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Estimation of arachidonic acid synthesis in full term neonates using natural variation of 13C content
H Demmelmair1, U von Schenck, E Behrendt
1Kinderpoliklinik, Ludwig-Maximilians-Universität, München, Germany.
Insights
Neonates can synthesize arachidonic acid (AA) from dietary linoleic acid (LA). This study used stable isotope tracing to demonstrate endogenous AA production in infants, crucial for their development.
Area of Science:
- Biochemistry
- Nutritional Science
- Pediatric Research
Background:
- Arachidonic acid (AA) is vital for neonatal tissue growth.
- The capacity of neonates to synthesize AA from dietary linoleic acid (LA) remains unclear.
- Dietary fats vary in their natural abundance of stable isotopes, such as carbon-13 (13C).
Purpose of the Study:
- To investigate the extent of endogenous arachidonic acid (AA) synthesis in neonates from dietary linoleic acid (LA).
- To assess the feasibility of using natural variations in 13C abundance in dietary fats to trace fatty acid synthesis in infants.
Main Methods:
- Utilized a stable isotope tracer method with varying natural 13C content in dietary fats.
- Administered a phenylalanine-free diet enriched with corn oil (high 13C-LA) to four infants with phenylketonuria.
- Measured 13C enrichment in serum linoleic acid (LA) and arachidonic acid (AA) using gas chromatography combustion isotope ratio mass spectrometry (GC-IRMS) over 3-4 days.
Main Results:
- Significant increases in 13C enrichment were observed in serum LA following the corn oil diet.
- A measurable, albeit smaller, increase in 13C enrichment was detected in serum AA, indicating its synthesis from LA.
- The method demonstrated reproducible detection of fatty acid synthesis via 13C tracing in small infant serum samples.
Conclusions:
- Full-term neonates possess the capacity for endogenous synthesis of arachidonic acid (AA) from dietary linoleic acid (LA).
- Gas chromatography combustion isotope ratio mass spectrometry (GC-IRMS) is a viable technique for studying infantile fatty acid metabolism using natural isotope variations.
- This finding has implications for understanding neonatal nutrition and optimizing infant formulas.
Abstract:
Neonates need arachidonic acid (AA) for their growing tissues, but it is unknown to what extent they can synthesize AA from dietary linoleic acid (LA). We studied infantile AA synthesis by using different natural 13C amounts in dietary fats. The diets of four infants ages 18 +/- 4 days (mean +/- SD) with newly diagnosed phenylketonuria were changed from breast milk or formula to a phenylalanine-free diet with corn oil as the only fat source. Compared with most dietary fats in Europe derived from C3 plants, corn oil LA has a higher 13C content. We determined the 13C content of LA and AA in 0.25-0.5 ml serum before and for 3-4 days after the diet change with gas chromatography combustion isotope ratio mass spectrometry (GC-IRMS). Baseline delta 13C values were -31.5 +/- 1.1% (mean +/- SD) for serum LA and -30.1 +/- 1.2% for AA. The corn oil diet induced changes of delta 13C values over baseline in LA of 8.9 +/- 1.0 on day 1 and 12.7 +/- 0.7 on day 4, respectively. The changes of AA delta 13C values were 0.5 +/- 0.7 and 2.7 +/- 0.7 on days 1 and 4. We conclude that reproducible detection of differences in delta 13C values of fatty acids in small samples of infantile serum, induced by dietary variation of natural 13C amounts, is feasible with GC-IRMS. Since the corn oil diet did not contain AA, the observed change of AA delta 13C shows active endogenous AA synthesis in full-term neonates.(ABSTRACT TRUNCATED AT 250 WORDS)