Browsing by Author "Fuenzalida, Karen"

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    Characterization of an Agarophyton chilense Oleoresin Containing PPARγ Natural Ligands with Insulin-Sensitizing Effects in a C57Bl/6J Mouse Model of Diet-Induced Obesity and Antioxidant Activity in Caenorhabditis elegans
    (2021) Pinto, Claudio; Raquel Ibanez, Maria; Loyola, Gloria; Leon, Luisa; Salvatore, Yasmin; Gonzalez, Carla; Barraza, Victor; Castaneda, Francisco; Aldunate, Rebeca; Contreras-Porcia, Loretto; Fuenzalida, Karen; Bronfman, Francisca C.
    The biomedical potential of the edible red seaweed Agarophyton chilense (formerly Gracilaria chilensis) has not been explored. Red seaweeds are enriched in polyunsaturated fatty acids and eicosanoids, which are known natural ligands of the PPAR gamma nuclear receptor. PPAR gamma is the molecular target of thiazolidinediones (TZDs), drugs used as insulin sensitizers to treat type 2 diabetes mellitus. Medical use of TZDs is limited due to undesired side effects, a problem that has triggered the search for selective PPAR gamma modulators (SPPARMs) without the TZD side effects. We produced Agarophyton chilense oleoresin (Gracilex(R)), which induces PPAR gamma activation without inducing adipocyte differentiation, similar to SPPARMs. In a diet-induced obesity model of male mice, we showed that treatment with Gracilex(R) improves insulin sensitivity by normalizing altered glucose and insulin parameters. Gracilex(R) is enriched in palmitic acid, arachidonic acid, oleic acid, and lipophilic antioxidants such as tocopherols and beta-carotene. Accordingly, Gracilex(R) possesses antioxidant activity in vitro and increased antioxidant capacity in vivo in Caenorhabditis elegans. These findings support the idea that Gracilex(R) represents a good source of natural PPAR gamma ligands and antioxidants with the potential to mitigate metabolic disorders. Thus, its nutraceutical value in humans warrants further investigation.
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    Fatty acid composition of Drosophila photoreceptor light-sensitive microvilli
    (2013) Munoz, Yorka; Fuenzalida, Karen; Bronfman, Miguel; Gatica, Arnaldo; Sepulveda, Marcelo; Bacigalupo, Juan; Roth, Alejandro D.; Delgado, Ricardo
    Phototransduction, the mechanism underlying the electrical response to light in photoreceptor cells, has been thoroughly investigated in Drosophila melanogaster, an essential model in signal transduction research. These cells present a highly specialized photosensitive membrane consisting of thousands of microvilli forming a prominent structure termed a rhabdomere. These microvilli encompass the phototransduction proteins, most of which are transmembrane and exclusively rhabdomeric. Rhabdomere membrane lipids play a crucial role in the activation of the transient receptor potential ionic channels (TRP and TRPL) responsible for initiating the photoresponse. Despite its importance, rhabdomere lipid composition has not been established. We developed a novel preparation enriched in rhabdomere membranes to perform a thorough characterization of the lipidomics of Drosophila rhabdomeres. Isolated eyes (500) were homogenized and subjected to a differential centrifugation protocol that generates a fraction enriched in rhabdomere membrane. Lipids extracted from this preparation were identified and quantified by gas chromatography coupled to mass spectrometry. We found an abundance of low sterol esters (C16:0, C18:0), highly abundant and diverse triglycerides, free fatty acids, a moderate variety of mono and diacyglycerols (C:16:0, 18:0, C18:1) and abundant phospholipids (principally C18:2). This preparation opens a new avenue for investigating essential aspects of phototransduction.
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    Hepatic fatty acid profile in mice with nonalcoholic fatty liver disease using magnetic resonance spectroscopy
    (2019) Xavier, Aline Carvalho da Silva; Zacconi, Flavia C. M.; Cabrera García, Daniel Alejandro; Fuenzalida, Karen; Andía Kohnenkampf, Marcelo Edgardo
    Nonalcoholic fatty liver disease (NAFLD) is characterized by the accumulation of intracellular fatty acids in the liver. The only method to confirm the stage of this disease is the biopsy, but it is invasive and risky to patients. The idea of defining a classifier using magnetic resonance spectroscopy (MRS) emerges due to the need to find a way to replace biopsy with a non-invasive method that can classify NAFLD based on the chemical structure of fatty acids stored in the liver. The purpose of this study is to investigate and compare the composition of fatty acids to the metabolites signals in MRS in NAFLD mice liver at 2 time-point during the progression of the disease. A group of C57BL/6 mice was fed with high-fat diet for one month (N = 8) and for three months (N = 6). First, we made a histological analysis to the liver. Then, we analysed the fatty acids with gas chromatography (GC) and MRS. As a result, the histological analysis showed the progression of fat content, and the GC analysis detected a different fatty acid liver composition during the progression of NAFLD along with an increase of the total fat storage in the liver. The differences in the composition fatty acids are also reflected in the MR Spectrum, which could have clinical potential for monitoring the progression of this disease with a non-invasive technique.
