Lactococcus lactis KF140 Ameliorates Nonalcoholic Fatty Liver Disease Induced by Nε-Carboxymethyl-Lysine and High-Fat Diet.

SCOPE: Long-term consumption of excessive dietary advanced glycation end-products such as Nε-carboxymethyl-lysine (CML), which are produced by the Maillard reaction during food thermal processing, leads to nonalcoholic fatty liver disease (NAFLD) along with high fat consumption. The study previously finds that administration of Lactococcus lactis KF140 (LL-KF140) detoxifies CML by decreasing CML absorption both in a rat model and clinical trial. METHODS AND RESULTS: The present study evaluates the ameliorative effect of LL-KF140 on NAFLD and fatty liver-related biomarkers in a mouse model induced by CML and high fat. LL-KF140 is orally administered to mice at a concentration of 1 × 107 or 1 × 108 colony-forming unit (CFU) per mouse for 8 weeks. LL-KF140 administration ameliorates the NAFLD-related symptoms by reducing body weight and fat mass gain along with levels of serum aspartate transaminase, alanine transferase, and lipids as well as glucose intolerance and insulin resistance in CML-treated mice. In addition, histological analysis including staining and western blotting shows that LL-KF140 suppresses the lipogenesis pathway and CML absorption, thereby suppressing CML-induced NAFLD. CONCLUSION: These findings suggest that LL-KF140 attenuates dietary CML-induced NAFLD by suppressing the de novo lipogenesis pathway, and it may be used as a probiotic strain.

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.

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.

Glycation in the cardiomyocyte.

Glycation is a protein post-translational modification that can occur on lysine and arginine residues as a result of a non-enzymatic process known as the Maillard reaction. This modification is irreversible, so the only way it can be removed is by protein degradation and replacement. Small reactive carbonyl species, glyoxal and methylglyoxal, are the primary glycating agents and are elevated in several conditions associated with an increased risk of cardiovascular disease, including diabetes, rheumatoid arthritis, smoking, and aging. Thus, how protein glycation impacts the cardiomyocyte is of particular interest, to both understand how these conditions increase the risk of cardiovascular disease and how glycation might be targeted therapeutically. Glycation can affect the cardiomyocyte through extracellular mechanisms, including RAGE-based signaling, glycation of the extracellular matrix that modifies the mechanical environment, and signaling from the vasculature. Intracellular glycation of the cardiomyocyte can impact calcium handling, protein quality control and cell death pathways, as well as the cytoskeleton, resulting in a blunted contractility. While reducing protein glycation and its impact on the heart has been an active area of drug development, multiple clinical trials have had mixed results and these compounds have not been translated to the clinic-highlighting the challenges of modulating myocyte glycation. Here we will review protein glycation and its effects on the cardiomyocyte, therapeutic attempts to reverse these, and offer insight as to the future of glycation studies and patient treatment.

Bone Fragility in High Fat Diet-induced Obesity is Partially Independent of Type 2 Diabetes in Mice.

Obesity and type 2 diabetes (T2D) are risk factors for fragility fractures. It is unknown whether this elevated risk is due to a diet favoring obesity or the diabetes that often occurs with obesity. Therefore, we hypothesized that the fracture resistance of bone is lower in mice fed with a high fat diet (45% kcal; HFD) than in mice that fed on a similar, control diet (10% kcal; LFD), regardless of whether the mice developed overt T2D. Sixteen-week-old, male NON/ShiLtJ mice (resistant to T2D) and age-matched, male NONcNZO10/LtJ (prone to T2D) received a control LFD or HFD for 21 weeks. HFD increased the bodyweight to a greater extent in the ShiLtJ mice compared to the NZO10 mice, while blood glucose levels were significantly higher in NZO10 than in ShiLtJ mice. As such, the glycated hemoglobin A1c (HbA1c) levels exceeded 10% in NZO10 mice, but it remained below 6% in ShiLtJ mice. Diet did not affect HbA1c. HFD lowered trabecular number and bone volume fraction of the distal femur metaphysis (micro-computed tomography or µCT) in both strains. For the femur mid-diaphysis, HFD significantly reduced the yield moment (mechanical testing by three-point bending) in both strains but did not affect cross-sectional bone area, cortical thickness, nor cortical tissue mineral density (µCT). Furthermore, the effect of diet on yield moment was independent of the structural resistance of the femur mid-diaphysis suggesting a negative effect of HFD on characteristics of the bone matrix. However, neither Raman spectroscopy nor assays of advanced glycation end-products identified how HFD affected the matrix. HFD also lowered the resistance of cortical bone to crack growth in only the diabetic NZO10 mice (fracture toughness testing of other femur), while HFD reduced the ultimate force of the L6 vertebra in both strains (compression testing). In conclusion, the HFD-related decrease in bone strength can occur in mice resistant and prone to diabetes indicating that a diet high in fat deleteriously affects bone without necessarily causing hyperglycemia.

