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Ceramides are signals of fatty acid excess that accumulate when a cell's energetic needs have been met and its nutrient storage has reached capacity. As these sphingolipids accrue, they alter the metabolism and survival of cells throughout the body including in the heart, liver, blood vessels, skeletal muscle, brain, and kidney. These ceramide actions elicit the tissue dysfunction that underlies cardiometabolic diseases such as diabetes, coronary artery disease, metabolic-associated steatohepatitis, and heart failure. Here, we review the biosynthesis and degradation pathways that maintain ceramide levels in normal physiology and discuss how the loss of ceramide homeostasis drives cardiometabolic pathologies. We highlight signaling nodes that sense small changes in ceramides and in turn reprogram cellular metabolism and stimulate apoptosis. Finally, we evaluate the emerging therapeutic utility of these unique lipids as biomarkers that forecast disease risk and as targets of ceramide-lowering interventions that ameliorate disease. [ABSTRACT FROM AUTHOR]

Background: Neurodegenerative disorders such as Alzheimer's Disease (AD) are increasingly associated with irregular lipid accumulation. Dysfunction in the catabolism of sphingolipids leads to many neurodegenerative disorders but has only recently garnered interest in AD. Excess ceramide deposition has been observed in Aβ‐plaques, plasma, and cerebrospinal fluid in AD patients and AD mouse models. Ceramide‐lowering strategies have been underexplored as a treatment for AD and may prove to be a beneficial target in mitigating the disease. Method: We have used both pharmaceutical and genetic approaches to target ceramide accumulation in the 5xFAD mouse model of AD. Myriocin was used block ceramide de novo synthesis. The drug was administered in mice on a normal chow diet and an obesogenic pro‐ceramide high‐fat diet. As a genetic approach, we developed an inducible loss‐of‐ceramides model by overexpressing Asah1, the gene encoding the ceramide degrading enzyme acid ceramidase specifically in neurons. We assessed the loss of ceramides as a preventative treatment (overexpression beginning at 6‐weeks) or mature disease treatment (overexpression beginning at 30 weeks). We assessed Aβ plaques and the activation and quantity of glia by immunohistochemistry. Cognitive behavior was assessed using the Barnes maze and fear conditioning chambers. Frailty index scores were generated through clinically equivalent tests. Result: Myriocin treatment reduced ceramide accumulation in the hippocampus of 5xFAD mice. Vehicle‐treated 5xFAD mice had significant memory deficits compared to myriocin‐treated mice. The myriocin‐treated mice had smaller and fewer Aβ plaques, fewer hippocampal microglia, and a reduction in astrocyte arborization and numbers in hippocampus and cortex. Early overexpression of Asah1 in neurons improved memory loss in fear conditioning chambers. Plaque size and number remained unchanged. However, IBA1+ microglia/monocyte and GFAP+ astrocyte activation and migration were eliminated in neuronal Asah1 overexpressing mice. Plaques in these mice had no associated glia and glia morphology resembled wild‐type mice. Late overexpression of Asah1 in neurons led to improved frailty index scores compared to 5xFAD mice at one year of age. Conclusion: Pharmaceutical inhibition of ceramide synthesis improved cognitive outcomes and reduced AD pathologies in 5xFAD mice. Reducing ceramides specifically in neurons in 5xFAD mice eliminated gliosis and improved cognitive function. [ABSTRACT FROM AUTHOR]

The bioactive sphingolipid sphingosine 1-phosphate (S1P) and its five cognate receptors (S1PR1-5) have been implicated to play important role in multiple aspects of human physiology and diseases. The S1P-S1PR1 signaling axis in endothelial cells is crucial for establishing flow competent blood vessels. The role of S1P in neovascular pathology is of great interest and is evolving as a promising target for treatment. Here we describe an easy and affordable in vivo model of corneal neovascularization using an alkali chemical burn to the cornea. This method gives a consistent and easy-to-quantitate procedure for neovascularization and angiogenesis studies., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Sucrose gradient centrifugation is a very useful technique for isolating specific membrane types based on their size and density. This is especially useful for detecting fatty acids and lipid molecules that are targeted to specialized membranes. Without fractionation, these types of molecules could be below the levels of detection after being diluted out by the more abundant lipid molecules with a more ubiquitous distribution throughout the various cell membranes. Isolation of specific membrane types where these lipids are concentrated allows for their detection and analysis. We describe herein our synaptic membrane isolation protocol that produces excellent yield and clear resolution of five major membrane fractions from a starting neural tissue homogenate: P1 (nuclear), P2 (cytoskeletal), P3 (neurosynaptosomal), PSD (post-synaptic densities), and SV (synaptic vesicle)., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

The role of sphingolipids, mainly sphingosine 1-phosphate (S1P) and the receptors for which it serves as a ligand, is an interesting and promising area in both sphingolipid and vascular biology. S1P is crucial for establishing blood flow competent blood vessels (Jung et al. Dev Cell 23(3):600-610, 2012). The role of S1P in neovascular pathology is of great interest and promising as a target for treatment. Here we describe an easy and affordable in vivo model of neovascularization by an alkali chemical burn to the cornea. This gives a consistent and easy way to quantitate methods for neovascularization.

Sucrose gradient centrifugation is a very useful technique for isolating specific membrane types based on their size and density. This is especially useful for detecting fatty acids and lipid molecules that are targeted to specialized membranes. Without fractionation, these types of molecules could be below the levels of detection after being diluted out by the more abundant lipid molecules with a more ubiquitous distribution throughout the various cell membranes. Isolation of specific membrane types where these lipids are concentrated allows for their detection and analysis. We describe herein our synaptic membrane isolation protocol that produces excellent yield and clear resolution of five major membrane fractions from a starting neural tissue homogenate: P1 (Nuclear), P2 (Cytoskeletal), P3 (Neurosynaptosomal), PSD (Post-synaptic Densities), and SV (Synaptic Vesicle).