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Journal ArticleDOI

3H-tetracycline as a proxy for 41Ca for measuring dietary perturbations of bone resorption

TL;DR: To better understand (41)Ca technology as a tool for measuring effective treatments on reducing bone Resorption, perturbed bone resorption by manipulating dietary calcium in rats and found that a single dose is feasible to study bone resOrption.

AbstractOur group is interested in evaluating early effects of dietary interventions on bone loss. Postmenopausal women lose bone following reduction in estrogen which leads to increased risk of fracture. Traditional means of monitoring bone loss and effectiveness of treatments include changes in bone density, which takes 6 months to years to observe effects, and changes in biochemical markers of bone turnover, which are highly variable and lack specificity. Prelabeling bone with 41Ca and measuring urinary 41Ca excretion with accelerator mass spectrometry provides a sensitive, specific, and rapid approach to evaluating effectiveness of treatment. To better understand 41Ca technology as a tool for measuring effective treatments on reducing bone resorption, we perturbed bone resorption by manipulating dietary calcium in rats. We used 3H-tetracycline (3H-TC) as a proxy for 41Ca and found that a single dose is feasible to study bone resorption. Suppression of bone resorption, as measured by urinary 3H-TC, by dietary calcium was observed in rats stabilized after ovariectomy, but not in recently ovariectomized rats.

Topics: Bone resorption (67%), Bone density (67%), Bone remodeling (66%), Ovariectomized rat (53%)

Summary (1 min read)

1. Introduction

  • Osteoporosis, a disease that is characterized by low bone mass, warrants attention.
  • Therefore, high dietary calcium reduces bone remodeling, which results in an immediate reduction in fracture risk before any changes in bone mass or bone balance are detected [6].
  • Therefore, there is a need for a more sensitive but yet direct method of assessing bone status in response to treatments.

2. Experimental

  • Sixty-four ovariectomized (OVX) 6-month-old rats were purchased from Harlan (Indianapolis, IN).
  • Rats were randomized to receive either 0.2% calcium or 0.5% dietary calcium treatment.
  • SAS statistical software (version 8.0, SAS Institute, Cary, NC) was used for all analyses.
  • Constant variance and normality assumptions were improved when 3H-TC in bone and urine was transformed by taking the log of the original data.

3. Results and discussion

  • The effect of calcium intake on calcium balance over time is shown in Fig.
  • Calcium retention differed between rats fed high and low calcium intakes in the rats stabilized to OVX, but in the early OVX rats, effects of loss of estrogen on bone resorption outweighed effects due to dietary calcium.
  • Others [14,15] have also demonstrated changes in urinary 3H-TC levels in an acute setting during dietary interventions that lasted for 10 days.
  • The authors are unable to resolve whether the effects of dietary calcium on bone turnover are transcient or chronic.

Acknowledgments

  • The authors thank Dr. Alan York (Purdue University, USA) for supplying Dermastid beetles, Ania Kempa-Steczko, Pamela Lachcik, Mary Larimore, and Doug Maish for their technical assistance.
  • This project was partially supported by NIH project P50 AT00477-01 and the Purdue botanicals research center.

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Purdue University
Purdue e-Pubs
Botanicals Research Center Publications Botanicals Research Center
6-1-2007
³H-tetracycline as a proxy for ⁴¹Ca for measuring
dietary perturbations of bone resorption
Connie Weaver
Purdue University - Main Campus
Jennifer Cheong
Purdue University - Main Campus
George Jackson
Purdue University - Main Campus
David Elmore
Purdue University - Main Campus
George McCabe
Purdue University - Main Campus
See next page for additional authors
Follow this and additional works at: hp://docs.lib.purdue.edu/brc
is document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu for
additional information.
Weaver, C.M., Cheong, J., Jackson, G., Elmore, D., McCabe, G., Martin, B. ³H-tetracycline as a proxy for ⁴¹Ca for measuring dietary
perturbations of bone resorption. Nuclear Instruments and Methods in Physics Research 259:1, 790-795, 2007.

