Drug targeting of leptin resistance.

Leptin regulates glucose, lipid and energy homeostasis as well as feeding behavior, serving as a bridge between peripheral metabolically active tissues and the central nervous system (CNS). Indeed, this adipocyte-derived hormone, whose circulating levels mirror fat mass, not only exerts its anti-obesity effects mainly modulating the activity of specific hypothalamic neurons expressing the long form of the leptin receptor (Ob-Rb), but it also shows pleiotropic functions due to the activation of Ob-Rb in peripheral tissues. Nevertheless, several mechanisms have been suggested to mediate leptin resistance, including obesity-associated hyperleptinemia, impairment of leptin access to CNS and the reduction in Ob-Rb signal transduction effectiveness, among others. During the onset and progression of obesity, the dampening of leptin sensitivity often occurs, preventing the efficacy of leptin replacement therapy from overcoming obesity and/or its comorbidities. This review focuses on obesity-associated leptin resistance and the mechanisms underpinning this condition, to highlight the relevance of leptin sensitivity restoration as a useful therapeutic strategy to treat common obesity and its complications. Interestingly, although promising strategies to counteract leptin resistance have been proposed, these pharmacological approaches have shown limited efficacy or even relevant adverse effects in preclinical and clinical studies. Therefore, the numerous findings from this review clearly indicate a lack of a single and efficacious treatment for leptin resistance, highlighting the necessity to find new therapeutic tools to improve leptin sensitivity, especially in patients with most severe disease profiles.