Non-enzymatic Glycation Of Proteins Research Articles

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 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.

The Inhibition Mechanisms of Three Structurally Different Salvianolic Acids on the Non-Enzymatic Glycation of Bovine Serum Albumin.

The antiglycation mechanisms of three structurally different salvianolic acids (Sals) including salvianolic acid A (Sal-A), salvianolic acid B (Sal-B) and salvianolic acid C (Sal-C) were investigated using the bovine serum albumin (BSA)-fructose model. The results showed that the three compounds could inhibit the formation of glycation products, maintain protein structural stability, mitigate the development of amyloid fibrils and scavenge radicals. Notably, Sal-A possessed the highest anti-glycated activity compared with Sal-B and Sal-C. This may be related to the fact that Sal-A contained the most molecules of caffeic acid (Sal-A, Sal-B, and Sal-C possessing two, one, and zero caffeic acid units, respectively), and caffeic acid played a leading role in the antiglycation properties relative to Danshensu. Moreover, these compounds quenched the intrinsic fluorescence intensity of BSA in a static mode, with the binding constants in the order of Sal-A > Sal-B > Sal-C. Obviously, Sal-A possessed the strongest binding affinity among these compounds, which may be one of the reasons why it exhibited the optimal antiglycation capability. Furthermore, molecular docking demonstrated that the three Sals exerted protective effects on BSA by preventing glycation modification of lysine and arginine residues. These findings would provide valuable insights into the potential application of Sals for alleviating non-enzymatic glycation of protein.

Identification of heavily glycated proteoforms by hydrophilic-interaction liquid chromatography and native size-exclusion chromatography – High-resolution mass spectrometry

BackgroundThe non-enzymatic glycation of proteins and their advanced glycation end products (AGEs) are associated with protein transformations such as in the development of diseases and biopharmaceutical storage. The characterization of heavily glycated proteins at the intact level is of high interest as it allows to describe co-occurring protein modifications. However, the high heterogeneity of glycated protein makes this process challenging, and novel methods are required to accomplish this. ResultsIn this study, we investigated two novel LC-HRMS methods to study glycated reference proteins at the intact protein level: low-flow hydrophilic-interaction liquid chromatography (HILIC) and native size-exclusion chromatography (SEC). Model proteins were exposed to conditions that favored extensive glycation and the formation of AGEs. After glycation, complicated MS spectra were observed, along with a sharply reduced signal response, possibly due to protein denaturation and the formation of aggregates. When using HILIC-MS, the glycated forms of the proteins could be resolved based on the number of reducing monosaccharides. Moreover, some positional glycated isomers were separated. The SEC-MS method under non-denaturing conditions provided insights into glycated aggregates but offered only a limited separation of glycated species based on molar mass. Overall, more than 25 different types of species were observed in both methods, differing in molar mass by 14–162 Da. 19 of these species have not been previously reported. SignificanceThe proposed strategies show great potential to characterize highly glycated intact proteins from native and denaturing perspectives and provide new opportunities for fast clinical diagnoses and investigating glycation-related diseases.

Glycation-induced Amyloid Formation in Proteins: An Emerging Perspective to Explore Diabetes Associated Onset of Neurodegenerative Symptoms

Abstract: Non-enzymatic protein glycation occurs spontaneously via the formation of sugarprotein Schiff adducts. The end products of this pathway are terminally misfolded proteins popularly known as Advanced Glycation End (AGE) Products. Glycated proteins account for a diverse spectrum of physiological maladies including arteriosclerosis, renal failure, diabetic complications, obesity, and neurological disorders. AGEs not only jeopardise the functionality of modified proteins but also induce the formation of Covalent protein cross-links. Glycation has the potential to induce the unfolding and refolding of globular proteins into cross-β structures thus resembling many amyloid deposits like amyloid beta, tau protein, and prions. However, glycation-induced amyloid formation is not a generic property of proteins; instead, it is guided by the nature and conformation of the protein, the type of glycation agent as well as the solution conditions governing the glycation reaction. The half-lives of AGE adducts are prolonged by their impaired proteasomal clearance since glycation modifies the lysine residues and renders them unavailable for ubiquitination. AGEs are cleared via sequestration with specific cell surface receptors (RAGE); subsequently, downstream signalling events involving MAPK and NF-κB result in the activation of inflammatory response or the apoptotic pathway. This perspective article discusses the current developments in understanding the various facets of glycationassociated protein aggregation and the corresponding development of amyloid-like entities.

