Perturbations in the HDL metabolic pathway predispose to the development of osteoarthritis in mice following long-term exposure to western-type diet

Obesity, Metabolic Syndrome, and Osteoarthritis Require Integrative Understanding and Management

Osteoarthritis (OA) is a progressive chronic disease affecting the articular joints, leading to pain and disability. Unlike traditional views that primarily link OA to aging, recent understanding portrays it as a multifactorial degenerative disease of the entire joint. Emerging research highlights metabolic and immune dysregulation in OA pathogenesis, emphasizing the roles of obesity, dyslipidemia, and insulin resistance in altering joint homeostasis. Recent studies have increasingly focused on the complex role of white adipose tissue (WAT) in OA. WAT not only serves metabolic functions but also plays a critical role in systemic inflammation through the release of various adipokines. These adipokines, including leptin and adiponectin, have been implicated in exacerbating cartilage erosion and promoting inflammatory pathways within joint tissues. The overlapping global crises of obesity and metabolic syndrome have significantly impacted joint health. Obesity, now understood to contribute to mechanical joint overload and metabolic dysregulation, heightens the risk of developing OA, particularly in the knee. Metabolic syndrome compounds these risks by inducing chronic inflammation and altering macrophage activity within the joints. The multifaceted effects of obesity and metabolic syndrome extend beyond simple joint loading. These conditions disrupt normal joint function by modifying tissue composition, promoting inflammatory macrophage polarization, and impairing chondrocyte metabolism. These changes contribute to OA progression, highlighting the need for targeted therapeutic strategies that address both the mechanical and biochemical aspects of the disease. Recent advances in understanding the molecular pathways involved in OA suggest potential therapeutic targets. Interventions that modulate macrophage polarization, improve chondrocyte function, or normalize adipokine levels could serve as preventative or disease-modifying therapies. Exploring the role of diet, exercise, and pharmacological interventions in modulating these pathways offers promising avenues for reducing the burden of OA. Furthermore, such methods could prove cost-effective, avoiding the increase in access to healthcare.

The metabolic characteristics and changes of chondrocytes in vivo and in vitro in osteoarthritis

Osteoarthritis (OA) is an intricate pathological condition that primarily affects the entire synovial joint, especially the hip, hand, and knee joints. This results in inflammation in the synovium and osteochondral injuries, ultimately causing functional limitations and joint dysfunction. The key mechanism responsible for maintaining articular cartilage function is chondrocyte metabolism, which involves energy generation through glycolysis, oxidative phosphorylation, and other metabolic pathways. Some studies have shown that chondrocytes in OA exhibit increased glycolytic activity, leading to elevated lactate production and decreased cartilage matrix synthesis. In OA cartilage, chondrocytes display alterations in mitochondrial activity, such as decreased ATP generation and increased oxidative stress, which can contribute to cartilage deterioration. Chondrocyte metabolism also involves anabolic processes for extracellular matrix substrate production and energy generation. During OA, chondrocytes undergo considerable metabolic changes in different aspects, leading to articular cartilage homeostasis deterioration. Numerous studies have been carried out to provide tangible therapies for OA by using various models in vivo and in vitro targeting chondrocyte metabolism, although there are still certain limitations. With growing evidence indicating the essential role of chondrocyte metabolism in disease etiology, this literature review explores the metabolic characteristics and changes of chondrocytes in the presence of OA, both in vivo and in vitro. To provide insight into the complex metabolic reprogramming crucial in chondrocytes during OA progression, we investigate the dynamic interaction between metabolic pathways, such as glycolysis, lipid metabolism, and mitochondrial function. In addition, this review highlights prospective future research directions for novel approaches to diagnosis and treatment. Adopting a multifaceted strategy, our review aims to offer a comprehensive understanding of the metabolic intricacies within chondrocytes in OA, with the ultimate goal of identifying therapeutic targets capable of modulating chondrocyte metabolism for the treatment of OA.

Efficacy and safety of pentosan polysulfate sodium in people with symptomatic knee osteoarthritis and dyslipidaemia: protocol of the MaRVeL trial

INTRODUCTION

Knee osteoarthritis (OA) is the most prevalent arthritis type and a leading cause of chronic mobility disability. While pain medications provide only symptomatic pain relief; growing evidence suggests pentosan polysulfate sodium (PPS) is chondroprotective and could have anti-inflammatory effects in knee OA. This study aims to explore the efficacy and safety of oral PPS in symptomatic knee OA with dyslipidaemia.

METHODS AND ANALYSIS

MaRVeL is a phase II, single-centre, parallel, superiority trial which will be conducted at Royal North Shore Hospital, Sydney, Australia. 92 participants (46 per arm) aged 40 and over with painful knee OA and mild to moderate structural change on X-ray (Kellgren and Lawrence grade 2 or 3) will be recruited from the community and randomly allocated to receive two cycles of either oral PPS or placebo for 5 weeks starting at baseline and week 11. Primary outcome will be the 16-week change in overall average knee pain severity measured using an 11-point Numeric Rating Scale. Main secondary outcomes include change in knee pain, patient global assessment, physical function, quality of life and other structural changes. A biostatistician blinded to allocation groups will perform the statistical analysis according to the intention-to-treat principle.

ETHICS AND DISSEMINATION

The protocol has been approved by the NSLHD Human Research Ethics Committee (HREC) (2021/ETH00315). All participants will provide written informed consent online. Study results will be disseminated through conferences, social media and academic publications.

TRIAL REGISTRATION NUMBERS

Australian New Zealand Clinical Trial Registry (ACTRN12621000654853); U1111-1265-3750.

Risk of metabolic abnormalities in osteoarthritis: a new perspective to understand its pathological mechanisms

Although aging has traditionally been viewed as the most important risk factor for osteoarthritis (OA), an increasing amount of epidemiological evidence has highlighted the association between metabolic abnormalities and OA, particularly in younger individuals. Metabolic abnormalities, such as obesity and type II diabetes, are strongly linked to OA, and they affect both weight-bearing and non-weight-bearing joints, thus suggesting that the pathogenesis of OA is more complicated than the mechanical stress induced by overweight. This review aims to explore the recent advances in research on the relationship between metabolic abnormalities and OA risk, including the impact of abnormal glucose and lipid metabolism, the potential pathogenesis and targeted therapeutic strategies.

Obesity, Metabolic Syndrome, and Osteoarthritis-An Updated Review

PURPOSE OF REVIEW

Metabolic syndrome (MetS), also called the 'deadly quartet' comprising obesity, diabetes, dyslipidemia, and hypertension, has been ascertained to have a causal role in the pathogenesis of osteoarthritis (OA). This review is aimed at discussing the current knowledge on the contribution of metabolic syndrome and its various components to OA pathogenesis and progression.

RECENT FINDINGS

Lately, an increased association identified between the various components of metabolic syndrome (obesity, diabetes, dyslipidemia, and hypertension) with OA has led to the identification of the 'metabolic phenotype' of OA. These metabolic perturbations alongside low-grade systemic inflammation have been identified to inflict detrimental effects upon multiple tissues of the joint including cartilage, bone, and synovium leading to complete joint failure in OA. Recent epidemiological and clinical findings affirm that adipokines significantly contribute to inflammation, tissue degradation, and OA pathogenesis mediated through multiple signaling pathways. OA is no longer perceived as just a 'wear and tear' disease and the involvement of the metabolic components in OA pathogenesis adds up to the complexity of the disease. Given the global surge in obesity and its allied metabolic perturbations, this review aims to throw light on the current knowledge on the pathophysiology of MetS-associated OA and the need to address MetS in the context of metabolic OA management. Better regulation of the constituent factors of MetS could be profitable in preventing MetS-associated OA. The identification of key roles for several metabolic regulators in OA pathogenesis has also opened up newer avenues in the recognition and development of novel therapeutic agents.

Alterations in skeletal muscle morphology and mechanics in juvenile male Sprague Dawley rats exposed to a high-fat high-sucrose diet

Although once a health concern largely considered in adults, the obesity epidemic is now prevalent in pediatric populations. While detrimental effects on skeletal muscle function have been seen in adulthood, the effects of obesity on skeletal muscle function in childhood is not clearly understood. The purpose of this study was to determine if the consumption of a high-fat high-sucrose (HFS) diet, starting in the post-weaning period, leads to changes in skeletal muscle morphology and mechanics after 14 weeks on the HFS diet. Eighteen 3-week-old male CD-Sprague Dawley rats were randomly assigned to a HFS (C-HFS, n = 10) or standard chow diet (C-CHOW, n = 8). Outcome measures included: weekly energy intake, activity levels, oxygen consumption, body mass, body composition, metabolic profile, serum protein levels, and medial gastrocnemius gene expression, morphology, and mechanics. The main findings from this study were that C-HFS rats: (1) had a greater body mass and percent body fat than control rats; (2) showed early signs of metabolic syndrome; (3) demonstrated potential impairment in muscle remodeling; (4) produced lower relative muscle force; and (5) had a shift in the force-length relationship, indicating that the medial gastrocnemius had shorter muscle fiber lengths compared to those of C-CHOW rats. Based on the results of this study, we conclude that exposure to a HFS diet led to increased body mass, body fat percentage, and early signs of metabolic syndrome, resulting in functional deficits in MG of childhood rats.