Authors
Connie Weaver, Jennifer Cheong, George Jackson, David Elmore, George McCabe, and Berdine Martin
is article is available at Purdue e-Pubs: hp://docs.lib.purdue.edu/brc/1

3
H-tetracycline as a proxy for
41
Ca for measuring dietary
perturbations of bone resorption
Connie Weaver
a,
*
, Jennifer Cheong
a
, George Jackson
b
, David Elmore
b
,
George McCabe
c
, Berdine Martin
a
a
Department of Foods and Nutrition, Purdue University, 700 W. State Street, West Lafayette, IN 47906-2059, USA
b
PRIME Lab, Purdue University, West Lafayette, IN, USA
c
Statistics, Purdue University, West Lafayette, IN, USA
Available online 8 February 2007
Abstract
Our group is interested in evaluating early effects of dietary interventions on bone loss. Postmenopausal women lose bone following
reduction in estrogen which leads to increased risk of fracture. Traditional means of monitoring bone loss and effectiveness of treatments
include changes in bone density, which takes 6 months to years to observe effects, and changes in biochemical markers of bone turnover,
which are highly variable and lack specificity. Prelabeling bone with
41
Ca and measuring urinary
41
Ca excretion with accelerator mass
spectrometry provides a sensitive, specific, and rapid approach to evaluating effectiveness of treatment. To better understand
41
Ca tech-
nology as a tool for measuring effective treatments on reducing bone resorption, we perturbed bone resorption by manipulating dietary
calcium in rats. We used
3
H-tetracycline (
3
H-TC) as a proxy for
41
Ca and found that a single dose is feasible to study bone resorption.
Suppression of bone resorption, as measured by urinary
3
H-TC, by dietary calcium was observed in rats stabilized after ovariectomy, but
not in recently ovariectomized rats.
Ó 2007 Elsevier B.V. All rights reserved.
PACS: 82.80.Ms; 87.58.Xs; 82.39.Rt
Keywords: Calcium; Bone; Rats;
41
Ca
1. Introduction
Osteoporosis, a disease that is characterized by low bone
mass, warrants attention. In 2002, the estimated national
direct expenditure for osteoporotic hip fractures was
$18 billion. It is projected that the number of people with
osteoporosis will increase from 10,100,000 in 2002 to
12,000,000 an d 13,900,000 in 2010 and 2020, respectively
[1]. Consequences of osteoporosis are potentially fatal as
an average of 24% of hip fracture in patients aged 50 and
over usually die within a year following fracture [1]. Man-
agement of osteoporosis is crucial because there are treat-
ments, but no cure, for the disease.
There are various ways to manage osteoporosis, includ-
ing medications such as bisphosphonates and hormone
therapy, as well as dietary means such as calcium and vita-
min D supplementation. There is a large body of evidence
to indicate that calcium supplementation has beneficial
effects on bone during the entire life span. During child-
hood and adolescence, calcium increases bone acquisition
that may ultimately protect against low bone mass an d
fracture later in life. It has been calculated from a meta-
bolic balance study that an increase of calcium intake from
an average of 920 mg/d to 1300 mg/d during adolescence
would increase net calcium retention by 112 mg/d [2]. This
translates to an additional 4% of skeletal mass accrual over
1 year if the increase in dietary calcium were maintained.
During adulthood, dietary calcium supplementatio n
reduces fractures and slows down age-related bone loss,
0168-583X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.nimb.2007.02.004
*
Corresponding author. Tel.: +1 765 494 8237; fax: +1 765 494 0674.
E-mail address: weavercm@purdue.edu (C. Weaver).
www.elsevier.com/locate/nimb
Nuclear Instruments and Methods in Physics Research B 259 (2007) 790–795
NIM
B
Beam Interactions
with Materials & Atoms

