Experimental cholestatic liver disease through bile-duct ligation in rats results in skeletal fragility and impaired osteoblastogenesis

Prognosis of Cirrhotic Patients After Osteoporotic Femoral Neck Fracture

Introduction and Objectives: Osteoporotic hip fractures in cirrhotic subjects are associated with increased post-fracture mortality. Our aim was to identify unfavorable factors that were associated with increased post-fracture mortality. Patients and Methods: We employed a retrospective evaluation of the short- and long-term prognosis of cirrhotic patients that were admitted with a hip fracture to our institution. Results: A total of 77 cirrhotic and 81 control patients were included. The majority of the patients who died either during the initial three months or during one year of follow-up after the hip fracture were cirrhotic. The patients that did not survive the three-month period suffered from decompensated cirrhosis. The variables that were associated upon multivariate analysis with increased one-year all-cause mortality in both the control and cirrhotic patients were the presence of either cirrhosis, congestive heart failure or low hemoglobin levels upon admission. The variables that were associated upon univariate analysis with increased one-year all-cause mortality only in the cirrhotic patients were the patient's age, the presence of hepatic encephalopathy, as well as the levels of serum albumin, PT (in %) and FIB-4. Our multivariate analysis disclosed that the admission level of PT (in %) was the only parameter that was associated with one-year all-cause mortality among the cirrhotic patients (adjusted OR 0.962, CI: 0.928-0.996, p = 0.029). Conclusions: Patients with decompensated cirrhosis are at an increased risk of dying during the first year after an osteoporotic hip fracture. Cirrhotic patients with osteoporosis who are at risk of hip fractures should be identified and measures to prevent this complication should be implemented.

Mining Candidate Genes and Identifying Risk Factors for Leg Disease in Broilers: A Mendelian Randomization Study

Clinical investigations have highlighted disruptions in bone metabolic processes and abnormal fluctuations in serum indicator levels during the onset of leg disease (LD) in broilers. However, the presence of a genetic causal relationship for this association remains undetermined. Therefore, the aim of this study is to discern the risk factors underlying LD development using 1235 sequenced white-feathered broilers. We employed Mendelian randomization (MR) analysis to assess the associations of bone strength (BS), bone mineral density (BMD), tibial bone weight (TBW), tibial bone length (TBL), tibial bone diameter (TBD), bone ash (BA), ash calcium (Ash Ca), ash phosphorus (Ash P), serum calcium (Ca), serum phosphorus (P), serum alkaline phosphatase (ALP), and serum osteoprotegerin (OPG) with the incidence of LD. Compelling evidence underscores a causal link between the risk of developing LD and decreased BMD (odds ratio (OR) = 0.998; 95% CI: 0.983, 0.993; P < 0.001) and narrower TBD (OR = 0.985, 95% CI: 0.975, 0.994, P = 0.002). Additionally, serum OPG concentrations (OR: 0.995, 95% CI: 0.992, 0.999, P = 0.008) were associated with BMD (OR = 0.0078, 95% CI = 0.0043 to 0.0140, P < 0.001), indicating a robust genetic relationship between ALP concentrations (OR: 0.988, 95% CI: 0.984, 0.993, P < 0.001) and TBD (OR = 0.0046, 95% CI = 0.0026, 0.0083, P < 0.001). Moreover, elevated serum Ca (OR: 0.564, 95% CI: 0.487, 0.655, P < 0.001) and P (OR: 0.614, 95% CI: 0.539, 0.699, P < 0.001) levels were associated with a narrower TBD. Elevated serum levels of Ca, P, ALP, and OPG contribute to disturbances in bone metabolism, while decreased BMD and narrower TBD are associated with a greater risk of developing LD in broilers. This discovery elucidates the metabolic risk factors for LD in broilers and could provide information on LDs, such as osteoporosis, in humans.

Aortic mineralization triggers the risk of acute type B aortic dissection

BACKGROUND AND AIMS

The role of aortic mineralization in the pathogenesis of acute type B aortic dissection (TBAD) is unclear. Whether thoracic aortic calcification (TAC) and circulating alkaline phosphatase (ALP) activity are associated with acute TBAD risk remains elusive.

