Interleukin-18 and the NLR family pyrin domain containing-3 inflammasome in adipose tissue are strongly associated with glucometabolic variables in a cohort of middle-aged men

Abstract

Background: Previous studies have indicated an association between interleukin-18 and glucose. Interleukin-18 becomes active when cleaved by caspase-1, activated by the NLR family pyrin domain containing-3 inflammasome. Aim: To investigate associations between glucometabolic variables and serum levels of interleukin-18 and genetic expression of interleukin-18, caspase-1 and NLR family pyrin domain containing-3 in adipose tissue and circulating leukocytes, and whether these mediators are related to the amount of abdominal adipose tissue. Materials and Methods: Fasting blood samples and subcutaneous adipose tissue were collected in a cohort of 103 middle-aged men. Serum levels of interleukin-18 were determined by enzyme-linked immunosorbent assay, gene expression by real-time polymerase chain reaction and insulin sensitivity by glucose clamp. The distribution of abdominal adipose tissue, separated into superficial- and deep subcutaneous, and visceral adipose tissue, was assessed by computed tomography scan. Results: Glucometabolic variables correlated significantly to serum levels of interleukin-18, and to the expression of interleukin-18 and NLR family pyrin domain containing-3 in subcutaneous adipose tissue (p < 0.05). Significant correlations were further observed between the amount of fat in the different compartments of abdominal adipose tissue and both serum levels of interleukin-18 and genetic expression of interleukin-18 and NLR family pyrin domain containing-3 in adipose tissue. Conclusion: The results implicate that the glucometabolic state is of importance for the inflammasome-related inflammation expressed both circulatory and genetically in subcutaneous adipose tissue, the latter highly reflected in the amount of abdominal adipose tissue.