Interrelation of adipose tissue macrophages and fibrosis in obesity

Obesity is characterized by adipose tissue expansion, extracellular matrix remodelling and unresolved inflammation that contribute to insulin resistance and fibrosis. Adipose tissue macrophages represent the most abundant class of immune cells in adipose tissue inflammation and could be key mediators of adipocyte dysfunction and fibrosis in obesity. Although macrophage activation states are classically defined by the M1/M2 polarization nomenclature, novel studies have revealed a more complex range of macrophage phenotypes in response to external condition or the surrounding microenvironment. Here, we discuss the plasticity of adipose tissue macrophages (ATMs) in response to their microenvironment in obesity, with special focus on macrophage infiltration and polarization, and their contribution to adipose tissue fibrosis. A better understanding of the role of ATMs as regulators of adipose tissue remodelling may provide novel therapeutic strategies against obesity and associated metabolic diseases

Impact of GLP-1 receptor agonist versus omega-3 fatty acids supplement on obesity-induced alterations of mitochondrial respiration

ObjectiveTo compare administration of the glucagon-like peptide-1 (GLP-1) analogue, exenatide, versus dietary supplementation with the omega-3 fatty acid-rich Calanus oil on obesity-induced alterations in mitochondrial respiration. MethodsSix-week-old female C57BL/6JOlaHSD mice were given high fat diet (HFD, 45% energy from fat) for 12 weeks to induce obesity. Thereafter, they were divided in three groups where one received exenatide (10 mu g/kg/day) via subcutaneously implanted mini-osmotic pumps, a second group received 2% Calanus oil as dietary supplement, while the third group received HFD without any treatment. Animals were sacrificed after 8 weeks of treatment and tissues (skeletal muscle, liver, and white adipose tissue) were collected for measurement of mitochondrial respiratory activity by high-resolution respirometry, using an Oroboros Oxygraph-2k (Oroboros instruments, Innsbruck, Austria). ResultsIt was found that high-fat feeding led to a marked reduction of mitochondrial respiration in adipose tissue during all three states investigated - LEAK, OXPHOS and ETS. This response was to some extent attenuated by exenatide treatment, but not with Calanus oil treatment. High-fat feeding had no major effect on hepatic mitochondrial respiration, but exenatide treatment resulted in a significant increase in the various respiratory states in liver. Mitochondrial respiration in skeletal muscle was not significantly influenced by high-fat diet or any of the treatments. The precise evaluation of mitochondrial respiration considering absolute oxygen flux and ratios to assess flux control efficiency avoided misinterpretation of the results. ConclusionsExenatide increased hepatic mitochondrial respiration in high-fat fed mice, but no clear beneficial effect was observed in skeletal muscle or fat tissue. Calanus oil did not negatively affect respiratory activity in these tissues, which maintains its potential as a dietary supplement, due to its previously reported benefits on cardiac functio

Effects of Lifestyle Intervention in Tissue-Specific Lipidomic Profile of Formerly Obese Mice

Lipids are highly diverse in their composition, properties and distribution in different biological entities. We aim to establish the lipidomes of several insulin-sensitive tissues and to test their plasticity when divergent feeding regimens and lifestyles are imposed. Here, we report a proton nuclear magnetic resonance (1H-NMR) study of lipid abundance across 4 tissues of C57Bl6J male mice that includes the changes in the lipid profile after every lifestyle intervention. Every tissue analysed presented a specific lipid profile irrespective of interventions. Glycerolipids and fatty acids were most abundant in epididymal white adipose tissue (eWAT) followed by liver, whereas sterol lipids and phosphoglycerolipids were highly enriched in hypothalamus, and gastrocnemius had the lowest content in all lipid species compared to the other tissues. Both when subjected to a high-fat diet (HFD) and after a subsequent lifestyle intervention (INT), the lipidome of hypothalamus showed no changes. Gastrocnemius and liver revealed a pattern of increase in content in many lipid species after HFD followed by a regression to basal levels after INT, while eWAT lipidome was affected mainly by the fat composition of the administered diets and not their caloric density. Thus, the present study demonstrates a unique lipidome for each tissue modulated by caloric intake and dietary composition. Keywords: lipidomics; tissue-specific; plasticity; energy intake; diet composition; exercise; hypothalamus; gastrocnemius; liver; white adipose tissu

NRF2 function in osteocytes is required for bone homeostasis and drives osteocytic gene expression

