Possible significance of advanced glycation end products in serum in end-stage renal disease and in late complications of diabetes

Exercise plus caloric restriction lowers soluble RAGE in adults with chronic kidney disease

INTRODUCTION

The incidence of chronic kidney disease (CKD) has increased in recent years. CKD is associated with obesity, type 2 diabetes, and cardiovascular disease, although the mechanism remains unclear. Elevated soluble form of the receptor for advanced glycation end products ( RAGE) is related to proinflammatory signaling pathways that may promote diabetic nephropathy and vascular dysfunction. Because lifestyle modification reduces systematic inflammation in adults with obesity and hyperglycaemia, the hypothesis that exercise plus caloric restriction would lower soluble RAGE in adults with CKD was tested in this study.

METHODS

Eight adults (n = 6 females; age: 56.3 ± 2.8 y; BMI: 43.7 ± 2.2 kg/m2; 2-h OGTT glucose: 215 ± 9.8 mg/dL; eGFR: 49.6 ± 3.3 mL/min/1.73 m2) were enrolled in a 12-week pilot lifestyle intervention (supervised aerobic exercise [5 d/wk, up to 60 min/d at approximately 65%-85% HRmax] plus low-fat dietary counseling). Body composition (DXA), aerobic fitness (VO2max), insulin sensitivity (120 min 75 g OGTT; Matsuda Index), plasma levels of soluble RAGE and fetuin-A were measured before and after the intervention.

RESULTS

Exercise reduced body weight, fasting glucose, and fetuin-A as well as increased VO2max, glucose tolerance, and insulin sensitivity (all P < .05). Lifestyle intervention decreased plasma soluble RAGE (pre: 1018.1 ± 163 vs post: 810.6 ± 119.6 ng/mL; P = .02), and the decrease was associated with a lower 2-hour blood glucose (r = 0.76, P = .03) and with increased insulin sensitivity (r = -0.90, P < .01).

CONCLUSIONS

Exercise and caloric restriction are effective at lowering soluble RAGE in relation to glucose regulation in patients with CKD.

Modulation of diabetic retinopathy pathophysiology by natural medicines through PPAR-γ-related pharmacology

Diabetic retinopathy (DR) is one of the most common microvascular complications of diabetes and remains a major cause of preventable blindness among adults at working age. DR involves an abnormal pathology of major retinal cells, including retinal pigment epithelium, microaneurysms, inter-retinal oedema, haemorrhage, exudates (hard exudates) and intraocular neovascularization. The biochemical mechanisms associated with hyperglycaemic-induced DR are through multifactorial processes. Peroxisome proliferator-activated receptor-γ (PPAR-γ) plays an important role in the pathogenesis of DR by inhibiting diabetes-induced retinal leukostasis and leakage. Despite DR causing eventual blindness, only a few visual or ophthalmic symptoms are observed until visual loss develops. Therefore, early medical interventions and prevention are the current management strategies. Laser photocoagulation therapy is the most common treatment. However, this therapy may cause retinal damage and scarring. Herbal and traditional natural medicines may provide an alternative to prevent or delay the progression of DR. This review provides an analysis of the therapeutic potential of herbal and traditional natural medicines or their active components for the slowdown of progression of DR and their possible mechanism through the PPAR-γ pathway.

Advanced glycosylation end products in skin, serum, saliva and urine and its association with complications of patients with type 2 diabetes mellitus

BACKGROUND

The accumulation of advanced glycation end products (AGEs) has a key role in the pathophysiology of diabetes complications. Comparison of AGEs measurement in serum, skin, saliva and urine has not been reported.

AIMS

To compare AGEs in serum, skin, saliva and urine in patients with Type 2 diabetes mellitus, with complications at different stages.

MATERIALS AND METHODS

We examined 50 patients with Type 2 diabetes mellitus (40 women and 10 men) grouped according to the progression of neuropathy, nephropathy and retinopathy. The AGEs content in serum, skin, saliva and urine was measured by spectrofluorometry HPLC.

RESULTS

The patients had a mean age of 56.5 +/- 7.7 yr and 12.8 +/- 6.7 yr since diagnosis. AGEs in skin correlated with years since diagnosis (p = 0.0005). AGEs in serum, skin and saliva increased with the progression of complications, nevertheless, in urine a trend to diminution was found. In the group with end-stage renal disease (ESRD), AGEs in serum increased in greater proportion. In order to account for the decreased AGEs clearance, we corrected the values for creatinine levels, and AGEs in skin gave a better association with complications.

CONCLUSIONS

The AGEs measurement in skin, serum and saliva are useful to evaluate diabetes complications. AGEs in skin are associated with years since diagnosis of diabetes. Correction for renal function might discriminate AGEs in situ formation from accumulation.

Advanced glycation end products and endothelial dysfunction in type 2 diabetes

OBJECTIVE

Data from experimental studies have suggested that the increased formation of advanced glycation end products (AGEs) is one of the causes of endothelial dysfunction in diabetes. This study was performed to investigate whether changes in endothelium-dependent vasodilation, a marker of endothelial function, were related to serum AGEs concentrations in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

For this study, 170 patients with type 2 diabetes and 83 healthy nondiabetic control subjects of similar age were recruited. Serum AGEs were assayed by competitive enzyme-linked immunosorbent assay. Endothelium-dependent and -independent vasodilation of the brachial artery was measured by high-resolution vascular ultrasound.

RESULTS

Serum AGEs were increased in diabetic patients compared with control subjects (4.6 +/- 0.7 vs. 3.1 +/- 0.8 unit/ml; P < 0.01), and both endothelium-dependent (5.1 +/- 2.5 vs. 9.1 +/- 4.1%; P < 0.01) and endothelium-independent vasodilation (13.2 +/- 4.6 vs. 16.4 +/- 5.5%; P < 0.01) were impaired. On univariate analysis of all subjects, serum AGEs correlated with endothelium-dependent vasodilation (r = -0.51, P < 0.01); a weaker association was found with endothelium-independent vasodilation (r = -0.24, P < 0.01). On multiple regression analyses including age, sex, smoking status, and plasma lipids, only serum AGEs remained a significant independent determinant of endothelium-dependent vasodilation (r(2) = 0.34, P < 0.01).

CONCLUSIONS

Increased serum concentrations of AGEs in patients with type 2 diabetes is associated with endothelial dysfunction, independent of other cardiovascular risk factors. Further studies to determine whether treatment targeting AGEs will lead to an amelioration of endothelial dysfunction are warranted.