Bone mineral metabolism changes in epileptic children receiving valproic acid

Maintaining strong bones: strong opinions, little evidence

Two Randomized Vitamin D Trials in Ambulatory Patients on Anticonvulsants: Impact on Bone. Mikati MA, Dib L, Yamout B, Sawaya R, Rahi AC, Fuleihan Gel-H. Neurology 2006;67(11):2005–2014. OBJECTIVE: To investigate the effects of two doses of vitamin D given over 1 year on bone density in ambulatory patients on long-term antiepileptic drug (AED) therapy. METHODS: We conducted two parallel, randomized, controlled trials in 72 adults (18–54 years old) and 78 children and adolescents (10–18 years) on long-term AED therapy. They received either low-dose vitamin D 400 IU/day or high-dose vitamin D 4,000 IU/day (adults) and 2,000 IU/day (children/adolescents). Bone mineral density (BMD) was measured using dual-energy x-ray absorptiometry. RESULTS: In adults, baseline BMD was lower than that of age- and gender-matched controls vs either a Western or an ethnically identical population. After 1 year, there were significant increases in BMD at all skeletal sites compared to baseline in the high-, but not in the low-dose treatment group. However, BMD at 1 year remained below normal. In children, baseline BMD was normal vs age- and gender-matched controls and showed significant and comparable increases in both treatment groups. CONCLUSIONS: In ambulatory adults on antiepileptic drugs, high-dose vitamin D therapy substantially increased bone mineral density at several skeletal sites. In children, both doses resulted in comparable increases in bone mass.

Levetiracetam, Phenytoin, and Valproate Act Differently on Rat Bone Mass, Structure, and Metabolism

PURPOSE

Long-term treatment with antiepileptic drugs (AEDs) is associated with increased risk of fractures. Phenytoin (PHT) and valproate (VPA) have both been suggested to influence bone health, whereas levetiracetam (LEV) is scarcely studied. The present study compares the effect of these AEDs on bone mass, biomechanical strength, and bone turnover in rats.

METHODS

Female rats received PHT (50 mg/kg), VPA (300 mg/kg), or LEV (50 and 150 mg/kg) for 90 days. Dissected femurs were analyzed using dual energy x-ray absorptiometry (DXA), three-point cantilever bending, and histomorphological evaluation. Serum levels of biochemical bone turnover markers were monitored using immunoassay quantification.

RESULTS

PHT and VPA reduced bone mineral density (BMD) and content (BMC) in one or more bone compartments, whereas LEV did not. VPA induced increased bone turnover, whereas modest changes were observed for PHT. Interestingly, low-dose LEV was associated with reduced biomechanical strength of the femoral neck (mainly trabecular bone). In addition, low-dose LEV treatment resulted in significantly reduced levels of serum osteocalcin, a marker of bone formation. Histomorphological analyses indicated increased retention of cartilage remnants at the growth plate metaphysis of rats treated with low-dose LEV vs. controls.

CONCLUSIONS

PHT, VPA, and LEV exert differential effects on bone mass and strength, suggesting different mechanisms of action. The weakening effect of low-dose LEV on the femoral neck, despite a constant BMD, suggests a primary effect on bone quality. These findings warrant further human studies of possible adverse effects of LEV on bone development and growth, particularly in children and adolescents.

Adverse effects of antiepileptic drugs on bone mineral density in children

Bone mineral content (BMC) or density (BMD) may be decreased in children with epilepsy either as a consequence of the epilepsy, the condition that caused the epilepsy or the treatment for epilepsy. This paper investigates the effects of antiepileptic drugs (AEDs) on BMD in children. A systematic search of Pubmed resulted in 14 papers that described changes in BMD in children on AEDs. For phenytoin, one study failed to show a decrease in femur BMD, whereas another study reported a decrease in total body and spine BMD, but only with the use of phenytoin for > 2 years. With phenytoin combined with a ketogenic diet, a decrease in forearm BMC was seen. For phenobarbital, one study showed a decrease in spine and total body BMD, but only among those who had used phenobarbital for > 2 years. Six studies were available for carbamazepine, and none of these showed a decrease in BMD in any skeletal site. For valproate, results were diverse; two studies reported a decrease in spine BMD, whereas two other studies did not. Two studies reported a decrease in hip BMD with valproate, whereas one did not. All three studies on forearm BMD in users of valproate described a decrease. Three studies reported an improvement in BMC with vitamin D supplementation in children on AEDs. No reports on changes in BMD among users of newer AEDs are available. In conclusion, more evidence is needed for the effects on BMD in children, especially for newer AEDs. The available studies have all been cross-sectional, and longitudianal studies are needed along with studies on potential interventions in children with decreased BMD.

