Insulin receptors in mouse brain: age-related modifications are corrected by thymus graft.

Recently, we have shown that insulin receptors (InsRs) in the brain undergo impairment with aging, as happens for other receptors such as alpha- and beta-adrenoceptors. Age-related alterations of adrenoceptors, which are modulated by brain InsRs, are not definitive as they can be recovered by a thymus graft. In this study we verified the possibility that the thymus graft can also recover the age-dependent modifications of brain InsRs. InsR characteristics were assayed in a group of 27 months old Balb/c-nu mice grafted with a neonatal thymus, under renal capsule, one month before the animals were killed. Another two groups of young (3 months) and old (27 months) mice were used as controls. A two-sites model analysis of receptor data confirmed the age-dependent decrease of InsR density previously observed in the high affinity population. Furthermore, a statistically significant recovery of this impairment was shown in thymus grafted animals. The low affinity receptor subset also showed some differences among the three animal models; however, they were not statistically significant. Thymus graft induced recovery of the age-related changes found in brain InsRs, together with the similar one observed on the adrenergic system, calls for deeper studies of their interaction and the role they can play on aging processes.