ABSTRACT
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 (ETB) improves insulin sensitivity in rats and leads to increased circulating adiponectin, suggesting that ETB 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 ETB receptor. METHODS: Male adipocyte-specific ETB receptor knockout (adETBKO), overexpression (adETBOX), 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 adETBKO mice. KEGG analysis indicated significant increase in metabolic signaling pathway. HFD adETBKO mice had significantly improved glucose and insulin tolerance compared to HFD control. In addition, adETBKO 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 ETB 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 ETB receptor on adipocytes.
Subject(s)
Adipocytes , Adiponectin , Diet, High-Fat , Insulin Resistance , Mice, Knockout , Obesity , Receptor, Endothelin B , Animals , Insulin Resistance/physiology , Receptor, Endothelin B/metabolism , Receptor, Endothelin B/genetics , Male , Adiponectin/metabolism , Adiponectin/genetics , Mice , Obesity/metabolism , Obesity/genetics , Adipocytes/metabolism , Mice, Obese , Mice, Inbred C57BLABSTRACT
PcsB of Streptococcus pneumoniae is an essential hydrolase involved in the separation of dividing cells. In this study, it was found that PcsB localizes to the plasma membrane and is released into the growth environment, yet it is detectable on the pneumococcal surface by flow cytometry analysis. High temperature and osmolarity led to upregulation of pcsB expression.