Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011860 (type 2 diabetes)
 57,723 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Amyloid in the islets of Langerhans is the uniform pathologic feature in the pancreata of patients with type II diabetes mellitus. Although the mechanisms of islet amyloid fibrillogenesis are unknown, the presence of heparan sulfate proteoglycan in many other forms of amyloid suggests a role for this proteoglycan in amyloidogenesis in general. In this study, islet amyloid was evaluated for the presence of the basement membrane heparan sulfate proteoglycan using histochemical and immunohistochemical techniques. Staining with sodium sulfate-alcian blue identified highly sulfated glycosaminoglycans within all islet amyloid deposits, and anti-basement membrane heparan sulfate proteoglycan antisera localized this specific proteoglycan within the islet amyloid. The presence of the basement membrane heparan sulfate proteoglycan links islet amyloid to other disparate forms of amyloid and further supports the hypothesis that it has a role in a common pathway of amyloid fibrillogenesis.
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PMID:Localization of the basement membrane heparan sulfate proteoglycan in islet amyloid deposits in type II diabetes mellitus. 152 61

Islet amyloidosis is characterized by the deposition and accumulation of amylin in pancreatic beta-cells and is observed in 90% of patients with type 2 diabetes. Previous studies have also revealed the presence of the specific heparan sulfate proteoglycan, perlecan, colocalized to islet amyloid deposits, similar to perlecan's known involvement with other amyloid proteins. In the present study, perlecan purified from the Engelbreth-Holm-Swarm (EHS) tumor was used to define perlecan's interactions with amylin (i.e., islet amyloid polypeptide) and its effects on amylin fibril formation. Using a solid phase-binding immunoassay, human amylin, but not rat amylin, bound immobilized EHS perlecan with a single dissociation constant (Kd) = 2.75 x 10(-6) mol/l. The binding of human amylin to perlecan was similarly observed using perlecan heparan sulfate glycosaminoglycans (GAGs), and was completely abolished by 10 micromol/l heparin. Using thioflavin T fluorometry, Congo red staining, and electron microscopy methodology, intact perlecan was found to enhance amylin fibril formation in a dosage-dependent manner, with the majority of these effects attributed to the heparan sulfate GAG chains of perlecan. Other sulfated GAGs and related macromolecules were also effective in the enhancement of amylin fibril formation in the order of heparin > heparan sulfate > chondroitin-4-sulfate = dermatan sulfate = dextran sulfate > pentosan polysulfate, implicating the importance of the specific GAG/carbohydrate backbone. The sulfate content of heparin/heparan sulfate was also important for the enhancement of amylin fibril formation in the order of heparin > N-desulfated N-acetylated heparin > completely desulfated N-sulfated heparin > completely desulfated N-acetylated heparin. These studies suggest that the enhancement effects of perlecan on amylin fibril formation are mediated primarily by both specific GAG chain backbone and GAG sulfate content, and implicate perlecan as an important macromolecule that is likely involved in the pathogenesis of islet amyloidosis.
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PMID:Sulfate content and specific glycosaminoglycan backbone of perlecan are critical for perlecan's enhancement of islet amyloid polypeptide (amylin) fibril formation. 956 95

In diabetes-associated microangiopathies and atherosclerosis, there are alterations of the extracellular matrix (ECM) in the intima of small and large arteries. High levels of circulating nonesterified fatty acids (NEFAs) are present in insulin resistance and type 2 diabetes. High concentrations of NEFAs might alter the basement membrane composition of endothelial cells. In arteries, smooth muscle cells (SMCs) are the major producers of proteoglycans and glycoproteins in the intima, and this is the site of lipoprotein deposition and modification, key events in atherogenesis. We found that exposure of human arterial SMCs to 100-300 micromol/albumin-bound linoleic acid lowered their proliferation rate and altered cell morphology. SMCs expressed 2-10 times more mRNA for the core proteins of the proteoglycans versican, decorin, and syndecan 4 compared with control cells. There was no change in expression of fibronectin and perlecan. The decorin glycosaminoglycan chains increased in size after exposure to linoleic acid. The ECM produced by cells grown in the presence of linoleic acid bound 125I-labeled LDL more tightly than that of control cells. Darglitazone, a peroxisome proliferator-activated receptor (PPAR)-gamma ligand, neutralized the NEFA-mediated induction of the decorin gene. This suggests that some of the NEFA effects are mediated by PPAR-gamma. These actions of NEFAs, if present in vivo, could contribute to changes of the matrix of the arterial intima associated with micro- and macroangiopathies.
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PMID:Fatty acids modulate the composition of extracellular matrix in cultured human arterial smooth muscle cells by altering the expression of genes for proteoglycan core proteins. 1007 65

