Aims/hypothesis: Intake of n-3 polyunsaturated fatty acids reduces adipose tissue mass, preferentially in the abdomen. The more pronounced effect of marine-derived eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids on adiposity, compared with their precursor α-linolenic acid, may be mediated by changes in gene expression and metabolism in white fat. Methods: The effects of EPA/ DHA concentrate (6% EPA, 51% DHA) admixed to form two types of high-fat diet were studied in C57BL/6J mice. Oligonucleotide microarrays, cDNA PCR subtraction and quantitative real-time RT-PCR were used to characterise gene expression. Mitochondrial proteins were quantified using immunoblots. Fatty acid oxidation and synthesis were measured in adipose tissue fragments. Results: Expression screens revealed upregulation of genes for mitochondrial proteins, predominantly in epididymal fat when EPA/DHA concentrate was admixed to a semisynthetic high-fat diet rich in α-linolenic acid. This was associated with a threefold stimulation of the expression of genes encoding regulatory factors for mitochondrial biogenesis and oxidative metabolism (peroxisome proliferator-activated receptor gamma coactivator 1 alpha [Ppargc1a, also known as Pgc1α] and nuclear respiratory factor-1 [Nrf1] respectively). Expression of genes for carnitine palmitoyltransferase 1A and fatty acid oxidation was increased in epididymal but not subcutaneous fat. In the former depot, lipogenesis was depressed. Similar changes in adipose gene expression were detected after replacement of as little as 15% of lipids in the composite highfat diet with EPA/DHA concentrate, while the development of obesity was reduced. The expression of Ppargc1a and Nrf1 was also stimulated by n-3 polyunsaturated fatty acids in 3T3-L1 cells. Conclusions/interpretation: The antiadipogenic effect of EPA/DHA may involve a metabolic switch in adipocytes that includes enhancement of β-oxidation and upregulation of mitochondrial biogenesis.

Omega-3 PUFA of marine origin reduce adiposity in animals fed a high-fat diet. Our aim was to learn whether EPA and DHA could limit development of obesity and reduce cellularity of adipose tissue and whether other dietary FA could influence the effect of EPA/DHA. Weight gain induced by composite high-fat diet in C57BL/6J mice was limited when the content of EPA/DHA was increased from 1 to 12% (wt/wt) of dietary lipids. Accumulation of adipose tissue was reduced, especially of the epididymal fat. Low ratio of EPA to DHA promoted the effect. A higher dose of EPA/DHA was required to reduce adiposity when admixed to diets that did not promote obesity, the semisynthetic high-fat diets rich in EFA, either alpha-linolenic acid (ALA, 18:3 n-3, the precursor of EPA and DHA) or linoleic (18:2 n-6) acid. Quantification of adipose tissue DNA revealed that except for the diet rich in ALA the reduction of epididymal fat was associated with 34-50% depression of tissue cellularity, similar to the 30% caloric restriction in the case of the high-fat composite diet. Changes in plasma markers and adipose gene expression indicated improvement of lipid and glucose metabolism due to EPA/DHA even in the context of the diet rich in ALA. Our results document augmentation of the antiadipogenic effect of EPA/DHA during development of obesity and suggest that EPA/DHA could reduce accumulation of body fat by limiting both hypertrophy and hyperplasia of fat cells. Increased dietary intake of EPA/DHA may be beneficial regardless of the ALA intake.

Aims/hypothesis: Diets rich in n-3 polyunsaturated fatty acids, namely eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), protect against insulin resistance and obesity in rodents and increase insulin sensitivity in healthy humans. We tested whether the anti-diabetic effects of EPA and DHA involve enhanced production of the endogenous insulin sensitiser, adiponectin. Methods: We studied the effects, in an obesity-promoting high-fat diet, of partial replacement of vegetable oils by EPA/DHA concentrate (6% EPA, 51% DHA) over a 5-week period in adult male C57BL/6J mice that either had free access to food or had their food intake restricted by 30%. At the end of the treatment, systemic markers of lipid and glucose metabolism and full-length adiponectin and leptin were measured. Adiponectin (Adipoq) and leptin (Lep) gene expression in dorsolumbar and epididymal white adipose tissue (WAT) and isolated adipocytes was quantified and adipokine production from WAT explants evaluated. Results: In mice with free access to food, plasma triacylglycerols, NEFA, and insulin levels were lower in the presence of EPA/DHA, while glucose and leptin levels were not significantly altered. Food restriction decreased plasma triacylglycerols, glucose, insulin and leptin, but not adiponectin. EPA/DHA increased plasma adiponectin levels, independent of food intake, reflecting the stimulation of Adipoq expression in adipocytes and the release of adiponectin from WAT, particularly from epididymal fat. Expression of Lep and the release of leptin from WAT, while being extremely sensitive to caloric restriction, was unaltered by EPA/DHA. Conclusions/interpretation: Intake of diets rich in EPA and DHA leads to elevated systemic concentrations of adiponectin, largely independent of food intake or adiposity and explain, to some extent, their anti-diabetic effects.