Apolipoprotein A1 is associated with osteocalcin and bone mineral density rather than high-density lipoprotein cholesterol in Chinese postmenopausal women with type 2 diabetes mellitus

Objective

Disturbances in high-density lipoprotein cholesterol (HDL-c) metabolic pathways can affect bone metabolism, which may rely on the particle function of apolipoprotein rather than HDL-c levels. This study aimed to evaluate the correlation of serum HDL-c and apolipoprotein A1 (APOA1) with bone metabolism in Chinese postmenopausal women with type 2 diabetes mellitus (T2DM).

Method

A total of 1,053 participants with complete data were enrolled and separated into three groups based on the HDL-c and APOA1 tertiles. The trained reviewer collected demographic and anthropometric information. Bone turnover markers (BTMs) were determined by standard methods. Bone mineral density (BMD) was measured by dual-energy x-ray absorptiometry.

Results

Overall, the prevalence of osteoporosis was 29.7%. Groups with higher APOA1 have a remarkably more elevated level of osteocalcin (OC), L1-L4 BMD, and T-score across the APOA1 tertiles. APOA1 presented a positive correlation with OC (r = 0.194, p < 0.001), L1-L4 BMD (r = 0.165, p < 0.001), and T-score (r = 0.153, p < 0.001) rather than HDL-c. Meanwhile, APOA1 remained independently associated with OC (β = 0.126, p < 0.001), L1-L4 BMD (β = 0.181, p < 0.001), and T-score (β = 0.180, p < 0.001) after adjustment for confounding factors. APOA1 is also shown to be independently correlated with osteoporosis after adjustment for confounding factors, and the OR (95%CI) was 0.851 (0.784-0.924). In contrast, there was no significant association between HDL-c and osteoporosis. Furthermore, APOA1 seemed to have the largest areas under the curve (AUC) for osteoporosis. The AUC (95% CI) of APOA1 identifying osteoporosis was 0.615 (0.577-0.652). The optimal cut-off value of APOA1 was 0.89 g/L (sensitivity: 56.5%, specificity: 67.9%).

Conclusion

APOA1 is independently associated with OC, L1-L4 BMD, and osteoporosis rather than HDL-c in Chinese postmenopausal women with T2DM.

Beyond mechanical loading: The metabolic contribution of obesity in osteoarthritis unveils novel therapeutic targets

Osteoarthritis (OA) is a prevalent progressive disease that frequently coexists with obesity. For several decades, OA was thought to be the result of ageing and mechanical stress on cartilage. Researchers' perspective has been greatly transformed when cumulative findings emphasized the role of adipose tissue in the diseases. Nowadays, the metabolic effect of obesity on cartilage tissue has become an integral part of obesity research; hoping to discover a disease-modifying drug for OA. Recently, several adipokines have been reported to be associated with OA. Particularly, metrnl (meteorin-like) and retinol-binding protein 4 (RBP4) have been recognized as emerging adipokines that can mediate OA pathogenesis. Accordingly, in this review, we will summarize the latest findings concerned with the metabolic contribution of obesity in OA pathogenesis, with particular emphasis on dyslipidemia, insulin resistance and adipokines. Additionally, we will discuss the most recent adipokines that have been reported to play a role in this context. Careful consideration of these molecular mechanisms interrelated with obesity and OA will undoubtedly unveil new avenues for OA treatment.

The roles of hepatokine and osteokine in liver-bone crosstalk: Advance in basic and clinical aspects

Both the liver and bone are important secretory organs in the endocrine system. By secreting organ factors (hepatokines), the liver regulates the activity of other organs. Similarly, bone-derived factors, osteokines, are created during bone metabolism and act in an endocrine manner. Generally, the dysregulation of hepatokines is frequently accompanied by changes in bone mass, and osteokines can also disrupt liver metabolism. The crosstalk between the liver and bone, particularly the function and mechanism of hepatokines and osteokines, has increasingly gained notoriety as a topic of interest in recent years. Here, based on preclinical and clinical evidence, we summarize the potential roles of hepatokines and osteokines in liver-bone interaction, discuss the current shortcomings and contradictions, and make recommendations for future research.

Excessive sucrose exacerbates high fat diet-induced hepatic inflammation and fibrosis promoting osteoarthritis in mice model

Osteoarthritis (OA) is marked by chronic low-grade systemic inflammation and cartilage destruction. High fat diet causes obesity and increases the risk of knee OA-development. However, the impact of high dietary sugar intake on OA pathogenesis has not been elucidated yet. Therefore, we investigated the effects of a high-fat and high-sucrose (HF+HS) diet in experimental OA mouse models. Eight-week-old male C57BL/6J mice were fed a standard chow (n=6), high-fat (HF) (n=5), or HF+HS (n=7) diets for 12 weeks; thereafter, the mice underwent surgical destabilization of the medial meniscus (DMM) and received the same experimental diets for an additional 8 weeks. The pathogenesis of knee OA, obesogenic parameters, and inflammation levels in the liver and adipose tissue were investigated. HF+HS diet induced severe cartilage erosion with osteophyte development and subchondral bone plate thickening, indicating that HF+HS diet exacerbated OA. Despite marginal differences in metabolic parameters, hepatic free cholesterol accumulation increased in mice with DMM-induced OA fed on HF+HS diet than in those fed HF diet. Notably, the levels of inflammatory cytokines and fibrosis markers were greater in the livers of mice with DMM-induced OA, fed on HF+HS diet than those in the control group. However, adipose tissue remodeling was not affected by the HF+HS diet. These findings indicate that excess sucrose intake along with a HF diet triggers hepatic inflammation and fibrosis, thereby, contributing to OA pathogenesis.

Liver-bone crosstalk in non-alcoholic fatty liver disease: Clinical implications and underlying pathophysiology

Osteoporosis is a common complication of many types of chronic liver diseases (CLDs), such as cholestatic liver disease, viral hepatitis, and alcoholic liver disease. Non-alcoholic fatty liver disease (NAFLD) is a highly prevalent metabolic liver disease, affecting almost one third of adults around the world, and is emerging as the dominant cause of CLDs. Liver serves as a hub for nutrient and energy metabolism in the body, and its crosstalk with other tissues, such as adipose tissue, heart, and brain, has been well recognized. However, much less is known about the crosstalk that occurs between the liver and bone. Moreover, the mechanisms by which CLDs increase the risk for osteoporosis remain unclear. This review summarizes the latest research on the liver-bone axis and discusses the relationship between NAFLD and osteoporosis. We cover key signaling molecules secreted by liver, such as insulin-like growth factor-1 (IGF-1), fibroblast growth factor 21 (FGF21), insulin-like growth factor binding protein 1 (IGFBP1), fetuin-A, tumor necrosis factor-alpha (TNF-α), and osteopontin (OPN), and their relevance to the homeostasis of bone metabolism. Finally, we consider the disordered liver metabolism that occurs in patients with NAFLD and how this disrupts signaling to the bone, thereby perturbing the balance between osteoclasts and osteoblasts and leading to osteoporosis or hepatic osteodystrophy (HOD).

Monocyte to high-density lipoprotein and apolipoprotein A1 ratios are associated with bone homeostasis imbalance caused by chronic inflammation in postmenopausal women with type 2 diabetes mellitus

Objective: Emerging evidences demonstrated that chronic inflammation can influence bone metabolism in type 2 diabetes mellitus (T2DM), leading to bone homeostasis imbalance. The aim of this study was to assess the correlations between novel pro-inflammatory indexes like monocyte to high-density lipoprotein (MHR), apolipoprotein A1 (MAR) ratios and bone mineral density (BMD), bone turnover markers in Chinese postmenopausal women with T2DM.

Method: In this study, a total of 619 participants with complete data were included in the final analysis. Demographic and anthropometric information was collected. Biochemical parameters and bone turnover markers were determined by standard methods. BMD was measured by dual-energy x-ray absorptiometry. Correlation analysis and regression models were conducted to assess the associations between MHR, MAR and bone turnover markers, BMD. Multiple binomial logistic regression model was used to estimate the independent variables of MHR and MAR for osteoporosis.

