Current trends in lactate metabolism: introduction.

In September 2006, at the Integrative Physiology of Exercise meeting in Indianapolis, IN, a symposium entitled "Current Trends in Lactate Metabolism" was presented. This short paper introduces two papers from that symposium. The first paper by L. Bruce Gladden briefly summarizes key pieces of evidence that support the cell-to-cell lactate shuttle, a concept that is no longer an hypothesis but that, instead, is now an established theory that provides the context for discussions of whole body metabolism. Gladden also offers a critical appraisal of the intracellular lactate shuttle and evaluates an ongoing controversy relative to the role of lactate in acid-base balance. In the second paper, Hashimoto and Brooks provide their evidence in support of the intracellular lactate shuttle and a lactate oxidation complex in the inner mitochondrial membrane. They also postulate that lactate is a cell-signaling molecule, "lactormone," that can upregulate gene and protein expression. Both papers have been updated since their original presentations and represent the current state of knowledge.