Circulating Interleukins-33 and -37 and Their Associations with Metabolic Syndrome in Arab Adults

Interleukins (ILs) are a group of cytokines known to have immunomodulatory effects; they include ILs–33 and –37 whose emerging roles in the pathogenesis of metabolic syndrome (MetS) remain under investigated. In this study, we compared circulating IL–33 and IL–37 in Arab adults with and without MetS to determine its associations with MetS components. A total of 417 Saudi participants (151 males, 266 females; mean age ± SD 41.3 ± 9.0 years; mean body mass index ± SD 30.7 ± 6.3 kg/m2) were enrolled and screened for MetS using the ATP III criteria. Anthropometrics and fasting blood samples were taken for the assessment of fasting glucose and lipids. Circulating levels of IL–33 and IL–37 were measured using commercially available assays. The results showed higher levels of serum IL–33 and IL–37 in participants with MetS than those without (IL-33, 3.34 3.42 (2.3–3.9) vs. (1–3.9), p = 0.057; IL-37, 5.1 (2.2–8.3) vs. 2.9 (2.1–6.1), p = 0.01). Additionally, having elevated levels of IL–33 was a risk factor for hypertension, low HDL-c, and hypertriglyceridemia. A stratification of the participants according to sex showed that males had higher IL-33 levels than females [3.7 (3.0–4.1) vs. 3.15 (1.4–3.8), p < 0.001], while females had higher levels of IL–37 than males [3.01 (2.2–7.0) vs. 2.9 (2.1–5.6), p = 0.06]. In conclusion, the presence of MetS substantially alters the expression of ILs–33 and -37. IL-33 in particular can be potentially used as a therapeutic target to prevent MetS progression. Longitudinal and interventional studies are warranted to confirm present findings.