Aspetti endocrini nel processo d'invecchiamento del cane

Several studies in humans have shown that the aging process is associated with endocrine disruption, in particular of the hypothalamic-pituitary-adrenal axis. Dehydroepiandrosterone (DHEA) and cortisol are steroid hormones secreted by the adrenal glands. They have pleiotropic biological effects, influencing a wide range of physiological functions. In humans, the biosynthetic dissociation of these steroids occurs during the aging process and this event becomes evident when age-related pathologies are clearly manifested. Recent works support the dog as a useful animal model for the study of human aging processes. The dog shows a remarkable similarity with the human cognitive decline. However, even if DHEA and cortisol have been extensively investigated in humans, little is known about these hormones in dogs. The main purpose of the first part of this thesis was to investigate whether and how the plasmatic concentrations of DHEA and cortisol (and their ratio) are affected by age and gender in the canine species. The evaluation of DHEA and cortisol concentrations has been determined by using radioimmunoassay analysis. In addition, these hormones have been also analyzed in different stages of estrous cycle and in ovariectomized bitches in order to detect changes associated with reproductive status. The results showed that the trend of both hormones did not change during aging in the dog, but the plasmatic concentration of DHEA is influenced by gender, reproductive status and presence of gonadectomy. The second part of this thesis aimed at assessing whether some behavioral tests, that are known to socially and psychologically stress the dog, finally induce a different activation of the hypothalamic-pituitary-adrenal axis in adult and elderly owned dogs. Salivary cortisol was chosen as marker of stress and was evaluated by radioimmunoassay analysis. The salivary cortisol concentrations of the recruited dogs were compared before and after each experimental protocols. However, circumstances prior to the test must have contributed to activate the hypothalamic-pituitary-adrenal axis, producing an increase of cortisol in samples taken before the behavioral tests. As a consequence, it has not been possible to evaluate the stressor effect of the experimental protocol in all the subjects of the recruited population, and to highlight a difference between adult and elderly dogs. However, in a subpopulation of dogs it was possible to show that the social emotional stress is able to induce an increase in cortisol concentrations. In conclusion, this thesis has allowed to obtain new insights into the physiological levels of the DHEA and cortisol hormones and their ratio in relation to age, gender, reproductive status and gonadectomy in dogs. It showed that for dogs an emotional event is more stressful than a psychological event. Future studies are needed to determine whether a different response exists between adult and elderly dogs.Parecchi studi condotti nell’ uomo hanno dimostrato che il processo d’ invecchiamento è associato ad alterazioni del sistema endocrino ed in particolare dell’ asse ipotalamo-ipofisi-surrene. Deidroepiandrosterone e cortisolo sono ormoni steroidei, secreti dalle ghiandole surrenali, che presentano attività biologica pleiotropica. La dissociazione biosintetica di questi steroidi che si verifica con il progredire dell’ età nella specie umana, diventa evidente soprattutto nel momento in cui molte patologie legate all’ invecchiamento iniziano a diventare marcatamente prevalenti. Recenti lavori supportano il cane come modello animale per lo studio dell’ invecchiamento umano, soprattutto per la notevole analogia esistente tra le due specie per quanto riguarda il declino neurologico e cognitivo. Tuttavia, se la letteratura umana presenta numerosi lavori inerenti questi steroidi, quella riguardante la specie canina e gli ormoni in questione È decisamente meno esaustiva. La prima parte di questa tesi ha avuto come principale obiettivo quello di indagare, attraverso l’ utilizzo dell’ analisi radioimmunologica, se ed in che modo le concentrazioni plasmatiche di DHEA e di cortisolo, ed il loro rapporto nella specie canina, siano influenzate da età e genere. Inoltre, una valutazione di questi ormoni È stata effettuata nelle diverse fasi del ciclo estrale ed in cagne ovariectomizzate al fine di individuare la presenza di variazioni associate alla condizione riproduttiva. I risultati ottenuti hanno evidenziato come l’ andamento di entrambi questi ormoni non subisca modificazioni durante l’ invecchiamento nel cane, mentre È emerso come le concentrazioni plasmatiche di DHEA sia influenzate da genere, condizione riproduttiva e presenza di gonadectomia. La seconda parte di questa tesi ha invece cercato di verificare se test comportamentali che creano situazioni di stress sociale e psicologico, siano in grado di determinare una differente attivazione dell’ asse ipotalamo-ipofisi-surrene in cani di proprietà adulti ed anziani. Attraverso l’ analisi radioimmunologica È stata effettuata una valutazione del cortisolo salivare, confrontando le concentrazioni dei campioni raccolti dai cani reclutati prima e dopo ciascuno di tre differenti protocolli sperimentali. Circostanze antecedenti ai test devono tuttavia aver contribuito a determinare un’ attivazione dell’ asse ipotalamo-ipofisi-surrene, che ha generato un aumento della cortisolemia nei prelievi effettuati prima dei tre test comportamentali. Questo non ha consentito di verificare l’ effetto dei test nell’ intera popolazione reclutata e soprattutto di evidenziare una differenza tra cani adulti ed anziani nella risposta allo stress. Tuttavia È stato possibile in una sottopopolazione di cani evidenziare come stress di tipo emozionale sociale sia in grado di indurre un aumento della cortisolemia nel cane. Per concludere, questa tesi ha consentito di ottenere nuove conoscenze sui livelli fisiologici basali che gli ormoni DHEA e cortisolo ed il loro rapporto assumono in relazione ad età , genere, condizione riproduttiva e gonadectomia nella specie canina. Essa ha inoltre consentito di evidenziare come per il cane un evento di natura emozionale sia maggiormente stressante rispetto ad uno di natura psicologica. La sperimentazione futura attuata con i dovuti accorgimenti dovrà in cani adulti ed anziani verificare se una diversa risposta È presente

