Putative protective role of autoantibodies against the insulin-like growth factor-1 receptor in Graves' Disease: results of a pilot study.

BACKGROUND: The insulin-like growth factor-1 receptor (IGF-1R) is a key element in the pathogenesis of Graves' Orbitopathy (GO), but the role of IGF-1R autoantibodies (IGF-1RAbs) has not been established. METHODS: We designed a cross-sectional investigation to measure IGF-1RAbs in patients with Graves' disease (GD), with or without GO, who underwent radioiodine therapy followed by glucocorticoids (GC). Twenty-nine patients were included, 15 of which with GO. Patients were evaluated at baseline and three and 6 months after radioiodine. The primary objective was the prevalence of positive tests for IGF-1RAbs. The secondary objectives were: (1) IGF-1RAbs concentrations and their variations; (2) relationship between IGF-1RAbs and the features of GO; (3) relationship between IGF-1RAbs and anti-thyroid autoantibodies. RESULTS: IGF-1RAbs above the cut-off value were found only in one patient with GD without GO. IGF-1RAb levels were greater in patients with GD without GO, at baseline (P < 0.0001), and after three (P < 0.0001) and six (P = 0.0001) months. No correlations were observed between IGF-1RAbs and the features of GO, nor between IGF-1RAbs and anti-thyroglobulin or anti-thyroperoxidase autoantibodies. There was an inverse correlation between anti-TSH receptor autoantibodies (TRAbs) and IGF-1RAb levels in GD patients with GO at 6 months (P = 0.03). CONCLUSIONS: IGF-1RAbs appear to be greater in patients with GD without GO compared with those with GO, suggesting a putative protective role of IGF-1RAbs on the development of GO, in line with the beneficial effects of Teprotumumab on GO. The inverse correlation between IGF-1RAbs and TRAbs 6 months after radioiodine may reflect antigen spreading and/or GC treatment.

Acromegaly in the setting of Tatton-Brown-Rahman Syndrome.

PURPOSE: Tatton-Brown-Rahman syndrome (TBRS) is a newly defined genetic entity characterized by overgrowth and intellectual disability, resulting from germline mutations in the gene encoding DNA methyltransferase 3 alpha (DNMT3A). Affected individuals with benign and malignant tumors have been reported; to our knowledge pituitary adenomas (and other tumors identified in our patient) have not yet been described in this syndrome. CASE: We report the case of a 34-year-old woman with TBRS who developed a GH-secreting pituitary macroadenoma and other benign tumors and cystic lesions involving diverse organ systems. Whole-exome sequencing revealed a heterozygous, likely pathogenic variant (c.700_709 del10, p. Gly234ArgfsX79) in exon7 of DNMT3A, and a heterozygous variant of uncertain significance (c.25 C>T, p.Arg9Trp) in exon 1 of the gene encoding aryl hydrocarbon receptor-interacting protein (AIP). The patient failed somatostatin analog treatment, and underwent surgery. The tumor retained AIP expression, and analysis of tumor DNA indicated the presence of both AIP alleles, consistent with no loss of heterozygosity. These findings suggest that the AIP variant was not the primary driver of pituitary adenoma development. CONCLUSION: Our case suggests that TBRS might be associated with pituitary adenoma and a broader spectrum of tumors than previously thought, making long-term follow up of these patients crucial to identify tumors early, and to elucidate the clinical spectrum of the disorder for optimization of management.

Serum antibodies against the insulin-like growth factor-1 receptor (IGF-1R) in Graves' disease and Graves' orbitopathy.

