An evaluation of level of oxidative stress and protein glycation in nondiabetic undialyzed chronic renal failure patients

1-Amino-1-deoxy-d-fructose ("fructosamine") and its derivatives

Fructosamine has long been considered as a key intermediate of the Maillard reaction, which to a large extent is responsible for specific aroma, taste, and color formation in thermally processed or dehydrated foods. Since the 1980s, however, as a product of the Amadori rearrangement reaction between glucose and biologically significant amines such as proteins, fructosamine has experienced a boom in biomedical research, mainly due to its relevance to pathologies in diabetes and aging. In this chapter, we assess the scope of the knowledge on and applications of fructosamine-related molecules in chemistry, food, and health sciences, as reflected mostly in publications within the past decade. Methods of fructosamine synthesis and analysis, its chemical, and biological properties, and degradation reactions, together with fructosamine-modifying and -recognizing proteins are surveyed.

Quantitative estimation of intracellular oxidative stress in human tissues

Oxidative stress is known to be involved in and possibly a key driver of the development of numerous chronic diseases, including cancer. It is highly desired to have a capability to reliably estimate the level of intracellular oxidative stress as it can help to identify functional changes and disease phenotypes associated with such a stress, but the problem proves to be very challenging. We present a novel computational model for quantitatively estimating the level of oxidative stress in tissues and cells based on their transcriptomic data. The model consists of (i) three sets of marker genes found to be associated with the production of oxidizing molecules, the activated antioxidation programs and the intracellular stress attributed to oxidation, respectively; (ii) three polynomial functions defined over the expression levels of the three gene sets are developed aimed to capture the total oxidizing power, the activated antioxidation capacity and the oxidative stress level, respectively, with their detailed parameters estimated by solving an optimization problem and (iii) the optimization problem is so formulated to capture the relevant known insights such as the oxidative stress level generally goes up from normal to chronic diseases and then to cancer tissues. Systematic assessments on independent datasets indicate that the trained predictor is highly reliable and numerous insights are made based on its application results to samples in the TCGA, GTEx and GEO databases.

Biochemical pathways to α-ketoglutarate, a multi-faceted metabolite

α-Ketoglutarate (AKG) also known as 2-oxoglutarate is an essential metabolite in virtually all organisms as it participates in a variety of biological processes including anti-oxidative defence, energy production, signalling modules, and genetic modification. This keto-acid also possesses immense commercial value as it is utilized as a nutritional supplement, a therapeutic agent, and a precursor to a variety of value-added products such as ethylene and heterocyclic compounds. Hence, the generation of KG in a sustainable and environmentally-neutral manner is a major ongoing research endeavour. In this mini-review, the enzymatic systems and the metabolic networks mediating the synthesis of AKG will be described. The importance of such enzymes as isocitrate dehydrogenase (ICDH), glutamate dehydrogenase (GDH), succinate semialdehyde dehydrogenase (SSADH) and transaminases that directly contribute to the formation of KG will be emphasized. The efficacy of microbial systems in providing an effective platform to generate this moiety and the molecular strategies involving genetic manipulation, abiotic stress and nutrient supplementation that result in the optimal production of AKG will be evaluated. Microbial systems and their components acting via the metabolic networks and the resident enzymes are well poised to provide effective biotechnological tools that can supply renewable AKG globally.

Quantitative Estimation of Oxidative Stress in Cancer Tissue Cells Through Gene Expression Data Analyses

Quantitative assessment of the intracellular oxidative stress level is a very important problem since it is the basis for elucidation of the fundamental causes of metabolic changes in diseased human cells, particularly cancer. However, the problem proves to be very challenging to solve in vivo because of the complex nature of the problem. Here a computational method is presented for predicting the quantitative level of the intracellular oxidative stress in cancer tissue cells. The basic premise of the predictor is that the genomic mutation level is strongly associated with the intracellular oxidative stress level. Based on this, a statistical analysis is conducted to identify a set of enzyme-encoding genes, whose combined expression levels can well explain the mutation rates in individual cancer tissues in the TCGA database. We have assessed the validity of the predictor by assessing it against genes that are known to have anti-oxidative functions for specific types of oxidative stressors. Then the applications of the predictor are conducted to illustrate its utility.

