Protein glycation: creation of catalytic sites for free radical generation

Targeting pericyte retention in Diabetic Retinopathy: a review

Diabetic retinopathy is a common yet severe complication of diabetes mellitus and is the leading cause of blindness in middle-aged adults. After years of poorly managed hyperglycemia, complications begin as non-proliferative diabetic retinopathy but can then progress into the proliferative stage marked by neovascularization of the retina. Multiple pathologic mechanisms caused by chronic hyperglycemia damage the retinal vasculature leading to pericyte drop out and the progression of the disease. This review outlines the major pathways of pathogenesis in diabetic retinopathy, highlighting the protective role pericytes play in preserving the blood-retinal barrier. Given the loss of this cell line is a defining feature of the disease, ways in which to prevent pericyte dropout within retinal vasculature is discussed, targeting various pathogenesis pathways of diabetic retinopathy.

Glyceraldehyde-3-phosphate dehydrogenase is involved in the pathogenesis of Alzheimer's disease

One of important characteristics of Alzheimer's disease is a persistent oxidative/nitrosative stress caused by pro-oxidant properties of amyloid-beta peptide (Aβ) and chronic inflammation in the brain. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is easily oxidized under oxidative stress. Numerous data indicate that oxidative modifications of GAPDH in vitro and in cell cultures stimulate GAPDH denaturation and aggregation, and the catalytic cysteine residue Cys152 is important for these processes. Both intracellular and extracellular GAPDH aggregates are toxic for the cells. Interaction of denatured GAPDH with soluble Aβ results in mixed insoluble aggregates with increased toxicity. The above-described properties of GAPDH (sensitivity to oxidation and propensity to form aggregates, including mixed aggregates with Aβ) determine its role in the pathogenesis of Alzheimer's disease.

Menstrual Blood-Derived Endometrial Stem Cell Transplantation Improves Male Reproductive Dysfunction in T1D Mice by Enhancing Antioxidative Capacity

Diabetes is known to negatively affect male reproduction. Recent clinical results have confirmed that mesenchymal stem cell (MSC)-based therapies are safe and effective for the treatment of diabetes. However, the effect and potential mechanism through which MSC transplantation improves diabetes-derived male reproductive dysfunction are still unknown. In the present study, we first established a male T1D mouse model through intraperitoneal injection of streptozotocin for five consecutive days. Subsequently, we evaluated the blood glucose levels, fertility, and histology and immunology of the pancreas, testes, and penis of T1D mice with or without transplantation of menstrual blood-derived endometrial stem cells (MenSCs) or umbilical cord mesenchymal stem cells (UCMSCs). Glucose was added to the medium in which the Leydig cells were cultured to imitate high glucose-injured cell viability. Subsequently, we evaluated the cellular viability, ROS levels, and mitochondrial membrane potential of Leydig cells treated with or without MenSC-conditioned medium (MenSC-CM) using a CCK8 assay, immunofluorescence, and flow cytometry. The targeted proteins are involved in the potential mechanism underlying MenSC-derived improvements, which was further validated via Western blotting. Collectively, our results indicated that MenSC transplantation significantly ameliorated reproductive dysfunction in male T1D mice by enhancing cellular antioxidative capacity and promoting angiogenesis. This study provides solid evidence and support for the application of MSCs to improve diabetes-induced male reproductive dysfunction.

Vitamin B6 and diabetes and its role in counteracting advanced glycation end products

Naturally occurring forms of vitamin B6 include six interconvertible water-soluble compounds: pyridoxine (PN), pyridoxal (PL), pyridoxamine (PM), and their respective monophosphorylated derivatives (PNP, PLP, and PMP). PLP is the catalytically active form which works as a cofactor in approximately 200 reactions that regulate the metabolism of glucose, lipids, amino acids, DNA, and neurotransmitters. Most of vitamers can counteract the formation of reactive oxygen species and the advanced glycation end-products (AGEs) which are toxic compounds that accumulate in diabetic patients due to prolonged hyperglycemia. Vitamin B6 levels have been inversely associate with diabetes, while vitamin B6 supplementation reduces diabetes onset and its vascular complications. The mechanisms at the basis of the relation between vitamin B6 and diabetes onset are still not completely clarified. In contrast more evidence indicates that vitamin B6 can protect from diabetes complications through its role as scavenger of AGEs. It has been demonstrated that in diabetes AGEs can destroy the functionality of macromolecules such as protein, lipids, and DNA, thus producing tissue damage that result in vascular diseases. AGEs can be in part also responsible for the increased cancer risk associated with diabetes. In this chapter the relationship between vitamin B6, diabetes and AGEs will be discussed by showing the acquired knowledge and questions that are still open.

Evaluation of the effects of dietary advanced glycation end products on inflammation

Advanced glycation end products (AGEs) are a large number of heterogeneous compounds formed by the glycation of proteins, fats or nucleic acids. Endogenous AGEs have been associated with various health problems such as obesity, type 2 diabetes mellitus and cardiovascular disease. Inflammation is thought to be one of the main mechanisms in the development of these disorders. Although AGEs are produced endogenously in the body, exogenous sources such as smoking and diet also contribute to the body pool. Therefore, when the AGE pool in the body rises above physiological levels, different pathological conditions may occur through various mechanisms, especially inflammation. While the effects of endogenous AGEs on the development of inflammation have been studied relatively extensively, and current evidence indicates that dietary AGEs (dAGEs) contribute to the body's AGE pool, it is not yet known whether dAGEs have the same effect on the development of inflammation as endogenous AGEs. Therefore, this review aimed to evaluate the results of cross-sectional and intervention studies to understand whether dAGEs are associated with inflammation and, if there is an effect on inflammation, through which mechanisms this effect might occur.

Dietary advanced glycation end products (dAGEs): An insight between modern diet and health

Advanced glycation end products (AGEs) are formed by a series of chemical reactions of amino acids, peptides, proteins, and ketones at normal temperature or heated non-enzymatic conditions. A large amount of AGEs derived from Maillard Reaction (MR) during the process of food heat-processing. After oral intake, dietary AGEs are converted into biological AGEs through digestion and absorption, and accumulated in almost all organs. The safety and health risk of dietary AGEs have attracted wide attention. Increasing evidence have shown that uptake of dietary AGEs is closely related to the occurrence of many chronic diseases, such as diabetes, chronic kidney disease, osteoporosis, and Alzheimer's disease. This review summarized the most updated information of production, bio-transport in vivo, detection technologies, and physiological toxicity of dietary AGEs, and also discussed approaches to inhibit dietary AGEs generation. Impressively, the future opportunities and challenges on the detection, toxicity, and inhibition of dietary AGEs are raised.

Current Approach to the Pathogenesis of Diabetic Cataracts

Cataracts remain the first or second leading cause of blindness in all world regions. In the diabetic population, cataracts not only have a 3–5 times higher incidence than in the healthy population but also affect people at a younger age. In patients with type 1 diabetes, cataracts occur on average 20 years earlier than in the non-diabetic population. In addition, the risk of developing cataracts increases with the duration of diabetes and poor metabolic control. A better understanding of the mechanisms leading to the formation of diabetic cataracts enables more effective treatment and a holistic approach to the patient.

