The interaction between obesity and RAGE polymorphisms on the risk of knee osteoarthritis in Chinese population

The Role of Genetics and Epigenetic Regulation in the Pathogenesis of Osteoarthritis

Osteoarthritis (OA) is progressive disease characterised by cartilage degradation, subchondral bone remodelling and inflammation of the synovium. The disease is associated with obesity, mechanical load and age. However, multiple pro-inflammatory immune mediators regulate the expression of metalloproteinases, which take part in cartilage degradation. Furthermore, genetic factors also contribute to OA susceptibility. Recent studies have highlighted that epigenetic mechanisms may regulate the expression of OA-associated genes. This review aims to present the mechanisms of OA pathogenesis and summarise current evidence regarding the role of genetics and epigenetics in this process.

Epistasis between ADIPOQ rs1501299 and PON1 rs662 polymorphisms is potentially associated with the development of knee osteoarthritis

Overweight produces oxidative stress (OS) on the articular cartilage, with the subsequent risk of developing knee osteoarthritis (OA). Associations between genetic polymorphisms related to OS and OA have been reported, but it is currently unknown whether there exist interactions among them that affect OA development. To identify and evaluate interactions between multiple SNPs related to OS in Mexican knee OA patients. Ninety-two knee OA patients were included in the study, which were compared to 147 healthy controls. Nine variants of six genes (PEPD, AGER, IL6, ADIPOQ, PON1, and CA6) related to OS were genotyped in both study groups through the OpenArray system. Epistasis was analyzed with the multifactor dimensionality reduction (MDR) method. The MDR analysis revealed a significant interaction (p = 0.0107) between polymorphisms rs1501299 (ADIPOQ) and rs662 (PON1), with an entropy value of 9.84%; in addition, high and low risk genotypes were identified between these two polymorphisms. The effect of the interaction between rs1501299 (ADIPOQ) and rs662 (PON1) polymorphisms seems to play an important role in OA pathogenesis; so the epistasis analysis may provide an excellent tool for identifying individuals at high risk for developing OA.

The interrelation of osteoarthritis and diabetes mellitus: considering the potential role of interleukin-10 and in vitro models for further analysis

INTRODUCTION

Today, not only the existence of an interrelation between obesity/adipositas and osteoarthritis (OA) but also the association of OA and diabetes mellitus (DM) are widely recognized. Nevertheless, shared influence factors facilitating OA development in DM patients still remain speculative up until now. To supplement the analysis of clinical data, appropriate in vitro models could help to identify shared pathogenetic pathways. Informative in vitro studies could later be complemented by in vivo data obtained from suitable animal models.

MATERIALS AND METHODS

Therefore, this detailed review of available literature was undertaken to discuss and compare the results of currently published in vitro studies focusing on the interrelation between OA, the metabolic syndrome and DM and to propose models to further study the molecular pathways.

RESULTS

The survey of literature presented here supports the hypothesis that the pathogenesis of OA in DM is based on imbalanced molecular pathways with a putative crucial role of antiinflammatory cytokines such as IL-10.

CONCLUSION

Future development of versatile micro-scaled in vitro models such as combining DM and OA on chip could allow the identification of common pathogenetic pathways and might help to develop novel therapeutic strategies.

Role of HIF-1α signaling pathway in osteoarthritis: a systematic review

Osteoarthritis (OA) is the most common form of arthritis and is frequently diagnosed and managed in primary care; it is characterized by loss of articular hyaline cartilage, which is a unique connective tissue that physiologically lacks blood vessels. Articular cartilage survives in a microenvironment devoid of oxygen, which is regulated by hypoxia inducible factor (HIF-1α). HIF-1α is considered the main transcriptional regulator of cellular and developmental response to hypoxia. To date, the relevance of HIF-1α in the assessment of cartilage has increased since its participation is essential in the homeostasis of this tissue. Taking into account the new emerging insights of HIF-1α in the scientific literature in the last years, we focused the present review on the potential role of HIF-1α signaling pathway in OA development, especially in how some genetic factors may influence the maintenance or breakdown of articular cartilage.

A prospective study of soluble receptor for advanced glycation end-products and colorectal cancer risk in postmenopausal women

OBJECTIVES

Receptor for advanced glycation end products (RAGE) expressed on adipocytes and immune cells can bind to ligand N(ε)-(carboxymethyl)-lysine (CML) and trigger dysregulation of adipokines and chronic inflammation. Soluble RAGE (sRAGE) mitigates the detrimental effect of RAGE. We examined the associations between circulating levels of CML-AGE and sRAGE and colorectal cancer (CRC).

METHODS

In a case-cohort study of the Women's Health Initiative Study, blood levels of CML-AGE and sRAGE were measured using ELISA. We used multivariable Cox regression model to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of incident CRC in relation to quartiles (Q) of biomarker levels.

RESULTS

Average follow-up was 7.8 years for 444 cases and 805 subcohort members. In the subcohort, CML-AGE and sRAGE were inversely correlated with BMI (P values<0.0001). Levels of CML-AGE and sRAGE were not associated with CRC. In BMI-specific analysis, the association between sRAGE and CRC was observed. Among women with BMI≥25kg/m(2), those with highest levels of sRAGE had significantly lower risk for CRC as compared to women with lowest levels of sRAGE (HRQ4versusQ1: 0.39; 95% CI: 0.17-0.91). This inverse association was not observed among women with BMI <25kg/m(2) (P value for interaction=0.01).

CONCLUSIONS

Among postmenopausal women, the RAGE pathway may be involved in obesity-related CRC.

RAGE-Mediated Inflammation, Type 2 Diabetes, and Diabetic Vascular Complication

Obesity is associated with inflammation and type 2 diabetes. Innate immune system comprised of cellular and molecular components plays an important role in the inflammatory reactions. Immune cells like macrophages and their cell surface pattern-recognition receptors (PRRs) are representative for innate immunity promoting inflammatory reactions. The receptor for advanced glycation end-products (RAGE) is a member of PRRs and a proinflammatory molecular device that mediates danger signals to the body. The expression of RAGE is observed in adipocytes as well as immune cells, endothelial cells, and pancreatic β cells under certain conditions. It has been reported that RAGE is implicated in adipocyte hypertrophy and insulin resistance. RAGE-mediated regulation of adiposity and inflammation may attribute to type 2 diabetes and diabetic vascular complications.