Neuroprotective potential of gliflozins

Gliflozins are a relatively new class of oral antihyperglycemic drugs that are increasingly being introduced into routine practice in the treatment of patients with type 2 diabetes mellitus (DM2). The hypoglycemic effect of gliflozins is associated with the stimulation of glucosuria, however, in addition to a pronounced hypoglycemic effect and high safety, these drugs also have many pleiotropic properties, due to the presence of many direct and indirect points of application. The purpose of this paper is to provide an overview of the currently best studied neuroprotective effects of this class of drugs. As materials in the course of the work, studies of foreign colleagues published in the period 2008–2022 were used. Analysis of the works showed that the neuroprotective effect of gliflozins is associated with many different mechanisms. Thus, gliflozins realize an anti-inflammatory effect by activating the M2 subpopulation of macrophages, reducing pro-inflammatory neurotransmitters (related primarily to the inflammasome). In addition, by reducing the activity of the mTOR signaling pathway, the drugs reduce the amount of beta-amyloid and improve neurotransmission. A group of works also showed the antiacetylcholinesterase effect of gliflozins, not to mention the decrease in the intensity of non-enzymatic protein glycation and insulin resistance. All of the above mechanisms provide an anti-inflammatory, anti-atherogenic effect, improve cognitive abilities in patients, reduce the frequency of hemorrhagic stroke, and can also potentially improve prognosis in patients with Alzheimer’s disease (AD). The effects described above were obtained during preclinical trials and many experimental studies, and some effects have already demonstrated their consistency in prospective clinical trials. However, the data obtained are still insufficient to form clear indications for this class of drugs in neurology, so the topic requires further study and clinical trials.

Antiglycation and antioxidant potential of coumaric acid isomers: a comparative in-vitro study

Advanced glycation end products (AGEs) are the product of non-enzymatic glycation of serum proteins. AGEs increase reactive oxygen species (ROS) formation, which leads to diabetic complications. Phytochemicals exhibit lesser side effects as compared to conventional therapy. In this study, three isomers of coumaric acid (ortho, meta, para) were used to deduce the better one in terms of reducing diabetic complications. For this purpose, human serum albumin (HSA) was incubated with glucose in the absence and presence of isomers for 28 days. To avoid any growth, NaN3 was added and temperature was kept constant throughout the incubation period. Studies like fluorescence, circular dichroism spectroscopy, fructosamine analysis, free lysine estimation, free thiol group estimation were done. To investigate the ROS production, fluorescence microscopy of isolated lymphocytes using DAPI and dichloro-dihydro-fluorescein diacetate were performed. Molecular docking and molecular dynamic simulations (root-mean-square deviation, root-mean-square fluctuations, radius of gyration and solvent-accessible surface area) of HSA and peroxisome proliferator activated receptor (PPAR) alpha and gamma were also done. It was observed that in glycated protein samples, the level of absorbance, fluorescence, fructosamine and carbonyl group increased along with the loss of secondary structure, free lysine and thiol group. These parameters were found gradually recovered in treated samples. ROS production and apoptosis were found to be reduced in lymphocytes treated with p-Coumaric acid (pCA)-treated protein samples as compared to lymphocyte treated with glycated protein. Computational modelling suggested a stable complex formation of HSA and PPARs with pCA. Results with pCA at 200 µM were consistently better than other two isomers. Our next step is to evaluate this study in rats. Communicated by Ramaswamy H. Sarma

