Advanced glycation end products in serum predict changes in the kidney morphology of patients with insulin-dependent diabetes mellitus

T cells and their products in diabetic kidney disease

Diabetic kidney disease (DKD) is the most common cause of end-stage renal disease and has gradually become a public health problem worldwide. DKD is increasingly recognized as a comprehensive inflammatory disease that is largely regulated by T cells. Given the pivotal role of T cells and T cells-producing cytokines in DKD, we summarized recent advances concerning T cells in the progression of type 2 diabetic nephropathy and provided a novel perspective of immune-related factors in diabetes. Specific emphasis is placed on the classification of T cells, process of T cell recruitment, function of T cells in the development of diabetic kidney damage, and potential treatments and therapeutic strategies involving T cells.

Kidney, heart and brain: three organs targeted by ageing and glycation

Advanced glycation end-product (AGE) is the generic term for a heterogeneous group of derivatives arising from a non-enzymatic reaction between reducing sugars and proteins. In recent years, evidence has accumulated that incriminates AGEs in pathogenic processes associated with both chronic hyperglycaemia and age-related diseases. Regardless of their exogenous or endogenous origin, the accumulation of AGEs and their derivatives could promote accelerated ageing by leading to protein modifications and activating several inflammatory signalling pathways via AGE-specific receptors. However, it remains to be demonstrated whether preventing the accumulation of AGEs and their effects is an important therapeutic option for successful ageing. The present review gives an overview of the current knowledge on the pathogenic role of AGEs by focusing on three AGE target organs: kidney, heart and brain. For each of these organs we concentrate on an age-related disease, each of which is a major public health issue: chronic kidney disease, heart dysfunction and neurodegenerative diseases. Even though strong connections have been highlighted between glycation and age-related pathogenesis, causal links still need to be validated. In each case, we report evidence and uncertainties suggested by animal or epidemiological studies on the possible link between pathogenesis and glycation in a chronic hyperglycaemic state, in the absence of diabetes, and with exogenous AGEs alone. Finally, we present some promising anti-AGE strategies that are currently being studied.

Growth arrest specific 2-like protein 1 expression is upregulated in podocytes through advanced glycation end-products

Background

Growth arrest specific 2-like protein 1 (GAS2L1) protein is a member of the GAS2 family of proteins, known to regulate apoptosis and cellular cytoskeleton reorganization in different cells. Recently we identified that Gas2l1 gene expression in podocytes is influenced by advanced glycation end product-bovine serum albumin(AGE-BSA).

Methods

The study was performed employing cultured podocytes and diabetic ( db/db ) mice, a model of type 2 diabetes. Akbuminuria as wellas urinary neutrophil gelatinase-associated lipocalin (NGAL) excretion as measured with specific ELISAs. Gene expression was analysed via semiquantitative and real-time polymerase chain reaction. The protein levels were determined by western blotting and immunostaining.

Results

We found that the Gas2l1 α isoform is expressed in podocytes. Treatment with AGE-BSA induced Gas2l1 α and Gas2 mRNA levels compared with controls incubated with non-glycated control BSA (Co-BSA). Moreover, application of the recombinant soluble receptor of AGEs (sRAGE), a competitor of cellular RAGE, reversed the AGE-BSA effect. Interestingly, AGE-BSA also increased the protein levels of GAS2L1α in a RAGE-dependent manner, but did not affect the GAS2 expression. Periodic acid-Schiff staining and albuminuria as well as urinary NGAL excretion revealed that db/db mice progressively developed diabetic nephropathy with renal accumulation of N ε -carboxy-methyl-lysine (immunohistochemistry, western blots). Analyses of GAS2L1α and GAS2 proteins in diabetic mice revealed that both were significantly elevated relative to their non-diabetic littermates. In addition, GAS2L1α and GAS2 proteins positively correlated with the accumulation of AGEs in the blood plasma of diabetic mice and the administration of sRAGE in diabetic mice reduced the glomerular expression of both proteins.

Conclusions

We show for the first time that the protein expression of GAS2L1α in vitro and in vivo is regulated by the AGE-RAGE axis. The suppression of AGE ligation with their RAGE in diabetic mice with progressive nephropathy reversed the GAS2L1α expression, thus suggesting a role of GAS2L1α in the development of diabetic disease, which needs to be further elucidated.

Exocytosis-Mediated Urinary Full-Length Megalin Excretion Is Linked With the Pathogenesis of Diabetic Nephropathy

Efficient biomarkers for diabetic nephropathy (DN) have not been established. Using ELISA, we found previously that urinary levels of full-length megalin (C-megalin), a multiligand endocytic receptor in proximal tubules, was positively correlated with DN progression in patients with type 2 diabetes mellitus (T2DM). Here, we found that urinary extracellular vesicle (UEV) excretion and C-megalin content in UEVs or in their exosomal fraction increased along with the progression of the albuminuric stages in patients with T2DM. Cultured immortalized rat proximal tubule cells (IRPTCs) treated with fatty acid-free BSA or advanced glycation end product-modified BSA (AGE-BSA), endocytic ligands of megalin, increased EV excretion, and their C-megalin content. C-megalin excretion from IRPTCs via extracellular vesicles was significantly blocked by an exosome-specific inhibitor, GW4869, indicating that this excretion is mainly exocytosis-mediated. AGE-BSA treatment of IRPTCs caused apparent lysosomal dysfunction, which stimulated multivesicular body formation, resulting in increased exosomal C-megalin excretion. In a high-fat diet-induced, megalin-mediated kidney injury model in mice, urinary C-megalin excretion also increased via UEVs. Collectively, exocytosis-mediated urinary C-megalin excretion is associated with the development and progression of DN in patients with T2DM, particularly due to megalin-mediated lysosomal dysfunction in proximal tubules, and hence it could be a candidate biomarker linked with DN pathogenesis.

Prevention of advanced glycation end-products formation in diabetic rats through beta-cell modulation by Aegle marmelos

Background

Although the anti-diabetic activity of Aegle marmelos (AM) is known, however, its anti-glycation activity is not reported yet. In this study, we have investigated its anti-glycation activity under in vitro and in vivo conditions and determined possible mechanism(s) in streptozotocin-induced diabetic rats.

Methods

Effective dose of AM (400 mg/kg) was administrated orally to diabetic rats for 42 days. Thereafter, blood glucose, serum insulin, HbA1c, antioxidant status, and advanced glycation end-products (AGEs) were measured. AGEs and its receptor (RAGE) in kidney were analyzed by immunohistochemistry and immunoblotting. Additionally, pancreatic sections were co-stained for insulin and glucagon and images were acquired using NIKON TE2000E fluorescence microscopy.

Results

Oral administration of AM extract resulted in a significant increase in serum insulin by better functioning of β-cell and preserving pancreatic β-cell integrity in diabetic rats. Treatment of AM extract significantly (p = 0.000) prevented the formation of HbA1c in the diabetic rats (8.20 ± 0.18% vs. 11.92 ± 0.59%). The circulatory AGEs level found in diabetic rat was significantly (p = 0.002) attenuated by AM treatment (0.66 ± 0.05 mg/ml vs. 1.18 ± 0.19 mg/ml). AM treatment also reduced AGEs accumulation around Bowman’s capsule and in tubular basement membrane around arteries in diabetic rat kidney. The accumulation of RAGE was very similar to that of AGEs in diabetic rats and RAGE accumulation was also prevented by AM treatment. The extract showed potent antioxidant activity both under in vitro and in vivo systems. Eugenol, one of the active constituent of AM fruit extract, showed acute blood glucose-lowering activity in diabetic rats and enhanced glucose-stimulated insulin secretion from mice islets.

Conclusion

AM extract prevents AGEs formation by modulating β-cell function, and eugenol may play important role in preventing complications of diabetes in this rat model.

