Delivery and turnover of plasma-derived essential PUFAs in mammalian brain

TLDR

Polyunsaturated fatty acids are essential for nervous system function and structure, yet their rates of incorporation from plasma into brain have not been quantified. Dietary supplementation can modulate plasma unesterified PUFA levels, thereby regulating brain PUFA content and potentially treating PUFA‑imbalanced brain disorders. In adult rats, 3–5 % of brain arachidonic acid and 2–8 % of docosahexaenoic acid are replaced daily by plasma unesterified PUFAs, yielding 1–2‑week half‑lives, while in humans the replacement rate is 0.3 % per day, showing that plasma PUFA incorporation compensates for losses and eliminates the need for lipoprotein transport.

Abstract

Polyunsaturated fatty acids (PUFAs) are critical to nervous system function and structure, but their rates of incorporation from plasma into brain have not been evaluated. In the adult rat, calculations based on our model show that at least 3–5% of esterified brain arachidonic acid (AA) and 2–8% of esterified brain docosahexaenoic acid (DHA) are replaced daily by unesterified PUFAs in plasma. These rates, when related to unlabeled brain PUFA composition, give half-lives of 1–2 weeks for plasma-brain exchange of AA and DHA. In the human brain, the arachidonate replacement rate is 0.3% per day.Although unesterified plasma PUFA concentrations are low, their rates of incorporation into brain are sufficient to compensate for metabolic and efflux losses, so that PUFA transport from plasma into brain as a component of a lipoprotein is unnecessary. Dietary supplementation, by altering plasma unesterified PUFA concentrations, can regulate brain PUFA content and may help to treat brain diseases involving PUFA imbalance.