Advanced protein glycosylation induces transendothelial human monocyte chemotaxis and secretion of platelet-derived growth factor: role in vascular disease of diabetes and aging

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.

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.

The relationship of serum AGE levels in diabetic mothers with adverse fetal outcome

OBJECTIVE

To investigate changes in serum-advanced glycosylation end product (AGE) levels in gestation diabetic mothers (GDMs) and its relationship with adverse fetal outcome.

STUDY DESIGN

A total of 60 GDMs in mid-gestation and 72 late-gestation GDMs fulfilling the inclusion criteria were recruited. Seventy-two mid-gestation and 80 late-gestation mothers with no pregnancy complications acted as controls. Fasting blood glucose and serum AGE levels were analyzed in each group. Clinical data on these women and their perinatal outcomes were collected. Maternal serum AGE levels and changes in blood glucose between mid-gestation groups and late-gestation groups were compared. Factors, including AGE levels, affecting the prevalence of complications of fetal outcome in GDMs were investigated.

RESULT

Mid-gestation and late-gestation GDMs had significantly higher serum AGE levels and fasting blood glucose than their respective controls (P<0.001 and P<0.05, respectively). After treatment mid-gestation GDMs had significantly lower blood glucose levels at late gestation (P<0.05), but their serum AGE levels remained relatively high. There were no significant changes in serum AGE levels from mid- to late gestation. Women with GDM who had abnormal fetal outcomes had significantly higher maternal serum AGE levels than controls with normal fetal outcome (P<0.05). Particularly, those pregnancies that resulted in birth asphyxia, congenital malformations or stillbirth had higher serum AGEs (P<0.05). Logistic regression analysis showed elevated AGEs as a predictor of adverse perinatal outcome in GDMs, OR=6.285 (P<0.001, 95% CI 2.561 to 15.534).

CONCLUSION

High-serum AGE is an adverse factor in perinatal outcomes in GDMs. Sustained high AGE levels from mid- to late gestation could be an indicator of adverse perinatal outcomes.

Effects of hyperglycemia and ageing on the healing of colonic anastomoses in rats

INTRODUCTION: Despite the significant advances in the knowledge of the healing process, there is a limited number of studies demonstrating the relationships of this healing with ageing and elevated levels of glycemia. PURPOSE: To evaluate the effects of ageing and hyperglycemia on the healing of colonic anastomosis. METHODS: 138 young and old male rats were utilized. Some of them were normoglycemic and others had hyperglycemia induced by streptozocin (50mg/kg). They were maintained under control for 90 days. They were then submitted to a termino-terminal anastomosis in the left colon. On the third, seventh and fourteenth days after surgery, their resistance was evaluated and a histopathological study of the anastomosis was carried out. RESULTS: Gain in resistance was similar for both groups. The additive effect of age with hyperglycemia made a significant difference to the collagen I (p<0.001), III (p=0.022) and total (p<0.001). Among the old animals, the glycemia was a determining factor for the occurrence of a significant difference in total collagen (p=0.029) and collagen I (p=0.013). Among the normoglycemics, age determined a lower density of collagen I (p=0.002). CONCLUSION: There is delayed collagen synthesis and maturation of the scars of older animals, a situation that becomes more serious in older hyperglycemic animals, but insufficient to adversely affect the gain in resistance.

Erythropoietic stress and anemia in diabetes mellitus

Anemia is one of the world's most common preventable conditions, yet it is often overlooked, especially in people with diabetes mellitus. Diabetes-related chronic hyperglycemia can lead to a hypoxic environment in the renal interstitium, which results in impaired production of erythropoietin by the peritubular fibroblasts and subsequent anemia. Anemia in patients with diabetes mellitus might contribute to the pathogenesis and progression of cardiovascular disease and aggravate diabetic nephropathy and retinopathy. Anemia occurs earlier in patients with diabetic renal disease than in nondiabetic individuals with chronic kidney disease. Although erythropoietin has been used to treat renal anemia for nearly two decades, debate persists over the optimal target hemoglobin level. Most guidelines recommend that hemoglobin levels be maintained between 105g/l and 125g/l. The suggested role of anemia correction--to prevent the progression of left ventricular hypertrophy in patients with diabetes mellitus--is yet to be established. However, an emphasis on regular screening for anemia, alongside that for other diabetes-related complications, might help to delay the progression of vascular complications in these patients.

Proposed criteria for metabolic syndrome in Japanese based on prospective evidence: the Hisayama study

BACKGROUND AND PURPOSE

The current criteria of metabolic syndrome (MetS) are not based on evidence derived from prospective studies on cardiovascular disease (CVD).

METHODS

In a 14-year follow-up study of 2452 community-dwelling Japanese individuals aged >or=40 years, we examined which of the MetS criteria are most predictive for the development of CVD. During the follow-up, 246 first-ever CVD events occurred.

RESULTS

An optimal cutoff point of waist circumference for predicting CVD was 90 cm in men (age-adjusted hazard ratio=1.81; 95% CI, 1.19 to 2.74; P=0.005) and 80 cm in women (age-adjusted hazard ratio=1.46; 95% CI, 0.99 to 2.16; P=0.05). A comparison of MetS criteria showed that the modified Japanese criteria using this cutoff point instead of the original definition were the strongest predictor of CVD events in both sexes (men: age-adjusted hazard ratio=2.58; 95% CI, 1.65 to 4.02; P<0.001; women: age-adjusted hazard ratio=2.39; 95% CI, 1.65 to 3.48; P<0.001). These observations remained robust even after adjustment for other confounding factors. According to this criteria set, only in the presence of central obesity, the hazard ratios for future CVD increased significantly as the number of MetS components increased, and a significant relationship was identified from 2 or more MetS components compared with individuals who had no MetS component.

CONCLUSIONS

Our findings suggest that the optimal cutoff point of waist circumference is 90 cm in men and 80 cm in women and that the modified Japanese criteria of MetS with this cutoff point as an essential component better predict CVD in the general Japanese population.

Serum carboxymethyl-lysine, an advanced glycation end product, is associated with increased aortic pulse wave velocity in adults

BACKGROUND

The relationship between advanced glycation end products and arterial stiffness has previously been examined in highly selected groups of patients with diabetes or hypertension. Our aim was to determine whether elevated serum advanced glycation end products are associated with increased arterial stiffness in relatively healthy, community-dwelling adults.

METHODS

Aortic pulse wave velocity (PWV), an index of aortic stiffness, and serum advanced glycation end products (AGEs), as represented by the specific AGE, serum carboxymethyl-lysine (CML), were measured in 493 adults, aged 26-93 years, who participated in the Baltimore Longitudinal Study of Aging (BLSA).

RESULTS

Mean (s.d.) PWV (m/s) was 6.6 (1.8) m/s. Mean CML was 0.47 (0.13) microg/ml. Serum CML (per 1 s.d.) was associated with PWV (beta = 0.16, s.e. = 0.07, P = 0.02), adjusting for age, sex, body mass index, mean arterial pressure, fasting plasma glucose, high-density lipoprotein cholesterol, smoking, and other covariates. After excluding all diabetic patients, serum CML (per 1 s.d.) was associated with PWV (beta = 0.18, s.e. = 0.07, P = 0.009), adjusting for the same covariates.

CONCLUSIONS

Elevated AGEs are associated with increased arterial stiffness, a known predictor of adverse cardiovascular outcomes, among relatively healthy community-dwelling adults. Interventions to lower levels of AGEs, such as altering the pattern of dietary intake, warrant examination as putative novel strategies to lower arterial stiffness in adults.

