The decrease of soluble RAGE levels in rheumatoid arthritis patients following hormone replacement therapy is associated with increased bone mineral density and diminished bone/cartilage turnover: a randomized controlled trial

Advanced glycation end products and bone - How do we measure them and how do they correlate with bone mineral density and fractures? A systematic review and evaluation of precision of measures

The role of advanced glycation end products (AGEs) in bone fragility especially in diabetic bone disease is increasingly recognized and researched. As skeletal frailty in diabetes does not correlate to bone mineral density (BMD) in the same way as in postmenopausal osteoporosis, BMD may not be a suitable measure of bone quality in persons with diabetes. Abundant research exists upon the effect of AGEs on bone, and though full understanding of the mechanisms of actions does not yet exist, there is little doubt of the clinical relevance. Thus, the measurement of AGEs as well as possible treatment effects on AGEs have become issues of interest. The aim of this report is to summarize results of measurements of AGEs. It consists of a systematic review of the existing literature on AGE measurements in clinical research, an evaluation of the precision of skin autofluorescence (SAF) measurement by AGE Reader® (Diagnoptics), and a short commentary on treatment of osteoporosis in patients with and without diabetes with respects to AGEs. We conclude that various AGE measures correlate well, both fluorescent and non-fluorescent and in different tissues, and that more than one target of measure may be used. However, pentosidine has shown good correlation with both bone measures and fracture risk in existing literature and results on SAF as a surrogate measurement is promising as some corresponding associations with fracture risk and bone measures are reported. As SAF measurements performed with the AGE Reader® display high precision and allow for a totally noninvasive procedure, conducting AGE measurements using this method has great potential and further research of its applicability is encouraged.

Phytochemicals from medicinal plants from African forests with potentials in rheumatoid arthritis management

OBJECTIVES

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by inflammation, pain, and cartilage and bone damage. There is currently no cure for RA. It is however managed using nonsteroidal anti-inflammatory drugs, corticosteroids and disease-modifying anti-rheumatic drugs, often with severe side effects. Hidden within Africa's lush vegetation are plants with diverse medicinal properties including anti-RA potentials. This paper reviews the scientific literature for medicinal plants, growing in Africa, with reported anti-RA activities and identifies the most abundant phytochemicals deserving research attention. A search of relevant published scientific literature, using the major search engines, such as Pubmed/Medline, Scopus, Google Scholar, etc. was conducted to identify medicinal plants, growing in Africa, with anti-RA potentials.

KEY FINDINGS

Twenty plants belonging to 17 families were identified. The plants are rich in phytochemicals, predominantly quercetin, rutin, catechin, kaempferol, etc., known to affect some pathways relevant in RA initiation and progression, and therefore useful in its management.

SUMMARY

Targeted research is needed to unlock the potentials of medicinal plants by developing easy-to-use technologies for preparing medicines from them. Research attention should focus on how best to exploit the major phytochemicals identified in this review for the development of anti-RA 'green pharmaceuticals'.

Impact of oral contraceptives and breastfeeding on disease activity in a sample of Egyptian rheumatoid arthritis patients

Background

Women are more affected by rheumatoid arthritis (RA) than men and the incidence of RA in women increases around the age of menopause indicating that hormonal factors may have a role in disease pathogenesis and progression. Despite several studies on the role of sex hormones and oral contraceptives (OCs) in RA patients, the effect of combined oral contraceptives on RA disease activity is still controversial, and since few studies have been performed in Egypt on this issue so we aimed to study the effect of OCs, breastfeeding, and prolactin on disease activity and their relation to the titer of autoantibodies in female Egyptian RA patients.

