GLUCOSE-HOMEOSTASIS DURING AGING

It has been assessed whether the impaired glucose homeostasis often observed in aged subjects is associated with changes in glucose-regulating hormones by measuring circulating levels of insulin, C-peptide, glucagon, growth hormone, somatostatin (SRIF) and somatomedin-C (SMC) together with blood glucose in baseline conditions and during oral glucose tolerance test (OGTT) in 6 aged and 5 adult healthy subjects. Areas under the curve (AUC) for all parameters measured during OGTT were calculated. Three out of the 6 aged subjects had reduced glucose tolerance. Fasting blood glucose was significantly higher in aged than in adult subjects (0.93 +/- 0.04 vs 0.81 +/- 0.01 g/l, p < 0.05) and also during OGTT (AUC: 2.48 +/- 0.56 vs 1.35 +/- 0.26 g/l/300 min, p < 0.05). These findings were associated with significantly increased SRIF (basal: 92.2 +/- 10.9 vs. 72.2 +/- 10.1 pg/ml, p < 0.05; AUC: 352.5 +/- 47.8 vs 244.2 +/- 38.1 pg/ml/300 min, p < 0.05) and decreased SMC values (basal: 0.31 +/- 0.04 vs 0.60 +/- 0.11 U/ml, p < 0.05; AUC: 1.36 +/- 0.16 vs. 2.92 +/- 0.48 U/ml/300 min. p < 0.01). No differences were found between the two groups in the other measured parameters. It is concluded that glucose homeostatis during aging has the following characteristic features: reduced glucose tolerance, increased SRIF, decreased SMC and normal growth hormone levels.