Biomechanics, obesity, and osteoarthritis. The role of adipokines: When the levee breaks

Implications of obesity-mediated cellular dysfunction and adipocytokine signaling pathways in the pathogenesis of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage degradation, bone sclerosis, and chronic low-grade inflammation. Aging and injury play key roles in OA pathogenesis by triggering the release of proinflammatory factors from adipose tissue and other sources. Obesity and aging impair the function of endoplasmic reticulum (ER) chaperones, leading to ER stress, protein misfolding, and cellular apoptosis. Obesity also induces mitochondrial dysfunction in OA through oxidative stress and disrupts mitochondrial dynamics, exacerbating chondrocyte damage. These factors contribute to inflammation, matrix imbalance, and chondrocyte apoptosis. Adipocytes, the primary source of adipokines, release inflammatory mediators that affect joint cells. Several adipocytokines have a central role in the regulation of many aspects of inflammation. Adiponectin and leptin are the two most abundant adipocytokines that are strongly associated with OA progression. This literature review suggests that adipokines activate many signaling pathways to exert downstream effects and play significant roles in obesity-induced OA. Understanding this rapidly growing family of mainly adipocyte-derived mediators and obesity-mediated cellular dysfunction may be important in the development of new therapies for obesity-associated OA management.

Investigating the Potential of Magnesium Microparticles on Cartilage and Bone Regeneration Utilizing an In Vitro Osteoarthritis Model

Osteoarthritis (OA) is a significant condition that profoundly impacts synovial joints, including cartilage and subchondral bone plate. Biomaterials that can impede OA progression are a promising alternative or supplement to anti-inflammatory and surgical interventions. Magnesium (Mg) alloys known for bone regeneration potential were assessed in the form of Mg microparticles regarding their impact on tissue regeneration and prevention of OA progression. In vitro assays based on mesenchymal stem cells (SCP-1) were applied to evaluate the Mg microparticle's compatibility and function. Biocompatibility documented through live-dead staining and lactate dehydrogenase assay revealed a 90% cell viability at a concentration below 10 mM after 3 days of exposure. An in vitro OA model based on the supplementation of the cytokines IL-1β, and TNF-α was established and disclosed the effect of Mg degradation products in differentiating SCP-1 cells. Sustained differentiation was confirmed through extracellular matrix staining and increased gene marker expression. The Mg supplementation reduced the release of inflammatory cytokines (IL-6 and IL-8) while promoting the expression of proteins such as collagen X, collagen I, and osteopontin in a time-dependent manner. The in vitro study suggests that Mg microparticles hold a therapeutic potential for OA treatment with their ability to support bone and cartilage repair mechanisms even under inflammatory conditions.

Therapeutic Ultrasound Modulates Cell Proliferation and Proinflammatory Cytokine Levels in Osteoarthritic Chondrocytes

The development and progression of osteoarthritis (OA) are believed to involve inflammation. This study aimed to investigate the effects of applying therapeutic ultrasound (US) to human osteoarthritic chondrocytes in continuous and pulsed modes on cell proliferation and proinflammatory cytokine levels. Human osteoarthritic chondrocytes (HC-OA 402OA-05a) were proliferated in appropriate media and then seeded into culture plates. The plates were grouped and exposed to underwater continuous, pulsed and control US at 0.1 W/cm2 and 1 MHz for 10 min daily for 10 days. Cell viability/proliferation was assessed using the MTT assay, total protein was measured by ELISA and cytokine levels per protein were determined. Cells were photographed using microscopic analysis. Both continuous and pulsed US groups showed a significant increase in viability compared to the control group. No significant difference was found between the continuous and pulsed US groups for IL-1β, TNF-α and IL-6 levels. Both groups showed significant cytokine reduction compared to the control group. For IL-17 and IL-32 levels, both US groups had reduced cytokine levels compared to the control group, but the results were not significant. Underwater US at 0.1 W/cm2 and 1 MHz stimulated cell proliferation and reduced proinflammatory cytokine levels in osteoarthritic chondrocyte cell cultures. This study extensively focused on proinflammatory IL levels, and the meaningful results may inspire future in vivo/in vitro studies. While adapting in vitro data to in vivo conditions poses challenges, our results could guide future in vivo studies and clinical applications.

The Role of Adipokines between Genders in the Pathogenesis of Osteoarthritis

Osteoarthritis (OA) is a chronic, progressive, degenerative joint disease characterized by joint pain, stiffness, and limited movement. It presents significant intra- and inter-individual variability-in particular, between genders. Recent research has increasingly focused on the role of adipokines-especially leptin, adiponectin, and resistin-in the development of OA. Adipokines, peptide hormones primarily secreted by adipose tissue, are involved in crucial physiological processes related to metabolism and immunity. They can also impact bone and cartilage turnover by interacting with joint cells such as osteoblasts, osteoclasts, chondrocytes, and mesenchymal stem cells, thereby linking inflammation with bone cartilage homeostasis. This review aims to elucidate the structure and functions of various adipokines, their serum and synovial levels, and their association with clinical presentation and radiographic progression in OA patients, with a focus on differences between sexes. A narrative literature review was conducted using three databases specifically analyzing sex differences. OA patients generally show elevated serum and synovial levels of leptin, chemerin, and visfatin, as well as high plasma levels of resistin and visfatin. In contrast, synovial levels of adiponectin and omentin are reduced in OA patients compared to healthy individuals, with an inverse relationship to disease severity, suggesting a potential protective role. Resistin and leptin were positively correlated with pain severity and radiographic progression, while adiponectin's role in OA remains controversial. Regarding sex differences, male OA patients exhibited higher serum levels of leptin, chemerin, and omentin compared to healthy controls, with a positive correlation to the BMI and estrogen levels, potentially explaining the sexual dimorphism observed in this condition. Studies on visfatin and lipocalin did not reveal significant differences in synovial or serum levels between the sexes. The role of resistin remains controversial. Adipokines influence the joint microenvironment and contribute to the progression of osteoarthritis (OA). However, the precise biological mechanisms are not yet fully understood due to the complex interactions between the metabolic, mechanical, and immune systems. Further research is needed to clarify their roles in OA and to identify targeted therapies for managing this degenerative disease.

Adipokines as potential pharmacological targets for immune inflammatory rheumatic diseases: Focus on rheumatoid arthritis, osteoarthritis, and intervertebral disc degeneration

Adipokines are a heterogeneous group of signalling molecules secreted prevalently by adipose tissue. Initially considered as regulators of energy metabolism and appetite, adipokines have been recognized for their substantial involvement in musculoskeletal disorders, including osteoarthritis, rheumatoid arthritis, and many others. Understanding the role of adipokines in rheumatic inflammatory and autoimmune diseases, as well as in other musculoskeletal diseases such as intervertebral disc degeneration, is crucial for the development of novel therapeutic strategies. Targeting adipokines, or their signalling pathways, may offer new opportunities for the treatment and management of these conditions. By modulating adipokines levels or activity, it may be possible to regulate inflammation, to maintain bone health, and preserve muscle mass, thereby improving the outcomes and quality of life for individuals affected by musculoskeletal diseases. The aim of this review article is to update the reader on the multifaceted role of adipokines in the main rheumatic diseases such as osteoarthritis and rheumatoid arthritis and to unravel the complex interplay among adipokines, cartilage metabolism, bone remodelling and muscles, which will pave the way for innovative therapeutic intervention in the future. For completeness, the role of adipokines in intervertebral disc degeneration will be also addressed.

Optimal timing of hip and knee arthroplasty after bariatric surgery: A systematic review

Background

Obesity is a risk factor for the development of osteoarthritis and contributes to the increasing demand for total joint arthroplasty (TJA). Because a lower preoperative weight decreases the risk of complications after TJA, and because bariatric surgery (BS) can reduce weight and comorbidity burden, orthopedic surgeons often recommend BS prior to TJA in patients with obesity. However, the optimal timing of TJA after BS in terms of complications, revisions and dislocations is unknown.

Methods

PubMed, Embase and Cochrane CENTRAL databases were systematically searched for any type of study reporting rates of complications, revisions and dislocations in patients who had TJA after BS. The included studies' quality was assessed using the Newcastle-Ottawa Scale.

Results

Out of the 16 studies eligible for review, eight registry-based retrospective studies of high to moderate quality compared different time periods between BS and TJA and overall their results suggest little differences in complication rates. The remaining eight retrospective studies evaluated only one time period and had moderate to poor quality. Overall, there were no clear differences in outcomes after TJA for the different time frames between BS and TJA.

Conclusion

The results of this systematic review suggest that there is limited and insufficient high-quality evidence to determine the optimal timing of TJA after BS in terms of the rates of complications, revisions and dislocations. Given this lack of evidence, timing of TJA after BS will have to be decided by weighing the individual patients' risk factors against the expected benefits of TJA.