BACKGROUND: A role of the insulin-like growth factor-1 receptor (IGF-1R) in the pathogenesis of Graves' orbitopathy (GO) has been proposed, but the existence and function of anti-IGF-1R-antibodies (IGF-1R-Abs) are debated. METHODS: We designed a cross-sectional investigation to measure serum IGF-1R-Abs by a commercial assay in consecutive patients with Graves' disease (GD) compared with healthy subjects and patients with autoimmune thyroiditis (AT). A total of 134 subjects were screened including 27 healthy subjects, 80 GD patients (54 of whom with GO), and 27 AT patients. The main outcome measure was the prevalence of positive serum IGF-1R-Abs in GO, compared with GD without GO and with the other study groups. RESULTS: Having established a cut-off value at 55.2 ng/ml for positive tests, positive IGF-1R-Abs were more frequent in GD (25%), than in AT (3.7%, P = 0.003) and healthy subjects (0%, P = 0.006). Within GD, there was no difference between patients with or without GO. Serum levels of IGF-1R-Abs differed across the study population (P < 0.0001), reflecting their higher concentrations in GD (P < 0.0001 vs both AT and healthy subjects), but with no difference between patients with or without GO. In patients with GO, there was an inverse correlation between serum IGF-1R-Abs and CAS (R = - 0.376, 95% CI: from - 0.373 to - 0.631; P = 0.005), the significance of which remains to be investigated. CONCLUSIONS: Serum autoantibodies against the IFG-1R are present in one-fourth of GD patients, regardless of the presence of GO. Further functional studies are needed to investigate the significance of their inverse correlation with GO activity.

Relationship between serum cholesterol and Graves' orbitopathy (GO): a confirmatory study.

BACKGROUND: It has been suggested that high cholesterol represents a risk factor for Graves' orbitopathy (GO). In a recent cross-sectional study, a correlation between cholesterol and the presence of GO was found in patients with a Graves' disease (GD) of recent onset. To confirm this observation, we conducted a retrospective investigation in consecutive patients with GD. The primary outcome was the relationship between the presence of GO and low-density lipoprotein (LDL)-cholesterol. METHODS: The design entailed the inclusion of consecutive patients with a GD of recent onset, with or without GO, who came to our observation to receive radioiodine over a period of 6 months, and a stratification aimed at having two homogeneous group of patients in terms of thyroid function. A total of 86 patients fulfilled the inclusion and evaded the exclusion criteria. All patients underwent an ophthalmological assessment and serum lipids were measured. RESULTS: Serum levels of LDL-cholesterol were significantly higher in patients with GO (135.3 ± 41.3 mg/dL) compared with those without GO (106.6 ± 23.9 mg/dL, P = 0.0007). In a similar manner, serum levels of total cholesterol were higher in patients with GO (211.6 ± 44.0 mg/dL) than in those without GO (176.0 ± 27.2 mg/dL, P = 0.0001). There was no relationship between GO severity and activity and cholesterol. There was no relationship between GO and high-density lipoprotein-cholesterol or triglycerides. CONCLUSIONS: Our study confirms a relationship between the presence of GO and cholesterol in patients with GD of recent onset. Whether lowering of cholesterol ameliorates, GO remains to be established.

Use of low-dose radioiodine ablation for Graves' orbitopathy: results of a pilot, perspective study in a small series of patients.

OBJECTIVE: Elimination of thyroid antigens by total thyroid ablation (TTA), namely, thyroidectomy followed by radioiodine, may be beneficial for Graves' Orbitopathy (GO). TTA is usually performed with a 131I dose of 30 mCi. In Italy, this dose must be followed by a 24-h protected hospitalization, with increase in the waiting lists. In contrast, a 15 mCi dose can be given without hospitalization and with lower costs. Here, we investigated whether a lower dose of radioiodine can be used to ablate thyroid remnants in patients with GO, after thyroidectomy. METHODS: The study was performed in two small groups of consecutive thyroidectomized patients (six patients per group) with Graves' hyperthyroidism and GO. Patients underwent ablation with either 15 or 30 mCi of 131I following treatment with recombinant human TSH (rhTSH). The primary outcome was rhTSH-stimulated serum thyroglobulin (Tg) at 6 months. The secondary outcome was baseline Tg at 6 months. RESULTS: Baseline Tg and rhTSH-stimulated Tg after at 6 months did not differ between two groups, suggesting a similar extent of ablation. rhTSH-stimulated Tg was reduced significantly compared with rhTSH-stimulated Tg at ablation in both groups. GO outcome following treatment with intravenous glucocorticoids did not differ between the two groups. CONCLUSIONS: Our findings may provide a preliminary basis for the use of a 15 mCi dose of radioiodine upon rhTSH stimulation in thyroidectomized patients with Graves' hyperthyroidism and GO.