Generation and Accumulation of Various Advanced Glycation End-Products in Cardiomyocytes May Induce Cardiovascular Disease.

Cardiomyocyte dysfunction and cardiovascular diseases (CVDs) can be classified as ischemic or non-ischemic. We consider the induction of cardiac tissue dysfunction by intracellular advanced glycation end-products (AGEs) in cardiomyocytes as a novel type of non-ischemic CVD. Various types of AGEs can be generated from saccharides (glucose and fructose) and their intermediate/non-enzymatic reaction byproducts. Recently, certain types of AGEs (Nε-carboxymethyl-lycine [CML], 2-ammnonio-6-[4-(hydroxymetyl)-3-oxidopyridinium-1-yl]-hexanoate-lysine [4-hydroxymethyl-OP-lysine, hydroxymethyl-OP-lysine], and Nδ-(5-hydro-5-methyl-4-imidazolone-2-yl)-ornithine [MG-H1]) were identified and quantified in the ryanodine receptor 2 (RyR2) and F-actin-tropomyosin filament in the cardiomyocytes of mice or patients with diabetes and/or heart failure. Under these conditions, the excessive leakage of Ca2+ from glycated RyR2 and reduced contractile force from glycated F-actin-tropomyosin filaments induce cardiomyocyte dysfunction. CVDs are included in lifestyle-related diseases (LSRDs), which ancient people recognized and prevented using traditional medicines (e.g., Kampo medicines). Various natural compounds, such as quercetin, curcumin, and epigallocatechin-3-gallate, in these drugs can inhibit the generation of intracellular AGEs through mechanisms such as the carbonyl trap effect and glyoxalase 1 activation, potentially preventing CVDs caused by intracellular AGEs, such as CML, hydroxymethyl-OP, and MG-H1. These investigations showed that bioactive herbal extracts obtained from traditional medicine treatments may contain compounds that prevent CVDs.

Toxic Advanced Glycation End-Products Inhibit Axonal Elongation Mediated by ß-Tubulin Aggregation in Mice Optic Nerves.

Advanced glycation end-products (AGEs) form through non-enzymatic glycation of various proteins. Optic nerve degeneration is a frequent complication of diabetes, and retinal AGE accumulation is strongly linked to the development of diabetic retinopathy. Type 2 diabetes mellitus is a major risk factor for Alzheimer's disease (AD), with patients often exhibiting optic axon degeneration in the nerve fiber layer. Notably, a gap exists in our understanding of how AGEs contribute to neuronal degeneration in the optic nerve within the context of both diabetes and AD. Our previous work demonstrated that glyceraldehyde (GA)-derived toxic advanced glycation end-products (TAGE) disrupt neurite outgrowth through TAGE-ß-tubulin aggregation and tau phosphorylation in neural cultures. In this study, we further illustrated GA-induced suppression of optic nerve axonal elongation via abnormal ß-tubulin aggregation in mouse retinas. Elucidating this optic nerve degeneration mechanism holds promise for bridging the knowledge gap regarding vision loss associated with diabetes mellitus and AD.

Glucoselysine, a unique advanced glycation end-product of the polyol pathway and its association with vascular complications in type 2 diabetes.