Mechanism of inactivation of glyceraldehyde-3-phosphate dehydrogenase in the presence of methylglyoxal

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is known to be one of the targets of methylglyoxal (MGO), a metabolite of glycolysis that increased in diabetes. However, the mechanism of GAPDH inactivation in the presence of MGO is unclear. The purpose of the work was to study the reaction of GAPDH with MGO and to identify the products of the reaction. It was shown that incubation of recombinant human GAPDH with MGO leads to irreversible inactivation of the enzyme, which is accompanied by a decrease in SH-group content by approximately 3.3 per tetramer GAPDH. MALDI-TOF MS analysis showed that the modification of GAPDH with MGO results in the oxidation of the catalytic cysteine residues (Cys152) to form cysteine-sulfinic acid. In addition, 2 arginine residues (R80 and R234) were identified that react with MGO to form hydroimidazolones. Incubation of SH-SY5Y neuroblastoma cells with MGO resulted in the inactivation of GAPDH and inhibition of glycolysis. The mechanism of GAPDH oxidation in the presence of MGO suggests the participation of superoxide anion, which is formed during the reaction of amino groups with methylglyoxal. The role of GAPDH in protection against the damaging effect of ROS in cells in the case of inefficiency of MGO removal by the GSH-dependent glyoxalase system is discussed.

Potential mechanisms underlying the association between type II diabetes mellitus and cognitive dysfunction in rats: a link between miRNA-21 and Resveratrol's neuroprotective action

Cognitive impairment is considered as a typical feature of neurodegenerative diseases in diabetes mellitus (DM). However, the exact link between cognitive dysfunction and diabetes mellitus is still vague. This study aims to investigate some of the mechanisms underlying cognitive impairment that associates diabetes mellitus and insulin resistance. We investigated the role of resveratrol as well on cognitive function in experimentally induced type 2 diabetes highlighting on its influence on the expression of brain miRNA 21. Resveratrol is a naturally occurring, biologically active compound that has numerous significant impacts on the body. Type 2 diabetes mellitus was induced by high fat diet followed a single dose of streptozotocin. Diabetic rats were treated with resveratrol for four weeks. Rats were sacrificed after neurobehavioral testing. Hippocampal tissues were used to assess expression of miRNA 21, GSK and oxidative stress markers. Serum samples were obtained to determine glucose levels, lipid profile and insulin levels. Hippocampal and serum AGEs were measured as well and HOMA IR was calculated. We detected memory impairment and disturbed insulin signaling in diabetic rats. These derangements were reversed by resveratrol treatment partially due to increased expression of miRNA-21. Our study pins the role of miRNA-21 in modulating brain insulin signaling and hence alleviating cognitive dysfunction accompanying diabetes mellitus.

Advanced Glycation End Products: key player of the pathogenesis of atherosclerosis

Atherosclerosis is the most common type of cardiovascular disease, and it causes intima thickening, plaque development, and ultimate blockage of the artery lumen. Advanced glycation end products (AGEs) are thought to have a role in the development and progression of atherosclerosis. there is developing an enthusiasm for AGEs as a potential remedial target. AGES mainly induce arterial damage and exacerbate the development of atherosclerotic plaques by triggering cell receptor-dependent signalling. The interplay of AGEs with RAGE, a transmembrane signalling receptor present across all cells important to atherosclerosis, changes cell activity, boosts expression of genes, and increases the outflow of inflammatory compounds, resulting in arterial wall injury and plaque formation. Here in this review, function of AGEs in the genesis, progression, and instability of atherosclerosis is discussed. In endothelial and smooth muscle cells, as well as platelets, the interaction of AGEs with their transmembrane cell receptor, RAGE, triggers intracellular signalling, resulting in endothelial damage, vascular smooth muscle cell function modification, and changed platelet activity.

Oxidative stress in the pathophysiology of type 2 diabetes and related complications: Current therapeutics strategies and future perspectives

Type 2 diabetes (T2DM) is a persistent metabolic disorder rising rapidly worldwide. It is characterized by pancreatic insulin resistance and β-cell dysfunction. Hyperglycemia induced reactive oxygen species (ROS) production and oxidative stress are correlated with the pathogenesis and progression of this metabolic disease. To counteract the harmful effects of ROS, endogenous antioxidants of the body or exogenous antioxidants neutralise it and maintain bodily homeostasis. Under hyperglycemic conditions, the imbalance between the cellular antioxidant system and ROS production results in oxidative stress, which subsequently results in the development of diabetes. These ROS are produced in the endoplasmic reticulum, phagocytic cells and peroxisomes, with the mitochondrial electron transport chain (ETC) playing a pivotal role. The exacerbated ROS production can directly cause structural and functional modifications in proteins, lipids and nucleic acids. It also modulates several intracellular signaling pathways that lead to insulin resistance and impairment of β-cell function. In addition, the hyperglycemia-induced ROS production contributes to micro- and macro-vascular diabetic complications. Various in-vivo and in-vitro studies have demonstrated the anti-oxidative effects of natural products and their derived bioactive compounds. However, there is conflicting clinical evidence on the beneficial effects of these antioxidant therapies in diabetes prevention. This review article focused on the multifaceted role of oxidative stress caused by ROS overproduction in diabetes and related complications and possible antioxidative therapeutic strategies targeting ROS in this disease.

Advanced Glycation End Products and Diabetes Mellitus: Mechanisms and Perspectives

Persistent hyperglycemic state in type 2 diabetes mellitus leads to the initiation and progression of non-enzymatic glycation reaction with proteins and lipids and nucleic acids. Glycation reaction leads to the generation of a heterogeneous group of chemical moieties known as advanced glycated end products (AGEs), which play a central role in the pathophysiology of diabetic complications. The engagement of AGEs with its chief cellular receptor, RAGE, activates a myriad of signaling pathways such as MAPK/ERK, TGF-β, JNK, and NF-κB, leading to enhanced oxidative stress and inflammation. The downstream consequences of the AGEs/RAGE axis involve compromised insulin signaling, perturbation of metabolic homeostasis, RAGE-induced pancreatic beta cell toxicity, and epigenetic modifications. The AGEs/RAGE signaling instigated modulation of gene transcription is profoundly associated with the progression of type 2 diabetes mellitus and pathogenesis of diabetic complications. In this review, we will summarize the exogenous and endogenous sources of AGEs, their role in metabolic dysfunction, and current understandings of AGEs/RAGE signaling cascade. The focus of this review is to recapitulate the role of the AGEs/RAGE axis in the pathogenesis of type 2 diabetes mellitus and its associated complications. Furthermore, we present an overview of future perspectives to offer new therapeutic interventions to intervene with the AGEs/RAGE signaling pathway and to slow down the progression of diabetes-related complications.

Fisetin, potential flavonoid with multifarious targets for treating neurological disorders: An updated review

Neurodegenerative disorders pose a significant health burden and imprint a debilitative impact on the quality of life. Importantly, aging is intricately intertwined with the progression of these disorders, and their prevalence increases with a rise in the aging population worldwide. In recent times, fisetin emerged as one of the potential miracle molecules to address neurobehavioral and cognitive abnormalities. These effects were attributed to its actions on several macromolecules and multiple molecular mechanisms. Fisetin belongs to a class of flavonoids, which is found abundantly in several fruits and vegetables. Fisetin has manifested several health benefits in preclinical models of neurodegenerative diseases such as Alzheimer's disease, Vascular dementia, and Schizophrenia. Parkinson's disease, Amyotrophic Lateral Sclerosis, Huntington's disease, Stroke, Traumatic Brain Injury (TBI), and age-associated changes. This review aimed to evaluate the potential mechanisms and pharmacological effects of fisetin in treating several neurological diseases. This review also provides comprehensive data on up-to-date recent literature and highlights the various mechanistic pathways pertaining to fisetin's neuroprotective role.

