Collagen Glycation Research Articles

Early Stages of Ex Vivo Collagen Glycation Disrupt the Cellular Interaction and Its Remodeling by Mesenchymal Stem Cells-Morphological and Biochemical Evidence.

Mesenchymal stem cells (MSCs), pivotal for tissue repair, utilize collagen to restore structural integrity in damaged tissue, preserving its organization through concomitant remodeling. The non-enzymatic glycation of collagen potentially compromises MSC communication, particularly upon advancing the process, underlying various pathologies such as late-stage diabetic complications and aging. However, an understanding of the impact of early-stage collagen glycation on MSC interaction is lacking. This study examines the fate of in vitro glycated rat tail collagen (RTC) upon exposure to glucose for 1 or 5 days in contact with MSCs. Utilizing human adipose tissue-derived MSCs (ADMSCs), we demonstrate their significantly altered interaction with glycated collagen, characterized morphologically by reduced cell spreading, diminished focal adhesions formation, and attenuated development of the actin cytoskeleton. The morphological findings were confirmed by ImageJ 1.54g morphometric analysis with the most significant drop in the cell spreading area (CSA), from 246.8 μm2 for the native collagen to 216.8 μm2 and 163.7 μm2 for glycated ones, for 1 day and 5 days, respectively, and a similar trend was observed for cell perimeter 112.9 μm vs. 95.1 μm and 86.2 μm, respectively. These data suggest impaired recognition of early glycated collagen by integrin receptors. Moreover, they coincide with the reduced fibril-like reorganization of adsorbed FITC-collagen (indicating impaired remodeling) and a presumed decreased sensitivity to proteases. Indeed, confirmatory assays reveal diminished FITC-collagen degradation for glycated samples at 1 day and 5 days by attached cells (22.8 and 30.4%) and reduced proteolysis upon exogenous collagenase addition (24.5 and 40.4%) in a cell-free system, respectively. The mechanisms behind these effects remain uncertain, although differential scanning calorimetry confirms subtle structural/thermodynamic changes in glycated collagen.

Diabetes Mellitus Predicts Severe Respiratory Failure After Aortic Arch Replacement

Objective: The lung is a target organ of diabetes mellitus (DM) via glycation of pulmonary elastin and collagen. In addition, hyperglycemia facilitates hypercapnic respiratory failure, which is instead mitigated by low‐carbohydrate high‐lipid (LC‐HL) nutrition. We sought to determine the association between diabetes and severe respiratory failure (SRF, i.e., need of reintubation\tracheostomy) after open aortic arch replacement (AAR).Methods: Machine learning algorithms were evaluated for precision and recall (F2 score) and for clinical applicability to predict SRF. Conditional regression evaluated independent predictors of SRF after 1:2 propensity‐score matching.Results: Information on diabetic status was available in 1275 patients undergoing AAR (1997–2023). Although support vector machine presented the highest F2 score (F2 = 0.337), conditional inference trees provided the most clinically applicable algorithm: diabetes was the best predictor of SRF, which occurred in 20/150 diabetics (13.3%) vs. 40/1125 nondiabetics (3.6%) (p < 0.01). In diabetics, left ventricular ejection fraction (LVEF) was the next best predictor of SRF, which occurred in 8/20 diabetics with LVEF ≤ 30% (40%) vs. 12/130 diabetics with LVEF >30% (9.2%) (p = 0.02). In nondiabetics, chronic obstructive pulmonary disease (COPD) was the next best predictor of respiratory failure, which occurred in 14/177 nondiabetics with COPD (7.9%) vs. 26/948 nondiabetics without COPD (2.7%) (p = 0.01). In the matched sample, diabetes was independently able to predict SRF (OR 2.20, 95% CI 1.10 | 4.42).Conclusions: DM was the best predictor of SRF after AAR. Strict glycemic control and LC‐HL nutrition should be evaluated as measures to reduce postoperative SRF in diabetic patients.

Identification of Desiccation Stress-Inducible Antioxidative and Antiglycative Ultraviolet-Absorbing Oxylipins, Saclipin A and Saclipin B, in an Edible Cyanobacterium Aphanothece sacrum.

