Heart failure with preserved ejection fraction (HFpEF) is commonly found in persons living with HIV (PLWH) even when antiretroviral therapy suppresses HIV viremia. However, studying this condition has been challenging because an appropriate animal model is not available. In this article, we studied calcium transient in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in culture to simulate the cardiomyocyte relaxation defect noted in PLWH and HFpEF and assess whether various drugs have an effect. We show that treatment of hiPSC-CMs with inflammatory cytokines (such as interferon-γ or TNF-α) impairs their Ca 2+ uptake into sarcoplasmic reticulum and that SGLT2 inhibitors, clinically proven as effective for HFpEF, reverse this effect. Additionally, treatment with mitochondrial antioxidants (like mito-Tempo) and certain antiretrovirals resulted in the reversal of the effects of these cytokines on calcium transient. Finally, incubation of hiPSC-CMs with serum from HIV patients with and without diastolic dysfunction did not alter their Ca 2+ -decay time, indicating that the exposure to the serum of these patients is not sufficient to induce the decrease in Ca 2+ uptake in vitro. Together, our results indicate that hiPSC-CMs can be used as a model to study molecular mechanisms of inflammation-mediated abnormal cardiomyocyte relaxation and screen for potential new interventions.

Sirtuins (SIRT) exhibit deacetylation or ADP-ribosyltransferase activity and regulate a wide range of cellular processes in the nucleus, mitochondria and cytoplasm. The role of the only sirtuin that resides in the cytoplasm, SIRT2, in the development of heart failure (HF) and cardiac hypertrophy is not known. In this paper, we show that the hearts of mice with deletion of Sirt2 ( Sirt2 -/- ) display improved cardiac function after ischemia-reperfusion (I/R) and pressure overload (PO), suggesting that SIRT2 exerts maladaptive effects in the heart in response to stress. Similar results were obtained in mice with cardiomyocyte-specific Sirt2 deletion. Mechanistic studies suggest that SIRT2 modulates cellular levels and activity of nuclear factor (erythroid-derived 2)-like 2 (NRF2), which results in reduced expression of antioxidant proteins. Deletion of Nrf2 in the hearts of Sirt2 -/- mice reversed protection after PO. Finally, treatment of mouse hearts with a specific SIRT2 inhibitors reduces cardiac size and attenuates cardiac hypertrophy in response to PO. These data indicate that SIRT2 has detrimental effects in the heart and plays a role in the progression of HF and cardiac hypertrophy, which makes this protein a unique member of the SIRT family. Additionally, our studies provide a novel approach for treatment of cardiac hypertrophy by targeting SIRT2 pharmacologically, providing a novel avenue for the treatment of this disorder.

Sirtuins (SIRT) exhibit deacetylation or ADP-ribosyltransferase activity and regulate a wide range of cellular processes in the nucleus, mitochondria, and cytoplasm. The role of the only sirtuin that resides in the cytoplasm, SIRT2, in the development of ischemic injury and cardiac hypertrophy is not known. In this paper, we show that the hearts of mice with deletion of Sirt2 (Sirt2-/-) display improved cardiac function after ischemia-reperfusion (I/R) and pressure overload (PO), suggesting that SIRT2 exerts maladaptive effects in the heart in response to stress. Similar results were obtained in mice with cardiomyocyte-specific Sirt2 deletion. Mechanistic studies suggest that SIRT2 modulates cellular levels and activity of nuclear factor (erythroid-derived 2)-like 2 (NRF2), which results in reduced expression of antioxidant proteins. Deletion of Nrf2 in the hearts of Sirt2-/- mice reversed protection after PO. Finally, treatment of mouse hearts with a specific SIRT2 inhibitor reduced cardiac size and attenuates cardiac hypertrophy in response to PO. These data indicate that SIRT2 has detrimental effects in the heart and plays a role in cardiac response to injury and the progression of cardiac hypertrophy, which makes this protein a unique member of the SIRT family. Additionally, our studies provide a novel approach for treatment of cardiac hypertrophy and injury by targeting SIRT2 pharmacologically, providing a novel avenue for the treatment of these disorders.