METHODS

Observational and Mendelian randomization (MR) studies were conducted sequentially. Using propensity score matching (1:1) by age and sex, patients with acute TBAD (n = 125) were compared with control patients (n = 125). Qualitative (score) and quantitative (volume) analyses of the TAC burden on different thoracic aortic segments were conducted using non-enhanced computed tomography. Univariate and multivariate analyses were used to identify significant independent risk factors for TBAD and TAC burden, respectively. MR was finally used to determine the causal relationship between elevated ALP activity and TBAD risk.

RESULTS

The qualitative and quantitative analyses revealed that TAC burden was significantly higher in the TBAD group, except for in the ascending aortic segment (both p < 0.05). Preoperative circulating ALP was significantly elevated in the TBAD group (p < 0.001). The elevated TAC burden score on the descending thoracic aortic segment (odds ratio [OR] 3.31, 95% confidence interval [CI] 1.31-8.37) and increased ALP activity (OR 1.03, 95% CI 1.01-1.06) was independently associated with TBAD risk. Interestingly, ALP was significantly positively associated with TAC burden, and MR analyses confirmed that ALP genetically predicted TBAD risk.

CONCLUSIONS

Elevated ALP may trigger TBAD risk via the increased volume of TAC. Aortic mineralization may not protect the aorta itself.

Mendelian randomization to evaluate the causal relationship between liver enzymes and the risk of six specific bone and joint-related diseases

Background

Studies of liver dysfunction in relation to bone and joint-related diseases are scarce, and its causality remains unclear. Our objective was to investigate whether serum liver enzymes are causally associated with bone and joint-related diseases using Mendelian randomization (MR) designs.

Methods

Genetic data on serum liver enzymes (alkaline phosphatase (ALP); alanine transaminase (ALT); gamma-glutamyl transferase (GGT)) and six common bone and joint-related diseases (rheumatoid arthritis (RA), osteoporosis, osteoarthritis (OA), ankylosing spondylitis, psoriatic arthritis, and gout) were derived from independent genome-wide association studies of European ancestry. The inverse variance-weighted (IVW) method was applied for the main causal estimate. Complementary sensitivity analyses and reverse causal analyses were utilized to confirm the robustness of the results.

Results

Using the IVW method, the positive causality between ALP and the risk of osteoporosis diagnosed by bone mineral density (BMD) at different sites was indicated (femoral neck, lumbar spine, and total body BMD, odds ratio (OR) [95% CI], 0.40 [0.23-0.69], 0.35 [0.19-0.67], and 0.33 [0.22-0.51], respectively). ALP was also linked to a higher risk of RA (OR [95% CI], 6.26 [1.69-23.51]). Evidence of potential harmful effects of higher levels of ALT on the risk of hip and knee OA was acquired (OR [95% CI], 2.48 [1.39-4.41] and 3.07 [1.49-6.30], respectively). No causal relationship was observed between GGT and these bone and joint-related diseases. The study also found that BMD were all negatively linked to ALP levels (OR [95% CI] for TBMD, FN-BMD, and LS-BMD: 0.993 [0.991-0.995], 0.993 [0.988-0.998], and 0.993 [0.989, 0.998], respectively) in the reverse causal analysis. The results were replicated via sensitivity analysis in the validation process.

Conclusions

Our study revealed a significant association between liver function and bone and joint-related diseases.