Results: Overall, the prevalence of osteoporosis was 38.3%. MHR and MAR were significantly correlated with C-terminal cross linking of type I collagen (β-CTX), L1-L4, femoral neck BMD and T scores. These correlations remained significant after adjustment for other confounding factors. Meanwhile, MHR and MAR were also significantly associated with higher odds of osteoporosis, the odds ratios (ORs) (95%CI) were 1.88 (1.49–2.38) and 2.30 (1.72–3.09) respectively. Furthermore, MHR and MAR seemed to have a good identifying value for osteoporosis. The area under the curve of MHR and MAR identifying osteoporosis were 0.791 (95% CI: 0.753–0.828) and 0.843 (95% CI: 0.809–0.877) respectively (p &lt; 0.001). The optimal cut-off values of MHR and MAR were 4.53 × 108/mmol (sensitivity: 60.8%, specificity: 85.9%) and 4.74 × 108/g (sensitivity: 71.7%, specificity: 89.3%) respectively.

Conclusion: MHR and MAR were significantly associated with osteoporosis. These two novel pro-inflammatory indexes may be ideal markers to reflect bone homeostasis imbalance caused by chronic inflammation in Chinese postmenopausal women with T2DM.

The role of metabolites under the influence of genes and lifestyles in bone density changes

Purpose

Osteoporosis is a complex bone disease influenced by numerous factors. Previous studies have found that some metabolites are related to bone mineral density (BMD). However, the associations between metabolites and BMD under the influence of genes and lifestyle have not been fully investigated.

Methods

We analyzed the effect of metabolites on BMD under the synergistic effect of genes and lifestyle, using the data of 797 participants aged 55–65 years from the Taizhou Imaging Study. The cumulative sum method was used to calculate the polygenic risk score of SNPs, and the healthful plant-based diet index was used to summarize food intake. The effect of metabolites on BMD changes under the influence of genes and lifestyle was analyzed through interaction analysis and mediation analysis.

Results

Nineteen metabolites were found significantly different in the osteoporosis, osteopenia, and normal BMD groups. We found two high-density lipoprotein (HDL) subfractions were positively associated with osteopenia, and six very-low-density lipoprotein subfractions were negatively associated with osteopenia or osteoporosis, after adjusting for lifestyles and genetic factors. Tea drinking habits, alcohol consumption, smoking, and polygenic risk score changed BMD by affecting metabolites.

Conclusion

With the increased level of HDL subfractions, the risk of bone loss in the population will increase; the risk of bone loss decreases with the increased level of very-low-density lipoprotein subfractions. Genetic factors and lifestyles can modify the effects of metabolites on BMD. Our results show evidence for the precise prevention of osteoporosis.

ApoA1 Deficiency Reshapes the Phenotypic and Molecular Characteristics of Bone Marrow Adipocytes in Mice

In the present study, we studied the effect of apolipoprotein A-1 (APOA1) on the spatial and molecular characteristics of bone marrow adipocytes, using well-characterized ApoA1 knockout mice. APOA1 is a central regulator of high-density lipoprotein cholesterol (HDL-C) metabolism, and thus HDL; our recent work showed that deficiency of APOA1 increases bone marrow adiposity in mice. We found that ApoA1 deficient mice have greatly elevated adipocytes within their bone marrow compared to wild type counterparts. Morphologically, the increased adipocytes were similar to white adipocytes, and displayed proximal tibial-end localization. Marrow adipocytes from wild type mice were significantly fewer and did not display a bone-end distribution pattern. The mRNA levels of the brown/beige adipocyte-specific markers Ucp1, Dio2, Pat2, and Pgc1a; and the expression of leptin were greatly reduced in the ApoA1 knock-out in comparison to the wild-type mice. In the knock-out mice, adiponectin was remarkably elevated. In keeping with the close ties of hematopoietic stem cells and marrow adipocytes, using flow cytometry we found that the elevated adiposity in the ApoA1 knockout mice is associated with a significant reduction in the compartments of hematopoietic stem cells and common myeloid, but not of the common lymphoid, progenitors. Moreover, the 'beiging'-related marker osteopontin and the angiogenic factor VEGF were also reduced in the ApoA1 knock-out mice, further supporting the notion that APOA1-and most probably HDL-C-regulate bone marrow microenvironment, favoring beige/brown adipocyte characteristics.

Reverse cholesterol transport and hepatic osteodystrophy

In this issue of Cell Metabolism, Lu et al. show that chronic liver disease increases the expression and activity of PP2Ac, a phosphatase that downregulates the excretion of lecithin-cholesterol aceyltransferase (LCAT). LCAT, a liver-derived enzyme, protects bone and prevents bone loss, and its lowered levels in progressive liver injury cause hepatic osteodystrophy (HOD) and worsen liver fibrosis. These discoveries open the possibility that recombinant LCAT may be a treatment for both HOD and liver fibrosis.

Role of Apolipoprotein A1 in PPAR Signaling Pathway for Nonalcoholic Fatty Liver Disease

Peroxisome proliferator-activated receptors (PPARs) have been suggested to play crucial roles in the pathology of NAFLD with a vague understanding of the underlying mechanism. Here, we integrated large-scale literature data and clinical data to explore the potential role of the PPAR-APOA1 signaling pathway in the pathology of NAFLD. First, the signaling pathway connecting PPARs, APOA1, and NAFLD was constructed. Then, we employed clinical data to explore the association between APOA1 levels and NAFLD. In addition, we built the APOA1-driven pathway analysis to explore the potential mechanism of the APOA1-NAFLD association. Pathway analysis showed that APOA1 serves as a hubprotein connecting PPARs and NAFLD through a beneficial modulation of 16 out of 21 NAFLD upstream regulators. Each relationship within the composed pathway was supported by results from multiple previous studies. Clinical data analysis showed that an increase of APOA1 level was associated with a significantly decreased NAFLD prevalence (χ² = 292.109; P < 0.001). When other confounding factors were adjusted, serum APOA1 level was shown as an independent risk factor for the prevalence of NAFLD (P value<.0001; OR = 0.562). Our results suggested that the three PPARs (PPARA, PPARD, and PPARG) might promote the expression and molecular transportation of APOA1 to form a PPAR-APOA1 signaling pathway that demonstrated a beneficial role in the pathogenesis of NAFLD.

Association of Serum Low-Density Lipoprotein, High-Density Lipoprotein, and Total Cholesterol With Development of Knee Osteoarthritis

OBJECTIVE

Studies suggest an association between elevated total serum cholesterol, particularly low-density lipoprotein (LDL), and osteoarthritis (OA). The present study was undertaken to evaluate the association between total cholesterol, LDL, and high-density lipoprotein (HDL) and risk of knee OA.

METHODS

We studied participants from the Multicenter Osteoarthritis study (MOST) cohort at risk of developing knee OA. From baseline through 7 years, repeated knee radiographs and magnetic resonance images (MRIs) were obtained, and knee symptoms were queried. From baseline fasting blood samples, lipids and lipoproteins were analyzed using standard assays. After excluding participants with baseline OA, we defined 2 sets of patients: those developing radiographic OA, and those developing symptomatic OA (knee pain and radiographic OA). Controls did not develop these outcomes. Additionally, we examined worsening of cartilage loss and synovitis on MRI and of knee pain using the Western Ontario and McMaster Universities Osteoarthritis Index scale. We carried out logistic regression adjusting for age, sex, body mass index, education, baseline pain, and depressive symptoms, testing total cholesterol and lipoproteins as continuous measures, and we performed sensitivity analyses examining whether commonly used thresholds for high cholesterol, LDL, or low HDL increased risk.

RESULTS

We studied 337 patients with incident symptomatic OA and 283 patients with incident radiographic OA. The mean age at baseline was 62 years (55% women). Neither total cholesterol, LDL, nor HDL showed a significant association with radiographic or symptomatic OA. Additionally, we found no association of these lipid measures with cartilage loss, worsening synovitis, or worsening knee pain.

CONCLUSION

Our data do not support an association between total cholesterol, LDL, or HDL with OA outcomes.