The product of hexokinase (HK) enzymes, glucose-6-phosphate, can be metabolized through glycolysis or directed to alternative metabolic routes, such as the pentose phosphate pathway (PPP) to generate anabolic intermediates. HK1 contains an N-terminal mitochondrial binding domain (MBD), but its physiologic significance remains unclear. To elucidate the effect of HK1 mitochondrial dissociation on cellular metabolism, we generated mice lacking the HK1 MBD (ΔE1HK1). These mice produced a hyper-inflammatory response when challenged with lipopolysaccharide. Additionally, there was decreased glucose flux below the level of GAPDH and increased upstream flux through the PPP. The glycolytic block below GAPDH is mediated by the binding of cytosolic HK1 with S100A8/A9, resulting in GAPDH nitrosylation through iNOS. Additionally, human and mouse macrophages from conditions of low-grade inflammation, such as aging and diabetes, displayed increased cytosolic HK1 and reduced GAPDH activity. Our data indicate that HK1 mitochondrial binding alters glucose metabolism through regulation of GAPDH.

Pregnancy is associated with substantial physiological changes of the heart, and disruptions in these processes can lead to peripartum cardiomyopathy (PPCM). The molecular processes that cause physiological and pathological changes in the heart during pregnancy are not well characterized. Here, we show that mTORc1 was activated in pregnancy to facilitate cardiac enlargement that was reversed after delivery in mice. mTORc1 activation in pregnancy was negatively regulated by the mRNA-destabilizing protein ZFP36L2 through its degradation of Mdm2 mRNA and P53 stabilization, leading to increased SESN2 and REDD1 expression. This pathway impeded uncontrolled cardiomyocyte hypertrophy during pregnancy, and mice with cardiac-specific Zfp36l2 deletion developed rapid cardiac dysfunction after delivery, while prenatal treatment of these mice with rapamycin improved postpartum cardiac function. Collectively, these data provide what we believe to be a novel pathway for the regulation of mTORc1 through mRNA stabilization of a P53 ubiquitin ligase. This pathway was critical for normal cardiac growth during pregnancy, and its reduction led to PPCM-like adverse remodeling in mice.

Introduction: It is reported that endothelial cell (EC) dysfunction underlies the pathogenesis of heart failure with preserved ejection fraction (HFpEF). EC are known to highly rely on glycolysis to keep their function, but the metabolism of EC under the situation with HFpEF is poorly understood. Objective: We sought to elucidate the role of hexokinase 1 (HK1) in ECs for the development of HFpEF. Results: Isolated ECs from mouse hearts showed higher protein expression of HK1 than isolated cardiomyocytes and fibroblasts, suggesting HK1 has an important role in EC function. Immunogold-staining of HK1 in hearts from C57BL6 mice treated with high fat diet and LNAME, a mouse model of HFpEF, showed increased dislocation of HK1 from the mitochondria in ECs. To study the role of HK1 dislocation, we generated ΔE1HK1 mice with mitochondrial-binding domain of the endogenous HK1 replaced with Flag tag. Subcellular fractionation confirmed that HK1 was dislocated from mitochondria in these mice. Echocardiography showed that the mice developed impaired cardiac relaxation at 20 weeks of age and HFpEF at 40 weeks of age. Significant increased fibrosis and microvascular rarefaction (MR) were observed at 40 weeks of age, but only MR was observed at 20 weeks of age, suggesting EC dysfunction likely precedes and promotes the development of HFpEF in these mice. To study the angiogenic ability of ECs with HK1 dislocation, we isolated ECs from ΔE1HK1 hearts and performed a tubing assay, and observed significantly less tubing in ΔE1HK1 ECs. To elucidate the mechanism by which angiogenesis is reduced in ΔE1HK1 ECs, we next performed metabolomics analysis in these cells. Our data indicated that the levels of metabolites in hexosamine-biosynthetic pathway (HBP) were altered between wild-type (WT) and ΔE1HK1 EC. We next analyzed the levels of O-GlcNAcylation, and showed that ECs from ΔE1HK1 hearts have higher O-GlcNAcylation than those from WT. Finally, treatment with ST045849, an inhibitor of O-GlcNAc transferase (OGT), rescued the less angiogenic ability in ECs from ΔE1HK1 hearts. Conclusion: Our studies demonstrate that dislocation of HK1 plays an important role in the development of HFpEF through hyper-O-GlcNAcylation. Drugs that inhibit OGT may provide a therapeutic option for HFpEF.

