Advanced glycation end products, diabetes and ageing. Z Gerontol Geriatr. 2007;40:349-356. [PMID: 17943238 DOI: 10.1007/s00391-007-0484-9]

Oxysterols, age-related-diseases and nutritherapy: Focus on 7-ketocholesterol and 7β-hydroxycholesterol

Age-related diseases are often associated with a disruption of RedOx balance that can lead to lipid peroxidation with the formation of oxysterols, especially those oxidized on carbon-7: 7-ketocholesterol (also known as 7-oxo-cholesterol) and 7β-hydroxycholesterol. Like cholesterol, these oxysterols have 27 carbons, they are composed of a sterane nucleus and have a hydroxyl function in position 3. The oxysterols 7-ketocholesterol and 7β-hydroxycholesterol are mainly formed by cholesterol autoxidation and are biomarkers of oxidative stress. These two oxysterols are frequently found at increased levels in the biological fluids (plasma, cerebrospinal fluid), tissues and/or organs (arterial wall, retina, brain) of patients with age-related diseases, especially cardiovascular diseases, neurodegenerative diseases (mainly Alzheimer's disease), ocular diseases (cataract, age-related macular degeneration), and sarcopenia. Depending on the cell type considered, 7-ketocholesterol and 7β-hydroxycholesterol induce either caspase- dependent or -independent types of cell death associated with mitochondrial and peroxisomal dysfunctions, autophagy and oxidative stress. The caspase dependent type of cell death associated with oxidative stress and autophagy is defined as oxiapoptophagy. These two oxysterols are also inducers of inflammation. These biological features associated with the toxicity of 7-ketocholesterol, and 7β-hydroxycholesterol are often observed in patients with age-related diseases, suggesting an involvement of these oxysterols in the pathophysiology of these disorders. The cytotoxic effects of 7-ketocholesterol and 7β-hydroxycholesterol are counteracted on different cell models by representative nutrients of the Mediterranean diet: ω3 and ω9 fatty acids, polyphenols, and tocopherols. There are also evidences, mainly in cardiovascular diseases, of the benefits of α-tocopherol and phenolic compounds. These in vitro and in vivo observations on 7-ketocholesterol and 7β-hydroxycholesterol, which are frequently increased in age-related diseases, reinforce the interest of nutritherapeutic treatments to prevent and/or cure age-related diseases currently without effective therapies.

Forensic Age Estimation From Blood Samples by Combining DNA Methylation and MicroRNA Markers Using Droplet Digital PCR

Age estimation is important in criminal investigations and forensic practice, and extensive studies have focused on age determination based on DNA methylation (DNAm) and miRNA markers. Interestingly, it has been reported that combining different types of molecular omics data helps build more accurate predictive models. However, few studies have compared the application of combined DNAm and miRNA data to predict age in the same cohort. In this study, a novel multiplex droplet digital PCR (ddPCR) system that allows for the simultaneous detection of age-associated DNAm and miRNA markers, including KLF14, miR-106b-5p, and two reference genes (C-LESS-C1 and RNU6B), was developed. Next, we examined and calculated the methylation levels of KLF14 and relative expression levels of miR-106b-5p in 132 blood samples. The collected data were used to establish age prediction models. Finally, the optimal models were evaluated using bloodstain samples. The results revealed that the random forest (RF) model had a minimum mean absolute deviation (MAD) value of 3.51 years and a maximum R2 of 0.84 for the validation sets in the combined age prediction models. However, the MAD was 5.66 years and the absolute error ranged from 3.16 to 10.54 years for bloodstain samples. Larger sample sizes and validation datasets are required to confirm these results in future studies. Overall, a stable method for the detection of KLF14, miR-106b-5p, C-LESS-C1, and RNU6B by 4-plex ddPCR was successfully established, and our study suggests that combining DNAm and miRNA data can improve the accuracy of age prediction, which has potential applications in forensic science.

Pathophysiology of vascular ageing and the effect of novel cardio-renal protective medications in preventing progression of chronic kidney disease in people living with diabetes

AIM

Among people with diabetes those with chronic kidney disease (CKD) have a reduced life expectancy with increased risk of cardiovascular disease (CVD) a major contributor to morbidity and mortality. CKD related to diabetes is growing worldwide and is one of the leading causes of kidney failure globally. Diabetes is associated with accelerated vascular ageing and the related mechanisms and mediators that drive the progression of CKD and CVD disease in people with diabetes may help provide insights into the pathophysiology of cardio-renal complications and guide treatment interventions in people with diabetes.

METHODS

We conducted a narrative review of the literature using PubMed for English language articles that contained keywords that related to diabetes, chronic or diabetic kidney disease, ageing, cellular senescence, arterial stiffness, Klotho and sirtuins, sodium-glucose co-transporter-2 (SGLT-2) inhibitors, renin angiotensin aldosterone system (RAAS) and glucagon-like peptide-1 (GLP-1) receptor agonists.

RESULTS

Progressive kidney disease in diabetes is associated with accelerated ageing driven in part by multiple processes such as cellular senescence, inflammation, oxidative stress and circulating uremic toxins. This accelerated ageing phenotype contributes to increased arterial stiffness, endothelial dysfunction, cognitive decline and muscle wasting, thereby elevating morbidity and mortality in individuals with diabetes and CKD. Deficiency of the kidney-derived anti-ageing hormone Klotho and reduced sirtuin levels play pivotal roles in these ageing pathways. Dietary, lifestyle and pharmacological interventions targeting vascular ageing may help reduce the progression of CKD and associated CVD in people with diabetes. The current standard of care and pillars of treatment for kidney disease such as RAAS inhibitors, SGLT-2 inhibitors and GLP-1 receptor agonists all influence pathways involved in vascular ageing.

CONCLUSIONS

A multifactorial intervention to prevent the development of CKD by targeting traditional risk factors as well as treatment with novel agents with cardio-renal beneficial effects can prevent accelerated ageing and extend lifespan in people with diabetes.

The Maillard reactions: Pathways, consequences, and control

The century old Maillard reactions continue to draw the interest of researchers in the fields of Food Science and Technology, and Health and Medical Sciences. This chapter seeks to simplify and update this highly complicated, multifaceted topic. The simple nucleophilic attack of an amine onto a carbonyl group gives rise to a series of parallel and subsequent reactions, occurring simultaneously, resulting into a vast array of low and high mass compounds. Recent research has focused on: (1) the formation and transformation of α-dicarbonyl compounds, highly reactive intermediates which are essential in the development of the desired color and flavor of foods, but also lead to the production of the detrimental advanced glycation end products (AGEs); (2) elucidation of the structures of melanoidins in different foods and their beneficial effects on human health; and (3) harmful effects of AGEs on human health. Considering that MRs have both positive and negative consequences, their control to accentuate the former and to mitigate the latter, is also being conscientiously investigated with the use of modern techniques and technology.

Mechanical Models of Collagen Networks for Understanding Changes in the Failure Properties of Aging Skin

Skin undergoes mechanical alterations due to changes in the composition and structure of the collagenous dermis with aging. Previous studies have conflicting findings, with both increased and decreased stiffness reported for aging skin. The underlying structure-function relationships that drive age-related changes are complex and difficult to study individually. One potential contributor to these variations is the accumulation of nonenzymatic crosslinks within collagen fibers, which affect dermal collagen remodeling and mechanical properties. Specifically, these crosslinks make individual fibers stiffer in their plastic loading region and lead to increased fragmentation of the collagenous network. To better understand the influence of these changes, we investigated the impact of nonenzymatic crosslink changes on the dermal microstructure using discrete fiber networks representative of the dermal microstructure. Our findings suggest that stiffening the plastic region of collagen's mechanical response has minimal effects on network-level stiffness and failure stresses. Conversely, simulating fragmentation through a loss of connectivity substantially reduces network stiffness and failure stress, while increasing stretch ratios at failure.

