Reproduction Nutrition Development, formerly Annales de Biologie Animale Biochimie Biophysique

FOXN1, a transcription factor expressed in the epidermis, regulates keratinocyte differentiation and participates in skin wound healing. In this study, we explored the impact of FOXN1 insufficiency on diet-stimulated weight gain and dermal white adipose tissue regulation in the intact and wounded skin of FOXN1eGFP/+ (heterozygotes, FOXN1-insufficient) mice in the context of age and diet. The results showed that on a high-fat diet, FOXN1eGFP/+ mice gained significantly less body weight than their FOXN1+/+ counterparts (FOXN1-sufficient mice). The intact and wounded skin of FOXN1eGFP/+ mice displayed abrogated expression of the master regulators of adipogenesis, PPARγ, FABP4, and leptin, which decreased with age in FOXN1+/+ mice. FOXN1 insufficiency also resulted in a decreased percentage of adipocyte-committed precursor cells (CD24+) in the skin. The proadipogenic pathway genes Bmp2, Igf2, and Mest showed a gradual decrease in expression that accompanied the gradual inactivation of FOXN1 in the skin of FOXN1+/+, FOXN1eGFP/+, and FOXN1eGFP/eGFP (lack of FOXN1) mice. Bone morphogenetic protein 2 and insulin-like growth factor 2 signals colocalized with FOXN1-eGFP in the epidermis and in hair follicles. These data demonstrated that FOXN1 initiates the cascade of adipogenic signaling that regulates skin homeostasis and wound healing and affects susceptibility to diet-induced obesity.

Reproduction Nutrition Development, formerly Annales de Biologie Animale Biochimie Biophysique

Glucocorticoids (GCs) and adrenocorticotropic hormone (ACTH) are major components of the classic endocrine stress response. Free-living vertebrates are characterized by circannual changes in the baseline and/or stress-induced secretion of GCs and ACTH. In mammalian species, GC and ACTH levels vary seasonally but there is no consensus to the season in which animals have elevated GC and ACTH levels. The aim of our study was to determine, for the first time, the type and amount of glucocorticoids produced in free-living beaver (Castor fiber L.) the largest rodent in Eurasia, and to find out whether stress-induced plasma GC and ACTH levels show seasonal variations. Blood samples were obtained, from animals under general anesthesia in April (pregnancy in females), July (offspring rearing) and November (preparing for the winter). The adrenals of beavers produce both cortisol and corticosterone, and plasma cortisol levels were higher than corticosterone. In the current experiment, plasma cortisol concentrations in beavers were affected by the season. The highest stress-associated cortisol levels were noted in males in July during offspring rearing. Corticosterone and ACTH concentrations in beavers remained generally constant, regardless of the season and sex. In conclusion, seasonal changes were observed only in relation to stress-induced plasma cortisol levels in the beaver.