possibly by replacing the daily excretory and cutaneous
losses that would otherwise have drained skeletal calcium.
The importance of adeq uate dietary calcium during adult-
hood has also been shown through an increase in bone
mineral density when hormone therapy was administered
in the presence of sufficient calcium [3].
The mechanism by which calcium exerts a positive
effect on bone has been examined by kinetic studies. In a
randomized, cross over, study of calcium kinetics in adoles-
cent girls, the increased retention seen on a high calcium
diet (47.5 ± 3.9 mmol/day) versus a low calcium diet
(21.5 ± 2.0 mmol/day) was due to an increase in absorbed
calcium and suppression of bone resorption without affect-
ing bone formation [4]. This is in contrast to another kinet-
ics study in normal adults that assessed the response in
calcium metabolism to dietary calcium perturbation [5].
In this study, a high dietary calcium intake did not result
in an increase in absorbed calcium for all the subjects.
However, when absorbed calcium increased in some
subjects, bone resorption was decreased, while renal and
gastrointestinal calcium clearance were increa sed. A low
calcium intake (0.2 g/day) resulted in a reduction of
absorbed calcium, an increase in bone resorption rate,
and a decrease in renal and gastrointestinal rate constants,
possibly suggesting that an increase in parathyroid hor-
mone (PTH) is the common mediating factor since PTH
exerts its action on the kidney, intestine, and bone.
There is emerging evidence that calcium functions as an
indirect regulator of remodeling of the skeleton [6]. During
bone remodeling, the bone mineral that is being released
after bone is resorbed is either recycled or used to counter-
balance excretory losses. When dietary calcium intake is
low for a prolonged period of time, bone remodeling con-
tinues to be high, resulting in an increase in bone fragility.
Therefore, high dietary calcium reduces bone remodeling,
which results in an immediate reduction in fracture risk
before any changes in bone mass or bone balance are
detected [6].
Calcium status is a crucial factor in determining bone
health and fracture risk. Calcium status is difficult to assess
because serum calcium levels are tightly controlled. Bone
mineral content (BMC) measured by dual X-ray absorpt i-
ometry (DXA) is a proxy for cumulative calcium status
because 99% of the body’s calcium is in the bones. Indirect
measures of bone metabolism which impinge on calcium
status include bone biochemical markers of turnover that
measure substances that are relea sed by osteoblasts and
osteoclasts, as well as substances produced during the for-
mation or breakdown of collagen, a main protein found in
bone. Although DXA is considered the gold standar d for
assessing bone status, it is limited by the long lag time that
is required between measurements (6 months to years ) in
order to show changes in bone mineral density (BMD)
and BMC. In addition, biochemical markers of bone turn-
over have huge variation. Therefore, there is a need for a
more sensitive but yet direct method of assessing bone sta-
