Submitted on December 11, 2007
Accepted on February 26, 2008
Seasonal acclimatization of brain lipidome in a eurythermal fish (Carassius carassius, L.) is mainly determined by temperature
Reijo Tapio Kakela1*, Minja Mattila2, Martin Hermansson3, Perttu Haimi3, Andreas Uphoff4, Vesa Paajanen5, Pentti Somerharju3, and Matti Vornanen6
1 Institute of Biomedicine, University of Helsinki, Helsinki, Finland; , Finland
2 Faculty of Biosciences, University of Joensuu, Joensuu, Finland
3 Helsinki, Finland; Institute of Biomedicine, University of Helsinki, Helsinki, Finland
4 Institute of Biomedicine, University of Helsinki, Helsinki, Finland; Helsinki, Finland
5 Helsinki, Finland; Faculty of Biosciences, University of Joensuu, Joensuu, Finland
6 Joensuu, Finland; Faculty of Biosciences, University of Joensuu, Joensuu, Finland
* To whom correspondence should be addressed. E-mail: reijo.kakela{at}helsinki.fi.
Crucian carp (Carassius carassius) is an excellent vertebrate model for studies on temperature adaptation in biological excitable membranes, since the species can tolerate temperatures from 0 to +36 °C. To determine how temperature affects the lipid composition of brain, the fish were acclimated for 4 weeks at +30, +16 or +4 degree C in the laboratory, or seasonally acclimatized individuals were captured from the wild throughout the year (T = +1 - +23 °C), and the brain glycerophospholipid and sphingolipid compositions were analyzed in detail by electrospray-ionization mass spectrometry. Numerous significant temperature-related changes were found in the molecular species composition of the membrane lipids. The most notable and novel finding was a large (~3-fold) increase of the di-22:6n-3 phosphatidylserine and -ethanolamine species in the cold. Since the increase of 22:6n-3 in the total fatty acyl pool of the brain was small, the formation of di-22:6n-3 aminophospholipid species appears to be a specific adaptation to low temperature. Such highly unsaturated species could be needed to maintain adequate membrane fluidity in the vicinity of transporters and other integral membrane proteins. Plasmalogens increased somewhat at higher temperatures, possibly to protect membranes against oxidation. The modifications of brain lipidome during the 4-week laboratory acclimation were in many respects similar to those found in the wild, which indicates that the seasonal changes observed in the wild are temperature-dependent rather than induced by other environmental factors.
