The effect of short post-apnea time on plasma triglycerides, lipoprotein and cholesterol derived oxysterols levels

Apnea diving is characterized by extreme hypoxia and hypercapnia. Possible pathophysiological processes concerning the cardiovascular system are not yet fully understood. Hypoxia has effects on triglyceride metabolism and circulating blood lipids. To date, in voluntary apnea divers, no short-time hypoxia expositions focusing on plasma triglycerides, lipoprotein and cholesterol derived oxysterols levels have been performed. We hypothesize that short time hypoxemia leads to altered triglyceride, cholesterol, and oxysterol plasma levels in voluntary apnea divers.Ten athletes performed apnea under dry conditions in a horizontal position. Plasma levels of lipids, lipoproteins and oxysterols were determined with turbidimetric immunoassays, gas chromatography (GC) - flame ionization detection (FID) and GC-MS-SIM before apnea, immediately after apnea and 0.5 h after apnea. All sterols and oxysterols were corrected for GC-FID cholesterol as measured in the same sample. Spearman’s rank correlation test was performed and pairwise comparison of absolute and cholesterol corrected plasma levels from the different sampling dates was conducted using a robust mixed linear model.We observed significantly reduced levels of apolipoprotein B, triglycerides, cholesterol, high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, and oxysterols (7β-OHC, 24-OHC, 27-OHC and 7-KC) for different time points. Cholesterol corrected plasma levels of the oxysterols showed no significant changes after short post-apnea time except for a significant elevation of the cholestane-3β, 5α, 6β-triol ratio.We could observe that a single short time hypoxemia under dry conditions in voluntary apnea divers leads to altered triglyceride, cholesterol and oxysterol plasma levels.