[Ageing related changes of insulin secretion and insulin sensitivity among normal glucose tolerance individuals in China].

OBJECTIVE

To explore the aging-related changes of insulin secretion and insulin sensitivity among normal glucose tolerance (NGT) individuals in China.

METHODS

A total of 34 293 individuals were recruited. All of them were described as NGT by 75 g oral glucose tolerance test (75 g OGTT) according to the diagnostic criterion of WHO, 1999. HOMA-β, ΔI(30)/ΔG(30), InsAuc30/GluAuc30, InsAuc120/GluAuc120 were calculated to estimate insulin secretion; HOMA-IR and Matsuda index measured to estimate insulin sensitivity; Disposition index: DI(30) and DI(120) were used to estimate β-cell function.

RESULTS

HOMA-β, ΔI(30)/ΔG(30), InsAuc30/GluAuc30 and InsAuc120/GluAuc120 were all lower in the elder group then the younger group (P trend < 0.05). The mean HOMA-β dropped from 192 ± 16 (20 - 29 years) to 115 ± 7 (70 or elder) among men and from 162 ± 8 (20 - 29 years) to 120 ± 12 (70 or elder) among women. The mean ΔI(30)/ΔG(30) dropped from 20.0 ± 2.0 (20 - 29 years) to 8.6 ± 0.6 (70 or elder) among men and from 22.4 ± 1.6 (20 - 29 years) to 12.5 ± 1.7 (70 or elder) among women. The above index were negatively correlated with age in univariate linear regression (P < 0.05), the results among men and overall still existed after adjusted for BMI and waist circumference in multivariate linear regression, while the relation between HOMA-β and age disappeared among women. Matsuda Index was positively correlated with age (β = 0.02, P = 0.001) and HOMA-IR were negatively correlated with age (β = -0.01, P = 0.001) among men even after adjusted for BMI and waist circumference and the above correlation between Matsuda Index/HOMA-IR and ageing was not significant until adjusted for BMI and waist circumference in multivariate linear regression. Among women HOMA-IR (β = -0.01, P = 0.000), Matsuda index (β = 0.03, P = 0.000). DI(30) and DI(120) were negatively correlated with age in both univariate and multivariate linear regression.

CONCLUSIONS

The basal, postchallenge insulin secretion and postchallenge islet compensatory function decreases with ageing, while insulin sensitivity does not deteriorate with ageing and its related change of body composition and weight gain.