Islet amyloid has been recognized as a pathological entity in type 2 diabetes since the turn of the century. It has as its unique component the islet beta-cell peptide islet amyloid polypeptide (IAPP), or amylin, which is cosecreted with insulin. In addition to this unique component, islet amyloid contains other proteins, such as apolipoprotein E and the heparan sulfate proteoglycan perlecan, which are typically observed in other forms of generalized and localized amyloid. Islet amyloid is observed at pathological examination in the vast majority of individuals with type 2 diabetes but is rarely observed in humans without disturbances of glucose metabolism. In contrast to IAPP from rodents, human IAPP has been shown to form amyloid fibrils in vitro. Because all human subjects produce and secrete the amyloidogenic form of IAPP, yet not all develop islet amyloid, some other factor(s) must be involved in islet amyloid formation. One hypothesis is that an alteration in beta-cell function resulting in a change in the production, processing, and/or secretion of IAPP is critical to the initial formation of islet amyloid fibrils in human diabetes. This nidus of amyloid fibrils then allows the progressive accumulation of IAPP-containing fibrils and the eventual replacement of beta-cell mass by amyloid and contributes to the development of hyperglycemia. One factor that may be involved in producing the changes in the beta-cell that result in the initiation of amyloid formation is the consumption of increased dietary fat. Dietary fat is known to alter islet beta-cell peptide production, processing, and secretion, and studies in transgenic mice expressing human IAPP support the operation of this mechanism. Further investigation using this and other models should provide insight into the mechanism(s) involved in islet amyloidogenesis and allow the development of therapeutic agents that inhibit or reverse amyloid fibril formation, with the goal being to preserve beta-cell function and improve glucose control in type 2 diabetes.
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PMID:Islet amyloid: a long-recognized but underappreciated pathological feature of type 2 diabetes. 1033 97

Treatment with moderate levels of albumin-bound, nonesterified fatty acids (NEFA) induce important alterations of the structure and functionality of proteoglycans secreted by endothelial cells and arterial smooth muscle cells. In endothelial cell monolayers, the reduction on relative amount and sulfation of heparan sulfate proteoglycans is associated with an increased permeability to albumin. In smooth muscle cells, NEFA-albumin complex increased the expression of the genes for the core proteins of the proteoglycans syndecan, decorin and perlecan. This effect appears mediated by peroxisome proliferator-activated receptor gamma (PPARg). The matrix produced by the cells treated with NEFA-albumin had a higher affinity with low-density lipoproteins (LDLs). We speculate about the possibility that under dyslipidemias associated with increased exposure of vascular cells to NEFA, like in type 2 diabetes, similar alterations may contribute to associated macrovascular and microvascular complications.
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PMID:Lipid mediators that modulate the extracellular matrix structure and function in vascular cells. 1112 3

Islet amyloid deposits are a characteristic pathologic lesion of the pancreas in type 2 diabetes and are composed primarily of the islet beta cell peptide islet amyloid polypeptide (IAPP or amylin) as well as the basement membrane heparan sulfate proteoglycan perlecan. Impaired processing of the IAPP precursor has been implicated in the mechanism of islet amyloid formation. The N- and C-terminal cleavage sites where pro-IAPP is processed by prohormone convertases contain a series of basic amino acid residues that we hypothesized may interact with heparan sulfate proteoglycans. This possibility was tested using affinity chromatography by applying synthetic fragments of pro-IAPP to heparin-agarose and heparan sulfate-Sepharose. An N-terminal human pro-IAPP fragment (residues 1-30) was retained by both heparin-agarose and heparan sulfate-Sepharose, eluting at 0.18 m NaCl at pH 7.5. Substitution of alanine residues for two basic residues in the N-terminal cleavage site abolished heparin and heparan sulfate binding activity. At pH 5.5, the affinity of the wild-type peptide for heparin/heparan sulfate was increased, implying a role for histidine residues at positions 6 and 28 of pro-IAPP. A C-terminal pro-IAPP fragment (residues 41-67) had no specific affinity for either heparin or heparan sulfate, and the N- or C-terminal fragments had only weak affinity for chondroitin sulfate. These data suggest that monomeric N-terminal human pro-IAPP contains a heparin binding domain that is lost during normal processing of pro-IAPP.
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PMID:Identification of a heparin binding domain in the N-terminal cleavage site of pro-islet amyloid polypeptide. Implications for islet amyloid formation. 1114 57

