MOLECULAR CONTROL OF GLUCOSE METABOLISM

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this collaboration is (a) to determine the biochemical mechanism for the reduced REDOX state of liver of ChREBP-/-, and (b) to determine the source of pyruvate in the liver of ChREBP-/- mice fed high starch diet. We determined enzyme mRNA levels and enzyme activities of the Krebs cycle, electron shuttle enzymes and metabolite concentrations in the freeze-clamped liver of ChREBP-/- mice, isolated mitochondria and hepatocytes. A limitation of this approach is that changes in enzyme expression often do not match changes in flux. Because NMR isotopomer analysis is an excellent method for measuring fluxes in intact tissue, we took this approach to investigate the metabolism of hepatic pyruvate and lactate in ChREBP-/- mice. Substrate preference experiments were performed by perfusing isolated perfused livers with a mixture 13C labeled FFA, glucose, lactate and pyruvate. Preliminary results from this experiment indicate that FFA oxidation in the TCA cycle is reduced by half, from 80% in WT to 40% in the ChREBP -/-. Concordantly, pyruvate and lactate oxidation were higher in the ChREBP -/- mice compared to controls, in agreement with a 74% reduction in liver PDK3 enzyme activity.