Organ-organ communication: The liver's perspective

Communication between organs participates in most physiological and pathological events. Owing to the importance of precise coordination among the liver and virtually all organs in the body for the maintenance of homeostasis, many hepatic disorders originate from impaired organ-organ communication, resulting in concomitant pathological phenotypes of distant organs. Hepatokines are proteins that are predominantly secreted from the liver, and many hepatokines and several signaling proteins have been linked to diseases of other organs, such as the heart, muscle, bone, and eyes. Although liver-centered interorgan communication has been proposed in both basic and clinical studies, to date, the regulatory mechanisms of hepatokine production, secretion, and reciprocation with signaling factors from other organs are obscure. Whether other hormones and cytokines are involved in such communication also warrants investigation. Herein, we summarize the current knowledge of organ-organ communication phenotypes in a variety of diseases and the possible involvement of hepatokines and/or other important signaling factors. This provides novel insight into the underlying roles and mechanisms of liver-originated signal transduction and, more importantly, the understanding of disease in an integrative view.

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.

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.

Rat model of cholelithiasis with human gallstones implanted in cholestasis-induced virtual gallbladder

AIM: To facilitate translational research on cholelithiasis, we have developed a rat model of human gallstones by exploiting the unique biliopancreatic features of this species.

METHODS: Under anesthesia, 16 adult rats of equal genders underwent two times of abdominal surgery. First, their common bile duct (CBD) was ligated to cause cholestasis by total biliary obstruction (TBO). On day 0, 1, 3, 7, 14, 21 and 28 after TBO, magnetic resonance imaging (MRI) was conducted to monitor the dilatation of the CBD, and blood was sampled to analyze total serum bilirubin (TSB). Secondly, on day 30, the abdomen was re-opened and gallstone(s) collected from human patients were implanted in the dilated CBD as a virtual gallbladder (VGB), which was closed by suture ligation. This rat cholelithiasis model was examined by MRI, clinical observation, microcholangiography and histology.

RESULTS: All rats survived two laparotomies. After ligation, the CBD was dilated to a stable size of 4 to 30 mm in diameter on day 21-28, which became a VGB. The rats initially showed signs of jaundice that diminished over time, which paralleled with the evolving TSB levels from 0.6 ± 0.3 mg/dL before ligation, through a peak of 10.9 ± 1.9 mg/dL on day 14, until a nearly normalized value after day 28. The dilated CBD with thickened wall allowed an incision for implantation of human gallstones of 1-10 mm in diameter. The rat cholelithiasis was proven by in vivo MRI and postmortem microcholangiography and histomorphology.

CONCLUSION: A rat model cholelithiasis with human gallstones has been established, which proves feasible, safe, reliable, nontoxic and cost-effective. Given the gallstones of human origin, applications of this model may be of help in translational research such as optical detection and lysis of gallstones by systemic drug administration.

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.

Developmental assessment of infants with biliary atresia: differences between boys and girls

OBJECTIVE

The aim of the present study was to investigate whether male and female infants with biliary atresia (BA) differ cognitively and to confirm previously documented developmental lags in infants with BA before liver transplantation.

METHODS

With the Mullen Scales of Early Learning, we examined 21 female and 12 male infants (ages 3-20 months) with BA, comparing scores across indices by sex and correlating Mullen Scales of Early Learning scores with standard clinical and biochemical parameters.

RESULTS

Overall, both boys and girls were found to be vulnerable to developmental lags in the areas of expressive language (EL) and gross motor skills. In comparison with their male peers, girls were found to be weaker in the area of visual reception skills (P=0.05) with a trend found for EL (P=0.08). Girls were also found to have higher C-bilirubin levels and to be of shorter length. Growth parameters were found to be correlated with EL scores. International normalized ratio was found to be correlated with gross motor performance and with a trend also noted for fine motor skills. Age at Kasai predicted receptive language skills.

CONCLUSIONS

As has been shown, infants with BA appear to be vulnerable to developmental lags before transplantation. In particular, female infants appear to be vulnerable to cognitive and skill delays in comparison with their male peers. C-bilirubin levels may play a role in this increased vulnerability for females.

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.

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.

