Endocrine Abstracts

Background: Diets rich in polyunsaturated fatty acids (PUFA) n-3 may change the fluidity and composition of membrane phospholipids, leading to different prostanoids formation, decreasing IL-1β and TNFα releases and increasing the basal levels of corticosterone, important factors to promote acute phase response (APR) to stimuli. This study proposes to verify if PUFA n-3 or n-6 rich diets alters the APR of fibrinogen and haptoglobin after turpentine stimulus.

Methods: Three male Wistar rat groups were differently fed, one with standard chow diet (control group), another with standard chow diet plus 15% of soybean oil (PUFA n-6) (soybean group), and the last one with standard chow diet plus 15% of fish oil (PUFA n-3) (fish group), for seven weeks. Each experimental group was split into four different induction procedures: standard APR, APR under sham-adrenalectomy (6th week of diet treatment), APR under adrenalectomy (6th week of diet treatment), and APR under indomethacin (5.54 mg/mL–1 mg/100 g rat weight, 7th week of diet treatment). The APR was induced in the by turpentine (0.5 mL, sc) on the 7th week of diet and blood samples were collected before and 24 hours after turpentine, under ether anaesthesia. IL-1β and TNFα were collected 90 min after stimulus and corticosterone plasmatic samples were collected at baseline and one hour after turpentine stimulus.

Results: The corticosterone baseline levels were significantly elevated in the fish group and, the response to turpentine was similar among the three experimental groups. The fibrinogen and haptoglobin baseline levels were significantly increased and the response of this proteins to turpentine was significantly reduced in fish group, compared to control groups. These findings were not altered by sham-adrenalectomy nor by adrenalectomy, suggesting that adrenocortical hormones are not responsible for the changes observed in fish group. IL-1b and TNFa plasmatic were not detected after turpentine stimulation. After LPS stimulus, IL-1b was reduced in the fish group compared to the control one. When indomethacin was administered, the response of fibrinogen and haptoglobin was statistically reduced in control groups compared to the related standard procedure animals, suggesting that prostanoids participate in the full acute phase response of these proteins. The reduced response of fibrinogen and haptoglobin observed in the fish group disappears on the indomethacin treated animals.

Conclusions: PUFA n-3 are precursors for less inflammatory series of prostanoids and probably they compromise a full acute phase response of fibrinogen and haptoglobin observed in fish group.