Hyperbilirubinemia is not a major contributing factor to altered bone mineral density in patients with chronic liver disease

Association between total bilirubin and bone mineral density level in adolescents

Background

Increasing bone mass accumulation in adolescence and obtaining greater peak bone mass is one of the effective methods to prevent osteoporosis in the future. We aimed to examine the association between total bilirubin and bone mineral density (BMD) level in adolescents.

Methods

We used the data from 2005–2010 and 2013–2014 cycles of National Health and Nutrition Examination Survey (NHANES). The BMD levels in the region of lumbar spine and femoral regions, including total femur, femoral neck, trochanter, and intertrochanter were measured. Univariable and multivariable linear regression model were used to assess the relationship between total bilirubin concentration and BMD.

Results

A total of 3741 participants aged 12–19 years were ultimately included in the study. There were 1997 (53.38%) males and 1744 (46.62%) females. Univariate analysis results showed that age, sex, race, education, income, body mass index, dietary calcium intake, and diabetes were correlated with BMD levels. Compared with the lowest quartile of total bilirubin concentration, the highest quartile of total bilirubin concentration was positively associated with BMD levels in the regions of total femur (β = 0.036, 95% CI = 0.021 to 0.050, P < 0.001), femur neck (β = 0.030, 95% CI = 0.016 to 0.044, P < 0.001), trochanter (β = 0.033, 95% CI = 0.019 to 0.046, P < 0.001), intertrochanter (β = 0.040, 95% CI = 0.023 to 0.056, P < 0.001), and lumbar spine (β = 0.032, 95% CI = 0.018 to 0.045, P < 0.001). We also observe the same trend in sensitivity analysis (P for trend < 0.001).

Conclusion

Our study demonstrated that total bilirubin concentration was positively associated with BMD levels in adolescents in United States. Total bilirubin concentration might be a protective marker against bone loss in adolescents.

Genetic predisposition to increased serum calcium, bone mineral density, and fracture risk in individuals with normal calcium levels: mendelian randomisation study

OBJECTIVE

To determine if genetically increased serum calcium levels are associated with improved bone mineral density and a reduction in osteoporotic fractures.

DESIGN

Mendelian randomisation study.

SETTING

Cohorts used included: the UK Biobank cohort, providing genotypic and estimated bone mineral density data; 25 cohorts from UK, USA, Europe, and China, providing genotypic and fracture data; and 17 cohorts from Europe, providing genotypic and serum calcium data (summary level statistics).

PARTICIPANTS

A genome-wide association meta-analysis of serum calcium levels in up to 61 079 individuals was used to identify genetic determinants of serum calcium levels. The UK Biobank study was used to assess the association of genetic predisposition to increased serum calcium with estimated bone mineral density derived from heel ultrasound in 426 824 individuals who had, on average, calcium levels in the normal range. A fracture genome-wide association meta-analysis comprising 24 cohorts and the UK Biobank including a total of 76 549 cases and 470 164 controls, who, on average, also had calcium levels in the normal range was then performed.

RESULTS

A standard deviation increase in genetically derived serum calcium (0.13 mmol/L or 0.51 mg/dL) was not associated with increased estimated bone mineral density (0.003 g/cm2, 95% confidence interval -0.059 to 0.066; P=0.92) or a reduced risk of fractures (odds ratio 1.01, 95% confidence interval 0.89 to 1.15; P=0.85) in inverse-variance weighted mendelian randomisation analyses. Sensitivity analyses did not provide evidence of pleiotropic effects.

CONCLUSIONS

Genetic predisposition to increased serum calcium levels in individuals with normal calcium levels is not associated with an increase in estimated bone mineral density and does not provide clinically relevant protection against fracture. Whether such predisposition mimics the effect of short term calcium supplementation is not known. Given that the same genetically derived increase in serum calcium is associated with an increased risk of coronary artery disease, widespread calcium supplementation in the general population could provide more risk than benefit.