Protective Role of Black Tea Extract against Nonalcoholic Steatohepatitis-Induced Skeletal Dysfunction

Aim. This paper aimed to examine the chemoprotective actions of aqueous black tea extract (BTE) against nonalcoholic steatohepatitis- (NASH-) induced skeletal changes in rats. Material. Wistar rats (body wt. 155-175 g) of both sexes, aged 4-5 months, were randomly assigned to 3 groups; Group A (control), Group B (60% high-fat diet; HFD), and Group C (HFD + 2.5% BTE). Methods. Several urinary (calcium, phosphate, creatinine, and calcium-to-creatinine ratio) serum (alkaline phosphatase and serum tartrate-resistant acid phosphatase), and molecular markers of bone turnover (receptor activator of NF-κB ligand (RANKL), osteoprotegerin (OPG), and estrogen) were tested. Also, several bone parameters (bone density, bone tensile strength, bone mineral content, and bone histology) and calcium homeostasis were checked. Results. Results indicated that HFD-induced alterations in urinary, serum, and bone parameters as well as calcium homeostasis, all could be significantly ameliorated by BTE supplementation. Conclusion. Results suggest a potential role of BTE as a protective agent against NASH-induced changes in bone metabolism in rats.

Upregulation of heme oxygenase-1 inhibits the maturation and mineralization of osteoblasts

Heme-oxygenase-1 (HO-1), an important enzyme involved in vascular disease, transplantation, and inflammation, catalyzes the degradation of heme into carbon monoxide and biliverdin. It has been reported that overexpression of HO-1 inhibits osteoclastogenesis. However, the effect of HO-1 on osteoblast differentiation is still not clear. We here used adenoviral vector expressing recombinant human HO-1 and HO-1 inducer hemin to study the effects of HO-1 in primary cultured osteoblasts. The results showed that induction of HO-1 inhibited the maturation of osteoblasts including mineralized bone nodule formation, alkaline phosphatase activity and decreased mRNA expression of several differentiation markers such as alkaline phosphatase, osteocalcin, and RUNX2. Furthermore, downstream products of HO-1, bilirubin, carbon monoxide, and iron, are involved in the inhibitory action of HO-1. HO-1 can be induced by H(2)O(2), lipopolysaccharide and inflammatory cytokines such as TNF-alpha and IL-1beta in osteoblasts and also in STZ-induced diabetic mice. In addition, endogenous PPARgamma ligand, 15-deoxy-Delta(12,14)-prostaglandin-J2 (15d-PGJ2) markedly increased both mRNA and protein levels of HO-1 in osteoblasts via PI3K-Akt and MAPK pathways. Blockade of HO activity by ZnPP IX antagonized the inhibitory action on osteocalcin expression by hemin and 15d-PGJ2. Our results indicate that upregulation of HO-1 inhibits the maturation of osteoblasts and HO-1 may be involved in oxidative- or inflammation-induced bone loss.

Etiopathogenesis of hepatic osteodystrophy in Wistar rats with cholestatic liver disease

The pathophysiology of hepatic osteodystrophy (HO) remains poorly understood. Our aim was to evaluate bone histomorphometry, biomechanical properties, and the role of the growth hormone (GH)/insulin-like growth factor-I (IGF-I) system in the onset of this disorder. Forty-six male Wistar rats were divided into two groups: sham-operated (SO, n = 23) and bile duct-ligated (BDL, n = 23). Rats were killed on day 30 postoperatively. Immunohistochemical expression of IGF-I and GH receptor was determined in liver tissue and in the proximal growth plate cartilage of the left tibia. Histomorphometric analysis was performed in the right tibia, and the right femur was used for biomechanical analysis. The maximal force at fracture and the stiffness of the mid-shaft femur were, respectively, 53% and 24% lower in BDL compared to SO. Histomorphometric measurements showed low cancellous bone volume and decreased cancellous bone connectivity in BDL, compatible with osteoporosis. This group also showed increased mineralization lag time, indicating disturbance in bone mineralization. Serum levels of IGF-I were lower in BDL (basal 1,816 +/- 336 vs. 30 days 1,062 +/- 191 ng/ml, P < 0.0001). BDL also showed higher IGF-I expression in the liver tissue but lower IGF-I and GH receptor expression in growth plate cartilage than SO. Osteoporosis is the most important feature of HO; BDL rats show striking signs of reduced bone volume and decreased bone strength, as early as after 1 month of cholestasis. The endocrine and autocrine-paracrine IGF-I systems are deeply affected by cholestasis. Further studies will be necessary to establish their role in the pathogenesis of HO.

