Abstract
Leptin is an endogenous hormone that regulates the appetite, energy metabolism, and glucose intake in the central nervous system (CNS) and is a potential therapeutic agent for obesity. In the normal healthy condition, peripherally secreted leptin is transported across the blood-brain barrier (BBB) to the target brain site, in particular the hypothalamus. However, it was reported that the progression of obesity causes diminished permeation of leptin across the BBB. The present study therefore aimed to effectively deliver leptin to the brain via intranasal coadministration with penetratin, an amphipathic cell-penetrating peptide (CPP), for potential treatment and prevention of obesity. The single administration study with normal rats demonstrated that leptin coadministered with L-penetratin was efficiently absorbed into the systemic circulation and accumulated in the anterior part of brain. Furthermore, chronic delivery of leptin via repeated intranasal coadministrations with L-penetratin suppressed the appetite and the body weight increase of the rats and lowered their plasma triglyceride levels. Analysis of brain samples after repeated administration suggested that Stat3 phosphorylation via leptin receptor stimulation potentially contributed to the therapeutic effect of leptin in the CNS. Thus, the present study suggests that intranasal coadministration with CPPs will become a promising strategy for delivering leptin to treat and prevent the progression of obesity.