Role of neuritic acid in erythrocyte sphingomyelin of premature infants

The brain development of premature infants is an important research direction in neonatal science. The present study addresses the question whether nervonic acid (24:1n-9) accumulation in sphingomyelin (SM) of red blood cells (RBC) could yield information on cerebrum maturation in premature infants. The study included 28 premature eutrophic infants of 31.5 wk gestational age. Eleven were fed with human milk, nine with a regular formula and eight with an alpha-linolenate-enriched formula. The fatty acid composition of the SM fraction was determined by gas-liquid chromatography on a 50-m fused silica capillary column. At 32 wk gestational age, the main fatty acids in SM were 16:0, 18:0, 20:0, 22:0, 24:0 and 24:1n-9. After five weeks of feeding, at week 37 of postconceptional age, the most striking variation was a rise in 24:1n-9, from 9.9 +/- 0.7 to 12.8 +/- 0.9 (P < 0.02), regardless of regimen in all three feeding groups. The rise in 24:1n-9 after birth in premature eutrophic infants is the beginning of a trend toward the higher levels in 24:1n-9 observed in mature newborns and older infants. The 24:1n-9 level in SM of RBC from premature infants may reflect 24:1n-9 levels in SM of brain and could thus reflect brain maturity.

The results are expressed as a percentage distribution of individual fatty acids, as well as grams per milliliter of red blood cells. Over time, the main changes are related to nervonic acid (24:ln-9). The value of nerve acid between D2 and Dterm increased significantly, from 9.9 ±0.7 to 12.8 ±0.9 (P < 0.02). Similar observations can be obtained when the results are expressed as ~ g of fatty acids per milliliter of red blood cells. During the period from D2 to Dterm, the total amount of SM fatty acids decreased, while the average concentration of nervonic acid increased from 29.8 ±3.6to 34.4 ±3.4, reflecting the increase of the contribution of this acid to the total SM fatty acids in RBC.

The binding of nervonic acid to cell membrane, as reflected by its level in red blood cells, increased between 32 and 37 weeks. It is reported that the figure for 5-year-old children is 25.4%. Since the proportion of nervonic acid in red blood cell SM has remained stable since then, it may reach a stable state, and it is reported that the content of nervonic acid in adults is between 21-25%. Therefore, the study laid a theoretical foundation for the appropriate supplement of nervonic acid in premature infants in the future.