Results

One hundred twenty married female RA patients were classified into three groups based on the OCs use (n = 40 each); current, past and non-users and according to lactation into three groups; lactating using OCs (n = 22), lactating not using OCs (n = 30), and non-lactating (n = 68). Our patients were using combined estrogen-progestin oral contraceptives. Clinical manifestations, disease activity, and laboratory findings were determined. The clinical manifestations including arthritis, and morning stiffness were significantly reduced in current users in comparison to past and non-users. Mean DAS28 was reduced significantly (p < 0.05) in current and past users of OCs. Also, using OCs during lactation reduced the clinical manifestations significantly. Lactating women who were not using OCs had significantly high DAS28 and ESR (p < 0.05) in comparison to lactating using OCs and non-lactating. On the other hand, using OCs reduced serum prolactin significantly. Lactating women not using OCs had significantly high serum prolactin (p < 0.05) and (p < 0.001) in comparison to lactating using OCs and non-lactating respectively which was correlated with DAS28 score.

Conclusion

Oral contraceptives may be considered in RA female patients not only as a suitable birth control method but also it has a controlling effect on disease activity even during lactation.

Message

Oral contraceptives ameliorate disease activity in RA patients

Advanced Glycation End Products (AGEs), Receptor for AGEs, Diabetes, and Bone: Review of the Literature

Diabetes compromises bone cell metabolism and function, resulting in increased risk of fragility fracture. Advanced glycation end products (AGEs) interact with the receptor for AGEs (RAGE) and can make a meaningful contribution to bone cell metabolism and/or alter function. Searches in PubMed using the key words "advanced glycation end-product," "RAGE," "sRAGE," "bone," and "diabetes" were made to explain some of the clinical outcomes of diabetes in bone metabolism through the AGE-RAGE signaling pathway. All published clinical studies were included in tables. The AGE-RAGE signaling pathway participates in diabetic complications, including diabetic osteopathy. Some clinical results in diabetic patients, such as reduced bone density, suppressed bone turnover markers, and bone quality impairment, could be potentially due to AGE-RAGE signaling consequences. However, the AGE-RAGE signaling pathway has some helpful roles in the bone, including an increase in osteogenic function. Soluble RAGE (sRAGE), as a ligand decoy, may increase in either conditions of RAGE production or destruction, and then it cannot always reflect the AGE-RAGE signaling. Recombinant sRAGE can block the AGE-RAGE signaling pathway but is associated with some limitations, such as accessibility to AGEs, an increase in other RAGE ligands, and a long half-life (24 hours), which is associated with losing the beneficial effect of AGE/RAGE. As a result, sRAGE is not a helpful marker to assess activity of the RAGE signaling pathway. The recombinant sRAGE cannot be translated into clinical practice due to its limitations.

Soluble Forms of the Receptor for Advanced Glycation Endproducts (RAGE) in Periodontitis

The receptor for advanced glycation endproducts (RAGE) is critically involved in the pathobiology of chronic inflammatory diseases. Soluble forms of RAGE have been proposed as biomarkers of severity in inflammatory and metabolic conditions, and in monitoring therapeutic responses. The aim of the present study was to determine circulating levels of the soluble forms of RAGE in periodontitis and to evaluate the expression of cell-bound, full-length RAGE and its antagonist AGER1 locally, in gingival tissues. Periodontitis patients and periodontally healthy, sex- and age-matched controls (50 per group) were included. Serum levels of total soluble RAGE and cleaved RAGE (cRAGE) were significantly lower in periodontitis patients. Levels of the endogenous secretory esRAGE were similar in the two groups. cRAGE remained significantly lower in the periodontitis group following multiple adjustments, and had a statistically significant inverse correlation with body mass index and all periodontal parameters. In periodontitis patients, gene expression of full-length RAGE and of AGER1 were significantly higher in periodontitis-affected gingival tissues compared to healthy gingiva. Soluble forms of RAGE, particularly cRAGE, may serve as biomarkers for the presence and severity/extent of periodontitis, and may be implicated in its pathogenesis and its role as a systemic inflammatory stressor.

Implications and Future Perspectives of AGEs in PCOS Pathophysiology

Human, animal, and in vitro studies provide evidence that advanced glycation end-products (AGEs) may contribute to the pathogenesis of polycystic ovary syndrome (PCOS) and its metabolic and reproductive consequences. AGEs are able to induce, via activation of key intracellular signaling pathways, the generation of oxidative stress and proinflammatory cytokines, thus contributing to the adverse health impact of PCOS. This review presents the implications of AGEs in several disease pathophysiologies, including PCOS, as well as the cellular and systemic effects of AGEs on insulin resistance (IR), hyperandrogenemia, endoplasmic reticulum (ER) stress, hypoxia, and ovarian function. The gaps in our knowledge will serve as launching pad for future developments ranging from dietary and lifestyle changes to pharmaceutical interventions aiming at potential applications in women with PCOS.

