Gelatinase B (MMP-9) deficiency does not affect murine adipose tissue development

This study was performed to follow up on the observation that gelatinase A (MMP-2) deficiency impairs adipose tissue development in mice. The aim was to evaluate the role of its functional homologue gelatinase B (MMP-9) in adipose tissue growth. MMP-9 antigen levels were determined in lean and in obese women before and after weight loss. MMP-9-deficient mice and wild-type littermates (genetic background 50% 129sv : 50 % CDI or 99.975% C57Bl/6, ten generations backcrossed into C57Bl/6 background) were kept on a high-fat diet (HFD) for 15 weeks. Subcutaneous and gonadal fat pads were analysed in terms of weight and size/density of adipocytes and blood vessels. Obese women had higher MMP-9 serum levels than lean controls (383 +/- 29 vs. 304 +/- 27 ng/ml, p = 0.02); after weight reduction MMP-9 levels dropped to 334 +/- 17 ng/ml (p = 0.1 vs. obese). However, MMP-9-deficient and littermate wild-type mice kept on HFD were indistinguishable in terms of body and fat weight. No effect of MMP-9 deficiency was observed on size or density of adipocytes or blood vessels in subcutaneous or gonadal fat depots. Similar observations were made when mice were kept on normal chow. In conclusion, in lean and obese women, body mass index correlates positively with MMP-9 serum levels (p < 0.0001). However, MMP-9 does not seem to play a major role in adipose tissue development in murine models of diet-induced obesity.