Differential Insulin Sensitivities of Glucose, Amino Acid, and Albumin Metabolism in Elderly Men and Women

• Published in: The journal of clinical endocrinology and metabolism Vol. 86; no. 2; pp. 638 - 644
• Main Authors: Boirie, Yves, Gachon, Pierre, Cordat, Nathalie, Ritz, Patrick, Beaufrère, Bernard
• Format: Journal Article
• Language: English
• Published: Endocrine Society 01-02-2001
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jcem.86.2.7193

Regulation of glucose homeostasis by insulin is modified during aging,
but whether this alteration is associated with changes in protein
metabolism is less defined. Insulin dose responses of whole body
glucose, leucine, and albumin metabolism have been investigated using
isotopic dilution of d-[6,
6-2H2]glucose and
l-[1-13C]leucine in 14 young (Y; 24.0 ±
0.9 yr; mean ± sem, 20.5 ± 0.4
kg/m2) and 12 healthy elderly subjects (E; 69.4 ± 0.6
yr; 24.6 ± 0.8 kg/m2) using a euglycemic and
euaminoacidemic hyperinsulinemic clamp at two insulin infusion rates of
0.2 and 0.5 mU/kg·min (CL1 and CL2, respectively). Despite
significantly higher plasma insulin in E than in Y, the glucose
disposal rate was lower in E than in Y at both insulin levels, whereas
glucose production was normally suppressed. Whole body protein
breakdown was less inhibited by insulin in E than in Y at CL1
(−13.5 ± 1.4% vs. −8.8 ± 1.3%, Y
vs. E, P < 0.05), but not
significantly at CL2 (−22.0 ± 1.4% vs.−
18.8 ± 1.7%, Y vs. E, P =
NS). The albumin synthesis rate was identical and stimulated to the
same extent by insulin in groups Y and E. Gender affected basal leucine
metabolism, but the response to insulin was similar in both groups. In
conclusion, decreased insulin action on glucose disposal is associated
with a reduced insulin sensitivity for protein breakdown in healthy
elderly subjects at low insulin concentrations. Higher insulin levels
compensate for a reduced insulin action on protein metabolism in
elderly subjects.