| 1. |
- Bauzá-Thorbrügge, Marco, et al.
(författare)
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Adipocyte-specific ablation of the Ca2+ pump SERCA2 impairs whole-body metabolic function and reveals the diverse metabolic flexibility of white and brown adipose tissue.
- 2022
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Ingår i: Molecular metabolism. - : Elsevier BV. - 2212-8778. ; 63
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Tidskriftsartikel (refereegranskat)abstract
- Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) transports Ca2+ from the cytosol into the endoplasmic retitculum (ER) and is essential for appropriate regulation of intracellular Ca2+ homeostasis. The objective of this study was to test the hypothesis that SERCA pumps are involved in the regulation of white adipocyte hormone secretion and other aspects of adipose tissue function and that this control is disturbed in obesity-induced type-2 diabetes.SERCA expression was measured in isolated human and mouse adipocytes as well as in whole mouse adipose tissue by Western blot and RT-qPCR. To test the significance of SERCA2 in adipocyte functionality and whole-body metabolism, we generated adipocyte-specific SERCA2 knockout mice. The mice were metabolically phenotyped by glucose tolerance and tracer studies, histological analyses, measurements of glucose-stimulated insulin release in isolated islets, and gene/protein expression analyses. We also tested the effect of pharmacological SERCA inhibition and genetic SERCA2 ablation in cultured adipocytes. Intracellular and mitochondrial Ca2+ levels were recorded with dual-wavelength ratio imaging and mitochondrial function was assessed by Seahorse technology.We demonstrate that SERCA2 is downregulated in white adipocytes from patients with obesity and type-2 diabetes as well as in adipocytes from diet-induced obese mice. SERCA2-ablated adipocytes display disturbed Ca2+ homeostasis associated with upregulated ER stress markers and impaired hormone release. These adipocyte alterations are linked to mild lipodystrophy, reduced adiponectin levels, and impaired glucose tolerance. Interestingly, adipocyte-specific SERCA2 ablation leads to increased glucose uptake in white adipose tissue while the glucose uptake is reduced in brown adipose tissue. This dichotomous effect on glucose uptake is due to differently regulated mitochondrial function. In white adipocytes, SERCA2 deficiency triggers an adaptive increase in fibroblast growth factor 21 (FGF21), increased mitochondrial uncoupling protein 1 (UCP1) levels, and increased oxygen consumption rate (OCR). In contrast, brown SERCA2 null adipocytes display reduced OCR despite increased mitochondrial content and UCP1 levels compared to wild type controls.Our data suggest causal links between reduced white adipocyte SERCA2 levels, deranged adipocyte Ca2+ homeostasis, adipose tissue dysfunction and type-2 diabetes.
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| 2. |
- Bauzá-Thorbrügge, Marco, et al.
(författare)
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NRF2 is essential for adaptative browning of white adipocytes.
- 2023
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Ingår i: Redox biology. - : Elsevier. - 2213-2317. ; 68
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Tidskriftsartikel (refereegranskat)abstract
- White adipose tissue browning, defined by accelerated mitochondrial metabolism and biogenesis, is considered a promising mean to treat or prevent obesity-associated metabolic disturbances. We hypothesize that redox stress acutely leads to increased production of reactive oxygen species (ROS), which activate electrophile sensor nuclear factor erythroid 2-Related Factor 2 (NRF2) that over time results in an adaptive adipose tissue browning process. To test this, we have exploited adipocyte-specific NRF2 knockout mice and cultured adipocytes and analyzed time- and dose-dependent effect of NAC and lactate treatment on antioxidant expression and browning-like processes. We found that short-term antioxidant treatment with N-acetylcysteine (NAC) induced reductive stress as evident from increased intracellular NADH levels, increased ROS-production, reduced oxygen consumption rate (OCR), and increased NRF2 levels in white adipocytes. In contrast, and in line with our hypothesis, longer-term NAC treatment led to a NRF2-dependent browning response. Lactate treatment elicited similar effects as NAC, and mechanistically, these NRF2-dependent adipocyte browning responses in vitro were mediated by increased heme oxygenase-1 (HMOX1) activity. Moreover, this NRF2-HMOX1 axis was also important for β3-adrenergic receptor activation-induced adipose tissue browning in vivo. In conclusion, our findings show that administration of exogenous antioxidants can affect biological function not solely through ROS neutralization, but also through reductive stress. We also demonstrate that NRF2 is essential for white adipose tissue browning processes.
