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Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nonenzymatic glycation of neural proteins could underlie diabetic peripheral neuropathy. Cytoskeletal and myelin protein fractions of central nervous system and peripheral nervous system (PNS) tissue from rats with streptozotocin-induced diabetes of 1.5 and 8 months duration were analyzed for glycation products. In sciatic nerve cytoskeletal preparations from both diabetic and control animals we found high levels of the early glycation product (measured as furosine) after 6 weeks, which had fallen markedly by 8 months. Conversely the advanced glycation end product (AGE), pentosidine, was low at 6 weeks and high by 8 months in diabetic animals. The levels of glycation products were much lower in spinal cord and spinal nerve from diabetic animals. There was increased borotritride labeling of neurofilament subunits, and of cross-linked material, in cytoskeletal fractions of diabetic sciatic nerves. These results show that the PNS cytoskeleton is vulnerable to nonenzymatic glycation, resulting in AGE formation, in diabetic rats and to a lesser extent in normals.
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PMID:Nonenzymatic glycation of peripheral and central nervous system proteins in experimental diabetes mellitus. 914 Mar 64

Advanced glycation end-products and glycoxidation products, such as Nepsilon-(carboxymethyl)lysine (CML) and pentosidine, accumulate in long-lived tissue proteins with age and are implicated in the aging of tissue proteins and in the development of pathology in diabetes, atherosclerosis and other diseases. In this paper we describe a new advanced glycation end-product, Nepsilon-(carboxyethyl)lysine (CEL), which is formed during the reaction of methylglyoxal with lysine residues in model compounds and in the proteins RNase and collagen. CEL was also detected in human lens proteins at a concentration similar to that of CML, and increased with age in parallel with the concentration of CML. Although CEL was formed in highest yields during the reaction of methylglyoxal and triose phosphates with lysine and protein, it was also formed in reactions of pentoses, ascorbate and other sugars with lysine and RNase. We propose that levels of CML and CEL and their ratio to one another in tissue proteins and in urine will provide an index of glyoxal and methylglyoxal concentrations in tissues, alterations in glutathione homoeostasis and dicarbonyl metabolism in disease, and sources of advanced glycation end-products in tissue proteins in aging and disease.
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PMID:N-epsilon-(carboxyethyl)lysine, a product of the chemical modification of proteins by methylglyoxal, increases with age in human lens proteins. 918 19

The glycoxidation products Nepsilon-(carboxymethyl)lysine and pentosidine increase in skin collagen with age and at an accelerated rate in diabetes. Their age-adjusted concentrations in skin collagen are correlated with the severity of diabetic complications. To determine the relative roles of increased glycation and/or oxidation in the accelerated formation of glycoxidation products in diabetes, we measured levels of amino acid oxidation products, distinct from glycoxidative modifications of amino acids, as independent indicators of oxidative stress and damage to collagen in aging and diabetes. We show that ortho-tyrosine and methionine sulfoxide are formed in concert with Nepsilon-(carboxymethyl)lysine and pentosidine during glycoxidation of collagen in vitro, and that they also increase with age in human skin collagen. The age-adjusted levels of these oxidized amino acids in collagen was the same in diabetic and nondiabetic subjects, arguing that diabetes per se does not cause an increase in oxidative stress or damage to extracellular matrix proteins. These results provide evidence for an age-dependent increase in oxidative damage to collagen and support previous conclusions that the increase in glycoxidation products in skin collagen in diabetes can be explained by the increase in glycemia alone, without invoking a generalized, diabetes-dependent increase in oxidative stress.
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PMID:Age-dependent increase in ortho-tyrosine and methionine sulfoxide in human skin collagen is not accelerated in diabetes. Evidence against a generalized increase in oxidative stress in diabetes. 925 83

Advanced glycation end products (AGEs) such as pentosidine and N epsilon-(carboxymethyl)lysine (CML) have been traditionally quantified by HPLC or gas chromatography--mass spectrometry (GC/MS). Enzyme-linked immunosorbent assays (ELISA) have been introduced as a convenient alternative to simplify the detection and measurement of AGEs in proteins and tissues, but some of these studies are limited by the lack of information on the structure of the epitopes recognized by antibodies to AGE-proteins. In this work we demonstrate that an antibody used in a previous study, reporting increased levels of AGEs in patients with diabetes or on continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD), recognizes CML as its major epitope. We also show that there is a significant correlation between the concentration of AGEs in serum measured by ELISA and a GC/MS assay for CML in serum proteins. Both analyses yielded comparable results, with patients on CAPD and HD having about threefold higher AGE- or CML-concentrations in their serum. Our data suggest that ELISA assays for CML should be useful for the clinical measurement of AGEs in serum proteins.
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PMID:Technical note. The serum concentration of the advanced glycation end-product N epsilon-(carboxymethyl)lysine is increased in uremia. 932 46

