Beta-Hydroxybutyric acid

Beta-Hydroxybutyric acid (also known as 3-hydroxybutyric acid or 3-Hydroxybutanoic acid) is a organic acid that plays a significant role in human metabolism. It is one of the three ketone bodies produced by the liver, primarily from fatty acids, for use as energy by the brain when glucose is low.

Chemistry

Beta-Hydroxybutyric acid is a chiral compound with two enantiomers: D-3-hydroxybutyric acid and L-3-hydroxybutyric acid. The D-isomer is the biologically active form that is endogenously synthesized by humans.

Biosynthesis

Beta-Hydroxybutyric acid is synthesized in the liver from acetyl-CoA in a reaction catalyzed by the enzyme beta-hydroxybutyrate dehydrogenase. This process is part of the ketogenesis pathway, which occurs during periods of low glucose availability, such as fasting, prolonged exercise, or in untreated diabetes mellitus.

Physiological role

In humans, beta-Hydroxybutyric acid serves as a circulating energy source for various tissues during fasting or exercise. It is particularly important for the brain, which cannot directly metabolize fatty acids for energy due to the blood-brain barrier. Instead, the brain uses ketone bodies, including beta-Hydroxybutyric acid, as an alternative energy source during periods of low glucose availability.

Clinical significance

Elevated levels of beta-Hydroxybutyric acid can be indicative of ketosis, a metabolic state that can occur in conditions such as diabetes mellitus, starvation, and alcoholic ketoacidosis. Measurement of beta-Hydroxybutyric acid levels in the blood can be used as a diagnostic tool for these conditions.