Anti-Obesity Effect of n-3 Polyunsaturated Fatty Acids in Mice Fed High-Fat Diet Is Independent of Cold-Induced Thermogenesis

Fatty Acids and their Proteins in Adipose Tissue Inflammation

Chronic low-grade adipose tissue inflammation is associated with metabolic disorders. Inflammation results from the intertwined cross-talks of pro-inflammatory and anti-inflammatory pathways in the immune response of adipose tissue. In addition, adipose FABP4 levels and lipid droplet proteins are involved in systemic and tissue inflammation. Dysregulated adipocytes help infiltrate immune cells derived from bone marrow responsible for producing cytokines and chemokines. When adipose tissue expands in excess, adipocyte exhibits increased secretion of adipokines and is implicated in metabolic disturbances due to the release of free fatty acids. This review presents an emerging concept in adipose tissue fat metabolism, fatty acid handling and binding proteins, and lipid droplet proteins and their involvement in inflammatory disorders.

Overview of Natural Supplements for the Management of Diabetes and Obesity

Bioactive compounds found in various natural sources, such as fruits, vegetables, and herbs, have been studied for their potential benefits in managing obesity and diabetes. These compounds include polyphenols, flavonoids, other antioxidants, fiber, and certain fatty acids. Studies have found that these compounds may improve insulin sensitivity, regulate blood sugar levels, and promote weight loss. However, the effects of these compounds can vary depending on the type and amount consumed, as well as individual factors, such as genetics and lifestyle. Nutraceutical substances have multifaceted therapeutic advantages, and they have been reported to have disease-prevention and health-promoting properties. Several clinically used nutraceuticals have been shown to target the pathogenesis of diabetes mellitus, obesity, and metabolic syndrome and their complications and modulate various clinical outcomes favorably. This review aims to highlight and comment on some of the most prominent natural components used as antidiabetics and in managing obesity.

Hepatoprotective and Anti-Obesity Properties of Sardine By-Product Oil in Rats Fed a High-Fat Diet

Excess lipid intake can trigger liver lipid accumulation and oxidative responses, which can lead to metabolic disturbances and contribute to hepatic steatosis and obesity and increase the risk of cardiovascular disease. Production of fish oil rich in omega-3 is a good opportunity for valorizing fish by-products in the therapeutic field. In this study, we explored the effects of oil from Sardina pilchardus by-products on cardiometabolic and oxidative disorders caused by toxic effects of excess lipids in obese rats. Three groups of obese rats received either 20% sardine by-product oil (SBy-Ob-HS; experimental group), 20% fillet oil (SF-Ob-HS; positive control group), or a high-fat diet (Ob-HS). Normal weight rats received a standard diet (normal). There was a significant decrease in serum total cholesterol (TC), triacylglycerols (TG), and insulin concentrations in the SBy-Ob-HS group compared with the SF-Ob-HS group. Compared with the Ob-HS group, TC and TG, glycemia, glycosylated hemoglobin, and insulinemia were decreased in the SBy-Ob-HS (more notably) and SF-Ob-HS groups. Furthermore, hepatic lipids, low density lipoprotein-cholesterol (C), the non-esterified cholesterol/phos-pholipids ratio, serum transaminases activities and lipid peroxidation were lower and serum high density lipoproteins-C were higher in the SBy-Ob-HS and SF-Ob-HS groups compared with the Ob-HS group. Serum isoprostane concentrations were reduced in the SBy-Ob-HS (more notably) and SF-Ob-HS groups compared with the Ob-HS and normal groups. The activities of antioxidant enzymes in tissues were enhanced, particularly in the by-product oil group. The oil extracted from by-products demonstrate anti-obesity properties (hypolipemiant, hepatoprotective, antiatherogenic, antidiabetic, and antioxidant) that may be beneficial for the management of obesity and its complications, such as hepatic steatosis.

Fish oil extracted from Coregonus peled improves obese phenotype and changes gut microbiota in a high-fat diet-induced mouse model of recurrent obesity

Recurrent obesity is rapidly emerging as a public health problem. Previous studies have confirmed that fish oil supplementation can alleviate obesity in mice; however, the effect of fish oil on recurrent obesity remains unclear. In the present study, the modulatory effects of fish oil extracted from Coregonus peled on the phenotypes and gut microbiota of recurrent obese mice were evaluated by MRI, OGTT, and bioinformatics analysis. We found that fish oil supplementation could significantly reduce the body weight gain, net weight gain, body fat distribution, and glucose tolerance. In addition, the composition and structure of gut microbiota were significantly shifted toward those of the control group by fish oil treatment. Moreover, the relative abundance of gut microbiota, such as Bacteroidetes, Bacteroidia, Lachnospiraceae, and Bifidobacterium, was markedly responding to the rapid dietary changes between fish oil and high-fat diet. Overall, our results confirmed that the alleviation of recurrent obesity using fish oil supplementation might be modulated by altering the hysteretic behavior and memory-like function of gut microbiota. We proposed that further studies are needed to elucidate the modulation mechanism.

