Human Obesity Reduces the Number of Hepatic Leptin Receptor (Ob-R) Expressing NK Cells

Abstract

Objective. In the industrialized world, obesity is an increasing socioeconomic health problem. Obese subjects have a higher risk of developing several types of cancer. NK cells are an integral component of the innate immune system, able to destruct tumor cells. The adipokine leptin plays a crucial role in the development of obesity and its related diseases. Peripheral leptin signaling is modulated by the liver. Methods. The aim of this study was to evaluate the number of hepatic NK cells (CD56⁺) and the number of leptin-receptor positive (Ob-R⁺) cells in the livers of five normal-weight and five obese humans. Livers were removed during autopsy and accurately defined sections were stained immunohistochemically and CD56⁺, Ob-R⁺, and double-positive cells were quantified. Results. Results revealed a dramatic reduction of NK cells and Ob-R-expressing NK cells in the livers of obese individuals. Conclusions. The present study demonstrates, for the first time, body-weight-dependent numbers of hepatic NK cells. This supports the hypothesis of obesity-associated alterations of immune cell numbers in different human organs.