Psoriatic arthritis is a painful, disabling disease which involves inflammation of the skin and joints.
Psoriatic arthritis is characterized by synovitis and enthesitis. Synovitis is inflammation of the membrane that covers synovial joints. Enthesitis is inflammation of the entheses, which are the regions where tendons or ligaments attach to the bone.
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Swelling, pain and stiffness are the major symptoms associated with psoriatic arthritis. Psoriatic arthritis can affect any part of the body; however, the fingers and toes are most often affected.
Evidence suggests that both psoriasis and psoriatic arthritis are associated with obesity and the metabolic syndrome. These two conditions increase the risk of heart disease, type 2 diabetes and stroke.
Observational studies show that obesity is present in 45% of psoriatic arthritis patients. Obesity in psoriasis and psoriatic arthritis leads to higher disease activity, decreased responses to therapies, and lower probability of achieving minimal disease activity (MDA).
The mechanisms linking psoriatic arthritis with obesity
Obesity may negatively impact the disease onset as well as the disease severity of psoriatic arthritis. Though the exact mechanisms linking psoriatic arthritis with obesity is not fully elucidated, the following are proposed as some possible ways.
1. Common immunologic pathways
Both psoriatic arthritis and obesity are characterized by chronic inflammation, which involves similar immunologic pathways. The key cytokines involved in the development of psoriatic arthritis are tumor necrosis factor α (TNFα) and interleukins (IL).
White adipose tissue, also termed white fat, is a type of adipose tissue found in human body which plays a key role in maintaining the energy homeostasis of the body. White fats produce the same cytokines (TNFα and IL) as those involved in the pathogenesis of psoriatic arthritis.
In addition to TNFα and IL, white fats also produce pro-inflammatory adipokines such as leptin, resistin, and anti-inflammatory adipokines such as adiponektin, omentin.
In people who are obese, white fats are infiltrated by macrophages, dendritic cells and lymphocytes. Additionally, the pro-inflammatory cytokines and adipokines are overproduced in obesity, which propels the inflammatory processes in psoriatic arthritis.
Apart from systemic immune mediated inflammation, localized inflammation in fat cells inside joints and beneath the psoriatic skin lesions can also lead to progression of psoriatic arthritis.
2. Biomechanical stress
Biomechanical stress is another mechanism which links obesity with psoriatic arthritis. The extra weight around the joints can cause biomechanical stress and damage.
Psoriatic arthritis causes enthesitis or inflammation at site of tendons and ligaments where they attach to bones.
These sites of attachment are often subject to mechanical stress. In obese individuals, the weight load causes increased mechanical stress; it is also associated with increased possibility of local microdamage.
3. Behavioural factors
Another interesting mechanism linking psoriatic arthritis and obesity is behavioural factors. The pain and skin lesions associated with psoriasis can lead to behavioural changes in the patient, which leads to lowered physical activity and over-eating.
This ultimately result leads to obesity, which may further reduce the patient’s mobility and physical activity. In such cases, it is suggested to seek physician advice and follow an efficient weight loss treatment.
Weight Loss Benefits
As per a recent study published in the journal Arthritis research & therapy, short-term weight loss treatment with VLED (very low energy diet), a diet that is low in energy/calories, can have significant positive effects on disease activity in joints, entheses and skin in patients with psoriatic arthritis and obesity.
Psoriatic arthritis patients who lose weight are found to have better treatment outcomes with disease-modifying anti-rheumatic drugs (DMARDs) and biological drugs.
As per a study published in 2016, in the journal Rheumatology (Oxford), obesity is associated with diminished treatment response and adherence to the biological drug, TNF-α inhibitor (TNFI), in psoriatic arthritis.
A combination of pharmacological drugs and weight loss treatment is recommended in patients presenting with psoriatic arthritis and obesity. Weight loss can lead to improvements in disease activity, treatment responses and also decrease the risk of cardiovascular diseases.
- Klingberg E., et al. (2019) Weight loss improves disease activity in patients with psoriatic arthritis and obesity: an interventional study. Arthritis Res Ther. 21(1):17. doi:10.1186/s13075-019-1810-5
- How Overweight and Obesity Affect Psoriatic Arthritis. Arthritis Foundation. Available at: www.arthritis.org/.../obesity-psoriatic-arthritis.php
- Højgaard P., et al. (2016) The influence of obesity on response to tumor necrosis factor-α inhibitors in psoriatic arthritis: results from the DANBIO and ICEBIO registries. Rheumatology (Oxford). 55(12):2191-2199.