Resistin is a new adipocytokine which is expressed in rat, mouse and possibly 
human adipose tissue. Its putative role as a mediator of insulin resistance is 
controversial. We hypothesized that resistin, like leptin, would have multiple 
roles in non-adipose tissues and we reported that resistin is expressed in mouse 
brain and pituitary. Moreover, resistin expression in female mouse pituitary is 
developmentally regulated and maximal expression occurs peripubertally. Although 
the role of endogenous resistin in mouse brain and pituitary has not been 
determined, our data suggest that resistin could be important in the postnatal 
maturation of the hypothalamic-pituitary system. In the present study we 
compared the ontogeny of resistin gene expression in the pituitary of male and 
female mice using semi-quantitative RT-PCR analysis. We show that resistin 
expression is developmentally regulated in the pituitary of male and female CD1 
mice. However, significant gender differences were evident (male > female at 
postnatal day 28 and 42) and this was not modified by neonatal treatment of 
female pups with testosterone. Since resistin expression in adipose tissue is 
also influenced by obesity, we evaluated resistin expression in fat, brain and 
pituitary of the obese ob/ob mouse. Resistin mRNA was significantly increased in 
both visceral and subcutaneous adipose depots in postnatal day 28 ob/ob mice 
compared to controls, but pituitary resistin expression was significantly 
reduced. In contrast to the prepubertal levels, and in agreement with other 
reports, adipose resistin expression was reduced in adult ob/ob mice. In a third 
set of experiments we examined the influence of food deprivation on pituitary 
and fat resistin mRNA. Resistin gene expression was severely down-regulated by a 
24-hour fast in adipose and pituitary tissue but not in hypothalamus. In 
conclusion, pituitary resistin expression is age- and gender-dependent. In ob/ob 
mice, and in fasted mice, resistin is regulated in a tissue-specific manner. 
Thus in visceral fat obesity increases but starvation decreases resistin mRNA. 
In contrast, pituitary levels are decreased in the presence of both high (ob/ob) 
and low (fasting) adipose stores. Further studies are required to define the 
unexpected hormonal regulation of resistin gene expression in the pituitary.