Original Research
Omega-3 Fatty Acid Supplementation Affects Selected Phospholipids in Peripheral White Blood Cells and in Plasma of Full-Sized and Miniature Mares

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Abstract

Dietary omega-3 fatty acids (n-3 PUFA), notably eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), impart health benefits in humans and animals. In horses, dietary n-3 PUFAs elevate EPA and DHA and may promote anti-inflammatory effects. No reports document effects of dietary n-3 PUFA on fatty acyl components of circulating and cellular phospholipids in horses nor whether responses to dietary n-3 PUFA are similar among horse breeds. Ten Quarter Horse and 10 American Miniature Horse mares were assigned to n-3 PUFA (64.4 mg· kg body weight [BW]−1·d−1) or control diet for 56 days. Blood was sampled at 0, 28, and 56 days. Apparent phospholipid molecular species from several classes (phosphatidylcholine [PC]; “ether-linked” phosphatidylcholine [i.e., alk(en)yl, acyl glycerophosphocholine] [ePC]; phosphatidylethanolamine [PE]; phosphatidylinositol [PI]; and phosphatidylserine [PS]) were determined in plasma and peripheral blood mononuclear cells (PBMC) by mass spectrometry. Statistical analysis showed that six phospholipid species had diet × day interactions (P < .05) for both plasma and PBMC. Further evaluation of these species demonstrated that the mole percentage of PC(38:6), PC(40:7), PC(42:10), PE(38:5), PE(40:6), and PE(40:7) (where x:y represents total acyl carbon:total carbon-carbon double bonds) in both plasma and PBMC phospholipids was elevated in horses fed n-3 PUFA (P < .001 for all). Analysis of the acyl product ions revealed that these contained an acyl chain of mass consistent with an n-3 PUFA. Thus, supplementation increased n-3 PUFA in selected plasma and PBMC phospholipids. The absence of breed effects suggests that miniature and full-size horses responded similarly to dietary treatment.

Introduction

The effects of omega-3 fatty acids have been extensively studied in humans and in laboratory rodents, namely rats and mice. These studies have shown that omega-3 polyunsaturated fatty acids (n-3 PUFA) generally decrease the inflammatory response to certain stimuli. Much of the research relates to cardiac or chronic diseases which have been associated with inflammation [1], [2]. Omega-3 fatty acids are presumed to exert anti-inflammatory effects via their incorporation into phospholipids of cellular membranes and organelles. This incorporation occurs at the expense of arachidonic acid and results in reduced production of inflammatory eicosanoids from arachidonic acid [3]. Studies with humans and rats indicate that the phospholipid profile of the studied cells (e.g., leukocytes, red blood cells), plasma, or organelles (mitochondria) changes during the administration or dietary supplementation of n-3 PUFA. Indeed, the cells or organelles incorporate a greater percentage of n-3 PUFA [4], [5], [6].

There are a few published reports documenting effects of dietary supplementation of horses with n-3 PUFA. In those studies, dietary supplementation, usually a combination of both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), rapidly and consistently elevated circulating n-3 PUFA [7], [8], [9], [10]. One study indicated that the administration of seal blubber (a rich source of omega-3 fatty acids) changed the lipid profile in the immune cells of horses [11]. However, that study did not include a control group of horses and used a source of n-3 PUFA not readily available to feed manufacturers.

To our knowledge, there are no published reports that document responses of miniature horses to dietary n-3 PUFA supplementation in relation to that of full-size horses. Miniature horses are potentially attractive as a model animal for full-size horses because of obvious cost, safety and management advantages they could afford.

The primary objective to the current study was to test the hypothesis that dietary supplementation of n-3 PUFA EPA and DHA would increase their abundance in the fatty acyl components of phospholipids. A secondary objective was to determine whether a small horse breed, the American Miniature Horse, would respond to dietary supplementation similarly to a common full-size breed of horse (e.g., American Quarter Horse), and therefore provide evidence that this breed of horse could be a useful experimental model for full-size horse breeds.

Section snippets

Animal Housing and Feeding Management

This study was conducted in tandem with two other studies focused on different experimental objectives. Detailed descriptions of the feeding and housing management and blood sampling protocols are described elsewhere [12]. Briefly, the study consisted of a group of 10 miniature horses and 10 full-size horses. Each of these groups was evenly split into a control and a study group, making five total animals in each dietary treatment-horse body type subgroup. Horses were fed 1.69 kg total diet/100

Results

Polar glycerophospholipids, including phosphatidic acid and those with choline, ethanolamine, inositol, and serine head groups, and the phosphosphingolipid, sphingomyelin, were determined in plasma and PBMC. The complete data set is available as Supplemental Table E1 (plasma) and Table E2 (PBMC).

The probabilities of statistically significant main and interactive effects are detailed in Table 1, Table 2 for plasma and PBMC phospholipids, respectively. Our primary focus was on the interaction of

Discussion

Although the body of published results of research for horses fed dietary n-3 PUFA is far from exhaustive, there is a growing body of literature documenting the physiological effects of n-3 PUFA supplementation. For example, it is clear that supplementation results in a rapid, dramatic and consistent increase in circulating n-3 PUFA in horses. Additionally, a limited number of studies document anti-inflammatory actions of n-3 PUFA in horses. For example, dietary linseed oil supplementation [18]

Acknowledgments

This work was supported by contribution 12-466-J from the Kansas Agricultural Experiment Station. Lipid analyses were performed at the Kansas Lipidomics Research Center Analytical Laboratory, with funding from the Targeted Excellence Program of Kansas State University. Instrument acquisition and method development at the Kansas Lipidomics Research Center was supported by National Science Foundation (EPS 0236913, MCB 0455318, DBI 0521587), Kansas Technology Enterprise Corp., K-IDeA Networks of

References (20)

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