IRE1α Mediates the Hypertrophic Growth of Cardiomyocytes Through Facilitating the Formation of Initiation Complex to Promote the Translation of TOP-Motif Transcripts.

BACKGROUND: Cardiomyocyte growth is coupled with active protein synthesis, which is one of the basic biological processes in living cells. However, it is unclear whether the unfolded protein response transducers and effectors directly take part in the control of protein synthesis. The connection between critical functions of the unfolded protein response in cellular physiology and requirements of multiple processes for cell growth prompted us to investigate the role of the unfolded protein response in cell growth and underlying molecular mechanisms. METHODS: Cardiomyocyte-specific inositol-requiring enzyme 1α (IRE1α) knockout and overexpression mouse models were generated to explore its function in vivo. Neonatal rat ventricular myocytes were isolated and cultured to evaluate the role of IRE1α in cardiomyocyte growth in vitro. Mass spectrometry was conducted to identify novel interacting proteins of IRE1α. Ribosome sequencing and polysome profiling were performed to determine the molecular basis for the function of IRE1α in translational control. RESULTS: We show that IRE1α is required for cell growth in neonatal rat ventricular myocytes under prohypertrophy treatment and in HEK293 cells in response to serum stimulation. At the molecular level, IRE1α directly interacts with eIF4G and eIF3, 2 critical components of the translation initiation complex. We demonstrate that IRE1α facilitates the formation of the translation initiation complex around the endoplasmic reticulum and preferentially initiates the translation of transcripts with 5' terminal oligopyrimidine motifs. We then reveal that IRE1α plays an important role in determining the selectivity and translation of these transcripts. We next show that IRE1α stimulates the translation of epidermal growth factor receptor through an unannotated terminal oligopyrimidine motif in its 5' untranslated region. We further demonstrate a physiological role of IRE1α-governed protein translation by showing that IRE1α is essential for cardiomyocyte growth and cardiac functional maintenance under hemodynamic stress in vivo. CONCLUSIONS: These studies suggest a noncanonical, essential role of IRE1α in orchestrating protein synthesis, which may have important implications in cardiac hypertrophy in response to pressure overload and general cell growth under other physiological and pathological conditions.

The MYPT2-regulated striated muscle-specific myosin light chain phosphatase limits cardiac myosin phosphorylation in vivo.

The physiological importance of cardiac myosin regulatory light chain (RLC) phosphorylation by its dedicated cardiac myosin light chain kinase has been established in both humans and mice. Constitutive RLC-phosphorylation, regulated by the balanced activities of cardiac myosin light chain kinase and myosin light chain phosphatase (MLCP), is fundamental to the biochemical and physiological properties of myofilaments. However, limited information is available on cardiac MLCP. In this study, we hypothesized that the striated muscle-specific MLCP regulatory subunit, MYPT2, targets the phosphatase catalytic subunit to cardiac myosin, contributing to the maintenance of cardiac function in vivo through the regulation of RLC-phosphorylation. To test this hypothesis, we generated a floxed-PPP1R12B mouse model crossed with a cardiac-specific Mer-Cre-Mer to conditionally ablate MYPT2 in adult cardiomyocytes. Immunofluorescence microscopy using the gene-ablated tissue as a control confirmed the localization of MYPT2 to regions where it overlaps with a subset of RLC. Biochemical analysis revealed an increase in RLC-phosphorylation in vivo. The loss of MYPT2 demonstrated significant protection against pressure overload-induced hypertrophy, as evidenced by heart weight, qPCR of hypertrophy-associated genes, measurements of myocyte diameters, and expression of ß-MHC protein. Furthermore, mantATP chase assays revealed an increased ratio of myosin heads distributed to the interfilament space in MYPT2-ablated heart muscle fibers, confirming that RLC-phosphorylation regulated by MLCP, enhances cardiac performance in vivo. Our findings establish MYPT2 as the regulatory subunit of cardiac MLCP, distinct from the ubiquitously expressed canonical smooth muscle MLCP. Targeting MYPT2 to increase cardiac RLC-phosphorylation in vivo may improve baseline cardiac performance, thereby attenuating pathological hypertrophy.

Anisometropia and Amblyopia Outcomes in Early Versus Late Resolution of Congenital Nasolacrimal Duct Obstruction in Older Infants.

