Irisin expression in subcutaneous adipose tissue in obese patients with type 2 diabetes increases one year after bariatric surgery

Aim: Gastric bypass surgery improves glycaemic control, but the underlying mechanisms including potential changes in adipoinsular axis are incompletely understood. The aim of this study was to investigate potentially causal or associated alterations in gene expression of adipokines, myokines and hormones in the subcutaneous and visceral adipose tissue of diabetic and non-diabetic obese subjects before and after gastric bypass.

Material and methods: Biopsy specimens from the subcutaneous adipose tissue of 12 diabetic and 12 non-diabetic patients at and one year after gastric bypass were analyzed with quantitative real-time PCR for the expression levels of various adipokines, myokines and hormones such as adiponectin, leptin, irisin (FNDC5), osteocalcin and osteopontin.

Results: Non-diabetic subjects were found to express significantly higher levels of FNDC5 in the subcutaneous adipose tissue than diabetic subjects before gastric bypass (p = 0.0167). FNDC5 expression in the subcutaneous adipose tissue of diabetic patients was significantly increased one year after surgery (p < 0.001). In non-diabetic subjects, there was no significant increase observable (p = 0.158). The increase in FNDC5 in diabetic subjects correlated with reduction in BMI (Pearson's r = 0.718, p = 0.009). No correlation was observed between FNDC5 expression and early insulin response or insulin sensitivity index.

Conclusion: To our knowledge, this is the first study to investigate the role of the novel myokine irisin in bariatric surgery mediated weight loss. The results of this study demonstrate that exercise-independent weight loss increases irisin expression levels in subcutaneous adipose tissue of diabetic subjects