Leptin was discovered in 1994 by Jeffrey M. Friedman and his colleagues at Rockefeller University. It is encoded by the obese (ob) gene. Leptin’s primary function is to regulate energy intake and expenditure, including appetite and metabolism. It acts on receptors in the hypothalamus of the brain where it inhibits appetite by counteracting the effects of neuropeptide Y (a potent feeding stimulant secreted by cells in the gut and in the hypothalamus) and anandamide (another potent feeding stimulant that binds to the same receptors as THC, the active ingredient in marijuana). Leptin also promotes the synthesis of α-MSH, an appetite suppressant.
Leptin signals the brain to reduce appetite and increase the amount of energy used. When fat mass decreases, the level of plasma leptin falls, which stimulates appetite and suppresses energy expenditure until fat mass is restored. Conversely, when fat mass increases, so do leptin levels, which suppress appetite until weight is lost. This feedback loop helps to maintain body weight within a relatively narrow range.
Recombinant human leptin is a form of leptin that is produced through recombinant DNA technology. This involves inserting the gene that encodes leptin into bacteria (such as E. coli), which then produce the hormone. The recombinant form is used in research and has potential therapeutic applications.
Recombinant human leptin retains the biological activity of the native hormone. It can stimulate the proliferation of cells expressing the leptin receptor (OB-R), such as in the BaF3 mouse pro-B cell line transfected with human leptin receptor . The activity is typically measured by the leptin-dependent stimulation of these cells, with an effective dose (ED50) in the range of 0.4-2 ng/mL .
Recombinant human leptin is used in various research applications, including:
Leptin therapy has been explored for treating conditions such as congenital leptin deficiency, lipodystrophy, and hypothalamic amenorrhea. However, its effectiveness in treating common obesity is limited due to leptin resistance, a condition where the body does not respond adequately to leptin signals.