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The origin of palmitic acid in brain of the developing rat
B N Marbois1, H O Ajie, R A Korsak
1Department of Biological Chemistry, UCLA School of Medicine 90024.
Insights
The developing brain synthesizes its own palmitic acid, as dietary palmitic acid does not enter the brain in rat pups. This study tracked labeled palmitic acid in organs of young rats.
Area of Science:
- Biochemistry
- Developmental Biology
- Nutritional Science
Background:
- Palmitic acid is a crucial fatty acid for infant development.
- The source of palmitic acid for the developing brain is not fully understood.
- Rat milk contains high levels of palmitic and oleic acids.
Purpose of the Study:
- To investigate whether dietary palmitic acid contributes to the palmitic acid content of developing organs in rats.
- To determine if exogenous palmitic acid can be incorporated into the developing brain.
Main Methods:
- Artificially reared rat pups were fed a milk substitute with deuterated palmitic acid.
- Control pups received a milk substitute with unlabeled palmitic acid.
- Fatty acid analysis was performed using gas chromatography and mass spectrometry.
Main Results:
- Deuterated palmitic acid was detected in the liver (32%) and lung (12%) of rat pups.
- The brain did not contain detectable levels of deuterated palmitic acid.
- Significant accumulation of palmitic acid and total fatty acids occurred in organs between 7 and 14 days of age.
Conclusions:
- Dietary palmitic acid does not appear to contribute to the palmitic acid pool in the developing rat brain.
- The developing brain synthesizes its own palmitic acid via de novo synthesis.
- The brain's unique metabolic pathway for fatty acid synthesis is highlighted.
Abstract:
A rat milk substitute containing lower amounts of palmitic and oleic acid in the triacylglycerols in comparison to natural rat milk was fed to artificially reared rat pups from day 7 after birth to day 14. Pups reared by their mother served as controls. Free trideuterated (D3) palmitic acid [(C2H3)(CH2)14COOH, 98 atom % D] and free perdeuterated (D31) palmitic acid [C15(2)H31COOH, 99 atom % D] in equal quantity were mixed into the triacylglycerols of the milk substitute in an amount equal to 100% of the palmitic acid in the triacylglycerols. A control milk substitute contained unlabeled free palmitic acid in an amount equal to 100% of the palmitic acid in the triacylglycerols of the milk substitute. The objective was to determine if palmitic acid in the diet contributed significantly to the palmitic acid content of developing brain and other organs. The methyl esters of the fatty acids were analyzed by gas chromatography and the palmitic acid methyl ester was examined by fast atom bombardment mass spectrometry. The proportion of deuterated methyl palmitate as a percentage of total palmitate was determined; 32% of the palmitic acid in liver and 12% of the palmitic acid in lung were trideuterated and perdeuterated palmitic acid in approximately equal amounts. The brain, by contrast, did not contain the deuterated palmitic acid moiety. Quantitation of palmitic acid and total fatty acids revealed a significant accumulation in organs in the interval from 7 to 14 days of age. Under our experimental conditions, labeled palmitic acid does not enter the brain. Consequently, we conclude that the developing brain produces all required palmitic acid by de novo synthesis.