J Alzheimers Dis. 2009 Dec 14; doi: 10.3233/JAD-2009-1308. Epub 2009 Dec 14.

Chronic Leptin Supplementation Ameliorates Pathology and Improves Cognitive Performance in a Transgenic Mouse Model of Alzheimer's Disease.

Journal of Alzheimer's disease : JAD

Steven J Greco, Kathryn J Bryan, Sraboni Sarkar, Xiongwei Zhu, Mark A Smith, J Wesson Ashford, Jane M Johnston, Nikolaos Tezapsidis, Gemma Casadesus

PMID: 20009219 DOI: 10.3233/JAD-2009-1308

Abstract

We have previously reported anti-amyloidogenic effects of leptin using in vitro and in vivo models and, more recently, demonstrated the ability of leptin to reduce tau phosphorylation in neuronal cells. The present study examined the efficacy of leptin in ameliorating the Alzheimer's disease (AD)-like pathology in 6-month old CRND8 transgenic mice (TgCRND8) following 8 weeks of treatment. Leptin-treated transgenic mice showed significantly reduced levels of amyloid-beta (Abeta){1-40} in both brain extracts (52% reduction, p= 0.047) and serum (55% reduction, p= 0.049), as detected by ELISA, and significant reduction in amyloid burden (47% reduction, p=0.041) in the hippocampus, as detected by immunocytochemistry. The decrease in the levels of Abeta in the brain correlated with a decrease in the levels of C99 C-terminal fragments of the amyloid-beta protein precursor, consistent with a role for beta -secretase in mediating the effect of leptin. In addition, leptin-treated TgCRND8 mice had significantly lower levels of phosphorylated tau, as detected by AT8 and anti-tau-Ser{396} antibodies. Importantly, after 4 or 8 weeks of treatment, there was no significant increase in the levels of C-reactive protein, tumor necrosis factor-alpha, and cortisol in the plasma of leptin-treated TgCRND8 animals compared to saline-treated controls, indicating no inflammatory reaction. These biochemical and pathological changes were correlated with behavioral improvements, as early as after 4 weeks of treatment, as recorded by a novel object recognition test and particularly the contextual and cued fear conditioning test after 8 weeks of treatment. Leptin-treated TgCRND8 animals significantly outperformed saline-treated littermates in these behavioral tests. These findings solidly demonstrate the potential for leptin as a disease modifying therapeutic in transgenic animals of AD, driving optimism for its safety and efficacy in humans.

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