Recombinant Leptin Promotes Atherosclerosis and Thrombosis in Apolipoprotein E–Deficient Mice

Abstract

Objective-The direct role of leptin in vascular disease remains controversial. The objective of this study was to examine the effects of leptin treatment on atherosclerosis and thrombosis in atherosclerotic-prone mice. Methods and Results-Sixteen-week-old, male apolipoprotein E-deficient mice were treated with injections of recombinant leptin (125 g per day IP; nϭ10) or vehicle (nϭ10) 4 and platelets. 5 Plasma leptin levels have also been correlated with cardiovascular complications in humans, an effect independent of body mass index and traditional risk factors. 6 -8 Nevertheless, the direct role of leptin in vascular disease remains controversial. Atherosclerotic mouse models with complete deficiency of leptin suggest that the absence of leptin might promote atherosclerosis. 9,10 However, these studies have been confounded by the extreme obesity and dyslipidemia that result from the loss of leptin-mediated central effects. 9,10 As a result, the direct effect of leptin on atherosclerosis has not yet been addressed. Therefore, to examine the direct role of leptin in atherosclerosis, we analyzed the effect of exogenous recombinant murine leptin on atherosclerosis using apolipoprotein E (apoE)-deficient mice.In addition, we tested the effects of chronic leptin therapy on thrombosis in these atherosclerotic-prone mice to determine whether potential metabolic improvements achieved with leptin therapy would outweigh the acute prothrombotic effect of leptin described previously. 11,12 Methods MiceMale apoE-deficient mice were purchased from the Jackson Laboratory (stock No. 002052; Bar Harbor, Maine) and provided Western chow (TD88137; Harlan Teklad) from 14 to 20 weeks of age. All procedures complied with the principles of laboratory and animal care established by the National Society for Medical Research and were approved by the University of Michigan committee on use and care of animals. Leptin TreatmentBeginning at 16 weeks of age, mice received 200 L intraperitoneal injections daily of either 125 g of recombinant murine leptin (R & D Systems) or vehicle control (nϭ10 per group). The dose of leptin chosen was based on a protocol used to achieve weight loss and fertility in leptin-deficient mice. 13 We determined that a 4-week duration of injections at this dose would be adequate to test the hypothesis that leptin promotes atherosclerosis in this particular model of hyperlipidemia. 14 http://atvb.ahajournals.org/ Downloaded from esthesia (100 mg/kg). Mice were perfused with saline and fixed using formalin with a 25-gauge needle inserted into the left ventricle at a rate of 1 mL/min. After formalin fixation, the arterial tree was meticulously dissected from the carcass and placed in 70% ethanol for Ն72 hours. The surface area occupied by atherosclerosis was then quantitated at the thoracic aorta and major branches, including the brachiocephalic, carotid, and subclavian arteries, via Oil Red O staining and quantitative morphometry, as described previously. 15 The lesion area was calculated for the control and treat...

Carotid cross-sectional wall area is significantly associated with serum leptin levels, independent of body mass index: the SABPA study

“…In this study, the association of CSWA with leptin remained significant even after adjusting for BMI as well as body surface area and waist-to-hip ratio in sensitivity analysis. 35,36 This suggests that the increase in CSWA was not due to functional changes to normalize tensile stress, which occur with volume loading due to an increase in fat mass, 37 but rather that elevated leptin levels contribute to thickening of the arterial wall via mechanisms that are independent of obesity per se. The association between CSWA and leptin may be explained by multiple mechanisms.…”

Critical role of the NADPH oxidase subunit p47phox on vascular TLR expression and neointimal lesion formation in high-fat diet-induced obesity

“…Neointima and media areas were measured using Image-Pro Plus software (Media Cybernetics). 14,19 Neointimal CD31 and ICAM-1 Immunostaining Carotid arteries were sectioned (10 mm) and incubated with FITC-monoclonal anti-mouse CD31 antibody (1:50; Sigma, MO, USA) or ICAM-1 antibody (1:50; Santa Cruz, CA, USA). Staining for CD31 was examined using confocal microscopy.…”

“…14,19 Angiogenesis has likewise been implicated in neointimal formation. 41 Animal models also reveal that angiogenesis is increased after the first 4 weeks of an HF diet.…”

The adipokine Retnla modulates cholesterol homeostasis in hyperlipidemic mice

“…The progression of atherosclerosis is affected by various adipokines, cytokines produced primarily by adipose tissue 2,3 . Most adipokines, including leptin 4 , tumor necrosis factor-a (TNF-a) 5 , interleukin (IL)-18 (ref. 6) and resistin 7 , have been shown to promote atherosclerosis.…”