The glomerular basement membrane (GBM) is damaged in diabetes through complex mechanisms that are not fully understood. Prominent among them is nonenzymatic protein glycation leading to the formation of so-called advanced glycation end products (AGEs). We examined the effects of in vitro glycation of intact collagen type IV in bovine lens capsule (LBM) and kidney glomerular (GBM) basement membranes on their susceptibility to matrix metalloproteinases, using stromelysin 1 (MMP-3) and gelatinase B (MMP-9). Sites of cleavage of unmodified LBM collagen were located in the triple helical region. In vitro glycation by glucose severely inhibited the release of soluble collagen cleavage peptides by MMP-3 and MMP-9. The distribution of AGEs within the three domains of collagen IV (7S, triple helical, and noncollagenous NC1) were compared for LBM glycation using AGE fluorescence, pentosidine quantitation, and immunoreactivity towards anti-AGE antibodies that recognize the AGE carboxymethyllysine (CML). Marked asymmetry was observed, with the flexible triple helical domain having the most pentosidine and fluorescent AGEs but the least CML. The in vivo relevance of these findings is supported by preliminary studies of AGE distribution in renal basement membrane (RBM) collagen IV domains from human kidneys of two insulin-dependent diabetics and one normal subject. Pentosidine and fluorescent AGE distributions of diabetic RBM were similar to LBM, but the CML AGE in diabetic kidney was less in the triple helical domain than in NC1. Our results support the hypothesis that nonenzymatic glycation of collagen IV contributes to the thickening of basement membranes, a hallmark of diabetic nephropathy.
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PMID:Nonenzymatic glycation of type IV collagen and matrix metalloproteinase susceptibility. 935 Jun 53

Advanced glycation end products (AGEs) have been noted in the peritoneal tissue of continuous ambulatory peritoneal dialysis (CAPD) patients, and this may cause an increase in membrane permeability. In vivo and in vitro kinetic analysis was carried out on furosine and pentosidine, early and late glycation products. Plasma furosine and pentosidine were measured by HPLC in patients with renal dysfunction with or without diabetes mellitus (DM) and dialysate pentosidine and furosine in CAPD patients. Only those dialysis patients without residual renal function were used in this study. Plasma furosine was remarkably high in DM, hemodialysis (HD), and CAPD patients. Plasma pentosidine appeared to depend on renal function and was not influenced by diabetic condition. Plasma pentosidine was significantly higher in CAPD than HD patients. A weak positive correlation was noted between dialysate and plasma furosine and pentosidine, indicating the main source of furosine and pentosidine in PD effluent to be plasma. Serial dialysate sampling showed furosine and pentosidine to increase linearly. Mean dialysate/plasma (D/P) of furosine and pentosidine were 0.043 and 0.012, respectively. Protein-bound product size and in situ formation of furosine in the peritoneal cavity would be the reason for these differences in D/P. In situ formation of early glycation products in the peritoneal cavity may be concluded to take place in CAPD patients, and high plasma pentosidine may lead to its accumulation in tissue, resulting, possibly, in pathological change.
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PMID:Kinetic analysis of furosine and pentosidine in CAPD patients. 936 Jun 51

Pentosidine, an advanced glycation endproduct, may cause the increased fluorescence found in the lenses of diabetic patients. We measured the autofluorescence in human lenses, in vitro, and quantified the pentosidine to examine its relationship to the autofluorescence. Lens autofluorescence was higher in diabetic than non-diabetic subjects; pentosidine quantities were significantly higher in the diabetic than the non-diabetic group indicating that pentosidine was involved in the greater intensity of autofluorescence in the lenses of patients with diabetes mellitus.
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PMID:Pentosidine and autofluorescence in lenses of diabetic patients. 936 54

