ABSTRACT
Background: The physiological ratio of T3:T4 is
essential to trigger the biological actions, since the T3:T4 ratio is efficiently regulated by extrathyroidal selenodeiodinases. Thr92Ala is
a common variant in the DIO2 gene, which may have an implication in decreased
phenotypic expression, but previous studies had conflicting outcomes.
Consequently, we have undertaken this study to understand the effect of this
SNP on CVD risk among type 2 diabetics. Methods: We included 130 T2DM patients
without signs of CVD as controls and 106 proved CVD patients with T2DM as
cases. The entire subjects were genotyped for Thr92Ala of DIO2 gene. FBG, lipid
& thyroid profile, HDL sub-fractionations, type II deiodinase, malondialdehyde,
paraoxonase, and superoxide dismutase were measured according to standard
procedures. Results: The mean DIO2 levels in Ala/Ala genotypes were
significantly lower than Thr/Thr + Thr/Ala genotypes (122 ± 39 ng/ml & 161
± 32 ng/ml respectively). The thyroid profile was normal in all the subjects;
merely it was altered significantly among the Ala/Ala genotypes when compared
with Thr/Thr + Thr/Ala genotypes. Remarkably, there is a significant decrease
in T3:T4 and HDL3:HDL2 ratios and
paraoxonase activity among Ala/Ala genotypes when compared with Thr/Thr +
Thr/Ala genotypes. TSH and T4 levels were near to upper normal
levels among Ala/Ala genotype. HDL3:HDL2 ratio is
positively correlated with paraoxonase activity among Thr/Thr + Thr/Ala
genotypes (r = 0.36, p < 0.05). Conclusion: Phenotype expression of DIO2
gene, thyroid profile, HDL2:HDL2 ratio and paraoxonase
activity are altered among the Ala/Ala genotype. Thus, Ala/Ala genotype plays a
key role in thyroid dysfunction, dyslipidemia and the development of CVD risk
among type 2 diabetics.