Statins are not a risk factor for liver damage associated with intravenous glucocorticoid pulse therapy for Graves' orbitopathy.

OBJECTIVE: Acute liver damage (ALD) is associated with high-dose intravenous (iv) glucocorticoid (GC) (ivGC) pulse therapy in ~1 % of patients for Graves' orbitopathy (GO). It has been proposed that statins may increase the risk of ALD. Here we investigated the frequency of ALD according to the assumption of statins in a large retrospective cohort study. METHODS: We studied 1076 consecutive patients with GO given ivGC. ALD was defined as an increase in alanine aminotransferase ≥300 U/l. RESULTS: At the time of ivGC, 62 patients were taking statins and 1014 were not. The frequency of ALD has been reported to be 1.2 cases/100,000 statins users and 1300/100,000 in GO patients given ivGC. Thus, the expected frequency of ALD in patients given both statins and ivGC is 1560/100,000. Transferring these data to our series, one would have expected at least 0.96 cases of ALD (~one case), in the 62 patients given both ivGC and statins. However, no cases of ALD were observed in patients given statins, and the previously reported 14 cases of ALD in this series were seen in patients who were not taking statins. CONCLUSIONS: The lack of observation of cases of ALD in patients given ivGC and statins is quite reassuring. Although caution should be applied to any patient candidate to ivGC treatment and this should be particularly accurate in patients given statins, our findings somehow justify the use of ivGC in patients under statins, although further studies in larger cohorts are needed to confirm our conclusions.

Crystal structures of the components of the Staphylococcus aureus leukotoxin ED.

Staphylococcal leukotoxins are a family of ß-barrel, bicomponent, pore-forming toxins with membrane-damaging functions. These bacterial exotoxins share sequence and structural homology and target several host-cell types. Leukotoxin ED (LukED) is one of these bicomponent pore-forming toxins that Staphylococcus aureus produces in order to suppress the ability of the host to contain the infection. The recent delineation of the important role that LukED plays in S. aureus pathogenesis and the identification of its protein receptors, combined with its presence in S. aureus methicillin-resistant epidemic strains, establish this leukocidin as a possible target for the development of novel therapeutics. Here, the crystal structures of the water-soluble LukE and LukD components of LukED have been determined. The two structures illustrate the tertiary-structural variability with respect to the other leukotoxins while retaining the conservation of the residues involved in the interaction of the protomers in the bipartite leukotoxin in the pore complex.

Degradation of mannan I and II crystals by fungal endo-beta-1,4-mannanases and a beta-1,4-mannosidase studied with transmission electron microscopy.

We have used the endo-beta-1,4-mannanase from Trichoderma reesei (Tr Man5A), the endo-beta-1,4-mannanase from Aspergillus niger (An Man5A) and the exo-beta-1,4-mannosidase from A. niger (An Mnd2A) to follow the enzymatic degradation of mannan I and II crystals. The degradation process was studied by transmission electron microscopy and also followed by analysis of the released soluble reducing sugars. The mannan crystals were degraded by the endo-beta-1,4-mannanases and to a lesser extent by the exo-beta-1,4-mannosidase. The observed hydrolysis pattern on mannan I crystals is fully consistent with the current view of the molecular structure of these crystals. The molecular organization of the mannan chains in mannan II crystals is less clear and the digestion results give some further information about the ultrastructure of mannan II. In addition, insight is provided into the mode of the enzymatic attack on the crystals of mannan I and mannan II.

