Advanced glycation end products and the kidney

Effect of Lactobacillus reuteri GMNL-263 treatment on renal fibrosis in diabetic rats

Hyperglycemia is the most important factor in the progression of renal fibrosis in diabetic kidney. Prevention and treatment of renal fibrosis may improve diabetic nephropathy. To explore whether probiotic Lactobacillus reuteri GMNL-263 treatment was linked to altered hyperglycemia-mediated renal fibrosis in diabetic kidney, the mechanisms of L. reuteri GMNL-263 treatment responsible for the inhibition of renal fibrosis in streptozotocin (STZ)-induced diabetic rats were examined. Diabetic rats were induced by intraperitoneal injection of STZ (50 mg/kg). Induction of diabetes was confirmed by measurement of the blood glucose using the glucose oxidase method, and hyperglycemic rats with levels >16 mmol/L were used. We found that L. reuteri GMNL-263 treatment caused reduction of glycated hemoglobin and blood glucose levels in STZ-induced diabetic rats for 28 days (all p<0.05). Treatment with L. reuteri GMNL-263 increased body weight but decreased kidney weight in diabetic rats as compared to diabetic control (p<0.05). In diabetic renal cortex, the Janus kinase 2/signal transducers and activators of transcription 1 (but not extracellular signal-regulated kinase/c-Jun N-terminal kinase/p38 mitogen-activated protein kinase) activation was markedly blocked by L. reuteri GMNL-263 treatment. The ability of L. reuteri GMNL-263 treatment to inhibit renal fibrosis was verified by the observation that it significantly decreased protein levels of plasminogen activator inhibitor-1, p21(Waf1/Cip1), α-smooth muscle actin, and fibronectin in diabetic renal cortex. The results obtained in this study indicate that L. reuteri GMNL-263 treatment may protect STZ-induced diabetic rats from hyperglycemia-enhanced renal fibrosis.

Advanced glycation end-products and the kidney

BACKGROUND

Advanced glycation end-products (AGEs) are increased in situations with hyperglycemia and oxidative stress such as diabetes mellitus. They are products of nonenzymatic glycation and oxidation of proteins and lipids. The kidney plays an important role in clearance and metabolism of AGEs.

METHODS

Medline and other relevant databases were searched. In addition, key review articles were scanned for relevant original publication. Finally, original data from our research group were also included.

RESULTS

Kidney podocytes and endothelial cells express specific receptors for AGEs. Their activation leads to multiple pathophysiological effects including hypertrophy with cell cycle arrest and apoptosis, altered migration, and generation of proinflammatory cytokines. AGEs have been primarily implicated in the pathophysiology of diabetic nephropathy and diabetic microvascular complications. AGEs are also involved in other primary renal diseases as well as in the development and progression of atherosclerosis. However, serum or plasma concentrations of AGEs do not correlate well with cardiovascular events in patients with chronic kidney disease (CKD). This is likely due to the fact that serum concentrations failed to correlate with AGEs deposited in target tissues. Several inhibitors of the AGE-RAGE axis are currently tested for various indications.

CONCLUSION

AGEs and their receptors are involved in the pathogenesis of vascular and kidney disease. The role of circulating AGEs as biomarkers for cardiovascular risk estimation is questionable. Whether putative inhibitors of AGEs will get the maturity for its therapeutic use in the future remains open.

Relationship of a dominant advanced glycation end product, serum carboxymethyl-lysine, and abnormal glucose metabolism in adults: the Baltimore Longitudinal Study of Aging

BACKGROUND AND OBJECTIVES

Although hyperglycemia is thought to increase the generation of advanced glycation end products (AGEs), studies have not shown a consistent relationship between abnormal glucose metabolism and serum AGEs. We investigated the relationship between a dominant serum AGE, N-carboxymethyl-lysine (CML), and glucose metabolism.

SUBJECTS AND METHODS

Serum CML, fasting plasma glucose, and glucose tolerance were measured in 755 adults in the Baltimore Longitudinal Study of Aging. Fasting plasma glucose was categorized as normal (< or = 99 mg/dL), impaired (100-125 mg/dL), and diabetic (> 125 mg/dL). Two-hour plasma glucose on oral glucose tolerance testing was categorized as normal (< or = 139 mg/dL), impaired (140-199 mg/dL), and diabetic (> or = 200 mg/dL).

RESULTS

The proportion of adults with normal, impaired, and diabetic fasting plasma glucose was 73.8%, 22.9%, and 2.9%, respectively, and the proportion with normal, impaired, and diabetic 2-hour plasma glucose was 73.1%, 19.2%, and 7.7%, respectively. Serum CML (microg/mL) was not associated with abnormal fasting plasma glucose (Odds Ratio [O.R.] 0.60, 95% Confidence Interval [C.I.] 0.15-2.36, P = 0.47) in a multivariate, ordered logistic regression model, adjusting for age, race, gender, body mass index, and chronic diseases. Serum CML (microg/mL) was associated with abnormal 2-hour plasma glucose on glucose tolerance testing (O.R. 0.15, 95% C.I. 0.04-0.63, P = 0.009) in a multivariate, ordered logistic regression model, adjusting for the same covariates.

CONCLUSIONS

Elevated CML, a dominant AGE, was not associated with elevated fasting plasma glucose and was associated with a reduced odds of abnormal glucose tolerance in older community-dwelling adults.

Advanced glycation end products in foods and a practical guide to their reduction in the diet

Modern diets are largely heat-processed and as a result contain high levels of advanced glycation end products (AGEs). Dietary advanced glycation end products (dAGEs) are known to contribute to increased oxidant stress and inflammation, which are linked to the recent epidemics of diabetes and cardiovascular disease. This report significantly expands the available dAGE database, validates the dAGE testing methodology, compares cooking procedures and inhibitory agents on new dAGE formation, and introduces practical approaches for reducing dAGE consumption in daily life. Based on the findings, dry heat promotes new dAGE formation by >10- to 100-fold above the uncooked state across food categories. Animal-derived foods that are high in fat and protein are generally AGE-rich and prone to new AGE formation during cooking. In contrast, carbohydrate-rich foods such as vegetables, fruits, whole grains, and milk contain relatively few AGEs, even after cooking. The formation of new dAGEs during cooking was prevented by the AGE inhibitory compound aminoguanidine and significantly reduced by cooking with moist heat, using shorter cooking times, cooking at lower temperatures, and by use of acidic ingredients such as lemon juice or vinegar. The new dAGE database provides a valuable instrument for estimating dAGE intake and for guiding food choices to reduce dAGE intake.

Aberrant cytokines/chemokines production correlate with proteinuria in patients with overt diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN) occurs in 20% to 30% of all patients with type 2 diabetes mellitus (DM) and is the most common cause of end-stage renal disease. However, the definite pathogenesis, especially the role of immune response, is still unclear.

