title: Short-term and long-term leptin exposure differentially affect human natural killer cell immune functions.
abstract: Epidemiological studies have indicated that obesity is associated with a higher risk for certain cancers caused by elevated levels of adipocyte-derived hormones. Leptin, one such hormone produced by adipocytes, is a major regulator of metabolism and has also been shown to modulate immunity. However, its role in regulating human natural killer (NK) cell functions is largely unknown. Here, we show that the leptin receptor (Ob-R) is expressed on 5% of NK cells isolated from blood donors, as measured with flow cytometry, and expression of the signal-transducing long form of the leptin receptor Ob-Rb was confirmed with quantitative PCR. The Ob-R+ subpopulation displayed a lower expression of CD16, a cell surface receptor mediating antibody-dependent activation. Short-term stimulation with leptin increased IFNγ secretion, CD69 activation marker expression, and cytotoxic lysis of tumor cells; this was mediated by an improved conjugate forming between NK cells and tumor cells as well as higher expression of tumor necrosis factor-related apoptosis-inducing ligand. On the contrary, long-term incubation with leptin significantly impaired these NK cell immune functions and decreased cell proliferation. In addition, phosphorylation of Jak-2 after leptin stimulation was reduced in peripheral mononuclear blood cells from obese humans compared with normal-weight controls. NK cells represent an immune cell population that is crucial for an effective antitumor response. Here, we show that long-term exposure to leptin, similarly to the situation in obese individuals with elevated serum leptin levels, significantly impairs integral parts of NK cell immune functions, possibly linking leptin to increased cancer susceptibility in obesity.
authors.affiliation: Div. of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA. cwrann@bidmc.harvard.edu
authors.forename: Christiane D
authors.initials: CD
authors.lastname: Wrann
authors.forename: Tobias
authors.initials: T
authors.lastname: Laue
authors.forename: Lena
authors.initials: L
authors.lastname: Hübner
authors.forename: Susanne
authors.initials: S
authors.lastname: Kuhlmann
authors.forename: Roland
authors.initials: R
authors.lastname: Jacobs
authors.forename: Lilia
authors.initials: L
authors.lastname: Goudeva
authors.forename: Heike
authors.initials: H
authors.lastname: Nave
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000276:immunology / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002478:Cells, Cultured; D057899:Cytophagocytosis; D005786:Gene Expression Regulation; D006801:Humans; D007371:Interferon-gamma / Q000097:blood / Q000378:metabolism; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism; D020738:Leptin / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009369:Neoplasms / Q000150:complications / Q000276:immunology; D009765:Obesity / Q000097:blood / Q000150:complications / Q000276:immunology* / Q000378:metabolism; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D017452:Receptors, IgG / Q000378:metabolism; D054411:Receptors, Leptin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism
chemical_list: C515448:LEPR protein, human; D020738:Leptin; D020033:Protein Isoforms; D012333:RNA, Messenger; D017452:Receptors, IgG; D054411:Receptors, Leptin; D011994:Recombinant Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D007371:Interferon-gamma