title: Effect of calcitriol supplementation and tail suspension on serum biomarkers of bone formation in rats.
abstract: BACKGROUND
  Calcitriol is documented to cause significant increase in bone mass densitometry counteracting osteoporosis. Promising results of calcitriol supplementation in studies aiming space flight induced osteoporosis is little and the effect of this hormone on biomarkers of bone metabolism is not examined yet in space flight models of osteoporosis in rats.
  
  
  METHODS
  This was an interventional animal study being performed in a 1-month period. We included 21 Sprague Dawley strain rats (>200 gr, >6 week) who were randomly assigned to receive daily supplementation of oral 0.03μgr calcitriol and to be submitted to tail suspension model. Rats were followed for 1 month and were tested for serum osteocalcin (OC), alkaline phosphatase (ALP) and serum calcium at the beginning and the end of the study period. The results were analyzed and compared between groups.
  
  
  RESULTS
  Although serum levels of osteocalcin and alkaline phosphatase biomarkers and total serum calcium were not significantly different within and between study groups, their levels were increased in tail suspension model compared to control group. The levels of these biomarkers were lower in those who were submitted to tail suspension model and received calcitriol supplementation compared to those who were only submitted to tail suspension (60.14 ± 11.73 ng/mL vs. 58.29 ± 2.69 ng/mL; p = 0.696 for osteocalcin and 381.86 ± 99.16 mU/mL vs. 362.57 ± 27.41 ng/mL; p = 0.635 for alkaline phosphatase).
  
  
  CONCLUSIONS
  Supplementation of daily diet with calcitriol in rats under weightlessness conditions may results in lower values for bone metabolic biomarkers of alkaline phosphatase and osteocalcin and serum calcium. This pattern of change in biomarkers of bone formation, may point to the capacity of calcitriol supplementation in preventing cellular process of osteoporosis. Thus calcitriol supplementation could be an available, economic and effective strategy for preventing bone metabolic changes related to weightlessness commonly encountered in space flight. The outcome of this study needs to be further studied in future trying to find more definite results.
authors: Diabetes Research Center, Endocrinology and Metabolism Clinical Science Institute, Tehran University of Medical Sciences, Tehran, Iran.
authors: Seyed Jafar
authors: SJ
authors: Hashemian
authors: Department of Neurology, Shiraz University of Medical Sciences, Shiraz, Iran.
authors: Mojtaba
authors: M
authors: Rismanchi
authors: Diabetes Research Center, Endocrinology and Metabolism Clinical Science Institute, Tehran University of Medical Sciences, Tehran, Iran.
authors: Ensiyeh Nasli
authors: EN
authors: Esfahani
authors: Faculty of Aerospace and Sub-Aquatic Medicine, AJA University of Medical Sciences, Tehran, Iran.
authors: Amir
authors: A
authors: Khoshvaghti
authors: Diabetes Research Center, Endocrinology and Metabolism Clinical Science Institute, Tehran University of Medical Sciences, Tehran, Iran.
authors: Farideh
authors: F
authors: Razi
keywords: Alkaline phosphatase (ALP); Calcitriol; Osteocalcin (OC); Tail suspension model; Vitamin D