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.

Human parathyroid hormone 1-34 prevents bone loss in experimental biliary cirrhosis in rats

BACKGROUND & AIMS

Reduced bone mass and increased fracture rate are complications of primary biliary cirrhosis (PBC). The effect of intermittent administration of human parathyroid hormone (hPTH) 1-34 on bone mass and architecture in bile duct-ligated (BDL) rats was studied.

METHODS

Six-month-old male rats were subjected to BDL or sham operation (SO) and were treated from the second postoperative week intermittently with either hPTH 1-34 40 microg/kg per day, 80 microg/kg per day, or a vehicle for 4 weeks. Femoral and tibial bones were evaluated ex vivo by dual x-ray absorptiometry, microcomputed tomography, and histomorphometry. Serum osteocalcin and urinary deoxypyridinoline cross-links (DPD) were determined.

RESULTS

BDL rats had decreased bone mass compared with SO rats as indicated by a 6% decrease in femoral and tibial bone mineral density (BMD), 18% reduction in femoral trabecular bone volume (bone volume/total volume [BV/TV]), 17% decrease in trabecular thickness, and 10% decrease in tibial cortical thickness. The administration of hPTH 1-34 at 40 microg/kg per day increased femoral and tibial BMD (9% and 9%), femoral trabecular BV/TV (50%), trabecular thickness (50%), tibial cortical thickness (17%), and serum osteocalcin (82%). On the other hand, hPTH 1-34 80 microg/kg per day had no effect on BMD and tibial cortical thickness, was associated with a smaller increase in trabecular BV/TV (24%), and had a higher osteoclast number and DPD compared with untreated BDL rats and the lower hPTH 1-34 dose treatment group.

CONCLUSIONS

BDL rats exhibit loss of bone mass and structure, which can be prevented by the intermittent administration of hPTH 1-34, a potential therapy for osteoporosis in PBC.

Analysis of ribavirin mutagenicity in human hepatitis C virus infection

The addition of ribavirin to alpha interferon therapy significantly increases response rates for patients with chronic hepatitis C virus (HCV) infection, but ribavirin's antiviral mechanisms are unknown. Ribavirin has been suggested to have mutagenic potential in vitro that would lead to "error catastrophe," i.e., the generation of nonviable viral quasispecies due to the increment in the number of mutant genomes, which prevents the transmission of meaningful genetic information. We used extensive sequence-based analysis of two independent genomic regions in order to test in vivo the hypothesis that ribavirin administration accelerates the accumulation of mutations in the viral genome and that this acceleration occurs only when HCV replication is profoundly inhibited by coadministered alpha interferon. The rate of variation of the consensus sequence, the frequency of mutation, the error generation rate, and the between-sample genetic distance were measured for patients receiving ribavirin monotherapy, a combination of alpha interferon three times per week plus ribavirin, or a combination of alpha interferon daily plus ribavirin. Ribavirin monotherapy did not increase the rate of variation of the consensus sequence, the mutation frequency, the error generation rate, or the between-sample genetic distance. The accumulation of nucleotide substitutions did not accelerate, relative to the pretreatment period, during combination therapy with ribavirin and alpha interferon, even when viral replication was profoundly inhibited by alpha interferon. This study strongly undermines the hypothesis whereby ribavirin acts as an HCV mutagen in vivo.