Cordyceps militaris Treatment Preserves Renal Function in Type 2 Diabetic Nephropathy Mice

Diabetic nephropathy is derived from long-term effects of high blood glucose on kidney function in type 2 diabetic patients. Several antidiabetic drugs and herbal medications have failed to prevent episodes of DN. Hence, this study aimed to further investigate the renal injury-reducing effect of antidiabetic CmNo1, a novel combination of powders of fruiting bodies and mycelia of Cordyceps militaris. After being administered with streptozotocin-nicotinamide and high-fat-diet, the diabetic nephropathy mouse model displayed elevated blood glucose and renal dysfunction markers including serum creatinine and kidney-to-body weight ratio. These elevated markers were significantly mitigated following 8 weeks CmNo1 treatment. Moreover, the chronic hyperglycemia-induced pathological alteration in renal tissue were also ameliorated. Besides, immunohistochemical study demonstrated a substantial reduction in elevated levels of carboxymethyl lysine, an advanced glycation end product. Elevated collagenous deposition in DN group was also attenuated through CmNo1 administration. Moreover, the enhanced levels of transforming growth factor-β1, a fibrosis-inducing protein in glomerulus were also markedly dampened. Furthermore, auxiliary risk factors in DN like serum triglycerides and cholesterol were found to be increased but were decreased by CmNo1 treatment. Conclusively, the results suggests that CmNo1 exhibit potent and efficacious renoprotective action against hyperglycemia-induced DN.

New and old agents in the management of diabetic nephropathy

PURPOSE OF REVIEW

Diabetic nephropathy is a long-standing complication of diabetes mellitus and is responsible for more than 40% of end-stage renal disease cases in developed countries. Unfortunately, conventional renin-angiotensin-aldosterone system (RAAS) inhibitor medications only partially protect against the development and progression of diabetic nephropathy. Moreover, RAAS inhibitors have failed as primary prevention therapy in type 1 diabetes. Thus, agents targeting alternative pathogenic mechanisms leading to diabetic nephropathy have been intensively investigated, which is the topic of this review.

RECENT FINDINGS

Promising emerging agents have targeted neurohormonal activation (alternative components of the RAAS and neprilysin inhibition), tubuloglomerular feedback mechanisms (sodium glucose cotransporter 2 inhibition and incretin-based therapy) and renal inflammation/fibrosis.

SUMMARY

Evidence demonstrating the potential of these agents to protect and prevent progression of diabetic nephropathy is summarized in this review. There are dedicated clinical trials ongoing with these therapies, which have the potential to change the clinical practice.

Clinical efficacy of 'Spleen-kidney-care' Yiqi Huayu and Jiangzhuo traditional Chinese medicine for the treatment of patients with diabetic nephropathy

The aim of the present study was to investigate the effect of the traditional Chinese medicine (TCM), 'Spleen-kidney-care' Yiqi Huayu and Jiangzhuo decoction (SKC-YJ), as an adjuvant therapy in diabetic nephropathy (DN) treatment. In total, 72 patients with DN were randomly divided into control (n=54) and experimental (n=18) groups, with the latter administered SKC-YJ treatment. Indicators for determining the condition of the patients included the levels of proteinuria, blood glucose, glycosylated hemoglobin, blood lipids, blood viscosity and C-reactive protein, which were used to analyze the treatment protocols for DN. Following SKC-YJ treatment, the urinary albumin excretion rate, fasting blood glucose, 2 h-postprandial blood glucose, glycosylated hemoglobin, triglyceride, total cholesterol, blood viscosity, fibrinogen and C-reactive protein levels were detected in the two groups, and were all demonstrated to decrease significantly following treatment with SKC-YJ. Furthermore, the results revealed that SKC-YJ treatment exhibited no significant side-effects on the blood, liver and renal functions or gastrointestinal reactions. By contrast, SKC-YJ improved the symptoms of nausea, vomiting and diarrhea in the patients with DN, while showing no allergic reaction during the observation period. Therefore, SKC-YJ treatment was shown to significantly improve the clinical efficacy of DN treatment, illustrating novel roles for TCM in DN treatment.

Glycated serum albumin: a potential disease marker and an intermediate index of diabetes control

Glycation is a non-enzymatic spontaneous process in proteins which has remarkable impact on its physical and functional aspect. This alteration with addition of carbohydrate residue to human serum albumin leads to several pathological events such as diabetic nephropathy, neuropathy, retinopathy and cardiovascular complications. Human serum albumin is the major protein and is most susceptible to non-enzymatic glycation. Structural and biological properties of functional albumin alter due to the addition of reducing carbohydrate to free amino terminal residues vivo. These irreversible changes in functional albumin are stable which makes this modified albumin as new gold standard future diagnostic marker in diabetes associated complications. Glycated albumin can be used to determine the glycemic control due to short half life than erythrocytes which makes it an alternate reliable disease marker in diabetes. In this review, Human serum albumin glycation has been overviewed, stating concept of glycation and sites that are prone to this modifications. Impact of non-enzymatic addition of carbohydrate to albumin's structural and biological properties has also been elaborated. Accurate measurements of glycated albumin with implications of new highly sensitive techniques have also been described briefly. Interestingly human serum albumin imposed glycation can serve as future tool not for diagnosing diabetes but also its potential in assessment of diabetes associated complications.

Molecular mechanisms of diabetic vascular complications

Diabetic complications are the major causes of morbidity and mortality in patients with diabetes. Microvascular complications include retinopathy, nephropathy and neuropathy, which are leading causes of blindness, end‐stage renal disease and various painful neuropathies; whereas macrovascular complications involve atherosclerosis related diseases, such as coronary artery disease, peripheral vascular disease and stroke. Diabetic complications are the result of interactions among systemic metabolic changes, such as hyperglycemia, local tissue responses to toxic metabolites from glucose metabolism, and genetic and epigenetic modulators. Chronic hyperglycemia is recognized as a major initiator of diabetic complications. Multiple molecular mechanisms have been proposed to mediate hyperglycemia’s adverse effects on vascular tissues. These include increased polyol pathway, activation of the diacylglycerol/protein kinase C pathway, increased oxidative stress, overproduction and action of advanced glycation end products, and increased hexosamine pathway. In addition, the alterations of signal transduction pathways induced by hyperglycemia or toxic metabolites can also lead to cellular dysfunctions and damage vascular tissues by altering gene expression and protein function. Less studied than the toxic mechanisms, hyperglycemia might also inhibit the endogenous vascular protective factors such as insulin, vascular endothelial growth factor, platelet‐derived growth factor and activated protein C, which play important roles in maintaining vascular homeostasis. Thus, effective therapies for diabetic complications need to inhibit mechanisms induced by hyperglycemia’s toxic effects and also enhance the endogenous protective factors. The present review summarizes these multiple biochemical pathways activated by hyperglycemia and the potential therapeutic interventions that might prevent diabetic complications. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00018.x, 2010)

Pyridoxamine, an inhibitor of protein glycation, in relation to microalbuminuria and proinflammatory cytokines in experimental diabetic nephropathy

Diabetic nephropathy (DN) is one of the major complications that develop as consequence of chronic and uncontrolled hyperglycaemia. Hyperglycaemia initiates various processes, one of which is protein glycation, leading to the formation of advanced glycation end products. Alteration of intracellular signalling, gene expression, release of proinflammatory molecules and free radicals are examples of such changes and they contribute to the initiation of diabetic complications. In the current manuscript, we studied the effect of pyridoxamine (PM) on protein glycation, oxidative stress, interleukin-1α (IL-1α), IL-6, C-reactive protein (CRP), gene expression of tumour necrosis factor-α (TNF-α) and transforming growth factor-β1 (TGF-β1) in relation to microalbuminuria and kidney functions in a model of alloxan-induced diabetic rats. We have observed that onset of microalbuminuria has preceded the gradual increase of blood sugar level in diabetic rats. In diabetic rats, gene expression of TNF-α and TGF-β1 recorded a gradual increase and marked increase was observed after one and two weeks of alloxan administration, in comparison with normal rats. PM induced significant decrease in kidney malondialdehyde content and the gene expression of TNF-α and TGF-β1, in addition to levels of serum glucose, fructosamine, urea, creatinine, IL-1α, IL-6, CRP and urine microalbumin. Histopathological examination of kidney tissues showed certain improvements as compared with diabetic control. In conclusion, our results may provide a supporting evidence for the therapeutic benefit of PM in DN.

