Association of serum levels of glycated albumin, C-reactive protein and tumor necrosis factor-alpha with the severity of coronary artery disease and renal impairment in patients with type 2 diabetes mellitus

Associations between Inflammation, Hemoglobin Levels, and Coronary Artery Disease in Non-Albuminuric Subjects with and without Type 2 Diabetes Mellitus

In this cross-sectional study, we evaluated the associations of inflammation and hemoglobin with coronary artery disease (CAD) in subjects with type 2 diabetes mellitus (T2DM) and preserved kidney function. We recruited 638 participants-254 with T2DM-subjected to coronary angiography with no known cardiovascular disease, normal glomerular filtration rates, and without albuminuria. The hemoglobin and serum levels of inflammatory markers, including high-sensitivity C-reactive protein (hs-CRP), were measured. Multivariable analyses showed that inflammatory markers were not related to the severity of the stenosis in the group of subjects with diabetes. Conversely, inflammatory cytokines and albuminuria were directly related to the percentage of stenosis in subjects without T2DM (R2 = 0.038, p < 0.001). Patients with diabetes presented lower hemoglobin levels, particularly in those who also had significant CAD (14.4 [13.6-15.1] vs. 13.6 [12.2-14.8] g/dL, p = 0.03). Similarly, hemoglobin levels and albuminuria were inversely related to the severity of stenosis exclusively in subjects with diabetes, even after adjusting for multiple confounding factors (R2 = 0.081, p < 0.001). We conclude that reductions in hemoglobin levels in subjects with T2DM and normoalbuminuria may constitute a more relevant risk factor for CAD than inflammation.

Serum glycated albumin as a predictive biomarker for renal involvement of antineutrophil cytoplasmic antibody-associated vasculitis in non-diabetic patients

Background

Glycated albumin (GA) is known to reflect the current inflammatory burden in non-diabetes mellitus (DM) patients. In this study, we investigated whether GA at diagnosis could reflect the cross-sectional activity and predict poor outcomes during follow-up in non-DM patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV).

Methods

The medical records of 118 immunosuppressive drug-naïve AAV patients were retrospectively reviewed, and 76 patients who had both GA and glycated haemoglobin (HbA1c) results but not DM were included in this study. Demographic, clinical, and laboratory data at diagnosis were assessed.

Results

The median age of AAV patients was 61 years, and 31 patients were male. GA was positively correlated with five-factor score (r = 0.282), Birmingham vasculitis activity score (BVAS) assigned to renal manifestation (r = 0.315), and blood urea nitrogen (r = 0.382), whereas negatively correlated with haemoglobin (r = -0.345). AAV patients with end-stage renal disease (ESRD) exhibited significantly higher GA than those without ESRD (15.8% vs. 13.6%). When the cut-off of GA at diagnosis for ESRD was set at GA ≥ 14.25%, AAV patients with GA ≥ 14.25% had a significantly higher risk for ESRD development than those without (relative risk 12.040). In addition, AAV patients with GA ≥ 14.25% exhibited significantly lower cumulative ESRD-free survival rates than those without (P = 0.020).

Conclusion

In conclusion, GA at diagnosis can reflect the cross-sectional BVAS assigned to renal manifestation of AAV and predict ESRD development during follow-up better than HbA1c or GA/HbA1c in AAV patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02913-5.

Novel molecular markers of cardiovascular disease risk in type 2 diabetes mellitus

Diabetes represents the leading risk factor for the development of cardiovascular disease (CVD). Chronic hyperglycemia and/or acute post-prandial changes in blood glucose determine an increase in reactive oxygen species (ROS), which play a fundamental role in endothelial dysfunction and in the nuclear transport of pro-atherogenic transcription factors that activate the "inflammasome". In addition, the glycemic alteration favors the formation and stabilization of atherosclerotic plaque through the mechanism of non-enzymatic glycation of different molecules, with the establishment of the so-called "advanced glycosylation end products" (AGE). Laboratory information provided by the level of biomarkers could make a quantitative and qualitative contribution to the clinical process of screening, prediction, prevention, diagnosis, prognosis and monitoring of cardiovascular (CV) risk linked to diabetes. This review describes the importance of specific biomarkers, with particular focus on novel ones, for stratifying and management of diabetes CV risk.

Recent Updates and Advances in the Use of Glycated Albumin for the Diagnosis and Monitoring of Diabetes and Renal, Cerebro- and Cardio-Metabolic Diseases

Diabetes mellitus is a heterogeneous and dysmetabolic chronic disease in which the laboratory plays a fundamental role, from diagnosis to monitoring therapy and studying complications. Early diagnosis and good glycemic control should start as early as possible to delay and prevent metabolic and cardio-vascular complications secondary to this disease. Glycated hemoglobin is currently used as the reference parameter. The accuracy of the glycated hemoglobin dosage may be compromised in subjects suffering from chronic renal failure and terminal nephropathy, affected by the reduction in the survival of erythrocytes, with consequent decrease in the time available for glucose to attach to the hemoglobin. In the presence of these renal comorbidities as well as hemoglobinopathies and pregnancy, glycated hemoglobin is not reliable. In such conditions, dosage of glycated albumin can help. Glycated albumin is not only useful for short-term diagnosis and monitoring but predicts the risk of diabetes, even in the presence of euglycemia. This protein is modified in subjects who do not yet have a glycemic alteration but, as a predictive factor, heralds the risk of diabetic disease. This review summarizes the importance of glycated albumin as a biomarker for predicting and stratifying the cardiovascular risk linked to multiorgan metabolic alterations.

