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Insulin and leptin acutely regulate cholesterol ester metabolism in macrophages by novel signaling pathways

Lookup NU author(s): Emeritus Professor Steve Yeaman

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Abstract

Leptin is produced in adipose tissue and acts in the hypothalamus to regulate food intake. However, recent evidence also indicates a potential for direct roles for leptin in peripheral tissues, including those of the immune system. In this study, we provide direct evidence that macrophages are a target tissue for leptin. We found that J774.2 macrophages express the functional long form of the leptin receptor (ObRb) and that this becomes tyrosine-phosphorylated after stimulation with low doses of leptin. Leptin also stimulates both phosphoinositide 3-kinase (PI 3-kinase) activity and tyrosine phosphorylation of JAK2 and STAT3 in these cells. We investigated the effects of leptin on hormone-sensitive lipase (HSL), which acts as a neutral cholesterol esterase in macrophages and is a rate-limiting step in cholesterol ester breakdown. Leptin significantly increased HSL activity in J774.2 macrophages, and these effects were additive with the effects of cAMP and were blocked by PI 3-kinase inhibitors. Conversely, insulin inhibited HSL in macrophages, but unlike adipocytes, this effect did not require PI 3-kinase. These results indicate that leptin and insulin regulate cholesterol-ester homeostasis in macrophages and, therefore, defects in this process caused by leptin and/or insulin resistance could contribute to the increased incidence of atherosclerosis found associated with obesity and type 2 diabetes.

Publication metadata

Author(s): Yeaman SJ; O'Rourke L; Shepherd PR

Publication type: Article

Publication status: Published

Journal: Diabetes

Year: 2001

Volume: 50

Issue: 5

Pages: 955-961

Print publication date: 01/01/2001

ISSN (print): 0012-1797

ISSN (electronic): 1939-327X

Publisher: The American Diabetes Association

URL: http://dx.doi.org/10.2337/diabetes.50.5.955

DOI: 10.2337/diabetes.50.5.955

PubMed id: 11334438

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