Medium-chain, even-numbered dicarboxylic acids as novel energy substrates: an update

Medium-chain dicarboxylic acids are produced by higher plants and animals via fatty acid [omega]-oxidation or by [beta]-oxidation of longer-chain dicarboxylic acids. In plants, dicarboxylic acids are components of the natural protective polymers cutin and suberin; in animals, dicarboxylic acids are mainly oxidized in mitochondria, where they are transported through four different pathways. Their energy density is intermediate between glucose and fatty acids. Dicarboxylic acid administration does not require insulin or stimulate insulin secretion, and the [beta]-oxidation of dicarboxylic acids produces succinic acid, a gluconeogenic substrate. Therefore, dicarboxylic acids might be a suitable fuel substrate, particularly in clinical conditions in which marked insulin resistance and/or impairment of aerobic glycolysis occur. Key words: dicarboxylic acids, fuel substrates, gluconeogenesis, nutrition