title: The association between the serum C-peptide level and bone mineral density.
abstract: OBJECTIVE
  Although serum C-peptide was previously considered biologically inactive, a growing number of recent studies have shown that it is an active peptide with important physiologic functions. The present study aimed to investigate the association of serum C-peptide level with bone mineral density (BMD) in residents of the United States.
  
  
  METHODS
  The study included 6,625 participants aged 12-85 years. Total and regional BMD were measured using dual-energy X-ray absorptiometry. Stratified multiple linear regression analysis was performed to determine the association of the serum C-peptide level with BMD. Three regression models were produced for each stratum. All models were adjusted for ethnicity, height, weight, education level, physical activity, smoking status, alcohol use, triglycerides and creatinine level, and models 2 and 3 were further adjusted for the fasting plasma glucose (FPG) and alkaline phosphatase (ALP) levels, respectively.
  
  
  RESULTS
  Sex-specific results showed a significant association between the serum C-peptide level and total BMD in both sexes. Stratified analyses based on age and body mass index showed that serum C-peptide levels were significantly negatively associated with most regional BMD, and most of these associations remained significant after stratification based on the serum insulin level.
  
  
  CONCLUSIONS
  The serum C-peptide level was significantly negatively associated with the total and most regional BMD. These findings suggest that serum C-peptide may have biological activity associated with bone metabolism and therefore serum C-peptide control is advisable in order to reduce the risk of low bone mineral density.
authors.affiliation: Department of Social Medicine, School of Public Health, Zhejiang University, Zhejiang, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Basic Medical Sciences, Zhejiang University, Zhejiang, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Liu
authors.affiliation: Department of Hygiene and Public Health II, Tokyo Women's Medical University, Tokyo, Japan.
authors.forename: Yasuto
authors.initials: Y
authors.lastname: Sato
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015519:Bone Density; D002096:C-Peptide / Q000097:blood*; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D010024:Osteoporosis / Q000097:blood / Q000453:epidemiology; D014481:United States / Q000453:epidemiology; D055815:Young Adult
chemical_list: D002096:C-Peptide