroprotective effects of PG and its possible neuroprotective mechanisms in advanced glycation end product (AGE)-induced AD in a rat model.

METHODS

Advanced glycation end products were injected bilaterally into the CA3 region of the rats' brains. The Morris water maze test and step-down type passive avoidance test were performed to evaluate their memory and cognitive abilities. The oxidation indexes in the hippocampus were detected. Immunohistochemistry was conducted to visualize the receptors for advanced glycation end products (RAGEs) and nuclear factor-kappa-light-chain-enhancer of activated B cell (NF-κB).

RESULTS

Behavioral results showed that PG (1 g/kg, 0.5 g/kg, and 0.25 g/kg) significantly shortened the escape latency, remarkably increased the number of crossing times, significantly decreased the number of errors, and prolonged the latency in rats with AGE-induced AD. Panax ginseng also significantly reduced the malondialdehyde level, increased the glutathione content, and increased superoxide dismutase activity in the hippocampus. Panax ginseng significantly decreased the expression of RAGE and NF-κB. The blockade of anti-RAGE antibody could significantly reduce AGE-induced impairments and regulate these expressions.

CONCLUSION

Our results demonstrated that PG significantly inhibits AGE-induced memory impairment and attenuates Alzheimer-like pathophysiological changes. These neuroprotective effects of PG may be associated with the RAGE/NF-κB pathway. Our results provided the experimental basis for applying PG in preventing and treating AD.

Nε-(carboxymethyl)lysine-receptor for advanced glycation end product axis is a key modulator of obesity-induced dysregulation of adipokine expression and insulin resistance

OBJECTIVE

Dysregulation of inflammatory adipokines by the adipose tissue plays an important role in obesity-associated insulin resistance. Pathways leading to this dysregulation remain largely unknown. We hypothesized that the receptor for advanced glycation end products (RAGE) and the ligand N(ε)-(carboxymethyl)lysine (CML) are increased in adipose tissue and, moreover, that activation of the CML-RAGE axis plays an important role in obesity-associated inflammation and insulin resistance.

APPROACH AND RESULTS

In this study, we observed a strong CML accumulation and increased expression of RAGE in adipose tissue in obesity. We confirmed in cultured human preadipocytes that adipogenesis is associated with increased levels of CML and RAGE. Moreover, CML induced a dysregulation of inflammatory adipokines in adipocytes via a RAGE-dependent pathway. To test the role of RAGE in obesity-associated inflammation further, we constructed an obese mouse model that is deficient for RAGE (ie, RAGE(-/-)/Leptr(Db-/-) mice). RAGE(-/-)/Leptr(Db-/-) mice displayed an improved inflammatory profile and glucose homeostasis when compared with RAGE(+/+)/Leptr(Db-/-) mice. In addition, CML was trapped in adipose tissue in RAGE(+/+)/Leptr(Db-/-) mice but not in RAGE(-/-)/Leptr(Db-/-). RAGE-mediated trapping in adipose tissue provides a mechanism underlying CML accumulation in adipose tissue and explaining decreased CML plasma levels in obese subjects. Decreased CML plasma levels in obese individuals were strongly associated with insulin resistance.

CONCLUSIONS

RAGE-mediated CML accumulation in adipose tissue and the activation of the CML-RAGE axis are important mechanisms involved in the dysregulation of adipokines in obesity, thereby contributing to the development of obesity-associated insulin resistance.

A review on plant-based rutin extraction methods and its pharmacological activities

ETHNOPHARMACOLOGICAL RELEVANCE

Rutin is a common dietary flavonoid that is widely consumed from plant-derived beverages and foods as traditional and folkloric medicine worldwide. Rutin is believed to exhibit significant pharmacological activities, including anti-oxidation, anti-inflammation, anti-diabetic, anti-adipogenic, neuroprotective and hormone therapy. Till date, over 130 registered therapeutic medicinal preparations are containing rutin in their formulations. This article aims to critically review the extraction methods for plant-based rutin and its pharmacological activities. This review provides comprehensive data on the performance of rutin extraction methods and the extent of its pharmacological activities using various in vitro and in vivo experimental models.

MATERIALS AND METHODS

Literatures including journals, patents, books and leaflets reporting on rutin from natural resources are systematically reviewed, particularly in the aspect of its extraction methods and biological activities. Factors affecting the efficiency of rutin extraction such as extraction temperature, duration and solvent to sample ratio are presented based on the findings of previous studies. The observed biological activities followed by clear explanation are also provided accordingly.

RESULTS

The biological activities of rutin varied largely dependent on the geographical and plant origins. The complexity of natural rutin has impeded the development of rutin derived drugs. The detail mechanism of rutin in human body after consumption is still unclear. Therefore, studies are intensively carried out both in vitro and in vivo for the better understanding of the underlying mechanism. The studies are not limited to the pharmacological properties, but also on the extraction methods of rutin. Many studies have focused on the optimization of extraction method to increase the extraction yield of rutin. Currently, the performances of modern extraction approaches have also been compared to the conventional heat reflux method as a benchmark.

