Postmenopausal osteoporosis in the dialysis patient

Sex-specific relationship between vascular calcification and incident fracture in patients with end-stage renal disease

Background

Vascular calcification (VC) is a major component of mineral bone disorders in patients with end-stage renal disease (ESRD). Bone metabolism is affected by various factors, including sex hormones. This study investigated whether there was a sex-specific relationship between VC and incident fracture in patients with ESRD.

Methods

This was a retrospective cohort study of dialysis patients from a single center. VC was assessed by the aortic calcification index (ACI) using abdominal computed tomography. Patients were grouped by sex and stratified into low or high ACI groups, according to the median ACI value. The association between ACI and incident fracture was analyzed.

Results

Data from 593 patients (male n = 328, median ACI, 14.57; female n = 265, median ACI, 19.44) were included. During a median follow-up of 36.7 months, 71 patients (12.0%) developed fractures. The fracture-free survival rate was significantly lower in the high ACI group versus the low ACI group, both in males (P = 0.021) and females (P = 0.001). In males, multivariate analysis showed that the high ACI group and ACI per se were not significant risks for fracture. However, in females, both the high ACI group (adjusted hazard ratio, 2.720; P = 0.003) and ACI per se (adjusted hazard ratio, 1.768; P = 0.035) were independently associated with fracture after adjustment for confounding variables.

Conclusion

VC was independently associated with incident fracture in female patients with ESRD. There may be a sex-specific relationship between VC and fracture in patients with ESRD.

Effects of hepatitis C virus infection on menopause status and symptoms

OBJECTIVE

To examine the relationship between hepatitis C virus (HCV) infection with menopause status and vasomotor symptoms among middle-aged, impoverished women.

METHODS

The baseline interview and laboratory data from a study on menopause were used for a cross-sectional analysis of HCV antibody and HCV-RNA levels and their relationship to menopause status and symptoms, using logistic regression. For HCV-infected and HCV-uninfected women, menopause status was defined according to the World Health Organization criteria.

RESULTS

Of 559 participants, 48% were black, 38.6% were Hispanic, and 267 (47.8%) were HCV seropositive; of these, 189 (72.1%) had detectable HCV-RNA levels. The median age was 43 years [interquartile range (IQR), 40-46 years]; 50.2% of the women were premenopausal, 31.8% were perimenopausal, and 18% were postmenopausal. Median age at natural menopause was 46 years (IQR, 42.25-49 years) in HCV-infected women compared with 47 years (IQR, 40.25-48 years) in uninfected controls. Women infected with HCV were more likely to be postmenopausal than were uninfected women (adjusted odds ratio [ORadj], 1.68; 95% CI, 1.02-2.77). Human immunodeficiency virus status (ORadj, 1.69; 95% CI, 1.04-2.75), drug use (ORadj, 2.34; 95% CI, 1.42-3.86), and nulliparity (ORadj, 2.74; 95% CI, 1.42-5.29) were independently associated with natural menopause, whereas being more physically active (ORadj, 0.90; 95% CI, 0.85-0.95) was inversely associated with menopause. Women infected with HCV were more likely than uninfected women to report vasomotor symptoms (ORadj, 1.52; 95% CI, 1.06-2.18).

CONCLUSIONS

Hepatitis C virus infection is independently associated with natural menopause, controlling for age. In addition, HCV was associated with vasomotor symptoms. Further studies are warranted to better understand the menopausal transition in HCV-infected women.

The nitroxide tempol has similar antioxidant effects as physiological levels of 17beta-oestradiol in reversing ovariectomy-induced oxidative stress in mice liver and kidney

OBJECTIVE

Oestrogen defciency increases oxidative stress postmenopause, while tempol is an intracellular radical scavenger that interferes with the formation or effects of many radicals. We aimed to investigate the effects of oestrogen and tempol on oxidative stress parameters in the kidney and liver of ovariectomized mice.

