Heart failure (HF) is a major health epidemic in developed countries, however, its underlying pathology is not
well characterized. Tristetraprolin (TTP) is a tandem zinc finger protein that binds to AU-rich elements (ARE) in
the 3’-untranslated region (UTR) of target mRNA molecules, and induces their degradation. Global TTP knockout
(KO) mice display systemic inflammation, since TNFα mRNA is normally degraded by TTP, and deletion of TTP
leads to elevated TNFα levels. Thus, very few studies have assessed the role of TTP in metabolism despite its
original discovery as an insulin-inducible gene, and genetic studies linking TTP to metabolic syndrome. We are
addressing this fundamental gap in knowledge, and our strong preliminary data suggest critical activities by TTP
in cardiac metabolism and the development of HF. Specifically, we have shown that TTP inhibits fatty acid (FA)
and branched-chain amino acid (BCAA) metabolism (independent of its effects on inflammation), and reduces
the mRNA levels of key proteins in these processes, i.e., peroxisome proliferator-activated receptor (PPAR)-α
and branched-chain α–ketoacid acid dehydrogenase complex (BCKDC)-E2 subunits. The central hypothesis
of this proposal is that TTP inhibits cardiac FA and BCAA metabolism by binding to and degrading
PPARα and BCKDC-E2 mRNAs, and that TTP exacerbates the development of HF by impairing FA and
BCAA metabolism. In Aim 1, we will assess whether TTP inhibits cardiac FA metabolism by binding to PPARα
mRNA and promoting its degradation. We will assess whether TTP binds to PPARα mRNA by performing RNA
co-immunopreciptation (co-IP) and deletion studies of PPARα 3’-UTR AREs. We will also measure FA uptake
and metabolism in the hearts from cardiac-specific TTP KO (csTTP-KO) mice, and will determine whether these
changes are through PPARα using TTP/PPARα double KO mice. In Aim 2, we will determine whether TTP
decreases BCAA catabolism through binding and degradation of BCKDC-E2 mRNA. We will first determine
whether TTP binds BCKDC-E2 mRNA by performing RNA co-IP and deletion studies on BCKDC-E2 3’-UTR
AREs. We will also measure BCAA levels and BCKDC activity in heart tissue from csTTP-KO mice. To
demonstrate whether the reduction in BCAA catabolism with TTP KO is through BCKDC-E2, we will perform
similar studies with knockdown of TTP and BCKDC-E2. In Aim 3, we will determine whether TTP has detrimental
effects on the heart under stress conditions, and whether this depends upon impaired FA and BCAA metabolism.
We will subject csTTP-KO mice to pressure overload and ischemia, then assess their cardiac function and
metabolism. To determine the role of PPARα and BCKDC in this process, we will use csTTP/PPARα double KO
mice and will cross csTTP-KO with protein phosphatase 2Cm KO mice (which have reduced BCKDC activity),
and assess cardiac response to stress. We will also show our studies to develop novel drugs that target TTP
without inducing inflammation, providing potential clinical implications for Aim 3. These studies will improve our
understanding of cardiac metabolism, and may lead to new avenues for treatment of HF.
