Protein Glycation

The transcription factor known as sterol regulatory element-binding protein (SREBP) and the glycation pathways, specifically the formation of Advanced Glycation End Products (AGEs), have a significant and deleterious impact on the kidney. They alter renal lipid metabolism and promote glomerulosclerosis, mesangial cell expansion, tubulointerstitial fibrosis, and inflammation, leading to diabetic nephropathy (DN) progression. Although several pieces of scientific evidence are reported for potential causes of glycation and lipotoxicity in DN, the underlying mechanism of renal lipid accumulation still needs to be fully understood. We provide a rationalized view on how AGEs exert multiple effects that cause SREBP activation and inflammation, contributing to DN through Receptor for AGEs (RAGE) signaling, AGE-R1-dependent downregulation of Sirtuin 1 (SIRT-1), and increased SREBP Cleavage Activating Protein (SCAP) glycosylation. This review emphasizes the association between glycation and the SREBP pathway and how it affects the onset of DN associated with obesity. Finally, we discuss the correlation of glycation and the SREBP pathway with insulin resistance (IR), oxidative stress, endoplasmic reticulum stress, inflammation, and existing and emerging therapeutic approaches toward better controlling obesity-related DN.

Type 2 diabetes mellitus (T2DM) is associated with oxidative stress and perturbed iron metabolism. Serotransferrin (Trf) and ceruloplasmin (Cp) are two key proteins involved in iron metabolism and anti-oxidant defense. Non-enzymatic glycation and oxidative modification of plasma proteins are known to occur under hyperglycemia and oxidative stress. In this study, shotgun proteomics and 2H2O-based metabolic labeling were used to characterize post-translational modifications and assess the kinetics of Trf and Cp in T2DM patients and matched controls in vivo. Six early lysine (Amadori) and one advanced arginine glycation were detected in Trf. No glycation, but five asparagine deamidations, were found in Cp. T2DM patients had increased fractional catabolic rates of both Trf and Cp that correlated with HbA1c (p < 0.05). The glycated Trf population was subject to an even faster degradation compared to the total Trf pool, suggesting that hyperglycemia contributed to an increased Trf degr...

After a long struggle and patience, we have been rewarded with the publication of our second major reference work, on the pathophysiological implications of diversified receptor for advanced glycation end (RAGE) products. The terms Glycation and Glycosylation describe the striking distinctions in which sugars exhibit proximity for physiological proteins. While glycation is spontaneous and nonenzymatic binding of sugars to proteins, the glycosylation is an enzyme assisted process, involved by well-regulated conjugation of carbohydrates addition to proteins. Glycosylation is more like a posttranslational modification (enzymatic), the abrupt patterns of which are associated with impaired body functions. This book focuses on the diversified RAGE actions, broadly its oxidative status modulating role in cancers, cardiovascular and neurological complications. The molecular significance of RAGE has received recent interest from clinicians, utilizing it as a targeting moiety in the actions of chemotherapeutic drugs. The biochemistry of RAGE is highly diverse with a functioning through its diverse ligands. Readers are please requested to share their suggestions and valuable feedbacks.

Type 2 diabetes mellitus (T2DM) is associated with oxidative stress and perturbed iron metabolism. Serotransferrin (Trf) and ceruloplasmin (Cp) are two key proteins involved in iron metabolism and anti-oxidant defense. Non-enzymatic glycation and oxidative modification of plasma proteins are known to occur under hyperglycemia and oxidative stress. In this study, shotgun proteomics and 2 H 2 O-based metabolic labeling were used to characterize posttranslational modifications and assess the kinetics of Trf and Cp in T2DM patients and matched controls in vivo. Six early lysine (Amadori) and one advanced arginine glycation were detected in Trf. No glycation, but five asparagine deamidations, were found in Cp. T2DM patients had increased fractional catabolic rates of both Trf and Cp that correlated with HbA 1c (p < 0.05

Type 2 diabetes mellitus (T2DM) is associated with oxidative stress and perturbed iron metabolism. Serotransferrin (Trf) and ceruloplasmin (Cp) are two key proteins involved in iron metabolism and anti-oxidant defense. Non-enzymatic glycation and oxidative modification of plasma proteins are known to occur under hyperglycemia and oxidative stress. In this study, shotgun proteomics and 2H2O-based metabolic labeling were used to characterize post-translational modifications and assess the kinetics of Trf and Cp in T2DM patients and matched controls in vivo. Six early lysine (Amadori) and one advanced arginine glycation were detected in Trf. No glycation, but five asparagine deamidations, were found in Cp. T2DM patients had increased fractional catabolic rates of both Trf and Cp that correlated with HbA1c (p &lt; 0.05). The glycated Trf population was subject to an even faster degradation compared to the total Trf pool, suggesting that hyperglycemia contributed to an increased Trf degr...

