Non-enzymatic Glycation Of Proteins Research Articles

5176 Time In Range Preferred Over A1c And Fructosamine To Monitor Glycemic Control In Sickle Cell Disease

Abstract Disclosure: A. Patel: None. B. Simon: None. Introduction: In sickle cell disease, hemoglobin A1c is unreliable due to anemia, hemolysis, transfusions, and increased red blood cell turnover. In this population, plasma glucose should be used to make a diagnosis of diabetes, but there are no reliable long-term measures of glycemic control. Measures of serum protein glycation such as fructosamine are often used as markers of short-term control[1]. Continuous glucose monitoring (CGM) time in range (TIR) may offer another more reliable metric of control in this population2. Case: A 58-year-old male presented to the office for uncontrolled type 2 diabetes mellitus. His medical history included sickle cell anemia (Hb SS disease), hypertension, monoclonal gammopathy, and priapism. He was diagnosed with type 2 diabetes mellitus approximately one year prior based on a fructosamine level of 470 umol/L (0-285 umol/L) and elevated fasting glucose level of 128 mg/dL. He started metformin 500 mg daily. Three months later, repeat fructosamine was 401 umol/L, and metformin was increased. Months later, fructosamine levels remained elevated at 419 umol/L; metformin was increased to 2 grams daily and he was referred to endocrinology. The patient was given a CGM (Freestyle Libre 2 system, Abbott Diabetes Care) as an additional method to assess control. CGM showed an excellent 2-week TIR (70-180mg/ dL) of 98%. Repeat fructosamine after 2 weeks of CGM wear was elevated at 500 umol/L. It was hypothesized that the history of IgG kappa monoclonal gammopathy was falsely elevating his fructosamine level. A glycated albumin level was 13.5% (10.7-13.5%). The patient was advised to discontinue his metformin. Four months later, his glycated albumin remained in range, and a 2-week TIR was 100%. Discussion: This case demonstrates how sickle cell disease and monoclonal gammopathy affect laboratory values typically used to diagnose and monitor type 2 diabetes. Fructosamine, a measure of non-enzymatic glycation of serum proteins, is non-specific2. Increased protein from monoclonal gammopathy (giving more protein glycation sites) was the probable cause of the persistently elevated fructosamine, leading to overtreatment of what may not have been a true diagnosis of diabetes. This case also demonstrates the value of CGM, with glucose values and TIR indicating near normoglycemia. Diagnostic CGM may be a useful measure of glucose control in patients with hemoglobinopathies.

Inhibitory Effects of Aqueous Ethanol Extracts of Poplar-Type Propolis on Advanced Glycation End Products and Protein Oxidation

(1) Background: The non-enzymatic glycation of proteins is a significant contributor to the formation of advanced glycation end products (AGEs) and intermediates that are responsible for diabetic complications. It is imperative to explore effective inhibitors to prevent protein glycation. (2) Methods: This study aimed to investigate the inhibitory potential of various aqueous ethanol extracts of poplar-type propolis on AGEs and oxidative modifications in bovine serum albumin (BSA)-glucose and BSA-methylglyoxal models. (3) Results: The results revealed that these propolis extracts exhibited significant effectiveness in inhibiting the formation of total AGEs, pentosidine, and Nε-carboxymethyllysine (CML). Furthermore, the investigation discovered that these propolis extracts can effectively inhibit oxidative modification, based on measuring the levels of carbonyl and thiol groups and analyzing tryptophan fluorescence quenching. Notably, 75% ethanol extracts of propolis (EEP) exhibited the highest inhibitory activity, surpassing the chemical inhibitor aminoguanidine (AG). (4) Conclusions: The remarkable anti-glycation potency of aqueous ethanol extracts of poplar-type propolis can be attributed to their elevated contents of phenolic compounds, especially abundant flavonoids, which inhibit the formation of AGEs by scavenging free radicals, decreasing the levels of reactive oxygen species (ROS), and capturing reactive carbonyl species (RCS) in the protein glycation process. Our results indicate that poplar-type propolis may be a potential AGE inhibitor and could be used to develop functional foods and nutraceuticals to prevent diabetic complications.

