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Journal of Nutrition and Metabolism
Volume 2017, Article ID 4297025, 14 pages
https://doi.org/10.1155/2017/4297025
Research Article

Diet-Induced Obesity Is Associated with an Impaired NK Cell Function and an Increased Colon Cancer Incidence

1Institute of Anatomy and Cell Biology, Faculty of Medicine, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
2Institute of Pathology, University Hospital of Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
3Clinic for Internal Medicine IV, Department of Hematology and Oncology, University Hospital of Martin Luther University Halle-Wittenberg, Halle (Saale), Germany

Correspondence should be addressed to Ina Bähr; ed.ellah-inu.nizidem@rheab.ani

Received 7 October 2016; Revised 6 February 2017; Accepted 15 February 2017; Published 5 March 2017

Academic Editor: Phillip B. Hylemon

Copyright © 2017 Ina Bähr et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Obesity is associated with an increased colon cancer incidence, but underlying mechanisms remained unclear. Previous studies showed altered Natural killer (NK) cell functions in obese individuals. Therefore, we studied the impact of an impaired NK cell functionality on the increased colon cancer risk in obesity. In vitro investigations demonstrated a decreased IFN-γ secretion and cytotoxicity of human NK cells against colon tumor cells after NK cell preincubation with the adipokine leptin. In addition, leptin incubation decreased the expression of activating NK cell receptors. In animal studies, colon cancer growth was induced by injection of azoxymethane (AOM) in normal weight and diet-induced obese rats. Body weight and visceral fat mass were increased in obese animals compared to normal weight rats. AOM-treated obese rats showed an increased quantity, size, and weight of colon tumors compared to the normal weight tumor group. Immunohistochemical analyses demonstrated a decreased number of NK cells in spleen and liver in obesity. Additionally, the expression levels of activating NK cell receptors were lower in spleen and liver of obese rats. The results show for the first time that the decreased number and impaired NK cell function may be one cause for the higher colon cancer risk in obesity.