Silvia M. Friedman

Salivary bone turnover markers in healthy pre- and postmenopausal women: daily and seasonal rhythm

No studies had investigated circadian and circannual rhythms of bone biomarkers in whole saliva. We evaluated the salivary daily and seasonal rhythm of carboxy-terminal telopeptide of type I collagen (CTX) and bone alkaline phosphatase (b-ALP). Forty clinical and oral healthy ambulatory pre- and postmenopausal women from two southern Argentine cities: Comodoro Rivadavia (latitude 45º S) and Ushuaia (latitude 54º S) were included in the study. CTX levels were evaluated in serum, urine, and saliva, and b-ALP levels were measured in serum and saliva. In both groups of women, salivary CTX showed a maximum percentage of change early in the morning (80%) and a minimum in the late afternoon (45%), similarly to the pattern observed in urinary samples. No daily rhythm was observed in serum or salivary b-ALP. 25-Hydroxyvitamin D levels decreased in winter vs. summer (p < 0.01) without differences between the two studied groups. Conversely, parathormone reached higher levels in winter (p < 0.05) which induced a slight non-significant increment in salivary CTX and b-ALP levels. The results showed that, as in serum and urinary samples, salivary CTX exhibits daily and a slight seasonal rhythmicity. Whole non-stimulated saliva is a useful tool to detect several oral and systemic diseases because it has important advantages compared to serum and urinary samples. Then, it may also be a promising sample to test changes in bone metabolism contributing to diagnose and to monitor the therapy of several metabolic bone diseases.

BONE MASS RECOVERY OF OSTEOPENIC VITAMIN D INSUFFICIENT RATS FROM STRONTIUM RANELATE TREATMENT: DOES THE RESPONSE DEPEND ON VITAMIN D NUTRITIONAL STATUS OR ON SOURCE OF VITAMIN D (D2 VERSUS D3)?

It was investigated if Vitamin D (Vit D) status or source (Vitamin D2 vs. Vitamin D3) interferes with bone mass recovery from strontium ranelate (SrRa) treatment of rats with Vit D insufficiency and established osteopenia. Osteopenic and Vit D insufficient rats were divided in groups to complete a 105-day period. First experiment: The rats were fed with diets that only varied in Vit D (100 vs. 0 IU%) and/or SrRa (0 vs. 900 mg/kg/day) content. A SHAM group received Vit D throughout the experience. Second experiment: Rats were divided into groups and received Vit D2 or Vit D3 through diet and SrRa by gavages in a fasting state. Two SHAM groups received Vit D2 or Vit D3 throughout the study. Results: Levels of 25-hydroxyvitamin 25OHD were reduced in groups lacking dietary Vit D (p < 0.001). Independently of Vit D status or source, SrRa did not affect body weight gain or bone alkaline phosphatase levels; osteocalcin and C-terminal telopeptide of type I collagen levels were reduced (p < 0.05) and bone Sr content was increased (p < 0.0001). Although no improvement in biomechanical parameters was observed, total skeletal bone mineral content and proximal tibial bone mineral density were increased (p < 0.05). There was a reduction in the trabecular number and an increase in the trabecular surface and bone volume without reaching SHAM levels. Conclusion: This is the first study that examined SrRa effects in an osteopenic vitamin D–insufficient experimental model. Under our experimental conditions, SrRa increased bone Sr content independently of Vit D status or source; however, no evidence of an anabolic or antifracture effect was found, and only a slight decrease in some bone resorption parameters was observed.