Receptor for advanced glycation end-products (RAGE) modulates neutrophil adhesion and migration on glycoxidated extracellular matrix

AGEs (advanced glycation end-products) accumulate in collagen molecules during uraemia and diabetes, two diseases associated with high susceptibility to bacterial infection. Because neutrophils bind to collagen during their locomotion in extravascular tissue towards the infected area we investigated whether glycoxidation of collagen (AGE-collagen) alters neutrophil migration. Type I collagen extracted from rat tail tendons was used for in vitro glycoxidation (AGE-collagen). Neutrophils were obtained from peripheral blood of healthy adult volunteers and were used for the in vitro study of adhesion and migration on AGE- or control collagen. Glycoxidation of collagen increased adhesion of neutrophils to collagen surfaces. Neutrophil adhesion to AGE-collagen was inhibited by a rabbit anti-RAGE (receptor for AGEs) antibody and by PI3K (phosphoinositide 3-kinase) inhibitors. No effect was observed with ERK (extracellular-signal-regulated kinase) or p38 MAPK (mitogen-activated protein kinase) inhibitors. AGE-collagen was able to: (i) induce PI3K activation in neutrophils, and (ii) inhibit chemotaxis and chemokinesis of chemoattractant-stimulated neutrophils. Finally, we found that blocking RAGE with anti-RAGE antibodies or inhibiting PI3K with PI3K inhibitors restored fMLP (N-formylmethionyl-leucyl-phenylalanine)-induced neutrophil migration on AGE-collagen. These results show that RAGE and PI3K modulate adhesion and migration rate of neutrophils on AGE-collagen. Modulation of adhesiveness may account for the change in neutrophil migration rate on AGE-collagen. As neutrophils rely on their ability to move to perform their function as the first line of defence against bacterial invasion, glycoxidation of collagen may participate in the suppression of normal host defence in patients with diabetes and uraemia.

Structural alterations of the erythrocyte membrane proteins in diabetic retinopathy

BACKGROUND

Several rheological disorders of the erythrocytes, such as increased aggregation and decreased deformability, have been observed in diabetes mellitus and have been implicated in the development of diabetic microangiopathy. Structural alterations of the erythrocyte membrane proteins caused by the diabetic process may be at the origin of those observations. In the present study, we searched for erythrocyte membrane protein alterations in diabetic retinopathy.

METHODS

We examined peripheral blood samples from 40 type-2 diabetic patients with diabetic retinopathy of variable severity (19 males and 21 females, mean age 66.8 years, Group A) and we compared them with samples from 19 type-2 diabetic patients without diabetic retinopathy (13 males and six females, mean age 66.5 years, Group B) and 16 healthy volunteers (eight males and eight females, mean age 65.6 years, Group C). Erythrocyte membrane ghosts from all samples were subjected to SDS-PAGE, and the electrophoretic pattern of transmembrane and cytoskeletal proteins was analysed for each sample. The protein quantification of each electrophoretic band was accomplished through scanning densitometry.

RESULTS

No significant deviations from normal electrophoresis were observed in Groups B and C, apart from an increase in band 8 in two samples from Group B (11%). In contrast, in 14 samples from Group A (35%) we detected increases in protein band 8 and/or membrane-bound haemoglobin along with a decrease in spectrin. Moreover, increased mobility of band 3, an aberrant high molecular weight (MW) (> 255 kDa) band and a low MW (42 kDa) band were evident in ten samples from Group A (25%). Glycophorins were altered in 46% of Group-A patients versus 38% of Group-B patients. Females and patients with long duration of diabetes presented more electrophoretic abnormalities.

CONCLUSIONS

Structural alterations of the erythrocyte membrane proteins are shown for the first time in association with diabetic retinopathy. Their detection may serve as a blood marker for the development of diabetic microangiopathy. Further studies are needed to assess whether pharmaceutical intervention to the rheology of erythrocytes can prevent or alleviate microvascular diabetic complications.

Persistent perioperative hyperglycemia as an independent predictor of poor outcome after aneurysmal subarachnoid hemorrhage

OBJECT

The authors of previous studies have shown that admission hyperglycemia or perioperative hyperglycemic events may predispose a patient to poor outcome after aneurysmal subarachnoid hemorrhage (SAH). The results of experimental evidence have suggested that hyperglycemia may exacerbate ischemic central nervous system injury. It remains to be clarified whether a single hyperglycemic event or persistent hyperglycemia is predictive of poor outcome after aneurysmal SAH.

METHODS

Ninety-seven patients undergoing treatment for aneurysmal SAH were observed, and all perioperative variables were entered into a database of prospectively recorded data. Daily serum glucose values were retrospectively added. Patients were examined at hospital discharge (14-21 days after SAH onset), and Glasgow Outcome Scale (GOS) scores were prospectively documented. The GOS score at last follow-up was retrospectively determined. Serum glucose greater than 200 mg/dl for 2 or more consecutive days was defined as persistent hyperglycemia. Outcome was categorized as "poor" (dependent function [GOS Score 1-3]) or "good" (independent function [GOS Score 4 or 5]) at discharge. The independent association of 2-week and final follow-up outcome (GOS score) with the daily serum glucose levels was assessed using a multivariate analysis.

RESULTS

In the univariate analysis, increasing age, increasing Hunt and Hess grade, hypertension, ventriculomegaly on admission computed tomography scan, Caucasian race, and higher mean daily glucose levels were associated with poor (dependent) 2-week outcome after aneurysmal SAH. In the multivariate analysis, older age, the occurrence of symptomatic cerebral vasospasm, increasing admission Hunt and Hess grade, and persistent hyperglycemia were independent predictors of poor (dependent) outcome 2 weeks after aneurysmal SAH. Admission Hunt and Hess grade and persistent hyperglycemia were independent predictors of poor outcome at last follow-up examination a mean 10 +/- 3 months after aneurysmal SAH. Isolated hyperglycemic events did not predict poor outcome. Patients with persistent hyperglycemia were 10-fold more likely to have a poor (dependent) 2-week outcome and sevenfold more likely to have a poor outcome a mean 10 months after aneurysmal SAH independent of admission Hunt and Hess grade, occurrence of cerebral vasospasm, or all comorbidities.

CONCLUSIONS

Patients with persistent hyperglycemia were seven times more likely to have a poor outcome at a mean of 10 months after aneurysmal SAH. Isolated hyperglycemic events were not predictive of poor outcome. Serum glucose levels in the acute setting of aneurysmal SAH may help predict outcomes months after surgery.

In vitro glycation of brain aminophospholipids by acetoacetate and its inhibition by urea

Amino groups of amino acids, nucleic acids and lipids can react non-enzymatically with reducing sugars to form unstable Schiff bases that can then undergo the Amadori rearrangement to form irreversible advanced glycation end products (AGEs). Ketoacidosis is a life-threatening complication in patients with untreated diabetes mellitus and it is characterized by increased circulating ketone body concentrations. Recently, the in vitro glycation of hemoglobin by beta-hydroxybutyrate and acetone was described by our laboratory. This study was designed to evaluate the in vitro effect of acetoacetate on brain aminophospholipids at similar concentrations to that observed in ketoacidosis (16.13 mM total ketone bodies). The effect of acetoacetate was compared to that of glucose and the other ketone bodies; beta-hydroxybutyrate and acetone. The antiglycating activity of urea and glycylglycine was also investigated. The incubation of aminophospholipids with acetoacetate results in the formation of a new compound with an absorption peak at 280 nm. When this reaction product was analyzed by thin layer chromatography using an elusion system of methanol:chloroform:acetic acid:water (8:1:1:0.4), the R(f) value obtained (0.24-0.26) was similar to that of the compound formed by aminophospholipids with glucose. In contrast, this reaction product was not detected in those samples containing beta-hydroxybutyrate and acetone. The formation of this new compound was inhibited by urea more effectively than glycylglycine. In conclusion, this study provides the evidence that brain aminophospholipids react with acetoacetate forming AGEs and that this glycating effect of acetoacetate was remarkably decreased by urea, suggesting a protective physiological role for urea in the body as it was previously stated. Finally, this information adds knowledge about the contribution of ketoacidosis in the pathophysiology of diabetic complications, especially in type 1 diabetic patients.

