Seasonality and fasting effect in raccoon dog Nyctereutes procyonoides serum leptin levels determined by canine leptin‐specific enzyme‐linked immunosorbent assay

Abstract

Leptin is an adipocyte-derived peptide hormone that acts on the brain and regulates food intake and energy balance. Several previous reports have suggested that overwintering raccoon dogs Nyctereutes procyonoides are able to control their adiposity efficiently, but the contribution of leptin to weight regulation in these animals remains unclear. To study the seasonality of overwintering raccoon dogs as well as the effects of fasting on them, serum leptin levels were investigated using a newly established canine leptin-specific enzyme-linked immunosorbent assay (ELISA) kit. Of the nine animals studied, five were fed and four were fasted (deprived of food for 2 months in winter). Blood samples and body fat weights were monitored once a month throughout the experimental period (July 2007-March 2008). Leptin concentrations obtained by ELISA were significantly higher than and had a positive correlation with those obtained by previously used multispecies radioimmunoassay (RIA) kits. Moreover, ELISA showed a clearer correlation between the body fat weight and leptin levels compared with RIA, suggesting the efficacy of canine leptin-specific ELISA kit for leptin estimation in raccoon dogs. Autumnal fattening was observed in both groups of animals, but the wintertime loss of adipose tissue was more obvious in the fasted group. Serum leptin concentrations determined by ELISA showed seasonal changes without significant differences between the fed and fasted animals. Therefore, high levels of leptin may be responsible for the suppression of feeding behavior in raccoon dogs before winter.

Hormonal responses to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups

“…However, the current knowledge about the factors regulating those adaptations mostly originates from short-term starvation experiments carried out on laboratory animals that are not adapted to food deprivation. In fact, whereas long-term fasts are natural components of the life history of many vertebrates (13,48,71), few data exist on the hormonal changes associated with prolonged, active fasting in mammals in their natural habitat (40,57,58,70). Understanding the links between nutritional state and free-ranging animal physiology is, however, crucial in understanding the mechanisms regulating energy balance and feeding behavior in free-ranging animals (18).…”