Oligosaccharide binding to family 11 xylanases: both covalent intermediate and mutant product complexes display (2,5)B conformations at the active centre.

The glycoside hydrolase sequence-based classification reveals two families of enzymes which hydrolyse the beta-1,4-linked backbone of xylan, xylanases, termed families GH-10 and GH-11. Family GH-11 xylanases are intriguing in that catalysis is performed via a covalent intermediate adopting an unusual (2,5)B (boat) conformation, a conformation which also fulfils the stereochemical constraints of the oxocarbenium ion-like transition state. Here, the 1.9 A structure of a nucleophile, E94A, mutant of the Xyn11 from Bacillus agaradhaerens in complex with xylotriose is presented. Intriguingly, this complex also adopts the (2,5)B conformation in the -1 subsite, with the vacant space provided by the Glu-->Ala mutation allowing the sugar to adopt the alpha-configuration at C1. The structure of the covalent 2-deoxy-2-fluoroxylobiosyl-enzyme intermediate has been extended to atomic (1.1 A) resolution.

Digestion of single crystals of mannan I by an endo-mannanase from Trichoderma reesei.

The enzymatic degradation of single crystals of mannan I with the catalytic core domain of a beta-mannanase (EC 3.2.1.78 or Man5A) from Trichoderma reesei was investigated by transmission electron microscopy and electron diffraction. The enzyme attack took place at the edge of the crystals and progressed towards their centres. Quite remarkably the crystalline integrity of the crystals was preserved almost to the end of the digestion process. This behaviour is consistent with an endo-mechanism, where the enzyme interacts with the accessible mannan chains located at the crystal periphery and cleaves one mannan molecule at a time. The endo mode of digestion of the crystals was confirmed by an analysis of the soluble degradation products.

The three-dimensional structure of a Trichoderma reesei beta-mannanase from glycoside hydrolase family 5.

The crystal structure of the catalytic core domain of beta-mannanase from the fungus Trichoderma reesei has been determined at a resolution of 1.5 A. The structure was solved using the anomalous scattering from a single non-isomorphous platinum complex with two heavy-metal sites in space group P2(1). The map computed with the experimental phases was enhanced by the application of an automated model building and refinement procedure using the amplitudes and experimental phases as observations. This approach is expected to be of more general application. The structure of the native enzyme and complexes with Tris-HCl and mannobiose are also reported: the mannobiose binds in subsites +1 and +2. The structure is briefly compared with that of the homologous beta-mannanase from the bacterium Thermomonospora fusca.

Binding of non-catalytic ATP to human hexokinase I highlights the structural components for enzyme-membrane association control.

BACKGROUND: Hexokinase I sets the pace of glycolysis in the brain, catalyzing the ATP-dependent phosphorylation of glucose. The catalytic properties of hexokinase I are dependent on product inhibition as well as on the action of phosphate. In vivo, a large fraction of hexokinase I is bound to the mitochondrial outer membrane, where the enzyme adopts a tetrameric assembly. The mitochondrion-bound hexokinase I is believed to optimize the ATP/ADP exchange between glucose phosphorylation and the mitochondrial oxidative phosphorylation reactions. RESULTS: The crystal structure of human hexokinase I has been determined at 2.25 A resolution. The overall structure of the enzyme is in keeping with the closed conformation previously observed in yeast hexokinase. One molecule of the ATP analogue AMP-PNP is bound to each N-terminal domain of the dimeric enzyme in a surface cleft, showing specific interactions with the nucleotide, and localized positive electrostatic potential. The molecular symmetry brings the two bound AMP-PNP molecules, at the centre of two extended surface regions, to a common side of the dimeric hexokinase I molecule. CONCLUSIONS: The binding of AMP-PNP to a protein site separated from the catalytic centre of human hexokinase I can be related to the role played by some nucleotides in dissociating the enzyme from the mitochondrial membrane, and helps in defining the molecular regions of hexokinase I that are expected to be in contact with the mitochondrion. The structural information presented here is in keeping with monoclonal antibody mapping of the free and mitochondrion-bound forms of the enzyme, and with sequence analysis of hexokinases that differ in their mitochondria binding properties.