Hepatic Osteodystrophy-Molecular Mechanisms Proposed to Favor Its Development

Almost all patients with chronic liver diseases (CLD) show altered bone metabolism. Depending on the etiology, this manifests in a severe osteoporosis in up to 75% of the affected patients. Due to high prevalence, the generic term hepatic osteodystrophy (HOD) evolved, describing altered bone metabolism, decreased bone mineral density, and deterioration of bone structure in patients with CLD. Once developed, HOD is difficult to treat and increases the risk of fragility fractures. Existing fractures affect the quality of life and, more importantly, long-term prognosis of these patients, which presents with increased mortality. Thus, special care is required to support the healing process. However, for early diagnosis (reduce fracture risk) and development of adequate treatment strategies (support healing of existing fractures), it is essential to understand the underlying mechanisms that link disturbed liver function with this bone phenotype. In the present review, we summarize proposed molecular mechanisms favoring the development of HOD and compromising the healing of associated fractures, including alterations in vitamin D metabolism and action, disbalances in transforming growth factor beta (TGF-β) and bone morphogenetic protein (BMP) signaling with histone deacetylases (HDACs) as secondary regulators, as well as alterations in the receptor activator of nuclear factor kappa B ligand (RANKL)–osteoprotegerin (OPG) system mediated by sclerostin. Based on these mechanisms, we give an overview on the limitations of early diagnosis of HOD with established serum markers.

Increased risk of osteoporosis in patients with primary biliary cirrhosis

BACKGROUND

We evaluated the risk of osteoporosis in patients with primary biliary cirrhosis (PBC) using a nationwide population-based dataset.

METHODS

In a cohort study of 986,713 individuals, we selected 2,493 PBC patients who were aged 18 years or older and had been diagnosed with PBC, based on the International Classification of Disease (ICD-9-CM) codes 571.6, during 20002010. The control cohort comprised 9,972 randomly selected, propensity matched patients (by age, gender, and index date), without PBC. Using this adjusted data, a possible association between PBC and the risk of developing osteoporosis was estimated using a Cox proportional hazard regression model.

RESULTS

During the follow-up period, osteoporosis was diagnosed in 150 (6.02%) patients in the PBC cohort and in 539 (5.41%) patients in the non-PBC cohort. After adjusting for covariates, osteoporosis risk was found to be 3.333 times greater in the PBC cohort than in the non-PBC cohort when measured over 6 years after PBC diagnosis. Stratification revealed that the use of ursodeoxycholic acid (UDCA) had no significance in decreasing the risk of osteoporosis when comparing the PBC cohorts with the non-PBC cohorts (P = 0.124). Additionally, osteoporosis risk was significantly higher in PBC patients with steroid use (aHR: 6.899 vs 3.333). Moreover, when comparing the PBC cohorts to the non-PBC cohorts, the non-cirrhotic patients were prone to osteoporosis at a younger age compared to those in the cirrhotic cohorts. We also found that the associated risk of fractures is only prominent for vertebral and wrist fractures in the PBC cohort compared to that in the non-PBC cohort.

CONCLUSION

A significant association exists between PBC and subsequent risk for osteoporosis. Therefore, PBC patients, particularly those treated with steroids, should be evaluated for subsequent risk of osteoporosis.

Diagnosis and Management of Cirrhosis-Related Osteoporosis

Management of cirrhosis complications has greatly improved, increasing survival and quality of life of the patients. Despite that, some of these complications are still overlooked and scarcely treated, particularly those that are not related to the liver. This is the case of osteoporosis, the only cirrhosis complication that is not solved after liver transplantation, because bone loss often increases after immunosuppressant therapy. In this review, the definitions of bone conditions in cirrhotic patients are analyzed, focusing on the more common ones and on those that have the largest impact on this population. Risk factors, physiopathology, diagnosis, screening strategies, and treatment of osteoporosis in cirrhotic patients are discussed, presenting the more striking data on this issue. Therapies used for particular conditions, such as primary biliary cirrhosis and liver transplantation, are also presented.