Dietary resistant starch prevents urinary excretion of 25-hydroxycholecalciferol and vitamin D-binding protein in type 1 diabetic rats

Diabetes is a rapidly growing epidemic affecting millions of Americans and has been implicated in a number of devastating secondary complications. We previously demonstrated that type 2 diabetic rats exhibit vitamin D deficiency due to aberrant megalin-mediated endocytosis and excessive urinary excretion of 25-hydroxycholecalciferol (25D3) and vitamin D-binding protein (DBP). Here, we examined whether a model of type 1 diabetes [T1D; streptozotocin (STZ)-treated Sprague-Dawley rats] would similarly excrete abnormally high concentrations of 25D3 and DBP due to renal damage and compromised expression of megalin and its endocytic partner, disabled-2 (Dab2). Moreover, we tested whether feeding diabetic rats starch that is resistant to digestion could alleviate these abnormalities. Control (n = 12) rats were fed a standard, semipurified diet (AIN-93G) containing 55% total dietary starch and STZ-treated rats were fed the AIN-93G diet (n = 12) or a diet containing 55% high-amylose maize that is partially resistant to digestion [20% total dietary resistant starch (RS); n = 12] for 2 and 5 wk. The RS diet attenuated weight loss and polyuria in STZ-treated rats. Histology and immunohistochemistry revealed that dietary RS also attenuated the loss of Dab2 expression in renal proximal tubules. Moreover, urinary concentrations of both 25D3 and DBP were elevated ∼10-fold in STZ-treated rats (5 wk post STZ injection), which was virtually prevented by the RS. We also observed a ∼1.5-fold increase in megalin mRNA expression in STZ-treated rats, which was attenuated by feeding rats the RS diet for 2 wk. Taken together, these studies indicate that consumption of low-glycemic carbohydrates can attenuate disruption of vitamin D homeostasis in T1D through the rescue of megalin-mediated endocytosis in the kidney.

Glyoxalase 1 enzyme activity in erythrocytes and Ala111Glu polymorphism in type 1-diabetes patients

AIMS/HYPOTHESIS

The enzyme glyoxalase 1 (GLO1) can inactivate the glycoxidation product methylglyoxal that is thought to be an important contributor to the pathogenesis of vascular complications in diabetes. We aimed to study erythrocyte GLO1 activity and whether the Ala111Glu GLO1 gene polymorphism affected GLO1 activity.

METHODS

Fasting erythrocyte GLO1 activity was measured spectrophotometrically. The A111G gene polymorphism, assessed in DNA from leucocytes was analyzed in patients with type 1-diabetes and normal kidney function and compared with a control group.

RESULTS

Sixty-one patients with type 1-diabetes duration of 26.1 (10.7) years, mean (SD) with a HbA1c of 7.8 (0.9)%, 61.7 (9.9) mmol/mol and normal glomerular filtration rate were compared with 62 age- and sex-matched healthy controls. GLO1 activity was 0.206 (0.183-0.231) median (25-75% percentiles) U/mg Hb in the control group vs. 0.192 (0.165-0.224) in the diabetes group, (p = 0.149). In the diabetes group GLO1 correlated with HbA1c (r = 0.33, p < 0.01) and oxidized glutathione (GSSG) (r = - 0.34, p < 0.01) and in the control group with GSH (r = 0.37, p < 0.005) and fasting glucose (r = 0.26, p < 0.04). In a multiple regression analysis with GLO1 activity as the dependent variable, including the Ala111Glu polymorphism, the significant independent variables were log GSSG (ß - 0.318, p = 0.02) and HbA1c (ß 0.285, p = 0.041) in the diabetes group and log GSH, (ß 0.407, p = 0.004) in the control group.

CONCLUSIONS/INTERPRETATION

Erythrocyte glyoxalase 1 activity did not differ between patients with type 1-diabetes and controls. The Ala111Glu glyoxalase gene polymorphism did not have an effect on glyoxalase 1 activity in either group.

Pentosidine and N-carboxymethyl-lysine: biomarkers for type 2 diabetic retinopathy

PURPOSE

Advanced glycation end products (AGEs) accumulation may result from chronic hyperglycemia promoting generation and onset of microangiopathy. The aim of this study was to investigate the association between diabetic retinopathy (DR) and levels of AGEs, pentosidine, and N-carboxymethyl-lysine (CML) in aqueous humor and serum of human patients and their role in predicting the progression of DR.

METHODS

Ninety patients with type 2 diabetes mellitus and 30 nondiabetic patients underwent cataract surgery. The diabetic group was divided into 3 subgroups: 35 patients with mild nonproliferative diabetic retinopathy (mild NPDR), 30 patients with severe nonproliferative diabetic retinopathy (severe NPDR), and 25 patients with proliferative diabetic retinopathy (PDR). In the samples, pentosidine was measured by high-performance liquid chromatography and CML using a competitive enzyme-linked immunosorbent assay.

RESULTS

Serum levels of pentosidine and CML were significantly increased in patients with type 2 diabetes compared to nondiabetic controls (p<0.001). In diabetic patients, serum pentosidine and CML levels were significantly higher in patients who had PDR than in those with mild NPDR or severe NPDR (both p<0.001). A significant difference was found between aqueous humor CML levels in diabetic and nondiabetic patients and increased along with progression of DR. Significant correlations existed between serum pentosidine and aqueous CML in severe NPDR and PDR (p<0.001).

CONCLUSIONS

In patients with type 2 DM, serum levels of pentosidine and CML are related to severity of retinopathy. In addition, aqueous humor level of CML increased along with progression of DR. Pentosidine and CML can be used as biochemical markers of glycoxidation and related to onset or progression of DR.

Non-enzymatic glycation of proteins: from diabetes to cancer

Incubation of proteins with glucose leads to their non-enzymatic glycation and formation of Amadori products known as an early glycation product. Oxidative cleavage of Amadori products is considered as a major route to advanced glycation endproducts (AGEs) formation in vivo. Nonenzymatic glycation of proteins or Maillard reaction is increased in diabetes mellitus due to hyperglycemia and leads to several complications such as blindness, heart disease, nerve damage and kidney failure. Accumulation of the early and advanced glycation products in plasma and tissues of diabetic patients and causes production of autoantibodies against corresponding products. The advanced glycation products are also associated with other diseases like cancer. This review summarizes current knowledge of these stage specific glycated products as common and early diagnostic biomarkers for the associated diseases and the complications with the aim of a novel therapeutic target for the diseases.

Relationship between glyco-oxidation, antioxidant status and microalbuminuria in type 2 diabetic patients

AIMS/HYPOTHESIS

This study examined the relationship, if any, between glucose-induced oxidative stress, antioxidant status and microalbuminuria in patients with type 2 diabetes.

METHODS

The study involved 99 consecutive type 2 diabetic patients (57 men, 42 women). Patients with persistent microalbuminuria were identified and the following variables evaluated: fasting plasma glucose, HbA(1c), malonyldialdehyde (MDA), pentosidine, AGE, the total radical-trapping antioxidant parameter (TRAP), vitamin E, creatinine, estimated GFR and lipid profile.