Anti-epileptic medication and bone health

BACKGROUND

Epilepsy is a common chronic neurological disorder, usually requiring long-term treatment with anti-epileptic drugs (AED). Many studies have reported that AED therapy is associated with metabolic bone disease and is a major iatrogenic risk factor for fractures. There remains uncertainty about the type(s) of bone disease due to AED treatment, and the pathogenesis of AED-associated fractures.

RATIONALE

Deficits in bone mineral density (BMD) are widely reported in AED-treated patient populations. However, much of the research conducted to date has been limited by factors such as small sample size, potentially biased subject selection, a lack of selection of appropriate control data, and failure to take account of important confounding influences. The pathogenesis of AED-associated fractures is likely to be multifactorial, due to factors including reduced BMD, impaired bone quality (due to osteoporosis and/or osteomalacia), increased propensity to fall, and fractures associated with seizures or loss of consciousness.

RECOMMENDATIONS

Patients receiving long-term AED should be monitored for indices of bone health, including BMD and vitamin D status. Lifestyle factors should be optimized, vitamin D status maintained, and fall prevention strategies introduced as appropriate. Good seizure control is important. The use of additional, specific osteoporosis therapy is not evidence-based in this setting, but would appear reasonable in patients with clinically significant decreases in BMD, applying current treatment guidelines for osteoporosis.

CONCLUSION

There is a pressing need for improved understanding of the pathogenesis of AED-associated bone disease, for better definition of the risk associated with specific AED regimens, and for the development of evidence-based preventive and treatment approaches in this common but neglected disorder.

Antiepileptic drugs and bone metabolism

Anti-epileptic medications encompass a wide range of drugs including anticonvulsants, benzodiazepines, enzyme inducers or inhibitors, with a variety effects, including induction of cytochrome P450 and other enzyme, which may lead to catabolism of vitamin D and hypocalcemia and other effects that may significantly effect the risk for low bone mass and fractures. With the current estimates of 50 million people worldwide with epilepsy together with the rapid increase in utilization of these medications for other indications, bone disease associated with the use of anti-epileptic medications is emerging as a serious health threat for millions of people. Nevertheless, it usually goes unrecognized and untreated. In this review we discuss the pathophysiologic mechanisms of bone disease associated with anti-epileptic use, including effect of anti-epileptic agents on bone turnover and fracture risk, highlighting various strategies for prevention of bone loss and associated fractures a rapidly increasing vulnerable population.

Osteoporosis in children and adolescents: etiology and management

Bone mass increases progressively during childhood, but mainly during adolescence when approximately 40% of total bone mass is accumulated. Peak bone mass is reached in late adolescence, and is a well recognised risk factor for osteoporosis later in life. Thus, increasing peak bone mass can prevent osteoporosis. The critical interpretation of bone mass measurements is a crucial factor for the diagnosis of osteopenia/osteoporosis in children and adolescents. To date, there are insufficient data to formally define osteopenia/osteoporosis in this patient group, and the guidelines used for adult patients are not applicable. In males and females aged <20 years the terminology 'low bone density for chronologic age' may be used if the Z-score is less than -2. For children and adolescents, this terminology is more appropriate than osteopenia/osteoporosis. Moreover, the T-score should not be used in children and adolescents. Many disorders, by various mechanisms, may affect the acquisition of bone mass during childhood and adolescence. Indeed, the number of disorders that have been identified as affecting bone mass in this age group is increasing as a consequence of the wide use of bone mass measurements. The increased survival of children and adolescents with chronic diseases or malignancies, as well as the use of some treatment regimens has resulted in an increase in the incidence of reduced bone mass in this age group. Experience in treating the various disorders associated with osteoporosis in childhood is limited at present. The first approach to osteoporosis management in children and adolescents should be aimed at treating the underlying disease. The use of bisphosphonates in children and adolescents with osteoporosis is increasing and their positive effect in improving bone mineral density is encouraging. Osteoporosis prevention is a key factor and it should begin in childhood. Pediatricians should have a fundamental role in the prevention of osteoporosis, suggesting strategies to achieve an optimal peak bone mass.