Osteodystrophy in Cholestatic Liver Diseases Is Attenuated by Anti-γ-Glutamyl Transpeptidase Antibody

BACKGROUND

Cholestatic liver diseases exhibit higher levels of serum γ-glutamyl transpeptidase (GGT) and incidence of secondary osteoporosis. GGT has been identified as a novel bone-resorbing factor that stimulates osteoclast formation. The aim of this study was to elucidate the interaction of elevated GGT levels and cholestatic liver disease-induced bone loss.

METHODS

Wistar rats were divided into three groups: sham-operated control (SO) rats, bile duct ligation (BDL) rats, and anti-GGT antibody-treated BDL rats (AGT). Serum GGT level was measured. Bone mineral density (BMD) was analyzed by dual-energy X-ray absorptiometry. Bone morphometric parameters and microarchitectural properties were determined by micro-computed tomography and histomorphometry of the distal metaphysis of femurs. Alterations of bone metabolism-related factors were evaluated by cytokine array. Effects of GGT on osteoblasts or stromal cells were evaluated by RT-PCR, enzyme activity, and mineralization ability.

RESULTS

Serum levels of GGT were significantly elevated in the BDL-group. In the BDL group, BMD, bone mass percentage, and osteoblast number were significantly decreased, whereas osteoclast number was significantly increased. These alterations were markedly attenuated in the AGT group. The mRNA levels of vascular endothelial growth factor-A, LPS-induced CXC chemokine, monocyte chemoattractant protein-1, tumor necrosis factor-α interleukin-1β and receptor activator of nuclear factor-kappa B ligand were upregulated, and those of interferon-γ and osteoprotegerin were downregulated in the GGT-treated stromal cells. Furthermore, GGT inhibited mineral nodule formation and expression of alkaline phosphatase and bone sialo-protein in osteoblastic cells.

CONCLUSION

Our results indicate that elevated GGT level is involved in hepatic osteodystrophy through secretion of bone resorbing factor from GGT-stimulated osteoblasts/bone marrow stromal cells. In addition, GGT also possesses suppressive effects on bone formation. Managing elevated GGT levels by anti-GGT antibody may become a novel therapeutic agent for hepatic osteodystrophy in chronic liver diseases.

Osteodystrophy in chronic liver diseases

Osteoporosis and osteomalacia are, to date, among the most common metabolic diseases in the world. Lately, an association between metabolic bone diseases and chronic liver disease has been increasingly reported, inducing many authors to create a new nosographic entity known as 'hepatic osteodystrophy.' The importance of such a condition is further increased by the morbidity of these two diseases, which greatly reduce the quality of life because of frequent fractures, especially vertebral and femoral neck ones. For this reason, early identification of high-risk patients should be routinely performed by measuring bone mass density. The explanation for the association between bone diseases and chronic liver disease is still uncertain, and involves many factors: from hypogonadism to use of corticosteroid drugs, from genetic factors to interferon therapy. To date, few studies have been conducted, and all with a small number of patients to establish definitive conclusions about the possible treatment, but some evidence is beginning to emerge about the safety and efficacy of bisphosphonates.

High serum total bilirubin as a protective factor against hip bone loss in healthy middle-aged men