RESULTS

Patients were divided into two groups, i.e. 37 individuals without microalbuminuria (AER <20 microg/min) and 62 with microalbuminuria (AER > or =20 microg/min). The following variables were significantly higher in patients with microalbuminuria than in those without microalbuminuria (mean +/- SD): fasting plasma glucose 9.41 +/- 2.88 vs 8.19 +/- 1.93 mmol/l, p < 0.05; HbA(1c) 7.97 +/- 1.51 vs 7.39 +/- 1.03%, p < 0.05; MDA 1.18 +/- 0.35 vs 1.02 +/- 0.29 micromol/l, p < 0.05; pentosidine 98.5 +/- 24.6 vs 82.9 +/- 20.9 pmol/ml, p < 0.005; and AGE 13.2 +/- 4.8 vs 10.6 +/- 3.8 microg/mg protein, p < 0.01. However, vitamin E and TRAP did not differ between the two groups. Serum creatinine values and estimated GFR were similar in the two groups. Only in patients with microalbuminuria were significant linear correlations seen between AER and both oxidation (HbA(1c) r = 0.33, p < 0.01; MDA r = 0.59, p < 0.001; pentosidine r = 0.48, p < 0.001; and AGE r = 0.44, p < 0.001) and antioxidation variables (vitamin E r = -0.55, p < 0.001; TRAP r = -0.49, p < 0.001). Considering all variables together, multiple regression revealed a correlation between microalbuminuria and vitamin E, TRAP, HbA(1c) and MDA, but not pentosidine or AGE.

CONCLUSIONS/INTERPRETATION

Our data suggest that microalbuminuria in type 2 diabetic patients might be promoted by an insufficient counter-regulation of the antioxidant system in the event of increased glyco-oxidation/glycation.

Advanced glycation end products in pregnancies complicated with diabetes mellitus or preeclampsia

OBJECTIVE

Preeclampsia (PE) and diabetes mellitus (DM) are associated with oxidative stress. DM is complicated with formation of advanced glycation end products (AGEs), which are associated with oxidative stress. We hypothesized that elevated serum AGE would be found in pregnancies complicated by PE or DM.

METHODS

Circulating AGEs, 8-isoprostane, vitamin E, and antioxidant capacity were analyzed from study patients.

RESULTS

Serum AGE was elevated both in patients with type 1 DM and gestational DM, but not in PE, compared with controls. 8-isoprostane was elevated in patients with type 1 DM and PE compared with controls.

CONCLUSION

AGEs and 8-isoprostane are not elevated in parallel in pregnancies complicated with PE or DM, suggesting biological heterogeneity.

Therapeutic interventions and oxidative stress in diabetes

Many therapeutic agents that are used in patients with diabetes mitigate oxidative stress. These agents are of particular interest because oxidative stress is elevated in diabetes and is thought to contribute to vascular dysfunction. Agents that merely quench already formed reactive oxygen species have demonstrated limited success in improving cardiovascular outcomes. Thus, although vitamin E, C, and alpha lipoic acid appeared promising in animal models and initial human studies, subsequent larger trials have failed to demonstrate improvement in cardiovascular outcomes. Drugs that limit the production of oxidative stress are more successful in improving vascular outcomes in patients with diabetes. Thus, although statins, ACE inhibitors, ARBs and thiazolinediones are used for varied clinical purposes, their increased efficacy in improving cardiovascular outcomes is likely related to their success in reducing the production of reactive oxygen species at an earlier part of the cascade, thereby more effectively decreasing the oxidative stress burden. In particular, statins and ACE inhibitors/ ARBs appear the most successful at reducing oxidative stress and vascular disease and have potential for synergistic effects.

The relationship between nitric oxide and leptin in the lung of rat with streptozotocin-induced diabetes

Lung structural changes and immunoreactivity of endothelial (eNOS)- and inducible nitric oxide synthase (iNOS) were investigated by light microscopy in lungs of treated and untreated diabetic rats. Diabetes was induced by a single intraperitoneal (i.p.) injection of 65 mg kg(-1) streptozotocin (STZ) in Wistar albino male rats. Diabetic rats received daily i.p. doses of dexamethasone (2 mg kg(-1)), leptin (0.5 microg kg(-1)) and intramuscular insulin (20 U kg(-1)) or a combination of these drugs for 1 week starting 4 weeks after the STZ injections. After treatment, the blood levels of glucose, leptin, insulin and nitrate/nitrite (NO(3) (-)/NO(2) (-)) were measured. Dilatation of alveoli and alveolar ducts, partial alveolar wall thickening and increased eNOS- and iNOS characterized the diabetic rat lungs. High blood glucose and nitrate/nitrite levels as well as low insulin and leptin levels were also present. Treatment with insulin, dexamethasone and a combination of these drugs resulted in improvement of the structural and immunohistochemical abnormalities. The most effective treatment was insulin therapy. Leptin administration resulted in increased relative amounts of extracellular material, which led to noticeable respiratory efficiency in the diabetic rat lungs. All treatments except leptin lowered blood glucose levels. The combination of insulin and dexamethasone increased blood leptin and insulin, while the remaining diabetic rats had blood with low leptin and insulin concentrations. These results suggest that therapy with insulin plus dexamethasone but not therapy with leptin is beneficial for diabetics.

A review of albumin binding in CKD

Hypoalbuminemia is associated with excess mortality in patients with kidney disease. Albumin is an important oxidant scavenger and an abundant carrier protein for numerous endogenous and exogenous compounds. Several specific binding sites for anionic, neutral, and cationic ligands were described. Overall, the extent of binding depends on the ligand and albumin concentration, albumin-binding affinity, and presence of competing ligands. Chronic kidney disease affects all these determinants. This may result in altered pharmacokinetics and increased risk of toxicity. Renal clearance of albumin-bound solutes mainly depends on tubular clearance. Dialytic clearance by means of conventional hemodialysis/hemofiltration and peritoneal dialysis is limited. Other epuration techniques combining hemodialysis with adsorption have been developed. However, the benefit of these techniques remains to be proved.

Involvement of advanced glycation end products in the pathogenesis of diabetic complications: the protective role of regular physical activity

Advanced glycation end products (AGEs) may play an important role in the pathogenesis of chronic diabetic complications and in the natural process of biological aging. In fact, maintained hyperglycaemia favours the formation of AGEs at the tissue level in diabetic patients, which may influence the triggering of different chronic pathologies of diabetes such as retinopathy, nephropathy, neuropathy and macro- and micro-vascular diseases. Moreover, the literature has also demonstrated the involvement of AGEs in biological aging, which may explain the accelerated process of aging in diabetic patients. The practice of regular physical activity appears to positively influence glycaemic control, particularly in type 2 diabetes mellitus patients. This occurs through the diminution of fasting glycaemia, with a consequent reduction of glycation of plasmatic components suggested by the normalisation of HbA1c plasmatic levels. This exercise-induced positive effect is evident in the blood of diabetic patients and may also reach the endothelium and connective tissues of different organs, such as the kidneys and eyes, and systems, such as the cardiovascular and nervous systems, with a local reduction of AGEs production and further deceleration of organ dysfunction. The aim of this paper was to review the literature concerning this topic to coherently describe the harmful effects of AGEs in organ dysfunction induced by diabetes in advanced age as well as the mechanisms behind the apparent protection given by the practice of regular physical activity.

Novel insights in the treatment of diabetic nephropathy

Diabetes is currently one of the leading causes of end-stage renal failure requiring renal replacement therapy in the Western World. About 15% to 20% of type 1 diabetic patients and 30% to 40% of type 2 diabetic patients will eventually develop end-stage renal failure. To prevent the development or progression of diabetic kidney disease, good glycaemic control remains the cornerstone in the management of diabetic patients. Beyond glycaemic control, other metabolic factors have been shown to be involved in the development of diabetic kidney disease, i.e. advanced glycation endproducts (AGEs) and the aldose reductase pathway. Furthermore, an adequate control of high blood pressure and treatment of microalbuminuria are major therapeutic targes. To achieve adequate blood pressure control, a combination therapy with different classes of antihypertensive agents is often necessary, especially including angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. Other vasoactive factors involved in diabetic nephropathy such as endothelin and nitric oxide will be covered briefly. Besides hyperglycaemia and high blood pressure, other risk factors have been identified in the development or progression of diabetic kidney disease: smoking, hyperlipidaemia, obesity and high protein intake. Their impact on renal function will be highlighted. Finally, recent research has also identified intracellular pathways such as the diacylglycerol-protein kinase C pathway and several growth factors, such as growth hormone, insulin-like growth factor, transforming growth factor-beta, vascular endothelial growth factor, and platelet derived growth factor as players in diabetic kidney disease.