Protein posttranslational modification (PTM) by glycation: Role in lens aging and age-related cataractogenesis

Crystallins, the most prevalent lens proteins, have no turnover throughout the entire human lifespan. These long-lived proteins are susceptible to post-synthetic modifications, including oxidation and glycation, which are believed to be some of the primary mechanisms for age-related cataractogenesis. Thanks to high glutathione (GSH) and ascorbic acid (ASA) levels as well as low oxygen content, the human lens is able to maintain its transparency for several decades. Aging accumulates substantial changes in the human lens, including a decreased glutathione concentration, increased reactive oxygen species (ROS) formation, impaired antioxidative defense capacity, and increased redox-active metal ions, which induce glucose and ascorbic acid degradation and protein glycation. The glycated lens crystallins are either prone to UVA mediated free radical production or they attract metal ion binding, which can trigger additional protein oxidation and modification. This vicious cycle is expected to be exacerbated with older age or diabetic conditions. ASA serves as an antioxidant in the human lens under reducing conditions to protect the human lens from damage, but ASA converts to the pro-oxidative role and causes lens protein damage by ascorbylation in high oxidation or enriched redox-active metal ion conditions. This review is dedicated in honor of Dr. Frank Giblin, a great friend and superb scientist, whose pioneering and relentless work over the past 45 years has provided critical insight into lens redox regulation and glutathione homeostasis during aging and cataractogenesis.

The Taming of Nuclear Factor Erythroid-2-Related Factor-2 (Nrf2) Deglycation by Fructosamine-3-Kinase (FN3K)-Inhibitors-A Novel Strategy to Combat Cancers

Simple Summary

Aim of this review is to provide an overview on (a) Fructosamine-3-Kinase (FN3K) and its role in regulating Nuclear Factor Erythorid-2-Related Factor-2 (Nrf2); (b) the role of glycation and deglycation mechanisms in modulating the functional properties of proteins, in particular, the Nrf2; (c) the dual role of Nrf2 in the prevention and treatment of cancers. Since controlling the glycation of Nrf2 is one of the key mechanisms determining the fate of a cell; whether to get transformed into a cancerous one or to stay as a normal one, it is important to regulate Nrf2 and deglycating FN3K using pharmacological agents. Inhibitors of FN3K are being explored currently to modulate Nrf2 activity thereby control the cancers.

Abstract

Glycated stress is mediated by the advanced glycation end products (AGE) and the binding of AGEs to the receptors for advanced glycation end products (RAGEs) in cancer cells. RAGEs are involved in mediating tumorigenesis of multiple cancers through the modulation of several downstream signaling cascades. Glycated stress modulates various signaling pathways that include p38 mitogen-activated protein kinase (p38 MAPK), nuclear factor kappa–B (NF-κB), tumor necrosis factor (TNF)-α, etc., which further foster the uncontrolled proliferation, growth, metastasis, angiogenesis, drug resistance, and evasion of apoptosis in several cancers. In this review, a balanced overview on the role of glycation and deglycation in modulating several signaling cascades that are involved in the progression of cancers was discussed. Further, we have highlighted the functional role of deglycating enzyme fructosamine-3-kinase (FN3K) on Nrf2-driven cancers. The activity of FN3K is attributed to its ability to deglycate Nrf2, a master regulator of oxidative stress in cells. FN3K is a unique protein that mediates deglycation by phosphorylating basic amino acids lysine and arginine in various proteins such as Nrf2. Deglycated Nrf2 is stable and binds to small musculoaponeurotic fibrosarcoma (sMAF) proteins, thereby activating cellular antioxidant mechanisms to protect cells from oxidative stress. This cellular protection offered by Nrf2 activation, in one way, prevents the transformation of a normal cell into a cancer cell; however, in the other way, it helps a cancer cell not only to survive under hypoxic conditions but also, to stay protected from various chemo- and radio-therapeutic treatments. Therefore, the activation of Nrf2 is similar to a double-edged sword and, if not controlled properly, can lead to the development of many solid tumors. Hence, there is a need to develop novel small molecule modulators/phytochemicals that can regulate FN3K activity, thereby maintaining Nrf2 in a controlled activation state.

The Development of Maillard Reaction, and Advanced Glycation End Product (AGE)-Receptor for AGE (RAGE) Signaling Inhibitors as Novel Therapeutic Strategies for Patients with AGE-Related Diseases

Advanced glycation end products (AGEs) are generated by nonenzymatic modifications of macromolecules (proteins, lipids, and nucleic acids) by saccharides (glucose, fructose, and pentose) via Maillard reaction. The formed AGE molecules can be catabolized and cleared by glyoxalase I and II in renal proximal tubular cells. AGE-related diseases include physiological aging, neurodegenerative/neuroinflammatory diseases, diabetes mellitus (DM) and its complications, autoimmune/rheumatic inflammatory diseases, bone-degenerative diseases, and chronic renal diseases. AGEs, by binding to receptors for AGE (RAGEs), alter innate and adaptive immune responses to induce inflammation and immunosuppression via the generation of proinflammatory cytokines, reactive oxygen species (ROS), and reactive nitrogen intermediates (RNI). These pathological molecules cause vascular endothelial/smooth muscular/connective tissue-cell and renal mesangial/endothelial/podocytic-cell damage in AGE-related diseases. In the present review, we first focus on the cellular and molecular bases of AGE–RAGE axis signaling pathways in AGE-related diseases. Then, we discuss in detail the modes of action of newly discovered novel biomolecules and phytochemical compounds, such as Maillard reaction and AGE–RAGE signaling inhibitors. These molecules are expected to become the new therapeutic strategies for patients with AGE-related diseases in addition to the traditional hypoglycemic and anti-hypertensive agents. We particularly emphasize the importance of “metabolic memory”, the “French paradox”, and the pharmacokinetics and therapeutic dosing of the effective natural compounds associated with pharmacogenetics in the treatment of AGE-related diseases. Lastly, we propose prospective investigations for solving the enigmas in AGE-mediated pathological effects.

Mechanical and structural changes in human thoracic aortas with age

Aortic mechanical and structural characteristics have profound effects on pathophysiology, but many aspects of physiologic stress-stretch state and intramural changes due to aging remain poorly understood in human tissues. While difficult to assess in vivo due to residual stresses and pre-stretch, physiologic stress-stretch characteristics can be calculated using experimentally-measured mechanical properties and constitutive modeling. Mechanical properties of 76 human descending thoracic aortas (TA) from 13 to 78-year-old donors (mean age 51±18 years) were measured using multi-ratio planar biaxial extension. Constitutive parameters were derived for aortas in 7 age groups, and the physiologic stress-stretch state was calculated. Intramural characteristics were quantified from histological images and related to aortic morphometry and mechanics. TA stiffness increased with age, and aortas became more nonlinear and anisotropic. Systolic and diastolic elastic energy available for pulsation decreased with age from 30 to 8 kPa and from 18 to 5 kPa, respectively. Cardiac cycle circumferential stretch dropped from 1.14 to 1.04, and circumferential and longitudinal physiologic stresses decreased with age from 90 to 72 kPa and from 90 to 17 kPa, respectively. Aortic wall thickness and radii increased with age, while the density of elastin in the tunica media decreased. The number of elastic lamellae and circumferential physiologic stress per lamellae unit remained constant with age at 102±10 and 0.85±0.04 kPa, respectively. Characterization of mechanical, physiological, and structural features in human aortas of different ages can help understand aortic pathology, inform the development of animal models that simulate human aging, and assist with designing devices for open and endovascular aortic repairs. STATEMENT OF SIGNIFICANCE: This manuscript describes mechanical and structural changes occurring in human thoracic aortas with age, and presents material parameters for 4 commonly used constitutive models. Presented data can help better understand aortic pathology, inform the development of animal models that simulate human aging, and assist with designing devices for open and endovascular aortic repairs.

