Synovial fluid and plasma n3 long chain polyunsaturated fatty acids in patients with inflammatory arthritis

Role of specialized pro-resolving mediators on inflammation, cardiometabolic health, disease progression, and quality of life after omega-3 PUFA supplementation and aerobic exercise training in individuals with rheumatoid arthritis: a randomized 16-week, placebo-controlled interventional trial

Background: Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by autoantibody production and synovial membrane damage. It significantly impairs overall function and quality of life. Consumption of omega-3 (n-3) polyunsaturated fatty acids (PUFAs) and regular aerobic exercise (AEx) training are reported to have positive effects on the progression of RA. However, the mechanisms behind these benefits are still inconclusive. This study protocol will investigate the effects of n-3 PUFA supplementation and AEx training on disease progression, cardiometabolic health, and quality of life, and their association with the plasma and synovial fluid levels of specialized pro-resolving mediators (SPMs) in subjects with RA. Methods: The study consists of a 16-week intervention period, during which participants will be randomly assigned in a double-blinded manner to one of four groups: placebo control (PLA), PLA+AEx, n-3, or n-3+AEx. The PLA groups will be given a gelatin-filled capsule, while the n-3 groups will be given n-3 PUFAs equivalent to 2.5 g/d of docosahexaenoic acid and 0.5 g/d of eicosapentaenoic acid. The AEx groups will perform exercise three times per week on a stationary electronically braked cycle ergometer at 60-70% of their VO2peak for 50-60 minutes. Before and after the intervention, participants will undergo RA-specific and functional measurements, peak aerobic capacity test, and a dietary and physical activity assessment. Venous blood and synovial fluid from the knee joint will be collected. Changes in disease progression, cardiometabolic health, and quality of life, as well as erythrocyte membrane composition to assess n-3 incorporation, SPM levels, inflammatory markers, and gene expression from blood and synovial fluid will be analyzed. Conclusions: The study aims to elucidate the SPMs that regulate the inflammatory gene expression pathways and associate them with the improvements in disease progression, cardiometabolic health, and quality of life after n-3 PUFA supplementation and AEx training. Registration: ClinicalTrials.gov #NCT05945693.

Short- and Long-Term Effects of Dietary Supplementation with Fish Oil on Inflammatory Pain in Rats

INTRODUCTION

Dietary supplementation with fish oil is promising as a complementary therapy for inflammatory pain. However, further studies are needed to support its therapeutic potential. For example, the antinociceptive effect of fish oil is widely suggested to be dependent on decreased prostaglandin E₂ (PGE₂) synthesis, but no previous study has investigated if it affects PGE₂-induced nociceptive response. Similarly, beneficial long-term effects on inflammatory response are related to early exposure to fish oil, however, whether these effects include decreased inflammatory pain throughout life is not known.

OBJECTIVE

The aim of this study was to investigate the short- and long-term effects of fish oil on inflammatory pain.

METHODS

Dietary fish oil supplementation was performed through two protocols: in adult rats, during 20 days, or in dams, during pregnancy and lactation, with tests performed in adult offspring. The hyperalgesic response induced by carrageenan and its final mediators PGE₂ and norepinephrine was used to model inflammatory pain.

RESULTS

The findings demonstrated for the first time that dietary fish oil (1) decreases the hyperalgesia induced by carrageenan; (2) but not that induced by its final mediator PGE₂ and norepinephrine; (3) increase omega-3 polyunsaturated fatty acids in peripheral neural tissue; and (4) attenuates inflammatory pain in individuals exposed to fish oil during pre-natal life and lactation.

CONCLUSION

Together, these findings support that fish oil decreases inflammatory pain either when consumed during adult life or during prenatal development. Future studies should confirm the therapeutic potential of fish oil in humans, which is essential for the development of public policies to encourage a fish oil richer diet.

The Influence of Dietary Fatty Acids on Immune Responses

Diet-derived fatty acids (FAs) are essential sources of energy and fundamental structural components of cells. They also play important roles in the modulation of immune responses in health and disease. Saturated and unsaturated FAs influence the effector and regulatory functions of innate and adaptive immune cells by changing membrane composition and fluidity and by acting through specific receptors. Impaired balance of saturated/unsaturated FAs, as well as n-6/n-3 polyunsaturated FAs has significant consequences on immune system homeostasis, contributing to the development of many allergic, autoimmune, and metabolic diseases. In this paper, we discuss up-to-date knowledge and the clinical relevance of the influence of dietary FAs on the biology, homeostasis, and functions of epithelial cells, macrophages, dendritic cells, neutrophils, innate lymphoid cells, T cells and B cells. Additionally, we review the effects of dietary FAs on the pathogenesis of many diseases, including asthma, allergic rhinitis, food allergy, atopic dermatitis, rheumatoid arthritis, multiple sclerosis as well as type 1 and 2 diabetes.