tus in response to treatments. A direct method for assessing
release of calcium from the skeleton uses a calcium isotopic
tracer to assess bone changes in response to treatments.
However, some calcium isotopic tracers have limitations
for use in humans due to their short half life or radioactive
nature. Fortunately,
41
Ca has a long half life of 100,000
years and is safe for use in humans due to the low level
of radioactivity required. Recently,
41
Ca has been proposed
as a tool in bone research [7]. However, there is much to
learn about designing studies and interpreting data for
optimizing
41
Ca technology as a tool for assessing bone
metabolism. In order to further our understanding of
41
Ca technology, we utilized
3
H-tetracycline (
3
H-TC) as a
proxy for
41
Ca in an animal study, with the ultimate goal
of developing the use of urinary
41
Ca appearance from
bone to directly measure bone resorption in humans. Previ-
ous studies have shown that upon injection of
3
H-TC in
animals, it chelates with calcium and is incorporated into
the skeleton. During bone resorption,
3
H-TC is released
in a form that cannot be reincorporated into the skeleton
[8]. Thus, urinary
3
H-TC is thought to reflect bone
resorption.
The aim of our study was to use a single
3
H-TC injec-
tion, as a proxy for
41
Ca, to understand timing of label
incorporation and release when bone resorption was
manipulated by dietary calcium.
2. Experimental
Sixty-four ovariectomized (OVX) 6-month-old rats were
purchased from Harlan (Indianapolis, IN). All the rats
were fed an AIN 93 M diet [9] (Dyets Inc., Bethlehem,
PA) during the acclimation period at our animal research
facility. This is a standard semi-purified diet that uses
casein as the protein source and meets nutrient require-
ments except as adjusted for calcium. Each rat was dosed
with 30 uCi of
3
H-TC. The early OVX rats were dosed with
3
H-TC within 1 month after OVX while the OVX stabilized
rats were dosed 3 months after OVX. Rats were random-
ized to receive eithe r 0.2% calcium or 0.5% dietary calcium
treatment. The recommended calcium intake is 0.5% which
is the level in the standard diet and serves as the control.
The 0.2% calcium intake was selected to be marginally defi-
cient without inducing weight loss. Within each dietary cal-
cium level, rats were further randomized according to time
of sacri fice (1 week, 1 month, 3 months, or 6 months).
There was no difference in average baseline weight among
groups. Urine and feces were collected for 2–4 days at 1
week, 1 month, 3 months, and 6 months post dose. Imme-
diately after collection, urine samples were centrifuged at
4000 RPM for 20 min. The supernatants were stored in a
20 °C freezer. After all the metabolic collections for the
entire study were completed, urine samples were thawed
at room temperature and centrifuged again at 3000 RPM
for 20 min. The supernatants were analyzed for calcium
and
3
H-TC content. Feces were ashed for 4 days at
600 °C, diluted with 0.5% Lanthan ium Chloride to 25 mL
and analyzed for calcium. Whole skeletons were recovered
C. Weaver et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 790–795 791