Aphanothece sacrum, a freshwater cyanobacterium, is an edible cyanobacterial strain. We identified two compounds belonging to the oxylipin family that possess UV-absorbing abilities and accumulate in the dried sample of A. sacrum. The compounds, named saclipin A and saclipin B, exhibited strong UV-absorption properties with the absorption maxima at 316 and 319 nm, respectively, and the molar extinction coefficients of 26,454 and 30,555 M-1 cm-1, respectively. The chemical structures of saclipins A and B have been elucidated, revealing that they have an all-E and a 12Z isomeric relationship within the triene structure. The saclipins could be isomerized by photoirradiation, with the cis-form saclipin B proving to be more stable in methanol, ethanol, or acetonitrile. Under drought stress conditions, the accumulation of saclipins A and B in A. sacrum was found to be increased 20- and 10-fold, respectively. Purified saclipins from A. sacrum showed biocompatibility and valuable bioactivities. Specifically, saclipins exhibited radical scavenging activity, maintaining their activity even 40 min after the reaction began. Additionally, they demonstrated inhibitory activity against glycation of elastin and collagen, which are constituents of dermal tissue. Notably, saclipins showed higher activity than the well-known glycation inhibitor aminoguanidine against collagen glycation.

The effect of antioxidant therapy on the course of predialysis chronic kidney disease in a patient with comorbidity

Chronic kidney disease (CKD) is almost always associated with comorbidities such as diabetes, hyperuricemia/gout, urolithiasis, often with urinary tract infection, hypertension, polycystic kidney disease, and other conditions. Autosomal dominant polycystic kidney disease is an inherited kidney disease (1/1000–1/400 worldwide) affecting mainly adults, caused predominantly by mutations in PKD1 (85–90 % of cases) and PKD2 genes (10–15 % of cases), which encode polycystin-1 and polycystin-2 proteins, respectively. In adults with preserved kidney function, the prevalence of gout increases from 1 to 2 % (hyperuricemia up to 11 %), in patients with CKD stage 4 — up to 32 % (hyperuricemia up to 80 %). 70 % of patients with gout and 50 % of patients with hyperuricemia have stage 2 CKD. CKD contributes to a decrease in the urinary excretion of uric acid. In patients with CKD, hyperuricemia is considered to be a serum uric acid level > 6 mg/dL in women and > 7 mg/dL in men. Hyperuricemia is very often observed in hypertension and type 2 diabetes. In patients with kidney disease, diabetes is a major factor of mortality and morbidity. Diabetic nephropathy can be suspected in a patient with type 2 diabetes in the presence of albuminuria and/or diabetic retinopathy. Signs of diabetic nephropathy: basement membrane thickening, mesangial expansion, and increased vascular permeability to albumin induced by nonenzymatic glycation of collagen and laminin. Comorbidity has a negative impact on patients’ health due to increased morbidity and mortality. Such patients are at risk of rapid progression of CKD into the end stage, which requires renal replacement therapy. Therefore, early diagnosis, treatment and prevention of CKD complications are important for such patients. This article highlights the impact of antioxidant therapy and phytoneering on the course of CKD in patients with comorbidities.

Exploration of nutritional, pharmacological, and the processing trends for valorization of finger millet (Eleusine coracana): A review.

High nutrient variability and food security are the needs of the hour. Millets may be as effective as other cereal crops for dealing with severe malnutrition and increasing global population problems. Due to their physiologically active components, millets have attracted more research interest. Finger millet (FM), one of the climate-resilient and minor cereal crop species, is well known for several health benefits, primarily attributed to its nutritional value and polyphenolic content. FM seed coat phenolics exhibit excellent anti-diabetic, anti-oxidant, antimicrobial, anti-osteoporosis, wound healing, anti-lithiatic, inhibiting collagen glycation, cross-linking, and enzyme properties, which may serve well for the pharmacological purposes. Furthermore, the processing of FM is an important factor in its commercial use. It is necessary to invent some novel technologies to increase the productivity of FM by lowering the cost of processing and its effective utilization in the pharmaceutical and food industries. The literature presented will further explore the potential prospects of processing as well as value-added utilization and its nutritional and pharmacological aspects in view of initiating further research in the food industry to formulate ready-to-eat and ready-to-cook products, thereby acting as future crops for sustainability.