No Effect of Dietary Fish Oil Supplementation on the Recruitment of Brown and Brite Adipocytes in Mice or Humans under Thermoneutral Conditions

SCOPE

Brown and brite adipocytes within the mammalian adipose organ provide non-shivering thermogenesis and thus, have an exceptional capacity to dissipate chemical energy as heat. Polyunsaturated fatty acids (PUFA) of the n3-series, abundant in fish oil, have been repeatedly demonstrated to enhance the recruitment of thermogenic capacity in these cells, consequently affecting body adiposity and glucose tolerance. These effects are scrutinized in mice housed in a thermoneutral environment and in a human dietary intervention trial.

METHODS AND RESULTS

Mice are housed in a thermoneutral environment eliminating the superimposing effect of mild cold-exposure on thermogenic adipocyte recruitment. Dietary fish oil supplementation in two different inbred mouse strains neither affects body mass trajectory nor enhances the recruitment of brown and brite adipocytes, both in the presence and absence of a β3-adrenoreceptor agonist imitating the effect of cold-exposure on adipocytes. In line with these findings, dietary fish oil supplementation of persons with overweight or obesity fails to recruit thermogenic adipocytes in subcutaneous adipose tissue.

CONCLUSION

Thus, the authors' data question the hypothesized potential of n3-PUFA as modulators of adipocyte-based thermogenesis and energy balance regulation.

Additive Effects of Omega-3 Fatty Acids and Thiazolidinediones in Mice Fed a High-Fat Diet: Triacylglycerol/Fatty Acid Cycling in Adipose Tissue

Long-chain n-3 polyunsaturated fatty acids (Omega-3) and anti-diabetic drugs thiazolidinediones (TZDs) exhibit additive effects in counteraction of dietary obesity and associated metabolic dysfunctions in mice. The underlying mechanisms need to be clarified. Here, we aimed to learn whether the futile cycle based on the hydrolysis of triacylglycerol and re-esterification of fatty acids (TAG/FA cycling) in white adipose tissue (WAT) could be involved. We compared Omega-3 (30 mg/g diet) and two different TZDs—pioglitazone (50 mg/g diet) and a second-generation TZD, MSDC-0602K (330 mg/g diet)—regarding their effects in C57BL/6N mice fed an obesogenic high-fat (HF) diet for 8 weeks. The diet was supplemented or not by the tested compound alone or with the two TZDs combined individually with Omega-3. Activity of TAG/FA cycle in WAT was suppressed by the obesogenic HF diet. Additive effects in partial rescue of TAG/FA cycling in WAT were observed with both combined interventions, with a stronger effect of Omega-3 and MSDC-0602K. Our results (i) supported the role of TAG/FA cycling in WAT in the beneficial additive effects of Omega-3 and TZDs on metabolism of diet-induced obese mice, and (ii) showed differential modulation of WAT gene expression and metabolism by the two TZDs, depending also on Omega-3.

A review on differential effects of dietary fatty acids on weight, appetite and energy expenditure

The association between weight and chronic diseases is well defined. The quality and quantity of dietary fatty acids is an important external factor and appetite and energy expenditure, are important internal factors in determining body weight. On the other hand, dietary fatty acids composition can modulate appetite and energy metabolism, but not all fats are equal in producing metabolic responses.Given the accumulating evidence for differential effects of various dietary fatty acids, one important area of investigation is to scrutinize their roles in weight, appetite and energy expenditure modulation. There is substantial evidence to suggest that saturated fatty acids have a greater effect on appetite control, although in the long run may result in more weight gain than unsaturated fatty acids due to a weaker stimulation of energy expenditure. In contrast, mono-unsaturated fats do not have much effects on appetite control, but they can be beneficial in weight control over the long term due to stimulatory effects on energy expenditure. Interestingly, in case of poly unsaturated fats, including n-3 and n-6, their effect on increasing energy expenditure is aligned, but they act differently in controlling weight and appetite.

Modeling Diet-Induced Metabolic Syndrome in Rodents

Standardized animal models represent one of the most valuable tools available to understand the mechanism underlying the metabolic syndrome (MetS) and to seek for new therapeutic strategies. However, there is considerable variability in the studies conducted with this essential purpose. This review presents an updated discussion of the most recent studies using diverse experimental conditions to induce MetS in rodents with unbalanced diets, discusses the key findings in metabolic outcomes, and critically evaluates what we have been learned from them and how to advance in the field. The study includes scientific reports sourced from the Web of Science and PubMed databases, published between January 2013 and June 2020, which used hypercaloric diets to induce metabolic disorders, and address the impact of the diet on metabolic parameters. The collected data are used as support to discuss variables such as sex, species, and age of the animals, the most favorable type of diet, and the ideal diet length to generate metabolic changes. The experimental characteristics propose herein improve the performance of a preclinical model that resembles the human MetS and will guide researchers to investigate new therapeutic alternatives with confidence and higher translational validity.

n-3 PUFA Sources (Precursor/Products): A Review of Current Knowledge on Rabbit

This review compares the effects of different n-3 polyunsaturated fatty acid (PUFA) sources on biological activity, physiological/reproductive endpoints, and health implications with a special emphasis on a rabbit case study. Linoleic acid (LA) and α-linolenic acid (ALA) are members of two classes of PUFAs, namely the n-6 and n-3 series, which are required for normal human health. Both are considered precursors of a cascade of molecules (eicosanoids), which take part in many biological processes (inflammation, vasoconstriction/vasodilation, thromboregulation, etc.). However, their biological functions are opposite and are mainly related to the form (precursor or long-chain products) in which they were administered and to the enzyme-substrate preference. ALA is widely present in common vegetable oils and foods, marine algae, and natural herbs, whereas its long-chain PUFA derivatives are available mainly in fish and animal product origins. Recent studies have shown that the accumulation of n-3 PUFAs seems mostly to be tissue-dependent and acts in a tissue-selective manner. Furthermore, dietary n-3 PUFAs widely affect the lipid oxidation susceptibility of all tissues. In conclusion, sustainable sources of n-3 PUFAs are limited and exert a different effect about (1) the form in which they are administered, precursor or derivatives; (2) their antioxidant protections; and (3) the purpose to be achieved (health improvement, physiological and reproductive traits, metabolic pathways, etc.).