Introduction: It is reported that endothelial cell (EC) dysfunction underlies the pathogenesis of heart failure with preserved ejection fraction (HFpEF). EC are known to highly rely on glycolysis to keep their function, but the metabolism of EC under the situation with HFpEF is poorly understood. Objective: We sought to elucidate the role of hexokinase 1 (HK1) in ECs for the development of HFpEF. Results: Isolated ECs from mouse hearts showed higher protein expression of HK1 than isolated cardiomyocytes and fibroblasts, suggesting HK1 has an important role in EC function. Immunogold-staining of HK1 in hearts from C57BL6 mice treated with high fat diet and LNAME, a mouse model of HFpEF, showed increased dislocation of HK1 from the mitochondria in ECs. To study the role of HK1 dislocation, we generated ΔE1HK1 mice with mitochondrial-binding domain of the endogenous HK1 replaced with Flag tag. Subcellular fractionation confirmed that HK1 was dislocated from mitochondria in these mice. Echocardiography showed that the mice developed impaired cardiac relaxation at 20 weeks of age and HFpEF at 40 weeks of age. Significant increased fibrosis and microvascular rarefaction (MR) were observed at 40 weeks of age, but only MR was observed at 20 weeks of age, suggesting EC dysfunction likely precedes and promotes the development of HFpEF in these mice. To study the angiogenic ability of ECs with HK1 dislocation, we isolated ECs from ΔE1HK1 hearts and performed a tubing assay, and observed significantly less tubing in ΔE1HK1 ECs. To elucidate the mechanism by which angiogenesis is reduced in ΔE1HK1 ECs, we next performed metabolomics analysis in these cells. Our data indicated that the levels of metabolites in hexosamine-biosynthetic pathway (HBP) were altered between wild-type (WT) and ΔE1HK1 EC. We next analyzed the levels of O-GlcNAcylation, and showed that ECs from ΔE1HK1 hearts have higher O-GlcNAcylation than those from WT. Finally, treatment with ST045849, an inhibitor of O-GlcNAc transferase (OGT), rescued the less angiogenic ability in ECs from ΔE1HK1 hearts. Conclusion: Our studies demonstrate that dislocation of HK1 plays an important role in the development of HFpEF through hyper-O-GlcNAcylation. Drugs that inhibit OGT may provide a therapeutic option for HFpEF.

Iron is an essential nutrient for anabolic and catabolic metabolism. However, the mechanisms by which cells sense iron to regulate anabolism are unclear. Here, we report that the iron-binding histone-demethylase KDM3B is an iron sensor for mTORC1. Iron starvation results in genome-wide H3K9me2 hyper-methylation, suppression of leucine-signaling and RAPTOR expression, and mTORC1 inactivity despite sufficient levels of other nutrients. This process occurs in vivo, and is conserved throughout the eukaryotic kingdoms. Elevated expression of KDM3B targets are associated with reduced survival in a subset of cancers, and iron chelation represses mTORC1 in patient-derived tumor cells and sensitizes cancer cells to chemotherapy. Together, these data demonstrate a novel mechanism of iron sensing by KDM3B and repression of mTORC1 activity through disrupted leucine-signaling and RAPTOR downregulation. Due to ancestral eukaryotes sharing homologues of KDMs and mTORC1 core components, this pathway likely predated the emergence of the other nutrient sensors for mTORC1.

Introduction: Sirtuins are NAD+ dependent deacetylases and critical regulators of energy metabolism and response to oxidative stress. Sirtuin2 (SIRT2) is a cytoplasmic member of the sirtuin family, and has been shown to regulate cellular iron homeostasis through deacetylation of nuclear factor erythroid-derived 2-related factor 2 (NRF2). However, whether SIRT2-NRF2 pathway is involved in the development of heart failure remains unknown. Methods and results: To investigate the functional role of SIRT2 in the response to cardiac stress, SIRT2 knockout (KO) mice and their littermate controls were subjected to pressure overload by transverse aortic constriction (TAC). SIRT2 KO had normal appearance and cardiovascular parameters at baseline. However, in response to TAC, Sirt2 -/- mice displayed resistance to the pathological hypertrophic response, whereas wild type (WT) mice developed cardiac hypertrophy and heart failure. In addition, SIRT2 KO mice displayed less cardiac damage after /reperfusion injury. SIRT2 knockdown in neonatal rat cardiomyocytes (NRCM) reduced reactive oxygen species (ROS) production and cell death after H2O2 treatment. Since cellular oxidative stress is one of major contributor of cardiac dysfunction caused by both I/R injury and pressure overload, we examined whether NRF2 is associated with SIRT2-mediated cardiac response to oxidative stress. Levels of NRF2 was upregulated in NRCM with SIRT2 knockdown and treated with H2O2 compared to wild type (WT) cells. Moreover, NRF2 is translocated into the nucleus and its anti-oxidant target proteins are upregulated in NRCM with SIRT2 knockdown. SIRT2 was also found to bind and deacetylate NRF2 directly as determined by co-immunoprecipitation studies. This led to a reduction of its nuclear translocation and transcriptional activity. Finally, knockdown of both SIRT2 and NRF2 diminished the effects of SIRT2 knockdown on ROS production and cellular damage. Conclusion: These results indicate that SIRT2 contributes to pressure overload and I/R injury induced heart impairment in mice, and promotes oxidative stress injury in cardiomyocytes via deacetylating NRF2 and altering its activity.

