Polyunsaturated fatty acids and seasonal acclimatization
Hibernators and daily heterotherms cope with cold and limited feed supply during winter with a considerable reduction of metabolic rate and body temperature (Tb). We found similar reactions in several non-hibernating large mammals, except that Tb changes were substantial only in peripheral body parts. Reduction of Tb during hibernation and daily torpor is preceded by incorporation of n-6 linoleic acid (LA), an essential polyunsaturated fatty acid (PUFA), into phospholipids (PL). This PL-environment apparently ensures proper muscular function in the cold by attenuating the retardation of the trans-membrane sarcoplasmic reticulum Ca++-ATPase caused by low Tb. In contrast, the PL-content of docosahexaenoic acid (DHA) correlates positively with metabolic demands. Key enzymes of the Krebs cycle and β-oxidation work faster if PL contain high amounts of DHA, facilitating ATP production. In summary, profound changes of metabolic rate and Tb seem to be ubiquitous among birds and mammals living in seasonal environments, as is associated membrane remodelling. However, specific effects of PUFA in PL suggest trade-offs determining seasonal changes of the fatty acid composition of membranes that is largely independent of direct dietary intake.
In this study we investigate in detail effects of PUFA on seasonal acclimatization in red deer, a model species for large seasonal non-hibernating mammals. We are for the first time trying to disentangle experimentally the role of dietary and photoperiodic origin of changes in membrane PL composition and its effect on membrane-bound enzymes. We expect to find profound consequences of seasonal acclimatization at this molecular level on thermoregulation and energetics of the whole organism. Our approach is a longitudinal study on a herd of red deer kept under close to natural conditions, but subjected to a feeding experiment manipulating the availability of food, of dietary supply of PUFA, and of photoperiodic control of seasonal acclimatization. Analyses of PL-composition, expression and activity of key membrane enzymes in muscle cells of winter and summer acclimatized deer are sampled repeatedly using a well established telemetry system, combined with the continuous measurement of heart rate as an indicator of metabolic rate, core and peripheral Tb, and locomotor activity of the deer.
Principal investigator is Univ.Prof.Dr. Walter Arnold, head of the Research Institute of Wildlife Ecology. The PI is supported by Dr. Omid Hekmat, head of the institute’s chemistry lab, and Dr. Steve Smith, head of the institute’s genetics lab.
Project duration 03/2017-12/2020