Circulating isthmin-1 is associated with short-term metabolic changes after sleeve gastrectomy.

Isthmin-1 (ISM1) is a recently identified adipokine implicated in glucose and lipid metabolism. This prospective cohort study investigated early changes in circulating ISM1 after sleeve gastrectomy (SG) in patients with severe obesity. Thirty-three patients with severe obesity undergoing SG and 29 age- and sex-matched lean controls were included. Dietary history, anthropometric and bioimpedance-based body composition measurements, and fasting blood samples were obtained preoperatively and at the third postoperative month. Serum ISM1, leptin, and adiponectin were measured by enzyme-linked immunosorbent assay (ELISA); biochemical and hormonal parameters were analyzed using standard laboratory methods. Preoperative ISM1 and leptin levels were higher in patients with severe obesity than in controls (p < 0.001), whereas adiponectin was lower (p = 0.002). ISM1 correlated positively with body fat percentage and leptin levels, and negatively with neck circumference in the preoperative severe obesity group. Three months after SG, anthropometric measures, insulin resistance, and inflammatory parameters changed significantly. ISM1 and leptin decreased by 82.7 and 83.1%, respectively, while adiponectin increased by 12.6%. In exploratory correlation analyses, percentage changes in ISM1 were associated with percentage changes in insulin and homeostatic model assessment of insulin resistance (HOMA-IR). Circulating ISM1 levels were elevated in patients with severe obesity and decreased markedly three months after SG. Postoperative percentage changes in ISM1 were associated with early changes in insulin resistance-related parameters, particularly fasting insulin and HOMA-IR. These findings suggest that circulating ISM1 may reflect early metabolic changes after sleeve gastrectomy, particularly in relation to insulin resistance-related changes, and warrant validation in larger longitudinal studies.