The diuretic indapamide increases bone mass and decreases bone resorption in spontaneously hypertensive rats supplemented with sodium

Na-Cl Co-transporter (NCC) gene inactivation is associated with improved bone microstructure

Gitelman syndrome (GS) is the disease model of the inactivation of thiazide-sensitive sodium chloride cotransporter (NCC), which is believed to benefit bone mass and reduce fracture risk. In this study, we found that GS patients have superior bone microarchitecture, which is associated with the disease status. Several decreased bone parameters with aging in healthy controls were reversed in GS patients to a certain extent.

PURPOSE

To evaluate the impact of the inactivation of NCC on bone turnover and microarchitecture in Gitelman syndrome patients.

METHODS

A cross-sectional study was conducted in 45 GS patients (25 males and 20 females). Serum procollagen type 1 N-terminal propeptide (P1NP), β-carboxy-terminal crosslinked telopeptide of type 1 collagen (β-CTX), and osteocalcin were measured. High-resolution peripheral quantitative computed tomography (HR-pQCT) was conducted to evaluate bone microarchitecture in GS patients and age- and sex-matched healthy controls. Areal bone mineral density (aBMD) was measured by dual-energy X-ray absorptiometry (DXA) simultaneously.

RESULTS

GS patients had a relatively lower level of β-CTX. aBMD at several skeletal sites was improved in GS patients. HR-pQCT assessment revealed that GS patients had slightly thinner but significantly more compact trabecular bone (increased trabecular number and decreased thickness), notably decreased cortical porosity, and increased volume BMD (vBMD) at both the radius and tibia compared with controls. The disease severity, represented as the relationship with the minimum level of magnesium during the course and standard base excess, was associated with bone microarchitecture parameters after adjusting for age, sex, and BMI. The decreased vBMD and Tb.BV/TV, and increased Tb.Sp and Ct.Po with aging, were reversed in GS patients to a certain extent.

CONCLUSION

GS patients have superior bone microarchitecture, which suggests that the inactivation of NCC might be beneficial for avoiding osteoporosis.

Thiazide and thiazide-like diuretics in nephrolithiasis

Thiazide and thiazide-like diuretics are widely used for the management of hypercalciuria among stone-forming patients. Although the effects of different thiazides should be relatively similar in terms of prevention of stone recurrence, their potency and side effects may differ. However, there is scarce data concerning the metabolic and bone effects of these agents among recurrent nephrolithiasis patients with hypercalciuria. The aim of this update article was to compare our experience in the use of thiazide and thiazide- like diuretics with that of the current literature, concerning their anticalciuric properties and consequent reduction of recurrent stone formation. Their impact on bone mass and potential side effects were also discussed.

The challenges of diagnosis and management of Gitelman syndrome

Gitelman syndrome is an inherited tubulopathy characterized by renal salt wasting from the distal convoluted tubule. Defects in the sodium chloride cotransporter (encoded by SLC12A3) underlie this autosomal recessive condition. This article focuses on the specific challenges of diagnosing and treating Gitelman syndrome, with use of an illustrative case report. Symptoms relate to decreased serum potassium and magnesium levels, which include muscle weakness, tetany, fatigue and palpitations. Sudden cardiac deaths have been reported. Making a diagnosis may be difficult given its rarity but is important. A knowledge of the serum and urine biochemical picture is vital to distinguish it from a broad differential diagnosis, and application of genetic testing can resolve difficult cases. There is a group of Gitelman syndrome heterozygous carriers that experience symptoms and electrolyte disturbance and these patients should be managed in a similar way, though here genetic investigations become key in securing a difficult diagnosis. Potassium and magnesium replacement is the cornerstone of treatment, though practically this can be hard for patients to manage and often does not fully relieve symptoms even when serum levels are normalized. Challenges arise due to the lack of randomized controlled trials focussing on treatment of this rare disease; hence, clinicians endorse strategies in line with correction of the underlying pathophysiology such as sodium loading or pharmacological treatments, which seem to help some patients. Focussed dietary advice and knowing the best tolerated preparations of potassium and magnesium medications are useful tools for the physician, as well as an awareness of the specific burdens that this patient group face in order to signpost appropriate support.