Bilirubin is known to have a physiologic role as an antioxidant that efficiently scavenges peroxyl radicals and suppresses oxidation, and oxidative stress has detrimental effects on bone metabolism. In the present study, we performed a 3-year longitudinal study of healthy middle-aged men, investigating the association between serum total bilirubin concentrations and annualized changes in bone mineral density (BMD). The study enrolled a total of 917 Korean men aged 40 years or older who had undergone comprehensive routine health examinations with an average follow-up interval of 3 years. BMD at proximal femur sites was measured with dual-energy X-ray absorptiometry using the same equipment at baseline and follow-up. The overall mean annualized rates of bone loss at the total femur, femoral neck, and trochanter were -0.25 %/year, -0.34 %/year, and -0.44 %/year, respectively. After adjustment for potential confounders, the rates of bone loss at all proximal femur sites were significantly attenuated in a dose-response fashion across increasing bilirubin concentrations (P = 0.006-0.046). Moreover, compared to subjects in the lowest bilirubin quartile category, those in the highest bilirubin quartile category showed significantly less bone loss at all proximal femur sites after adjustment for confounding factors (P = 0.010-0.048). This study provides the first clinical evidence that serum total bilirubin could be a protective marker against future bone loss, especially in subjects without liver diseases.

Iron homeostasis in osteoporosis and its clinical implications

Osteoporosis has until now been considered to be a disease associated with abnormal calcium metabolism. However, an increasing number of clinical observations strongly suggest the association of iron overload with bone diseases, particularly in osteoporosis in menopausal women. The recent identification of hepcidin sheds new light into the crucial role of iron homeostasis in bone metabolism. Decreasing iron overload in cell studies as well as in animal experiments has been shown to improve bone cell metabolism and growth in vitro and in vivo. In view of the significant iron overload found in the aging population, especially in females, the therapeutic potential of lowering iron overload for the treatment of osteoporosis is suggested.

Hepatic osteodystrophy: An important matter for consideration in chronic liver disease

Hepatic osteodystrophy (HO) is the generic term defining the group of alterations in bone mineral metabolism found in patients with chronic liver disease. This paper is a global review of HO and its main pathophysiological, epidemiological and therapeutic aspects. Studies examining the most relevant information concerning the prevalence, etiological factors, diagnostic and therapeutic aspects involved in HO were identified by a systematic literature search of the PubMed database. HO generically defines overall alterations in bone mineral density (BMD) (osteoporosis or osteopenia) which appear as a possible complication of chronic liver disease. The origin of HO is multifactorial and its etiology and severity vary in accordance with the underlying liver disease. Its exact prevalence is unknown, but different studies estimate that it could affect from 20% to 50% of patients. The reported mean prevalence of osteoporosis ranges from 13%-60% in chronic cholestasis to 20% in chronic viral hepatitis and 55% in viral cirrhosis. Alcoholic liver disease is not always related to osteopenia. HO has been commonly studied in chronic cholestatic disease (primary biliary cirrhosis and primary sclerosing cholangitis). Several risk factors and pathogenic mechanisms have been associated with the loss of BMD in patients with chronic liver disease. However, little information has been discovered in relationship to most of these mechanisms. Screening for osteopenia and osteoporosis is recommended in advanced chronic liver disease. There is a lack of randomized studies assessing specific management for HO.

Bisphosphonates for osteoporosis in primary biliary cirrhosis

BACKGROUND

Bisphosphonates are widely used for treatment of postmenopausal osteoporosis. Patients with primary biliary cirrhosis often have osteoporosis - either postmenopausal or secondary to the liver disease. No systematic review or meta-analysis has assessed the effects of bisphosphonates for osteoporosis in patients with primary biliary cirrhosis.

OBJECTIVES

To assess the beneficial and harmful effects of bisphosphonates for osteoporosis in primary biliary cirrhosis.

SEARCH METHODS

The Cochrane Hepato-Biliary Group Controlled Trials Register, The Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded, LILACS, clinicaltrials.gov, the WHO International Clinical Trials Registry Platform, and full text searches were conducted until November 2011. Manufacturers and authors were contacted for additional studies during the conductance of the review.

SELECTION CRITERIA

All randomised clinical trials of bisphosphonates in primary biliary cirrhosis compared with placebo or no intervention, or another bisphosphonate, or any other drug.

