Liver and Skeletal Muscle Interorgan Crosstalk: The Effects of Electrical Pulse Stimulation as an Exercise Mimetic on Lipid Accumulation in a Human Hepatocytes Model of Hepatic Steatosis

Introduction: Exercise can reduce the risk of developing liver disease by improving hepatic metabolism, however, the cellular mechanisms which underpin exercise-induced improves is not fully established. Myokines secreted from skeletal muscle (SkM) during exercise could mediate changes in hepatocyte metabolism via interorgan crosstalk. These experiments aimed to establish if conditioned media (CM) from electrical pulse stimulation (EPS) induced human SkM myotubes could attenuate lipids accumulation and alter cell respiration in a human hepatocyte model of hepatic steatosis. Methods: LHCN-M2 human SkM myotubes were exposed to 8 hours of EPS (12V, 3Hz, 2ms), following which CM was collected immediately post-stimulation. Huh7 human hepatocytes cultured in the presence of CM from EPS induced SkM for two days with a pathophysiological concentration (800µM) of lipids, to replicate hepatic steatosis. Immunofluorescence imaging with BODIPY was employed to detect the presence of neutral lipids. In addition, cell respiration analysis assessed the impact of CM on oxygen consumption rate (OCR) and extracellular acidification rate (ECAR). Results: EPS of LHCN myotubes increased AMPK and p38 MAPK phosphorylation (p < 0.05), with RNAseq analysis showing an increase in the expression of genes which regulate cytokine and chemokine proteins (adj.p < 0.05). Immunofluorescence analysis showed that the total intensity of BODIPY in Huh7 hepatocytes was reduced when exposed to CM from SkM cells compared to without cells however, there was no effect of EPS (p < 0.05). Cell respiration analysis showed there to be no effect of CM or Control media on OCR between conditions (p > 0.05). In hepatocytes exposed to 800µM of lipids, CM from SkM exposed to EPS resulted in lower basal ECAR compared to CM from SkM not exposed to EPS. Conclusions: These experiments show that CM SkM myotubes modulate lipids accumulation in a model of hepatic steatosis, however, EPS CM provides no additional benefits on lipid accumulation or cellular respiration. Additional experiments are required to further establish the effects of CM from EPS SkM myotubes on substrate utilisation in hepatocytes.