Thioredoxin 1 (Trx1) is a 12-kDa oxidoreductase that catalyzes thiol-disulfide exchange reactions to reduce proteins with disulfide bonds. As such, Trx1 helps protect the heart against stresses, such as ischemia and pressure overload. Mechanistic target of rapamycin (mTOR) is a serine/threonine kinase that regulates cell growth, metabolism, and survival. We have shown previously that mTOR activity is increased in response to myocardial ischemia-reperfusion injury. However, whether Trx1 interacts with mTOR to preserve heart function remains unknown. Using a substrate-trapping mutant of Trx1 (Trx1C35S), we show here that mTOR is a direct interacting partner of Trx1 in the heart. In response to HO treatment in cardiomyocytes, mTOR exhibited a high molecular weight shift in non-reducing SDS-PAGE in a 2-mercaptoethanol-sensitive manner, suggesting that mTOR is oxidized and forms disulfide bonds with itself or other proteins. The mTOR oxidation was accompanied by reduced phosphorylation of endogenous substrates, such as S6 kinase (S6K) and 4E-binding protein 1 (4E-BP1) in cardiomyocytes. Immune complex kinase assays disclosed that HO treatment diminished mTOR kinase activity, indicating that mTOR is inhibited by oxidation. Of note, Trx1 overexpression attenuated both HO-mediated mTOR oxidation and inhibition, whereas Trx1 knockdown increased mTOR oxidation and inhibition. Moreover, Trx1 normalized HO-induced down-regulation of metabolic genes and stimulation of cell death, and an mTOR inhibitor abolished Trx1-mediated rescue of gene expression. HO-induced oxidation and inhibition of mTOR were attenuated when Cys-1483 of mTOR was mutated to phenylalanine. These results suggest that Trx1 protects cardiomyocytes against stress by reducing mTOR at Cys-1483, thereby preserving the activity of mTOR and inhibiting cell death.

Background: Proper dynamics of RNA polymerase II, such as promoter recruitment and elongation, are essential for transcription. PGC-1α (peroxisome proliferator-activated receptor [PPAR]-γ coactivator-1α), also termed PPARGC1a, is a transcriptional coactivator that stimulates energy metabolism, and PGC-1α target genes are downregulated in the failing heart. However, whether the dysregulation of polymerase II dynamics occurs in PGC-1α target genes in heart failure has not been defined. Methods and Results: Chromatin immunoprecipitation-sequencing revealed that reduced promoter occupancy was a major form of polymerase II dysregulation on PGC-1α target metabolic gene promoters in the pressure-overload–induced heart failure model. PGC-1α-cKO (cardiac-specific PGC-1α knockout) mice showed phenotypic similarity to the pressure-overload–induced heart failure model in wild-type mice, such as contractile dysfunction and downregulation of PGC-1α target genes, even under basal conditions. However, the protein levels of PGC-1α were neither changed in the pressure-overload model nor in human failing hearts. Chromatin immunoprecipitation assays revealed that the promoter occupancy of polymerase II and PGC-1α was consistently reduced both in the pressure-overload model and PGC-1α-cKO mice. In vitro DNA binding assays using an endogenous PGC-1α target gene promoter sequence confirmed that PGC-1α recruits polymerase II to the promoter. Conclusions: These results suggest that PGC-1α promotes the recruitment of polymerase II to the PGC-1α target gene promoters. Downregulation of PGC-1α target genes in the failing heart is attributed, in part, to a reduction of the PGC-1α occupancy and the polymerase II recruitment to the promoters, which might be a novel mechanism of metabolic perturbations in the failing heart.

Peroxisome proliferator-activated receptor-α (PPARα), a nuclear receptor, plays an important role in the transcription of genes involved in fatty acid metabolism through heterodimerization with the retinoid x receptor (RXR). The consensus sequence of the PPAR response element (PPRE) is composed of two AGGTCA-like sequences directionally aligned with a single nucleotide spacer. PPARα and RXR bind to the 5’ and 3’ hexad sequences, respectively. However, the precise sequence definition of the PPRE remains obscure, and thus, the consensus sequence currently available remains AGGTCANAGGTCA with unknown redundancy. The vague PPRE sequence definition poses an obstacle to understanding how PPARα regulates fatty acid metabolism. Here we show that, rather than the generally accepted 6-bp sequence, PPARα actually recognized a 12-bp DNA sequence, of which the preferred binding sequence was WAWVTRGGBBAH. Additionally, the optimized RXRα hexad binding sequence was RGKTYA. Thus, the optimal PPARα/RXRα heterodimer binding sequence was WAWVTRGGBBAHRGKTYA. The single nucleotide substitution, which reduces binding of RXRα to DNA, attenuated PPARα-induced transcriptional activation, but this is not always true for PPARα. Using the definition of the PPRE sequence, novel PPREs were successfully identified. Taken altogether, the provided PPRE sequence definition contributes to the understanding of PPARα signaling by identifying PPARα direct target genes with functional PPARα response elements.

Background Increased blood pressure ( BP ) variability and nondipping status seen on 24‐hour ambulatory BP monitoring are often observed in autonomic failure ( ATF ). Methods and Results We assessed BP variability and nocturnal BP dipping in 273 patients undergoing ambulatory BP monitoring at Southwestern Medical Center between 2010 and 2017. SD , average real variability, and variation independent of mean were calculated from ambulatory BP monitoring. Patients were divided into a discovery cohort (n=201) and a validation cohort (n=72). ATF was confirmed by formal autonomic function test. In the discovery cohort, 24‐hour and nighttime average real variability, SD , and variation independent of mean did not differ significantly between ATF (n=25) and controls (n=176, all P >0.05). However, daytime SD, daytime coefficient of variation, and daytime variation independent of mean of systolic BP ( SBP ) were all significantly higher in patients with ATF than in controls in both discovery and validation cohorts. Nocturnal BP dipping was more blunted in ATF patients than controls in both cohorts (both P <0.01). Using the threshold of 16 mm Hg, daytime SD SBP yielded a sensitivity of 77% and specificity of 82% in detecting ATF in the validation cohort, whereas nondipping status had a sensitivity of 80% and specificity of 44%. The area under the receiver operator characteristic of daytime SD SBP was greater than the area under the receiver operator characteristic of nocturnal SBP dipping (0.79 [0.66‐0.91] versus 0.73 [0.58‐0.87], respectively). Conclusions Daytime SD of SBP is a better screening tool than nondipping status in detecting autonomic dysfunction.

Guideline-directed management of heart failure includes assessment of volume status, 1 for which estimation of jugular venous pressure (JVP) is the most reliable bedside marker. [2][3][4] Whether JVP can be assessed remotely, as would occur during a telemedicine visit, is unknown. Given the dramatic increase in telemedicine visits during the coronavirus disease 2019 (COVID-19) pandemic, this question has gained further importance. We conducted a prospective observational study comparing JVP estimates performed at bedside and over video chat with invasively measured right atrial pressure (RAP).