Metabolic-associated enthesitis: a review on pathophysiology, clinical relevance, diagnostic challenges, and perspective on target treatments.

Entheses are specialized tissues that connect ligaments and tendons to the bone surface and are frequently involved in seronegative spondyloarthritis. Enthesitis can also be detected in patients with metabolic disorders (MD), regardless of baseline autoimmune rheumatic disease, posing real diagnostic challenges. The present review discusses the pathophysiology of enthesitis and metabolic-associated enthesitis, the clinical relevance of metabolic disorders on enthesitis-related outcomes, diagnostic challenges for adequate differential diagnosis, and possible therapeutic strategies to improve clinical outcomes. PubMed/MEDLINE and the Cochrane Library were searched for original articles, systematic reviews, and meta-analyses. References were screened according to a hierarchical analysis of studies by title, abstract, and full text, collected, presented, and discussed. Metabolic-associated enthesitis is attributable to mechanical stress/overload due to weight excess typically observed in metabolic disorders (MD), such as overweight/obese comorbid patients, metabolic syndrome (MS), and type 2 diabetes (T2D). Interleukin 1β, 6, 17, 18, and 23 and tumor necrosis factor-α play a crucial role in initiating and maintaining entheseal inflammation. Chronic hyperglycemia and insulin resistance lead to a vicious circle as they stimulate, upon activated, specialized T cells to produce these specific cytokines, thus maintaining entheseal inflammation chronically. MD is associated with more severe clinical presentation, worse response to pharmacological treatments, and poor entheseal outcomes also in patients with existing seronegative spondyloarthritis. Non-immune-mediated metabolic-associated enthesitis poses a real diagnostic challenge, possibly underestimating cases and potential misdiagnoses. From a therapeutic viewpoint, glucose control improvement and weight loss are associated with relevant amelioration of entheseal-related outcomes. Pharmacological and non-pharmacological interventions aiming to reduce body weight, improve glucose control and insulin sensitivity, and attenuate inflammation are desirable to achieve the therapeutic target. Glucagon-like peptide 1 receptor agonists and sodium-glucose co-transporter type 2 inhibitors, in add-on to non-steroidal anti-inflammatory drugs and immunomodulators when necessary, may have a therapeutic rationale in patients with metabolic-associated enthesitis. Awareness of metabolic-associated enthesitis is essential to improve the accuracy of differential diagnosis in patients with MD and prescribe appropriate therapeutic strategies. However, basic and clinical research is needed to understand the role of "antihyperglycemic" agents in better managing metabolic-associated enthesitis.