Neuroendocrine System and Mental Function in Sedentary and Endurance-Trained Elderly Males

Hypothalamic-pituitary-adrenal (HPAA) and -gonadal (HPGA) axis modification and cognitive impairments have been reported in elderly subjects and related to physical training status. The aim of this study was to investigate if HPAA and HPGA regulation are altered in elderly distance runners (RUNI; n = 8; age: 68.9 ± 4.2 yrs; training: 65±20km/wk over the last 20yrs; means ± SD) or are affected in elderly sedentary indiividuals (SED; n = 11; age: 69.1 ± 2.6yrs) by an aerobic training over 20 weeks (3 times/week, 30-60 min walking), respectively. The protocol included assessment of the hormone profile iin basal non-suppressed state as well as evaluation of hormonal [responses to dexamethasone (DEX, 1.5 mg) induced adrenal suppression, to post-DEX combined corticotrophin releasing hormone (CRH; 0.7μg/kg) and luteinizing hormone releasing hormone (LHRH, 0.7μg/kg) stimulation and to exercise challenge (30 min cycle ergometry at 65 % V02max). Mental functions influenced by HPAA and HPGA activity were also assessed in RUN aind SED before (SED-PRE) and after (SED-POST) the training program. Basal and post-DEX plasma concentrations of adrenocorticotropic hormone (ACTH), Cortisol (CSL), luteinizing hormome (LH), follicle stimulating hormone (FSH) and testosterone (T) did not differ between RUN and SED-PRE. Basal plasma free T concentration was significantly lower in RUN (RUN: 10.23 ± 2.41 pg · ml^-1 vs. SED-PRE: 16.6 ± 5.59 pg · ml^-1). During releasing hormone challenge test after DEX administration (DEX/RH), no differences. were found between RUN and SED-PRE in plasma ACTH, LH, FSH and T response. During this stimulation test, plasima CSL was significantly higher in RUN than in SED-PRE after 90min (RUN: 5.86 ± 3.65 μg · dl^-1 vs. SED-PRE: 2.74 ± 2.09 μg · dl^-1). Differences in plasma CSL concentrations between groups w/ere not induced by 30-min exercise challenge. Basal hormone profile was not altered by training in SED. During DEX/RH only plasma

ACTH concentration was significantly higher in SED-POST compared to SED-PRE. Long and short-term memory function did not differ between RUN, SED-PRE and SED-POST. Our data suggest that following post-DEX CRH/LHRH challenge elderly endurance athletes reveal-in the absence of altered peak values-a pattern of prolonged secretion of glucocorticoids. However, the high interindividual variability of plasma ACTH and CSL concentrations shows that reduced corticotropic sensitivity to negative feedback is not always induced by chronic exercise stress. Lower plasma free T concentrations in RUN compared to SED are not caused by modified LH synthesis-secretion capacity.

Key words

Aging - dexamethasone - releasing hormones - reproductive system - training