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| 3. |
- Greiner, Thomas U., 1977, et al.
(författare)
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GLP-1R signaling modulates colonic energy metabolism, goblet cell number and survival in the absence of gut microbiota
- 2024
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Ingår i: MOLECULAR METABOLISM. - 2212-8778. ; 83
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Gut microbiota increases energy availability through fermentation of dietary fibers to short-chain fatty acids in conventionally raised mice. Energy deficiency in germ-free (GF) mice increases glucagon-like peptide-1 (GLP-1) levels, which slows intestinal transit. To further analyze the role of GLP-1-mediated signaling in this model of energy deficiency, we re-derived mice lacking GLP-1 receptor (GLP-1R KO) as GF. Methods: GLP-1R KO mice were rederived as GF through hysterectomy and monitored for 30 weeks. Mice were subjected to rescue experiments either through feeding an energy-rich diet or colonization with a normal cecal microbiota. Histology and intestinal function were assessed at different ages. Intestinal organoids were assessed to investigate stemness. Results: Unexpectedly, 25% of GF GLP-1R KO mice died before 20 weeks of age, associated with enlarged ceca, increased cecal water content, increased colonic expression of apical ion transporters, reduced number of goblet cells and loss of colonic epithelial integrity. Colonocytes from GLP-1R KO mice were energy-deprived and exhibited increased ER-stress; mitochondrial fragmentation, increased oxygen levels and loss of stemness. Restoring colonic energy levels either by feeding a Western-style diet or colonization with a normal gut microbiota normalized gut phenotypes and prevented lethality. Conclusions: Our findings reveal a heretofore unrecognized role for GLP-1R signaling in the maintenance of colonic physiology and survival during energy deprivation.
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| 4. |
- Komai, Ali, 1987, et al.
(författare)
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White Adipocyte Adiponectin Exocytosis Is Stimulated via beta(3)-Adrenergic Signaling and Activation of Epac1: Catecholamine Resistance in Obesity and Type 2 Diabetes
- 2016
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Ingår i: Diabetes. - : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 65:11, s. 3301-3313
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the physiological regulation of adiponectin exocytosis in health and metabolic disease by a combination of membrane capacitance patch-clamp recordings and biochemical measurements of short-term (30-min incubations) adiponectin secretion. Epinephrine or the beta(3)-adrenergic receptor (AR) agonist CL 316,243 (CL) stimulated adiponectin exocytosis/secretion in cultured 3T3-L1 and in primary subcutaneous mouse adipocytes, and the stimulation was inhibited by the Epac (Exchange Protein directly Activated by cAMP) antagonist ESI-09. The beta(3)AR was highly expressed in cultured and primary adipocytes, whereas other ARs were detected at lower levels. 3T3-L1 and primary adipocytes expressed Epac1, whereas Epac2 was undetectable. Adiponectin secretion could not be stimulated by epinephrine or CL in adipocytes isolated from obese/type 2 diabetic mice, whereas the basal (unstimulated) adiponectin release level was elevated twofold. Gene expression of beta(3)AR and Epac1 was reduced in adipocytes from obese animals, and corresponded to a respective similar to 35% and similar to 30% reduction at the protein level. Small interfering RNA-mediated knockdown of beta(3)AR (similar to 60%) and Epac1 (similar to 50%) was associated with abrogated catecholamine-stimulated adiponectin secretion. We propose that adiponectin exocytosis is stimulated via adrenergic signaling pathways mainly involving beta(3)ARs. We further suggest that adrenergically stimulated adiponectin secretion is disturbed in obesity/type 2 diabetes as a result of the reduced expression of beta(3)ARs and Epac1 in a state we define as "catecholamine resistance."
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| 5. |
- Micallef, Peter, 1988, et al.
(författare)
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Adipose Tissue-Breast Cancer Crosstalk Leads to Increased Tumor Lipogenesis Associated with Enhanced Tumor Growth.