DATA COLLECTION AND ANALYSIS

Two authors extracted data. RevMan Analysis was used for statistical analysis of dichotomous data with risk ratio (RR) or risk difference (RD) and of continuous data with mean difference (MD) or standardised mean difference (SMD), all with 95% confidence intervals (CI). Methodological components were used to assess risk of systematic errors (bias). Trial sequential analysis was also used to control for random errors (play of chance).

MAIN RESULTS

Six trials were included. Three trials with 106 participants, of which two trials with high risk of bias, did not demonstrate significant effects of bisphosphonates (etidronate or alendronate) versus placebo or no intervention regarding mortality (RD 0.00; 95% CI -0.12 to 0.12, I² = 0%), fractures (RR 0.87; 95% CI 0.29 to 2.66, I² = 0%), or adverse events (RR 1.00; 95% CI 0.49 to 2.04). Two trials with 62 participants with high risk of bias compared one bisphosphonate (etidronate or alendronate) versus another (alendronate or ibandronate) and found no significant difference regarding mortality (RD -0.03; 95% CI -0.14 to 0.07, I² = 0%), fractures (RR 0.95; 95% CI 0.18 to 5.06, I² = 0%), or adverse events (RR 1.00; 95% CI 0.49 to 2.04, I² = 0%). Bisphosphonates had no significant effect on liver-related mortality, liver transplantation, or liver-related morbidity compared with placebo or no intervention, or another bisphosphonate. Bisphosphonates had no significant effect on bone mineral density compared with placebo or no intervention, or another bisphosphonate. Bisphosphonates compared with placebo or no intervention seem to decrease the urinary amino telopeptides of collagen I (NTx) concentration (MD -16.93 nmol bone collagen equivalents/mmol creatinine; 95% CI -23.77 to -10.10; 2 trials with 88 patients; I² = 0%) and serum osteocalcin (SMD -0.81; 95% CI -1.22 to -0.39; 3 trials with 100 patients; I² = 34 %) concentration. The former result was supported by trial sequential analysis, but not the latter. Alendronate compared with another bisphosphonate (ibandronate) had no significant effect on serum osteocalcin concentration (MD -3.61 ng/ml, 95% CI -9.41 to 2.18; 2 trials with 47 patients; I² = 82%) in a random-effects meta-analysis, but it significantly decreased serum osteocalcin (MD -4.40 ng/ml, 95% CI -6.75 to -2.05; 2 trials with 47 patients; I² = 82%), the procollagen type I N-terminal propeptide (MD -8.79 ng/ml, 95% CI -15.96 to -1.63; 2 trials with 47 patients; I² = 38%), and NTx concentration (MD -14.07 nmol bone collagen equivalents/mmol creatinine, 95% CI -24.23 to -3.90; 2 trials with 46 patients; I²=0%) in a fixed-effect model. The latter two results were not supported by trial sequential analyses. There was no statistically significant difference in the number of patients having bisphosphonates withdrawn due to adverse events compared with placebo or no intervention (RD -0.04; 95% CI -0.21 to 0.12; 2 trials with 46 patients; I² = 0%), or another bisphosphonate (RR 0.56; 95% CI 0.14 to 2.17; 2 trials with 62 patients; I² = 0%). One trial with 32 participants and with high risk of bias compared etidronate versus sodium fluoride without finding significant difference regarding mortality, fractures, adverse events, or bone mineral density. Etidronate compared with sodium fluoride significantly decreased serum osteocalcin, urinary hydroxyproline, and parathyroid hormone concentration.

AUTHORS' CONCLUSIONS

We did not find evidence to support or refute the use of bisphosphonates for patients with primary biliary cirrhosis. The data seem to indicate a possible positive intervention effect of bisphosphonates on decreasing urinary amino telopeptides of collagen I concentration compared with placebo or no intervention with no risk of random error. There is need for more randomised clinical trials assessing the effects of bisphosphonates for osteoporosis on patient-relevant outcomes in primary biliary cirrhosis.

