Table of Contents
Advances in Radiology
Volume 2014 (2014), Article ID 109252, 9 pages
http://dx.doi.org/10.1155/2014/109252
Review Article

Identifying Sources of Hepatic Lipogenic Acetyl-CoA Using Stable Isotope Tracers and NMR

1Center for Neurosciences and Cell Biology, University of Coimbra, UC-Biotech, Biocant Park, Nucleo 8, Lote 4, 3060-197 Cantanhede, Portugal
2Portuguese Diabetes Association, 1250-189 Lisbon, Portugal

Received 30 April 2014; Accepted 24 July 2014; Published 11 August 2014

Academic Editor: Sergio Casciaro

Copyright © 2014 John G. Jones. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The role of hepatic de novo lipogenesis (DNL) in promoting fatty liver disease and hypertriglyceridemia during excessive nutrient intake is becoming firmly established. Certain nutrients such as fructose promote hepatic DNL activity and this has been at least partly attributed to their efficient conversion to the acetyl-CoA precursors of DNL. However, tracer studies indicate a paradoxically low level of fructose incorporation into lipids, which begs the question of what the actual lipogenic acetyl-CoA sources are under these and other conditions. Here, we describe novel approaches for measuring substrate contributions to lipogenic hepatic acetyl-CoA using 13C-tracers and 13C-NMR analysis of lipids and acetyl-CoA probes. We review and address aspects of hepatic intermediary fluxes and acetyl-CoA compartmentation that can confound the relationship between 13C-precursor substrate and lipogenic 13C-acetyl-CoA enrichments and demonstrate novel methodologies that can provide realistic estimates of 13C-enriched substrate contributions to DNL. The most striking realization is that the principal substrate contributors to lipogenic acetyl-CoA have yet to be identified, but they are probably not the so-called “lipogenic substrates” such as fructose. The proposed methods may improve our insight into the nutrient sources of DNL under various feeding and disease states.