title: High Levels of Serum DPP-4 Activity Are Associated with Low Bone Mineral Density in Obese Postmenopausal Women.
abstract: BACKGROUND
  Dipeptidyl peptidase 4/CD26 (DPP-4) is a widely expressed cell surface serine protease. DPP-4 inhibitors, one of common anti-diabetic agents play a protective role in bone metabolism in recent studies. A soluble form of DPP-4 is found in serum, and exhibits DPP-4 enzymatic activity. However, the physiological role of serum or soluble DPP-4 and its relationship with DPP-4 enzymatic function remain poorly understood. The aims of current study were to determine the association between serum DPP-4 activity and bone mineral density (BMD) in postmenopausal women.
  
  
  METHODS
  We recruited data and serum samples from 124 consecutive healthy postmenopausal women aged >50 years. We divided study subjects into obese (body mass index [BMI] ≥25 kg/m²) and non-obese (BMI <25 kg/m²) postmenopausal women and examined the correlation between serum DPP-4 activity and clinical variables in each groups.
  
  
  RESULTS
  A total of 124 postmenopausal women was enrolled, with a mean age of 59.9±7.1 years. The mean BMI of the study patients was 24.4±2.8 kg/m². Regarding bone turnover markers, serum DPP-4 activity was positively correlated with serum calcium concentrations, intact parathyroid hormone, and serum C-telopeptide levels in all of the study subjects. However, there was no association between serum DPP-4 activity and BMD in the spine or femoral neck in all of the study subjects. Serum DPP-4 activity was negatively correlated (R=-0.288, P=0.038) with BMD of the spine in obese postmenopausal women.
  
  
  CONCLUSIONS
  This study demonstrated for the first time that serum soluble DPP-4 activity was negatively correlated with BMD in obese postmenopausal women.
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon, Korea.
authors.forename: Sang Wook
authors.identifier: http://orcid.org/0000-0001-7445-3860
authors.initials: SW
authors.lastname: Kim
authors.affiliation: Division of Endocrinology and Metabolism, Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon, Korea. ehcho@kangwon.ac.kr.
authors.forename: Eun Hee
authors.identifier: http://orcid.org/0000-0002-1349-8894
authors.initials: EH
authors.lastname: Cho
keywords: Bone mineral density; Dipeptidyl peptidase 4; Postmenopause; Women