Administration of a murine diet supplemented with conjugated linoleic acid increases the expression and activity of hepatic uncoupling proteins

Abstract

Daily intake of conjugated linoleic acid (CLA) has been shown to reduce body fat accumulation and to increase body metabolism; this latter effect has been often associated with the up-regulation of uncoupling proteins (UCPs). Here we addressed the effects of a CLA-supplemented murine diet (~2 % CLA mixture, cis-9, trans-10 and trans-10, cis-12 isomers; 45 % of each isomer on alternating days) on mitochondrial energetics, UCP2 expression/activity in the liver and other associated morphological and functional parameters, in C57BL/6 mice. Diet supplementation with CLA reduced both lipid accumulation in adipose tissues and triacylglycerol plasma levels, but did not augment hepatic lipid storage. Livers of mice fed a diet supplemented with CLA showed high UCP2 mRNA levels and the isolated hepatic mitochondria showed indications of UCP activity: in the presence of guanosine diphosphate, the higher stimulation of respiration promoted by linoleic acid in mitochondria from the CLA mice was almost completely reduced to the level of the stimulation from the control mice. Despite the increased generation of reactive oxygen species through oxi-reduction reactions involving NAD(+)/NADH in the Krebs cycle, no oxidative stress was observed in the liver. In addition, in the absence of free fatty acids, basal respiration rates and the phosphorylating efficiency of mitochondria were preserved. These results indicate a beneficial and secure dose of CLA for diet supplementation in mice, which induces UCP2 overexpression and UCP activity in mitochondria while preserving the lipid composition and redox state of the liver.

c9,t11-Conjugated linoleic acid ameliorates steatosis by modulating mitochondrial uncoupling and Nrf2 pathway

“…Data showing the protective effects displayed by CLA administration to L-fed rats agree with the recently reported ability of CLA to improve liver status activity ( 17 ), Supplemental Material can be found at: may be hypothesized. As is consistent with the reported modulatory role of Nrf2 in metabolic pathways ( 13 ), the increase of PPAR ␣ and FGF21 mRNA expression in C9 may be a consequence of the Nrf2-mediated upregulation of phase 2 enzymes; in contrast, the marked decline of FGF21 and PPAR ␥ mRNA levels in the L9 and L10 groups is indicative of their protective effects ( 19,20 ). The inhibitory activity displayed by 9,11-CLA administration on FGF21 overexpression induced by the steatogenic diet may be explained on the basis of the reported role of the Nrf2-mediated hepatic antioxidant and detoxifi cation upon NAFLD progression ( 4 ), whereas the mechanisms underlying the benefi cial effects of 10,12-CLA (reduced liver steatosis in L-fed rats) remain to be clarifi ed.…”

“…PPAR ␥ is highly expressed in adipose tissue, where activation plays a major role in promoting FA uptake into adipocytes, thereby reducing FA delivery to the liver ( 51 ). The presented results showing a lack of infl uence by 9,11-CLA on PPAR ␥ expression in CD-fed rats are dissimilar to those reporting the positive correlation between Nrf2 and PPAR ␥ in adipose tissue ( 2,19 ) and to data showing the FGF21 upregulation by PPAR ␥ agonists in adipocytes ( 52,53 ). These discrepancies may be explained by the effect elicited by CLA on liver PPAR ␥ .…”

“…Among the possible isomers, two [namely, cis 9, trans 11-octadecadienoic acid ( 9,11 ) and trans 10, cis 12-octadecadienoic acid ( 10,12 ), which represent ‫ف‬ 90% and 10% of the CLA found in ruminant meats and dairy products, respectively] exhibited characteristic biological activities ( 16 ). Consequently, although the isomeric CLA mixture (1:1) has been shown to trigger off the Nrf2 pathway ( 17,18 ) and to modulate hepatic mitochondrial function ( 19 ), the effi cacy of specifi c isomers on these mechanisms remains unclear.…”

Alterações no metabolismo corporal e mitocondrial promovidas pela suplementação da dieta com ácido linoléico conjugado (CLA) e ácido oléico em camundongos

“…No fígado, o CLA é um ligante e potente ativador do PPARα (Forman, Chen e Evans, 1997;Kliewer et al, 1997;Moya-Camarena et al, 1999), o qual controla a expressão de uma série de genes envolvidos na elongação, dessaturação, oxidação e transporte de ácido-graxos (Jump, 2011) bem como a expressão de UCP2 (Choi et al, 2007;Rakhshandehroo et al, 2009;Pereira et al, 2012). Nosso grupo de pesquisa recentemente demonstrou que a suplementação da dieta de camundongos com uma mistura dos isômeros cis-9, trans-11 e trans-10, cis-12 do CLA promoveu um grande aumento na expressão e atividade de UCP2 (Pereira et al, 2012) (Haeiwa et al, 2014), sendo a produção de EROS em excesso um dos fatores-chave associado à síndromes metabólicas e suas manifestações (Kopelman, 2000;Odegaard e Chawla, 2011). Alguns estudos tem demonstrado que ácidos-graxos monoinsaturados (MUFAS), principalmente ácido oléico podem afetar favoravelmente a adiposidade e resistência a insulina em indivíduos obesos (Due et al, 2008) (Paniagua et al, 2007).…”

“…No entanto, esses trabalhos são ainda muito escassos e não descrevem os mecanismos pelos quais o ácido oléico exerce esses efeitos. (Alberici et al, 2006;Pereira et al, 2012): após 10 minutos de centrifugação a 700 g, o pellet foi descartado e o sobrenadante foi, então, novamente centrifugado durante 10 minutos 10000 g. A camada lipídica flutuante foi retirada com pipeta de Pasteur e em seguida o sobrenadante foi descartado. O pellet resultante foi ressuspendido delicadamente em 10 mL de meio contendo sacarose 250 mM, HEPES 10 mM (pH 7,2) e EGTA 0,1 mM a 4 ºC utilizando-se um pincel e novamente foi centrifugado durante 10 minutos a 6000 rpm.…”