Comparison of Periodontal Ligament Cell Lines with Adenovirus- and Lentivirus-Mediated Human Telomerase Reverse Transcription Expression

The aims of this study were to generate periodontal ligament (PDL) cells that have adenovirus- or lentivirus-mediated overexpression of human telomerase reverse transcriptase (hTERT) and to compare the osteogenic and proliferative abilities of the two cell lines to establish an efficient and stable cell model that will be more suitable for studies of PDL regeneration. After construction of the recombinant adenovirus plasmid pAd-pshuttle-cmv-hTERT, human PDL cells were infected by packaged adenovirus and lentivirus particles to establish two PDL cell lines. The expression levels of hTERT and mRNA for alkaline phosphatase, osteopontin, osteocalcin, bone sialoprotein, core-binding factor (runt-related transcription factor 2), and type I collagen were assessed for each cell line. After culture in osteoinductive culture medium for 14 days, the PDL cells were stained with alizarin red to observe formation of mineralized nodules, and proliferation activity was measured with a CCK-8 kit. A quantitative polymerase chain reaction assay indicated that the two transduced cell lines expressed hTERT levels that were significantly higher than that seen for normal PDL cells. Expression of all osteogenic genes tested, with the exception of osteopontin, was higher for both the adenovirus- and lentivirus-transduced cells relative to normal PDL cells. The expression of bone sialoprotein, osteocalcin, and runt-related transcription factor 2 in adenovirus-transduced cells was significantly higher than that for lentivirus-transduced cells. Alizarin red staining showed that the adenovirus-transduced cell line produced more mineralized nodules than the lentivirus-transduced cell line, whereas a CCK-8 test showed that the adenovirus-transduced cell line had higher proliferation activity than lentivirus-transduced cells. In conclusion, a PDL cell line established by adenovirus transduction had superior osteogenic differentiation and proliferative activity compared to the cell line produced by lentivirus transduction. The results indicate that PDL cells having adenovirus-mediated expression of hTERT would be a more suitable model for studies of PDL regeneration.

The relationships between serum fructosamine concentrations and lipid profiles in community-dwelling adults

We examined the epidemiological associations between serum fructosamine and dyslipidemia indices in community-dwelling adults. Clinical characteristics and lipid profiles were analyzed in 1352 community-dwelling adults. The demographic characteristics and laboratory results were grouped according to the quartiles of serum fructosamine concentrations in all eligible individuals. From the bottom to the top quartile of serum fructosamine, there were graded increases in age, total cholesterol (TC), fasting blood glucose (FBG), total protein (TP), triglyceride (TG), total cholesterol/ high density lipoprotein-cholesterol (TC/HDL-C) and atherogenic index of plasma (AIP). Serum fructosamine was positive correlated with age, TC, FBG, TP, TG, TC/HDL-C and AIP in whole individuals. The positive correlations were then observed in both genders between serum fructosamine and TC, FBG, TP, TG. Two dominant factors were identified by principal component analysis. Logistic regression analysis showed that the two factors were associated with increased serum fructosamine with adjustment for gender, age, body mass index (BMI), FBG and TP. The similar results were observed in males, but not in females. Dyslipidemia tends to contribute to increased serum fructosamine concentrations in study population, suggesting that elevated serum fructosamine may herald an increased risk of cardiovascular disease among community-dwelling adults, especially in males.

Carbamylation and oxidation of proteins lead to apoptotic death of lymphocytes

The apoptotic/necrotic changes in isolated human peripheral blood mononuclear cells (MNCs) subjected to hydrogen peroxide (H₂O₂), cyanate (NaOCN) and their combination were examined. The mitochondrial potential (ΔΨm), the activities of caspases (-2, -3, -6, -8 and -9) and the level of carbonyls and amino groups in proteins were determined and DNA fragmentation. Apoptotic or necrotic cells were identified by fluorescence microscopy using double staining with Hoechst 33258/propidium iodide. Treatment of MNCs with NaOCN (1 mmol/L and 2 mmol/L), alone and in combination with H₂O₂ (100 μmol/L), led to a significant decrease in the content of amine groups and a significant increase in the carbonyl level of MNCs in comparison with the control. Measurements taken at three time points (30, 60 and 150 min) showed a significant decrease in ΔΨm in MNCs incubated with H₂O₂, cyanate and their combination. The highest decrease in ΔΨm was observed after 150 min, when a combination of NaOCN and H₂O₂ was applied. We observed significant increases in the activities of caspases-2 and -3 in cells exposed to H₂O₂ and the combination of NaOCN and H₂O₂. An increase in caspase-2 but not in caspase-3 activity was noted in cells incubated with cyanate. A significant increase in caspase-9 activity in MNCs was observed in all arrangements of tested compounds in comparison with the control. In H₂O₂-treated cells, a higher level of necrotic cells was noted in comparison to apoptotic cells, whereas carbamylation led mainly to apoptotic cell death. The combination of cyanate and H₂O₂ increased the population of necrotic cells.