MATERIAL AND METHODS

Forty 8-week-old female Bald/c mice were divided into five groups: sham-operated, ovariectomized mice without treatment, ovariectomized mice treated with tempol, ovariectomized mice treated with 17beta-oestradiol and ovariectomized mice treated with 17beta-oestradiol and tempol. Oxidative stress in liver and kidney tissues was investigated by measuring 2-thiobarbituric acid reactive substances (TBA-RS), reduced glutathione, myeloperoxidase, superoxide dismutase and catalase levels.

RESULTS

TBA-RS levels were increased and reduced glutathione, myeloperoxidase, superoxide dismutase levels were decreased in the tissues of ovariectomized mice. This effect of ovariectomy on oxidative stress parameters was opposed significantly by the administration of tempol and 17beta-oestradiol either alone or in combination. Ovariectomy reduced the kidney catalase levels, but the effect was not statistically significant (p>0.05). On the other hand, catalase levels were elevated significantly in all treatment groups compared to those of the ovariectomized group (p<0.05).

CONCLUSION

These study findings demonstrate that tempol significantly opposes the oxidative stress generated by ovariectomy. This effect, which is evident in remote tissues such as liver and kidney, is comparable to that of physiological levels of oestradiol.

The impact of sex hormone changes on bone mineral deficit in chronic renal failure

In chronic renal failure several factors affect bone homeostasis leading to the development of renal osteodystrophy. Common calcitropic hormone derangements in renal failure play a central role in bone structure and mineral defects, which in turn accompany osteodystrophy frequently resulting in low bone mineral density (BMD) values. However, patients with end-stage renal disease (ESRD) suffer from several comorbidities, which may partly account for renal bone disease lesions. Hypogonadism in particular accompanies chronic renal failure frequently and exerts an additive effect on bone loss potential. Sex hormones contribute to the equilibrium of osteotropic hormones and cytokines, exerting a protective action on bone tissue. Estrogens have a regulatory effect on bone metabolism in women with renal failure as well. Hypogonadal ESRD women experience a higher bone turnover and more significant bone mass decrements than ESRD women with relatively normal hormone profile and menstrual habits. Female hemodialysis patients have lower BMD values than male patients on average, probably because of menstrual cycle irregularities. However, hypogonadal ESRD men may also experience bone mineral deficits and the severity of hypogonadism may correlate to their bone mineral status. Hormone replacement therapy (HRT) appears to reverse bone mineral loss to some extent in both sexes. In conclusion hypogonadism in renal failure contributes to the bone structure and mineral defects as well as the low-energy fracture risk, reflected in BMD measurements. HRT in ESRD patients should therefore not be overlooked in these patients in the face of their significant comorbidities.

Osteoporosis and chronic kidney disease

Osteoporosis (OP), the most frequent bone disease affecting the general population, is associated with high fracture risk. Patients with impaired kidney function have bone and mineral disturbances leading to extraskeletal calcifications and complex changes in bone turnover that predispose them to increased fracture risk accompanied by increased morbidity and mortality. The combination of these two bone disorders seems to have an additive effect with regard to fracture risk and its outcome, so that appropriate diagnosis and treatment of this disorder should be of primary concern when approaching patients with kidney disease. Nevertheless, the clinical and laboratory diagnostic tools used to identify OP in the general population do not suit the requirement for detecting the complex bone and metabolic changes that occur with chronic kidney disease, leading to the lack of or the initiation of inappropriate therapy. This review will focus on the bone pathophysiologic processes involved in OP and renal osteodystrophy and address some of the problems associated with our current diagnostic tools and aspects of the therapeutic approaches.