Effect of Indapamide on Urinary Calcium Excretion in Patients with and without Urinary Stone Disease

BACKGROUND:

Indapamide is an antihypertensive agent similar to thiazides, but with some different effects. Thiazide and thiazide-like diuretics are useful in preventing recurrent urinary stone formation due to their hypocalciuric effects.

OBJECTIVE:

To determine the hypocalciuric and other effects on certain laboratory parameters of indapamide 1.5 mg in different patient groups.

METHODS:

Four groups of patients recruited from urology and nephrology outpatient departments were experiencing non-hypercalciuric urinary stone disease (group 1), idiopathic hypercalciuria (group 2), urinary stone disease with hypercalciuria (group 3), and essential hypertension (group 4). In all patients, fasting serum uric acid, calcium, sodium, potassium, cholesterol, triglyceride, parathyroid hormone (PTH) values, and morning second-spot urine calcium and creatinine levels were assessed before and 8 weeks after treatment with indapamide.

RESULTS:

Urinary calcium excretion was reduced significantly in all groups: group 1 from 0.10 ± 0.02 to 0.07 ± 0.03 (mean ± SD; 30% reduction; p < 0.001), group 2 from 0.30 ± 0.15 to 0.15 ± 0.10 (50% reduction; p < 0.001), group 3 from 0.35 ± 0.15 to 0.20 ± 0.10 (43% reduction; p < 0.001), and group 4 from 0.10 ± 0.03 to 0.08 ± 0.02 (20% reduction; p < 0.0010). These results should be interpreted with caution since no control group was included in this study. Mean serum uric acid and triglyceride levels were significantly increased, and mean PTH and potassium levels and diastolic and systolic blood pressure were significantly decreased in all groups. Few temporary adverse effects, such as dizziness and fatigue, were noticed and none of them caused discontinuation of treatment.

CONCLUSIONS:

Indapamide 1.5 mg/day is effective in decreasing calciuria in patients with non-hypercalciuric urinary stone disease, idiopathic hypercalciuria, urinary stone disease with hypercalciuria, and essential hypertension. This could be achieved with few adverse effects similar to those of thiazides and indapamide 2.5 mg. Indapamide decreased the PTH levels in all groups. Long-term clinical benefits of these effects should be evaluated prospectively with further randomized studies.

Thiazide-sensitive Na+ -Cl- cotransporter (NCC) gene inactivation results in increased duodenal Ca2+ absorption, enhanced osteoblast differentiation and elevated bone mineral density

Inactivation of the thiazide-sensitive sodium chloride cotransporter (NCC) due to genetic mutations in Gitelman's syndrome (GS) or pharmacological inhibition with thiazide diuretics causes hypocalciuria and increased bone mineral density (BMD) with unclear extrarenal calcium (Ca(2+) ) regulation. We investigated intestinal Ca(2+) absorption and bone Ca(2+) metabolism in nonsense Ncc Ser707X (S707X) homozygous knockin mice (Ncc(S707X/S707X) mice). Compared to wild-type and heterozygous knockin littermates, Ncc(S707X/S707X) mice had increased intestinal absorption of (45) Ca(2+) and expression of the active Ca(2+) transport machinery (transient receptor potential vanilloid 6, calbindin-D9K , and plasma membrane Ca(2+) ATPase isoform 1b). Ncc(S707X/S707X) mice had also significantly increased Ca(2+) content accompanied by greater mineral apposition rate (MAR) in their femurs and higher trabecular bone volume, cortical bone thickness, and BMD determined by μCT. Their osteoblast differentiation markers, such as bone alkaline phosphatase, procollagen I, osteocalcin, and osterix, were also significantly increased while osteoclast activity was unaffected. Analysis of marrow-derived bone cells, either treated with thiazide or directly cultured from Ncc S707X knockin mice, showed that the differentiation of osteoblasts was associated with increased phosphorylation of mechanical stress-induced focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK). In conclusion, NCC inhibition stimulates duodenal Ca(2+) absorption as well as osteoblast differentiation and bone Ca(2+) storage, possibly through a FAK/ERK dependent mechanism.