by using Dermastid beetles (provided by Dr. Alan York,
Entomology Department, Purdue University) as described
by Hefti et al. [10] after the rats were sacrificed. The skele-
tons were separated into cortical-rich midshaft femur, tra-
becular-rich proximal tibia and L1-4, and the rest of the
skeleton. Bones were digested with nitric acid and brought
up to volume with nitric acid for the assessment of percent
3
H-TC present and
3
H-TC labeling efficiency. Total cal-
cium in bone, urine, and feces was measured by atomic
absorption spectrophotometry as previously described [4]
(A Analyst 300, Perkin Elmer). Urinary and skeletal
3
H-
TC content were measured by scintillation counting (LS
6500, Beckman Coulter Inc., Fullerton, CA) using a single
labeled disintegration per minute (DPM) program.
Calcium balance was determined as follows:
Calcium balance ¼ Dietary calcium intake ðurinary
þ fecal calcium excretionÞ
Percent calcium retention was determined as:
100% Calcium balance=Dietary calcium intake
Percent
3
H-TC present in bone was calculated as:
100%
3
H-TC in boneðdpmÞ=
3
H-TC dose given to ratðdpmÞ
3
H-TC labeling efficiency in bone was calculated as:
Percent
3
H-TC in bone=Calcium content in boneðgramsÞ
Bone mineral density (BMD) was determined by dual
energy X-ray absorpt iometry (Lunar DPX IQ 5455, Mad-
ison, WI) at the start of the study and again before sacrifice
at 1 week, 1 month, 3 months, and 6 months post dose to
assess change in BMD and total bone calcium. This study
was approved by the Purdue Animal Care and Use
Committee.
SAS statistical software (version 8.0, SAS Institute,
Cary, NC) was used for all analyses. Data were report ed
as mean ± standard deviation, unless otherwise indicated.
Urinary
3
H-TC, calcium balance, and percent calcium
retention were compared at all time points by repeated
measures analysis of va riance with multiple comparisons
of the means using Tukey’s test. Constant variance and
normality assumptions were improved when
3
H-TC in
bone and urine was transformed by taking the log of the
original data. Therefore, all analyses for
3
H-TC in bone
and urine were based on log transformed data. Tukey’s test
was used for multiple comparisons when the differences in
mean were significant. p values less than 0.05 were consid-
ered statistically significant.
3. Results and discussion
The effect of calcium intake on calcium balance over
time is shown in Fig. 1. In an overall statistical model, rats
that were fed the 0.5% calcium diet had significantly higher
calcium balance (p < 0.005) and percent calcium retention
(p = 0.052) up to 6 months post dose, but this was driven
by the rats stabilized to ovariectomy, as no time point
was statistically significant in the early OVX rats. Rats
fed adequate calcium were in net positive balance, whereas
rats fed low calcium intakes were in negative balance at
1 month and in positive balance by 3 months. Rats fed
the 0.5% calcium diet excreted more calcium in the urine
and feces than rats fed the 0.2% calcium diet. Calcium
excretion over time is shown in Fig. 2. Rats fed the 0.5%
calcium diet consumed 2.5 times more calcium and
excreted approximately 2.5 times more calcium in the feces
and 1.4 times more calcium in the urine than rats fed the
0.2% calcium. Urinary calcium loss accounted for 3–6%
of calcium intake in rats.
Bone resorption, as measured by urinary
3
H-TC, is
shown in Fig. 3. At 1 month post dose, higher calcium
intakes significantly (p = 0.013) suppressed bone resorp-
tion in the OVX stabilized rats. The lack of a significant
difference in urinary
3
H-TC due to calcium intake at 6
months (p = 0.2) despite a greater difference in means than
at 1 month, which was statistically significant, was
undoubtedly due to loss of power as rats were sacrificed
Early OVX rats
-5
0
0123456
0123456
5
10
15
20
25
30
Months post dose
0.2% Ca
0.5% Ca
Calcium balance (mg/d)
P= 0.37 81
P= 0.20 13
P=0.2013
OVX stabilized rats
*
*
-5
0
5
10
15
20
25
30
35
40
Months
p
ost dose
Calcium balance (mg/d)
0.2% Ca
0.5% Ca
P=0.1683
P= 0.00 57
P=0.5 96 3
Fig. 1. Effects of the level of dietary calcium on calcium balance (mg
calcium/day) in early OVX and OVX stabilized rats. Each line represents
the mean ± SD values of 4–16 rats, depending on the time of urine and
feces collection. Asterisks indicate dietary calcium effect *p < 0.05.
792 C. Weaver et al. / Nucl. Instr. and Meth. in Phys. Res. B 259 (2007) 790–795

