Thereza Cristina Lonzetti Bargut

A high-fish-oil diet prevents adiposity and modulates white adipose tissue inflammation pathways in mice

Fish oil improves obesity and its comorbidities, but its mechanisms of action remain unknown. We evaluate the effects of a diet rich in fish oil in white adipose tissue (WAT) inflammation pathways, renin-angiotensin system (RAS) and mitogen-activated protein kinases (MAPKs). To achieve our aims, four groups of male C57BL/6 mice were fed different diets: standard chow diet (SC; 10% energy from fat), SC+fish oil diet (SC-FO; 10% energy from fat), high-fat lard diet (HF-L; 50% energy from lard) and HF fish oil diet (HF-FO; 50% energy from fish oil). We evaluated body mass, epididymal fat pad mass, food intake and glucose tolerance. In WAT, we assessed adipocyte hypertrophy, monocyte chemotactic protein-1 immunofluorescence, and gene and protein expression of insulin signaling, inflammation, MAPKs, RAS, peroxisome proliferator-activated receptors (PPARs) and AMP-activated protein kinase (AMPK). In relation to the results, the HF-L group, as expected, showed elevated body mass and adiposity, glucose intolerance and hypertrophied adipocytes. In WAT, we found a defect in insulin signaling, infiltration of macrophages and inflammatory markers with the associated activation of MAPKs and local RAS. On the contrary, the HF-FO group did not present increased body mass, adiposity or glucose intolerance. In this group, insulin signaling, macrophage infiltration and inflammation were reduced in WAT in comparison with the HF-L group. We also observed decreases of MAPKs and local RAS and elevation of PPAR and AMPK. In summary, fish oil activates PPAR (the three isoforms) and AMPK, decreases WAT insulin resistance and inflammation, and inhibits MAPK and RAS pathways activation.

Brown adipose tissue: Updates in cellular and molecular biology.

Brown adipose tissue (BAT) is mainly composed of adipocytes, it is highly vascularized and innervated, and can be activated in adult humans. Brown adipocytes are responsible for performing non-shivering thermogenesis, which is exclusively mediated by uncoupling protein (UCP) -1 (a protein found in the inner mitochondrial membrane), the hallmark of BAT, responsible for the uncoupling of the proton leakage from the ATP production, therefore, generating heat (i.e. thermogenesis). Besides UCP1, other compounds are essential not only to thermogenesis, but also to the proliferation and differentiation of BAT, including peroxisome proliferator-activated receptor (PPAR) family, PPARgamma coactivator 1 (PGC1)-alpha, and PRD1-BF-1-RIZ1 homologous domain protein containing protein (PRDM) -16. The sympathetic nervous system centrally regulates thermogenesis through norepinephrine, which acts on the adrenergic receptors of BAT. This bound leads to the initialization of the many pathways that may activate thermogenesis in acute and/or chronic ways. In summary, this mini-review aims to demonstrate the latest advances in the knowledge of BAT.

Fish oil has beneficial effects on allergen-induced airway inflammation and hyperreactivity in mice.

Background Fish oil (FO) is rich in n-3 polyunsaturated fatty acids (PUFA), which have been suggested to be anti-inflammatory and are associated with improvement of several inflammatory diseases. In this study, we investigated the influence of FO on allergen-induced lung inflammation and airway hyperreactivity in mice. Methods Male A/J mice were fed either a standard-chow (SC) or a FO diet (FO) for 8 weeks. After 4 weeks, each group was further randomized for ovalbumin (SC-OVA and FO-OVA) or saline (SC-SAL and FO-SAL) challenge. Resistance and elastance were measured at baseline and after aerosolized methacholine, 24h after the last challenge. Bronchoalveolar lavage (BAL) was performed for leukocyte counts. Lung tissue mucus deposition, peribronchiolar matrix deposition and eosinophil infiltration were quantified. Serum immunoglobulin E (IgE) and IgG1 (ref 2.2), lung IL-4, IL-5, IL-10, IL-13, IL-17, INFγ and eotaxin-1 and 2 were detected by ELISA and nuclear factor kappa B (NFκB), GATA-3 and peroxisome proliferator-activated receptor gamma (PPARγ) expression was measured by Western blot. Results Levels of serum IgE and IgG1 were significantly higher in OVA sensitized mice. OVA challenge resulted in increased eosinophil infiltration, increased inflammatory cytokine production, peribronchiolar matrix and mucus deposition and airway hyperreactivity to aerosolized methacholine. Elevated lung NFκB and GATA-3 expression was noted in OVA-challenged mice. These changes were attenuated in mice fed with FO diet. Higher PPARγ expression was also detected in the lungs from the FO-fed groups. Conclusion Our results demonstrate that FO intake attenuated classical asthma features by suppressing the systemic sensitization, thus providing evidence that FO might be a prophylactic alternative for asthma prevention.