Glucoselysine (GL) is an unique advanced glycation end-product derived from fructose. The main source of fructose in vivo is the polyol pathway, and an increase in its activity leads to diabetic complications. Here, we aimed to demonstrate that GL can serve as an indicator of the polyol pathway activity. Additionally, we propose a novel approach for detecting GL in peripheral blood samples using liquid chromatography-tandem mass spectrometry and evaluate its clinical usefulness. We successfully circumvent interference from fructoselysine, which shares the same molecular weight as GL, by performing ultrafiltration and hydrolysis without reduction, successfully generating adequate peaks for quantification in serum. Furthermore, using immortalized aldose reductase KO mouse Schwann cells, we demonstrate that GL reflects the downstream activity of the polyol pathway and that GL produced intracellularly is released into the extracellular space. Clinical studies reveal that GL levels in patients with type 2 diabetes are significantly higher than those in healthy participants, while Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)ornithine (MG-H1) levels are significantly lower. Both GL and MG-H1 show higher values among patients with vascular complications; however, GL varies more markedly than MG-H1 as well as hemoglobin A1c, fasting plasma glucose, and estimated glomerular filtration rate. Furthermore, GL remains consistently stable under various existing drug treatments for type 2 diabetes, whereas MG-H1 is impacted. To the best of our knowledge, we provide important insights in predicting diabetic complications caused by enhanced polyol pathway activity via assessment of GL levels in peripheral blood samples from patients.

Developing a Portable Autofluorescence Detection System and Its Application in Biological Samples.

Advanced glycation end-products (AGEs) are complex compounds closely associated with several chronic diseases, especially diabetes mellitus (DM). Current methods for detecting AGEs are not suitable for screening large populations, or for long-term monitoring. This paper introduces a portable autofluorescence detection system that measures the concentration of AGEs in the skin based on the fluorescence characteristics of AGEs in biological tissues. The system employs a 395 nm laser LED to excite the fluorescence of AGEs, and uses a photodetector to capture the fluorescence intensity. A model correlating fluorescence intensity with AGEs concentration facilitates the detection of AGEs levels. To account for the variation in optical properties of different individuals' skin, the system includes a 520 nm light source for calibration. The system features a compact design, measuring only 60 mm × 50 mm × 20 mm, and is equipped with a miniature STM32 module for control and a battery for extended operation, making it easy for subjects to wear. To validate the system's effectiveness, it was tested on 14 volunteers to examine the correlation between AGEs and glycated hemoglobin, revealing a correlation coefficient of 0.49. Additionally, long-term monitoring of AGEs' fluorescence and blood sugar levels showed a correlation trend exceeding 0.95, indicating that AGEs reflect changes in blood sugar levels to some extent. Further, by constructing a multivariate predictive model, the study also found that AGEs levels are correlated with age, BMI, gender, and a physical activity index, providing new insights for predicting AGEs content and blood sugar levels. This research supports the early diagnosis and treatment of chronic diseases such as diabetes, and offers a potentially useful tool for future clinical applications.

A Protein Complex of Liver Origin Activates a Pro-inflammatory Program That Drives Hepatic and Intestinal Injury in Alcohol-Associated Liver Disease.

BACKGROUND & AIMS: There is limited information on how the liver-to-gut axis contributes to alcohol-associated liver disease (AALD). We previously identified that high-mobility group box-1 (HMGB1) undergoes oxidation in hepatocytes and demonstrated elevated serum levels of oxidized HMGB1 ([O] HMGB1) in alcoholic patients. Since interleukin-1 beta (IL-1B) increases in AALD, we hypothesized hepatocyte-derived [O] HMGB1 could interact with IL-1B to activate a pro-inflammatory program that, besides being detrimental to the liver, drives intestinal barrier dysfunction. RESULTS: Alcohol-fed RageΔMye mice exhibited decreased nuclear factor kappa B signaling, a pro-inflammatory signature, and reduced total intestinal permeability, resulting in protection from AALD. In addition, [O] HMGB1 bound and signaled through the receptor for advanced-glycation end-products (RAGE) in myeloid cells, driving hepatic inflammation, intestinal permeability, and increased portal blood lipopolysaccharide in AALD. We identified that [O] HMGB1 formed a complex with IL-1B, which was found in the livers of patients with acute alcoholic hepatitis and mice with AALD. This complex originated from the liver, because it was absent in the intestine when hepatocytes did not produce [O] HMGB1. Mechanistically, the complex bound RAGE in Kupffer cells and macrophages induced a pro-inflammatory program. Moreover, it bound RAGE in intestinal macrophages and epithelial cells, leading to intestinal inflammation, altered intestinal epithelial cell tight junction protein expression, increased intestinal permeability, and elevated portal blood lipopolysaccharide, enhancing AALD pathogenesis. CONCLUSIONS: We identified a protein complex of liver origin that amplifies the pro-inflammatory feedback loop in AALD; therefore, targeting this complex could have significant therapeutic potential.