Hyperglycemia plays a key role in the pathogenesis of cardiovascular complications of diabetes. T2DM is associated with high density lipoprotein (HDL) dysfunction and increased degradation of ApoAI. The mechanism(s) of these changes are largely unknown. To study the role of hyperglycemia-induced glycation on ApoAI kinetics and stability in patients with diet-controlled T2DM. 2H2O-metabolic labeling approach was used to study ApoAI turnover in patients with diet-controlled T2DM (N= 9 (5F), 59.3±8.5 yr.) and matched healthy controls (N= 8(4F), 50.7±11.6 yr.). The effect of Amadori glycation on in vivo ApoAI stability and HDL&#39;s anti-oxidant and cholesterol efflux properties were assessed using proteomics approach and in vitro assays. T2DM patients had increased turnover of ApoAI, and impaired cholesterol efflux and anti-oxidant properties of HDL. HbA1c was negatively correlated with the half-live of ApoAI, and cholesterol efflux function of HDL. Proteomic analysis identified severa...

Metabolic syndromes (eg, obesity, type 2 diabetes (T2D), atherosclerosis, and neurodegenerative diseases) and aging, they all have a strong component of carbonyl and reductive-oxidative (redox) stress. Reactive carbonyl (RCS) and oxidant (ROS) stress species are commonly generated as products or byproducts of cellular metabolism or are derived from the environment. RCS and ROS can play a dual role in living organisms. Some RCS and ROS function as signaling molecules, which control cellular defenses against biological and environmental assaults. However, due to their high reactivity, RCS and ROS inadvertently interact with different cellular and extracellular components, which can lead to the formation of undesired posttranslational modifications of bone matrix proteins. These are advanced glycation (AGEs) and glycoxidation (AGOEs) end products generated in vivo by non-enzymatic amino-carbonyl reactions. In this review, metabolic processes involved in generation of AGEs and AGOEs within and on protein surfaces including extracellular bone matrix are discussed from the perspective of cellular metabolism and biochemistry of certain metabolic syndromes. The impact of AGEs and AGOEs on some characteristics of mineral is also discussed. Different therapeutic approaches with the potential to prevent the formation of RCS, ROS, and the resulting formation of AGEs and AGOEs driven by these chemicals are also briefly reviewed. These are antioxidants, scavenging agents of reactive species, and newly emerging technologies for the development of synthetic detoxifying systems. Further research in the area of in vivo glycation and glycoxidation should lead to the development of diverse new strategies for halting the progression of metabolic complications before irreversible damage to body tissues materializes.

Background: One of the complications of diabetes mellitus is the glycosylation of various proteins in the body. The purpose of this study was to explore the glycosylation reaction of albumin (Alb) and hemoglobin (Hb) in the presence of varying concentrations of the hydroalcoholic extract derived from dried walnut leaves. Materials and Methods: The plants were gathered and then underwent extraction by employing the maceration technique. Next, 1 mL of the Alb solution, with a concentration of 50 mg/mL, and 1 mL of the Hb solution, with a concentration of 50 mg/mL, were separately exposed to various concentrations of the walnut leaf hydroalcoholic extract (0.1, 0.25, 0.5, 1, and 0 mg/ mL). Additionally, 1 mL of the glucose solution (30 mg/mL for Alb and 20 mg/mL for Hb) was added to each, along with 0.5 mL of phosphate buffer (pH = 7.4, concentration of 0.01 M). This mixture was left for 72 hours, and the absorbance of the final solution was measured at 443 nm. Results: According to the results, the most significant inhibition of Alb glycosylation was observed in the presence of the hydroalcoholic extract from walnut leaves at a concentration of 25% µg/ mL. Moreover, the highest percentage of inhibition of glycosylated Hb was found in the presence of 5% µg/mL of the hydroalcoholic extract from dried walnut leaves. Conclusion: The hydroalcoholic extract from dried walnut leaves was observed to moderately reduce the glycosylation of both Alb and Hb.

It is estimated that the global prevalence of dementia will rise as high as 24 million and predicted to be double in every 20 years which is attributed to the fact that the ageing population is increasing and so more individuals are at risk of developing neurodegenerative diseases like Alzheimer's. Many scientists favored glycation of proteins such as tau, amyloid beta (Aβ) etc. as one of the important risk factor in Alzheimer's disease (AD). Since, d-ribose shows highest glycation ability among other sugars hence, produces advanced glycation end products (AGEs) rapidly. However, there are several other mechanisms suggested by researchers through which d-ribose may cause cognitive impairments. There is a concern related to diabetic patients since they also suffer from d-ribose metabolism, may be more prone to AD risk. Thus, it is imperative that the pathogenesis and the pathways involved in AD progression are explored in the light of ribosylation and AGEs formation for identifying suitable diagnostics marker for early diagnosis or finding promising therapeutic outcomes.

In this work, the phenolic composition of E. umbellata leaves and berries is reported. Berries were rich in flavonols, whereas leaves presented abundant flavonols and ellagitannins. Then, the enzyme-inhibitory properties, anti-glycation and antioxidant activities of E. umbellata and Sambucus lanceolata (its phenolic profile has been already established in a previous work) were tested by several in vitro assays and compared. The simulated gastrointestinal digestion resulted in a decrease on their phenolic composition. Nevertheless, both species still had the ability to inhibit aldose reductase activity and protein glycation and scavenge free radicals at the end of the process. Thus, the potential beneficial effects of E. umbellata and S. lanceolata seems to be kept to some extent after passage throughout the digestive system. Altogether, this study provides further insight into investigation of these species as dietary sources of bioactive compounds to lower the risk of type-2 diabetes and obesity.