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Abstract: Both hormone replacement therapy (HRT) and bisphosphonates are efficacious in the prevention and treatment of postmenopausal osteoporosis. Combined therapy with bisphosphonate and HRT is likely to be used in clinical practice, and limited data are available regarding its efficacy and safety. This was a 1-yr, double blind, placebo-controlled study in which 524 postmenopausal women received daily treatment with conjugated equine estrogens (0.625 mg) alone or in combination with risedronate (5 mg). Women who had not undergone hysterectomy received medroxyprogesterone acetate (up to 5 mg, daily or cyclically) at the discretion of the investigator. The primary efficacy end point was the percent change from baseline in mean lumbar spine bone mineral density (BMD) at 1 yr. Changes in BMD at the proximal femur and forearm, bone turnover markers, and histology and histomorphometry were also assessed. At 12 months, significant (P < 0.05) increases from baseline in lumbar spine BMD were observed in both treatment gr...

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Abstract: Background Grapes and their associated phytochemicals have been investigated for beneficial effects on cardiovascular health, cancer prevention, and other chronic diseases, but the effect of grape consumption on bone health has not been fully determined. We previously found short-term benefits of grape products on reducing bone turnover in ovariectomized rats. Objective The objective of this study was to determine the long-term benefits of a grape-enriched diet on bone in ovariectomized rats. Methods Rats were ovariectomized at 3 mo of age and were administered a single dose of (45)Ca to prelabel bones at 4 mo of age. After a 1-mo equilibration period, baseline urinary (45)Ca excretion was determined. Rats (n = 22/group) were then randomly assigned to a modified AIN93M diet containing 25% freeze-dried grape powder or to a control diet for 8 wk. Urinary (45)Ca excretion was monitored throughout the study to determine changes in bone (45)Ca retention. Calcium balance was assessed after 1 and 8 wk of consuming the experimental diets, and a calcium kinetic study was performed at 8 wk. After 8 wk, femurs were collected for micro-computed tomographic imaging, 3-point bending, and reference point indentation. Results Rats fed the grape-enriched diet had 44% greater net bone calcium retention than did rats fed the control diet. There were no differences in calcium balance due to diet at either week 1 or week 8, but there was a significant increase in net calcium absorption (10.6%) and retention (5.7%) from week 1 to week 8 in the grape-enriched diet group only. Grape-enriched diet-fed rats had 3% greater cortical thickness and 11% greater breaking strength. There were no differences in femur bone mineral density, trabecular microarchitecture, or reference point indentation variables due to diet. Conclusion This study of ovariectomized rats indicates that the consumption of grape products may improve calcium utilization and suppress bone turnover, resulting in improvements in bone quality.

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01 Jan 2014
TL;DR: This study of ovariectomized rats indicates that the consumption of grape products may improve calcium utilization and suppress bone turnover, resulting in improvements in bone quality.
Abstract: Background: Grapes and their associated phytochemicals have been investigated for beneficial effects on cardiovascular health, cancer prevention, and other chronic diseases, but the effect of grape consumption on bone health has not been fully determined. We previously found short-term benefits of grape products on reducing bone turnover in ovariectomized rats. Objective: The objective of this study was to determine the long-term benefits of a grape-enriched diet on bone in ovariectomized rats. Methods: Rats were ovariectomized at 3 mo of age and were administered a single dose of 45 Ca to prelabel bones at 4 mo of age. After a 1-mo equilibration period, baseline urinary 45 Ca excretion was determined. Rats (n = 22/group) were then randomly assigned to a modified AIN93M diet containing 25% freeze-dried grape powder or to a control diet for 8 wk. Urinary 45 Ca excretion was monitored throughout the study to determine changes in bone 45 Ca retention. Calcium balance was assessedafter 1 and 8 wk with the experimental diets, and a calcium kinetic study was performed at 8 wk. After 8 wk, femurs were collected for micro-computed tomographic imaging, 3-point bending, and reference point indentation. Results: Rats fed the grape-enriched diet had 44% greater net bone calcium retention than did rats fed the control diet. There were no differences in calcium balance due to diet at either week 1 or week 8, but there was a significant increase in net calcium absorption (10.6%) and retention (5.7%) from week 1 to week 8 in the grape-enriched diet group only. Grapeenriched diet‐fed rats had 3% greater cortical thickness and 11% greater breaking strength. There were no differences in femur bone mineral density, trabecular microarchitecture, or reference point indentation variables due to diet. Conclusion: The consumption of grape products may improve calcium utilization and suppress bone turnover, resulting in improvements in bone quality. J Nutr doi: 10.3945/jn.114.198598.