GVHD in its sclerodermiform form revealing type 1 diabetes: A case report

Sclerodermiform syndrome is Common in diabetic, it encompasses a set of manifestations that preferentially affect the hands and back, but the association of type 1 diabetes with systemic sclerosis is a rare entity. We report the case of 18-year-old patient from a consanguineous marriage, with a history of acute myeloid leukemia which he was treated by an allograft in France associated with chemotherapy 9 session and immunosuppressants currently in complete remission, diabetic type 1 for 4 years, hypothyroidism under levothyrox 50ug / d. At the interrogation the patient reported the consequences of the graft were marked by stage I cutaneous GVHD confirmed by skin biopsy of which he received corticosteroid therapy at a dose of 10mg / day in addition to neoral or slightly atrophic hyperpigmented macules not sclerotic at the level of the back and the lateral surface of the left foot. The patient also had corticosteroid-induced complications, including diabetes and osteoporosis. On physical examination tendon retraction, elbows and finger, Amyotrophy of the hands, palpable thyroid not increased volume allowed for glycemic imbalance. At TSH biology = 6uui / ml, HBA1C = 8%, anti-GAD antibody negative to cervical ultrasound: thyroid hypotrophy with thyroid nodules classified EUTIRADS 2. The patient is referred for follow-up in dermatology. The association of sweet diabetes and sclerodermiform lesions is frequently linked to the glycemic imbalance responsible for an accumulation of extracellar matrix and excessive glycation of collagen. The search for signs of scleroderma should be evoked in front of a diabetic hand syndrome to Watch for and treat associated pathologies.

The Association of Diabetic Cheiroarthropathy With Microvascular Complications of Type 2 Diabetes Mellitus: A Cross-Sectional Study.

Introduction Diabetic cheiroarthropathy (DCA), also known as the syndrome of limited joint mobility (LJM), is among the most underdiagnosed complications of diabetes mellitus (DM). Although not severe, it can hamper the day-to-day activities of the patient and significantly reduce the quality of life. It is hypothesized to be due to increased glycation of collagen around joints. The objective of our study was to examine the association of diabetic cheiroarthropathy with microvascular complications of type 2 diabetes mellitus. Methods The study was conducted on 251 previously diagnosed cases of type 2 DM. Patients with previous contractures due to any other cause, who are diagnosed cases of rheumatoid arthritis and scleroderma, and other risk factors such as cardiac or renal disease were excluded from the study. All subjects were subjected to a detailed clinical history including a past history, thorough physical examination, prayer test, tabletop sign, and passive extension of fingers. Patients who are diagnosed with diabetic cheiroarthropathy were then screened for microalbuminuria, fundus examination, and monofilament testandclinical examination to look for the presence of microvascular complications. Results Out of the 251 patients, 46 (18.3%) were found to have diabetic cheiroarthropathy. Fifteen (34.9%) cheiroarthropathy patients had neuropathy compared to 14.9% without diabetic cheiroarthropathy, which was statistically significant. We found that there was an increased incidence of diabetic neuropathy in subjects with cheiroarthropathy. Thirty (35.7%) patients with diabetic cheiroarthropathy had diabetic retinopathy compared to 9.6% without diabetic cheiroarthropathy. Twenty-six (26.8%) patients with diabetic cheiroarthropathy had diabetic nephropathy compared to 13% without diabetic cheiroarthropathy. We identified from our study that patients with diabetic cheiroarthropathy had an increased risk of developing microvascular complications. Conclusion There is an increased prevalence of diabetic nephropathy, diabetic neuropathy, and diabetic retinopathy in patients with diabetic cheiroarthropathy. The presence of diabetic cheiroarthropathy hence warrants better control of the patient's glycemic status to preventfurther deterioration of diabetes-related complications.