Methylglyoxal (MG), a reactive ␣-oxoaldehyde that is produced in higher quantities in diabetes, uremia, oxidative stress, aging and inflammation, reacts with the thiol groups (in addition to the amino and guanidino groups) of proteins. This causes protein modification, formation of advanced glycated end products (AGEs) and cross-linking. Low molecular mass thiols can be used as competitive targets for MG, preventing the reactions mentioned above. Therefore, this paper investigated how the microenvironment of the thiol group in low molecular mass thiols (cysteine, N-acetylcysteine (NAcCys), carboxymethylcysteine (CMC) and glutathione (GSH)) and human serum albumin (HSA) affected the thiol reaction with MG. The SH group reaction course was monitored by 1 H-NMR spectroscopy and spectrophotometric quantification. Changes in the HSA molecules were monitored by SDS-PAGE. The microenvironment of the SH group had a major effect on its reactivity and on the product yield. The reactivity of SH groups decreased in the order Cys > GSH > NAcCys. CMC did not react. The percentages of the reacted SH groups in the equilibrium state were almost equal, regardless of the ratio of thiol compound/MG (1:1, 1:2, 1:5): 38.1 ± 0.9%; 38.2 ± 0.7% and 39.0 ± 0.8% for Cys; 26.5 ± 0.6%; 26.6 ± 2.6% and 27.4 ± 2.5% for GSH; 10.8 ± 0.9%; and 11.2 ± 0.7% and 12.2 ± 0.9% for NAcCys, respectively. Our results explain why substances containing ␣amino-␤-mercapto-ethane as a pharmacophore are successful scavengers of MG. In equilibrium, HSA SH reacted in high percentages both with an insufficient amount and with an excess of MG (55% and 65%, respectively). An analysis of the hydrophobicity of the microenvironment of the SH group on the HSA surface showed that it could contribute to high levels of SH modification, leading to an increase in the scavenging activity of the albumin thiol.

In this work, the phenolic composition of E. umbellata leaves and berries is reported. Berries were rich in flavonols, whereas leaves presented abundant flavonols and ellagitannins. Then, the enzyme-inhibitory properties, anti-glycation and antioxidant activities of E. umbellata and Sambucus lanceolata (its phenolic profile has been already established in a previous work) were tested by several in vitro assays and compared. The simulated gastrointestinal digestion resulted in a decrease on their phenolic composition. Nevertheless, both species still had the ability to inhibit aldose reductase activity and protein glycation and scavenge free radicals at the end of the process. Thus, the potential beneficial effects of E. umbellata and S. lanceolata seems to be kept to some extent after passage throughout the digestive system. Altogether, this study provides further insight into investigation of these species as dietary sources of bioactive compounds to lower the risk of type-2 diabetes and obesity.

The beginning and/or development of an expanding variety of human diseases has been linked to oxidative stress, inflammation, glycation, and advanced glycation endproducts. Large-scale research on complementary therapies with anti-oxidant and anti-inflammatory properties for the treatment or prevention of several diabetes-related diseases has not, however, been advised because there is insufficient data from meta-analyses and clinical trials. However, adverse effects and high cost of allopathic medicines force to investigate plant based therapeutic strategies for management of various diseases. This work aims to determine the impact of Curcuma longa extract on AGE production, oxidative stress, and glycation through in vitro experiments. Ascorbic acid's reducing power was comparable to that of C. longa extract (at 600 µg/ml). Additionally, C. longa suppresses the amount of browning intensity by 60.3%, the percent aggregation index by 57.38%, and the amyloid structure by 61.2%, preventing glycation of BSA's native structure. Consuming C. longa can therefore help avoid and treat issues associated with diabetes. To ascertain the processes of C. longa components in disease modulations, more thorough chemical and pharmacological investigation is necessary.

The beginning and/or development of an expanding variety of human diseases has been linked to oxidative stress, inflammation, glycation, and advanced glycation endproducts. Large-scale research on complementary therapies with anti-oxidant and anti-inflammatory properties for the treatment or prevention of several diabetes-related diseases has not, however, been advised because there is insufficient data from meta-analyses and clinical trials. However, adverse effects and high cost of allopathic medicines force to investigate plant based therapeutic strategies for management of various diseases. This work aims to determine the impact of Curcuma longa extract on AGE production, oxidative stress, and glycation through in vitro experiments. Ascorbic acid's reducing power was comparable to that of C. longa extract (at 600 µg/ml). Additionally, C. longa suppresses the amount of browning intensity by 60.3%, the percent aggregation index by 57.38%, and the amyloid structure by 61.2%, preventing glycation of BSA's native structure. Consuming C. longa can therefore help avoid and treat issues associated with diabetes. To ascertain the processes of C. longa components in disease modulations, more thorough chemical and pharmacological investigation is necessary.

