Osteodystrophy in chronic liver diseases

Compromised bone strength in patients with alcoholic liver cirrhosis

Osteoporosis and/or osteopenia are frequently observed complications in alcoholic liver disease patients, especially in its irreversible stage (alcoholic liver cirrhosis - ALC). Current literature review regarding osteoporosis incidence increased fracture risk, bone mineral density changes, micro-structural alteration and pathogenetic mechanisms leading to ALC - induced decrease in bone quality is presented. It has been reported that osteoporosis is influenceing significant number of ALC patients, with particular accent on lumbar spine, as most commonly affected skeletal site. Several risk factors and ethio-pathogenic mechanisms have been associated with the loss of bone mineral density, in patients with ALC and other cirrhosis. Certain authors claim that dominant mechanism in ALC-induced bone loss is decrease in bone formation and osteoblastic function, while other results suggest increased bone remodeling as underlying cause of increased bone fragility in ALC patients. Increased bone fragility and susceptibility to osteoporotic fractures significantly affect life expectancy and quality of life in patients with ALC. Thus, osteological screening and individual fracture risk assessment are highly recommended for all patients with alcoholic liver cirrhosis.

Chronic Liver Disease Patients have Worse Outcomes and Increased Postoperative Complications After Orthopedic Fractures

INTRODUCTION

Cirrhotic patients are at a higher risk for sustaining orthopedic fractures with a reported prevalence of 5% to 20%. Cirrhosis also affects wound healing and bleeding risk, and hence, impacts the postoperative outcomes after fracture repair. However, there is limited data available on the postoperative risk factors and clinical outcomes of fractures in patients with chronic liver disease (CLD).

METHODS

Data from the National Inpatient Sample for the years 2012 to 2015 were analyzed. Patients were identified using ICD-9 codes for any fracture. ICD-9 codes for CLD were used to categorize patients into CLD and non-CLD groups. Primary outcomes included inpatient mortality, length of stay (LOS), and total hospital charges. Secondary outcomes included complications such as postoperative infection, prosthetic failure, bleeding, and improper wound healing.

RESULTS

A total of 931,193 patient encounters for orthopedic fractures were identified and divided into 17,388 with CLD and 913,806 without CLD (non-CLD). The inpatient mortality in patients with CLD was almost twice that of non-CLD patients (odds ratio, 1.95; 95% confidence interval, 1.8-2.1). Patients with CLD also had a longer mean LOS at 7.4±8.6 days versus 5.6±7.2 days (P<0.001) and higher total hospital charges at $76,198±99,494 versus $64,294±95,673 (P<0.001). CLD patients also had higher rates of infections, improper wound healing, and bleeding.

DISCUSSION

In this large retrospective study, CLD patients with fractures had significantly higher mortality, LOS and hospital charges. These findings correlate with the higher rates of infection, bleeding, and poorer wound healing in this population. Increased clinician awareness of these risks is a key to improving the care of CLD patients.

Bone microarchitecture and bone turnover in hepatic cirrhosis

Liver cirrhosis leads to bone loss. To date, information on bone quality (three-dimensional microarchitecture) and, thus, bone strength is scarce. We observed decreased bone quality at both assessed sites, independent of disease severity. Therefore, all patients should undergo early-stage screening for osteoporosis.

INTRODUCTION

Recent studies found low bone mineral density in cirrhosis, but data on bone microstructure are scarce. This study assessed weight-bearing and non-weight-bearing bones in patients with cirrhosis and healthy controls. The primary objective was to evaluate trabecular and cortical microarchitecture.

METHODS

This was a single-center study in patients with recently diagnosed hepatic cirrhosis. Thirty-two patients and 32 controls participated in this study. After determining the type of cirrhosis, the parameters of bone microarchitecture were assessed by high-resolution peripheral quantitative computed tomography.

RESULTS

Both cortical and trabecular microarchitectures showed significant alterations. At the radius, trabecular bone volume fraction was 17% lower (corrected p = 0.028), and, at the tibia, differences were slightly more pronounced. Trabecular bone volume fraction was 19% lower (p = 0.024), cortical bone mineral density 7% (p = 0.007), and cortical thickness 28% (p = 0.001), while cortical porosity was 32% higher (p = 0.023), compared to controls. Areal bone mineral density was lower (lumbar spine - 13%, total hip - 11%, total body - 9%, radius - 17%, and calcaneus - 26%). There was no correlation between disease severity and microarchitecture. Areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry (DXA) correlated well with parameters of cortical and trabecular microarchitecture.

CONCLUSIONS

Hepatic cirrhosis deteriorates both trabecular and cortical microarchitecture, regardless of disease severity. Areal bone mineral density is diminished at all sites as a sign of generalized affection. In patients with hepatic cirrhosis, regardless of its origin or disease severity, aBMD measurements are an appropriate tool for osteologic screening.

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.

Modeling hepatic osteodystrophy in Abcb4 deficient mice

Hepatic osteodystrophy (HOD) denotes the alterations in bone morphology and metabolism frequently observed in patients with chronic liver diseases, in particular in case of cholestatic conditions. The molecular mechanisms underlying HOD are only partially understood. In the present study, we characterized the bone phenotypes of the ATP-binding cassette transporter B4 knockout mouse (Abcb4(-/-)), a well-established mouse model of chronic cholestatic liver disease, with the aim of identifying and characterizing a mouse model for HOD. Furthermore, we investigated the influence of vitamin D on bone quality in this model. The bone morphology analyses revealed reduced bone mineral contents as well as changes in trabecular bone architecture and decreased cortical bone densities in Abcb4(-/-) mice with severe liver fibrosis. We observed dysregulation of genes involved in bone remodeling (osteoprotegerin, osteocalcin, osteopontin) and vitamin D metabolism (7-dehydrocholesterol reductase, Gc-globulin, Cyp2r1, Cyp27a1) as well as alterations in calcium and vitamin D homeostasis. In addition, serum RANKL and TGF-β levels were increased in Abcb4(-/-) mice. Vitamin D dietary intervention did not restore the bone phenotypes of Abcb4(-/-) animals. We conclude that the Abcb4(-/-) mouse provides an experimental framework and a preclinical model to gain further insights into the molecular pathobiology of HOD and to study the systemic effects of therapeutic interventions.