Increased serum levels of advanced glycation endproducts predict total, cardiovascular and coronary mortality in women with type 2 diabetes: a population-based 18 year follow-up study

AIMS/HYPOTHESIS

AGEs, modification products formed by glycation or glycoxidation of proteins and lipids, have been linked to premature atherosclerosis in patients with diabetes. We investigated whether increased serum levels of AGEs predict total, cardiovascular (CVD) or CHD mortality in a population-based study.

SUBJECTS AND METHODS

Serum levels of AGEs were determined by immunoassay in a random sample of 874 Finnish diabetic study participants (488 men, 386 women), aged 45-64 years. These participants were followed for 18 years for total, CVD and CHD mortality.

RESULTS

Multivariate Cox regression models revealed that serum levels of AGEs were significantly associated with total (p = 0.002) and CVD mortality (p = 0.021) in women, but not in men. Serum levels of AGEs in the highest sex-specific quartile predicted all-cause (hazards ratio [HR] 1.51; 95% confidence intervals [CI], 1.14-1.99; p = 0.004), CVD (HR 1.56; 95% CI 1.12-2.19; p = 0.009), and CHD (HR 1.68; 95% CI 1.11-2.52; p = 0.013) mortality in women, even after adjustment for confounding factors, including high-sensitivity C-reactive protein.

CONCLUSIONS/INTERPRETATION

Increased serum levels of AGEs predict total and CVD mortality in women with type 2 diabetes.

Fluorescence, birefringence and confocal microscopy of the abdominal aorta from nonobese diabetic (NOD) mice

In this study, nonenzymatic glycosylation was assessed in aorta extracellular matrix (ECM) from nonobese diabetic (NOD) mice, using nitroblue tetrazolium (NBT). Molecular and structural changes were investigated in elastic lamellae and collagen fibers of diabetic mice aortas after staining with dansyl chloride and anilinonaphthalene sulfonate (ANS). Alterations in arterial autofluorescence and birefringence of collagen fibers were investigated in unstained aortas. Proliferation of smooth muscle cells (SMC) was also investigated by Feulgen reaction staining assessed by confocal microscopy and image analysis. Assessment of nonenzymatic glycosylation demonstrated glycosylation products in the aorta ECM of NOD mice. Elastic lamellae and collagen fibers from NOD mouse aortas presented less intense fluorescence after staining with dansyl chloride and ANS when compared to aortas of control nondiabetic mice. However, unstained NOD aortas showed more intense autofluorescence when compared to controls. Birefringence analysis suggests alterations in the higher molecular packing of the arterial collagen fibers in NOD aortas. In aortas stained by Feulgen reaction, no evidence of SMC proliferation was observed in diabetic aortas.

Gluconeogenic Substrates and Hepatic Gluconeogenic Enzymes in Streptozotocin-Diabetic Rats: Effect of Mulberry (Morus indicaL.) Leaves

Mulberry (Morus indica L.) leaves, the sole food of the silk worm, were evaluated for antidiabetic effects in streptozotocin (STZ)-diabetic rats. Treatment with dried mulberry leaf powder at 25% of the diet for a period of 8 weeks was found to be remarkably beneficial to STZ-diabetic rats as evidenced by controlled hyperglycemia and glycosuria. In addition, mulberry leaves countered (reversed) the alterations in gluconeogenic substrates in STZ-diabetic rats as indicated by significant reduction in serum pyruvic and lactic acid levels, a significant increase in proteins and a significant decrease in free amino acid, urea, and creatinine levels in blood, and a decreased urinary excretion of urea and creatinine. Anomalies in the activities of hepatic gluconeogenic enzymes associated with impaired glucose homeostasis in STZ-diabetic rats were ameliorated by feeding the mulberry leaf-supplemented diet, indicating that control over hyperglycemia and associated complications in the diabetic state by mulberry leaves is by way of regulation of gluconeogenesis. With respect to all the parameters, mulberry leaves were more effective than the oral hypoglycemic drug glibenclamide.

Plasma protein advanced glycation end products, carboxymethyl cysteine, and carboxyethyl cysteine, are elevated and related to nephropathy in patients with diabetes

In Diabetes Mellitus (DM), glucose and the aldehydes glyoxal and methylglyoxal modify free amino groups of lysine and arginine of proteins forming advanced glycation end products (AGEs). Elevated levels of these AGEs are implicated in diabetic complications including nephropathy. Our objective was to measure carboxymethyl cysteine (CMC) and carboxyethyl cysteine (CEC), AGEs formed by modification of free cysteine sulfhydryl groups of proteins by these aldehydes, in plasma proteins of patients with diabetes, and investigate their association with the albumin creatinine ratio (ACR, urine albumin (mg)/creatinine (mmol)), an indicator of nephropathy. Blood was collected from forty-two patients with type 1 and 2 diabetes (18-36 years) and eighteen individuals without diabetes (17-35 years). A liquid chromatography-mass spectrophotometric method was developed to measure plasma protein CMC and CEC levels. Values for ACR and hemoglobin A1C (HbA1C) were obtained. Mean plasma CMC (microg/l) and CEC (microg/l) were significantly higher in DM (55.73 +/- 29.43, 521.47 +/- 239.13, respectively) compared to controls (24.25 +/- 10.26, 262.85 +/- 132.02, respectively). In patients with diabetes CMC and CEC were positively correlated with ACR, as was HbA1C. Further, CMC or CEC in combination with HbA1C were better predictors of nephropathy than any one of these variables alone. These results suggest that glucose, glyoxal, and methylglyoxal may all be involved in the etiology of diabetic nephropathy.

Effects of simvastatin treatment on oxidant/antioxidant state and ultrastructure of streptozotocin-diabetic rat lung

In the present study, we investigated the effects of simvastatin, a 3-hydroxy-3-methyl-glutaryl coenzyme A reductase inhibitor, on lipid metabolism, lipid peroxidation, antioxidant enzyme activities and ultrastructure of diabetic rat lung. Diabetes was induced by a single injection of streptozotocin (45 mg kg(-1), i.p.). After 8 weeks induction of diabetes, some control and diabetic rats were treated with simvastatin (10 mg kg(-1) rat day(-1); orally) for 4 weeks. Diabetes resulted in significantly high levels of blood glucose and plasma lipids. Malondialdehyde levels were unchanged after 12-week-old diabetic rats, whereas catalase activity significantly decreased in the lung. Glutathione peroxidase activity and nitric oxide level were significantly elevated in the diabetic lung. Histological analysis of the diabetic lung revealed some deterioration in the structure. Simvastatin treatment reduced plasma lipid levels and partially decreased the severity of hyperglycaemia. Catalase, glutathione peroxidase activities and nitric oxide levels were partially restored and accompanied by improved structure in diabetic lung by the simvastatin treatment. These results suggest that structural disturbances and alteration of antioxidative enzyme activities occurred in diabetic lung. Simvastatin treatment may provide some benefits in the maintenance of antioxidant status and structural organization of diabetes-induced injury of lung.

