Molecular interplay between leptin, insulin-like growth factor-1, and β-amyloid in organotypic slices from rabbit hippocampus

• Published in: Molecular neurodegeneration Vol. 6; no. 1; p. 41
• Main Authors: Marwarha, Gurdeep, Prasanthi, Jaya Rp, Schommer, Jared, Dasari, Bhanu, Ghribi, Othman
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 08.06.2011; BioMed Central; BMC
• Subjects: Aβ42; C-EBPα; IGF-1; Leptin; mTORC1; Organotypic slices; STAT5
• ISSN: 1750-1326; 1750-1326
• DOI: 10.1186/1750-1326-6-41

Evidence shows that the insulin-like growth factor-1 (IGF-1) and leptin reduce β-amyloid (Aβ) production and tau phosphorylation, two major hallmarks of Alzheimer's disease (AD). IGF-1 expression involves the JAK/STAT pathway and the expression of leptin is regulated by the mammalian target of rapamycin complex 1 (mTORC1). We have previously shown that Aβ reduces leptin by inhibiting the mTORC1 pathway and Aβ was also suggested to inhibit the JAK/STAT pathway, potentially attenuating IGF-1 expression. As IGF-1 can activate mTORC1 and leptin can modulate JAK/STAT pathway, we determined the extent to which IGF-1 and leptin can upregulate the expression of one another and protect against Aβ-induced downregulation. We demonstrate that incubation of organotypic slices from adult rabbit hippocampus with Aβ42 downregulates IGF-1 expression by inhibiting JAK2/STAT5 pathway. Leptin treatment reverses these Aβ42 effects on IGF-1 and treatment with the STAT5 inhibitor completely abrogated the leptin-induced increase in IGF-1. Furthermore, EMSA and ChIP analyses revealed that leptin increases the STAT5 binding to the IGF-1 promoter. We also show that IGF-1 increases the expression of leptin and reverses the Aβ42-induced attenuation in leptin expression via the activation of mTORC1 signaling as the mTORC1 inhibitor rapamycin completely precluded the IGF-1-induced increase in leptin expression. Our results demonstrate for the first time that Aβ42 downregulates IGF-1 expression and that leptin and IGF-1 rescue one another from downregulation by Aβ42. Our study provides a valuable insight into the leptin/IGF-1/Aβ interplay that may be relevant to the pathophysiology of AD.