Summary
Following the observation by Brown et al. (Am J Physiol 1997; 272: C937-49) that primary
rat adipocytes in culture secrete gelatinase A (MMP-2), we have evaluated gelatinase
expression in adipose tissue with the use of mouse models of obesity. Wild-type mice
were kept on a standard fat diet (SFD) or on a high fat diet (42% fat, HFD) and genetically
obese db/db mice were kept on SFD; gonadal and subcutaneous fat pads were removed
and analysed ex vivo. These studies revealed that: 1) the HFD induced adipocyte hypertrophy;
2) after 32 weeks, significantly higher levels of 70 kDa (p <0.05) and 65 kDa proMMP-2
(p < 0.01) were observed in extracts of gonadal fat pads of mice on HFD; 3) the contribution
of active MMP-2 to the total level was comparable in SFD and HFD groups (20 to 30%);
and 4) gelatinase B (MMP-9) was not consistently detected. These findings were confirmed
by gelatin zymography and by mRNA determination using competitive RT-PCR. The presence
of MMP-2 in the adipose tissue was confirmed immunologically and its localization
in adipocytes revealed by immunogold electron microscopy. The potential functional
role of MMP-2 in adipose tissue remains to be determined.
Key words
Obesity - matrix metalloproteinases - gelatinase