CONCLUSION

There are various extraction methods for plant-based rutin ranging from conventional method up to the use of modern techniques such as ultrasound, mechanochemical, microwave, infrared and pressurized assisted methods. However, proper comparison between the methods is very difficult because of the variance in plant origin and extraction conditions. It is important to optimize the extraction method in order to produce high yield and acceptable purity of rutin with a reasonable cost. Even though rutin has been proven to be effective in numerous pharmacological activities, the dosage and toxicity of rutin for such activities are still unknown. Future research should relate the dosage and toxicity of rutin for the ethnobotanical claims based on the underlying mechanisms.

Identification of Maillard reaction products on peanut allergens that influence binding to the receptor for advanced glycation end products

BACKGROUND

Recent immunological data demonstrated that dendritic cells preferentially recognize advanced glycation end product (AGE)-modified proteins, upregulate expression of the receptor for AGE (RAGE), and consequently bias the immune response toward allergy.

METHODS

Peanut extract was characterized by mass spectrometry (MS) to elucidate the specific residues and specific AGE modifications found in raw and roasted peanuts and on rAra h 1 that was artificially glycated by incubation with glucose or xylose. The binding of the RAGE-V1C1 domain to peanut allergens was assessed by PAGE and Western analysis with anti-Ara h 1, 2, and 3 antibodies. IgE binding to rAra h 1 was also assessed using the same methods.

RESULTS

AGE modifications were found on Ara h 1 and Ara h 3 in both raw and roasted peanut extract. No AGE modifications were found on Ara h 2. Mass spectrometry and Western blot analysis demonstrated that RAGE binds selectively to Ara h 1 and Ara h 3 derived from peanut extract, whereas the analysis failed to demonstrate Ara h 2 binding to RAGE. rAra h 1 with no AGE modifications did not bind RAGE; however, after AGE modification with xylose, rAra h 1 bound to RAGE.

CONCLUSIONS

AGE modifications to Ara h 1 and Ara h 3 can be found in both raw and roasted peanuts. Receptor for AGE was demonstrated to selectively interact with AGE-modified rAra h 1. If sensitization to peanut allergens occurs in dendritic cells via RAGE interactions, these cells are likely interacting with modified Ara h 1 and Ara h 3, but not Ara h 2.

The neuroprotective effect of modified "Shengyu" decoction is mediated through an anti-inflammatory mechanism in the rat after traumatic brain injury

ETHNOPHARMACOLOGICAL RELEVANCE

"Shengyu" decoction, a traditional Chinese medicine, has been used to treat diseases with deficit in "qi" and "blood" induced frequently by profound loss of blood or by long sores with heavy pus, in which a potential anti-inflammatory effect is implied. The modified "Shengyu" decoction (MSD) used in the present study was designed on the basis of the "Shengyu" decoction, additional four herbs were added in. Many ingredients in these herbs have been demonstrated to be anti-inflammatory and thus MSD may be used for the treatment of traumatic brain injury (TBI). To evaluate the neuroprotective effect and the underlying mechanisms of MSD on the rat brain after TBI.

MATERIALS AND METHODS

TBI was induced in the right cerebral cortex of male adult rats using Feeney's weight-drop method. The rats were administered a gavage of MSD (0.5, 1.0 or 2.0 ml/200 g) 6h after TBI. The neurological functions, brain water content, contusion volume, and neuron loss were determined. The levels of TNF-α, IL-1β, IL-6, and IL-10 and the number of GFAP- and Iba1-positive cells in the brain ipsilateral to TBI were also measured. Moreover, the influence of MSD on these variables was observed at the same time.

RESULTS

The neurological deficits, brain water content, and neuron loss were significantly reduced after 1.0 or 2.0 ml/200 g of MSD treatment but not after 0.5 ml/200 g. In addition, treatment with MSD (1.0 ml/200 g) significantly increased the level of IL-10 and reduced the level of TNF-α and IL-1β and the number of GFAP- and Iba1-positive cells after TBI. However, the contusion volume of brain tissue and the expression of IL-6 were not significantly changed.

CONCLUSION

MSD may be a potential therapeutic for the treatment of TBI because MSD alleviated secondary brain injury induced by TBI. In addition, MSD inhibited the inflammatory response through reducing the expression of inflammatory cytokines and the activation of microglial cells and astrocytes in the brain tissue of rats after TBI. Therefore, a potential anti-inflammatory mechanism of the "Shengyu" decoction was confirmed, which may be one of the main reasons of "Shengyu" decoction used to treat diseases with obvious inflammatory responses.

