Mobilization of ectopic yolk in Gallus gallus domesticus: A novel reverse lipid transport process

Ingrid Cornax, Rosemary L. Walzem, Craig Larner, Ronald D. Macfarlane, Kirk C. Klasing

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

In many oviparous animals, bursting type atresia of ovarian follicles occurs during the reproductive cycle, resulting in the escape of yolk into the extracellular compartment. In birds, this ectopic yolk is rapidly cleared by an unknown process that involves the appearance of yolk-engorged macrophage-like cells. To study this unique type of lipid transport, we injected young male chickens intra-abdominally with egg yolk. Absorption of egg yolk from the body cavity markedly increased the triacylglyceride-rich fraction (TRL) of plasma lipoproteins and was coincident with increased levels of plasma triacylglycerides (TAGs) but not non-esterified fatty acids (NEFAs). Thus, the transport of yolk lipids from the abdominal cavity appears to occur in lipoproteins and be more similar to the transport of hepatic TAGs to the periphery via lipoproteins than to transport of adipose TAGs to the periphery via NEFAs released by the action of lipases. When macrophages were exposed to yolk in vitro, they quickly phagocytized yolk; however, it is unclear whether this level of phagocytosis contributes significantly to total yolk clearance. Instead, the chicken macrophage may function more as a facilitator of yolk clearance through the modification of yolk lipoproteins and the regulation of the local and systemic immune response to ectopic yolk. Yolk appears to be anti-inflammatory in nature. Yolk did not increase levels of the inflammatory cytokines IL-1, IL-6 and IFNγ either in vivo or in vitro; in fact, yolk dampened many inflammatory changes caused by lipopolysaccharide (LPS). Conversely, LPS-induced inflammation retarded yolk clearance from the abdominal cavity and plasma TAG levels.

Original languageEnglish (US)
Pages (from-to)1949-1958
Number of pages10
JournalJournal of Experimental Biology
Volume216
Issue number10
DOIs
StatePublished - May 2013

Keywords

  • Apolipoprotein A1
  • CD36
  • MARCO
  • Macrophage
  • Serum amyloid A
  • Toll-like receptor

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