Oxidative stress and increased eNOS and NADPH oxidase expression in mouse microvessel endothelial cells

Elevated oxidative stress plays a key role in diabetes-associated vascular disease. In this study, we tested the hypothesis that high glucose-induced oxidative stress was associated with changes in the expression of NADPH oxidase, superoxide dismutase (SOD) and endothelial nitric oxide synthase (eNOS). Oxidative stress was assessed in cell cultures of mouse microvessel endothelial cells (MMECs) by fluorescence labelling with dihydroethidium, lucigenin-enhanced chemiluminescence and determining NADPH oxidase subunit and eNOS expression with real-time polymerase chain reaction protocol and Western blotting. Oxidative stress and expression of the NADPH oxidase subunit, p22phox, were both increased, SOD1 and 3 expression lowered and eNOS significantly elevated in MMECs treated with 40 mM glucose for 72 h compared to low glucose medium. Oxidative stress, p22phox mRNA, eNOS mRNA, and protein were lowered by concurrent incubation with sepiapterin. When eNOS protein expression in endothelial cells was significantly decreased by eNOS siRNA treatment, superoxide generation was significantly higher in the MMECs grown in low glucose, but reduced in those grown in high glucose for 72 h. Thus, exposure of MMECs to high glucose results in increased oxidative stress that is associated with increased eNOS and NADPH oxidase subunit expression, notably p22phox, and decreased expression of SOD1 and 3.

Receptor for advanced glycation endproducts and atherosclerosis: From basic mechanisms to clinical implications

The receptor for advanced glycation endproducts (RAGE) is a member of the immunoglobulin superfamily of cell-surface molecules with a diverse repertoire of ligands. In the atherosclerotic milieu, three classes of RAGE ligands, i.e., products of non-enzymatic glycoxidation, S100 proteins and amphoterin, appear to drive receptor-mediated cellular activation and potentially, acceleration of vascular disease. The interaction of RAGE-ligands effectively modulates several steps of atherogenesis, triggering an inflammatory-proliferative process and furthermore, critically contributing to propagation of vascular perturbation, mainly in diabetes. RAGE has a circulating truncated variant isoform, soluble RAGE (sRAGE), corresponding to its extracellular domain only. By competing with cell-surface RAGE for ligand binding, sRAGE may contribute to the removal/neutralization of circulating ligands thus functioning as a decoy. The critical role of RAGE in the chronic vascular inflammation processes highlights this receptor-ligand axis as a possible and attractive candidate for therapeutic intervention to limit vascular damage and its associated clinical disorders.

Phosphorylation of pleckstrin increases proinflammatory cytokine secretion by mononuclear phagocytes in diabetes mellitus

The protein kinase C (PKC) family of intracellular enzymes plays a crucial role in signal transduction for a variety of cellular responses of mononuclear phagocytes including phagocytosis, oxidative burst, and secretion. Alterations in the activation pathways of PKC in a variety of cell types have been implicated in the pathogenesis of the complications of diabetes. In this study, we investigated the consequences of PKC activation by evaluating endogenous phosphorylation of PKC substrates with a phosphospecific PKC substrate Ab (pPKC(s)). Phosphorylation of a 40-kDa protein was significantly increased in mononuclear phagocytes from diabetics. Phosphorylation of this protein is downstream of PKC activation and its phosphorylated form was found to be associated with the membrane. Mass spectrometry analysis, immunoprecipitation, and immunoblotting experiments revealed that this 40-kDa protein is pleckstrin. We then investigated the phosphorylation and translocation of pleckstrin in response to the activation of receptor for advanced glycation end products (RAGE). The results suggest that pleckstrin is involved in RAGE signaling and advanced glycation end product (AGE)-elicited mononuclear phagocyte dysfunction. Suppression of pleckstrin expression with RNA interference silencing revealed that phosphorylation of pleckstrin is an important intermediate in the secretion and activation pathways of proinflammatory cytokines (TNF-alpha and IL-1beta) induced by RAGE activation. In summary, this study demonstrates that phosphorylation of pleckstrin is up-regulated in diabetic mononuclear phagocytes. The phosphorylation is in part due to the activation of PKC through RAGE binding, and pleckstrin is a critical molecule for proinflammatory cytokine secretion in response to elevated AGE in diabetes.

The dual face of endogenous alpha-aminoketones: pro-oxidizing metabolic weapons

Amino metabolites with potential prooxidant properties, particularly alpha-aminocarbonyls, are the focus of this review. Among them we emphasize 5-aminolevulinic acid (a heme precursor formed from succinyl-CoA and glycine), aminoacetone (a threonine and glycine metabolite), and hexosamines and hexosimines, formed by Schiff condensation of hexoses with basic amino acid residues of proteins. All these metabolites were shown, in vitro, to undergo enolization and subsequent aerobic oxidation, yielding oxyradicals and highly cyto- and genotoxic alpha-oxoaldehydes. Their metabolic roles in health and disease are examined here and compared in humans and experimental animals, including rats, quail, and octopus. In the past two decades, we have concentrated on two endogenous alpha-aminoketones: (i) 5-aminolevulinic acid (ALA), accumulated in acquired (e.g., lead poisoning) and inborn (e.g., intermittent acute porphyria) porphyric disorders, and (ii) aminoacetone (AA), putatively overproduced in diabetes mellitus and cri-du-chat syndrome. ALA and AA have been implicated as contributing sources of oxyradicals and oxidative stress in these diseases. The end product of ALA oxidation, 4,5-dioxovaleric acid (DOVA), is able to alkylate DNA guanine moieties, promote protein cross-linking, and damage GABAergic receptors of rat brain synaptosome preparations. In turn, methylglyoxal (MG), the end product of AA oxidation, is also highly cytotoxic and able to release iron from ferritin and copper from ceruloplasmin, and to aggregate proteins. This review covers chemical and biochemical aspects of these alpha-aminoketones and their putative roles in the oxidative stress associated with porphyrias, tyrosinosis, diabetes, and cri-du-chat. In addition, we comment briefly on a side prooxidant behaviour of hexosamines, that are known to constitute building blocks of several glycoproteins and to be involved in Schiff base-mediated enzymatic reactions.

