N-Palmitoylethanolamine depot injection increased its tissue levels and those of other acylethanolamide lipids

Abstract

N-Palmitoylethanolamine (NAE 16:0) is an endogenous lipid signaling molecule that has limited water solubility, and its action is short-lived due to its rapid metabolism. This poses a problem for use in vivo as oral administration requires a high concentration for significant levels to reach target tissues, and injection of the compound in a dimethyl sulfoxide- or ethanol-based vehicle is usually not desirable during long-term treatment. A depot injection of NAE 16:0 was successfully emulsified in sterile corn oil (10 mg/kg) and administered in young DBA/2 mice in order to elevate baseline levels of NAE 16:0 in target tissues. NAE 16:0 levels were increased in various tissues, particularly in the retina, 24 and 48 hours following injections. Increases ranged between 22% and 215% (above basal levels) in blood serum, heart, brain, and retina and induced an entourage effect by increasing levels of other 18 carbon N-Acylethanolamines (NAEs), which ranged between 31% and 117% above baseline. These results indicate that NAE 16:0 can be used as a depot preparation, avoiding the use of inadequate vehicles, and can provide the basis for designing tissue-specific dosing regimens for therapies involving NAEs and related compounds.

Keywords: DBA/2 mice; cannabinoid receptor; gas chromatography; lipid extraction; mass spectrometry; vanilloid receptor.

Figure 1

Comparison of control levels of NAE 16:0 in various tissues of DBA/2 mice. Notes: (A) Functional or (B) metabolic effect of depot injections 24 and 48 hours following administration, showing NAE 16:0 levels per g FW or g LM, respectively. Data within treatment groups or comparing control levels (bars) were statistically analyzed using a one-way ANOVA with a Dunnett’s or Bonferroni posttest, respectively. Data represented as Mean ± standard error of the mean, n = 3–4. *P < 0.05, **P < 0.01, ***P < 0.001. Abbreviations: FW, fresh weight; LM, lipid mass; NAE 16:0, N-Palmitoyl-ethanolamine.

Figure 2

Elevation above control levels of NAE 18:0, 18:1, 18:2, and 20:4, 24 and 48 hours following NAE 16:0 depot injection. Notes: Depot injection in (A) blood serum, (B) heart (C) brain, and (D) retina of DBA/2 mice. Data were statistically analyzed using a one-way analysis of variance (ANOVA) with a Dunnett’s post test. *P < 0.05, **P < 0.01. Mean ± standard error of the mean, n = 3–4. Abbreviations: FW, fresh weight; NAE, N-Acylethanolamine; NAE 16:0, N-Palmitoylethanolamine.