Cholesterol metabolism related genes in osteoarthritis

Cholesterol homeostasis plays a significant role in skeletal development and the dysregulation of cholesterol-related mechanism has been shown to be involved in the development of cartilage diseases including osteoarthritis (OA). Epidemiological studies have shown an association between elevated serum cholesterol levels and OA. Furthermore, abnormal lipid accumulation in chondrocytes as a result of abnormal regulation of cholesterol homeostasis has been demonstrated to be involved in the development of OA. Although, many in vivo and in vitro studies support the connection between cholesterol and cartilage degradation, the mechanisms underlying the complex interactions between lipid metabolism, especially HDL cholesterol metabolism, and OA remain unclear. The current review aims to address this problem and focuses on key molecular players of the HDL metabolism pathway and their role in ΟΑ pathogenesis. Understanding the complexity of biological processes implicated in OA pathogenesis, such as cholesterol metabolism, may lead to new targets for drug therapy of OA patients.

Evaluation of Deep Vein Thrombosis Risk Factors After Arthroscopic Posterior Cruciate Ligament Reconstruction: A Retrospective Observational Study

We evaluated the risk factors of deep venous thrombosis (DVT) after knee arthroscopic posterior cruciate ligament (PCL) reconstruction in patients with only PCL injury. From August 2014 to December 2020, a total of 172 patients who had accepted knee arthroscopic PCL reconstruction underwent the color Doppler ultrasound of bilateral lower-extremities deep veins on 3 days postoperatively. Based on the inspection results, patients were divided into DVT group (18 males and 8 females, mean age 43.62 years) and non-DVT group (108 males and 38 females, mean age 33.96 years). The potential associations of DVT risk and age, gender, body mass index (BMI), diabetes, hypertension, smoking and other factors were analyzed. An old age (OR = 1.090; 95% CI = 1.025-1.158; P = 0.006), a high BMI (OR = 1.509; 95% CI = 1.181-1.929; P = 0.001) and an increased post-surgery D-dimer (OR = 5.034; 95% CI = 2.091-12,117; P ≤ 0.001) value were significantly associated with an elevated DVT risk after knee arthroscopic PCL reconstruction. Increased age, BMI, and postoperative D-dimer were risk factors of DVT following knee arthroscopic PCL reconstruction in patients with only PCL injury.

The Lipoprotein Transport System in the Pathogenesis of Multiple Myeloma: Advances and Challenges

Multiple myeloma (MM) is an incurable neoplastic hematologic disorder characterized by malignant plasma cells, mainly in the bone marrow. MM is associated with multiple factors, such as lipid metabolism, obesity, and age-associated disease development. Although, the precise pathogenetic mechanisms remain unknown, abnormal lipid and lipoprotein levels have been reported in patients with MM. Interestingly, patients with higher APOA1 levels, the major apolipoprotein of high density lipoprotein (HDL), have better overall survival. The limited existing studies regarding serum lipoproteins in MM are inconclusive, and often contradictory. Nevertheless, it appears that deregulation of the lipoprotein transport system may facilitate the development of the disease. Here, we provide a critical review of the literature on the role of lipids and lipoproteins in MM pathophysiology. We also propose novel mechanisms, linking the development and progression of MM to the metabolism of blood lipoproteins. We anticipate that proteomic and lipidomic analyses of serum lipoproteins along with analyses of their functionality may improve our understanding and shed light on novel mechanistic aspects of MM pathophysiology.

An Update on the Role of Leptin in the Immuno-Metabolism of Cartilage

Since its discovery in 1994, leptin has been considered as an adipokine with pleiotropic effects. In this review, we summarize the actual information about the impact of this hormone on cartilage metabolism and pathology. Leptin signalling depends on the interaction with leptin receptor LEPR, being the long isoform of the receptor (LEPRb) the one with more efficient intracellular signalling. Chondrocytes express the long isoform of the leptin receptor and in these cells, leptin signalling, alone or in combination with other molecules, induces the expression of pro-inflammatory molecules and cartilage degenerative enzymes. Leptin has been shown to increase the proliferation and activation of immune cells, increasing the severity of immune degenerative cartilage diseases. Leptin expression in serum and synovial fluid are related to degenerative diseases such as osteoarthritis (OA), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Inhibition of leptin signalling showed to have protective effects in these diseases showing the key role of leptin in cartilage degeneration.

Exploring lipid biomarkers of coronary heart disease for elucidating the biological effects of gelanxinning capsule by lipidomics method based on LC-MS

High-throughput lipidomics technology was used to explore the potential therapeutic targets and mechanism of action of gelanxinning capsule on rat model with coronary heart disease (CHD). This study attempts to provide a novel method to interpret the molecular mechanism of traditional medicine. The lipid markers of CHD were determined by full-scan analysis based on ultra-performance liquid chromatography-high-definition mass spectrometry. Then, the metabolic changes associated with gelanxinning capsule treatment via the modulation of lipid biomarkers and pathway in rats were characterized. After gelanxinning treatment, the metabolic profile tended to recover compared with the model group. A total of 26 potential biomarkers were identified to represent the disorders of lipid metabolism in CHD animal model, of which 19 were regulated by gelanxinning capsule administration, and four metabolic pathways such as glycerophospholipid metabolism, sphingolipid metabolism, glycosylphosphatidylinositol-anchor biosynthesis, and glycerolipid metabolism were involved. From the pathway analysis, it was found that glycerophospholipid metabolism and sphingolipid metabolism with significant differences have the potential to be regarded as new targets for the treatment of CHD. Gelanxinning capsule with its good therapeutic effect protects against CHD by regulating lipid biomarkers and pathway from lipidomics-guided biochemical analysis.

Pain in women with knee and/or hip osteoarthritis is related to systemic inflammation and to adipose tissue dysfunction: Cross-sectional results of the KHOALA cohort

BACKGROUND

Considering the role of metabolic diseases in osteoarthritis (OA), we investigated whether biomarkers of adipose tissue dysfunction could be associated with OA-related pain.

DESIGN

We cross-sectionally analyzed patients with knee and/or hip OA at inclusion in the KHOALA cohort. We used visual analogic scale (VAS) for pain, the Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Osteoarthritis Knee and Hip Quality of Life (OAKHQOL) pain subscores. At inclusion, we measured ultra-sensitive CRP (usCRP), leptin and adiponectin for calculation of leptin:adiponectin ratio (LAR), a marker of adipose tissue dysfunction associated with central adiposity, high-molecular-weight adiponectin, visfatin and apolipoproteins. Univariate and multivariable analyses using stepwise linear regression models were performed to search for correlation between pain assessments and these biomarkers, with systematic adjustment on age.

RESULTS

In 596 women with hip and/or knee OA, multivariable analyses indicated that higher pain intensity was associated with higher LAR (VAS pain: β=0.49; p = 0.0001, OAKHQOL pain: β=-0.46; p = 0.0002, WOMAC pain: β=0.30; p = 0.001) in the whole group as well as in hip or knee OA patients considered separately. Pain intensity correlated also with usCRP level (VAS pain: β= 0.27; p = 0.02, OAKHQOL pain: β =-0.30; p = 0.01) and Kellgren-Lawrence score. In 267 men, no correlation between biomarkers and pain was found.

CONCLUSION

Serum LAR and usCRP level are associated with pain level, independently of radiographic structural severity in women with hip and/or knee OA, emphasizing the role of adipose tissue dysfunction and of meta-inflammation in pain experience in the female population.

Metabolic syndrome and subchondral bone alterations: The rise of osteoarthritis - A review

Metabolic syndrome (MS) has become one of the top major health burdens for over three decades not only due to its effects on cardiovascular health but also its implications in orthopedics. Extensive research has shown that MS is tightly linked to osteoarthritis and inflammation, a process which appears to primarily occur in the subchondral bone via the incidence of bone-marrow lesions (BMLs). Numerous studies identify obesity, dyslipidemia, insulin resistance and hypertension as the top metabolic risk factors, the so-called "deadly quartet". These factors are responsible for the disruptive physiological processes that culminate in detrimental alterations within the subchondral bone, cartilage damage and, overall, the predominant pro-inflammatory joint microenvironment. Although it has long been thought that osteoarthritis was limited to the cartilage component of the joint, other studies indicate that the disease may originate from the harmful alterations that occur primarily in the subchondral bone, especially via means of vascular pathology. Since metabolic risk factors are manageable to a certain extent, it is therefore possible to decelerate the progression of OA and mitigate its devastating effects on the subchondral bone and subsequent articular cartilage damage.

METHODS

Literature was reviewed using PubMed and Google Scholar in order to find a correlation between metabolic syndrome and osteoarthritic progression. The investigation included a combination of nomenclature such as: "metabolic syndrome", "obesity", "insulin resistance", "hypertension", "dyslipidemia", "low-grade systemic inflammation", "osteoarthritis", "subchondral bone", "cartilage" and "inflammatory biomarkers".

