Heart failure (HF) is a prominent fatal cardiovascular disorder afflicting 3.4% of the adult population despite the advancement of treatment options. Therefore, a better understanding of the pathogenesis of HF is essential for exploring novel therapeutic strategies. Hypertrophy and fibrosis are significant characteristics of pathological cardiac remodeling, contributing to HF. The mechanisms involved in the development of cardiac remodeling and consequent HF are multifactorial, and in this review, the key underlying mechanisms are discussed. These have been divided into the following categories thusly: (i) mitochondrial dysfunction, including defective dynamics, energy production, and oxidative stress; (ii) cardiac lipotoxicity; (iii) maladaptive endoplasmic reticulum (ER) stress; (iv) impaired autophagy; (v) cardiac inflammatory responses; (vi) programmed cell death, including apoptosis, pyroptosis, and ferroptosis; (vii) endothelial dysfunction; and (viii) defective cardiac contractility. Preclinical data suggest that there is merit in targeting the identified pathways; however, their clinical implications and outcomes regarding treating HF need further investigation in the future. Herein, we introduce the molecular mechanisms pivotal in the onset and progression of HF, as well as compounds targeting the related mechanisms and their therapeutic potential in preventing or rescuing HF. This, therefore, offers an avenue for the design and discovery of novel therapies for the treatment of HF.

BACKGROUND: Morbidity and mortality of heart failure with preserved ejection fraction (HFpEF) is increased in metabolic disorders. However, options for preventing and treating these prevalent outcomes are limited. Intramyocardial lipotoxicity contributes to cardiac dysfunction. Here, we investigate the mechanisms underlying EDEM2 (endoplasmic reticulum degradation–enhancing alpha-mannosidase–like protein 2) regulation of cardiac lipid homeostasis and assess strategies that inhibit the incidence and progression of HFpEF. METHODS: Metabolic stress was induced in C57BL/6 male mice using a high-fat diet and N ω-nitro-L-arginine methyl ester. The recombinant adeno-associated virus 9 delivery system was used for loss- and gain-of-function studies. Palmitic acid and oleic acid stimulation of rat cardiomyocytes and human induced pluripotent stem cell–derived cardiomyocytes imitated a condition of high lipids in vitro. Molecular mechanisms were investigated via RNA sequencing, mass spectrometry proteomics, lipidomic analyses, transmission electron microscopy, histology, and luciferase reporter assays. RESULTS: In the human heart, we first detected lipid overload accompanied by a reduction of XBP1 (X-box binding protein 1) under metabolic stress. Thereafter, a decrease in EDEM2 was confirmed in human and mouse HFpEF hearts. Given that XBP1s (spliced X-box binding protein 1) is a transcription factor, EDEM2 was identified as its new target in cardiomyocytes. EDEM2 knockdown mice manifested lipid droplet accumulation and higher levels of triglycerides and diglycerides in the myocardium, aggravating oxidative stress, hypertrophy, and the onset and progression of HFpEF under metabolic stress. XBP1s ablation mice displayed a similar myocardial lipid disturbance and cardiac phenotypes, which were reversed by EDEM2 overexpression. Mechanistically, the findings obtained from rat cardiomyocytes and human induced pluripotent stem cell–derived cardiomyocytes demonstrated that, in the presence of EDEM2, SEC23A mediated intracellular translocation of ATGL (adipose triglyceride lipase) under fatty acid stimulation, inhibiting ATGL degradation and excessive intracellular lipid droplets. Furthermore, the functional studies supported that EDEM2 prevention of lipid overload occurred in an ATGL-dependent manner. Therapeutically, cardiac XBP1s or EDEM2 restoration mitigated lipid deposition and preserved lipid profiles in the myocardium, thus preventing the development of HFpEF. CONCLUSIONS: We demonstrate a cardioprotective mechanism regulating myocardial lipid homeostasis. The findings provide a promising therapeutic target to prevent and treat HFpEF, a condition with limited treatment options.

