The altered osteocytic expression of connexin 43 and sclerostin in human cadaveric donors with alcoholic liver cirrhosis: Potential treatment targets

Emerging role of liver-bone axis in osteoporosis

Background

Increasing attention to liver-bone crosstalk has spurred interest in targeted interventions for various forms of osteoporosis. Liver injury induced by different liver diseases can cause an imbalance in bone metabolism, indicating a novel regulatory paradigm between the liver and bone. However, the role of the liver-bone axis in both primary and secondary osteoporosis remains inadequately elucidated. Therefore, exploring the exact regulatory mechanisms of the liver-bone axis may offer innovative clinical approaches for treating diseases associated with the liver and bone.

Methods

Here, we summarize the latest research on the liver-bone axis by searching the PubMed and Web of Science databases and discuss the possible mechanism of the liver-bone axis in different types of osteoporosis. The literature directly reporting the regulatory role of the liver-bone axis in different types of osteoporosis from the PubMed and Web of Science databases has been included in the discussion of this review (including but not limited to the definition of the liver-bone axis, clinical studies, and basic research). In addition, articles discussing changes in bone metabolism caused by different etiologies of liver injury have also been included in the discussion of this review (including but not limited to clinical studies and basic research).

Results

Several endocrine factors (IGF-1, FGF21, hepcidin, vitamin D, osteocalcin, OPN, LCAT, Fetuin-A, PGs, BMP2/9, IL-1/6/17, and TNF-α) and key genes (SIRT2, ABCB4, ALDH2, TFR2, SPTBN1, ZNF687 and SREBP2) might be involved in the regulation of the liver-bone axis. In addition to the classic metabolic pathways involved in inflammation and oxidative stress, iron metabolism, cholesterol metabolism, lipid metabolism and immunometabolism mediated by the liver-bone axis require more research to elucidate the regulatory mechanisms involved in osteoporosis.

Conclusion

During primary and secondary osteoporosis, the liver-bone axis is responsible for liver and bone homeostasis via several hepatokines and osteokines as well as biochemical signaling. Combining multiomics technology and data mining technology could further advance our understanding of the liver-bone axis, providing new clinical strategies for managing liver and bone-related diseases.The translational potential of this article is as follows: Abnormal metabolism in the liver could seriously affect the metabolic imbalance of bone. This review summarizes the indispensable role of several endocrine factors and biochemical signaling pathways involved in the liver-bone axis and emphasizes the important role of liver metabolic homeostasis in the pathogenesis of osteoporosis, which provides novel potential directions for the prevention, diagnosis, and treatment of liver and bone-related diseases.

Hepatocellular carcinoma and musculoskeletal system: A narrative literature review

Musculoskeletal alterations in hepatocellular carcinoma (HCC) are less common than liver-related complications. However, they can significantly impact the quality of life and overall prognosis of patients with HCC. The main obstacle in the clinical assessment of HCC-induced musculoskeletal alterations is related to effective and timely diagnosis because these complications are often asymptomatic and unapparent during routine clinical evaluations. This narrative literature review aimed to provide a comprehensive overview of the contemporary literature related to the changes in the musculoskeletal system in patients with HCC, focusing on its clinical implications and underlying etiopathogenetic mechanisms. Osteolytic bone metastases are the most common skeletal alterations associated with HCC, which could be associated with an increased risk of low-trauma bone fracture. Moreover, previous studies reported that osteopenia, sarcopenia, and myosteatosis are associated with poor clinical outcomes in patients with HCC. Even though low bone mineral density and sarcopenia are consistently reported as reliable predictors of pretransplantation and post-transplantation mortality in HCC patients, these complications are frequently overlooked in the clinical management of patients with HCC. Taken together, contemporary literature suggests that a multidisciplinary approach is essential for early recognition and clinical management of HCC-associated musculoskeletal alterations to improve patient prognosis. Further research into the mechanisms and treatment options for musculoskeletal complications is warranted to enhance our understanding and clinical management of this aspect of HCC.

