The calcium endocrine system of adolescent rhesus monkeys and controls before and after spaceflight

Abstract

. The calcium endocrine system of adolescent rhesus monkeys and controls before and after spaceflight. Am J Physiol Endocrinol Metab 282: E514-E521, 2002; 10.1152/ajpendo.00299.2001.-The calcium endocrine system of nonhuman primates can be influenced by chairing for safety and the weightless environment of spaceflight. The serum of two rhesus monkeys flown on the Bion 11 mission was assayed pre-and postflight for vitamin D metabolites, parathyroid hormone, calcitonin, parameters of calcium homeostasis, cortisol, and indexes of renal function. Results were compared with the same measures from five monkeys before and after chairing for a flight simulation study. Concentrations of 1,25-dihydroxyvitamin D were 72% lower after the flight than before, and more than after chairing on the ground (57%, P Ͻ 0.05). Decreases in parathyroid hormone did not reach significance. Calcitonin showed modest decreases postflight (P Ͻ 0.02). Overall, effects of spaceflight on the calcium endocrine system were similar to the effects of chairing on the ground, but were more pronounced. Reduced intestinal calcium absorption, losses in body weight, increases in cortisol, and higher postflight blood urea nitrogen were the changes in flight monkeys that distinguished them from the flight simulation study animals. rhesus monkey; 1,25-dihydroxyvitamin D EXPERIMENTS CONDUCTED on the Russian biosatellite missions have contributed a great deal of information on the effects of spaceflight on bone in the primate. Although each mission was limited to the participation of only two nonhuman primates in orbit for ϳ2 wk, the effects of microgravity on bone were evaluated by biopsies after the flight (38, 39). As well, exercise activity, which may confound the interpretation of bone responses, was controlled during the flight. Reduced mechanical stress is known to depress new bone formation in localized areas of the skeleton at any age (2) and to stimulate bone resorption in the mature skeleton (18,40). The role of the calcium endocrine system in this response of bone tissue has been studied through the analyses of blood samples acquired during ground-based simulations (2, 17, 40) and spaceflight (23, 30). Smith et. al (30) note in their detailed listing of human spaceflight results that the two major calcemic hormones, parathyroid hormone and 1,25-dihydroxyvitamin D, were suppressed and that calcitonin was unchanged. Decreases in parathyroid hormone are initiated by the release of calcium, not always detectable as an increase in serum, from an unloaded skeletal site. Suppressed parathyroid hormone would operate to reduce osteoclastic resorption and bone loss directly and indirectly by reduced intestinal absorption of calcium through decreases in the production of the vitamin D hormone. Collectively, these observations in humans place the calcium endocrine system in a role that responds to the biomechanical effects of weightlessness on bone that initiates increased resorption and decreased formation at different skeletal sites.In juvenile monkeys, pre...

Melatonin is a potential drug for the prevention of bone loss during space flight

“…This is the first report of the suppression of Calcitonin expression in bone tissues under microgravity conditions. Consistent with our findings, the serum CALCITONIN in monkeys exhibited modest decreases during space flight, while in humans, the blood CALCITONIN levels decreased during 120 days of head‐down tilt bed rest . Therefore, the suppression of CALCITONIN could play a key role in enhancing bone resorption during space flight.…”

Energy Restriction Reduces Fractional Calcium Absorption in Mature Obese and Lean Rats

“…Because elevated levels of glucocorticoid hormones are a risk factor for bone loss (31,32) and have recently been shown to be associated with calcium absorption (15), this may be one important mediator of the negative effects of weight reduction on calcium and bone metabolism.…”

“…In addition, intestinal Ca absorption is influenced by serum E 2 (12)(13)(14), and E 2 may decline with EnR (5,6), but the relationship between EnR, E 2 and Ca absorption is not known. Finally, there may also be an association between weight loss, increased glucocorticoids and decreased calcium absorption (15). We hypothesized that EnR in mature lean and obese rats would decrease Ca absorption and that this could be explained by changes in bone-regulating hormones.…”

Εκτίμηση Της Επίπτωσης Πρωτεϊνικού Και Θερμιδικού Υποσιτισμού Σε Ασθενείς Με Οστεοπορωτικά Κατάγματα Του Ισχίου

“…Είναι σημαντικό να τονιστεί ότι η συγκέντρωση IGF-I ορού είναι αντιστρόφως ανάλογη της κοιλιακής λιπώδους μάζας πριν και κατά τη διάρκεια της απώλειας σωματικού βάρους 157. Συγκεντρωτικά οι υπάρχουσες μελέτες στο αντικείμενο καταλήγουν στο συμπέρασμα ότι υπάρχει συσχέτιση ανάμεσα στον ενεργειακό περιορισμό και στην αυξημένη συγκέντρωση κορτιζόλης με τα τεκμηριωμένα αρνητικά συνεπακόλουθα στα οστεοκύτταρα και στην απορρόφηση του ασβεστίου 158,163. Πρωτεϊνική πρόσληψη και σκελετική υγεία σε ηλικιωμένα άτομα Υπάρχει έντονη ερευνητική δραστηριότητα στον τομέα της επίδρασης της χαμηλή πρωτεινικής πρόσληψης πρώτον στον οστικό μεταβολισμό και δεύτερον στον κίνδυνο εμφάνισης κατάγματος ισχίου.…”

“…Οι περισσότερες εργασίες στο αντικείμενο καταδεικνύουν ότι μείωση της ενεργειακής πρόσληψης οδηγεί σε υπερανδρενοκορτικισμό. 134,160,161,162 Στις εργασίες όπου πραγματοποιήθηκε ενεργειακός περιορισμός προκλήθηκε αύξηση της κορτιζολης ούρων, και στις περισσότερες αλλά όχι σε όλες αύξηση της κορτιζόλης ορού (ενδεχομένως τα μη συμβατά αποτελέσματα με την υπόθεση της αρνητικής συσχέτισης ενεργειακού περιορισμού και αύξησης κορτιζόλης ορού να οφείλονται σε διαφορές στο χρόνο μέτρησης κορτιζόλης163,164,165,166,167,168,169 .και στα δύο φύλα 176,177,178. Σε νοσηλευόμενους ηλικιωμένους, η χαμηλή πρόσληψη πρωτεΐνης σχετίζεται με μειωμένη οστική πυκνότητα ισχίου και μειωμένη λειτουργικότητα.…”