Increased oxidative stress in the streptozotocin-induced diabetic apoE-deficient mouse: Changes in expression of NADPH oxidase subunits and eNOS

Elevated oxidative stress plays a key role in the development of atherosclerosis and endothelial dysfunction in diabetes-associated vascular disease. Glucose-induced changes in the activity of NADPH oxidase and endothelial nitric oxide synthase (eNOS) may result in vascular endothelial cell dysfunction via dysregulation of eNOS and/or changes in the expression of the subunits of NADPH oxidase. In this study, we have investigated whether changes in the expression of the subunits of NADPH oxidase, or eNOS mRNA, can be associated with oxidative stress in the streptozotocin-induced type 1 diabetic apolipoprotein E-deficient (apoE(-/-)) diabetic mouse. Oxidative stress was assessed in aorta and mesenteric arteries by immunofluorescence labelling with dihydroethidium and levels of NADPH oxidase subunits and eNOS were determined by a real-time polymerase chain reaction protocol. Blood glucose levels and oxidative stress were significantly increased following 4, 8 and 16 weeks after treatment with streptozotocin in both streptozotocin-apoE(-/-) aorta and mesenteric arteries compared to the time- and age-matched vehicle (citrate buffer)-treated non-diabetic apoE(-/-). In the mesenteric arteries the expression of nox4 (4 weeks) and gp91phox (nox2) (8 weeks) subunits of NADPH oxidase from streptozotocin-apoE(-/-) were enhanced as were eNOS mRNA and protein (P<0.05). However, only eNOS mRNA and protein remained increased at 16 weeks. These data indicate that increased oxidative stress in the vasculature of streptozotocin-apoE(-/-) mice is linked to changes in eNOS, superoxide dismutase (SOD) and NADPH oxidase expression.

Role of insulin resistance and hyperglycemia in the development of atherosclerosis

Insulin resistance (IR) is the underlying defect in >90% of patients with type 2 diabetes mellitus and the major pathologic mechanism for the associated susceptibility to premature cardiovascular disease (CVD). The progression of IR to diabetes parallels the progression of endothelial dysfunction to atherosclerosis. The downregulation of the antiatherogenic phosphatidylinositol-3-kinase-mediated insulin receptor-signaling pathway, and maintained activity of the proatherogenic mitogenic-activated protein kinase pathway in insulin-resistant states, leads to accelerated atherosclerosis. Efforts to prevent or slow the epidemic of atherothrombotic CVD must focus on the reversal of the disturbances in glucose and lipid homeostasis through the amelioration of IR.

Genes, ageing and longevity in humans: problems, advantages and perspectives

Many epidemiological data indicate the presence of a strong familial component of longevity that is largely determined by genetics, and a number of possible associations between longevity and allelic variants of genes have been described. A breakthrough strategy to get insight into the genetics of longevity is the study of centenarians, the best example of successful ageing. We review the main results regarding nuclear genes as well as the mitochondrial genome, focusing on the investigations performed on Italian centenarians, compared to those from other countries. These studies produced interesting results on many putative "longevity genes". Nevertheless, many discrepancies are reported, likely due to the population-specific interactions between gene pools and environment. New approaches, including large-scale studies using high-throughput techniques, are urgently needed to overcome the limits of traditional association studies performed on a limited number of polymorphisms in order to make substantial progress to disentangle the genetics of a trait as complex as human longevity.

Immunohistochemical localization of advanced glycation end-products (AGEs) and their receptor (RAGE) in polycystic and normal ovaries

The aim of the present study was to investigate the localization/immunohistochemical distribution of AGEs and RAGE, as well as their putative signalling mediator NF-kappaB in ovaries of women with polycystic ovary syndrome (PCOS) compared to normal. Archival ovarian-tissue samples from biopsies of six women with PCOS and from six healthy of similar age women, were examined immunohistochemically with monoclonal anti-AGEs, anti-RAGE and anti-NF-kappaB(p50/p65) specific antibodies. In healthy women, AGE immunoreactivity was observed in follicular cell layers (granulosa and theca) and luteinized cells, but not in endothelial cells. PCOS specimens displayed AGE immunoexpression in theca interna and granulosa cells as well as in endothelial cells, but staining of granulosa cells was stronger than in that of normal ovaries. RAGE was highly expressed in normal and PCOS tissues. Normal tissue exhibited no staining differences between granulosa cell layer and theca interna. However, in PCOS ovaries, granulosa cells displayed stronger RAGE expression compared to theca interna cells in comparison to controls. NF-kappaB(p50/p65) was expressed in the cytoplasm of theca interna and granulosa cells of both normal and PCOS ovaries; whereas the NF-kappaB p65 subunit was only observed in granulosa cells nuclei in PCOS tissue. In conclusion, these findings demonstrate for the first time that RAGE and AGE-modified proteins with activated NF-kappaB are expressed in human ovarian tissue. Furthermore, a differential qualitative distribution of AGE, RAGE and NF-kappaB p65 subunit was observed in women with PCOS compared to healthy controls, where a stronger localization of both AGE and RAGE was observed in the granulosa cell layer of PCOS ovaries.

Circulating oxidised low-density lipoprotein and intercellular adhesion molecule-1 and risk of type 2 diabetes mellitus: the Atherosclerosis Risk in Communities Study

AIMS/HYPOTHESIS

To evaluate the role of oxidative stress and inflammation in the aetiology of type 2 diabetes, we examined the association of oxidised LDL (ox-LDL) and soluble intercellular adhesion molecule-1 (sICAM-1) levels with type 2 diabetes incidence over 9 years in the Atherosclerosis Risk in Communities Study.

MATERIALS AND METHODS

In a large, prospective, case-cohort design, ox-LDL and sICAM-1 were measured in stored plasma samples collected at baseline in stratified samples of 581 diabetes cases and 572 non-cases selected from 10,275 middle-aged men and women without prevalent diabetes at baseline.

RESULTS

Compared with non-cases, diabetes cases had significantly higher mean baseline levels of ox-LDL and sICAM-1. Elevated ox-LDL and sICAM-1 were both associated with increased risk of incident diabetes after adjustment for age, sex, race and centre, with hazard ratios for the highest vs lowest tertiles of 1.68 (95% CI 1.25-2.24) and 1.91 (95% CI 1.45-2.50), respectively. After additional adjustment for fasting glucose, waist circumference, HDL-cholesterol, triacylglycerol, hypertension and C-reactive protein, only sICAM-1 remained an independent predictor of incident diabetes (hazard ratio 1.50; 95% CI 1.02-2.23).

CONCLUSIONS/INTERPRETATION

In this community-based cohort of middle-aged US adults, elevated plasma ox-LDL and sICAM-1 levels were associated with increased risk of type 2 diabetes. Measurement of ICAM-1 or ox-LDL, or other measures related to inflammation or oxidative stress, may be helpful in identifying those patient populations in which to test whether novel therapies that inhibit specific pathways related to inflammation or oxidative stress are beneficial in the prevention of diabetes in humans.