Improved trabecular bone structure of 20-month-old male spontaneously hypertensive rats

A few clinical studies have reported that elderly male participants with hypertensive disease frequently have higher bone mineral density (BMD) than the normotensive participants at several skeletal sites. The detailed mechanism is still unknown; therefore, a study of bone structure and density using the hypertensive animal models could be informative. We used micro-computed tomography to quantitatively evaluate the tibial and 3rd lumbar vertebral bones in the 20-month-old male spontaneous hypertensive rat (SHR). The BMD, volume fraction, and the microarchitecture changes of the SHR were compared to those of same-age normotensive controls (Wistar-Kyoto rat, WKY). We found that in the very old (20 month) male rats, the trabecular bone fraction and microstructure were higher than those in the same-age normotensive controls. The observation of the association of hypertension with BMD and bone strength in hypertensive rats warrants further investigations of bone mass and strength in elderly males with hypertension.

Effects of three years of low-dose thiazides on mineral metabolism in healthy elderly persons

In this clinical trial of 12.5 or 25 mg/day of hydrochlorothiazide, the urine calcium showed significant decreases from placebo in men at one year, but the effects had waned by 3 years. Serum bicarbonate was consistently greater in the thiazide than in the placebo groups throughout the three years. These effects could be beneficial to the skeleton.

INTRODUCTION

Previous studies have shown increased bone density and reduced risk of fracture in patients taking thiazide diuretics. The long-term effects of low-dose thiazides on mineral metabolism have not been reported in normal subjects.

METHODS

We conducted a randomized, double-blinded trial in normals aged 60-79 years, using hydrochlorothiazide 12.5 or 25 mg/d or placebo for three years. Subjects were encouraged to maintain calcium intake of 1,000 to 1,500 mg/day. Measurements of serum and urine calcium metabolism were done at baseline, six months, and yearly. Data were analyzed in 88 men and 177 women who had taken study medication. Adjusted change in the measurements from baseline to one and three years were compared among groups.

RESULTS

The calcium intake increased in all groups. Urine calcium per day was significantly lower in thiazide than placebo groups in men at one year but not at three years; in women the changes were not significantly different. Serum bicarbonate was higher in thiazide compared to placebo groups at one and three years. No changes were seen in serum calcium, phosphate, parathyroid hormone, sodium or magnesium.

CONCLUSIONS

The results suggest that both increased calcium availability from a hypocalciuric effect and reduction in acid-induced bone buffering could be mechanisms for the beneficial skeletal effects.

Delapril plus indapamide: a review of the combination in the treatment of hypertension

Although many data indicate that the management of hypertension has improved over the last two decades, there is still a large proportion of hypertensive individuals who do not receive adequate management of their blood pressure (BP). Combination therapy with two or more antihypertensive agents from different drug classes is increasingly being recognised as the most effective means of achieving target BP values by pharmacological means, particularly in the large number of patients in whom monotherapy proves to be ineffective. Use of an angiotensin-converting enzyme (ACE) inhibitor combined with a diuretic is a well established antihypertensive combination that is very effective because of the different, yet synergistic, mechanisms of actions of agents from these two drug classes. Delapril is a potent antihypertensive ACE inhibitor, and indapamide is a thiazide-like diuretic with additional antihypertensive properties. The combination of delapril and indapamide provides renoprotective effects, and indapamide is also cardioprotective. Use of these two drugs together is therefore a rational selection for combination therapy, and one that has consistently demonstrated lowering of BP to target values with a level of efficacy that is at least as good as other combinations of ACE inhibitors and diuretics. This combination has also been found to provide favourable effects on haemodynamic parameters, including left ventricular mass index and ejection fraction. Furthermore, combining an ACE inhibitor and a thiazide-type diuretic has been associated with a decreased risk of stroke and is recommended for patients with cerebrovascular disease, a setting in which the combination of delapril and indapamide has therapeutic potential. Because of the additive mechanisms of delapril and indapamide, the dose required for an effective antihypertensive effect is relatively low, and the combination is well tolerated at such doses. In particular, metabolic effects normally associated with diuretics are rare at the therapeutic dose of indapamide used in combination with delapril, making the combination suitable for patients with metabolic disorders in whom diuretic therapy would otherwise not be recommended. Delapril 30 mg and indapamide 2.5mg have been combined in a fixed combination, offering the convenience of a one-tablet-per-day antihypertensive drug regimen for most patients, which, along with good tolerability, helps to address the issue of noncompliance.

