[The effect of age on glucose tolerance and B cell secretion]

Abstract

The aim of the study was to evaluate glucose tolerance, B cell secretion and hepatic clearance of insulin during the process of aging. 100 subjects of both sexes, in age range of 17 to 92 years and with BMI < 27 kg/m2 were studied. All subjects were divided in 4 groups according to age: 18 patients were in age from 17 to 59 years (group I--mean 46 +/- 12 (SD) years, 23 patients in age from 60 to 69 years (group II--mean 64 +/- 3 years), 33 patients in age from 70 to 79 years (group III--mean 75 +/- 3 years), 26 patients in age from 80 to 92 years (group IV--mean 84 +/- 4 years). In all participants oral glucose tolerance test (75 g) and the i.v. glucagon test (1 mg) were carried out and blood glucose, serum insulin (IRI) and C-peptide (CP) were measured. Hepatic clearance of insulin was calculated from the serum CP/IRI ratio. With advanced age the increase in fasting glycaemia (group I 4.25 +/- 0.6, group IV 4.7 +/- 0.5 mM, p = 0.02) and after applied stimuli, and a decrease in fasting (group I 0.6 +/- 0.2, group IV 0.35 +/- 0.13 nM, p < 0.05) and stimulated serum CP with no differences in serum IRI concentrations between groups was observed. Consequently the serum CP/IRI ratio decreased from 10 +/- 3.8 in group I to 5.4 +/- 1.7 in group IV (p < 0.05) indicating reduced insulin clearance in liver, probably as a compensatory adaptation to the deterioration of B cell secretory activity.