Effects of bilirubin and sera from jaundiced patients on osteoblasts: contribution to the development of osteoporosis in liver diseases

Low bone formation is considered to be the main feature in osteoporosis associated with cholestatic and end-stage liver diseases, although the consequences of retained substances in chronic cholestasis on bone cells have scarcely been studied. Therefore, we analyzed the effects of bilirubin and serum from jaundiced patients on viability, differentiation, mineralization, and gene expression in the cells involved in bone formation. The experiments were performed in human primary osteoblasts and SAOS-2 human osteosarcoma cells. Unconjugated bilirubin or serum from jaundiced patients resulted in a dose-dependent decrease in osteoblast viability. Concentrations of bilirubin or jaundiced serum without effects on cell survival significantly diminished osteoblast differentiation. Mineralization was significantly reduced by exposure to 50 μM bilirubin at all time points (from -32% to -55%) and jaundiced sera resulted in a significant decrease on cell mineralization as well. Furthermore, bilirubin down-regulated RUNX2 (runt-related transcription factor 2) gene expression, a basic osteogenic factor involved in osteoblast differentiation, and serum from jaundiced patients significantly up-regulated the RANKL/OPG (receptor activator of nuclear factor-κB ligand/osteoprotegerin) gene expression ratio, a system closely involved in osteoblast-induced osteoclastogenesis.

CONCLUSION

Besides decreased cell viability, unconjugated bilirubin and serum from jaundiced patients led to defective consequences on osteoblasts. Moreover, jaundiced serum up-regulates the system involved in osteoblast-induced osteoclastogenesis. These results support the deleterious consequences of increased bilirubin in advanced chronic cholestasis and in end-stage liver diseases, resulting in disturbed bone formation related to osteoblast dysfunction.

Osteoporosis in patients with primary biliary cirrhosis

Metabolic bone disease has been recognized as an important complication of chronic liver disease particularly in cholestatic disorders [primary biliary cirrhosis (PBC) and primary sclerosing cholangitis] and after liver transplantation. It includes osteoporosis and more rarely osteomalacia, which is more frequent in severe malabsorption and advanced liver disease. The pathogenesis of this disorder is complex and is likely to be multifactorial. Regardless of the etiology of osteoporosis in PBC patients, they have an increased risk of spontaneous or low-trauma fracturing leading to significant patient morbidity, deterioration of quality of life, and even patient mortality. The development of bone densitometry has allowed assessment of bone mass and then contributed in estimating the fracture risk. The gold standard of bone mineral density measurement is currently the dual- energy X-ray absorptiometry. Recommendations formulated by the World Health Organization have reported the diagnostic ranges of osteoporosis based on the t-score: patient with osteoporosis has a t-score less than -2.5 SD, osteopenia has a t-score between -1.0 and -2.5 SD and a normal individual has a t-score more than -1.0 SD. The risk of fracture shows a correlation with bone mineral density but no fracture threshold was determined and the best site of characterizing the hip fracture risk is the measure of the bone mineral density of the proximal femur. The treatment of osteoporosis in patients with PBC is largely based on trials of patients with postmenopausal osteoporosis as there are a few and smaller studies of osteoporotic patients with PBC. Bisphosphonates seem to be effective in biliary disease and are more tolerated.

Liver and bone

Osteoporosis is a frequent complication in patients with chronic liver disease, especially in end-stages and in cases with chronic cholestasis, hemochromatosis and alcohol abuse. The problem is more critical in transplant patients when bone loss is accelerated during the period immediately after transplantation, leading to a greater incidence of fractures. Advanced age, low body mass index and severity of the liver disease are the main risk factors for bone disease in patients with cholestasis. Mechanisms underlying osteoporosis in chronic liver disease are complex and poorly understood, but osteoporosis mainly results from low bone formation, related to the effects of retained substances of cholestasis, such as bilirubin and bile acids, or to the effects of alcohol on osteoblastic cells. Increased bone resorption has also been described in cholestatic women with advanced disease. Although there is no specific treatment, bisphosphonates associated with supplements of calcium and vitamin D are effective for increasing bone mass in patients with chronic cholestasis and after liver transplantation. The outcome in reducing the incidence of fractures has not been adequately demonstrated essentially because of the low number of patients included in the therapeutic trials. Randomized studies assessing bisphosphonates in larger series of patients, the development of new drugs for osteoporosis and the improvement in the management of liver transplant recipients may change the future.

