Leptin is a hormone that signals an organism to suppress appetite. Leptin is released from fat cells in white
adipose tissue and binds to receptors on cells in the hypothalamus, a region of the brain that controls appetite.
(a) Identify the way that leptin produced by fat cells of adipose tissue in the abdomen can send a signal to the
neuroendocrine cells in the hypothalamus.
(b) Researchers are investigating the effectiveness of various treatments on three individuals with a history of
increased appetite.
• Individual I does not produce leptin but does have functional leptin receptors.
• Individual II does produce leptin but does not have functional leptin receptors.
• Individual III does not produce leptin and does not have functional leptin receptors.
The first treatment involves injection of leptin into the blood. The second treatment involves gene therapy
that results in the production of functional leptin receptors in cells of the hypothalamus. The third treatment
combines both the injection of leptin and the leptin-receptor gene therapy.