Effects of eicosapentaenoic acid and docosahexaenoic acid on C2C12 cell adipogenesis and inhibition of myotube formation

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) modulate cellular metabolic functions and gene expression. This study investigated the impacts of EPA and DHA on gene expression and morphological changes during adipogenic inducement in C2C12 myoblasts. Cells were cultured and treated with differentiation medium with and without 50 μM EPA and DHA. Cells treated with fatty acids had noticeable lipid droplets, but no formation of myotubes compared to control group cells. The expression levels of key genes relevant to adipogenesis and inflammation were significantly higher (P < 0.05) in cells treated with fatty acids. Genes associated with myogenesis and mitochondrial biosynthesis and function had lower (P < 0.05) expression with fatty acids supplementation. Moreover, fatty acid treatment reduced (P < 0.05) oxygen consumption rate in the differentiated cells. This suggested blocking myotube formation through supplementation with EPA and DHA drove myoblasts to enter the quiescent state and enabled adipogenic trans-differentiation of the myoblasts. Data also suggested that overdosage of EPA and DHA during gestation may drive fetal mesenchymal stem cell differentiation to the fate of adipogenesis and have a long-term effect on childhood obesity.

Differential Anti-Adipogenic Effects of Eicosapentaenoic and Docosahexaenoic Acids in Obesity

SCOPE

To assess the associations of plasma eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) with body fat in a population-based sample and explore the mechanism of action based on browning of white adipose tissue (WAT) in high-fat-diet-induced obese (DIO) mice and 3T3-L1 adipocytes.

METHODS AND RESULTS

Plasma EPA and DHA of 1719 adults in the National Health and Nutrition Examination Survey (2003-2004) are determined by gas chromatography mass spectrometry, while total body fat is measured by dual-energy X-ray absorptiometry. DIO mice are fed a high-fat diet supplemented with EPA or DHA (1% wt/wt) for 15 weeks and 3T3-L1 preadipocytes are treated with EPA or DHA during differentiation. Plasma DHA but not EPA is associated with lower body fat mass (p_trend < 0.0001), which persists in overweight/obese subjects (p_trend = 0.02). DHA supplementation reduces inguinal WAT and exhibits a more pronounced thermogenic effect than EPA in DIO mice. In vitro, the browning process is induced after 2-day and 6-day treatment with DHA and EPA, respectively.

CONCLUSION

Plasma DHA but not EPA is inversely associated with body fat mass. The more potent anti-adipogenic effect of DHA than EPA may involve a better capability of inducing browning of WAT for DHA.

What is the best housing temperature to translate mouse experiments to humans?

OBJECTIVES

Ambient temperature impinges on energy metabolism in a body size dependent manner. This has implications for the housing temperature at which mice are best compared to humans. In 2013, we suggested that, for comparative studies, solitary mice are best housed at 23-25 °C, because this is 3-5 °C below the mouse thermoneutral zone and humans routinely live 3-5 °C below thermoneutrality, and because this generates a ratio of DEE to BMR of 1.6-1.9, mimicking the ratio found in free-living humans.

METHODS

Recently, Fischer et al. (2017) challenged this estimate. By studying mice at 21 °C and at 30 °C (but notably not at 23-25 °C) they concluded that 30 °C is the optimal housing temperature. Here, we measured energy metabolism of C57BL/6 mice over a range of temperatures, between 21.4 °C and 30.2 °C.

RESULTS

We observed a ratio of DEE to BMR of 1.7 at 27.6 °C and of 1.8 at 25.5 °C, suggesting that this is the best temperature range for housing C57BL/6 mice to mimic human thermal relations. We used a 24 min average to calculate the ratio, similar to that used in human studies, while the ratio calculated by Fisher et al. dependent on short, transient metabolic declines.

CONCLUSION

We concur with Fisher et al. and others that 21 °C is too cool, but we continue to suggest that 30 °C is too warm. We support this with other data. Finally, to mimic living environments of all humans, and not just those in controlled Western environments, mouse experimentation at various temperatures is likely required.

