An adiponectin-S1P autocrine axis protects skeletal muscle cells from palmitate-induced cell death

Abstract

Background: The prevalence of type 2 diabetes, obesity and their various comorbidities have continued to rise. In skeletal muscle lipotoxicity is well known to be a contributor to the development of insulin resistance. Here it was examined if the small molecule adiponectin receptor agonist AdipoRon mimicked the effect of adiponectin to attenuate palmitate induced reactive oxygen species (ROS) production and cell death in L6 skeletal muscle cells. Methods: L6 cells were treated ±0.1 mM PA, and ± AdipoRon, then assays analyzing reactive oxygen species (ROS) production and cell death, and intracellular and extracellular levels of sphingosine-1 phosphate (S1P) were conducted. To determine the mechanistic role of S1P gain (using exogenous S1P or using THI) or loss of function (using the SKI-II) were conducted. Results: Using both CellROX and DCFDA assays it was found that AdipoRon reduced palmitate-induced ROS production. Image-IT DEAD, MTT and LDH assays all indicated that AdipoRon reduced palmitate-induced cell death. Palmitate significantly increased intracellular accumulation of S1P, whereas in the presence of AdipoRon there was increased release of S1P from cells to extracellular medium. It was also observed that direct addition of extracellular S1P prevented palmitate-induced ROS production and cell death, indicating that S1P is acting in an autocrine manner. Pharmacological approaches to enhance or decrease S1P levels indicated that accumulation of intracellular S1P correlated with enhanced cell death. Conclusion: This data indicates that increased extracellular levels of S1P in response to adiponectin receptor activation can activate S1P receptor-mediated signaling to attenuate lipotoxic cell death. Taken together these findings represent a possible novel mechanism for the protective action of adiponectin.

Sphingosine 1-Phosphate Mediates Adiponectin Receptor Signaling Essential For Lipid Homeostasis And Embryogenesis

“…PA treatment of INS-1E cells reduced glucose stimulated insulin secretion (GSIS), which again was partially rescued by the addition of S1P (Figure 3F). This result is in line with previous results showing that S1P inhibits PA-induced apoptosis in INS-1 cells (Holland et al, 2011) and in L6 skeletal muscle cells (Botta et al, 2020).…”

Role of Perivascular Adipose Tissue-Derived Adiponectin in Vascular Homeostasis

“…Additionally, AdipoR2 has the ability to bind cellular ceramidase and enhance beneficial S1P production in cells [65]. This is consistent with a study that showed that in vitro myoblast treatment with AdipoRon (a small synthetic molecule that is known to activate both AdipoR1 and AdipoR2 [66]) enhanced ceramidase activity, resulting in higher cellular S1P levels and protecting cells against palmitate-induced lipotoxicity [67].…”

S1P Signalling Axis Is Necessary for Adiponectin-Directed Regulation of Electrophysiological Properties and Oxidative Metabolism in C2C12 Myotubes

“…In cardiac myocytes globular Adn is involved in mediating endothelial cell activation and behaves as physiological regulator of cyclooxigenase-2 signalling with a mechanism that depends on SK1: treatment with SK1 specific-siRNA reduced Adn-induced NF-kB activation and adhesion protein expression [ 22 ]. In ADN-KO mice restoration of Adn circulating levels reversed high fat diet-induced cardiac insulin resistance [ 23 ]. Moreover, treatment of H9C2 cardiomyoblasts and rat L6 skeletal muscle cells with AdipoRon, a small molecule agonist of AdipoR1 and AdipoR2, reduced palmitate-induced ROS production and lipotoxicity via the increase of S1P levels in the extracellular medium and activation of the S1P receptor-mediated signalling [ 23 ].…”