CONCLUSION

Based on several studies, there seems to be a significant association between The Deadly Quartet (metabolic syndrome), dysregulation of both pro- and anti-inflammatory biomarkers, and osteoarthritic progression arising from unbridled systemic inflammation.

Modulation of the Inflammatory Process by Hypercholesterolemia in Osteoarthritis

Objective: Several studies have linked metabolic syndrome to the development of osteoarthritis (OA) through hypercholesterolemia, one of its components. However, epidemiological studies showed contradictory results, and it is not clear how hypercholesterolemia itself, or oxidized LDL (oxLDL)-a pathological molecule potentially involved in this relationship-could be affecting OA. The objectives of this study were to investigate the effect of hypercholesterolemia induced by high-fat diet (HFD) in cartilage from OA rabbits, and how oxLDL affect human chondrocyte inflammatory and catabolic responses. Design: New Zealand rabbits were fed with HFD for 18 weeks. On week 6, OA was surgically induced. At the end of the study, cartilage damage and IL-1β, IL-6, MCP-1, MMP-13, and COX-2 expression in articular cartilage were evaluated. In addition, cultured human OA articular chondrocytes were treated with oxLDL at concentrations equivalent to those expected in synovial fluid from HFD rabbits, in the presence of IL-1β and TNFα. The effect of oxLDL on cell viability, nitric oxide production and catabolic and pro-inflammatory gene expression was evaluated. Results: HFD intake did not modify cartilage structure or pro-inflammatory and catabolic gene expression and protein presence, both in healthy and OA animals. OxLDL did not affect human chondrocyte viability, ADAMTS5 and liver X receptor (LXR) α gene expression, but decreased the induction of IL-1β, IL-6, MCP-1, MMP-13, iNOS, and COX-2 gene expression and MMP-13 and COX-2 protein presence, evoked by cytokines. Conclusions: Our data suggest that cholesterol intake per se may not be deleterious for articular cartilage. Instead, cholesterol de novo synthesis and altered cholesterol metabolism could be involved in the associations observed in human disease.

Association between statin use and incidence or progression of osteoarthritis: meta-analysis of observational studies

OBJECTIVE

The objective of the study was to determine whether statin use could reduce the risk of the incidence or progression of osteoarthritis (OA).

METHODS

The PubMed, Embase, and Cochrane databases were systematically searched for observational studies on the association between statin use and OA. ORs and 95% CIs were directly retrieved or calculated. The Newcastle-Ottawa quality assessment scale was used for study quality assessment. Subgroup analysis, sensitivity analysis, and publication bias were conducted using Stata software.

RESULTS

A total of 11 studies (679807 participants) were identified from the systematic literature search. No significant association between statin use and incidence (OR = 1.010; 95% CI: 0.968 to 1.055; P = 0.638) or progression (OR = 1.076; 95% CI: 0.824 to 1.405; P = 0.589) of OA was found in our meta-analysis. The meta-analysis according to the symptomatic or radiological OA also found no significant association between statin use and OA. The subgroup analysis showed that atorvastatin (OR = 0.953; 95% CI: 0.911 to 0.998; P = 0.041) and rosuvastatin (OR = 1.180; 95% CI: 1.122 to 1.241; P < 0.0001) had opposite effects on OA. The results of the analysis according to the joint site, interval, and statin dose were all not significant.

CONCLUSIONS

Statin use may not be associated with a lower risk of incidence and progression of OA, regardless of joint site. The opposite effects of atorvastatin and rosuvastatin were detected in OA.

Electroacupuncture Prevents Osteoarthritis of High-Fat Diet-Induced Obese Rats

The effects of acupuncture on osteoarthritis (OA) pathogenesis have been demonstrated in vitro and in animal models. However, the potential for acupuncture to mediate protective effects on obese-induced OA has not been examined. Here, we investigated the effects of different acupuncture patterns on OA pathogenesis in high-fat diet- (HFD-) induced obese rats. After 12-week diet-induced obesity, obese rats were treated with three acupuncture protocols for 2 weeks, including ST36, GB34, and ST36+GB34. The results showed that the three acupuncture protocols both prevented obesity-induced cartilage matrix degradation and MMP expression and mitigated obesity-induced systemic and local inflammation but had different regulatory effects on lipid metabolism and gut microbiota disorder of obese-induced OA rats. Furthermore, the three acupuncture protocols increased the microbial diversity and altered the structure of community of feces in obese rats. We found that ST36 and GB34 could inhibit proinflammatory shift in the gut microbiome with an increase in the ratio of Bacteroidetes/Firmicutes and promote the recovery of relative abundance of Clostridium, Akkermansia, Butyricimonas, and Lactococcus. Although both ST36 and GB34 had an anti-inflammatory effect on serum inflammatory mediators, only the acupuncture protocol with both ST36 and GB34 could effectively inhibit LPS-mediated joint inflammation in obesity rats. Therefore, relieving obesity-related chronic inflammation, lipid metabolism disorder, and gut microbiota disorder may be an important mechanism for acupuncture with ST36 and GB34 to promote OA recovery.

Pathophysiological landscape of osteoarthritis

A sharp rise in osteoarthritis (OA) incidence is expected as over 25% of world population ages in the coming decade. Although OA is considered a degenerative disease, mounting evidence suggests a strong connection with chronic metabolic conditions and low-grade inflammation. OA pathology is increasingly understood as a complex interplay of multiple pathological events including oxidative stress, synovitis and immune responses revealing its intricate nature. Cellular, biochemical and molecular aspects of these pathological events along with major outcomes of the relevant research studies in this area are discussed in the present review. With reference to their published and unpublished work, the authors strongly propose synovitis as a central OA pathology and the key OA pathological events are described in connection with it. Recent research outcomes also have succeeded to establish a linkage between metabolic syndrome and OA, which has been precisely included in the present review. Impact of aging process cannot be neglected in OA. Cell senescence is an important mechanism of aging through which it facilitates development of OA like other degenerative disorders, also discussed within a frame of OA. Conclusively, the reviewers urge low-grade inflammation linked to aging and derailed immune function as a pathological platform for OA development and progression. Thus, interventions targeted to prevent inflammaging hold a promising potential in effective OA management and efforts should be invested in this direction.

Correlation network analysis shows divergent effects of a long-term, high-fat diet and exercise on early stage osteoarthritis phenotypes in mice

BACKGROUND

Obesity increases knee osteoarthritis (OA) risk through metabolic, inflammatory, and biomechanical factors, but how these systemic and local mediators interact to drive OA pathology is not well understood. We tested the effect of voluntary running exercise after chronic diet-induced obesity on knee OA-related cartilage and bone pathology in mice. We then used a correlation-based network analysis to identify systemic and local factors associated with early-stage knee OA phenotypes among the different diet and exercise groups.

METHODS

Male C57BL/6J mice were fed a defined control (10% kcal fat) or high fat (HF) (60% kcal fat) diet from 6 to 37 weeks of age. At 25 weeks, one-half of the mice from each diet group were housed in cages with running wheels for the remainder of the study. Histology, micro computed tomography, and magnetic resonance imaging were used to evaluate changes in joint tissue structure and OA pathology. These local variables were then compared to systemic metabolic (body mass, body fat, and glucose tolerance), inflammatory (serum adipokines and inflammatory mediators), and functional (mechanical tactile sensitivity and grip strength) outcomes using a correlation-based network analysis. Diet and exercise effects were evaluated by two-way analysis of variance.

RESULTS

An HF diet increased the infrapatellar fat pad size and posterior joint osteophytes, and wheel running primarily altered the subchondral cortical and trabecular bone. Neither HF diet nor exercise altered average knee cartilage OA scores compared to control groups. However, the coefficient of variation was ≥25% for many outcomes, and some mice in both diet groups developed moderate OA (≥33% maximum score). This supported using correlation-based network analyses to identify systemic and local factors associated with early-stage knee OA phenotypes. In wheel-running cohorts, an HF diet reduced the network size compared to the control diet group despite similar running distances, suggesting that diet-induced obesity dampens the effects of exercise on systemic and local OA-related factors. Each of the 4 diet and activity groups showed mostly unique networks of local and systemic factors correlated with early-stage knee OA.

CONCLUSION

Despite minimal group-level effects of chronic diet-induced obesity and voluntary wheel running on knee OA pathology under the current test durations, diet and exercise substantially altered the relationships among systemic and local variables associated with early-stage knee OA. These results suggest that distinct pre-OA phenotypes may exist prior to the development of disease.