Seafood intake and the development of obesity, insulin resistance and type 2 diabetes

We provide an overview of studies on seafood intake in relation to obesity, insulin resistance and type 2 diabetes. Overweight and obesity development is for most individuals the result of years of positive energy balance. Evidence from intervention trials and animal studies suggests that frequent intake of lean seafood, as compared with intake of terrestrial meats, reduces energy intake by 4–9 %, sufficient to prevent a positive energy balance and obesity. At equal energy intake, lean seafood reduces fasting and postprandial risk markers of insulin resistance, and improves insulin sensitivity in insulin-resistant adults. Energy restriction combined with intake of lean and fatty seafood seems to increase weight loss. Marine n-3 PUFA are probably of importance through n-3 PUFA-derived lipid mediators such as endocannabinoids and oxylipins, but other constituents of seafood such as the fish protein per se, trace elements or vitamins also seem to play a largely neglected role. A high intake of fatty seafood increases circulating levels of the insulin-sensitising hormone adiponectin. As compared with a high meat intake, high intake of seafood has been reported to reduce plasma levels of the hepatic acute-phase protein C-reactive protein level in some, but not all studies. More studies are needed to confirm the dietary effects on energy intake, obesity and insulin resistance. Future studies should be designed to elucidate the potential contribution of trace elements, vitamins and undesirables present in seafood, and we argue that stratification into responders and non-responders in randomised controlled trials may improve the understanding of health effects from intake of seafood.

Fish Oil Protects Wild Type and Uncoupling Protein 1-Deficient Mice from Obesity and Glucose Intolerance by Increasing Energy Expenditure

SCOPE

The mechanisms and involvement of uncoupling protein 1 (UCP1) in the protection from obesity and insulin resistance induced by intake of a high-fat diet rich in omega-3 (n-3) fatty acids are investigated.

METHODS AND RESULTS

C57BL/6J mice are fed either a low-fat (control group) or one of two isocaloric high-fat diets containing either lard (HFD) or fish oil (HFN3) as fat source and evaluated for body weight, adiposity, energy expenditure, glucose homeostasis, and inguinal white and interscapular brown adipose tissue (iWAT and iBAT, respectively) gene expression, lipidome, and mitochondrial bioenergetics. HFN3 intake protected from obesity, glucose and insulin intolerances, and hyperinsulinemia. This is associated with increased energy expenditure, iWAT UCP1 expression, and incorporation of n-3 eicosapentaenoic and docosahexaenoic fatty acids in iWAT and iBAT triacylglycerol. Importantly, HFN3 is equally effective in reducing body weight gain, adiposity, and glucose intolerance and increasing energy expenditure in wild-type and UCP1-deficient mice without recruiting other thermogenic processes in iWAT and iBAT, such as mitochondrial uncoupling and SERCA-mediated calcium and creatine-driven substrate cyclings.

CONCLUSION

Intake of a high-fat diet rich in omega-3 fatty acids protects both wild-type and UCP1-deficient mice from obesity and insulin resistance by increasing energy expenditure through unknown mechanisms.

Increased triacylglycerol - Fatty acid substrate cycling in human skeletal muscle cells exposed to eicosapentaenoic acid

It has previously been shown that pretreatment of differentiated human skeletal muscle cells (myotubes) with eicosapentaenoic acid (EPA) promoted increased uptake of fatty acids and increased triacylglycerol accumulation, compared to pretreatment with oleic acid (OA) and palmitic acid (PA). The aim of the present study was to examine whether EPA could affect substrate cycling in human skeletal muscle cells by altering lipolysis rate of intracellular TAG and re-esterification of fatty acids. Fatty acid metabolism was studied in human myotubes using a mixture of fatty acids, consisting of radiolabelled oleic acid as tracer (14C-OA) together with EPA or PA. Co-incubation of myotubes with EPA increased cell-accumulation and incomplete fatty acid oxidation of 14C-OA compared to co-incubation with PA. Lipid distribution showed higher incorporation of 14C-OA into all cellular lipids after co-incubation with EPA relative to PA, with most markedly increases (3 to 4-fold) for diacylglycerol and triacylglycerol. Further, the increases in cellular lipids after co-incubation with EPA were accompanied by higher lipolysis and fatty acid re-esterification rate. Correspondingly, basal respiration, proton leak and maximal respiration were significantly increased in cells exposed to EPA compared to PA. Microarray and Gene Ontology (GO) enrichment analysis showed that EPA, related to PA, significantly changed i.e. the GO terms "Neutral lipid metabolic process" and "Regulation of lipid storage". Finally, an inhibitor of diacylglycerol acyltransferase 1 decreased the effect of EPA to promote fatty acid accumulation. In conclusion, incubation of human myotubes with EPA, compared to PA, increased processes of fatty acid turnover and oxidation suggesting that EPA may activate futile substrate cycling of fatty acids in human myotubes. Increased TAG-FA cycling may be involved in the potentially favourable effects of long-chain polyunsaturated n-3 fatty acids on skeletal muscle and whole-body energy metabolism.

Dietary n-3 long-chain polyunsaturated fatty acids upregulate energy dissipating metabolic pathways conveying anti-obesogenic effects in mice

Background

We previously reported on the anti-obesogenic and anti-inflammatory effects associated with n-3 long-chain polyunsaturated fatty acids (LCPUFA) in our diet-induced obesity (DIO) mouse model. Two isocaloric high-fat diets (HFDs; 48 kJ% fat), HFD (HF) and n-3 LCPUFA-enriched HFD (HF/n-3), and a control diet (C; 13 kJ% fat) were used. The underlying mechanisms however have largely remained unclear. Here, we assessed whether the reduced fat mass reflected n-3 LCPUFA-induced expression changes in lipid metabolism of the intestine, liver, and interscapular brown adipose tissue (iBAT), as well as increased iBAT thermogenic capacity.

