Extra virgin olive oil increases uncoupling protein 1 content in brown adipose tissue and enhances noradrenaline and adrenaline secretions in rats

Abstract

Olive oil is an integral ingredient of the Mediteranean diet. The effects of extra virgin olive oil (EVOO) on triglyceride metabolism were investigated by measuring the degree of thermogenesis in interscapular brown adipose tissue (IBAT), and the rates of noradrenaline and adrenaline secretions in rats, both in vivo(Experiment 1) and in situ(Experiment 2). In Experiment1, rats were given an isoenergetic high-fat diet containing corn oil, refined-olive oil or EVOO for 28 days. The phenolic contents in refined-olive oil and EVOO were 0 and 141mg (oleuropein aglycone 104mg)/kg respectively. After 28 days of feeding, the final body weight, perirenal adipose tissue, and epididymal fat pad and plasma triglyceride concentrations were the lowest in rats fed EVOO diet. The content of UCP1 in IBAT and the rates of urinary noradrenaline and adrenaline excretions were the highest in the rats fed the EVOO diet. In Experiment 2, the intravenous administration of oleuropein and oleuropein aglycone significantly increased plasma noradrenaline and adrenaline concentrations. Furthermore, oleuropein aglycone induced the secretions of noradrenaline and adrenaline about ten fold more potently than oleuropein. These results suggest that the phenolic compounds, oleuropein and oleuropein aglycone in EVOO enhance thermogenesis by increasing the UCP1 content in IBAT and noradrenaline and adrenaline secretions in rats.