In muscle tissue, the olive phytochemical oleuropein imitates the effect of insulin
Oleuropein is a phytochemical found in olives and olive oil. Especially green olives and virgins contain lots of it. According to Japanese researchers at the University of Ochanomizu and the Eisai Food & Chemical Corporation, oleuropein imitates the effect of insulin. It increases the uptake of glucose by muscle cells.
The researchers experimented with mice. For 12 weeks they gave a part of their lab animals standard feed [NFD], and another part feed in which they had hidden extra fat [HFD]. Some of the mice in the latter group were given oleuropein as well.
The human equivalent of the dose given to the mice was roughly 400-600 milligrams per day. That's pretty much.
Oleuropein supplementation had no effect on the body composition of the mice, but improved their sensitivity to insulin. Their HOMA-IR, a measure of insulin resistance, decreased. Oleuropein supplementation could roughly halve the negative effect of the high fat diet on insulin sensitivity.
When the researchers started experimenting with muscle cells in test tubes, they discovered that at a concentration of 10 and 100 micromoles oleuropein imitated the effect of insulin, and stimulated the muscle cells to absorb more glucose. In the muscle cells, oleuropein activated the glucose transporter GLUT4.
The switching on of GLUT4 was the result of an activation of the AMPK enzyme by oleuropein, and not of the activation of Akt. Insulin works via triggering Akt. The beneficial effect of oleuropein on glucose metabolism is therefore independent of that of insulin.
Muscle cells become insensitive to insulin due to high concentrations of saturated fatty acids, such as palmitic [PA]. Therefore, obesity can cause type-2 diabetes. Oleuropein could partially cancel that effect.
"Human studies that evaluated olive oil or Mediterranean diet demonstrated its beneficial effects on cardiovascular health and metabolic syndrome", write the researchers.
"We suggest that one of the mechanisms of oleuropein might be improvement of insulin sensitivity in skeletal muscle by stimulation of GLUT4 translocation independently of insulin signals."
J Clin Biochem Nutr. 2017 Nov;61(3):196-202.
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