3D human stem-cell-derived neuronal spheroids for in vitro neurotoxicity testing of methylglyoxal, highly reactive glycolysis byproduct and potent glycating agent

Human-derived three-dimensional (3D) in vitro models are advanced human cell-based model for their complexity, relevance and application in toxicity testing. Intracellular accumulation of methylglyoxal (MGO), the most potent glycating agent in humans, mainly generated as a by-product of glycolysis, is associated with age-related diseases including neurodegenerative disorders. In our study, 3D human stem-cell-derived neuronal spheroids were set up and applied to evaluate cytotoxic effects after short-term (5 to 48 h) treatments with different MGO concentrations, including low levels, taking into consideration several biochemical endpoints. In MGO-treated neurospheroids, reduced cell growth proliferation and decreased cell viability occurred early from 5-10 μM, and their compactness diminished starting from 100 μM, apparently without affecting spheroid size. MGO markedly caused loss of the neuronal markers MAP-2 and NSE from 10-50 μM, decreased the detoxifying Glo1 enzyme from 50 μM, and activated NF-kB by nuclear translocation. The cytochemical evaluation of the 3D sections showed the presence of necrotic cells with loss of nuclei. Apoptotic cells were observed from 50 μM MGO after 48 h, and from 100 μM after 24 h. MGO (50-10 µM) also induced modifications of the cell-cell and cell-ECM interactions. These effects worsened at the higher concentrations (300-500 µM). In 3D neuronal spheroids, MGO tested concentrations comparable to human samples levels measured in MGO-associated diseases, altered neuronal key signalling endpoints relevant for the pathogenesis of neurodegenerative diseases and aging. The findings also demonstrated that the use of 3D neuronal spheroids of human origin can be useful in a strategy in vitro for testing MGO and other dicarbonyls evaluation.

An overview on glycation: molecular mechanisms, impact on proteins, pathogenesis, and inhibition

The formation of a heterogeneous set of advanced glycation end products (AGEs) is the final outcome of a non-enzymatic process that occurs in vivo on long-life biomolecules. This process, known as glycation, starts with the reaction between reducing sugars, or their autoxidation products, with the amino groups of proteins, DNA, or lipids, thus gaining relevance under hyperglycemic conditions. Once AGEs are formed, they might affect the biological function of the biomacromolecule and, therefore, induce the development of pathophysiological events. In fact, the accumulation of AGEs has been pointed as a triggering factor of obesity, diabetes-related diseases, coronary artery disease, neurological disorders, or chronic renal failure, among others. Given the deleterious consequences of glycation, evolution has designed endogenous mechanisms to undo glycation or to prevent it. In addition, many exogenous molecules have also emerged as powerful glycation inhibitors. This review aims to provide an overview on what glycation is. It starts by explaining the similarities and differences between glycation and glycosylation. Then, it describes in detail the molecular mechanism underlying glycation reactions, and the bio-molecular targets with higher propensity to be glycated. Next, it discusses the precise effects of glycation on protein structure, function, and aggregation, and how computational chemistry has provided insights on these aspects. Finally, it reports the most prevalent diseases induced by glycation, and the endogenous mechanisms and the current therapeutic interventions against it.

Diabetic Pneumopathy- A Novel Diabetes-associated Complication: Pathophysiology, the Underlying Mechanism and Combination Medication

BACKGROUND

The "diabetic lung" has been identified as a possible target organ in diabetes, with abnormalities in ventilation control, bronchomotor tone, lung volume, pulmonary diffusing capacity, and neuroadrenergic bronchial innervation.

OBJECTIVE

This review summarizes studies related to diabetic pneumopathy, pathophysiology and a number of pulmonary disorders including type 1 and type 2 diabetes.

METHODS

Electronic searches were conducted on databases such as Pub Med, Wiley Online Library (WOL), Scopus, Elsevier, ScienceDirect, and Google Scholar using standard keywords "diabetes," "diabetes Pneumopathy," "Pathophysiology," "Lung diseases," "lung infection" for review articles published between 1978 to 2023 very few previous review articles based their focus on diabetic pneumopathy and its pathophysiology.

RESULTS

Globally, the incidence of diabetes mellitus has been rising. It is a chronic, progressive metabolic disease. The "diabetic lung" may serve as a model of accelerated ageing since diabetics' rate of respiratory function deterioration is two to three-times higher than that of normal, non-smoking people.

CONCLUSION

Diabetes-induced pulmonary dysfunction has not gained the attention it deserves due to a lack of proven causality and changes in cellular properties. The mechanism underlying a particular lung illness can still only be partially activated by diabetes but there is evidence that hyperglycemia is linked to pulmonary fibrosis in diabetic people.

The role of sRAGE in cardiovascular diseases

Advanced glycation end products (AGEs), by-products of glucose metabolism, have been linked to the emergence of cardiovascular disorders (CVD). AGEs can cause tissue damage in four different ways: (1) by altering protein function, (2) by crosslinking proteins, which makes tissue stiffer, (3) by causing the generation of free radicals, and (4) by activating an inflammatory response after binding particular AGE receptors, such as the receptor for advanced glycation end products (RAGE). It is suggested that the soluble form of RAGE (sRAGE) blocks ligand-mediated pro-inflammatory and oxidant activities by serving as a decoy. Therefore, several studies have investigated the possible anti-inflammatory and anti-oxidant characteristics of sRAGE, which may help lower the risk of CVD. According to the results of various studies, the relationship between circulating sRAGE, cRAGE, and esRAGE and CVD is inconsistent. To establish the potential function of sRAGE as a therapeutic target in the treatment of cardiovascular illnesses, additional studies are required to better understand the relationship between sRAGE and CVD. In this review, we explored the potential function of sRAGE in different CVD, highlighting unanswered concerns and outlining the possibilities for further investigation.

Inhibitory potential of N-acetylaspartate against protein glycation, AGEs formation and aggregation: Implication of brain osmolyte in glycation-related complications

Protein glycation and aggregation have a pivotal role in many diseases including diabetes and neurodegenerative disorders. N-acetyl aspartate (NAA), an osmolyte derived from L-aspartic acid, is one of the most abundant metabolites in the mammalian brain. Although NAA is supposed to be a substitute for a neuronal marker, its function is not fully elucidated. Herein, we have investigated the effect of NAA on glycation, AGEs formation and aggregation of irisin. AGE-specific fluorescence showed the strong inhibition of AGEs formation in the presence of NAA, demonstrating its anti-glycating property. The aggregates present in MG-modified irisin were also reduced by NAA, which was confirmed by Thioflavin T fluorescence and fluorescence microscopy. Further, for the explanation of the strong anti-glycating potential of NAA, the interaction between irisin and NAA was also examined. Interaction studies involving steady-state fluorescence and molecular docking demonstrated that hydrogen bonding and salt bridges by NAA stabilize the irisin. It was found that glycation-prone residues i.e., lysine and arginine are specifically involved in the interaction which might prevent them from getting modified during the process of glycation. This study for the first time reported the antiglycating potential of NAA which can be implicated in the therapeutic management of various glycation-related complications.

