To determine the requirement of cysteine in preterm infants with different gestational ages and postnatal age.

Cysteine is considered to be a conditionally essential amino acid in premature infants. This is due to immaturity of the enzymatic pathway responsible for conversion of methionine to cysteine.

Cysteine plays a key role in glutathione synthesis which is a very important antioxidant. Many complications of premature birth are based upon oxidant damage.

In this study we will investigate the cysteine requirement in premature infants. Infants born with a gestational age of 26-29 weeks will be studied at a post-conceptional age of 30-32 weeks and at a post-conceptional age of 35-37 weeks. Infants born at a gestational age of 32-34 weeks will also be studied at a post-conceptional age of 35-37 weeks. Preterm infants with the above described characteristics regarding postnatal and gestational age will be fed testdiets with graded amounts of cystine.
Fractional oxidation will be measured using the Indicator Amino Acid Oxidation method.

1. Cysteine is an essential amino acid for newborn preterm infants;

2. Cysteine requirements change rapidly with postnatal age;

3. The change in cysteine requirement with age is based upon cystathionase activity;

4. Intestinal cystathionase activity is of major importance for the conversion of methionine to cysteine.

N/A

Infants receive a testdiets with graded amounts of Cystine for 32 hours.