Sebaceous Lipid Profiling of Bat Integumentary Tissues: Quantitative Analysis of Free Fatty Acids, Monoacylglycerides, Squalene, and Sterols

Abstract

White-nose syndrome (WNS) is a fungal disease caused by Pseudogymnoascus destructans and is devastating North American bat populations. Sebaceous lipids secreted from host integumentary tissues are implicated in the initial attachment and recognition of host tissues by pathogenic fungi. We are interested in determining if ratios of lipid classes in sebum can be used as biomarkers to diagnose severity of fungal infection in bats. To first establish lipid compositions in bats, we isolated secreted and integral lipid fractions from the hair and wing tissues of three species: big brown bats (Eptesicus fuscus), Eastern red bats (Lasiurus borealis), and evening bats (Nycticeius humeralis). Sterols, FFAs, MAGs, and squalene were derivatized as trimethylsilyl esters, separated by gas chromatography, and identified by mass spectrometry. Ratios of sterol to squalene in different tissues were determined, and cholesterol as a disease biomarker was assessed. Free sterol was the dominant lipid class of bat integument. Squalene/sterol ratio is highest in wing sebum. Secreted wing lipid contained higher proportions of saturated FFAs and MAGs than integral wing or secreted hair lipid. These compounds are targets for investigating responses of P. destructans to specific host lipid compounds and as biomarkers to diagnose WNS.

Glycerophospholipid Analysis of Eastern Red Bat (Lasiurus Borealis) Hair by Electrospray Ionization Tandem Mass Spectrometry

“…With over 100 phospholipids known from mammals (Yamashita et al 2014), cataloging GPs present on fur, combined with sebum composition from other body regions (Pannkuk et al 2012, 2013a, 2013b), is a critical first step before making and testing predictions about the role of these lipid molecules in the ecology of free-living animals. L. borealis is a particularly interesting species for investigation due to a number of ecological and life history factors.…”

“…GPs are not usually detected in sebum sampled in vivo in most organisms (Emara and El-Mokaddem 1979), which may be due to GPs being converted to wax esters or FFAs by lipases or due to the use of analytical techniques with low sensitivity (e.g., thin-layer chromatography) (Downing et al 1974; Colton and Downing 1985). Another plausible explanation is low occurrence of lipase activity or oxidation present in bat pelage, as the lipid content of bat hair is found to resemble the sebocyte lipid rather than the secreted sebaceous lipid of wings (Pannkuk et al 2012, 2013a). On human hair surface, PS was found to be the dominant GP followed by PE, PC, and Lyso PC respectively (Singh and Gershbein, 1968).…”

“…Proportions and types of GPs are likely different among tissue types and possibly species. Secreted bat hair lipid proportions resembles intracellular membrane lipid more than wing sebum (Pannkuk et al 2012, 2013a). Similarities between hair surface lipid and wing keratinocyte lipid could be explained by lower oxidation or lipase activity in bat pelage or possibly a greater contribution from keratinocytes on the hair shaft secretions.…”

“…While reports have discussed in detail bat sebaceous glands ultrastructure (Cortese and Nicholl, 1979; Nassar et al 2008), the chemical composition of bat sebum (Pannkuk, et al 2012; 2013a), and bat stratum corneum lipids (Muñoz-Garcia et al 2012), surprisingly little on GP composition of bat integumentary lipids is known. Furthermore, few studies have reported GP content of the hair surface.…”

Changes in the Pseudogymnoascus destructans transcriptome during White-nose Syndrome reveal possible mechanisms for both virulence and host resistance

“…9,10 The epidermal lipids of bats also contain cerebrosides and monoacylglycerols. 11,12 Sebum accounts for almost all of the lipids found on the skin surface of mammals 13 , and the epidermis of M. lucifugus has a total lipid content of 47% dry matter mass.…”