Thermogenesis, fatty acid synthesis with oxidation, and inflammation in the brown adipose tissue of ob/ob (-/-) mice.

Brown adipose tissue (BAT) is specialized in heat production, but its metabolism in ob/ob mice is still a matter of debate. We aimed to verify ob/ob mice BAT using C57Bl/6 male mice (as the wild-type, WT) and leptin-deficient ob/ob mice (on the C57Bl/6 background strain), at three months of age (n=10/group). At euthanasia, animals had their interscapular BAT weighed, and prepared for analysis (Western blot, and RT-qPCR). In comparison with the WT group, the ob/ob group showed reduced thermogenic signaling markers (gene expression of beta 3-adrenergic receptor, beta3-AR; PPARgamma coactivator 1 alpha, PGC1alpha, and uncoupling protein 1, UCP1). The ob/ob group also showed impaired gene expression for lipid utilization (perilipin was increased, while other markers were diminished: carnitine palmitoyltransferase-1b, CPT-1b; cluster of differentiation 36, CD36; fatty acid binding protein 4, FABP4; fatty acid synthase, FAS, and sterol regulatory element-binding protein 1c, SREBP1c), and altered protein expression of insulin signaling (diminished pAKT, TC10, and GLUT-4). Lastly, the ob/ob group showed increased gene expression of markers of inflammation (interleukin 1 beta, IL-1beta; IL-6, tumor necrosis factor alpha, TNFalpha; and monocyte chemotactic protein-1, MCP-1). In conclusion, the ob/ob mice have decreased thermogenic markers associated with reduced gene expression related to fatty acid synthesis, mobilization, and oxidation. There were also alterations in insulin signaling and protein and gene expressions of inflammation. The findings suggest that the lack of substrate for thermogenesis and the local inflammation negatively regulated thermogenic signaling in the ob/ob mice.

Browning of white adipose tissue: lessons from experimental models

Abstract Beige or brite (brown-in-white) adipocytes are present in white adipose tissue (WAT) and have a white fat-like phenotype that when stimulated acquires a brown fat-like phenotype, leading to increased thermogenesis. This phenomenon is known as browning and is more likely to occur in subcutaneous fat depots. Browning involves the expression of many transcription factors, such as PR domain containing 16 (PRDM16) and peroxisome proliferator-activated receptor (PPAR)-γ, and of uncoupling protein (UCP)-1, which is the hallmark of thermogenesis. Recent papers pointed that browning can occur in the WAT of humans, with beneficial metabolic effects. This fact indicates that these cells can be targeted to treat a range of diseases, with both pharmacological and nutritional activators. Pharmacological approaches to induce browning include the use of PPAR-α agonist, adrenergic receptor stimulation, thyroid hormone administration, irisin and FGF21 induction. Most of them act through the induction of PPAR-γ coactivator (PGC) 1-α and the consequent mitochondrial biogenesis and UCP1 induction. About the nutritional inducers, several compounds have been described with multiple mechanisms of action. Some of these activators include specific amino acids restriction, capsaicin, bile acids, Resveratrol, and retinoic acid. Besides that, some classes of lipids, as well as many plant extracts, have also been implicated in the browning of WAT. In conclusion, the discovery of browning in human WAT opens the possibility to target the adipose tissue to fight a range of diseases. Studies have arisen showing promising results and bringing new opportunities in thermogenesis and obesity control.

Animal Models of Nutritional Induction of Type 2 Diabetes Mellitus

La diabetes mellitus tipo 2 (DM2) es la enfermedad metabolica cronica mas comun, afectando aproximadamente al 6% de la poblacion adulta en el mundo occidental. Esta condicion es una causa importante de las enfermedades cardiovasculares, la ceguera, la insuficiencia renal, y las amputaciones, con un aumento de su prevalencia en todo el mundo. El riesgo de obesidad en la diabetes tipo 2 esta determinado por el grado de obesidad y localizacion de la grasa corporal, siendo la resistencia a la insulina (RI) la principal relacion entre estas enfermedades metabolicas. Los estudios experimentales han demostrado que los factores dieteticos, y en particular los lipidos, se asocian de manera importante con la masa corporal (MC), la IR y la diabetes tipo 2. Asimismo, el consumo excesivo de alimentos ricos en carbohidratos de alto contenido energetico pueden provocar la diabetes tipo 2. Ademas, se ha sugerido que una dieta materna inadecuada al momento de concebir o durante el periodo de gestacion daria lugar al desarrollo de la excesiva MC y de trastornos metabolicos en los hijos, tales como la homeostasis anormal de la glucosa, reduccion de la sensibilidad a la insulina en todo el cuerpo, el deterioro en la funcion de celulas beta, resistencia a la insulina y cambios en la estructura del pancreas. La alteracion metabolica esta asociada de forma importante con los efectos daninos sobre el desarrollo y funcion de las celulas beta. Sin embargo, las alteraciones en la cantidad y la calidad de la grasa dietetica pueden modificar el metabolismo de la glucosa como tambien la sensibilidad a la insulina. De esta manera, la investigacion experimental ha enfocado la atencion en algunos aceites debido a sus efectos beneficiosos. El aceite de oliva, es una fuente de monoinsaturados y actualmente se sabe que este aceite tambien mejora la sensibilidad a la insulina y el control glucemico El aceite de canola, el aceite de linaza y especialmente el aceite de pescado (rico en omega-3 los acidos grasos poliinsaturados (PUFAs)) fueron descritos por primera vez como nutrientes de la dieta eficaces contra la hipertrigliceridemia, sin embargo, es sabido que ademas tienen efectos positivos sobre el metabolismo de la glucosa.