Thiourea derivatives inhibit key diabetes-associated enzymes and advanced glycation end-product formation as a treatment for diabetes mellitus

This study was designed to screen novel thiourea derivatives against different enzymes, such as α-amylase, α-glucosidase, protein tyrosine phosphatase 1 B, and advanced glycated end product (AGEs). A cytotoxicity analysis was performed using rat L6 myotubes and molecular docking analysis was performed to map the binding interactions between the active compounds and α-amylase and α-glucosidase. The data revealed the potency of five compounds, including E (1-(2,4-difluorophenyl)-3-(3,4-dimethyl phenyl) thiourea), AG (1-(2-methoxy-5-(trifluoromethyl) phenyl)-3-(3-methoxy phenyl) thiourea), AF (1-(2,4-dichlorophenyl)-3-(4-ethylphenyl) thiourea), AD (1-(2,4-dichlorophenyl)-3-(4-ethylphenyl) thiourea), and AH (1-(2,4-difluorophenyl)-3-(2-iodophenyl) thiourea), showed activity against α-amylase. The corresponding percentage inhibitions were found to be 85 ± 1.9, 82 ± 0.7, 75 ± 1.2, 72 ± 0.4, and 65 ± 1.1%, respectively. These compounds were then screened using in vitro assays. Among them, AH showed the highest activity against α-glucosidase, AGEs, and PTP1B, with percentage inhibitions of 86 ± 0.4% (IC₅₀  = 47.9 μM), 85 ± 0.7% (IC₅₀  = 49.51 μM), and 85 ± 0.5% (IC₅₀  = 79.74 μM), respectively. Compound AH showed an increased glucose uptake at a concentration of 100 μM. Finally, an in vivo study was conducted using a streptozotocin-induced diabetic mouse model and PTP1B expression was assessed using real-time PCR. Additionally, we examined the hypoglycemic effect of compound AH in diabetic rats compared to the standard drug glibenclamide.

Molecular age estimation based on posttranslational protein modifications in bone: why the type of bone matters

Age-at-death estimation is of great relevance for the identification of unknown deceased individuals. In skeletonised corpses, teeth and bones are theoretically available for age estimation, but in many cases, only single bones or even only bone fragments are available for examination. In these cases, conventional morphological methods may not be applicable, and the application of molecular methods may be considered. Protein-based molecular methods based on the D-aspartic acid (D-Asp) or pentosidine (Pen) content have already been successfully applied to bone samples. However, the impact of the analysed type of bone has not yet been systematically investigated, and it is still unclear whether data from samples of one skeletal region (e.g. skull) can also be used for age estimation for samples of other regions (e.g. femur). To address this question, D-Asp and Pen were analysed in bone samples from three skeletal regions (skull, clavicle, and rib), each from the same individual. Differences between the bone types were tested by t-test, and correlation coefficients (ρ) were calculated according to Spearman. In all types of bone, an age-dependent accumulation of D-Asp and Pen was observed. However, both parameters (D-Asp and Pen) exhibited significant differences between bone samples from different anatomical regions. These differences can be explained by differences in structure and metabolism in the examined bone types and have to be addressed in age estimation based on D-Asp and Pen. In future studies, bone type-specific training and test data have to be collected, and bone type-specific models have to be established.

RAGE-Dependent Effect of Exogenous Methylglyoxal Intake on Lung Biomechanics in Mice

Methylglyoxal (MG) is a known highly reactive dicarbonyl and precursor to free radicals and advanced glycation end-products (AGEs). It is discussed to be involved in tissue aging and in the pathogenesis of different degenerative diseases. The effect of long-term oral administration of MG, simulating dietary MG intake, on the lung biomechanics of wild type (WT) and receptor for advanced glycation end-products knockout (RAGE-KO) mice was studied using an ex vivo ventilation system starting at the age of 6 months and after feeding for 6 and 12 months with MG. Our results showed that MG was taken up in the circulation and efficiently excreted with urine. The amount of free urinary MG measured after 12 months of feeding was lowered. After 12 months feeding, a significant airway resistance increase accompanied by a decrease of the maximal inspiratory airflow was observed in WT animals. No effect of MG in lung function of RAGE-KO mice could be detected. Despite the evidence that MG entered the systemic circulation, no MG-derived AGE accumulation was detected in the lung lysates in dependency on MG-feeding. Our data indicate that the short-term feeding of MG has little effect in vivo. Only after long-term treatment was MG secretion reduced, leading to tissue impairment.

Accumulation of Advanced Glycation End-Products in the Body and Dietary Habits

The formation of advanced glycation end-products (AGE) in tissues is a physiological process; however, excessive production and storage are pathological and lead to inflammation. A sedentary lifestyle, hypercaloric and high-fructose diet and increased intake of processed food elements contribute to excessive production of compounds, which are created in the non-enzymatic multi-stage glycation process. The AGE’s sources can be endogenous and exogenous, mainly due to processing food at high temperatures and low moisture, including grilling, roasting, and frying. Accumulation of AGE increases oxidative stress and initiates various disorders, leading to the progression of atherosclerosis, cardiovascular disease, diabetes and their complications. Inborn defensive mechanisms, recovery systems, and exogenous antioxidants (including polyphenols) protect from excessive AGE accumulation. Additionally, numerous products have anti-glycation properties, occurring mainly in fruits, vegetables, herbs, and spices. It confirms the role of diet in the prevention of civilization diseases.

An inducible model for unraveling the effects of advanced glycation end-product accumulation in aging connective tissues

PURPOSE

In connective tissues there is a clear link between increasing age and degeneration. Advanced glycation end-products (AGEs) are believed to play a central role. AGEs are sugar-induced non-enzymatic crosslinks which accumulate in collagen with age and diabetes, altering tissue mechanics and cellular function. Despite ample correlative evidence linking collagen glycation to tissue degeneration, little is known how AGEs impact cell-matrix interactions, limiting therapeutic options. One reason for this limited understanding is that AGEs are typically induced using high concentrations of ribose which decrease cell viability, making it impossible to investigate cell-matrix interactions. The objective of this study was to develop a system to trigger AGE accumulation while maintaining cell viability.

MATERIALS AND METHODS

Using cell-seeded high density collagen gels, we investigated the effect of two systems for AGE induction, ribose at low concentrations (30, 100, and 200 mM) over 15 days of culture and riboflavin (0.25 and 0.75 mM) induced with blue light for 40 seconds (riboflavin-465 nm).

RESULTS

We found ribose and riboflavin-465 nm treatment produces fluorescent AGE quantities which match and/or exceed human fluorescent AGE levels for various tissues, ages, and diseases, without affecting cell viability or metabolism. Interestingly, a 40 second treatment of riboflavin-465 nm produced similar levels of fluorescent AGEs as 3 days of 100 mM ribose treatment.

CONCLUSIONS

Riboflavin-465 nm is a promising method to trigger AGEs on demand in vivo or in vitro without impacting cell viability and offers potential for unraveling the mechanism of AGEs in age and diabetes related tissue damage.

The Effects of Dietary Advanced Glycation End-Products on Neurocognitive and Mental Disorders

Advanced glycation end products (AGEs) are glycated proteins or lipids formed endogenously in the human body or consumed through diet. Ultra-processed foods and some culinary techniques, such as dry cooking methods, represent the main sources and drivers of dietary AGEs. Tissue accumulation of AGEs has been associated with cellular aging and implicated in various age-related diseases, including type-2 diabetes and cardiovascular disease. The current review summarizes the literature examining the associations between AGEs and neurocognitive and mental health disorders. Studies indicate that elevated circulating AGEs are cross-sectionally associated with poorer cognitive function and longitudinally increase the risk of developing dementia. Additionally, preliminary studies show that higher skin AGE accumulation may be associated with mental disorders, particularly depression and schizophrenia. Potential mechanisms underpinning the effects of AGEs include elevated oxidative stress and neuroinflammation, which are both key pathogenetic mechanisms underlying neurodegeneration and mental disorders. Decreasing dietary intake of AGEs may improve neurological and mental disorder outcomes. However, more sophisticated prospective studies and analytical approaches are required to verify directionality and the extent to which AGEs represent a mediator linking unhealthy dietary patterns with cognitive and mental disorders.