PURPOSE: Congenital nasolacrimal duct obstruction is a known risk factor for amblyopia and anisometropia. The purpose of this study was to investigate whether the rate of anisometropia and amblyopia development differed based on the age at CNLDO resolution in older infants. METHODS: This retrospective chart review at a single tertiary children's hospital from 2007 to 2017 compared early versus late spontaneous resolution (cutoff 12 months) and intervention (cutoff 15 months) groups presenting at ≥9 months of age, comparing visual outcomes, including anisometropia (≥1 D of sphere or cylinder) and amblyopia (≥2 levels difference in Teller acuity or optotype testing). Parents/guardians were contacted by phone for missing data on spontaneous resolution or intervention status. RESULTS: A total of 462 patients were included (152 early; 310 late group). The early group presented at a median age of 12.0 (interquartile range: 10.0, 13.0) months, while the late group presented at 21.0 (interquartile range: 15.0, 32.0) months. Unilateral disease occurred in 62% and 59%, respectively. Anisometropia was seen in (12/102) 12% of early versus (25/243) 10% of late patients (p = 0.686, 95% CI: -0.059, 0.088), and amblyopia in (4/131) 3% of early versus (14/286) 5% of late patients (p = 0.322, 95% CI: -0.061, 0.018). In patients presenting <24 months without undergoing surgery, spontaneous resolution occurred in 76% between 12 and 24 months (n = 41). CONCLUSIONS: Anisometropia and amblyopia rates did not significantly differ between early and delayed intervention for congenital nasolacrimal duct obstruction in this retrospective cohort presenting beyond 9 months of age to a children's hospital. This study found frequent late spontaneous resolution.

Single-cell transcriptional landscape of long non-coding RNAs orchestrating mouse heart development.

Long non-coding RNAs (lncRNAs) comprise the most representative transcriptional units of the mammalian genome. They are associated with organ development linked with the emergence of cardiovascular diseases. We used bioinformatic approaches, machine learning algorithms, systems biology analyses, and statistical techniques to define co-expression modules linked to heart development and cardiovascular diseases. We also uncovered differentially expressed transcripts in subpopulations of cardiomyocytes. Finally, from this work, we were able to identify eight cardiac cell-types; several new coding, lncRNA, and pcRNA markers; two cardiomyocyte subpopulations at four different time points (ventricle E9.5, left ventricle E11.5, right ventricle E14.5 and left atrium P0) that harbored co-expressed gene modules enriched in mitochondrial, heart development and cardiovascular diseases. Our results evidence the role of particular lncRNAs in heart development and highlight the usage of co-expression modular approaches in the cell-type functional definition.

Multivariate Models to Diagnose Early Referral-Warranted Retinopathy of Prematurity With Handheld Optical Coherence Tomography.

Purpose: The purpose of this study was to create multivariate models predicting early referral-warranted retinopathy of prematurity (ROP) using non-contact handheld spectral-domain optical coherence tomography (OCT) and demographic data. Methods: Between July 2015 and February 2018, infants ≤1500 grams birth weight or ≤30 weeks gestational age from 2 academic neonatal intensive care units were eligible for this study. Infants were excluded if they were too unstable to participate in ophthalmologic examination (2), had inadequate image quality (20), or received prior ROP treatment (2). Multivariate models were created using demographic variables and imaging findings to identify early referral-warranted ROP (referral-warranted ROP and/or pre-plus disease) by routine indirect ophthalmoscopy. Results: A total of 167 imaging sessions of 71 infants (45% male infants, gestational age 28.2+/-2.8 weeks, and birth weight 995.6+/-292.0 grams) were included. Twelve of 71 infants (17%) developed early referral-warranted ROP. The area under the receiver operating characteristic curve (AUC) was 0.94 for the generalized linear mixed model (sensitivity = 95.5% and specificity = 80.7%) and 0.83 for the machine learning model (sensitivity = 91.7% and specificity = 77.8%). The strongest variables in both models were birth weight, image-based Vitreous Opacity Ratio (an estimate of opacity density), vessel elevation, and hyporeflective vessels. A model using only birth weight and gestational age yielded an AUC of 0.68 (sensitivity = 77.3% and specificity = 63.4%), and a model using only imaging biomarkers yielded 0.88 (sensitivity = 81.8% and specificity = 84.8%). Conclusions: A generalized linear mixed model containing handheld OCT biomarkers can identify early referral-warranted ROP. Machine learning produced a less optimal model. Translational Relevance: With further validation, this work may lead to a better-tolerated ROP screening tool.