An update on the association between metabolic syndrome and osteoarthritis and on the potential role of leptin in osteoarthritis

Metabolic syndrome (MetS) has been associated with osteoarthritis (OA). Leptin, which is one of the markers of MetS, has been associated with OA pathophysiology. This study aimed to provide an update on the association between MetS and OA and on the potential role of leptin in OA. In this review, we summarized the current knowledge of the association between MetS and OA and updated the evidence on the potential role of leptin in OA. Clinical studies have investigated the epidemiologic association between MetS or its components and OA. Results suggested strong epidemiologic associations between MetS and OA, especially in the Asian population. Animal studies also indicated that metabolic dysregulation may lead to OA pathogenesis. The systemic role of MetS in OA pathophysiology is associated with obesity-related inflammation, the beneficial role of n-3 polyunsaturated fatty acids and deleterious role of cholesterol, physical inactivity, hypertension-induced subchondral ischemia, dyslipidemia-induced ectopic lipid deposition in chondrocytes, hyperglycemia-induced local effects of oxidative stress and advanced glycation end-products, low-grade systemic inflammation, and obesity-related adipokines by inducing the expression of proinflammtory factors. Leptin levels in serum/plasma and synovial fluid were associated with joint pain, radiographic progression, bone formation biomarkers, cartilage volume, knee OA incidence, and total joint arthroplasty in OA patients. Elevated leptin expression and increased effect of leptin on infrapatellar fat pad, synovium, articular cartilage, and bone were also involved in the pathogenesis of OA. Current knowledge indicates a convincing epidemiologic association between MetS and OA, especially in the Asian population. Animal studies have also shown that metabolic dysregulation may lead to OA pathogenesis. Accumulating evidence suggests that leptin may play a potential role in OA pathogenesis. Therefore, leptin and its receptor may be an emerging target for intervention in metabolic-associated OA.

Understanding the Molecular Mechanisms Underlying the Pathogenesis of Arthritis Pain Using Animal Models

Arthritis, including osteoarthritis (OA) and rheumatoid arthritis (RA), is the leading cause of years lived with disability (YLD) worldwide. Although pain is the cardinal symptom of arthritis, which is directly related to function and quality of life, the elucidation of the mechanism underlying the pathogenesis of pain in arthritis has lagged behind other areas, such as inflammation control and regulation of autoimmunity. The lack of therapeutics for optimal pain management is partially responsible for the current epidemic of opioid and narcotic abuse. Recent advances in animal experimentation and molecular biology have led to significant progress in our understanding of arthritis pain. Despite the inherent problems in the extrapolation of data gained from animal pain studies to arthritis in human patients, the critical assessment of molecular mediators and translational studies would help to define the relevance of novel therapeutic targets for the treatment of arthritis pain. This review discusses biological and molecular mechanisms underlying the pathogenesis of arthritis pain determined in animal models of OA and RA, along with the methodologies used.

Does a high-fat diet affect the development and progression of osteoarthritis in mice?: A systematic review

Aims

The aim of this study was to systematically review the literature for evidence of the effect of a high-fat diet (HFD) on the onset or progression of osteoarthritis (OA) in mice.

Methods

A literature search was performed in PubMed, Embase, Web of Science, and Scopus to find all studies on mice investigating the effects of HFD or Western-type diet on OA when compared with a control diet (CD). The primary outcome was the determination of cartilage loss and alteration. Secondary outcomes regarding local and systemic levels of proteins involved in inflammatory processes or cartilage metabolism were also examined when reported.

Results

In total, 14 publications met our inclusion criteria and were included in our review. Our meta-analysis showed that, when measured by the modified Mankin Histological-Histochemical Grading System, there was a significantly higher rate of OA in mice fed a HFD than in mice on a CD (standardized mean difference (SMD) 1.27, 95% confidence interval (CI) 0.63 to 1.91). Using the Osteoarthritis Research Society International (OARSI) score, there was a trend towards HFD causing OA (SMD 0.78, 95% CI -0.04 to 1.61). In terms of OA progression, a HFD consistently worsened the progression of surgically induced OA when compared with a CD. Finally, numerous inflammatory cytokines such as tumour necrosis factor alpha (TNF-α), interleukin (IL)-1β, and leptin, among others, were found to be altered by a HFD.

Conclusion

A HFD seems to induce or exacerbate the progression of OA in mice. The metabolic changes and systemic inflammation brought about by a HFD appear to be key players in the onset and progression of OA.

Cite this article:Bone Joint Res 2019;8:582–592.

Association of glucose homeostasis and metabolic syndrome with knee cartilage defects and cartilage volume in young adults

OBJECTIVE

To describe the associations of glucose homeostasis and metabolic syndrome (MetS) measures with knee cartilage defects and cartilage volume in young adults.

METHODS

Fasting blood biochemistry, waist circumference and blood pressure measures were collected 4-5 years prior to knee magnetic resonance imaging (MRI) scans. Blood measures included levels of glucose, insulin, triglyceride and high-density lipoprotein cholesterol (HDL-C). Homeostatic model assessment 2-insulin resistance (HOMA2-IR), HOMA2-beta cell function (HOMA2-β), HOMA2-insulin sensitivity (HOMA-S) and MetS were calculated or defined. Knee cartilage defects and cartilage volume were measured from MRI scans. Data were analysed using log binomial or linear regressions.

RESULTS

Among 328 participants (47.3% were females, aged 26-36 years at baseline), 40 (12.7%) had hyperglycaemia and 21 (6.7%) had MetS. Glucose homeostasis measures (except fasting glucose) were associated with tibiofemoral cartilage defects (fasting insulin: relative risk (RR) 1.05, 95% confidence interval (CI) 1.01 to 1.08; HOMA2-IR: 1.44, 1.08 to 1.92; HOMA2-β: 2.59, 1.33 to 5.07; HOMA2-S: 0.36, 0.18 to 0.72), but not patellar cartilage defects. There were no associations between glucose homeostasis measures and knee cartilage volume. High waist circumference (RR 2.32, 95% CI 1.18 to 4.54) and low HDL-C (RR 1.99, 95% CI 1.08 to 3.69) were associated with tibiofemoral cartilage defects, but no other associations were observed between MetS or its components and cartilage defects or volume.

CONCLUSION

Insulin resistance, high waist circumference and low HDL-C were associated with higher risk of tibiofemoral cartilage defects, suggesting glucose homeostasis and some MetS components may affect early cartilage damage in young adults.

Associations of Serum Lipids and Deep Venous Thrombosis Risk After Total Knee Arthroplasty in Patients With Primary Knee Osteoarthritis

Deep venous thrombosis (DVT) of the lower extremities is a common complication after total knee arthroplasty (TKA). This study aimed to investigate the potential associations between serum lipids and the risk of DVT after TKA in patients with primary knee osteoarthritis (OA). A total of 431 patients who received TKA caused by primary knee OA were randomly enrolled. According to the results of the color Doppler ultrasound of bilateral lower extremities deep veins on the third day postoperatively, patients were divided into DVT and non-DVT groups. Comparisons of preoperative serum levels of triglycerides, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol (LDL-C), apolipoprotein A1, and apolipoprotein B were then performed by the Student’s t test, χ2 test, and multivariate logistic regression analysis. For females, DVT patients had a higher serum LDL-C level at baseline ( P = .043) compared with non-DVT patients. A higher LDL-C value was significantly associated with an elevated DVT risk following TKA in female patients ( P = .037). In female patients with primary knee OA, preoperative serum LDL-C level may have an association with DVT risk after TKA. The relatively small male sample size may limit the accuracy of the findings.

Modulation of Bone and Marrow Niche by Cholesterol

Bone is a complex tissue composing of mineralized bone, bone cells, hematopoietic cells, marrow adipocytes, and supportive stromal cells. The homeostasis of bone and marrow niche is dynamically regulated by nutrients. The positive correlation between cardiovascular disease and osteoporosis risk suggests a close relationship between hyperlipidemia and/or hypercholesterolemia and the bone metabolism. Cholesterol and its metabolites influence the bone homeostasis through modulating the differentiation and activation of osteoblasts and osteoclasts. The effects of cholesterol on hematopoietic stem cells, including proliferation, migration, and differentiation, are also well-documented and further relate to atherosclerotic lesions. Correlation between circulating cholesterol and bone marrow adipocytes remains elusive, which seems opposite to its effects on osteoblasts. Epidemiological evidence has demonstrated that cholesterol deteriorates or benefits bone metabolism depending on the types, such as low-density lipoprotein (LDL) or high-density lipoprotein (HDL) cholesterol. In this review, we will summarize the latest progress of how cholesterol regulates bone metabolism and bone marrow microenvironment, including the hematopoiesis and marrow adiposity. Elucidation of these association and factors is of great importance in developing therapeutic options for bone related diseases under hypercholesterolemic conditions.

