`Polyphenol in EVOO May Shield Kidneys from Diabetes-Related Damage, Study Finds - Olive Oil Times

Polyphenol in EVOO May Shield Kidneys from Diabetes-Related Damage, Study Finds

By Simon Roots
Nov. 6, 2023 15:12 UTC

In the first study of its kind, a team from the Málaga Biomedical Research Institute and Nanomedicine Platform and the University of Málaga has exam­ined the abil­ity of a trace polyphe­nol found in extra vir­gin olive oil to pro­tect against kid­ney dam­age asso­ci­ated with type 1 dia­betes.

In addi­tion to the acute com­pli­ca­tions of dia­betes, long-term hyper­glycemia dam­ages the small blood ves­sels through­out the body.

This dam­age fre­quently leads to dia­betic nephropa­thy, the chronic loss of kid­ney func­tion in suf­fer­ers of dia­betes mel­li­tus and the lead­ing cause of chronic kid­ney dis­ease and end-stage renal dis­ease world­wide.

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Approximately 30 per­cent of type 1 dia­betes patients and 40 per­cent of type 2 dia­betes patients develop chronic kid­ney dis­ease.

Maintaining proper blood sugar lev­els through reg­u­lar mon­i­tor­ing, insulin ther­apy, diet and exer­cise is the most effec­tive cur­rent approach to delay­ing and less­en­ing the impact of these con­di­tions.

However, many patients strug­gle to man­age their blood glu­cose in real-world clin­i­cal set­tings.

Therefore, the research aimed to explore addi­tional meth­ods to shield the kid­neys from poten­tial dia­betes-related harm.

Given that oxida­tive stress is a fun­da­men­tal con­trib­u­tor to the for­ma­tion of kid­ney lesions in dia­betes and that numer­ous com­pounds present in extra vir­gin olive oil are known to exhibit antiox­i­dant effects, the team focused on extra vir­gin olive oil to mit­i­gate this mech­a­nis­m’s impact on kid­ney dam­age.

Oxidative stress, a com­mon fea­ture in uncon­trolled dia­betes, induces inflam­ma­tion, increases glomeru­lar (kid­ney fil­ter­ing) vol­ume, impairs glomeru­lar func­tion and ele­vates uri­nary pro­tein excre­tion.

Hydroxytyrosol, a polyphe­nol and par­tic­u­larly potent antiox­i­dant found in sig­nif­i­cant con­cen­tra­tions in extra vir­gin olive oil, has already shown poten­tial in pre­vent­ing car­dio­vas­cu­lar and neural dam­age in dia­betic rats.

Extra vir­gin olive oil also con­tains 3,4‑dihydroxyphenylglycol (DHPG), posited to enhance the effects of other polyphe­nols when admin­is­tered in con­junc­tion.


Polyphenols are a group of nat­ural com­pounds found in plants, includ­ing olives, known for their antiox­i­dant prop­er­ties. They have var­i­ous health ben­e­fits, includ­ing poten­tial pro­tec­tion against car­dio­vas­cu­lar and neu­rode­gen­er­a­tive dis­eases. Extra vir­gin olive oil is renowned for its rich polyphe­nol con­tent, which not only pro­vide it with most of its health ben­e­fits but also con­tribute to its unique fla­vor and aroma. Overall, there are 25 polyphe­nols in extar vir­gin olive oil, includ­ing oleo­can­thal, olea­cein, oleu­ropein and hydrox­y­ty­rosol.

While pre­vi­ous stud­ies have shown its effects in hypoxia-reoxy­gena­tion exper­i­ments and on car­dio­vas­cu­lar bio­mark­ers, its poten­tial to pro­tect the kid­neys from oxida­tive stress had not been explored.

DHPG, a minor phe­no­lic com­pound found in extra vir­gin olive oil, exhibits antiox­i­dant and anti-inflam­ma­tory prop­er­ties.