Inflammatory Mechanisms in Heart Failure with Preserved Ejection Fraction.

Heart failure with preserved ejection fraction (HFpEF) is now the most common form of heart failure and a significant public health concern for which limited effective therapies exist. Inflammation triggered by comorbidity burden is a critical element of HFpEF pathophysiology. Here, we discuss evidence for comorbidity-driven systemic and myocardial inflammation and the mechanistic role of inflammation in pathological myocardial remodeling in HFpEF.

Bilateral punctate keratitis and hurricane keratopathy following apremilast therapy.

Purpose: To report a unique case of bilateral punctate keratitis consistent with hurricane keratopathy during apremilast therapy. Observations: A 49-year-old female presented with severe, painful, bilateral, punctate keratitis following five months of apremilast therapy. The past ocular history was noncontributory. The past medical history included psoriasis refractory to topical corticosteroids. The patient subsequently received systemic apremilast therapy and noted improvement in her psoriatic rash. Five months later the patient presented to an outside eye care provider complaining of three weeks of progressive photophobia associated with pain and redness in both eyes. On examination, the patient had decreased visual acuity with diffuse conjunctival injection and punctate epithelial erosions in a whorl-like pattern in both eyes. The remainder of the ophthalmic exam was unremarkable. The patient was started on topical moxifloxacin drops, erythromycin ointment, and preservative free artificial tears, but did not improve. Apremilast was then discontinued and topical prednisolone was added once per day. Ten weeks after discontinuation of apremilast and topical steroid therapy, the patient had recovered normal vision with an intact and normal corneal epithelium. Conclusions and Importance: This is the first case report of cornea epithelial keratitis resembling hurricane keratopathy associated with apremilast treatment and should be recognized as a possible side effect of therapy with this class of drug.

Immunometabolic Mechanisms of Heart Failure with Preserved Ejection Fraction.

Heart failure with preserved ejection fraction (HFpEF) is increasing in prevalence worldwide, already accounting for at least half of all heart failure (HF). As most patients with HFpEF are obese with metabolic syndrome, metabolic stress has been implicated in syndrome pathogenesis. Recently, compelling evidence for bidirectional crosstalk between metabolic stress and chronic inflammation has emerged, and alterations in systemic and cardiac immune responses are held to participate in HFpEF pathophysiology. Indeed, based on both preclinical and clinical evidence, comorbidity-driven systemic inflammation, coupled with metabolic stress, have been implicated together in HFpEF pathogenesis. As metabolic alterations impact immune function(s) in HFpEF, major changes in immune cell metabolism are also recognized in HFpEF and in HFpEF-predisposing conditions. Both arms of immunity - innate and adaptive - are implicated in the cardiomyocyte response in HFpEF. Indeed, we submit that crosstalk among adipose tissue, the immune system, and the heart represents a critical component of HFpEF pathobiology. Here, we review recent evidence in support of immunometabolic mechanisms as drivers of HFpEF pathogenesis, discuss pivotal biological mechanisms underlying the syndrome, and highlight questions requiring additional inquiry.

ATF4 Protects the Heart From Failure by Antagonizing Oxidative Stress.

BACKGROUND: Cellular redox control is maintained by generation of reactive oxygen/nitrogen species balanced by activation of antioxidative pathways. Disruption of redox balance leads to oxidative stress, a central causative event in numerous diseases including heart failure. Redox control in the heart exposed to hemodynamic stress, however, remains to be fully elucidated. METHODS: Pressure overload was triggered by transverse aortic constriction in mice. Transcriptomic and metabolomic regulations were evaluated by RNA-sequencing and metabolomics, respectively. Stable isotope tracer labeling experiments were conducted to determine metabolic flux in vitro. Neonatal rat ventricular myocytes and H9c2 cells were used to examine molecular mechanisms. RESULTS: We show that production of cardiomyocyte NADPH, a key factor in redox regulation, is decreased in pressure overload-induced heart failure. As a consequence, the level of reduced glutathione is downregulated, a change associated with fibrosis and cardiomyopathy. We report that the pentose phosphate pathway and mitochondrial serine/glycine/folate metabolic signaling, 2 NADPH-generating pathways in the cytosol and mitochondria, respectively, are induced by transverse aortic constriction. We identify ATF4 (activating transcription factor 4) as an upstream transcription factor controlling the expression of multiple enzymes in these 2 pathways. Consistently, joint pathway analysis of transcriptomic and metabolomic data reveal that ATF4 preferably controls oxidative stress and redox-related pathways. Overexpression of ATF4 in neonatal rat ventricular myocytes increases NADPH-producing enzymes' whereas silencing of ATF4 decreases their expression. Further, stable isotope tracer experiments reveal that ATF4 overexpression augments metabolic flux within these 2 pathways. In vivo, cardiomyocyte-specific deletion of ATF4 exacerbates cardiomyopathy in the setting of transverse aortic constriction and accelerates heart failure development, attributable, at least in part, to an inability to increase the expression of NADPH-generating enzymes. CONCLUSIONS: Our findings reveal that ATF4 plays a critical role in the heart under conditions of hemodynamic stress by governing both cytosolic and mitochondrial production of NADPH.