Proteome analysis of human mesenchymal stem cells undergoing chondrogenesis when exposed to the products of various magnesium-based materials degradation

Treatment of physeal fractures (15%–30% of all paediatric fractures) remains a challenge as in approximately 10% of the cases, significant growth disturbance may occur. Bioresorbable Magnesium-based implants represent a strategy to minimize damage (i.e., load support until bone healing without second surgery). Nevertheless, the absence of harmful effects of magnesium-implants and their degradation products on the growth plate should be confirmed. Here, the proteome of human mesenchymal stem cells undergoing chondrogenesis was evaluated when exposed to the products of various Magnesium-based materials degradation. The results of this study indicate that the materials induced regulation of proteins associated with cell chondrogenesis and cartilage formation, which should be beneficial for cartilage regeneration.

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Degradation products from Mg-based materials generated changes in protein expression.

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Relevant proteins involved in cartilage formation were upregulated.

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Potential application of especially Pure-Mg and Mg-10Gd for cartilage regeneration.

Western-type diet differentially modulates osteoblast, osteoclast, and lipoblast differentiation and activation in a background of APOE deficiency

During the past few years, considerable evidence has uncovered a strong relationship between fat and bone metabolism. Consequently, alterations in plasma lipid metabolic pathways strongly affect bone mass and quality. We recently showed that the deficiency of apolipoprotein A-1 (APOA1), a central regulator of high-density lipoprotein cholesterol (HDL-C) metabolism, results in reduced bone mass in C57BL/6 mice. It is documented that apolipoprotein E (APOE), a lipoprotein know for its atheroprotective functions and de novo biogenesis of HDL-C, is associated with the accumulation of fat in the liver and other organs and regulates bone mass in mice. We further studied the mechanism of APOE in bone metabolism using well-characterized APOE knockout mice. We found that bone mass was remarkably reduced in APOE deficient mice fed Western-type diet (WTD) compared to wild type counterparts. Static (microCT-based) and dynamic histomorphometry showed that the reduced bone mass in APOΕ^-/- mice is attributed to both decreased osteoblastic bone synthesis and elevated osteoclastic bone resorption. Interestingly, histologic analysis of femoral sections revealed a significant reduction in the number of bone marrow lipoblasts in APOΕ^-/- compared to wild type mice under WTD. Analyses of whole bone marrow cells obtained from femora of both animal groups showed that APOE null mice had significantly reduced levels of the osteoblastic (RUNX2 and Osterix) and lipoblastic (PPARγ and CEBPα) cardinal regulators. Additionally, the modulators of bone remodeling RANK, RANKL, and cathepsin K were greatly increased, while OPG and the OPG/RANKL ratio were remarkably decreased in APOΕ^-/- mice fed WTD, compared to their wild-type counterparts. These findings suggest that APOE deficiency challenged with WTD reduces osteoblastic and lipoblastic differentiation and activity, whereas it enhances osteoclastic function, ultimately resulting in reduced bone mass, in mice.

Pro-inflammatory cytokines: The link between obesity and osteoarthritis

Osteoarthritis (OA), characterized by joint malfunction and chronic disability, is the most common form of arthritis. Clinical and animal experiments reveal that age-related OA is associated with many factors such as age, sex, trauma, and obesity. One of the most influential and modifiable risk factors is obesity. Obesity not only increases mechanical stress on the tibiofemoral cartilage, but also leads to a higher prevalence of OA in non-weight-bearing areas. There is a link between obesity and inflammation. Adipose tissues play a crucial role in this context because they are the major source of cytokines, chemokines, and metabolically-active mediators named adipokines. The adipokines, including adiponectin and leptin, have been demonstrated to regulate inflammatory immune responses in cartilage. Obese people and animals show a higher level of serum tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL)-1β and IL-6, all of which are produced by macrophages derived from adipose tissue. These pro-inflammatory cytokines regulate the proliferation and apoptosis of adipocytes, promote lipolysis, inhibit lipid synthesis and decrease blood lipids through autocrine and paracrine mechanisms. Elevated levels of TNF-α, IL-1 and IL-6 have been found in the synovial fluid, synovial membrane, subchondral bone and cartilage of OA patients, confirming their important roles in OA pathogenesis. TNF-α, IL-6 and IL-1 are the factors released by fat to negatively regulate cartilage directly. Moreover, TNF-α, IL-1 and IL-6 can induce the production of other cytokines, matrix metalloproteinases (MMPs) and prostaglandins and inhibit the synthesis of proteoglycans and type II collagen; thus, they play a pivotal role in cartilage matrix degradation and bone resorption in OA. Activated chondrocytes also produce MMP-1, MMP-3, MMP-13, and aggrecanase 1 and 2 (ADAMTS-4, ADAMTS-5). In addition, IL-1, TNF-α and IL-6 may cause OA indirectly by regulating release of adiponectin and leptin from adipocytes. In this review, we first summarize the relationship between obesity and inflammation. Then we summarize the roles of IL-1, TNF-α and IL-6 in OA. We further discuss how IL-1, TNF-α and IL-6 regulate the communication between fat and OA, and their pathological roles in obesity-related OA. Lastly, we discuss the possibility of using the pro-inflammatory signaling pathway as a therapeutic target to develop drugs for obesity-related OA.

Post-weaning high-fat diet results in growth cartilage lesions in young male rats

To determine if a high-fat diet (HF) from weaning would result in a pro-inflammatory state and affect joint cartilage, we fed male rats either HF or Chow diet post-weaning, and voluntary wheel exercise (EX) or cage only activity (SED) after 9 weeks of age. At 17 weeks body composition, plasma biomarkers and histomorphology scores of femoro-tibial cartilages of HF-SED, HF-EX, Chow-SED and Chow-EX groups were compared. Food intake and activity were not significantly different between groups. HF diet resulted in significantly higher weight gain, %fat, fat:lean ratio, and plasma leptin, insulin and TNFα concentrations, with significant interactions between diet and exercise. No abnormal features were detected in the hyaline articular cartilage or in the metaphyseal growth plate in all four groups. However, collagen type X- positive regions of retained epiphyseal growth cartilage (EGC) was present in all HF-fed animals and significantly greater than that observed in Chow-fed sedentary rats. Most lesions were located in the lateral posterior aspect of the tibia and/or femur. The severity of lesions was greater in HF-fed animals. Although exercise had a significantly greater effect in reducing adiposity and associated systemic inflammation in HF-fed rats, it had no effect on lesion incidence or severity. Lesion incidence was also significantly associated with indices of obesity and plasma markers of chronic inflammation. Clinically, EGC lesions induced by HF feeding in rats from very early in life, and possibly by insufficient activity, is typical of osteochondrosis in animals. Such lesions may be the precursor of juvenile osteochondritis dissecans requiring surgery in children/adolescents, conservative management of which could benefit from improved understanding of early changes in cellular and gene expression.

Statin use and knee osteoarthritis progression: Results from a post-hoc analysis of the SEKOIA trial

OBJECTIVE

Epidemiological and experimental studies have suggested that lipid disorders might be involved in the pathophysiology of knee osteoarthritis (OA). Studies assessing the effect of statins on knee OA progression have shown conflicting results. We investigated the impact of statin use on radiological progression in patients with radiological and symptomatic knee OA.

METHODS

In total, 336 patients from the placebo arm of SEKOIA trial completed the 3-year follow-up and were included in this post-hoc analysis. Statin use was recorded at baseline interview. Minimal medial tibiofemoral joint space was measured on plain radiographs by an automated method at baseline and then annually. Radiologic progression was defined as joint space narrowing≥0.5mm over 3 years.

RESULTS

Overall, 71 patients were statin users (21.1%). They had a higher BMI (31.1±5.3 vs. 29.3±5.2kg/m², P=0.008), a higher sum of metabolic factors (≥3 factors: 43.7% vs 7.2%; P for trend<0.001) and a higher rate of radiological progression (49.3% vs. 32.1%, P=0.007) as compared to statin non-users. The significant association between radiological progression and statin use was independent of age, gender, WOMAC global score, disease duration, baseline joint space width, hypertension, type 2 diabetes, obesity (BMI>30kg/m²) and cardiovascular diseases [relative risk 1.49 (95% CI: 1.10-2.02), P=0.010].

CONCLUSION

Among patients with knee OA, statin use was associated with radiological worsening over 3 years, regardless of other potential confounding factors (obesity, type 2 diabetes, hypertension, disease duration, symptom intensity and radiological severity).

