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Effects of aging on insulin secretion
B Gumbiner1, K S Polonsky, W F Beltz
1Department of Medicine, University of California, San Diego.
Diabetes
|December 1, 1989
Summary
Aging increases basal insulin secretion and glucose response, but insulin secretion adjusts similarly in older and younger adults when glucose levels are matched. This suggests aging impacts insulin secretion regulation differently than previously thought.
Area of Science:
- Endocrinology
- Gerontology
- Metabolic Research
Background:
- Aging is linked to hyperinsulinemia, but the causes—altered insulin clearance or secretion—are debated.
- Understanding insulin secretion's role in aging-related hyperinsulinemia is crucial for metabolic health insights.
Purpose of the Study:
- To investigate the specific role of insulin secretion in the hyperinsulinemia observed in aging.
- To compare insulin secretion rates in elderly versus young individuals under various physiological conditions.
Main Methods:
- Studied 10 elderly and 8 young subjects to assess insulin secretion during fasting, mixed meals, and glucose infusions.
- Utilized a two-compartment model with C-peptide kinetics to quantify insulin secretion rates.
- Employed hyperglycemic clamps and glucose infusions to standardize glucose levels between groups for direct comparison.
Main Results:
- Elderly subjects exhibited higher basal insulin secretion rates and elevated serum insulin levels compared to younger individuals.
- During a 24-hour meal, elderly subjects showed increased glucose response and total insulin secretion.
- When glycemia was experimentally matched, both groups displayed nearly identical insulin secretion profiles, indicating similar secretory capacity.
Conclusions:
- Basal insulin secretion is elevated in aging, contributing to hyperinsulinemia.
- Despite differences in overall secretion, the relative insulin secretory response to glucose is preserved in older adults when glycemia is controlled.
- These findings suggest that altered insulin clearance, rather than a diminished secretory capacity, may play a more significant role in age-related hyperinsulinemia.