- 2021
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Ingår i: International journal of molecular sciences. - 1422-0067. ; 22:21
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Tidskriftsartikel (refereegranskat)abstract
- We sought to identify therapeutic targets for breast cancer by investigating the metabolic symbiosis between breast cancer and adipose tissue. To this end, we compared orthotopic E0771 breast cancer tumors that were in direct contact with adipose tissue with ectopic E0771 tumors in mice. Orthotopic tumors grew faster and displayed increased de novo lipogenesis compared to ectopic tumors. Adipocytes release large amounts of lactate, and we found that both lactate pretreatment and adipose tissue co-culture augmented de novo lipogenesis in E0771 cells. Continuous treatment with the selective FASN inhibitor Fasnall dose-dependently decreased the E0771 viability in vitro. However, daily Fasnall injections were effective only in 50% of the tumors, while the other 50% displayed accelerated growth. These opposing effects of Fasnall in vivo was recapitulated in vitro; intermittent Fasnall treatment increased the E0771 viability at lower concentrations and suppressed the viability at higher concentrations. In conclusion, our data suggest that adipose tissue enhances tumor growth by stimulating lipogenesis. However, targeting lipogenesis alone can be deleterious. To circumvent the tumor's ability to adapt to treatment, we therefore believe that it is necessary to apply an aggressive treatment, preferably targeting several metabolic pathways simultaneously, together with conventional therapy.
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| 6. |
- Micallef, Peter, 1988, et al.
(författare)
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C1QTNF3 is Upregulated During Subcutaneous Adipose Tissue Remodeling and Stimulates Macrophage Chemotaxis and M1-Like Polarization
- 2022
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Ingår i: Frontiers in Immunology. - : Frontiers Media SA. - 1664-3224. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- The adipose tissue undergoes substantial tissue remodeling during weight gain-induced expansion as well as in response to the mechanical and immunological stresses from a growing tumor. We identified the C1q/TNF-related protein family member C1qtnf3 as one of the most upregulated genes that encode secreted proteins in tumor-associated inguinal adipose tissue - especially in high fat diet-induced obese mice that displayed 3-fold larger tumors than their lean controls. Interestingly, inguinal adipose tissue C1qtnf3 was co-regulated with several macrophage markers and chemokines and was primarily expressed in fibroblasts while only low levels were detected in adipocytes and macrophages. Administration of C1QTNF3 neutralizing antibodies inhibited macrophage accumulation in tumor-associated inguinal adipose tissue while tumor growth was unaffected. In line with this finding, C1QTNF3 exerted chemotactic actions on both M1- and M2-polarized macrophages in vitro. Moreover, C1QTNF3 treatment of M2-type macrophages stimulated the ERK and Akt pathway associated with increased M1-like polarization as judged by increased expression of M1-macrophage markers, increased production of nitric oxide, reduced oxygen consumption and increased glycolysis. Based on these results, we propose that macrophages are recruited to adipose tissue sites with increased C1QTNF3 production. However, the impact of the immunomodulatory effects of C1QTNF3 in adipose tissue remodeling warrants future investigations.
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| 7. |
- Mishra, Devesh, et al.
(författare)
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Parabrachial Interleukin-6 Reduces Body Weight and Food Intake and Increases Thermogenesis to Regulate Energy Metabolism
- 2019
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 26:11
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Tidskriftsartikel (refereegranskat)abstract
- Chronic low-grade inflammation and increased serum levels of the cytokine IL-6 accompany obesity. For brain-produced IL-6, the mechanisms by which it controls energy balance and its role in obesity remain unclear. Here, we show that brain-produced IL-6 is decreased in obese mice and rats in a neuro-anatomically and sex-specific manner. Reduced IL-6 mRNA localized to lateral parabrachial nucleus (IPBN) astrocytes, microglia, and neurons, including paraventricular hypothalamus-innervating IPBN neurons. IL-6 microinjection into IPBN reduced food intake and increased brown adipose tissue (BAT) thermogenesis in male lean and obese rats by increasing thyroid and sympathetic outflow to BAT. Parabrachial IL-6 interacted with leptin to reduce feeding. siRNA-mediated reduction of IPBN IL-6 leads to increased weight gain and adiposity, reduced BAT thermogenesis, and increased food intake. Ambient cold exposure partly normalizes the obesity-induced suppression of IPBN IL-6. These results indicate that IPBN-produced IL-6 regulates feeding and metabolism and pinpoints (patho)physiological contexts interacting with IPBN IL-6.
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| 8. |
- Peris, Eduard, et al.