Catalysis and specificity in enzymatic glycoside hydrolysis: a 2,5B conformation for the glycosyl-enzyme intermediate revealed by the structure of the Bacillus agaradhaerens family 11 xylanase.

BACKGROUND: The enzymatic hydrolysis of glycosides involves the formation and subsequent breakdown of a covalent glycosyl-enzyme intermediate via oxocarbenium-ion-like transition states. The covalent intermediate may be trapped on-enzyme using 2-fluoro-substituted glycosides, which provide details of the intermediate conformation and noncovalent interactions between enzyme and oligosaccharide. Xylanases are important in industrial applications - in the pulp and paper industry, pretreating wood with xylanases decreases the amount of chlorine-containing chemicals used. Xylanases are structurally similar to cellulases but differ in their specificity for xylose-based, versus glucose-based, substrates. RESULTS: The structure of the family 11 xylanase, Xyl11, from Bacillus agaradhaerens has been solved using X-ray crystallography in both native and xylobiosyl-enzyme intermediate forms at 1.78 A and 2.0 A resolution, respectively. The covalent glycosyl-enzyme intermediate has been trapped using a 2-fluoro-2-deoxy substrate with a good leaving group. Unlike covalent intermediate structures for glycoside hydrolases from other families, the covalent glycosyl-enzyme intermediate in family 11 adopts an unusual 2,5B conformation. CONCLUSIONS: The 2,5B conformation found for the alpha-linked xylobiosyl-enzyme intermediate of Xyl11, unlike the 4C1 chair conformation observed for other systems, is consistent with the stereochemical constraints required of the oxocarbenium-ion-like transition state. Comparison of the Xyl11 covalent glycosyl-enzyme intermediate with the equivalent structure for the related family 12 endoglucanase, CelB, from Streptomyces lividans reveals the likely determinants for substrate specificity in this clan of glycoside hydrolases.

Crystallization and preliminary X-ray crystallographic analysis of a Trichoderma reesei beta-mannanase from glycoside hydrolase family 5.

Crystals of the catalytic core domain of a Trichoderma reesei beta-mannanase belonging to glycoside hydrolase family 5 have been grown by the sitting-drop method at room temperature using ammonium sulfate as precipitant. The crystals grow as thin colourless plates and belong to space group P21, with unit-cell parameters a = 50.0, b = 54.3, c = 60.2 A, beta = 111.3 degrees, and have a single monomer of mannanase in the asymmetric unit. Native data to 2.0 A resolution have been collected at room temperature using synchrotron radiation. Data for a platinum derivative have been collected to 1.65 A at 110 K in a very short time at the CCLRC Daresbury synchrotron source, using a charge-coupled device (CCD) as detector.

Urokinase-type plasminogen activator overexpression enhances the invasive capacity of endothelial cells.

Fetal bovine aortic endothelial GM 7373 cells were transfected with a viral expression vector harboring the human urokinase-type plasminogen activator (uPA) gene. The stable transfectant clone uPA-R5 overexpressed and secreted human uPA as shown by Northern blot analysis, immunoprecipitation of metabolically labeled proteins, plasmin chromogenic assays, and SDS-PAGE zymography of cell extracts and conditioned media. The uPA-R5 cells were analyzed for their invasive capacity in vitro in the Matrigel chemoinvasion assay in the presence of serine- or metalloprotease inhibitors. uPA overexpression enhanced the invasive capacity of GM 7373 cells through a mechanism which differs from that mediated by metalloproteases. Endothelial cell uPA transfectants may represent an useful experimental model to investigate the role of uPA in angiogenesis and angioproliferative diseases.