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    Peroxisome Proliferator-activated Receptor γ Up-regulates the Bcl-2 Anti-apoptotic Protein in Neurons and Induces Mitochondrial Stabilization and Protection against Oxidative Stress and Apoptosis
    (AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2007) Fuenzalida, Karen; Quintanilla, Rodrigo; Ramos, Patricio; Piderit, Daniela; Fuentealba, Rodrigo A.; Martinez, Gabriela; Inestrosa, Nibaldo C.; Bronfman, Miguel
    Peroxisome proliferator-activated receptor gamma(PPAR gamma) has been proposed as a therapeutic target for neurodegenerative diseases because of its anti-inflammatory action in glial cells. However, PPAR gamma agonists prevent beta-amyloid (A beta)-induced neurodegeneration in hippocampal neurons, and PPAR gamma is activated by the nerve growth factor (NGF) survival pathway, suggesting a neuroprotective anti-inflammatory independent action. Here we show that the PPAR gamma agonist rosiglitazone (RGZ) protects hippocampal and dorsal root ganglion neurons against A beta-induced mitochondrial damage and NGF deprivation-induced apoptosis, respectively, and promotes PC12 cell survival. In neurons and in PC12 cells RGZ protective effects are associated with increased expression of the Bcl-2 anti-apoptotic protein. NGF-differentiated PC12 neuronal cells constitutively overexpressing PPAR gamma are resistant to A beta-induced apoptosis and morphological changes and show functionally intact mitochondria and no increase in reactive oxygen species when challenged with up to 50 mu M H2O2. Conversely, cells expressing a dominant negative mutant of PPAR gamma show increased A beta-induced apoptosis and disruption of neuronal-like morphology and are highly sensitive to oxidative stress-induced impairment of mitochondrial function. Cells overexpressing PPAR gamma present a 4-to 5-fold increase in Bcl-2 protein content, whereas in dominant negative PPAR gamma-expressing cells, Bcl-2 is barely detected. Bcl-2 knockdown by small interfering RNA in cells overexpressing PPAR gamma results in increased sensitivity to A beta and oxidative stress, further suggesting that Bcl-2 up-regulation mediates PPAR gamma protective effects. PPAR gamma prosurvival action is independent of the signal-regulated MAPK or the Akt prosurvival pathways. Altogether, these data suggest that PPAR gamma supports survival in neurons in part through a mechanism involving increased expression of Bcl-2.
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    Rosiglitazone treatment prevents mitochondrial dysfunction in mutant huntingtin-expressing cells -: Possible role of peroxisome proliferator-activated receptor-γ (PPARγ) in the pathogenesis of Huntington disease
    (2008) Quintanilla, Rodrigo A.; Jin, Youngnam N.; Fuenzalida, Karen; Bronfman, Miguel; Johnson, Gail V. W.
    Peroxisome proliferator-activated receptor-gamma (PPAR gamma) is a member of the PPAR family of transcription factors. Synthetic PPAR gamma agonists are used as oral anti-hyperglycemic drugs for the treatment of non-insulin-dependent diabetes. However, emerging evidence indicates that PPAR gamma activators can also prevent or attenuate neurodegeneration. Given these previous findings, the focus of this report is on the potential neuroprotective role of PPAR gamma activation in preventing the loss of mitochondrial function in Huntington disease (HD). For these studies we used striatal cells that express wild-type (STHdh(Q7/Q7)) or mutant (STHdh(Q111/Q111)) huntingtin protein at physiological levels. Treatment of mutant cells with thapsigargin resulted in a significant decrease in mitochondrial calcium uptake, an increase in reactive oxygen species production, and a significant decrease in mitochondrial membrane potential. PPAR gamma activation by rosiglitazone prevented the mitochondrial dysfunction and oxidative stress that occurred when mutant striatal cells were challenged with pathological increases in calcium. The beneficial effects of rosiglitazone were likely mediated by activation of PPAR gamma, as all protective effects were prevented by the PPAR gamma antagonist GW9662. Additionally, the PPAR gamma signaling pathway was significantly impaired in the mutant striatal cells with decreases in PPAR gamma expression and reduced PPAR gamma transcriptional activity. Treatment with rosiglitazone increased mitochondrial mass levels, suggesting a role for the PPAR gamma pathway in mitochondrial function in striatal cells. Altogether, this evidence indicates that PPAR gamma activation by rosiglitazone attenuates mitochondrial dysfunction in mutant huntingtin-expressing striatal cells, and this could be an important therapeutic avenue to ameliorate the mitochondrial dysfunction that occurs in HD.