(författare)
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Antioxidant treatment induces reductive stress associated with mitochondrial dysfunction in adipocytes
- 2019
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 294:7, s. 2340-2352
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Tidskriftsartikel (refereegranskat)abstract
- beta-Adrenergic stimulation of adipose tissue increases mitochondrial density and activity (browning) that are associated with improved whole-body metabolism. Whereas chronically elevated levels of reactive oxygen species (ROS) in adipose tissue contribute to insulin resistance, transient ROS elevation stimulates physiological processes such as adipogenesis. Here, using a combination of biochemical and cell and molecular biology-based approaches, we studied whether ROS or antioxidant treatment affects beta 3-adrenergic receptor (beta 3-AR) stimulation-induced adipose tissue browning. We found that beta 3-AR stimulation increases ROS levels in cultured adipocytes, but, unexpectedly, pretreatment with different antioxidants (N-acetylcysteine, vitamin E, or GSH ethyl ester) did not prevent this ROS increase. Using fluorescent probes, we discovered that the antioxidant treatments instead enhanced beta 3-AR stimulation-induced mitochondrial ROS production. This pro-oxidant effect of antioxidants was, even in the absence of beta 3-AR stimulation, associated with decreased oxygen consumption and increased lactate production in adipocytes. We observed similar antioxidant effects in WT mice: N-acetylcysteine blunted beta 3-AR stimulation-induced browning of white adipose tissue and reduced mitochondrial activity in brown adipose tissue even in the absence of beta 3-AR stimulation. Furthermore, N-acetylcysteine increased the levels of peroxiredoxin 3 and superoxide dismutase 2 in adipose tissue, indicating increased mitochondrial oxidative stress. We interpret this negative impact of antioxidants on oxygen consumption in vitro and adipose tissue browning in vivo as essential adaptations that prevent a further increase in mitochondrial ROS production. In summary, these results suggest that chronic antioxidant supplementation can produce a paradoxical increase in oxidative stress associated with mitochondrial dysfunction in adipocytes.
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| 9. |
- Peris Franquet, Eduard
(författare)
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Adipose tissue mitchondrial function is modulated by antioxidants
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Antioxidants are widely used as reactive oxygen species (ROS) scavenging agents in experimental research and in conditions where oxidative stress plays a primary role. However, the effect of antioxidant supplementation on white and brown adipose tissue functionality is understudied, and the role of ROS and/or antioxidant treatment during adipose tissue browning, a process in which the adipocytes’ mitochondrial density and activity increase, is largely unknown. In paper I, by using antioxidants and ROS-sensitive fluorescent probes in cultured β3-AR-stimulated adipocytes, we observed that 24-48-hour antioxidant treatment increases the mitochondrial ROS production associated with reduced respiration and increased glycolysis. Moreover, treatment of mice with the antioxidant N-acetylcysteine (NAC) blunted the β3-AR agonist-induced browning response of white adipose tissue and reduced the mitochondrial activity in brown adipose tissue even in the absence of β3-AR stimulation. Previous studies have shown positive effects of prolonged NAC treatment on whole-body metabolism in mice. In light of these seemingly contradictory results, we hypothesize that chronic antioxidant exposure, in a dose-dependent manner, can lead to so-called mitohormesis. Indeed, in paper II, by treating mice with a set of different NAC doses across a defined time course, we found that prolonged supplementation with a high dose of NAC leads to increased mitochondrial function of white adipose tissue, reduced fat mass and improved insulin sensitivity. In summary, this thesis demonstrates that the adipose tissue response to antioxidant treatment in mice is biphasic and tightly connected to the adipose tissue type, the dosage and the treatment duration. This thesis also provides an alternative explanation for previously reported controversial findings where antioxidants (such as NAC) have exerted deleterious effects on health. Finally, the results of this thesis provide new insights into the appropriate design of antioxidant treatment studies: optimizing treatment dosage and duration may be the key to achieve success with antioxidant therapy.Based on previous research, we hypothesized that reactive oxygen species (ROS)/redox signaling plays a role in β3-AR agonist-induced browning. To test this hypothesis, we analyzed the effect of antioxidant treatment on β3-AR agonist-induced browning in cultured adipocytes. Using ROS-sensitive fluorescent probes to measure changes in total and mitochondrial ROS production in combination with Seahorse