Related Experiment Videos
Arachidonic and docosahexaenoic acids are biosynthesized from their 18-carbon precursors in human infants
1Laboratory of Membrane Biochemistry and Biophysics, National Institute of Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, MD 20852, USA.
Insights
Human infants can convert essential fatty acids into longer-chain forms for development. However, the conversion rate of linolenic acid to docosahexaenoic acid may be insufficient for optimal infant neural development.
Area of Science:
- Biochemistry
- Human Physiology
- Nutritional Science
Background:
- Long-chain highly unsaturated fatty acids are crucial for infant nervous system development.
- The capacity of human infants to biosynthesize these fatty acids is not well understood.
Purpose of the Study:
- To investigate the in vivo capacity of human infants to convert 18-carbon essential fatty acids into their elongated and desaturated forms.
- To assess the conversion of linoleic acid to arachidonic acid and linolenic acid to docosahexaenoic acid in newborns.
Main Methods:
- Utilized a novel gas chromatography/negative chemical ionization/mass spectrometry method.
- Employed 2H-labeled essential fatty acids administered enterally as ethyl esters.
- Assessed in vivo conversion with high sensitivity and selectivity.
Main Results:
- Human infants can convert dietary essential fatty acids into longer-chain derivatives, transport them to plasma, and incorporate them into membrane lipids.
- Demonstrated in vivo conversion of linoleic acid (18:2n6) to arachidonic acid (20:4n6).
- Confirmed activity of elongases/desaturases for converting linolenic acid (18:3n3) to docosahexaenoic acid (22:6n3) within the first week of life.
Conclusions:
- Human infants possess the capability to biosynthesize docosahexaenoic acid, essential for neural development.
- While conversion occurs, the in vivo production from linolenic acid might be inadequate to match levels found in breast-fed infants.
- Further research is needed to determine optimal fatty acid supplementation for infant development.
Abstract:
It is becoming clear that an adequate level of long-chain highly unsaturated fatty acids in the nervous system is required for optimal function and development; however, the ability of infants to biosynthesize long-chain fatty acids is unknown. This study explores the capacity of human infants to convert 18-carbon essential fatty acids to their elongated and desaturated forms, in vivo. A newly developed gas chromatography/negative chemical ionization/mass spectrometry method employing 2H-labeled essential fatty acids allowed assessment of this in vivo conversion with very high sensitivity and selectivity. Our results demonstrate that human infants have the capacity to convert dietary essential fatty acids administered enterally as 2H-labeled ethyl esters to their longer-chain derivatives, transport them to plasma, and incorporate them into membrane lipids. The in vivo conversion of linoleic acid (18:2n6) to arachidonic acid (20:4n6) is demonstrated in human beings. All elongases/desaturases necessary for the conversion of linolenic acid (18:3n3) to docosahexaenoic acid (22:6n3) are also active in the first week after birth. Although the absolute amounts of n-3 fatty acid metabolites accumulated in plasma are greater than those of the n-6 family, estimates of the endogenous pools of 18:2n6 and 18:3n3 indicate that n-6 fatty acid conversion rates are greater than those of the n-3 family. While these data clearly demonstrate the capability of infants to biosynthesize 22:6n3, a lipid that is required for optimal neural development, the amounts produced in vivo from 18:3n3 may be inadequate to support the 22:6n3 level observed in breast-fed infants.