Evaluation of lipid markers in surfactant obtained from asthmatic horses exposed to hay

Equine Asthma Diagnostics: Review of Influencing Factors and Difficulties in Diagnosing Subclinical Disease

This literature review focuses on diagnostics of equine asthma (EA), possible influencing factors on diagnostic techniques and latest developments in diagnosing horses during EA remission or with subclinical disease. Routine EA diagnostics include a clinical examination of the respiratory system with percussion and auscultation including a rebreathing examination, and clinical pathology including white blood cells and arterial blood gas analysis. Subsequent diagnostics include bronchoscopy to evaluate the amount and viscosity of respiratory secretion, bronchoalveolar lavage, and the cytology of tracheal aspirates (TAs) and bronchoalveolar lavage fluid (BALF). The grading of EA severity is built on respiratory effort at rest, which is increased in severe equine asthma. The inflammatory subtype is based on BALF cytology, while TA cytology helps to rule out previous bacterial infections. Different factors have an impact on the airways regarding the structure of the epithelium, cytology, and inflammatory markers possibly influencing the diagnosis of EA. Short-term exercise increases the total cell count and inflammatory mediators identified in the BALF of human patients, asymptomatic horses, and other species. Other factors involve cold or chlorinated air, long-term training effects, and concurrent additional respiratory disease, in particular exercise-induced pulmonary hemorrhage. As BALF cytology may be unremarkable during EA remission and low-grade disease, exercise tests and other factors stressing the bronchial epithelium may help to diagnose these patients.

Lipids in Equine Airway Inflammation: An Overview of Current Knowledge

Mild-moderate and severe equine asthma (MEA and SEA) are prevalent inflammatory airway conditions affecting horses of numerous breeds and disciplines. Despite extensive research, detailed disease pathophysiology and the differences between MEA and SEA are still not completely understood. Bronchoalveolar lavage fluid cytology, broadly used in clinical practice and in equine asthma research, has limited means to represent the inflammatory status in the lower airways. Lipidomics is a field of science that can be utilized in investigating cellular mechanisms and cell-to-cell interactions. Studies in lipidomics have a broad variety of foci, of which fatty acid and lipid mediator profile analyses and global lipidomics have been implemented in veterinary medicine. As many crucial proinflammatory and proresolving mediators are lipids, lipidomic studies offer an interesting yet largely unexplored means to investigate inflammatory reactions in equine airways. The aim of this review article is to collect and summarize the findings of recent lipidomic studies on equine airway inflammation.

Lipid species profiling of bronchoalveolar lavage fluid cells of horses housed on two different bedding materials

The lipidome of equine BALF cells has not been described. The objectives of this prospective repeated-measures study were to explore the BALF cells' lipidome in horses and to identify lipids associated with progression or resolution of airway inflammation. BALF cells from 22 horses exposed to two bedding materials (Peat 1-Wood shavings [WS]-Peat 2) were studied by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The effects of bedding on lipid class and species compositions were tested with rmANOVA. Correlations between lipids and cell counts were examined. The BALF cells' lipidome showed bedding-related differences for molar percentage (mol%) of 60 species. Whole phosphatidylcholine (PC) class and its species PC 32:0 (main molecular species 16:0_16:0) had higher mol% after Peat 2 compared with WS. Phosphatidylinositol 38:4 (main molecular species 18:0_20:4) was higher after WS compared with both peat periods. BALF cell count correlated positively with mol% of the lipid classes phosphatidylserine, sphingomyelin, ceramide, hexosylceramide, and triacylglycerol but negatively with PC. BALF cell count correlated positively with phosphatidylinositol 38:4 mol%. In conclusion, equine BALF cells' lipid profiles explored with MS-based lipidomics indicated subclinical inflammatory changes after WS. Inflammatory reactions in the cellular lipid species composition were detected although cytological responses indicating inflammation were weak.

Fatty acid fingerprints in bronchoalveolar lavage fluid and its extracellular vesicles reflect equine asthma severity

Equine asthma (EA) is an inflammatory disease of the lower airways driven by mediators released from cells. Extracellular vesicles (EVs) are vehicles for lipid mediators, which possess either pro-inflammatory or dual anti-inflammatory and pro-resolving functions. In this study, we investigated how the respiratory fatty acid (FA) profile reflects airway inflammatory status. The FA composition of bronchoalveolar lavage fluid (BALF), BALF supernatant, and bronchoalveolar EVs of healthy horses (n = 15) and horses with mild/moderate EA (n = 10) or severe EA (SEA, n = 5) was determined with gas chromatography and mass spectrometry. The FA profiles distinguished samples with different diagnoses in all sample types, yet they were insufficient to predict the health status of uncategorized samples. Different individual FAs were responsible for the discrimination of the diagnoses in different sample types. Particularly, in the EVs of SEA horses the proportions of palmitic acid (16:0) decreased and those of eicosapentaenoic acid (20:5n-3) increased, and all sample types of asthmatic horses had elevated dihomo-γ-linolenic acid (20:3n-6) proportions. The results suggest simultaneous pro-inflammatory and resolving actions of FAs and a potential role for EVs as vehicles for lipid mediators in asthma pathogenesis. EV lipid manifestations of EA can offer translational targets to study asthma pathophysiology and treatment options.