Association between osteoarthritis and dyslipidaemia: a systematic literature review and meta-analysis

OBJECTIVES

We aimed to investigate the prevalence of dyslipidemia in patients with osteoarthritis (OA) and whether OA and dyslipidemia are associated.

METHODS

We performed a systematic literature review and a meta-analysis, including cross-sectional, cohort and case-control studies, to assess the number of patients with OA and/or dyslipidemia. We calculated the mean (±SD) prevalence of dyslipidemia in patients with and without OA and the risk of dyslipidemia (OR, 95% CI) among patients with OA.

RESULTS

From 605 articles screened, 48 were included in the analysis (describing 29 cross-sectional, 10 cohort and 9 case-control studies). The mean prevalence of dyslipidemia was 30.2%±0.6% among 14 843 patients with OA and 8.0%±0.1% among 196 168 without OA. The risk of dyslipidemia was greater with than without OA overall (OR 1.98,95% CI 1.43 to 2.75, p<0.0001) and with knee OA (OR 2.27, 1.33 to 3.89, p=0.003) and hand OA (OR 2.12, 1.46 to 3.07), p<0.0001).

CONCLUSION

The risk of dyslipidemia was twofold greater with than without OA, so lipid disturbances could be a risk factor for OA. Such a result supports the individualisation of the metabolic syndrome-associated OA phenotype.

High-density lipoprotein (HDL) metabolism and bone mass

It is well appreciated that high-density lipoprotein (HDL) and bone physiology and pathology are tightly linked. Studies, primarily in mouse models, have shown that dysfunctional and/or disturbed HDL can affect bone mass through many different ways. Specifically, reduced HDL levels have been associated with the development of an inflammatory microenvironment that affects the differentiation and function of osteoblasts. In addition, perturbation in metabolic pathways of HDL favors adipoblastic differentiation and restrains osteoblastic differentiation through, among others, the modification of specific bone-related chemokines and signaling cascades. Increased bone marrow adiposity also deteriorates bone osteoblastic function and thus bone synthesis, leading to reduced bone mass. In this review, we present the current knowledge and the future directions with regard to the HDL-bone mass connection. Unraveling the molecular phenomena that underline this connection will promote the deeper understanding of the pathophysiology of bone-related pathologies, such as osteoporosis or bone metastasis, and pave the way toward the development of novel and more effective therapies against these conditions.

Systemic and Local Adipose Tissue in Knee Osteoarthritis

Osteoarthritis is a common chronic joint disorder affecting older people. The knee is the major joint affected. The symptoms of osteoarthritis include limited range of motion, joint swelling, and pain causing disability. There are no disease modifying drugs available, and treatments are mainly focused on pain management. Total knee replacement performed at the end stage of the disease is considered the only cure available. It has been found that obese people have an increased risk to develop not only knee but also hand osteoarthritis. This supports the concept that adipose tissue might be related to osteoarthritis not only through overloading. As matter of fact, obesity induces a low grade systemic inflammatory state characterized by the production and secretion of several adipocytokines that may have a role in osteoarthritis development. Furthermore, hypertension, impaired glucose, and lipid metabolism, which are comorbidities associated with obesity, have been shown to alter the joint tissue homeostasis. Moreover, infrapatellar fat pad in the knee has been demonstrated to be a local source of adipocytokines and potentially contribute to osteoarthritis pathogenesis. Here, we discuss the role of systemic and local adipose tissue in knee osteoarthritis. J. Cell. Physiol. 232: 1971-1978, 2017. © 2016 Wiley Periodicals, Inc.

Novel effects of sarcopenic osteoarthritis on metabolic syndrome, insulin resistance, osteoporosis, and bone fracture: the national survey

This study compared the effects sarcopenic osteoarthritis on metabolic syndrome, insulin resistance, osteoporosis, and bone fracture. By using national survey data, we suggest that the relationship between sarcopenia and metabolic syndrome or insulin resistance is potentiated by the severity of osteoarthritis and is independent of body weight.

INTRODUCTION

Sarcopenia and osteoarthritis are known risk factors for metabolic syndrome. However, their combined effects on metabolic syndrome, insulin resistance and osteoporosis remain uncertain.

METHODS

We used data from the fifth Korean National Health and Nutrition Examination Survey using a total of 3158 adults (age >50 years). Sarcopenia was defined as a skeletal muscle index score (appendicular skeletal muscle mass/body weight) within the fifth percentile of sex-matched younger reference participants. Radiographic knee osteoarthritis was defined as a Kellgren-Lawrence (K-L) grade of 2 or greater. Metabolic syndrome was diagnosed using the National Cholesterol Education Program criteria. Insulin resistance was evaluated using the homeostasis model assessment-estimated insulin resistance index (HOMA-IR). Osteoporosis was defined using the World Health Organization T-score criteria.

RESULTS

In multivariable logistic regression analysis, the sarcopenic osteoarthritis group had a higher odds ratio (OR) for metabolic syndrome (OR = 11.00, 95 % confidential interval (CI) = 2.12-56.99, p = 0.013) than the non-sarcopenic osteoarthritis (OR = 1.02, 95 % CI = 0.65-1.62, p = 0.972) and sarcopenic non-osteoarthritis groups (OR = 7.15, 95 % CI = 1.57-32.53, p = 0.027). Similarly, sarcopenic osteoarthritis had a greater OR of highest HOMA-IR quartiles (OR = 8.19, 95 % CI = 2.03-33.05, p = 0.003) than the other groups. Overall, the association between the K-L grade and body mass index was significant; however, this significance was lower in individuals with sarcopenia and was lost in those with sarcopenic osteoarthritis. Additionally, osteoporosis and bone fracture were not associated to sarcopenic osteoarthritis (p > 0.05).

CONCLUSIONS

These results suggest that the relationship between sarcopenia and metabolic syndrome or insulin resistance is potentiated by the severity of osteoarthritis and is independent of body weight.

A Tale of Two Joints: The Role of Matrix Metalloproteases in Cartilage Biology

Matrix metalloproteinases are a class of enzymes involved in the degradation of extracellular matrix molecules. While these molecules are exceptionally effective mediators of physiological tissue remodeling, as occurs in wound healing and during embryonic development, pathological upregulation has been implicated in many disease processes. As effectors and indicators of pathological states, matrix metalloproteinases are excellent candidates in the diagnosis and assessment of these diseases. The purpose of this review is to discuss matrix metalloproteinases as they pertain to cartilage health, both under physiological circumstances and in the instances of osteoarthritis and rheumatoid arthritis, and to discuss their utility as biomarkers in instances of the latter.

Apolipoprotein A-1 regulates osteoblast and lipoblast precursor cells in mice

Imbalances in lipid metabolism affect bone homeostasis, altering bone mass and quality. A link between bone mass and high-density lipoprotein (HDL) has been proposed. Indeed, it has been recently shown that absence of the HDL receptor scavenger receptor class B type I (SR-B1) causes dense bone mediated by increased adrenocorticotropic hormone (ACTH). In the present study we aimed at further expanding the current knowledge as regards the fascinating bone-HDL connection studying bone turnover in apoA-1-deficient mice. Interestingly, we found that bone mass was greatly reduced in the apoA-1-deficient mice compared with their wild-type counterparts. More specifically, static and dynamic histomorphometry showed that the reduced bone mass in apoA-1(-/-) mice reflect decreased bone formation. Biochemical composition and biomechanical properties of ApoA-1(-/-) femora were significantly impaired. Mesenchymal stem cell (MSC) differentiation from the apoA-1(-/-) mice showed reduced osteoblasts, and increased adipocytes, relative to wild type, in identical differentiation conditions. This suggests a shift in MSC subtypes toward adipocyte precursors, a result that is in line with our finding of increased bone marrow adiposity in apoA-1(-/-) mouse femora. Notably, osteoclast differentiation in vitro and osteoclast surface in vivo were unaffected in the knock-out mice. In whole bone marrow, PPARγ was greatly increased, consistent with increased adipocytes and committed precursors. Further, in the apoA-1(-/-) mice marrow, CXCL12 and ANXA2 levels were significantly decreased, whereas CXCR4 were increased, consistent with reduced signaling in a pathway that supports MSC homing and osteoblast generation. In keeping, in the apoA-1(-/-) animals the osteoblast-related factors Runx2, osterix, and Col1a1 were also decreased. The apoA-1(-/-) phenotype also included augmented CEPBa levels, suggesting complex changes in growth and differentiation that deserve further investigation. We conclude that the apoA-1 deficiency generates changes in the bone cell precursor population that increase adipoblast, and decrease osteoblast production resulting in reduced bone mass and impaired bone quality in mice.