Adipocyte iron regulates leptin and food intake
Yan Gao, … , William T. Cefalu, Donald A. McClain
Yan Gao, … , William T. Cefalu, Donald A. McClain
Published August 24, 2015
Citation Information: J Clin Invest. 2015;125(9):3681-3691. https://doi.org/10.1172/JCI81860.
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Research Article Endocrinology

Adipocyte iron regulates leptin and food intake

Abstract

Dietary iron supplementation is associated with increased appetite. Here, we investigated the effect of iron on the hormone leptin, which regulates food intake and energy homeostasis. Serum ferritin was negatively associated with serum leptin in a cohort of patients with metabolic syndrome. Moreover, the same inverse correlation was observed in mice fed a high-iron diet. Adipocyte-specific loss of the iron exporter ferroportin resulted in iron loading and decreased leptin, while decreased levels of hepcidin in a murine hereditary hemochromatosis (HH) model increased adipocyte ferroportin expression, decreased adipocyte iron, and increased leptin. Treatment of 3T3-L1 adipocytes with iron decreased leptin mRNA in a dose-dependent manner. We found that iron negatively regulates leptin transcription via cAMP-responsive element binding protein activation (CREB activation) and identified 2 potential CREB-binding sites in the mouse leptin promoter region. Mutation of both sites completely blocked the effect of iron on promoter activity. ChIP analysis revealed that binding of phosphorylated CREB is enriched at these two sites in iron-treated 3T3-L1 adipocytes compared with untreated cells. Consistent with the changes in leptin, dietary iron content was also directly related to food intake, independently of weight. These findings indicate that levels of dietary iron play an important role in regulation of appetite and metabolism through CREB-dependent modulation of leptin expression.

Authors

Yan Gao, Zhonggang Li, J. Scott Gabrielsen, Judith A. Simcox, Soh-hyun Lee, Deborah Jones, Bob Cooksey, Gregory Stoddard, William T. Cefalu, Donald A. McClain

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Figure 5

Iron decreases leptin promoter activity and activates CREB.

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Iron decreases leptin promoter activity and activates CREB. (A) Distal l...
(A) Distal leptin promoter–driven luciferase activity (–5986 bp) in the presence or absence of 100 μg/ml FAC (n = 6). (B) Western blot for p-CREB, total CREB (t-CREB), and α-tubulin in 3T3-L1 adipocytes treated with 100 μg/ml FAC for 24 hours. Data are representative of 3 experiments with n = 3 per replicate. (C) Quantitation of Western blots normalized to α-tubulin (n = 3). (D) Distal leptin promoter luciferase activity in 3T3-L1 adipocytes treated with cAMP agonist, 8-Br-cAMP (1 mM), and/or 100 μg/ml FAC for 24 hours (n = 6). (E) Distal leptin promoter luciferase activity in 3T3-L1 adipocytes treated with cAMP agonist, forskolin (2 μM) and/or 100 μg/ml FAC for 24 hours (n = 5 or 6). (F) ACREB abolished the iron-mediated decrease of luciferase activity driven by the distal leptin promoter construct (n = 8). *P < 0.05, **P < 0.01, and ***P < 0.001 using 2-tailed Student’s t tests (A and C–F). Data represent mean ± SEM.