Anti-glycation and antioxidant effects of Chaga mushroom decoction extracted with a fermentation medium

Glycation reactions between proteins and sugars or their metabolites produce advanced glycation end-products, and the glycation of collagen in normal human dermal fibroblasts (NHDF) causes skin spots and freckles. UV exposure induces oxidative stress in NHDF, which overexpresses enzymes that degrade collagen, resulting in dry skin and wrinkling. Herein, we produced a novel polyphenolic decoction of Chaga mushroom extracted with a fermentation medium. Chaga polyphenol decoction (CPD) inhibited the glycation of albumin and collagen gel 3 to 4 times more than 2-aminoguanidine. The antioxidant effects of CPD were investigated using the fluorescence of an intracellular reactive oxygen species (ROS) scavenger, and NHDF exposed to UV-A for 60 min (9.5 J/cm2) after pre-treatment with 190 µg/mL of CPD suppressed ROS scavenger emission by 50 % compared to treatment with phosphate buffer saline. These results suggest that CPD might be a promising glycation inhibitor and ROS scavenger.

Extracellular Matrix Glycation and Crosslinking in Mammary Tumor Progression.

Breast cancer progression is accompanied by profound extracellular matrix (ECM) remodeling. A greater abundance of aligned fibrillar collagen is characteristic of invasive and aggressive breast cancers and has been associated with elevated activity of collagen crosslinking enzymes, such as lysyl oxidase (LOX) and lysyl hydroxylases (LH) and the formation of more mature collagen matrix crosslinks. Aligned collagen fibers can facilitate metastatic dissemination of tumor cells, and LOX inhibitors have been used to inhibit tumor progression and metastasis in experimental models. Thus, a better understanding of how matrix crosslinking alters tumor cell phenotypes, and behaviors would improve our ability to effectively treat aggressive metastatic breast cancer. Herein described is an experimental approach to glycate and crosslink a collagen-I/basement membrane extract ECM to study the impact of ECM crosslinking on mammary tumor progression in vivo. Moreover, glycation of collagen by sugars to form advanced glycation end products naturally occurs during aging, extending the potential relevance of this approach to research on mechanisms of aging involved in disease progression.

Cranberry Juice Polyphenols Inhibited the Formation of Advanced Glycation End Products in Collagens, Inhibited Advanced Glycation End Product-Induced Collagen Crosslinking, and Cleaved the Formed Crosslinks.

Collagens in the human skin are susceptible to glycation due to their long half-life of about 15 years, accumulating advanced glycation end products (AGEs). The formation of AGEs and the subsequent AGE-induced collagen crosslinking are major factors for skin aging. The objective of this study was to determine the capacity of cranberry juice polyphenols (CJPs) and their fractions to inhibit collagen glycation and to break AGE-induced crosslinks in collagens. Concentrated cranberry juice was extracted to obtain the CJP, which was further fractionated into an ethyl acetate fraction, water fraction, 30% methanol (MeOH) fraction, 60% MeOH fraction, MeOH fraction, and acetone fraction. CJPs and their fractions contained different ratios of anthocyanins, procyanidins, and flavonols. All the fractions significantly inhibited collagen glycation assessed with the collagen-methylglyoxal (MGO) or collagen-dehydroascorbic acid (DHAA) assays. The ethyl acetate fraction and 60% MeOH had the lowest IC50 values in the collagen-MGO and collagen-DHAA assays. The methanol fraction (IC50 = 0.52 μg/mL) and acetone fraction (IC50 = 0.019 mg/mL) had the lowest IC50 values in the inhibition and breakage of AGE-induced collagen crosslinking, respectively. The ethyl acetate fraction significantly scavenged the highest amount of MGO and DHAA after incubation compared to the other fractions. Results suggested that procyanidins were the most effective antiglycation agent in both collagen glycation assays, followed by flavonols and anthocyanins. High-performance liquid chromatography-electrospray ionization─tandem mass spectrometry showed that the reactions of DHAA with quercetin or epicatechin formed several adducts with unreported proposed structures. This study suggested that CJPs may be used as active ingredients in cosmetics to prevent skin collagen glycation and crosslinking and to break the formed crosslinks.

Pre-glycation impairs gelation of high concentration collagen solutions.

