Macrophage activation and preadipocyte apoptosis

Obesity is a major risk factor for insulin resistance, type 2 diabetes, and cardiovascular disease. Adipose tissue expansion, due to chronic positive energy balance, occurs via coordinated increases in adipocyte size (hypertrophy) and number (hyperplasia). In addition to preadipocytes and adipocytes, adipose tissue contains macrophages (adipose tissue macrophages (ATMs)).

Macrophage-secreted factors influence critical processes involved in adipose tissue homeostasis, including preadipocyte proliferation and differentiation into adipocytes. Macrophage-conditioned medium (MacCM) from J774A.1 macrophages protects 3T3-L1 preadipocytes from apoptosis through platelet-derived growth factor signalling. Molgat et al. investigated the effect of macrophage activation on MacCM-dependent preadipocyte survival. They found that the influence of MD-MacCM on human preadipocyte apoptosis appears to be activation dependent and as an initial step, they found that Akt and ERK1/2 activation occurs in human preadipocytes in response to MD-MacCM. These signalling responses were unaffected by the activation state of the macrophages.

Although their data, demonstrating that pro-inflammatory activation interferes with the anti-apoptotic activity of macrophages, are derived from cell culture models, their findings may be relevant to preadipocyte fate and adipose tissue remodelling in obesity. Molgat et al. (2012) Journal of Endocrinology 214 21-29.

Read the full article at: DOI: 10.1530/JOE-12-0114