Newsletter: Events, Recipes, and Tips

Support for an innovative idea

March 26, 2014

Hello Everyone,
It's been a while since I last wrote. I've been busy with the Breakfast Cookie business (www.susiesmartcookie.com) and have found it easier to tweet my thoughts (Susanallport) or post them on facebook (Susie's Smart Cookie) than to log into the Author's Guild site. So please sign up for one of those venues if you want more regular missives.

But I'm writing today because I just found this paper that was published last year and supports the most innovative aspect of The Queen of Fats. That is that the changing availability of omega-3s and omega-6s in the diets of foraging animals is, in effect, a marker of the changing seasons and helps animals to prepare for the changes to come: for times of activity and reproduction when omega-3s (green leaves and animals that eat green leaves) are available and times of hunkering down and survival when omega-6s (seeds) are abundant.

Here's the paper. Hope you find it as exciting as I do.
Best,
Susan

Membrane Phospholipid Fatty Acid Composition
Regulates Cardiac SERCA Activity in a Hibernator, the
Syrian Hamster (Mesocricetus auratus)
Sylvain Giroud1*., Carla Frare1.§, Arjen Strijkstra2,3,4, Ate Boerema3,5, Walter Arnold1, Thomas Ruf1
1 Research Institute of Wildlife Ecology, Department of Integrative Biology and Evolution, University of Veterinary Medicine, Vienna, Austria, 2 University Medical Center
Groningen, Departments of Chronobiology & Molecular Neurobiology, University of Groningen, Groningen, The Netherlands, 3 Department of Chronobiology, University
of Groningen, Groningen, The Netherlands, 4 Wildlife Management, University of Applied Sciences Van Hall Larenstein, Leeuwarden, The Netherlands, 5 University Medical
Center Groningen, Nuclear Medicine and Molecular Imaging, University of Groningen, Groningen, The Netherlands
Abstract
Polyunsaturated fatty acids (PUFA) have strong effects on hibernation and daily torpor. Increased dietary uptake of PUFA of
the n-6 class, particularly of Linoleic acid (LA, C18:2 n-6) lengthens torpor bout duration and enables animals to reach lower
body temperatures (Tb) and metabolic rates. As previously hypothesized, this well-known influence of PUFA may be
mediated via effects of the membrane fatty acid composition on sarcoplasmic reticulum (SR) Ca2+2ATPase 2a (SERCA) in the
heart of hibernators. We tested the hypotheses that high proportions of n-6 PUFA in general, or specifically high
proportions of LA (C18:2 n-6) in SR phospholipids (PL) should be associated with increased cardiac SERCA activity, and
should allow animals to reach lower minimum Tb in torpor. We measured activity of SERCA from hearts of hibernating and
non-hibernating Syrian hamsters (Mesocricetus auratus) in vitro at 35uC. Further, we determined the PL fatty acid
composition of the SR membrane of these hearts. We found that SERCA activity strongly increased as the proportion of LA
in SR PL increased but was negatively affected by the content of Docosahexaenoic acid (DHA; C22:6 n-3). SR PL from
hibernating hamsters were characterized by high proportions of LA and low proportions of DHA. As a result, SERCA activity
was significantly higher during entrance into torpor and in torpor compared to inter-bout arousal. Also, animals with
increased SERCA activity reached lower Tb during torpor. Interestingly, a subgroup of hamsters which never entered torpor
but remained euthermic throughout winter displayed a phenotype similar to animals in summer. This was characterized by
lower proportions of LA and increased proportions of DHA in SR membranes, which is apparently incompatible with torpor.
We conclude that the PUFA composition of SR membranes affects cardiac function via modulating SERCA activity, and
hence determines the minimum Tb tolerated by hibernators.
Citation: Giroud S, Frare C, Strijkstra A, Boerema A, Arnold W, et al. (2013) Membrane Phospholipid Fatty Acid Composition Regulates Cardiac SERCA Activity in
a Hibernator, the Syrian Hamster (Mesocricetus auratus). PLoS ONE 8(5): e63111. doi:10.1371/journal.pone.0063111
Editor: Wolf-Hagen Schunck, Max Delbrueck Center for Molecular Medicine, Germany
Received December 7, 2012; Accepted March 28, 2013; Published May 1, 2013
Copyright:  2013 Giroud et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: SG and this research work were financially supported by a postdoctoral fellowship of the University of Veterinary Medicine Vienna (Austria). The
funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: sylvain.giroud@vetmeduni.ac.at
§ Current address: Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, Alaska, United States of America
. These authors contributed equally to this work.
Introduction
Torpor and hibernation are states with reduced metabolic rate
and hence body temperatures (Tb), a strategy employed by many
birds and mammals to survive harsh environmental conditions [1].
However, vital organs must remain functional despite depressed
oxygen consumption and single-digit Tb. This is most important
for the heart that has to maintain circulation by regular
contractions to guarantee sufficient perfusion of the organism.
At Tb below 20uC, non-hibernators experience severe arrhythmias
and ventricular fibrillation that leads to cardiac arrest [2].
This heart dysfunction is due to a massive increase in cytosolic
calcium accompanied by calcium waves and by calcium overload
[3,4]. In contrast to non-hibernators, hibernating mammals
remain in sinus rhythm even if Tb approaches 0uC [2]. This
outstanding ability of the hibernatorís heart is due to the
maintenance of sufficiently fast calcium removal into the
sarcoplasmic reticulum (SR) after contraction, despite low Tb
(see [5] and [4] for reviews). Indeed, an increased rate of calcium
reuptake and larger calcium stores were reported in the SR of
hibernating Richardsonís ground squirrels [6]. Moreover, the
mRNA and protein levels of SR-calcium ATPase (SERCA 2a in
the heart, subsequently called SERCA for simplicity), the pump
removing calcium into the SR, were found to be increased by 3-
fold in myocytes of hibernating woodchucks compared to those of
animals in the non-hibernating season [7]. These results support
the role of SERCA as the key enzyme that ensures proper calcium
handling in cardiomyocytes and hence functioning of the heart at
low Tb.
Interestingly, the activity of this transmembrane pump seems to
be affected by the fatty acid composition of the surrounding
phospholipids (PL). Specifically, there are reports of positive effects
of certain polyunsaturated fatty-acids (PUFA), namely those of the
PLOS ONE | www.plosone.org 1 May 2013 | Volume 8 | Issue 5 | e63111