Adipocyte endothelin B receptor activation inhibits adiponectin production and causes insulin resistance in obese mice

Aims: Endothelin-1 (ET-1) is elevated in patients with obesity and adipose tissue of obese mice fed high-fat diet (HFD); however, its contribution to the pathophysiology of obesity is not fully understood. Genetic loss of endothelin type B receptors (ET_B) improves insulin sensitivity in rats and leads to increased circulating adiponectin, suggesting that ET_B activation on adipocytes may contribute to obesity pathophysiology. We hypothesized that elevated ET-1 in obesity promotes insulin resistance by reducing the secretion of insulin sensitizing adipokines, via ET_B receptor.

Methods: Male adipocyte-specific ET_B receptor knockout (adET_BKO), overexpression (adET_BOX), or control littermates were fed either normal diet (NMD) or high-fat diet (HFD) for 8 weeks.

Results: RNA-sequencing of epididymal adipose (eWAT) indicated differential expression of over 5500 genes (p < 0.05) in HFD compared to NMD controls, and changes in 1077 of these genes were attenuated in HFD adET_BKO mice. KEGG analysis indicated significant increase in metabolic signaling pathway. HFD adET_BKO mice had significantly improved glucose and insulin tolerance compared to HFD control. In addition, adET_BKO attenuated changes in plasma adiponectin, insulin, and leptin that is observed in HFD versus NMD control mice. Treatment of primary adipocytes with ET-1 caused a reduction in adiponectin production that was attenuated in cells pretreated with an ET_B antagonist.

Conclusion: These data indicate elevated ET-1 in adipose tissue of mice fed HFD inhibits adiponectin production and causes insulin resistance through activation of the ET_B receptor on adipocytes.