Fracture risk and the use of a diuretic (indapamide SR) +/- perindopril: a substudy of the Hypertension in the Very Elderly Trial (HYVET)

Background

The Hypertension in the Very Elderly Trial (HYVET) is a placebo controlled double blind trial of treating hypertension with indapamide Slow Release (SR) ± perindopril in subjects over the age of 80 years. The primary endpoints are stroke (fatal and non fatal). In view of the fact that thiazide diuretics and indapamide reduce urinary calcium and may increase bone mineral density, a fracture sub study was designed to investigate whether or not the trial anti-hypertensive treatment will reduce the fracture rate in very elderly hypertensive subjects.

Methods

In the trial considerable care is taken to ascertain any fractures and to identify risk factors for fracture, such as falls, co-morbidity, drug treatment, smoking and drinking habits, levels of activity, biochemical abnormalities, cardiac irregularities, impaired cognitive function and symptoms of orthostatic hypotension.

Potential results

The trial is expected to provide 10,500 patient years of follow-up. Given a fracture rate of 40/1000 patient years and a 20% difference in fracture rate, the power of the sub study is 58% to detect this difference at the 5% level of significance. The corresponding power for a reduction of 25% is 78%.

Conclusion

The trial is well under way, expected to complete in 2009, and on target to detect, if present, the above differences in fracture rate.

Bone loss in rats with aldosteronism

OBJECTIVE

We hypothesized that aldosteronism is accompanied by hypercalciuria and hypermagnesuria that lead to bone loss, which could be rescued by hydrochlorothiazide and spironolactone.

METHODS

We monitored 24-hour urinary Ca and Mg excretion; plasma ionized [Ca]o and [Mg]o and plasma K; and bone mineral density of the femur. The following groups (n=5 in each group) were studied: age- and gender-matched, untreated controls; controls + 4 weeks hydrochlorothiazide; 4 weeks aldosterone/salt treatment (ALDOST, 0.75 mug/h and dietary 1% NaCl/0.4% KCl); 4 weeks ALDOST+hydrochlorothiazide (50 mg/kg in prepared food); and 4 weeks ALDOST+hydrochlorothiazide+spironolactone (200 mg/kg day in divided doses by twice-daily gavage).

RESULTS

ALDOST increased (P<0.05) urinary Ca and Mg excretion four- and twofold, respectively; hydrochlorothiazide co-treatment attenuated (P<0.05) Ca excretion in controls and during ALDOST without affecting augmented Mg excretion whereas hydrochlorothiazide+spironolactone normalized Ca and reduced Mg excretion (P<0.05). Compared with controls, plasma [Ca]o at 4 weeks of ALDOST was reduced (0.89+/-0.02 versus 0.83+/-0.03 mmol/L; P<0.05) but remained no different from levels in controls with hydrochlorothiazide and hydrochlorothiazide+spironolactone (0.88+/-0.04 and 0.97+/-0.03 mmol/L, respectively). Plasma [Mg]o fell (P<0.05) with ALDOST+hydrochlorothiazide (0.23+/-0.01 versus 0.34+/-0.01 mmol/L) and was prevented with spironolactone co-treatment (0.33+/-0.01 mmol/ dL). Hypokalemia (2.9+/-0.2 mmol/L) occurred in rats with ALDOST+hydrochlorothiazide but not with spironolactone co-treatment. At 4 weeks of ALDOST, plasma parathyroid hormone was increased (30+/-4 versus 11+/-3 pg/mL; P<0.05) and bone mineral density was reduced (0.153+/-0.006 versus 0.170+/-0.002 g/cm; P<0.05). Co-treatments with either hydrochlorothiazide or hydrochlorothiazide+spironolactone each prevented bone loss.