Parameters for Measurement of Oxidative Stress in Diabetes Mellitus: Applicability of Enzyme-Linked Immunosorbent Assay for Clinical Evaluation

Investigations of the mechanisms involved in the onset and progression of diabetes have recently confronted the role of reactive oxygen species (ROS) and oxidative stress. Prolonged exposure to hyperglycemic conditions induces nonenzymatic glycation of protein via the so-called Maillard reaction, resulting in Schiff-base products and Amadori products that engender ROS production. These processes initiate and exacerbate micro- and macrovascular complications in diabetes. Increased oxidative stress is induced by excessive ROS production and inadequate antioxidant defenses. Recently, oxidative stress status markers have been associated directly with the severity and prognosis of diabetes. To examine oxidative stress, reliable and high-throughput methods are needed to examine large numbers of clinical samples. The emerging availability of enzyme-linked immunosorbent assay (ELISA) for oxidative stress status markers allows its application to assessment of various pathophysiologic conditions, including diabetes. This review outlines the recent achievements of ELISA application for clinical studies elucidating oxidative stress. It introduces the potential applicability of ELISA for investigating oxidative stress in diabetes.

High serum levels of advanced glycation end products predict increased coronary heart disease mortality in nondiabetic women but not in nondiabetic men: a population-based 18-year follow-up study

BACKGROUND

Advanced glycation end products (AGEs), modification products of glycation or glycoxidation of proteins and lipids, have been linked to premature atherosclerosis in patients with diabetes as well as in nondiabetic subjects.

METHODS AND RESULTS

Serum levels of AGEs were measured with an immunoassay in samples obtained at baseline examination of a random sample of 1141 nondiabetic individuals (535 men and 606 women), aged 45 to 64 years, living in Kuopio, East Finland, or Turku, West Finland in 1982 to 1984. After 18 years of follow-up, all-cause mortality, cardiovascular disease (CVD), and coronary heart disease (CHD) mortality were registered on the basis of copies of death certificates. Multivariate Cox regression model showed a significant association of serum AGEs with all-cause (P=0.012), CVD (P=0.018), and CHD (P=0.008) mortality in women but not in men. Fasting serum AGEs in the highest quartile were an independent risk factor for all-cause (hazards ratio [HR], 1.90; 95% CI, 1.16 to 3.11; P=0.011) and CHD (HR, 6.51; 95% CI, 1.78 to 23.79; P=0.005) mortality in women, even after the adjustment for confounding factors, including highly sensitive C-reactive protein.

CONCLUSIONS

The present study is the first to show that serum levels of AGEs can predict total, CVD, and CHD mortality in nondiabetic women.

Advanced glycation endproducts--role in pathology of diabetic complications

Diabetes mellitus is a common endocrine disorder characterised by hyperglycaemia and predisposes to chronic complications affecting the eyes, blood vessels, nerves and kidneys. Hyperglycaemia has an important role in the pathogenesis of diabetic complications by increasing protein glycation and the gradual build-up of advanced glycation endproducts (AGEs) in body tissues. These AGE form on intra- and extracellular proteins, lipids, nucleic acids and possess complex structures that generate protein fluorescence and cross-linking. Protein glycation and AGE are accompanied by increased free radical activity that contributes towards the biomolecular damage in diabetes. There is considerable interest in receptors for AGEs (RAGE) found on many cell types, particularly those affected in diabetes. Recent studies suggest that interaction of AGEs with RAGE alter intracellular signalling, gene expression, release of pro-inflammatory molecules and free radicals that contribute towards the pathology of diabetic complications. This review introduces the chemistry of glycation and AGEs and examines the mechanisms by which they mediate their toxicity. The role of AGEs in the pathogenesis of retinopathy, cataract, atherosclerosis, neuropathy, nephropathy, diabetic embryopathy and impaired wound healing are considered. There is considerable interest in anti-glycation compounds because of their therapeutic potential. The mechanisms and sites of action of selected inhibitors, together with their potential in preventing diabetic complications are discussed.

Interaction between the polyol pathway and non-enzymatic glycation on aortic smooth muscle cell migration and monocyte adhesion

We investigated for the interaction between the polyol pathway and enhanced non-enzymatic glycation, both implicated in the pathogenesis of diabetic atherosclerosis, in the activation of aortic smooth muscle cell (SMC) function. Mouse aortas and primary cultures of SMCs from wildtype (WT) mice and transgenic (TG) mice expressing human aldose reductase (AR) were studied regarding changes in AR activity, and SMC gene activation, migration and monocyte adhesion, in response to advanced glycation end-product modified BSA (AGE-BSA). Results showed that AGE-BSA increased AR activity in both WT and TG aortas, with greater increments (p < 0.05) in TG aortas which, basally, had elevated AR activity (2.8 fold of WT). These increments were attenuated by zopolrestat, an AR inhibitor. Similar AGE-induced increments in AR activity were observed in primary cultures of aortic SMCs from WT and TG mice (60% and 100%, respectively, P < 0.01). Such increments were accompanied by increases in intercellular adhesion molecule-1 (ICAM-1) and monocyte chemoattractant protein-1 (MCP-1) mRNA levels (both P < 0.05), activation of membrane-associated PKC-beta1 (P < 0.05) as well as increased SMC migration and Tamm-Horsfall protein (THP)-1 monocyte adhesion to SMCs (both p < 0.01), with all changes being significantly greater in TG SMCs (P < 0.05) and suppressible by either zopolrestat or transfection with an AR antisense oligonucleotide. Our findings suggest that the effects of AGEs on SMC activation, migration and monocyte adhesion are mediated partly through the polyol pathway and, possibly, PKC activation. The greater AGE-induced changes in the TG SMCs have provided further support for the dependency of such changes on polyol pathway hyperactivity.

Relationship between blood levels of N-carboxymethyl-lysine and pentosidine and the severity of microangiopathy in type 2 diabetes

The relationship between blood levels of N-carboxymethyl-lysine (CML) or pentosidine and the severity of microangiopathy was investigated in patients with type 2 diabetes. Blood CML and pentosidine levels were measured by ELISA in 97 type 2 diabetics (46 men and 51 women). CML and pentosidine levels were significantly higher in patients with chronic renal failure than in those with normoalbuminuria, microalbuminuria, or macroalbuminuria (all p < 0.05). Among the diabetics without nephropathy (n = 49), blood CML levels were significantly higher in the patients who had proliferative diabetic retinopathy than in those without retinopathy or those who had background retinopathy (both p < 0.01). In contrast, blood pentosidine levels showed no significant differences among the three retinopathy groups. These findings suggest that the blood level of CML is related to the severity of both nephropathy and retinopathy, while the pentosidine level is only related to the severity of nephropathy.

From hyperglycemia to diabetic kidney disease: the role of metabolic, hemodynamic, intracellular factors and growth factors/cytokines

At present, diabetic kidney disease affects about 15-25% of type 1 and 30-40% of type 2 diabetic patients. Several decades of extensive research has elucidated various pathways to be implicated in the development of diabetic kidney disease. This review focuses on the metabolic factors beyond blood glucose that are involved in the pathogenesis of diabetic kidney disease, i.e., advanced glycation end-products and the aldose reductase system. Furthermore, the contribution of hemodynamic factors, the renin-angiotensin system, the endothelin system, and the nitric oxide system, as well as the prominent role of the intracellular signaling molecule protein kinase C are discussed. Finally, the respective roles of TGF-beta, GH and IGFs, vascular endothelial growth factor, and platelet-derived growth factor are covered. The complex interplay between these different pathways will be highlighted. A brief introduction to each system and description of its expression in the normal kidney is followed by in vitro, experimental, and clinical evidence addressing the role of the system in diabetic kidney disease. Finally, well-known and potential therapeutic strategies targeting each system are discussed, ending with an overall conclusion.

Urinary excretion of advanced glycation endproducts in patients with type 2 diabetes and various stages of proteinuria

OBJECTIVE

The objective of the study was to detect AGE-immunoreactive proteins in urine, and to evaluate AGE excretion at various stages of diabetic nephropathy in type 2 diabetes assessed by the level of proteinuria.

METHODS

AGEs were measured in 24-h urine collection of patients with normoalbuminuria (N) (n=22), microalbuminuria (Mi) (n=31), macroalbuminuria (Ma) (n=28), and overt proteinuria with elevated serum creatinine level (PC) (n=25). A competitive ELISA with polyclonal anti-AGE antibodies was used to monitor AGE excretion.