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TL;DR: Two new diets may prove to be a better choice than AIN-76A for long-term as well as short-term studies with laboratory rodents because of a better balance of essential nutrients.
Abstract: For sixteen years, the American Institute of Nutrition Rodent Diets, AIN-76 and AIN-76A, have been used extensively around the world. Because of numerous nutritional and technical problems encountered with the diet during this period, it was revised. Two new formulations were derived: AIN-93G for growth, pregnancy and lactation, and AIN-93M for adult maintenance. Some major differences in the new formulation of AIN-93G compared with AIN-76A are as follows: 7 g soybean oil/100 g diet was substituted for 5 g corn oil/100 g diet to increase the amount of linolenic acid; cornstarch was substituted for sucrose; the amount of phosphorus was reduced to help eliminate the problem of kidney calcification in female rats; L-cystine was substituted for DL-methionine as the amino acid supplement for casein, known to be deficient in the sulfur amino acids; manganese concentration was lowered to one-fifth the amount in the old diet; the amounts of vitamin E, vitamin K and vitamin B-12 were increased; and molybdenum, silicon, fluoride, nickel, boron, lithium and vanadium were added to the mineral mix. For the AIN-93M maintenance diet, the amount of fat was lowered to 40 g/kg diet from 70 g/kg diet, and the amount of casein to 140 g/kg from 200 g/kg in the AIN-93G diet. Because of a better balance of essential nutrients, the AIN-93 diets may prove to be a better choice than AIN-76A for long-term as well as short-term studies with laboratory rodents.

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TL;DR: The primary hypothesis was that continuous administration of conjugated equine estrogen, 0.3 mg/d, combined with medroxyprogesterone, 2.5 mg/D, in elderly postmenopausal women would prevent bone loss in the spine over 3.5 years compared with placebo in the context of adequate calcium and vitamin D nutrition.
Abstract: Background: Hormone replacement therapy (HRT), the mainstay of osteoporosis prevention, is limited because of dose-related risks, side effects, and patient acceptance. The bone-sparing efficacy and tolerability of the lowest available doses of HRT have not been adequately studied in elderly women. Objective: To determine the bone-sparing effect of continuous low-dose HRT in elderly women. Design: Randomized, double-blind, placebo-controlled trial. Setting: University osteoporosis research and clinical center. Patients: 128 healthy white women (age > 65 years) with low bone mass recruited by word of mouth and by local advertisement. The principal eligibility criterion was spinal bone mineral density of 0.90 g/cm 2 or less. Intervention: Continuous therapy with conjugated equine estrogen, 0.3 mg/d, and medroxyprogesterone, 2.5 mg/d, or matching placebo. Sufficient calcium supplementation was given to bring all calcium intakes above 1000 mg/d in both groups; supplemental oral 25-hydroxyvitamin D was given to maintain serum 25-hydroxyvitamin D levels of at least 75 nmol/L in both groups. Measurements: Bone mineral density of the spine, hip, total body, and forearm; serum total alkaline phosphatase and serum osteocalcin levels at 6-month intervals; and 24-hour urine creatinine and hydroxyproline excretion at baseline, 12 months, and 42 months. Results: During 3.5 years of observation, spinal bone mineral density increased by 3.5% (P < 0.001) in an intention-to-treat analysis and by 5.2% among patients with greater than 90% adherence to therapy. Significant increases were seen in total-body and forearm bone density (P < 0.01). Symptoms related to HRT (breast tenderness, spotting, pelvic discomfort, and mood changes) were mild and short-lived. Conclusions: Continuous low-dose HRT with conjugated equine estrogen and oral medroxyprogesterone combined with adequate calcium and vitamin D provides a bone-sparing effect that is similar or superior to that provided by other, higher-dose HRT regimens in elderly women. This combination is well tolerated by most patients.

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Journal ArticleDOI
TL;DR: Calcium enhancement of estrogen's effects now have been clearly demonstrated and all currently approved bone active agents have been tested only in the presence of extra calcium, and newer anabolic agents create a skeletal need for mineral that will require even higher levels of calcium repletion.
Abstract: Calcium and vitamin D are essential for bone maintenance and for treatment-induced bone augmentation. Deficiencies of both nutrients are very common in the age group most afflicted by osteoporosis. Calcium enhancement of estrogen's effects now have been clearly demonstrated. Additionally, all currently approved bone active agents have been tested only in the presence of extra calcium, and newer anabolic agents create a skeletal need for mineral that will require even higher levels of calcium repletion. Prudent nutritional support for osteoporosis prevention and treatment consists of 30 to 40 mmol Ca/d together with sufficient vitamin D to maintain serum 25(OH)D levels above 80 nmol/L (i.e., approximately 25 microg vitamin D/d).

