Valine

The third BCAA – an essential building block of proteins and energy source in muscle; at the blood-brain barrier it competes with tryptophan and tyrosine for transport.

What valine does in the body

Valine is the third branched-chain amino acid and is essential. Like leucine and isoleucine, it is broken down mainly in muscle; its carbon skeleton becomes propionyl-CoA and, with biotin and vitamin B12, succinyl-CoA, which enters energy metabolism or can become glucose in the liver. Muscle cells release an intermediate breakdown product, 3-hydroxyisobutyrate; in studies it stimulated the uptake of fatty acids into muscle. The amino group leaves the muscle as alanine or glutamine. At the blood-brain barrier, valine competes with tryptophan, tyrosine and phenylalanine for the same transporter and so influences how much starting material for serotonin and dopamine reaches the brain.

Low valine – what happens in the body?

When little valine is available, building material for proteins and starting material for making new glucose are lacking, and muscle protein is broken down. At the blood-brain barrier, relatively more tryptophan reaches the brain; studies link this with central fatigue during prolonged exertion. With advanced liver disease the branched-chain amino acids fall, the aromatic ones rise, and the shifted ratio is considered in the concentration and alertness problems of hepatic encephalopathy. Other causes are low protein intake and malnutrition.

High valine – what happens in the body?

Raised values usually occur together with leucine and isoleucine when the breakdown of the branched-chain amino acids is slowed; this has been observed in studies with insulin resistance, excess weight and type 2 diabetes. In studies, the breakdown product 3-hydroxyisobutyrate promoted the storage of fat in muscle, which can further dampen the response to insulin. In the inherited maple syrup urine disease, valine is markedly raised together with the other two. The value rises temporarily after protein-rich meals.

The interpretation is given in your report.