Revisiting Methodologies for In Vitro Preparations of Advanced Glycation End Products

Chronic elevation of sugar and oxidative stress generally results in development of advanced glycation end products (AGEs) in diabetic individuals. Accumulation of AGEs in an individual can give rise to the activation of several pathways that will ultimately lead to various complications. Such AGEs can also be prepared in an in vitro environment. For an in vitro preparation of advanced glycation end products (AGEs), proteins, lipids, or nucleic acids are generally required to be incubated with reducing sugars at a physiological temperature or higher depending upon the protocol optimized for its preparation. Certain other factors are also optimized and added to the buffer to hasten its preparation or alter the properties of prepared AGEs. Through this review, we intend to highlight the various studies related to the experimental procedures for the preparation of different types of AGEs. In addition, we present the comparative study of methodologies optimized for the preparation of AGEs.

Nanomechanical and Molecular Characterization of Aging in Dentinal Collagen

Methylglyoxal (MGO) is an important molecule derived from glucose metabolism with the capacity of attaching to collagen and generating advanced glycation end products (AGEs), which accumulate in tissues over time and are associated with aging and diseases. However, the accumulation of MGO-derived AGEs in dentin and their effect on the nanomechanical properties of dentinal collagen remain unknown. Thus, the aim of the present study was to quantify MGO-based AGEs in the organic matrix of human dentin as a function of age and associate these changes with alterations in the nanomechanical and ultrastructural properties of dentinal collagen. For this, 12 healthy teeth from <26-y-old and >50-y-old patients were collected and prepared to obtain crown and root dentin discs. Following demineralization, MGO-derived AGEs were quantified with a competitive ELISA. In addition, atomic force microscopy nanoindentation was utilized to measure changes in elastic modulus in peritubular and intertubular collagen fibrils. Finally, principal component analysis was carried out to determine aging profiles for crown and root dentin. Results showed an increased presence of MGO AGEs in the organic matrix of dentin in the >50-y-old specimens as compared with the <26-y-old specimens in crown and root. Furthermore, an increase in peritubular and intertubular collagen elasticity was observed in the >50-y-old group associated with ultrastructural changes in the organic matrix as determined by atomic force microscopy analysis. Furthermore, principal component analysis loading plots suggested different "aging profiles" in crown and root dentin, which could have important therapeutic implications in restorative and adhesive dentistry approaches. Overall, these results demonstrate that the organic matrix of human dentin undergoes aging-related changes due to MGO-derived AGEs with important changes in the nanomechanical behavior of collagen that may affect diagnostic and restorative procedures in older people.

Isolation of Anti-Diabetic Active Compounds from Benincasae Exocarpium and Development of Simultaneous Analysis by HPLC-PDA

Diabetes is a chronic metabolic disease that is a constant problem. Previous studies have reported that Benincasa cerifera Savi. extracts are effective in treating diabetes and its complications. Benincasae Exocarpium (BE) is a fruit peel of B. cerifera that has been reported to be used for the prevention and treatment of metabolic diseases such as hyperglycemia, obesity, and hyperlipidemia. However, there are not enough studies on the compounds and bioassays to support the efficacy of BE. The inhibitory activity of the BE extracts and fractions against advanced glycation end-products (AGE) formation and α-glucosidase activity was evaluated. These assays are relevant for the treatment of type 2 diabetes and its complications. Based on these results, compounds 1-11 were isolated through bioassay-guided isolation. In addition, we developed a high-performance liquid chromatography (HPLC) method that can simultaneously analyze these 11 compounds. Activity evaluation of the compounds was also conducted, and eight compounds exhibited significant activity. Among these, flavonoid compounds showed strong activity. A quantitative evaluation of eight bioactive compounds (2, 5-11) was conducted. In conclusion, this study demonstrated the potential of BE for prevention and treatment of type 2 diabetes and its complications.

Glycation of Host Proteins Increases Pathogenic Potential of Porphyromonas gingivalis

The non-enzymatic addition of glucose (glycation) to circulatory and tissue proteins is a ubiquitous pathophysiological consequence of hyperglycemia in diabetes. Given the high incidence of periodontitis and diabetes and the emerging link between these conditions, it is of crucial importance to define the basic virulence mechanisms employed by periodontopathogens such as Porphyromonas gingivalis in mediating the disease process. The aim of this study was to determine whether glycated proteins are more easily utilized by P. gingivalis to stimulate growth and promote the pathogenic potential of this bacterium. We analyzed the properties of three commonly encountered proteins in the periodontal environment that are known to become glycated and that may serve as either protein substrates or easily accessible heme sources. In vitro glycated proteins were characterized using colorimetric assays, mass spectrometry, far- and near-UV circular dichroism and UV-visible spectroscopic analyses and SDS-PAGE. The interaction of glycated hemoglobin, serum albumin and type one collagen with P. gingivalis cells or HmuY protein was examined using spectroscopic methods, SDS-PAGE and co-culturing P. gingivalis with human keratinocytes. We found that glycation increases the ability of P. gingivalis to acquire heme from hemoglobin, mostly due to heme sequestration by the HmuY hemophore-like protein. We also found an increase in biofilm formation on glycated collagen-coated abiotic surfaces. We conclude that glycation might promote the virulence of P. gingivalis by making heme more available from hemoglobin and facilitating bacterial biofilm formation, thus increasing P. gingivalis pathogenic potential in vivo.

Hydroxytyrosol Selectively Affects Non-Enzymatic Glycation in Human Insulin and Protects by AGEs Cytotoxicity

Hydroxytyrosol (HT), the major phenolic compound in olive oil, is attracting increasing interest for its beneficial properties including a notable antioxidant and anti-inflammatory power. In this study, using a combination of biophysical and cell biology techniques, we have tested the role of HT in the formation of advanced glycation end-products (AGEs). AGEs have a key role in clinical sciences as they have been associated to diabetes, neurodegenerative and cardiovascular diseases. In addition, as the incidence of Alzheimer’s disease (AD) is strongly increased in diabetic patients, AGE formation is supposed to be involved in the development of the pathological hallmarks of AD. Our data show that HT selectively inhibits protein glycation reaction in human insulin, and it is able to counteract the AGE-induced cytotoxicity in human neurotypical cells by acting on SIRT1 level and oxidative stress, as well as on inflammatory response. This study identifies new beneficial properties for HT and suggests it might be a promising molecule in protecting against the AGE-induced toxicity, a key mechanism underlying the development and progression of neurodegenerative disorders.

The effects of different accumulated pressure-time integral stimuli on plantar blood flow in people with diabetes mellitus

Background

Exercise, especially weight-bearing exercise (e.g. walking), may affect plantar tissue viability due to prolonged repetitive high vertical and high shear pressure stimulus on the plantar tissue, and further induce development of diabetic foot ulcers (DFUs). This study aimed to investigate the effects of different accumulated pressure-time integral (APTI) stimuli induced by walking on plantar skin blood flow (SBF) responses in people with diabetes mellitus (DM).

Methods

A repeated measures design was used in this study. Two walking protocols (low APTI (73,000 kPa·s) and high APTI (73,000 × 1.5 kPa·s)) were randomly assigned to ten people with DM and twenty people without DM. The ratio of SBF measured by laser Doppler flowmetry after walking to that before (normalized SBF) was used to express the SBF responses.

Results

After low APTI, plantar SBF of people with DM showed a similar response to people without DM (P = 0.91). However, after high APTI, people with DM had a significantly lower plantar SBF compared to people without DM (P < 0.05). In people with DM, plantar SBF in the first 2 min after both APTI stimuli significantly decreased compared to plantar SBF before walking (P < 0.05).

Conclusions

People with DM had a normal SBF response after low APTI walking but had an impaired SBF response after high APTI walking, which suggests that they should avoid weight-bearing physical activity with intensity more than 73,000 kPa·s and should rest for more than 2 min after weight-bearing physical activity to allow a full vasodilatory response to reduce risk of DFUs.