Identification of core genes and pathways in type 2 diabetes mellitus by bioinformatics analysis

Type 2 diabetes mellitus (T2DM) is a metabolic disorder. Numerous proteins have been identified that are associated with the occurrence and development of T2DM. This study aimed to identify potential core genes and pathways involved in T2DM, through exhaustive bioinformatic analyses using GSE20966 microarray profiles of pancreatic β-cells obtained from healthy controls and patients with T2DM. The original microarray data were downloaded from the Gene Expression Omnibus database. Data were processed by the limma package in R software and the differentially expressed genes (DEGs) were identified. Gene Ontology functional analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis were carried out to identify potential biological functions and pathways of the DEGs. Key transcription factors were identified using the WEB-based GEne SeT AnaLysis Toolkit (WebGestalt) and Enrichr. The Search Tool for the Retrieval of Interacting Genes (STRING) database was used to establish a protein-protein interaction (PPI) network for the DEGs. In total, 329 DEGs were involved in T2DM, with 208 upregulated genes enriched in pancreatic secretion and the complement and coagulation cascades, and 121 downregulated genes enriched in insulin secretion, carbohydrate digestion and absorption, and the Toll-like receptor pathway. Furthermore, hepatocyte nuclear factor 1-alpha (HNF1A), signal transducer and activator of transcription 3 (STAT3) and glucocorticoid receptor (GR) were key transcription factors in T2DM. Twenty important nodes were detected in the PPI network. Finally, two core genes, serpin family G member 1 (SERPING1) and alanyl aminopeptidase, membrane (ANPEP), were shown to be associated with the development of T2DM. On the whole, the findings of this study enhance our understanding of the potential molecular mechanisms of T2DM and provide potential targets for further research.

Glycated albumin (GA) and inflammation: role of GA as a potential marker of inflammation

AIMS

Abnormal levels of glycated albumin (GA) are associated with the onset of both diabetes and inflammation. Although inflammation has long been associated with diabetes, this article aims to explore the underlying mechanisms of this relationship as it pertains to the role of GA.

METHODS

We have reviewed 52 research articles since the year 2000. Common search terms used were "(inflammatory mediator) and GA" or "inflammation and GA". The findings have been organized according to diabetic complications with respect to the interactions of GA and inflammatory mediators. Glycated albumin and specific inflammatory mediators have been reported to play various roles in the pathogenesis of insulin resistance, atherosclerosis, coronary artery disease, retinopathy, and nephropathy. In the case of nephropathy and recently retinopathy, there is considerable evidence for GA in concert with inflammation playing a direct role in organ pathology. There is copious literature detailing GA's involvement in stimulating inflammatory markers and certain pro-inflammatory cytokines. A recent clinical study has shown GA to be a marker for inflammation in non-diabetic rheumatoid arthritis patients with the significance of standard inflammatory markers.

CONCLUSIONS

The clinical utility of GA measurement may likely reside in its versatility as both a mediator of inflammation as well as a marker to track hyperglycemia and other diabetes complications. Further understanding of the role GA plays in glycemic and inflammatory diseases could lead to its acceptance as an independent bio-inflammatory marker.

Metrics Beyond Hemoglobin A1C in Diabetes Management: Time in Range, Hypoglycemia, and Other Parameters

We review clinical instances in which A1C should not be used and reflect on the use of other glucose metrics that can be used, in substitution of or in combination with A1C and SMBG, to tailor an individualized approach that will result in better outcomes and patient empowerment.

Update on pre-diabetes: Focus on diagnostic criteria and cardiovascular risk

Pre-diabetes, which is typically defined as blood glucose concentrations higher than normal but lower than the diabetes threshold, is a high-risk state for diabetes and cardiovascular disease development. As such, it represents three groups of individuals: Those with impaired fasting glucose (IFG), those with impaired glucose tolerance (IGT) and those with a glycated haemoglobin (HbA_1c) between 39-46 mmol/mol. Several clinical trials have shown the important role of IFG, IGT and HbA_1c-pre-diabetes as predictive tools for the risk of developing type 2 diabetes. Moreover, with regard to cardiovascular disease, pre-diabetes is associated with more advanced vascular damage compared with normoglycaemia, independently of confounding factors. In view of these observations, diagnosis of pre-diabetes is mandatory to prevent or delay the development of the disease and its complications; however, a number of previous studies reported that the concordance between pre-diabetes diagnoses made by IFG, IGT or HbA_1c is scarce and there are conflicting data as to which of these methods best predicts cardiovascular disease. This review highlights recent studies and current controversies in the field. In consideration of the expected increased use of HbA_1c as a screening tool to identify individuals with alteration of glycaemic homeostasis, we focused on the evidence regarding the ability of HbA_1c as a diagnostic tool for pre-diabetes and as a useful marker in identifying patients who have an increased risk for cardiovascular disease. Finally, we reviewed the current evidence regarding non-traditional glycaemic biomarkers and their use as alternatives to or additions to traditional ones.

