Do low EPA levels and a high arachidonic acid–to–EPA ratio drive persistent low-grade inflammation?

The balance between omega-6 arachidonic acid (AA) and omega-3 eicosapentaenoic acid (EPA) is a critical determinant of systemic inflammatory tone. When this ratio is skewed, it alters cellular signaling pathways and prevents the normal resolution of inflammatory responses.

Mechanistic pathways of eicosanoid signaling

• Enzymatic competition: A high AA/EPA ratio increases the relative availability of AA substrate. This allows AA to outcompete EPA for cyclooxygenase (COX) and lipoxygenase (LOX) enzymes.
• Pro-inflammatory mediator production: This enzymatic dominance drives the synthesis of classic pro-inflammatory eicosanoids, such as prostaglandin E2 (PGE2) and leukotriene B4 (LTB4), which promote vascular permeability and leukocyte recruitment.
• Downstream biomarker elevation: These AA-derived mediators stimulate the production of interleukin-6 (IL-6), which subsequently triggers hepatic synthesis of high-sensitivity C-reactive protein (hs-CRP), a key clinical marker of systemic inflammation.

Impaired resolution and systemic inflammation

• Deficiency in resolving mediators: Low circulating EPA levels restrict the biological substrate required to synthesize E-series resolvins and other specialized pro-resolving mediators (SPMs).
• Failure to terminate inflammation: Without adequate SPMs, the active processes required to clear cellular debris, decrease vascular permeability, and cease leukocyte activity are severely compromised.
• Sustained inflammatory state: The combination of active pro-inflammatory eicosanoid signaling and failed resolution pathways prevents the termination of the inflammatory response, allowing low-grade systemic inflammation to persist.

Bottom line

• An elevated AA/EPA ratio and low EPA levels drive chronic, low-grade inflammation. This state is maintained by a dual mechanism: the overproduction of pro-inflammatory eicosanoids (PGE2, LTB4) and a compromised capacity to synthesize the specialized pro-resolving mediators (E-series resolvins) necessary to actively terminate the inflammatory response.