The present study demonstrates, for the first time, that IL-34 is expressed in human adipose tissues and the circulating concentration is significantly elevated in obese patients. This suggests that IL-34 is associated with insulin resistance.

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Visceral adipose tissue‐derived serpin (vaspin) has been regarded as a novel adipokine with potential insulin sensitizing properties. We investigated the changes of serum vaspin concentration in response to weight reduction, and the associations between changes in serum vaspin concentrations and changes of anthropometric and metabolic variables in obese subjects after weight reduction. We performed a longitudinal clinical intervention study on 63 obese persons enrolled in a 12‐week weight reduction program that included lifestyle modification and adjuvant treatment with the antiobesity agent orlistat. Anthropometric variables, lipid profiles, fasting glucose, fasting insulin, and serum vaspin concentrations were measured. Statistical analyses were performed according to the homeostasis model assessment of insulin resistance (HOMAIR). Serum vaspin concentrations decreased significantly in responders (≥2% reduction in baseline weight), but not in nonresponders (<2% reduction in baseline weight). Changes in serum vaspin concentrations were significantly correlated with body weight, BMI, waist circumference, and hip circumference in the higher, but not in the lower, HOMAIR group. In multivariate linear regression analysis, change in serum vaspin concentrations in the higher, but not in the lower, HOMAIR group was positively correlated with change in BMI and negatively correlated with initial HOMAIR level. The associations between changes in serum vaspin concentrations and changes in anthropometric and metabolic parameters differed according to insulin resistance status in obese subjects. These relationships were more prominent in the higher HOMAIR group. Insulin resistance may influence the correlations between changes in serum vaspin concentration and related metabolic variables.