Association of body composition and physical activity with pain and function in knee osteoarthritis patients: a cross-sectional study

OBJECTIVE

The objective of this study is to delineate disparities between patients with knee osteoarthritis (KOA) based on obesity status, investigate the interplay among body composition, physical activity and knee pain/function in patients with KOA and conduct subgroup analyses focusing on those with KOA and obesity.

DESIGN

Cross-sectional study.

SETTING

Residents of eight communities in Shijiazhuang, Hebei Province, China, were surveyed from March 2021 to November 2021.

PARTICIPANTS

178 patients with symptomatic KOA aged 40 years or older were included.

MAIN OUTCOMES AND MEASURES

The primary outcome measure was knee pain, assessed using the Western Ontario and McMaster Universities Osteoarthritis Index-pain (WOMAC-P) scale. Secondary outcome measures included function, evaluated through the WOMAC-function (WOMAC-F) scale and the Five-Time-Sit-to-Stand Test (FTSST). Data analysis involved t-tests, Wilcoxon rank-sum tests, χ2 tests, linear and logistical regression analysis.

RESULTS

Participants (n=178) were 41-80 years of age (median: 65, P25-P75: 58-70), and 82% were female. Obese patients (n=103) had worse knee pain and self-reported function (p<0.05). In general patients with KOA, body fat mass was positively associated with bilateral knee pain (β=1.21 (95% CI 0.03 to 0.15)), WOMAC-P scores (β=0.25 (95% CI 0.23 to 1.22)), WOMAC-F scores (β=0.28 (95% CI 0.35 to 1.29)) and FTSST (β=0.19 (95% CI 0.03 to 0.42)), moderate-intensity to low-intensity physical activity was negatively associated with bilateral knee pain (β=-0.80 (95% CI -0.10 to -0.01)) and Skeletal Muscle Index (SMI) was negatively associated with WOMAC-F scores (β=-0.16 (95% CI -0.66 to -0.03)). In patients with KOA and obesity, SMI was negatively associated with FTSST (β=-0.30 (95% CI -3.94 to -0.00)).

CONCLUSION

Patients with KOA and obesity had worse knee pain and self-reported function compared with non-obese patients. Greater fat mass, lower muscle mass and lower moderate-intensity to low-intensity physical activity were associated with increased knee pain and poor self-reported function. More skeletal muscle mass was associated with the improvement of objective function.

Network Pharmacology-Based Approach to Investigate the Active Ingredients and Therapeutic Mechanisms of Jingu Tongxiao Pill against Osteoarthritis

This study aimed to investigate the active ingredients and therapeutic mechanisms of Jingu Tongxiao Pill (JGTXP), a commonly used Chinese patent medicine, in treating osteoarthritis (OA) via network pharmacology analysis combined with experimental validation. First, we administered JGTXP to rat plasma and identified the candidate active compounds. Next, target prediction, protein-protein interaction, compound-target network construction, gene ontology (GO), and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were conducted for JGTXP. Lastly, the network-derived key targets and pathways were validated in vitro and in vivo. Finally, we identified 106 compounds in JGTXP and 24 absorbed compounds in the rat plasma. Network analysis revealed that JGTXP interferes with OA mainly via regulating the inflammatory response, collagen catabolic process, and osteoclast differentiation, and the nuclear factor kappa B (NF-κB) signaling pathway plays a pivotal role in these processes. Experimentally, JGTXP exerted potential protective effects on articular cartilage and inhibited expression of inflammatory mediators and collagen catabolism-related proteins, including interleukin 1 beta (IL-1β), interleukin 6, tumor necrosis factor alpha (TNF-α), and matrix metalloproteinase (MMP) 3 and MMP13, in a papain-induced OA rat model. Consistently, mRNA expression levels of these factors and nitric oxide release were suppressed by JGTXP in an LPS-induced RAW 264.7 inflammation model. The reporter gene assay showed that JGTXP could reduce the transcriptional activity of NF-κB. Consecutive western blot analysis demonstrated that nuclear NF-κB p65, inducible nitric oxide synthase (iNOS), and cyclooxygenase 2 (COX-2) expression were inhibited while cytoplasmic NF-κB p65 was upregulated by JGTXP. Using a combination of chemical profiling, network pharmacology analysis, and experimental validation, we preliminarily clarified the active ingredients of JGTXP intervention for OA and demonstrated that JGTXP ameliorates OA, at least partially, by regulating the NF-κB signaling pathway.

Relationship Between Body Mass Index and Osteoarthritis for Single and Multisite Osteoarthritis of the Hand, Hip, or Knee: Findings From a Canadian Longitudinal Study on Aging

OBJECTIVE

To determine whether an apparent association between hand osteoarthritis (OA) and adiposity is explained by the presence of OA at other joint sites.

METHODS

Data from the Canadian Longitudinal Study on Aging, first cycle, comprehensive cohort, were used. Respondents age 45-85 years (n = 18,279) were asked separate questions about doctor-diagnosed OA in the hand, hip, or knee. Multinomial logistic regression was used to investigate the relationship between all combinations of hand, hip, and knee OA and body mass index (BMI) and waist-to-height ratio (WHtR).

RESULTS

OA was reported by 34.6% of respondents, 28.0% with OA at >1 joint site. Hand OA was not significantly associated with BMI after accounting for OA at other joint sites, with similar findings for WHtR. All joint site combinations containing the knee were strongly associated with BMI, with odds ratios (ORs) ranging from OR 2.92 (95% confidence interval [95% CI] 2.53-3.37) for knee OA only with obesity class I to OR 9.98 (95% CI 7.12-13.88) for multi-joint knee, hip, hand OA with obesity class II/III. BMI distributions including knee OA were broader and shifted to higher BMI levels than those for hand or hip OA.

CONCLUSION

Apparent associations between hand OA and BMI may be explained by concurrent OA at other joint sites. Recognizing that OA is a multi-joint disease is crucial for studies of the associations of adiposity with OA in a particular joint, especially the hand. The association between knee OA and BMI appears to be distinct from those for OA at other joint sites.

Senescent preosteoclast secretome promotes metabolic syndrome associated osteoarthritis through cyclooxygenase 2

Background

Metabolic syndrome-associated osteoarthritis (MetS-OA) is a distinct osteoarthritis phenotype defined by the coexistence of MetS or its individual components. Despite the high prevalence of MetS-OA, its pathogenic mechanisms are unclear. The aim of this study was to determine the role of cellular senescence in the development of MetS-OA.

Methods

Analysis of the human osteoarthritis initiative (OAI) dataset was conducted to investigate the MRI subchondral bone features of MetS-human OA participants. Joint phenotype and senescent cells were evaluated in two MetS-OA mouse models: high-fat diet (HFD)-challenged mice and STR/Ort mice. In addition, the molecular mechanisms by which preosteoclasts become senescent as well as how the senescent preosteoclasts impair subchondral bone microenvironment were characterized using in vitro preosteoclast culture system.

Results

Humans and mice with MetS are more likely to develop osteoarthritis-related subchondral bone alterations than those without MetS. MetS-OA mice exhibited a rapid increase in joint subchondral bone plate and trabecular thickness before articular cartilage degeneration. Subchondral preosteoclasts undergo senescence at the pre- or early-osteoarthritis stage and acquire a unique secretome to stimulate osteoblast differentiation and inhibit osteoclast differentiation. Antagonizing preosteoclast senescence markedly mitigates pathological subchondral alterations and osteoarthritis progression in MetS-OA mice. At the molecular level, preosteoclast secretome activates COX2-PGE2, resulting in stimulated differentiation of osteoblast progenitors for subchondral bone formation. Administration of a selective COX2 inhibitor attenuated subchondral bone alteration and osteoarthritis progression in MetS-OA mice. Longitudinal analyses of the human Osteoarthritis Initiative (OAI) cohort dataset also revealed that COX2 inhibitor use, relative to non-selective nonsteroidal antiinflammatory drug use, is associated with less progression of osteoarthritis and subchondral bone marrow lesion worsening in participants with MetS-OA.

Conclusions

Our findings suggest a central role of a senescent preosteoclast secretome-COX2/PGE2 axis in the pathogenesis of MetS-OA, in which selective COX2 inhibitors may have disease-modifying potential.

Funding

This work was supported by the National Institutes of Health grant R01AG068226 and R01AG072090 to MW, R01AR079620 to SD, and P01AG066603 to XC.

