Aims: "Aging obesity" in middle-aged and "cachexia of aging" in old individuals present population-wide public health challenges. In the background, complex age-related alterations in the anabolic and catabolic peptide systems may be assumed. Our previous studies revealed well-defined age-related shifts in the responsiveness of energy balance to the centrally applied infusion of melanocortin (MC) agonist alpha-melanocyte-stimulating-hormone. Other catabolic mediators downstream of MCs include the corticotropin system. Corticotropin-releasing factor (CRF, a 41-amino-acid peptide) is produced in significant quantities in the hypothalamic paraventricular nucleus. Its coordinated catabolic actions include anorexigenic and hypermetabolic components. In addition to catabolic, stress-related and anxiety-inducing, etc. functions, antipyretic actions of CRF are also known. have also been described In the present study age-related changes in the responsiveness of the corticotropin system was tested regarding parameters of energy balance.

Methods: 

The effects of a 7-day intracerebroventricular CRF infusion (0.3 mg/ml/h) were measured in various age-groups of ad libitum fed male Wistar rats (aged 3-months: young adult, 12-months: middle-aged, 18-months: aging and 24-months: old). Core temperature (Tc), heart rate and spontaneous horizontal activity of freely moving animals were continuously recorded in a biotelemetric system (MiniMitter). Food intake (FI) and body weight (BW) were measured daily.

Results: 

The CRF infusion significantly suppressed BW in the young, aging and old rats, but failed to reduce BW in middle-aged animals. The anorexigenic response was especially pronounced in old rats. Hypermetabolic effects, indicated by the increase in mean daytime Tc were detected in the youngest and oldest group.

Conclusions: 

Our results show that middle-aged rats show the weakest, the old age-group the strongest catabolic (anorexigenic and hypermetabolic) responsiveness to CRF. These age-related alterations differentially affect the anorexigenic and hypermetabolic effects of corticotropins, probably via signal transduction pathways. These results are similar as those obtained during the study of the MC system. Support: OTKA PD84241, PTE-AOK-KA-34039-25/2009, PTE AOK-KA-34039-02/2010