Applying stable carbon isotopic analysis at the natural abundance level to determine the origin of docosahexaenoic acid in the brain of the fat-1 mouse

Abstract

A key factor limiting the study of the origin and metabolism of brain fatty acids is the lack of cost-efficient methods available to trace fatty acids. Here, through the application of compound-specific isotope analysis (CSIA), a novel, cost-efficient method, we successfully differentiated between brain DHA originating directly from dietary omega (n)-3 polyunsaturated fatty acids (PUFA), and brain DHA biochemically synthesized to determine the origin of brain DHA in fat-1 mice. Fat-1 mice and their wild-type littermates were either weaned onto n-6 PUFA rich, n-3 PUFA deficient diets or diets rich in both n-3 and n-6 PUFA. Isotopic analysis of fatty acid methyl esters from brain and liver tissue was conducted via gas chromatography- isotope ratio mass spectrometry. Our data demonstrates that in the presence of n-3 and n-6 PUFA, fat-1 mice obtain their brain DHA solely from n-3 PUFA sources. This study reflects the first application of CSIA to a complex multivariate model to determine the origin of brain fatty acids.

Dietary docosahexaenoic acid (DHA) downregulates liver DHA synthesis by inhibiting eicosapentaenoic acid elongation

“…We demonstrated no significant effects of the ALA, DHA, and ALA + DHA diets on brain DHA concentrations, but with CSIA determined that in the absence of dietary DHA the brain receives DHA synthesized from ALA, confirming our previous results in C57Bl/6J and BALB/c mice ( 37 , 46 , 47 ). Furthermore, the pattern for brain δ 13 C-DHA (DHA > ALA+DHA > ALA, Fig.…”

The majority of brain palmitic acid is maintained by lipogenesis from dietary sugars and is augmented in mice fed low palmitic acid levels from birth

“…Carbon isotopic analysis was conducted on tissue PAM FAMEs and dietary PAM and OLA FAMEs via GC‐C‐IRMS performed by the Analytical Facility for Bioactive Molecules (AFBM), The Hospital for Sick Children, Toronto, Canada, in a blinded manner. Methodology for stable carbon isotope analysis of fatty acids are as described previously by our group (Giuliano et al, 2018; Lacombe et al, 2017, 2018; Metherel et al, 2017, 2019; Metherel, Irfan, Chouinard‐Watkins, et al, 2019). Using multi‐point linear regression, the δ 13 C of tissue PAM, in addition to the δ 13 C of the FAMEs in the diet measured by GC‐C‐IRMS were normalized to the international stable isotope reference scale (Vienna Peedee Belemnite) and reported in milliuery (mUr).…”

Higher Increase in Plasma DHA in Females Compared to Males Following EPA Supplementation May Be Influenced by a Polymorphism in ELOVL2: An Exploratory Study

“…The plasma δ 13 C of FAME was determined by GC‐IRMS, as previously described by our laboratory (Giuliano et al, 2018; Lacombe et al, 2017, 2018; Metherel et al, 2017, 2019a, b). Briefly, the δ 13 C of plasma fatty acids collected by IRMS was normalized and converted to the international reference scale (Vienna Peedee Belemnite) by multipoint linear normalization and reported in mUr.…”