The effects of intermittent hypoxia on hepatic expression of fatty acid translocase CD36 in lean and diet-induced obese mice

Abstract

BackgroundBoth obstructive sleep apnea (OSA) and non-alcoholic fatty liver disease (NAFLD) are prevalent within obese individuals. We aimed to investigate the effects of intermittent hypoxia (IH), a clinical feature of OSA, on hepatic expression of fatty acid translocase (CD36) in relation to liver injury in lean and diet-induced obese mice. MethodsFour-week-old male C57BL/6J mice were randomized to standard diet (SD) or high fat (HF) diet groups. At 13-week-old, all mice were exposed to either air or IH (IH30; thirty hypoxic episodes per hour) for four weeks. We assessed liver injury through lipid profile, oxidative and inflammatory stress, histological scoring and hepatic CD36 expression. ResultsIn lean mice, IH elevated serum and hepatic triglyceride and free fatty acid (FFA) levels, in line with upregulation of hepatic CD36 expression and myeloperoxidase (MPO)-positive cells in support of inflammatory infiltrates along with increase in serum malondialdehyde (MDA), C-X-C motif chemokine ligand 1(CXCL-1) and monocyte chemoattractant protein-1 (MCP-1). In diet-induced obese mice, an increase in hepatic alanine transaminase (ALT) activity, serum and hepatic levels of lipid parameters and inflammatory markers, serum MDA level, hepatic expressions of CD36 and α-smooth muscle actin (α-SMA), and MPO-positive cells was observed. IH potentiated hepatic ALT activity, serum CXCL-1 and hepatic interleukin-6 (IL-6), in line with inflammatory infiltrates, but paradoxically, reduced hepatic FFA level and hepatic CD36 expression, compared to obese mice without IH exposure. However, IH further augmented diet-induced liver steatosis and fibrosis as shown by histological scores. ConclusionThis study contributes to support that IH featuring OSA may lead to liver injury via differential regulation of hepatic CD36 expression in lean and diet-induced obese mice.