RESULTS

Multiple comparison of urine AGE content among various stages of proteinuria showed significant differences (summary p<0.000). Fifty percent of samples from the group of normoalbuminuric, and only 15% of samples from the group of microalbuminuria patients were AGE negative. However, there was no significant difference in AGE excretion between the patients with persistent proteinuria and elevated serum creatinine, and those with macroalbuminuria (PC vs Ma, p=0.265). None of the samples from these two groups of patients with highest AGE content in 24-h urine was negative for AGE-immunoreactivity. In addition, the ratio between 24-h urinary AGEs and urinary albumin excretion was calculated to determine whether total 24-h urinary AGE content is an index of the toxic form of albumin released in the course of diabetic nephropathy. The ratio values were log-transformed and bivariate comparison showed significant differences between the N vs Mi (p=0.006) and Mi vs Ma (p=0.000) groups. However, there was no significant difference (p=0.407) between values in the Ma and PC groups of patients. Multiple stepwise regression analysis indicated a relationship of urinary AGE-immunoreactivity with creatinine clearance values (r=0.52, p<0.001).

CONCLUSION

The study demonstrated the presence of AGE-immunoreactivity in the urine of diabetic patients with various stages of proteinuria. Study results pointed to creatinine clearance as the main predictor of AGE excretion. Therefore, the measurement of urinary AGE appears to offer limited extra information in patients with impaired renal function.

Morphologic Findings of Coronary Atherosclerotic Plaques in Diabetics

OBJECTIVE

Coronary atherosclerotic plaque composition of diabetic subjects and localization of receptor for advanced glycation end products (RAGE) and its ligands have not been extensively studied.

METHODS AND RESULTS

Hearts from diabetic subjects and age, race, and sex-matched nondiabetic subjects dying suddenly were examined. Coronary arteries were dissected and lesions were evaluated for plaque burden, necrotic core size, and inflammatory infiltrate. The expression of RAGE, the RAGE-binding protein (S100-A12, EN-RAGE), and cell death (apoptosis) were also determined. Lesions from type II diabetic subjects had larger mean necrotic cores (P=0.01) and greater total and distal plaque load (P<0.001) than nondiabetic subjects. Necrotic core size correlated positively with diabetic status, independent of other risk factors. Intimal staining for macrophages, T-cells, and HLA-DR was also significantly greater in diabetic subjects (P=0.03, P=0.003, and P<0.0001), respectively. The association of increased macrophage infiltrate was independent of cholesterol levels and patient age. Expression of RAGE and EN-RAGE was significantly greater in diabetic subjects (P=0.004) and was associated with apoptotic smooth muscle cells and macrophages.

CONCLUSIONS

In sudden coronary death, inflammation and necrotic core size play a greater role in the progression of atherosclerosis in diabetic subjects. The expression of RAGE and EN-RAGE may further compromise cell survival and promote plaque destabilization.

Early glycemic control, age at onset, and development of microvascular complications in childhood-onset type 1 diabetes: a population-based study in northern Sweden

OBJECTIVE

The aim of this work was to study the impact of glycemic control (HbA(1c)) early in disease and age at onset on the occurrence of incipient diabetic nephropathy (MA) and background retinopathy (RP) in childhood-onset type 1 diabetes.

RESEARCH DESIGN AND METHODS

All children, diagnosed at 0-14 years in a geographically defined area in northern Sweden between 1981 and 1992, were identified using the Swedish Childhood Diabetes Registry. From 1981, a nationwide childhood diabetes care program was implemented recommending intensified insulin treatment. HbA(1c) and urinary albumin excretion were analyzed, and fundus photography was performed regularly. Retrospective data on all 94 patients were retrieved from medical records and laboratory reports.

RESULTS

During the follow-up period, with a mean duration of 12 +/- 4 years (range 5-19), 17 patients (18%) developed MA, 45 patients (48%) developed RP, and 52% had either or both complications. A Cox proportional hazard regression, modeling duration to occurrence of MA or RP, showed that glycemic control (reflected by mean HbA(1c)) during the follow-up was significantly associated with both MA and RP when adjusted for sex, birth weight, age at onset, and tobacco use as potential confounders. Mean HbA(1c) during the first 5 years of diabetes was a near-significant determinant for development of MA (hazard ratio 1.41, P = 0.083) and a significant determinant of RP (1.32, P = 0.036). The age at onset of diabetes significantly influenced the risk of developing RP (1.11, P = 0.021). Thus, in a Kaplan-Meier analysis, onset of diabetes before the age of 5 years, compared with the age-groups 5-11 and >11 years, showed a longer time to occurrence of RP (P = 0.015), but no clear tendency was seen for MA, perhaps due to lower statistical power.

CONCLUSIONS

Despite modern insulin treatment, >50% of patients with childhood-onset type 1 diabetes developed detectable diabetes complications after approximately 12 years of diabetes. Inadequate glycemic control, also during the first 5 years of diabetes, seems to accelerate time to occurrence, whereas a young age at onset of diabetes seems to prolong the time to development of microvascular complications.

Randomized trial of an inhibitor of formation of advanced glycation end products in diabetic nephropathy

BACKGROUND/AIMS

Pimagedine inhibits the formation of advanced glycation end products and slows the progression of diabetic complications in experimental models. This study was undertaken to determine if pimagedine ameliorates nephropathy in type 1 (insulin-dependent) diabetes mellitus.

METHODS

This was a randomized, double-masked, placebo-controlled study performed in 690 patients with type 1 diabetes mellitus, nephropathy, and retinopathy. The patients received twice daily dosing with placebo, pimagedine 150 mg, or pimagedine 300 mg for 2-4 years. The primary end point was the time to doubling of serum creatinine; the secondary end points included evaluations of proteinuria, kidney function, and retinopathy.

RESULTS

Serum creatinine doubled in 26% (61/236) of the placebo-treated patients and in 20% (91/454) of those who received pimagedine (p = 0.099). The estimated glomerular filtration rate decreased more slowly in the pimagedine-treated patients with a 36-month decrease from baseline of 6.26 ml/min/1.73 m(2) as compared with 9.80 ml/min/1.73 m(2) in the placebo-treated patients (p = 0.05), and pimagedine reduced the 24-hour total urinary proteinuria. (The mean reduction from baseline at month 36 was 732 mg/24 h at the low dose and 329 mg/24 h at the high dose as compared with 35 mg/24 h in the placebo group; p </= 0.001.) Fewer pimagedine-treated patients with baseline and end point evaluations (31/324; 10%) as compared with those receiving placebo (16%; 28/179) experienced a three-step or greater progression of the retinopathy (Early Treatment of Diabetic Retinopathy Study) score (p = 0.030). Three patients receiving high-dose pimagedine but none receiving low-dose treatment developed glomerulonephritis.

CONCLUSIONS

While this study did not demonstrate a statistically significant beneficial effect of pimagedine on the progression of overt nephropathy resulting from type 1 diabetes, it is noteworthy in providing the first clinical proof of the concept that inhibiting advanced glycation end product formation can result in a clinically important attenuation of the serious complications of type 1 diabetes mellitus.

Upregulation of CD40–CD40 ligand system in patients with diabetes mellitus

BACKGROUND

Diabetes is associated with an increased risk of cardiovascular disease and atherosclerosis. Increasing evidence shows that CD40-CD40L interaction plays a crucial role in the pathogenesis of atherosclerosis and coronary artery disease. The purpose of this study was to assess whether CD40 system expressions were disrupted in patients with diabetes.

METHODS

Sixteen normal controls and 72 patients including 20 with type 2 diabetes mellitus (DM), 15 with type 1 DM, 20 with coronary heart disease (CHD) and 17 CHD with coexisting DM were investigated. The expression of CD40 and CD40L on platelet was analyzed by indirect-immunofluorescence flow cytometry and serum-soluble CD40L level was determined by a commercially available ELISA. Serum of AGE was detected by fluorescence spectroscopy.