In-Vitro Evaluation of Anti-Glycation Potential of Bruguiera Sexangula

Diabetes mellitus (DM) is a metabolic disorder that affects people all over the world and causes hyperglycemia. Further, chronic hyperglycemia may lead to non-enzymatic protein glycation where the excess blood glucose reacts with free amino acids in proteins to form a labile Schiff's base. Then the base gets stabilized to form advanced glycation end products (AGEs), one of the hallmark compounds of glycation. Therefore, antiglycation therapy is considered as one of the important aspects of post diabetic treatment. Recently, many phytochemicals have been reported for their antiglycation potential. In the present study, Bruguiera sexangula an medicinal mangrove plant from the Eastern coastal regions of Odisha has been evaluated for its antiglycation potential using in vitro techniques. The anti-glycation activities of aqueous bark extract of this plant were determined by bovine serum albumin-fructose glycation model. The multistage glycation markers-fructosamines, thiols and β aggregation of albumin using amyloid-specific dyes–Congo red were evaluated. The studies were carried out for the 0th,1st, 2nd , 3 rd and 4th consecutive weeks. The present study showed aqueous bark extract of Bruguiera sexangula at 1mg/ml concentration could inhibit amyloid cross beta aggregation in the 0th, first, third and the fourth week. However, no inhibition was observed in the second week. On the other hand, the standard anti-oxidant compound Quercetin could inhibit the amyloid beta aggregation in all the 4 weeks in the Congo red assay. And the extract could only show amadori product inhibition potential during the 1st and the 4th week of study. While, the compound Quercetin could inhibit the amadori product in 1st, 3rd and 4th week of the fructosamine assay. Free thiols were significantly protected from oxidation by the plant extracts. The active phytocompounds were isolated by column chromatography by using different fractions of solvents (petroleum ether, chloroform and methanol) on the basis of their polarity and it is stored for further assays. The results of the present study indicated that B.sexangula can provide protection against long term glycation associated complications. However, more in depth studies need to be carried out to decipher its antiglycation potential. Further, the bioactive phytochemicals responsible for this activity may be isolated to access its antiglycation potential in suitable model organism.

Synergistic interaction between Bambusa arundinacea and Euphorbia hirta leaf extract on antioxidant, antiglycation and DNA protective properties.

Oxidative stress and enhanced non-enzymatic protein glycation result in the pathogenesis of various disorders in humans, including diabetes mellitus. This study examined the synergistic action of Bambusa arundinacea with Euphorbia hirta leaf extract for anti-oxidant potential, antiglycation effect on fructose-mediated proteins, and DNA-protective properties. The methanolic extract shows significantly (P<0.01) higher total phenolic and flavonoid content when compared with ethyl acetate and hexane extract in both plants. The combined methanolic extract (CME) of both plants exhibits higher antioxidant potential, as indicated by the lower IC50 values obtained for DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity (4.82 μg/ml) and NO (nitric oxide) scavenging activity (3.94 μg/ml) with stronger Trolox equivalent antioxidant capacity when compared to B. arundinacea and E. hirta individually. The antiglycation analysis revealed that CME is more potent to inhibit fructose-mediated glycation of human serum albumin (HSA) at the early and middle stages. In addition to this, CME more effectively inhibits protein glycation in the late phase, which was confirmed by declining fluorescence intensity. Furthermore, a high degree of positive correlation was obtained between antioxidant and antiglycation capacities through Pearson’s correlation coefficient. The results also demonstrated that CME displays a synergistic effect in protecting DNA from oxidative damage and preventing the formation of glycation of DNA.

Neuroprotective potential of incretinomimetics

In the prescriptions of an endocrinologist to patients with diabetes mellitus, glucagon-like peptide agonists, belonging to the group that affects the incretin system of the body, have recently been increasingly appearing. In addition to the pronounced hypoglycemic effect and high safety, these drugs also have many pleiotropic properties due to the presence of glucagon-like peptide receptors in the vascular endothelium, kidneys, heart and nervous tissue. The purpose of this work is to describe the most studied neuroprotective effects of this class of drugs. As materials in the course of the work, studies of domestic and foreign colleagues published in the period from 2008 to 2022 were used. Our work has shown that the neuroprotective effect of GLP-1 is associated with the activation of the corresponding receptor systems in the central nervous system, which leads to increased cellular survival in ischemic conditions by reducing reactive oxygen species, stimulating beta-oxidation by mitochondria, and reducing pro-inflammatory cytokines. In addition, the analysis of the literature also established the positive role of GLP-1 in neurodegenerative diseases – drugs reduce the amount of unnormal proteins (alphasynuclein, microtubular T-peptide, etc.), reduce the activity of non-enzymatic glycation of proteins in hyperglycemia, as well as reduce insulin resistance. The effects described above were analyzed during preclinical trials of GLP-1, and also demonstrated their validity in human models during some clinical trials. However, the data obtained is not yet sufficient to form clear indications for this class of drugs in neurology, so the topic requires further study and large clinical trials.

Influence of Nitrosyl Iron Complex with Thiosulfate Ligands on Therapeutically Important Targets Related to Type 2 Diabetes Mellitus.