Integrated metabolomics and transcriptomics reveal the anti-aging effect of melanin from Sepiella maindroni ink (MSMI) on D-galactose-induced aging mice

Sepiella maindroni ink, a flavoring and coloring agent in food, has attracted considerable attention due to its various pharmacological activities. Our previous study showed that the melanin of Sepiella maindroni ink (MSMI) can alleviate oxidative damage and delay aging in D-galactose(D-gal)-induced aging mice. This study aimed to reveal the possible mechanisms of the anti-aging effect of MSMI. In this article, a comprehensive analysis of gas chromatography-mass spectrometry (GC-MS)-based metabolomics and microarray-based transcriptomics revealed that 221 mRNAs were differentially expressed and 46 metabolites were significantly changed in the anti-aging progress of MSMI. Integrated analysis of transcript and metabolic profiles indicated that MSMI mainly altered carbohydrate metabolism, lipid metabolism, and insulin signaling pathway. MSMI achieved anti-aging effects not only by reducing oxidative damage and sorbitol toxicity but also by regulating lipid metabolism, improving insulin sensitivity, and reducing the formation of advanced glycation end products (AGEs). Moreover, our findings firstly demonstrated that MSMI could increase the expression of interferon-induced proteins and might be a potential antiviral compound.

Molecular clocks in ancient proteins: Do they reflect the age at death even after millennia?

Age at death estimation in cases of human skeletal finds is an important task in forensic medicine as well as in anthropology. In forensic medicine, methods based on “molecular clocks” in dental tissues and bone play an increasing role. The question, whether these methods are applicable also in cases with post-depositional intervals far beyond the forensically relevant period, was investigated for two “protein clocks”, the accumulation of D-aspartic acid (D-Asp) and the accumulation of pentosidine (Pen) in dentine. Eight teeth of skeletons from different burial sites in Austria and with post-depositional intervals between c. 1216 and c. 8775 years were analysed. The results of age at death estimation based on D-Asp and Pen in dentine were compared to that derived from a classical morphological examination. Age at death estimation based on D-Asp resulted consistently in false high values. This finding can be explained by a post-mortem accumulation of D-Asp that may be enhanced by protein degradation. In contrast, the Pen-based age estimates fitted well with the morphological age diagnoses. The described effect of post-mortem protein degradation is negligible in forensically relevant time horizons, but not for post-depositional intervals of thousands of years. That means that the “D-Asp clock” loses its functionality with increasing post-depositional intervals, whereas Pen seems to be very stable. The “Pen-clock” may have the potential to become an interesting supplement to the existing repertoire of methods even in cases with extremely long post-depositional intervals. Further investigations have to test this hypothesis.

Glyoxalase System as a Therapeutic Target against Diabetic Retinopathy

Hyperglycemia, a defining characteristic of diabetes, combined with oxidative stress, results in the formation of advanced glycation end products (AGEs). AGEs are toxic compounds that have adverse effects on many tissues including the retina and lens. AGEs promote the formation of reactive oxygen species (ROS), which, in turn, boost the production of AGEs, resulting in positive feedback loops, a vicious cycle that compromises tissue fitness. Oxidative stress and the accumulation of AGEs are etiologically associated with the pathogenesis of multiple diseases including diabetic retinopathy (DR). DR is a devastating microvascular complication of diabetes mellitus and the leading cause of blindness in working-age adults. The onset and development of DR is multifactorial. Lowering AGEs accumulation may represent a potential therapeutic approach to slow this sight-threatening diabetic complication. To set DR in a physiological context, in this review we first describe relations between oxidative stress, formation of AGEs, and aging in several tissues of the eye, each of which is associated with a major age-related eye pathology. We summarize mechanisms of AGEs generation and anti-AGEs detoxifying systems. We specifically feature the potential of the glyoxalase system in the retina in the prevention of AGEs-associated damage linked to DR. We provide a comparative analysis of glyoxalase activity in different tissues from wild-type mice, supporting a major role for the glyoxalase system in the detoxification of AGEs in the retina, and present the manipulation of this system as a therapeutic strategy to prevent the onset of DR.

Glyoxalase 1 expression analysis by immunohistochemistry in breast cancer

Glyoxalase-1 (GLO-1) is the key enzyme in aldehyde defence in cancer cells. We here evaluated the prognostic impact and association with clinico-pathological parameters and relapse-free as well as overall survival in tumor samples from 187 breast cancer patients. The determined GLO1-immunoreactive score (GLO1-IRS) did not correlate with parameters such as grading, size, hormone receptors or ki67. However, an association of GLO1-IRS with the advanced glycation end product N^ε-(carboxymethyl)lysine (p = 0.07) and HER2 (p = 0.06), and a strong correlation with VEGF (p = 0.008) was found. In survival analysis, no significant impact of GLO-1 IRS could be deduced for all patients. However, GLO1-IRS correlated with treatment by radiotherapy (p = 0.008) and high GLO1-IRS predicted a shorter relapse free survival after radiotherapy (log-rank p = 0.067). METABRIC- and TCGA expression-data were analyzed for correlation of regulatory genes of the NF-κB-pathway (RELA, RELB, IRAK1), the oxidative-stress associated transcription factor nrf2 (NFE2L2), the receptor for AGEs (AGER, RAGE) as well as enzymes associated with aldehyde defense. Here, RELA, RELB and NFE2L2 correlated significantly with GLO1 expression, but there were conflicting results between the two data sources. In conclusion, GLO1 was highly expressed in cancer cells, correlated surprisingly weak with survival, but we could show a positive association with the AGE CML as well as VEGF. Gene expression data suggest a regulation of GLO-1 mRNA via both, inflammation (NF-kB) and oxidative stress (NFE2L2) in tumors.

Pathophysiology of atherosclerosis: Association of risk factors and treatment strategies using plant-based bioactive compounds

Under physiological conditions, endothelial cells act as protective barrier which prevents direct contact of blood with circulating factors via production of tissue plasminogen activator. Risk factors of metabolic disorders are responsible to induce endothelial dysfunction and may consequently lead to prognosis of atherosclerosis. This article summarizes the process of atherosclerosis which involves number of sequences including formation and interaction of AGE-RAGE, activation of polyol pathway, protein kinase C, and hexosamine-mediated pathway. All these mechanisms can lead to the development of oxidative stress which may further aggravate condition. Different pharmacological interventions are being used to treat atherosclerosis, however, these might be associated with mild to severe side effects. Therefore, plant-based bioactive compounds having potential to combat and prevent atherosclerosis in diabetic patients are attaining recent focus. By understanding process of development and mechanisms involved in atherosclerotic plaque formation, these bioactive compounds can be better option for future therapeutic interventions for atherosclerosis treatment. PRACTICAL APPLICATIONS: Atherosclerosis is one of major underlying disorders of cardiovascular diseases which occur through multiple mechanisms and is associated with metabolic disorders. Conventional therapeutic interventions are not only used to treat atherosclerosis, but are also commonly associated with mild to severe side effects. Therefore, nowadays, bioactive compounds having potential to combat and prevent atherosclerosis in diabetic patients are preferred. By understanding mechanisms involved in atherosclerotic plaque formation, bioactive compounds can be better understood for treatment of atherosclerosis. In this manuscript, we have focused on treatment strategies of atherosclerosis using bioactive compounds notably alkaloids and flavonoids having diverse pharmacological and therapeutic potentials with special focus on the mechanism of action of these bioactive compounds suitable for treatment of atherosclerosis. This manuscript will provide the scientific insights of bioactive compounds to researchers who are working in the area of drug discovery and development to control pathogenesis and development of atherosclerosis and its associated cardiometabolic disorders.

Ipriflavone and Ipriflavone loaded albumin nanoparticles reverse lipopolysaccharide induced neuroinflammation in rats

BACKGROUND

Neuroinflammation causes neurodegenerative conditions like Alzheimer's disease (AD). Ipriflavone (IP), therapeutic compound to postmenopausal osteoporosis, has limited estrogenic activity and is accounted as AChE inhibitor. The developing of drug delivery systems to enable drug targeting to specific sites increases the drug therapeutic effect.