Hypercholesterolemia is involved in the development of atherosclerosis and is a risk factor for coronary artery disease, stroke, and peripheral vascular disease. This paper deals with the mechanism of development of hypercholesterolemic atherosclerosis. Hypercholesterolemia increases the formation of numerous atherogenic biomolecules including reactive oxygen species (ROS), proinflammatory cytokines [interleukin (IL)-1, IL-2, IL-6, IL-8, tumor necrosis factor-alpha (TNF-α)], expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, monocyte chemoattractant protein-1 (MCP-1), granulocyte macrophage-colony stimulating factor (GM-CSF) and numerous growth factors [insulin-like growth factor-1 (IGF-1), platelet-derived growth factor-1 (PDGF-1) and transforming growth factor-beta (TGF-β)]. ROS mildly oxidizes low-density lipoprotein-cholesterol (LDL-C) to form minimally modified LDL (MM-LDL) which is further oxidized to form oxidized LDL (OX-LDL). Hypercholesterolemia also activates nuclear factor-kappa-B (NF-κB). The above atherogenic biomolecules are involved in the development of atherosclerosis which has been described in detail. Hypercholesterolemia also assists in the development of atherosclerosis through AGE (advanced glycation end-products)-RAGE (receptor for AGE) axis and C-reactive protein (CRP). Hypercholesterolemia is associated with increases in AGE, oxidative stress [AGE/sRAGE (soluble receptor for AGE)] and C-reactive protein, and decreases in the sRAGE, which are known to be implicated in the development of atherosclerosis. In conclusion, hypercholesterolemia induces atherosclerosis through increases in atherogenic biomolecules, AGE-RAGE axis and CRP.

This work aimed to evaluate the contribution of isoflavones and melatonin to the aqueous extract obtained from the coffee silverskin (CSE) antiglycative properties, which has not been previously studied. To achieve this goal, two model systems constituted by bovine serum albumin (BSA) and reactive carbonyls (glucose or methylglyoxal) in the presence or absence of pure phytochemicals (chlorogenic acid (CGA), genistein, and melatonin) and CSE were employed. Glucose was used to evaluate the effect on the formation of glycation products formed mainly in the early stage of the reaction, while methylglyoxal was employed for looking at the formation of advanced products of the reaction, also called methylglyoxal-derivative advanced glycation end products (AGE) or glycoxidation products. CGA inhibited the formation of fructosamine, while genistein and melatonin inhibited the formation of advanced glycation end products and protein glycoxidation. It was also observed that phenolic compounds from CSE inhibited protein glycation and glycoxidation by forming BSA-phytochemical complexes. CSE showed a significant antiglycative effect (p < 0.05). Variations in the UV-Vis spectrum and the antioxidant capacity of protein fractions suggested the formation of protein-phytochemical complexes. Fluorescence quenching and in silico analysis supported the formation of antioxidant-protein complexes. For the first time, we illustrate that isoflavones and melatonin may contribute to the antiglycative/antiglycoxidative properties associated with CSE. CGA, isoflavones, and melatonin composing CSE seem to act simultaneously by different mechanisms of action.

Under hyperglycaemic conditions non-enzymatic glycation of proteins gives rise to advanced glycation end products (AGEs). The AGEs thus formed generate free radicals, which foster the development of diabetes and its associated complications. Inhibition of glycation is expected to play a role in controlling diabetes. Plant derived antioxidants like cinnamic acid (CA) are known for limiting AGE formation, however, the mechanism involved is poorly understood. Therefore, we aimed to investigate the possible mechanism of inhibition of AGEs formation by CA through various experimental approaches. Glycation of HSA was achieved by incubating the reaction mixture with glucose for 30 days at 37 C. The protein samples were tested for levels of free lysine & thiol groups, carbonyl content and reactive oxygen species (ROS). Interaction between CA and HSA was also studied through various biophysical techniques. Thermodynamic studies showed a strong exothermic interaction between CA and HSA. The positive value of TDS and negative value of DH indicates that the HSA-CA complex is mainly stabilized by a hydrophobic interaction and hydrogen bond. Further, molecular docking reveals that CA binds to HSA subdomain IIA (Sudlow's site I) with a binding energy of À7.0 kcal mol À1 , nearly the same as obtained in isothermal titration calorimetry (ITC) and fluorescence spectroscopy. The results of various spectroscopic techniques along with molecular docking and examination of many biomarkers highlights the role of CA in preventing disease progression.

Glycation plays an important role in various oxidative stress related diseases. Superoxide dismutase (SOD) constitutes an essential defense against oxidative stress. The damage caused by oxidative stress is exacerbated if the antioxidant enzymes themselves are inactivated by glycation. Thymoquinone (TQ) has been reported to have various pharmacological activities. Therefore, the glycation of SOD by glucose or methylglyoxal (MG) and its protection by TQ has been investigated. Incubation of SOD with glucose, MG or both at 37 • C resulted in a progressive decrease in the activity of the enzyme, and a parallel decrease in the amount of protein on SDS-PAGE gels for glucose incubated SOD and formation of high molecular weight aggregates for MG or both glucose and MG incubated enzyme. TQ offered protection against glucose or MG induced loss in SOD activity and fragmentation/cross-linking. The antiglycating activity of TQ appears to be better for mild glycating agents. It is also effective in protecting against strong glycating agents, more when the exposure time to the glycating agent is short. TQ has also earlier been reported to have anti-diabetic effects, and this along with the observed antiglycating effect makes it an effective compound against diabetes and its complications.