Hepatocellular carcinoma and musculoskeletal system: A narrative literature review

Musculoskeletal alterations in hepatocellular carcinoma (HCC) are less common than liver-related complications. However, they can significantly impact the quality of life and overall prognosis of patients with HCC. The main obstacle in the clinical assessment of HCC-induced musculoskeletal alterations is related to effective and timely diagnosis because these complications are often asymptomatic and unapparent during routine clinical evaluations. This narrative literature review aimed to provide a comprehensive overview of the contemporary literature related to the changes in the musculoskeletal system in patients with HCC, focusing on its clinical implications and underlying etiopathogenetic mechanisms. Osteolytic bone metastases are the most common skeletal alterations associated with HCC, which could be associated with an increased risk of low-trauma bone fracture. Moreover, previous studies reported that osteopenia, sarcopenia, and myosteatosis are associated with poor clinical outcomes in patients with HCC. Even though low bone mineral density and sarcopenia are consistently reported as reliable predictors of pretransplantation and post-transplantation mortality in HCC patients, these complications are frequently overlooked in the clinical management of patients with HCC. Taken together, contemporary literature suggests that a multidisciplinary approach is essential for early recognition and clinical management of HCC-associated musculoskeletal alterations to improve patient prognosis. Further research into the mechanisms and treatment options for musculoskeletal complications is warranted to enhance our understanding and clinical management of this aspect of HCC.

Novel insights into osteocyte and inter-organ/tissue crosstalk

Osteocyte, a cell type living within the mineralized bone matrix and connected to each other by means of numerous dendrites, appears to play a major role in body homeostasis. Benefiting from the maturation of osteocyte extraction and culture technique, many cross-sectional studies have been conducted as a subject of intense research in recent years, illustrating the osteocyte-organ/tissue communication not only mechanically but also biochemically. The present review comprehensively evaluates the new research work on the possible crosstalk between osteocyte and closely situated or remote vital organs/tissues. We aim to bring together recent key advances and discuss the mutual effect of osteocyte and brain, kidney, vascular calcification, muscle, liver, adipose tissue, and tumor metastasis and elucidate the therapeutic potential of osteocyte.

Micro-scale vertebral features in postmenopausal women with alcohol-associated and metabolic-associated fatty liver disease: ex vivo bone quality analyses

PURPOSE

Although epidemiological studies indicate increased fracture risk in women with alcohol-associated liver disease (AALD) and metabolic-associated fatty liver disease (MAFLD), data about their micro-scale bone features are still limited. We aimed to characterize bone quality changes in the anterior mid-transverse part of the first lumbar vertebral body collected from 32 adult postmenopausal females. Based on pathohistological assessment of the liver tissue, individuals were divided into AALD (n = 13), MAFLD (n = 9), and control group (n = 10).

METHODS

We analyzed trabecular and cortical micro-architecture (using micro-computed tomography), bone mechanical properties (using Vickers microhardness tester), osteocyte lacunar network and bone marrow adiposity morphology (using optic microscopy). Data were adjusted to elude the covariant effects of advanced age and body mass index on our results.

RESULTS

Our data indicated a minor trend toward deteriorated bone quality in MAFLD women, presented in impaired trabecular and cortical micro-architectural integrity, which could be associated with bone marrow adiposity alterations noted in these women. Additionally, we observed a significant decline in micro-architectural, mechanical, and osteocyte lacunar features in lumbar vertebrae collected from the AALD group. Lastly, our data indicated that vertebral bone deterioration was more prominent in the AALD group than in the MAFLD group.

CONCLUSION

Our data suggested that MAFLD and AALD are factors that could play a part in compromised vertebral strength of postmenopausal women. Also, our data contribute to understanding the multifactorial nature of bone fragility in these patients and highlight the necessity for developing more effective patient-specific diagnostic, preventive, and therapeutic strategies.

Bone loss in chronic liver diseases: Could healthy liver be a requirement for good bone health?

Given that the liver is involved in many metabolic mechanisms, it is not surprising that chronic liver disease (CLD) could have numerous complications. Secondary osteoporosis and increased bone fragility are frequently overlooked complications in CLD patients. Previous studies implied that up to one-third of these individuals meet diagnostic criteria for osteopenia or osteoporosis. Recent publications indicated that CLD-induced bone fragility depends on the etiology, duration, and stage of liver disease. Therefore, the increased fracture risk in CLD patients puts a severe socioeconomic burden on the health system and urgently requires more effective prevention, diagnosis, and treatment measures. The pathogenesis of CLD-induced bone loss is multifactorial and still insufficiently understood, especially considering the relative impact of increased bone resorption and reduced bone formation in these individuals. It is essential to note that inconsistent findings regarding bone mineral density measurement were previously reported in these individuals. Bone mineral density is widely used as the “golden standard” in the clinical assessment of bone fragility although it is not adequate to predict individual fracture risk. Therefore, microscale bone alterations (bone microstructure, mechanical properties, and cellular indices) were analyzed in CLD individuals. These studies further support the thesis that bone strength could be compromised in CLD individuals, implying that an individualized approach to fracture risk assessment and subsequent therapy is necessary for CLD patients. However, more well-designed studies are required to solve the bone fragility puzzle in CLD patients.

