Anti-sRAGE autoimmunity in obesity: downturn after bariatric surgery is independent of previous diabetic status.

AIM: Morbid obesity increases the risk of cardiovascular disease (CVD). The receptor for advanced glycation end-products (RAGE) is implicated in proinflammatory processes that underlie CVD. Its soluble form (sRAGE) has been proposed as a vascular biomarker. Recently, anti-sRAGE autoantibodies were described and found to be increased in diseases where RAGE is overexpressed. This study aimed to investigate serum levels of anti-sRAGE autoantibodies in morbidly obese patients. METHODS: After exclusion based on specific criteria, 150 subjects (50 normoglycemics, 50 glucose-intolerants and 50 diabetics) were randomly recruited from a cohort of 750 obese patients (ABOS). Serum sRAGE and anti-sRAGE autoantibodies were measured before bariatric surgery. Sixty-nine patients were followed for up to 1year after gastric bypass, and their levels of sRAGE and anti-sRAGE autoantibodies measured. The control group consisted of healthy blood donors. RESULTS: Compared with controls, baseline levels of sRAGE and anti-sRAGE autoantibodies were significantly higher in all obese patients independently of glucose regulation (P<0.001). At 1year after gastric bypass, sRAGE and anti-sRAGE were decreased (P<0.001). The decrease in anti-sRAGE autoantibodies was correlated with an increase in high-density lipoprotein (HDL; P=0.02). CONCLUSION: Independently of previous diabetic status, morbid obesity increases sRAGE and anti-sRAGE levels. Weight loss after gastric bypass is followed by a decrease in both titres. The decrease in anti-sRAGE correlates with an increase in HDL.

Glycation: the angiogenic paradox in aging and age-related disorders and diseases.

Angiogenesis is generally a quiescent process which, however, may be modified by different physiological and pathological conditions. The "angiogenic paradox" has been described in diabetes because this disease impairs the angiogenic response in a manner that differs depending on the organs involved and disease evolution. Aging is also associated with pro- and antiangiogenic processes. Glycation, the post-translational modification of proteins, increases with aging and the progression of diabetes. The effect of glycation on angiogenesis depends on the type of glycated proteins and cells involved. This complex link could be responsible for the "angiogenic paradox" in aging and age-related disorders and diseases. Using diabetes as a model, the present work has attempted to review the age-related angiogenic paradox, in particular the effects of glycation on angiogenesis during aging.

Differential effect of plasma or erythrocyte AGE-ligands of RAGE on expression of transcripts for receptor isoforms.

AIM: Binding of advanced glycation end-products (AGEs) to the receptor for AGEs (RAGE) contributes to diabetic vascular complications. RAGE transcript splicing generates membrane-bound proteins [full-length (FL) and N-truncated (Nt)] and a soluble protein [endogenous secretory (esRAGE)] that may act as a decoy. We tested the effect of AGE-ligands on the regulation of RAGE isoforms and the consequences on red blood cell (RBC) adhesion. METHODS: RAGE isoforms were measured by real-time RT-PCR assay, using a LightCycler System, in human umbilical vein endothelial cells (HUVECs), incubated with either characterized AGEs [Nvarepsilon-(carboxymethyl)lysine human serum albumin (CML-HSA) and methylglyoxal-modified HSA (MG-HSA)] or with RBCs from diabetic patients (DRBCs). Inhibition of RAGE access was achieved by using blocking either anti-RAGE antibodies or recombinant RAGE. Adhesion of DRBCs to endothelium was measured under flow conditions using HUVECs stimulated with MG-HSA or CML-HSA. Antibodies directed to RBC membrane proteins were tested for blocking DRBC adhesion in static conditions. RESULTS: MG-HSA stimulated the expression of membrane-bound RAGE (FL+Nt) and esRAGE transcripts to similar extents, while CML-HSA and DRBC more selectively induced mRNA for FL and Nt-RAGE. Anti-RAGE antibody inhibited the effect of glycated proteins. Stimulation of HUVECs with CML-HSA enhanced DRBC adhesion, while MG-HSA had no effect. CD233 (band 3) was glycated in DRBC membrane, and anti-CD233 antibodies inhibited the adhesion of DRBCs, as did the anti-RAGE and anti-AGE antibodies. CONCLUSIONS: Receptor engagement by distinct AGEs differentially enhances expression of RAGE isoforms and DRBC adhesion. The CML-adduct, by facilitating adhesion, has more deleterious effects than MG-derived AGEs.

Severity of diabetic microvascular complications is associated with a low soluble RAGE level.

AIMS: The receptor for advanced glycation end-products (RAGE) has been implicated in diabetic microvascular complications, but several lines of evidence suggest that the soluble isoform of RAGE (sRAGE) may protect against AGE-mediated vessel damage. The characterized AGE Nepsilon-carboxymethyllysine (CML) is associated with diabetic microvascular complications. In the present study, we measured blood levels of sRAGE and CML-protein in diabetic patients with and without microvascular complications. METHODS: Thirty patients with type-2 diabetes were recruited into the study, comprising 20 who had no microvascular complications, and 10 who had both retinal and renal complications. sRAGE was measured in serum by ELISA, and CML by competitive ELISA. RESULTS: sRAGE blood levels were similar in both the controls and diabetic patients without microvascular complications. In patients with complications, the mean sRAGE blood level was significantly decreased (1068+/-231pg/mL) compared with diabetic patients without complications (P=0.028). CML-protein was increased in all diabetic patients, but to a higher extent in those who had microvascular complications. CONCLUSION: The association of low sRAGE with high CML-protein levels in diabetic patients who developed severe diabetic complications supports the hypothesis that sRAGE protects vessels against AGE-mediated diabetic microvascular damage.

Mesothelial RAGE activation by AGEs enhances VEGF release and potentiates capillary tube formation.

Advanced glycation end-products (AGEs) inhibit ischemia-induced angiogenesis but are potential triggers of neoangiogenesis that occurs in peritoneal dialysis (PD) patients. We investigated whether the effect of glucose and AGEs on human peritoneal mesothelial cells (HPMCs) might alter the release of vascular endothelial growth factor (VEGF) and subsequently the formation of capillary tubes by human umbilical vein endothelial cells (HUVECs). HPMCs were exposed to glucose and the glycated protein Nvarepsilon-(carboxymethyl)lysine-human serum albumin (CML-HSA) and VEGF production was measured by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. Capillary tube formation by HUVECs in presence of HPMC supernatant or co-cultured with HPMC was investigated. AGE and VEGF levels in PD effluents from 11 patients were measured. CML-HSA stimulated VEGF production by HPMCs, P<0.001. Glucose and AGE inhibited capillary tube formation by HUVECs, P<0.001. HPMC supernatant potentiated capillary tube formation, P<0.001. In co-culture with HPMC capillary tube formation was increased, especially by HPMCs stimulated by CML-HSA, P<0.001. Anti-VEGF antibody limited this effect, P<0.001. Preincubation of HPMCs with anti-receptor for AGEs (RAGE) antibody reduced capillary tube formation, P<0.001. AGE and VEGF levels in PD effluents were increased during long dwell time, P<0.05 and P<0.001, respectively. In a co-culture system, we showed that VEGF production by HPMC favors capillary tube formation through mesothelial RAGE activation and could explain neoangiogenesis in PD patient.