title: Effects of sex and scotorefractory state on obesity induced by photostimulation and serum leptin in Siberian hamsters (Phodopus sungorus).
abstract: The rising prevalence of obesity is associated with an increasing incidence of heart disease, diabetes and other health risks. In addition, severe cases of obesity are associated with an even greater risk of morbidity and mortality. Therefore, animal models of morbid obesity are required to better elucidate the underlying mechanisms. Our investigations in the Siberian hamster (Phodopus sungorus) suggest that pronounced obesity can be reliably induced in this species without relying on genetic manipulation or overly fatty and palatable foods. In a prior study on reproductive aging in female Siberian hamsters, we incidentally observed marked obesity in a group of hamsters that were exposed to a particular photoperiodic regime. In short day (SD) lengths, Siberian hamsters inhibit their reproductive physiology and reduce food intake and body mass. However, hamsters become refractory to SD after 15-20weeks and revert to the long day (LD) phenotype. In the previous study, refractory animals appeared to be particularly sensitive to photostimulation (transfer to LD), in terms of increasing body mass. To test the hypothesis that refractoriness to SD predisposes hamsters to severe obesity, we photostimulated females and males in different states of SD responsiveness (inhibited or refractory). We determined that photostimulation during the SD-refractory state is particularly effective in inducing pronounced obesity and high serum leptin concentration in female hamsters. We propose that this experimental framework is a useful model to investigate the factors and signals that create a predisposition to excessive food intake and body mass, without having to rely on genetic or dietary manipulations.
authors.affiliation: Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Cudney
authors.forename: Ned J
authors.initials: NJ
authors.lastname: Place
mesh_terms: D000818:Animals; D006224:Cricetinae; D005260:Female; D020738:Leptin / Q000097:blood*; D008027:Light; D008297:Male; D009765:Obesity / Q000097:blood; D017111:Phodopus; D012737:Sex Factors
chemical_list: D020738:Leptin