Advanced Glycation End Products in Chinese Medicine Mediated Aging Diseases: A Review

Aging has become a worldwide problem. During this process, the incidence of related diseases such as diabetes and atherosclerosis increases dramatically. Studies within the most recent two decades suggest a pivotal role of Advanced Glycation End Products (AGEs) in the aging process. This review aims to systemically summarize the effects and potential mechanism of Chinese Medicines on inhibiting AGEs-related aging diseases.

Dietary Advanced Glycation End Products: Digestion, Metabolism and Modulation of Gut Microbial Ecology

The formation of advanced glycation end products (AGEs) in foods is accelerated with heat treatment, particularly within foods that are cooked at high temperatures for long periods of time using dry heat. The modern processed diet is replete with AGEs, and excessive AGE consumption is thought to be associated with a number of negative health effects. Many dietary AGEs have high molecular weight and are not absorbed in the intestine, and instead pass through to the colon, where they are available for metabolism by the colonic bacteria. Recent studies have been conducted to explore the effects of AGEs on the composition of the gut microbiota as well as the production of beneficial microbial metabolites, in particular, short-chain fatty acids. However, there is conflicting evidence regarding the impact of dietary AGEs on gut microbiota reshaping, which may be due, in part, to the formation of alternate compounds during the thermal treatment of foods. This review summarises the current evidence regarding dietary sources of AGEs, their gastrointestinal absorption and role in gut microbiota reshaping, provides a brief overview of the health implications of dietary AGEs and highlights knowledge gaps and avenues for future study.

Reduced salivary amylase activity in metabolic syndrome patients with obesity could be improved by treatment with a dipeptidyl peptidase IV inhibitor

OBJECTIVES

The present study is to investigate the salivary gland function of metabolic syndrome (MetS) patients, as indicated by salivary flow rate, amylase activity, and salivary oxidative stress, by measuring MDA level.

MATERIALS AND METHODS

One hundred and eighty-one MetS patients from Maharaj Nakorn Chiang Mai Hospital were enrolled onto this study. The metabolic parameters of each patient were collected and evaluated. Unstimulated saliva was also collected for 5 min. Salivary gland functions, including salivary flow rate, amylase activity, and salivary MDA levels, were investigated.

RESULTS

High levels of triglycerides, high-density lipoprotein, blood pressure, and waist circumference in MetS patients did not show a correlation with altered salivary gland function. However, a decrease in salivary flow rate was observed in MetS patients with hyperglycemia. In addition, decreased amylase activity was found in MetS patients with obesity (BMI ≥ 23 kg/m²). Salivary amylase activity of MetS patients treated with dipeptidyl peptidase IV (DPP-IV) inhibitor was significantly greater than that observed in MetS patients without a DPP-IV inhibitor. Moreover, the salivary amylase activity in MetS patients was found to be independently positively correlated with DPP-IV inhibitor therapy (r = 0.708, p < 0.01).

CONCLUSION

These findings suggest that obesity and hyperglycemia in MetS patients were associated with the impairment of salivary glands. Treatment with a DPP-IV inhibitor was found to exert beneficial effects on the salivary gland.

CLINICAL RELEVANCE

This study demonstrated the impairment of salivary glands of MetS patients and the beneficial effect of DPP-IV inhibitor treatment in the salivary glands.

Comparative Genomics of Sibling Species of Fonsecaea Associated with Human Chromoblastomycosis

Fonsecaea and Cladophialophora are genera of black yeast-like fungi harboring agents of a mutilating implantation disease in humans, along with strictly environmental species. The current hypothesis suggests that those species reside in somewhat adverse microhabitats, and pathogenic siblings share virulence factors enabling survival in mammal tissue after coincidental inoculation driven by pathogenic adaptation. A comparative genomic analysis of environmental and pathogenic siblings of Fonsecaea and Cladophialophora was undertaken, including de novo assembly of F. erecta from plant material. The genome size of Fonsecaea species varied between 33.39 and 35.23 Mb, and the core genomes of those species comprises almost 70% of the genes. Expansions of protein domains such as glyoxalases and peptidases suggested ability for pathogenicity in clinical agents, while the use of nitrogen and degradation of phenolic compounds was enriched in environmental species. The similarity of carbohydrate-active vs. protein-degrading enzymes associated with the occurrence of virulence factors suggested a general tolerance to extreme conditions, which might explain the opportunistic tendency of Fonsecaea sibling species. Virulence was tested in the Galleria mellonella model and immunological assays were performed in order to support this hypothesis. Larvae infected by environmental F. erecta had a lower survival. Fungal macrophage murine co-culture showed that F. erecta induced high levels of TNF-α contributing to macrophage activation that could increase the ability to control intracellular fungal growth although hyphal death were not observed, suggesting a higher level of extremotolerance of environmental species.

A Perspective on Reagent Diversity and Non-covalent Binding of Reactive Carbonyl Species (RCS) and Effector Reagents in Non-enzymatic Glycation (NEG): Mechanistic Considerations and Implications for Future Research

This perspective focuses on illustrating the underappreciated connections between reactive carbonyl species (RCS), initial binding in the nonenzymatic glycation (NEG) process, and nonenzymatic covalent protein modification (here termed NECPM). While glucose is the central species involved in NEG, recent studies indicate that the initially-bound glucose species in the NEG of human hemoglobin (HbA) and human serum albumin (HSA) are non-RCS ring-closed isomers. The ring-opened glucose, an RCS structure that reacts in the NEG process, is most likely generated from previously-bound ring-closed isomers undergoing concerted acid/base reactions while bound to protein. The generation of the glucose RCS can involve concomitantly-bound physiological species (e.g., inorganic phosphate, water, etc.); here termed effector reagents. Extant NEG schemes do not account for these recent findings. In addition, effector reagent reactions with glucose in the serum and erythrocyte cytosol can generate RCS (e.g., glyoxal, glyceraldehyde, etc.). Recent research has shown that these RCS covalently modify proteins in vivo via NECPM mechanisms. A general scheme that reflects both the reagent and mechanistic diversity that can lead to NEG and NECPM is presented here. A perspective that accounts for the relationships between RCS, NEG, and NECPM can facilitate the understanding of site selectivity, may help explain overall glycation rates, and may have implications for the clinical assessment/control of diabetes mellitus. In view of this perspective, concentrations of ribose, fructose, Pi, bicarbonate, counter ions, and the resulting RCS generated within intracellular and extracellular compartments may be of importance and of clinical relevance. Future research is also proposed.