Osteocytes, the most abundant bone cell type, are derived from osteoblasts through a process in which they are embedded in an osteoid. We previously showed that nutrient restriction promotes the osteocyte transcriptional program and is associated with increased mitochondrial biogenesis. Here, we show that increased mitochondrial biogenesis increase reactive oxygen species (ROS) levels and consequently, NRF2 activity during osteocytogenesis. NRF2 activity promotes osteocyte-specific expression of Dmp1, Mepe, and Sost in IDG-SW3 cells, primary osteocytes, and osteoblasts, and in murine models with Nfe2l2 deficiency in osteocytes or osteoblasts. Moreover, ablation of Nfe2l2 in osteocytes or osteoblasts generates osteopenia and increases osteoclast numbers with marked sexual dimorphism. Finally, treatment with dimethyl fumarate prevented the deleterious effects of ovariectomy in trabecular bone masses of mice and restored osteocytic gene expression. Altogether, we uncovered the role of NRF2 activity in osteocytes during the regulation of osteocyte gene expression and maintenance of bone homeostasis

Remission of obesity and insulin resistance is not sufficient to restore mitochondrial homeostasis in visceral adipose tissue

Metabolic plasticity is the ability of a biological system to adapt its metabolic phenotype to different environmental stressors. We used a whole-body and tissue-specific phenotypic, functional, proteomic, metabolomic and transcriptomic approach to systematically assess metabolic plasticity in diet-induced obese mice after a combined nutritional and exercise intervention. Although most obesity and overnutrition-related pathological features were successfully reverted, we observed a high degree of metabolic dysfunction in visceral white adipose tissue, characterized by abnormal mitochondrial morphology and functionality. Despite two sequential therapeutic interventions and an apparent global healthy phenotype, obesity triggered a cascade of events in visceral adipose tissue progressing from mitochondrial metabolic and proteostatic alterations to widespread cellular stress, which compromises its biosynthetic and recycling capacity. In humans, weight loss after bariatric surgery showed a transcriptional signature in visceral adipose tissue similar to our mouse model of obesity reversion. Overall, our data indicate that obesity prompts a lasting metabolic fingerprint that leads to a progressive breakdown of metabolic plasticity in visceral adipose tissue

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

White adipose tissue characterization and lipid profiling in obesity

[eng] Obesity has become exceedingly pervasive, a resultant of amplified food availability and reshaped human behavior stimulated by urbanization. It poses as a major challenge for human metabolic physiology testing the limitations of metabolic plasticity; an adaptive capacity against internal or environmental stressors. A stressor persisting and turning into a chronic situation, diminishes the ability to adapt, thus debilitating metabolic plasticity. In the face of the various strategies for combatting obesity, it has become increasingly crucial to further advance the understanding of obesity-associated metabolic adaptations at a systemic and a tissue-specific level. Committed towards this purpose, the LiMa (Lifestyle Matters) project aimed at an integrative multidisciplinary approach addressing phenotypical and functional transitions induced by obesity and weight loss. A combined nutritional and exercise intervention was implemented on a mouse model of diet-induced obesity in order to evaluate metabolic plasticity and interpret the crosstalk among tissues and its manifestation systemically. An assessment of several parameters, systemically and in major tissues dictating metabolic responses, revealed an impressive capacity to overcome the impairment induced by obesity. However, a lack of plasticity emphasized by a deteriorating mitochondrial function in epididymal white adipose tissue (eWAT) was evident in our study. The aim of this doctoral thesis is to gain further insight on metabolic plasticity of formerly obese mice by adding on to the description of the phenotypes of the experimental groups and by focusing on different depots of white adipose tissue and their stromal vascular fraction. A lipidomic study identified lipid profiles as tissue specific, and reported lipidomes of liver and skeletal muscle reflective of energy balance contrary to eWAT lipidome, which was reflective of the content of the administered diet. With the attention shifted towards adipose tissue, eWAT seemed to be more susceptible than the other adipose tissue depot investigated – subcutaneous white adipose tissue (sWAT) – to damage initiated by high-fat feeding. This vulnerability was highlighted by an intense inflammatory profile, as indicated by the M1 proinflammatory phenotype of infiltrating macrophages in eWAT and the presence of crown-like structures surrounding adipocytes, together with worsening of mitochondrial function of adipose-derived stem cells in eWAT. Moreover, other macrophage subtypes seem to participate in eWAT expansion and remodeling, including M2a macrophages induced by HFD, which are involved in endocytic processes, as well as M2b macrophages, controlling the intensity of inflammatory reactions, and M2c macrophages, involved in the phagocytosis of apoptotic adipocytes. eWAT remodeling also involved significant changes in the composition and appearance of the extracellular matrix, with HFD increasing the expression of both collagens and proteoglycans involved in fibrosis, such as COL1, COL3 or COL6, and lumican and versican, respectively. Notably, intervention studies aimed at reducing body weight (exercise and decreased feeding) reverted, though only partially, the matrisome of eWAT while the macrophage population recovered the original, lean phenotype upon weight loss. Hence, data from previous LiMa studies combined with data from this doctoral thesis illustrate visceral white adipose tissue as the most affected tissue in the progression of obesity. In addition, the deterioration in its mitochondrial function despite improvements in tissue morphology hints at mitochondrial health as a key determinator of the state of metabolic plasticity

