title: Effects of age and sex on postprandial glucose metabolism: differences in glucose turnover, insulin secretion, insulin action, and hepatic insulin extraction.
abstract: To determine the effects of age and sex on the regulation of postprandial glucose metabolism, glucose turnover, insulin secretion, insulin action, and hepatic insulin extraction were concurrently measured in 145 healthy elderly (aged 70 +/- 1 years) and in 58 young (aged 28 +/- 1 years) men and women before and after ingestion of a mixed meal containing [1-(13)C]glucose. At the time of meal ingestion, [6-(3)H]glucose and [6,6-(2)H(2)]glucose were infused intravenously to enable concurrent measurement of the rates of postprandial endogenous glucose production (EGP), meal appearance, and glucose disappearance. Fasting and postprandial glucose concentrations were higher (P < 0.001) in both elderly women and elderly men compared with young individuals of the same sex. The higher postprandial glucose concentrations in the elderly than young women were caused by higher rates of meal appearance (P < 0.01) and slightly lower (P < 0.05) rates of glucose disappearance immediately after eating. In contrast, higher glucose concentrations in the elderly than young men were solely due to decreased (P < 0.001) glucose disappearance. Although postprandial glucose concentrations did not differ in elderly women and elderly men, rates of meal appearance and glucose disappearance rates both were higher (P < 0.001) in the women. Fasting EGP was higher (P < 0.05) in elderly than young subjects of both sexes and in women than men regardless of age. On the other hand, postprandial suppression of EGP was rapid all groups. Insulin action and secretion were lower (P < 0.001) in the elderly than young men but did not differ in the elderly and young women. This resulted in lower (P < 0.001) meal disposition indexes in elderly than young men but no difference in elderly and young women. Total meal disposition indexes were lower (P < 0.05) in elderly men than elderly women, indicating impaired insulin secretion, whereas disposition indexes were higher (P < 0.05) in young men than young women. Hepatic insulin clearance was greater (P < 0.001) in the elderly than young subjects of both sexes but did not differ between men and women regardless of age. In contrast, the ability of glucose to facilitate its own uptake (glucose effectiveness) was higher (P < 0.001) in women than men but did not differ in elderly and young subjects. Thus, age and sex impact on insulin secretion, insulin action, hepatic insulin extraction, and glucose effectiveness, resulting in substantial differences in the regulation of postprandial glucose metabolism in men and women and in elderly and young subjects.
authors.affiliation: Mayo Clinic College of Medicine, 200 1st St. SW, Rm. 5-194 Joseph, Rochester, MN 55905, USA.
authors.forename: Rita
authors.initials: R
authors.lastname: Basu
authors.forename: Chiara
authors.initials: C
authors.lastname: Dalla Man
authors.forename: Marco
authors.initials: M
authors.lastname: Campioni
authors.forename: Ananda
authors.initials: A
authors.lastname: Basu
authors.forename: George
authors.initials: G
authors.lastname: Klee
authors.forename: Gianna
authors.initials: G
authors.lastname: Toffolo
authors.forename: Claudio
authors.initials: C
authors.lastname: Cobelli
authors.forename: Robert A
authors.initials: RA
authors.lastname: Rizza
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism*; D002096:C-Peptide / Q000097:blood; D002247:Carbon Isotopes; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*; D000078790:Insulin Secretion; D007553:Isotope Labeling; D007700:Kinetics; D008099:Liver / Q000502:physiology*; D008297:Male; D012727:Sex Characteristics
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D002247:Carbon Isotopes; D007328:Insulin