Islet amyloid deposits are a characteristic pathological hallmark of type 2 diabetes mellitus. Islet amyloid polypeptide (IAPP), also referred to as amylin, aggregates in the islet extracellular space to form amyloid deposits in up to 95% of patients with the disease. IAPP is stored with insulin in beta-islet cells and is processed in parallel by subtilisin-like prohormone convertases prior to secretion. There is indirect evidence that normal processing of the prohormone precursor, proIAPP, at the N-terminal cleavage site is defective in type 2 diabetes and results in secretion of an N-terminal extended proIAPP intermediate. The N-terminal flanking region of proIAPP is detected in amyloid deposits; however, the C-terminal flanking region is not. Immunohistochemical studies implicate the presence of the heparan sulfate proteoglycan (HSPG) perlecan in islet amyloid deposits, suggesting a role for HSPGs in mediating amyloid deposition in type 2 diabetes and implicating a binding domain in the N-terminus of proIAPP. Initial studies of proIAPP indicated that the HSPG binding region is contained within the first 30 residues. Here, we characterize the potential HSPG binding site of proIAPP in detail by analyzing a set of peptide fragments. Binding is tighter at low pH due to protonation of histidine residues. Deletion studies show that Arg-22 and His-29 play a role in binding. Reduction of the Cys-13 to Cys-18 disulfide leads to a noticeable decrease in binding. We demonstrate the ability of heparan sulfate to induce amyloid formation in N-terminal fragments of proIAPP. The oxidized peptide forms amyloid more rapidly than the reduced variant in the presence of heparan sulfate, but the reduced peptide ultimately forms more extensive amyloid deposits. The potential implications for islet amyloid formation in vivo are discussed.
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PMID:Characterization of the heparin binding site in the N-terminus of human pro-islet amyloid polypeptide: implications for amyloid formation. 1686 69

Arteriosclerosis with its clinical sequelae (cardiac infarction, stroke, peripheral arterial occlusive disease) and vascular/Alzheimer dementia not only result in far more than half of all deaths but also represent dramatic economic problems. The reason is, among others, that diabetes mellitus is an independent risk factor for both disorders, and the number of diabetics strongly increases worldwide. More than one-half of infants in the first 6months of life have already small collections of macrophages and macrophages filled with lipid droplets in susceptible segments of the coronary arteries. On the other hand, the authors of the Bogalusa Heart Study found a strong increase in the prevalence of obesity in childhood that is paralleled by an increase in blood pressure, blood lipid concentration, and type 2 diabetes mellitus. Thus, there is a clear linkage between arteriosclerosis/Alzheimer's disease on the one hand and diabetes mellitus on the other hand. Furthermore, it has been demonstrated that distinct apoE isoforms on the blood lipids further both arteriosclerotic and Alzheimer nanoplaque formation and therefore impair flow-mediated vascular reactivity as well. Nanoplaque build-up seems to be the starting point for arteriosclerosis and Alzheimer's disease in their later full clinical manifestation. In earlier work, we could portray the anionic biopolyelectrolytes syndecan/perlecan as blood flow sensors and lipoprotein receptors in cell membrane and vascular matrix. We described extensively molecular composition, conformation, form and function of the macromolecule heparan sulfate proteoglycan (HS-PG). In two supplementary experimental settings (ellipsometry, myography), we utilized isolated HS-PG for in vitro nanoplaque investigations and isolated human coronary artery segments for in vivo tension measurements. With the ellipsometry-based approach, we were successful in establishing a direct connection on a molecular level between diabetes mellitus on the one side and arteriosclerosis/Alzheimer's disease on the other side. Application of glucose at a concentration representative for diabetics and leading to glycation of proteins and lipids, entailed a significant increase in arteriosclerotic and Alzheimer nanoplaque formation. IDLapoE4/E4 was by far superior to IDLapoE3/E3 in plaque build-up, both in diabetic and non-diabetic patients. Recording vascular tension of flow-dependent reactivity in blood substitute solution and under application of different IDLapoE isoforms showed an impaired vasorelaxation for pooled IDL and IDLapoE4/E4, thus confirming the ellipsometric investigations. Incubation in IDLapoE0/E0 (apoE "knockout man"), however, resulted in a massive flow-mediated contraction, also complemented by strongly aggregated nanoplaques. In contrast, HDL was shown to present a powerful protection against nanoplaque formation on principle, both in the in vitro model and the in vivo scenario on the endothelial cell membrane. The competitive interplay with LDL is highlighted through the flow experiment, where flow-mediated, HDL-induced vasodilatation remains untouched by additional incubation with LDL. This is due to the four times higher affinity for the proteoglycan receptor of HDL as compared to LDL. Taken together, the studies demonstrate that while simplistic, the ellipsometry approach and the endothelial-mimicking proteoglycan-modified surfaces provide information on the initial steps of lipoprotein-related plaque formation, which correlates with findings on endothelial cells and blood vessels, and afford insight into the role of lipoprotein deposition and exchange phenomena at the onset of these pathophysiologies.
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PMID:Lipoprotein binding to anionic biopolyelectrolytes and the effect of glucose on nanoplaque formation in arteriosclerosis and Alzheimer's disease. 2696 81