technology-based oxygen consumption measurements, we made the surprising observation that antioxidant treatment has a negative impact on adipocyte mitochondrial function even in absence of β3-AR-stimulation. This effect associated with increased mitochondrial ROS production. While similar pro-oxidant effects of antioxidants - sometimes referred to as reductive stress, where electrons are donated to oxygen leading to increased ROS-production - have been reported in a few other studies, it’s an understudied and, in our opinion, an underappreciated phenomenon. In fact, antioxidants are routinely used as a therapeutic or experimental tool to neutralize ROS and one may not necessarily detect potential pro-oxidant effects within the mitochondria unless such impact is directly measured. Therefore, we decided to expand our study and examine whether this deleterious effect of antioxidants also occurs in vivo using wild type mice. In line with our findings in vitro, treatment with the antioxidant N-acetylcystein blunts the β3-AR agonist browning response of white adipose tissue as well as reduces the mitochondrial activity in brown adipose tissue even in the absence of β3-AR stimulation, as it is observed by CARS microscopy in explanted tissue. Other studies have however shown positive effects of prolonged N-acetylcystein treatment on adipose tissue functionality and whole-body metabolism in mice. While such findings may seem contradictory to ours, we argued that prolonged N-acetylcystein exposure may lead to a so-called mitohormesis effect where the initial increase in mitochondrial ROS production upregulates the endogenous antioxidant system leading to positive effects on mitochondrial function in the long run. Indeed, we found that adipose tissue levels of mitochondrial antioxidant proteins in N-acetylcystein treated mice are increased. Moreover, prolonged treatment with a high dose of N-acetylcystein (in contrast to shorter or lower dose treatment regimens) is associated with increased mitochondrial function of white and brown adipose tissue and improved insulin sensitivity as judged by respectively, increased mRNA and protein expression of browning markers and reduced fasting insulin levels. The therapeutic effects of antioxidants (such as N-acetylcystein) have been studied in a broad range of health conditions including obesity, neurodegenerative diseases and cancer. The results of these studies are inconclusive. We believe that our data open up the possibility that positive and negative effects of antioxidant treatment on disease progression may not chiefly depend on ROS neutralization, but can be due to reductive stress that in a dose- and time-dependent manner may lead to an adaptive upregulation of the endogenous antioxidant system.
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| 10. |
- Svahn, Sara L, et al.
(författare)
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Six Tissue Transcriptomics Reveals Specific Immune Suppression in Spleen by Dietary Polyunsaturated Fatty Acids
- 2016
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:5
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Tidskriftsartikel (refereegranskat)abstract
- Dietary polyunsaturated fatty acids (PUFA) are suggested to modulate immune function, but the effects of dietary fatty acids composition on gene expression patterns in immune organs have not been fully characterized. In the current study we investigated how dietary fatty acids composition affects the total transcriptome profile, and especially, immune related genes in two immune organs, spleen (SPL) and bone marrow cells (BMC). Four tissues with metabolic function, skeletal muscle (SKM), white adipose tissue (WAT), brown adipose tissue (BAT), and liver (LIV), were investigated as a comparison. Following 8 weeks on low fat diet (LFD), high fat diet (HFD) rich in saturated fatty acids (HFD-S), or HFD rich in PUFA (HFD-P), tissue transcriptomics were analyzed by microarray and metabolic health assessed by fasting blood glucose level, HOMA-IR index, oral glucose tolerance test as well as quantification of crown-like structures in WAT. HFD-P corrected the metabolic phenotype induced by HFD-S. Interestingly, SKM and BMC were relatively inert to the diets, whereas the two adipose tissues (WAT and BAT) were mainly affected by HFD per se (both HFD-S and HFD-P). In particular, WAT gene expression was driven closer to that of the immune organs SPL and BMC by HFDs. The LIV exhibited different responses to both of the HFDs. Surprisingly, the spleen showed a major response to HFD-P (82 genes differed from LFD, mostly immune genes), while it was not affected at all by HFD-S (0 genes differed from LFD). In conclusion, the quantity and composition of dietary fatty acids affected the transcriptome in distinct manners in different organs. Remarkably, dietary PUFA, but not saturated fat, prompted a specific regulation of immune related genes in the spleen, opening the possibility that PUFA can regulate immune function by influencing gene expression in this organ.
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