Osteoporosis in hemodialysis patients revisited by bone histomorphometry: a new insight into an old problem

Osteoporosis in hemodialysis patients is associated with high morbidity and mortality and, although extensively studied by noninvasive methods, has never been assessed through bone biopsy. The aim of this study was to use histomorphometry to evaluate osteoporosis and identify factors related to its development in hemodialysis patients. We conducted a cross-sectional study involving 98 patients (35 women and 63 men; mean age: 48.4 +/- 13 years) on hemodialysis for 36.9 +/- 24.7 months. Patients were submitted to transiliac bone biopsy with double tetracycline labeling. The bone metabolism factors ionized calcium, phosphorus, bone alkaline phosphatase, deoxypyridinoline, intact parathyroid hormone, and 25(OH) vitamin D were evaluated, as were the bone remodeling cytokines osteoprotegerin (OPG), soluble receptor-activator of NF-kappabeta ligand (sRANKL) and tumor necrosis factor-alpha (TNF)alpha. Osteoporosis was defined as trabecular bone volume (BV/TV) greater than 1 s.d. below normal (men <17.4%; women <14.7%). Forty-five patients (46%) presented osteoporosis, which was correlated with white race. We found BV/TV to correlate with age, OPG/sRANKL ratio, TNFalpha levels, and length of amenorrhea. In multiple regression analysis adjusted for sex and age, length of amenorrhea, white race, and OPG/sRANKL ratio were independent determinants of BV/TV. Histomorphometric analysis demonstrated that osteoporotic patients presented normal eroded surface and low bone formation rate (BFR/BS). Osteoporosis is prevalent in hemodialysis patients. Low BFR/BS could be involved in its development, even when bone resorption is normal. Cytokines may also play a role as may traditional risk factors such as advanced age, hypogonadism, and white race.

Bone disease after renal transplantation

It has been well established that a rapid decrease in bone mineral density (BMD) occurs in the first 6 to 12 mo after a successful renal transplantation and persists, albeit at a lower rate, for many years. This rapid BMD loss significantly increases the fracture risk of these patients to levels that are even higher than those of patients who have chronic kidney disease stage 5 and are on dialysis. The presence of low BMD in renal transplant patients as a predictor of risk fracture is controversial. Indeed, as has been suggested also for patients with postmenopausal osteoporosis, there is not a compelling correlation between the decline in BMD and skeletal fractures. However, bone disease after renal transplantation probably represents a unique bone disorder that must encompass underlying renal osteodystrophy. In fact, this syndrome results from multiple factors that include pretransplantation bone status, use of glucocorticoids and other immunosuppressive drugs, hypophosphatemia, and alterations of the calcium-vitamin D axis. Recent studies have demonstrated decreased osteoblast number, reduced bone formation rate, delayed mineralization, and increased osteoblast and osteocyte apoptosis. Bisphosphonates and vitamin D metabolites may be valuable in preventing or diminishing early bone loss. However, clinicians should be careful with the use of bisphosphonates and oversuppression of bone, especially in patients with low bone turnover. New prospective, controlled trials are required to confirm the real efficacy of these drugs, particularly in long-term renal transplant patients.

Pharmacokinetic changes of ipriflavone in rats with acute renal failure induced by uranyl nitrate

Pharmacokinetic parameters of ipriflavone were compared after intravenous (20 mg/kg) and oral (200 mg/kg) administration in control rats and in rats with acute renal failure induced by uranyl nitrate (U-ARF rats). It was expected that the time-averaged nonrenal clearance (Cl(nr)) of ipriflavone in U-ARF rats could be significantly slower than in the control rats, since it was reported that ipriflavone was metabolized via the hepatic microsomal cytochrome P450 (CYP) 1A1/2 and 2C11 and the expression and mRNA level of CYP1A2 were not changed, but those of CYP2C11 were decreased in U-ARF rats compared with control rats. Unexpectedly, after intravenous administration in U-ARF rats, the Cl(nr) of ipriflavone was significantly faster than in the controls (40.8 compared with 29.0 ml/min/kg). This may be due to an increase in the glucuronide conjugate formation of ipriflavone metabolites in U-ARF rats. After oral administration of ipriflavone in U-ARF rats, the AUC(0-24 h) was significantly smaller (194 compared with 295 microg min/ml) than in the controls.