Diagnostic Utility of Serum Glycated Albumin for Diabetes Mellitus and Its Correlation With Hyperlipidemia

BACKGROUND

Glycated albumin (GA) is a better marker of short-term glycemic control than glycated hemoglobin (A1c). Dyslipidemia is the main cause of cardiovascular complications in diabetes mellitus (DM). Studies on the correlation of GA with lipid indices are sparse. We investigated the diagnostic utility of GA for DM and its relationship with serum lipid profiles compared with that of A1c.

METHODS

The GA enzymatic method was used to determine the diagnostic utility of GA for DM by using samples from 163 normal subjects (group 1) and 102 patients newly diagnosed with type 2 DM (T2DM; group 2). To analyze the lipid profiles, 263 patients with T2DM receiving treatment (group 3) were recruited.

RESULTS

GA correlated with A1c (r=0.934, P<0.0001). Linear regression analysis indicated that GA levels were about 2.48 folds those of A1c. In the ROC analysis for GA to diagnose DM, the areas under the curve (0.988, 95% confidence interval 0.972-1.004) was excellent. HDL levels were significantly lower in groups 2 and 3. In group 1, positive correlations were observed between A1c and triglyceride (TG), total cholesterol (TC), LDL, TG/HDL, TC/HDL, and LDL/HDL levels. A negative correlation was observed between HDL and A1c levels. In group 3, HDL levels (P=0.0124 and P=0.0141, respectively) were significantly higher and LDL levels tended to be lower, not statistically significant, in the well-controlled group categorized using the A1c and GA cut-off values.

CONCLUSIONS

GA is a potential diagnostic tool for DM. Compared with A1c, GA seems less relevant to dyslipidemia.

Type 2 diabetes and cardiovascular disease: Have all risk factors the same strength?

Diabetes mellitus is a chronic condition that occurs when the body cannot produce enough or effectively use of insulin. Compared with individuals without diabetes, patients with type 2 diabetes mellitus have a considerably higher risk of cardiovascular morbidity and mortality, and are disproportionately affected by cardiovascular disease. Most of this excess risk is it associated with an augmented prevalence of well-known risk factors such as hypertension, dyslipidaemia and obesity in these patients. However the improved cardiovascular disease in type 2 diabetes mellitus patients can not be attributed solely to the higher prevalence of traditional risk factors. Therefore other non-traditional risk factors may be important in people with type 2 diabetes mellitus. Cardiovascular disease is increased in type 2 diabetes mellitus subjects due to a complex combination of various traditional and non-traditional risk factors that have an important role to play in the beginning and the evolution of atherosclerosis over its long natural history from endothelial function to clinical events. Many of these risk factors could be common history for both diabetes mellitus and cardiovascular disease, reinforcing the postulate that both disorders come independently from “common soil”. The objective of this review is to highlight the weight of traditional and non-traditional risk factors for cardiovascular disease in the setting of type 2 diabetes mellitus and discuss their position in the pathogenesis of the excess cardiovascular disease mortality and morbidity in these patients.

Beyond HbA1c and glucose: the role of nontraditional glycemic markers in diabetes diagnosis, prognosis, and management

Fasting glucose and hemoglobin A1c (HbA1c) are the standard measures for diagnosis and monitoring of diabetes. There has been recent interest in nontraditional markers of hyperglycemia, including fructosamine, glycated albumin, and 1,5-anhydroglucitol (1,5-AG), as alternatives or adjuncts to standard measures. There is a growing literature linking these nontraditional markers with microvascular and macrovascular complications. Fructosamine and glycated albumin have also been shown to improve identification of persons with diabetes. However, long-term prospective studies with clinical outcomes are lacking. Some modern laboratory assays for fructosamine, glycated albumin, and 1,5-AG have excellent performance. Expanded use of these tests has the potential to improve diabetes care as these measures may overcome limitations of HbA1c in certain patients, complement traditional measures by providing additional information on shorter-term glycemic control, and improve risk stratification for diabetes and its complications. Nonetheless, studies are needed to demonstrate if their routine use will benefit patients and improve outcomes.

Association of increased serum glycated albumin levels with low coronary collateralization in type 2 diabetic patients with stable angina and chronic total occlusion

BACKGROUND

We investigated whether serum glycated albumin (GA) levels are related to coronary collateralization in type 2 diabetic patients with chronic total occlusion.

METHODS

Blood levels of GA and glycosylated hemoglobin (HbA1c) were determined in 317 diabetic and 117 non-diabetic patients with stable angina and angiographic total occlusion of at least one major coronary artery. The degree of collaterals supplying the distal aspect of a total occlusion from the contra-lateral vessel was graded as low (Rentrop score of 0 or 1) or high collateralization (Rentrop score of 2 or 3).

RESULTS

For diabetic patients, GA (21.2 ± 6.5% vs. 18.7 ± 5.6%, P < 0.001) but not HbA1c levels (7.0 ± 1.1% vs. 6.8 ± 1.3%, P = 0.27) was significantly elevated in low collateralization than in high collateralization group, and correlated inversely with Rentrop score (Spearmen's r = -0.28, P < 0.001; Spearmen's r = -0.10, P = 0.09, respectively). There was a trend towards a larger area under the curve of GA compared with that of HbA1c for detecting the presence of low collateralization (0.64 vs. 0.58, P = 0.15). In non-diabetic patients, both GA and HbA1c levels did not significantly differ regardless the status of coronary collateralization. In multivariable analysis, female gender, age > 65 years, smoke, non-hypertension, duration of diabetes > 10 years, metabolic syndrome, eGFR < 90 ml/min/1.73 m2, and GA > 18.3% were independently determinants for low collateralization in diabetic patients.