Molecular determination of liver fibrosis by synchrotron infrared microspectroscopy

Liver fibrosis is an adaptive response to various injuries and may eventually progress to cirrhosis. Although there are several non-invasive methods available to monitor the progression of liver fibrogenesis, they cannot reliably detect fibrosis in its early stages, when the process can be stopped or reversed by removing or eliminating the underlying etiological agent that cause the hepatic injury. In this study, early fibrosis alterations were characterized biochemically, morphologically, and spectroscopically in a rat bile duct ligation (BDL) model. Progressive elevations in serum alanine transaminase (ALT), aspartate transaminase (AST), and bilirubin levels in the BDL rats were found indicating the dynamic deterioration of hepatocellular function. Immunofluorescence microscopy using monoclonal anti-collagen III antibody further revealed abnormal intertwined networks of collagen fibres surrounding the portal areas and extending into the lobules towards the central veins in all BDL samples starting from week one. Synchrotron infrared microspectroscopy of liver sections was exploited to generate false color spectral maps based upon a unique and strong collagen absorption at 1340 cm(- 1), revealing a collagen distribution that correlated very well with corresponding images provided by immunofluorescence imaging. We therefore suggest that infrared microspectroscopy may provide an additional and sensitive means for the early detection of liver fibrosis.

The anti-yellow fever virus activity of ribavirin is independent of error-prone replication

The precise mechanism by which the broad-spectrum anti-RNA virus agent ribavirin elicits its in vitro antiviral effect has remained a matter of debate. We have demonstrated that inhibition of cellular inosine monophosphate dehydrogenase (IMPDH) activity, and thus depletion of intracellular GTP pools, is the predominant mechanism by which ribavirin inhibits the replication of four flavi- and two paramyxoviruses (J Virol 79:1943-1947, 2005). As a consequence, induction of error catastrophe, which has been proposed as a mechanism by which ribavirin may elicit its anti-RNA virus activity, may be expected to have little, if any, impact on its antiviral effect. The flavivirus yellow fever virus (17D vaccine strain) was cultured for five consecutive passages in the presence of 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide (ribavirin), 5-ethynyl-1-beta-D-ribo-furanosylimidazole-4-carboxamide (EICAR) (the 5-ethynyl analog of ribavirin), or mycophenolic acid (MPA; a compound that exclusively inhibits IMPDH). The reduction in infectious virus yield brought about by ribavirin (as well as MPA and EICAR) was paralleled by a similar reduction in viral RNA yield; in case of error-prone replication, the infectious virus yield is expected to decrease significantly faster than the viral RNA yield. In addition, pre-extinction populations of the virus that has suffered a maximum impact of treatment with ribavirin did not accumulate an increased number of mutations. Very similar observations were obtained with EICAR and with MPA, a molecule that cannot be incorporated into viral RNA. These data thus allow us to conclude that the in vitro anti-yellow fever virus activity of ribavirin is independent of error-prone replication.

Therapy of hepatitis C: from empiricism to eradication

The complications of chronic hepatitis C virus infection can be prevented by antiviral therapy. The initial choice of interferon alfa and, subsequently, ribavirin as potential treatments for chronic hepatitis C was empirical. Nevertheless, the combination of pegylated interferon alfa and ribavirin has become the standard treatment of chronic hepatitis C. Since the advent of interferon-based therapy, enormous progress has been made in understanding the mechanisms of treatment efficacy and failure, and in everyday patient management. The principal advances are: a better understanding of hepatitis C virus steady-state kinetics and the antiviral mechanisms of interferon and ribavirin; easier treatment decisions thanks to novel assays to assess liver disease severity and the virological characteristics of infection; a better use of virological tests to tailor therapy; a better management of adverse effects; a better understanding of virological treatment failure; and a better management of "special" populations, including patients with decompensated cirrhosis and end-stage liver disease, liver transplant recipients, hemodialysis patients and renal transplant recipients, human immunodeficiency virus-coinfected patients, intravenous drug users and patients on opiate replacement therapy, or virological non responders to previous therapies. Steady-state HCV kinetics offers several potential targets for new drugs. These targets should ideally be hit simultaneously in order to achieve viral eradication within a reasonable time frame. Future drugs for HCV infection will belong to four main categories, including new interferons, alternatives to ribavirin, specific HCV inhibitors, and immune modulators. New treatments and vaccines might make it possible to eradicate HCV in the future.