The high prevalence of type 2 diabetes mellitus (T2DM), and the lack of effective therapy, determine the need for new treatment options. The present study is focused on the NO-donors drug class as effective antidiabetic agents. Since numerous biological systems are involved in the pathogenesis and progression of T2DM, the most promising approach to the development of effective drugs for the treatment of T2DM is the search for pharmacologically active compounds that are selective for a number of therapeutic targets for T2DM and its complications: oxidative stress, non-enzymatic protein glycation, polyol pathway. The nitrosyl iron complex with thiosulfate ligands was studied in this work. Binuclear iron nitrosyl complexes are synthetic analogues of [2Fe-2S] centers in the regulatory protein natural reservoirs of NO. Due to their ability to release NO without additional activation under physiological conditions, these compounds are of considerable interest for the development of potential drugs. The present study explores the effects of tetranitrosyl iron complex with thiosulfate ligands (TNIC-ThS) on T2DM and its complications regarding therapeutic targets in vitro, as well as its ability to bind liposomal membrane, inhibit lipid peroxidation (LPO), and non-enzymatic glycation of bovine serum albumin (BSA), as well as aldose reductase, the enzyme that catalyzes the reduction in glucose to sorbitol in the polyol pathway. Using the fluorescent probe method, it has been shown that TNIC-ThS molecules interact with both hydrophilic and hydrophobic regions of model membranes. TNIC-ThS inhibits lipid peroxidation, exhibiting antiradical activity due to releasing NO (IC50 = 21.5 ± 3.7 µM). TNIC-ThS was found to show non-competitive inhibition of aldose reductase with Ki value of 5.25 × 10-4 M. In addition, TNIC-ThS was shown to be an effective inhibitor of the process of non-enzymatic protein glycation in vitro (IC50 = 47.4 ± 7.6 µM). Thus, TNIC-ThS may be considered to contribute significantly to the treatment of T2DM and diabetic complications.

Glycation Inhibition of Bovine Serum Albumin by Extracts of Momordica charantia L. using Spectroscopic and Computational Methods.

Momordica charantia (M. charantia) has been used in traditional medicine for the management of complications associated with diabetes mellitus. Several phytochemicals with different pharmacological properties have been previously identified from the botanical; however, the mechanisms of actions of this plant vis-à-vis inhibition of non-enzymatic protein glycation are not known. This study aimed at understanding the putative mechanisms underlying the antiglycation properties of M. charantia extracts experimental and theoretical approaches. The antiglycation properties of the plant were evaluated by studying the inhibitory actions of methanol and aqueous extracts on glucose-induced glycation of Bovine Serum Albumin (BSA) and protein aggregation. The mode of binding of identified phenolics of the botanical with BSA, amyloid beta-peptide (1-42) and 3D amyloid beta (1-42) fibrils were also investigated. The in vitro experimental properties of the extracts showed that the extracts could prevent inductions of protein glycation and protein folding. The molecular docking analyses revealed that phenolics had better binding affinities with chlorogenic acid showing the highest binding score (-7.13±0.04 kcal/mol) towards BSA than glucose and their respective interactions with BSA could prevent glucose-induced protein aggregation. Consequently, the results of this study provide insight into the probable mechanisms of actions of the extracts of M. charantia against the inhibition of advanced glycation end products formation.

Advanced glycation end products and their soluble receptor (sRAGE) in patients with Hashimoto's thyroiditis on levothyroxine substitution.

Advanced glycation end products (AGEs) are heterogenous group of irreversible chemical moieties originated from non-enzymatic glycation and oxidation of proteins, nucleic acids, and lipids. The engagement of AGEs with their chief cellular receptor (RAGE) activates a myriad of signaling pathways contributing to the progression of chronic diseases like autoimmune thyroiditis, type 2 diabetes mellitus and its complications. Soluble RAGE (sRAGE) prevents AGE-RAGE interaction in a competitive manner. We investigated the association between serum AGE, sRAGE and thyroid function in 73 Hashimoto thyroiditis patients (HT) on levothyroxine substitution, and in 83 age, BMI and gender-matched healthy controls. The serum AGEs levels were determined by autofluorescence on a multi-mode microplate reader, and the serum sRAGE levels by ELISA method. Mean AGE level was lower (10.71 vs 11.45 AU/µg protein; p=0.046), while mean sRAGE level was higher (923 vs 755 pg/mL; p<0.0005) in the serum of HT patients than the controls. AGE correlated with age, while sRAGE correlated negatively with BMI in both groups. We found negative correlation between AGE and fT3 levels (r=-0.32; p=0.006) and sRAGE and TSH levels (r=-0.27; p=0.022) in HT patients, while we failed to find association between AGE, sRAGE and parameters of thyroid function in the control group. Median AGE/sRAGE ratio was lower in HT patients than in controls (2.4, IQR 1.9 - 3.1 vs 3.3, IQR 2.3 - 4.1 AU/pg; p < 0.001). In HT patients, the AGE/sRAGE ratio correlated positively with BMI and correlated negatively with fT3. According to our results in HT patients lower TSH and higher fT3 levels within the reference range is accompanied by a favorable AGE/RAGE balance. Further investigations are needed to confirm these results.