CONCLUSIONS

Hypercalciuria and hypermagnesuria accompany aldosteronism and account for a decline in their plasma ionized concentrations and secondary hyperparathyroidism with bone resorption. Attenuation of bone loss in aldosteronism can be achieved with hydrochlorothiazide; however, mono- and divalent cation homeostasis, together with bone integrity, are each preserved with the combination hydrochlorothiazide+spironolactone.

Inactivation of the Na-Cl co-transporter (NCC) gene is associated with high BMD through both renal and bone mechanisms: analysis of patients with Gitelman syndrome and Ncc null mice

Chronic thiazide treatment is associated with high BMD. We report that patients and mice with null mutations in the thiazide-sensitive NaCl cotransporter (NCC) have higher renal tubular Ca reabsorption, higher BMD, and lower bone remodeling than controls, as well as abnormalities in Ca metabolism, mainly caused by Mg depletion.

INTRODUCTION

Chronic thiazide treatment decreases urinary Ca excretion (UVCa) and increases BMD. To understand the underlying mechanisms, Ca and bone metabolism were studied in two models of genetic inactivation of the thiazide-sensitive NaCl cotransporter (NCC): patients with Gitelman syndrome (GS) and Ncc knockout (Ncc(-/-)) mice.

MATERIALS AND METHODS

Ca metabolism was analyzed in GS patients and Ncc(-/-) mice under conditions of low dietary Ca. BMD was measured by DXA in patients and mice, and bone histomorphometry was analyzed in mice.

RESULTS

GS patients had low plasma Mg. They exhibited reduced UVCa, but similar serum Ca and GFR as control subjects, suggesting increased renal Ca reabsorption. Blood PTH was lower despite lower serum ionized Ca, and Mg repletion almost corrected both relative hypoparathyroidism and low UVCa. BMD was significantly increased in GS patients at both lumbar (+7%) and femoral (+16%) sites, and osteocalcin was reduced. In Ncc(-/-) mice, serum Ca and GFR were unchanged, but UVCa was reduced and PTH was elevated; Mg repletion largely corrected both abnormalities. Trabecular and cortical BMD were higher than in Ncc(+/+) mice (+4% and +5%, respectively), and despite elevated PTH, were associated with higher cortical thickness and lower endosteal osteoclastic surface.

CONCLUSIONS

Higher BMD is observed in GS patients and Ncc(-/-) mice. Relative hypoparathyroidism (human) and bone resistance to PTH (mice), mainly caused by Mg depletion, can explain the low bone remodeling and normal/low serum Ca despite increased renal Ca reabsorption.

In vivo inhibition of osteoblastic metalloproteinases leads to increased trabecular bone mass

Mice specifically overexpressing TIMP-1 in osteoblasts have been generated to investigate the role of MMPs in bone in vivo. These mice displayed increased trabecular bone volume and decreased bone turnover. This model provides evidence of the role played by the MMPs in bone remodeling and balance.

INTRODUCTION

Although it has been suggested that the matrix metalloproteinases (MMPs) may play a role in initiating the bone resorption process in vitro, there is no evidence that they play any role in in vivo bone maintenance.

MATERIALS AND METHODS

We used an artificial promoter specifically driving cells of the osteoblastic lineage to overexpress the tissue inhibitor of MMPs (TIMP-1) cDNA in mice. Densitometric analysis, using DXA and pQCT, and static and dynamic histomorphometry were used to evaluate the bone phenotype both in male and female transgenic mice. We evaluated osteoblastic differentiation using a primary osteoblast culture and osteoclast activity using an ex vivo organ culture.

RESULTS AND CONCLUSION

We showed that at 1 and 2.5 months of age, only the female mice exhibited a bone phenotype. These mice displayed specific increases in the BMD and bone volume of trabecular bone. This increase was accompanied by decreased trabecular separation, suggesting a decrease in bone resorption. Using an ex vivo resorption assay, we demonstrated that parathyroid hormone (PTH)-stimulated bone resorption was reduced in these mice. Evaluation of the bone histomorphometric dynamic parameters showed that the mineralizing surfaces and bone formation rate were both reduced. There was no change in the mineralization lag time or number of osteocyte lacunae. Using primary osteoblast culture and molecular analysis, we showed that the differentiation and function of osteoblasts from transgenic mice were normal, but that the ex vivo formation of mineralized nodules was delayed. This model is the first to show that in vivo MMPs play a role in bone remodeling and bone balance. Moreover, our data suggest that MMP activity could be involved in the hormonal regulation of bone resorption by osteoblasts.