Oxygen depletion is well recognized for its role in the degradation of tropical coral reefs. Extreme acute hypoxic events that lead to localized mass mortality and the formation of ‘dead zones’ (a region where few or no organisms can survive due to a lack of oxygen) are particularly concerning as they can result in wide-ranging losses of biodiversity, ecosystem productivity and functioning, economic prosperity, and wellbeing. In March of 2022, the annual coral spawning event at Bills Bay (Coral Bay, Ningaloo Reef, Western Australia) coincided with elevated seawater temperature, calm weather conditions and a flood tide resulting in coral spawn becoming trapped in Bills Bay. Immediately after, there was a mass fish kill, which is believed to have been caused by local eutrophication resulting in severe oxygen depletion. The impact the deoxygenation and thermal stress event had on benthic communities has not yet been quantified; hence, the principal aim of this study is to document the extent of change that occurred in the benthic communities before and after the 2022 coral spawning event over a spatial gradient from the nearshore to mid-reef. Percent coral cover in the Bay decreased from 55.62 ± 2.26% in 2016–2018 and 70.44 ± 5.24% in 2021 to 1.16 ± 0.51% in 2022. Over the same period, the percent cover of turf algae increased from 27.40 ± 2.00% in 2016–2018 and 24.66 ± 6.67% in 2021 to 78.80 ± 3.06% in 2022, indicating a dramatic phase shift occurred at Bills Bay. The abundance of healthy coral colonies recorded on replicated belt transects at nine sites declined from 3452 healthy individuals in 2018 to 153 individuals in 2022 and coral generic richness decreased by 84.61%, dropping from 26 genera in 2018 to 4 genera in 2022. Previously dominant genera such as Acropora,Montipora and Echinopora, were extirpated from survey sites. Isolated colonies of massive Porites spp. and encrusting Cyphastrea sp. survived the event and understanding the mechanisms underpinning their greater survivorship is an important area of future research. Long-term monitoring is recommended to track the community recovery process and improve our understanding of the longer-term implications of this acute mortality event on the ecological, socio-economic and cultural values of Ningaloo Reef.

BACKGROUND: Endothelial defects in the heart are a contributor to cardiac pathological remodeling and dysfunction, which can be influenced by cardiomyocytes. Here, we explore cardioprotective crosstalk between cardiomyocytes and endothelial cells under diabetic conditions. METHODS: Type 2 diabetes was induced in male and female mice using a high-fat, high-sucrose diet in conjunction with low-dose streptozotocin. Cardiomyocyte-specific deletion of FGFR1 (fibroblast growth factor receptor 1) or KLB (beta-Klotho) was achieved by crossing floxed mice with αMHC (alpha-myosin heavy chain)-Cre transgenic mice, while the treatment potential was assessed by recombinant adeno-associated virus 9 delivery systems or administration of recombinant protein. Various in vitro models were used to investigate the mechanisms under a diabetes-like condition. The molecular mechanisms were explored through transcriptomics, proteomics, cytokine arrays, angiogenesis assays, histology, and luciferase reporter assays. RESULTS: Human diabetic hearts exhibited impaired angiogenic pathways with a marked reduction in myocardial capillary density. Multiomics profiling also revealed alterations in the FGFR1 (fibroblast growth factor receptor 1) pathway in mouse diabetic hearts. Both cardiomyocyte-specific FGFR1- and KLB- knockout mice exhibited reduced capillary abundance and developed decompensated cardiac remodeling. Mechanistic studies identified CEBPβ (CCAAT/enhancer binding protein beta) as a downstream transcription factor of the FGFR1/KLB pathway regulating MFG-E8 (milk fat globule-EGF factor 8) expression in cardiomyocytes. Cardiomyocyte-secreted MFG-E8 enhanced endothelial viability and branching. Importantly, the detrimental effects on the heart were rescued by corestoration of cardiac FGFR1 and KLB, whereas neither alone was sufficient, underscoring their synergistic action against diabetic stress. Finally, genetic or pharmacological enhancement of MFG-E8 reversed myocardial capillary rarefaction and led to an improvement in cardiac function, albeit with more pronounced therapeutic effects in males. CONCLUSIONS: Our findings demonstrate FGFR1/KLB-mediated cardioprotective mechanisms through cardiomyocyte-endothelial cell crosstalk and provide evidence that preserving adaptive remodeling represents a promising strategy to alleviate heart failure in both sexes.

Increased consumption of ultra-processed foods (UPFs) is a risk factor for metabolic disorder–associated heart failure (HF). Here, we demonstrate that UPF-induced calpain-1 aggravated oxidative stress, thereby increasing high mobility group box 1–mediated (HMGB1-mediated) myocardial inflammation, which contributes to cardiac dysfunction. After illustrating the dysregulated inflammatory pathways in human and murine hearts upon metabolic stress, we revealed an increase in calpain-1 alongside profound oxidative stress and inflammation in the failing myocardium. Mechanistically, in neonatal rat cardiomyocytes and human induced pluripotent stem cell–derived cardiomyocytes, HMGB1 was upregulated by calpain-1 and reactive oxygen species (ROS) upon stress of saturated and trans fatty acids. Consequently, HMGB1 promoted a proinflammatory response in macrophages. In contrast, inhibition of calpain or ROS efficiently repressed HMGB1 in cardiomyocytes. Therapeutically, either recombinant adeno-associated virus 9–delivered inhibitor of calpain-1 or its pharmacological inhibitor attenuated ROS and HMGB1-induced inflammation in the myocardium and mitigated HF in both male and female mice fed with an ultra-processed diet. Collectively, we have demonstrated the effects of suppressing calpain-1 and oxidative stress on alleviating myocardial inflammation via blockage of HMGB1 and cardiac dysfunction. The results provide a promising therapeutic strategy for preventing or treating HF in metabolic disorders.