Trapping mechanism by di-d-psicose anhydride with methylglyoxal for prevention of diabetic nephropathy.

Di-d-psicose anhydride (DPA), derived from functional rare saccharide as d-psicose, is investigated for its strong chelating ability. Methylglyoxal (MGO), an important precursor of advanced glycation end-products (AGEs), promotes obesity, and causes complications such as diabetic nephropathy. On mesangial cells, DPA can substantially reduce the negative effects of MGO. DPA effectively trapping MGO in mesangial cells. The bonding properties of the DPA-MGO adduct were discussed by mass spectrometry and nuclear magnetic resonance (NMR). The NMR spectra of the DPA-MGO adduct provide evidence for chelation bonding. The inhibition of AGE formation and the mass spectrometry results of the DPA-MGO adduct indicate that DPA can scavenge MGO at a molar ratio of 1:1. DPA suppressed 330 % of the up-regulated receptor for an AGEs protein expression to a normal level and restored the suppressed glyoxalase 1 level to 86 % of the normal group. This research provides important evidence and theoretical basis for the development of AGE inhibitors derived from rare saccharide.

Deciphering the inhibitory mechanisms of betanin and phyllocactin from Hylocereus polyrhizus peel on protein glycation, with insights into their application in bread.

Protein glycation closely intertwines with the pathogenesis of various diseases, sparking a growing interest in exploring natural antiglycation agents. Herein, high-purity betacyanins (betanin and phyllocactin) derived from Hylocereus polyrhizus peel were studied for their antiglycation potential using an in vitro bovine serum albumin (BSA)-glucose model. Notably, betacyanins outperformed aminoguanidine, a recognized antiglycation agent, in inhibiting glycation product formation across different stages, especially advanced glycation end-products (AGEs). Interestingly, phyllocactin displayed stronger antiglycation activity than betanin. Subsequent mechanistic studies employing molecular docking analysis and fluorescence quenching assay unveiled that betacyanins interact with BSA endothermically and spontaneously, with hydrophobic forces playing a dominant role. Remarkably, phyllocactin demonstrated higher binding affinity and stability to BSA than betanin. Furthermore, the incorporation of betacyanins into bread dose-dependently suppressed AGEs formation during baking and shows promise for inhibiting in vivo glycation process post-consumption. Overall, this study highlights the substantial potential of betacyanins as natural antiglycation agents.

Accumulation of Non-Pathological Liver Fat Is Associated with the Loss of Glyoxalase I Activity in Humans.

The underlying molecular mechanisms for the development of non-alcoholic fatty liver (NAFL) and its progression to advanced liver diseases remain elusive. Glyoxalase 1 (Glo1) loss, leading to elevated methylglyoxal (MG) and dicarbonyl stress, has been implicated in various diseases, including obesity-related conditions. This study aimed to investigate changes in the glyoxalase system in individuals with non-pathological liver fat. Liver biopsies were obtained from 30 individuals with a narrow range of BMI (24.6-29.8 kg/m2). Whole-body insulin sensitivity was assessed using HOMA-IR. Liver biopsies were analyzed for total triglyceride content, Glo1 and Glo2 mRNA, protein expression, and activity. Liquid chromatography-tandem mass spectrometry determined liver dicarbonyl content and oxidation and glycation biomarkers. Liver Glo1 activity showed an inverse correlation with HOMA-IR and liver triglyceride content, but not BMI. Despite reduced Glo1 activity, no associations were found with elevated liver dicarbonyls or glycation markers. A sex dimorphism was observed in Glo1, with females exhibiting significantly lower liver Glo1 protein expression and activity, and higher liver MG-H1 content compared to males. This study demonstrates that increasing liver fat, even within a non-pathological range, is associated with reduced Glo1 activity.

Inhibition and Mechanism of Protein Nonenzymatic Glycation by Lactobacillus fermentum.