Effects of valsartan therapy on protein glycoxidation

Several lines of evidence suggest that both advanced glycation end products (AGEs) and oxidation processes play key roles in the physiology of aging and age-related pathologies, leading to irreversible proteins modifications in both tissues and the extracellular matrix. Such an accelerated accumulation of these modifications has been reported to be present in several age-related chronic diseases, such as atherosclerosis, diabetes, arthritis, and neurodegenerative diseases. The current literature reveals that the specific inhibition of AGEs may constitute an innovative therapeutic goal. In experimental animals, the use of sartans significantly reduces blood pressure and kidney pentosidine content, improving both histologic renal damage and proteinuria. In this study, 12 subjects who were affected by diabetes mellitus and hypertension were subjected to oral antihypertensive therapy with valsartan (class of sartans) with timed sampling of plasma and urine pentosidine, N(epsilon)-(carboxymethyl)lysine (CML), malondialdehyde, and isoprostanes levels, respectively, at baseline and after both 3 and 6 months, with parallel ongoing evaluation of glycemic control and blood pressure levels. Valsartan elicited a good antihypertensive effect with a 30% decrease in plasma pentosidine levels (P < .05) after 3 months of therapy, followed by a slight increase after 6 months. Urinary pentosidine concentrations exhibited a 40% decrease after 3 months (215 +/- 19 vs 129 +/- 23 nmol/24 h) and a further significant reduction after 6 months of therapy (105 +/- 24 nmol/24 h). Plasma CML levels showed a progressive decrease after 3 months (23.15 +/- 3.215 vs 19.88 +/- 1.684 micromol/mL) and achieved a further slight reduction after 6 months of therapy (19.48 +/- 1.339 micromol/mL); for urinary CML, a statistically significant reduction was gained after the sixth month of therapy (48.51 +/- 5.70 vs 30.30 +/- 2.77 micromol/24 h after 3 months and 27.02 +/- 4.13 micromol/24 h after 6 months; F = 7.62, P < .005). Plasma and urinary concentrations of malondialdehyde were slightly modified by valsartan treatment; the mean levels after both 3 and 6 months did not significantly differ from baseline. Urinary 15-F2t-isoprostanes (2.96 +/- 0.45 ng/24 h) levels displayed a progressive decrease after both 3 (2.27 +/- 0.31 ng/24 h) and 6 months (1.70 +/- 0.23 ng/24 h) with statistical significance achieved only at the end of the study (P < .05). The present data suggest interesting in vivo antiglycation and antioxidation effects of this angiotensin II receptor antagonist with reductions in plasma and urinary pentosidine, plasma CML, and urinary isoprostanes levels. The present study supports an antagonistic role of valsartan in the production of AGEs precursors through the chelation of transition metals and an antioxidant activity that scavenges reactive oxygen species. This property of valsartan may broaden the scope of newly developed pharmacologic inhibitors of advanced glycoxidation.

Activation of RAGE induces elevated O2- generation by mononuclear phagocytes in diabetes

Oxidative stress has been found to play a role in the pathogenesis of diabetic complications. The aim of this study was to define the oxidative burst of diabetic monocytes to characterize the phenotype associated with poor diabetic control. Superoxide (O(2)(-)) is the first molecule generated during the respiratory burst of phagocytes by NADPH oxidase, and its generation by monocytes from 26 controls and 34 diabetic subjects was evaluated in this study. Under resting states or stimulation by PMA or opsonized zymosan, diabetic monocytes produce significantly more O(2)(-) than nondiabetic cells. The increased O(2)(-) generation was found to be correlated with glycemic control (glycated hemoglobin) of patients. To clarify the effects of hyperglycemia on O(2)(-) generation, normal human monocytes were treated with receptor for advanced glycation endproducts (RAGE) ligands (AGE protein and S100B) or high glucose media before stimulation. RAGE ligands and high glucose concentration increased O(2)(-) generation from human mononuclear phagocytes. RAGE ligands, specifically and potently, increased O(2)(-) generation from mononuclear phagocytes, and high-glucose effects were associated with correspondingly increased osmotic pressure. Differentiated THP-1 cells, from a human monocytic cell line, were used as a model of human monocytes to study the effects of S100B, the RAGE ligand. It was confirmed that RAGE is involved in the priming of O(2)(-) generation by S100B. This study demonstrates that RAGE ligands can contribute significantly to the hyper-responsive phenotype of diabetic monocytes, which might be reversible by blocking the RAGE or controlling the presence of RAGE ligands by controlling hyperglycemia.

Interferon-gamma-inducible protein (IP)-10 mRNA stabilized by RNA-binding proteins in monocytes treated with S100b

Chemokines mediate the recruitment and activation of blood monocyte/macrophages and lymphocytes to sites of inflammation. Expression of the chemokine IP-10 (interferon-gamma-inducible protein) has been documented in several inflammatory and autoimmune disorders including type 1 diabetes. However, the mechanism of its expression in monocytes or its functional role in diabetes is not known. Advanced glycation end products acting via their receptor, RAGE, play major roles in diabetic complications. In this study, we observed for the first time that S100b, an inflammatory protein as well as a specific RAGE ligand, significantly increased IP-10 mRNA and protein levels in THP-1 monocytes as well as peripheral blood monocytes. Promoter luciferase assays showed that IP-10 mRNA accumulation by S100b was not via increased transcription. On the other hand, S100b significantly increased IP-10 mRNA half-life and stability. This appeared to be mediated by S100b-induced binding of specific RNA-binding protein(s) to a 3'-untranslated region-responsive region of the IP-10 mRNA. Our results demonstrate for the first time that diabetic stimuli such as RAGE ligands can induce inflammatory gene expression in monocytes via increased message stability.

Hyperglycemia independently increases the risk of perioperative stroke, myocardial infarction, and death after carotid endarterectomy

OBJECTIVE

Clinical and experimental evidence suggests that hyperglycemia lowers the neuronal ischemic threshold, potentiates stroke volume in focal ischemia, and is associated with morbidity and mortality in the surgical critical care setting. It remains unknown whether hyperglycemia during carotid endarterectomy (CEA) predisposes patients to perioperative stroke and operative related morbidity and mortality.

METHODS

The clinical and radiological records of all patients undergoing CEA and operative day glucose measurement from 1994 to 2004 at an academic institution were reviewed and 30-day outcomes were assessed. The independent association of operative day glucose before CEA and perioperative morbidity and mortality were assessed via multivariate logistic regression analysis.

RESULTS

One thousand two hundred and one patients with a mean age of 72 +/- 10 years (748 men, 453 women) underwent CEA (676 asymptomatic, 525 symptomatic). Overall, stroke occurred in 46 (3.8%) patients, transient ischemic attack occurred in 19 (1.6%), myocardial infarction occurred in 19 (1.6%), and death occurred in 17 (1.4%). Increasing operative day glucose was independently associated with perioperative stroke or transient ischemic attack (Odds ratio [OR], 1.005; 95% confidence interval [CI], 1.00-1.01; P = 0.03), myocardial infarction (OR, 1.01; 95% CI, 1.004-1.016; P = 0.017), and death (OR, 1.007; 95% CI, 1.00-1.015; P = 0.04). Patients with operative day glucose greater than 200 mg/dl were 2.8-fold, 4.3-fold, and 3.3-fold more likely to experience perioperative stroke or transient ischemic attack (OR, 2.78; 95% CI, 1.37-5.67; P = 0.005), myocardial infarction (OR, 4.29; 95% CI, 1.28-14.4; P = 0.018), or death (OR, 3.29; 95% CI, 1.07-10.1; P = 0.037), respectively. Median and interquartile range length of hospitalization was greater for patients with operative day glucose greater than 200 mg/dl (4 d [interquartile range, 2-15 d] versus 3 d [interquartile range, 2-7 d]; P < 0.05).

CONCLUSION

Independent of previous cardiac disease, diabetes, or other comorbidities, hyperglycemia at the time of CEA was associated with an increased risk of perioperative stroke or transient ischemic attack, myocardial infarction, and death. Strict glucose control should be attempted before surgery to minimize the risk of morbidity and mortality after CEA.

The expression of apolipoprotein B epitopes is normal in LDL of diabetic and end-stage renal disease patients

AIMS/HYPOTHESIS

When LDLs are exposed to glucose in vitro, glycation of apolipoprotein B100 (apoB) leads to a loss in its affinity for the LDL receptor and reproducible alterations in the immunoreactivity of specific apoB epitopes, including several epitopes close to the LDL receptor binding site. The aim of this work was to determine if similar immunological changes are observed in vivo in LDLs of diabetic and end-stage renal disease (ESRD) patients.

SUBJECTS, MATERIALS AND METHODS

The immunoreactivity of LDLs isolated from 14 diabetic patients with normal renal function and 13 patients with ESRD was studied with a panel of 25 well-characterised anti-apoB monoclonal antibodies.