METHODS

We studied the production and expression of Th1 (IFN-gamma, IL-2R), Th2 (IL-4, IL-10), proinflammatory cytokines (IL-1beta, and TNF-alpha), and chemokines (MCP-1, and RANTES) in patients with DN. The correlation among cytokines, chemokines, and clinical parameters were examined.

RESULTS

A patient with DN presented with longer disease duration, heavy proteinuria, and impaired renal function. Our results demonstrated increased proinflammatory cytokines, Th1 cytokines and chemokines, but not Th2 cytokines, in the plasma and urine of patients with DN as compared to patients with DM without overt nephropathy. Enhanced cytokine/chemokine activation in DN was also demonstrated by positive immunohistochemical staining of kidney tissue. We found a positive correlation between daily protein loss and plasma IFN-gamma and IL-2R, and urinary MCP-1, as well as a negative correlation between creatinine clearance and plasma TNF-alpha and urinary MCP-1.

CONCLUSIONS

There were aberrant cytokines/chemokines production correlated with the degree of proteinuria in patient with overt DN and gross proteinuria. Inflammation may be important in the pathogenesis of DN.

Reactive oxygen species promote caspase-12 expression and tubular apoptosis in diabetic nephropathy

Apoptosis of tubular epithelial cells contributes to the tubular atrophy that accompanies diabetic nephropathy. Reactive oxygen species (ROS) promote tubular apoptosis, but the mechanisms by which this occurs are incompletely understood. Here, we sought proapoptotic genes that ROS differentially upregulate in renal proximal tubular cells of diabetic (db/db) mice. We performed microarray analysis using total RNA from freshly isolated renal proximal tubules of nondiabetic, diabetic, and diabetic transgenic mice overexpressing catalase in the proximal tubule (thereby attenuating ROS). We observed greater expression of caspase-12 in the proximal tubules of the diabetic mice compared with the nondiabetic and diabetic transgenic mice. Quantitative PCR and immunohistochemistry confirmed the enhanced expression of caspase-12, as well as members of the endoplasmic reticulum stress-induced apoptotic pathway. Ex vivo, albumin induced caspase-12 activity and expression (protein and mRNA) and mRNA expression of the CCAT/enhancer-binding protein homologous protein in freshly isolated wild-type proximal tubules but not in catalase-overexpressing proximal tubules. In vitro, albumin stimulated activity of both caspase-12 and caspase-3 as well as expression of caspase-12 and CCAT/enhancer-binding protein homologous protein in a human proximal tubule cell line (HK-2). The free radical scavenger tiron inhibited these effects. Furthermore, knockdown of caspase-12 with small interfering RNA reduced albumin-induced apoptosis in HK-2 cells. Taken together, these studies demonstrate that albuminuria may induce tubular apoptosis through generation of ROS and the subsequent expression and activation of endoplasmic reticulum stress genes in the diabetic kidney.

Advanced glycation end products, oxidative stress and diabetic nephropathy

About 246 million people worldwide have diabetes in 2007. The global figure of people with diabetes is projected to increase to 370 million in 2030. As the prevalence of diabetes has risen to epidemic proportions worldwide, diabetic nephropathy has become one of the most challenging health problems. Therapeutic options such as strict blood glucose and blood pressure controls are effective for preventing diabetic nephropathy, but are far from satisfactory, and the number of diabetic patients on end-stage renal disease is still increasing. Therefore, a novel therapeutic strategy that could halt the progression of diabetic nephropathy should be developed. There is accumulating evidence that advanced glycation end products (AGEs), senescent macroprotein derivatives formed at an accelerated rate under diabetes, play a role in diabetic nephropathy via oxidative stress generation. In this paper, we review the pathophysiological role of AGEs and their receptor (RAGE)-oxidative stress system in diabetic nephropathy.

Cinnamaldehyde impairs high glucose-induced hypertrophy in renal interstitial fibroblasts

Cinnamaldehyde is a major and a bioactive compound isolated from the leaves of Cinnamomum osmophloeum kaneh. To explore whether cinnamaldehyde was linked to altered high glucose (HG)-mediated renal tubulointerstitial fibrosis in diabetic nephropathy (DN), the molecular mechanisms of cinnamaldehyde responsible for inhibition of HG-induced hypertrophy in renal interstitial fibroblasts were examined. We found that cinnamaldehyde caused inhibition of HG-induced cellular mitogenesis rather than cell death by either necrosis or apoptosis. There were no changes in caspase 3 activity, cleaved poly(ADP-ribose) polymerase (PARP) protein expression, and mitochondrial cytochrome c release in HG or cinnamaldehyde treatments in these cells. HG-induced extracellular signal-regulated kinase (ERK)/c-Jun N-terminal kinase (JNK)/p38 mitogen-activated protein kinase (MAPK) (but not the Janus kinase 2/signal transducers and activators of transcription) activation was markedly blocked by cinnamaldehyde. The ability of cinnamaldehyde to inhibit HG-induced hypertrophy was verified by the observation that it significantly decreased cell size, cellular hypertrophy index, and protein levels of collagen IV, fibronectin, and alpha-smooth muscle actin (alpha-SMA). The results obtained in this study suggest that cinnamaldehyde treatment of renal interstitial fibroblasts that have been stimulated by HG reduces their ability to proliferate and hypertrophy through mechanisms that may be dependent on inactivation of the ERK/JNK/p38 MAPK pathway.

Body weight control by a high-carbohydrate/low-fat diet slows the progression of diabetic kidney damage in an obese, hypertensive, type 2 diabetic rat model

Obesity is one of several factors implicated in the genesis of diabetic nephropathy (DN). Obese, hypertensive, type 2 diabetic rats SHR/NDmcr-cp were given, for 12 weeks, either a normal, middle-carbohydrate/middle-fat diet (MC/MF group) or a high-carbohydrate/low-fat diet (HC/LF group). Daily caloric intake was the same in both groups. Nevertheless, the HC/LF group gained less weight. Despite equivalent degrees of hypertension, hyperglycemia, hyperlipidemia, hyperinsulinemia, and even a poorer glycemic control, the HC/LF group had less severe renal histological abnormalities and a reduced intrarenal advanced glycation and oxidative stress. Mediators of the renoprotection, specifically linked to obesity and body weight control, include a reduced renal inflammation and TGF-beta expression, together with an enhanced level of adiponectin. Altogether, these data identify a specific role of body weight control by a high-carbohydrate/low-fat diet in the progression of DN. Body weight control thus impacts on local intrarenal advanced glycation and oxidative stress through inflammation and adiponectin levels.

Role of the receptor for advanced glycation end products in hepatic fibrosis

AIM: To study the role of advanced glycation end products (AGE) and their specific receptor (RAGE) in the pathogenesis of liver fibrogenesis.