Ellagic acid (EA) has been reported to have various beneficial pharmacological properties, including strong antidiabetic activity. Glycation plays an important role in diabetes-associated complications. In this study, we have investigated the antiglycating potential of EA by using the important antioxidant enzyme, superoxide dismutase (SOD). The glycation of SOD by glucose or methyglyoxal (MG) and its protection by EA has been studied by activity, SDS-PAGE, ELISA, absorbance and fluorescence measurements. Glycation of SOD resulted in a decrease in enzyme activity, fragmentation/cross-linking, reduced cross-reactivity with anti-SOD antibodies, structural changes, and formation of advanced glycation end products (AGEs) and fibrils. EA provided protection against glucose or MG induced glycation of SOD. The antiglycating potential of EA appears to be comparable with that of quercetin which is reported to be a potent natural inhibitor of glycation. Therefore, EA is an effective anti-diabetic compound, which can be used as a supplement in treating diabetes and its complications.

Non-enzymatic glycosylation (glycation) plays an important role in the development of physiological and pathophysiological processes such as aging, diabetes, atherosclerosis, neurodegenerative diseases and chronic renal failure. Preventing glycation can minimize diabetic complications. Glycation can be prevented by the natural defence system in the body, synthetic inhibitors and natural inhibitors. Synthetic inhibitors may prevent glycation through several possible mechanisms. They might inhibit the glycation by interfering with the attachment of sugars with proteins, by inhibiting the late stage of glycation or by preventing Amadori product formation. Furthermore, their ability to scavenge free radicals and to break cross-links might be other mechanisms responsible for their potential to inhibit glycation. Naturally occurring phytochemicals/products have been found to be relatively non-toxic as compared to synthetic compounds, and are inexpensive and available in an ingestible form. A large number of plants and natural biomolecules have been shown to have antidiabetic effects. Several hypoglycaemic compounds have anti-oxidant properties. The present review describes the various ways in which glycation can be prevented.

Growing evidence supports the role of advanced glycation end products (AGEs) in the development of diabetic vascular complications and cardiovascular diseases (CVDs). We have shown that high-molecular-weight AGEs (HMW-AGEs), present in our Western diet, impair cardiac function. Whether HMW-AGEs affect vascular function remains unknown. In this study, we aimed to investigate the impact of chronic HMW-AGEs exposure on vascular function and structure. Adult male Sprague Dawley rats were daily injected with HMW-AGEs or control solution for 6 weeks. HMW-AGEs animals showed intracardiac pressure overload, characterized by increased systolic and mean pressures. The contraction response to PE was increased in aortic rings from the HMW-AGEs group. Relaxation in response to ACh, but not SNP, was impaired by HMW-AGEs. This was associated with reduced plasma cyclic GMP levels. SOD restored ACh-induced relaxation of HMW-AGEs animals to control levels, accompanied by a reduced half-maximal effect...

Growing evidence supports the role of advanced glycation end products (AGEs) in the development of diabetic vascular complications and cardiovascular diseases (CVDs). We have shown that high-molecular-weight AGEs (HMW-AGEs), present in our Western diet, impair cardiac function. Whether HMW-AGEs affect vascular function remains unknown. In this study, we aimed to investigate the impact of chronic HMW-AGEs exposure on vascular function and structure. Adult male Sprague Dawley rats were daily injected with HMW-AGEs or control solution for 6 weeks. HMW-AGEs animals showed intracardiac pressure overload, characterized by increased systolic and mean pressures. The contraction response to PE was increased in aortic rings from the HMW-AGEs group. Relaxation in response to ACh, but not SNP, was impaired by HMW-AGEs. This was associated with reduced plasma cyclic GMP levels. SOD restored ACh-induced relaxation of HMW-AGEs animals to control levels, accompanied by a reduced half-maximal effect...

Our skin is an organ with the largest contact area between the human body and the external environment. Skin aging is affected directly by both endogenous factors and exogenous factors (e.g., UV exposure). Skin saccharification, a non-enzymatic reaction between proteins, e.g., dermal collagen and naturally occurring reducing sugars, is one of the basic root causes of endogenous skin aging. During the reaction, a series of complicated glycation products produced at different reaction stages and pathways are usually collectively referred to as advanced glycation end products (AGEs). AGEs cause cellular dysfunction through the modification of intracellular molecules and accumulate in tissues with aging. AGEs are also associated with a variety of age-related diseases, such as diabetes, cardiovascular disease, renal failure (uremia), and Alzheimer’s disease. AGEs accumulate in the skin with age and are amplified through exogenous factors, e.g., ultraviolet radiation, resulting in wrinkle...