There remains a need for stiffer collagen hydrogels for tissue engineering and disease modeling applications. Pre-glycation, or glycation of collagen in solution prior to gelation, has been shown to increase the mechanics of collagen hydrogels while maintaining high viability of encapsulated cells. The stiffness of glycated collagen gels can be increased by increasing the collagen concentration, sugar concentration, and glycation time. However, previous studies on pre-glycation of collagen have used low collagen concentrations and/or low sugar concentrations and have not investigated the effect of glycation time. Therefore, the objective of this study was to determine the effects of pre-glycation with high sugar concentrations (up to 500 mM) and extended glycation times (up to 21 days) on high concentration collagen (8mg/ml). The addition of sugar to the collagen and the formation of advanced glycation end products (AGEs) were quantified. The ability to gel successfully and rheological properties were determined and correlated with biochemical characterizations. Successful collagen gelation and rheological properties of pre-glycated collagen were found to be strongly dependent on the ratio of added sugars to added AGEs with high ratios impairing gelation and low ratios resulting in optimal storage moduli. There is likely a competing effect during pre-glycation of the formation of AGEs resulting in crosslinking of collagen and the formation of Amadori intermediates acting to increase collagen solubility. Overall, this study shows that collagen glycation can be optimized by increasing the formation of AGEs while maintaining a low ratio of added sugar to added AGEs.

Birefringence effect studies of collagen formed by nonenzymatic glycation using dual-retarder Mueller polarimetry.

.Significance: Nonenzymatic glycation of collagen covalently attaches an addition of sugar molecules that initially were involved in a reversibly reaction with amino groups on the protein. Due to the ultimate formation of stable irreversible advanced glycation end products, the process of glycation leads to abnormal irreversible cross-linking, which ultimately accumulates with age and/or diabetes in the extracellular matrix, altering its organization.Aim: We report the use of dual-retarder Mueller polarimetry in conjunction with phase retardance to differentiate collagen cross-linking in a normal collagen gel matrix from that in tissues with nonenzymatic cross-linking.Approach: A dual-liquid crystal-based Mueller polarimetry system that involves electronic modulation of polarization state generators (PSGs) was employed to produce all types of polarization states without moving any part and enable detection of the signal directly using a Stokes polarimeter. The linear phase retardance response was obtained for the characterization of the solution and gel forms of collagen using differential Mueller matrix analysis.Results: We found that linear phase retardance measurements via differential Mueller matrix polarimetry successfully differentiated collagen gel matrices with different degrees of cross-linking formed by a nonenzymatic glycation process and demonstrated that this technology constitutes a quick and simple modality.Conclusions: This approach has high sensitivity for studying differences in fibrillar cross-linking in glycated collagen. Further, our work suggests that this method of structural analysis has potential clinical diagnostic value owing to its noninvasive and cost-efficient nature.

Nanomechanical and Nonlinear Optical Properties of Glycated Dental Collagen

Nonenzymatic glycation is a multistep, slow reaction between reducing sugars and free amino groups of long-lived proteins, which affects the structural and mechanical properties of collagen-rich tissues via accumulation of advanced glycation end products (AGEs). Dental collagen is exposed to glycation as part of the natural aging process. However, in case of chronically high blood glucose, the process can be accelerated, resulting in premature stiffening of dentin, leading to tooth fragility. The molecular mechanisms whereby collagen glycation evokes the loss of mechanical stability in teeth are currently unknown. In this study, we used 2-photon and atomic force microscopies to correlate structural and mechanical changes in dental collagen induced by in vitro glycation. Young tooth samples were demineralized and cut longitudinally into 30-µm sections, then artificially glycated in 0.5 M ribose solution for 10 wk. Two-photon microscopy analysis showed that both the autofluorescence and second harmonic–generated (SHG) signal intensities of glycated samples were significantly greater than those of the controls. Regarding the structural alteration of individual collagen fibers, a remarkable increase could be measured in fiber length of ribose-treated sections. Furthermore, nanoindentation of intertubular dentin regions revealed significantly higher stiffness in the ribose-treated samples, which points at a significant accumulation of AGEs. Thus, collagen glycation occurring during sustained exposure to reducing sugars leads to profound structural and mechanical changes in dentin. Besides the numerous oral complications associated with type 2 diabetes, the premature structural and mechanical deterioration of dentin may also play an important role in dental pathology.

