Age-related reduction in glucose elimination is accompanied by reduced glucose effectiveness and increased hepatic insulin extraction in man

J Clin Endocrinol Metab. 1998 Sep;83(9):3350-6. doi: 10.1210/jcem.83.9.5107.

Abstract

This study examined whether insulin secretion, insulin sensitivity, glucose effectiveness (SG), and hepatic extraction (HE) of insulin are altered by age when glucose tolerance is normal. A frequently sampled i.v. glucose tolerance test was performed in 20 elderly (E, 10/10 male/female, all 63 yr old) and in 20 young subjects (Y, 10/10 male/female, all 27 yr old), who were similar in body mass index and 2-h blood glucose during oral glucose tolerance test. E exhibited impaired glucose elimination (i.v. tolerance index, 1.31 +/- 0.10 vs. 1.70 +/- 0.12% min-1; P = 0.019). First-phase insulin secretion and SI did not differ between the groups, whereas E had lower glucose sensitivity of second-phase insulin secretion (0.40 +/- 0.07 vs. 0.70 +/- 0.08 (pmol/L)min-2/(mmol/L), P = 0.026), lower SG, 0.017 +/- 0.002 vs. 0.025 +/- 0.002 min-1, P = 0.004), and higher HE (81.3 +/- 2.4 vs. 73.2 +/- 2.1%, P = 0.013). Across both groups, SG correlated positively with glucose tolerance index (r = 0.58, P < 0.001) and negatively with HE (r = -0.54, P < 0.001). Plasma leptin and glucagon did not change by age, whereas plasma pancreatic polypeptide (PP) was higher in E (122 +/- 18 vs. 66 +/- 6 pg/mL, P = 0.004). PP did not, however, correlate to any other parameter. We conclude that E subjects with normal oral glucose tolerance have reduced SG, impaired second-phase insulin secretion, and increased HE, whereas SI and first-phase insulin secretion seem normal. SG seems most related to age-dependent impairment of glucose elimination, whereas leptin, glucagon, and PP do not seem to contribute.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aging / metabolism*
  • Blood Glucose / metabolism*
  • C-Peptide / blood
  • Female
  • Glucagon / blood
  • Glucose Tolerance Test
  • Humans
  • Insulin / blood*
  • Insulin / metabolism
  • Insulin Secretion
  • Kinetics
  • Leptin
  • Liver / metabolism*
  • Male
  • Middle Aged
  • Pancreatic Polypeptide / blood
  • Proteins / metabolism

Substances

  • Blood Glucose
  • C-Peptide
  • Insulin
  • Leptin
  • Proteins
  • Pancreatic Polypeptide
  • Glucagon