The Future of Biomarkers in Veterinary Medicine: Emerging Approaches and Associated Challenges

Simple Summary

In this review we seek to outline the role of new technologies in biomarker discovery, particularly within the veterinary field and with an emphasis on ‘omics’, as well as to examine why many biomarkers-despite much excitement-have not yet made it to clinical practice. Further we emphasise the critical need for close collaboration between clinicians, researchers and funding bodies and the need to set clear goals for biomarker requirements and realistic application in the clinical setting, ensuring that biomarker type, method of detection and clinical utility are compatible, and adequate funding, time and sample size are available for all phases of development.

Abstract

New biomarkers promise to transform veterinary practice through rapid diagnosis of diseases, effective monitoring of animal health and improved welfare and production efficiency. However, the road from biomarker discovery to translation is not always straightforward. This review focuses on molecular biomarkers under development in the veterinary field, introduces the emerging technological approaches transforming this space and the role of ‘omics platforms in novel biomarker discovery. The vast majority of veterinary biomarkers are at preliminary stages of development and not yet ready to be deployed into clinical translation. Hence, we examine the major challenges encountered in the process of biomarker development from discovery, through validation and translation to clinical practice, including the hurdles specific to veterinary practice and to each of the ‘omics platforms–transcriptomics, proteomics, lipidomics and metabolomics. Finally, recommendations are made for the planning and execution of biomarker studies with a view to assisting the success of novel biomarkers in reaching their full potential.

Dynamics of DHA and EPA supplementation: incorporation into equine plasma, synovial fluid, and surfactant glycerophosphocholines

INTRODUCTION

Horses with asthma or osteoarthritis frequently receive ω-3 fatty acid supplements. Docosahexaenoic (DHA; 22:6) and eicosapentaenoic (EPA; 20:5) acids are essential ω-3 fatty acid precursors of anti-inflammatory mediators and components of structural glycerophospholipids (GPL) that act as reservoirs of these fatty acids. Analysis of the incorporation of dietary DHA + EPA into GPL pools in different body compartments has not been undertaken in horses.

OBJECTIVES

We undertook a detailed study of dietary supplementation with DHA + EPA in horses and monitored incorporation into DHA- and EPA-containing glycerophosphocholines (GPC) 38:5, 38:6, 40:5, and 40:6 in plasma, synovial fluid (SF), and surfactant.

METHODS

Horses (n = 20) were randomly assigned to the supplement or control group and evaluated on days 0, 30, 60, and 90. GPC in plasma, SF, and surfactant were measured by high-resolution mass spectrometry with less than 3 ppm mass error. Validation of DHA and EPA incorporation into these GPC was conducted utilizing MS² of the [M + Cl]^- adducts of GPC.

RESULTS

Dietary supplementation resulted in augmented levels of GPC 38:5, 38:6, 40:5, and 40:6 in all compartments. Maximum incorporation into GPCs was delayed until 60 days. Significant increases in the levels of GPC 38:5, 40:5, and 40:6, containing docosapentaenoic acid (DPA; 22:5), also was noted.

CONCLUSIONS

DHA and EPA supplementation results in augmented storage pools of ω-3 essential fatty acids in SF and surfactant GPC. This has the potential to improve the ability of anti-inflammatory mechanisms to resolve inflammatory pathways in these critical compartments involved in arthritis and asthma.

Lipidomics of the chicken egg yolk: high-resolution mass spectrometric characterization of nutritional lipid families

While previous studies have characterized the fatty acids and global lipid families of the chicken egg yolk, there have been no publications characterizing the individual lipids in these lipid families. Such an in-depth characterization of egg yolk lipids is essential to define the potential benefits of egg yolk consumption for the supply of structural and anti-inflammatory lipids. Historically, the major focus has been on the cholesterol content of eggs and the potential negative health benefits of this lipid, while ignoring the essential roles of cholesterol in membranes and as a precursor to other essential sterols. A detailed analysis of egg yolk lipids, using high-resolution mass spectrometric analyses and tandem mass spectrometry to characterize the fatty acid substituents of complex structural lipids, was used to generate the first in-depth characterization of individual lipids within lipid families. Egg yolks were isolated from commercial eggs (Full Circle Market) and lipids extracted with methyl-t-butylether before analyses via high-resolution mass spectrometry. This analytical platform demonstrates that chicken egg yolks provide a rich nutritional source of complex structural lipids required for lipid homeostasis. These include dominant glycerophosphocholines (GPC) (34:2 and 36:2), plasmalogen GPC (34:1, 36:1), glycerophosphoethanolamines (GPE) 38:4 and 36:2), plasmalogen GPE (36:2 and 34:1), glycerophosphoserines (36:2 and 38:4), glycerophosphoinositols (38:4), glycerophosphoglycerols (36:2), N-acylphosphatidylethanolamines (NAPE) (56:6), plasmalogen NAPE (54:4 and 56:6), sphingomyelins (16:0), ceramides (22:0 and 24:0), cyclic phosphatidic acids (16:0 and 18:0), monoacylglycerols (18:1 and 18:2), diacylglycerols (36:3 and 36:2), and triacylglycerols (52:3). Our data indicate that the egg yolk is a rich source of structural and energy-rich lipids. In addition, the structural lipids possess ω-3 and ω-6 fatty acids that are essential precursors of endogenous anti-inflammatory lipid mediators. These data indicate that eggs are a valuable nutritional addition to the diets of individuals that do not have cholesterol issues.