Hepatic palmitoyl-proteomes and acyl-protein thioesterase protein proximity networks link lipid modification and mitochondria

Semaglutide normalizes increased cardiomyocyte calcium transients in a rat model of high fat diet-induced obesity

AIMS

Obesity increases the risk of heart failure with preserved (HFpEF), but not reduced ejection fraction (HFrEF). The glucagon-like peptide-1 receptor agonist (GLP-1-RA) semaglutide improves outcome of patients with obesity with or without HFpEF, while GLP-1-RAs were associated with adverse outcome in patients with HFrEF. Here, we investigate the effect of in vivo treatment with semaglutide on excitation-contraction coupling in a rat model of obesity.

METHODS AND RESULTS

Rats received high-fat/high-fructose diet for 8 weeks and were then randomized to semaglutide (HFD/Sema) or vehicle (HFD/Veh) for another 8 weeks, during which they could choose between HFD and a low-fat/high-fructose diet (LFD). Control rats received either standard chow (CON), HFD or LFD only, without treatment. After 16 weeks, sarcomere shortening and cytosolic Ca2+ concentrations ([Ca2+]c) were determined in isolated cardiomyocytes. Compared with CON, HFD/Veh increased the amplitude of [Ca2+]c transients and systolic sarcomere shortening in absence or presence of β-adrenergic stimulation, which was reversed by HFD/Sema. Caffeine-induced sarcoplasmic reticulum (SR) Ca2+ release and L-type Ca2+ channel (LTCC) currents were reduced by HFD/Sema versus HFD/Veh, while SR Ca2+ ATPase activity remained unaffected. Compared with HFD, LFD increased [Ca2+]c transients and sarcomere shortening further despite similar effects on body weight.

CONCLUSIONS

While HFD increased cardiomyocyte [Ca2+]c transients and systolic sarcomere shortening, semaglutide normalized these alterations, mediated by reduced SR Ca2+ load and LTCC currents. Because increased LTCC currents were previously traced to cardiac hypertrophy, these effects may explain why GLP-1-RAs provide benefits for patients with obesity with or without HFpEF, but rather adverse outcome in HFrEF.

Exploring glycolytic enzymes in disease: potential biomarkers and therapeutic targets in neurodegeneration, cancer and parasitic infections

Glycolysis, present in most organisms, is evolutionarily one of the oldest metabolic pathways. It has great relevance at a physiological level because it is responsible for generating ATP in the cell through the conversion of glucose into pyruvate and reducing nicotinamide adenine dinucleotide (NADH) (that may be fed into the electron chain in the mitochondria to produce additional ATP by oxidative phosphorylation), as well as for producing intermediates that can serve as substrates for other metabolic processes. Glycolysis takes place through 10 consecutive chemical reactions, each of which is catalysed by a specific enzyme. Although energy transduction by glucose metabolism is the main function of this pathway, involvement in virulence, growth, pathogen-host interactions, immunomodulation and adaptation to environmental conditions are other functions attributed to this metabolic pathway. In humans, where glycolysis occurs mainly in the cytosol, the mislocalization of some glycolytic enzymes in various other subcellular locations, as well as alterations in their expression and regulation, has been associated with the development and progression of various diseases. In this review, we describe the role of glycolytic enzymes in the pathogenesis of diseases of clinical interest. In addition, the potential role of these enzymes as targets for drug development and their potential for use as diagnostic and prognostic markers of some pathologies are also discussed.

Mechanisms and functions of protein S-acylation

Over the past two decades, protein S-acylation (often referred to as S-palmitoylation) has emerged as an important regulator of vital signalling pathways. S-Acylation is a reversible post-translational modification that involves the attachment of a fatty acid to a protein. Maintenance of the equilibrium between protein S-acylation and deacylation has demonstrated profound effects on various cellular processes, including innate immunity, inflammation, glucose metabolism and fat metabolism, as well as on brain and heart function. This Review provides an overview of current understanding of S-acylation and deacylation enzymes, their spatiotemporal regulation by sophisticated multilayered mechanisms, and their influence on protein function, cellular processes and physiological pathways. Furthermore, we examine how disruptions in protein S-acylation are associated with a broad spectrum of diseases from cancer to autoinflammatory disorders and neurological conditions.

Deacylases-structure, function, and relationship to diseases

Reversible S-acylation plays a pivotal role in various biological processes, modulating protein functions such as subcellular localization, protein stability/activity, and protein-protein interactions. These modifications are mediated by acyltransferases and deacylases, among which the most abundant modification is S-palmitoylation. Growing evidence has shown that this rivalrous pair of modifications, occurring in a reversible cycle, is essential for various biological functions. Aberrations in this process have been associated with various diseases, including cancer, neurological disorders, and immune diseases. This underscores the importance of studying enzymes involved in acylation and deacylation to gain further insights into disease pathogenesis and provide novel strategies for disease treatment. In this Review, we summarize our current understanding of the structure and physiological function of deacylases, highlighting their pivotal roles in pathology. Our aim is to provide insights for further clinical applications.

Depalmitoylation and cell physiology: APT1 as a mediator of metabolic signals

More than half of the global population is obese or overweight, especially in Western countries, and this excess adiposity disrupts normal physiology to cause chronic diseases. Diabetes, an adiposity-associated epidemic disease, affects >500 million people, and cases are projected to exceed 1 billion before 2050. Lipid excess can impact physiology through the posttranslational modification of proteins, including the reversible process of S-palmitoylation. Dynamic palmitoylation cycling requires the S-acylation of proteins by acyltransferases and the depalmitoylation of these proteins mediated in part by acyl-protein thioesterases (APTs) such as APT1. Emerging evidence points to tissue-specific roles for the depalmitoylase APT1 in maintaining homeostasis in the vasculature, pancreatic islets, and liver. These recent findings raise the possibility that APT1 substrates can be therapeutically targeted to treat the complications of metabolic diseases.