UMLS:C0011860 - FACTA Search

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Query: UMLS:C0011860 (type 2 diabetes)
57,723 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Amylin is the major component of the amyloid found in the pancreases of noninsulin-dependent diabetics (type 2 diabetes). It is a 37 amino acid polypeptide and has been shown to have 46% sequence identity with the neuropeptide alpha-calcitonin gene-related peptide (alpha-CGRP). Both amylin and alpha-CGRP are known to be potent inhibitors of glycogen synthesis in stripped rat soleus muscle. Secondary structure prediction and tertiary structure model-building show the two polypeptides to have an alpha-helix/beta-strand motif similar to that observed in the insulin B-chain. The results have been supported by CD spectroscopy, although there is no sequence similarity between insulin and amylin/alpha-CGRP. Aggregation states have been predicted based on the dimeric and hexameric arrangements seen in porcine insulin. Rat and hamster amylin have a changed sequence motif in the beta-strand which results in lack of amyloid formation and type 2 diabetes. This, we propose, is caused by disruption of hydrogen bonding which prevents the formation of the dimer.
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PMID:Molecular model-building of amylin and alpha-calcitonin gene-related polypeptide hormones using a combination of knowledge sources. 189 61

Resistin, a recently discovered 92 amino acid protein involved in the development of insulin resistance, has been associated with obesity and type 2 diabetes. The elevated serum resistin in human diabetes is often associated with a pro-inflammatory milieu. However, the role of resistin in the development of inflammation is not well understood. Addition of recombinant human resistin protein (hResistin) to macrophages (both murine and human) resulted in enhanced secretion of pro-inflammatory cytokines, TNF-alpha and IL-12, similar to that obtained using 5 microg/ml lipopolysaccharide. Both oligomeric and dimeric forms of hResistin were able to activate these cytokines suggesting that the inflammatory action of resistin is independent of its conformation. Heat denatured hResistin abrogated cytokine induction while treatment of recombinant resistin with polymyxin B agarose beads had no effect thereby ruling out the role of endotoxin in the recombinant hResistin mediated cytokine induction. The pro-inflammatory nature of hResistin was further evident from the ability of this protein to induce the nuclear translocation of NF-kappaB transcription factor as seen from electrophoretic mobility shift assays. Induction of TNF-alpha in U937 cells by hResistin was markedly reduced in the presence of either dominant negative IkappaBalpha plasmid or PDTC, a pharmacological inhibitor of NF-kappaB. A protein involved in conferring insulin resistance is also a pro-inflammatory molecule that has important implications.
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PMID:Human resistin stimulates the pro-inflammatory cytokines TNF-alpha and IL-12 in macrophages by NF-kappaB-dependent pathway. 1603 94

Using a focused screening approach, acyl ureas have been discovered as a new class of inhibitors of human liver glycogen phosphorylase (hlGPa). The X-ray structure of screening hit 1 (IC50 = 2 microM) in a complex with rabbit muscle glycogen phosphorylase b reveals that 1 binds at the AMP site, the main allosteric effector site of the dimeric enzyme. A first cycle of chemical optimization supported by X-ray structural data yielded derivative 21, which inhibited hlGPa with an IC50 of 23 +/- 1 nM, but showed only moderate cellular activity in isolated rat hepatocytes (IC50 = 6.2 microM). Further optimization was guided by (i) a 3D pharmacophore model that was derived from a training set of 24 compounds and revealed the key chemical features for the biological activity and (ii) the 1.9 angstroms crystal structure of 21 in complex with hlGPa. A second set of compounds was synthesized and led to 42 with improved cellular activity (hlGPa IC50 = 53 +/- 1 nM; hepatocyte IC50 = 380 nM). Administration of 42 to anaesthetized Wistar rats caused a significant reduction of the glucagon-induced hyperglycemic peak. These findings are consistent with the inhibition of hepatic glycogenolysis and support the use of acyl ureas for the treatment of type 2 diabetes.
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PMID:Acyl ureas as human liver glycogen phosphorylase inhibitors for the treatment of type 2 diabetes. 1619 Jul 45

