Diabetes, Vol 40, Issue 4 509-515, Copyright © 1991 by American Diabetes Association
Higher insulin and C-peptide concentrations in Hispanic population at high risk for NIDDM. San Luis Valley Diabetes Study
EJ Boyko, EM Keane, JA Marshall and RF Hamman
Department of Medicine, University of Washington, Seattle.
Hyperinsulinemia has been demonstrated in Hispanics with normal glucose
tolerance and in other populations at higher risk for non-insulin-dependent
diabetes mellitus (NIDDM). We compared fasting and glucose-stimulated
insulin and C-peptide levels in a community-based sample of 464 Hispanic
and 676 non-Hispanic white adult residents of the San Luis Valley of
Colorado. All subjects had normal glucose tolerance as confirmed by oral
glucose tolerance testing interpreted with World Health Organization
criteria. Mean fasting and 1- and 2-h post-glucose load insulin levels were
significantly higher in Hispanics versus non-Hispanic whites (fasting 0.08
vs. 0.07 nM, P = 0.0026; 1 h 0.52 vs. 0.47 nM, P = 0.0129; 2 h 0.36 vs.
0.27 nM, P less than 0.0001), even after adjustment for age, sex, body mass
index, waist-hip ratio, family history of diabetes mellitus, concurrent
plasma glucose level, and fasting insulin level. Mean fasting and 1- and
2-h glucose-stimulated C-peptide levels in Hispanics also significantly
exceeded those in non-Hispanic whites (fasting 0.58 vs. 0.54 nM, P =
0.0119; 1 h 2.72 vs. 2.46 nM, P less than 0.0001; 2 h 2.25 vs. 1.97 nM, P
less than 0.0001). The C-peptide-insulin molar ratio was greater in
non-Hispanic whites than Hispanics at all times measured. These findings
confirm that Hispanics with normal glucose tolerance are hyperinsulinemic
and that increased insulin secretion is at least partly responsible for
this phenomenon. The lower levels of C-peptide compared with insulin in
Hispanics suggest that the hyperinsulinemia seen in this ethnic group may
be due in part to decreased hepatic insulin extraction.