title: Regulation of hypothalamic-pituitary-adrenal axis by circulating free fatty acids in male Wistar rats: role of individual free fatty acids.
abstract: We previously showed that a fall in the plasma free fatty acid (FFA) level increases plasma corticosterone levels in rats by activating the hypothalamic-pituitary-adrenal axis. In the present study, we tested whether this regulation is mediated by specific or all species of FFAs. Nicotinic acid (NA) (30 μmol/h) was infused in rats to decrease plasma FFAs and increase plasma ACTH and corticosterone. The NA infusion was combined with an infusion of lipids with different FFA compositions to selectively prevent falls in individual FFA levels; coconut, olive, and safflower oils (n = 7 for each), which are predominantly (>70%) composed of saturated, monounsaturated (oleic acid), and polyunsaturated (linoleic acid) FFAs, respectively, were used. At an infusion rate (0.1 g/h) that only partially prevented a fall in the total FFA level, coconut oil, but not olive or safflower oil, completely prevented NA-induced increases in plasma ACTH or corticosterone, suggesting that these responses are mainly mediated by saturated FFAs. In addition, quantification of individual FFA species in the blood using FFA-specific fluorescent probes revealed that plasma corticosterone and ACTH correlated significantly with plasma palmitate but not with other FFAs, such as oleate, linoleate, or arachidonate. Taken together, our data suggest that the regulation of the hypothalamic-pituitary-adrenal axis by FFAs is mainly mediated by the saturated fatty acid palmitate, but not by unsaturated fatty acids, such as oleate and linoleate.
authors.affiliation: Department of Physiology and Biophysics (Y.T.O., J.K., J.H.Y.), University of Southern California, Keck School of Medicine, Los Angeles, California 90089; and Department of Biochemistry and Molecular Biology (I.K., J.H.Y.), Kyung Hee University, School of Medicine, Seoul 130-701, Korea.
authors.forename: Young Taek
authors.initials: YT
authors.lastname: Oh
authors.forename: Jinyub
authors.initials: J
authors.lastname: Kim
authors.forename: Insug
authors.initials: I
authors.lastname: Kang
authors.forename: Jang H
authors.initials: JH
authors.lastname: Youn
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism; D003345:Corticosterone / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology*; D019787:Linoleic Acid / Q000378:metabolism; D008297:Male; D009525:Niacin / Q000378:metabolism; D019301:Oleic Acid / Q000378:metabolism; D019308:Palmitic Acid / Q000378:metabolism*; D010913:Pituitary-Adrenal System / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D009525:Niacin; D016718:Arachidonic Acid; D019301:Oleic Acid; D019308:Palmitic Acid; D000324:Adrenocorticotropic Hormone; D019787:Linoleic Acid; D003345:Corticosterone