CONCLUSIONS

Increased GA levels in serum are associated with impaired collateral growth in type 2 diabetic patients with stable angina and chronic total occlusion.

Clinical, pathophysiological and structure/function consequences of modification of albumin by Amadori-glucose adducts

BACKGROUND

The nonenzymatic condensation of glucose with albumin results in the formation of albumin modified by Amadori glucose adducts, the principal form in which glycated albumin exists in vivo.

SCOPE OF REVIEW

This review focuses on (a) the utility of measurement of Amadori-modified glycated albumin (AGA) as a biomarker in diabetes, where elevated levels attend the hyperglycemic state; (b) the role of AGA as a causal factor in the pathogenesis of complications of diabetes; (c) effects on transport properties; and (d) structural and functional consequences of the modification of albumin by Amadori glucose adducts. It does not discuss counterparts with respect to Advanced Glycation Endproducts (AGE), which may be found in other publications.

MAJOR CONCLUSIONS

Nonenzymatic glycation of albumin, which is increased in diabetes, has clinical relevance and pathophysiologic importance, with ramifications for the management of this disease, the development of its complications, and the transport of endogenous and exogenous ligands.

GENERAL SIGNIFICANCE

Appreciation of the manifold consequences of AGA has afforded new avenues for assessing clinical management of diabetes, awareness of the impact of nonenzymatic glycation on albumin biology, insights into the pathogenesis of vascular complications of diabetes, and avenues of investigation of and intervention strategies for these complications. This article is part of a Special Issue on albumin. This article is part of a Special Issue entitled Serum Albumin.

Serum advanced glycation end-products and receptors as prognostic biomarkers in diabetics undergoing coronary artery stent implantation

BACKGROUND

This study investigated the impact of elevated glycated albumin (GA) and reduced soluble receptor for advanced glycation end-products (sRAGE) and endogenous secretory receptor for advanced glycation end-products (esRAGE) levels in serum on the severity of albuminuria, occurrence of contrast-induced acute kidney injury (CI-AKI) and 1-year clinical outcome in type 2 diabetic patients undergoing sirolimus-eluting stent-based percutaneous coronary intervention.

METHODS

We compared serum levels of GA, sRAGE, esRAGE, and glycosylated hemoglobin (HbA1c), occurrence of CI-AKI, and major adverse cardiac events at 1-year clinical follow-up in 3 groups of type 2 diabetes based on 24-hour urinary albumin excretion: I = normoalbuminuria (< 30 mg; n = 190); II = microalbuminuria (30-300 mg; n = 102); and III = macroalbuminuria (≥ 300 mg; n = 86).

RESULTS

Serum levels of GA and HbA1c increased step-wise from group I to III, and serum levels of sRAGE and esRAGE were decreased in the groups with albuminuria, with the lowest values in those with microalbuminuria. GA (Pearson's r = 0.264; P < 0.001), sRAGE (Pearson's r = -0.210; P < 0.001), esRAGE (Pearson's r = -0.145; P = 0.04), and HbA1c (Pearson's r = 0.214; P < 0.001) correlated significantly with urinary albumin excretion. After adjusting for confounding factors, GA, sRAGE, esRAGE, and albuminuria status remained independently associated with both CI-AKI and 1-year major adverse cardiac events.

CONCLUSIONS

Elevated GA and reduced sRAGE and esRAGE levels in serum are associated with severity of albuminuria and postprocedural CI-AKI, and exert a negative impact on 1-year clinical outcome in patients with type 2 diabetes undergoing percutaneous coronary intervention with sirolimus-eluting stent implantation.

Glycated albumin in diabetic patients with chronic kidney disease

Chronic hyperglycemia results in a non-enzymatic glycation of proteins, and produces Amadori products, such as glycated albumin (GA), glycosylated hemoglobin (HbA1c), and fructosamine. In current clinical practice, long-term glycemic control is assessed by quarterly measurements of HbA1c. Since the degree of hemoglobin glycosylation depends not only on the level of glycemic control, but also on the lifespan of red blood cells, patients with hemoglobin disorders or anemia of any cause may have erroneous HbA1c levels, and consequently receive insufficient treatment. Patients with chronic kidney disease (CKD) often suffer from various types of anemia, and consequently, they are frequently treated with iron and/or erythropoietin therapy or frequent blood transfusion. Thus, serum GA is a potentially useful glycemic index in diabetic patients with CKD, since it is not influenced by anemia and associated treatments. GA may also reflect the status of blood glucose more rapidly (2-3 weeks) than HbA1c (2-3 months), and is beneficial in those with wide variations in blood glucose or at higher risk for hypoglycemia. If clinical investigations support its utility, it may be applicable as a screening tool for all patients with diabetes during routine health examinations. Serum GA levels are also associated with AGE-related fluorescence and the number of glycation sites, and it may influence the structural and functional changes inalbumin. Since end-stage renal disease is an extreme microvascular complication of diabetic nephropathy, CKD patients with diabetes should be carefully managed to prevent disease progression. In this review, the clinical aspects of GA were discussed, including a comparison of GA with other glycated proteins, the utility and limitations of GA as a glycemic index, its influence on the therapeutic effects of hypoglycemic agents, its correlations with vascular complications, and its potential role in pathogenesis, specifically in diabetic patients with CKD.

