Beneficial effects of omega-3 fatty acids on the consequences of a fructose diet are not mediated by PPAR delta or PGC1 alpha.

PURPOSE: To study, in high-fructose-fed rats, the effect of a dietary enrichment in omega-3 polyunsaturated fatty acids (n-3 PUFA) on the expression of genes involved in lipid metabolism and cardiovascular function. METHODS: Twenty-eight male "Wistar Han" rats received for 8 weeks, either a standard chow food or an isocaloric 67% fructose diet enriched or not in alpha-linolenic acid (ALA) or in docosahexaenoic (DHA) and eicosapentaenoic acids (EPA) mix (DHA/EPA). After sacrifice, blood was withdrawn for biochemical analyses; heart, periepididymal adipose tissue and liver were collected and analyzed for the expression of 22 genes by real-time PCR. RESULTS: Fructose intake resulted in an increase in liver weight and triglyceride content, plasma triglyceride and cholesterol concentrations, although no difference in glucose and insulin. In the liver, lipogenesis was promoted as illustrated by an increase in stearoyl-CoA desaturase and fatty acid synthase (Fasn) together with a decrease in PPAR gamma, delta and PPAR gamma coactivator 1 alpha (PGC1 alpha) expression. In the heart, Fasn and PPAR delta expression were increased. The addition of ALA or DHA/EPA into the diet resulted in a protection against fructose effects except for the decreased expression of PPARs in the liver that was not counterbalanced by n-3 PUFA suggesting that n-3 PUFA and fructose act independently on the expression of PPARs and PGC1 alpha. CONCLUSIONS: In liver, but not in heart, the fructose-enriched diet induces an early tissue-specific reduction in PPAR gamma and delta expression, which is insensitive to n-3 PUFA intake and dissociated from lipogenesis.

I-FABP expression alters the intracellular distribution of the BODIPY C16 fatty acid analog.

To investigate the structure-function relationships of intestinal fatty acid-binding protein (I-FABP) in cellular fatty acid (FA) trafficking, we compared the distribution of a fluorescent FA analog (BODIPY FL C16) in Cos-1 cells transiently transfected with the wild type protein (wt I-FABP) to that of a variant deleted of the alpha helical domain (HL I-FABP). In vector-only cells, BODIPY fluorescence was distributed throughout the cytoplasm. In the absence of added FA, wt I-FABP was found largely in the perinuclear region with some cytoplasmic staining as well. Addition of BODIPY FL C16 to transfected cells showed that the fluorescent FA was essentially completely colocalized with the protein in the cytoplasmic and perinuclear regions as well as in cytoplasmic clusters that are not observed in the absence of wt I-FABP. For HL I-FABP, the distribution of the protein in the absence of FA was diffusely cytoplasmic, in marked contrast to the wt protein. Addition of BODIPY led to less extensive colocalization than that observed for wt I-FABP. In particular, no localization to the perinuclear region was found. Organelle colocalization studies showed that both proteins colocalized with mitochondria and endoplasmic reticulum/golgi markers, but little with a lysosomal marker. The perinuclear localization for wt I-FABP and BODIPY did not show colocalization with any of the markers tested. Taken together, these results indicate that I-FABP binds FA in vivo and that the helical domain may be important for targeting I-FABP to a perinuclear domain but not, perhaps, to the endoplasmic reticulum, golgi apparatus or mitochondria.

Proinflammatory properties of murine aortic endothelial cells exclusively expressing a non cleavable form of TNFalpha. Effect on tumor necrosis factor alpha receptor type 2.

Soluble (sTNF) and transmembrane (tmTNF) forms of TNFalpha (TNF) have distinct proinflammatory effects. We investigated whether tmTNF altered the synthesis of some proinflammatory proteins involved in atherothrombosis, in murine aortas and aortic endothelial cells (MAEC). Samples were obtained from wild-type (WT) mice and TNF-deficient mice that express a mutated non cleavable tmTNF transgene (tmTNFnc). The levels of secreted MCP-1, RANTES, IL-6, PAI-1, soluble ICAM-1, and soluble TNF receptor type 1 (TNFR1; CD120a) antigens, MMP-9 activity and of cell surface ICAM-1 were not significantly different between the two types of MAEC. The magnitude of endotoxin-stimulated production of RANTES, MCP-1 and IL-6 was similar in the two types of cells. Of note, the amount of synthesized TNF receptor type 2 (TNFR2; CD120b), measured by its secreted (in aorta and MAEC), intracellular and mRNA levels (in MAEC), was significantly 4-fold lower in tmTNFnc than in WT mice, both in basal and endotoxin-stimulated conditions. A neutralizing anti-TNF antibody or the recombinant murine TNF did not modify the magnitude of the difference in TNFR2 production between the two types of cells, suggesting a preponderant role of tmTNF in the down-regulation of TNFR2 synthesis. Macrophages of tmTNFnc mice also produced less TNFR2 than WT macrophages (-30%). Plasmas of tmTNFnc mice contained significantly less sTNFR2 than WT mice (-75%). In conclusion, an increase in tmTNF levels, rather than the lack of sTNF, significantly down-modulated TNFR2 synthesis in aortic endothelial cells, but had no major influence on the synthesis of some major pro-inflammatory and pro-atherothrombotic proteins.