Oxidative stress during erythropoietin hyporesponsiveness anemia at end stage renal disease: Molecular and biochemical studies

Inflammation and oxidative stress are two faces of one coin in end stage renal disease patients (ESRD) on maintenance hemodialysis. Their interconnection induces anemia complicated with erythropoietin hyporesponsiveness. The biochemical bases behind the resistance to erythropoietin therapy with frequent hemoglobinemia, oxidative stress and iron status have not been fully understood. Here two equal groups (40 patients each) of responders and non-responders to recombinant human erythropoietin therapy (higher than 300 IU/kg/wk of epoetin) were investigated. Hematological and biochemical analyses of collected blood and serum samples were performed along with serum electrophoretic protein footprinting. The leukocytic DNA fragmentation was used to evaluate the degree of oxidative insult. The good responders showed lower erythrocyte malondialdehyde (E-MDA) level and less DNA fragmentation of circulating leukocytes than poor responders with elevated hemoglobin, albumin, A/G ratio, total iron, and ferritin levels. Contrariwise, lower erythrocyte superoxide dismutase (E-SOD) and catalase activities in EPO poor responder group were noticed. Neither other serum constituents nor electrophoretic protein pattern showed any difference between the two groups. There were higher levels of inflammatory markers, interleukin-6 (IL6) and C-reactive protein (CRP) in EPO poor responder than good responder. The negative correlations between Hb and both IL6 and CRP levels in the present data remotely indicate a positive correlation between inflammatory markers and severity of anemia. A direct correlation between Hb and antioxidant enzymes (E-SOD and catalase) was noticed, while inverse correlation with E-MDA was recorded. The study proved that oral supplementation of vitamin C to ESRD patients might mitigate the previously elevated serum MDA level in these patients.

Association between Serum Fructosamine and Kidney Function in Nondiabetic Individuals without Chronic Kidney Disease

Background

Serum fructosamine (SF) has been considered to be an indicator that estimates glycemic control in patients with diabetes mellitus (DM). There is increasing evidence that SF concentration and oxidative stress are significantly elevated in patients with chronic kidney disease (CKD). However, the data about SF and its association with kidney function are lacking in nondiabetic individuals without CKD. We included 1891 nondiabetic individuals who had not been diagnosed with CKD to determine the association between SF and kidney function.

Material/Methods

We conducted a retrospective analysis on the basis of the biochemistry database in nondiabetic individuals without CKD.

Results

When eligible participants were stratified in accordance with SF quartiles, from the bottom to the top quartile of SF, a significant decrease of estimated glomerular filtration rate (GFR) was observed in baseline data. SF concentration was negatively associated with estimated GFR (r=−0.066, P=0.004) in the Pearson correlation analysis. Estimated GFR was associated with SF levels independently of glucose (GLU), total cholesterol (TC), triglyceride (TG), and total protein (TP) in multivariable logistic regression analysis (OR=0.984; CI 95% 0.977–0.991; P<0.001).

Conclusions

We suggest that mild elevation of SF concentration is associated with estimated GFR in nondiabetic individuals without CKD. These findings indicate that SF may underlie CKD in nondiabetic individuals.

Low levels of serum soluble receptors for advanced glycation end products, biomarkers for disease state: myth or reality

Advanced glycation end products (AGEs) interact with the receptor for AGEs (RAGE) on the membrane and induce deleterious effects via activation of nuclear factor kappa-B, and increased oxidative stress and inflammatory mediators. AGEs also combine with circulating soluble receptors (endogenous secretory RAGE [esRAGE] and soluble receptor for RAGE [sRAGE]) and sequester RAGE ligands and act as a cytoprotective agent. esRAGE is secreted from the cells and is a spliced variant of RAGE. The sRAGE on the other hand is proteolytically cleaved from cell surface receptor via matrix metalloproteinase (MMPs). sRAGE is elevated in type 1 and type 2 diabetes and in patients with decreased renal function. Serum levels of sRAGE are reduced in diseases including coronary artery disease, atherosclerosis, essential hypertension, chronic obstructive lung disease, heart failure, and hypercholesterolemia. Serum levels of AGEs are elevated in patients with coronary artery disease and atherosclerosis. However, the increases in serum AGEs are very high in patients with diabetes and renal disease. There is a positive correlation between serum levels of AGEs and RAGE and sRAGE. The elevated levels of sRAGE in patients with diabetes and impaired renal function may be due to increased levels of MMPs. AGEs increase in the expression and production of MMPs, which would increase the cleavage of sRAGE from cell surface. In conclusion, low level of serum sRAGE is a good biomarker for disease other than diabetes and renal disease. A unified formula that takes into consideration of AGEs, sRAGE, and esRAGE such as AGE/sRAGE or AGEs/esRAGE would be better biomarker than sRAGE or esRAGE for all AGE-RAGE-associated diseases including diabetes and renal disease.

Glycated albumin is independently associated with estimated glomerular filtration rate in nondiabetic patients with chronic kidney disease

BACKGROUND

Glycated albumin (GA) may contribute to diabetic nephropathy, but the clinical significance of GA in patients with chronic kidney disease (CKD) is unknown.

METHODS

Patients were classified with the NKF/DOQI classification system as mild (stage I, II), moderate (stage III), or advanced CKD (stage IV). Those undergoing dialysis or with CKD stage V were excluded. GA was measured using the Lucica TM GA-L assay kit. The relationship between GA and renal dysfunction was analyzed in patients with or without diabetes.