Low bone mass and severity of cholestasis affect fracture risk in patients with primary biliary cirrhosis

BACKGROUND & AIMS

The influence of osteoporosis and liver disease on fracture risk is not well characterized in patients with primary biliary cirrhosis (PBC). We studied a large series of women with PBC to assess the prevalence and risk factors for fractures and the fracture threshold.

METHODS

In female patients with PBC (n = 185; age, 55.7 +/- 0.7 years; range 28-79 years), age, duration of PBC, menopausal status, and histologic stage and severity of liver disease were assessed. Vertebral and non-vertebral fractures were recorded in 170 and 172 patients, respectively. Osteoporosis and osteopenia were diagnosed based on densitometry analysis.

RESULTS

The prevalences of vertebral, non-vertebral, and overall fractures were 11.2%, 12.2%, 20.8%, respectively. Osteoporosis was significantly more frequent in patients with PBC than in normal women. Osteoporosis was associated with age, weight, height, histologic stage, severity, and duration of liver damage; fractures were associated with osteoporosis, menopause, age, and height but not with severity of PBC. Osteoporosis was a risk factor for vertebral fracture (odds ratio [OR], 8.48; 95% confidence interval [CI]: 2.67-26.95). Lumbar T score <-1.5 (OR, 8.27; 95% CI: 1.84-37.08) and femoral neck T score <-1.5 (OR, 6.83; 95% CI: 1.48-31.63) were significant risk factors for vertebral fractures.

CONCLUSIONS

Fractures, particularly vertebral fractures, are associated with osteoporosis, osteopenia, and T scores less than -1.5, whereas osteoporosis and osteopenia are associated with the severity of liver damage. Patients with T scores less than -1.5 might require additional monitoring and be considered for therapy to prevent fractures.

Current understanding of osteoporosis associated with liver disease

Osteoporosis is a common complication of many types of liver disease. Research into the pathogenesis of osteoporosis has revealed that the mechanisms of bone loss differ between different types of liver disease. This Review summarizes our current understanding of osteoporosis associated with liver disease and the new advances that have been made in this field. The different mechanisms by which cholestatic and parenchymal liver disease can lead to reduced bone mass, the prevalence of osteopenia and osteoporosis in patients with early and advanced liver disease, and the influence of osteoporotic fractures on patient survival are discussed along with the advances in our understanding of the molecular pathways associated with bone loss. The role of the CSF1-RANKL system and that of the liver molecule, oncofetal fibronectin, a protein that has traditionally been viewed as an extracellular matrix protein are also discussed. The potential impact that these advances may have for the treatment of osteoporosis associated with liver disease is also reviewed.

Cholestasis and metabolic bone disease - a clinical review

Metabolic bone disease, mainly osteopenia/osteoporosis and occasionally osteomalacia, is a major extrahepatic manifestation of chronic cholestatic liver disease (synonym: hepatic osteodystrophy). Reduced bone mineral density is found in up to 60% and atraumatic fractures in about 20% of patients with chronic liver disease. Hepatic osteodystrophy is characterized by reduced formation and increased resorption of bone; major risk factors are chronic cholestasis and advanced cirrhosis. Pathogenetic mechanisms include genetic factors, abnormalities of calcium, vitamin D, vitamin K and bilirubin metabolism, IGF-1 deficiency, the RANKL/OPG-system, hypogonadism, drugs harmful to bone, lifestyle factors (smoking, alcoholism, immobility), malnutrition and low body mass index. Screening for osteopenia should be performed and reversible risk factors must be corrected. At present, bisphosphonates are the predominantly used specific drugs for the treatment of osteoporosis in chronic liver disease. After orthotopic liver transplantation bone mineral density improves in long-term follow-up. Studies are needed for fracture prevention in chronic liver disease.