Histone deacetylase inhibitors promote osteoblast maturation

HDIs are potential therapeutic agents for cancer and neurological diseases because of their abilities to alter gene expression, induce growth arrest or apoptosis of tumors cells, and stimulate differentiation. In this report, we show that several HDIs promote osteoblast maturation in vitro and in calvarial organ cultures.

INTRODUCTION

Histone deacetylase inhibitors (HDIs) are currently in phase I and II clinical trials as anticancer agents. Some HDIs are also commonly prescribed treatments for epilepsy and bipolar disorders. Although administered systemically, the effects of HDIs on osteoblasts and bone formation have not been extensively examined. In this study, we investigated the effect of histone deacetylase inhibition on osteoblast proliferation and differentiation.

MATERIALS AND METHODS

MC3T3-E1 cells, calvarial-derived primary osteoblasts, and calvarial organ cultures were treated with various commercially available HDIs (trichostatin A [TSA], sodium butyrate [NaB], valproic acid [VPA], or MS-275). The effects of these inhibitors on cell proliferation, viability, cell cycle progression, Runx2 transcriptional activity, alkaline phosphatase production, and matrix mineralization were determined. Expression levels of osteoblast maturation genes, type I collagen, osteopontin, bone sialoprotein, and osteocalcin in response to TSA were measured by quantitative PCR.

RESULTS

Concentrations of HDIs that caused hyperacetylation of histone H3 induced transient increases in osteoblast proliferation and viability but did not alter cell cycle profiles. These concentrations of HDIs also increased the transcriptional activity of Runx2. TSA accelerated alkaline phosphatase production in MC3T3-E1 cells and calvarial organ cultures. In addition, TSA accelerated matrix mineralization and the expression of osteoblast genes, type I collagen, osteopontin, bone sialoprotein, and osteocalcin in MC3T3-E1 cells.

CONCLUSIONS

These studies show that histone deacetylase activity regulates osteoblast differentiation and bone formation at least in part by enhancing Runx2-dependent transcriptional activation. Therefore, HDIs are a potentially new class of bone anabolic agents that may be useful in the treatment of diseases that are associated with bone loss such as osteoporosis and cancer.

Epilepsy, osteoporosis and fracture risk - a meta-analysis

This meta-analysis assesses the effects of epilepsy on fracture risk and changes in bone mineral density (BMD) in patients with epilepsy. A search of PubMed was conducted using the key words epilepsy, fracture, and bone mineral. A weighted estimate of relative risk of fractures and changes in BMD (Z-score) was calculated. From the changes in BMD, expected increase in relative fracture risk was calculated. A total of 11 studies on fracture risk and 12 studies on BMD were retrieved. The relative risk of any fracture was increased (2.2, 95% CI: 1.9-2.5, five studies), as was the risk of hip (5.3, 3.2-8.8, six studies), forearm (1.7, 1.2-2.3, six studies), and spine fractures (6.2, 2.5-15.5, three studies). A large proportion of fractures (35%) seemed related to seizures. Spine (mean +/- SEM: -0.38 +/- 0.06) and hip (-0.56 +/- 0.06) BMD Z-scores were significantly decreased, hip more than spine (2P < 0.05). The expected increases in relative risk of any fracture from BMD Z-scores were 1.2-1.3, and significantly lower than observed (2P < 0.05). The deficit in BMD in patients with epilepsy is too small to explain the observed increase in fracture risk. The remainder of the increase in fracture risk may be linked to seizures.