Bone marrow neutrophil density regulates myelopoiesis during obesity and weight loss.

The bone marrow (BM) is altered in obesity to promote myeloid cell generation, but the mechanisms driving these changes remain unclear. Here, we show that obesogenic stimuli promote adipose tissue macrophages to recruit neutrophils from the BM in mice. Recruitment of BM neutrophils activates hematopoietic stem cells, which produce myeloid cells that accumulate in the circulation and drive inflammation. This recruitment is not resolved by weight loss, leading to sustained myelopoiesis in previously obese mice. Inhibiting neutrophil recruitment out of the BM in obese mice or during weight loss reduces BM myelopoiesis and adipose tissue inflammation, and improves glucose tolerance. In humans with obesity, plasma neutrophil chemokines are increased, correlate with increased insulin resistance, but do not decrease with weight loss. Our results demonstrate that neutrophil recruitment is a key mediator of myelopoiesis during obesity, and targeting this pathway is a potential strategy to improve inflammation during obesity and weight loss.