Impact of elevated serum glycated albumin levels on contrast-induced acute kidney injury in diabetic patients with moderate to severe renal insufficiency undergoing coronary angiography

BACKGROUND

Glycated albumin (GA) has been shown to be a better indicator than glycosylated hemoglobin A1c (HbA1c) in terms of severity of renal impairment in patients with type 2 diabetes mellitus (T2DM). This study aimed to determine whether elevated serum GA levels are associated with an increased risk for contrast-induced acute kidney injury (CI-AKI) and worse clinical outcome in patients with T2DM and at least moderate renal insufficiency (RI) undergoing coronary angiography.

METHODS

Serum levels of fasting blood glucose (FBG), HbA1c and GA were measured in 1030 patients with T2DM and moderate to severe RI (eGFR 15-59 mL/min/1.73 m(2)). CI-AKI was defined as ≥ 25% increase in serum creatinine within 72 h after the procedure. Receiver-operating characteristic curve was constructed to assess the predictive value of GA, HbA1c and FBG for CI-AKI. Multivariable logistic regression model was developed to identify risk factors for CI-AKI, and Kaplan-Meier curve analysis was used to compare the rates of dialysis and major adverse cardiac events (MACE) during one-year follow-up.

RESULTS

The overall rate of CI-AKI was 11.1%. GA was significantly higher in patients with CI-AKI than in those without, and correlated positively with changes of renal function after the procedure. After adjusting for age, sex, left ventricular ejection fraction, multi-vessel disease, type and volume of contrast media, FBG, and HbA1c, GA remained an independent risk factor for CI-AKI. GA ≥ 21% was associated with increased rates of dialysis and MACE during one-year follow-up in patients with or without CI-AKI.

CONCLUSIONS

Increased GA level serves as a valuable risk factor for CI-AKI and indicates poor one-year clinical outcome in patients with T2DM and moderate to severe RI.

C-reactive protein induces interleukin-6 and thrombospondin-1 protein and mRNA expression through activation of nuclear factor-ĸB in HK-2 cells

BACKGROUND

Although C-reactive protein (CRP) is significantly increased in patients with diabetic nephropathy, whether CRP exerts direct proinflammatory effects on human renal tubular epithelial cells (HK-2 cells) is still unclear.

METHODS

HK-2 cells were incubated with purified CRP at clinically relevant concentrations (0, 5, 10, 20 and 40 μg/ml). The protein and transcript levels of thrombospondin-1 (TSP-1) and interleukin-6 (IL-6) were determined by ELISA and RT-PCR. Phosphorylation of p38MAPK was investigated through Western blot analysis in HK-2 cells induced by CRP. The activation of nuclear factor-kappa B (NF-κB) was studied via EMSA. A specific p38MAPK inhibitor (SB203580) and an NF-κB inhibitor (PDTC; pyrrolidine dithiocarbamate) were used to analyze the signal transduction in CRP induction. To explore the direct or indirect role of CRP in HK-2 cells, IL-6 or TSP-1 antibodies were used. The expression of IL-6, TSP-1 and transforming growth factor-β(1 )(TGF-β(1)) were determined through Western blot analysis in HK-2 cells.

RESULTS

In HK-2 cells, purified CRP significantly induced protein release and mRNA expression of IL-6 and TSP-1 in a dose- and time-dependent manner. TGF-β(1) protein was overexpressed in HK-2 cells induced by CRP, which cannot be inhibited by IL-6 or TSP-1 antibodies. CRP triggered phosphorylation of p38MAPK and activation of NF-κB-mediated signal transduction. SB203580 (5 μM) and PDTC (50 μM) efficiently suppressed those effects of CRP in HK-2 cells.

CONCLUSIONS

CRP induces IL-6 and TSP-1 protein release and mRNA expression from HK-2 cells via activation of the p38MAPK and NF-κB signaling pathways and TGF-β(1) was highly expressed in HK-2 cells, suggesting that CRP plays an important role in the propagation and prolongation of inflammation in renal fibrosis.

Effects of atorvastatin on progression of diabetic nephropathy and local RAGE and soluble RAGE expressions in rats

OBJECTIVE

Advanced glycation end-products (AGEs) exert inflammatory and oxidative stress insults to produce diabetic nephropathy mainly through the receptor for AGEs (RAGE). This study aimed to assess the effect of atorvastatin on diabetic nephropathy via soluble RAGE (sRAGE) and RAGE expressions in the rat kidney.

METHODS

Thirty-two male Sprague-Dawley rats were divided into four groups based on the presence or absence of streptozotocin-induced diabetes with or without atorvastatin treatment (10 mg/kg for 24 weeks). Serum sRAGE and glycated albumin (GA) levels were measured with enzyme-linked immunosorbent assay (ELISA) and improved bromocresol purple methods. Renal AGEs, RAGE, endogenous secretory RAGE (esRAGE), and sRAGE were determined with reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting.

RESULTS

Mesangial expansion and microalbuminuria were aggravated in diabetic rats, and improved with atorvastatin treatment. Serum sRAGE levels were lower in diabetic than in normal rats. After atorvastatin treatment, serum and renal sRAGE levels were up-regulated, while renal RAGE expression was decreased in diabetic rats, associated with a reduction in accumulation of AGEs, though renal esRAGE mRNA expression was not significantly increased.