Methods

For HF/n-3, saturated and monounsaturated fatty acids were partially substituted by n-3 LCPUFA eicosapentaenoic acid and docosahexaenoic acid to achieve a balanced n-6/n-3 PUFA ratio (0.84) compared to the unbalanced ratios of HF (13.5) and C (9.85). Intestine, liver and iBAT from male C57BL/6 J mice, fed defined soybean/palm oil-based diets for 12 weeks, were further analysed. Gene and protein expression analyses, immunohistochemistry and correlation analyses for metabolic interactions were performed.

Results

Compared to HF and C, our analyses suggest significantly diminished de novo lipogenesis (DNL) and/or increased hepatic and intestinal fatty acid oxidation (ω-oxidation and peroxisomal β-oxidation) in HF/n-3 mice. For iBAT, the thermogenic potential was enhanced upon HF/n-3 consistent with upregulated expression for uncoupling protein-1 and genes involved in mitochondrial biogenesis. In addition, a higher capacity for the supply and oxidation of fatty acids was observed and expression and correlation analyses indicated a coordinated regulation of energy metabolism and futile cycling of triacylglycerol (TAG). Moreover, HF/n-3 significantly increased the number of anti-inflammatory macrophages and eosinophils and significantly enhanced the levels of activated AMP-activated protein kinase α (AMPKα), peroxisome proliferator-activated receptor α (PPARα) and fibroblast growth factor 21 (FGF21).

Conclusions

Our data suggest that by targeting transcriptional regulatory pathways, AMPKα, and FGF21 as potential mediators, HF/n-3 activated less efficient pathways for energy production, such as peroxisomal β-oxidation, increased ATP consumption upon the induction of futile cycling of TAG, and additionally increased the thermogenic and oxidative potential of iBAT. Therefore, we consider n-3 LCPUFA as the potent inducer for upregulating energy dissipating metabolic pathways conveying anti-obesogenic effects in mice.

Electronic supplementary material

The online version of this article (10.1186/s12986-018-0291-x) contains supplementary material, which is available to authorized users.

Mechanisms by Which Dietary Fatty Acids Regulate Mitochondrial Structure-Function in Health and Disease

Mitochondria are the energy-producing organelles within a cell. Furthermore, mitochondria have a role in maintaining cellular homeostasis and proper calcium concentrations, building critical components of hormones and other signaling molecules, and controlling apoptosis. Structurally, mitochondria are unique because they have 2 membranes that allow for compartmentalization. The composition and molecular organization of these membranes are crucial to the maintenance and function of mitochondria. In this review, we first present a general overview of mitochondrial membrane biochemistry and biophysics followed by the role of different dietary saturated and unsaturated fatty acids in modulating mitochondrial membrane structure-function. We focus extensively on long-chain n-3 (ω-3) polyunsaturated fatty acids and their underlying mechanisms of action. Finally, we discuss implications of understanding molecular mechanisms by which dietary n-3 fatty acids target mitochondrial structure-function in metabolic diseases such as obesity, cardiac-ischemia reperfusion injury, obesity, type 2 diabetes, nonalcoholic fatty liver disease, and select cancers.

Differential modulation of white adipose tissue endocannabinoid levels by n-3 fatty acids in obese mice and type 2 diabetic patients

n-3 polyunsaturated fatty acids (n-3 PUFA) might regulate metabolism by lowering endocannabinoid levels. We examined time-dependent changes in adipose tissue levels of endocannabinoids as well as in parameters of glucose homeostasis induced by n-3 PUFA in dietary-obese mice, and compared these results with the effect of n-3 PUFA intervention in type 2 diabetic (T2DM) subjects. Male C57BL/6J mice were fed for 8, 16 or 24 weeks a high-fat diet alone (cHF) or supplemented with n-3 PUFA (cHF + F). Overweight/obese, T2DM patients on metformin therapy were given for 24 weeks corn oil (Placebo; 5 g/day) or n-3 PUFA concentrate as above (Omega-3; 5 g/day). Endocannabinoids were measured by liquid chromatography-tandem mass-spectrometry. Compared to cHF-fed controls, the cHF + F mice consistently reduced 2-arachidonoylglycerol (up to ~2-fold at week 24) and anandamide (~2-fold) in adipose tissue, while the levels of endocannabinoid-related anti-inflammatory molecules N-eicosapentaenoyl ethanolamine (EPEA) and N-docosahexaenoyl ethanolamine (DHEA) increased more than ~10-fold and ~8-fold, respectively. At week 24, the cHF + F mice improved glucose tolerance and fasting blood glucose, the latter being positively correlated with adipose 2-arachidonoylglycerol levels only in obese cHF-fed controls, like fasting insulin and HOMA-IR. In the patients, n-3 PUFA failed to reduce 2-arachidonoylglycerol and anandamide levels in adipose tissue and serum, but they increased both adipose tissue and serum levels of EPEA and DHEA. In conclusion, the inability of n-3 PUFA to reduce adipose tissue and serum levels of classical endocannabinoids might contribute to a lack of beneficial effects of these lipids on glucose homeostasis in T2DM patients.