OBJECTIVE

The aim of the present study was to formulate and evaluate ipriflavone loaded albumin nanoparticles (IP-Np) along with free ipriflavone against lipopolysaccharide (LPS) induced neuroinflammation in rats.

METHODS

Neuroinflammation was induced by intra-peritoneal (i.p) injection of LPS (250 μg/kg rat body weight) then treatments were conducted with (1) ipriflavone at two doses 50 mg/kg and 5 mg/kg, (2) IP-Np (5 mg ipriflavone/kg) or (3) IP-Np coated with polysorbate 80 (IP-Np-T80) (5 mg ipriflavone/kg). The alteration of the inflammatory response in male adult Wistar rats' brain hippocampus was investigated by examining associated indices using biochemical and molecular analyses.

RESULTS

A significant upsurge in inflammatory mediators and decline in antioxidant status were observed in LPS-induced rats. In one hand, ipriflavone (50 mg/kg), IP-Np and IP-Np-T80 ameliorated LPS induced brain hippocampal inflammation where they depreciated the level of pro-inflammatory cytokines (TNF-α, IL-6, IL-1β) and enhanced antioxidant status. In another hand, ipriflavone at dose (5 mg/kg) didn't show the same therapeutic effect.

CONCLUSION

The current study provides evidence for the potential neuroprotective effect of ipriflavone (50 mg/kg) against LPS-induced neuroinflammation in rats through its anti-inflammatory and antioxidant activities. Moreover, nanoparticles significantly attenuated neuroinflammation in concentration lower than the effective therapeutic dose of free drug ten times.

Glycation and Oxidative Stress Increase Autoantibodies in the Elderly

Aging causes gradual changes in free radicals, antioxidants, and immune-imbalance in the elderly. This study aims to understand links among aging, gluco-oxidative stress, and autoantibodies in asymptomatic individuals. In vitro glycation of human serum albumin (Gly-HSA) induces appreciable biochemical changes. Significant inhibition of advanced glycation end products (AGEs) formation was achieved using garlic extract (53.75%) and epigallocatechin-3-gallate from green tea (72.5%). Increased amounts of serum carbonyl content (2.42 ± 0.5) and pentosidine (0.0321 ± 0.0029) were detected in IV-S (S represent smokers) vs. IV group individuals. Direct binding ELISA results exhibited significantly high autoantibodies against Gly-HSA in group IV-S (0.55 ± 0.054; p < 0.001) and III-S (0.40 ± 0.044; p < 0.01) individuals as compared to the age matched subjects who were non-smokers (group IV and III). Moreover, high average percent inhibition (51.3 ± 4.1%) was obtained against Gly-HSA in IV-S group individuals. Apparent association constant was found to be high for serum immunoglobulin-G (IgG) from group IV-S (1.18 × 10⁻⁶ M) vs. serum IgG from IV group (3.32 × 10⁻⁷ M). Aging induced gluco-oxidative stress and AGEs formation may generate neo-epitopes on blood-proteins, contributing to production of autoantibodies in the elderly, especially smokers. Use of anti-glycation natural products may reduce age-related pathophysiological changes.

Modulatory Effect of Glycated Collagen on Oral Streptococcal Nanoadhesion

Biofilm-mediated oral diseases such as dental caries and periodontal disease remain highly prevalent in populations worldwide. Biofilm formation initiates with the attachment of primary colonizers onto surfaces, and in the context of caries, the adhesion of oral streptococci to dentinal collagen is crucial for biofilm progression. It is known that dentinal collagen suffers from glucose-associated crosslinking as a function of aging or disease; however, the effect of collagen crosslinking on the early adhesion and subsequent biofilm formation of relevant oral streptococci remains unknown. Therefore, the aim of this work was to determine the impact of collagen glycation on the initial adhesion of primary colonizers such as Streptococcus mutans UA159 and Streptococcus sanguinis SK 36, as well as its effect on the early stages of streptococcal biofilm formation in vitro. Type I collagen matrices were crosslinked with either glucose or methylglyoxal. Atomic force microscopy nanocharacterization revealed morphologic and mechanical changes within the collagen matrix as a function of crosslinking, such as a significantly increased elastic modulus in crosslinked fibrils. Increased nanoadhesion forces were observed for S. mutans on crosslinked collagen surfaces as compared with the control, and retraction curves obtained for both streptococcal strains demonstrated nanoscale unbinding behavior consistent with bacterial adhesin-substrate coupling. Overall, glucose-crosslinked substrates specifically promoted the initial adhesion, biofilm formation, and insoluble extracellular polysaccharide production of S. mutans, while methylglyoxal treatment reduced biofilm formation for both strains. Changes in the adhesion behavior and biofilm formation of oral streptococci as a function of collagen glycation could help explain the biofilm dysbiosis seen in older people and patients with diabetes. Further studies are necessary to determine the influence of collagen crosslinking on the balance between acidogenic and nonacidogenic streptococci to aid in the development of novel preventive and therapeutic treatment against dental caries in these patients.

Accelerated Kidney Aging in Diabetes Mellitus

With aging, the kidney undergoes inexorable and progressive changes in structural and functional performance. These aging-related alterations are more obvious and serious in diabetes mellitus (DM). Renal accelerated aging under DM conditions is associated with multiple stresses such as accumulation of advanced glycation end products (AGEs), hypertension, oxidative stress, and inflammation. The main hallmarks of cellular senescence in diabetic kidneys include cyclin-dependent kinase inhibitors, telomere shortening, and diabetic nephropathy-associated secretory phenotype. Lysosome-dependent autophagy and antiaging proteins Klotho and Sirt1 play a fundamental role in the accelerated aging of kidneys in DM, among which the autophagy-lysosome system is the convergent mechanism of the multiple antiaging pathways involved in renal aging under DM conditions. Metformin and the inhibitor of sodium-glucose cotransporter 2 are recommended due to their antiaging effects independent of antihyperglycemia, besides angiotensin-converting enzyme inhibitors/angiotensin receptor blockers. Additionally, diet intervention including low protein and low AGEs with antioxidants are suggested for patients with diabetic nephropathy (DN). However, their long-term benefits still need further study. Exploring the interactive relationships among antiaging protein Klotho, Sirt1, and autophagy-lysosome system may provide insight into better satisfying the urgent medical needs of elderly patients with aging-related DN.

Advanced Glycation End Products (AGEs) May Be a Striking Link Between Modern Diet and Health

The Maillard reaction is a simple but ubiquitous reaction that occurs both in vivo and ex vivo during the cooking or processing of foods under high-temperature conditions, such as baking, frying, or grilling. Glycation of proteins is a post-translational modification that forms temporary adducts, which, on further crosslinking and rearrangement, form permanent residues known as advanced glycation end products (AGEs). Cooking at high temperature results in various food products having high levels of AGEs. This review underlines the basis of AGE formation and their corresponding deleterious effects on the body. Glycated Maillard products have a direct association with the pathophysiology of some metabolic diseases, such as diabetes mellitus type 2 (DM2), acute renal failure (ARF), Alzheimer’s disease, dental health, allergies, and polycystic ovary syndrome (PCOS). The most glycated and structurally abundant protein is collagen, which acts as a marker for diabetes and aging, where decreased levels indicate reduced skin elasticity. In diabetes, high levels of AGEs are associated with carotid thickening, ischemic heart disease, uremic cardiomyopathy, and kidney failure. AGEs also mimic hormones or regulate/modify their receptor mechanisms at the DNA level. In women, a high AGE diet directly correlates with high levels of androgens, anti-Müllerian hormone, insulin, and androstenedione, promoting ovarian dysfunction and/or infertility. Vitamin D3 is well-associated with the pathogenesis of PCOS and modulates steroidogenesis. It also exhibits a protective mechanism against the harmful effects of AGEs. This review elucidates and summarizes the processing of infant formula milk and the associated health hazards. Formulated according to the nutritional requirements of the newborn as a substitute for mother’s milk, formula milk is a rich source of primary adducts, such as carboxy-methyl lysine, which render an infant prone to inflammation, dementia, food allergies, and other diseases. We therefore recommend that understanding this post-translational modification is the key to unlocking the mechanisms and physiology of various metabolic syndromes.