CONCLUSIONS

Atorvastatin exerted a beneficial effect on diabetic nephropathy with reduced AGE accumulation, down-regulating RAGE expression and up-regulating sRAGE in the kidney.

Utility of glycated albumin for the diagnosis of diabetes mellitus in a Japanese population study: results from the Kyushu and Okinawa Population Study (KOPS)

AIMS/HYPOTHESIS

Glycated albumin is a measure of the mean plasma glucose concentration over approximately 2-3 weeks. We determined reference values for glycated albumin, and assessed its utility for the diagnosis of type 2 diabetes mellitus in the general population.

METHODS

We studied 1,575 men and women (mean age, 49.9 years; range, 26-78 years) who participated in a periodic health examination in a suburban Japanese town. HbA(1c) and fasting plasma concentrations of glucose (FPG) and glycated albumin were measured. Participants with FPG ≥ 7.0 mmol/l or HbA(1c) ≥ 6.5% (48 mmol/mol) were diagnosed as having diabetes. In our laboratory, the glycated albumin assay had intra-assay and inter-assay CVs of 1.1% and 1.6%, respectively.

RESULTS

Glycated albumin levels were significantly correlated with HbA(1c) levels (r = 0.766, p < 0.001) and FPG (r = 0.706, p < 0.001). The presence of diabetes was significantly higher in participants with glycated albumin levels between 15.0% and 15.9% (five of 276, 1.81%) than in those with glycated albumin <14% (three of 672, 0.45%) (p = 0.037), and was markedly increased in those with a glycated albumin level >16% (58 of 207, 28.0%). Receiver operating characteristic curve analysis indicated that a glycated albumin level of ≥15.5% was optimal for predicting diabetes, with a sensitivity of 83.3% and a specificity of 83.3%.

CONCLUSIONS/INTERPRETATION

There is merit to further investigating the potential for glycated albumin to be used as an alternative measure of dysglycaemia for future research and clinical practice.

Combined use of high-sensitivity C-reactive protein and apolipoprotein B/apolipoprotein A-1 ratio prior to elective coronary angiography and oral glucose tolerance tests

OBJECTIVES

The study aimed to investigate the predictive value of the combination of high-sensitivity C-reactive protein (hs-CRP) and apolipoprotein B (apoB)/apoA-1 ratio for the outcomes of coronary angiography (CAG), echocardiography and oral glucose tolerance tests (OGTTs).

DESIGN AND METHODS

Hs-CRP, apoB, apoA-1, and the profiles of CAG, echocardiography and OGTTs as well as traditional risk factors were measured in 1757 cardiology patients.

RESULTS

Hs-CRP or apoB/apoA-1 ratio was significantly correlated with the presence and severity of angiographic profiles, the levels of left ventricular (LV) ejection fraction, LV mass and LV mass index, and the presence of abnormal glucose metabolism. The combination of hs-CRP and apoB/apoA-1 ratio had greater correlation with abnormal glucose metabolism than its individual components in patients with normal fasting glucose, and was an independent predictor for coronary artery disease.

CONCLUSIONS

The combination of hs-CRP and apoB/apoA-1 ratio may be a strong predictor for coronary artery disease and abnormal glucose metabolism.

The glycation of albumin: structural and functional impacts

Oxidative stress and protein modifications are frequently observed in numerous disease states. Glucose constitutes a vital nutrient necessary to cellular oxygen metabolism. However, hyperglycemia-associated damage is an important factor in diabetes disorders. Albumin, the major circulating protein in blood, can undergo increased glycation in diabetes. From recent studies, it has become evident that protein glycation has important implications for protein activity, unfolding, and degradation, as well as for cell functioning. After giving a brief overview of the key role of albumin in overall antioxidant defense, this review examines its role as a target of glycation reactions. A synthesis of state of the art methods for measuring and characterizing albumin glycation is detailed. In light of recent data, we then report the impact of glycation on the structure of albumin and its various activities, especially its antioxidant and binding capacities. The biological impact of glycated albumin on cell physiology is also discussed, specifically the role of the protein as a biological marker of diabetes.

Diabetes and inflammation: fundamental aspects and clinical implications

AIM

The aim of this paper is to provide the fundamental background of the inflammation theory associated with type 2 diabetes, to discuss the clinical consequences of low-grade inflammation, particularly in terms of cardiovascular risk, and to infer some clinical therapeutic strategies deriving from drugs that already exist or are in development.

METHODS

This non-exhaustive work is the result of a Pubmed(®) research, based on requests including the following keywords: diabetes, inflammation, innate immunity, obesity, reticulum endoplasmic stress, cytokines, endothelial dysfunction.

RESULTS

Obesity and type 2 diabetes are linked with a low-grade inflammation state that reflects the activation of innate immunity where metabolic, environmental and genetic factors are implicated. The role of endoplasmic reticulum stress and unfold protein response is underlined. Inflammation markers are predictive for the risk to develop diabetes, and are associated with an increased cardiovascular risk. While lifestyle modifications are followed by an improvement in inflammation markers, treatments inferred from the inflammation theory are of great interest, although quite moderate effects on glycaemic control have been observed with some of them.

CONCLUSION

The development of molecules targeting different inflammatory mechanisms could lead in diabetic patients to improvement of both glycaemia and cardiovascular prognosis.