Targeting cannabinoid signaling for peritoneal dialysis-induced oxidative stress and fibrosis

Long-term exposure to bioincompatible peritoneal dialysis (PD) solutions frequently results in peritoneal fibrosis and ultrafiltration failure, which limits the life-long use of and leads to the cessation of PD therapy. Therefore, it is important to elucidate the pathogenesis of peritoneal fibrosis in order to design therapeutic strategies to prevent its occurrence. Peritoneal fibrosis is associated with a chronic inflammatory status as well as an elevated oxidative stress (OS) status. Beyond uremia per se, OS also results from chronic exposure to high glucose load, glucose degradation products, advanced glycation end products, and hypertonic stress. Therapy targeting the cannabinoid (CB) signaling pathway has been reported in several chronic inflammatory diseases with elevated OS. We recently reported that the intra-peritoneal administration of CB receptor ligands, including CB₁ receptor antagonists and CB₂ receptor agonists, ameliorated dialysis-related peritoneal fibrosis. As targeting the CB signaling pathway has been reported to be beneficial in attenuating the processes of several chronic inflammatory diseases, we reviewed the interaction among the cannabinoid system, inflammation, and OS, through which clinicians ultimately aim to prolong the peritoneal survival of PD patients.

Schiff bases of putrescine with methylglyoxal protect from cellular damage caused by accumulation of methylglyoxal and reactive oxygen species in Dictyostelium discoideum

Polyamines protect protein glycation in cells against the advanced glycation end product precursor methylglyoxal, which is inevitably produced during glycolysis, and the enzymes that detoxify this α-ketoaldehyde have been widely studied. Nonetheless, nonenzymatic methylglyoxal-scavenging molecules have not been sufficiently studied either in vitro or in vivo. Here, we hypothesized reciprocal regulation between polyamines and methylglyoxal modeled in Dictyostelium grown in a high-glucose medium. We based our hypothesis on the reaction between putrescine and methylglyoxal in putrescine-deficient (odc^-) or putrescine-overexpressing (odc^oe) cells. In these strains, growth and cell cycle were found to be dependent on cellular methylglyoxal and putrescine contents. The odc^- cells showed growth defects and underwent G1 phase cell cycle arrest, which was efficiently reversed by exogenous putrescine. Cellular methylglyoxal, reactive oxygen species (ROS), and glutathione levels were remarkably changed in odc^oe cells and odc̄ cells. These results revealed that putrescine may act as an intracellular scavenger of methylglyoxal and ROS. Herein, we observed interactions of putrescine and methylglyoxal via formation of a Schiff base complex, by UV-vis spectroscopy, and confirmed this adduct by liquid chromatography with mass spectrometry via electrospray ionization. Schiff bases were isolated, analyzed, and predicted to have molecular masses ranging from 124 to 130. We showed that cellular putrescine-methylglyoxal Schiff bases were downregulated in proportion to the levels of endogenous or exogenous putrescine and glutathione in the odc mutants. The putrescine-methylglyoxal Schiff base affected endogenous metabolite levels. This is the first report showing that cellular methylglyoxal functions as a signaling molecule through reciprocal interactions with polyamines by forming Schiff bases.

Food-advanced glycation end products aggravate the diabetic vascular complications via modulating the AGEs/RAGE pathway

The aim of this study was to investigate the effects of high-advanced glycation end products (AGEs) diet on diabetic vascular complications. The Streptozocin (STZ)-induced diabetic mice were fed with high-AGEs diet. Diabetic characteristics, indicators of renal and cardiovascular functions, and pathohistology of pancreas, heart and renal were evaluated. AGEs/RAGE/ROS pathway parameters were determined. During the experiments, the diabetic mice exhibited typical characteristics including weight loss, polydipsia, polyphagia, polyuria, high-blood glucose, and low-serum insulin levels. However, high-AGEs diet effectively aggravated these diabetic characteristics. It also increased the 24-h urine protein levels, serum levels of urea nitrogen, creatinine, c-reactive protein (CRP), low density lipoprotein (LDL), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in the diabetic mice. High-AGEs diet deteriorated the histology of pancreas, heart, and kidneys, and caused structural alterations of endothelial cells, mesangial cells and podocytes in renal cortex. Eventually, high-AGEs diet contributed to the high-AGE levels in serum and kidneys, high-levels of reactive oxygen species (ROS) and low-levels of superoxide dismutase (SOD) in serum, heart, and kidneys. It also upregulated RAGE mRNA and protein expression in heart and kidneys. Our results showed that high-AGEs diet deteriorated vascular complications in the diabetic mice. The activation of AGEs/RAGE/ROS pathway may be involved in the pathogenesis of vascular complications in diabetes.

Effect of diet-derived advanced glycation end products on inflammation

Advanced glycation end products (AGEs) formed via the Maillard reaction during the thermal processing of food contributes to the flavor, color, and aroma of food. A proportion of food-derived AGEs and their precursors is intestinally absorbed and accumulates within cells and tissues. AGEs have been implicated in the pathogenesis of diabetes-related complications and several chronic diseases via interaction with the receptor for AGEs, which promotes the transcription of genes that control inflammation. The dicarbonyls, highly reactive intermediates of AGE formation, are also generated during food processing and may incite inflammatory responses through 1) the suppression of protective pathways, 2) the incretin axis, 3) the modulation of immune-mediated signaling, and 4) changes in gut microbiota profile and metabolite sensors. In animal models, restriction of dietary AGEs attenuates chronic low-grade inflammation, but current evidence from human studies is less clear. Here, the emerging relationship between excess dietary AGE consumption and inflammation is explored, the utility of dietary AGE restriction as a therapeutic strategy for the attenuation of chronic diseases is discussed, and possible avenues for future investigation are suggested.

Vitamin B and its derivatives for diabetic kidney disease

BACKGROUND

Diabetes is a leading cause of end-stage kidney disease (ESKD) mainly due to development and progression of diabetic kidney disease (DKD). In absence of definitive treatments of DKD, small studies showed that vitamin B may help in delaying progression of DKD by inhibiting vascular inflammation and endothelial cell damage. Hence, it could be beneficial as a treatment option for DKD.

OBJECTIVES

To assess the benefits and harms of vitamin B and its derivatives in patients with DKD.

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register to 29 October 2012 through contact with the Trials' Search Co-ordinator using search terms relevant to this review.

SELECTION CRITERIA

We included randomised controlled trials comparing vitamin B or its derivatives, or both with placebo, no treatment or active treatment in patients with DKD. We excluded studies comparing vitamin B or its derivatives, or both among patients with pre-existing ESKD.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study eligibility, risk of bias and extracted data. Results were reported as risk ratio (RR) or risk differences (RD) with 95% confidence intervals (CI) for dichotomous outcomes and mean difference (MD) with 95% CI for continuous outcomes. Statistical analyses were performed using the random-effects model.