RESULTS

A total of 187 subjects were enrolled. GA values in those with normal, mild, moderate and advanced CKD were 18.4 ± 1.4%, 18.4 ± 3.1%, 19.0 ± 3.8%, 20.4 ± 6.4%, respectively, in diabetic patients (N=67, p=0.5), and were 14.1 ± 1.9%, 14.2 ± 2.2%, 15.9 ± 1.9%, 15.0 ± 1.7%, respectively, in nondiabetic patients (N=120, p=0.004). GA value was negatively correlated to eGFR in nondiabetic patients (r=-0.35, p<0.001) but not in diabetic patients (r=-0.11, p=0.39). In the adjusted model, GA is independently correlated to eGFR only in nondiabetic subjects.

CONCLUSIONS

Increased GA concentrations are independently associated with renal dysfunction in nondiabetic patients with CKD.

Advanced glycation end products and antioxidant status in nondiabetic and streptozotocin induced diabetic rats: effects of copper treatment

The effects of Cu(II) supplementation on glycemic parameters, advanced glycation end products (AGEs), antioxidant status (glutathione; GSH and total antioxidant capacity; TAOC) and lipid peroxidative damage (thiobarbituric acid-reactive substances, TBARS) were investigated in streptozotocin (STZ) induced diabetic rats. The study was carried out on Wistar albino rats grouped as control (n = 10), CuCl(2) treated (n = 9), STZ (n = 10) and STZ,CuCl(2) treated (n = 9). STZ was administered intraperitoneally at a single dose of 65 mg/kg and CuCl(2), 4 mg copper/kg, subcutaneously, every 2 days for 60 days. At the end of this period, glucose(mg/dl), Cu(microg/dl), TBARS(micromol/l), TAOC(mmol/l) were measured in plasma, GSH(mg/gHb) in erythrocytes and glycated hemoglobin (GHb)(%) in blood. Plasma AGE-peptides(%) were measured by HPLC flow system with spectrofluorimetric and spectrophotometric detectors connected on-line. Data were analyzed by the non-parametric Kruskal-Wallis and Mann-Whitney U test. In the STZ group glucose, GHb and AGE-peptide levels were all significantly higher than the control group (P < 0.01, P < 0.05, and P < 0.01, respectively). CuCl(2) treated group had significantly lower glucose but significantly higher GHb, TAOC and TBARS levels than the control group (P < 0.05, P < 0.001, P < 0.05 and P < 0.001, respectively). STZ,CuCl(2) treated group had significantly higher GHb, TAOC and TBARS levels compared with the control group (P < 0.001, P < 0.05 and P < 0.05, respectively); but only TAOC level was significantly higher than the STZ group (P < 0.01). This experimental study provides evidence that copper intake increases total antioxidant capacity in both nondiabetic and diabetic states. However despite the potentiated antioxidant defence, lipid peroxidation and glycation enhancing effects of CuCl(2) are evident under nondiabetic conditions.

Non enzymatic glycosylation of IgG and their urinary excretion in patients with diabetic nephropathy

Diabetic nephropathy is a major cause of end stage renal disease. Increased excretion of albumin has widely been recognized as an early manifestation of diabetic nephropathy particularly in subjects with diabetes mellitus. However, certain other proteins besides albumin may be excreted in high amount during early phase of diabetic nephropathy. The serum and urinary IgG, Glycosylated hemoglobin, fructosamine and glycosylated IgG were evaluated in the present study. Thirty-two patients of Type 2 Diabetes without any complications, thirty-one patients of Type 2 Diabetes with nephropathy, twenty-six patients of non-diabetic nephropathy and forty normal healthy individuals were enrolled in this study. Subjects were grouped based on their serum creatinine level. Serum IgG, glycosylation of IgG and urinary IgG excretion were increased significantly in diabetic patients compared to healthy controls, which were further increased significantly in chronic renal failure patients with respect to the clinical stage of nephropathy. A positive correlation was observed between glycosylation of IgG and IgG excretion (R(2)=0.5995, 0.7114 respectively) in diabetic patients without any complications and diabetic nephropathy patients only, suggesting a significant role of IgG glycosylation in the vascular clearances of IgG during diabetic nephropathy.

Oxidative stress: Does it play a role in the genesis of early glycated proteins?

Glycation and oxidative stress are two important processes known to play a key role in complications of many pathophysiological processes. The two traditional factors found to modulate the early glycation of proteins are the prevailing concentration of glucose and half life of the protein. But evidences in the literature have documented an increased glycated protein levels in some non-diabetic pathological states. So it stands to reason that hyperglycemia, while clearly the culprit in diabetes, is not the complete answer to the etiology of increased early glycated products in non-diabetic conditions. A common denominator in all these above mentioned non-diabetic pathological conditions is oxidative stress. Collective evidences from the literature reveal that malondialdehyde, reduced glutathione, vitamin C, vitamin E and drugs with antioxidant properties mitigate the process of protein glycation. Taking all the above factors into account, we hypothesis that oxidative stress either via increasing reactive oxygen species or by depleting the antioxidants may modulate the genesis of early glycated proteins in vivo.