Inhibition of Jumonji demethylases reprograms severe dilated cardiomyopathy and prolongs survival.

Hypertrophic/dilated cardiomyopathy, often a prequel to heart failure, is accompanied by maladaptive transcriptional changes that contribute to arrythmias and contractile misfunction. Transgenic mice constitutively expressing high levels of calcineurin are known to develop extreme heart hypertrophy, which progresses to dilated cardiomyopathy, and to die several weeks after birth. Here, we characterized aberrant transcriptional and epigenetic pathways in this mouse model and established a pharmacological approach to treat established cardiomyopathy. We found that H3K4me3 (trimethyl histone 3 lysine 4) and H3K9me3 (trimethyl histone 3 lysine 9) Jumonji histone demethylases are markedly increased at the protein level and show enhanced enzymatic activity in diseased hearts. These epigenetic regulators continued to increase with time, further affecting cardiac gene expression. Our findings parallel the lower H3K4me3 and H3K9me3 levels seen in human patients. Inhibition of Jumonji demethylase activities in vivo results in lower histone demethylase enzymatic function in the heart and higher histone methylation levels and leads to partial reduction of heart size, reversal of maladaptive transcriptional programs, improved heart function, and prolonged survival. At the molecular level, target genes of transcription factor myocyte enhancer factor 2 are specifically regulated in response to pharmacological or genetic inhibition of Jumonji demethylases. Similar transcriptional reversal of disease-associated genes is seen in a second disease model based on cardiac mechanical overload. Our findings validate pharmacological inhibitors of Jumonji demethylases as potential therapeutics for the treatment of cardiomyopathies across disease models and provide evidence of the reversal of maladaptive transcriptional reprogramming leading to partial restoration of cardiac function. In addition, this study defines pathways of therapeutic resistance upregulated with disease progression.

Integrated Stress Response Couples Mitochondrial Protein Translation With Oxidative Stress Control.

BACKGROUND: The integrated stress response (ISR) is an evolutionarily conserved process to cope with intracellular and extracellular disturbances. Myocardial infarction is a leading cause of death worldwide. Coronary artery reperfusion, the most effective means to mitigate cardiac damage of myocardial infarction, causes additional reperfusion injury. This study aimed to investigate the role of the ISR in myocardial ischemia/reperfusion (I/R). METHODS: Cardiac-specific gain- and loss-of-function approaches for the ISR were used in vivo. Myocardial I/R was achieved by ligation of the cardiac left anterior descending artery for 45 minutes followed by reperfusion for different times. Cardiac function was assessed by echocardiography. Cultured H9c2 cells, primary rat cardiomyocytes, and mouse embryonic fibroblasts were used to dissect underlying molecular mechanisms. Tandem mass tag labeling and mass spectrometry was conducted to identify protein targets of the ISR. Pharmacologic means were tested to manipulate the ISR for therapeutic exploration. RESULTS: We show that the PERK (PKR-like endoplasmic reticulum resident kinase)/eIF2α (α subunit of eukaryotic initiation factor 2) axis of the ISR is strongly induced by I/R in cardiomyocytes in vitro and in vivo. We further reveal a physiologic role of PERK/eIF2α signaling by showing that acute activation of PERK in the heart confers robust cardioprotection against reperfusion injury. In contrast, cardiac-specific deletion of PERK aggravates cardiac responses to reperfusion. Mechanistically, the ISR directly targets mitochondrial complexes through translational suppression. We identify NDUFAF2 (NADH:ubiquinone oxidoreductase complex assembly factor 2), an assembly factor of mitochondrial complex I, as a selective target of PERK. Overexpression of PERK suppresses the protein expression of NDUFAF2 and PERK inhibition causes an increase of NDUFAF2. Silencing of NDUFAF2 significantly rescues cardiac cell survival from PERK knockdown under I/R. We show that activation of PERK/eIF2α signaling reduces mitochondrial complex-derived reactive oxygen species and improves cardiac cell survival in response to I/R. Moreover, pharmacologic stimulation of the ISR protects the heart against reperfusion damage, even after the restoration of occluded coronary artery, highlighting clinical relevance for myocardial infarction treatment. CONCLUSIONS: These results suggest that the ISR improves cell survival and mitigates reperfusion damage by selectively suppressing mitochondrial protein synthesis and reducing oxidative stress in the heart.