Effect of Eicosapentaenoic Acid and Docosahexaenoic Acid on Myogenesis and Mitochondrial Biosynthesis during Murine Skeletal Muscle Cell Differentiation

Polyunsaturated fatty acids are important nutrients for human health, especially omega-3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which have been found to play positive roles in the prevention of various diseases. However, previous studies have reported that excessive omega-3 fatty acids supplement during pregnancy caused side effects such as slower neural transmission times and postnatal growth restriction. In this study, we investigated the effect of EPA and DHA on mitochondrial function and gene expression in C2C12 myoblasts during skeletal muscle differentiation. C2C12 myoblasts were cultured to confluency and then treated with differentiation medium that contained fatty acids (50-µM EPA and DHA). After 72 h of myogenic differentiation, mRNA was collected, and gene expression was analyzed by real-time PCR. Microscopy was used to examine cell morphology following treatment with fatty acids. The effect of EPA and DHA on cellular oxygen consumption was measured using a Seahorse XF24 Analyzer. Cells treated with fatty acids had fewer myotubes formed (P ≤ 0.05) compared with control cells. The expression of the genes related to myogenesis was significantly lower (P ≤ 0.05) in cells treated with fatty acids, compared with control cells. Genes associated with adipogenesis had higher (P ≤ 0.05) expression after treatment with fatty acids. Also, the mitochondrial biogenesis decreased with lower (P ≤ 0.05) gene expression and lower (P ≤ 0.05) mtDNA/nDNA ratio in cells treated with fatty acids compared with control cells. However, the expression of genes related to peroxisome biosynthesis was higher (P ≤ 0.05) in cells treated with fatty acids. Moreover, fatty-acid treatment reduced (P ≤ 0.05) oxygen consumption rate under oligomycin-inhibited (reflecting proton leak) and uncoupled conditions. Our data imply that fatty acids might reduce myogenesis and increase adipogenesis in myotube formation. Fatty acids may also decrease cell metabolism by reducing mitochondrial biogenesis as well as respiration rate. This study suggests that the maternal overdosage of EPA and DHA may influence fetal muscle development, increase intramuscular adipose tissue deposition in offspring, and have a long-term effect on the development of metabolic diseases such as obesity and diabetes in adult offspring.

Omega-3 fatty acids in obesity and metabolic syndrome: a mechanistic update

Strategies to reduce obesity have become public health priorities as the prevalence of obesity has risen in the United States and around the world. While the anti-inflammatory and hypotriglyceridemic properties of long-chain omega-3 polyunsaturated fatty acids (n-3 PUFAs) are well known, their antiobesity effects and efficacy against metabolic syndrome, especially in humans, are still under debate. In animal models, evidence consistently suggests a role for n-3 PUFAs in reducing fat mass, particularly in the retroperitoneal and epididymal regions. In humans, however, published research suggests that though n-3 PUFAs may not aid weight loss, they may attenuate further weight gain and could be useful in the diet or as a supplement to help maintain weight loss. Proposed mechanisms by which n-3 PUFAs may work to improve body composition and counteract obesity-related metabolic changes include modulating lipid metabolism; regulating adipokines, such as adiponectin and leptin; alleviating adipose tissue inflammation; promoting adipogenesis and altering epigenetic mechanisms.

Omega-3 fatty acids and adipose tissue biology

This review provides evidence for the importance of white and brown adipose tissue (i.e. WAT and BAT) function for the maintenance of healthy metabolic phenotype and its preservation in response to omega-3 polyunsaturated fatty acids (omega-3 PUFA), namely in the context of diseased states linked to aberrant accumulation of body fat, systemic low-grade inflammation, dyslipidemia and insulin resistance. More specifically, the review deals with (i) the concept of immunometabolism, i.e. how adipose-resident immune cells and adipocytes affect each other and define the immune-metabolic interface; and (ii) the characteristic features of "healthy adipocytes" in WAT, which are relatively small fat cells endowed with a high capacity for mitochondrial oxidative phosphorylation, triacylglycerol/fatty acid (TAG/FA) cycling and de novo lipogenesis (DNL). The intrinsic metabolic features of WAT and their flexible regulations, reflecting the presence of "healthy adipocytes", provide beneficial local and systemic effects, including (i) protection against in situ endoplasmic reticulum stress and related inflammatory response during activation of adipocyte lipolysis; (ii) prevention of ectopic fat accumulation and dyslipidemia caused by increased hepatic VLDL synthesis, as well as prevention of lipotoxic damage of insulin signaling in extra-adipose tissues; and also (iii) increased synthesis of anti-inflammatory and insulin-sensitizing lipid mediators with pro-resolving properties, including the branched fatty acid esters of hydroxy fatty acids (FAHFAs), also depending on the activity of DNL in WAT. The "healthy adipocytes" phenotype can be induced in WAT of obese mice in response to various stimuli including dietary omega-3 PUFA, especially when combined with moderate calorie restriction, and possibly also with other life style (e.g. physical activity) or pharmacological (e.g. thiazolidinediones) interventions. While omega-3 PUFA could exert beneficial systemic effects by improving immunometabolism of WAT without a concomitant induction of BAT, it is currently not clear whether the metabolic effects of the combined intervention using omega-3 PUFA and calorie restriction or thiazolidinediones depend also on the activation of BAT function and/or the induction of brite/beige adipocytes in WAT. It remains to be established why omega-3 PUFA intervention in type 2 diabetic subjects does not improve insulin sensitivity and glucose homeostasis despite inducing various anti-inflammatory mediators in WAT, including the recently discovered docosahexaenoyl esters of hydroxy linoleic acid, the lipokines from the FAHFA family, as well as several endocannabinoid-related anti-inflammatory lipids. To answer the question whether and to which extent omega-3 PUFA supplementation could promote the formation of "healthy adipocytes" in WAT of human subjects, namely in the obese insulin-resistant patients, represents a challenging task that is of great importance for the treatment of some serious non-communicable diseases.