Are we really what we eat? Nutrition and its role in the onset of rheumatoid arthritis

Accumulating research evidence suggests that individual dietary factors and dietary patterns might be implicated in the risk of development of rheumatoid arthritis (RA). This narrative review aims to present this evidence and provide nutritional recommendations for reducing RA risk in susceptible individuals. Overall, a 'Western' type diet rich in energy intake, total and saturated fat, an unbalanced ratio of n-3 to n-6 fatty acids, high in refined carbohydrates and sugar and low in fiber and antioxidants might increase the risk of RA both directly through increasing inflammation and indirectly through increasing insulin resistance and obesity, with the latter being a known risk factor for RA. On the contrary, consumption of long-chain omega-3 polyunsaturated fatty acids, derived from fish and fish oil, is associated with a reduced risk of RA probably due to their anti-inflammatory properties. The Mediterranean diet (MD), rich in plant-based foods such as wholegrains, legumes, fruit, vegetables, extra-virgin olive oil and low in red meat consumption, might have the potential to reduce the risk of RA. Based on current research evidence, it is suggested that adherence to the MD enhanced with an increased consumption of fatty fish, reduced consumption of sugar-sweetened drinks and maintenance of a normal body weight, contributes to reducing the risk of RA. Further research on RA susceptibility will allow for more specific dietary recommendations to be made.

Long-term dietary quality and risk of developing rheumatoid arthritis in women

OBJECTIVES

To evaluate the association between long-term dietary quality, measured by the 2010 Alternative Healthy Eating Index, and risk of rheumatoid arthritis (RA) in women.

METHODS

We prospectively followed 76 597 women in the Nurses' Health Study aged 30-55 years and 93 392 women in the Nurses' Health Study II aged 25-42 years at baseline and free from RA or other connective tissue diseases. The lifestyle, environmental exposure and anthropometric information were collected at baseline and updated biennially. Cumulative follow-up rates were more than 90% for both cohorts. The primary outcome was RA alone with two subtypes of the disease: seropositive and seronegative RA.

RESULTS

During 3 678 104 person-years, 1007 RA cases were confirmed. In the multivariable-adjusted model, long-term adherence to healthy eating patterns was marginally associated with reduced RA risk. To assess potential effect modification by age at diagnosis, we stratified by age. Among women aged ≤55 years, better quality diet was associated with lower RA risk (HRQ4 vs Q1: 0.67; 95% CI 0.51 to 0.88; p trend: 0.002), but no significant association was found for women aged >55 years (p interaction: 0.005). When stratifying by serostatus, the inverse association among those aged ≤55 years was strongest for seropositive RA (HRQ4 vs Q1: 0.60; 95% CI 0.42 to 0.86; p trend: 0.003).

CONCLUSIONS

A healthier diet was associated with a reduced risk of RA occurring at 55 years of age or younger, particularly seropositive RA.

Specialised pro-resolving mediators of inflammation in inflammatory arthritis

INTRODUCTION

Specialised pro-resolving mediators (SPM) are derived from n-3 long chain polyunsaturated fatty acids (n-3FA). They promote resolution of inflammation and may contribute to the beneficial effects of n-3FA in patients with arthritis. This study compared SPM in knee effusions and plasma of patients with arthritis taking n-3FA, and plasma of healthy volunteers taking n-3FA.

METHODS

Thirty six patients taking n-3FA undergoing arthrocentesis for an inflammatory knee effusion and 36 healthy volunteers who had taken n-3FA (2.4g/day) for 4 weeks were studied. SPM in synovial fluid and plasma were measured by liquid chromatography-tandem mass spectrometry included 18-hydroxyeicosapentaenoic acid (18-HEPE), the precursor of the E-series SPM (RvE1, RvE2, RvE3, 18R-RvE3), and 17-hydroxydocosahexaenoic acid (17-HDHA), the precursor of the D-series SPM (RvD1, 17R-RvD1, RvD2). Other SPM included protectin D1 (PD1), 10S,17S-dihydroxydocosahexaenoic acid (10,17S-DHDHA), maresin-1 (MaR-1) and 14-hydroxydocosahexaenoic acid (14-HDHA) derived from docosahexaenoic acid (DHA).

RESULTS

E- and D-series SPM and the precursors 18-HEPE and 17-HDHA were present in synovial fluid and plasma of the patients with inflammatory arthritis. Plasma SPM were negatively related to erythrocyte sedimentation rate in arthritis patients (P<0.01) and synovial fluid RvE2 was negatively associated with pain score (P=0.02). Conversion from 18-HEPE and 17-HDHA to E- and D-series SPM was greater in synovial fluid (P<0.01). Most plasma SPM in arthritis patients were elevated (P<0.05) compared with healthy volunteers, and conversion to E- and D-series SPM was greater (P<0.01).

CONCLUSIONS

SPM are present in chronic knee effusions and although the levels are lower than in plasma, the association between synovial fluid RvE2 and reduced pain scores suggests that synthesis of SPM at the site of inflammation is a relevant mechanism by which n-3FA alleviate the symptoms of arthritis.