J Obes Metab Syndr 2018; 27(1): 73-74
Published online March 30, 2018 https://doi.org/10.7570/jomes.2018.27.1.73
Copyright © Korean Society for the Study of Obesity.
Ji Yeon Lee1, Byoung Kuk Jang1,2, Min Kyung Song3, Hye Soon Kim1, and Mi-Kyung Kim 1,*
1Department of Internal Medicine, Keimyung University School of Medicine, Daegu, Korea; 2Institute for Cancer Research, Keimyung University, Daegu, Korea; 3Department of Food Science and Nutrition, Graduate School, Keimyung University, Daegu, Korea
Correspondence to:
Mi-Kyung Kim,
https://orcid.org/0000-0001-5750-3598,
Department of Internal Medicine, Keimyung University School of Medicine, 56 Dalseong-ro, Jung-gu, Daegu 41931, Korea,
Tel: +82-53-250-7486,
Fax: +82-53-250-7982,
E-mail: mdkmk@dsmc.or.kr
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Dipeptidyl peptidase-4 (DPP-4), a serine protease, degrades peptides containing alanine or proline residues and amino-terminal residues of proteins.1 It is an aminopeptidase found in most tissues of the body, including the liver, lung, kidney, intestine, lymph nodes, and endothelial cells, and resides on cell membranes, where it exerts its effect. Physiological effects of DPP-4 can be broadly divided into enzymatic effects such as the inhibition of incretins and non-enzymatic effects associated with immune regulation, behavioral response, and inflammation depending on the substance on which DPP-4 acts.2,3 Since Lamers et al.4 reported DPP-4 as novel adipokine, many studies have shown serum DPP-4 level or activity to be associated with obesity, diabetes mellitus, and fatty liver.5,6 Our previous study showed serum DPP-4 concentration was positively correlated with lean body mass, total cholesterol, and creatinine and was elevated in the obese group compared to the normal weight group, as reported in
Our studies evaluated whether serum DPP-4 concentration is associated with obesity and obesity-related factors such as glucose, lipid profile, and body fat using blood test and bio-impedance analysis. Even though our study showed that serum DPP-4 level was higher in the obese group, these studies indirectly reflect the relationship between DPP-4 and obesity. Therefore, there is a limitation to understanding the mechanism and role of DPP-4 in adipose tissue. Recently, some studies have supported the association between DPP-4 and obesity. Lamer et al.4 showed higher release of DPP-4 in fully differentiated adipocytes than in preadipocytes, and that direct addition of DPP-4 to fat and skeletal muscles impaired insulin signaling, suggesting that DPP-4 is an adipokine and might have direct effects on adipose tissue. To assess the tissue sources of circulating DPP-4, Sell et al.8 assessed DPP-4 expression and release in the adipose tissue of lean and obese patients. Their results showed that DPP-4 expression was correlated with body mass index and was higher in visceral adipose tissue (VAT) than subcutaneous adipose tissue (SAT). It was also increased in VAT of lean patients with impaired glucose tolerance. In addition, DPP-4 release is higher in VAT than in SAT in both lean and obese patients. Moreover, Stengel et al.9 showed that DPP-4 protein level in the plasma was higher in obese patients and correlated with body mass index. These studies suggest that adipose tissue could be a primary source of higher serum DPP-4 or activity. However, the exact mechanisms of DPP-4 on adipose tissue are not known yet. Therefore, further studies are needed to elucidate the functional role of DPP-4 and its contribution to the incretin system. Finally, we thank you for the Letter and the opportunity to respond. We hope that
The authors declare no conflict of interest.
Online ISSN : 2508-7576Print ISSN : 2508-6235
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