Maturity-onset diabetes of the young (MODY3), a monogenic form of type II diabetes mellitus, results most commonly from mutations in hepatocyte nuclear factor 1alpha (HNF-1alpha). Diabetes-associated mutation G20R perturbs the dimerization domain of HNF-1alpha, an intertwined four-helix bundle. In the wild-type structure G20 participates in a Schellman motif to cap an alpha-helix; its dihedral angles lie in the right side of the Ramachandran plot (alpha(L) region; phi 97 degrees). Substitutions G20R and G20A lead to dimeric molten globules of low stability, suggesting that the impaired function of the diabetes-associated transcription factor is due in large part to a main-chain perturbation rather than to specific features of the Arg side-chain. This hypothesis is supported by the enhanced stability of non-standard analogues containing D-Ala or D-Ser at position 20. The crystal structure of the D-Ala20 analogue, determined to a resolution of 1.4 A, is essentially identical to the wild-type structure in the same crystal form. The mean root-mean-square deviation between equivalent C(alpha) atoms (residues 5-28) is 0.3 A; (phi, psi) angles of D-Ala20 are the same as those of G20 in the wild-type structure. Whereas the side-chain of A20 or R20 would be expected to clash with the preceding carbonyl oxygen (thus accounting for its frustrated energy landscape), the side-chain of D-Ala20 projects into solvent without perturbation of the Schellman motif. Calorimetric studies indicate that the increased stability of the D-Ala20 analogue (DeltaDeltaG(u) 1.5 kcal/mol) is entropic in origin, consistent with a conformational bias toward native-like conformations in the unfolded state. Studies of multiple substitutions at G20 and neighboring positions highlight the essential contributions of a glycine-specific tight turn and adjoining inter-subunit side-chain hydrogen bonds to the stability and architectural specificity of the intertwined dimer. Comparison of L- and D amino acid substitutions thus provides an example of the stereospecific control of an energy landscape by a helix-capping residue.
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PMID:Diabetes mellitus due to misfolding of a beta-cell transcription factor: stereospecific frustration of a Schellman motif in HNF-1alpha. 1693 Jun 18

Iron-sulfur (Fe-S) proteins are key players in vital processes involving energy homeostasis and metabolism from the simplest to most complex organisms. We report a 1.5 A x-ray crystal structure of the first identified outer mitochondrial membrane Fe-S protein, mitoNEET. Two protomers intertwine to form a unique dimeric structure that constitutes a new fold to not only the approximately 650 reported Fe-S protein structures but also to all known proteins. We name this motif the NEET fold. The protomers form a two-domain structure: a beta-cap domain and a cluster-binding domain that coordinates two acid-labile 2Fe-2S clusters. Binding of pioglitazone, an insulin-sensitizing thiazolidinedione used in the treatment of type 2 diabetes, stabilizes the protein against 2Fe-2S cluster release. The biophysical properties of mitoNEET suggest that it may participate in a redox-sensitive signaling and/or in Fe-S cluster transfer.
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PMID:MitoNEET is a uniquely folded 2Fe 2S outer mitochondrial membrane protein stabilized by pioglitazone. 1776 40

Calpains, particularly conventional dimeric calpains, have claimed to be involved in the cell degeneration processes that characterize numerous disease conditions linked to dysfunctions of cellular Ca2+ homeostasis. The evidence supporting their involvement has traditionally been indirect and circumstantial, but recent work has added more solid evidence supporting the role of ubiquitous dimeric calpains in the process of neurodegeneration. The only disease condition in which a calpain defect has been conclusively involved concerns an atypical monomeric calpain: the muscle specific calpain-3, also known as p94. Inactivating defects in its gene cause a muscular dystrophy termed LGMD-2A. The molecular mechanism by which the absence of the proteolytic activity of calpain-3 causes the dystrophic process is unknown. Another atypical calpain, which has been characterized recently as a Ca2(+)-dependent protease, calpain 10, appears To be involved in the etiology of type 2 diabetes. The involvement has been inferred essentially from genetic evidence. Also in the case of type 2 diabetes the molecular mechanisms that could link the disease to calpain 10 are unknown.
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PMID:Calpains and human disease. 1819 33

