Recent studies describe a genetic "switch" in the brain that is regulated by the hormone leptin and appears to link reproductive function and body weight. Scientists are closer to understanding the links between body weight and fertility after finding a genetic "master switch" that influences both.
Although the switch was characterized in the brains of mice, lead study author Marc Montminy from the Clayton Foundation Laboratories for Peptide Biology in La Jolla, San Diego, California, USA, noted that, "because this gene is crucial to the daisy chain of signals that run between body fat and the brain, it likely plays a pivotal role in how much we, as humans, eat and whether we have offspring."
Montminy and colleagues discovered the gene, known as TORC1, while studying appetite-regulating hormones such as leptin that carry information from fat tissues to the brain.
The investigators studied mice lacking TORC1 and found that these animals rapidly became obese after birth and were usually infertile.
Further study showed that TORC1 responds to leptin by up-regulating the Cocaine and Amphetamine Regulated Transcript gene (CART), which suppresses appetite, and turning on the KISS1 gene, which is essential for normal reproductive function.
In the absence of leptin, therefore, appetite is not adequately suppressed and reproductive functioning is abnormal, the researchers explain.
They conclude that, since TORC1 is kinase regulated, it should make a good target for therapeutic intervention to treat both obesity and infertility.
Source: Nature Medicine 2008
