Increased glycated albumin and decreased esRAGE levels are related to angiographic severity and extent of coronary artery disease in patients with type 2 diabetes

Glycated albumin, a precursor of advanced glycation end-products, up-regulates NADPH oxidase and enhances oxidative stress in human endothelial cells: molecular correlate of diabetic vasculopathy

BACKGROUND

Hyperglycaemia induces non-enzymatic glycation reactions in proteins which generate Amadori products and advanced glycation end-products; the latter are thought to participate in the vascular complications of diabetic patients. However, the exact mechanisms concerning the effects of glycated proteins on vascular tissue remain to be determined. Therefore, the effects of glycated human serum albumin on human umbilical vein endothelial cells were studied.

METHODS

Reactive oxygen species production was measured by the cytochrome C reduction method and by 5(6)-carboxy-2',7'-dichlorofluorescein diacetate (c-DCF-DA) fluorescence after treating human umbilical vein endothelial cells with glycated human serum albumin (6-200 µg/mL). The expression of Nox4 and p22phox mRNAs were analysed by reverse transcription-quantitative polymerase chain reactions and the levels of their proteins were measured by immunofluorescence.

RESULTS

Low concentrations of glycated human serum albumin enhanced reactive oxygen species production in human umbilical vein endothelial cells after 4 h of treatment at both extracellular and intracellular sites. This enhanced production was sustained, although to a lesser extent, after 6 and 12 h of treatment. The gene expression study revealed that Nox4 and p22phox mRNA levels were elevated after 4 h of treatment with glycated human serum albumin. This mRNA elevation and enhanced reactive oxygen species production correlated with an increased expression of the Nox4 protein.

CONCLUSIONS

The results revealed that a circulating and abundant modified glycated human serum albumin protein in diabetic patients induced a sustained reactive oxygen species production in human endothelial cells. This effect may have been due to an up-regulation of Nox4, the main subunit of NADPH oxidase in the endothelium.

Soluble receptor of advanced glycation end products levels are related to ischaemic aetiology and extent of coronary disease in chronic heart failure patients, independent of advanced glycation end products levels: New Roles for Soluble RAGE

AIMS

Knowledge of the role of advanced glycation end products (AGE), their receptor (RAGE), and the receptor's soluble form (sRAGE), in heart failure (HF) is very limited. We evaluated the clinical role of the AGE-RAGE system in HF and in particular any association it might have with ischaemic aetiology.

METHODS AND RESULTS

We measured fluorescent AGE, glycated albumin and sRAGE in 103 patients with chronic HF. We showed that sRAGE but not AGE was related to ischaemic aetiology (1638.3 ± 207.4 ischaemic vs. 1065.1 ± 94.2 pg/mL non-ischaemic group; P =0.016) independent of age, sex, diabetes, renal function, clinical severity, or other variables (OR: 1.091; 95% CI (confidence interval): 1.032-1.153; P =0.007). Moreover, sRAGE was directly associated with extent of coronary disease (OR for three vessel disease compared with non-coronary lesions: 1.186; 95% CI: 1.065-1.322; P =0.002). We also found a correlation between sRAGE and severity of HF, which increased with New York Heart Association (NYHA) class (741.9 ± 88.9 pg/mL in class 1, 1195.9 ± 113.2 pg/mL in class II, and 1724.8 ± 245.7 pg/mL in class III (P < 0.05)) and brain natriuretic peptide (BNP) levels (667.4 ± 68.0 vs. 1344.5 ± 126.0 pg/mL for BNP < and ≥400 pg/mL, respectively).

CONCLUSION

sRAGE is an indicator of chronic heart failure severity and an independent marker of coronary artery disease and its severity in patients with CHF.

Higher plasma soluble Receptor for Advanced Glycation End Products (sRAGE) levels are associated with incident cardiovascular disease and all-cause mortality in type 1 diabetes: a 12-year follow-up study

OBJECTIVE

To investigate the associations of plasma levels of soluble receptor for advanced glycation end products (sRAGE) with incident cardiovascular disease (CVD) and all-cause mortality in type 1 diabetes and the extent to which any such associations could be explained by endothelial and renal dysfunction, low-grade inflammation, arterial stiffness, and advanced glycation end products (AGEs).

RESEARCH DESIGN AND METHODS

We prospectively followed 169 individuals with diabetic nephropathy and 170 individuals with persistent normoalbuminuria who were free of CVD at study entry and in whom levels of sRAGE and other biomarkers were measured at baseline. The median follow-up duration was 12.3 years (7.6-12.5).

RESULTS

The incidence of fatal and nonfatal CVD and all-cause mortality increased with higher baseline levels of log-transformed sRAGE (Ln-sRAGE) independently of other CVD risk factors: hazard ratio (HR) 1.90 (95% CI 1.13-3.21) and 2.12 (1.26-3.57) per 1-unit increase in Ln-sRAGE, respectively. Adjustments for estimated glomerular filtration rate (eGFR(MDRD)), but not or to a smaller extent for markers of endothelial dysfunction, low-grade inflammation, arterial stiffness, and AGEs, attenuated these associations to HR 1.59 (95% CI 0.91-2.77) for fatal and nonfatal CVD events and to 1.90 (1.09-3.31) for all-cause mortality. In addition, in patients with nephropathy, the rate of decline of GFR was 1.38 ml/min/1.73 m(2) per year greater per 1-unit increase of Ln-sRAGE at baseline (P = 0.036).

CONCLUSIONS

Higher levels of sRAGE are associated with incident fatal and nonfatal CVD and all-cause mortality in individuals with type 1 diabetes. sRAGE-associated renal dysfunction may partially explain this association.

AGEs/RAGE in CKD: irreversible metabolic memory road toward CVD?

BACKGROUND

Cardiovascular disease is the major cause of death in patients with renal insufficiency, accounting for 50% of all deaths in renal replacement therapy patients. Mortality from cardiovascular diseases in these patients is approximately 9% per year, which is about 30 times the risk in the general population. So far, intensive interventions to the general risk factors, such as high LDL-cholesterol or C-reactive protein, have not been successful in improving their cardiovascular outcomes, suggesting that the beneficial effect of risk reduction may be overwhelmed by accumulated risk memorized by long-term exposure to oxidative stress during the progression of renal failure.

DESIGN

In this review, we propose that this irreversible memory effect in renal failure may be mediated by advanced glycation end-products (AGEs).

RESULTS

The generation of AGEs has been implicated to be deeply associated with increased oxidative stress. Moreover, interaction of the receptor for AGEs (RAGE) with AGEs leads to crucial biomedical pathway generating intracellular oxidative stress and inflammatory mediators, which could result in further amplification of the pathway involved in AGE generation. Several lines of evidence suggest that AGEs/RAGE axis can profoundly be involved in cardiovascular diseases. Recent advances in AGEs and RAGE measurements led us to be capable of understanding more about the role of AGEs/RAGE axis as a risk for cardiovascular diseases in patients with renal failure.

CONCLUSION

AGEs/RAGE axis could be a crucial mediator of oxidative stress in renal failure. RAGE could be not only a useful biomarker, but also a potentially therapeutic target to overcome the accumulated adverse metabolic memory in renal failure.