12 January - 20 June 2016

The health benefits of olive oil and olives uncovered

The health benefit of olives and olive oil has long been recognised, however little has been known about what specific compounds are responsible. A study published in the journal Biochemistry by a Virginia Tech research team, has investigated the compound oleuropein, a natural product derived from olive leaves which has been reported to have beneficial anti-diabetic properties, although the mechanisms by which oleuropein contributes to this anti-diabetes function has, up until now been poorly understood.

The health benefit of olives and olive oil has long been recognised, however little has been known about what specific compounds are responsible. A study published in the journal Biochemistry by a Virginia Tech research team, has investigated the compound oleuropein, a natural product derived from olive leaves which has been reported to have beneficial anti-diabetic properties, although the mechanisms by which oleuropein contributes to this anti-diabetes function has, up until now been poorly understood. 

By screening a library of natural compounds, which have been reported to have anti-diabetic functions in complementary medicine, based on a thioflavin T fluorescence assay, Xu et al. discovered multiple health benefits of oleuropein.  The scientists hypothesised that oleuropein may have similar biological functions to gensitein (an isoflavone, found in a number of plants including lupin, fava beans, soybeans, kudzu, and psoralea – Wikipedia) as both compounds have "the potential to active G-protein-coupled estrogen receptor GPER/GPR30."  Genistein has a biological function of anti-diabetic insulin secretion (GSIS).  Therefore Xu et al. investigated the effect of oleuropein on INS-1 β-cells (cells in the pancreas that produce, store and release the hormone insulin) followed by enzyme linked immunosorbent assay measurement of secreted insulin concentrations.

Increasing doses of oleuropein caused significant increases in the level of insulin secretion.  "Increases of 10-20% in the levels of insulin secretion were observed at 30 µM" of oleuropein, a level of increase similar to that of genistein.  The GSIS agonist, glucagon-like peptide 1, was used as a positive control.  The team then further investigated structural analogues (a compound having a structure similar to that of another one, but differing from it in respect of a certain component).  Ligostride was found to retain GSIS function "with a potency similar to that of oleuropein", whilst another structural component of oleuropein, elenolic acid showed no GSIS activity.

Xu et al. also performed cell signalling analyses in INS-1 β-cells using a pharmacological inhibitor approach, testing the involvement of major kinase pathways related to metabolism.  Oleuropein detoxifies another signalling molecule, amylin, that over-produces and forms harmful aggregates in type 2 diabetes.  "Insulin resistance associated hyper-amylineamia can lead to toxic amylin amyloid deposits in the pancreas, which occurs in up to 90% of type 2 diabetes patients.  Together this, and its ability to help the body secrete more insulin, can help prevent the onset of disease."  

In conclusion, the authors state "our work provides new mechanistic insights into the long-standing question of why olives products can be anti-diabetic". They report that the next steps are testing the compound in a diabetic animal model and testing its additional new function on metabolism and aging.

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