Fli1 Promotes Vascular Morphogenesis by Regulating Endothelial Potential of Multipotent Myogenic Progenitors.

[Figure: see text].

Activation of Autophagic Flux Blunts Cardiac Ischemia/Reperfusion Injury.

[Figure: see text].

PKM1 Exerts Critical Roles in Cardiac Remodeling Under Pressure Overload in the Heart.

BACKGROUND: Metabolic remodeling precedes most alterations during cardiac hypertrophic growth under hemodynamic stress. The elevation of glucose utilization has been recognized as a hallmark of metabolic remodeling. However, its role in cardiac hypertrophic growth and heart failure in response to pressure overload remains to be fully illustrated. Here, we aimed to dissect the role of cardiac PKM1 (pyruvate kinase muscle isozyme 1) in glucose metabolic regulation and cardiac response under pressure overload. METHODS: Cardiac-specific deletion of PKM1 was achieved by crossing the floxed PKM1 mouse model with the cardiomyocyte-specific Cre transgenic mouse. PKM1 transgenic mice were generated under the control of tetracycline response elements, and cardiac-specific overexpression of PKM1 was induced by doxycycline administration in adult mice. Pressure overload was triggered by transverse aortic constriction. Primary neonatal rat ventricular myocytes were used to dissect molecular mechanisms. Moreover, metabolomics and nuclear magnetic resonance spectroscopy analyses were conducted to determine cardiac metabolic flux in response to pressure overload. RESULTS: We found that PKM1 expression is reduced in failing human and mouse hearts. It is important to note that cardiomyocyte-specific deletion of PKM1 exacerbates cardiac dysfunction and fibrosis in response to pressure overload. Inducible overexpression of PKM1 in cardiomyocytes protects the heart against transverse aortic constriction-induced cardiomyopathy and heart failure. At the mechanistic level, PKM1 is required for the augmentation of glycolytic flux, mitochondrial respiration, and ATP production under pressure overload. Furthermore, deficiency of PKM1 causes a defect in cardiomyocyte growth and a decrease in pyruvate dehydrogenase complex activity at both in vitro and in vivo levels. CONCLUSIONS: These findings suggest that PKM1 plays an essential role in maintaining a homeostatic response in the heart under hemodynamic stress.

Dome-shaped macula in premature infants visualized by handheld spectral-domain optical coherence tomography.

PURPOSE: To describe dome-shaped macula and associated clinical findings in premature infants. METHODS: This prospective, observational cohort study included a consecutive sample of premature infants screened for retinopathy of prematurity (ROP) with 9-month follow-up. Handheld spectral domain optical coherence tomography (SD-OCT) was performed at the time of ROP screening. Images were assessed for dome-shaped macula, cystoid macular edema, epiretinal membrane, vitreous bands, and punctate hyperreflective vitreous opacities. Dome height measurements were performed in a subset of images. Teller visual acuity and cycloplegic refraction were performed at an adjusted age of 8-10 months. RESULTS: Of 37 infants (74 eyes; 49% male; mean gestational age 27.8 ± 3.2 weeks; mean birth weight 949 ± 284 g), 24/37 (65%) demonstrated dome-shaped macula in at least one eye (13 both eyes, 5 right eye only, and 6 left eye only). Of the 74 eyes, 26 (35%) could be reliably measured, with a mean dome height of 139.0 ± 72.3 µm (range, 54-369 µm). Presence of dome-shaped macula was associated with a diagnosis of ROP (P = 0.02; OR, 3.03; 95% CI, 1.18-7.82) and pre-plus or plus disease (P = 0.02; OR, 4.20; 95% CI, 1.05-16.78). Infants with dome-shaped macula had lower birth weight compared with those without (877 vs 1081 g; P = 0.04). No associations with other demographics, OCT findings, and 9-month refractive outcomes were found. CONCLUSIONS: Dome-shaped macula was frequently identified by handheld SD-OCT in premature infants, especially those with lower birth weight and severe ROP. The long-term clinical significance of this finding is unknown.