Enhanced glycation of hemoglobin and plasma proteins is associated with increased lipid peroxide levels in non-diabetic hypertensive subjects

BACKGROUND

Accumulating evidences indicate that lipid peroxidation and protein glycation play a vital role in the pathogenesis of cardiovascular disease. The purpose of the present study was to evaluate the levels of lipid peroxides and glycated proteins in non-diabetic hypertensive patients and to assess the possible nexus between them, among these subjects.

METHODS

Thirty hypertensive patients and 25 normotensive subjects were enrolled in the present study. Lipid peroxides, glycated hemoglobin, and fructosamine levels were estimated in both groups.

RESULTS

Lipid peroxides, glycated hemoglobin, and fructosamine levels were significantly increased in hypertensive subjects in comparison with normotensive subjects. When partial correlation analysis was performed, malondialdehyde was significantly associated with glycated hemoglobin and fructosamine.

CONCLUSIONS

An increased glycation of proteins was found in non-diabetic hypertensive subjects. These data also support the premise that lipid peroxidation per se plays a role in glycation of hemoglobin and plasma proteins.

Increased plasma malondialdehyde and fructosamine in iron deficiency anemia: effect of treatment

Glycation and lipid peroxidation are spontaneous reactions that are believed to play a key role in the pathogenesis of many clinical disorders. Glycation of proteins is enhanced by elevated glucose concentrations. However, increased glycated hemoglobin levels have been documented in iron deficiency anemic patients without any history of diabetes. Collective evidences reveal that lipid peroxidation can modulate protein glycation. This study was undertaken to unravel the possible association of malondialdehyde and fructosamine in iron deficient anemic patients and to observe the possible alteration in malondialdehyde and fructosamine levels in these patients after one month supplementation with iron. Twenty non-diabetic anemic patients and 16 age-matched healthy subjects were enrolled for this study. Plasma lipid peroxides, fasting glucose, fructosamine, iron, ferritin and hemoglobin were analyzed in both the groups. Partial correlation analysis was performed to predict the independent association of malondialdehyde and fasting glucose on fructosamine. In anemic patients, while fructosamine and malondialdehyde levels were found to be significantly increased, hemoglobin, iron and ferritin levels decreased significantly when compared to before treatment. Fructosamine was found to have a significant positive correlation with malondialdehyde even after nullifying the effect of glucose. After one month supplementation with iron, both fructosamine and malondialdehyde levels decreased significantly when compared to before treatment. There was a significant increase in iron, ferritin and hemoglobin levels in anemic patients after one month of treatment. In conclusion, an increased level of fructosamine and malondialdehyde was found in anemic patients. These data suggest that fructosamine levels are closely associated with malondialdehyde concentrations in iron deficient anemic patients.

Increased plasma malondialdehyde and fructosamine in anemic H pylori infected patients: Effect of treatment

AIM: To unravel the possible association of malon-dialdehyde (MDA) and fructosamine in anemic H pylori infected patients and to observe the alteration in MDA and fructosamine levels in these patients after treatment for one month.

METHODS: Fructosamine, MDA and glucose were estimated in 22 anemic H pylori infected patients and 16 healthy controls. Hematological parameters were also evaluated in both the groups using Sysmex-K-100 automated cell counter. The H pylori infected patients were randomly divided into two groups. H pylori infected patients in GroupIreceived both iron supplementation and anti-H pylori therapy, while patients in Group II received only iron supplementation. All the biochemical and hematological parameters were estimated after one month of treatment.

RESULTS: In anemic H pylori infected patients, while MDA (5.41 ± 2.16 vs 2.26 ± 0.50; P < 0.05) and fructosamine (2.64 ± 0.93 vs 1.60 ± 0.35; P < 0.05) were significantly increased, iron (32.72 ± 14.93 vs 110.25 ± 26.58; P < 0.05), hemoglobin (6.9 ± 2.6 vs 12.66 ± 0.74; P < 0.05) and ferritin (28.82 ± 16.27 vs 140.43 ± 30.72; P < 0.05) levels were significantly decreased compared with the controls. With partial correlation analysis, fructosamine was found to have a significant positive correlation with MDA. In GroupI, while MDA level decreased significantly (3.11 ± 1.73 vs 5.50 ± 2.46; P < 0.05), there was a significant increase in iron (84.09 ± 29.51 vs 36.09 ± 17.81; P < 0.05), hemoglobin (10.40 ± 1.11 vs 7.42 ± 1.90; P < 0.05) and ferritin (116.91 ± 63.34 vs 30.46 ± 17.81; P < 0.05) levels after one month. There was no significant change in the levels of fructosamine in groupIafter treatment. Similarly, no significant alterations were noted in the levels of MDA, fructosamine, hemoglobin or ferritin in Group II patients after one month of treatment.