METHODS: In vitro RAGE expression and extracellular matrix-related gene expression in both rat and human hepatic stellate cells (HSC) were measured after stimulation with the two RAGE ligands, advanced glycation end product-bovine serum albumin (AGE-BSA) and N^ε-(carboxymethyl) lysine (CML)-BSA, or with tumor necrosis factor-α (TNF-α). In vivo RAGE expression was examined in models of hepatic fibrosis induced by bile duct ligation or thioacetamide. The effects of AGE-BSA and CML-BSA on HSC proliferation, signal transduction and profibrogenic gene expression were studied in vitro.

RESULTS: In hepatic fibrosis, RAGE expression was enhanced in activated HSC, and also in endothelial cells, inflammatory cells and activated bile duct epithelia. HSC expressed RAGE which was upregulated after stimulation with AGE-BSA, CML-BSA, and TNF-α. RAGE stimulation with AGE-BSA and CML-BSA did not alter HSC proliferation, apoptosis, fibrogenic signal transduction and fibrosis- or fibrolysis-related gene expression, except for marginal upregulation of procollagen α1(I) mRNA by AGE-BSA.

CONCLUSION: Despite upregulation of RAGE in activated HSC, RAGE stimulation by AGE does not alter their fibrogenic activation. Therefore, RAGE does not contribute directly to hepatic fibrogenesis.

Diabetes reduces the cholesterol exporter ABCA1 in mouse macrophages and kidneys

Accumulation of cholesterol in arterial macrophages may contribute to diabetes-accelerated atherosclerotic cardiovascular disease. The ATP-binding cassette transporter ABCA1 is a cardioprotective membrane protein that mediates cholesterol export from macrophages. Factors elevated in diabetes, such as reactive carbonyls and free fatty acids, destabilize ABCA1 protein in cultured macrophages, raising the possibility that impaired ABCA1 plays an atherogenic role in diabetes. We therefore examined the modulation of ABCA1 in two mouse models of diabetes. We isolated peritoneal macrophages, livers, kidneys, and brains from type 1 non-obese diabetic (NOD) mice and mice made diabetic by viral-induced autoimmune destruction of pancreatic beta-cells, and we measured ABCA1 protein and mRNA levels and cholesterol contents. ABCA1 protein levels and cholesterol export activity were reduced by 40-44% (P<0.01) in peritoneal macrophages and protein levels by 48% (P<0.001) in kidneys in diabetic NOD mice compared with nondiabetic animals, even though ABCA1 mRNA levels were not significantly different. A similar selective reduction in ABCA1 protein was found in peritoneal macrophages (33%, P<0.05) and kidneys (35%, P<0.05) from the viral-induced diabetic mice. In liver and brain, however, diabetes had no effect or slightly increased ABCA1 protein and mRNA levels. The reduced ABCA1 in macrophages and kidneys was associated with increased cholesterol content. Impaired ABCA1-mediated cholesterol export could therefore contribute to the increased atherosclerosis and nephropathy associated with diabetes.

XLF-III-43, a novel coumarin-aspirin compound, prevents diabetic nephropathy in rats via inhibiting advanced glycation end products

Advanced glycation end products (AGE) have been implicated in the pathogenesis of diabetic complications. The purpose of this study was to examine the novel coumarin-aspirin compound XLF-III-43 in the inhibition of AGE formation in diabetic nephropathy. In vitro analysis showed XLF-III-43 in a dose-dependent manner decreased glucose induced formation of glycation adducts on albumin and inhibited AGE-lysozyme crosslinking. The streptozotocin-induced diabetic rats were used to investigate the beneficial effects of XLF-III-43 treatment on diabetic nephropathy. Administration of XLF-III-43 significantly decreased (P<0.05) blood urea nitrogen and urinary albumin excretion. Moreover, XLF-III-43 ameliorated kidney hypertrophy, mesangial expansion and glomerulosclerosis in diabetic rats relative to untreated model group. These data correlated with decreased both AGE and downstream markers of AGE stress (TGF-beta1, CTGF, fibronectin and collagen IV fibrolysis) in kidneys of diabetic rats. These data support further development of XLF-III-43 for prevention of nephropathy via inhibition of AGE formation consequent to chronic hyperglycemia.

Myeloperoxidase: molecular mechanisms of action and their relevance to human health and disease

Myeloperoxidase (MPO) is a heme-containing peroxidase abundantly expressed in neutrophils and to a lesser extent in monocytes. Enzymatically active MPO, together with hydrogen peroxide and chloride, produces the powerful oxidant hypochlorous acid and is a key contributor to the oxygen-dependent microbicidal activity of phagocytes. In addition, excessive generation of MPO-derived oxidants has been linked to tissue damage in many diseases, especially those characterized by acute or chronic inflammation. It has become increasingly clear that MPO exerts effects that are beyond its oxidative properties. These properties of MPO are, in many cases, independent of its catalytic activity and affect various processes involved in cell signaling and cell-cell interactions and are, as such, capable of modulating inflammatory responses. Given these diverse effects, an increased interest has emerged in the role of MPO and its downstream products in a wide range of inflammatory diseases. In this article, our knowledge pertaining to the biologic role of MPO and its downstream effects and mechanisms of action in health and disease is reviewed and discussed.

Regular moderate exercise reduces advanced glycation and ameliorates early diabetic nephropathy in obese Zucker rats

Advanced glycation end products (AGEs) play a key role in the pathogenesis of diabetes and its complications, including the diabetic nephropathy. The renoprotective effects of exercise are well known; however, the mechanisms remain elusive. Here we examined whether a regular moderate exercise in obese Zucker rats (OZR), a model of diabetes- and obesity-associated nephropathy, will affect the development of early renal injury in OZR possibly via alteration of AGEs formation. The OZR were left without exercise (sedentary) or subjected to 10 weeks intermittent treadmill running of moderate intensity. Compared with sedentary OZR, kidneys of running OZR had significantly less glomerular mesangial expansion and tubulointerstitial fibrosis. Running OZR had significantly lower plasma AGEs-associated fluorescence and N(epsilon)-carboxymethyllysine. Correspondingly, renal AGEs and N(epsilon)-carboxymethyllysine content were lower in running OZR. Systemically, exercise increased aerobic metabolism, as apparent from urinary metabolite profiling. No differences in plasma glucose, insulin, or lipid profile were found between the 2 groups. Apart from lower advanced oxidation protein products (a marker of myeloperoxidase activity), no other marker of inflammation was altered by exercise, either systemically or locally in kidneys. No indication of changed oxidative status was revealed between the groups. Exercise in OZR decreased advanced glycation. This might represent the early event of exercise-induced renoprotection in diabetic nephropathy in OZR. If confirmed in clinical studies, regular moderate exercise could represent an easy and effective nonpharmacologic approach to reduce advanced glycation.