Advanced glycation end products and their ratio to soluble receptor are associated with limitations in physical functioning only in women: results from the CARLA cohort

BACKGROUND

Advanced glycation end products (AGEs), modifications of proteins or amino acids, are increasingly produced and accumulated with age-related diseases. Recent studies suggested that the ratio of AGEs and their soluble receptor (sRAGE) is a more accurate biomarker for age-related diseases than each separately. We aim to investigate whether this also applies for physical functioning in a broad age-spectrum.

METHODS

AGE and sRAGE levels, and physical functioning (SF-12 questionnaire) of 967 men and 812 women (45-83 years) were measured in the CARLA study. We used ordinal logistic regression to examine associations between AGEs, sRAGE, and AGE/sRAGE ratio with physical functioning in sex- and age-stratified models.

RESULTS

Higher levels of AGEs and AGE/sRAGE ratio were associated with lower physical functioning only in women, even after consideration of classical lifestyle and age-related factors (education, BMI, smoking, alcohol consumption, diet, creatinine clearance, diabetes mellitus, lipid lowering and antihypertensive drugs) (odds ratio (OR) =0.86, 95%confidence interval = 0.74-0.98 and OR = 0.86, 95%CI = 0.75-0.98 for AGEs and AGE/sRAGE ratio respectively). We could not demonstrate a significant difference across age.

CONCLUSIONS

We showed a sex-specific association between physical functioning and AGEs and AGE/sRAGE, but no stronger associations of the latter with physical functioning. Further investigation is needed in the pathophysiology of this association.

Advanced Glycation End Products of Bovine Serum Albumin Suppressed Th1/Th2 Cytokine but Enhanced Monocyte IL-6 Gene Expression via MAPK-ERK and MyD88 Transduced NF-κB p50 Signaling Pathways

Advanced glycation end products (AGE), the most known aging biomarker, may cause “inflamm-aging” (i.e., chronic low-grade inflammation that develops with aging) in both aged and diabetes groups. However, the molecular bases of inflamm-aging remain obscure. We prepared AGE by incubating BSA (0.0746 mmol/L) + glucose (0.5 mol/L) at 37 °C in 5% CO₂–95% air for 1–180 days. The lysine glycation in BSA–AGE reached 77% on day 30 and 100% after day 130, whereas the glycation of arginine and cysteine was minimal. The N^ε-(carboxymethyl)-lysine content in BSA–AGE was also increased with increasing number of incubation days. The lectin-binding assay revealed that the glycation of BSA not only altered the conformational structure, but lost binding capacity with various lectins. An immunological functional assay showed that BSA–AGE > 8 μg/mL significantly suppressed normal human Th1 (IL-2 and IFN-γ) and Th2 (IL-10) mRNA expression, whereas AGE > 0.5 μg/mL enhanced monocyte IL-6 production irrelevant to cell apoptosis. The AGE-enhanced monocyte IL-6 production was via MAPK–ERK and MyD88-transduced NF-κBp50 signaling pathways. To elucidate the structure–function relationship of BSA–AGE-enhanced IL-6 production, we pre-preincubated BSA–AGE with different carbohydrate-degrading, protein-degrading, and glycoprotein-degrading enzymes. We found that trypsin and carboxypeptidase Y suppressed whereas β-galactosidase enhanced monocyte IL-6 production. In conclusion, BSA–AGE exerted both immunosuppressive and pro-inflammatory effects that are the molecular basis of inflamm-aging in aged and diabetes groups.

Glycation of Plant Proteins: Regulatory Roles and Interplay with Sugar Signalling?

Glycation can be defined as an array of non-enzymatic post-translational modifications of proteins formed by their interaction with reducing carbohydrates and carbonyl products of their degradation. Initial steps of this process rely on reducing sugars and result in the formation of early glycation products-Amadori and Heyns compounds via Schiff base intermediates, whereas their oxidative degradation or reactions of proteins with α-dicarbonyl compounds yield a heterogeneous group of advanced glycation end products (AGEs). These compounds accompany thermal processing of protein-containing foods and are known to impact on ageing, pathogenesis of diabetes mellitus and Alzheimer's disease in mammals. Surprisingly, despite high tissue carbohydrate contents, glycation of plant proteins was addressed only recently and its physiological role in plants is still not understood. Therefore, here we summarize and critically discuss the first steps done in the field of plant protein glycation during the last decade. We consider the main features of plant glycated proteome and discuss them in the context of characteristic metabolic background. Further, we address the possible role of protein glycation in plants and consider its probable contribution to protein degradation, methylglyoxal and sugar signalling, as well as interplay with antioxidant defense.

Immunomodulation by Processed Animal Feed: The Role of Maillard Reaction Products and Advanced Glycation End-Products (AGEs)

The immune system provides host protection to infection with pathogenic organisms, while at the same time providing tolerance upon exposure to harmless antigens. Thus, an impaired immune function is associated with increased susceptibility to infections with increased disease severity and thereby necessitating the therapeutic use of antibiotics. Livestock performance and feed efficiency, in addition to their health status, are dependent on the microbial load of their gut, the barrier function of the intestinal epithelium and the activity of the mucosal immune system, all of which can be modulated by dietary components. The majority of feeds that are consumed in pets and livestock have been processed. Processing promotes a non-enzymatic reaction between proteins and sugars called Maillard reaction (MR). Maillard reaction products (MRPs) and advanced Maillard reaction products (AGEs) determine taste, smell, and color of many food products therefore the MR is highly relevant for the feed industry. MRPs interact with different types of immune receptors, including the receptor for advanced glycation end products (RAGE) and immunomodulatory potential of feed proteins can be modified by Maillard reaction. This MR has become an important concern since MRPs/AGEs have been shown to contribute to increasing prevalence of diet-related chronic inflammatory states in the gut with negative health consequences and performance. The immunomodulatory effects of dietary MRPs and AGEs in livestock and pet animals are far less well-described, but widely considered to be similar to the relevant concepts and mechanisms obtained in the human field. This review will highlight immunological mechanisms underlying initiation of the innate and adaptive immune responses by MRPs/AGEs present in animal feeds, which are currently not completely understood. Bridging this knowledge gap, and taking advantage of progress in the human field, will significantly improve nutritional quality of feed and increase the prevention of diet-mediated inflammation in animals.

Expression of macrophage migration inhibitory factor in footpad skin lesions with diabetic neuropathy

Background

Diabetic neuropathy originating in distal lower extremities is associated with pain early in the disease course, overwhelming in the feet. However, the pathogenesis of diabetic neuropathy remains unclear. Macrophage migration inhibitory factor has been implicated in the onset of neuropathic pain and the development of diabetes. Objective of this study was to observe pain syndromes elicited in the footpad of diabetic neuropathy rat model and to assess the contributory role of migration inhibitory factor in the pathogenesis of diabetic neuropathy.

Methods

Diabetic neuropathy was made in Sprague Dawley rats by streptozotocin. Pain threshold was evaluated using von Frey monofilaments for 24 weeks. On comparable experiment time after streptozotocin injection, all footpads were prepared for following procedures; glutathione assay, terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling staining, immunohistochemistry staining, real-time reverse transcription polymerase chain reaction, and Western blot. Additionally, human HaCaT skin keratinocytes were treated with methylglyoxal, transfected with migration inhibitory factor/control small interfering RNA, and prepared for real-time reverse transcription polymerase chain reaction and Western blot.