Although it is in smaller quan­ti­ties than other polyphe­nols such as hydrox­y­ty­rosol, DHPG has demon­strated its effects in in vitro and ex vivo exper­i­ments, includ­ing in a pre­vi­ous type 1 dia­betes model.


The research team found that DHPG decreased blood glu­cose lev­els in their sub­jects, a valu­able attribute as sus­tained hyper­glycemia is a fun­da­men­tal ele­ment in the pro­gres­sion of renal dam­age in dia­betes.

DHPG also demon­strated an antiox­i­dant effect on all mea­sured para­me­ters, albeit quan­ti­ta­tively lower than the antiox­i­dant impact ascribed to hydrox­y­ty­rosol. While DHPG’s antiox­i­dant effect has been shown in other tis­sues, data spe­cific to kid­ney tis­sue has not pre­vi­ously been widely pub­lished.

In addi­tion, the researchers found that DHPG par­tially reduces throm­box­ane pro­duc­tion (which nar­rows the blood ves­sels) and coun­ter­acts the reduced pro­duc­tion of prosta­cy­clin (which widens the blood ves­sels) induced by dia­betes mel­li­tus.

This effect was sta­tis­ti­cally sig­nif­i­cant at a dose of 1 mil­ligram per kilo­gram daily. An imbal­ance in the throm­box­ane-to-prosta­cy­clin ratio is tra­di­tion­ally asso­ci­ated with an increased risk of throm­bo­sis.

Therefore, DHPG’s influ­ence on this ratio could improve renal blood flow and poten­tially decrease dia­betic nephropa­thy.

Finally, the study demon­strated that DHPG impacts sev­eral key para­me­ters related to renal func­tion.

It reduces pro­tein excre­tion in urine, increases cre­a­ti­nine clear­ance and lessens the increase in glomeru­lar vol­ume and the extent of glomeru­loscle­ro­sis (hard­en­ing or scar­ring of the kidney’s fil­ter­ing blood ves­sels.)

The reduc­tion in pro­tein­uria was deemed par­tic­u­larly sig­nif­i­cant, as it is linked to slow­ing nephropa­thy pro­gres­sion.

When ana­lyz­ing these para­me­ters with bio­chem­i­cal vari­ables, the researchers con­cluded that DHPG’s mech­a­nisms are sig­nif­i­cantly related to renal func­tion and struc­ture changes. Consequently, the over­all effect of DHPG may be a com­bi­na­tion of mod­i­fi­ca­tions in these bio­chem­i­cal vari­ables.

The team believes their study shows promis­ing evi­dence that the admin­is­tra­tion of DHPG to rodents with type 1 dia­betes pro­duces a nephro­pro­tec­tive effect.”

This is prob­a­bly due to the sum of its antiox­i­dant, anti-nitrosative and prosta­cy­clin-pro­duc­tion reg­u­lat­ing effects,” they added. It is expected that the syn­ergy of this prod­uct with other polyphe­no­lic com­pounds will improve renal pro­tec­tion [against con­di­tions] induced by dia­betes mel­li­tus.”

They also hope their research will lead to fur­ther stud­ies into how the effects of DHPGs might inter­act with the estab­lished ben­e­fi­cial effects of extra vir­gin olive oil attrib­uted to its polyphe­nol con­tent. The pos­si­bil­ity of DHPG exert­ing a syn­er­gis­tic influ­ence with hydrox­y­ty­rosol has been pos­tu­lated since both polyphe­nols are com­po­nents of extra vir­gin olive oil.

Previous stud­ies have shown that extra vir­gin olive oil’s car­dio­vas­cu­lar and neu­ro­pro­tec­tive effects are not solely attrib­ut­able to hydrox­y­ty­rosol.

DHPG, in par­tic­u­lar, has been iden­ti­fied as one of the key polyphe­nols in extra vir­gin olive oil that exhibits an in vitro neu­ro­pro­tec­tive syn­er­gis­tic effect with hydrox­y­ty­rosol in a pro­por­tion sim­i­lar to that found in extra vir­gin olive oil itself.


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