Lactobacillus fermentum (L. fermentum) was first evaluated as a potential advanced glycation end-product (AGE) formation inhibitor by establishing a bovine serum albumin (BSA) + glucose (glu) glycation model in the present study. The results showed that the highest inhibition rates of pentosidine and total fluorescent AGEs by L. fermentum were approximately 51.67% and 77.22%, respectively, which were higher than that of aminoguanidine (AG). Mechanistic analysis showed that L. fermentum could capture methylglyoxal and glyoxal, inhibit carbonyl and sulfhydryl oxidation, reduce the binding of glucose and amino groups, increase total phenolic content and antioxidant activity, and release intracellular substances to scavenge free radicals; these abilities were the basis of the antiglycation mechanism of L. fermentum. In addition, L. fermentum significantly prevented conformational changes in proteins during glycation, reduced protein cross-linking by 35.67%, and protected the intrinsic fluorophore. Therefore, the inhibition of L. fermentum on glycation mainly occurs through antioxidation, the capture of dicarbonyl compounds, and the protection of the BSA structure. These findings collectively suggest that Lactobacillus is an inhibitor of protein glycation and AGE formation and has the potential for nutraceutical applications.

The effects of advanced glycation end-products on skin and potential anti-glycation strategies.

The advanced glycation end-products (AGEs) are produced through non-enzymatic glycation between reducing sugars and free amino groups, such as proteins, lipids or nucleic acids. AGEs can enter the body through daily dietary intake and can also be generated internally via normal metabolism and external stimuli. AGEs bind to cell surface receptors for AGEs, triggering oxidative stress and inflammation responses that lead to skin ageing and various diseases. Evidence shows that AGEs contribute to skin dysfunction and ageing. This review introduces the basic information, the sources, the metabolism and absorption of AGEs. We also summarise the detrimental mechanisms of AGEs to skin ageing and other chronic diseases. For the potential strategies for counteracting AGEs to skin and other organs, we summarised the pathways that could be utilised to resist glycation. Chemical and natural-derived anti-glycation approaches are overviewed. This work offers an understanding of AGEs to skin ageing and other chronic diseases and may provide perspectives for the development of anti-glycation strategies.

Association between advanced glycation end-products and fall risk in older adults: The Yakumo Study.

AIM: Advanced glycation end-products (AGEs) are irreversibly and heterogeneously formed compounds during the non-enzymatic modification of macromolecules, such as proteins. Aging and lifestyle habits, such as high-fat and high-protein diets, and smoking, promote AGEs accumulation. This study aimed to investigate the relationship between fall risk and AGEs in community-dwelling older adults. METHODS: This cross-sectional study included patients from the 2022 Yakumo Study who were evaluated for fall risk index 5-items version, locomotive syndrome stage and AGEs. AGEs were evaluated using Skin autofluorescence (SAF) measured by the AGE reader (DiagnOptics Technologies BV, Groningen, the Netherlands). We divided the participants into two groups according to the presence or absence of fall risk (fall risk index 5-items version ≥6 or not), and investigated the factors associated with fall risk. RESULTS: The fall risk group had a higher age and SAF, and a higher proportion of locomotive syndrome stage >2 than the without fall risk group in patients aged ≥65 years (P < 0.01). The multivariate logistic regression analysis after adjustment of age, sex and body mass index showed that locomotive syndrome stage ≥2 and SAF were independent associators of fall risk in older adults (odds ratio 3.26, P < 0.01, odds ratio 2.96, P < 0.05, respectively). The optimal cutoff value of the SAF for fall risk was 2.4 (area under the curve 0.631; 95% CI 0.53-0.733; sensitivity 0.415; specificity 0.814; P < 0.05). CONCLUSION: The accumulation of AGEs in skin tissues can be used to screen for fall risk comprehensively. Geriatr Gerontol Int 2024; 24: 517-522.

The antiglycation potential of H1 receptor antagonists - in vitro studies in bovine serum albumin model and in silico molecular docking analyses.

The H1 receptor belongs to the family of rhodopsin-like G-protein-coupled receptors activated by the biogenic amine histamine. H1 receptor antagonists are widely used in the treatment of allergies. However, these drugs could have a much broader spectrum of activity, including hypoglycemic effects, which can broaden the spectrum of their use. The aim of the study was to evaluate the antiglycation potential of twelve H1 receptor antagonists (diphenhydramine, antazoline, promethazine, ketotifen, clemastine, pheniramine, cetirizine, levocetirizine, bilastine, fexofenadine, desloratadine, and loratadine). Bovine serum albumin (BSA) was glycated with sugars (glucose, fructose, galactose, and ribose) and aldehydes (glyoxal and methylglyoxal) in the presence of H1 blockers. The tested substances did not induce a significant decrease in the content of albumin glycation end-products, and the inhibition rate of glycoxidation was not influenced by the chemical structure or generation of H1 blockers. None of the tested H1 receptor antagonists exhibited strong antiglycation activity. Antiglycemic potential of H1 blockers could be attributed to their antioxidant and anti-inflammatory activity, as well as their effects on carbohydrate metabolism/metabolic balance at the systemic level.