Testing AI predictions that hyperglycemia-induced non-enzymatic glycation of immune system proteins impairs diabetic immunity

People with type 1, type 2 and gestational diabetes, and newborns of diabetic mothers, have increased risks of contracting microbial infections such as SARS-CoV-2, amplifying comorbidity and mortality risks. Hyperglycemia and its associated hyperinflammation mediate these risks but by unknown mechanisms. We hypothesize that hyperglycemia results in glycation (non-enzymatic addition of sugars to free amino groups such as lysines) of antimicrobial and anti-inflammatory proteins and peptides that mediate innate and adaptive immunity. While glycation of hemoglobin A1c is used as a benchmark for glycemic control, studies of the effects of the glycation of immune system molecules are almost non-existent. Three AI protein-glycation prediction models demonstrate that immune system proteins and peptides such as serotransferrin, lactotransferrin, lysozyme, complement proteins, immunoglobulins, Toll-like receptors, etc., probably glycate at multiple sites affecting function. However, the AI-predicted glycation sites differed significantly among the three models employed. Therefore, three tests of these predictions were carried out. Predicted glycation sites were first evaluated in terms of clinically or experimentally identified glycation sites of homologous proteins and known effects of lysine substitutions at predicted glycation sites. Second, mass spectrometry was used to identify glycation sites on lactoferrin and human lysozyme. Third, the effects on the antimicrobial activity of lactotransferrin and lysozyme glycation were tested using a Candida albicans assay. Results of tests demonstrate that protein glycation occurs and interferes with immune function but that AI glycation prediction models are very inaccurate. Suggestions for improving AI accuracy are provided.

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

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

Fenfuro®-mediated arrest in the formation of protein-methyl glyoxal adducts: a new dimension in the anti-hyperglycemic potential of a novel fenugreek seed extract

The fenugreek plant (Trigonella foenum-graecum) is traditionally known for its anti-diabetic properties owing to its high content of furostanolic saponins, which can synergistically treat many human ailments. Non-enzymatic protein glycation leading to the formation of Advanced Glycation End products (AGE) is a common pathophysiology observed in diabetic or prediabetic individuals, which can initiate the development of neurodegenerative disorders. A potent cellular source of glycation is Methyl Glyoxal, a highly reactive dicarbonyl formed as a glycolytic byproduct. We demonstrate the in vitro glycation arresting potential of Fenfuro®, a novel patented formulation of Fenugreek seed extract with clinically proven anti-diabetic properties, in Methyl-Glyoxal (MGO) adducts of three abundant amyloidogenic cellular proteins, alpha-synuclein, Serum albumin, and Lysozyme. A 0.25% w/v Fenfuro® was able to effectively arrest glycation by more than 50% in all three proteins, as evidenced by AGE fluorescence. Glycation-induced amyloid formation was also arrested by more than 36%, 14% and 15% for BSA, Alpha-synuclein and Lysozyme respectively. An increase in MW by attachment of MGO was also partially prevented by Fenfuro® as confirmed by SDS-PAGE analysis. Glycation resulted in enhanced aggregation of the three proteins as revealed by Native PAGE and Dynamic Light Scattering. However, in the presence of Fenfuro®, aggregation was arrested substantially, and the normal size distribution was restored. The results cumulatively indicated the lesser explored potential of direct inhibition of glycation by fenugreek seed in addition to its proven role in alleviating insulin resistance. Fenfuro® boosts its therapeutic potential as an effective phytotherapeutic to arrest Type 2 diabetes.

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.

Attenuation of albumin glycation and oxidative stress by minerals and vitamins: An in vitro perspective of dual-purpose therapy.

Nonenzymatic glycation of proteins is accelerated in the context of elevated blood sugar levels in diabetes. Vitamin and mineral deficiencies are strongly linked to the onset and progression of diabetes. The antiglycation ability of various water- and fat-soluble vitamins, along with trace minerals like molybdenum (Mo), manganese (Mn), magnesium (Mg), chromium, etc., have been screened using Bovine Serum Albumin (BSA) as in vitro model. BSA was incubated with methylglyoxal (MGO) at 37°C for 48h, along with minerals and vitamins separately, along with controls and aminoguanidine (AG) as a standard to compare the efficacy of the minerals and vitamins. Further, their effects on renal cells' (HEK-293) antioxidant potential were examined. Antiglycation potential is measured by monitoring protein glycation markers, structural and functional modifications. Some minerals, Mo, Mn, and Mg, demonstrated comparable inhibition of protein-bound carbonyl content and ß-amyloid aggregation at maximal physiological concentrations. Mo and Mg protected the thiol group and free amino acids and preserved the antioxidant potential. Vitamin E, D, B1 and B3 revealed significant glycation inhibition and improved antioxidant potential in HEK-293 cells as assessed by estimating lipid peroxidation, SOD and glyoxalase activity. These results emphasize the glycation inhibitory potential of vitamins and minerals, indicating the use of these micronutrients in the prospect of the therapeutic outlook for diabetes management.

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.