Different Dietary Proportions of Fish Oil Regulate Inflammatory Factors but Do Not Change Intestinal Tight Junction ZO-1 Expression in Ethanol-Fed Rats

Sixty male Wistar rats were fed a control or an ethanol-containing diet in groups C or E. The fat compositions were adjusted with 25% or 57% fish oil substituted for olive oil in groups CF25, CF57, EF25, and EF57. Hepatic thiobarbituric acid-reactive substance (TBARS) levels, cytochrome P450 2E1 protein expression, and tumor necrosis factor- (TNF-) α, interleukin- (IL-) 1β, IL-6, and IL-10 levels, as well as intracellular adhesion molecule (ICAM)-1 levels were significantly elevated, whereas plasma adiponectin level was significantly reduced in group E (p < 0.05). Hepatic histopathological scores of fatty change and inflammation, in group E were significantly higher than those of group C (p < 0.05). Hepatic TBARS, plasma ICAM-1, and hepatic TNF-α, IL-1β, and IL-10 levels were significantly lower, and plasma adiponectin levels were significantly higher in groups EF25 and EF57 than those in group E (p < 0.05). The immunoreactive area of the intestinal tight junction protein, ZO-1, showed no change between groups C and E. Only group CF57 displayed a significantly higher ZO-1 immunoreactive area compared to group C (p = 0.0415). 25% or 57% fish oil substituted for dietary olive oil could prevent ethanol-induced liver damage in rats, but the mechanism might not be related to intestinal tight junction ZO-1 expression.

FFA4 (GPR120) as a fatty acid sensor involved in appetite control, insulin sensitivity and inflammation regulation

Unsaturated long-chain fatty acids have been suggested to be beneficial in the context of cardiovascular disorders based in epidemiologic studies conducted in Greenland and Mediterranean. DHA and EPA are omega-3 polyunsaturated fatty acids that are plentiful in fish oil, and oleic acid is an omega-9 monounsaturated fatty acid, rich in olive oil. Dietary intake of these unsaturated long-chain fatty acids have been associated with insulin sensitivity and weight loss, which contrasts with the impairment of insulin sensitivity and weight gain associated with high intakes of saturated long-chain fatty acids. The recent discovery that free fatty acid receptor 4 (FFA4, also known as GPR120) acts as a sensor for unsaturated long-chain fatty acids started to unveil the molecular mechanisms underlying the beneficial functions played by these unsaturated long-chain fatty acids in various physiological processes, which include the secretions of gastrointestinal peptide hormones and glucose homeostasis. In this review, the physiological roles and therapeutic significance of FFA4 in appetite control, insulin sensitization, and inflammation reduction are discussed in relation to obesity and type 2 diabetes from pharmacological viewpoints.

Induction of lipogenesis in white fat during cold exposure in mice: link to lean phenotype

BACKGROUND/OBJECTIVE

Futile substrate cycling based on lipolytic release of fatty acids (FA) from intracellular triacylglycerols (TAG) and their re-esterification (TAG/FA cycling), as well as de novo FA synthesis (de novo lipogenesis (DNL)), represent the core energy-consuming biochemical activities of white adipose tissue (WAT). We aimed to characterize their roles in cold-induced thermogenesis and energy homeostasis.

METHODS

Male obesity-resistant A/J and obesity-prone C57BL/6J mice maintained at 30 °C were exposed to 6 °C for 2 or 7 days. In epididymal WAT (eWAT), TAG synthesis and DNL were determined using in vivo ²H incorporation from ²H₂O into tissue TAG and nuclear magnetic resonance spectroscopy. Quantitative real-time-PCR and/or immunohistochemistry and western blotting were used to determine the expression of selected genes and proteins in WAT and liver.

RESULTS

The mass of WAT depots declined during cold exposure (CE). Plasma levels of TAG and non-esterified FA were decreased by day 2 but tended to normalize by day 7 of CE. TAG synthesis (reflecting TAG/FA cycle activity) gradually increased during CE. DNL decreased by day 2 of CE but increased several fold over the control values by day 7. Expression of genes involved in lipolysis, glyceroneogenesis, FA re-esterification, FA oxidation and mitochondrial biogenesis in eWAT was induced during CE. All these changes were more pronounced in obesity-resistant A/J than in B6 mice and occurred in the absence of uncoupling protein 1 in eWAT. Expression of markers of glyceroneogenesis in eWAT correlated negatively with hepatic FA synthesis by day 7 in both strains. Leptin and fibroblast growth factor 21 plasma levels were differentially affected by CE in the two mouse strains.

CONCLUSIONS

Our results indicate integrated involvement of (i) TAG/FA cycling and DNL in WAT, and (ii) hepatic very-low-density lipoprotein-TAG synthesis in the control of blood lipid levels and provision of FA fuels for thermogenesis in cold. They suggest that lipogenesis in WAT contributes to a lean phenotype.

