ABSTRACT
OBJECTIVE: The adipocytokine leptin has been proposed to increase cardiovascular risk in both obese and diabetic individuals. In the current study, therefore, we used apoE-deficient mice to examine the effects of leptin on both lesion size and calcification. METHODS AND RESULTS: Mice were treated with once daily intraperitoneal injections of leptin (125 microg/mouse/d) for 2 months. The mice were then euthanized, and sections of the aortic root and thoracic aorta analyzed histomorphometrically. Measurements of lesion size and surface area occupied by atherosclerotic lesions did not reveal any differences between nontreated and leptin-treated animals. However, von Kossa staining of the aortic root demonstrated an 8.3+/-2.0-fold increase in lesion calcification as well as a 2.5+/-0.6-fold increase in valvular calcification in those animals treated with leptin. In addition, the percent total lesion area demonstrating ALP-positive staining was 5.4+/-2.1-fold greater in leptin-treated mice when compared to nontreated control mice. This increase in ALP staining was also accompanied by an increase in the expression of the osteoblast-specific markers, osteocalcin, and osteopontin. CONCLUSIONS: Based on these observations, we conclude that leptin may increase cardiovascular risk by promoting osteogenic differentiation and thus vascular calcification.
Subject(s)
Apolipoproteins E/deficiency , Atherosclerosis/etiology , Calcinosis/etiology , Leptin/pharmacology , Alkaline Phosphatase/metabolism , Animals , Aorta/metabolism , Aorta/pathology , Aortic Valve/metabolism , Aortic Valve/pathology , Apolipoproteins E/genetics , Atherosclerosis/blood , Atherosclerosis/metabolism , Atherosclerosis/pathology , Body Weight/drug effects , Calcinosis/metabolism , Calcinosis/pathology , Cattle , Cell Differentiation/drug effects , Cells, Cultured , Disease Models, Animal , Female , Humans , Lipids/blood , Mice , Mice, Knockout , Myocytes, Smooth Muscle/drug effects , Myocytes, Smooth Muscle/pathology , Osteoblasts/drug effects , Osteoblasts/metabolism , Osteoblasts/pathology , Osteocalcin/metabolism , Osteopontin/metabolism , Recombinant Proteins/pharmacology , Risk FactorsABSTRACT
In the current study, we examine heparin's anti-metastatic properties by using a well-defined mouse model of osteolytic bone metastasis. C57BL/6 mice were treated with increasing doses of unfractionated heparin (15, 20, or 25 units/mouse) 30 min prior to the left ventricular injection of GFP-transfected B16F10 melanoma cells. Heparin's effect on tumour burden and bone strength was then quantified 14 days later by bone histomorphometry and biomechanical testing, respectively. Based on histomorphometric analysis of the femurs, injection of GFP-transfected melanoma cells resulted in a 37% decrease in cancellous bone volume and a 68% increase in osteoclast surface. This was associated with a 13% reduction in bone strength as measured by biomechanical testing. However, when the mice were first pre-treated with 25 units of heparin, tumour burden was decreased by 73% and tumour cell-dependent decreases in both cancellous bone volume and bone strength were prevented. Based on these observations, we conclude that heparin inhibits the ability of tumour cells to metastasize to bone and that as such, prevents tumour cell-induced decreases in bone strength.