Compartmental analyses of 2H5-alpha-linolenic acid and C-U-eicosapentaenoic acid toward synthesis of plasma labeled 22:6n-3 in newborn term infants.
BACKGROUND
During early postnatal development, the nervous system accretes docosahexaenoic acid (DHA; 22:6n-3), a highly unsaturated n-3 (omega-3) fatty acid (FA) used in the formation of neural cell membranes. DHA, which is present in human breast milk, may also be biosynthesized from n-3 FAs such as 18:3n-3 [alpha-linolenic acid (ALA)] or 20:5n-3 [eicosapentaenoic acid (EPA)]. An important concern is to what extent these precursors can supply DHA to the developing infant.


OBJECTIVE
We analyzed measurements of fractional percentages of plasma (2)H(5)-ALA and (13)C-U-EPA directed toward the synthesis of labeled 22:6n-3 in 11 newborn infants by using compartmental modeling procedures.


METHODS
One-week-old infants received doses of (2)H(5)-ALA and (13)C-U-EPA ethyl esters enterally. We drew blood from the infants periodically and analyzed the plasma for endogenous and labeled n-3 FAs. From the time-course concentrations of the labeled FAs, we determined rate constant coefficients, fractional synthetic rates, and plasma turnover rates of n-3 FAs.


RESULTS
In infants, approximately 0.04% of the (2)H(5)-ALA dose converted to plasma (2)H(5)-EPA. Plasma (2)H(5)-EPA and (2)H(5)-22:5n-3 [docosapentaenoic acid (DPA)] efficiently converted to (2)H(5)-DPA and (2)H(5)-DHA, respectively. The percentage of plasma (13)C-U-EPA directed toward the synthesis of (13)C-DHA was lower than the percentage of plasma (2)H(5)-EPA that originated from (2)H(5)-ALA.


CONCLUSIONS
Endogenously synthesized EPA was efficiently converted to DHA. In comparison, preformed EPA was less efficiently used for DHA biosynthesis, which suggests a differential metabolism of endogenous EPA compared with exogenous EPA. However, on a per mole basis, preformed EPA was 3.6 times more effective toward DHA synthesis than was ALA. Newborns required an intake of approximately 5 mg preformed DHA. kg(-1) x d(-1) to maintain plasma DHA homeostasis.
Laboratory of Membrane Biochemistry and Biophysics and Laboratory of Metabolic Control, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD, USA.
Yu Hong
YH
Lin
Adolfo
A
Llanos
Patricia
P
Mena
Ricardo
R
Uauy
Norman
N
Salem
Robert J
RJ
Pawlosky
D004281:Docosahexaenoic Acids / Q000378:metabolism*; D015118:Eicosapentaenoic Acid / Q000031:analogs & derivatives / Q000097:blood / Q000378:metabolism*; D005231:Fatty Acids, Unsaturated / Q000097:blood / Q000378:metabolism*; D006706:Homeostasis; D006801:Humans; D007231:Infant, Newborn / Q000097:blood*; D007234:Infant, Premature / Q000097:blood*; D017962:alpha-Linolenic Acid / Q000378:metabolism*
D005231:Fatty Acids, Unsaturated; D017962:alpha-Linolenic Acid; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid; C026219:docosapentaenoic acid