| Summary: | Abstract Seasonal animal species utilize various adaptive mechanisms to survive in different environments and conditions. This thesis work examines metabolic regulation in two animal models with seasonal adaptations. The raccoon dog is a canid species originating from East Asia that has also been introduced to Europe and is rapidly dispersing. Genetic changes that have enabled the adaptation to new environments were evaluated by comparing the transcriptome profiles of raccoon dogs from the original habitation areas in South Korea and Japan to the more recent introduction area in Finland. The results revealed novel aspects on the history of the raccoon dog and on the genes that might have aided in the diversification process. During the cold winter season, the raccoon dog can enter a state of winter lethargy, characterized by reduced activity and modest body temperature reduction. The role of thermoregulation in the energy homeostasis was evaluated, and our results demonstrated a lack of BAT and UCP1-dependent thermogenesis in the adult raccoon dog, indicating resilience to cold weather. The reindeer is a semi-domesticated ruminant species that spends the winter actively ranging and foraging for food sources. The transcriptome profiles were compared along with metabolic and thermoregulatory markers from reindeer populations in Finland and Siberia at different seasons. Our results identified candidate genes involved in the immune response, fat deposition, and energy metabolism as well as the potential for UCP1-dependent thermogenesis in the adipose tissues, which have likely contributed to the adaptation to arctic environments. Raccoon dogs prepare for winter by seasonal hyperphagia and can survive long periods of fasting relying on the accumulated adipose tissues. These opposite conditions were studied, and the results revealed that the studied key central and peripheral regulatory peptides and plasma metabolic profiles remained similar after autumnal fattening and winter fasting. Also, no inflammatory response ...
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