Sclerostin, vascular risk factors, and brain atrophy in excessive drinkers

Objective

Heavy alcohol consumption causes several organic complications, including vessel wall calcification. Vascular damage may be involved in the development of brain atrophy and cognitive impairment. Recently, sclerostin (whose levels may be altered in alcoholics) has emerged as a major vascular risk factor. The objective of the present study is to analyze the prevalence of vascular calcifications in alcoholics, and the relationships of these lesions with brain atrophy, as well as the role of sclerostin on these alterations.

Patients and methods

A total of 299 heavy drinkers and 32 controls were included. Patients underwent cranial computed tomography, and several indices related to brain atrophy were calculated. In addition, patients and controls underwent plain radiography and were evaluated for the presence or absence of vascular calcium deposits, cardiovascular risk factors, liver function, alcohol intake, serum sclerostin, and routine laboratory variables.

Results

A total of 145 (48.47%) patients showed vascular calcium deposits, a proportion significantly higher than that observed in controls (χ² = 16.31; p < 0.001). Vascular calcium deposits were associated with age (t = 6.57; p < 0.001), hypertension (t = 5.49; p < 0.001), daily ethanol ingestion (Z = 2.18; p = 0.029), duration of alcohol consumption (Z = 3.03; p = 0.002), obesity (χ² = 4.65; p = 0.031), total cholesterol (Z = 2.04; p = 0.041), triglycerides (Z = 2.05; p = 0.04), and sclerostin levels (Z = 2.64; p = 0.008). Calcium deposits were significantly related to Bifrontal index (Z = 2.20; p = 0.028) and Evans index (Z = 2.25; p = 0.025). Serum sclerostin levels were related to subcortical brain atrophy, assessed by cella media index (Z = 2.43; p = 0.015) and Huckmann index (ρ = 0.204; p = 0.024). Logistic regression analyses disclosed that sclerostin was the only variable independently related to brain atrophy assessed by altered cella media index. Sclerostin was also related to the presence of vascular calcifications, although this relationship was displaced by age if this variable was also included.

Conclusion

Prevalence of vascular calcification in alcoholics is very high. Vascular calcium deposits are related to brain atrophy. Serum sclerostin is strongly related to brain shrinkage and also shows a significant relationship with vascular calcifications, only displaced by advanced age.

Micro-scale assessment of bone quality changes in adult cadaveric men with congestive hepatopathy

Congestive hepatopathy (CH) is a chronic liver disease (CLD) caused by impaired hepatic venous blood outflow, most frequently resulting from congestive heart failure. Although it is known that heart failure and CLDs contribute to increased risk for age-related fractures, an assessment of CH-induced skeletal alterations has not been made to date. The aim of our study was to characterize changes in bone quality in adult male cadavers with pathohistologically confirmed CH compared with controls without liver disease. The anterior mid-transverse part of the fifth lumbar vertebral body was collected from 33 adult male cadavers (age range 43-89 years), divided into the CH group (n = 15) and the control group (n = 18). We evaluated trabecular and cortical micro-architecture and bone mineral content (using micro-computed tomography), bone mechanical competence (using Vickers micro-hardness tester), vertebral cellular indices (osteocyte lacunar network and bone marrow adiposity), and osteocytic sclerostin and connexin 43 expression levels (using immunohistochemistry staining and analysis). Deterioration in trabecular micro-architecture, reduced trabecular and cortical mineral content, and decreased Vickers microhardness were noted in the CH group (p < 0.05). Reduced total number of osteocytes and declined connexin 43 expression levels (p < 0.05) implied that harmed mechanotransduction throughout the osteocyte network might be present in CH. Moreover, elevated expression levels of sclerostin by osteocytes could indicate the role of sclerostin in mediating low bone formation in individuals with CH. Taken together, these micro-scale bone alterations suggest that vertebral strength could be compromised in men with CH, implying that vertebral fracture risk assessment and subsequent therapy may need to be considered in these patients. However, further research is required to confirm the clinical relevance of our findings.