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Association between Stimulated Plasma C‐peptide and Age: The Wadena City Health Study
Author(s) -
French L. Ronald,
Goetz Frederick C.,
Martinez Anita M.,
Boen James R.,
Bushhouse Sally A.,
Sprafka J. Michael
Publication year - 1992
Publication title -
journal of the american geriatrics society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.992
H-Index - 232
eISSN - 1532-5415
pISSN - 0002-8614
DOI - 10.1111/j.1532-5415.1992.tb02127.x
Subject(s) - medicine , association (psychology) , gerontology , epistemology , philosophy
Objective To assess age‐related changes in stimulated plasma C‐peptide in a population‐based sample of adults. Design Cross‐sectional study. Setting Wadena, Minnesota, a city of 4,699 residents (1980 census) in west central Minnesota, approximately 150 miles from Minneapolis/St. Paul. Study Subjects 344 non‐diabetic subjects (NDDG standards) from a stratified random sample of the total adult population of Wadena, MN. The six‐study strata were men and women from three age groups: young, 20–39 years of age; middle‐aged, 40–59; and older, >60 years of age. Measurements During a liquid meal of Ensure‐Plus (Ensure‐Plus® challenge test; EPCT; Ross Laboratories), blood samples were taken for glucose, free fatty acids, creatinine, and C‐peptide. Plasma C‐peptide taken 90 minutes after the EPCT was used as a surrogate measure for insulin. Clinical tests included one‐time samples for hemoglobin, glycosylated hemoglobin, plasma cholesterol, triglycerides, and lipoproteins. Physical measurements included height, weight, and blood pressure. Urine was assayed for C‐peptide and creatinine. Assays of urine and plasma C‐peptide used antibody M1221 (from Novo; Copenhagen, Denmark). Main Results No differences were observed for the relationship between age and C‐peptide within each of the three age groups for men and the three age groups for women. However, the levels of plasma C‐peptide for older men or women were statistically significantly higher than levels for the young age groups of the same sex; fasting plasma glucose also was higher for older groups of both sexes, and postmeal glucose was significantly higher for older women. There were decreases with age in urine C‐peptide clearance for women and men; the decline for women was statistically significant. In multiple regression models for men alone and women alone, that controlled for age, post‐meal plasma glucose best explained plasma C‐peptide levels. For young men, plasma glucose alone provided the best prediction of plasma C‐peptide levels; body mass index (BMI) and plasma glucose provided the best prediction for young women. For older men and both middle‐aged and older women, a combination of urine C‐peptide clearance and plasma glucose best predicted plasma C‐peptide levels; for middle‐aged men, BMI also contributed to the prediction. Conclusions Secretion of insulin in response to an orally administered mixed meal is undiminished with age in non‐diabetic adults.