CONCLUSION: An increased level of fructosamine and MDA was found in anemic H pylori infected patients. Present data supports the premise that lipid peroxides per se do play a role in the glycation of plasma proteins. Furthermore, the findings from this study indicate that treatment for both anemia and H pylori infections is required for lowering the levels of lipid peroxides in these patients.

Increased glycation of hemoglobin and plasma proteins in normotensive, non-diabetic obese Indian subjects: putative role of lipid peroxides

BACKGROUND

Glycation and lipid peroxidation are spontaneous reactions believed to contribute to the pathogenesis of many clinical disorders. The purpose of the present study was to evaluate the levels of lipid peroxides and glycated proteins in normotensive, non-diabetic obese Indian subjects and to assess possible associations between them.

METHODS

A total of 28 obese male subjects and 20 non-obese subjects were included in the present study. Whole blood glycated hemoglobin, plasma lipid peroxides and fructosamine levels were estimated in both groups.

RESULTS

Lipid peroxides, glycated hemoglobin and fructosamine levels were significantly higher in obese subjects in comparison with non-obese subjects. We also found a significant association between malondialdehyde and body mass index (r=0.424, p=0.025). Partial correlation analysis revealed that malondialdehyde was significantly correlated with glycated hemoglobin (r=0.590, p=0.01) and fructosamine (r=0.442, p=0.021) after controlling for glucose.

CONCLUSIONS

Increased glycation of proteins was found in normotensive, non-diabetic obese Indian subjects. These data also support the premise that lipid peroxides per se play a role in the glycation of hemoglobin and plasma proteins.

LDL oxidation is associated with increased blood hemoglobin A1c levels in diabetic patients

AIM

To investigate whether levels of blood HbA1c in diabetic patients are associated with susceptibility of LDL to oxidation.

METHODS

LDL was separated from blood of 40 diabetic patients with known blood glucose and HbA1c levels. The tendency to undergo lipid peroxidation was assessed via lag time required for initiation of LDL oxidation. HbA1c formation was measured in vitro following incubation of red blood cell (RBC) hemolysate for 3 months with increasing concentrations of glucose in the absence or presence of LDL or oxidized LDL.

RESULTS

Lag time for copper-induced LDL oxidation was twice as long in normal subjects compared to diabetic patients. Correlation analyses between LDL oxidation lag time and HbA1c blood levels revealed an R value of 0.74. Incubation of RBC hemolysate with high glucose concentration (up to 400 mg/dl) resulted in increased blood HbA1c concentration by up to 107%. Addition of LDL to this hemolysate over a period of 3 months resulted in LDL oxidation and an increase in HbA1c levels by up to 168%. Similarly, addition of oxidized LDL to the hemolysate increased HbA1c by up to 240%.

CONCLUSIONS

Increased tendency of LDL to undergo lipid peroxidation in diabetic patients contributes to increased levels of blood HbA1c, mainly in those with HbA1c<7.3.

Positive association between serum levels of advanced glycation end products and the soluble form of receptor for advanced glycation end products in nondiabetic subjects

The advanced glycation end products (AGEs)-receptor for AGE (RAGE) axis is implicated in diabetic vascular complications. Administration of soluble form of RAGE (sRAGE) to mice has been shown to block the AGE-elicited tissue damage by acting as a decoy. These observations suggest that endogenous sRAGE may capture and eliminate circulating AGEs and decrease its serum levels. However, because AGEs up-regulate tissue RAGE expression and endogenous sRAGE could be generated from the cleavage of cell surface RAGE, sRAGE may be positively, rather than inversely, associated with circulating AGEs by reflecting tissue RAGE expression. In this study, we investigated the association of sRAGE with serum levels of AGEs in humans. Data for fasting serum sRAGE and AGE levels of 184 nondiabetic subjects were obtained from a general population in Japan. We also measured body mass index (BMI), waist circumference, blood pressure, and blood biochemistries in this population. Uni- and multivariate analyses were applied for the determinants of serum sRAGE levels. The average sRAGE levels were 0.40 +/- 0.17 ng/mL in males and 0.43 +/- 0.14 ng/mL in females, respectively. In the univariate analysis, BMI (P < .05, inversely), waist circumference (P < .05, inversely), AGEs (P < .05), and alcohol intake (P < .05, inversely) were significantly associated with sRAGE levels. After performing multivariate analyses, BMI (P < .05, inversely) and AGEs (P < .05) still remained significant independently. The present study is the first demonstration that serum sRAGE levels were positively associated with circulating AGEs in the nondiabetic general population. Endogenous sRAGE levels are elevated in parallel with serum AGE levels.

