Made available in DSpace on 2014-06-11T19:31:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-05-12Bitstream added on 2014-06-13T19:41:12Z : No. of bitstreams: 1 cardoso_mjl_dr_botfmvz.pdf: 248290 bytes, checksum: 9109a7b559aa1fe60811340d1a417214 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Os efeitos do hipertireoidismo experimental (150 g/kg/dia/42 dias) na homeostase do cálcio e nos marcadores do metabolismo ósseo foram estudados em 14 gatos sem raça definida, com idade entre um e três anos. Houve uma clara tendência de aumento das concentrações séricas de PTH intacto a partir do momento inicial com diferença significativa entre este e os demais momentos. O cálcio ionizado demonstrou uma diminuição significativa aos 14 dias em relação ao momento inicial e aos 42 dias em relação aos 14 dias. Os hormônios tireoidianos apresentaram correlação positiva com o PTH e negativa com o cálcio ionizado. Já a densidade mineral óssea (DMO) apresentou tendência de correlação negativa com o PTH a partir dos 28 dias. Observou-se correlação negativa do PTH com o cálcio ionizado aos 14, 28 e 42 dias. Conclui-se que o hipertireoidismo em gatos adultos jovens sem doenças concomitantes apresenta hiperparatireoidismo secundário. As concentrações séricas da OC apresentaram diferença significativa (p<0,05) entre si, nos quatro momentos. O ICTP, um marcador específico da reabsorção óssea, não apresentou diferença significativa entre os momentos. Provavelmente o remodelamento ósseo foi provocado pelo estado hipertireóideo, visto que tanto a OC como o ICTP apresentou forte correlação positiva com a TT4 e um pouco inferior com a FT4. A FT4 não apresentou correlação positiva com o ICTP, excetuando-se aos 28 dias. Observou-se baixa correlação, em todos os momentos, entre os marcadores do metabolismo ósseo e a densidade mineral óssea. Conclui-se que o excesso dos hormônios tireoidianos em gatos provocou aumento do remodelamento ósseo visto que ocorreu alta correlação entre estes hormônios e os marcadores do metabolismo ósseo. O hipertireoidismo provocou diminuição da DMO óssea, porém a OC e o ICTP apresentaram baixa correlação com esta variável. / The effect of experimental hyperthyroidism (150 g/kg/day/42 days) on calcium homeostasis and markers of bone metabolism was studied in fourteen shorthair cats from one to three years of age. Serum concentrations of unbroken PTH had a clear tendency to increase from beginning with significant differences from the initial to other moments. The ionized calcium significantly decreased at the 14 days in comparison to the initial moment and at the 42 days in comparison to the 14 days. The thyroid hormones showed positive correlation with PTH and negative with ionized calcium. In contrast, bone mineral density had a tendency of negative correlation with the PTH from the 28 days. Negative correlation of the PTH and calcium ionized was observed at 14, 28 and 42 days. In the present study, hyperthyroidism in young adult cats without concomitant illnesses did not present secondary hyperparathyroidism. However, increase of PTH and reduction of ionized calcium were observed. Serum concentrations of osteocalcin (OC) were significantly different among all four moments. The carboxi-terminal telopeptides of collagen type I (ICTP), a specific marker of the bone reabsorption, did not significantly differ (p<0.05) between moments. Bone turnover was probably caused by the hyperthyroid state, since OC and ICTP presented strong positive correlation with TT4 and a little less with free T4 (FT4). The FT4 did not present positive correlation with the ICTP, excepting at the 28 days. Positive correlation in all the moments between markers of bone metabolism and bone mineral density was very low. In conclusion, the high correlation between thyroid hormones and markers of bone metabolism indicates that the excess of thyroid hormones in cats may cause an increase of the bone turnover. Moreover, hyperthyroidism may cause reduction of the bone DMO, although OC and the ICTP had low correlation with DMO.