Effect of age and sex on plasma cortisol and dehydroepiandrosterone concentrations in the dog (Canis familiaris)

Limited data exist on age-related physiological variations in plasma concentrations of cortisol and dehydroepiandrosterone (DHEA) in dogs, despite their potential role in the pathophysiology of ageing. This study examined plasma cortisol and DHEA concentrations and cortisol/DHEA ratio variations, according to age and sex in 311 dogs, aged from two months to 16 years. Before adulthood, DHEA concentrations were higher in peri-pubertal males. During adulthood, cortisol and DHEA were higher in males than females. Among females, DHEA was lower in older dogs, but the decrease was observed at an older age in intact than ovariectomised females. Variations in the cortisol/DHEA ratio inversely reflected those of DHEA. Results indicate that testicles are an important source of DHEA in males, and that DHEA is mainly secreted by the adrenal glands in females. The ovaries\u2019 contribution to circulating DHEA appears to be limited, although it may partially compensate an age-related decrease in adrenal secretion

Dehydroepiandrosterone and cortisol concentrations in the cerebrospinal fluid of dogs

none6noConcentrations of cortisol, dehydroepiandrosterone and dehydroepiandrosterone-sulphate were measured by radioimmunoassay in the cerebrospinal fluid of 68 dogs, diagnosed with idiopathic epilepsy, inflammatory-, degenerative-, or non-neurological- disease. No differences in steroid concentrations were found between diagnoses. Dehydroepiandrosterone and dehydroepiandrosterone-sulphate concentrations were higher in males and dehydroepiandrosterone-sulphate decreased with increasing age. No sex or age effect was found on cortisol or on hormone ratios. Although limited to a relatively small sample, our results show sex and age dependent variations of these neurosteroids’ concentrations in the cerebrospinal fluid. The role of such variations in the pathophysiology of the dog brain warrants further investigation.noneMongillo, Paolo; Bernardini, Marco; Prana, Elisa; Federica, Balducci; Gabai, Gianfranco; Marinelli, LietaMongillo, Paolo; Bernardini, Marco; Prana, Elisa; Federica, Balducci; Gabai, Gianfranco; Marinelli, Liet

Detailed functional studies on androgen receptor mild mutations demonstrate their association with male infertility

CONTEXT: Mutations in the androgen receptor (AR) gene can cause the androgen insensitivity syndrome (AIS). For complete and severe partial AIS, well-characterized in vitro functional assays can be used for genotype-phenotype correlation; however, for mild forms of AIS, as associated with male infertility, experimental evidence is scarce or lacking. In particular, optimal in vitro functional tests informative about the genotype-phenotype relation have not been described. OBJECTIVE: The objective of this study was to investigate the association among genotype and phenotype for AR mutations found in infertile males by conventional functional assays and additional in-depth studies performed with several gene reporters. DESIGN: To this aim, we selected four AR missense mutations associated with isolated male infertility (L547F and two novel mutations A474V and S650G) or partial AIS (Y571H). After introduction of the specific mutations in AR expression plasmid, we performed classical in vitro studies (Western immunoblotting, electrophoretic mobility shift assay, hormone-response curves) and transactivation assays with different reporter constructs (MMTV, Sc-ARU-TK, TAT-GRE- 2X, Slp-ARU-TK and PEM). RESULTS AND CONCLUSIONS: Our results showed that standard functional tests provide sufficient information only for severe AR mutations, whereas for AR mutations found in mild AIS patients with male infertility, only an extensive analysis with different in vitro systems, and in particular with PEM promoter, can give information on the functionality of the AR and therefore on the pathogenicity of the mutations and on genotype-phenotype correlation