Effect of Diabetes on Tendon Structure and Function: Not Limited to Collagen Crosslinking.

Diabetes mellitus (DM) is associated with musculoskeletal complications-including tendon dysfunction and injury. Patients with DM show altered foot and ankle mechanics that have been attributed to tendon dysfunction as well as impaired recovery post-tendon injury. Despite the problem of DM-related tendon complications, treatment guidelines specific to this population of individuals are lacking. DM impairs tendon structure, function, and healing capacity in tendons throughout the body, but the Achilles tendon is of particular concern and most studied in the diabetic foot. At macroscopic levels, asymptomatic, diabetic Achilles tendons may show morphological abnormalities such as thickening, collagen disorganization, and/or calcific changes at the tendon enthesis. At smaller length scales, DM affects collagen sliding and discrete plasticity due to glycation of collagen. However, how these alterations translate to mechanical deficits observed at larger length scales is an area of continued investigation. In addition to dysfunction of the extracellular matrix, tendon cells such as tenocytes and tendon stem/progenitor cells show significant abnormalities in proliferation, apoptosis, and remodeling capacity in the presence of hyperglycemia and advanced glycation end-products, thus contributing to the disruption of tendon homeostasis and healing. Improving our understanding of the effects of DM on tendons-from molecular pathways to patients-will progress toward targeted therapies in this group at high risk of foot and ankle morbidity.

Intervertebral disc degeneration in warmblood horses: Histological and biochemical characterization.

Gross morphology of healthy and degenerated intervertebral discs (IVDs) is largely similar in horses as in dogs and humans. For further comparison, the biochemical composition and the histological and biochemical changes with age and degeneration were analyzed in 41 warmblood horses. From 33 horses, 139 discs and 2 fetal vertebral columns were evaluated and scored histologically. From 13 horses, 73 IVDs were assessed for hydration, DNA, glycosaminoglycans, total collagen, hydroxyl-lysyl-pyridinoline, hydroxylysine, and advanced glycation end-product (AGE) content. From 7 horses, 20 discs were assessed for aggrecan, fibronectin, and collagen type 1 and 2 content. Histologically, tearing of the nucleus pulposus (NP) and cervical annulus fibrosus (AF), and total histological score (tearing and vascular proliferation of the AF, and chondroid metaplasia, chondrocyte-like cell proliferation, presence of notochordal cells, matrix staining, and tearing of the NP) correlated with gross degeneration. Notochordal cells were not seen in IVDs of horses. Age and gross degeneration were positively correlated with AGEs and a fibrotic phenotype, explaining gross degenerative changes. In contrast to dogs and humans, there was no consistent difference in glycosaminoglycan content and hydration between AF and NP, nor decrease of these variables with age or degeneration. Hydroxylysine decrease and collagen 1 and AGEs increase were most prominent in the NP, suggesting degeneration started in the AP. In caudal cervical NPs, AGE deposition was significantly increased in grossly normal IVDs and total collagen significantly increased with age, suggesting increased biomechanical stress and likelihood for spinal disease in this part of the vertebral column.

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

ABSTRACT 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.

In Vitro and In Vivo Antiglycation Effects of Connarus ruber Extract.

