Vaspin, designated as visceral adipose tissue-derived serpin A12, is an adipokine with insulin-sensitizing effects. Vaspin mRNA expression is specific for visceral adipose tissues and it is also found circulating in serum. The level of serum vaspin increases with age up to the peak of obesity, body weight, and insulin resistance in OLETF rats, an animal model of abdominal obesity with type 2 diabetes. Treatment with insulin or pioglitazone normalizes serum vaspin concentrations in this model. As such, vaspin may be regarded as a potential biomarker for obesity and impaired insulin sensitivity. Cayman's Vaspin (human) EIA Kit can be used to measure vaspin in human serum, plasma, or cell culture supernatants.