RESULTS

Although diabetic and ESRD LDLs showed evidence of glycation modification, none of the changes in the apoB immunoreactivity induced by glucose in vitro was observed in vivo, including those for epitopes close to the LDL receptor binding domain.

CONCLUSIONS/INTERPRETATION

These results suggest that in vivo glycation of LDLs is a complex process that is not mimicked by in vitro exposure of LDLs to high concentrations of glucose. This questions the clinical significance of the in vitro glycation studies used to understand the pathophysiological consequences of LDL glycation in diabetes and ESRD.

Insulin resistance and atherosclerosis

The epidemic of obesity in the developed world over the last two decades is driving a large increase in type 2 diabetes and consequentially setting the scene for an impending wave of cardiovascular morbidity and mortality. It is only now being recognized that the major antecedent of type 2 diabetes, insulin resistance with its attendant syndrome, is the major underlying cause of the susceptibility to type 2 diabetes and cardiovascular disease. In metabolic tissues, insulin signaling via the phosphatidylinositol-3-kinase pathway leads to glucose uptake so that in insulin resistance a state of hyperglycemia occurs; other factors such as dyslipidemia and hypertension also arise. In cardiovascular tissues there are two pathways of insulin receptor signaling, one that is predominant in metabolic tissues (mediated by phosphatidylinositol-3-kinase) and another being a growth factor-like pathway (mediated by MAPK); the down-regulation of the former and continued activity of the latter pathway leads to atherosclerosis. This review addresses the metabolic consequences of the insulin resistance syndrome, its relationship with atherosclerosis, and the impact of insulin resistance on processes of atherosclerosis including insulin signaling in cells of the vasculature.

Glycated albumin and cross-linking of CD44 induce scavenger receptor expression and uptake of oxidized LDL in human monocytes

Functional role of CD44, a principal receptor of hyaluronan, and glycated albumin for differentiation of resting human monocytes isolated by counterflow centrifugal elutriation was investigated. Flow cytometric analysis revealed that amadori-modified glycated albumin induced expression of CD44 as well as macrophage scavenger receptors (MSRs) such as CD36 and CD68 on resting monocytes. Crosslinking of CD44 on monocytes also induced MSR expression. Furthermore, CD44 crosslinking and/or glycated albumin enhanced the uptake of oxidized-low density lipoprotein in monocytes and foam cell formation. Taken together, engagement of CD44 (e.g., hyaluronan) and glycated albumin induced the differentiation of resting monocytes into foam macrophages through the induction of MSRs, implying that CD44 could be involved in atherosclerotic lesions of those such as diabetic patients.

ε-Glycation, APP and Aβ in ageing and Alzheimer disease: A hypothesis

The post-translational modifications of protein molecules include glycation, which may not only occur enzymatically controlled in N and O position, but also wherever proteins meet reducing sugars non-enzymatically in epsilon position at lysines (non-enzymatic (epsilon) glycation (NEG)). The formation of keto-amines from the amine-sugar compounds (Amadori re-arrangement) and further processing of the largely undigestible Amadori compounds eventually results in insoluble advanced glycation end products (AGEs). The latter can induce or favour disease including mental disorders. Preferential targets of NEG include large cell surface proteins. Ample evidence has been provided that NEG also occurs in the brain where cross-linking of epsilon-glycated proteins, induction of oxidative stress and signalling of AGEs through their specific receptor (RAGE) likely play a role in (brain) ageing and Alzheimer disease (AD). This is underscored by the demonstration of particular interactions between AGE/RAGE and amyloid-beta (Abeta) that favour the aggregation and deposition of Abeta and, perhaps, the formation of Abeta itself. The close relationship between NEG and Abeta, as well as other facts foster the hypothesis that NEG of the large trans-membrane amyloid precursor protein (APP) might be a significant factor in the induction of aberrant APP cleavage with production of Abeta, not only in normal ageing, but also in AD. Blockade of lysine cleavage sites on APP by sugar chains or marker effects induced by NEG akin to ubiquitination of proteins for degradation at lysines could be expected to contribute to altered processing of APP. The hypothesis of epsilon-glycation in APP proposed here and the review of evidences for the significance of NEG in brain ageing and AD are aimed at the stimulation of investigations into the still open question which role NEG plays with respect to APP and its abnormal processing in AD. It can be rendered likely that such research might open new avenues towards decreasing the risk of AD and/or slowing its progression through the prevention of NEG in APP with aberrant APP processing, increased generation of Abeta and the formation of AGEs from epsilon-glycated APP.

Diabetes mellitus-associated atherosclerosis: mechanisms involved and potential for pharmacological invention

While diabetes mellitus is most often associated with hypertension, dyslipidemia, and obesity, these factors do not fully account for the increased burden of cardiovascular disease in patients with the disease. This strengthens the need for comprehensive studies investigating the underlying mechanisms mediating diabetic cardiovascular disease and, more specifically, diabetes-associated atherosclerosis. In addition to the recognized metabolic abnormalities associated with diabetes mellitus, upregulation of putative pathological pathways such as advanced glycation end products, the renin-angiotensin system, oxidative stress, and increased expression of growth factors and cytokines have been shown to play a causal role in atherosclerotic plaque formation and may explain the increased risk of macrovascular complications. This review discusses the methods used to assess the development of atherosclerosis in the clinic as well as addressing novel biomarkers of atherosclerosis, such as low-density lipoprotein receptor-1. Experimental models of diabetes-associated atherosclerosis are discussed, such as the streptozocin-induced diabetic apolipoprotein E knockout mouse. Results of major clinical trials with inhibitors of putative atherosclerotic pathways are presented. Other topics covered include the role of HMG-CoA reductase inhibitors and fibric acid derivatives with respect to their lipid-altering ability, as well as their emerging pleiotropic anti-atherogenic actions; the effect of inhibiting the renin-angiotensin system by either ACE inhibition or angiotensin II receptor antagonism; the effect of glycemic control and, in particular, the promising role of thiazolidinediones with respect to their direct anti-atherogenic actions; and newly emerging mediators of diabetes-associated atherosclerosis, such as advanced glycation end products, vascular endothelial growth factor and platelet-derived growth factor. Overall, this review aims to highlight the observation that various pathways, both independently and in concert, appear to contribute toward the pathology of diabetes-associated atherosclerosis. Furthermore, it reflects the need for combination therapy to combat this disease.

Advanced glycation end products in intervertebral discs and hip joint capsules: correlation with senile amyloid?

Advanced glycation end-products (AGEs) may be involved in either amyloidogenesis or complications related to amyloid. The incidence of AGE increases with age as does the prevalence of amyloid affecting the hip joint capsule and intervertebral discs. We hypothesized that AGEs may be involved in the pathology of these amyloidoses and investigated the spatial and temporal relationship between AGEs and amyloid of intervertebral discs and hip joint capsules. Using immunohistochemistry, AGEs were found in all 71 intervertebral discs and all 87 hip joint capsules. Amyloid was present in 59 (83%) intervertebral discs and 65 (75%) hip joint capsules. AGEs were found in the immediate vicinity of amyloid deposits in 104 of 253 (41%) investigated amyloid deposits of the intervertebral discs and 159 of 311 (51%) investigated amyloid deposits of the hip joint capsules. However, only rarely were AGEs demonstrated within amyloid deposits. No linear correlation was found between the amount of AGEs and the amount of amyloid deposited. As AGEs are more common than amyloid in intervertebral discs and hip joint capsules, it is conceivable to suggest that AGEs might be involved in the pathogenesis of amyloid at these anatomical sites. However, the amyloid proteins appear not to be modified and AGE modification is not a general characteristic of senile amyloidoses.

