Gestational profile of leptin messenger ribonucleic acid (mRNA) content inthe placenta and adipose tissue in the rat, and regulation of the mRNA levels of the leptin receptor subtypes in the hypothalamus during pregnancy and lactation
Md. Garcia et al., Gestational profile of leptin messenger ribonucleic acid (mRNA) content inthe placenta and adipose tissue in the rat, and regulation of the mRNA levels of the leptin receptor subtypes in the hypothalamus during pregnancy and lactation, BIOL REPROD, 62(3), 2000, pp. 698-703
Serum leptin levels were significantly increased during rat gestation. Our
data showed that leptin mRNA levels in both the adipose tissue and placenta
were higher as pregnancy progressed, suggesting a role for both tissues in
the hyperproduction of leptin. This paradoxical increase in leptin concent
ration during gestation suggests that a physiological state of leptin resis
tance may exist at the hypothalamic level that may explain the hyperphagia
observed in pregnant rats. In order to study this issue further, levels of
the mRNA encoding the different leptin receptor isoforms were determined in
the hypothalamus of pregnant and nonpregnant rats. We found a specific red
uction of the mRNA levels encoding the leptin receptor isoform Ob-Rb in the
hypothalamus of pregnant rats compared to nonpregnant animals, suggesting
that during pregnancy the hypothalamus shows a physiological resistance to
the high levels of leptin due, at least in part, to a decrease in the expre
ssion of the long, biologically active form of the leptin receptor (Ob-Rb).
During lactation, serum leptin levels returned to values observed in nonpr
egnant rats. In the hypothalami of these animals, Ob-Rb mRNA content was si
milar to that observed in nonpregnant rats, but we found an increased expre
ssion of some of the short forms of the leptin receptor (Ob-Re and Ob-Rf).
This could contribute to induction of the hyperphagia present during lactat
ion. These data provide new insights into the adaptive mechanisms that take
place during pregnancy and lactation in order to meet increased metabolic
requirements.