Serum carboxymethyl-lysine, a dominant advanced glycation end product, is associated with chronic kidney disease: the Baltimore longitudinal study of aging

OBJECTIVE

Advanced glycation end products (AGEs) are modifiable risk factors for renal disease that were primarily studied in persons with diabetes or endstage renal disease. Our objective was to characterize the relationship between AGEs and renal function in community-dwelling adults.

DESIGN

The presence of serum L-carboxymethyl-lysine (CML), a dominant AGE, was compared with renal function in a cross-sectional analysis.

SETTING

This study was part of the Baltimore Longitudinal Study of Aging in Baltimore, Maryland.

PATIENTS OR OTHER PARTICIPANTS

Participants included community-dwelling men and women, aged 26 to 93 years, seen during a regular follow-up visit to the Baltimore Longitudinal Study of Aging between 2002 and 2007.

MAIN OUTCOME MEASURES

The main outcome measures included chronic kidney disease (CKD) at stage >/=3 of the National Kidney Foundation classification (estimated glomerular filtration rate [eGFR] of<60 mL/minute/1.73 m(2)) and eGFR.

RESULTS

Of 750 adults, 121 (16.1%) had CKD. Serum CML was associated with CKD (odds ratio expressed per one standard deviation, 1.37; 95% confidence interval, 1.11 to 1.67; P=.003) in a multivariate logistic regression model adjusting for age, race, smoking, and chronic diseases. Serum CML was associated with eGFR (mL/minute/1.73 m(2)) (beta=-2.21, standard error=0.57, P=.0001) in a multivariate linear regression model, adjusting for age, race, smoking, and chronic diseases. After excluding patients with diabetes, serum CML was associated with CKD (odds ratio per one standard deviation, 1.38; 95% confidence interval, 1.12 to 1.70; P=.003) and eGFR (beta=-2.09, standard error=0.59, P=.0005), adjusting for the same covariates.

CONCLUSION

Serum CML, a dominant AGE, is independently associated with CKD and eGFR.

The role of tubular injury in diabetic nephropathy

Diabetic nephropathy is associated with increased mortality in diabetic patients and is a major cause of end-stage renal disease in most countries. Understanding its pathogenesis is important as it may equip us with novel ways in its prevention and in slowing its progression. To date, attempts to unravel the complex pathogenesis and pathophysiology of diabetic nephropathy have mostly focused on the glomerulus. However, recently a lot of data has accumulated that implicates the tubules as playing a key role. This article reviews these data and the light they throw on the role of renal tubules in the pathogenesis of diabetic nephropathy.

Relationship of an advanced glycation end product, plasma carboxymethyl-lysine, with slow walking speed in older adults: the InCHIANTI study

Advanced glycation end products (AGEs) are bioactive molecules found in foods and generated endogenously in the body. AGEs induce cross-linking of collagen and increase the stiffness of skeletal muscle and cartilage. We characterized the relationship between a plasma AGE, carboxymethyl-lysine (CML), and slow walking speed (lowest quintile of walking speed) in older adults. Walking speed over a 4 m course was assessed in 944 adults, aged >or=65 years, in the InCHIANTI study, a population-based study of aging and mobility disability conducted in two towns in Tuscany, Italy. Participants in the highest quartile of plasma CML were at higher risk of slow walking speed (Odds Ratio [O.R.] 1.56, 95% Confidence Interval [C.I.] 1.02-2.38, P = 0.04) compared to those in the lower three quartiles of plasma CML in a logistic regression models adjusting for age, education, cognitive function, smoking, and chronic diseases. After exclusion of participants with diabetes, participants in the highest quartile of plasma CML were at higher risk of slow walking speed (O.R. 1.87, 95% C.I. 1.15-3.04, P = 0.01) adjusting for the same covariates. In older community-dwelling adults, elevated plasma CML is independently associated with slow walking speed.

Advanced glycation end products induce cell cycle arrest and proinflammatory changes in osteoarthritic fibroblast-like synovial cells

INTRODUCTION

Advanced glycation end products (AGEs) have been introduced to be involved in the pathogenesis of osteoarthritis (OA). The influence of AGEs on osteoarthritic fibroblast-like synovial cells (FLS) has been incompletely understood as yet. The present study investigates a potential influence of AGE-modified bovine serum albumin (AGE-BSA) on cell growth, and on the expression of proinflammatory and osteoclastogenic markers in cultured FLS.

METHODS

FLS were established from OA joints and stimulated with AGE-BSA. The mRNA expression of p27Kip1, RAGE (receptor for AGEs), nuclear factor kappa B subunit p65 (NFkappaB p65), tumor necrosis factor alpha (TNF-alpha, interleukin-6 (IL-6), receptor activator of NFkappaB ligand (RANKL) and osteoprotegerin was measured by real-time PCR. The respective protein expression was evaluated by western blot analysis or ELISA. NFkappaB activation was investigated by luciferase assay and electrophoretic mobility shift assay (EMSA). Cell cycle analysis, cell proliferation and markers of necrosis and early apoptosis were assessed. The specificity of the response was tested in the presence of an anti-RAGE antibody.

RESULTS

AGE-BSA was actively taken up into the cells as determined by immunohistochemistry and western blots. AGE-induced p27Kip1 mRNA and protein expression was associated with cell cycle arrest and an increase in necrotic, but not apoptotic cells. NFkappaB activation was confirmed by EMSAs including supershift experiments. Anti-RAGE antibodies attenuated all AGE-BSA induced responses. The increased expression of RAGE, IL-6 and TNF-alpha together with NFkappaB activation indicates AGE-mediated inflammation. The decreased expression of RANKL and osteoprotegerin may reflect a diminished osteoclastogenic potential.

CONCLUSIONS

The present study demonstrates that AGEs modulate growth and expression of genes involved in the pathophysiological process of OA. This may lead to functional and structural impairment of the joints.

Plasma carboxymethyl-lysine, an advanced glycation end product, and all-cause and cardiovascular disease mortality in older community-dwelling adults

OBJECTIVES

To determine whether older adults with high plasma carboxymethyl-lysine (CML), an advanced glycation end product, are at higher risk of all-cause and cardiovascular disease (CVD) mortality.

DESIGN

Prospective cohort study.

SETTING

Population-based sample of adults aged 65 and older residing in Tuscany, Italy.

PARTICIPANTS

One thousand thirteen adults participating in the Invecchiare in Chianti study.

MEASUREMENTS

Anthropometric measures, plasma CML, fasting plasma total, high-density and low-density lipoprotein cholesterol, triglycerides, glucose, creatinine. Clinical measures: medical assessment, diabetes mellitus, hypertension, coronary heart disease, heart failure, stroke, cancer. Vital status measures: death certificates and causes of death according to the International Classification of Diseases. Survival methods were used to examine the relationship between plasma CML and all-cause and CVD mortality, adjusting for potential confounders.