RAGE Signaling in Skeletal Biology

PURPOSE OF REVIEW

The receptor for advanced glycation end products (RAGE) and several of its ligands have been implicated in the onset and progression of pathologies associated with aging, chronic inflammation, and cellular stress. In particular, the role of RAGE and its ligands in bone tissue during both physiological and pathological conditions has been investigated. However, the extent to which RAGE signaling regulates bone homeostasis and disease onset remains unclear. Further, RAGE effects in the different bone cells and whether these effects are cell-type specific is unknown. The objective of the current review is to describe the literature over RAGE signaling in skeletal biology as well as discuss the clinical potential of RAGE as a diagnostic and/or therapeutic target in bone disease.

RECENT FINDINGS

The role of RAGE and its ligands during skeletal homeostasis, tissue repair, and disease onset/progression is beginning to be uncovered. For example, detrimental effects of the RAGE ligands, advanced glycation end products (AGEs), have been identified for osteoblast viability/activity, while others have observed that low level AGE exposure stimulates osteoblast autophagy, which subsequently promotes viability and function. Similar findings have been reported with HMGB1, another RAGE ligand, in which high levels of the ligand are associated with osteoblast/osteocyte apoptosis, whereas low level/short-term administration stimulates osteoblast differentiation/bone formation and promotes fracture healing. Additionally, elevated levels of several RAGE ligands (AGEs, HMGB1, S100 proteins) induce osteoblast/osteocyte apoptosis and stimulate cytokine production, which is associated with increased osteoclast differentiation/activity. Conversely, direct RAGE-ligand exposure in osteoclasts may have inhibitory effects. These observations support a conclusion that elevated bone resorption observed in conditions of high circulating ligands and RAGE expression are due to actions on osteoblasts/osteocytes rather than direct actions on osteoclasts, although additional work is required to substantiate the observations. Recent studies have demonstrated that RAGE and its ligands play an important physiological role in the regulation of skeletal development, homeostasis, and repair/regeneration. Conversely, elevated levels of RAGE and its ligands are clearly related with various diseases associated with increased bone loss and fragility. However, despite the recent advancements in the field, many questions regarding RAGE and its ligands in skeletal biology remain unanswered.

Dangguijihwang-tang and Dangguijakyak-san Prevent Menopausal Symptoms and Dangguijihwang-tang Prevents Articular Cartilage Deterioration in Ovariectomized Obese Rats with Monoiodoacetate-Induced Osteoarthritis

We investigated whether dangguijakyak-san (DJY) and dangguijihwang-tang (DJH), oriental medicines traditionally used for inflammatory diseases, could prevent and/or delay the progression of postmenopausal symptoms and osteoarthritis in osteoarthritis-induced estrogen-deficient rats. Treated ovariectomized (OVX) rats consumed either 1% DJY or 1% DJH in the diets. Positive-control rats were given 30 μg/kg bw 17β-estradiol and control rats were given 1% fat as were the normal-control rats. All rats received high-fat diets for 8 weeks. At the 9th week, OVX rats received articular injections of monoiodoacetate (MIA) or saline (normal control) into the right knee. At 3 weeks after MIA injection, DJY reduced visceral-fat mass and improved glucose metabolism by reducing insulin resistance, whereas DJH increased BMD and decreased insulin resistance. DJH improved weight distribution in the right knee and maximum running velocity on a treadmill at days 14 and 21 as much as those of the positive control. TNF-α, IL-1β, and IL-6 levels in articular cartilage were much higher in the control than the positive control, whereas both DJY and DJH reduced the levels to those of the positive control. The histological analysis assessed articular cartilage damage near the tidemark and proteoglycan loss in the control versus the positive control; DJY and DJH prevented this damage and proteoglycan loss. In conclusion, DJY may provide an effective treatment for improving glucose tolerance, and DJH may be appropriate for preventing osteoarthritis.