MAIN RESULTS

Nine studies compared 1354 participants randomised to either vitamin B or its derivatives with placebo or active control were identified. A total of 1102 participants were randomised to single vitamin B derivatives, placebo or active control in eight studies, and 252 participants randomised to multiple vitamin B derivatives or placebo. Monotherapy included different dose of pyridoxamine (four studies), benfotiamine (1), folic acid (1), thiamine (1), and vitamin B12 (1) while combination therapy included folic acid, vitamin B6, and vitamin B12 in one study. Treatment duration ranged from two to 36 months. Selection bias was unclear in three studies and low in the remaining six studies. Two studies reported blinding of patient, caregiver and observer and were at low risk of performance and detection bias, two studies were at high risk bias, and five studies were unclear. Attrition bias was high in one study, unclear in one study and low in seven studies. Reporting bias was high in one study, unclear in one study, and low in the remaining seven studies. Four studies funded by pharmaceutical companies were judged to be at high risk bias, three were at low risk of bias, and two were unclear.Only a single study reported a reduction in albuminuria with thiamine compared to placebo, while second study reported reduction in glomerular filtration rate (GFR) following use of combination therapy. No significant difference in the risk of all-cause mortality with pyridoxamine or combination therapy was reported. None of the vitamin B derivatives used either alone or in combination improved kidney function: increased in creatinine clearance, improved the GFR; neither were effective in controlling blood pressure significantly compared to placebo or active control. One study reported a significant median reduction in urinary albumin excretion with thiamine treatment compared to placebo. No significant difference was found between vitamin B combination therapy and control group for serious adverse events, or one or more adverse event per patient. Vitamin B therapy was reported to well-tolerated with mild side effects in studies with treatment duration of more than six months. Studies of less than six months duration did not explicitly report adverse events; they reported that the drugs were well-tolerated without any serious drug related adverse events. None of the included studies reported cardiovascular death, progression from macroalbuminuria to ESKD, progression from microalbuminuria to macroalbuminuria, regression from microalbuminuria to normoalbuminuria, doubling of SCr, and quality of life. We were not able to perform subgroup or sensitivity analyses or assess publication bias due to insufficient data.

AUTHORS' CONCLUSIONS

There is an absence of evidence to recommend the use of vitamin B therapy alone or combination for delaying progression of DKD. Thiamine was found to be beneficial for reduction in albuminuria in a single study; however, there was lack of any improvement in kidney function or blood pressure following the use of vitamin B preparations used alone or in combination. These findings require further confirmation given the limitations of the small number and poor quality of the available studies.

Chemical reactivity drives spatiotemporal organisation of bacterial metabolism

In this review, we examine how bacterial metabolism is shaped by chemical constraints acting on the material and dynamic layout of enzymatic networks and beyond. These are moulded not only for optimisation of given metabolic objectives (e.g. synthesis of a particular amino acid or nucleotide) but also for curbing the detrimental reactivity of chemical intermediates. Besides substrate channelling, toxicity is avoided by barriers to free diffusion (i.e. compartments) that separate otherwise incompatible reactions, along with ways for distinguishing damaging vs. harmless molecules. On the other hand, enzymes age and their operating lifetime must be tuned to upstream and downstream reactions. This time dependence of metabolic pathways creates time-linked information, learning and memory. These features suggest that the physical structure of existing biosystems, from operon assemblies to multicellular development may ultimately stem from the need to restrain chemical damage and limit the waste inherent to basic metabolic functions. This provides a new twist of our comprehension of fundamental biological processes in live systems as well as practical take-home lessons for the forward DNA-based engineering of novel biological objects.

The interplay between hyperglycemia-induced oxidative stress markers and the level of soluble receptor for advanced glycation end products (sRAGE) in K562 cells

Formation and accumulation of advanced glycation end-products (AGE) and also generation of reactive oxygen species (ROS), the main causative players in the context of diabetes, are intensified under hyperglycemic condition. The consequences from AGE/RAGE interaction could be attenuated by the soluble form of RAGE, termed sRAGE. In the current study, we studied the link between hyperglycemia-induced oxidative stress and the level of soluble form of RAGE in K562 cells. Our data revealed a positive correlation between high glucose and/or AGE-modified albumin treatment and oxidative stress status. Besides, a significant decrease in soluble RAGE level following treatments with either AGE-modified albumin or high glucose was observed. However, pretreatment with an appropriate antioxidant such as Resveratrol, markedly elevated the sRAGE level. Hence, sRAGE therapy could be further evaluated as an effective therapeutical approach to attenuate some of the diabetes complications.

Effect of dietary prebiotic supplementation on advanced glycation, insulin resistance and inflammatory biomarkers in adults with pre-diabetes: a study protocol for a double-blind placebo-controlled randomised crossover clinical trial

BACKGROUND

Advanced glycation endproducts (AGEs) contribute to the development of vascular complications of diabetes and have been recently implicated in the pathogenesis of diabetes. Since AGEs are generated within foodstuffs upon food processing, it is increasingly recognised that the modern diet is replete with AGEs. AGEs are thought to stimulate chronic low-grade inflammation and promote oxidative stress and have been linked to the development of insulin resistance. Simple therapeutic strategies targeted at attenuating the progression of chronic low-grade inflammation and insulin resistance are urgently required to prevent or slow the development of type 2 diabetes in susceptible individuals. Dietary modulation of the human colonic microbiota has been shown to confer a number of health benefits to the host, but its effect on advanced glycation is unknown. The aim of this article is to describe the methodology of a double-blind placebo-controlled randomised crossover trial designed to determine the effect of 12 week consumption of a prebiotic dietary supplement on the advanced glycation pathway, insulin sensitivity and chronic low-grade inflammation in adults with pre-diabetes.

METHODS/DESIGN

Thirty adults with pre-diabetes (Impaired Glucose Tolerance or Impaired Fasting Glucose) aged between 40-60 years will be randomly assigned to receive either 10 grams of prebiotic (inulin/oligofructose) daily or 10 grams placebo (maltodextrin) daily for 12 weeks. After a 2-week washout period, study subjects will crossover to receive the alternative dietary treatment for 12 weeks. The primary outcome is the difference in markers of the advanced glycation pathway carboxymethyllysine (CML) and methylglyoxal (MG) between experimental and control treatments. Secondary outcomes include HbA1c, insulin sensitivity, lipid levels, blood pressure, serum glutathione, adiponectin, IL-6, E-selectin, myeloperoxidase, C-reactive protein, Toll-like Receptor 4 (TLR4), soluble receptor for AGE (sRAGE), urinary 8-isoprostanes, faecal bacterial composition and short chain fatty acid profile. Anthropometric measures including BMI and waist circumference will be collected in addition to comprehensive dietary and lifestyle data.

DISCUSSION

Prebiotics which selectively stimulate the growth of beneficial bacteria in the human colon might offer protection against AGE-related pathology in people at risk of developing type 2 diabetes.

TRIAL REGISTRATION

Australia and New Zealand Clinical Trials Register (ANZCTR): ACTRN12613000130763.

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

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

Reactive carbonyl species in vivo: generation and dual biological effects

Reactive carbonyls are widespread species in living organisms and mainly known for their damaging effects. The most abundant reactive carbonyl species (RCS) are derived from oxidation of carbohydrates, lipids, and amino acids. Chemical modification of proteins, nucleic acids, and aminophospholipids by RCS results in cytotoxicity and mutagenicity. In addition to their direct toxicity, modification of biomolecules by RCS gives rise to a multitude of adducts and cross links that are increasingly implicated in aging and pathology of a wide range of human diseases. Understanding of the relationship between metabolism of RCS and the development of pathological disorders and diseases may help to develop effective approaches to prevent a number of disorders and diseases. On the other hand, constant persistence of RCS in cells suggests that they perform some useful role in living organisms. The most beneficial effects of RCS are their establishment as regulators of cell signal transduction and gene expression. Since RCS can modulate different biological processes, new tools are required to decipher the precise mechanisms underlying dual effects of RCS.