This paper investigates the sensory acceptability and textural properties of leavened wheat bread and sponge cake fortified with cow protein isolates that had been denatured and glycated by thermal treatment. Defatted cowpea flour was prepared from cow pea beans and the protein isolate was prepared (CPI) and thermally denatured (DCPI). To prepare glycated cowpea protein isolate (GCPI) the cowpea flour slurry was heat treated before isolation of the protein. CPI was more susceptible to thermal denaturation than GCPI as determined by turbidity and sulphydryl groups resulting in greater loss of solubility. This is attributed to the higher glycation degree and higher carbohydrate content of GCPI as demonstrated by glycoprotein staining of SDS PAGE gels. Water absorption of bread dough was significantly enhanced by DCPI and to a larger extent GCPI compared to the control, resulting in softer texture. CPI resulted in significantly increased crumb hardness in baked bread than the control w...

Dry and subsequent wet heating were used to glycate soy proteins with dextran or glucose, followed by fractionation based on size and solubility. Dry heating led to protein glycation (formation of furosine, Nε-(carboxymethyl)-L-lysine, Nε-(carboxyethyl)-L-lysine, and protein-bound carbonyls) and aggregation (increased particle size); while subsequent wet heating induced partial unfolding and de-aggregation. The measurable free amino group content of soy proteins changed from 0.77 to 0.14, then to 0.62 mmol/g upon dry and subsequent wet heating; this non-monotonic evolution is probably due to protein structural changes, and shows that this content should be interpreted with caution as a glycation marker. After both heating steps, the smaller-sized watersoluble fractions showed higher surface activity than the larger insoluble ones, and dextran conjugates exhibited a higher surface activity than their glucose counterparts. We thereby achieved a comprehensive understanding of the properties of various fractions in plant protein fractions, which is essential when targeting applications.

This paper investigates the sensory acceptability and textural properties of leavened wheat bread and sponge cake fortified with cow protein isolates that had been denatured and glycated by thermal treatment. Defatted cowpea flour was prepared from cow pea beans and the protein isolate was prepared (CPI) and thermally denatured (DCPI). To prepare glycated cowpea protein isolate (GCPI) the cowpea flour slurry was heat treated before isolation of the protein. CPI was more susceptible to thermal denaturation than GCPI as determined by turbidity and sulphydryl groups resulting in greater loss of solubility. This is attributed to the higher glycation degree and higher carbohydrate content of GCPI as demonstrated by glycoprotein staining of SDS PAGE gels. Water absorption of bread dough was significantly enhanced by DCPI and to a larger extent GCPI compared to the control, resulting in softer texture. CPI resulted in significantly increased crumb hardness in baked bread than the control w...

Dehydroascorbate is a by-product of copper-catalysed azide-alkyne click (CuAAC) reactions and also forms advanced glycation end products (AGEs) in tissues undergoing oxidative stress. Here we isolate and characterize an arginine-dehydroascorbate adduct formed during CuAAC reactions, investigate strategies for preventing its formation, and propose its biological relevance as an AGE.

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 &lt; 0.001) and III-S (0.40 ± 0.044; p &lt; 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 ...

Acinetobacter baumannii has recently been increasing as an aggressive pathogen in immunocompromised persons. In the present study, we determined the in vitro antibacterial and anti-biofilm activity of thymoquinone (TQ) against A. baumannii. A liposomal formulation of TQ (Lip-TQ) was prepared and its therapeutic potential was investigated in the treatment of A. baumannii infection in immunocompromised mice. Leukopenia was induced in mice by injecting cyclophosphamide (CYP) at a dose of 200 mg/kg and the leukopenic mice were infected with 1 × 106 CFUs of A. baumannii. The effectiveness of free TQ or Lip-TQ against A. baumannii infection was assessed by analyzing the survival rate and bacterial burden. Moreover, the efficacy of Lip-TQ was also studied by examining the systemic inflammatory markers and the histological changes in the lung tissues. The results showed that the mice in the group treated with Lip-TQ at a dose of 10 mg/kg exhibited a 60% survival rate on day 40 post-infectio...

Bunium persicum Boiss. seeds have been used for medicinal and nutritional properties such as antioxidant, antihelmetic and antimicrobial activity. The aim of this study was to to tested protective role of cumin extract against abiotic stress by microRNA markers. Secondary also was to evaluate antioxidant activity as well as total polyphenol, flavonoid and phenolic acid content of cumin extract. We observed that cumin DNA itself has not been damaged by sonication teratment. This protective impact indicates that cumin antioxidant properties can efficiently quench free radicals induced by sonication. On the other side, ultrasound-mediated formation of reactive oxygen species did induce the DNA polymorphism of lettuce samples which was detected by miRNAs-based markers. The range of sonication impact was time-dependent. Markers based of miRNA-DNA sequences has proven to be an effective tool. We have confirmed statistically significant differences (p ≤0.01) in miRNAs markers ability to de...

