Abstract
Purpose: :
Low molecular weight molecules that act as UV filters protecting retina are derived from tryptophan catabolism via, kynurenine pathway by the enzyme indoleamine-2, 3, dioxygenase (IDO). This enzyme is induced mainly by Interferon IFN-γ in infections, inflammations etc. IFN-γ gene shows polymorphism that may be differentially related with induction of IDO.
Methods: :
We studied 426 cataract cases (102 Nuclear-NC, 99 cortical- CC, 94 posterior subcapsular-PSC and 131 mixed-MC type) and 123 controls to predict risk for IFN-γ genotypes. In all types of cataracts there was preponderance of females and non obese subjects with later onset in NCs and early onset in PSCs
Results: :
While frequencies of IFN-γ genotypes did not differ significantly in NC and CC, a higher frequency of AT heterozygotes was observed in PSC (50.0%) and MC (48.1%) patients as compared to controls (34.9%). Heterozygous females showed high frequency in PSC (53.8%) and MC (44.5%) cases and that of AA homozygotes in CC (61.3%) cases compared to controls (AT-32.1%, AA-54.7%). There was high risk for AT hetrozygotes for PSC (OR-1.86; CI-1.07-3.21; p≤0.02) and MC (OR-1.72; CI-1.04-2.85; p≤0.03) and low risk for AA homozygotes for MC (OR-0.44; CI-0.27-0.74; p≤0.001).Between the cataract types MCs differed significantly from other types in the distribution of IFN-γ polymorphism (MC vs. NC x2-10.90, 2d.f. p-≤0.004; MC vs. CC x2 -12.99, 2d.f. p- ≤0.001 and MC vs. PSC x2-6.04, 2d.f. p-≤0.04). Considering gender variation while both the sexes showed significant difference when CCs were compared to MC type (males: x2-6.29, 2d.f. p- ≤0.04; females: x2-7.68, 2d.f. p-≤0.02) in PSCs the difference was significant only in females(x2-6.93, 2d.f. p-≤0.03).
Conclusions: :
Present results showed high risk for heterozygotes of IFNγ genotypes for PSCs and MCs. Study of these individuals for variation in the regulation of IDO seems worth pursuing to have better understanding of the process of cataractogenesis.
Keywords: cataract • genetics • mutations