Accumulation of advanced glycation end products (AGEs) of the Maillard reaction has been implicated in the pathogenesis of diabetes and its complications. Connarus ruber has been used as a folk remedy for several diseases, including diabetes; however, its underlying mechanism has not yet been investigated. This study investigated the effects of C. ruber extract against glycation on collagen-linked AGEs in vitro and streptozotocin-induced diabetic rats (STZ-DM rats) in vivo. The antiglycation activities of C. ruber extract and aminoguanidine (AG) were examined using a collagen glycation assay kit. Nonfluorescent AGE, Nε-carboxymethyl lysine (CML), Nω-carboxymethyl arginine, and Nε-carboxyethyl lysine levels were measured via electrospray ionization-liquid chromatography-tandem mass spectrometry. The effect of the extract on the cytotoxicity of methylglyoxal (MG), a precursor of AGEs, was examined in HL60 cells. STZ-DM rats were treated with the extract for 4 wk, and the effect was assessed using biochemical markers in the serum and CML-positive cells in renal tissues. C. ruber extract dose-dependently inhibited the glycation of collagen and formation of nonfluorescent AGEs, which was comparable to AG, and it significantly attenuated MG-induced cytotoxicity in HL60 cells. Furthermore, the glycated albumin levels in STZ-DM rats decreased, the increase in serum lipid levels was reversed, and immunohistochemistry demonstrated that CML deposition in the glomerulus of STZ-DM rats significantly decreased. Although further studies are needed, C. ruber could be a potential therapeutic for preventing and progressing many pathological conditions, including diabetes.

Time scale of glycation in collagen of bovine pericardium-derived bio-tissues.

Glycosyl-ation is the process of combining one or more glucose molecules (or other monosaccharides) with molecules of a different nature (which are therefore glycosyl-ated). In biochemistry, glycosyl-ation is catalyzed by several specific enzymes, and assumes considerable importance since it occurs mainly at the expense of proteins and phospho-lipids which are thus transformed into glycoproteins and glycolipids. Conversely, in diabetes and aging, glycation of proteins is a phenomenon of non-enzymatic nature and thus not easily controlled. Glycation of collagen distorts its structure, renders the extracellular matrix stiff and brittle and at the same time lowers the degradation susceptibility thereby preventing renewal. Based on models detailed in this paper and with parameters determined from experimental data, we describe the glycation of type 1 collagen in bovine pericardium derived bio-tissues, upon incubation in glucose and ribose. With arginine and lysine/hy-droxy-lysine amino acids as the primary sites of glycation and assuming that the topological polar surface area of the sugar molecules determines the glycation rates, we modelled the glycation as a function of time and determined the glycation rate and thus the progression of glycation as well as the resulting volume increase.

Collagen Glycation Detected by Its Intrinsic Fluorescence.

Collagen’s long half-life (in skin approximately 10 years) makes this protein highly susceptible to glycation and formation of the advanced glycation end products (AGEs). Accumulation of cross-linking AGEs in the skin collagen has several detrimental effects; thus, the opportunity for non-invasive monitoring of skin glycation is essential, especially for diabetic patients. In this paper, we report using the time-resolved intrinsic fluorescence of collagen as a biomarker of its glycation. Contrary to the traditional fluorescence intensity decay measurement at the arbitrarily selected excitation and detection wavelengths, we conducted systematic wavelength- and time-resolved measurements to achieve time-resolved emission spectra. Changes in the intrinsic fluorescence kinetics, caused by both collagen aggregation and glycation, have been detected.

Decellularized pericardium tissues at increasing glucose, galactose and ribose concentrations and at different time points studied using scanning X-ray microscopy.

Diseases like widespread diabetes or rare galactosemia may lead to high sugar concentrations in the human body, thereby promoting the formation of glycoconjugates. Glycation of collagen, i.e. the formation of glucose bridges, is nonenzymatic and therefore cannot be prevented in any other way than keeping the sugar level low. It relates to secondary diseases, abundantly occurring in aging populations and diabetics. However, little is known about the effects of glycation of collagen on the molecular level. We studied in vitro the effect of glycation, with d-glucose and d-galactose as well as d-ribose, on the structure of type 1 collagen by preparing decellularized matrices of bovine pericardia soaked in different sugar solutions, at increasing concentrations (0, 2.5, 5, 10, 20 and 40 mg ml-1), and incubated at 37°C for 3, 14, 30 and 90 days. The tissue samples were analyzed with small- and wide-angle X-ray scattering in scanning mode. We found that glucose and galactose produce similar changes in collagen, i.e. they mainly affect the lateral packing between macromolecules. However, ribose is much faster in glycation, provoking a larger effect on the lateral packing, but also seems to cause qualitatively different effects on the collagen structure.