NGF promotes, in an autocrine-paracrine manner, metabolic and anti-inflammatory pathways in human and mouse...

Nerve growth factor (NGF) affects the development and survival of sympathetic neurons. NGF is also found in non-neural cell lineages that are implicated in immune-endocrine interactions associated with metabolic diseases. Although NGF is expressed in white adipose tissue (WAT), little is known about the regulation of its expression and role in adipocytes.

To determine whether NGF and its receptors are expressed in human adipocytes and demonstrate their role in adipocyte metabolic and inflammatory phenotypes.

The expression of NGF and its receptors, tropomyosin-related kinase A (TrkA) and pan-neurotrophin receptor (p75NTR), and their effects on metabolic and inflammatory responses were examined in freshly isolated adipocytes from human abdominal WAT and mouse 3T3L1 cells.

TrkA and p75NTR were expressed in both human and mouse adipocytes and pre-adipocytes. NGF was secreted by human white adipocytes and their exogenous exposure to NGF increased mitochondrial mass and activity, peroxisome proliferator-activated receptor gamma, CCAAT/enhancer binding protein alpha, and adiponectin levels. Additionally, NGF increased lipolysis in human WAT explants and suppressed lipids accumulation, lipoprotein lipase, and pro-inflammatory mediators interleukin (IL)-6 and IL-8 in human white adipocytes. The pro-inflammatory factor lipopolysaccharide downregulated the levels of NGF receptors in human white adipocytes. NGF also affected mitochondrial activity in both human and mouse pre-adipocytes and TrkA appeared to mediate, at least partially, the effects of NGF on adipocytes.

Our data suggest that NGF is produced locally within the adipose tissue where it upregulates mitochondrial function while it suppresses the pro-inflammatory phenotype of human and mouse adipocytes.