RESULTS

During 6 years of follow-up, 227 (22.4%) adults died, of whom 105 died with CVD. Adults with plasma CML in the highest tertile had greater all-cause (hazard ratio (HR)=1.84, 95% confidence interval) CI)=1.30-2.60, P<.001) and CVD (HR=2.11, 95% CI=1.27-3.49, P=.003) mortality than those in the lower two tertiles after adjusting for potential confounders. In adults without diabetes mellitus, those with plasma CML in the highest tertile had greater all-cause (HR=1.68, 95% CI=1.15-2.44, P=.006) and CVD (HR=1.74, 95% CI=1.00-3.01, P=.05) mortality than those in the lower two tertiles after adjusting for potential confounders.

CONCLUSION

Older adults with high plasma CML are at higher risk of all-cause and CVD mortality.

DD genotype of angiotensin-converting enzyme in type 2 diabetes mellitus with renal disease in Mexican Mestizos

AIM

The DD genotype of angiotensin-converting enzyme (ACE) has been suggested as a major contributor of diabetic nephropathy in several populations. The purpose of the present study was to determine whether micro/macroalbuminuria is associated with ACE insertion/deletion (I/D) polymorphism in Mexican Mestizos with type 2 diabetes mellitus.

METHODS

A total of 435 patients with type 2 diabetes mellitus, of whom 233 had albuminuria, were characterized for the ACE I/D polymorphism by the polymerase chain reaction method.

RESULTS

Clinical and biochemical characteristics and frequencies according to DD, ID and II genotypes in patients with and without albuminuria showed no significant differences. However, only females with micro/macroalbuminuria showed higher frequency of a DD genotype than those without albuminuria (27.9%, 21.2% and 10.5%, respectively; P <or= 0.044). In addition, female patients with macroalbuminuria without dialysis showed no significant differences with patients undergoing dialysis.

CONCLUSION

The ACE DD genotype is a risk factor for the development of renal disease in Mexican Mestizo females with type 2 diabetes, indicating a possible DD genotype-associated sex effect in renal disease.

Blockade of advanced glycation end product formation attenuates bleomycin-induced pulmonary fibrosis in rats

BACKGROUND

Advanced glycation end products (AGEs) have been proposed to be involved in pulmonary fibrosis, but its role in this process has not been fully understood. To investigate the role of AGE formation in pulmonary fibrosis, we used a bleomycin (BLM)-stimulated rat model treated with aminoguanidine (AG), a crosslink inhibitor of AGE formation.

METHODS

Rats were intratracheally instilled with BLM (5 mg/kg) and orally administered with AG (40, 80, 120 mg/kg) once daily for two weeks. AGEs level in lung tissue was determined by ELISA and pulmonary fibrosis was evaluated by Ashcroft score and hydroxyproline assay. The expression of heat shock protein 47 (HSP47), a collagen specific molecular chaperone, was measured with RT-PCR and Western blot. Moreover, TGFbeta1 and its downstream Smad proteins were analyzed by Western blot.

RESULTS

AGEs level in rat lungs, as well as lung hydroxyproline content and Ashcroft score, was significantly enhanced by BLM stimulation, which was abrogated by AG treatment. BLM significantly increased the expression of HSP47 mRNA and protein in lung tissues, and AG treatment markedly decreased BLM-induced HSP47 expression in a dose-dependent manner (p < 0.05). In addition, AG dose-dependently downregulated BLM-stimulated overexpressions of TGFbeta1, phosphorylated (p)-Smad2 and p-Smad3 protein in lung tissues.

CONCLUSION

These findings suggest AGE formation may participate in the process of BLM-induced pulmonary fibrosis, and blockade of AGE formation by AG treatment attenuates BLM-induced pulmonary fibrosis in rats, which is implicated in inhibition of HSP47 expression and TGFbeta/Smads signaling.

Effects of nitric oxide and antioxidants on advanced glycation end products-induced hypertrophic growth in human renal tubular cells

The accumulation of advanced glycation end products (AGE) is a key mediator of renal tubular hypertrophy in diabetic nephropathy (DN). Reactive oxygen species and nitric oxide (NO) were involved in the progression of DN. In this study, the molecular mechanisms of NO and antioxidants responsible for inhibition of AGE-induced renal tubular hypertrophy were examined. We found that AGE (but not nonglycated bovine serum albumin) significantly suppressed the NO/cGMP/PKG signaling in human renal proximal tubular cells. NO donors S-nitroso-N-acetylpenicillamine (SNAP)/sodium nitroprusside (SNP) and antioxidants N-acetylcysteine (NAC)/taurine treatments significantly attenuated AGE-inhibited NO production, cGMP synthesis, and inducible NO synthase/cGMP-dependent protein kinase (PKG) activation. Moreover, AGE-induced extracellular signal-regulated kinase/c-Jun N-terminal kinase/p38 mitogen-activated protein kinase activation was markedly blocked by antireceptor for AGE (RAGE), SNAP, SNP, NAC, and taurine. The abilities of NO and antioxidants to inhibit AGE/RAGE-induced hypertrophic growth were verified by the observation that SNAP, SNP, NAC, and taurine inhibited fibronectin, p21(Waf1/Cip1), and RAGE expression. Therefore, antioxidants significantly attenuated AGE/RAGE-enhanced cellular hypertrophy partly through induction of the NO/cGMP/PKG signaling.

Elevated serum advanced glycation end products and their circulating receptors are associated with anaemia in older community-dwelling women

OBJECTIVE

to determine whether serum carboxymethyl-lysine, a dominant advanced glycation end product (AGE), and circulating total receptor for AGEs (sRAGE) and endogenous secretory receptor for AGEs (esRAGE) are associated with anaemia.

DESIGN

cross-sectional analysis.

SETTING

moderately severely disabled women, > or =65 years, living in the community in Baltimore, MD (the Women's Health and Aging Study I).

PARTICIPANTS

519 women with and without anaemia.

MAIN OUTCOME MEASURE

haemoglobin and anaemia (haemoglobin <12 g/dL).

RESULTS

of 519 women, 128 (24.7%) had anaemia. All odds ratios (OR) were expressed per one standard deviation. Serum CML was associated with anaemia [OR 1.47, 95% confidence interval (CI) 1.11-1.95, P = 0.008] in a multivariate logistic regression model adjusting for age, race, smoking, education and chronic diseases. Serum sRAGE (ng/mL) and esRAGE (ng/mL) were associated with anaemia (OR 1.52, 95% CI 1.21-1.92, P = 0.0004; OR 1.49, 95% CI 1.18-1.87, P = 0.0006, respectively) in separate multivariate logistic regression models, adjusting for the same covariates mentioned above. Serum CML (P = 0.004), sRAGE (P < 0.0001) and esRAGE (P < 0.0001) were inversely and independently associated with haemoglobin concentrations.

CONCLUSION

AGEs and circulating RAGE are independently associated with haemoglobin and anaemia in older women. AGEs are amenable to interventions, as serum AGEs can be lowered by a change in dietary pattern and pharmacological treatment.