Diabetic cardiomyopathy: understanding the molecular and cellular basis to progress in diagnosis and treatment

Diabetes mellitus is an important and prevalent risk factor for congestive heart failure. Diabetic cardiomyopathy has been defined as ventricular dysfunction that occurs in diabetic patients independent of a recognized cause such as coronary artery disease or hypertension. The disease course consists of a hidden subclinical period, during which cellular structural insults and abnormalities lead initially to diastolic dysfunction, later to systolic dysfunction, and eventually to heart failure. Left ventricular hypertrophy, metabolic abnormalities, extracellular matrix changes, small vessel disease, cardiac autonomic neuropathy, insulin resistance, oxidative stress, and apoptosis are the most important contributors to diabetic cardiomyopathy onset and progression. Hyperglycemia is a major etiological factor in the development of diabetic cardiomyopathy. It increases the levels of free fatty acids and growth factors and causes abnormalities in substrate supply and utilization, calcium homeostasis, and lipid metabolism. Furthermore, it promotes excessive production and release of reactive oxygen species, which induces oxidative stress leading to abnormal gene expression, faulty signal transduction, and cardiomyocytes apoptosis. Stimulation of connective tissue growth factor, fibrosis, and the formation of advanced glycation end-products increase the stiffness of the diabetic hearts. Despite all the current information on diabetic cardiomyopathy, translational research is still scarce due to limited human myocardial tissue and most of our knowledge is extrapolated from animals. This paper aims to elucidate some of the molecular and cellular pathophysiologic mechanisms, structural changes, and therapeutic strategies that may help struggle against diabetic cardiomyopathy.

Advanced glycation end products: Key players in skin aging?

Aging is the progressive accumulation of damage to an organism over time leading to disease and death. Aging research has been very intensive in the last years aiming at characterizing the pathophysiology of aging and finding possibilities to fight age-related diseases. Various theories of aging have been proposed. In the last years advanced glycation end products (AGEs) have received particular attention in this context. AGEs are formed in high amounts in diabetes but also in the physiological organism during aging. They have been etiologically implicated in numerous diabetes- and age-related diseases. Strategies inhibiting AGE accumulation and signaling seem to possess a therapeutic potential in these pathologies. However, still little is known on the precise role of AGEs during skin aging. In this review the existing literature on AGEs and skin aging will be reviewed. In addition, existing and potential anti-AGE strategies that may be beneficial on skin aging will be discussed.

Oxidative stress and myocardial injury in the diabetic heart

Reactive oxygen or nitrogen species play an integral role in both myocardial injury and repair. This dichotomy is differentiated at the level of species type, amount and duration of free radical generated. Homeostatic mechanisms designed to prevent free radical generation in the first instance, scavenge, or enzymatically convert them to less toxic forms and water, playing crucial roles in the maintenance of cellular structure and function. The outcome between functional recovery and dysfunction is dependent upon the inherent ability of these homeostatic antioxidant defences to withstand acute free radical generation, in the order of seconds to minutes. Alternatively, pre-existent antioxidant capacity (from intracellular and extracellular sources) may regulate the degree of free radical generation. This converts reactive oxygen and nitrogen species to the role of second messenger involved in cell signalling. The adaptive capacity of the cell is altered by the balance between death or survival signal converging at the level of the mitochondria, with distinct pathophysiological consequences that extends the period of injury from hours to days and weeks. Hyperglycaemia, hyperlipidaemia and insulin resistance enhance oxidative stress in the diabetic myocardium that cannot adapt to ischaemia-reperfusion. Altered glucose flux, mitochondrial derangements and nitric oxide synthase uncoupling in the presence of decreased antioxidant defence and impaired prosurvival cell signalling may render the diabetic myocardium more vulnerable to injury, remodelling and heart failure.

Current understanding of ovarian aging

The reproductive system of human female exhibits a much faster rate of aging than other body systems. Ovarian aging is thought to be dominated by a gradual decreasing numbers of follicles, coinciding with diminished quality of oocytes. Menopause is the final step in the process of ovarian aging. This review focuses on the mechanisms underlying the ovarian aging involving a poor complement of follicles at birth and a high rate of attrition each month, as well as the alternated endocrine factors. We also discuss the possible causative factors that contribute to ovarian aging, e.g., genetic factors, accumulation of irreparable damage of microenvironment, pathological effect and other factors. The appropriate and reliable methods to assess ovarian aging, such as quantification of follicles, endocrine measurement and genetic testing have also been discussed. Increased knowledge of the ovarian aging mechanisms may improve the prevention of premature ovarian failure.

Diabetic cardiomyopathy and diastolic heart failure -- difficulties with relaxation

Diabetic patients carry a four- to five-fold increased risk of heart failure. Hyperglycaemia plays a central role in the pathogenesis of diabetic cardiomyopathy. Diabetic cardiomyopathy represents a distinct structural and functional disorder of the myocardium characterized by cardiac hypertrophy and an increased myocardial stiffness. At an early stage, diabetic cardiomyopathy is manifested by diastolic heart failure with preserved ejection fraction. In some patients, diastolic dysfunction may progress to heart failure with reduced ejection fraction and result in overt systolic heart failure. Diastolic dysfunction can accurately be diagnosed by echocardiography and BNP measurement in daily clinical practice. Early treatment is prognostically important. Optimal control of blood glucose levels and blood pressure is beneficial. So far metformin is the only antidiabetic agent not associated with harm in diabetic patients with heart failure. Incretin-based therapies potentially provide cardiovascular benefits. ACE inhibitors, angiotensin-1 receptor antagonists and beta-blockers should be preferred in heart failure therapy.

Caffeoylquinic acid-rich extract from chicory seeds improves glycemia, atherogenic index, and antioxidant status in rats

OBJECTIVE

Comparison of the effects of a high-fructose diet supplemented with rutin, a phenolic compound with well-recognized bioavailability and bioactivity, and a chicory (Cichorium intybus L.) seed extract rich in caffeoylquinic acids (CQA) on gut physiology and the development of disorders related to metabolic syndrome.

METHODS

A 28-d experiment was conducted on 32 young male Wistar rats. In comparison with control rats fed a standard corn starch diet (group C), the experimental group (group E) was fed a diet with an increased content of cholesterol and fructose (to 1% and 66% of the diet, respectively), as well as with oxidized soybean oil. Rats from the other two experimental groups were administered the same diet as group E during the first 2 wk of feeding, whereas at the beginning of the last 2 wk, the diet was enriched with rutin (group ER) or the CQA-rich ethanol extract from chicory seeds (9.6% of CQA, group EC), so the amount of added phenolics was equal in both dietary groups (0.15%).

RESULTS

The diet administered in group E caused hyperglycemia and increased blood serum atherogenicity in rats, but did not induce other manifestations of the metabolic syndrome, i.e., dyslipidemia and oxidative stress. Additionally, it affected gut physiology through increasing mucosal sucrase activity and disturbing fermentative processes in the cecum, such as the production of short-chain fatty acids and the activity of microbial enzymes. Similarly to rutin, the dietary addition of the chicory seed extract improved glycemia, which was comparable to that determined in group C. In addition, the extract was found to decrease the atherogenic index to the level observed in group C and to increase blood antioxidant status. Both dietary supplements reduced the content of thiobarbituric acid-reactive substances in kidney and heart tissue when compared with group E.

CONCLUSION

The potential efficacy of the CQA-rich extract from chicory seeds in improving diet-induced metabolic disturbances proved to be better than that of rutin; thus, the extract might be considered as a dietary supplement for carrying out clinical trials.

Diabetic cardiomyopathy--fact or fiction?