Evidence for the role of lipid peroxides on glycation of hemoglobin and plasma proteins in non-diabetic asthma patients

BACKGROUND

Collective evidences reveal that malondialdehyde (MDA), reduced glutathione (GSH) and ascorbic acid can modulate protein glycation. We investigated the concentrations of MDA, GSH, ascorbic acid and protein glycation in asthma patients to delineate the possible association among these parameters.

METHODS

Blood was collected from 18 asthma patients and 16 age and sex matched control subjects. Glycated hemoglobin (HbA1C), GSH, MDA, vitamin C, fructosamine and glucose were assessed in both groups. The effect of H2O2 on glycation of hemoglobin was studied by incubating normal healthy erythrocytes with either 5 or 50 mmol/l glucose concentration.

RESULTS

Plasma of asthma patients revealed significantly higher concentrations of lipid peroxides and fructosamine concentrations than the matched controls. Glycated hemoglobin concentrations were also found to be significantly increased. Ascorbic acid and GSH concentrations were decreased significantly in the test group when compared with the healthy control group. When the effects of fasting glucose, GSH and ascorbic acid on the concentrations of HbA1C and fructosamine were refuted by partial correlation analysis, MDA was found to be a significant determinant of HbA1c and fructosamine in patients with asthma. The in vitro model with human erythrocytes showed an enhancement of protein glycation by H2O2.

CONCLUSION

An increased glycation of proteins was found in asthma patients. These data also support the premise that lipid peroxides per se do have a role to play in glycation of hemoglobin and plasma proteins.

Reassessing the increased glycation of hemoglobin in nondiabetic chronic renal failure patients: a hypothesis on the role of lipid peroxides

BACKGROUND

Glycated hemoglobin (HbA(1C)) is considered clinically useful for assessing long-term integrated control of blood glucose in diabetes. However, an increased HbA(1C) concentration has been documented in chronic renal failure (CRF) patients without any history of diabetes. Collective evidences reveal that lipid peroxidation (MDA) can modulate protein glycation. We evaluated the relationship between glycated hemoglobin (HbA(1C)) and lipid peroxidation in non-diabetic CRF patients.

METHODS

Twenty-eight nondiabetic CRF and 23 age- and sex-matched healthy subjects were enrolled for this study. Plasma urea, creatinine, lipid peroxides, fasting glucose and HbA(1C) were analyzed in both the groups. The in-vitro effect of MDA on glycation of hemoglobin was studied by incubating healthy erythrocytes with either 5 or 50 mmol/l glucose concentration.

RESULTS

The percentage of HbA(1C) concentrations and plasma malondialdehyde (MDA) were significantly increased in CRF patients compared to control subjects. When the effects of uremia and blood glucose on the concentration of HbA(1C) was refuted by partial correlation analysis, MDA was found to be a significant determinant of HbA(1C) (r=0.41, p=0.04) in patients with renal failure. In-vitro incubation of RBC with glucose along with MDA was found to enhance the process of hemoglobin glycation.

CONCLUSION

Our results suggest that lipid peroxidation per se can contribute to glycation of hemoglobin, warranting extra-precaution in interpreting HbA(1C) as a measure of glycemic control in CRF.

Effect of lipid peroxides and antioxidants on glycation of hemoglobin: an in vitro study on human erythrocytes

BACKGROUND

Glycation and lipid peroxidation are two important processes known to play a key role in complications of many pathophysiological process. We sought to assess the possibility of an interaction between these processes in vitro and to examine the effect of lipoic acid and taurine on the glycation of hemoglobin and lipid peroxidation.

METHODS

Human erythrocytes in phosphate buffered saline (pH 7.4) were incubated with 5 or 50 mmol/l glucose. To study the effect of antioxidants on glycation of hemoglobin, erythrocytes were incubated with either lipoic acid or taurine and then exposed to glucose concentration of either 5 or 50 mmol/l. To clarify if lipid peroxides per se enhances the glycated hemoglobin level, an in vitro study was performed by incubating erythrocyte suspension containing either 5 or 50 mmol/l glucose with or without MDA. Lipid peroxides and glycated hemoglobin levels were determined in the glucose treated cells.

RESULTS

Glycated hemoglobin levels were higher in erythrocytes incubated with 50 mmol/l glucose concentrations than in erythrocytes incubated with 5 mmol/l glucose. The increase in glycated hemoglobin levels was blocked significantly when erythrocytes were pretreated with either lipoic acid or taurine. Both the antioxidants used in the present study markedly reduced the MDA levels. The level of glycated hemoglobin in erythrocyte incubated in the presence of MDA was increased significantly when compared to erythrocyte incubated with glucose alone.

