Project Summary. Adaptive metabolic responses to hypoxia reflect essential evolutionary survival
strategies in all eukaryotes. We recently identified a unique metabolite that increases in cardiovascular
(CV) cells in response to hypoxia, L-2-hydroxyglutarate (L2HG). This metabolite is derived from a-
ketoglutarate, or 2-oxoglutarate (2OG), a key intermediate in the tricarboxylic acid cycle. Once formed
from 2OG and NADH, L2HG has no other metabolic fate except to undergo oxidation back to 2OG by the
stereospecific dehydrogenase, L2HG dehydrogenase (L2HGDH), suggesting that it accommodates
(‘buffers’) the increase in reducing equivalents accompanying hypoxia. L2HG has two other unique
actions: it suppresses glycolysis and, as we show here, it increases pentose phosphate pathway (PPP)
activity. The central hypothesis of this proposal is that L2HG suppresses glycolysis and enhances PPP
activity in CV cells to eliminate reactive oxygen species (ROS), maintain cell redox potential, and preserve
cell function in hypoxia. To address this hypothesis, we will focus on three specific aims. First, we will
determine the molecular metabolic mechanisms underlying the effects of L2HG on glycolysis and PPP
activity. In particular, we will focus on the unique role of a specific phosphofructokinase-2 isoform,
PFKFB4, as a key regulatory determinant of increased flux through the PPP in hypoxia. Second, we will
determine the effect of this L2HG-induced increased PPP activity in hypoxia on cellular redox potential
and intra- and extracellular ROS elimination. Here, we will focus on PPP-derived NADPH and GSH as
key cofactors in NADPH oxidase and glutathione peroxidase activities, respectively, in order to enhance
elimination of excess ROS. Third, we will study the effects of L2HG in hypoxia or ischemia on cellular and
cardiac function, respectively, using unique cellular and genetic murine models. Taken together, these
studies should provide insights into the mechanisms by which L2HG promotes metabolic remodeling to
preserve cell and cardiac function in oxygen-limited states.