218 citations


"3H-tetracycline as a proxy for 41Ca..." refers methods in this paper

  • ...It has been calculated from a metabolic balance study that an increase of calcium intake from an average of 920 mg/d to 1300 mg/d during adolescence would increase net calcium retention by 112 mg/d [2]....

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Journal ArticleDOI
TL;DR: The combined treatment with risedronate-HRT and HRT had a favorable effect on BMD similar to that of HRT alone at the lumbar spine and slightly, but significantly, greater than that ofHRTalone at the femoral neck and midshaft radius.
Abstract: Both hormone replacement therapy (HRT) and bisphosphonates are efficacious in the prevention and treatment of postmenopausal osteoporosis. Combined therapy with bisphosphonate and HRT is likely to be used in clinical practice, and limited data are available regarding its efficacy and safety. This was a 1-yr, double blind, placebo-controlled study in which 524 postmenopausal women received daily treatment with conjugated equine estrogens (0.625 mg) alone or in combination with risedronate (5 mg). Women who had not undergone hysterectomy received medroxyprogesterone acetate (up to 5 mg, daily or cyclically) at the discretion of the investigator. The primary efficacy end point was the percent change from baseline in mean lumbar spine bone mineral density (BMD) at 1 yr. Changes in BMD at the proximal femur and forearm, bone turnover markers, and histology and histomorphometry were also assessed. At 12 months, significant (P < 0.05) increases from baseline in lumbar spine BMD were observed in both treatment gr...

151 citations


Journal ArticleDOI
TL;DR: It is concluded that calcium supplementation substantially reduces cortical and trabecular bone loss in the years immediately preceding menopause, and although it reduces postmenopausal cortical bone loss to some extent, it does not prevent theMenopause‐related lumbar bone loss.
Abstract: We observed in a controlled 2 year longitudinal trial in 248 perimenopausal women that a daily calcium supplement of either 1000 or 2000 mg Ca2+ significantly reduced lumbar bone loss and bone turnover in the first year of calcium supplementation. In the second supplementation year the rate of lumbar bone loss in the treated subjects was not significantly different from that in the control group, although two of the three biochemical parameters of bone turnover remained decreased throughout the study. To quantify further the long-term effect of calcium supplementation, we extended the study for another year in 214 women. In the women of the control group who were menstruating until the last year of the trial, the mean change in lumbar bone mineral density after 3 years was -3.2% of the initial value versus 1.6% in the calcium-supplemented groups (p < 0.01). The decrease in lumbar bone loss in these supplemented premenopausal and early perimenopausal women remained statistically significant in the second and third years of supplementation. In the women who stopped menstruating before or during the study, the long-term reduction in lumbar bone loss was not significant (mean difference between control and treatment groups < 0.6% points after 3 years). The decrease in metacarpal cortical thickness (MCT) in the treated subjects during 3 years was on average -3.0% of the initial value in the control versus -2.0% in the supplemented subjects (P < 0.01). The effect of calcium supplementation on MCT was not significantly related to the menopausal status of the subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

150 citations


Frequently Asked Questions (2)
Q1. What are the contributions in "3h-tetracycline as a proxy for 41ca for measuring dietary perturbations of bone resorption" ?

The authors used H-tetracycline ( H-TC ) as a proxy for Ca and found that a single dose is feasible to study bone resorption. 

Further research is needed with increased power to evaluate chronic effects of diet on urinary 3H-TC.