Identification of Key Genes Related to the Obesity Patients with Osteoarthritis Based on Weighted Gene Coexpression Network Analysis (WGCNA)

Background. Increasing evidence has suggested that obesity affects the occurrence and progression of osteoarthritis (OA). However, the underlying molecular mechanism that obesity affects the course of OA is not fully understood and remains to be studied. Methods. The gene expression profiles of the GSE117999 and GSE98460 datasets were derived from the Gene Expression Omnibus (GEO) database. Firstly, we explored the correlation between obesity and OA using chi-square test. Next, weighted gene coexpression network analysis (WGCNA) was executed to identify obesity patients with OA- (obesity OA-) related genes in the GSE117999 dataset by “WGCNA” package. Moreover, differential expression analysis was performed to select the hub genes by “limma” package. Furthermore, ingenuity pathway analysis (IPA) and functional enrichment analysis (“clusterProfiler” package) were conducted to investigate the functions of genes. Finally, the regulatory networks of hub genes and protein-protein interaction (PPI) network were created by the Cytoscape 3.5.1 software and STRING. Results. A total of 15 differentially expressed obesity OA-related genes, including 9 lncRNAs and 6 protein coding genes, were detected by overlapping 66 differentially expressed genes (DEGs) between normal BMI samples and obesity OA samples and 451 obesity OA-related genes. Moreover, CCR10, LENG8, QRFPR, UHRF1BP1, and HLA-DRB4 were identified as hub genes. IPA results indicated that the hub genes were noticeably enriched in antimicrobial response, inflammatory response, and humoral immune response. PPI network showed that CCR10 interacted more with other proteins. Gene set enrichment analysis (GSEA) indicated that the hub genes were related to protein translation, cancer, chromatin modification, antigen processing, and presentation. Conclusion. Our results further demonstrated the role of obesity in OA and might provide new targets for the treatment of obesity OA.

Can metformin relieve tibiofemoral cartilage volume loss and knee symptoms in overweight knee osteoarthritis patients? Study protocol for a randomized, double-blind, and placebo-controlled trial

BACKGROUND

Osteoarthritis (OA) is the most common joint disease, and is most frequently seen in the knees. However, there is no effective therapy to relieve the progression of knee OA. Metformin is a safe, well-tolerated oral medication that is extensively used as first-line therapy for type 2 diabetes. Previous observational studies and basic researches suggested that metformin may have protective effects on knee OA, which needs to be verified by clinical trials. This study, therefore, aims to examine the effects of metformin versus placebo on knee cartilage volume loss and knee symptoms in overweight knee OA patients by a randomized controlled trial over 24 months.

METHODS

This protocol describes a multicenter, randomized, double-blind, and placebo-controlled clinical trial aiming to recruit 262 overweight knee OA patients. Participants will be randomly allocated to the two arms of the study, receiving metformin hydrochloride sustained-release tablets or identical inert placebo for 24 months (start from 0.5 g/day for the first 2 weeks, and increase to 1 g/day for the second 2 weeks, and further increase to 2 g/day for the remaining period if tolerated). Primary outcomes will be changes in tibiofemoral cartilage volume and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score over 24 months. Secondary outcomes will be changes in visual analogue scale (VAS) knee pain, tibiofemoral cartilage defects, effusion-synovitis volume, and tibiofemoral bone marrow lesions maximum size over 24 months. The primary analyses will be intention-to-treat analyses of primary and secondary outcomes. Per-protocol analyses will be performed as the secondary analyses.

DISCUSSION

If metformin is proved to slow knee cartilage volume loss and to relieve knee symptoms among overweight knee OA patients, it will have the potential to become a disease modifying drug for knee OA. Metformin is a convenient intervention with low cost, and its potential effects on slowing down the structural progression and relieving the symptoms of knee OA would effectively reduce the disease burden worldwide.

TRIAL REGISTRATION

ClinicalTrials. gov NCT05034029 . Registered on 30 Sept 2021.

Role of Bioactive Compounds in Obesity: Metabolic Mechanism Focused on Inflammation

Obesity is a disease characterized by an inflammatory process in the adipose tissue due to diverse infiltrated immune cells, an increased secretion of proinflammatory molecules, and a decreased secretion of anti-inflammatory molecules. On the other hand, obesity increases the risk of several diseases, such as cardiovascular diseases, diabetes, and cancer. Their treatment is based on nutritional and pharmacological strategies. However, natural products are currently implemented as complementary and alternative medicine (CAM). Polyphenols and fiber are naturally compounds with potential action to reduce inflammation through several pathways and play an important role in the prevention and treatment of obesity, as well as in other non-communicable diseases. Hence, this review focuses on the recent evidence of the molecular mechanisms of polyphenols and dietary fiber, from Scopus, Science Direct, and PubMed, among others, by using key words and based on recent in vitro and in vivo studies.

Leptin in Osteoarthritis and Rheumatoid Arthritis: Player or Bystander?

White adipose tissue (WAT) is a specialized tissue whose main function is lipid synthesis and triglyceride storage. It is now considered as an active organ secreting a plethora of hormones and cytokines namely adipokines. Discovered in 1994, leptin has emerged as a key molecule with pleiotropic functions. It is primarily recognized for its role in regulating energy homeostasis and food intake. Currently, further evidence suggests its potent role in reproduction, glucose metabolism, hematopoiesis, and interaction with the immune system. It is implicated in both innate and adaptive immunity, and it is reported to contribute, with other adipokines, in the cross-talking networks involved in the pathogenesis of chronic inflammation and immune-related diseases of the musculo-skeletal system such as osteoarthritis (OA) and rheumatoid arthritis (RA). In this review, we summarize the most recent findings concerning the involvement of leptin in immunity and inflammatory responses in OA and RA.

The Association of Blood Biomarkers and Body Mass Index in Knee Osteoarthritis: A Cross-Sectional Study

OBJECTIVE

Despite massive efforts, there are no diagnostic blood biomarkers for knee osteoarthritis (KOA). This study investigated several candidate diagnostic biomarkers and the metabolic phenotype in end-stage KOA in the context of obesity.

DESIGN

In this cross-sectional study, adult patients undergoing knee arthroplasty were enrolled and KOA severity was assessed using the Lequesne index. Blood biomarkers with an important role in obesity, the metabolic syndrome, or KOA (oxidized form of low-density lipoprotein [oxLDL], advanced glycation end product [AGE], soluble AGE receptor [sRAGE], fatty acid binding protein 4 [FABP4], phospholipase A2 group IIA [PLA2G2A], fibroblast growth factor 23 [FGF-23], ghrelin, leptin, and resistin) were measured using enzyme-linked immunosorbent assay (ELISA; n = 70) or Luminex technique (subgroup of n = 35). H1-NMR spectroscopy was used for the quantification of metabolite levels (subgroup of n = 31). The hip-knee-ankle angle was assessed. Multivariable and multivariate regression analysis was used to examine the relationship of biomarkers with body mass index (BMI) and KOA severity in complete case and multiple imputation analysis.

RESULTS

While most of the investigated biomarkers were not associated with KOA severity, FABP4 and leptin were found to correlate with BMI and gender. Resistin was associated with Lequesne index in complete case analysis. Using a targeted metabolomics approach, BMI-dependent changes in the metabolome were hardly visible.

CONCLUSIONS

Our findings confirm studies on FABP4, leptin, and resistin with regard to obesity and the metabolic syndrome. There was no association of the investigated biomarkers with KOA severity, most likely due to the patient selection (end-stage KOA patients). Based on this absence of BMI-dependent changes in the metabolome, we might assume that BMI is not correlated with KOA severity in this specific patient group.

Disease burden of osteoarthritis of the knee and hip due to a high body mass index in China and the USA: 1990-2019 findings from the global burden of disease study 2019

Background

Osteoarthritis (OA) is a leading cause of disability and a source of societal costs among older adults, especially with an increasingly obese population. However, very few published studies have investigated the burden of knee and hip OA due to a high body mass index (BMI). Therefore, this study aimed to systematically summarize the trends of knee and hip OA due to a high BMI in China and the USA between 1990 and 2019.

Methods

Data from the Global Burden of Disease Study 2019 were used to estimate the age-standardized prevalence, disability-adjusted life years (DALYs) rates of knee and hip OA, and the burden of knee and hip OA due to a high BMI by sex. Joinpoint regression analysis was used to determine the temporal trend changes in the related DALYs rates of knee and hip OA.

Results

The trends in the DALYs rates of knee OA due to a high BMI have shown a steady and large increase in China, while the trends first showed an increase followed by a large decrease near 2001-2005 and finally a steady increase in the USA. The trends in the DALYs rates of hip OA due to a high BMI have shown a steady and large increase in both men and women in China and the USA from 1990 to 2019. For the comparison by age categories from 30 to 34 years to 90–94 years in 2019, the age-standardized DALYs rates due to a high BMI first increased and then decreased after 60–64 years and 70-74 years in both men and women from China and the USA for knee OA, respectively. For hip OA, the age-standardized DALYs rates first increased and then decreased after 70–74 years in both men and women from China and the USA.

Conclusions

The burden of knee and hip OA due to a high BMI is substantially increasing in China and the USA in recent years. Researchers and health policy makers should assess the changing patterns of high BMI on the burden of OA and devise corresponding weight-control strategies.

A new immunometabolic perspective of intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is a common finding on spine imaging that increases in prevalence with age. IVD degeneration is a frequent cause of low back pain, which is a leading cause of disability. The process of IVD degeneration consists of gradual structural change accompanied by severe alterations in metabolic homeostasis. IVD degeneration, like osteoarthritis, is a common comorbidity in patients with obesity and type 2 diabetes mellitus, two metabolic syndrome pathological conditions in which adipokines are important promoters of low-grade inflammation, extracellular matrix degradation and fibrosis. Impairment in white adipose tissue function, due to the abnormal fat accumulation in obesity, is characterized by increased production of specific pro-inflammatory proteins such as adipokines by white adipose tissue and of cytokines such as TNF by immune cells of the stromal compartment. Investigations into the immunometabolic alterations in obesity and type 2 diabetes mellitus and their interconnections with IVD degeneration provide insights into how adipokines might affect the pathogenesis of IVD degeneration and impair IVD function and repair. Toll-like receptor-mediated signalling has also been implicated as a promoter of the inflammatory response in the metabolic alterations associated with IVD and is thus thought to have a role in IVD degeneration. Pathological starvation, obesity and adipokine dysregulation can result in immunometabolic alterations, which could be targeted for the development of new therapeutics.

Recent Advances in Pharmacological Intervention of Osteoarthritis: A Biological Aspect

Osteoarthritis (OA) is a degenerative joint disease in the musculoskeletal system with a relatively high incidence and disability rate in the elderly. It is characterized by the degradation of articular cartilage, inflammation of the synovial membrane, and abnormal structure in the periarticular and subchondral bones. Although progress has been made in uncovering the molecular mechanism, the etiology of OA is still complicated and unclear. Nevertheless, there is no treatment method that can effectively prevent or reverse the deterioration of cartilage and bone structure. In recent years, in the field of pharmacology, research focus has shifted to disease prevention and early treatment rather than disease modification in OA. Biologic agents become more and more attractive as their direct or indirect intervention effects on the initiation or development of OA. In this review, we will discuss a wide spectrum of biologic agents ranging from DNA, noncoding RNA, exosome, platelet-rich plasma (PRP), to protein. We searched for key words such as OA, DNA, gene, RNA, exosome, PRP, protein, and so on. From the pharmacological aspect, stem cell therapy is a very special technique, which is not included in this review. The literatures ranging from January 2016 to August 2021 were included and summarized. In this review, we aim to help readers have a complete and precise understanding of the current pharmacological research progress in the intervention of OA from the biological aspect and provide an indication for the future translational studies.

Monomeric C reactive protein (mCRP) regulates inflammatory responses in human and mouse chondrocytes

C-reactive protein (CRP) is an acute-phase protein that is used as an established biomarker to follow disease severity and progression in a plethora of inflammatory diseases. However, its pathophysiologic mechanisms of action are still poorly defined and remain elusive. CRP, in its pentameric form, exhibits weak anti-inflammatory activity. On the contrary, the monomeric isoform (mCRP) exhibits potent pro-inflammatory properties in endothelial cells, leukocytes, and platelets. So far, no data exists regarding mCRP effects in human or mouse chondrocytes. This work aimed to verify the pathophysiological relevance of mCRP in the etiology and/or progression of osteoarthritis (OA). We investigated the effects of mCRP in cultured human primary chondrocytes and in the chondrogenic ATDC5 mouse cell line. We determined mRNA and protein levels of relevant factors involved in inflammatory responses and the modulation of nitric oxide synthase type II (NOS2), an early inflammatory molecular target. We demonstrate, for the first time, that monomeric C reactive protein increases NOS2, COX2, MMP13, VCAM1, IL-6, IL-8, and LCN2 expression in human and murine chondrocytes. We also demonstrated that NF-kB is a key factor in the intracellular signaling of mCRP-driven induction of pro-inflammatory and catabolic mediators in chondrocytes. We concluded that mCRP exerts a sustained catabolic effect on human and murine chondrocytes, increasing the expression of inflammatory mediators and proteolytic enzymes, which can promote extracellular matrix (ECM) breakdown in healthy and OA cartilage. In addition, our results implicate the NF-kB signaling pathway in catabolic effects mediated by mCRP.

Visfatin promotes intervertebral disc degeneration by inducing IL-6 expression through the ERK/JNK/p38 signalling pathways

Visfatin reportedly induces the expression of proinflammatory cytokines. Severe grades of intervertebral disc disease (IVDD) exhibit higher expression of visfatin than mild ones. However, the direct relationship between visfatin and IVDD remains to be elucidated. This study aimed to clarify whether stimulation of visfatin in IVDD is mediated by IL-6. To investigate the role of visfatin in IVDD, a rat model of anterior disc puncture was established by injecting visfatin or PBS using a 27-gauge needle. Results revealed an obvious aggravation of the histological morphology of IVDD in the visfatin group. On treating human NP cellswith visfatin, the levels of collagenII and aggrecan decreased and those of matrix metallopeptidase 3 and IL-6 gradually increased. A rapid increase in ERK, JNK, and p38 phosphorylation was also noted after visfatin treatment. Compared to those treated with visfatin alone, NP cells pretreated with ERK1/2, JNK, and p38 inhibitors or siRNA targeting p38, ERK, and JNK exhibited a significant suppression of IL-6. Our data represent the first evidence that visfatin promotes IL-6 expression in NP cells via the JNK/ERK/p38-MAPK signalling pathways. Further, our findings suggest epidural fat and visfatin as potential therapeutic targets for controlling IVDD-associated inflammation.

Cellular senescence in musculoskeletal homeostasis, diseases, and regeneration

Emerging insights into cellular senescence highlight the relevance of senescence in musculoskeletal disorders, which represent the leading global cause of disability. Cellular senescence was initially described by Hayflick et al. in 1961 as an irreversible nondividing state in in vitro cell culture studies. We now know that cellular senescence can occur in vivo in response to various stressors as a heterogeneous and tissue-specific cell state with a secretome phenotype acquired after the initial growth arrest. In the past two decades, compelling evidence from preclinical models and human data show an accumulation of senescent cells in many components of the musculoskeletal system. Cellular senescence is therefore a defining feature of age-related musculoskeletal disorders, and targeted elimination of these cells has emerged recently as a promising therapeutic approach to ameliorate tissue damage and promote repair and regeneration of the skeleton and skeletal muscles. In this review, we summarize evidence of the role of senescent cells in the maintenance of bone homeostasis during childhood and their contribution to the pathogenesis of chronic musculoskeletal disorders, including osteoporosis, osteoarthritis, and sarcopenia. We highlight the diversity of the senescent cells in the microenvironment of bone, joint, and skeletal muscle tissue, as well as the mechanisms by which these senescent cells are involved in musculoskeletal diseases. In addition, we discuss how identifying and targeting senescent cells might positively affect pathologic progression and musculoskeletal system regeneration.

Serum Leptin and Resistin Levels in Knee Osteoarthritis-Clinical and Radiologic Links: Towards Precise Definition of Metabolic Type Knee Osteoarthritis

Obesity is considered a major risk factor for the development and progression of knee osteoarthritis (OA). Apart from the mechanical effect of obesity via increase in mechanical overload of weight-bearing joints, an association with hand OA has been observed. There has been increasing interest in the role of adipokines in the pathogenesis of OA in the recent years. It has been suggested that their systemic effects link obesity and OA. In this regard, the aim of the current study was measurement and analysis of serum levels of leptin and resistin in patients with knee OA with different body mass index (BMI). Seventy-three patients with primary symptomatic knee OA at the age between 35 and 87 years (mean age 66 years) were included in the study (67 women and 6 men). The patients were from 2nd to 4th radiographic stage according to Kellgren–Lawrence scale. 43 patients were with concomitant obesity (BMI ≥ 30 kg/m², mean values 38.34 ± 8.20) and 30 patients with BMI < 30 kg/m² (mean values 25.07 ± 2.95). Eleven individuals with different BMIs, including cases with obesity but without radiographic knee OA, were examined as a control group. Serum levels of leptin and resistin were measured via ELISA method. In patients with knee OA and BMI ≥ 30 kg/m², serum levels of leptin (39.546 ± 12.918 ng/mL) were significantly higher as compared with healthy individuals (15.832 ± 16.531 ng/mL, p < 0.05) and the patients with low BMI (p < 0.05). In patients with BMI < 30 kg/m² the levels of leptin (13.010 ± 10.94 ng/mL) did not differ significantly from the respective values in the control group (p = 0.48). Serum levels of resistin were also higher in knee OA patients in comparison with healthy controls, but the difference was statistically significant only for patients with high BMI (2.452 ± 1.002 ng/mL in the group with BMI ≥ 30 kg/m²; 2.401 ± 1.441 ng/mL in patients with BMI < 30 kg/m²; 1.610 ± 1.001 ng/mL in the control group, p < 0.05). A correlation was found between the serum levels of leptin and radiographic stage of OA, i.e., higher leptin levels were present in the more advanced 3rd and 4th radiographic stage, while for resistin a correlation was observed in the patient subgroup with BMI < 30 kg/m². Serum leptin and resistin levels and clinical characteristics were analyzed in patients with different clinical forms of OA. Novel clinical correlations have been found in the current study in patients with isolated knee OA vs. cases with presence of other disease localizations. It has been observed that patients with isolated knee OA were significantly younger and had higher BMI as compared with cases in whom OA is combined with other localizations i.e., spondyloarthritis ± presence of hip OA and with generalized OA. This supports the hypothesis that presence of obesity promotes earlier development of knee OA as an isolated localization of the disease in younger patients before appearance of osteoarthritic changes at other sites. The levels of leptin and resistin in isolated knee OA were also higher. Serum levels of leptin and resistin in combination with patients’ clinical characteristics suggest existence of different clinical and laboratory profile through which more precise definition of metabolic phenotype of knee OA would be possible. Considering the fact that obesity is a modifiable risk factor that has an impact on progression of knee OA, different approaches to influence obesity may offer potential for future disease-modifying therapeutic interventions.

Comparison of gluteus medius strength between individuals with obesity and normal-weight individuals: a cross-sectional study

Background

The hip abductor muscles, primarily the gluteus medius, play an important role in stabilizing the pelvis during gait. Gluteus medius weakness is associated with biomechanical changes and musculoskeletal disorders. Individuals with obesity can have great difficulty maintaining abductor muscular function due to being overweight and possibly experiencing a decrease in muscle mass. However, it is still unclear whether the musculature of person with obesity can compensate for these changes. Therefore, the aim of this study was to compare gluteus medius strength between individuals with obesity and normal-weight individuals using a digital hand-held dynamometer.

Methods

Twenty-five participants with obesity (BMI > 35 kg/m²) were matched for sex, age, and height with normal-weight individuals. Gluteus medius strength was measured by a single examiner using a belt-stabilized hand-held digital dynamometer placed on the knee of the individuals positioned in lateral decubitus. Three measurements were recorded with rest intervals, and only the highest value measured for each limb was used for analysis. The differences between pairs were calculated, and the normality of the data was assessed using the Shapiro-Wilk test (p < 0.05). The matrices of the variables were standardized and analysed using principal component analysis (PCA).

Results

For the strength variables (Newtons) on both sides, no significant differences were detected between the groups (p > 0.05). However, significant differences were detected in these variables between the groups (p < 0.05) when the measurements were normalized to body weight (Newtons/kilograms). PCA indicated that both the absolute and normalized values of strength are lower in participants with obesity than in normal-weight.

Conclusions

These findings suggest that people with obesity could have the same or less strength (PCA) to move more mass, which may imply a relative weakness that induces functional limitations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04470-8.

The Causal Relationship Between Body Mass Index and the Risk of Osteoarthritis

Objective

The study aimed to explore the causal effect of body mass index (BMI) on osteoarthritis.

Methods

The genome-wide association data of BMI and osteoarthritis were obtained via the Mendelian randomization (MR)-base platform. Single nucleotide polymorphisms (SNPs) significantly associated with BMI were identified and used as instrumental variables, and the causal relationship between BMI and osteoarthritis was examined using the two-sample MR research method. Three statistical methods including inverse-variance weighted (IVW) method, weighted median estimator, and MR-Egger regression were employed.

Results

A total of 79 SNPs significantly associated with BMI were identified in the study (P<5×10⁻⁸; linkage disequilibrium r² <0.1). Consistent association between BMI and osteoarthritis was observed when evaluated by different methods (IVW: odds ratio (OR) 1.028, 95% confidence interval (CI) 1.021–1.036; weighted median estimator: OR 1.028, 95% CI 1.019–1.037; MR-Egger regression: OR 1.028, 95% CI 1.009–1.046), which suggests that BMI is positively associated with increased risk of osteoarthritis. There was no evidence that the observed causal effect between BMI and the risk of osteoarthritis was affected by genetic pleiotropy (MR-Egger intercept 1.3×10⁻⁵, P=0.959).

Conclusion

The MR analysis provided the strong evidence to indicate that BMI might be causally associated with the risk of osteoarthritis.

Complication rates and resource utilization after total hip and knee arthroplasty stratified by body mass index

Over 295,000 patients from 2016 to 2018 in a national database were grouped into normal weight (BMI 18.5 to <25 kg/m²), overweight (25 to <30), type-1 obese (30 to <35), type-2 obese (35 to <40), and type-3 obese (40 or higher). Differences in resource utilization and complication rates across BMI categories were compared. In comparison to normal weight patients, overweight and obese patients undergoing TJA were at risk for increased resource utilization and various early complications. Patients undergoing TKA with a BMI up to 45 kg/m² are at similar risk for 30-day postoperative complications when compared to type-1 obese patients.

Exploring the Crosstalk between Hydrostatic Pressure and Adipokines: An In Vitro Study on Human Osteoarthritic Chondrocytes

Obesity is a risk factor for osteoarthritis (OA) development and progression due to an altered biomechanical stress on cartilage and an increased release of inflammatory adipokines from adipose tissue. Evidence suggests an interplay between loading and adipokines in chondrocytes metabolism modulation. We investigated the role of loading, as hydrostatic pressure (HP), in regulating visfatin-induced effects in human OA chondrocytes. Chondrocytes were stimulated with visfatin (24 h) and exposed to high continuous HP (24 MPa, 3 h) in the presence of visfatin inhibitor (FK866, 4 h pre-incubation). Apoptosis and oxidative stress were detected by cytometry, B-cell lymphoma (BCL)2, metalloproteinases (MMPs), type II collagen (Col2a1), antioxidant enzymes, miRNA, cyclin D1 expressions by real-time PCR, and β-catenin protein by western blot. HP exposure or visfatin stimulus significantly induced apoptosis, superoxide anion production, and MMP-3, -13, antioxidant enzymes, and miRNA gene expression, while reducing Col2a1 and BCL2 mRNA. Both stimuli significantly reduced β-catenin protein and increased cyclin D1 gene expression. HP exposure exacerbated visfatin-induced effects, which were counteracted by FK866 pre-treatment. Our data underline the complex interplay between loading and visfatin in controlling chondrocytes' metabolism, contributing to explaining the role of obesity in OA etiopathogenesis, and confirming the importance of controlling body weight for disease treatment.

Screening and verification of hub genes involved in osteoarthritis using bioinformatics

Osteoarthritis (OA) is one of the most common causes of disability and its development is associated with numerous factors. A major challenge in the treatment of OA is the lack of early diagnosis. In the present study, a bioinformatics method was employed to filter key genes that may be responsible for the pathogenesis of OA. From the Gene Expression Omnibus database, the datasets GSE55457, GSE12021 and GSE55325 were downloaded, which comprised 59 samples. Of these, 30 samples were from patients diagnosed with osteoarthritis and 29 were normal. Differentially expressed genes (DEGs) were obtained by downloading and analyzing the original data using bioinformatics. The Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathways were analyzed using the Database for Annotation, Visualization and Integrated Discovery online database. Protein-protein interaction network analysis was performed using the Search Tool for the Retrieval of Interacting Genes/proteins online database. BSCL2 lipid droplet biogenesis associated, seipin, FOS-like 2, activator protein-1 transcription factor subunit (FOSL2), cyclin-dependent kinase inhibitor 1A (CDKN1A) and kinectin 1 (KTN1) genes were identified as key genes by using Cytoscape software. Functional enrichment revealed that the DEGs were mainly accumulated in the ErbB, MAPK and PI3K-Akt pathways. Reverse transcription-quantitative PCR analysis confirmed a significant reduction in the expression levels of FOSL2, CDKN1A and KTN1 in OA samples. These genes have the potential to become novel diagnostic and therapeutic targets for OA.

Mini-Review: The Contribution of Adipokines to Joint Inflammation in Inflammatory Rheumatic Diseases

Inflammatory rheumatic diseases (IRD) are complex disorders characterized by chronic inflammation of the joints and related skeletal structures. The most common forms of IRD are rheumatoid arthritis (RA) and spondyloarthritis (SpA), including axial SpA (axSpA) and psoriatic arthritis (PsA). Obesity is a frequent comorbidity in RA and PsA, and to a lesser extend in axial SpA. The association between obesity and IRD may be explained by the release from fat tissue of several bioactive proteins, namely adipokines. Adipokines are involved in the regulation of various processes such as lipid or glucose metabolism, but also inflammation. Adipokines are interrelated with the immune system, with both innate and adaptive immune cell connections. Several adipokines with pro-inflammatory effects have been identified such as leptin, visfatin or resistin. Conversely, adiponectin and more specifically its low molecular weight isoform, is considered to have antiinflammatory properties. In this review, we discuss the contribution of adipokines to the joint inflammation of IRD, the relation they have with immune pathways of these diseases, their links with the structural impact on peripheral joints and/or axial skeleton, and also the influence they may have on the cardiometabolic risk of IRD.

Effectiveness of Traditional Chinese Exercise for Symptoms of Knee Osteoarthritis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background: Growing evidences have advocated the potential benefits of traditional Chinese exercise (TCE) on symptomatic improvement of knee osteoarthritis (KOA). However, most of them have been derived from cross-sectional studies or case reports; the effectiveness of TCE therapies has not been fully assessed with a randomized control trial (RCT). In order to evaluate the combined clinical effectiveness of TCE for KOA, we conducted a systematic review and meta-analysis on the existing RCTs on KOA. Methods: A systematic search was performed in four electronic databases: PubMed, Web of Science, Cochrane Library, and EMBASE from the time of their inception to February 2020. All eligible RCTs were included in which TCE was utilized for treating KOA as compared to a control group. Two reviewers independently extracted the data and evaluated the risk of bias following the Cochrane Risk of Bias Tool for RCT. The symptoms of KOA evaluated by the Western Ontario and McMaster Universities Arthritis Index (WOMAC) and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were regarded as the primary outcomes in this study. Each outcome measure was pooled by a standardized mean difference (SMD) with 95% confidence intervals (CI). A meta-analysis was applied with a random or fixed effect model for the collected data to calculate the summary SMD with 95% CI based on different statistical heterogeneity. In addition, subgroup analyses were used to investigate heterogeneity and sensitivity analysis was carried out for the results of the meta-analysis. Egger’s test and the funnel plots were used to examine the potential bias in the RCTs. Results: A total of 14 RCTs involving 815 patients with KOA were included. Compared with a control group; the synthesized data of TCE showed a significant improvement in WOMAC/KOOS pain score (SMD = −0.61; 95% CI: −0.86 to −0.37; p < 0.001), stiffness score (SMD = −0.75; 95% CI: −1.09 to −0.41; p < 0.001), and physical function score (SMD = −0.67; 95% CI: −0.82 to −0.53; p < 0.001). Conclusions: Our meta-analysis suggested that TCE may be effective in alleviating pain; relieving stiffness and improving the physical function for patients with KOA. Yet; given the methodological limitations of included RCTs in this meta-analysis; more high-quality RCTs with large sample size and long-term intervention are required to further confirm the effectiveness and underlying mechanisms of TCE for treating KOA.

The Effect of Body Mass Index Class on Patient-Reported Health-Related Quality of Life Before and After Total Hip Arthroplasty for Osteoarthritis: Registry-Based Cohort Study of 64,055 Patients

BACKGROUND

Overweight status and obesity represent a global epidemic, with serious consequences at the individual and community levels. The number of total hip arthroplasties (THAs) among overweight and obese patients is expected to rise. Increasing body mass index (BMI) has been associated with a higher risk of mortality and reoperation and lower implant survival. The evaluation of perioperative health-related quality of life (HRQoL) has recently gained importance because of its direct relation to, and impact on, patients' physical, mental, and social well-being as well as health-service utilization. We sought to evaluate the influence of BMI class on HRQoL preoperatively and at 1 year following THA in a register-based cohort study.

METHODS

This observational cohort study was designed and conducted on the basis of registry data derived from the Swedish Hip Arthroplasty Register (SHAR) and included 64,055 primary THAs registered between January 1, 2008, and December 31, 2015. Patients' baseline preoperative and 1-year postoperative EuroQol-5 Dimension-3 Level (EQ-5D-3L) responses were documented by the treating department and reported to the SHAR through the patient-reported outcome measures program. The EQ-5D-3L includes a visual analogue scale (EQ VAS), which measures the patient's overall health status.

RESULTS

At 1 year of follow-up, all BMI classes showed significant and clinically relevant improvements in all HRQoL measures compared with preoperative assessment (p < 0.05). Patients reported improved perception of current overall health status for the EQ VAS. Underweight, overweight, and all obesity classes showed increasingly worse 1-year HRQoL compared with normal weight, both with unadjusted and adjusted calculations.

CONCLUSIONS

In this study, we found that all BMI classes had significant improvement in HRQoL at 1 year following THA. Patients who were underweight, overweight, or obese (classes I to III), compared with those of normal weight, reported worse hip pain and EQ-5D-3L and EQ VAS responses prior to THA and at 1 year postoperatively. These results can assist both health-care providers and patients in establishing reasonable expectations about THA outcomes.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Pathogenesis of Osteoarthritis: Risk Factors, Regulatory Pathways in Chondrocytes, and Experimental Models

As the most common chronic degenerative joint disease, osteoarthritis (OA) is the leading cause of pain and physical disability, affecting millions of people worldwide. Mainly characterized by articular cartilage degradation, osteophyte formation, subchondral bone remodeling, and synovial inflammation, OA is a heterogeneous disease that impacts all component tissues of the articular joint organ. Pathological changes, and thus symptoms, vary from person to person, underscoring the critical need of personalized therapies. However, there has only been limited progress towards the prevention and treatment of OA, and there are no approved effective disease-modifying osteoarthritis drugs (DMOADs). Conventional treatments, including non-steroidal anti-inflammatory drugs (NSAIDs) and physical therapy, are still the major remedies to manage the symptoms until the need for total joint replacement. In this review, we provide an update of the known OA risk factors and relevant mechanisms of action. In addition, given that the lack of biologically relevant models to recapitulate human OA pathogenesis represents one of the major roadblocks in developing DMOADs, we discuss current in vivo and in vitro experimental OA models, with special emphasis on recent development and application potential of human cell-derived microphysiological tissue chip platforms.

Target-based approach for osteoarthritis treatment

There is still no definitive treatment for knee osteoarthritis (OA). We are certainly far from a consensus on the best form of treatment or on an effective treatment recommendation. There are reasons for the current equivocal treatment recommendations in the face of this very serious health problem. The greatest of these reasons, undoubtedly, is the great complexity of the factors involved in the development and progression of knee OA and the complex pathophysiology including mechanical, inflammatory, metabolic, post-traumatic, molecular, genetic, and psychological changes. For several years, an attempt has been made to correlate different patient phenotypes to different patterns of response to treatment, thus creating the possibility of developing specific treatments for certain groups of patients and theoretically allowing better treatment efficacy. However, in practice we still find totally different responses and evolutions even in individuals belonging to the same phenotype. Thus, classification by phenotypes, despite being an advance, is not sufficient. The present article proposes a fragmented look at each of the many factors or targets involved in the genesis and evolution of OA. Therefore, we propose not the treatment of OA per se but the management of an individual set of targets to achieve personalized OA management. We believe that, paradoxically, by fragmenting the view of the disease we will be able to treat our patients more holistically in an individualized way.

Hydrostatic Pressure Regulates Oxidative Stress through microRNA in Human Osteoarthritic Chondrocytes

Hydrostatic pressure (HP) modulates chondrocytes metabolism, however, its ability to regulate oxidative stress and microRNAs (miRNA) has not been clarified. The aim of this study was to investigate the role of miR-34a, miR-146a, and miR-181a as possible mediators of HP effects on oxidative stress in human osteoarthritis (OA) chondrocytes. Chondrocytes were exposed to cyclic low HP (1–5 MPa) and continuous static HP (10 MPa) for 3~h. Metalloproteinases (MMPs), disintegrin and metalloproteinase with thrombospondin motif (ADAMTS)-5, type II collagen (Col2a1), miR-34a, miR-146a, miR-181a, antioxidant enzymes, and B-cell lymphoma 2 (BCL2) were evaluated by quantitative real-time polymerase chain reaction qRT-PCR, apoptosis and reactive oxygen species ROS production by cytometry, and β-catenin by immunofluorescence. The relationship among HP, the studied miRNA, and oxidative stress was assessed by transfection with miRNA specific inhibitors. Low cyclical HP significantly reduced apoptosis, the gene expression of MMP-13, ADAMTS5, miRNA, the production of superoxide anion, and mRNA levels of antioxidant enzymes. Conversely, an increased Col2a1 and BCL2 genes was observed. β-catenin protein expression was reduced in cells exposed to HP 1–5 MPa. Opposite results were obtained following continuous static HP application. Finally, miRNA silencing enhanced low HP and suppressed continuous HP-induced effects. Our data suggest miRNA as one of the mechanisms by which HP regulates chondrocyte metabolism and oxidative stress, via Wnt/β-catenin pathway.

Risk Factors for Canine Osteoarthritis and Its Predisposing Arthropathies: A Systematic Review

Osteoarthritis is a common clinical and pathological end-point from a range of joint disorders, that ultimately lead to structural and functional decline of the joint with associated lameness and pain. Increasing understanding of the risk factors associated with osteoarthritis will assist in addressing the significant threat it poses to the welfare of the dog population and implementing preventive measures. Presented here, is the first comprehensive systematic review and evaluation of the literature reporting risk factors for canine osteoarthritis. This paper aimed to systematically collate, review and critically evaluate the published literature on risk factors for canine osteoarthritis and its predisposing conditions such as developmental joint dysplasias, cruciate ligament degeneration, and patellar luxation. Peer-reviewed publications were systematically searched for both osteoarthritis and predisposing arthropathies on Web of Science and PubMed following PRISMA (2009) guidelines, using pre-specified combinations of keywords. Sixty-two papers met the inclusion criteria and were evaluated and graded on reporting quality. Identified risk factors included both modifiable factors (neuter status and body weight) for which intervention can potentially affect the risk of occurrence of osteoarthritis, and unmodifiable factors (sex, breed, and age) which can be used to identify individuals most “at risk.” Osteoarthritis in dogs frequently develops from predisposing arthropathies, and therefore risk factors for these are also important to consider. Papers evaluated in this study were rated as medium to high-quality; gap analysis of the literature suggests there would be significant benefit from additional research into the interactions between and relative weighting of risk factors. There are a number of examples where research outcomes are conflicting such as age and sex; and further investigation into these factors would be beneficial to attain greater understanding of the nature of these risks. Comprehensively collating the published risk factors for osteoarthritis and its predisposing conditions offers opportunities to identify possible means for control and reduction within the population through preventative methods and control strategies. These factors are highlighted here, as well as current literature gaps where further research is warranted, to aid future research direction.

Impaired Metabolic Flexibility in the Osteoarthritis Process: A Study on Transmitochondrial Cybrids

Osteoarthritis (OA) is the most frequent joint disease; however, the etiopathogenesis is still unclear. Chondrocytes rely primarily on glycolysis to meet cellular energy demand, but studies implicate impaired mitochondrial function in OA pathogenesis. The relationship between mitochondrial dysfunction and OA has been established. The aim of the study was to examine the differences in glucose and Fatty Acids (FA) metabolism, especially with regards to metabolic flexibility, in cybrids from healthy (N) or OA donors. Glucose and FA metabolism were studied using D-[¹⁴C(U)]glucose and [1-¹⁴C]oleic acid, respectively. There were no differences in glucose metabolism among the cybrids. Osteoarthritis cybrids had lower acid-soluble metabolites, reflecting incomplete FA β-oxidation but higher incorporation of oleic acid into triacylglycerol. Co-incubation with glucose and oleic acid showed that N but not OA cybrids increased their glucose metabolism. When treating with the mitochondrial inhibitor etomoxir, N cybrids still maintained higher glucose oxidation. Furthermore, OA cybrids had higher oxidative stress response. Combined, this indicated that N cybrids had higher metabolic flexibility than OA cybrids. Healthy donors maintained the glycolytic phenotype, whereas OA donors showed a preference towards oleic acid metabolism. Interestingly, the results indicated that cybrids from OA patients had mitochondrial impairments and reduced metabolic flexibility compared to N cybrids.

[Research progress on the role of adipokines in intervertebral disc degeneration]

OBJECTIVE

To review the research progress of the role and mechanism of adipokines in intervertebral disc degeneration (IVDD) in recent years.

METHODS

The domestic and foreign literature related to adipokines in the process of IVDD was extensively reviewed. The types and functions of adipokines, the role and mechanism in the process of IVDD, and the application prospects of intervertebral disc biotherapy were reviewed.

RESULTS

As a kind of bioactive substance secreted by adipose tissue, adipokine plays an important role in bone and joint diseases, metabolic diseases, and breast cancer. During IVDD, most adipokines can activate multiple signaling pathways by binding to autoreceptors, cause the proliferation and apoptosis of cells and proinflammatory and anti-inflammatory factors parasecretions in the intervertebral disc, and lead to imbalance of intradiscal metabolism and establishment of the initial inflammatory environment, and finally cause the IVDD.

CONCLUSION

Adipokines, as a biologically active substance with metabolic and immunomodulatory functions, play important roles in the occurrence, development, and biological treatment of IVDD.

Spontaneous dog osteoarthritis - a One Medicine vision

Osteoarthritis (OA) is a global disease that, despite extensive research, has limited treatment options. Pet dogs share both an environment and lifestyle attributes with their owners, and a growing awareness is developing in the public and among researchers that One Medicine, the mutual co-study of animals and humans, could be beneficial for both humans and dogs. To that end, this Review highlights research opportunities afforded by studying dogs with spontaneous OA, with a view to sharing this active area of veterinary research with new audiences. Similarities and differences between dog and human OA are examined, and the proposition is made that suitably aligned studies of spontaneous OA in dogs and humans, in particular hip and knee OA, could highlight new avenues of discovery. Developing cross-species collaborations will provide a wealth of research material and knowledge that is relevant to human OA and that cannot currently be obtained from rodent models or experimentally induced dog models of OA. Ultimately, this Review aims to raise awareness of spontaneous dog OA and to stimulate discussion regarding its exploration under the One Medicine initiative to improve the health and well-being of both species.

Osteoarthritis occurs spontaneously in pet dogs, which often share environmental and lifestyle risk-factors with their owners. This Review aims to stimulate cooperation between medical and veterinary research under the One Medicine initiative to improve the welfare of dogs and humans.

Dogs have many analogous spontaneous diseases that result in end-stage osteoarthritis (OA).

Inbreeding and the predisposition of certain dog breeds for OA enable easier identification of candidate genetic associations than in outbred humans.

Dog OA subtypes offer a potential stratification rationale for aetiological differences and alignment to analogous human OA phenotypes.

The relatively compressed time course of spontaneous dog OA offers longitudinal research opportunities.

Collaboration with veterinary researchers can provide tissue samples from early-stage OA and opportunities to evaluate new therapeutics in a spontaneous disease model.

Awareness of the limitations and benefits of using clinical veterinary patients in research is important.

Dietary Saturated Fatty Acids Modulate Pain Behaviour in Trauma-Induced Osteoarthritis in Rats

Osteoarthritis (OA) is a degenerative condition of joints, causing pain and swelling, and can be caused or worsened by trauma and obesity. The objectives of this study were to determine whether pain behaviour and progression of OA were increased in rats with trauma-induced OA fed dietary saturated fatty acids (SFA). Male Wistar rats were fed either a corn starch diet (C) or high-carbohydrate high-fat diet (H) with either 20% beef tallow or SFA (lauric (HLA), myristic (HMA), palmitic (HPA) or stearic (HSA) acids) for 16 weeks prior to and 8 weeks after excision of the medial meniscus of right knee joint to initiate OA when pain behaviour, glial activity, progression of knee OA, inflammatory mediators and signs of metabolic syndrome were assessed. Rats fed beef tallow, palmitic or stearic acids showed increased pain symptoms characterised by decreased hind paw/limb withdrawal thresholds and grip strengths and increased spinal astrogliosis and microgliosis compared to rats fed lauric or myristic acids. However, the severity of OA joint damage was unchanged by these dietary manipulations. We conclude that pain symptoms of trauma-induced OA in rats worsen with increased dietary beef tallow or palmitic or stearic acids, but improve with lauric or myristic acids, despite unchanged OA cartilage damage.

Nesfatin-1 suppresses interleukin-1β-induced inflammation, apoptosis, and cartilage matrix destruction in chondrocytes and ameliorates osteoarthritis in rats

Osteoarthritis (OA) is a chronic degenerative joint disease, related to the overexpression of matrix metalloproteinases (MMPs), a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS), inflammation, and chondrocyte apoptosis. Nesfatin-1 is an adipokine, which plays an important role in the development of OA, especially in obese people. In the present study, cartilage degradation and apoptosis observed in OA patients was evaluated. Furthermore, the anti-inflammatory and anti-apoptotic effects of nesfatin-1, and its underlying in vitro and in vivo mechanisms were investigated. The results showed that nesfatin-1 increased significantly the expression of collagen type II alpha 1 chain (Col2a1), and reduced the expression of MMPs, ADAMTS5, cyclooxygenase (COX)-2, caspase-3, nitric oxide (NO), inducible nitric oxide synthase (iNOS), prostaglandin E2 (PGE2), interleukin (IL)-6, and chondrocyte apoptosis rate, which may be induced by IL-1β in rat chondrocytes. Furthermore, nesfatin-1 treatment prevented cartilage degeneration in the rat OA model. It was found that nesfatin-1 suppressed the IL-1β-induced activation of NF-κB, the mitogen-activated protein kinase (MAPK), and the Bax/Bcl-2 signal pathway in chondrocytes. These results suggest that in vivo nesfatin-1 could play a protective role in the development of OA and can be potentially used for its treatment.