Advanced glycation end products and their circulating receptors predict cardiovascular disease mortality in older community-dwelling women

AIMS

To characterize the relationship between advanced glycation end products (AGEs) and circulating receptors for AGEs (RAGE) with cardiovascular disease mortality.

METHODS

The relationships between serum AGEs, total RAGE (sRAGE), and endogenous secretory RAGE (esRAGE), and mortality were characterized in 559 community-dwelling women, double dagger 65 years, in Baltimore, Maryland.

RESULTS

During 4.5 years of follow-up, 123 (22%) women died, of whom 54 died with cardiovascular disease. The measure of serum AGEs was carboxymethyl-lysine (CML), a dominant AGE. Serum CML predicted cardiovascular disease mortality (Hazards Ratio [HR] for highest vs lower three quartiles, 1.94, 95% Confidence Interval [CI] 1.08-3.48, p=0.026), after adjusting for age, race, body mass index, and renal insufficiency. Serum sRAGE (ng/mL) and esRAGE (ng/mL) predicted cardiovascular disease mortality (HR per 1 Standard Deviation [SD] 1.27, 95% CI 0.98-1.65, p=0.07; HR 1.28, 95% CI 1.02-1.63, p=0.03), after adjusting for the same covariates. Among non-diabetic women, serum CML, sRAGE, and esRAGE, respectively, predicted cardiovascular disease mortality (HR for highest vs lower three quartiles, 2.29, 95% CI 1.21-4.34, p=0.01; HR per 1 SD, 1.24, 95% CI 0.92-1.65, p=0.16; HR per 1 SD 1.45, 95% CI 1.08-1.93, p=0.01), after adjusting for the same covariates.

CONCLUSIONS

High circulating AGEs and RAGE predict cardiovascular disease mortality among older community-dwelling women. AGEs are a potential target for interventions, as serum AGEs can be lowered by change in dietary pattern and pharmacological treatment.

Receptor for AGE (RAGE) and its ligands-cast into leading roles in diabetes and the inflammatory response

The actors in the pathogenesis of diabetes and its complications are many and multifaceted. The effects of elevated levels of glucose are myriad; among these is the generation of advanced glycation end products (AGEs), the products of nonenzymatic glycoxidation of proteins and lipids. The finding that AGEs stimulate signal transduction cascades through the multiligand receptor RAGE unveiled novel insights into diabetes and its complications. Inextricably woven into AGE-RAGE interactions in diabetes is the engagement of the innate and adaptive immune responses. Although glucose may be the triggering stimulus to draw RAGE into diabetes pathology, consequent cellular stress results in release of proinflammatory RAGE ligands S100/calgranulins and HMGB1. We predict that once RAGE is engaged in the diabetic tissue, a vicious cycle of ligand-RAGE perturbation ensues, leading to chronic tissue injury and suppression of repair mechanisms. Targeting RAGE may be a beneficial strategy in diabetes, its complications, and untoward inflammatory responses.

Diabetic foot syndrome and renal function in type 1 and 2 diabetes mellitus show close association

BACKGROUND

Diabetic nephropathy and diabetic foot syndrome (DFS) are two major complications of diabetes. Surprisingly, little is known of a potential relationship between renal function and the development of DFS in patients with preterminal renal insufficiency. A retrospective cohort study at a single tertiary university centre caring for a large collective of patients with type 1 and 2 diabetes was performed. Patients and methods. All patients with type 1 or 2 diabetes from 1989 to 2007 on the electronic patient sheet who had standardized food examination, albuminuria and serum creatinine were analysed. A total number of 899 patients with type 1 and 4007 individuals with type 2 diabetes were studied. Estimated glomerular filtration rate (eGFR) was calculated according to the modified equation 7 MDRD formula. Patients were grouped into the chronic kidney disease (CKD) stages according to the eGFR and presence of albuminuria. DFS was classified according to Wagner as well as Armstrong stages.

RESULTS

Forty-six patients (5.1%) of 899 patients with type 1 diabetes have active or a history of DFS. Patients with type 1 diabetes and DSF had significantly higher serum creatinine levels, lower eGFR, higher systolic blood pressure and higher HbA1c levels compared to those without DFS. There was a significant negative correlation between eGFR and the presence of DFS in patients with type 1 diabetes (r = -0.155, P < 0.01). In type 1 diabetes patients, there was a significant negative correlation (Spearman test) between eGFR and Wagner stages (r = -0.218, P = 0.01) as well as Armstrong stages (r = -0.255, P = 0.01). Multiple logistic regression analysis revealed a significant association between the presence of DFS and eGFR (odds ratio 0.696 per 10 ml/min increase, 95% confidence interval 0.627-0.773, P < 0.001). A total of 532 type 2 patients from 4007 patients had DFS (13.7%). Compared with type 2 patients without DFS, those with DFS were significantly older (P < 0.005), exhibited a higher HbA1c, had a longer duration of diabetes (P < 0.005), higher serum creatinine levels (P < 0.005) and a lower eGFR (P < 0.005). There was a significant negative correlation between the Wagner stages and eGFR (r = -0.104, P < 0.01) as well as Armstrong stages and eGFR (r = -0.125, P < 0.01) in all patients with type 2 diabetes (Spearman test). Multiple logistic regression analysis revealed a significant association between the presence of DFS and eGFR (odds ratio 0.873 per 10 ml/min increase, 95% confidence interval 0.842-0.904, P < 0.001). There were also significant associations between DFS and duration of diabetes as well as diastolic blood pressure. In addition, the Jonckheere-Terpstra test confirmed the decrease of eGFR with increasing Wagner and Armstrong stages in patients with type 2 diabetes. Smoking was not associated with a higher prevalence of DFS in type 1 and 2 diabetic patients.

CONCLUSION

There was a strong association between the degree of renal function impairment and DFS in this observational study. Data show that diabetics with DFS undergo a higher incidence of amputation; thus, it should be recommended that diabetic patients with renal insufficiency should be regularly screened for the presence of DFS.

RAGE polymorphisms, renal function and histological finding at 12 months after renal transplantation

OBJECTIVES

Rage (receptor for advanced glycation end products) is involved in pathogenesis of many diseases. The aim of the study was to test whether polymorphisms of RAGE gene are associated with the outcome of kidney transplantation.

DESIGN AND METHODS

Four polymorphisms of the RAGE gene (-429T/C, -374T/A, Gly82Ser and 2184A/G) were assessed in 145 renal transplant recipients and their relationship to histological changes in 12 months protocol kidney graft biopsy and renal function was examined.

RESULTS

Genotype frequencies of each polymorphism corresponded to expected frequencies according to Hardy-Weinberg equilibrium. No differences between allelic and genotype frequencies among patients with normal histological findings, chronic allograft nephropathy and subclinical rejection were observed.

