The authors thank A. van Cruchten and W. Smit for the serum analysis of 2-AA. The CoLaus study received financial contributions from GlaxoSmithKline, the Faculty of Biology and Medicine of Lausanne, and the Swiss National Science Foundation (SNSF; 33CSCO-122661). The authors thank P. Vollenweider, G. Waeber, V. Mooser and D. Waterworth, Co-PIs of the CoLaus study. Special thanks to M. Bochud, Y. Barreau, M. Firmann, V. Mayor, A. Bastian, B. Ramic, M. Moranville, M. Baumer, M. Sagette, J. Ecoffey and S. Mermoud for data collection. YW was supported by the ERC (Proteomics v3.0; AdG-233226 to RA), and the LiverX program and EGW by a fellowship from the Fondation Romande pour la Recherche sur le Diabète. JA is the Nestlé Chair in Energy Metabolism. Research was supported by the EPFL, ETHZ, ERC (Sirtuins; AdG-231138 and Proteomics v3.0; AdG-233226), Velux Stiftung, LiverX and AgingX programs of the Swiss Initiative for Systems Biology (51RTP0-151019 and 2013/153), SNSF (31003A-140780, 31003A-143914, and CSRII3-136201), and the NIH (R01AG043930).