Soluble RAGEs - Prospects for treating & tracking metabolic and inflammatory disease

Emerging evidence links the receptor for advanced glycation endproducts (RAGE) to the pathogenesis of tissue damage in chronic metabolic and inflammatory diseases. In human subjects, multiple reports suggest that in the plasma/serum, circulating levels of distinct forms of soluble RAGEs may be biomarkers of the presence or absence, and the extent of chronic disease. These considerations prompt us to consider in this review, what are soluble RAGEs; how are they formed; what might be their natural functions; and may they serve as biomarkers of inflammatory and metabolic disease activity? In this brief review, we seek to address what is known and suggest new areas for scientific investigation to uncover the biology of soluble RAGEs.

Relationship of Advanced Glycation End Products With Cardiovascular Disease in Menopausal Women

Cardiovascular disease (CVD) represents the most significant cause of death in postmenopausal women. Advanced glycation end products (AGEs) are formed by nonenzymatic modification of proteins, lipids, and nucleic acids by glucose. This review focuses on the contribution of AGEs and their receptors to the development of CVD in menopause. Advanced glycation end products circulate and activate the proinflammatory endothelial cell surface receptor called RAGE, bind to the extracellular matrix of the cardiovascular system, or bind to the circulating anti-inflammatory soluble form of RAGE (sRAGE). Data emerging from human and animal studies suggest that AGEs and both receptors (RAGE and sRAGE) are implicated in the pathophysiology of CVD. Particular emphasis has been given to the role of AGE-RAGE axis in oxidative stress, inflammation, endothelial cell toxicity, and progression of atherosclerosis in menopause. Data accruing from human and animal studies suggest that RAGE expression level and circulating sRAGE level are associated with estradiol and are correlated with CVD risk factors, such as adiposity, dyslipidemia, insulin resistance, diabetes, and metabolic syndrome. By recognizing the impact of AGEs on atherosclerosis, pharmacological strategies targeting the AGE-RAGE pathway hold therapeutic potential for CVD in menopausal women.

Serum soluble receptor for advanced glycation end products levels and aortic augmentation index in early rheumatoid arthritis--a prospective study

OBJECTIVE

We assessed whether a serum soluble receptor for advanced glycation end product (sRAGE) levels were associated with a progression of carotid atherosclerosis and arterial stiffness indexes in a cohort of early rheumatoid arthritis (RA) patients.

METHODS

RA patients with symptoms onset <2 years were recruited. Vascular assessments and serum sRAGE levels were measured at baseline and 1 year later. Arterial stiffness was determined by pulse wave velocity and aortic augmentation index (AIx). Carotid intima-media thickness was measured using high-resolution ultrasound.

RESULTS

Ninety-four patients completed the 1-year study. Fifty-three (56.4%) achieved disease remission [28-joint disease activity score (DAS28 < 2.6)] at 12 months. Improvement in arterial stiffness was observed as reflected by the significant reductions in AIx and pulse wave velocity. At 12 months, the sRAGE levels increased significantly compared with baseline (939.8 ± 517.7 pg/ml to 1272.1 ± 567.3 pg/ml, P < 0.001). Changes in sRAGE levels were significantly higher in men compared to women (768 ± 510 pg/ml versus 271 ± 490 pg/ml, P < 0.05) and was negatively associated with the change in AIx (r = -0.259, P = 0.023). Changes in sRAGE level were not associated with other demographic, clinical, cardiovascular risk factors or treatment. Using multivariate analysis, the change in sRAGE levels and baseline high-density lipoprotein were independent predictors associated with the change in AIx.

CONCLUSIONS

Arterial stiffness improved significantly in patients with early RA after effective control of inflammation. Increase in sRAGE level was associated with a decrease in AIx, suggesting that sRAGE may play an important role in the ligand-soluble receptor for advanced glycation end product interaction propagated inflammation and vascular stiffness in these patients.