Results

As compared to sham group, pain threshold was significantly reduced in diabetic neuropathy group, and glutathione was decreased in footpad skin, simultaneously, cell death was increased. Over-expression of migration inhibitory factor, accompanied by low expression of glyoxalase-I and intraepidermal nerve fibers, was shown on the footpad skin lesions of diabetic neuropathy. But, there was no significance in expression of neurotransmitters and inflammatory mediators such as transient receptor potential vanilloid 1, mas-related G protein coupled receptor D, nuclear factor kappa B, tumor necrosis factor-alpha, and interleukin-6 between diabetic neuropathy group and sham group. Intriguingly, small interfering RNA-transfected knockdown of the migration inhibitory factor gene in methylglyoxal-treated skin keratinocytes increased expression of glyoxalase-I and intraepidermal nerve fibers in comparison with control small interfering RNA-transfected cells, which was decreased by induction of methylglyoxal.

Conclusions

Our findings suggest that migration inhibitory factor can aggravate diabetic neuropathy by suppressing glyoxalase-I and intraepidermal nerve fibers on the footpad skin lesions and provoke pain. Taken together, migration inhibitory factor might offer a pharmacological approach to alleviate pain syndromes in diabetic neuropathy.

Tissue intrinsic fluorescence recovering by an empirical approach based on the PSO algorithm and its application in type 2 diabetes screening

In order to reduce the influence of scattering and absorption on tissue fluorescence spectra, after tissue fluorescence and diffuse reflectance in different tissue optical properties were simulated by the Monte Carlo method, a tissue intrinsic fluorescence recovering algorithm making use of diffuse reflectance spectrum was developed. The empirical parameters in the tissue intrinsic fluorescence recovering algorithm were coded as a particle in the solution domain, the classification performance was defined as the fitness, and then a particle swarm optimization (PSO) algorithm was established for empirical parameters optimization. The skin autofluorescence and diffuse reflectance spectra of 327 subjects were collected in Anhui Provincial Hospital. The skin intrinsic autofluorescence spectra were recovered by using the empirical approach and the integration area of the spectra were calculated as fluorescence intensity. Receiver operating characteristic (ROC) analysis for fluorescence intensity was applied to evaluate the classification performance in type 2 diabetes screening. In addition, a support vector machine (SVM) method was implemented to improve the performance of the classification. The results showed that the sensitivity and specificity were 32% and 76% respectively, and the area under the curve was 0.54 before recovering, while the sensitivity and specificity were 72% and 86% respectively, and the area under the curve was 0.86 after recovering. Furthermore, the sensitivity and specificity increased to 83% and 86% respectively when using linear SVM while 84% and 88%, respectively, when using nonlinear SVM. The results indicate that using the tissue fluorescence spectrum recovery algorithm based on PSO can improve the application of tissue fluorescence spectroscopy effectively.

Circulating Concentrations of Advanced Glycation end Products, its Association With the Development of Diabetes Mellitus

BACKGROUND

Diabetes Mellitus (DM) is characterized by the production and accumulation of advanced glycation end products (AGEs), which are one of the key mechanisms in the development of its chronic complications.

AIMS OF THE STUDY

To assess the serum AGEs concentration by a radioimmunoassay (RIA) developed in our laboratory, to establish reference values in healthy population and to evaluate the diagnostic potential of measuring longitudinal changes in circulating AGEs concentrations to predict the development of DM.

METHODS

Clinical and metabolic parameters were obtained from a cohort of 781 Mexican people, initially and then seven years later. AGEs were quantified by a specific RIA. Associations of the changes in circulating levels of AGEs with the appearance of impaired fasting glucose (IFG), and the development of DM were evaluated.

RESULTS

Diabetic subjects had higher circulating levels of AGEs than normoglycemic subjects or individuals with IFG in both samples studied (471 vs. 246 and 342 μU/mL, p <0.001; and 912 vs. 428 and 519 μU/mL, p <0.001; respectively). A multinomial logistic regression analysis showed that subjects who had AGEs concentration ≥400 μU/mL in the baseline sample had a relative risk ratio of 1.98 to develop IFG seven years later (p = 0.003). While the subjects who had AGEs concentration ≥450 μU/mL in the baseline sample had a relative risk ratio of 10.7 to develop DM seven years later (p <0.001).

CONCLUSIONS

Circulating AGEs concentration is a good early marker to predict risk of developing DM.

Matrine-Type Alkaloids Inhibit Advanced Glycation End Products Induced Reactive Oxygen Species-Mediated Apoptosis of Aortic Endothelial Cells In Vivo and In Vitro by Targeting MKK3 and p38MAPK Signaling

Background

The matrine‐type alkaloids are bioactive components extracted from Sophora flavescens, which is used in treatment of diabetes mellitus in traditional Chinese medicine. Advanced glycation end products mediate diabetic vascular complications. This study was aimed to investigate the protective effects and molecular mechanisms of matrine‐type alkaloids on advanced glycation end products–induced reactive oxygen species–mediated endothelial apoptosis.

Methods and Results

Rats aorta and cultured rat aortic endothelial cells were exposed to advanced glycation end products. Matrine‐type alkaloids, p38 mitogen‐activated protein kinase (MAPK) inhibitor, and small interference RNAs against p38 MAPK kinases MAPK kinase kinase (MKK)3 and MKK6 were administrated. Intracellular reactive oxygen species production, cell apoptosis, phosphorylation of MKKs/p38 MAPK, and expression levels of heme oxygenase/NADPH quinone oxidoreductase were assessed. The nuclear factor erythroid 2‐related factor 2 nuclear translocation and the binding activity of nuclear factor erythroid 2‐related factor 2 with antioxidant response element were also evaluated. Matrine‐type alkaloids suppressed intracellular reactive oxygen species production and inhibited endothelial cell apoptosis in vivo and in vitro by recovering phosphorylation of MKK3/6 and p38 MAPK, nuclear factor erythroid 2‐related factor 2 nuclear translocation, and antioxidant response element binding activity, as well as the expression levels of heme oxygenase/NADPH quinone oxidoreductase. p38 MAPK inhibitor treatment impaired the effects of matrine‐type alkaloids in vivo and in vitro. MKK3/6 silencing impaired the effects of matrine‐type alkaloids in vitro.

Conclusions

Matrine‐type alkaloids exert endothelial protective effects against advanced glycation end products induced reactive oxygen species–mediated apoptosis by targeting MKK3/6 and enhancing their phosphorylation.

Modifications of hemoglobin and myoglobin by Maillard reaction products (MRPs)

High performance liquid chromatography (HPLC) coupled with a Fraction Collector was employed to isolate Maillard reaction products (MRPs) formed in model systems comprising of asparagine and monosaccharides in the 60-180°C range. The primary MRP which is detected at 60°C is important for Acrylamide content and color/aroma development in foods and also in the field of food biotechnology for controlling the extent of the Maillard reaction with temperature. The discrete fractions of the reaction products were reacted with Hemoglobin (Hb) and Myoglobin (Mb) at physiological conditions and the reaction adducts were monitored by UV-vis and Attenuated Total Reflection-Fourier transform infrared (FTIR) spectrophotometry. The UV-vis kinetic profiles revealed the formation of a Soret transition characteristic of a low-spin six-coordinated species and the ATR-FTIR spectrum of the Hb-MRP and Mb-MRP fractions showed modifications in the protein Amide I and II vibrations. The UV-vis and the FTIR spectra of the Hb-MRPs indicate that the six-coordinated species is a hemichrome in which the distal E7 Histidine is coordinated to the heme Fe and blocks irreversibly the ligand binding site. Although the Mb-MRPs complex is a six-coordinated species, the 1608 cm-1 FTIR band characteristic of a hemichrome was not observed.