Osteoporosis in primary biliary cirrhosis: pathogenesis and treatment

Osteoporosis, characterized by loss of bone strength leading to fragility fractures, is a common event in patients who have primary biliary cirrhosis. Although its pathogenesis is not well known, it results mainly from low bone formation. There is no specific treatment, but bisphosphonates, especially alendronate, effectively increases bone mass and prevents bone loss. Despite these favorable effects on bone mass, no clear effects on decreasing the fracture rate are demonstrated, probably because of the low number of patients included in the trials. The potential usefulness of new agents requires further evaluation.

Bone disorders in chronic liver disease

Osteomalacia rarely occurs in adult patients with chronic liver disease despite a low serum vitamin D level being reported in up to two-thirds of patients with cirrhosis. In contrast, osteoporosis, which increases the risk of vertebral fractures, occurs in 12%-55% of patients with cirrhosis. Although the prevalence is probably falling, as shown by a fall from 57%-26% in patients with biliary disease requiring liver transplantation over the last 2 decades, it still accounts for significant patient morbidity. Bone density also falls in the first 3 months after liver transplantation, and pretransplant fractures are predictive of posttransplant fractures. Many of the known risk factors for postmenopausal osteoporosis exist in the cirrhotic population, such as excess alcohol intake, steroid use, poor nutrition, and hypogonadism. There is also an increased risk of osteoporosis in patients without cirrhosis, particularly those with hemochromatosis and biliary disease. The diagnosis is made with bone density measurements. The effective treatment is largely based on evidence from postmenopausal osteoporosis as there have been only a few small clinical trials of patients with chronic liver disease. Bisphosphonates are the mainstay of treatment; they have been shown to be effective in biliary disease and are well tolerated.

Impairment of bone mass development in children with chronic cholestatic liver disease

OBJECTIVE

To analyse aspects of mineral metabolism, bone mineral density (BMD), bone remodelling activity and serum IGF-1 levels in children with chronic cholestatic disease (CCLD).

PATIENTS AND MEASUREMENTS

A total of 13 children with chronic cholestatic liver disease (CCLD; mean age 7.2 +/- 4.8 years) and 22 control subjects (mean age 7.6 +/- 4.5 years) were studied. Serum osteocalcin, bone alkaline phosphatase (BAP), 25-hydroxyvitamin D, PTH and IGF-1 levels and urinary deoxypyridinoline were determined. BMD was measured by dual-energy X-ray absorptiometry in the lumbar spine, total hip and whole body. Lumbar spine areal BMD was converted mathematically to apparent volumetric BMD (aBMD) and corrected for the bone age of the patient.

RESULTS

Z-score of lumbar spine BMD was lower in CCLD patients than in controls and the difference was maintained when BMD was expressed as aBMD (control = 0.107 +/- 0.02 vs. CCLD = 0.092 +/- 0.02 g/cm(3), P < 0.05) and after conversion for bone age. All participants showed normal 25-hydroxyvitamin D levels, with no significant differences in serum levels of 25-hydroxyvitamin D and PTH between groups. IGF-1 levels were significantly lower in the CCLD group (control = 19.6 +/- 16.8 vs. CCLD = 6.4 +/- 7.6 nmol/l, P < 0.05) and a positive correlation was observed between whole body BMD and IGF-1 in this group.

CONCLUSIONS

These results indicate that CCLD limits bone mass gain in children. A reduction in hepatic IGF-1 production might be responsible, at least in part, for the low bone mass of these patients.