Mineral and cross-linking in collagen fibrils: The mechanical behavior of bone tissue at the nano-scale.

The mineralized collagen fibril is the main building block of hard tissues and it directly affects the macroscopic mechanics of biological tissues such as bone. The mechanical behavior of the fibril itself is determined by its structure: the content of collagen molecules, minerals, and cross-links, and the mechanical interactions and properties of these components. Advanced-Glycation-Endproducts (AGEs) cross-linking between tropocollagen molecules within the collagen fibril is one important factor that is believed to have a major influence on the tissue. For instance, it has been shown that brittleness in bone correlates with increased AGEs densities. However, the underlying nano-scale mechanisms within the mineralized collagen fibril remain unknown. Here, we study the effect of mineral and AGEs cross-linking on fibril deformation and fracture behavior by performing destructive tensile tests using coarse-grained molecular dynamics simulations. Our results demonstrate that after exceeding a critical content of mineral, it induces stiffening of the collagen fibril at high strain levels. We show that mineral morphology and location affect collagen fibril mechanics: The mineral content at which this stiffening occurs depends on the mineral's location and morphology. Further, both, increasing AGEs density and mineral content lead to stiffening and increased peak stresses. At low mineral contents, the mechanical response of the fibril is dominated by the AGEs, while at high mineral contents, the mineral itself determines fibril mechanics.

The RAGE Axis: A Relevant Inflammatory Hub in Human Diseases.

In 1992, a transcendental report suggested that the receptor of advanced glycation end-products (RAGE) functions as a cell surface receptor for a wide and diverse group of compounds, commonly referred to as advanced glycation end-products (AGEs), resulting from the non-enzymatic glycation of lipids and proteins in response to hyperglycemia. The interaction of these compounds with RAGE represents an essential element in triggering the cellular response to proteins or lipids that become glycated. Although initially demonstrated for diabetes complications, a growing body of evidence clearly supports RAGE's role in human diseases. Moreover, the recognizing capacities of this receptor have been extended to a plethora of structurally diverse ligands. As a result, it has been acknowledged as a pattern recognition receptor (PRR) and functionally categorized as the RAGE axis. The ligation to RAGE leads the initiation of a complex signaling cascade and thus triggering crucial cellular events in the pathophysiology of many human diseases. In the present review, we intend to summarize basic features of the RAGE axis biology as well as its contribution to some relevant human diseases such as metabolic diseases, neurodegenerative, cardiovascular, autoimmune, and chronic airways diseases, and cancer as a result of exposure to AGEs, as well as many other ligands.

Age-dependent changes in collagen crosslinks reduce the mechanical toughness of human meniscus.

The mechanical resilience of the knee meniscus is provided by a group of structural proteins in the extracellular matrix. Aging can alter the quantity and molecular structure of these proteins making the meniscus more susceptible to debilitating tears. In this study, we determined the effect of aging on the quantity of structural proteins and collagen crosslinks in human lateral meniscus, and examined whether the quantity of these molecules was predictive of tensile toughness (area under the stress-strain curve). Two age groups were tested: a young group under 40 and an older group over 65 years old. Using mass spectrometry, we quantified the abundance of proteins and collagen crosslinks in meniscal tissue that was adjacent to the dumbbell-shaped specimens used to measure uniaxial tensile toughness parallel or perpendicular to the circumferential fiber orientation. We found that the enzymatic collagen crosslink deoxypyridinoline had a significant positive correlation with toughness, and reductions in the quantity of this crosslink with aging were associated with a loss of toughness in the ground substance and fibers. The non-enzymatic collagen crosslink carboxymethyl-lysine increased in quantity with aging, and these increases corresponded to reductions in ground substance toughness. For the collagenous (Types I, II, IV, VI, VIII) and non-collagenous structural proteins (elastin, decorin, biglycan, prolargin) analyzed in this study, only the quantity of collagen VIII was predictive of toughness. This study provides valuable insights on the structure-function relationships of the human meniscus, and how aging causes structural adaptations that weaken the tissue's mechanical integrity.