Cells respond to iron deficiency by activating iron-regulatory proteins to increase cellular iron uptake and availability. However, it is not clear how cells adapt to conditions when cellular iron uptake does not fully match iron demand. Here, we show that the mRNA-binding protein tristetraprolin (TTP) is induced by iron deficiency and degrades mRNAs of mitochondrial Fe/S-cluster-containing proteins, specifically Ndufs1 in complex I and Uqcrfs1 in complex III, to match the decrease in Fe/S-cluster availability. In the absence of TTP, Uqcrfs1 levels are not decreased in iron deficiency, resulting in nonfunctional complex III, electron leakage, and oxidative damage. Mice with deletion of Ttp display cardiac dysfunction with iron deficiency, demonstrating that TTP is necessary for maintaining cardiac function in the setting of low cellular iron. Altogether, our results describe a pathway that is activated in iron deficiency to regulate mitochondrial function to match the availability of Fe/S clusters.

Introduction: BCAA are essential nutrients that are obtained exclusively from diet, and their cellular levels are regulated by their catabolism. Heart failure is associated with increased levels of...

Nature Communications 8: Article number: 14095 (2017); Published: 24 January 2017; Updated: 30 August 2017. The authors inadvertently omitted Eltyeb Abdelwahid, who contributed to the generation of animal models and their initial evaluation, from the author list. This has now been corrected in both the PDF and HTML versions of the Article.

SIRT2 is a cytoplasmic sirtuin that plays a role in various cellular processes, including tumorigenesis, metabolism, and inflammation. Since these processes require iron, we hypothesized that SIRT2 directly regulates cellular iron homeostasis. Here, we have demonstrated that SIRT2 depletion results in a decrease in cellular iron levels both in vitro and in vivo. Mechanistically, we determined that SIRT2 maintains cellular iron levels by binding to and deacetylating nuclear factor erythroid-derived 2-related factor 2 (NRF2) on lysines 506 and 508, leading to a reduction in total and nuclear NRF2 levels. The reduction in nuclear NRF2 leads to reduced ferroportin 1 (FPN1) expression, which in turn results in decreased cellular iron export. Finally, we observed that Sirt2 deletion reduced cell viability in response to iron deficiency. Moreover, livers from Sirt2-/- mice had decreased iron levels, while this effect was reversed in Sirt2-/- Nrf2-/- double-KO mice. Taken together, our results uncover a link between sirtuin proteins and direct control over cellular iron homeostasis via regulation of NRF2 deacetylation and stability.

Excess cellular iron increases reactive oxygen species (ROS) production and causes cellular damage. Mitochondria are the major site of iron metabolism and ROS production; however, few studies have investigated the role of mitochondrial iron in the development of cardiac disorders, such as ischemic heart disease or cardiomyopathy (CM). We observe increased mitochondrial iron in mice after ischemia/reperfusion (I/R) and in human hearts with ischemic CM, and hypothesize that decreasing mitochondrial iron protects against I/R damage and the development of CM. Reducing mitochondrial iron genetically through cardiac-specific overexpression of a mitochondrial iron export protein or pharmacologically using a mitochondria-permeable iron chelator protects mice against I/R injury. Furthermore, decreasing mitochondrial iron protects the murine hearts in a model of spontaneous CM with mitochondrial iron accumulation. Reduced mitochondrial ROS that is independent of alterations in the electron transport chain's ROS producing capacity contributes to the protective effects. Overall, our findings suggest that mitochondrial iron contributes to cardiac ischemic damage, and may be a novel therapeutic target against ischemic heart disease.

