Proteomics of orbital tissue in thyroid-associated orbitopathy

Abstract

Context: A potentially altered protein expression profile in orbital tissue from patients with thyroid-associated orbitopathy (TAO) is suspected. Objective: To detect for the first time changes in proteomic patterns of orbital connective tissue in TAO and compare these with control tissue using mass spectrometry. Design: Proteomics cross-sectional, comparative study. Setting: Two academic endocrine institutions. Samples: A total of 64 orbitalandperipheral adipose tissue sampleswerecollected from 39 patients with TAO and 25 control subjects. Methods: Samples were analyzed and identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry technology. Main Outcome Measures: Mean intensity values of all identified peptides per protein. Results: Thirty-one proteins were identified, of which 16 differentiated between controls and patients with TAO. Different protein patterns between orbital and peripheral adipose tissue were observed. Compared to controls, 10 proteins were markedly up-regulated (-2-fold) in the orbital tissue of untreated patients: beta IV spectrin (6.2-fold), GTP binding G protein 2 (5.6-fold), POTE ankyrin domain family member F (5.4-fold), xylulokinase (4.1-fold), kinesin family member 1A and lipocalin 1 (both 3.6-fold), semicarbazide-sensitive metalloproteinase amine oxidase 3 and polymerase I transcript release factor (both 3.4-fold), cell-cycle protein elongin A binding protein 1 (3.3-fold), annexin A2 and cavin (both 3-fold), protein pointing to cell proliferation histone H4 (2.8-fold), andADAMmetallopeptidase with thrombospondin type 1 motif 14 (2.7-fold). The highest protein up-regulations were noted in the orbital tissue of medically untreated patients. Steroid therapy markedly reduced up-regulation of these proteins, foremost in nonsmokers. Conclusions: Proteins involved in tissue inflammation, adipose tissue differentiation, lipid metabolism, and tissue remodeling were up-regulated in orbital tissue of untreated patients with TAO. Steroids decreased the expression of these proteins, whereas smoking attenuated such effect.