view - Department of Reproduction, Obstetrics and Herd Health

GENERAL DISCUSSION
DISTRIBUTION OR REDISTRIBUTION OF FATTY ACIDS TO THE REPRODUCTIVE
TRACT
One of the most trivial processes when evaluating the link between the
metabolism and the ovarian compartment, especially when evaluating the effect of FA, is
the physical barrier between the blood and the follicular cavity which serves as an
avascular compartment in which the oocyte is subdued to a highly orchestrated process
of growth, prematuration and maturation (Picton et al., 2008; Ferreira et al., 2009). The
pathway via which FA intervene in these processes is partly mediated in the way they
are being released into the bloodstream, transported to and subsequently are taken up
by e.g. the ovary, but experiments in this research area are rare.
During lipolysis, TAG catabolism is initiated by adipose tissue lipases which
transform the insoluble TAG into NEFA which are released via FA transfer proteins
(FATP) and FA translocase (FAT) into the blood (Bionaz and Loor, 2008; Contreras and
Sordillo, 2011; Figure 4). Typically, NEFA are bound to albumin, although a very small
portion can be transported as unbound monomers in aqueous solution (Richieri and
Kleinfeld, 1995). The follicular wall has been documented to be permeable via
paracellular transport for molecules such as albumin and other proteins (Edwards, 1974;
Gosden et al., 1988). In Chapters 5.1 and 5.2, albumin concentration did not differ
between plasma and FF, which implies differences in NEFA concentrations cannot be
attributed to differences in the concentration of their carrier molecule. The higher NEFA
in plasma compared to the FF, as in our (Chapters 5.1 and 5.2) and other studies (Leroy
et al., 2005; Shehab-El-Deen et al., 2010), has been explained by Chung et al. (1995) by a
substantial partitioning of NEFA into low density lipoproteins (LDL) in case of excessive
plasma NEFA concentrations. Interestingly in the same study, the partitioning of FA was
shown to be ‘saturation dependent’ with saturated FA mainly being partitioned to the
LDL whereas unsaturated FA remained albumin bound (Chung et al., 1995). The latter
might explain the higher PUFA content which has been observed in NEFA FF when
compared to plasma (Moallem et al., 1999; Leroy et al., 2005; Renaville et al., 2010).
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