Bone mineral density changes in hypercalciuretic osteoporotic men treated with thiazide diuretics

A few studies suggest that thiazide diuretic agents may have modest beneficial effects on bone. Few data are available on the effects of these medications in patients with osteoporosis and hypercalciuria.

OBJECTIVE

To evaluate the effects of thiazide diuretic therapy on bone mass and urinary calcium excretion in hypercalciuretic osteoporotic male patients.

PATIENTS AND METHODS

Osteoporosis was defined as a greater than 2.5 standard deviation (S.D.) decrease in bone mineral density (BMD) at the lumbar spine or hip (T-score). We used an open-label prospective design to compare 14 patients with hypercalciuretic osteoporosis treated with a thiazide diuretic for 18 months and 13 patients with primary osteoporosis treated with calcium and vitamin D supplementation. Mean age was 53.5 +/- 9.6 years in the thiazide group and 48.7 +/- 8.4 years in the calcium-vitamin D supplementation group. The following serum parameters were assayed at baseline: 25OH-D3, 1,25OH-D3, parathyroid hormone (PTH), and bone turnover markers. Urinary calcium excretion and BMD by dual-energy X-ray absorptiometry at the spine and hip were determined at baseline and after 18 months of treatment.

RESULTS

Annual BMD increases were similar in the two groups during the 18-month treatment period: lumbar spine, 0.6 +/- 2.5% (P = 0.47) in the thiazide group and 0.004 +/- 3% (P = 0.78) in the supplementation group; femoral neck, 0.47 +/- 2.6% (P = 0.89) and 1.1 +/- 3.2% (P = 0.22); total hip, 0.65 +/- 2.5% (P = 0.37) and 0.12 +/- 2.1% (P = 0.51). Urinary calcium excretion fell by 45.9% in the thiazide group from baseline to study completion (P = 0.0015).

CONCLUSION

We found no evidence that thiazide therapy increased bone mass in patients with hypercalciuria and osteoporosis as compared to calcium-vitamin D supplementation in patients with osteoporosis but no hypercalciuria. In contrast, our results establish the efficacy of thiazide diuretics in reducing urinary calcium excretion, an effect that may decrease the risk of urinary lithiasis. Studies in larger patient cohorts treated for longer periods are needed to confirm or refute our findings.

Increased bone mineral density in a population-based group of 70-year-old women on thiazide diuretics, independent of parathyroid hormone levels

BACKGROUND

Several studies have shown greater bone mineral density (BMD) in people receiving thiazide diuretics compared with controls. Most researchers have related this association to the hypocalciuric effect of thiazides with subsequent rise in serum calcium and fall in parathyroid hormone (PTH) levels. Recent experimental evidence suggests, however, a direct effect of thiazides on osteoblast-like cells.

OBJECTIVE

To test the hypothesis that the association of thiazides and raised BMD is independent of PTH levels in humans.

SUBJECTS

A population-based group of 248 70-year-old Icelandic women, 51 receiving thiazide diuretics, 39 receiving other antihypertensive therapy and the rest acting as controls.

MAIN OUTCOME MEASURES

The independent contribution of thiazide usage and PTH to BMD in a multivariate analysis.

RESULTS

The mean BMD was 9.6% greater in the lumbar spine (P < 0.01) and 5.4% greater in the whole skeleton (P < 0.01) amongst thiazide users than in controls, reduced to 7.6% (P < 0.02) and 4.5% (P < 0.01), respectively, when corrected for fat mass which was 5.8 kg greater in the thiazide group. In a multivariate analysis, corrected for body weight and body composition, serum calcium and ln-PTH, thiazides remained a significant independent predictor of BMD in the total skeleton and lumbar spine, but not in the total hip or femoral neck. Thiazides explained about 3% of the variability in whole body and lumbar spine BMD.

