Lysosome-related genes are regulated in the orbital fat of patients with graves' ophthalmopathy.
OBJECTIVE
The molecular mechanism involved in the hypertrophy of the orbital fat in patients with Graves' ophthalmopathy or thyroid eye disease (TED) remains unclear. Comparison of genome-wide expression profiles may help in the search for the gene sets involved in TED.


METHODS
Twenty-five orbital adipose tissue specimens were obtained, from which the RNA was isolated. Four of the tissue specimens (from four individuals, two with TED and two control subjects) were subjected to cDNA microarray analysis. The data were analyzed by the gene set enrichment analysis (GSEA) to survey the biological pathways involved in the pathogenesis of TED. Messenger RNA levels of some top-ranked genes in GSEA-selected pathways are validated by quantitative PCR (QPCR).


RESULTS
The expression of specific gene sets related to lytic vacuoles, lysosomes, and vacuoles were different between the specimens obtained from patients with TED and control subjects (P < 0.001). These three gene sets overlapped. For QPCR, four top-ranked genes were selected from these overlapping gene sets and another one that related to visual failure, using 21 independent samples of patients with TED (n = 15) and control subjects (n = 6). The results showed that ceroid-lipofuscinosis, neuronal 2, late infantile (CLN2; P = 0.044) and ceroid-lipofuscinosis, neuronal 3, juvenile (CLN3, which related to visual failure; P = 0.012) were significantly downregulated in the orbital fat of patients with TED. The expression of the beta subunit of hexosaminidase A (HEXB) was reduced as well, but the change did not reach statistical significance (P = 0.058).


CONCLUSIONS
Lysosome-related genes, such as CLN2, CLN3, and HEXB, may be involved in the pathogenesis of adipose tissue hypertrophy in TED.
Chen
Mei-Hsiu
MH
Graduate Institute of Clinical Medicine, National Taiwan University Medical College, Taipei, Taiwan.
Liao
Shu-Lang
SL
Chen
Ming-Hong
MH
Tsou
Pei-Ling
PL
Shih
Mei-Ju
MJ
Chang
Tien-Chun
TC
Chuang
Lee-Ming
LM
D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D000626:Aminopeptidases; D015415:Biomarkers / Q000378:metabolism; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D010450:Endopeptidases / Q000096:biosynthesis / Q000235:genetics*; D005260:Female; D005786:Gene Expression Regulation; D049970:Graves Ophthalmopathy / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics*; D046228:Microarray Analysis; D008875:Middle Aged; D018832:Molecular Chaperones / Q000096:biosynthesis / Q000235:genetics*; D009472:Neuronal Ceroid-Lipofuscinoses; D009915:Orbit; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics*; D057057:Serine Proteases; D000091346:Tripeptidyl-Peptidase 1; D054821:beta-Hexosaminidase beta Chain / Q000096:biosynthesis / Q000235:genetics*
D015415:Biomarkers; C105199:CLN3 protein, human; D008562:Membrane Glycoproteins; D018832:Molecular Chaperones; D012333:RNA, Messenger; D000091346:Tripeptidyl-Peptidase 1; C513386:HEXB protein, human; D054821:beta-Hexosaminidase beta Chain; D010450:Endopeptidases; D057057:Serine Proteases; D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; C000717267:TPP1 protein, human