Oxidative, carbonyl, and glycative stress have gained substantial attention recently for their alleged influence on cancer progression. Oxidative stress can trigger variable transcription factors, such as nuclear factor erythroid-2-related factor (Nrf2), nuclear factor kappa B (NF-κB), protein-53 (p-53), activating protein-1 (AP-1), hypoxia-inducible factor-1α (HIF-1α), β-catenin/Wnt and peroxisome proliferator-activated receptor-γ (PPAR-γ). Activated transcription factors can lead to approximately 500 different alterations in gene expression, and can alter expression patterns of inflammatory cytokines, growth factors, regulatory cell cycle molecules, and anti-inflammatory molecules. These alterations of gene expression can induce a normal cell to become a tumor cell. Glycative stress resulting from advanced glycation end products (AGEs) and reactive dicarbonyls can significantly affect cancer progression. AGEs are fashioned from the multifaceted chemical reaction of reducing sugars...

This paper investigates the sensory acceptability and textural properties of leavened wheat bread and sponge cake fortified with cow protein isolates that had been denatured and glycated by thermal treatment. Defatted cowpea flour was prepared from cow pea beans and the protein isolate was prepared (CPI) and thermally denatured (DCPI). To prepare glycated cowpea protein isolate (GCPI) the cowpea flour slurry was heat treated before isolation of the protein. CPI was more susceptible to thermal denaturation than GCPI as determined by turbidity and sulphydryl groups resulting in greater loss of solubility. This is attributed to the higher glycation degree and higher carbohydrate content of GCPI as demonstrated by glycoprotein staining of SDS PAGE gels. Water absorption of bread dough was significantly enhanced by DCPI and to a larger extent GCPI compared to the control, resulting in softer texture. CPI resulted in significantly increased crumb hardness in baked bread than the control w...

Ellagic acid (EA) has been reported to have various beneficial pharmacological properties, including strong antidiabetic activity. Glycation plays an important role in diabetes-associated complications. In this study, we have investigated the antiglycating potential of EA by using the important antioxidant enzyme superoxide dismutase (SOD). The glycation of SOD by glucose or methyglyoxal (MG) and its protection by EA has been studied by activity, SDS-PAGE, ELISA, absorbance and fluorescence measurements. Glycation of SOD resulted in a decrease in enzyme activity, fragmentation/cross-linking, reduced cross-reactivity with anti-SOD antibodies, structural changes, and formation of advanced glycation end products (AGEs) and fibrils. EA provided protection against glucose or MG induced glycation of SOD. The antiglycating potential of EA appears to be comparable with that of quercetin which is reported to be a potent natural inhibitor of glycation. Therefore, EA is an effective anti-diabe...

Highlights  Inhibition of glycation is an important for alleviating diabetic complications.  Alliin protects against glucose or MG induced glycation of SOD.  The antiglycating potential of alliin is comparable with that of quercetin.  Alliin can be used for preventing glycation-mediated diabetic complications.

Glycation plays an important role in various oxidative stress related diseases. Superoxide dismutase (SOD) constitutes an essential defense against oxidative stress. The damage caused by oxidative stress is exacerbated if the antioxidant enzymes themselves are inactivated by glycation. Thymoquinone (TQ) has been reported to have various pharmacological activities. Therefore, the glycation of SOD by glucose or methylglyoxal (MG) and its protection by TQ has been investigated. Incubation of SOD with glucose, MG or both at 37 • C resulted in a progressive decrease in the activity of the enzyme, and a parallel decrease in the amount of protein on SDS-PAGE gels for glucose incubated SOD and formation of high molecular weight aggregates for MG or both glucose and MG incubated enzyme. TQ offered protection against glucose or MG induced loss in SOD activity and fragmentation/cross-linking. The antiglycating activity of TQ appears to be better for mild glycating agents. It is also effective in protecting against strong glycating agents, more when the exposure time to the glycating agent is short. TQ has also earlier been reported to have anti-diabetic effects, and this along with the observed antiglycating effect makes it an effective compound against diabetes and its complications.

Non-enzymatic glycosylation (glycation) plays an important role in the development of physiological and pathophysiological processes such as aging, diabetes, atherosclerosis, neurodegenerative diseases and chronic renal failure. Preventing glycation can minimize diabetic complications. Glycation can be prevented by the natural defence system in the body, synthetic inhibitors and natural inhibitors. Synthetic inhibitors may prevent glycation through several possible mechanisms. They might inhibit the glycation by interfering with the attachment of sugars with proteins, by inhibiting the late stage of glycation or by preventing Amadori product formation. Furthermore, their ability to scavenge free radicals and to break cross-links might be other mechanisms responsible for their potential to inhibit glycation. Naturally occurring phytochemicals/products have been found to be relatively non-toxic as compared to synthetic compounds, and are inexpensive and available in an ingestible form. A large number of plants and natural biomolecules have been shown to have antidiabetic effects. Several hypoglycaemic compounds have anti-oxidant properties. The present review describes the various ways in which glycation can be prevented.