Zuni Indians are experiencing simultaneous epidemics of type 2 diabetes mellitus (T2DM) and renal disease [Scavini, M., Stidley, C. A., Shah, V. O., Narva, A. S., Tentori, F., Kessler, D. S., et al. (2003). Prevalence of diabetes is higher among female than male Zuni Indians: Diabetes among Zuni Indians. Diabetes Care, 26 (1), 55-60; Shah, V. O., Scavini, M., Stidley, C., Tentori, F., Welty, T., Maccluer, J. W., et al. (2003). Epidemic of diabetic and nondiabetic renal disease among the Zuni Indians: The Zuni Kidney Project. Journal of the American Society of Nephrology, 14, 1320-1329]. Methylglyoxal (MG), a highly reactive, cytotoxic, cross-linking endogenous aldehyde involved in the modification of biologic macromolecules, is elevated among patients with T2DM. Glyoxalase I (Glo1) is the initial enzyme involved in the detoxification of MG. Glo1 is a dimeric enzyme with three isoforms Glo1-1, Glo2-1, and Glo2-2, resulting from a point mutation (A-->C) at position 332 of cDNA. The present study was conducted to explore the hypothesis that specific polymorphisms of the Glo1 gene are associated with diabetes and/or albuminuria in Zuni Indians. We studied four groups of Zuni Indians stratified by diabetes status and albuminuria, as assessed by the urinary albumin:creatinine ratio (UACR): Group I--normal controls; Group II--T2DM and UACR<0.03; Group III--T2DM and UACR>or=0.03; and Group IV--nondiabetic participants with UACR>or=0.03. Genomic DNA was used as template for polymerase chain reaction amplification of the Glo1 gene. Products were digested to yield 110-bp bands (homozygous, CC); 54- and 45-bp bands (homozygous, AA); or all three bands (heterozygous CA). Data on age, gender, UACR, serum creatinine, hemoglobin A1(c), serum glucose, systolic and diastolic blood pressures, and the duration of T2DM among participants in Groups II and III were analyzed using analysis of variance. A generalized linear model logistic regression analysis was used to assess the relationships between specific Glo1 polymorphisms to T2DM and UACR. All three Glo1 genotypes were present among Zuni Indians. There were no significant differences in the distributions of Glo1 genotypes among the study groups (chi-square test, P=.5590). The prevalence of Glo1 A allele was higher among diabetic participants (Groups II and III combined) than among nondiabetic participants (Groups I and IV combined) (chi-square test, P=.0233). There was an association (odds ratio=2.9; 95% confidence interval=1.3-7.2) between the Glo1 A allele and T2DM.
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PMID:Distribution of glyoxalase I polymorphism among Zuni Indians: the Zuni Kidney Project. 1841 87

The insulin-like growth factor-1 receptor (IGF1R) is a receptor tyrosine kinase (RTK) that has a critical role in mitogenic signalling during embryogenesis and an antiapoptotic role in the survival and progression of many human tumours. Here, we present the crystal structure of the tyrosine kinase domain of IGF1R (IGF1RK), in its unphosphorylated state, in complex with a novel compound, cis-3-[3-(4-methyl-piperazin-l-yl)-cyclobutyl]-1-(2-phenyl-quinolin-7-yl)-imidazo[1,5-a]pyrazin-8-ylamine (PQIP), which we show is a potent inhibitor of both the unphosphorylated (basal) and phosphorylated (activated) states of the kinase. PQIP interacts with residues in the ATP-binding pocket and in the activation loop, which confers specificity for IGF1RK and the highly related insulin receptor (IR) kinase. In this crystal structure, the IGF1RK active site is occupied by Tyr1135 from the activation loop of an symmetry (two-fold)-related molecule. This dimeric arrangement affords, for the first time, a visualization of the initial trans-phosphorylation event in the activation loop of an RTK, and provides a molecular rationale for a naturally occurring mutation in the activation loop of the IR that causes type II diabetes mellitus.
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PMID:Small-molecule inhibition and activation-loop trans-phosphorylation of the IGF1 receptor. 1856 89

