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1.
Osteoporos Int ; 22(1): 153-7, 2011 Jan.
Article in English | MEDLINE | ID: mdl-20480145

ABSTRACT

UNLABELLED: Urinary excretion of tritiated tetracycline ((3)H-TC) and (41)Ca tracers was validated as reflecting skeletal disappearance of these bone-seeking tracers as a direct measure of bone turnover following ovariectomy in rats. INTRODUCTION: Tritiated tetracycline ((3)H-TC) and Ca tracers have been used to measure bone resorption in animal models, but urinary excretion of these labels has not been directly compared to skeletal turnover. We aimed to evaluate the use of bone-seeking labels by comparing label release into urine with label in the skeleton when bone turnover was perturbed following ovariectomy. METHODS: Sixty-four 6-month-old ovariectomized (OVX) rats were randomized to one of eight groups in a 2 × 4 design that differed in time of (3)H-TC and (41)Ca administration following ovariectomy (1 month, when bone turnover would be accelerated following estrogen depletion or 3 months when bone loss due to OVX had slowed down) and time of euthanasia (1 week, 1 month, 3 months, and 6 months post-dose). Twenty-four-hour urine pools over two to four consecutive days and total skeleton were collected and recovered for the assessment of (3)H-TC and (41)Ca. RESULTS: Urinary (3)H-TC levels reflected skeletal (3)H-TC levels (r = 0.93; p < 0.0001) over a wide range of bone turnover rates in response to an intervention. Urinary (41)Ca and (3)H-TC excretion were highly correlated (r = 0.95, p < 0.0001). CONCLUSION: This study confirms that bone-seeking label excretion into the urine directly measures bone turnover.


Subject(s)
Biomarkers/urine , Bone Resorption/diagnosis , Animals , Bone Remodeling/physiology , Bone Resorption/etiology , Calcium Radioisotopes/pharmacokinetics , Disease Models, Animal , Female , Femur/metabolism , Lumbar Vertebrae/metabolism , Ovariectomy , Rats , Rats, Sprague-Dawley , Reproducibility of Results , Tetracycline/pharmacokinetics , Tibia/metabolism , Tritium/pharmacokinetics
2.
J Clin Endocrinol Metab ; 92(2): 577-82, 2007 Feb.
Article in English | MEDLINE | ID: mdl-17148567

ABSTRACT

INTRODUCTION: The purpose of this 3-way crossover study was to identify the effective dose of soy protein isolate enriched with isoflavones for suppressing bone resorption in postmenopausal women using a novel, rapid assessment of antibone resorbing treatments. METHODS: Thirteen postmenopausal women (>or=6 yr since menopause) were predosed with 41Ca iv. After a 200-d baseline period, subjects were given 43 g soy protein/d that contained 0, 97.5, or 135.5 mg total isoflavones in randomized order. The soy protein isolate powder was incorporated into baked products and beverages. Each 50-d intervention phase was preceded by a 50-d pretreatment phase for comparison. Serum isoflavone levels and biochemical markers were measured at the end of each phase. Twenty-four-hour urine samples were collected approximately every 10 d during each phase for 41Ca/Ca analysis by accelerator mass spectrometry. RESULTS: Serum isoflavone levels reflected the amount of isoflavones consumed in a dose-dependent manner. None of the isoflavone levels had a significant effect on biochemical markers of bone turnover, urinary cross-linked N teleopeptides of type I collagen and serum osteocalcin, or bone turnover as assessed by urinary 41Ca/Ca ratios. CONCLUSIONS: Soy protein with isoflavone doses of up to 135.5 mg/d did not suppress bone resorption in postmenopausal women. This is the first efficacy trial using the novel technique of urinary 41Ca excretion from prelabeled bone.


Subject(s)
Bone Resorption/drug therapy , Bone Resorption/metabolism , Bone and Bones/metabolism , Isoflavones/administration & dosage , Phytotherapy , Soybean Proteins/administration & dosage , Adult , Calcium/urine , Calcium Radioisotopes/urine , Collagen Type I/urine , Cross-Over Studies , Double-Blind Method , Female , Humans , Middle Aged , Osteocalcin/urine , Peptides/urine , Postmenopause
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