Fasting plasma C-peptide levels in health and impaired glucose tolerance: relations to blood glucose and relative body weight

Abstract

Birgerstam G, Malmquist J. Fasting plasma C-peptide levels in health and impaired glucose tolerance: relations to blood glucose and relative body weight. Scand J Clin Lab Invest 1985; 45: 707–712.

Pancreatic B-cell function was studied as part of a health control examination by measuring fasting plasma C-peptide concentration in 433 44–55 year-old males with normal glucose tolerance. Fasting C-peptide levels were correlated with relative body weight (r=0.48) and fasting blood glucose concentrations (r=0.43), yielding a multiple correlation coefficient of 0.56, and the multiple regression equation: FCP (nmoL/l)=-0.89+0.61×RBW+0.16×FBG (mmol/1). (FCP=fasting plasma C-peptide, RBW=relative body weight, FBG=fasting blood glucose). In 26 subjects with impaired glucose tolerance, fasting plasma C-peptide levels were even more strongly correlated with relative body weight (r=0.63) and fasting blood glucose concentrations (r=0.47). Subjects older than 52 years had a significantly higher fasting C-peptide level than younger subjects (p<0.01). In the 26 subjects with impaired glucose tolerance, fasting plasma C-peptide levels were not significantly different from those in the 433 men with normal glucose tolerance. However, when compared to a group with normal glucose tolerance matched for relative body weight, the subjects with impaired glucose tolerance had an elevated fasting blood glucose level (p<0.01) without difference in C-peptide level, suggesting a reduced insulin sensitivity. It is concluded that, in order to evaluate B-cell secretory function by determining fasting plasma C-peptide concentration, the relative body weight and simultaneous blood glucose concentration should be taken into consideration.

Key Words:

• insulin resistance
• insulin secretion
• non-insulin-dependent diabetes mellitus
• obesity
• radioimmunoassay