Topical Application of Deglycating Enzymes as an Alternative Non-Invasive Treatment for Presbyopia.

Presbyopia is an age-related vision disorder that is a global public health problem. Up to 85% of people aged ≥40 years develop presbyopia. In 2015, 1.8 billion people globally had presbyopia. Of those with significant near vision disabilities due to uncorrected presbyopia, 94% live in developing countries. Presbyopia is undercorrected in many countries, with reading glasses available for only 6-45% of patients living in developing countries. The high prevalence of uncorrected presbyopia in these parts of the world is due to the lack of adequate diagnosis and affordable treatment. The formation of advanced glycation end products (AGEs) is a non-enzymatic process known as the Maillard reaction. The accumulation of AGEs in the lens contributes to lens aging (leading to presbyopia and cataract formation). Non-enzymatic lens protein glycation induces the gradual accumulation of AGEs in aging lenses. AGE-reducing compounds may be effective at preventing and treating AGE-related processes. Fructosyl-amino acid oxidase (FAOD) is active on both fructosyl lysine and fructosyl valine. As the crosslinks encountered in presbyopia are mainly non-disulfide bridges, and based on the positive results of deglycating enzymes in cataracts (another disease caused by glycation of lens proteins), we studied the ex vivo effects of topical FAOD treatment on the power of human lenses as a new potential non-invasive treatment for presbyopia. This study demonstrated that topical FAOD treatment resulted in an increase in lens power, which is approximately equivalent to the correction obtained by most reading glasses. The best results were obtained for the newer lenses. Simultaneously, a decrease in lens opacity was observed, which improved lens quality. We also demonstrated that topical FAOD treatment results in a breakdown of AGEs, as evidenced by gel permeation chromatography and a marked reduction in autofluorescence. This study demonstrated the therapeutic potential of topical FAOD treatment in presbyopia.

FREE RADICALS AND DIABETES MELLITUS

Oxidative stress or free radicals has been found in many studies to participate in progression of diabetes mellitus which plays an important role during diabetes, including impairment of insulin action and increase in complicated incidence. This review was based on the detection of roles of free radicals in the progression of diabetes mellitus thru using different sites like PubMed, Medline, Scopus etc. Endothelial cells also contain high amounts of aldo-keto reductase, and are thus prone to increased polyol pathway activation. Moreover, a large body of evidence supports hypothesis that hyperglycaemia or diabetes leads to vascular diacylglycerol accumulation and subsequent PKC activation, causing a variety of cardiovascular defects. Increase in the levels of oxygen and nitrogen free radicals (ROS/RNS) has been linked with lipid peroxidation, non-enzymatic glycation of proteins and oxidation of glucose which contributes toward diabetes mellitus and its complications. Most of the studies have shown relationship between oxidative stress and diabetes along with their complications related to heart, liver kidney and eye. Thus, oxidative stress seems to be more worrying in metabolic disorders specially NIDDM. It concludes that metabolic oxidation is the strongest factor behind insulin dependent and non-insulin dependent diabetes mellitus.

Evaluation of Dry Fasting Effect during Ramadan on Protein Glycation in Saudi Individuals

Introduction: The non-enzymatic protein glycation alters protein function and contributes to many biochemical disorders. The accumulation of advanced glycation end-products (AGEs) is associated with the complications of diabetes, kidney disease, metabolic disorders and degenerative diseases. &#x0D; Objectives: This study was designed to measure the level of some glycated proteins such as glycated insulin and glycated hemoglobin in Saudi volunteers before and after dry fasting in Ramadan.&#x0D; Methods: Blood samples were collected twice; first sample (before) and second sample (after) dry fasting. The study included 45 Saudi male volunteers, whose ages ranged between23 and 52 years They were divided into four groups: healthy, type II diabetic patients, smokers, and obese individuals. Plasma glucose level and HbA1c were measured immediately using (Beckman coulter). Assessment of insulin resistance was determined using the equation of homeostasis model for insulin resistance (HOMA-IR). Plasma insulin level and glycated insulin % were assayed by TSQ Vantage Triple Stage Quadruple LC/MS Mass Spectrometer from Thermo Scientific.&#x0D; Results: Level of HbA1c, HOMA IR and glycated insulin in healthy, type II diabetic patients, smokers, and obese individuals showed significant decrease in the second sample. The level of HbA1c showed a significant decrease (p-value &lt;0.0001) after dry fasting (5.69 ± 1.55 %), (6.14 ± 1.77%). The level of HOMA IR showed significant decrease (p-value &lt;0.0001) after dry fasting (1.97 ± 1), (2.46 ± 1.28). The level of glycated insulin showed significant decrease (p-value &lt;0.0001) after dry fasting (6.25 ± 2%), (7.71 ± 2.48%).&#x0D; Conclusion: Glucose, HbA1c, HOMA IR, and glycated insulin levels showed a significant decrease after dry fasting. Reduced protein glycation and formation of advanced glycation end products, can improve the clinical course of many medical disorders. More researches are needed to understand the molecular mechanisms behind glycation-induced clinical disorders and diseases, as well as to correlate these mechanisms to the diagnosis and prevention of lifestyle-related diseases.

Antioxidant and anti-inflammatory activities of Centratherum anthelminticum (L.) Kuntze seed oil in diabetic nephropathy via modulation of Nrf-2/HO-1 and NF-κB pathway

BackgroundType 2 diabetes mellitus (T2DM) approximately constitutes 90% of the reported cases. 30-40% of diabetics eventually develop diabetic nephropathy (DN); accounting for one of the major causes of morbidity and mortality. Increased glucose autoxidation and non-enzymatic glycation of proteins in diabetic kidneys lead to the excessive generation of reactive oxygen species (ROS) that results in lipid peroxidation and activation of inflammatory mediators which overwhelms the scavenging capacity of the antioxidant defense system (Nrf2/Keap1/HO-1). Centratherum anthelminticum commonly called as kali zeeri (bitter cumin) and its seeds are well known for culinary purposes in Asia (Pakistan). It has reported anti-inflammatory, antioxidant, and anti-diabetic activities. The present study has attempted to explore the in-vivo anti-inflammatory, antioxidant and antihyperglycemic potential of the C. anthelminticum seed’s fixed oil (FO) and its fractions in high fat-high fructose-streptozotocin (HF-HFr-STZ) induced T2DM rat model.MethodsThe T2DM rat model was developed by giving a high-fat and high-fructose diet followed by a single intraperitoneal injection of streptozotocin (STZ 60 mg/kg) on 28th day of the trial. After 72 hours of this injection, rats showing fasting blood glucose (FBG) levels≥230 mg/dL were recruited into six groups. These groups were orally administered distilled water (1 mL/kg), Gliclazide (200 mg/kg), Centratherum anthelminticum seed (FO) and its hexane (HF), chloroform (CF) and ethanol (EF) soluble fractions (200 mg/kg each), respectively for 4 weeks (i.e. 28 days). Blood, serum, and kidney tissue samples of euthanized animals were used for biochemical, pro-inflammatory, and antioxidant markers (ELISA, qRT-PCR, and spectrophotometric assays) and histology, respectively.ResultsC. anthelminticum FO and its fractions reduced the lipid peroxidation, and improved the antioxidant parameters: enzymatic (SOD, CAT, and GPx), non-enzymatic (GSH), and mRNA expression of anti-inflammatory markers (Nrf-2, keap1, and HO-1). mRNA expression of inflammatory and apoptotic markers (TNF-α, IL-1β, COX-1, NF-κB, Bax, and Bcl-2) were attenuated along with improved kidney architecture.ConclusionC. anthelminticum can mitigate inflammation and oxidative stress in early DN. The anti-nephropathic effect can be attributed to its ability to down-regulate NF-κB and by bringing the Nrf-2 expression levels to near normal.

Advanced glycation end products in diabetic retinopathy and phytochemical therapy.