CONCLUSION

This is the first study on polymorphisms of the RAGE gene in patients with the transplanted kidney. No association of RAGE selected gene polymorphisms with 12-months outcome of renal transplants was shown in study.

Carboxymethyl-lysine, an advanced glycation end product, and decline of renal function in older community-dwelling adults

BACKGROUND

Advanced glycation end products (AGEs) are bioactive molecules found in greater concentrations in foods that have been processed at high temperatures. AGEs have been associated with impaired renal function in diabetes and in uremia. The relationship between AGEs and renal function in community-dwelling adults has not been well characterized.

AIM OF THE STUDY

The objective was to determine whether plasma AGEs are independently associated with chronic kidney disease (CKD) and predictive of renal function in older adults.

METHODS

The relationship between plasma carboxymethyl-lysine (CML), an AGE, and CKD (>or= stage 3 of National Kidney Foundation classification; estimated glomerular filtration rate [eGFR] <60 ml/min/1.73 m(2)) and eGFR at 3- and 6-years follow-up was examined in a population-based study of aging, the InCHIANTI study, in Tuscany, Italy.

RESULTS

Of 1,008 adults, aged >or=65 years, 153 (15.2%) had CKD at enrollment. Mean (standard deviation [S.D.]) plasma CML was 365 (110) ng/ml. Plasma CML was associated with CKD (odds ratio [O.R.] expressed per 1 S.D., 1.53, 95% confidence interval [C.I.] 1.27-1.84, P < 0.0001) in a multivariate logistic regression model, adjusting for potential confounders. Plasma CML was associated with eGFR (beta = -2.77, standard error [S.E.] = 0.51, P < 0.0001) at baseline, 3-year (beta = -2.54, S.E. = 0.61, P < 0.0001) and 6-year follow-up visits (beta = -1.21, S.E. = 0.70, P = 0.08) in multivariate linear regression models, adjusting for potential confounders. The associations between plasma CML and prevalent CKD, eGFR, and eGFR at 3- and 6-year follow-up were significant and nearly unchanged after exclusion of adults with diabetes.

CONCLUSION

Plasma CML is independently associated with CKD and is an independent predictor of decline in renal function in older community-dwelling adults.

Advanced glycation end products and their circulating receptors and level of kidney function in older community-dwelling women

BACKGROUND

Advanced glycation end products (AGEs) and the receptor for AGE (RAGE) are implicated in the pathogenesis of kidney disease; however, their relation with level of kidney function has not been well characterized.

STUDY DESIGN

Cross-sectional and prospective.

SETTING & PARTICIPANTS

548 moderately to severely disabled community-dwelling women in the Women's Health and Aging Study I in Baltimore, MD.

PREDICTOR

Serum carboxymethyl-lysine (CML), a dominant AGE; total soluble RAGE (sRAGE); and endogenous secretory RAGE (esRAGE).

OUTCOMES & MEASUREMENTS

Glomerular filtration rate (GFR), prevalent and incident decreased GFR (GFR < 60 mL/min/1.73 m(2)). Serum CML, sRAGE, and esRAGE.

RESULTS

Of 548 women, 283 (51.6%) had decreased GFR at baseline. Serum CML level was associated with decreased GFR (OR [all expressed per 1 SD], 1.98; 95% CI, 1.41 to 2.76; P < 0.001) in a multivariate logistic regression model adjusting for age, race, hemoglobin A(1c) level, and chronic diseases. Serum sRAGE and esRAGE levels (both in nanograms per milliliter) were associated with decreased GFR (OR, 1.42; 95% CI, 1.12 to 1.79; P = 0.003; OR, 1.42; 95% CI, 1.14 to 1.77; P = 0.001, respectively) in separate multivariate logistic regression models adjusting for potential confounders. Of 230 women without decreased GFR at baseline, 32 (13.9%) developed decreased GFR by the follow-up visit 12 months later. Serum CML (in micrograms per milliliter), sRAGE, and esRAGE levels at baseline were associated with the prevalence of decreased GFR 12 months later (OR, 1.80; 95% CI, 1.19 to 2.71; P = 0.005; OR, 1.32; 95% CI, 1.01 to 1.74; P = 0.05; and OR, 1.33; 95% CI, 1.01 to 1.77; P = 0.05, respectively) in separate multivariate logistic regression models adjusting for potential confounders.

LIMITATIONS

Small number of incident cases, limited follow-up, creatinine values not standardized.

CONCLUSIONS

AGE and circulating RAGE levels are independently associated with decreased GFR and seem to predict decreased GFR. AGEs are amenable to interventions because serum AGE levels can be decreased by change in dietary pattern and pharmacological treatment.

Immunogenicity of advanced glycation end products in diabetic patients and in nephropathic non-diabetic patients on hemodialysis or after renal transplantation

Advanced glycation end products (AGE) increase as a consequence of diabetic hyperglycemia and, in nephropathic patients, following renal function loss. Protein-bound AGE behave as immunogens, inducing formation of specific antibodies (Ab-AGE). In this work AGE immunogenicity was studied in 42 diabetic patients, 26 nephropathic patients on hemodialysis and 26 patients with end-stage renal disease who underwent kidney transplantation and in 20 normal subjects. Non-oxidation-derived AGE (nox-AGE), oxidation-derived AGE (ox-AGE) and Ab-AGE were measured by competitive or direct enzyme-linked immunosorbent assay (ELISA) and circulating immune complexes (CIC) by C1q ELISA. Nox- AGE increased significantly in all patient groups (p < or = 0.05 to < or = 0.0001) except in patients on hemodialysis for less than 6 yr. Ox-AGE were only significantly increased in patients transplanted more than 3 yr previously (p < 0.05). Ab-AGE were significantly lower than controls in both diabetic groups and in patients on hemodialysis for more than 6 yr (p < 0.005 to < 0.0001) and not unlike controls in the other groups. These results demonstrate that hemodialysis or renal transplantation can, initially, reduce either nox- or ox-AGE levels, which however go back to being high in time. Renal transplantation fails to normalize nox-AGE. More importantly, plasma Ab-AGE levels are reduced or unchanged in all patient groups in comparison with controls, despite higher circulating AGE levels. This suggests the importance of tissue-bound AGE as Ab-AGE targets. Additional interventions are needed to control AGE levels in treated nephropathic patients. The search and quantification of specific Ab-AGE would give more meaningful results if performed over specific tissue specimens.

