The further development in research of bone regeneration is necessary to meet the clinical demand for bone reconstruction. Plasminogen is a critical factor of the tissue fibrinolytic system, which mediates tissue repair in the skin and liver. However, the role of the fibrinolytic system in bone regeneration remains unknown. Herein, we investigated bone repair and ectopic bone formation using plasminogen-deficient (Plg -/-) mice. Bone repair of the femur is delayed in Plg -/-mice, unlike that in the wild-type (Plg þ/þ ) mice. The deposition of cartilage matrix and osteoblast formation were both decreased in Plg -/-mice. Vessel formation, macrophage accumulation, and the levels of vascular endothelial growth factor (VEGF) and transforming growth factor-b (TGF-b) were decreased at the site of bone damage in Plg -/-mice. Conversely, heterotopic ossification was not significantly different between Plg þ/þ and Plg -/-mice. Moreover, angiogenesis, macrophage accumulation, and the levels of VEGF and TGF-b were comparable between Plg þ/þ and Plg -/-mice in heterotopic ossification. Our data provide novel evidence that plasminogen is essential for bone repair. The present study indicates that plasminogen contributes to angiogenesis related to macrophage accumulation, TGF-b, and VEGF, thereby leading to the enhancement of bone repair.

Objective-Recently, adipose tissue inflammation induced by macrophage infiltration through MCP-1/C-C chemokine receptor-2 (CCR2) pathway is considered to play a role in the development of visceral obesity and insulin resistance.In the present study, to further examine the role of CCR2 in the development of obesity and type 2 diabetes, we studied the effect of pharmacological inhibition of CCR2 from the early stage of obesity in db/db mice. Methods and Results-Db/ϩm (lean control) and db/db mice were fed with a standard diet with or without 0.005% propagermanium, as a CCR2 inhibitor for 12 weeks from 6 weeks of age. Propagermanium treatment decreased body weight gain, visceral fat accumulation, and the size of adipocytes only in db/db mice. Further, propagermanium suppressed macrophage accumulation and inflammation in adipose tissue. Propagermanium treatment also ameliorated glucose tolerance and insulin sensitivity, and decreased hepatic triglyceride contents in db/db mice. Key Words: cytokines Ⅲ diabetes mellitus Ⅲ insulin resistance Ⅲ macrophages Ⅲ receptors T he metabolic syndrome, characterized by a clustering of visceral obesity, impaired glucose tolerance, hypertension, and dyslipidemia, is a major cause of type 2 diabetes mellitus and cardiovascular disease. 1 Visceral obesity and insulin resistance are thought to represent common underlying factors of the syndrome. 2 Therefore, it is very important to clarify the mechanism of the development of obesity and insulin resistance and to establish the therapeutic method based on its mechanism. Conclusions-PropagermaniumMany reports have shown that obesity is associated with a state of chronic, low-grade inflammation, suggesting that inflammation may be a potential mechanism whereby obesity leads to insulin resistance. 3 Indeed, obesity and insulin resistance are strongly associated with systemic markers of inflammation, and clinically, inflammation has been recognized as a major predictor of atherosclerotic disease. 3,4 The adipose tissue is an important endocrine organ that secretes many biologically active molecules, such as leptin, adiponectin, tumor necrosis factor (TNF-␣), and monocyte chemoattractant protein 1 (MCP-1), which are collectively termed adipocytokines. 5-8 Dysregulated production of proinflammatory and antiinflammatory adipocytokines seen in visceral fat obesity is associated with the metabolic syndrome, 5,9 suggesting that inflammatory changes in the adipose tissue may contribute to the development of many aspects of the metabolic syndrome and result in type 2 diabetes and atherosclerosis.Recent studies have demonstrated that obese adipose tissue is characterized by increased infiltration of macrophages, suggesting that they are important sources of inflammation in adipose tissue. 10,11 C-C chemokine receptor-2 (CCR2), known as a receptor for MCP-1, play a role in monocyte/ macrophage recruitment and macrophage-dependent inflammatory response and the development of atherosclerosis. 12 Mouse models have demonstrated that adipose tissue macrop...

Aim: Adipose tissue inflammation induced by macrophage infiltration through the MCP-1/CCR2 pathway is considered to play a pivotal role in the development of visceral obesity and insulin resistance. In the present study, therefore, we examined whether pharmacological inhibition of CCR2 is effective against the development of diet-induced metabolic disorders. Methods: C57BL/6 mice were fed a high fat and sucrose diet with or without propagermanium (CCR2 inhibitor, 5 or 50 mg/kg BW/day) for 12 weeks from 6 weeks of age. Then we analyzed lipid and glucose metabolism and tissue inflammation in the liver and adipose tissues along with serum markers in those mice.

In diabetic patients, the risk of fracture is high because of impaired bone formation. However, the details of the mechanisms in the development of diabetic osteoporosis remain unclear. In the current study, we investigated the role of plasminogen activator inhibitor (PAI)-1 in the pathogenesis of type 1 diabetic osteoporosis by using PAI-1–deficient mice. Quantitative computed tomography analysis showed that PAI-1 deficiency protected against streptozotocin-induced bone loss in female mice but not in male mice. PAI-1 deficiency blunted the changes in the levels of Runx2, osterix, and alkaline phosphatase in tibia as well as serum osteocalcin levels suppressed by the diabetic state in female mice only. Furthermore, the osteoclast levels in tibia, suppressed in diabetes, were also blunted by PAI-1 deficiency in female mice. Streptozotocin markedly elevated the levels of PAI-1 mRNA in liver in female mice only. In vitro study demonstrated that treatment with active PAI-1 suppressed the levels of osteogenic genes and mineralization in primary osteoblasts from female mouse calvaria. In conclusion, the current study indicates that PAI-1 is involved in the pathogenesis of type 1 diabetic osteoporosis in females. The expression of PAI-1 in the liver and the sensitivity of bone cells to PAI-1 may be an underlying mechanism.

Long-term use of glucocorticoids (GCs) causes numerous adverse effects, including glucose/lipid abnormalities, osteoporosis, and muscle wasting. The pathogenic mechanism, however, is not completely understood. In this study, we used plasminogen activator inhibitor-1 (PAI-1)–deficient mice to explore the role of PAI-1 in GC-induced glucose/lipid abnormalities, osteoporosis, and muscle wasting. Corticosterone markedly increased the levels of circulating PAI-1 and the PAI-1 mRNA level in the white adipose tissue of wild-type mice. PAI-1 deficiency significantly reduced insulin resistance and glucose intolerance but not hyperlipidemia induced by GC. An in vitro experiment revealed that active PAI-1 treatment inhibits insulin-induced phosphorylation of Akt and glucose uptake in HepG2 hepatocytes. However, this was not observed in 3T3-L1 adipocytes and C2C12 myotubes, indicating that PAI-1 suppressed insulin signaling in hepatocytes. PAI-1 deficiency attenuated the GC-induced bone loss presumably via inhibition of apoptosis of osteoblasts. Moreover, the PAI-1 deficiency also protected from GC-induced muscle loss. In conclusion, the current study indicated that PAI-1 is involved in GC-induced glucose metabolism abnormality, osteopenia, and muscle wasting in mice. PAI-1 may be a novel therapeutic target to mitigate the adverse effects of GC.