Diet-derived advanced glycation end products or lipofuscin disrupts proteostasis and reduces life span in Drosophila melanogaster

Advanced glycation end product (AGE)-modified proteins are formed by the nonenzymatic glycation of free amino groups of proteins and, along with lipofuscin (a highly oxidized aggregate of covalently cross-linked proteins, sugars, and lipids), have been found to accumulate during aging and in several age-related diseases. As the in vivo effects of diet-derived AGEs or lipofuscin remain elusive, we sought to study the impact of oral administration of glucose-, fructose-, or ribose-modified albumin or of artificial lipofuscin in a genetically tractable model organism. We report herein that continuous feeding of young Drosophila flies with culture medium enriched in AGEs or in lipofuscin resulted in reduced locomotor performance and in accelerated rates of AGE-modified proteins and carbonylated proteins accumulation in the somatic tissues and hemolymph of flies, as well as in a significant reduction of flies health span and life span. These phenotypic effects were accompanied by reduced proteasome peptidase activities in both the hemolymph and the somatic tissues of flies and higher levels of oxidative stress; furthermore, oral administration of AGEs or lipofuscin in flies triggered an upregulation of the lysosomal cathepsin B, L activities. Finally, RNAi-mediated cathepsin D knockdown reduced flies longevity and significantly augmented the deleterious effects of AGEs and lipofuscin, indicating that lysosomal cathepsins reduce the toxicity of diet-derived AGEs or lipofuscin. Our in vivo studies demonstrate that chronic ingestion of AGEs or lipofuscin disrupts proteostasis and accelerates the functional decline that occurs with normal aging.

An update on oxidative stress-mediated organ pathophysiology

Exposure to environmental pollutants and drugs can result in pathophysiological situations in the body. Research in this area is essential as the knowledge on cellular survival and death would help in designing effective therapeutic strategies that are needed for the maintenance of the normal physiological functions of the body. In this regard, naturally occurring bio-molecules can be considered as potential therapeutic targets as they are normally available in commonly consumed foodstuffs and are thought to have minimum side effects. This review article describes the detailed mechanisms of oxidative stress-mediated organ pathophysiology and the ultimate fate of the cells either to survive or to undergo necrotic or apoptotic death. The mechanisms underlying the beneficial role of a number of naturally occurring bioactive molecules in oxidative stress-mediated organ pathophysiology have also been included in the review. The review provides useful information about the recent progress in understanding the mechanism(s) of various types of organ pathophysiology, the complex cross-talk between these pathways, as well as their modulation in stressed conditions. Additionally, it suggests possible therapeutic applications of a number of naturally occurring bioactive molecules in conditions involving oxidative stress.

Na+/H+ exchanger 1 inhibition reverses manifestation of peripheral diabetic neuropathy in type 1 diabetic rats

Evidence for an important role for Na(+)/H(+) exchangers in diabetic complications is emerging. The aim of this study was to evaluate whether Na(+)/H(+) exchanger 1 inhibition reverses experimental peripheral diabetic neuropathy. Control and streptozotocin-diabetic rats were treated with the specific Na(+)/H(+) exchanger 1 inhibitor cariporide for 4 wk after 12 wk without treatment. Neuropathy end points included sciatic motor and sensory nerve conduction velocities, endoneurial nutritive blood flow, vascular reactivity of epineurial arterioles, thermal nociception, tactile allodynia, and intraepidermal nerve fiber density. Advanced glycation end product and markers of oxidative stress, including nitrated protein levels in sciatic nerve, were evaluated by Western blot. Rats with 12-wk duration of diabetes developed motor and sensory nerve conduction deficits, thermal hypoalgesia, tactile allodynia, and intraepidermal nerve fiber loss. All these changes, including impairment of nerve blood flow and vascular reactivity of epineurial arterioles, were partially reversed by 4 wk of cariporide treatment. Na(+)/H(+) exchanger 1 inhibition was also associated with reduction of diabetes-induced accumulation of advanced glycation endproduct, oxidative stress, and nitrated proteins in sciatic nerve. In conclusion, these findings support an important role for Na(+)/H(+) exchanger 1 in functional, structural, and biochemical manifestations of peripheral diabetic neuropathy and provide the rationale for development of Na(+)/H(+) exchanger 1 inhibitors for treatment of diabetic vascular and neural complications.

Simultaneous analysis of Nε-(carboxymethyl)lysine, reducing sugars, and lysine during the dairy thermal process

A new analytical method allowing the simultaneous quantification of Nε-(carboxymethyl)lysine (CML), lysine, and reducing sugars (glucose, lactose, and galactose) is described. It is based on high performance anion-exchange chromatography with pulsed amperometric electrochemical detection. This method demonstrated a low limit of quantification (0.385 to 0.866 mg/L), excellent linear correlation (R(2)>0.997), and desired calibration range (3.125 to 25 mg/L). In addition, lactose-lysine solutions containing sulfite (4 to 400 mmol/L) were heated at 110°C for 2h. The results showed that sulfite inhibited the formation of CML and promoted the consumption of reducing sugars and lysine in the Maillard reaction model. The method proved to be useful for simultaneous analysis of CML, lysine, and reducing sugars (glucose, galactose, and lactose) in the Maillard reaction system. Moreover, sulfite was an effective inhibitor of CML formation.