RAGE: developmental expression and positive feedback regulation by Egr-1 during cigarette smoke exposure in pulmonary epithelial cells

The receptor for advanced glycation end-products (RAGE) is a member of the immunoglobin superfamily of multiligand receptors. Following ligand binding, mechanisms associated with host defense, tissue remodeling, and inflammation are activated. RAGE is highly expressed in pulmonary epithelium transitioning from alveolar type (AT) II to ATI cells and is upregulated in the presence of ligand; however, the regulation and function of RAGE during development are less clear. Herein, immunohistochemistry demonstrated a temporal-spatial pattern of RAGE expression in pulmonary epithelial cells from embryonic day 17.5 to postnatal day 10. Cotransfection experiments revealed that the mouse RAGE promoter was activated by early growth response gene 1 (Egr-1) and inhibited by thyroid transcription factor-1 (TTF-1) via interaction with specific regulatory elements. A rat ATI cell line (R3/1) with endogenous RAGE expression also differentially regulated RAGE when transfected with TTF-1 or Egr-1. Because Egr-1 is markedly induced in pulmonary epithelial cells exposed to cigarette smoke extract (CSE; Reynolds PR, Hoidal JR. Am J Respir Cell Mol Biol 35: 314-319, 2006.), we sought to investigate RAGE induction by CSE. Employing RT-PCR and Western blotting, RAGE and common ligands (amphoterin and S100A12) were upregulated in epithelial (R3/1 and A549) and macrophage (RAW) cell lines following exposure to CSE. Immunostaining for RAGE in cells similarly exposed and in lungs from mice exposed to cigarette smoke for 6 mo revealed elevated RAGE expression in pulmonary epithelium. After the addition of glyoxylated BSA, an advanced glycation end-product that binds RAGE, real-time RT-PCR detected a 200-fold increase in Egr-1. These results indicate that Egr-1 regulates RAGE expression during development and the likelihood of positive feedback involving Egr-1 and RAGE in cigarette smoke-related disease.

Cellular and molecular aspects of ovarian follicle ageing

It is well established that age-related decline of the biological capacity of a woman to reproduce is primarily related to the poor developmental potential of her gametes. This renders female ageing the most significant determinant of success in IVF. Starting with a reference picture of the main molecular and cellular failures of aged oocytes, granulosa cells and follicular microenvironment, this review focuses on age-related biochemical mechanisms underlying these changes. According to the most relevant concept of ageing, age-associated malfuction results from physiological accumulation of irreparable damage to biomolecules as an unavoidable side effect of normal metabolism. More than a decade after the free radical theory of ovarian ageing, biological and clinical research supporting the involvement of oxidative injuries in follicle ageing is discussed. Looking for the aetiology of oxidative stress, we consider the effect of ageing on ovarian and follicular vascularization. Then, we propose a potential role of advanced glycation end-products known to be involved in the physiological ageing of most tissues and organs. We conclude that future investigation of age-related molecular damage in the different ovarian components will be imperative in order to evaluate the possibility to save or rescue the developmental potential of aged oocytes.

Advanced glycation and lipoxidation end products--amplifiers of inflammation: the role of food

BACKGROUND

High levels of glycated and lipoxidated proteins and peptides in the body are repeatedly associated with chronic diseases. These molecules are strongly associated with activation of a specific receptor called RAGE and a long-lasting exaggerated level of inflammation in the body.

METHODS

PubMed reports over 5000 papers plus >13,500 articles about the related HbA(1c), most of them published in the past 5 years. Most of the available abstracts have been read and approximately 800 full papers have been studied.

RESULTS

RAGE, a member of the immunoglobulin superfamily of cell surface molecules and receptor for advanced glycation end products, known since 1992, functions as a master switch, induces sustained activation of nuclear factor kappaB (NFkappaB), suppresses a series of endogenous autoregulatory functions, and converts long-lasting proinflammatory signals into sustained cellular dysfunction and disease. Its activation is associated with high levels of dysfunctioning proteins in body fluids and tissues, and is strongly associated with a series of diseases from allergy and Alzheimers to rheumatoid arthritis and urogenital disorders. Heat treatment, irradiation, and ionization of foods increase the content of dysfunctioning molecules.

CONCLUSIONS

More than half of the studies are performed in diabetes and chronic renal diseases; there are few studies in other diseases. Most of our knowledge is based on animal studies and in vitro studies. These effects are worth further exploration both experimentally and clinically. An avoidance of foods rich in deranged proteins and peptides, and the consumption of antioxidants, especially polyphenols, seem to counteract such a development.

Thiazolidinediones provide better renoprotection than insulin in an obese, hypertensive type II diabetic rat model

Hyperinsulinemia has been implicated in the development of diabetic nephropathy. In the present study we compared the renoprotective effects of the thiazolidinedione, pioglitazone (PGZ), to that of insulin in a hypertensive, obese, type II diabetic rat model. PGZ aggravated obesity and gave less glycemic control than insulin. However, renoprotection was markedly better with PZG compared to insulin as shown by lower proteinuria, improved renal function, and less histological evidence of diabetic glomerular and tubulointerstitial lesions. PZG and insulin both reduced renal accumulation of pentosidine and oxidative stress to a similar extent. In contrast, PGZ but not insulin suppressed enhanced transforming growth factor-beta (TGF-beta) expression. We further confirmed in cultured rat proximal tubular cells that insulin enhanced TGF-beta mRNA expression and protein production. Our results identify hyperinsulinemia and the attendant increase of TGF-beta expression as potential therapeutic targets in diabetes independent of glycemic control. This confirms prior clinical evidence that PZG provides renoprotection in obese, diabetic patients with nephropathy.

The role of the receptor for advanced glycation end-products in lung fibrosis

The pathogenesis of pulmonary fibrosis remains unclear. The receptor for advanced glycation end-products (RAGE) is a multi-ligand receptor known to be involved in the process of fibrotic change in several organs, such as peritoneal fibrosis and kidney fibrosis. The aim of this study was to examine the contribution of RAGE during the acute inflammation and chronic fibrotic phases of lung injury induced by intratracheal instillation of bleomycin in mice. Bleomycin-induced lung fibrosis was evaluated in wild-type and RAGE-deficient (RAGE-/-) mice. Bleomycin administration to wild-type mice caused an initial pneumonitis that evolved into fibrosis. While RAGE-/- mice developed a similar early inflammatory response, the mice were largely protected from the late fibrotic effects of bleomycin. The protection afforded by RAGE deficiency was accompanied by reduced pulmonary levels of the potent RAGE-inducible profibrotic cytokines transforming growth factor (TGF)-beta and PDGF. In addition, bleomycin administration induced high mobility group box 1 (HMGB-1) production, one of the ligands of RAGE, from inflammatory cells that accumulated within the air space. Coculture with HMGB-1 induced epithelial-mesenchymal transition (EMT) in alveolar type II epithelial cells from wild-type mice. However, alveolar type II epithelial cells derived from RAGE-/- mice did not respond to HMGB-1 treatment, such that the RAGE/HMGB-1 axis may play an important role in EMT. Also, bleomycin administration induced profibrotic cytokines TGF-beta and PDGF only in wild-type mouse lungs. Our results suggested that RAGE contributes to bleomycin-induced lung fibrosis through EMT and profibrotic cytokine production. Thus, RAGE may be a new therapeutic target for pulmonary fibrosis.