Orientador: Lucy Marie Ribeiro Muniz / Resumo: Os efeitos do hipertireoidismo experimental (150 g/kg/dia/42 dias) na homeostase do cálcio e nos marcadores do metabolismo ósseo foram estudados em 14 gatos sem raça definida, com idade entre um e três anos. Houve uma clara tendência de aumento das concentrações séricas de PTH intacto a partir do momento inicial com diferença significativa entre este e os demais momentos. O cálcio ionizado demonstrou uma diminuição significativa aos 14 dias em relação ao momento inicial e aos 42 dias em relação aos 14 dias. Os hormônios tireoidianos apresentaram correlação positiva com o PTH e negativa com o cálcio ionizado. Já a densidade mineral óssea (DMO) apresentou tendência de correlação negativa com o PTH a partir dos 28 dias. Observou-se correlação negativa do PTH com o cálcio ionizado aos 14, 28 e 42 dias. Conclui-se que o hipertireoidismo em gatos adultos jovens sem doenças concomitantes apresenta hiperparatireoidismo secundário. As concentrações séricas da OC apresentaram diferença significativa (p<0,05) entre si, nos quatro momentos. O ICTP, um marcador específico da reabsorção óssea, não apresentou diferença significativa entre os momentos. Provavelmente o remodelamento ósseo foi provocado pelo estado hipertireóideo, visto que tanto a OC como o ICTP apresentou forte correlação positiva com a TT4 e um pouco inferior com a FT4. A FT4 não apresentou correlação positiva com o ICTP, excetuando-se aos 28 dias. Observou-se baixa correlação, em todos os momentos, entre os marcadores do metabolismo ósseo e a densidade mineral óssea. Conclui-se que o excesso dos hormônios tireoidianos em gatos provocou aumento do remodelamento ósseo visto que ocorreu alta correlação entre estes hormônios e os marcadores do metabolismo ósseo. O hipertireoidismo provocou diminuição da DMO óssea, porém a OC e o ICTP apresentaram baixa correlação com esta variável. / Abstract: The effect of experimental hyperthyroidism (150 g/kg/day/42 days) on calcium homeostasis and markers of bone metabolism was studied in fourteen shorthair cats from one to three years of age. Serum concentrations of unbroken PTH had a clear tendency to increase from beginning with significant differences from the initial to other moments. The ionized calcium significantly decreased at the 14 days in comparison to the initial moment and at the 42 days in comparison to the 14 days. The thyroid hormones showed positive correlation with PTH and negative with ionized calcium. In contrast, bone mineral density had a tendency of negative correlation with the PTH from the 28 days. Negative correlation of the PTH and calcium ionized was observed at 14, 28 and 42 days. In the present study, hyperthyroidism in young adult cats without concomitant illnesses did not present secondary hyperparathyroidism. However, increase of PTH and reduction of ionized calcium were observed. Serum concentrations of osteocalcin (OC) were significantly different among all four moments. The carboxi-terminal telopeptides of collagen type I (ICTP), a specific marker of the bone reabsorption, did not significantly differ (p<0.05) between moments. Bone turnover was probably caused by the hyperthyroid state, since OC and ICTP presented strong positive correlation with TT4 and a little less with free T4 (FT4). The FT4 did not present positive correlation with the ICTP, excepting at the 28 days. Positive correlation in all the moments between markers of bone metabolism and bone mineral density was very low. In conclusion, the high correlation between thyroid hormones and markers of bone metabolism indicates that the excess of thyroid hormones in cats may cause an increase of the bone turnover. Moreover, hyperthyroidism may cause reduction of the bone DMO, although OC and the ICTP had low correlation with DMO. / Doutor

