Regulation of ryanodine receptors by sphingosylphosphorylcholine: involvement of both calmodulin-dependent and -independent mechanisms

Choline: An Essential Nutrient for Skeletal Muscle

BACKGROUND

Choline is an essential micronutrient with a pivotal role in several metabolic pathways contributing to liver, neurological, and hematological homeostasis. Although choline is commonly administered to improve physical performance, its effects on muscle are still unclear. The aim of this scoping review is to analyze the role of choline on skeletal muscle in terms of biological effects and clinical implications.

METHODS

A technical expert panel (TEP) of 6 medical specialists with expertise in muscle physiology and skeletal muscle disorders performed the review following the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews) model. The TEP planned a research on PubMed selecting "choline" as MeSH (Medical Subject Headings) term adding to PubMed Search Builder the terms "skeletal muscle" and "muscle striated". TEP considered for eligibility articles published in the last 30 years, including original researches, particularly in vitro studies, and animal and clinical studies in the English language.

RESULTS

From the 1239 studies identified, TEP included 14 studies, 3 in vitro, 9 animal, and 2 clinical studies.

CONCLUSIONS

Our scoping review elucidates and summarizes the crucial role of choline in modulating muscle fat metabolism, muscle proteins homeostasis, and the modulation of inflammation and autophagy.

Role of Sphingosylphosphorylcholine in Tumor and Tumor Microenvironment

Sphingosylphosphorylcholine (SPC) is a unique type of lysosphingolipid found in some diseases, and has been studied in cardiovascular, neurological, and inflammatory phenomena. In particular, SPC’s studies on cancer have been conducted mainly in terms of effects on cancer cells, and relatively little consideration has been given to aspects of tumor microenvironment. This review summarizes the effects of SPC on cancer and tumor microenvironment, and presents the results and prospects of modulators that regulate the various actions of SPC.

Emerging roles of sphingosylphosphorylcholine in modulating cardiovascular functions and diseases

Sphingosylphosphorylcholine (SPC) is a bioactive sphingolipid in blood plasma that is metabolized from the hydrolysis of the membrane sphingolipid. SPC maintains low levels in the circulation under normal conditions, which makes studying its origin and action difficult. In recent years, however, it has been revealed that SPC may act as a first messenger through G protein-coupled receptors (S1P_1-5, GPR12) or membrane lipid rafts, or as a second messenger mediating intracellular Ca²⁺ release in diverse human organ systems. SPC is a constituent of lipoproteins, and the activation of platelets promotes the release of SPC into blood, both implying a certain effect of SPC in modulating the pathological process of the heart and vessels. A line of evidence indeed confirms that SPC exerts a pronounced influence on the cardiovascular system through modulation of the functions of myocytes, vein endothelial cells, as well as vascular smooth muscle cells. In this review we summarize the current knowledge of the potential roles of SPC in the development of cardiovascular diseases and discuss the possible underlying mechanisms.

Malignant hyperthermia: clinical and molecular aspects

CONTENT

Malignant hyperthermia (MH) is a potentially lethal pharmacogenetic disorder that affects genetically predisposed individuals. It manifests in susceptible individuals in response to exposure to Inhalant anesthetics, depolarizing muscle relaxants or extreme physical activity in hot environments. During exposure to these triggering agents, there is a rapid and sustained increase of myoplasmic calcium (Ca(2+)) concentration induced by hyperactivation of ryanodine receptor of skeletal muscle (RyR1), causing a profound change in Ca(2+) homeostasis, featuring a hypermetabolic state. RyR1, Ca(2+) release channels of sarcoplasmic reticulum, is the primary locus for MH susceptibility. Several mutations in the gene encoding the protein RyR1 have been identified; however, other genes may be involved. Actually, the standard method for diagnosing MH susceptibility is the muscle contracture test for exposure to halothane-caffeine (CHCT) and the only treatment is the use of dantrolene. However, with advances in molecular genetics, a full understanding of the disease etiology may be provided, favoring the development of an accurate diagnosis, less invasive, with DNA test, and also will provide the development of new therapeutic strategies for treatment of MH. Thus, this brief review aims to integrate molecular and clinical aspects of MH, gathering input for a better understanding of this channelopathy.