Epidemiologic as well as clinical studies confirm the close link between diabetes mellitus and heart failure. Diabetic cardiomyopathy (DCM) is still a poorly understood "entity", however, with several contributing pathogenetic factors which lead in different stages of diabetes to characteristic clinical phenotypes. Hyperglycemia with a shift from glucose metabolism to increased beta-oxidation and consecutive free fatty acid damage (lipotoxicity) to the myocardium, insulin resistance, renin-angiotensin-aldosterone system (RAAS) activation, altered calcium homeostasis and structural changes from the natural collagen network to a stiffer matrix due to advanced glycation endproduct (AGE) formation, hypertrophy and fibrosis contribute to the respective clinical phenotypes of DCM. We propose the following classification of cardiomyopathy in diabetic patients: a) Diastolic heart failure with normal ejection fraction (HFNEF) in diabetic patients often associated with hypertrophy without relevant hypertension. Relevant coronary artery disease (CAD), valvular disease and uncontrolled hypertension are not present. This is referred to as stage 1 DCM. b) Systolic and diastolic heart failure with dilatation and reduced ejection (HFREF) in diabetic patients excluding relevant CAD, valvular disease and uncontrolled hypertension as stage 2 DCM. c) Systolic and/or diastolic heart failure in diabetic patients with small vessel disease (microvascular disease) and/or microbial infection and/or inflammation and/or hypertension but without CAD as stage 3 DCM. d) If heart failure may also be attributed to infarction or ischemia and remodeling in addition to stage 3 DCM the term should be heart failure in diabetes or stage 4 DCM. These clinical phenotypes of diabetic cardiomyopathy can be separated by biomarkers, non-invasive (echocardiography, cardiac magnetic resonance imaging) and invasive imaging methods (levocardiography, coronary angiography) and further analysed by endomyocardial biopsy for concomitant viral infection. The role of specific diabetic drivers to the clinical phenotypes, to macro- and microangiopathy as well as accompanying risk factors or confounders, e.g. hypertension, autoimmune factors or inflammation with or without viral persistence, need to be identified in each individual patient separately. Thus hyperglycemia, hyperinsulinemia and insulin resistance as well as lipotoxicity by free fatty acids (FFAs) are the factors responsible for diabetic cardiomyopathy. In stage 1 and 2 DCM diabetic cardiomyopathy is clearly a fact. However, precise determination of to what degree the various underlying pathogenetic processes are responsible for the overall heart failure phenotype remains a fiction.

A constituent-based model of age-related changes in conduit arteries

In the present report, a constituent-based theoretical model of age-related changes in geometry and mechanical properties of conduit arteries is proposed. The model was based on the premise that given the time course of the load on an artery and the accumulation of advanced glycation end-products in the arterial tissue, the initial geometric dimensions and properties of the arterial tissue can be predicted by a solution of a boundary value problem for the governing equations that follow from finite elasticity, structure-based constitutive modeling within the constrained mixture theory, continuum damage theory, and global growth approach for stress-induced structure-based remodeling. An illustrative example of the age-related changes in geometry, structure, composition, and mechanical properties of a human thoracic aorta is considered. Model predictions were in good qualitative agreement with available experimental data in the literature. Limitations and perspectives for refining the model are discussed.

Dietary antioxidant interventions in type 2 diabetes patients: a meta-analysis

An imbalance between reactive oxygen species (ROS) production and antioxidant scavenging has been implicated in type 2 diabetes. ROS are a byproduct in type 2 diabetes, generated during protein glycation and as a consequence of advanced glycation end-products-receptor binding; they impair insulin signalling pathways and induce cytotoxicity in pancreatic beta cells. Neutralisation of oxidants by increased antioxidant availability may mitigate these effects. Several human intervention studies have been undertaken to determine whether dietary antioxidants exert beneficial effects for type 2 diabetes patients. This paper describes a systematic review and meta-analysis of the effects of dietary supplementation with antioxidant vitamins C or E on (1) plasma glucose and insulin concentrations, as an indicator of the capacity for antioxidant to interfere with disease process and (2) on glycated haemoglobin A1C as a measure of antioxidant effects on posttranslational protein modification implicated in disease complications. Combined analysis of 14 studies that met inclusion criteria revealed that dietary antioxidant supplementation did not affect plasma glucose or insulin levels, suggesting that they could not interfere with the pathogenesis of insulin resistance. However, HbA1C levels were significantly reduced by antioxidant supplementation, suggesting that antioxidants may have some benefit in protecting against the complications of type 2 diabetes.

Advances in metal-induced oxidative stress and human disease

Detailed studies in the past two decades have shown that redox active metals like iron (Fe), copper (Cu), chromium (Cr), cobalt (Co) and other metals undergo redox cycling reactions and possess the ability to produce reactive radicals such as superoxide anion radical and nitric oxide in biological systems. Disruption of metal ion homeostasis may lead to oxidative stress, a state where increased formation of reactive oxygen species (ROS) overwhelms body antioxidant protection and subsequently induces DNA damage, lipid peroxidation, protein modification and other effects, all symptomatic for numerous diseases, involving cancer, cardiovascular disease, diabetes, atherosclerosis, neurological disorders (Alzheimer's disease, Parkinson's disease), chronic inflammation and others. The underlying mechanism of action for all these metals involves formation of the superoxide radical, hydroxyl radical (mainly via Fenton reaction) and other ROS, finally producing mutagenic and carcinogenic malondialdehyde (MDA), 4-hydroxynonenal (HNE) and other exocyclic DNA adducts. On the other hand, the redox inactive metals, such as cadmium (Cd), arsenic (As) and lead (Pb) show their toxic effects via bonding to sulphydryl groups of proteins and depletion of glutathione. Interestingly, for arsenic an alternative mechanism of action based on the formation of hydrogen peroxide under physiological conditions has been proposed. A special position among metals is occupied by the redox inert metal zinc (Zn). Zn is an essential component of numerous proteins involved in the defense against oxidative stress. It has been shown, that depletion of Zn may enhance DNA damage via impairments of DNA repair mechanisms. In addition, Zn has an impact on the immune system and possesses neuroprotective properties. The mechanism of metal-induced formation of free radicals is tightly influenced by the action of cellular antioxidants. Many low-molecular weight antioxidants (ascorbic acid (vitamin C), alpha-tocopherol (vitamin E), glutathione (GSH), carotenoids, flavonoids, and other antioxidants) are capable of chelating metal ions reducing thus their catalytic activity to form ROS. A novel therapeutic approach to suppress oxidative stress is based on the development of dual function antioxidants comprising not only chelating, but also scavenging components. Parodoxically, two major antioxidant enzymes, superoxide dismutase (SOD) and catalase contain as an integral part of their active sites metal ions to battle against toxic effects of metal-induced free radicals. The aim of this review is to provide an overview of redox and non-redox metal-induced formation of free radicals and the role of oxidative stress in toxic action of metals.

Protective measures against ultrafiltration failure in peritoneal dialysis patients

Ultrafiltration failure in patients undergoing peritoneal dialysis is a condition with an incidence that increases over time. It is related to increased cardiovascular morbidity and mortality and is a major cause of the abandonment of the treatment technique. Because the number of patients undergoing renal replacement therapy is increasing with society aging and because approximately 10% of this population is treated with peritoneal dialysis, this matter is becoming more common in everyday practice for clinicians involved in the care of patients with chronic renal failure. In this review, we summarize the available measures used to prevent and treat ultrafiltration failure and the current state of research in the field, both in the experimental and clinical settings, focusing on the possible clinical applications of recent findings.