Eicosapentaenoic acid (EPA) vs. Docosahexaenoic acid (DHA): Effects in epididymal white adipose tissue of mice fed a high-fructose diet

BACKGROUND Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been demonstrated to be beneficial for many diseases, including those associated with the metabolic syndrome (e.g. insulin resistance and hypertension). Nevertheless, not only their actions are not entirely understood, but also their only effects were not yet elucidated. Therefore, we aimed to compare the effects of EPA and DHA, alone or in combination, on the epididymal white adipose tissue (WAT) metabolism in mice fed a high-fructose diet. METHODS 3-mo-old C57Bl/6 mice were fed a control diet (C) or a high-fructose diet (HFru). After three weeks on the diets, the HFru group was subdivided into four new groups for another five weeks: HFru, HFru+EPA, HFru+DHA, and HFru-EPA+DHA (n=10/group). Besides evaluating biometric and metabolic parameters of the animals, we measured the adipocyte area and performed molecular analyses (inflammation and lipolysis) in the epididymal WAT. RESULTS The HFru group showed adipocyte hypertrophy, inflammation, and uncontrolled lipolysis. The treated animals showed a reversion of adipocyte hypertrophy, inhibition of inflammation with activation of anti-inflammatory mediators, and regularization of lipolysis. Overall, the beneficial effects were more marked with DHA than EPA. CONCLUSION Although the whole-body metabolic effects were similar between EPA and DHA, DHA appeared to be the central actor in WAT metabolism, modulating pro and anti-inflammatory pathways and alleviating adipocytes abnormalities. Therefore, when considering fructose-induced adverse effects in WAT, the most prominent actions were observed with DHA.

Treating fructose-induced metabolic changes in mice with high-intensity interval training: insights in the liver, white adipose tissue, and skeletal muscle

Fructose-rich caloric sweeteners induce adverse changes in the metabolism of humans. The study evaluated the effects of high-intensity interval training (HIIT) on a fructose feeding model, focusing on the liver, white adipose tissue (WAT), skeletal muscle, and their interplay. Male C57BL/6 mice were fed for 18 wk one of the following diets: control (C; 5% of total energy from fructose) or fructose (F; 55% of total energy from fructose). In the 10th week, for an additional 8-wk period, the groups were divided into nontrained (NT) or HIIT groups, totaling four groups: C-NT, C-HIIT, F-NT, and F-HIIT. At the end of the experiment, fructose consumption in the F-NT group led to a high systolic blood pressure, high plasma triglycerides, insulin resistance with glucose intolerance, and lower insulin sensitivity. We also observed liver steatosis, adipocyte hypertrophy, and diminished gene expressions of peroxisome proliferator-activated receptor-γ coactivator 1-α and fibronectin type III domain containing 5 (FNDC5; irisin) in this F-NT group. These results were accompanied by decreased gene expressions of nuclear respiratory factor 1 and mitochondrial transcription factor A (markers of mitochondrial biogenesis), and peroxisome proliferator-activated receptor-α and carnitine palmitoyltransferase 1 (markers of β-oxidation). HIIT improved all of these data in the C-HIIT and F-HIIT groups. In conclusion, in mice fed a fructose diet, HIIT improved body mass, blood pressure, glucose metabolism, and plasma triglycerides. Liver, WAT, and skeletal muscle were positively modulated by HIIT, indicating HIIT as a coadjutant treatment for diseases affecting these tissues.NEW & NOTEWORTHY We investigated the effects of high-intensity interval training (HIIT) in mice fed a fructose-rich diet and the resulting severe negative effect on the liver, white adipose tissue (WAT), and skeletal muscle, which reduced the expression of fibronectin type III domain containing 5 (FNDC5, irisin) and PGC1α and, consequently, affected markers of mitochondrial biogenesis and β-oxidation. Because HIIT may block these adverse effects in all of these three tissues, it might be suggested that it functions as a coadjutant treatment in combatting the alterations caused by high-fructose intake.