Deciphering metal-induced oxidative damages on glycated albumin structure and function

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 48 h, 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.

A Long Journey into the Investigation of the Structure–Dynamics–Function Paradigm in Proteins through the Activities of the Palermo Biophysics Group

An overview of the biophysics activity at the Department of Physics and Chemistry Emilio Segrè of the University of Palermo is given. For forty years, the focus of the research has been on the protein structure–dynamics–function paradigm, with the aim of understanding the molecular basis of the relevant mechanisms and the key role of solvent. At least three research lines are identified; the main results obtained in collaboration with other groups in Italy and abroad are presented. This review is dedicated to the memory of Professors Massimo Ugo Palma, Maria Beatrice Palma Vittorelli, and Lorenzo Cordone, which were the founders of the Palermo School of Biophysics. We all have been, directly or indirectly, their pupils; we miss their enthusiasm for scientific research, their deep physical insights, their suggestions, their strict but always constructive criticisms, and, most of all, their friendship. This paper is dedicated also to the memory of Prof. Hans Frauenfelder, whose pioneering works on nonexponential rebinding kinetics, protein substates, and energy landscape have inspired a large part of our work in the field of protein dynamics.

Piperine exhibits preventive and curative effect on erythrocytes membrane modifications and oxidative stress against in vitro albumin glycation

Inhibition of non-enzymatic glycation processes is an essential aspect of treating type 2 diabetes and related complications. In this study, piperine's preventative, simultaneous and curative effect in glucose-induced albumin glycation was examined by analyzing the structural and functional markers of albumin. The protective and antioxidant influence of piperine on erythrocytes was assessed by examining cellular membrane modifications with antioxidant status. Albumin glycation was performed in three different experimental sets of 21 days at 37°C in dark conditions-using different piperine concentrations (250, 500, and 1,000 μM) and time of addition of glucose (30 mM)/piperine (1,000 μM) in a respective solution at 10th day. Piperine with glycated albumin leads to decreased fructosamine, carbonyl group, and protein-bound glucose. It had protected free amino groups, thiol group, and reduced beta-amyloid, protein aggregates formation. The presence of piperine with glycated albumin prevented erythrocytes hemolysis, membrane modifications, and maintained the antioxidant status. Piperine showed the antiglycation effects in a dose-dependent manner, additionally, its pre-treatment exhibited maximum attenuation by manifesting its primarily preventive role. PRACTICAL APPLICATIONS: Piperine is a natural alkaloid compound found in pepper, has been reported to possess anti-cancer, anti-microbial, and anti-inflammatory properties. The present study evaluated the antiglycation potential of piperine in albumin's glycation and it displayed preventive action, protected erythrocytes from oxidative damage induced by glycated albumin. We concluded that the daily intake of piperine can be adequate to prevent glycation-induced diabetic complications development in hyperglycemic conditions.

The effect of Kappaphycus alvarezii fraction on plasma glucose, Advanced Glycation End-products formation, and renal RAGE gene expression

BACKGROUND

Kappaphycus alvarezii (Doty) Doty ex P.C.Silva is a red algae with antioxidant and antiglycation activities. Algae still have not been widely used for treating diabetes, especially to prevent complications. The purpose of this study was to examine the effect of active fractions from Kappaphycus alvarezii on plasma glucose level, glycation process and renal RAGE gene expression.

METHODS

This study used bioassay-guided fractionation, consisting of three stages: extraction, partition, and fractionation. These processes were monitored with Thin Layer Chromatography and the BSA-Glucose method to select the best extract with antiglycation activity (calculated as the percentage of inhibition and IC50). The selected active fraction from four fractions was further used for in vivo study, which was conducted with hyperglycemic Wistar male rats. Plasma glucose level was measured using GOD-PAP methods, while plasma glycated albumin (GA) and Nε- (carboxymethyl) lysine (CML) levels were measured using ELISA. Renal RAGE gene expression was analyzed using qPCR.

RESULTS

Fraction II was selected as the active fraction of Kappaphycus alvarezii showing antiglycation activity with the highest percentage of inhibition and the lowest IC50. This fraction significantly reduced plasma GA and CML levels, but it did not significantly reduce plasma glucose level. Furthermore, renal RAGE gene expression was lower in the diabetic rat group treated with this active fraction compared to the untreated group.

CONCLUSIONS

This study successfully identified an active fraction of Kappaphycus alvarezii with antiglycation activity to reduce plasma GA and CML levels as well as renal RAGE gene expression. Therefore, this fraction could be developed as a potential candidate for treating diabetes.

Effect of Cu(ii) on in vitro glycation of human serum albumin by methylglyoxal: a LC-MS-based proteomic approach

It has been reported that glycation of human serum albumin (HSA) changes its capability for copper binding whereas the increase of free copper might have an impact on protein glycation - a key process in diabetes progression. In this work, proteomic analysis of non-glycated HSA and HSA glycated with methylglyoxal (MGo) in the absence or in the presence of Cu(ii) (0.1; 1.0; 5.0 mg Cu L^-1) has been undertaken. Trypsin hydrolysates were subjected to capillary HPLC-ESI-QTOF-MS and MS/MS. Raw data were analyzed using two proteomic platforms: MaxQuant () and ProteinScape (Bruker). Considering seven MGo-derived modifications, the sequence coverage was 98% for non-modified HSA and ≥93% for HSA incubated with MGo or MGo + Cu(ii). Peptide mapping yielded 76 identical peptides in all samples though important differences were found between non-modified HSA and protein glycated with or without Cu(ii). Overall, 46 peptides with residues from 1 to 3 modified were detected/sequenced; the MGo-derived modifications found were: hydroimidazolone, argpyrimidine, N^ε-carboxyethyl-lysine and S-carboxyethyl-cysteine; 39 modified sites were identified (22 on arginine, 12 on lysine, and 5 on cysteine) and among them, 27 were common for ProteinScape and MaxQuant. The count of the modified peptides and the comparative analysis of their abundance in different samples indicated that Cu(ii) at physiological and sub-physiological concentrations inhibited HSA glycation as compared to the glycation of the Cu-devoid protein; at higher concentrations (5 mg Cu L^-1), this inhibitory effect tends to be inverted. The results obtained suggest that increased protein glycation might be associated with Cu-deficiency and with excessive Cu(ii) concentrations, calling for more detailed studies performed on real-world samples with a strict control of copper concentration.

