Circulating Omentin-1 levels and altered iron balance in chronic haemodialysis patients

BACKGROUND: Iron deficiency is highly prevalent among patients undergoing chronic haemodialysis (HD) but its correct identification is often problematic as common biomarkers of iron status, such as transferrin saturation (TSAT) and ferritin, can be altered by inflammation or malnutrition. METHODS: In this pilot multicentre study, we aimed at evaluating circulating levels of Omentin-1, a novel fat depot-specific adipokine that is also involved in iron regulation, in a cohort of 85 chronic HD patients with relation to their iron status. RESULTS: Omentin-1 levels in HD were statistically higher than in healthy controls (P = 0.03) and there was a significant, growing trend in all iron parameters across Omentin-1 tertiles (P < 0.001). Compared with patients with optimal iron status, Omentin-1 levels were lower in subjects categorized according to TSAT ≤20% or serum ferritin ≤200 μg/L (both P < 0.001) and even more reduced in 19 patients (22%) simultaneously displaying low levels of both markers (P < 0.001). In this latter group, Omentin-1 levels increased in parallel to all other iron markers after iron correction by i.v. supplementation. At multivariate regression analyses, ferritin (β = 0.71; P < 0.001) and TSAT (β = 0.32; P = 0.03) remained the sole independent predictors of Omentin-1 levels. This biomarker also showed a remarkable diagnostic capacity at receiver operating characteristic analyses in identifying iron-depleted HD patients according to a criterion of TSAT ≤20% [area under the curve (AUC) 0.827], ferritin ≤200 μg/L (AUC 0.863) or low levels of both parameters (AUC 0.907). CONCLUSIONS: Findings obtained indicate that Omentin-1 is somewhat involved in iron balance regulation and might be a candidate biomarker for diagnosing and managing altered iron conditions in HD patients.