Brown fat thermogenesis in rats fed high-fat diets enriched with n-3 polyunsaturated fatty acids

Abstract

OBJECTIVE:To examine the possible involvement of an increase in diet-induced thermogenesis from brown adipose tissue (BAT) in the n-3 polyunsaturated fatty acids (n-3 PUFA) induced limitation of the development of white fat pads during high-fat feeding. DESIGN: Rats fed for four weeks on a low-fat/high-carbohydrate diet (C group) or high-fat diet without n-3 PUFA (REF group), with eicosapentaenoic acid (EPA group), with docosahexaenoic acid (DHA group) or with a mixture of these two fatty acids (MIX group). MEASUREMENTS: Epididymal and retroperitoneal fat pad mass, BAT composition, Guanosine 5'-diphosphate (GDP) binding and uncoupling protein (UCP) content were measured in the ®ve groups of rats. RESULTS: The masses of retroperitoneal and epididymal white fat pads were lower in the groups fed n-3 PUFA than in the C and REF groups. The total BAT GDP binding was 1.6 times higher in the MIX and EPA groups than in the REF group. The BAT from the EPA group presented an enrichment in mitochondria compared to the C and REF groups whereas the BAT from the DHA and REF groups presented a hyperplasia and an increase in thermogenic activity of the mitochondria compared to the C group. The higher thermogenic activity of BAT was observed in the MIX group and is due to hyperplasia and to an increase in thermogenic activity of mitochondria. CONCLUSIONS: n-3 PUFA induce a marked stimulation of BAT thermogenic activity without changes in the UCP content compared to a high-fat diet without n-3 PUFA. The mixture of EPA and DHA has the more pronounced effect while EPA and DHA seem to act in synergy on BAT thermogenesis via different mechanisms.

Effect of a cachectic factor on carbohydrate metabolism and attenuation by eicosapentaenoic acid

“…EPA also increased glucose consumption in brown fat, which would correlate with the report of a marked stimulation of brown adipose tissue (BAT) thermogenic activity by n-3 polyunsaturated fatty acids (Oudart et al, 1997).…”

Selectivity of fatty acids on lipid metabolism and gene expression

“…In the whole animal the effect was detected by the measurement by indirect calorimetry of postprandial energy expenditure, which is higher in rats fed on n-6 PUFA than in saturated or monounsaturated fatty acid-fed rats . n-3 PUFA are also potent stimulators of diet-induced thermogenesis, as was clearly shown in BAT from rats fed on a diet enriched with fish oil fatty acids, which had a higher BAT thermogenic activity (Oudart et al 1997) and a higher UCP1 content (Sadurkis et al 1995;Kawada et al 1998) than rats fed on a lard-based diet. The results of all these studies are in accordance with a role for BAT thermogenesis in the limiting effect of PUFA on body fat accumulation.…”

“…A selective energy-dissipative process to counteract body fat accretion during high-fat feeding has been demonstrated (Rothwell & Stock, 1979), and may be implicated in the regulation of energy balance during high-fat feeding according to the fatty acid composition of dietary fat (Trayhurn, 1986). It has been shown that PUFA lead to a higher increase in diet-induced thermogenesis than saturated or monounsaturated fatty acids during high-fat feeding, suggesting that dietary fatty acids could be selectively thermogenic Oudart et al 1997). Diet-induced thermogenesis is brought about mainly by BAT, which is under the control of the sympathetic nervous system, through the activity of the uncoupling protein (UCP) 1. n-6 PUFA are more potent stimulators of the BAT sympathetic nervous system than saturated or monounsaturated fatty acids, as has been assessed by the higher BAT noradrenaline turnover in rats fed on n-6 PUFA than that in saturated or monounsaturated fatty acid-fed rats (Young & Walgren, 1994;Matsuo et al 1995).…”

CORPS GRAS ET OBESITE Acides gras alimentaires et obésité : aspects qualitatifs et quantitatifs

“…La spécificité de l'effet biologique des acides gras alimentaires d'huile de poisson a été clairement montrée en utilisant des proportions similaires d'AGPI n-3, d'AGPI n-6, et d'acides gras saturés et mono-insaturés dans l'alimentation entre les différents groupes expérimentaux [7,15]. Ainsi, les effets des acides gras d'huile de poisson peuvent être attribués sans équivoque aux AGPI n-3.…”

“…Dans une étude récente, des rats ont été nourris pendant 4 semaines avec quatre régimes riches en graisses différant par leur composition en acide gras mais contenant la même proportion d'AGPI n-3 (20:5n-3, groupe EPA ; 22:6n-3, groupe DHA ; 20:5n-3 plus 22:6n-3, groupe MIX), ou pas d'AGPI n-3 (groupe C). En parfait accord avec les études antérieures rapportées précédemment, la consommation d'AGPI n-3 influence le développement du tissu adipeux [15,16]. À l'issue du traitement nutritionnel, la masse de lipides et la taille des cellules adipeuses diminuent dans le tissu adipeux rétropéritonéal dans l'ordre suivant : groupe C > groupe EPA > groupe DHA > groupe MIX, mais restent inchangées dans le tissu adipeux sous-cutané (figure 2).…”