B lymphocyte stimulator (BLyS) is a novel adipokine in humans in vivo being related to obesity but not to insulin resistance
Background and Objective: B lymphocyte stimulator (BLyS) was considered as a novel adipokine in mice inducing low-grade inflammation and insulin resistance in obesity. Therefore, our aim was to examine (1) whether BLyS expression in human adipocytes in vivo differs between lean and obese ± insulin resistant subjects, (2) whether BLyS serum concentrations are dysregulated in obesity ± insulin resistance, (3) whether BLyS responds to different weight loss therapies and (4) whether inhibition of BLyS in humans in vivo by a neutralizing antibody (belimumab) alters insulin sensitivity.
Methodology: BLyS expression in adipose tissue biopsies was examined by immunohistology and RT-PCR. BLyS levels during human preadipocyte differentiation were determined by western-blotting. Serum samples were studied by ELISA in three study populations (1) 10 lean controls and 20 obese human subjects ± insulin resistance, (2) 16 obese patients receiving a very-low-calorie-diet (VLCD) and (3) 26 obese patients undergoing bariatric surgery. Furthermore, insulin sensitivity was measured in 5 human subjects treated with belimumab.
Results: BLyS is expressed in mature adipocytes in vivo and during human preadipocyte differentiation ex vivo. Expression levels in adipose tissue are increased in obesity but are not related to insulin resistance. Weight loss due to bariatric surgery significantly altered BLyS serum concentrations, whereas a VLCD had no effect. Finally, BLyS inhibition in humans by belimumab treatment did not affect in vivo insulin sensitivity.
Conclusion: BLyS is a novel adipokine in humans which is induced in obesity but seems to have only a minor role in the pathogenesis of insulin resistance.