Increased C-reactive protein is associated with future development of diabetes mellitus in essential hypertensive patients

Coexistence of hypertension and diabetes mellitus (DM) increases the risk of cardiovascular disease. However, factors associated with future development of DM have not been well elucidated in patients already having essential hypertension. This study prospectively included 168 patients (mean age 41 +/- 7 years, 112 men) with essential hypertension. All patients did not have DM and vascular or renal complications initially. Baseline demographic data, blood pressure, body mass index, and antihypertensive agents were carefully evaluated and serum high-sensitivity C-reactive protein (hsCRP) was measured at the beginning of the study. All of the patients were followed for at least 6 months. The study endpoint was occurrence of new DM. After a mean follow-up period of 32 +/- 10 months, 22 subjects (13.1%) developed new DM. Patients with new DM had higher baseline glucose (105.2 +/- 11.8 vs 94.2 +/- 8.0 mg/dl, P < 0.001), triglyceride level (213.7 +/- 112.4 vs 155.6 +/- 83.2 mg/dl, P = 0.04), log hsCRP (0.31 +/- 0.44 vs 0.19 +/- 0.25 mg/dl, P = 0.016), and lower high-density lipoprotein (40.2 +/- 7.8 vs 46.6 +/- 14.4 mg/dl, P = 0.045). Total cholesterol, low-density lipoprotein, homeostasis model assessment index, and adiponectin were not different in patients with or without new DM. Among antihypertensive agents, only use of beta-blocker was significantly associated with new DM (P = 0.008). Multivariate Cox regression analysis showed log hsCRP (hazard ratio [HR] 9.77, 95% confidence interval [CI] 2.97-32.10, P < 0.001), age (HR 1.21, 95% CI 1.06-1.38, P = 0.004), and baseline glucose level (HR 1.11, 95% CI 1.06-1.15, P < 0.001) to be independent predictors for occurrence of new DM. High-sensitivity CRP was an independent factor for future development of DM in essential hypertensive patients. Increased inflammation might have a key role in the pathogenesis of DM in hypertension.

Clinical impact of glycated albumin as another glycemic control marker

It is known that glycation among various proteins is increased in diabetic patients compared with non-diabetic subjects. Currently, among these glycated proteins, glycated hemoglobin (HbA(1C)) is used as the gold standard index of glycemic control in clinical practice for diabetes treatment. However, HbA(1C) does not accurately reflect the actual status of glycemic control in some conditions where plasma glucose changes during short term, and in patients who have diseases such as anemia and variant hemoglobin. In comparison, another index of glycemic control, glycated albumin (GA), more accurately reflects changes in plasma glucose during short term and also postprandial plasma glucose. Although GA is not influenced by disorders of hemoglobin metabolism, it is affected by disorders of albumin metabolism. This review summarizes diseases and pathological conditions where GA measurement is useful. These include the status of glycemic control changes during short term, diseases which cause postprandial hyperglycemia, iron deficiency anemia, pregnancy, chronic liver disease (liver cirrhosis), chronic renal failure (diabetic nephropathy), and variant hemoglobin.

Combined effects of atorvastatin and metformin on glucose-induced variations of inflammatory process in patients with diabetes mellitus

BACKGROUND

Statin treatment improves survival in patients with atherosclerosis, but their effect on the glucose-induced variations of inflammatory markers, is unknown. We examined the effect of combined therapy with atorvastatin and metformin on glucose-induced variations of inflammatory molecules in patients with newly diagnosed diabetes mellitus type 2 (DM).

METHODS

Thirty five subjects with newly diagnosed DM were randomized to receive metformin 850 mg/d (M, n=17) or metformin 850 mg/d+atorvastatin 10mg (n=18). All subjects underwent glucose loading (75 g oral glucose) at baseline and after 12 weeks of treatment. Blood samples were obtained at baseline and 3h post-loading, while serum tumor necrosis factor alpha (TNF-α) levels were determined at baseline and at 3h.

RESULTS

Serum TNF-α remained unchanged in metformin at baseline (1.36±0.18 to 1.47±0.21 pg/ml p=NS) and after treatment (1.44±0.71 to 1.31±0.17 pg/ml, p=NS), while it was reduced in metformin+atorvastatin (2.3±0.3 to 2.0±0.4 pg/ml, p=NS at baseline and 1.80±0.2 to 1.65±0.2 pg/ml, p=0.03 after treatment).

CONCLUSIONS

Interestingly, the combination of metformin and atorvastatin partly prevents the glucose-loading induced elevation of glucose levels (at 1 h), suggesting a better response to glucose intake than monotherapy with metformin. In addition, combined treatment with atorvastatin and metformin reduces the post-glucose loading levels of TNF-α compared to metformin monotherapy.

Glycated albumin levels are higher relative to glycated haemoglobin levels in gastrectomized subjects

Background

In gastrectomized subjects, oral glucose tolerance test often shows marked hyperglycaemia (oxyhyperglycaemia) after glucose loading. Because serum glycated albumin (GA) has been shown to better reflect postprandial and maximum plasma glucose levels, we investigated whether or not the clinical significance of serum GA and glycated haemoglobin (HbA1C) in non-diabetic gastrectomized subjects differs.

Methods

During health examinations, 62 non-diabetic subjects with a history of gastrectomy and 87 non-diabetic control subjects were selected in the present study. Body mass index (BMI) in the gastrectomy group was significantly lower than in the control group.