Protein tyrosine phosphatase 1B (PTP1B) has emerged as a promising target for type 2 diabetes. We have successfully synthesized dimeric acetylated and benzoylated beta-C-d-glucosyl and beta-C-D-galactosyl 1,4-dimethoxy benzenes or naphthalenes by click chemistry. These compounds were further transformed into the corresponding beta-C-D-glycosyl-1,4-quinone derivatives by CAN oxidation. The in vitro inhibition test showed that dimeric benzoylated beta-C-D-glycosyl 1,4-dimethoxybenzenes or 1,4-benzoquinones were good inhibitors of PTP1B (IC(50): 0.62-0.88 miroM), with no significant difference between gluco and galacto derivatives.
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PMID:Synthesis of triazole-linked beta-C-glycosyl dimers as inhibitors of PTP1B. 1892 97

The assembly of amyloidogenic proteins into toxic oligomers is a seminal event in the pathogenesis of protein misfolding diseases, including Alzheimer's, Parkinson's, and Huntington's diseases, hereditary amyotrophic lateral sclerosis, and type 2 diabetes. Owing to the metastable nature of these protein assemblies, it is difficult to assess their oligomer size distribution quantitatively using classical methods, such as electrophoresis, chromatography, fluorescence, or dynamic light scattering. Oligomers of amyloidogenic proteins exist as metastable mixtures, in which the oligomers dissociate into monomers and associate into larger assemblies simultaneously. PICUP stabilizes oligomer populations by covalent cross-linking and when combined with fractionation methods, such as sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) or size-exclusion chromatography (SEC), PICUP provides snapshots of the oligomer size distributions that existed before cross-linking. Hence, PICUP enables visualization and quantitative analysis of metastable protein populations and can be used to monitor assembly and decipher relationships between sequence modifications and oligomerization(1). Mechanistically, PICUP involves photo-oxidation of Ru(2+) in a tris(bipyridyl)Ru(II) complex (RuBpy) to Ru(3+) by irradiation with visible light in the presence of an electron acceptor. Ru(3+) is a strong one-electron oxidizer capable of abstracting an electron from a neighboring protein molecule, generating a protein radical(1,2). Radicals are unstable, highly-reactive species and therefore disappear rapidly through a variety of intra- and intermolecular reactions. A radical may utilize the high energy of an unpaired electron to react with another protein monomer forming a dimeric radical, which subsequently loses a hydrogen atom and forms a stable, covalently-linked dimer. The dimer may then react further through a similar mechanism with monomers or other dimers to form higher-order oligomers. Advantages of PICUP relative to other photo- or chemical cross-linking methods(3,4) include short (<or=1 s) exposure to non-destructive visible light, no need for pre facto modification of the native sequence, and zero-length covalent cross-linking. In addition, PICUP enables cross-linking of proteins within wide pH and temperature ranges, including physiologic parameters. Here, we demonstrate application of PICUP to cross-linking of three amyloidogenic proteins the 40- and 42-residue amyloid beta-protein variants (Abeta40 and Abeta42), and calcitonin, and a control protein, growth-hormone releasing factor (GRF).
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PMID:Photo-induced cross-linking of unmodified proteins (PICUP) applied to amyloidogenic peptides. 1922 75

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