Introduction: Heart failure is associated with a change in cardiac energy metabolism and increased oxidative stress. Sirtuins (SIRTs) are NAD+-dependent deacetylases, and critical regulators of energy metabolism and oxidative stress response. However, the function of SIRT2, the only cytosolic sirtuin protein, in regulating the development of heart failure is largely unknown. Methods and results: To explore the role of SIRT2 in the development of heart failure, we examined the response of Sirt2 -/- mice and their littermate controls to pressure overload by transverse aortic constriction (TAC) and cardiac ischemia/reperfusion (I/R). Sirt2 -/- mice had normal appearance and cardiovascular parameters at baseline. However, in response to TAC, Sirt2 -/- mice displayed resistance to the pathological hypertrophic response. In the I/R injury model, Sirt2 -/- mice had better cardiac function and less cardiac fibrosis after 28 days of surgeries compared to WT mice. In vitro , Sirt2 knockdown reduced reactive oxygen species (ROS) production and cell death in neonatal rat cardiomyocytes (NRCM) after H 2 O 2 treatment. Since cellular oxidative stress is a key contributing factor to both I/R and cardiac hypertrophy, and nuclear factor (erythroid-derived 2)-like 2 (NRF2) plays a major role in antioxidant activity of the cell through regulation of several antioxidant proteins, we tested whether NRF2 is involved in SIRT2-mediated cardiac response to oxidative stress. We found that NRF2 expression is higher in NRCM with Sirt2 knockdown compared to WT cells after H 2 O 2 stimulation. And NRF2 is translocated into the nucleus and its anti-oxidant target proteins are upregulated in NRCM with Sirt2 knockdown. Further experiments demonstrated that SIRT2 directly interacts with and deacetylates NRF2, and reduces its nuclear translocation and transcriptional activity. In addition, Sirt2 -/- mice have higher levels of acetylated NRF2 in the heart. Finally, knockdown of both Sirt2 and Nrf2 abrogates the effects of Sirt2 knockdown on ROS production and cellular damage. Conclusion: Our results indicate that SIRT2 contributes to the development of heart failure in mice, and promotes oxidative stress injury in cardiomyocytes by deacetylating NRF2 and altering its activity.

Introduction: Altered substrate utilization has been described in type II diabetes and heart failure (HF), but current therapies do not target the metabolic derangements in these disorders. Identification of novel pathways regulating cellular metabolism could facilitate the development of new therapies. Tristetraprolin (TTP) is a tandem zinc finger protein that binds to AU-rich regions in the 3’ untranslated region (UTR) of mRNA molecules and causes their degradation. Its expression is reduced in patients with diabetes, and its cellular level is regulated by mTOR, a key protein involved in cellular metabolism. Furthermore, the yeast homolog of TTP has been suggested to play a role in metabolism. Thus, we hypothesized that TTP regulates cardiac metabolism and plays a role in the development of HF through its effects on substrate utilization in the heart. Results: We first assessed the effects of TTP modulation on cellular substrate utilization, and found that TTP downregulation in cultured cardiomyocytes resulted in higher palmitate uptake and oxidation while its overexpression had the opposite effect. Since TTP regulates its targets at the mRNA level, we studied the mRNA levels of all genes involved in lipid metabolism, and found that only PPARα mRNA to be significantly increased with TTP downregulation. Furthermore, we demonstrated that TTP physically interacts with PPARα mRNA, and the activity of a luciferase reporter harboring full-length PPARα 3’UTR is increased with TTP downregulation. Additionally, PPARα mRNA is stabilized with TTP knockdown. We then studied the role of TTP in cardiac metabolism using mice with cardiac-specific TTP knockout. Although cardiac-specific TTP knockout mice had normal cardiac function at baseline, they displayed higher fatty acid utilization compared to wild type littermate control in an ex vivo heart perfusion setup. We also demonstrated a significantly higher TTP levels in failing human and mouse cardiac samples, suggesting that TTP levels are altered in HF. Conclusion: Our results demonstrate that TTP is a novel regulator of cardiac fatty acid metabolism through its effect on PPARα, and that its levels are increased in HF. Thus, modulation of TTP may be a viable therapeutic approach for HF.