Hyperglycemia and the accumulation of advanced glycation endproducts (AGEs) in tissues and serum have important roles in diabetic complications. Therefore, the identification of anti-glycation compounds is attracting considerable interest. In this study the antioxidant activity of ethanolic extract of Nigella sativa seeds and the interaction of human serum albumin (HSA) with glucose in the absence and presence of extract was studied by tryptophan fluorescence, AGE fluorescence and SDS-PAGE. The results indicate that Nigella sativa extract has significant amount of total phenolic content and reducing power. Furthermore, it also causes conformational changes in HSA, decrease in AGEs formation, increase in tryptophan fluorescence and decreased cross linking of proteins. Hence, it can be deduced that Nigella sativa has a potent antioxidant and antiglycating activity, which can be employed to delay or prevent the secondary complications of diabetes mellitus.

Bunium persicum Boiss. seeds have been used for medicinal and nutritional properties such as antioxidant, antihelmetic and antimicrobial activity. The aim of this study was to to tested protective role of cumin extract against abiotic stress by microRNA markers. Secondary also was to evaluate antioxidant activity as well as total polyphenol, flavonoid and phenolic acid content of cumin extract. We observed that cumin DNA itself has not been damaged by sonication teratment. This protective impact indicates that cumin antioxidant properties can efficiently quench free radicals induced by sonication. On the other side, ultrasound-mediated formation of reactive oxygen species did induce the DNA polymorphism of lettuce samples which was detected by miRNAs-based markers. The range of sonication impact was time-dependent. Markers based of miRNA-DNA sequences has proven to be an effective tool. We have confirmed statistically significant differences (p ≤0.01) in miRNAs markers ability to de...

NMR reveals numerous early and advanced glycation products, including a newly recognized ‘norpronyl-lysine,’ and cross links in solution, intact collagen and model systems. Solid state methods are directly applicable to in vitro and in vivo glycation pathway and product characterization.

Glycation plays an important role in various oxidative stress related diseases. Superoxide dismutase (SOD) constitutes an essential defense against oxidative stress. The damage caused by oxidative stress is exacerbated if the antioxidant enzymes themselves are inactivated by glycation. Thymoquinone (TQ) has been reported to have various pharmacological activities. Therefore, the glycation of SOD by glucose or methylglyoxal (MG) and its protection by TQ has been investigated. Incubation of SOD with glucose, MG or both at 37 • C resulted in a progressive decrease in the activity of the enzyme, and a parallel decrease in the amount of protein on SDS-PAGE gels for glucose incubated SOD and formation of high molecular weight aggregates for MG or both glucose and MG incubated enzyme. TQ offered protection against glucose or MG induced loss in SOD activity and fragmentation/cross-linking. The antiglycating activity of TQ appears to be better for mild glycating agents. It is also effective in protecting against strong glycating agents, more when the exposure time to the glycating agent is short. TQ has also earlier been reported to have anti-diabetic effects, and this along with the observed antiglycating effect makes it an effective compound against diabetes and its complications.

Background: Glucose-induced protein glycation has been implicated in the progression of diabetic complications and age-related diseases. The anti-glycation potential of polyphenol-rich plant extracts has been shown previously. Bunium Persicum has been demonstrated to possess a high level of polyphenols. The aim of current in vitro study was to determine the possible inhibitory effect of Bunium Persicum hydroalcoholic extract (BPE) on glucose-induced bovine serum albumin (BSA) glycation, oxidation, and aggregation. Methods: Folin-Ciocalteu assay was used to measure the content of total phenolic compounds of BPE. To test the in vitro effect of BPE on the formation of glycated BSA, thiol group oxidation, and protein aggregation of BSA, various concentrations of BPE were incubated with BSA and glucose at 37 °C for 72 hr. Glycation, thiol group oxidation, and aggregation of BSA were then measured using thiobarbituric acid, 2, 4-dinitrophenylhydrazine, and Congo red colorimetric methods, ...

The binding of glucose to serum proteins in a non-enzymatic reaction occurs proportionately to the prevailing serum glucose concentration during the lifespan of each protein. The non-enzymatic reaction of proteins with reducing sugars results in the formation of glycated proteins that are indicative of the relative amount of reducing sugars present. Hemoglobin, albumin, lipoproteins and other tissue proteins can be non-enzymatically glycated. Hence, estimation of these glycated proteins can be used for the estimation of average glycemic status. Spectrophotometric, chromatographic and immunoassays techniques are used for the detection and quantitation of these glycated proteins.

Objectives: The study aimed to determine the effect of coffee intake on AGEs formation and platelet aggregation in diabetic Wistar rats. Methods: Coffee powder samples were used to prepare a 10% beverage. Diabetes mellitus was induced in the animals by administering 2% alloxan. All animal experiments were approved by the ethics committee for animal experiments under N°. 420/2012 and 536/2013. Diabetic and non-diabetic rats were divided into 6 groups treated and untreated with coffee (7.2 mL/Kg body weight) and aminoguanidine (AGE inhibiting agent) (100 mg/Kg body weight) for 50 days. After 50 days, the animals were fasted for 12 h and anesthetized (40 mg/Kg sodium pentobarbital) intraperitoneally. Blood samples were collected from the abdominal artery puncture. Hematological parameters (red cells, hemoglobin, hematocrit and leukocyte) and glycemic and HbA1c levels were measured. AGEs quantification (spectrofluorometric method) and the platelet aggregation test (aggregation of cuvett...