title: [Replacement of insulin by fasting C-peptide in modified homeostasis model assessment to evaluate insulin resistance and islet beta cell function].
abstract: OBJECTIVE
  To investigate the possibility of using C-peptide to replace insulin in homeostasis model assessment (Homa) to evaluate insulin resistance and islet beta cell function.
  
  
  METHODS
  Oral glucose tolerance test (OGTT) was performed in 21 normal subjects, whose venous blood was drawn before taking glucose and 30, 60, 120 minutes after taking glucose. Insulin and C-peptide were determined with radioimmune assay. Homa indices of insulin resistance and islet beta cell function were calculated. Multiple stepwise linear regression model of insulin resistance was measured using C-peptide x blood glucose as independent variables and Homa-IR was used as the dependent variable, while the model of islet beta cell function was determined using C-peptide/(fasting blood glucose - 3.5) as the independent variable and Homaislet as the dependent variable.
  
  
  RESULTS
  The modified Homa formula were: Homa-IR (CP) = 1.5 + fasting blood glucose x fasting C-peptide/2800 (F = 5. 511, P = 0.029), Homa-islet (CP-Normal) = 0.27 x fasting C-peptide /(fasting blood glucose - 3.5) + 50, and Homa-islet (CP-DM) = 0.27 x fasting C-Peptide/(fasting blood glucose - 3.5) (F = 212.961, P = 0.000), respectively. The modified Homa-IR (CP) and Homa-IR, Homa-islet (CP) and Homa-islet were highly correlated (r =0.689 and r = 0.788; all P = 0.000). Using Homa and modified Homa formula to evaluate the insulin resistance and islet beta cell function both in the normal and diabetic subjects was similar.
  
  
  CONCLUSIONS
  Fasting C-peptide can substitute insulin in Homa model to assess insulin resistance and islet beta cell function. The modified homeostasis model assessment may be applied in the diabetics using exogenous insulin.
authors.affiliation: Department of Endocrinology, Second Xiangya Hospital, Central South University, Changsha, China.
authors.forename: Xia
authors.initials: X
authors.lastname: Li
authors.forename: Zhi-Guang
authors.initials: ZG
authors.lastname: Zhou
authors.forename: Hai-Ying
authors.initials: HY
authors.lastname: Qi
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Chen
authors.forename: Gan
authors.initials: G
authors.lastname: Huang
mesh_terms: D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism; D002096:C-Peptide / Q000097:blood*; D003920:Diabetes Mellitus / Q000097:blood / Q000503:physiopathology*; D005260:Female; D005951:Glucose Tolerance Test; D006706:Homeostasis; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology*; D007515:Islets of Langerhans / Q000503:physiopathology*; D008297:Male; D008433:Mathematics; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin