Adiposity and hand osteoarthritis: the Netherlands Epidemiology of Obesity study

Do Comorbidities Play a Role in Hand Osteoarthritis Disease Burden? Data from the Hand Osteoarthritis in Secondary Care Cohort

Objective.

Because the association and its clinical relevance between comorbidities and primary hand osteoarthritis (OA) disease burden is unclear, we studied this in patients with hand OA from our Hand OSTeoArthritis in Secondary care (HOSTAS) cohort.

Methods.

Cross-sectional data from the HOSTAS study were used, including consecutive patients with primary hand OA. Nineteen comorbidities were assessed: 18 self-reported (modified Charlson index and osteoporosis) and obesity (body mass index ≥ 30 kg/m2). Mean differences were estimated between patients with versus without comorbidities, adjusted for age and sex: for general disease burden [health-related quality of life (HRQOL), Medical Outcomes Study Short Form-36 physical component scale (0–100)] and disease-specific burden [self-reported hand function (0–36), pain (0–20; Australian/Canadian Hand OA Index), and tender joint count (TJC, 0–30)]. Differences above a minimal clinically important improvement/difference were considered clinically relevant.

Results.

The study included 538 patients (mean age 61 yrs, 86% women, 88% fulfilled American College of Rheumatology classification criteria). Mean (SD) HRQOL, function, pain, and TJC were 44.7 (8), 15.6 (9), 9.3 (4), and 4.8 (5), respectively. Any comorbidity was present in 54% (287/531) of patients and this was unfavorable [adjusted mean difference presence/absence any comorbidity (95% CI): HRQOL −4.4 (−5.8 to −3.0), function 1.9 (0.4–3.3), pain 1.4 (0.6–2.1), TJC 1.3 (0.4–2.2)]. Number of comorbidities and both musculoskeletal (e.g., connective tissue disease) and nonmusculoskeletal comorbidities (e.g., pulmonary and cardiovascular disease) were associated with disease burden. Associations with HRQOL and function were clinically relevant.

Conclusion.

Comorbidities showed clinically relevant associations with disease burden. Therefore, the role of comorbidities in hand OA should be considered when interpreting disease outcomes and in patient management.

Adipokine genes and radiographic hand osteoarthritis in Finnish women: a cross-sectional study

OBJECTIVES

Available evidence suggests that genetic factors and overweight play major roles in the aetiology of osteoarthritis (OA). We analysed the association of 18 single-nucleotide polymorphisms (SNPs) from nine adipokine and adipokine receptor genes (LEP, LEPR, ADIPOQ, RETN, NAMPT, SERPINA12, ITLN1, RARRES2, and APLN) with radiographic hand OA.

METHOD

The study design was cross-sectional. Bilateral hand radiographs of 542 occupationally active Finnish female dentists and teachers aged 45-63 years were examined and classified for the presence of hand OA using reference images. Hand OA was defined as at least three finger joints with radiographic OA of grade 2-4. The genotypes were determined using polymerase chain reaction-based methods. Body mass index (BMI) was calculated based on self-reported height and measured weight. Associations of the individual SNPs and their haplotypes with hand OA were tested using logistic regression analysis.

RESULTS

The minor allele of RETN rs10401670 was associated with a decreased [odds ratio (OR) = 0.73, 95% confidence interval (CI) 0.55-0.97, p = 0.03] and RARRES2 rs4721 with an increased (OR 1.41, 95% CI 1.07-1.87, p = 0.01) prevalence of hand OA. Also, LEPR AC (OR 1.54, 95% CI 1.01-2.35, p = 0.05) and RETN GGTT (OR 0.58, 95% CI 0.37-0.93, p = 0.02) haplotypes were associated with hand OA. These associations were modified by BMI when comparing normal and overweight women. However, the associations lost their statistical significance after adjusting for multiple testing.

CONCLUSION

Our results suggest weak associations between the studied variations in LEPR, RARRES2, and RETN genes and hand OA in Finnish women, and that the associations are modified by BMI. However, these associations could not be verified in the current study.

The Prevalence, Incidence, and Progression of Hand Osteoarthritis in Relation to Body Mass Index, Smoking, and Alcohol Consumption

OBJECTIVE

To estimate the extent that overweight/obesity, smoking, and alcohol are associated with prevalence and longitudinal changes of radiographic hand osteoarthritis (OA).

METHODS

Participants from the Osteoarthritis Initiative (n = 1232) were included, of whom 994 had 4-year followup data. In analyses on incident hand OA, only persons without hand OA at baseline were included (n = 406). Our exposure variables were overweight/obesity [body mass index (BMI), waist circumference], smoking (current/former, smoking pack-yrs), and alcohol consumption (drinks/week). Using linear and logistic regression analyses, we analyzed possible associations between baseline exposure variables and radiographic hand OA severity, erosive hand OA, incidence of hand OA, and radiographic changes. Analyses were adjusted for age, sex, and education.

RESULTS

Neither overweight nor obesity were associated with hand OA. Current smoking was associated with less hand OA in cross-sectional analyses, whereas longitudinal analyses suggested higher odds of incident hand OA in current smokers (OR 2.20, 95% CI 1.02-4.77). Moderate alcohol consumption was associated with higher Kellgren-Lawrence sum score at baseline (1-3 drinks: 1.55, 95% CI 0.43-2.67) and increasing sum score during 4-year followup (4-7 drinks: 0.33, 95% CI 0.01-0.64). Moderate alcohol consumption (1-7 drinks/week) was associated with 2-fold higher odds of erosive hand OA, which was statistically significant. Additional adjustment for BMI gave similar strengths of associations.

CONCLUSION

Overweight/obesity were not associated with hand OA. Contrasting results were observed for smoking and hand OA, suggesting lack of association. Moderate alcohol consumption was associated with hand OA severity, radiographic changes, and erosive hand OA, warranting further investigation.

Suppressive Effects of Insulin on Tumor Necrosis Factor-Dependent Early Osteoarthritic Changes Associated With Obesity and Type 2 Diabetes Mellitus

Objective

Obesity is a state of chronic inflammation that is associated with insulin resistance and type 2 diabetes mellitus (DM), as well as an increased risk of osteoarthritis (OA). This study was undertaken to define the links between obesity‐associated inflammation, insulin resistance, and OA, by testing the hypotheses that 1) tumor necrosis factor (TNF) is critical in mediating these pathologic changes in OA, and 2) insulin has direct effects on the synovial joint that are compromised by insulin resistance.

Methods

The effects of TNF and insulin on catabolic gene expression were determined in fibroblast‐like synoviocytes (FLS) isolated from human OA synovium. Synovial TNF expression and OA progression were examined in 2 mouse models, high‐fat (HF) diet–fed obese mice with type 2 DM and TNF‐knockout mice. Insulin resistance was investigated in synovium from patients with type 2 DM.

Results

Insulin receptors (IRs) were abundant in both mouse and human synovial membranes. Human OA FLS were insulin responsive, as indicated by the dose‐dependent phosphorylation of IRs and Akt. In cultures of human OA FLS with exogenous TNF, the expression and release of MMP1, MMP13, and ADAMTS4 by FLS were markedly increased, whereas after treatment with insulin, these effects were selectively inhibited by >50%. The expression of TNF and its abundance in the synovium were elevated in samples from obese mice with type 2 DM. In TNF‐knockout mice, increases in osteophyte formation and synovial hyperplasia associated with the HF diet were blunted. The synovium from OA patients with type 2 DM contained markedly more macrophages and showed elevated TNF levels as compared to the synovium from OA patients without diabetes. Moreover, insulin‐dependent phosphorylation of IRs and Akt was blunted in cultures of OA FLS from patients with type 2 DM.

Conclusion

TNF appears to be involved in mediating the advanced progression of OA seen in type 2 DM. While insulin plays a protective, antiinflammatory role in the synovium, insulin resistance in patients with type 2 DM may impair this protective effect and promote the progression of OA.

Lifetime Risk of Symptomatic Hand Osteoarthritis: The Johnston County Osteoarthritis Project

OBJECTIVE

Symptomatic hand osteoarthritis (OA) is a common condition that affects hand strength and function, and causes disability in activities of daily living. Prior studies have estimated that the lifetime risk of symptomatic knee OA is 45% and that of hip OA is 25%. The objective of the present study was to estimate the overall lifetime risk of symptomatic hand OA, and the stratified lifetime risk according to potential risk factors.

METHODS

Data were obtained from 2,218 adult subjects (ages ≥45 years) in the Johnston County Osteoarthritis Project, a population-based prospective cohort study among residents of Johnston County, North Carolina. Data for the present study were collected from 2 of the follow-up cycles (1999-2004 and 2005-2010). Symptomatic hand OA was defined as the presence of both self-reported symptoms and radiographic OA in the same hand. Lifetime risk, defined as the proportion of the population who will develop symptomatic hand OA in at least 1 hand by age 85 years, was estimated from models using generalized estimating equations.

RESULTS

Overall, the lifetime risk of symptomatic hand OA was 39.8% (95% confidence interval [95% CI] 34.4-45.3%). In this population, nearly 1 in 2 women (47.2%, 95% CI 40.6-53.9%) had an estimated lifetime risk of developing symptomatic hand OA by age 85 years, compared with 1 in 4 men (24.6%, 95% CI 19.5-30.5%). Race-specific symptomatic hand OA risk estimates were 41.4% (95% CI 35.5-47.6%) among whites and 29.2% (95% CI 20.5-39.7%) among African Americans. The lifetime risk of symptomatic hand OA among individuals with obesity (47.1%, 95% CI 37.8-56.7%) was 11 percentage points higher than that in individuals without obesity (36.1%, 95% CI 29.7-42.9%).

CONCLUSION

These findings demonstrate the substantial burden of symptomatic hand OA overall and in sociodemographic and clinical subgroups. Increased use of public health and clinical interventions is needed to address its impact.

Potential of specialized pro-resolving lipid mediators against rheumatic diseases

While arachidonic acid (AA), which is classified into n-6 polyunsaturated fatty acid (PUFA), has been mainly recognized as a substrate of pro-inflammatory mediators, eicosapentaenoic acid or docosahexaenoic acid, which are classified into n-3 PUFA, is currently identified as substrates of mediators inducing resolution of inflammation, namely pro-resolving mediators (SPM). As with any other pathological conditions, it is gradually elucidated that SPMs contributes a certain effect on joint inflammation. In osteoarthritis (OA), Lipid fractions extracted from adipocytes, especially in infrapatellar fat pad rather than subcutaneous tissue induce T cell skewing for producing IFN-γ or decrease the production of IL-12p40 from macrophages. In synovial tissues form OA, there are some of known receptors for SPM. In the synovial fluid from rheumatoid arthritis (RA), it could be identified and quantified a certain kind of SPMs such as maresin 1, lipoxin A4 and resolvin D5. In murine models of arthritis, some of SPMs are found to have some functions to reduce tissue damage. Correctively, SPMs might have some potential to a novel therapeutic target for arthritis or any other rheumatic diseases.

Higher Fat Mass Is Associated With a History of Knee Injury in Youth Sport

Study Design Historical cohort study. Background History of a knee joint injury and increased fat mass are risk factors for joint disease. Objective The objective of this study was to examine differences in adiposity, physical activity, and cardiorespiratory fitness between youths with a 3- to 10-year history of sport-related intra-articular knee injury and uninjured controls. Methods One hundred young adults (aged 15-26 years; 55% female) with a sport-related intra-articular knee injury sustained 3 to 10 years previously and 100 controls matched for age, sex, and sport, who had no history of intra-articular knee injury, were recruited. Fat mass index (FMI) and abdominal fat (fat mass at the L1 to L4 vertebral levels) were derived using dual-energy X-ray absorptiometry. Physical activity and cardiorespiratory fitness were measured using the Godin Leisure-Time Exercise Questionnaire and the multistage 20-meter shuttle run test for aerobic fitness, respectively. Results Previously injured participants demonstrated higher FMI (within-pair difference, 1.05 kg/m²; 95% confidence interval [CI]: 0.53, 1.57) and abdominal fat (461 g; 95% CI: 228, 694) than uninjured controls. In multivariable linear regression analysis, previous injury was significantly associated with increased FMI. This increase was attenuated in those who participated in higher levels of physical activity or had higher estimated maximum volume of oxygen. Conclusion As a risk factor for osteoarthritis in an already susceptible group, excess adiposity is an undesirable trait in the potential pathway to joint disease. Increasing physical activity in this population may be a potential intervention to reduce adiposity thus impede disease initiation and/or progression. Level of Evidence Level 2b. J Orthop Sports Phys Ther 2017;47(2):80-87. doi:10.2519/jospt.2017.7101.

Molecular genetics of human obesity: A comprehensive review

Obesity and its related health complications is a major problem worldwide. Hypothalamus and their signalling molecules play a critical role in the intervening and coordination with energy balance and homeostasis. Genetic factors play a crucial role in determining an individual's predisposition to the weight gain and being obese. In the past few years, several genetic variants were identified as monogenic forms of human obesity having success over common polygenic forms. In the context of molecular genetics, genome-wide association studies (GWAS) approach and their findings signified a number of genetic variants predisposing to obesity. However, the last couple of years, it has also been noticed that alterations in the environmental and epigenetic factors are one of the key causes of obesity. Hence, this review might be helpful in the current scenario of molecular genetics of human obesity, obesity-related health complications (ORHC), and energy homeostasis. Future work based on the clinical discoveries may play a role in the molecular dissection of genetic approaches to find more obesity-susceptible gene loci.

In silico approach to identify non-synonymous SNPs in human obesity related gene, MC3R (melanocortin-3-receptor)

The melanocortin-3-receptor (MC3R) is a novel gene candidate for human obesity, which involved in controlling the energy homeostasis and food intake behavior. The main aim behind this work is to investigate the potentially deleterious non-synonymous single nucleotide polymorphisms (nsSNPs) in obesity related gene MC3R by using six computational tools viz., PolyPhen, I-Mutant, PROVEAN, SIFT, PANTHER and PhD-SNP. In our study, we predicted eight nsSNPs i.e., rs74315393 (Ile146Asn), rs368205448 (Asp121Tyr), rs143321797 (Phe45Ser), rs17847261 (Cys274Ser), rs144166442 (Pro257His), rs370533946 (Leu224Pro), rs371354428 (Pro72Leu) and rs373708098 (Gly249Ser) found to be potentially deleterious. The functional impact of three nsSNPs i.e., rs74315393, rs368205448 and rs143321797 have already been validated experimentally in the context of human obesity. Moreover, Homology modeling and structural analysis were carried out for already experimentally validated nsSNPs i.e., rs74315393, rs368205448 and rs143321797 to check the stability of predicted models. The mutant models showed higher energy and RMSD (Root mean square deviation) values. In addition, FTSite server predicted one nsSNP i.e., rs368205448 (Asp121Tyr) out of eight identified nsSNPs found in the MC3R protein binding site. Thus, the present computational study may suggest that predicted nsSNPs possibly be a better drug target and contribute to the treatment and better understanding of human obesity.

No association between impaired glucose metabolism and osteoarthritis

OBJECTIVE

To investigate the association between markers of glucose metabolism and hand and knee osteoarthritis (OA).

METHODS

This is a cross-sectional analysis of baseline measurements of the Netherlands Epidemiology of Obesity (NEO) study, a population-based prospective cohort study. Fasting glucose, insulin and glycated hemoglobulin A1c (HbA1c) concentrations were measured, Homeostasis Model Assessment for Insulin Resistance (HOMA-IR) was calculated and clinical OA was defined following the American College of Rheumatology (ACR) criteria. After exclusion of participants on glucose-lowering drugs, odds ratios (ORs) with 95% confidence intervals (CIs) for either hand, knee or both hand and knee OA were calculated (no OA as reference), as a function of each marker of glucose metabolism, with logistic regression analyses. Models were adjusted for age, ethnicity, education, height, weight and total body fat, and stratified by sex.

RESULTS

In 6197 participants (age 45-65 years, 56% women, mean body mass index (BMI) 26 kg/m(2)), prevalences of hand OA, knee OA or both were 7%, 10% or 4%, respectively. In men, the adjusted OR (95%CI) for hand OA was 1.18 (1.01-1.39) per standard deviation (SD) increase in plasma glucose (0.85 mmol/L). There were no further associations of glucose, HbA1c, insulin and HOMA-IR with the different types of OA, neither in men nor in women.

CONCLUSION

An impaired glucose metabolism does not seem be related to OA. In men, an association was observed for fasting glucose concentrations and hand OA. Future studies should investigate the presence of sex differences in the pathogenesis of hand OA.

Association of urinary metabolites with radiographic progression of knee osteoarthritis in overweight and obese adults: an exploratory study

INTRODUCTION

Metabolic factors may contribute to osteoarthritis (OA). This study employed metabolomics analyses to determine if differences in metabolite profiles could distinguish people with knee OA who exhibited radiographic progression.

METHODS

Urine samples obtained at baseline and 18 months from overweight and obese adults in the Intensive Diet and Exercise for Arthritis (IDEA) trial were selected from two subgroups (n = 22 each) for metabolomics analysis: a group that exhibited radiographic progression (≥0.7 mm decrease in joint space width, JSW) and an age, gender, and body mass index (BMI) matched group who did not progress (≤0.35 mm decrease in JSW). Multivariate analysis methods, including orthogonal partial least square discriminate analysis, were used to identify metabolite profiles that separated progressors and non-progressors. Plasma levels of IL-6 and C-reactive protein (CRP) were evaluated as inflammatory markers.

RESULTS

Multivariate analysis of the binned metabolomics data distinguished progressors from non-progressors. Library matching revealed that glycolate, hippurate, and trigonelline were among the important metabolites for distinguishing progressors from non-progressors at baseline whereas alanine, N,N-dimethylglycine, glycolate, hippurate, histidine, and trigonelline, were among the metabolites that were important for the discrimination at 18 months. In non-progressors, IL-6 decreased from baseline to 18 months while IL-6 was unchanged in progressors; the change over time in IL-6 was significantly different between groups.

CONCLUSION

These findings support a role for metabolic factors in the progression of knee OA and suggest that measurement of metabolites could be useful to predict progression. Further investigation in a larger sample that would include targeted investigation of specific metabolites is warranted.

Impact of Bariatric Surgery on Patients With Rheumatoid Arthritis

OBJECTIVE

To investigate the effect of weight loss after bariatric surgery among patients with rheumatoid arthritis (RA).

METHODS

We conducted a retrospective cohort study of RA patients who underwent bariatric surgery (Roux-en-Y gastric bypass, laparoscopic adjustable gastric banding, or sleeve gastrectomy) at 2 medical centers. We obtained information on anthropometrics, laboratory values, RA disease activity, and medication use at baseline (prior to surgery), at 6 and 12 months following surgery, and at the most recent followup visits. RA disease activity was determined by clinical or validated measures. At each postsurgical visit, characteristics were compared to baseline.

RESULTS

We identified 53 RA patients who underwent bariatric surgery. At baseline prior to surgery, mean ± SD body mass index was 47.8 ± 7.7 kg/m(2), mean ± SD weight was 128.2 ± 24.1 kg, and 57% had moderate to high RA disease activity. Twelve months following surgery, subjects lost a mean ± SD weight of 41.0 ± 17.3 kg, mean ± SD 70% ± 24% excess weight (P < 0.001). RA disease activity significantly improved at postsurgical visits (P < 0.001). At 12 months following surgery, 6% had moderate to high disease activity, compared to 57% at baseline (P < 0.001). At the most recent followup (mean ± SD 5.8 ± 3.2 years after surgery), 74% were in remission, compared to 26% at baseline (P < 0.001). Subjects had significantly lower erythrocyte sedimentation rate, C-reactive protein level, and RA-related medication use at followup visits compared to baseline (P < 0.05).

CONCLUSION

After substantial weight loss from bariatric surgery, RA patients had lower disease activity, decreased serum inflammatory markers, and less RA-related medication use. Weight loss may be an important nonpharmacologic strategy to reduce RA disease activity. However, other factors, such as improved efficacy of medications, improved physical activity, and metabolic changes, may also have contributed to these postsurgical improvements.

Associations between body composition measurements of obesity and radiographic osteoarthritis in older adults: Data from the Dong-gu Study

Background

We examined the effects of fat deposition on radiographic osteoarthritis (OA) to determine the role of obesity in the pathogenesis of radiographic OA.

Methods

Data were taken from the Dong-gu cohort, a cross-sectional study of 2,367 subjects. Baseline characteristics, waist circumference (WC), waist-to-hip ratio (WHR), fat mass, and fat percentage were collected, along with X-rays of the knees and hands. Total knee and hand radiographic OA scores were summed using a semi-quantitative grading system, and then stratified by gender using a multiple linear regression model.

Results

After adjusting for confounders, weight was the only factor significantly associated with knee radiographic OA, regardless of gender (all p < 0.01). Regarding the hand, fat percentage had the largest effect on radiographic OA in males (p = 0.008), while WHR was the most significant factor in females (p = 0.001). For the knee, fat mass was the most important factor for radiographic OA in males (p = 0.001), while in females, body mass index was the most important factor (p < 0.001). Among the variables, only fat percentage was significantly related to both hand and knee radiographic OA in both genders (all p < 0.01).

Conclusions

Regardless of gender, weight was significantly associated with knee radiographic OA. Otherwise, fat deposition correlated with hand and knee radiographic OA in both genders, while the distribution of fat tissue was significantly associated with hand and knee radiographic OA only in females.

Strong association of the polymorphisms in PBEF1 and knee OA risk: a two-stage population-based study in China

The association of Pre-B cell colony enhancing factor 1 (PBEF1) with obesity, together with its pro-inflammatory properties suggests that PBEF1 might be another crucial mediator that links inflammation with obesity and primary osteoarthritis (OA). We hypothesized that polymorphisms in PBEF1 may modify the risk of developing OA. Thus we systematically screened 4 tagging polymorphisms (rs4730153, rs2058540, rs3801267 and rs16872158) in PBEF1 and evaluated the association between the genetic variants and OA risk in a two-stage case-control study including 196 cases and 442 controls in the first stage and 143 cases and 238 controls in the second stage. In the first stage, two SNPs (rs4730153 and rs16872158) were found to be potentially associated with OA risk (P < 0.05), which were further confirmed in the second stage with similar effects. After combining the two stages, we found that rs4730153 was significantly associated with decreased risk of OA in an additive genetic model (P < 0.05), while rs16872158 showed increased risk of developing OA (P < 0.05). Combined analysis of these 2 SNPs showed a significant allele-dosage association between the number of risk alleles and OA risk (Ptrend = 5.25 × 10(-5)). These findings indicate that genetic variants in PBEF1 gene may modify individual susceptibility to OA in the Chinese population.

Osteoarthritis year in review 2015: clinical

The purpose of this review is to highlight clinical research in osteoarthritis (OA). A literature search was conducted using PubMed (http://www.ncbi.nlm.nih.gov/pubmed/) with the search terms "osteoarthritis [All Fields] AND treatment [All Fields]" and the following limits activated: humans, English language, all adult 19+ years, published between April 1, 2014 and April 1, 2015. A second literature search was then conducted with the search terms "osteoarthritis [All Fields] AND epidemiology [All Fields]", with the same limits. Reports of surgical outcome, case series, surgical technique, tissue sample or culture studies, trial protocols, and pilot studies were excluded. Of 1523, 150 were considered relevant. Among epidemiologic and observational clinical studies, themes included physical activity, early knee OA, and confidence/instability/falls. Symptom outcomes of pharmacologic treatments were reported for methotrexate, adalimumab, anti-nerve growth factor monoclonal antibodies, strontium ranelate, bisphosphonates, glucosamine, and chondroitin sulfate, and structural outcomes of pharmacologic treatments for strontium ranelate, recombinant human fibroblast growth factor 18, and glucosamine and chondroitin sulfate. Symptom outcomes of non-pharmacologic interventions were reported for: neuromuscular exercise, quadriceps strengthening, weight reduction and maintenance, TENS, therapeutic ultrasound, stepped care strategies, cognitive behavior therapy for sleep disturbance, acupuncture, gait modification, booster physical therapy, a web-based therapeutic exercise resource center for knee OA; hip physical therapy for hip OA; and joint protection and hand exercises for hand OA. Structure outcomes of non-pharmacologic interventions were reported for patellofemoral bracing.

State of the evidence

PURPOSE OF REVIEW

This review focuses on recent studies of osteoarthritis epidemiology, including research on prevalence, incidence, and a broad array of potential risk factors at the person level and joint level.

RECENT FINDINGS

Studies continue to illustrate the high impact of osteoarthritis worldwide, with increasing incidence. Person-level risk factors with strong evidence regarding osteoarthritis incidence and/or progression include age, sex, socioeconomic status, family history, and obesity. Joint-level risk factors with strong evidence for incident osteoarthritis risk include injury and occupational joint loading; the associations of injury and joint alignment with osteoarthritis progression are compelling. Moderate levels of physical activity have not been linked to increased osteoarthritis risk. Some topics of high recent interest or emerging evidence for association with osteoarthritis include metabolic pathways, vitamins, joint shape, bone density, limb length inequality, muscle strength and mass, and early structural damage.

SUMMARY

Osteoarthritis is a complex, multifactorial disease, and there is still much to learn regarding mechanisms underlying incidence and progression. However, there are several known modifiable and preventable risk factors, including obesity and joint injury; efforts to mitigate these risks can help to lessen the impact of osteoarthritis.

Relationship between inflammation, the gut microbiota, and metabolic osteoarthritis development: studies in a rat model

Osteoarthritis (OA) may result from intrinsic inflammation related to metabolic disturbance. Obesity-associated inflammation is triggered by lipopolysaccharide (LPS) derived from the gut microbiota. However, the relationship between gut microbiota, LPS, inflammation, and OA remain unclear.

OBJECTIVE

To evaluate the associations between gut microbiota, systemic LPS levels, serum and local inflammatory profiles, and joint damage in a high fat/high sucrose diet induced obese rat model.

METHODS

32 rats were randomized to a high fat/high sucrose diet (diet-induced obese (DIO), 40% fat, 45% sucrose, n = 21) or chow diet group (12% fat, 3.7% sucrose n = 11) for 28 weeks. After a 12-week obesity induction period, DIO animals were stratified into Obesity Prone (DIO-P, top 33% by change in body mass, n = 7), and Obesity Resistant groups (DIO-R, bottom 33%, n = 7). At sacrifice, joints were scored using a Modified Mankin Criteria. Blood and synovial fluid analytes, serum LPS, and fecal gut microbiota were analyzed.

RESULTS

DIO animals had greater Modified Mankin scores than chow animals (P = 0.002). There was a significant relationship (r = 0.604, p = 0.001) between body fat, but not body mass, and Modified Mankin score. Eighteen synovial fluid and four serum analytes were increased in DIO animals. DIO serum LPS levels were increased compared to chow (P = 0.031). Together, Lactobacillus species (spp.) and Methanobrevibacter spp. abundance had a strong predictive relationship with Modified Mankin Score (r(2) = 0.5, P < 0.001).

CONCLUSIONS

Increased OA in DIO animals is associated with greater body fat, not body mass. The link between gut microbiota and adiposity-derived inflammation and metabolic OA warrants further investigation.

Metabolic stress-induced joint inflammation and osteoarthritis

Osteoarthritis (OA) is a heterogeneous disorder with several risk factors. Among them, obesity has a major impact on both loading and non-loading joints. Mechanical overload and activity of systemic inflammatory mediators derived from adipose tissue (adipokines, free fatty acids (FFA), reactive oxygen species (ROS)) provide clues to the increased incidence and prevalence of OA in obesity. Recently, research found greater OA prevalence and incidence in obese patients with cardiometabolic disturbances than "healthy" obese patients, which led to the description of a new OA phenotype - metabolic syndrome (MetS)-associated OA. Indeed, individual metabolic factors (diabetes, dyslipidemia, and hypertension) may increase the risk of obesity-induced OA. This review discusses hypotheses based on pathways specific to a metabolic factor in MetS-associated OA, such as the role of advanced glycation end products (AGEs) and glucose toxicity. A better understanding of these phenotypes based on risk factors will be critical for designing trials of this specific subset of OA.

An assessment of molecular pathways of obesity susceptible to nutrient, toxicant and genetically induced epigenetic perturbation

In recent years, the etiology of human disease has greatly improved with the inclusion of epigenetic mechanisms, in particular as a common link between environment and disease. However, for most diseases we lack a detailed interpretation of the epigenetic regulatory pathways perturbed by environment and causal mechanisms. Here, we focus on recent findings elucidating nutrient-related epigenetic changes linked to obesity. We highlight studies demonstrating that obesity is a complex disease linked to disruption of epigenetically regulated metabolic pathways in the brain, adipose tissue and liver. These pathways regulate (1) homeostatic and hedonic eating behaviors, (2) adipocyte differentiation and fat accumulation, and (3) energy expenditure. By compiling these data, we illustrate that obesity-related phenotypes are repeatedly linked to disruption of critical epigenetic mechanisms that regulate key metabolic genes. These data are supported by genetic mutation of key epigenetic regulators, and many of the diet-induced epigenetic mechanisms of obesity are also perturbed by exposure to environmental toxicants. Identifying similarly perturbed epigenetic mechanisms in multiple experimental models of obesity strengthens the translational applications of these findings. We also discuss many of the ongoing challenges to understanding the role of environmentally induced epigenetic pathways in obesity and suggest future studies to elucidate these roles. This assessment illustrates our current understanding of molecular pathways of obesity that are susceptible to environmental perturbation via epigenetic mechanisms. Thus, it lays the groundwork for dissecting the complex interactions between diet, genes and toxicants that contribute to obesity and obesity-related phenotypes.

Osteoarthritis of the Distal Interphalangeal and First Carpometacarpal Joints is Associated with High Bone Mass in Women and Small Bone Size and Low Lean Mass in Men

Objective:

To determine if primary hand osteoarthritis (OA) is associated with abnormal bone and anthropometric traits.

Methods:

We used DXA to measure total body bone mineral density (BMD), femoral neck width (bone size) and total body lean and fat mass in 39 subjects with hand OA (primary DIP and/or CMC I) and 164 controls. Data are presented as mean Z-scores or Odds Ratios (OR) with 95% confidence intervals.

Results:

Women with hand OA had (compared to controls) higher BMD (0.5(0.1,0.9)) but similar bone size (-0.3(-0.8,0.2)), lean mass (0.3(-0.3,0.9)), fat mass (-0.1(-0.6,0.5)) and BMI (0.0(-0.6,0.6)). Men with hand OA had (compared to controls) similar BMD (-0.1(-0.7,0.6)), smaller bone size (-0.5(-1.1,-0.01)), lower lean mass (-0.6(-1.1,-0.04)), and similar fat mass (-0.2(-0.7,0.4)) and BMI -0.1(-0.6,0.6). In women, each SD higher BMD was associated with an OR of 1.8 (1.03, 3.3) for having hand OA. In men each SD smaller bone size was associated with an OR of 1.8 (1.02, 3.1) and each SD lower proportion of lean body mass with an OR of 1.9 (1.1, 3.3) for having hand OA.

Conclusion:

Women with primary DIP finger joint and/or CMC I joint OA have a phenotype with higher BMD while men with the disease have a smaller bone size and lower lean body mass.

An indicator of subclinical cardiovascular disease in patients with primary osteoarthritis: epicardial fat thickness

Osteoarthritis (OA) is one of the most common chronic diseases seen in the elderly, and it is associated with increased cardiovascular morbidity and mortality. The cause of this association is not fully known. We aimed to investigate the relationship between epicardial fat and the presence and the grade of primary knee OA for analyzing the relationship between visceral adiposity and primary OA, thereby revealing the increased subclinical atherosclerosis and cardiovascular risk in OA patients. In this cross-sectional study, subjects with primary knee osteoarthritis and a control group were compared with regard to epicardial fat thickness through transthoracic echocardiography. In addition, OA was divided into four stages and the relationship between the grade of OA and epicardial fat thickness was analyzed. Eighty subjects with primary knee OA and 50 controls were analyzed. There was no difference between groups with regard to age, gender and BMI. Epicardial fat thickness was greater in patients in the primary OA group compared to the control group (3.73±1.08 vs 3.30±0.61, respectively, P=0.005). In-group comparison of OA patients revealed that epicardial fat thickness was detected to increase as the grade of OA increased (P=0.001). A relationship was detected between the presence of OA and epicardial fat thickness and CRP levels in multivariate logistic analysis (P=0.017, P=0.047, respectively). There is a significant relationship between primary OA and epicardial fat thickness, which is a part of visceral adipose tissue. These results may indicate the relationship between OA and visceral fat tissue and, consequently, cardiovascular risk, so body weight alone may not be an identifying co-factor.