Introduction: Altered cardiac insulin sensitivity, substrate utilization, and energetics have been reported in diabetic cardiomyopathy. However, the mechanism behind insulin resistance in the heart in diabetes remain poorly understood. Hypoxia inducible factors (HIFs) have been linked to cellular metabolism, and their deletion in the heart resulted in metabolic changes. We have previously demonstrated that cardiac-specific knockout of ARNT, the obligatory binding partner of HIFs, causes spontaneous cardiomyopathy bearing similarity to diabetic cardiomyopathy, and its levels are reduced in genetic- and diet-induced obesity models. Here, we hypothesize that downregulation of ARNT in vivo exacerbates cardiac insulin resistance after high fat diet (HFD). Results: Mice with cardiac-specific heterozygous deletion of ARNT (cs-ARNT +/- ) had normal cardiac function at baseline, and had comparable food intake and weight gain during HFD treatment. We then evaluated cardiac substrate utilization using an ex vivo heart perfusion system. When perfused with a buffer without insulin, hearts from wild type (WT) and cs-ARNT +/- mice displayed comparable substrate utilization both after normal chow and after HFD. Addition of insulin to the perfusion system led to comparable increase in glucose utilization in hearts from normal chow-fed WT and ARNT +/- mice. However, the increased glucose utilization in response to insulin was attenuated in hearts from WT mice after HFD, while hearts from cs-ARNT +/- after HFD demonstrated virtually no increase in glucose utilization in response to insulin. This difference was not due to cardiac function as the cardiac work (assessed by heart rate and developing pressure) is comparable among all groups. Using neonatal rat cardiomyocytes, we also demonstrated that ARNT knockdown decreased glucose uptake and AKT phosphorylation in response to insulin, consistent with a blunted insulin-signaling pathway. Conclusion: Cardiac-specific ARNT heterozygote deletion exacerbates insulin resistance in a diet-induced obesity model, and the reduction of ARNT levels in various mouse models of diabetes is likely be a maladaptive response. Therefore, increasing ARNT signaling can be a potential therapy for diabetic cardiomyopathy.

Introduction: Type II diabetes mellitus (T2DM) is a growing health problem affecting over 29 million Americans and individuals with T2DM have increased mortality after myocardial infarction and stroke. Thus, it is imperative to find novel treatments for diabetes to offset the increased risk of cardiovascular disease (CVD) related mortality. Tristetraprolin (TTP) is an mRNA binding protein first identified as an insulin responsive gene. It binds to AU-rich elements (AREs) in the 3’ untranslated region (UTR) of certain transcripts and promotes their degradation. Reduced TTP expression has been observed in human patients with obesity and insulin resistance, and computational analysis suggests that TTP may bind to and degrade the mRNA of key enzymes involved in glucose oxidation. Thus, we hypothesized that downregulation of TTP would increase glucose oxidation and protect against T2DM. Results: We found hepatic expression of TTP to be decreased in diabetic mice. Using an in silico analysis to identify mRNAs that are targeted by TTP and play a role in glucose metabolism, we identified the pyruvate dehydrogenase-E2 subunit (PDH-E2) to contain several conserved TTP binding sites in its 3’ UTR. PDH-E2 expression was significantly increased (mRNA > 1.4-fold; protein > 2-fold) in hepatocytes isolated from liver-specific TTP knockout (KO) mice. Furthermore, measurement of PDH-E2 mRNA stability showed that PDH-E2 mRNA is significantly stabilized with TTP deletion, indicating that TTP regulates PDH-E2 mRNA. We then assessed whether the regulation of PDH-E2 by TTP alters glucose metabolism. Using Seahorse, we found a 1.7-fold increase in oxidative metabolism in TTP KO cells fed with glucose and pyruvate. This increase was reversed with siRNA mediated downregulation of PDH-E2. Systemically, liver-specific TTP KO mice fed a high-fat diet had significantly lower blood glucose levels after glucose tolerance tests and insulin tolerance tests. Conclusion: Our results suggest that a decrease in TTP protects against the development of T2DM by increasing PDH-E2 expression and subsequent glucose oxidation in the liver. Together, these data provide a novel, potential therapeutic target for T2DM, a significant modifiable risk factor contributing to CVD mortality.