Pluronic modified leptin with increased systemic circulation, brain uptake and efficacy for treatment of obesity

Modification of hydrophilic proteins with amphiphilic block copolymers capable of crossing cell membranes is a new strategy to improve protein delivery to the brain. Leptin, a candidate for the treatment of epidemic obesity, has failed in part because of impairment in its transport across the blood–brain barrier (BBB) that develops with obesity. We posit that modification of leptin with poly(ethylene oxide)-b-poly(propylene oxide)-b-poly (ethylene oxide), Pluronic P85 (P85) might permit this protein to penetrate the BBB independently of its transporter, thereby overcoming peripheral leptin resistance. Here we report that peripherally administered leptin–P85 conjugates exhibit biological activity by reducing food intake in mouse models of obesity (ob/ob, and diet-induced obese mouse). We further generated two new leptin–P85 conjugates: one, Lep(ss)–P85(L), containing one P85 chain and another, Lep(ss)–P85(H), containing multiple P85 chains. We report data on their purification, analytical characterization, peripheral and brain pharmacokinetics (PK). Lep(ss)–P85(L) crosses the BBB using the leptin transporter, and exhibits improved peripheral PK along with increased accumulation in the brain compared to unmodified leptin. Lep(ss)–P85(H) also has improved peripheral PK but in a striking difference to the first conjugate penetrates the BBB independently of the leptin transporter via a non-saturable mechanism. The results demonstrate that leptin analogs can be developed through chemical modification of the native leptin with P85 to overcome leptin resistance at the level of the BBB, thus improving the potential for the treatment of obesity

Liquid-State Structure via Very High-Field Nuclear Magnetic Resonance Discriminates among Force Fields

Deuterium nuclear magnetic resonance (²H NMR) spectra of labeled molecular liquids obtained at high fields, for example, |<b>B</b>| = 22.3 T (950 MHz proton NMR), exhibit resolved quadrupolar splittings that reflect the average orientation of the molecules relative to <b>B</b>. Those residual nuclear spin interactions exhibited by benzene and chloroform provide an experimental determination of the leading tensor component of the pair correlation function for these two molecular liquids. In this way, very high-field ²H NMR may be used to extract unambiguous information about liquid-state structure. Additionally, replicating the experimentally derived pair correlation function using molecular dynamics simulations provides a critical test of simulation force fields

Pluronic modified leptin with increased systemic circulation, brain uptake and efficacy for treatment of obesity

Modification of hydrophilic proteins with amphiphilic block copolymers capable of crossing cell membranes is a new strategy to improve protein delivery to the brain. Leptin, a candidate for the treatment of epidemic obesity, has failed in part because of impairment in its transport across the blood–brain barrier (BBB) that develops with obesity. We posit that modification of leptin with poly(ethylene oxide)-b-poly(propylene oxide)-b-poly (ethylene oxide), Pluronic P85 (P85) might permit this protein to penetrate the BBB independently of its transporter, thereby overcoming peripheral leptin resistance. Here we report that peripherally administered leptin–P85 conjugates exhibit biological activity by reducing food intake in mouse models of obesity (ob/ob, and diet-induced obese mouse). We further generated two new leptin–P85 conjugates: one, Lep(ss)–P85(L), containing one P85 chain and another, Lep(ss)–P85(H), containing multiple P85 chains. We report data on their purification, analytical characterization, peripheral and brain pharmacokinetics (PK). Lep(ss)–P85(L) crosses the BBB using the leptin transporter, and exhibits improved peripheral PK along with increased accumulation in the brain compared to unmodified leptin. Lep(ss)–P85(H) also has improved peripheral PK but in a striking difference to the first conjugate penetrates the BBB independently of the leptin transporter via a non-saturable mechanism. The results demonstrate that leptin analogs can be developed through chemical modification of the native leptin with P85 to overcome leptin resistance at the level of the BBB, thus improving the potential for the treatment of obesity