BioProject

In this study we used the d337T TRb transgenic mouse that has been created to reproduce the human genetic disease known as resistance to thyroid hormone (RTH) as a model to determine if the d337T TRb mutation would have an effect on PPARa activation. A single amino acid deletion (d337T) abrogates thyroid hormone (T3) binding and transforms the thyroid hormone receptor (TRb) into a constitutive repressor. The principle goal was to determine if T3 regulates myocardial energy metabolism through its nuclear receptors. We introduced a known PPARa activator (WY14, 643) into control and d337T TRb transgenic mice then examined cardiac gene expression using Affymetrix 430_2 expression arrays and RT-PCR. We compared the gene expression of PPARa, RXRb and TRa,b and three PPARa target genes among four studies groups [control, control with WY14, 643, d337T TRb, and d337T TRb with WY14, 643] consisting of seven mice per group. Microarray analysis revealed that these genes responded to the WY14, 643 treatments of control and d337T TRb mice. Analysis of the array and RT-PCR data indicates that mRNA expression levels of PPARa and mRXRb decrease after a six hour drug treatment in both control and d337T TRb mice (P<0.01) as did the array mRNA expression levels for TRa & b (P<0.025). Three target genes (AMPD3, PDK4 and UCP3) of PPARa were up regulated in control and down regulated in the d337T TRb transgenic mouse, indicating a direct action on these metabolic genes when the TRb becomes a repressor. In conclusion, PPARa activation by WY14, 643 has a positive effect on control mice and a negative effect on the TRb transgenic mice which supports our hypothesis that T3 regulates myocardial energy metabolism through its nuclear receptors. Keywords: treatment and deletion effects Overall design: 7 control, 7 deletion strain individuals, 7 controls with a PPARalpha activator, 7 deletion strain individuals with a PPARalpha activator