CONCLUSIONS

Thiazides augment or preserve BMD independent of PTH, implying other mechanisms.

Indapamide, a thiazide-like diuretic, decreases bone resorption in vitro

We recently showed that indapamide (IDP), a thiazide-related diuretic, increases bone mass and decreases bone resorption in spontaneously hypertensive rats supplemented with sodium. In the present study, we evaluated the in vitro effects of this diuretic on bone cells, as well as those of hydrochlorothiazide (HCTZ), the reference thiazide, and acetazolamide (AZ), a carbonic anhydrase (CA) inhibitor. We showed that 10(-4) M IDP and 10(-4) M AZ, as well as 10(-5) M pamidronate (APD), decreased bone resorption in organ cultures and in cocultures of osteoblast-like cells and bone marrow cells in the presence of 10(-8) M 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. We investigated the mechanism of this antiresorptive effect of IDP; IDP decreased osteoclast differentiation as the number of osteoclasts developing in coculture of marrow and osteoblast-like cells was decreased markedly. We then investigated whether IDP affected osteoblast-like cells because these cells are involved in the osteoclast differentiation. Indeed, IDP increased osteoblast-like cell proliferation and alkaline phosphatase (ALP) expression. Nevertheless, it did not modify the colony-stimulating factor 1 (CSF-1) production by these cells. In addition, osteoblast-like cells expressed the Na+/Cl- cotransporter that is necessary for the renal action of thiazide diuretics, but IDP inhibited bone resorption in mice lacking this cotransporter, so the inhibition of bone resorption and osteoclast differentiation did not involve this pathway. Thus, we hypothesized that IDP may act directly on cells of the osteoclast lineage. We observed that resorption pits produced by spleen cells cultured in the presence of soluble osteoclast differentiation factor (sODF) and CSF-1 were decreased by 10(-4) M IDP as well as 10(-5) M APD. In conclusion, in vitro IDP increased osteoblast proliferation and decreased bone resorption at least in part by decreasing osteoclast differentiation via a direct effect on hematopoietic precursors.

Hydrochlorothiazide reduces loss of cortical bone in normal postmenopausal women: a randomized controlled trial

PURPOSE

Thiazide diuretics reduce urine calcium excretion and might therefore reduce postmenopausal bone loss. In some, but not all, case-control studies, their use has been associated with a reduced incidence of hip fractures. We studied the effects of hydrochlorothiazide on bone loss in normal postmenopausal women.

SUBJECTS AND METHODS

We performed a randomized, double-blind, 2-year trial of the effects of hydrochlorothiazide (50 mg per day) and placebo on bone mineral density in normal postmenopausal women. Participants were not required to have either low bone mineral density or hypertension. Bone mineral density was measured using dual-energy x-ray absorptiometry.

RESULTS

One hundred eighty-five women entered the study, of whom 138 completed 2 years of follow-up. In an intention-to-treat analysis, hydrochlorothiazide produced significant benefits on bone mineral density of the total body (between-group difference at 2 years of 0.8%, 95% confidence interval [CI]: 0.3% to 1.3%, P <0.0001), legs (0.9%, 95% CI: 0.2% to 1.7%, P <0.0001), mid-forearm (1.2%, 95% CI: 0.2% to 2.2%, P = 0.02), and ultradistal forearm (1.7%, 95% CI: 0.1% to 3.2%, P = 0.04). There was no effect in the lumbar spine (0.5%, 95% CI: -0.5% to 1.6%) or femoral neck (0.2%, 95% CI: 1.3% to 1.7%). The between-group changes tended to be greatest during the first 6 months, except in the mid-forearm where there appeared to be a progressive divergence. An as-treated analysis produced similar results. Urine calcium excretion and indices of bone turnover decreased in the thiazide group, but parathyroid hormone concentrations did not differ between the groups. Treatment was tolerated well.

CONCLUSIONS

Hydrochlorothiazide (50 mg per day) slows cortical bone loss in normal postmenopausal women. It may act directly on bone as well as on the renal tubule. The small size of the effect suggests that thiazides may have a role in the prevention of postmenopausal bone loss, but that they are not an appropriate monotherapy for treating osteoporosis.