Role of Brown and Beige Adipose Tissues in Seasonal Adaptation in the Raccoon Dog (Nyctereutes procyonoides)

Abstract

Brown adipose tissue (BAT) expresses uncoupling protein-1 (UCP1), which enables energy to be exerted towards needed thermogenesis. Beige adipocytes are precursor cells interspersed among white adipose tissue (WAT) that possess similar UCP1 activity and capacity for thermogenesis. The raccoon dog (Nyctereutes procyonoides) is a canid species that utilizes seasonal obesity to survive periods of food shortage in climate zones with cold winters. The potential to recruit a part of the abundant WAT storages as beige adipocytes for UCP1-dependent thermogenesis was investigated in vitro by treating raccoon dog adipocytes with different browning inducing factors. In vivo positron emission tomography/computed tomography (PET/CT) imaging with the glucose analog 18F-FDG showed that BAT was not detected in the adult raccoon dog during the winter season. In addition, UCP1 expression was not changed in response to chronic treatments with browning inducing factors in adipocyte cultures. Our results demonstrated that most likely the raccoon dog endures cold weather without the induction of BAT or recruitment of beige adipocytes for heat production. Its thick fur coat, insulating fat, and muscle shivering seem to provide the adequate heat needed for surviving the winter.

Physiological, Immune Response, Antioxidant Capacity and Lipid Metabolism Changes in Grazing Sheep during the Cold Season

“…The white adipose tissue “browning” process can consume stored fat for energy expenditure via nonshivering thermogenesis to generate body heat under cold exposure and can be accompanied by body weight loss [ 22 ]. In addition, the relative fur coat weight increased in the cold season, and similar findings have been reported for raccoon dogs [ 3 ]. From our data, it seems that grazing Mongolian sheep can increase the thickness of their fur coat and insulating fat as well as utilize lipid metabolism to maintain their body temperature to resist cold weather.…”

“…To tolerate cold exposure induced by low environmental temperatures, vertebrates have developed complex, effective, and diverse adaptation mechanisms. For example, mammals endure cold exposure via increased physical activity and food intake, improvement of their thick fur coats and insulating fat layers, or induction of the formation of brown adipose tissue and recruitment of beige adipocytes for heat production and body temperature maintenance [ 2 , 3 ]. More importantly, various systemic functions of organisms, including immune regulation, antioxidant defense systems, and glucose and lipid metabolism, are also stimulated appropriately to resist cold stress [ 4 , 5 , 6 ].…”

Malicious Mites—Sarcoptes scabiei in Raccoon Dogs (Nyctereutes procyonoides) in Schleswig-Holstein, Germany

“…The score of "moderate" included animals not matching the other categories. In addition, season was taken into account, as raccoon dogs do show seasonal obesity in regions with cold winters to survive periods of food shortages [31]. However, juveniles in the process of building up fat reserves could not be assessed regarding their nutritional status.…”