Perlecan (HSPG2) play an important role in the lipoprotein metabolisms. The G allele of the HSPG2-rs3767140 may affect the binding of heparan sulfate (HS) chains and hence cause loss of HS from the basement membrane. HSPG2-rs3767140 was studied in 60 T2DM patients and 109 healthy controls. In diabetic patients HSPG2-rs3767140 T variant allele carriers (TT+GT) have decreased fasting plasma glucose (FPG) and serum LDL-C levels (p=0.071 and p=0.060, respectively) versus GG genotype carriers. Moreover, in both of the two groups in which the T allele carriers HDL-cholesterol levels tend to be high. We investigated that the HSPG2-rs3767140 promoted to the dyslipidemic phenotype in the type 2 diabetes mellitus (T2DM) patients. We suggest that the HSPG2-rs3767140 might be associated with the decreased FPG and LDL-C and with the increased HDL-C in diabetics. Therefore, the HSPG2-rs3767140 might be a protective for the diabetes mellitus due to its ameliorating effect on the dyslipidemic phenotype.
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PMID:Can rs3767140 SNP of the perlecan (HSPG2) gene affect the diabetes mellitus through the dyslipidemia? 2754 12

Diabetic nephropathy (DN) is the major cause of end-stage kidney disease, but early biomarkers of DN risk are limited. Herein we examine urinary IgG4 and Smad1 as additional early DN biomarkers. We recruited 815 patients with type 2 diabetes; 554 patients fulfilled the criteria of an estimated glomerular filtration rate (eGFR) >60 mL/min and no macroalbuminuria at baseline, with follow-up for 5 years. Patients without macroalbuminuria were also recruited for renal biopsies. Urinary IgG4 and Smad1 were determined by enzyme-linked immunoassays using specific antibodies. The specificity, sensitivity, and reproducibility were confirmed for each assay. Increased urinary IgG4 was significantly associated with lower eGFR. The level of urinary IgG4 also significantly correlated with surface density of peripheral glomerular basement membrane (Sv PGBM/Glom), whereas Smad1 was associated with the degree of mesangial expansion-both classic pathological findings in DN. Baseline eGFR did not differ between any groups; however, increases in both urinary IgG4 and Smad1 levels at baseline significantly predicted later development of eGFR decline in patients without macroalbuminuria. These data suggest that urinary IgG4 and Smad1 at relatively early stages of DN reflect underlying DN lesions and are relevant to later clinical outcomes.
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PMID:Urinary IgG4 and Smad1 Are Specific Biomarkers for Renal Structural and Functional Changes in Early Stages of Diabetic Nephropathy. 2949 Sep 4


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