Expression of Ceramide Synthases in Mice and Their Roles in Regulating Acyl-Chain Sphingolipids: A Framework for Baseline Levels and Future Implications in Aging and Disease

Sphingolipid signaling in kidney diseases

Sphingolipids are a family of bioactive lipids. The key components include ceramides, ceramide-1-phosphate, sphingosine, and sphingosine-1-phosphate. Sphingolipids were originally considered to be primarily structural elements of cell membranes but were later recognized as bioactive signaling molecules that play diverse roles in cellular behaviors such as cell differentiation, migration, proliferation, and death. Studies have demonstrated changes in key components of sphingolipids in the kidneys under different conditions and their important roles in the renal function and the pathogenesis of various kidney diseases. This review summarizes the most recent advances in the role of sphingolipid signaling in kidney diseases.

Safe and Orally Bioavailable Inhibitor of Serine Palmitoyltransferase Improves Age-Related Sarcopenia

The accumulation of ceramides and related metabolites has emerged as a pivotal mechanism contributing to the onset of age-related diseases. However, small molecule inhibitors targeting the ceramide de novo synthesis pathway for clinical use are currently unavailable. We synthesized a safe and orally bioavailable inhibitor, termed ALT-007, targeting the rate-limiting enzyme of ceramide de novo synthesis, serine palmitoyltransferase (SPT). In a mouse model of age-related sarcopenia, ALT-007, administered through the diet, effectively restored muscle mass and function compromised by aging. Mechanistic studies revealed that ALT-007 enhances protein homeostasis in Caenorhabditis elegans and mouse models of aging and age-related diseases, such as sarcopenia and inclusion body myositis (IBM); this effect is mediated by a specific reduction in very-long chain 1-deoxy-sphingolipid species, which accumulate in both muscle and brain tissues of aged mice and in muscle cells from IBM patients. These findings unveil a promising therapeutic avenue for developing safe ceramide inhibitors to address age-related neuromuscular diseases.

Evolutionary conservation analysis of human sphingomyelin metabolism pathway genes

Sphingomyelin is an important member of the sphingolipid family and was first reported more than a century ago. It has been demonstrated that sphingomyelin plays a crucial role in compositing cell membranes and signaling pathways. Despite extensive functional studies on the sphingolipid metabolism pathway genes, one intriguing question remains: how does the emergence of these genes during evolution correlate with the acquisition of new functions in different species? By employing an evolutionary conservation analysis, the sequence of occurrence of biological processes during evolutionary history can be elucidated. Here we summarize and analyze the conservation status of the genes involved in sphingomyelin metabolism.

Potential Vitamin E Signaling Mediators in Skeletal Muscle

Vitamin E (Vit E) deficiency studies underline the relevance of this vitamin in skeletal muscle (SkM) homeostasis. The knowledge of the effectors and modulators of Vit E action in SkM cells is limited, especially in aging and chronic diseases characterized by a decline in musculoskeletal health. Vit E comprises eight fat-soluble compounds grouped into tocopherols and tocotrienols, which share the basic chemical structure but show different biological properties and potentials to prevent diseases. Vit E has antioxidant and non-antioxidant activities and both favorable and adverse effects depending on the specific conditions and tissues. In this review, we focus on the actual knowledge of Vit E forms in SkM functions and new potential signaling effectors (i.e., bioactive sphingolipids and myokines). The possible advantages of Vit E supplementation in counteracting SkM dysfunctions in sarcopenia and under microgravity will also be discussed.

Ceramides-Emerging Biomarkers of Lipotoxicity in Obesity, Diabetes, Cardiovascular Diseases, and Inflammation

Abnormalities in lipid homeostasis have been associated with many human diseases, and the interrelation between lipotoxicity and cellular dysfunction has received significant attention in the past two decades. Ceramides (Cers) are bioactive lipid molecules that serve as precursors of all complex sphingolipids. Besides their function as structural components in cell and mitochondrial membranes, Cers play a significant role as key mediators in cell metabolism and are involved in numerous cellular processes, such as proliferation, differentiation, inflammation, and induction of apoptosis. The accumulation of various ceramides in tissues causes metabolic and cellular disturbances. Recent studies suggest that Cer lipotoxicity has an important role in obesity, metabolic syndrome, type 2 diabetes, atherosclerosis, and cardiovascular diseases (CVDs). In humans, elevated plasma ceramide levels are associated with insulin resistance and impaired cardiovascular and metabolic health. In this review, we summarize the role of ceramides as key mediators of lipotoxicity in obesity, diabetes, cardiovascular diseases, and inflammation and their potential as a promising diagnostic tool.

Application of sphingolipid-based nanocarriers in drug delivery: an overview

Sphingolipids (SL) are well recognized for their cell signaling through extracellular and intracellular pathways. Based on chemistry different types of SL are biosynthesized in mammalian cells and have specific function in cellular activity. SL has an ampiphilic structure with have hydrophobic body attached to the polar head enables their use as a drug delivery agent in the form of nanocarriers. SL-based liposomes can improve the solubility of lipophilic drugs through host and drug complexes and are more stable than conventional liposomal formulations. Preclinical studies of SL nanocarriers are reported on topical delivery, oral delivery, ocular delivery, chemotherapeutic delivery, cardiovascular delivery and Alzheimer's disease. The commercial challenges and patents related to SL nanoformulations are highlighted in this article.

Perspective: Therapeutic Implications for Sphingolipids in Health and Disease

Long thought to be structural components of cell membranes, sphingolipids (SLs) have emerged as bioactive molecules whose metabolism is tightly regulated. These bioactive lipids and their metabolic enzymes have been implicated in numerous disease states, including lysosomal storage disorders, multiple sclerosis, inflammation, and cancer as well as metabolic syndrome and obesity. In addition, the indications for many of these lipids to potentially serve as biomarkers for disease continue to emerge with increasing metabolomic and lipidomic studies. The implications of these studies have, in turn, led to the examination of SL enzymes and their bioactive lipids as potential therapeutic targets and as markers for therapeutic efficacy. SIGNIFICANCE STATEMENT: Many sphingolipids (SLs) and their metabolizing enzymes have been implicated in disease. This perspective highlights the potential for SLs to serve as therapeutic targets and diagnostic markers and discusses the implications for the studies and reviews highlighted in this Special Section on Therapeutic Implications for Sphingolipids in Health and Disease.