Advanced glycation end products (AGEs) are generated by the nonenzymatic glycation of proteins or lipids. Diabetic retinopathy (DR) is one common complication in patients with diabetes. The accumulation of AGEs in retinal cells is strongly associated with the development of DR. AGEs can induce the breakdown of redox balance and then cause oxidative stress in retinal cells, exerting cytopathic effects in the progression of DR. The interaction between AGEs and the receptor for AGE (RAGE) is involved in multiple cellular pathological alterations in the retina. This review is to elucidate the pathogenetic roles of AGEs in the progression of DR, including metabolic abnormalities, lipid peroxidation, structural and functional alterations, and neurodegeneration. In addition, disorders associated with AGEs can be used as potential therapeutic targets to explore effective and safe treatments for DR. In this review, we have also introduced antioxidant phytochemicals as potential therapeutic strategies for the treatment of DR.

The Influence of Cationic Nitrosyl Iron Complex with Penicillamine Ligands on Model Membranes, Membrane-Bound Enzymes and Lipid Peroxidation.

This paper shows the biological effects of cationic binuclear tetranitrosyl iron complex with penicillamine ligands (TNIC-PA). Interaction with a model membrane was assessed using a fluorescent probes technique. Antioxidant activity was studied using a thiobarbituric acid reactive species assay (TBARS) and a chemiluminescence assay. The catalytic activity of monoamine oxidase (MAO) was determined by measuring liberation of ammonia. Antiglycation activity was determined fluometrically by thermal glycation of albumine by D-glucose. The higher values of Stern-Volmer constants (KSV) obtained for the pyrene located in hydrophobic regions (3.9 × 104 M-1) compared to KSV obtained for eosin Y located in the polar headgroup region (0.9 × 104 M-1) confirms that TNIC-PA molecules prefer to be located in the hydrophobic acyl chain region, close to the glycerol group of lipid molecules. TNIC-PA effectively inhibited the process of spontaneous lipid peroxidation, due to additive contributions from releasing NO and penicillamine ligand (IC50 = 21.4 µM) and quenched luminol chemiluminescence (IC50 = 3.6 μM). High activity of TNIC-PA in both tests allows us to assume a significant role of its radical-scavenging activity in the realization of antioxidant activity. It was shown that TNIC-PA (50-1000 μM) selectively inhibits the membrane-bound enzyme MAO-A, a major source of ROS in the heart. In addition, TNIC-PA is an effective inhibitor of non-enzymatic protein glycation. Thus, the evaluated biological effects of TNIC-PA open up the possibility of its practical application in chemotherapy for socially significant diseases, especially cardiovascular diseases.

The Inhibition of α-Glucosidase, α-Amylase and Protein Glycation by Phenolic Extracts of Cotoneaster bullatus, Cotoneaster zabelii, and Cotoneaster integerrimus Leaves and Fruits: Focus on Anti-Hyperglycemic Activity and Kinetic Parameters.

Cotoneaster species have gained significant importance in traditional Asian medicine for their ability to prevent and treat hyperglycemia and diabetes. Therefore, in this study, some aspects of the beneficial health effects of hydromethanolic extracts of C. bullatus, C. zabelii, and C. integerrimus leaves and fruits were evaluated, including their influence on α-glucosidase, α-amylase, and nonenzymatic protein glycation. The activity was investigated in relation to the polyphenolic profile of the extracts determined by UV-spectrophotometric and HPLC-PDA-fingerprint methods. It was revealed that all leaf and fruit extracts are a promising source of biological components (caffeic acid pseudodepsides, proanthocyanidins, and flavonols), and the leaf extracts of C. bullatus and C. zabelii contain the highest levels of polyphenols (316.3 and 337.6 mg/g in total, respectively). The leaf extracts were also the most effective inhibitors of digestive enzymes and nonenzymatic protein glycation. IC50 values of 8.6, 41.8, and 32.6 µg/mL were obtained for the most active leaf extract of C. bullatus (MBL) in the α-glucosidase, α-amylase, and glycation inhibition tests, respectively. In the kinetic study, MBL was displayed as a mixed-type inhibitor of both enzymes. The correlations between the polyphenol profiles and activity parameters (|r| > 0.72, p < 0.05) indicate a significant contribution of proanthocyanidins to the tested activity. These results support the traditional use of Cotoneaster leaves and fruits in diabetes and suggest their hydrophilic extracts be promising in functional applications.