All Up in Knots

Food full of sat­u­rated fat is the usual sus­pect, but could clogged ar­ter­ies be due to bac­te­ria?

ZOOMER Magazine - - CONTENTS - By Dr. Zachary Levine

Could clogged ar­ter­ies be due to bac­te­ria in­stead of fatty foods?

HEART AT­TACKS and strokes are caused by blocked ar­ter­ies, which are the blood ves­sels – es­sen­tially pipes – that de­liver oxy­gen- and nu­tri­ent-rich blood through­out the body, in­clud­ing to the heart and brain. Ath­er­o­scle­ro­sis is the term used to de­scribe the process whereby fatty sub­stances (lipids) stick to blood ves­sel walls and nar­row them. The ves­sel walls be­come in­flamed, and this leads to pro­gres­sion. An atheroma is an ac­cu­mu­la­tion of de­gen­er­a­tive ma- terial in the in­ner layer of an artery wall, con­sist­ing mostly of cells, de­bris, lipids, cal­cium and fi­brous con­nec­tive tis­sue.

It was as­sumed un­til re­cently that the lipids that con­trib­ute to ath­er­o­scle­ro­sis come from eat­ing foods high in fat and choles­terol, such as but­ter, eggs, meat and fried foods. There is new ev­i­dence, how­ever, that shows that the lipids in the plaque that clogs up our ar­ter­ies are ac­tu­ally made from bac­te­ria that live in most hu­mans’ mouths and guts, not only from what we eat. That said, re­gard­less of th­ese find­ings, trans fats are just bad for us, pe­riod. And con­sum­ing a large amount of sat­u­rated fat, such as those from the list above, can drive up bad choles­terol, so moder­a­tion or re­plac­ing sat­u­rated fat with polyun­sat­u­rated fats – nuts, fish, seeds, etc. – is still best for de­creas­ing the risk of heart dis­ease.

Re­searchers at the Univer­sity of Con­necti­cut found that the lipids found in athero­mas are made by a spe­cific fam­ily of bac­te­ria called Bac­teroidetes. Th­ese bac­te­ria, which col­o­nize the mouth and gut, do not usu­ally cause harm. The lipids they se­crete, how­ever, can get through cell walls and into the blood­stream.

The team sug­gests that per­haps the im­mune sys­tem trig­gers in­flam­ma­tion be­cause, when it en­coun­ters the fatty de­posits in the artery walls, it rec­og­nizes that the lipids are for­eign. The re­searchers also found that there is an en­zyme that breaks down the bac­te­rial lipids into start­ing ma­te­ri­als for mak­ing mol­e­cules that pro­mote in­flam­ma­tion.

The pres­ence of bac­te­rial lipids may cause harm in two ways: first, the im­mune sys­tem spots them and sets off alarm sig­nals, and se­condly, the en­zyme breaks them down into ma­te­ri­als that as­sist in­flam­ma­tion. All this would lead to worse ath­er­o­scle­ro­sis and in­crease the risk of heart at­tack and stroke. Re­searchers are in­ves­ti­gat­ing what af­fects the rel­a­tive amount of the bac­te­ria we have and if low­er­ing the counts will de­crease heart dis­ease risk. The next step is to con­firm that th­ese bac­te­ria are in­deed in­volved in the de­vel­op­ment of ath­er­o­scle­ro­sis and to find treat­ments that will tar­get the bac­te­ria and thereby de­crease the risk of heart at­tack and stroke.

Stay tuned!

Dr. Zachary Levine is an as­sis­tant pro­fes­sor in the fac­ulty of medicine at McGill Univer­sity Health Cen­tre and med­i­cal cor­re­spon­dent for AM740 (a ZoomerMe­dia prop­erty).

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