Glycated human albumin alters mitochondrial respiration in preadipocyte 3T3-L1 cells

Diabetes and obesity are strongly associated with increased levels of circulating advanced glycation end products (AGEs) and reactive oxygen species (ROS). These two molecular phenomena affect the physiology of adipose tissue, a biological driver of the metabolic syndrome, leading to an inflammatory profile and insulin resistance, which could contribute to obesity/diabetes-associated complications, such as cardiovascular diseases. Herein, we investigated the impact of AGEs on mitochondrial bioenergetics in murine preadipocyte cells (3T3-L1) and cellular redox homeostasis. We show that incubation of preadipocytes with AGEs stimulates mitochondrial activity and respiration while inducing oxidative stress. This AGE-induced intracellular ROS production was blocked by diphenylene iodonium, an NAD(P)H oxidase inhibitor. In parallel, antioxidant enzymes (catalase, superoxide dismutase, and glutathione peroxidase) were found to be activated upon AGE treatment. Our results suggest that AGE-induced oxidative stress is generated by NAD(P)H oxidase and leads to a cellular proliferation arrest associated with enhanced mitochondrial metabolism and biogenesis, and with increased levels of ROS-detoxifying enzymes, as well. These new data show how AGEs may be involved in hyperglycemia-induced oxidative damage in preadipocytes and their potential links to diabetes progression. © 2017 BioFactors, 43(4):577-592, 2017.

HSA targets multiple Aβ42 species and inhibits the seeding-mediated aggregation and cytotoxicity of Aβ42 aggregates

HSA inhibits Aβ42 fibrillation and cytotoxicity through interfering with different stages of Aβ42 fibrillation and targeting different Aβ42 intermediate aggregates.

Zinc and diabetes mellitus: understanding molecular mechanisms and clinical implications

Background

Diabetes mellitus is a leading cause of morbidity and mortality worldwide. Studies have shown that Zinc has numerous beneficial effects in both type-1 and type-2 diabetes. We aim to evaluate the literature on the mechanisms and molecular level effects of Zinc on glycaemic control, β-cell function, pathogenesis of diabetes and its complications.

Methods

A review of published studies reporting mechanisms of action of Zinc in diabetes was undertaken in PubMed and SciVerse Scopus medical databases using the following search terms in article title, abstract or keywords; (“Zinc” or “Zn”) and (“mechanism” or “mechanism of action” or “action” or “effect” or “pathogenesis” or “pathology” or “physiology” or “metabolism”) and (“diabetes” or “prediabetes” or “sugar” or “glucose” or “insulin”).

Results

The literature search identified the following number of articles in the two databases; PubMed (n = 1799) and SciVerse Scopus (n = 1879). After removing duplicates the total number of articles included in the present review is 111. Our results show that Zinc plays an important role in β-cell function, insulin action, glucose homeostasis and the pathogenesis of diabetes and its complications.

Conclusion

Numerous in-vitro and in-vivo studies have shown that Zinc has beneficial effects in both type-1 and type-2 diabetes. However further randomized double-blinded placebo-controlled clinical trials conducted for an adequate duration, are required to establish therapeutic safety in humans.

Electronic supplementary material

The online version of this article (doi:10.1186/s40199-015-0127-4) contains supplementary material, which is available to authorized users.

Effect of different glycation agents on Cu(II) binding to human serum albumin, studied by liquid chromatography, nitrogen microwave-plasma atomic-emission spectrometry, inductively-coupled-plasma mass spectrometry, and high-resolution molecular-mass spectrometry

The ability of human serum albumin to capture unbound copper under different clinical conditions is an important variable potentially affecting homeostasis of this element. Here, we propose a simple procedure based on size-exclusion chromatography with on-line UV and nitrogen microwave-plasma atomic-emission spectrometry (MP-AES) for quantitative evaluation of Cu(II) binding to HSA upon its glycation in vitro. The Cu-to-protein molar ratio for non-glycated albumin was 0.98 ± 0.09; for HSA modified with glyoxal (GO), methylglyoxal (MGO), oxoacetic acid (GA), and glucose (Glc), the ratios were 1.30 ± 0.22, 0.72 ± 0.14, 0.50 ± 0.06, and 0.95 ± 0.12, respectively. The results were confirmed by using ICP-MS as an alternative detection system. A reduced ability of glycated protein to coordinate Cu(II) was associated with alteration of the N-terminal metal-binding site during incubation with MGO and GA. In contrast, glycation with GO seemed to generate new binding sites as a result of tertiary structural changes in HSA. Capillary reversed-phase liquid chromatography with electrospray-ionization quadrupole-time-of-flight tandem mass spectrometry enabled detection and identification of Cu(II) coordinated to the N-terminal metal-binding site (Cu(II)-DAHK) in all tryptic digests analyzed. This is the first report confirming Cu(II)-DAHK species in HSA by means of high-resolution tandem mass spectrometry, and the first report on the use of MP-AES in combination with chromatographic separation.