Leucine, an essential amino acid, was low in this specimen. Leucine is a branched-chain amino acid that is a common constituent of proteins, peptides and hormones. It also promotes wound healing, insulin releasefrom the pancreas, and is a component of elastin (ligaments).

– Low leucine can result from protein malnutrition, zinc deficiency (Zn dependent peptidase), or other gastrointestinal dysfunctions such as hypochlorhydria (aka achlorhydria). Food intolerances and malabsorptionmay be coincident with subnormal leucine.

– Low leucine can point to potential catabolism of skeletal muscle. Check 3-Methylhistidine to confirm this.

Subnormal leucine is unusual but can coincide with:

– deficient activity of digestive peptidases

– zinc deficiency

– pancreatic dysfunction

– or poor quality diet.

– Leucine can also be subnormal in hepatic encephalopathy (=decline in brain function that occurs as a result of severe liver disease), and absorption and uptake can also be deficient following intestinal bypass procedures.

High fasting levels of leucine may be caused by a deficiency of vitamin B6, elevated insulin levels, or excessive supplementation.

Leucine, isoleucine and valine are branched-chain structural amino acids whose catabolism requires multiple nutrient co-factors including:

– P-5-P (vitamin B6)

– thiamin (vitamin B1)

– riboflavin (vitamin B2)

– lipoic acid

– Coenzyme-A

– biotin (vitamin B7)

– magnesium

Branched chain amino acids are often elevated as a result of deficiency of B-6and/or B-1, or excessive supplementation with protein (eg. whey protein) or the specific amino acids for body building/exercise recovery purposes.

A more serious, but rare cause of branched-chain hyperaminoacidurea is known as Maple Syrup Urine Disease (MSUD) that results from an inheritedenzymatic defect. Symptoms of MSUD may be episodic with protein intake.

In infants and children MSUD symptoms include:

– vomiting

– irritability

– lethargy

– food refusal

– muscle hypertonicity

– respiratory

Convulsions and seizures may occur in acute cases. Individuals presenting with moderate branched-chain hyperaminoacidemia should be retested afterreduction in protein intake and supplementation with vitamins B-6 and B-1. Those with MSUD should pursue professional advice regarding the avoidance of foods that are high in branched-chain amino acids.