RESULTS

Type 1 DM, type 2 DM, CHD and CHD Patients with coexisting diabetes showed a significant increase of CD40 (81.8 +/- 11.7, 70.7 +/- 11.6, 68.5 +/- 10.2, 79.9 +/- 11.9 MIF, respectively) and CD40L (18.4 +/- 5.1, 13.9 +/- 4.1, 13.5 +/- 3.7, 16.7 +/- 4.7 MIF, respectively) coexpression on platelets as well as sCD40L (15.6 +/- 3.5, 14.1 +/- 3.3, 12.2 +/- 3.5, 13.5 +/- 3.6 ng/ml, respectively) compared with controls (p < 0.01). A positive correlation was found between serum AGE levels in patients with DM and CD40-CD40L system. We also observed a significant correlation between hemoglobinA1c (HbA1c) concentration and CD40L on platelets (r = 0.71, p < 0.001) as well as sCD40L (r = 0.69, p < 0.001), but not for CD40 on platelets.

CONCLUSIONS

Patients with diabetes show increased coexpression of CD40 system, especially CD40L, which may create a proinflammatory and prothrombotic milieu for aggravating the development of atherosclerosis.

Formation of advanced glycosylation end products and oxidative stress in young patients with type 1 diabetes

Increased production of advanced glycosylation end products (AGEs) and augmented oxidative stress may contribute to vascular complications in diabetes. Little is known about the formation and accumulation of AGEs in young patients with type 1 diabetes. The aim of the present study was to investigate whether AGE production and oxidative stress are augmented in young patients with type 1 diabetes at early clinical stages of the disease. Urine samples of 38 patients with type 1 diabetes [mean age (+/-SD), 12.8 +/- 4.5 y; diabetes duration, 5.7 +/- 4.3 y; HbA1c, 8.0 +/- 1.6%; urinary albumin excretion, 12.6 +/- 14.4 mg/g creatinine (Cr)] and those of 60 age-matched healthy control subjects were assayed for AGEs, pentosidine and pyrraline, and markers of oxidative stress, 8-hydroxy-2'-deoxyguanosine (8-OHdG) and acrolein-lysine. Of these four markers, urinary concentrations of pentosidine, 8-OHdG, and acrolein-lysine were significantly higher in the patients with diabetes than in the healthy control subjects. For the patient group, pentosidine correlated significantly with 8-OHdG and acrolein-lysine, and pyrraline correlated significantly with acrolein-lysine. Urinary pentosidine, 8-OHdG, and acrolein-lysine but not pyrraline correlated significantly with urinary albumin excretion. Patients with microalbuminuria (> or =15 mg/g Cr) showed significantly higher levels of all four markers than did normoalbuminuric patients and control subjects. The present study indicates that accumulation of AGEs, whose formation is closely linked to oxidative stress, and resultant endothelial dysfunction may start early in the course of type 1 diabetes. This means that the risk of vascular complications may be present at an early age and that the best possible glycemic control should be emphasized from the diagnosis of diabetes.

Serum levels of low molecular weight advanced glycation end products in diabetic subjects

AIMS

One of the principal theories of the development of diabetic complications proposes that increased levels of advanced glycation end products (AGE) are formed in diabetes by prolonged exposure of proteins, lipids and nucleotides to glucose. Such AGEs may contribute to the development of diabetic complications by a number of mechanisms. Circulating AGEs can be detected in serum, and in the present study, we analysed the clinical correlates of circulating serum low molecular weight AGE (LMW-AGE).

METHODS

Serum LMW-AGE was measured in 106 non-diabetic and 499 diabetic subjects using fluorescence spectroscopy. Results were calibrated against an in-house AGE albumin preparation, and expressed as absolute fluorescence units (AFU).

RESULTS

Serum LMW-AGE values were significantly higher in diabetic than non-diabetic subjects [median 7.5 (range 0-595.5) vs. 5.3 (1.0-15.5) AFU, P<0.01]. In the normal subjects, there were significant correlations between serum LMW-AGE and age (r=0.42, P<0.01) and serum creatinine (r=0.39, P<0.01). In the diabetic patients, serum LMW-AGE correlated significantly with age (r=0.315, P<0.01), systolic blood pressure (r=0.141, P=0.002), serum creatinine (r=0.449, P<0.01) and urinary albumin/creatinine ratio (ACR) (r=0.265, P<0.01). There was no correlation between serum LMW-AGE and HbA1c. On regression analysis, with serum LMW-AGE as the dependent variable, serum creatinine emerged as the most significant factor (t=8.1, P<0.01), followed by age (t=4.0, P<0.01) and ACR (t=2.9, P=0.004). There was no significant difference in serum LMW-AGE between those with and without retinopathy or in those with vascular disease.

CONCLUSIONS

We conclude that circulating LMW-AGEs are increased in diabetic subjects. The major determinant appears to be renal dysfunction in the form of raised albumin/creatinine ratio or creatinine. There was no association with other markers of vascular disease or presence of diabetic complications.

New therapies for advanced glycation end product nephrotoxicity: current challenges

BACKGROUND

The role of advanced glycation end products (AGEs) in diabetic nephropathy has been developed during several years of research and increasingly complex AGE biochemistry. However, the structural diversity of AGE chemistry has created new challenges in the search for AGE-based inhibition therapies.

RESULTS

The challenges include the need to standardize measurements of serum and tissue AGE levels, identifying nephrotoxic AGE compounds, understanding the cell biological state of AGEs in the diabetic kidney, determining the mechanism of action of selective inhibition of the glycation cascade, and forming complementary therapies.

CONCLUSION

Current challenges in the development of new therapies for AGE nephrotoxicity are reviewed.

Increased serum levels of the specific AGE-compound methylglyoxal-derived hydroimidazolone in patients with type 2 diabetes

A time-delayed fluorescence immunoassay was developed for the determination of serum levels of methylglyoxal (MG)-derived hydroimidazolone using a monoclonal antiserum raised against Nalpha-acetyl-Ndelta-(5-hydro-5-methyl)-4-imidazolone, Europium-labeled anti-mouse IgG antiserum as indicator, and MG modified bovine serum albumin (BSA) as standard. Serum levels of hydroimidazolone were measured in 45 patients with type 2 diabetes aged 59.4 +/- 6.1 (mean +/- SD) years and with duration of diabetes of 7.3 +/- 3.1 years, and in 19 nondiabetic controls aged 56.3 +/- 4.3 years. The serum levels of hydroimidazolone were significantly higher in patients compared to controls: median, 3.0 (5-95 percentile, 1.6 to 5.4) U/mg protein versus 1.9 (1.2 to 2.8) U/mg protein (P =.0005). Significant positive correlations were observed between the serum levels of hydroimidazolone and serum levels of advanced glycation end products (AGEs), measured with a polyclonal anti-AGE antibody: r = 0.59 for patients (P <.0001), and r = 0.65 for controls (P =.002). Similarly, significant correlations were also found between serum levels of hydroimidazolone and N(epsilon)-(carboxymethyl)-lysine (CML): r = 0.36 in patients and r = 0.55 for controls (both P =.02). Serum hydroimidazolone levels did not correlate with fasting plasma glucose or hemoglobin A(1c) (HbA(1c)) levels. The observed differences between patients with diabetes and nondiabetic controls seem to be comparable to differences measured for other AGE compounds.

Chemical Modification of Proteins by Lipids in Diabetes

Advanced glycation and lipoxidation end-products (AGE/ALE) increase in tissue proteins with age and at an accelerated rate in diabetes. This Review focuses on the nature and source of AGEs/ALEs and the factors affecting their formation in tissue and plasma proteins. Lipids are identified as an important source of chemical modification of proteins in diabetes, and the role of diabetes, dyslipidemia and renal disease in formation of AGEs/ALEs is reviewed. The article concludes with a discussion of ELISA assays for AGEs/ALEs and the merits of measuring AGEs/ALEs in the clinical laboratory.