Metabolic Activity of the Liver during Exercise—A Metabolomics Approach

The liver plays a pivotal role in substrate metabolism during fasting and exercise. Chances in the hepatic uptake or release of metabolites regulate the hepatic energy supply for other organs. Here we evaluated substrate flow over the hepato-splanchnic bed by assessing arterial-to-venous differences based on UPLC and CE-MS metabolomics analysis at rest and during exercise. Catheterized healthy young male subjects (n = 10) performed 2 h of ergometer cycling followed by 4 h of recovery. In response to exercise there was pronounced hepatic uptake of lactate, pyruvate, various amino acids and dicarboxylic acids, indicating high demand for gluconeogenic substrates and increase in anaplerotic reactions of the citric acid cycle. Medium chain fatty acids e.g., caproic acid showed a clear hepatic uptake during exercise, underlining their potential role as regulators of gluconeogenesis and mitochondrial substrate oxidation. While most long chain fatty acids showed increased hepatic uptake, saturated fatty acids with carbon chain > 18 were released. In contrast to other amino acids, branched chain amino acids were not taken up or released from the liver at any time point. Notably, the hepato-splanchnic bed showed pronounced uptake of oxygen and release of CO2 during exercise indicating up-regulation of energy consuming metabolic processes. In conclusion, the data provide novel insight in the regulation of hepatic metabolism at rest and during exercise. Disclosure P. Plomgaard: None. C. Hu: None. J.S. Hansen: Employee; Self; Novo Nordisk A/S. X. Zhao: None. M. Hoene: None. X. Wang: None. N. Secher: None. H. Haering: None. R. Lehmann: None. G. Xu: None. C. Weigert: None.