Advanced glycation end products (AGEs) generated through the Maillard reaction significantly alter protein characteristics. Their accumulation has been incriminated in tissue injury associated with aging, diabetes, and renal failure. However, little is known about their clearance from the body. The present study delineates the catabolic pathway of a well-defined AGE product, pentosidine. Synthesized pentosidine given intravenously in rats with normal renal function was rapidly eliminated from the circulation through glomerular filtration, but was undetectable in the urine by chemical analysis. Immunohistochemistry with anti-pentosidine antibody disclosed that pentosidine accumulated transiently in the proximal renal tubule one hour after its administration, but had disappeared from the kidney at 24 hours. After an intravenous load of radiolabeled pentosidine, radioactivity peaked in the kidney at one hour and subsequently decreased, whereas it rose progressively in the urine. Over 80% of the radioactivity was recovered in the 72-hour collected urine. However, only 20% of urine radioactivity was associated with intact pentosidine chemically or immunochemically. In gentamicin-treated rats with tubular dysfunction, up to 30% of the pentosidine load was recovered as intact pentosidine in the urine. The present study suggests that free pentosidine (and possibly other AGEs) is filtered by renal glomeruli, reabsorbed in the proximal tubule where it is degraded or modified, and eventually excreted in the urine. Kidney thus plays a key role in pentosidine disposal.
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PMID:Renal catabolism of advanced glycation end products: the fate of pentosidine. 946 Nov 1

Advanced glycosylation end products (AGEs) are thought to play an important role in the development of diabetic complications. Oxidative reactions are essential for the formation of some AGEs, termed glycoxidation products. Increased concentrations of pentosidine, one of such products, are found in tissue and serum in diabetes mellitus and in end-stage renal disease, suggesting that hyperglycemia and impaired renal function are important factors in AGE accumulation. We hypothesized that increased concentrations of pentosidine would also be found in pathological conditions associated with increased oxidative stress. We measured pentosidine in sera of patients with rheumatoid arthritis (RA), systemic lupus erythematosus, and diabetes. Increased serum pentosidine was found in RA (108.4 +/- 146.5 nmol/L, P < 0.002) and in diabetes (69.6 +/- 42.4 nmol/L, P < 0.001) as compared with healthy subjects (48.3 +/- 12.0 nmol/L). These results prove that AGEs may accumulate in the absence of hyperglycemia or impaired kidney function.
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PMID:Increased concentrations of serum pentosidine in rheumatoid arthritis. 947 20

Glycoxidation reactions lead to the formation of permanent, irreversible chemical modifications and cross-links in protein, such as the glycoxidation products carboxymethyllysine (CML) and pentosidine. It has been implicated that CML as well as Amadori products play a role in the formation of superoxidative products, such as H2O2 and advanced glycosylation endproducts in trapping LDL. Therefore, a possible relationship between glycoxidation and lipoperoxidation might exist because oxidized lipoprotein, which has been directly linked to atheroma formation, could be produced by the superoxidative products released from the pathway of CML formation. Using a CML-specific monoclonal antibody (6D12) and a specific antiserum against hexitol-lysine (HL), an Amadori product, we studied the relationship between glycoxidation and lipoperoxidation by determining the aortic CML contents with ELISA and the fluorescence levels of lipoperoxidation side products, malondialdehyde (MDA) and hydroxynonenal (HNE) from STZ-induced diabetic rats and age-matched control rats. The immunohistochemical and ultrastructural changes relevant to glycoxidation and lipoperoxidation were also studied. The CML content measured by ELISA in DM rats was significantly higher than that in the control rats at 28 weeks (n = 11, P < 0.01). The levels of MDA-linked and HNE-linked fluorescence in the DM rats increased in a similar way and were significantly higher than the levels in control rats at 28 weeks (n = 11, both P < 0.01 at 28 weeks). The CML contents correlated with the fluorescence levels of both MDA-linked (n = 19, r = 0.638, P < 0.01) and HNE-linked fluorescence (n = 19, r = 0.629, P < 0.01) only in the DM rats, but not in the control rats. Our immunohistochemical study thus demonstrated that CML was initially formed in the aortic media of diabetic rats in the 16th week of diabetes, localized primarily in the extracellular matrix surrounding the aortic smooth muscle cells after HL occurred early in the 2nd week of diabetes. Consequently, a significant increase in the extracellular matrix and decrease in the area of the SMCs were observed in the aortic media in the DM rats by a morphometrical study. The in vivo results of this study provided the first evidence that CML correlated with fluorescence levels of MDA and HNE, and thus suggested the existence of a close relationship between glycoxidation and lipoperoxidation in vivo. This information is thus considered to shed some new light on the etiology of atherogenesis in diabetes.
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PMID:Glycoxidation in aortic collagen from STZ-induced diabetic rats and its relevance to vascular damage. 954 7


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