Influence of t-PA and u-PA on Adipose Tissue Development in a Murine Model of Diet-Induced Obesity

Summary

To investigate the potential role of tissue-type plasminogen activator (t-PA) or urokinase-type plasminogen activator (u-PA) in development of adipose tissue, we have used a nutritionally induced obesity model in t-PA (t-PA−/−) and u-PA (u-PA−/−) deficient mice. Five week old male wild-type (WT), t-PA−/− or u-PA−/− mice (n = 9 to 16) were fed a high fat diet (HFD, 42% fat). After 16 weeks of HFD, the body weight of t-PA−/− mice was significantly higher than that of WT mice (48 ± 1.1 g vs. 39 ± 2.2 g, p = 0.004). The total weight of the isolated subcutaneous (sc) fat deposit was higher in t-PA−/− than in WT mice (2.4 ± 0.22 g vs. 1.2 ± 0.29 g, p = 0.002), accompanied with higher adipocyte diameters (80 ± 1.7 µm vs. 61 ± 4.7 µm, p < 0.01). These differences were not observed in the intra-abdominal fat deposit. The number of stroma cells in both adipose tissue territories was increased in t-PA−/− as compared to WT mice (2.0 ± 0.13 vs. 1.5 ± 0.10 p = 0.02 and 3.0 ± 0.17 vs 1.6 ± 0.17, p = 0.0001, stroma cells/ adipocytes in sc and intra-abdominal tissue, respectively), partly as a result of an increased number of endothelial cells (192 ± 9 vs. 154 ± 18 p = 0.06 and 108 ± 13 vs. 69 ± 8 p = 0.04 CD31 stained/adipocyte area). In contrast the weight gain and adipose tissue development in u-PA−/− mice was not different from that in WT mice. These data suggest that t-PA but not u-PA plays a role in adipose tissue development.

Keywords

Obesity - fibrinolysis - t-PA - u-PA - mice

• References

• 1 Carmeliet P, Collen D. Development and disease in proteinase-deficient mice: role of the plasminogen, matrix metalloproteinase and coagulation system. Thromb Res 1998; 91: 225-85.
• 2 Bajou K, Noël A, Gerard RD, Masson V, Brunner N, Holst-Hansen C, Skobe M, Fusenig NE, Carmeliet P, Collen D, Foidart JM. Absence of host plasminogen activator inhibitor 1 prevents cancer invasion and vascularization. Nat Med 1998; 04: 923-8.
• 3 Nakajima I, Yamagushi T, Ozutsumi K, Aso H. Adipose tissue extracellular matrix: newly organized by adipocytes during differentiation. Differentiation 1998; 63: 193-200.
• 4 Morange PE, Lijnen HR, Alessi MC, Kopp F, Collen D, Juhan-Vague I. Influence of PAI-1 on adipose tissue growth and metabolic parameters in a model of diet-induced obesity. Arterioscler Thromb Vasc Biol 2000; 20: 1150-4.
• 5 Carmeliet P, Schoonjans L, Kieckens L, Ream B, Degen J, Bronson R, De Vos R, Van den Oord JJ, Collen D, Mulligan RC. Physiological consequences of loss of plasminogen activator gene function in mice. Nature 1994; 368: 419-24.
• 6 Giles AR. Guidelines for the use of animals in biomedical research. Thromb Haemost 1987; 58: 1078-84.
• 7 Sjöström L, Bjöntorp P, Vrana J. Microscopic fat cell size measurements on frozen-cut adipose tissue in comparison with automatic determinations of osmium-fixed fat cells. J Lipid Res 1971; 12: 521-30.
• 8 Lemonnier D. Effect of age, sex, and site on the cellularity of the adipose tissue in mice and rats rendered obese by a high fat diet. J Clin Invest 1972; 51: 2907-15.
• 9 Folch J, Lees M, Sloane-Stanley GH. A simple method for the isolation and purification of total lipids from animal tissue. J Biol Chem 1957; 226: 497-509.
• 10 Gliemann J, Osterlind K, Vinten J, Gammeltoft S. A procedure for measurements of distribution spaces in isolated fat cells. Biochim Biophys Acta 1972; 286: 1-9.
• 11 Declerck PJ, Verstreken M, Collen D. Immunoassay of murine t-PA, u-PA and PAI-1 using monoclonal antibodies raised in gene-inactivated mice. Thromb Haemost 1995; 74: 1305-9.
• 12 Lijnen HR, Van Hoef B, Lupu F, Moons L, Carmeliet P, Collen D. Function of the plasminogen/plasmin and matrix metalloproteinase systems in mice with targeted inactivation of fibrinolytic system genes. Arterioscler Thromb Vasc Biol 1998; 18: 1035-45.
• 13 Ailhaud G. Molecular and cellular determinants of body weight regulation. In: Bouchard C, Bray GA. eds. Regulation of Body Weight: Biological and Behavioral Mechanism. New York, NY: Wiley and Sons; 1996: 211-22.
• 14 Carmeliet P, Collen D. Transgenic mouse models in angiogenesis and cardiovascular disease. J Pathol 2000; 190: 387-405.
• 15 Bajou K, Masson V, Gerard RD, Schmitt PM, Albert V, Praus M, Lund LR, Frandsen TL, Brunner N, Dano K, Fusenig NE, Weidle U, Carmeliet G, Loskutoff D, Collen D, Carmeliet P, Froidart JM, Noël A. The plasminogen activator inhibitor PAI-1 controls in vivo tumor vascularization by interaction with proteases, not vitronectin: implications for angiogenic strategies. J Cell Biol 2001; 52: 777-84.
• 16 Bouloumié A, Drexler HCA, Lafontan M, Busse R. Leptin, the product of ob gene, promotes angiogenesis. Circ Res 1998; 83: 1059-66.
• 17 Samad F, Loskutoff DJ. Tissue distribution and regulation of plasminogen activator inhibitor-1 in obese mice. Mol Med 1996; 02: 568-82.
• 18 Chandler WL, Alessi MC, Aillaud MF, Henderson P, Vague P, Juhan-Vague I. Clearance of tissue plasminogen activator (t-PA) and t-PA/plasminogen activator inhibitor type 1 (PAI-1) complex: relationship to elevated tPA antigen in patients with high PAI-1 activity levels. Circulation 1997; 96: 761-8.