Washington: Scientists claim to have pinpointed a tiny site in the brain where the hormone leptin may help trigger the onset of puberty.
The findings in mice indicate that a site within the hypothalamus called the ventral premammillary nucleus, or PMV, is the target where the hormone leptin effectively kick starts puberty in females, according to a team from Texas University.
Researchers have long known that puberty starts when individuals have enough energy stores or fat to meet the demands of reproduction, and that leptin -- a hormone produced
by fat cells -- acts in the brain to mediate this process, but the site where leptin exerts this effect remained unclear.
"We found that the PMV is a key site of leptin action non puberty. This may not be the only site, considering the importance of the reproductive function for species survival,
but the role played by PMV neurons has not been recognised before.
"Our findings show that leptin action only in the PMV is sufficient to induce puberty in female mice," said Dr Carol Elias, who led the team.
Prior research has shown that in mice and humans lacking leptin, puberty grinds to a screeching halt at the prepubescent level, and the animals are infertile. Studies
also have shown that reintroducing leptin to leptin-deficient people causes puberty to resume.
"We are witnessing an alarming situation in which the increasing incidence of childhood obesity may be inducing an advance in the onset of puberty in girls. The main obstacle
for researchers in the field has been identifying the cell population involved in this event," Dr Elias said.
In this study, the scientists wanted to determine where leptin plays its role. To do this, they developed transgenic mouse models in which the mice had functional
leptin receptors only in the PMV.
Because of the lack of leptin signalling everywhere else in the body, the mice were obese but showed pubertal development and were able to get pregnant.
"One result that surprised us was that leptin acting only in the PMV was sufficient to induce puberty and improve fertility in females, but not in males. We`re now trying to
understand what`s going on with males and whether leptin acts in different brain sites to induce puberty and fertility in males," Dr Elias said.
The findings are to be published in the `Journal of Clinical Investigation`.