White adipose tissue characterization and lipid profiling in obesity

Programa de Doctorat en Biomedicina[eng] Obesity has become exceedingly pervasive, a resultant of amplified food availability and reshaped human behavior stimulated by urbanization. It poses as a major challenge for human metabolic physiology testing the limitations of metabolic plasticity; an adaptive capacity against internal or environmental stressors. A stressor persisting and turning into a chronic situation, diminishes the ability to adapt, thus debilitating metabolic plasticity. In the face of the various strategies for combatting obesity, it has become increasingly crucial to further advance the understanding of obesity-associated metabolic adaptations at a systemic and a tissue-specific level. Committed towards this purpose, the LiMa (Lifestyle Matters) project aimed at an integrative multidisciplinary approach addressing phenotypical and functional transitions induced by obesity and weight loss. A combined nutritional and exercise intervention was implemented on a mouse model of diet-induced obesity in order to evaluate metabolic plasticity and interpret the crosstalk among tissues and its manifestation systemically. An assessment of several parameters, systemically and in major tissues dictating metabolic responses, revealed an impressive capacity to overcome the impairment induced by obesity. However, a lack of plasticity emphasized by a deteriorating mitochondrial function in epididymal white adipose tissue (eWAT) was evident in our study. The aim of this doctoral thesis is to gain further insight on metabolic plasticity of formerly obese mice by adding on to the description of the phenotypes of the experimental groups and by focusing on different depots of white adipose tissue and their stromal vascular fraction. A lipidomic study identified lipid profiles as tissue specific, and reported lipidomes of liver and skeletal muscle reflective of energy balance contrary to eWAT lipidome, which was reflective of the content of the administered diet. With the attention shifted towards adipose tissue, eWAT seemed to be more susceptible than the other adipose tissue depot investigated – subcutaneous white adipose tissue (sWAT) – to damage initiated by high-fat feeding. This vulnerability was highlighted by an intense inflammatory profile, as indicated by the M1 proinflammatory phenotype of infiltrating macrophages in eWAT and the presence of crown-like structures surrounding adipocytes, together with worsening of mitochondrial function of adipose-derived stem cells in eWAT. Moreover, other macrophage subtypes seem to participate in eWAT expansion and remodeling, including M2a macrophages induced by HFD, which are involved in endocytic processes, as well as M2b macrophages, controlling the intensity of inflammatory reactions, and M2c macrophages, involved in the phagocytosis of apoptotic adipocytes. eWAT remodeling also involved significant changes in the composition and appearance of the extracellular matrix, with HFD increasing the expression of both collagens and proteoglycans involved in fibrosis, such as COL1, COL3 or COL6, and lumican and versican, respectively. Notably, intervention studies aimed at reducing body weight (exercise and decreased feeding) reverted, though only partially, the matrisome of eWAT while the macrophage population recovered the original, lean phenotype upon weight loss. Hence, data from previous LiMa studies combined with data from this doctoral thesis illustrate visceral white adipose tissue as the most affected tissue in the progression of obesity. In addition, the deterioration in its mitochondrial function despite improvements in tissue morphology hints at mitochondrial health as a key determinator of the state of metabolic plasticity

Tambjamines and prodiginines: biocidal activity against trypanosoma cruzi

The aim of this work was to explore new therapeutic options against Chagas disease by the in vitro analysis of the biocidal activities of several tambjamine and prodiginine derivatives, against the Trypanosoma cruzi CLB strain (DTU TcVI). The compounds were initially screened against epimastigotes. The five more active compounds were assayed in intracellular forms. The tambjamine MM3 and both synthetic and natural prodigiosins displayed the highest trypanocidal profiles, with IC50 values of 4.52, 0.46, and 0.54 µM for epimastigotes and 1.9, 0.57, and 0.1 µM for trypomastigotes/amastigotes, respectively. Moreover, the combination treatment of these molecules with benznidazole showed no synergism. Finally, oxygen consumption inhibition determinations performed using high-resolution respirometry, revealed a potent effect of prodigiosin on parasite respiration (73% of inhibition at ½ IC50), suggesting that its mode of action involves the mitochondria. Moreover, its promising selectivity index (50) pointed out an interesting trypanocidal potential and highlighted the value of prodigiosin as a new candidate to fight Chagas disease