IL-6 gene expression in adipose tissue of postmenopausal women and its association with metabolic risk factors

• Interleukin 6 (IL-6) secreted by visceral or subcutaneous adipose may be associated with metabolic risk factor in postmenopausal women.
• In postmenopausal women with metabolic syndrome, the relative mean IL-6 mRNA expression in subcutaneous adipose tissue (SAT) was significantly higher than visceral adipose tissue (VAT).
• In postmenopausal women with metabolic syndrome, relative VAT IL-6 mRNA expression significantly and inversely correlated with WC, WHR, glucose, HOMA, TC, LDL and estrogen while relative SAT IL-6 mRNA expression significantly and inversely correlated with WC, WHR and estrogen.
• In postmenopausal women with metabolic syndrome, relative VAT IL-6 mRNA expression may be a significant and independent predictor of metabolic risk factors WC, HOMA, TC, LDL and estrogen while relative SAT IL-6 mRNA expression may be a significant an independent predictor of TG and VLDL.
• Subcutaneous adipose tissue with increased IL-6 may be a pathogenic depot.

Adipose tissue secretes various kinds of adipokines that controls the glucose and lipid metabolism in humans. The abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) both are associated with metabolic syndrome and insulin resistance. IL-6 is one of the adipokines, which promotes insulin resistance and dyslipidemia in humans. The association of adipokines with metabolic syndrome at protein levels are well documented. However, their association at gene expression level are lacking. The present study was design to investigate IL-6 mRNA expression in adipose tissues (VAT and SAT) and its correlation with metabolic risk factors and insulin resistance (HOMA) in post menopausal women. A total of 108 Asian North Indian post menopausal women, 54 without metabolic syndrome (controls) and 54 with metabolic syndrome (cases) were recruited and evaluated. Overnight fasting blood samples were collected at admission and abdominal visceral and subcutaneous adipose tissues were collected during open abdomen surgery. The results showed significantly (p < 0.05 or p < 0.01 or p < 0.001) higher mean SBP, glucose, insulin, HOMA, TG, VLDL and serum IL-6 while significantly (p < 0.001) lower HDL and estrogen in cases as compared to controls. In cases, the relative mean SAT IL-6 expression was also significantly (p < 0.05) higher as compared to VAT. Further, in cases, the VAT IL-6 expression showed significant (p < 0.05 or p < 0.001) and negative correlation with WC, WHR, glucose, HOMA, TC, LDL and estrogen while SAT IL-6 expression also showed significant (p < 0.05 or p < 0.01 or p < 0.001) and negative correlation with WC, WHR and estrogen. The Cox regression analysis found VAT IL-6 mRNA expression the significant (p < 0.05 or p < 0.01) an independent predictor of WC, HOMA, TC, LDL and estrogen while SAT IL-6 mRNA expression the significant (p < 0.01) an independent predictor of TG and VLDL. The study concluded that IL-6 expressions of both visceral and subcutaneous tissues may be associated with metabolic risk factors in postmenopausal Asian North Indian women.