Accumulation of advanced glycation end products in women with preeclampsia: possible involvement of placental oxidative and nitrative stress

Advanced glycation end products (AGEs) are known to cause oxidative damage in various cells by binding with its receptor, RAGE. We measured the serum level of AGEs and examined the AGEs, RAGE, and the other biomarkers of oxidative stress in the placentas from preeclamptic women. Competitive ELISA was carried out to measure the AGEs in serum. Western blotting was performed to analyze AGEs and RAGE in the placenta. Immunohistochemical analyses were performed to examine the localization of AGEs, RAGE, and other biomarkers of oxidative stress in the placenta. The mean level of serum AGEs in preeclamptic women was significantly higher than that in healthy non-pregnant women or healthy pregnant women. Western blotting revealed that the level of AGEs or RAGE in preeclamptic placenta was significantly higher than that in normal placenta. Immunohistochemical analyses showed that levels of nitrotyrosine and nitroguanosine, which are formed by reactive nitrogen species, in preeclamptic placenta were higher than those in normal placenta. Accumulation of 4-hydroxy-2-nonenal and 8-hydroxy-2'-deoxyguanosine indicated enhanced oxidative modifications of lipids and DNA in preeclamptic placenta. The AGE-RAGE system, which is upregulated in preeclampsia, is likely to be involved in the oxidative stress of preeclampsia.

Mechanisms for the induction of HNE- MDA- and AGE-adducts, RAGE and VEGF in retinal pigment epithelial cells

Pathological features of age-related macular degeneration such as the formation of extracellular deposits and neovascularization are frequently viewed as outcomes of compromising processes within retinal pigment epithelial cells, but the initiating circumstances are poorly understood. Here we tested the hypothesis that photooxidation events initiated by A2E, a blue light-excitable aging fluorophore of the retinal pigment epithelium, can set the stage for altered cellular signaling and changes in the expression of genes that can impact the extracellular milieu. Proteins modified by lipid peroxidation products (4-hydroxynonenal; malondialdhyde) and advanced glycation end products were detected at sites of blue light irradiation both in association with the cultured A2E-laden retinal pigment epithelial cells and within the fibronectin substrate on which the cells were grown. RAGE, the cell surface receptor that transduces the effects of advanced glycation end products, was also upregulated, and RAGE expression co-localized with the deposition of advanced glycation end products. Blue light triggered alterations in gene expression was also evidenced by elevations in both transcripts and protein for vascular endothelial growth factor, a potent angiogenic and permeability-enhancing factor. These findings indicate that cell associated and extracellular modification of proteins by lipid peroxidation products and advanced glycation end products together with increased expression of RAGE and vascular endothelial growth factor may be induced consequent to blue light illumination of A2E-burdened retinal pigment epithelial cells. Thus, photooxidative events that are not an immediate threat to retinal pigment epithelial cell viability may nevertheless elicit sustained perturbation that could ultimately alter neighboring tissues and impact retinal pigment epithelial cell function.

Increase in the Deposition of Aggregated Protein in the Glomeruli of Spontaneously Diabetic Mice

The aim of this study was to investigate the disposal of aggregated protein in the glomeruli of spontaneously diabetic mice. Diabetic mice, KK-A(y) and db/db, and age-matched ICR mice were injected intravenously with aggregated bovine serum albumin (a-BSA) at 0.6 mg/g, and the glomeruli and the blood were obtained. Diabetic mice had larger amounts of a-BSA in their glomeruli than the ICR mice, threefold in KK-A(y) and twofold in db/db, at 3 h after the a-BSA injection. Additionally, the disappearance of a-BSA was retarded in the diabetic glomeruli. KK-A(y) displayed a-BSA in the glomeruli 24 h after the a-BSA injection and db/db did after 12 h, while the ICR did by 8 h. In spite of increases of insulin to similar degrees in both strains of diabetic mice after the a-BSA injection, blood glucose levels markedly decreased in KK-A(y) compared with db/db. There were no histopathological alterations in the glomeruli of the diabetic mice. Depositions of a-BSA were confirmed to be higher in the diabetic glomeruli by the immunofluorescence technique, and KK-A(y) displayed higher depositions of a-BSA than did db/db. The present study suggests that hyperglycemia is involved in the increased deposition of aggregated protein in the glomeruli and that the degradation of aggregated protein is retarded in diabetic glomeruli.

Insulin, C-Peptide, and Restenosis after Femoral Artery Balloon Angioplasty in Type II Diabetic and Nondiabetic Patients

PURPOSE

Endogenous and exogenous insulin is suggested to stimulate hypertrophic wound-healing responses and therefore may promote neointimal hyperplasia and restenosis after balloon angioplasty. The ratio of C-peptide to insulin reflects endogenous insulin secretion. In diabetic patients with insulin substitution, lower ratios display a higher proportion of exogenous insulin. The association and interaction of insulin and C-peptide with restenosis after percutaneous transluminal angioplasty (PTA) was investigated in type II diabetic and nondiabetic patients.

MATERIALS AND METHODS

The study group included 76 patients (median age, 68 years; interquartile range [IQR], 58-74 years; 55 men [72%]; 31 patients [41%] with type II diabetes) with intermittent claudication (n = 49; 64%) or critical limb ischemia (n = 27; 36%) who underwent primary successful femoral PTA. C-peptide and insulin levels were measured at baseline, and patients were followed to determine restenosis (> or =50%) at 12 months by color-coded duplex sonography.

RESULTS

Restenosis was found in 34 patients (45%) at 12 months. Patients with restenosis had higher insulin levels (median, 21.3 microU/mL IQR, 11.3-35.5 microU/mL) and a lower C-peptide/insulin ratio (median, 16; IQR, 10-21) compared with patients without restenosis (median insulin level, 11.6 microU/mL; IQR, 9.1-22.0 microU/mL [P = .008]; median ratio, 19 [IQR, 17-25], P = .039). In nondiabetic patients, insulin levels were significantly associated with restenosis (P = .046), whereas the ratio of C-peptide to insulin showed no association with restenosis. In patients with type II diabetes (n = 31; 41%), in contrast, the C-peptide/insulin ratio was associated with restenosis (P = .047), whereas insulin levels showed no significant association with restenosis (P = .14).

CONCLUSIONS

Insulin levels and the C-peptide/insulin ratio were associated with restenosis after femoral PTA. Exogenous and endogenous insulin may play a role in the pathogenesis of recurrent lumen loss after balloon angioplasty.

Macrophages in streptozotocin-induced diabetic nephropathy: potential role in renal fibrosis

BACKGROUND

Renal fibrosis is central to the progression of diabetic nephropathy; however, the mechanisms responsible for fibroblast and matrix accumulation in this disease are only partially understood. Macrophages accumulate in diabetic kidneys, but it is unknown whether macrophages contribute to renal fibrosis. Therefore, we examined whether macrophage accumulation is associated with the progression of renal injury and fibrosis in type 1 diabetic nephropathy and whether macrophages exposed to the diabetic milieu could promote fibroblast proliferation.

METHODS

Kidney macrophages, renal injury and fibrosis were analysed in diabetic C57BL/6J mice at 2, 8, 12 and 18 weeks after streptozotocin injection. Isolated rat bone marrow macrophages were stimulated with diabetic rat serum or carboxymethyllysine (CML)-bovine serum albumin (BSA) to determine whether macrophage-conditioned medium could promote the proliferation of rat renal (NRK-49F) fibroblasts.

