Decreased NK cell functions in obesity can be reactivated by fat mass reduction

Abstract

Objective Natural killer (NK) cells are the first defense against malignant cells, and their functions are severely impaired in individuals with obesity. However, it is not known whether functions can be re-activated after weight loss. The alterations of NK cell functions after fat mass reduction were investigated. Methods Thirty-two healthy adults with obesity were divided into control and experimental groups. Participants of the experimental group performed a 3-month program of exercise training and nutrition. Anthropometric, physiological, and metabolic parameters and plasma adipocytokines were determined. Peripheral blood mononuclear cells were analyzed by means of flow cytometry and Western blot assay for various NK cell-specific functional parameters and leptin signaling components. NK cell-mediated cytotoxicity assay with leptin stimulation was performed. Results Male participants significantly decreased their body fat mass (P < 0.05) and increased physical fitness (P < 0.05). Plasma leptin levels were significantly reduced (P < 0.05) and intracellular interferon gamma (IFN-γ) expression in CD56dim NK cells was significantly increased (P < 0.001) 3 months after study end. Stimulation of NK-92 cells with different leptin dosages revealed a significant dose-dependent decrease of specific tumor cell lysis. Conclusions The present study demonstrates a reactivation of NK cell functionality after body fat mass reduction in persons with obesity.