Cooperative Binding of ETS2 and NFAT Links Erk1/2 and Calcineurin Signaling in the Pathogenesis of Cardiac Hypertrophy.

BACKGROUND: Cardiac hypertrophy is an independent risk factor for heart failure, a leading cause of morbidity and mortality globally. The calcineurin/NFAT (nuclear factor of activated T cells) pathway and the MAPK (mitogen-activated protein kinase)/Erk (extracellular signal-regulated kinase) pathway contribute to the pathogenesis of cardiac hypertrophy as an interdependent network of signaling cascades. How these pathways interact remains unclear and few direct targets responsible for the prohypertrophic role of NFAT have been described. METHODS: By engineering cardiomyocyte-specific ETS2 (a member of the E26 transformation-specific sequence [ETS] domain family) knockout mice, we investigated the role of ETS2 in cardiac hypertrophy. Primary cardiomyocytes were used to evaluate ETS2 function in cell growth. RESULTS: ETS2 is phosphorylated and activated by Erk1/2 on hypertrophic stimulation in both mouse (n=3) and human heart samples (n=8 to 19). Conditional deletion of ETS2 in mouse cardiomyocytes protects against pressure overload-induced cardiac hypertrophy (n=6 to 11). Silencing of ETS2 in the hearts of calcineurin transgenic mice significantly attenuates hypertrophic growth and contractile dysfunction (n=8). As a transcription factor, ETS2 is capable of binding to the promoters of hypertrophic marker genes, such as ANP, BNP, and Rcan1.4 (n=4). We report that ETS2 forms a complex with NFAT to stimulate transcriptional activity through increased NFAT binding to the promoters of at least 2 hypertrophy-stimulated genes: Rcan1.4 and microRNA-223 (=n4 to 6). Suppression of microRNA-223 in cardiomyocytes inhibits calcineurin-mediated cardiac hypertrophy (n=6), revealing microRNA-223 as a novel prohypertrophic target of the calcineurin/NFAT and Erk1/2-ETS2 pathways. CONCLUSIONS: Our findings point to a critical role for ETS2 in calcineurin/NFAT pathway-driven cardiac hypertrophy and unveil a previously unknown molecular connection between the Erk1/2 activation of ETS2 and expression of NFAT/ETS2 target genes.

NAD+ Repletion Reverses Heart Failure With Preserved Ejection Fraction.

[Figure: see text].

Xbp1s-FoxO1 axis governs lipid accumulation and contractile performance in heart failure with preserved ejection fraction.

Heart failure with preserved ejection fraction (HFpEF) is now the dominant form of heart failure and one for which no efficacious therapies exist. Obesity and lipid mishandling greatly contribute to HFpEF. However, molecular mechanism(s) governing metabolic alterations and perturbations in lipid homeostasis in HFpEF are largely unknown. Here, we report that cardiomyocyte steatosis in HFpEF is coupled with increases in the activity of the transcription factor FoxO1 (Forkhead box protein O1). FoxO1 depletion, as well as over-expression of the Xbp1s (spliced form of the X-box-binding protein 1) arm of the UPR (unfolded protein response) in cardiomyocytes each ameliorates the HFpEF phenotype in mice and reduces myocardial lipid accumulation. Mechanistically, forced expression of Xbp1s in cardiomyocytes triggers ubiquitination and proteasomal degradation of FoxO1 which occurs, in large part, through activation of the E3 ubiquitin ligase STUB1 (STIP1 homology and U-box-containing protein 1) a novel and direct transcriptional target of Xbp1s. Our findings uncover the Xbp1s-FoxO1 axis as a pivotal mechanism in the pathogenesis of cardiometabolic HFpEF and unveil previously unrecognized mechanisms whereby the UPR governs metabolic alterations in cardiomyocytes.