RESULTS

Progressive injury and fibrosis in diabetic nephropathy was associated with increased numbers of kidney macrophages. Macrophage accumulation in diabetic mice correlated with hyperglycaemia (blood glucose, HbA1c levels), renal injury (albuminuria, plasma creatinine), histological damage and renal fibrosis (myofibroblasts, collagen IV). Culture supernatant derived from bone marrow macrophages incubated with diabetic rat serum or CML-BSA induced proliferation of fibroblasts, which was inhibited by pre-treating fibroblasts with interleukin-1 (IL-1) receptor antagonist or the platelet-derived growth factor (PDGF) receptor kinase inhibitor, STI-571.

CONCLUSION

Kidney macrophage accumulation is associated with the progression of renal injury and fibrosis in streptozotocin-induced mouse diabetic nephropathy. Elements of the diabetic milieu can stimulate macrophages to promote fibroblast proliferation via IL-1- and PDGF-dependent pathways which may enhance renal fibrosis.

Pyridoxal Phosphate and Hepatocyte Growth Factor Prevent Dialysate-Induced Peritoneal Damage

Glucose-based peritoneal dialysate (PD) is responsible for increased accumulation of advanced glycation end products (AGE) in the peritoneum of continuous ambulatory peritoneal dialysis patients. Pyridoxal 5'-phosphate (PLP), a derivative of vitamin B(6), protects proteins from glycation. Hepatocyte growth factor (HGF) heals damaged tissues in a reciprocal manner against TGF-beta1. First, with the use of gas chromatography-mass spectrometry, whether PLP traps 3-deoxyglucosone (3DG), a major glucose degradation product in PD, was determined. Then, whether rat peritoneal tissue damages induced by intraperitoneal administration of glucose-based PD is ameliorated by PLP or HGF was examined. In vitro incubation with PLP markedly decreased concentration of 3DG in a dose-dependent manner, demonstrating the 3DG-trapping effect of PLP. The peritoneum of PD-treated rats was significantly thickened compared with that of physiologic saline-treated rats. Both PLP and HGF prevented the thickening of rat peritoneum induced by PD and ameliorated accumulation of AGE and expression of TGF-beta1, vascular endothelial growth factor, and type 1 collagen and a number of blood vessels. Furthermore, expression of HGF was significantly increased in the peritoneum of PLP-treated rats compared with that of PD-treated rats. In conclusion, PLP shows 3DG-trapping effect. PLP and HGF prevented peritoneal thickening; accumulation of AGE; expression of TGF-beta1, vascular endothelial growth factor, and type 1 collagen; and neoangiogenesis in rat peritoneum induced by PD.

Mechanisms of the hypoglycaemic and immunopotentiating effects of Nigella sativa L. oil in streptozotocin-induced diabetic hamsters

The aim of this study was to elucidate the mechanisms underlying the hypoglycaemic effect of N. sativa oil (Nigella sativa oil) in streptozotocin (STZ)-induced diabetic hamsters, in terms of hepatic glucose production, and to investigate the possible immunopotentiating effect of N. sativa oil on peritoneal macrophages. Diabetes was induced by intraperitoneal injection of 65 mg/kg body weight of STZ. Treatment with N. sativa oil commenced 6 weeks after induction of diabetes at a dose of 400 mg/kg body weight by gastric gavage. Isolated hepatocytes were collected using collagenase to determine liver glucose production. Phagocytic activity was evaluated by injection of fluorescent latex (2 microm diameter) intraperitoneally, followed 24 h later by collection of peritoneal macrophages. N. sativa oil reduced blood glucose from 391+/-3.0 mg/dl before treatment to 325+/-4.7, 246+/-5.9, 208+/-2.5 and 179+/-3.1 mg/dl after the first, second, third and fourth weeks of treatment, respectively. Hepatic glucose production from gluconeogenic precursors (alanine, glycerol and lactate) was significantly lower in treated hamsters. Treatment with N. sativa oil significantly increased the phagocytic activity and phagocytic index of peritoneal macrophages and lymphocyte count in peripheral blood compared with untreated diabetic hamsters. Our data indicate that the hypoglycaemic effect of N. sativa oil is due to, at least in part, a decrease in hepatic gluconeogenesis, and that the immunopotentiating effect of N. sativa oil is mediated through stimulation of macrophage phagocytic activity either directly or via activation of lymphocytes.

Histological analysis of the ligamentum flavum of patients with dialysis-related spondyloarthropathy

Dialysis-related spondyloarthropathy (DRS) is a severe complication of long-term hemodialysis that ultimately leads to functional disability of the upper and lower extremities. Although the cause of this disease is still unknown, it is thought that amyloid deposits are involved. beta2-Microglobulin (beta2M) is a major component of amyloid fibrils, some of which are modified with the advanced glycation end-product (AGE). To clarify the pathophysiology of DRS we histologically examined the ligamentum flavum of the cervical spine in 15 patients with DRS. The mean duration of hemodialysis was 20 years (12-27 years). In addition to the congo red stain for amyloid, beta2M and AGE were detected by immunohistochemical methods. Macrophages were stained with CD68 antibody. Amyloid deposits were found in tissues, although the extent of the stained area differed among the patients. Part of the amyloid deposit area was positively immunostained for beta2M and AGE. In 10 cases macrophages positive for CD68 infiltrated around the amyloid deposits. Comparing these histological findings with the dialysis duration, more positive staining areas for beta2M and AGE were found in the tissue from patients with long-term dialysis. These findings suggest that both beta2M and AGE play roles in the pathogenesis of DRS.

Advanced glycation end product (AGE)-immunoreactive materials in chronic prurigo patients receiving a long-standing haemodialysis

We report two patients with chronic prurigo who suffered from chronic renal failure and were treated by haemodialysis. Histological examination of pruritic nodules revealed that the papillary dermis of the lesional skin was eosinophilic and amorphous, and free from dermal cell infiltration. Immunohistochemical study demonstrated that advanced glycation end product (AGE)-immunoreactive materials accumulated in the papillary dermis of the lesional skin. This immunohistochemical finding was never observed in the nonlesional skin adjacent to prurigo nodules of the present cases, and renal disease-free prurigo skin (n = 6) and nonprurigo skin of haemodialysis patients (n = 3). AGE-modified materials in the papillary dermis may be related to the pathogenesis of prurigo nodules in the haemodialysis patients.

Divergent pathways of gene expression are activated by the RAGE ligands S100b and AGE-BSA

Activation of the receptor for advanced glycation end products (RAGE) reportedly triggers a variety of proinflammatory responses. However, our previous work revealed that RAGE-binding AGEs free of endotoxin were incapable of inducing vascular cell adhesion molecule-1 (VCAM-1) or tumor necrosis factor-alpha (TNF-alpha) expression. Thus, the objective of this study was to clarify the role of AGEs in cell activation through gene expression profiling using both in vitro and in vivo model systems. Endothelial cells treated with AGE-BSA, previously shown to bind RAGE with high affinity, did not show gene expression changes indicative of an inflammatory response. In contrast, the alternate RAGE ligand, S100b, triggered an increase in endothelial mRNA expression of a variety of immune-related genes. The effects of AGEs were studied in vivo using healthy mice exposed to two different treatment conditions: 1) intravenous injection of a single dose of model AGEs or 2) four intraperitoneal injections of model AGEs (once per day). In both cases, the liver was extracted for gene expression profiling. Both of the short-term AGE treatments resulted in a moderate increase in liver mRNA levels for genes involved in macrophage-based clearance/detoxification of foreign agents. Our findings using AGEs with strong RAGE-binding properties indicate that AGEs may not uniformly play a role in cellular activation.