Implications of evaluating leg muscle mass and fat mass separately for quadriceps strength in knee osteoarthritis: the SPSS-OK study

OBJECTIVE

To examine the influence of obesity on quadriceps strength by separately analyzing body mass index (BMI) as fat mass and leg muscle mass in patients with knee osteoarthritis (KOA).

METHODS

The Screening for People Suffering Sarcopenia in Orthopedic cohort of Kobe (SPSS-OK) study was a single-center cross-sectional study that recruited 906 patients with KOA. Fat mass and leg muscle mass were measured by bio-impedance. Isometric knee extension torque (Nm) was measured as quadriceps strength. A series of general linear models were fitted to estimate the continuous associations of BMI and fat mass with quadriceps strength, with adjustment of confounders. In the fitted models, both BMI and fat mass were treated as restricted cubic spline functions.

RESULTS

A continuous, non-linear relationship between BMI and quadriceps strength was found (P = 0.008 for non-linearity). In patients with a BMI of 16-25 kg/m², increasing quadriceps strength was observed. However, in patients with a BMI of 25-40 kg/m², quadriceps strength seemed similar. Additionally, an inverted U-shaped relationship between fat mass and quadriceps strength was demonstrated (P = 0.04 for non-linearity). In those with a fat mass of 10-20 kg, increasing quadriceps strength was seen. However, in patients with a fat mass of 20-30 kg, quadriceps strength showed a decreasing trend. Independent of fat mass, leg muscle mass was linearly associated with greater quadriceps strength.

CONCLUSION

Our study suggests that there are independent associations between the leg muscle mass, fat mass, and quadriceps strength. It is difficult to easily predict quadriceps strength using only BMI.

KEY POINTS

• An increase in body mass index (BMI) up to 25 kg/m²was associated with increasing quadriceps strength. • Quadriceps strength remained almost unchanged among patients with a BMI of > 25 kg/m². • The association between fat mass and quadriceps strength had an inverted U-shaped relationship, suggesting the importance of the separate assessment of fat mass and muscle mass in patients with knee osteoarthritis, especially those who are overweight or obese.

The Adipokine Network in Rheumatic Joint Diseases

Rheumatic diseases encompass a diverse group of chronic disorders that commonly affect musculoskeletal structures. Osteoarthritis (OA) and rheumatoid arthritis (RA) are the two most common, leading to considerable functional limitations and irreversible disability when patients are unsuccessfully treated. Although the specific causes of many rheumatic conditions remain unknown, it is generally accepted that immune mechanisms and/or uncontrolled inflammatory responses are involved in their etiology and symptomatology. In this regard, the bidirectional communication between neuroendocrine and immune system has been demonstrated to provide a homeostatic network that is involved in several pathological conditions. Adipokines represent a wide variety of bioactive, immune and inflammatory mediators mainly released by adipocytes that act as signal molecules in the neuroendocrine-immune interactions. Adipokines can also be synthesized by synoviocytes, osteoclasts, osteoblasts, chondrocytes and inflammatory cells in the joint microenvironment, showing potent modulatory properties on different effector cells in OA and RA pathogenesis. Effects of adiponectin, leptin, resistin and visfatin on local and systemic inflammation are broadly described. However, more recently, other adipokines, such as progranulin, chemerin, lipocalin-2, vaspin, omentin-1 and nesfatin, have been recognized to display immunomodulatory actions in rheumatic diseases. This review highlights the latest relevant findings on the role of the adipokine network in the pathophysiology of OA and RA.

MicroRNA-34a and MicroRNA-181a Mediate Visfatin-Induced Apoptosis and Oxidative Stress via NF-κB Pathway in Human Osteoarthritic Chondrocytes

Current evidence suggests a complex interaction between adipokines and microRNA (miRNA) in osteoarthritis (OA) pathogenesis. The present study explored the role of miR-34a and miR-181a in regulating apoptosis and oxidative stress induced by visfatin in human OA chondrocytes. Chondrocytes were transfected with miR-34a and miR-181a inhibitors and stimulated with visfatin for 24 h, in the presence of nuclear factor (NF)-κB inhibitor (BAY-11-7082, 2 h pre-incubation). Apoptosis and reactive oxygen species (ROS) production were detected by cytometry, miRNA, antioxidant enzymes, nuclear factor erythroid (NRF)2 and B-cell lymphoma (BCL)2 expressions by quantitative real time polymerase chain reaction (real time PCR) and western blot. P50 NF-κB subunit was measured by immunofluorescence. Visfatin significantly induced apoptosis and superoxide anion production, increased miR-34a, miR-181a, superoxide dismutase (SOD)-2, catalase (CAT), NRF2 and decreased BCL2 gene and protein expression in OA chondrocytes. All the visfatin-caused effects were suppressed by using miR-34a and miR-181a inhibitors. Pre-incubation with BAY-11-7082 counteracted visfatin-induced expression of miRNA, BCL2, SOD-2, CAT and NRF2. Inhibition of miR-34a and miR-181a significantly reduced the activation of p50 NF-κB. Visfatin confirms its ability to induce apoptosis and oxidative stress in human OA chondrocytes; these effects appeared mediated by miR-34a and miR-181a via NF-κB pathway. We highlight the relevance of visfatin as potential therapeutic target for OA treatment.

Molecular Relationships among Obesity, Inflammation and Intervertebral Disc Degeneration: Are Adipokines the Common Link?

Intervertebral disc degeneration (IVDD) is a chronic, expensive, and high-incidence musculoskeletal disorder largely responsible for back/neck and radicular-related pain. It is characterized by progressive degenerative damage of intervertebral tissues along with metabolic alterations of all other vertebral tissues. Despite the high socio-economic impact of IVDD, little is known about its etiology and pathogenesis, and currently, no cure or specific treatments are available. Recent evidence indicates that besides abnormal and excessive mechanical loading, inflammation may be a crucial player in IVDD. Furthermore, obese adipose tissue is characterized by a persistent and low-grade production of systemic pro-inflammatory factors. In this context, chronic low-grade inflammation associated with obesity has been hypothesized as an important contributor to IVDD through different, but still unknown, mechanisms. Adipokines, such as leptin, produced prevalently by white adipose tissues, but also by other cells of mesenchymal origin, particularly cartilage and bone, are cytokine-like hormones involved in important physiologic and pathophysiological processes. Although initially restricted to metabolic functions, adipokines are now viewed as key players of the innate and adaptative immune system and active modulators of the acute and chronic inflammatory response. The goal of this review is to summarize the most recent findings regarding the interrelationships among inflammation, obesity and the pathogenic mechanisms involved in the IVDD, with particular emphasis on the contribution of adipokines and their potential as future therapeutic targets.

Associations between Adipokines in Arthritic Disease and Implications for Obesity

Secretion from adipose tissue of adipokines or adipocytokines, comprising of bioactive peptides or proteins, immune molecules and inflammatory mediators, exert critical roles in inflammatory arthritis and obesity. This review considers the evidence generated over the last decade regarding the effects of several adipokines including leptin, adiponectin, visfatin, resistin, chemerin and apelin, in cartilage and bone homeostasis in the pathogenesis of rheumatoid arthritis and osteoarthritis, which has important implications for obesity.

CITED2 mediates the mechanical loading-induced suppression of adipokines in the infrapatellar fat pad

Adipokines secreted from the infrapatellar fat pad (IPFP), such as adipsin and adiponectin, have been implicated in osteoarthritis pathogenesis. CITED2, a mechanosensitive transcriptional regulator with chondroprotective activity, may modulate their expression. Cited2 haploinsufficient mice (Cited2^+/- ) on a high-fat diet (HFD) exhibited increased body weight and increased IPFP area compared to wild-type (WT) mice on an HFD. While an exercise regimen of moderate treadmill running induced the expression of CITED2, as well as PGC-1α, and reduced the expression of adipsin and adiponectin in the IPFP of WT mice on an HFD, Cited2 haploinsufficiency abolished the loading-induced expression of PGC-1α and loading-induced suppression of adipsin and adiponectin. Furthermore, knocking down or knocking out CITED2 in adipose stem cells (ASCs)/preadipocytes derived from the IPFP in vitro led to the increased expression of adipsin and adiponectin and reduced PGC-1α, and abolished the loading-induced suppression of adipsin and adiponectin and loading-induced expression of PGC-1α. Overexpression of PGC-1α in these ASC/preadipocytes reversed the effects caused by CITED2 deficiency. The current data suggest that CITED2 is a critical regulator in physiologic loading-induced chondroprotection in the context of an HFD and PGC-1α is required for the inhibitory effects of CITED2 on the expression of adipokines such as adipsin and adiponectin in the IPFP.