Lactate

Chronically high levels of Lactic acid are associated with at least a dozen inborn errors of metabolism including: 2-Methyl-3-hydroxybutyryl CoA dehydrogenase deficiency, Biotinidase deficiency, Fructose-1,6-diphosphatase deficiency, Glycogen Storage Disease Type 1A (GSD1A) or Von Gierke Disease, Glycogenosis, Type IB, Glycogenosis, Type IC, Glycogenosis, Type VI. Hers disease, Lactic Acidemia, Leigh Syndrome, Methylmalonate Semialdehyde Dehydrogenase Deficiency, Pyruvate Decarboxylase E1 Component Deficiency, Pyruvate dehydrogenase complex deficiency, Pyruvate dehydrogenase deficiency, Short Chain Acyl CoA Dehydrogenase Deficiency (SCAD Deficiency).

Accumulation of L-lactic acid in the body has been shown to be toxic. At times of lactic acidosis, when excess intracellular lactate is released into the blood, maintenance of electroneutrality of the blood requires that a cation be released into the blood, as well. This can reduce blood pH. Lactate may exert a strong action over GABAergic networks in the developing brain, making them more inhibitory than it was previously assumed, acting either through better support of metabolites, or alterations in base intracellular pH levels, or both. (Wikipedia)