Results

Fasting plasma glucose levels were significantly lower in the gastrectomized subjects than in the control subjects. Although both HbA1C and serum GA were significantly higher in the gastrectomized subjects, there was a significant difference in GA/HbA1C ratio between the gastrectomized subjects and the control subjects. BMI-adjusted serum GA, based on our previous finding of inverse influence of BMI on serum GA, was also significantly higher in the gastrectomized subjects than in the controls.

Conclusions

Serum GA is higher relative to HbA1C in gastrectomized subjects. This suggests that serum GA may be a better marker than HbA1C for glycaemic excursion in these subjects.

Decreased serum esRAGE level is associated with angiographically determined coronary plaque progression in diabetic patients

OBJECTIVE

This study evaluated the relationship between serum levels of endogenous secretory receptor for advanced glycation endproducts (esRAGE) and coronary plaque progression in diabetic and nondiabetic patients.

DESIGN AND METHODS

Serum esRAGE level was measured and quantitative coronary angiography (QCA) was performed in 265 consecutive patients at baseline and 1-year follow-up.

RESULTS

Comparing to baseline, serum esRAGE level was significantly increased during follow-up in nondiabetic patients without plaque progression (p=0.014), unchanged in nondiabetic patients with plaque progression and diabetic patients without plaque progression, and decreased in diabetic patients with plaque progression (p=0.011). Moreover, change of esRAGE levels correlated with change of QCA measurements. Multivariable regression analyses revealed that high-density lipoprotein cholesterol (OR=0.214, p=0.037), hypertension (OR=2.755, p=0.011), high-sensitivity C-reactive protein (OR=1.083, p<0.001) and change of esRAGE (OR=23.477, p<0.001) were independent risk factors for plaque progression in diabetic patients.

CONCLUSIONS

This study demonstrated an association of decreased serum esRAGE level with coronary plaque progression in patients with diabetes.

The hexosamine biosynthesis inhibitor azaserine prevents endothelial inflammation and dysfunction under hyperglycemic condition through antioxidant effects

Hexosamine biosynthetic pathway (HBP) accounts for some cardiovascular adverse effects of hyperglycemia. We investigated whether the HBP inhibitor azaserine protects against hyperglycemia-induced endothelial damage dependently of HBP. Human endothelial cells isolated from umbilical veins were exposed either to a high (30.5 mmol/l) or low concentration of glucose (5.5 mmol/l) for 4 days, followed by a stimulation with TNF-alpha (1 ng/ml, 24 h). The blockade of the rate-limiting enzyme glutamine:fructose-6-phosphate amidotransferase inhibited HBP flux and oxidative stress (generation of superoxide and peroxynitrite) under the hyperglycemic condition and prevented the synergistic stimulation of VCAM-1 and ICAM-1 expression by hyperglycemia and TNF-alpha. In the cells cultured under a low-glucose condition when no increased HBP flux occurred, azaserine enhanced the manganese-superoxide dismutase (MnSOD) protein level and also inhibited the oxidative stress and the expression of VCAM-1 and ICAM-1 in response to TNF-alpha. Moreover, the polyphenol resveratrol inhibited the oxidative stress and adhesion molecule expression and did not decrease the HBP flux under the hyperglycemia condition. In addition, in isolated rat aortas exposed to hyperglycemic buffer for 5 h when no significant HBP flux occurred, azaserine upregulated the MnSOD protein level and prevented decreased endothelium-dependent relaxations to acetylcholine. In conclusion, hyperglycemia independently increases oxidative stress and HBP flux, amplifies endothelial inflammation, and impairs endothelial function mainly through oxidative stress and not the HBP pathway. Azaserine protects against hyperglycemic endothelial damage through its antioxidant effect independently of inhibiting HBP pathway.

The proinflammatory cytokine tumor necrosis factor-alpha increases the amount of glucose transporter-4 at the surface of muscle cells independently of changes in interleukin-6

TNFalpha is a proinflammatory cytokine secreted by macrophages in response to bacterial infection. Recently new evidence has emerged suggesting that stressed or injured myocytes produce TNFalpha that then acts as an autocrine and/or paracrine mediator. TNFalpha receptors types 1 and 2 are present in skeletal muscle cells, and muscle cells can secrete, in addition to TNFalpha, other cytokines such as IL-1beta or IL-6. Furthermore, the plasma concentration of TNFalpha is elevated in insulin-resistant states associated with obesity and type 2 diabetes. Here we show that TNFalpha increased the amount of glucose transporter (GLUT)-4 at the plasma membrane and also glucose uptake in the L6 muscle cell line stably expressing GLUT4 tagged with the c-myc epitope. Regardless of the state of differentiation of the L6 cells, TNFalpha did not affect the rate of proliferation or of apoptosis. The stimulatory effects of TNFalpha on cell surface GLUT4 and glucose uptake were blocked by nuclear factor-kappaB and p38MAPK pathway specific inhibitors (Bay 11-7082 and SB220025), and these two pathways were stimulated by TNFalpha. Furthermore, although TNFalpha increased IL-6 mRNA and protein expression, IL-6 did not mediate the effects of TNFalpha on cell surface GLUT4 levels, which also did not require de novo protein synthesis. The results indicate that TNFalpha can stimulate glucose uptake in L6 muscle cells by inducing GLUT4 translocation to the plasma membrane, possibly through activation of the nuclear factor-kappaB and p38MAPK signaling pathways and independently of the production of IL-6.