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We would like to thank Dr. Ferrero for the comments regarding our study, which demonstrated that obesity was associated with an increase in serum hepatocyte growth factor (HGF) levels (1). Our study also showed a nonsignificant trend toward higher vascular endothelial growth factor (VEGF) levels in the serum of obese subjects. As Dr. Ferrero correctly points out, the time between collection of blood samples and the time when the serum is centrifuged can affect the concentrations of growth factors like VEGF. We are not aware of any clear directional bias in our study related to serum collection that would have resulted in low levels of serum VEGF in obese subjects and thus masked higher circulating VEGF levels. However, VEGF levels did demonstrate marked interindividual variability, and this may have contributed to the absence of a statistically significant difference of VEGF levels between obese and nonobese subjects. It is quite possible that serum HGF levels may be more robustly associated with obesity, whereas serum VEGF levels may be a reflection of not just obesity but also other co-morbidities and factors like the serum clotting time.
Furthermore, a more recent study was indeed able to show that serum VEGF levels are associated with obesity (2). Interestingly, the researchers in that study found that visceral fat area showed a better correlation with circulating VEGF levels than did body mass index. This may reflect a greater contribution of visceral fat to circulating VEGF levels than other fat tissues.
Finally, we believe that the association between obesity and vascular growth factor is an exciting and rapidly growing area of research, and it will continue to enhance our knowledge of how obesity can affect both the vasculature and atherosclerosis.
- American College of Cardiology Foundation