Leptin administered in physiological or pharmacological doses does not regulate circulating angiogenesis factors in humans

Abstract

Aim/hypothesis: Leptin has been shown to regulate angiogenesis in animal and in vitro studies by upregulating the production of several pro-angiogenic factors, but its role in regulating angiogenesis has never been studied in humans.

Methods: The potential angiogenic effect of two doses of metreleptin (50 and 100 ng/ml) was evaluated in vitro, using a novel three-dimensional angiogenesis assay. Fifteen healthy, normoleptinaemic volunteers were administered both a physiological (0.1 mg/kg) and a pharmacological (0.3 mg/kg) single dose of metreleptin, in vivo, on two different inpatient admissions separated by 1-12 weeks. Serum was collected at 0, 6, 12 and 24 h after metreleptin administration. Twenty lean women, with leptin levels <5 ng/ml, were randomised in a 1:1 fashion to receive either physiological replacement doses of metreleptin (0.04-0.12 mg/kg q.d.) or placebo for 32 weeks. Serum was collected at 0, 8, 20 and 32 weeks after randomisation. Proteomic angiogenesis array analysis was performed to screen for angiogenic factors. Circulating concentrations of angiogenin, angiopoietin-1, platelet derived endothelial factor (PDGF)-AA, matrix metalloproteinase (MMP) 8 and 9, endothelial growth factor (EGF) and vascular EGF (VEGF) were also measured.

Results: Both metreleptin doses failed to induce angiogenesis in the in vitro model. Although leptin levels increased significantly in response to both short-term and long-term metreleptin administration, circulating concentrations of angiogenesis markers did not change significantly in vivo.

Conclusions/interpretations: This is the first study that examines the effect of metreleptin administration in angiogenesis in humans. Metreleptin administration does not regulate circulating angiogenesis related factors in humans.

Clinical trial registration: ClinicalTrials.gov NCT00140205 and NCT00130117.

Funding: This study was supported by National Institutes of Health-National Center for Research Resources grant M01-RR-01032 (Harvard Clinical and Translational Science Center) and grant number UL1 RR025758. Funding was also received from the National Institute of Diabetes and Digestive and Kidney Diseases grants 58785, 79929 and 81913, and AG032030.

Conflict of interest statement

Duality of interest The authors declare that they have no duality of interest associated with this manuscript.

Figures

Fig. 1

In vitro three-dimensional HUVEC angiogenesis model. Cells were treated with leptin (50 and 100 ng/ml, c and d) and VEGF (20 ng/ml as positive control, b) for 48 h. a The negative control. e Sprout counts; f sprout cumulative length. aNo statistical significance at the 0.05 level. bBox plot are statistically different from those marked with a. Statistical outliers are denoted with black circles