[Leptin in the regulation of energy balance]

Leptin, identified in 1994 as a substance synthesized in adipose tissue in amounts that are proportional to the magnitude of fat reserves, has been described as an important factor in the regulation of the body's energy homeostasis as it is capable of inhibiting intake, stimulating energy expenditure and regulating other peripheral metabolic processes involved in the control of the spread of body fat (secretion of insulin, lipolysis, glucose transport). Nonetheless, leptin is a pleotropic substance also involved in fertility, inflammation and angiogenesis processes, among others. Although these actions have been well defined in certain animal models of obesity, the role played by leptin in humans is less clear since, at least at the hypothalamic level, there seems to be considerable resistance to the effects of this hormone. The trials which administered recombinant leptin to humans recently have not provided sufficiently hopeful results as the weight reductions obtained have not been greater than those achieved with other drugs currently available on the market and its subcutaneous administration has led to some undesirable side effects. In any case, the results obtained must be treated with caution, with further trials being needed on the biological activity of leptin in humans in order to determine the clinical repercussions of the administration of this hormone.