Alterations in levels and ratios of n-3 and n-6 polyunsaturated fatty acids in the temporal cortex and liver of vervet monkeys from birth to early adulthood

Abstract

Deficiencies in omega-3 (n-3) long chain polyunsaturated fatty acids (LC-PUFAs) and increases in the ratio of omega-6 (n-6) to n-3 LC-PUFAs in brain tissues and blood components have been associated with psychiatric and developmental disorders. Most studies have focused on n-3 LC-PUFA accumulation in the brain from birth until 2years of age, well before the symptomatic onset of such disorders. The current study addresses changes that occur in childhood and adolescence. Postmortem brain (cortical gray matter, inferior temporal lobe; n=50) and liver (n=60) from vervet monkeys fed a uniform diet from birth through young adulthood were collected from archived tissues. Lipids were extracted and fatty acid levels determined. There was a marked reduction in the ratio of n-6 LC-PUFAs, arachidonic acid (ARA) and adrenic acid (ADR), relative to the n-3 LC-PUFA, docosahexaenoic acid (DHA), in temporal cortex lipids from birth to puberty and then a more gradual decrease though adulthood. This decrease in ratio resulted from a 3-fold accumulation of DHA levels while concentrations of ARA remained constant. Early childhood through adolescence appears to be a critical period for DHA accretion in the cortex of vervet monkeys and may represent a vulnerable stage where lack of dietary n-3 LC-PUFAs impacts development in humans.

Keywords: Arachidonic acid; Brain; Docosahexaenoic acid; Omega-3 deficiency; Psychiatric and developmental disorders.

Figure 1. Levels and ratios of select PUFAs in brain tissue

PUFA levels are expressed as % of total mass and the ratio of DHA:ARA in brain tissue as a functions of animal age.

Figure 2. Mass concentration (μmol/mg tissue) of ARA and DHA in (A) brain tissue and (B) liver tissue in Vervet monkeys

Linear regressions are shown for brain (ARA: R²=0.031, p=0.206; DHA: R²=0.539, p<0.0001 for Age≤3, filled markers; and R²=0.0071, p=0.843 for Age>3 years, unfilled markers) and liver (ARA: R²=0.0012, p=0.788; DHA: R²=0.017, p=0.295). Equations for linear regressions are shown in Table 5.