CONCLUSIONS

Lipid peroxides per se may have a role to play in glycation of hemoglobin and antioxidants (lipoic acid and taurine) can partially inhibit the formation of glycated hemoglobin by lowering the levels of lipid peroxides.

Possible link between glycated hemoglobin and lipid peroxidation in hyperthyroidism

BACKGROUND

Glycated hemoglobin (HbA1C) levels are enhanced by elevated glucose concentrations. Glycation of hemoglobin is also modulated by lipid peroxides, ascorbic acid and reduced glutathione (GSH). We determined the strength of the relationships among these variables in a group of hyperthyroid patients.

METHODS

Twenty-two untreated hyperthyroid patients and 17 healthy controls were recruited for the study. Whole blood GSH, HbA1C, plasma lipid peroxides, ascorbic acid and fasting glucose were analyzed in both the groups. Direct and partial correlation analysis was performed to explore the possible relationships between these variables.

RESULTS

In hyperthyroid patients, HbA1C and lipid peroxides levels were found to be significantly increased than the controls. Ascorbic acid and GSH were decreased significantly in the test group when compared with the healthy control group. With partial correlation analysis, fasting glucose and lipid peroxides were found to have a significant positive correlation with HbA1C. Ascorbic acid and GSH showed no significant association with HbA1C levels.

CONCLUSION

These data suggest that HbA1C levels are closely associated with fasting glucose and lipid peroxides in hyperthyroid patients. Therefore, serum lipid peroxides level should be kept in mind while interpreting HbA1C as a long-term glycemic index in hyperthyroid cases.

Oxidative Stress in Patients with End-Stage Renal Disease prior to the Start of Renal Replacement Therapy

BACKGROUND/AIM

In patients with end-stage renal disease (ESRD), cardiovascular complications are the main cause of death. Increased oxidative stress is one of the risk factors for enhanced atherosclerosis in this population. Literature data vary partially dependent on differences in methodology. The present study compares three different methods: plasma lipid peroxides, the newly developed measurement of circulating oxidized LDL (Ox-LDL) particles and the frequently used copper-induced LDL oxidation lag time.

METHODS

We assessed plasma lipid peroxides, circulating Ox-LDL and in vitro copper-induced LDL oxidation lag time in 47 non-diabetic patients with ESRD, at the start of renal replacement therapy, and compared these with 41 age- and sex-matched controls.

RESULTS

In ESRD, total cholesterol (4.6 +/- 1.1 vs. 5.6 +/- 0.9 mmol/l; p < 0.001), LDL cholesterol (2.8 +/- 0.8 vs. 3.5 +/- 0.7 mmol/l; p < 0.001) and HDL cholesterol (1.0 +/- 0.3 vs. 1.4 +/- 0.4 mmol/l; p < 0.001) were lower compared to controls. Plasma lipid peroxides were higher (1.1 +/- 0.5 vs. 0.8 +/- 0.5 micromol/l; p = 0.003) in ESRD. No differences were observed in plasma Ox-LDL (63.1 +/- 62.0 vs. 55.3 +/- 48.0 mg/l). However, due to the lower plasma LDL cholesterol in ESRD, LDL oxidation level was increased in ESRD (7.1 +/- 0.1 vs. 4.2 +/- 0.3%; p = 0.03). LDL lag time was slightly longer (89 +/- 11 vs. 84 +/- 11 min; p = 0.04) in ESRD. There were no significant differences regarding the amount and rate of dienes produced.

CONCLUSIONS

Elevated levels of lipid peroxides and higher LDL oxidation levels support the theory that ESRD is associated with increased oxidative stress, which may explain the accelerated atherosclerosis. The measured amount of oxidative stress is not reflected by in vitro oxidizability of LDL.

Increased protein glycation in non-diabetic pediatric nephrotic syndrome: possible role of lipid peroxidation

BACKGROUND

Malondialdehyde (MDA), ascorbic acid and reduced glutathione (GSH) have been reported to play a possible role in glycation of proteins. This study was performed to evaluate this correlation in nephrotic syndrome patients by comparing the levels of fructosamine with MDA, ascorbic acid and GSH.

METHODS

Fifteen children with nephrotic syndrome during relapse and 10 age- and sex-matched healthy controls were enrolled for this study. Whole blood GSH, plasma MDA, total ascorbic acid and fasting glucose were analyzed in both the groups. Partial correlation analysis was performed to predict the independent association of MDA, ascorbic acid and GSH on fructosamine.

RESULTS

Plasma MDA and fructosamine levels were found to be increased in nephrotic syndrome patients when compared with controls. Plasma ascorbic acid and whole blood GSH were decreased in nephrotic group vs. healthy controls. Partial correlation analysis showed a significant positive correlation between fructosamine and MDA.

CONCLUSIONS

Present data point to a possible involvement of MDA in the glycation of protein in non-diabetic nephrotic syndrome patients, and provide support for the potential use of an antioxidant therapy in these patients.