Animal eyes are morphologically diverse. Their assembly, however, always relies on the same basic principle, i.e., photoreceptors located in the vicinity of dark shielding pigment. Cnidaria as the likely sister group to the Bilateria are the earliest branching phylum with a well developed visual system. Here, we show that cameratype eyes of the cubozoan jellyfish, Tripedalia cystophora, use genetic building blocks typical of vertebrate eyes, namely, a ciliary phototransduction cascade and melanogenic pathway. Our findings indicative of parallelism provide an insight into eye evolution. Combined, the available data favor the possibility that vertebrate and cubozoan eyes arose by independent recruitment of orthologous genes during evolution.T he assembly of diverse animal eyes requires two fundamental building blocks, photoreceptors and dark shielding pigment. The function of photoreceptors is to convert light (stream of photons) into intracellular signaling. The photoreceptor cells (PRCs) are classified into two distinct types: rhabdomeric, characteristic of vision in invertebrate eyes; and ciliary, characteristic of vision in vertebrate eyes (1). In both ciliary and rhabdomeric PRCs, the seven-transmembrane receptor (opsin) associates with retinal to constitute a functional photosensitive pigment. Each photoreceptor type uses a separate phototransduction cascade. Rhabdomeric photoreceptors employ r-opsins and a phospholipase C cascade, whereas ciliary photoreceptors use c-opsins and a phosphodiesterase (PDE) cascade (2, 3). In general, the dark pigment reduces photon scatter and orients the direction optimally sensitive to light. The biochemical nature of the dark pigment appears more diverse than the phototransduction cascades used by the PRCs. Vertebrate eyes use melanin as their exclusive dark pigment. However, among invertebrates, pterins constitute the eye pigment in the polychaete Platynereis dumerilii (4), pterins and ommochromes are accumulated in eyes of Drosophila (5), and melanin is found rarely such as in the inverse cup-like eyes of the planarian, Dugesia (6).Cnidaria, the likely sister group to the Bilateria, constitute the earliest branching phylum containing a well developed visual system. For example, Cubozoa (known as ''box jellyfish'') have camera-type eyes with cornea, lens, and retina; unexpectedly, the cubozoan retina has ciliated PRCs that are typical for vertebrate eyes (7-9). Cubomedusae are active swimmers that are able to make directional changes in response to visual stimuli (10). The cubozoan jellyfish, Tripedalia cystophora (Fig. 1A), has four sensory structures called rhopalia that are equally spaced around the bell. In addition to two camera-type lens containing eyes at right angles to one another, each rhopalium has two pit-shaped and two slit-shaped pigment cup eyes (Fig. 1B). Thus, with six eyes located on each rhopalium, Tripedalia has 24 eyes altogether. Because the visual fields of individual eyes of the rhopalium partly overlap, Tripedalia (like other Cubomedusae) has an al...

beta-Catenin plays a key role in cadherin-mediated cell adhesion as well as in canonical Wnt signaling. To study the role of beta-catenin during eye development, we used conditional Cre/loxP system in mouse to inactivate beta-catenin in developing lens and retina. Inactivation of beta-catenin does not suppress lens fate, but instead results in abnormal morphogenesis of the lens. Using BAT-gal reporter mice, we show that beta-catenin-mediated Wnt signaling is notably absent from lens and neuroretina throughout eye development. The observed defect is therefore likely due to the cytoskeletal role of beta-catenin, and is accompanied by impaired epithelial cell adhesion. In contrast, inactivation of beta-catenin in the nasal ectoderm, an area with active Wnt signaling, results in formation of crystallin-positive ectopic lentoid bodies. These data suggest that, outside of the normal lens, beta-catenin functions as a coactivator of canonical Wnt signaling to suppress lens fate.

Lens formation in mouse is critically dependent on proper development of the retinal neuroectoderm that is located close beneath the head surface ectoderm. Signaling from the prospective retina triggers lens-specific gene expression in the surface-ectoderm. Supression of canonical Wnt/beta-catenin signaling in the surface ectoderm is one of the prerequisites for lens development because, as we show here, ectopic Wnt activation in the retina and lens abrogates lens formation. Wnt inhibiton is mediated by signals coming from the retina but its exact mechanism is unknown. We show that Pax6 directly controls expression of several Wnt inhibitors such as Sfrp1, Sfrp2, and Dkk1 in the presumptive lens. In accordance, absence of Pax6 function leads to aberrant canonical Wnt activity in the presumptive lens that subsequently impairs lens development. Thus Pax6 is required for down-regulation of canonical Wnt signaling in the presumptive lens ectoderm.

As indicated by in vitro studies, both lipogenesis and lipolysis in adipocytes depend on the cellular ATP levels. Ectopic expression of mitochondrial uncoupling protein 1 (UCP1) in the white adipose tissue of the aP2-Ucp1 transgenic mice reduced obesity induced by genetic or dietary manipulations. Furthermore, respiratory uncoupling lowered the cellular energy charge in adipocytes, while the synthesis of fatty acids (FA) was inhibited and their oxidation increased. Importantly, the complex metabolic changes triggered by ectopic UCP1 were associated with the activation of AMP-activated protein kinase (AMPK), a metabolic master switch, in adipocytes. Effects of several typical treatments that reduce adiposity, such as administration of leptin, b-adrenoceptor agonists, bezafibrate, dietary n-3 polyunsaturated FA or fasting, can be compared with a phenotype of the aP2-Ucp1 mice. These situations generally lead to the upregulation of mitochondrial UCPs and suppression of the cellular energy charge and FA synthesis in adipocytes. On the other hand, FA oxidation is increased. Moreover, it has been shown that AMPK in adipocytes can be activated by adipocyte-derived hormones leptin and adiponectin, and also by insulin-sensitizes thiazolidinediones. Thus, it is evident that metabolism of adipose tissue itself is important for the control of body fat content and that the cellular energy charge and AMPK are involved in the control of lipid metabolism in adipocytes. The reciprocal link between synthesis and oxidation of FA in adipocytes represents a prospective target for the new treatment strategies aimed at reducing obesity.

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