RESUMEN
Conjugated linoleic acid (CLA) and some trans fatty acids (FA) decrease tumor growth and alter tumor and host lipid uptake and storage. The goal of this study was to test the hypothesis that the acute inhibitory effects of CLA isomers and trans FAs on FA transport in tumors and white adipose tissue are mediated via an inhibitory G-protein coupled (GPC), FFA receptor (FFAR). Experiments were performed in hepatoma 7288CTC and inguinal fat pads in Buffalo rats during perfusion in situ. CLA isomers and trans FAs (0.03-0.4 mmol/L, in plasma) were added to the arterial blood, and FA uptake or release was measured by arterial minus venous difference. In hepatoma 7288CTC, the CLA isomers, t10,c12-CLA > (+/-)-9-HODE [13-(S)-hydroxyoctadecadienoic acid] > t9,t11-CLA, and the trans FAs, linolelaidic = vaccenic > elaidic, decreased cAMP content and inhibited FA uptake, 13(S)-HODE release, extracellular signal-regulated kinase p44/p42 phosphorylation, and [(3)H]thymidine incorporation. Other CLA isomers, c9,t11-CLA, 13-(S)-HODE, c9,c11-CLA, and c11,t13-CLA, had no effect. In inguinal fat pads, FA transport was inhibited by t10,c12-CLA = linolelaidic acid > trans vaccenic acid, whereas c9,t11-CLA had no effect. In both hepatoma 7288CTC and inguinal fat pad, addition of either pertussis toxin or 8-Br-cAMP to the arterial blood reversed the inhibitions of FA transport. These results support the idea that an inhibitory GPC FFAR reduces cAMP and controls FA transport by CLA isomers and trans FAs. Ligand activity is conferred by the presence of a trans double bond proximal to the carboxyl group.
Asunto(s)
Ácidos Grasos/farmacocinética , Ácidos Linoleicos Conjugados/farmacología , Neoplasias Hepáticas Experimentales/metabolismo , Ácidos Grasos trans/farmacología , Tejido Adiposo/efectos de los fármacos , Tejido Adiposo/metabolismo , Animales , Ácidos Linoleicos Conjugados/sangre , Masculino , Ratas , Ratas Endogámicas BUF , Ratas Sprague-Dawley , Ácidos Grasos trans/sangreRESUMEN
OBJECTIVE: To review the effect of a diet supplemented with polyunsaturated fatty acids (PUFA) on prevention or treatment of osteoporosis. METHODS: MEDLINE (1966-April 2001), Allied Complementary Medicine (1985-2001), Cochrane Library and Database of Systematic Reviews (1st Quarter 2001) was searched. Five reviews and no systematic reviews were found on this topic in the Cochrane Library. Eleven relevant in-vivo studies were identified on the effect of these compounds on bone. Eight were animal studies and three were randomised control trials (RCT) in human. RESULTS: There are two classes of PUFA designated as n-3 and n-6 with alpha-linolenic acid (ALA). These two different types of PUFA differently influence prostaglandin formation and hence modulate bone metabolism differently. These are several in vitro and animal data suggesting that diet with a low n-6/n-3 ratio may have beneficial effects on bone mineral density. Only three, short-term, small studies have been performed in human so far. Two studies, one performed with bone markers and one with bone density showed a positive effect of PUFA on bone. While a third study showed no effect. CONCLUSIONS: Preliminary, data have suggested that a diet with a low n-6/n-3 ratio may have beneficial effects on bone mineral density. Further studies are, however, required to fully assess the dose and type of PUFA to be used for optimum bone effects. This may be useful particularly for the prevention of disease in the elderly, since a diet rich in n-3 PUFA has been shown to have additional benefit on the cardiovascular, central nervous system and joints.