Circadian desynchronization and metabolic stress disrupt mito-nuclear signaling to drive heart failure with preserved ejection fraction (HFpEF)

Summary: Background: Heart failure with preserved ejection fraction (HFpEF) constitutes half of all heart failure, yet mechanisms driving its pathogenesis remain unclear. Shift workers and individuals with chronic circadian disruption face a higher risk for cardiovascular diseases and HFpEF comorbidities, underscoring the need to define cellular mechanisms impaired by circadian misalignment. During cardiac stress, cardiomyocytes have an increased protein processing burden, leading to mitochondrial misfolded protein accumulation. The mitochondrial unfolded protein response (UPRmt) regulated by Activating Transcription Factor 5 (ATF5) mitigates mitochondrial stress to maintain protein homeostasis and mitochondrial bioenergetics. Hypothesis: The combination of circadian and metabolic stressors impairs the ATF5-UPRmt axis, disrupting protein homeostasis, reducing mitochondrial function, and driving maladaptive cardiac remodeling. Methods: High fat diet (HFD) fed C57BL6 male mice were subjected to chronic shifted light-dark (LD) cycles mimicking human shift work (Shift), with appropriate controls. Metabolic function (glucose tolerance, insulin sensitivity, body fat) and cardiac function (treadmill fatigue testing, echocardiography, cardiac MRI, and terminal PV-loops) were assessed. ELISA was used to quantify serum heart failure biomarkers. Cardiac tissue was analyzed using proteomics, bulk RNA-seq, western blot, spatial transcriptomics, and histology. Mitochondrial function and morphology were evaluated via a substrate-dependent respiration assay (Orboros), membrane potential, and TEM. In vitro, Bmal1 was deleted in human iPSC-derived and AC16 cardiomyocytes using CRISPR/Cas9, and UPRmt was induced with gamitrinib-TPP. Mitonuclear signaling was evaluated by western blot and immunofluorescence. Results: ‘HS’ mice (HFD & Shift) exhibited the highest insulin resistance, glucose intolerance, and obesity, compared to ‘HR’ (HFD & Regular LD), ‘CS’ (Chow & Shift) and ‘CR’ (Chow and Regular LD cycle) groups. While all groups maintained preserved EF, HS mice showed diastolic dysfunction (↑MV E/E’, ↓MV E/A, and ↓LV diastolic strain) and reduced compliance (↑β in EDPVR), with increased lung weight, NT-proBNP, and exercise intolerance consistent with HFpEF. Gene and protein expression analysis revealed marked dysregulation of ATF5 and downstream targets in ‘HS’ mice, with accompanying mitochondrial impairment. ‘HS’ mouse hearts showed increased fibrosis, and spatial transcriptomics confirmed differential ATF5 pathway activation in cardiomyocytes. Mechanistically, Bmal1 deletion disrupted UPRmt gene expression and impaired Atf5-UPRmt mitonuclear signaling. Conclusions: The combination of chronic circadian disruption and metabolic stress induces cardiometabolic HFpEF in mice, with dysregulated cardiac ATF5-UPRmt signaling. This study identifies a novel link between circadian regulation and mitochondrial proteostasis in HFpEF. Jeongkyung Lee, Rajaganapathi Jagannathan, Ping Yang, Amit Kumar, Joseph Danvers, Vinny Negi, Mohamed Rahmdel, Olayemi Akinyele, Ian Sipula, Michael Jurczak, Yijen Wu, Dhivyaa Rajasundaram, Vijay K Yechoor, and Mousumi Moulik