Το αξιόπιστο πειραματικό μοντέλο της ωοθηκεκτομής σε επίμυες εφαρμόστηκε για τη μελέτη των παθογενετικών μηχανισμών της οστεοπόρωσης. Σκοπός της παρούσας διδακτορικής διατριβής ήταν η διερεύνηση του ρόλου της λεπτίνης και των κυτοκινών RANKL και οστεοπροτεγερίνης (OPG) στην εξέλιξη της οστεοπόρωσης. Για την διεκπεραίωση της μελέτης χρησιμοποιήθηκαν 40 ενήλικοι θηλυκοί επίμυες ηλικίας 9 μηνών. Πριν την ωοθηκεκτομή στους επίμυες εφαρμόστηκε η τεχνική της ποσοτικής υπολογιστικής τομογραφίας (pQCT) παράλληλα με την πρωτοποριακή μη επεμβατική τεχνική του θερμοδυναμικού συντελεστή εσωτερικής απόσβεσης (MDF) ώστε να διαπιστωθεί η κατάσταση της οστικής πυκνότητας των πειραματόζωων. Σε χρονικά διαστήματα 20, 40 και 60 ημερών μετά την ωοθηκεκτομή πραγματοποιήθηκαν τυχαίες ομαδικές θυσίες με σκοπό τη συλλογή αίματος και την απομόνωση μηριαίων οστών και οστών κνήμης. Την 60η ημέρα πριν τη θυσία στην τελευταία ομάδα των ωοθηκεκτομήθέντων επίμυων επαναλήφθηκαν οι μετρήσεις pQCT και MDF για να διαπιστωθεί η εγκατάσταση σοβαρής οστεοπόρωσης με τη λήξη της πειραματικής πορείας. Οι οροί αίματος που συλλέχθηκαν από όλα τα χρονικά πειραματικά σημεία χρησιμοποιήθηκαν για τη διερεύνηση των επιπέδων έκφρασης των βιοχημικών δεικτών του οστικού μεταβολισμού NTx και οστεοκαλσίνης καθώς και της ελεύθερης λεπτίνης με την τεχνική της ενζυμικής ανοσοπροσρόφησης (ELISA). Στα οστά της κνήμης εφαρμόστηκε η τεχνική της ιστομορφομετρίας για τη μελέτη των μεταβολών της μικροαρχιτεκτονικής δομής των οστών κατά την εξέλιξη της οστεοπόρωσης. Επιπρόσθετα η τεχνική της ανοσοϊστοχημείας εφαρμόστηκε στα οστά της κνήμης για τη διερεύνηση των μεταβολών που προκαλεί η ωοθηκεκτομή στα επίπεδα έκφρασης του υποδοχέα της λεπτίνης και των κυτοκινών RANKL και οστεοπροτεγερίνης στους οστικούς κυτταρικούς πληθυσμούς. Στα μηριαία οστά εφαρμόστηκαν οι τεχνικές της ηλεκτροφόρησης σε πηκτή πολυακρυλαμιδίου (SDS-PAGE electrophoresis) και του ανοσοστυπώματος (Western Blot) για να συλλεχθούν επιπλέον πληροφορίες σχετικά με τις μεταβολές στα επίπεδα έκφρασης του υποδοχέα της λεπτίνης και των κυτοκινών RANKL και οστεοπροτεγερίνης κατά την εξέλιξη της οτεοπόρωσης. Τα συμπεράσματα που διεξάγονται από τα επιμέρους πειραματικά δεδομένα επιβεβαιώνουν την υπόθεση ότι η λεπτίνη κατέχει σημαντικό ρόλο στη ρύθμιση του οστικού μεταβολισμού και συμμετέχει ενεργά μέσω κάποιου άγνωστου μέχρι στιγμής μηχανισμού στη διαδικασία της οστικής ανακατασκευής στην οστεοπόρωση. Όσον αφορά τις ρυθμιστικές κυτοκίνες της οστεοκλαστογένεσης RANKL και OPG, διαπιστώθηκε ότι μεταβάλλονται σημαντικά κατά την εξέλιξη της οστεοπόρωσης στους ωοθηκεκτομηθέντες επίμυες, υποδηλώνοντας τη σημαντικότητα του ρόλου τους στον οστικό μεταβολισμό. / Ovariectomy in mature rats mimics the changes in bone metabolism observed in postmenopausal women and results in osteoporosis. The aim of this thesis was to investigate the role of leptin and the cytokine RANKL and Osteoprotegerin (OPG) in the progression of ovariectomy-induced osteoporosis. Nine–month-old female Wistar rats were bilaterally ovariectomized (n=40). Before the operation, pQCT and MDF technology were applied on rats in order to estimate the bone mineral density of the animals. On days 20, 40 and 60 after the operation the rats were randomly sacrificed and blood samples, dissected knees and femurs were collected. On day 60, pQCT and MDF techniques were applied in order to confirm the establishment of severe osteoporosis until the end of the experimental procedure. Leptin, and the biochemical markers of bone metabolism, osteocalcin and NTx, were measured in blood serum from all time points, by an ELISA method. Bone sections from the knees of the rats were examined by histomorphometric techniques in order to investigate the alterations in the micro-architectural structure of the skeleton caused by ovariectomy. Furthermore, immunohistochemistry was applied on knee sections and SDS-PAGE electrophoresis and western blot techniques were performed in femur homogenized tissueς, in order to investigate whether the expression levels of leptin receptor, RANKL and OPG were altered during the progression of osteoporosis. The results indicate that leptin is involved in the molecular mechanisms of bone remodeling in osteoporosis. The regulators of osteoclastogenesis, RANKL and OPG are also important players in the field of bone metabolism