'Browning' the cardiac and peri-vascular adipose tissues to modulate cardiovascular risk

Excess visceral adiposity, in particular that located adjacent to the heart and coronary arteries is associated with increased cardiovascular risk. In the pathophysiological state, dysfunctional adipose tissue secretes an array of factors modulating vascular function and driving atherogenesis. Conversely, brown and beige adipose tissues utilise glucose and lipids to generate heat and are associated with improved cardiometabolic health. The cardiac and thoracic perivascular adipose tissues are now understood to be composed of brown adipose tissue in the healthy state and undergo a brown-to-white transition i.e. during obesity which may be a driving factor of cardiovascular disease. In this review we discuss the risks of excess cardiac and vascular adiposity and potential mechanisms by which restoring the brown phenotype i.e. “re-browning” could potentially be achieved in clinically relevant populations.

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Epicardial, paracardial and thoracic perivascular adipose tissues resemble BAT at birth.

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Despite ‘whitening’ in early life these depots remain metabolically active and potentially thermogenic into adulthood.

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Obesity induces further ‘whitening’ and inflammation in these depots likely driving the atherogenesis.

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Maintaining or inducing the brown phenotype in these depots could prevent atherosclerotic disease.

Natural Dietary and Herbal Products in Anti-Obesity Treatment

The prevalence of overweight and obesity is on the rise around the world. Common comorbidities associated with obesity, particularly diabetes, hypertension, and heart disease have an impact on social and financial systems. Appropriate lifestyle and behavior interventions are still the crucial cornerstone to weight loss success, but maintaining such a healthy lifestyle is extremely challenging. Abundant natural materials have been explored for their obesity treatment potential and widely used to promote the development of anti-obesity products. The weight loss segment is one of the major contributors to the overall revenue of the dietary supplements market. In this review, the anti-obesity effects of different dietary or herbal products, and their active ingredients and mechanisms of action against obesity will be discussed.

Eicosapentaenoic acid promotes mitochondrial biogenesis and beige-like features in subcutaneous adipocytes from overweight subjects

Eicosapentaenoic acid (EPA), a n-3 long-chain polyunsaturated fatty acid, has been reported to have beneficial effects in obesity-associated metabolic disorders. The objective of the present study was to determine the effects of EPA on the regulation of genes involved in lipid metabolism, and the ability of EPA to induce mitochondrial biogenesis and beiging in subcutaneous adipocytes from overweight subjects. Fully differentiated human subcutaneous adipocytes from overweight females (BMI: 28.1-29.8kg/m²) were treated with EPA (100-200 μM) for 24 h. Changes in mRNA expression levels of genes involved in lipogenesis, fatty acid oxidation and mitochondrial biogenesis were determined by qRT-PCR. Mitochondrial content was evaluated using MitoTracker® Green stain. The effects on peroxisome proliferator-activated receptor gamma, co-activator 1 alpha (PGC-1α) and AMP-activated protein kinase (AMPK) were also characterized. EPA down-regulated lipogenic genes expression while up-regulated genes involved in fatty acid oxidation. Moreover, EPA-treated adipocytes showed increased mitochondrial content, accompanied by an up-regulation of nuclear respiratory factor-1, mitochondrial transcription factor A and cytochrome c oxidase IV mRNA expression. EPA also promoted the activation of master regulators of mitochondrial biogenesis such as sirtuin 1, PGC1-α and AMPK. In parallel, EPA induced the expression of genes that typify beige adipocytes such as fat determination factor PR domain containing 16, uncoupling protein 1 and cell death-inducing DFFA-like effector A, T-Box protein 1 and CD137. Our results suggest that EPA induces a remodeling of adipocyte metabolism preventing fat storage and promoting fatty acid oxidation, mitochondrial biogenesis and beige-like markers in human subcutaneous adipocytes from overweight subjects.

Effects of Fish Oil Supplementation on Gestational Diabetes Mellitus (GDM): A Systematic Review

Context

One of the most common complications of pregnancy is gestational diabetes mellitus (GDM), which is increasing worldwide. Experimental and epidemiological studies have shown that higher intake of n-3 long-chain polyunsaturated fatty acids may decrease the risk of various diseases such as diabetes. The objective of this study was to assess the effect of fish oil supplementation on the prevention and treatment of GDM.

Evidence Acquisition

This systematic review was performed by searching several databases, including PubMed, Scopus, Google Scholar, the Cochrane Library, ProQuest, Science Direct SID, Magiran and IranMedex since 1983. The researchers also searched for references in reviewed clinical trial articles in which fish oil supplementation was compared with placebo or no supplementation.

Results

Only two published and in-press articles are included in this review. Based on these studies, docosahexaenoic acid (DHA)-enriched fish oil (800 mg/d) had no effect on prevention of GDM [0.97 (95% CI: 0.74, 1.27)]. Furthermore, omega-3 fatty acid supplementation containing 180 mg of eicosapentaenoic acid (EPA) and 120 mg DHA had beneficial effects on insulin resistance in women with GDM (change from baseline: 1.5 ± 7.5 vs ‏3.5 ± 8.5 mIU/mL, P = 0.02) but did not influence fasting plasma glucose, homeostatic model assessment-Beta cell function (HOMA-B), the quantitative insulin sensitivity check index (QUICKI), or lipid profiles (P > 0.05).

Conclusions

There is not enough evidence to support or refute the routine use of fish oil supplements during pregnancy for the prevention or treatment of diabetes. It is suggested that further randomized controlled trials be conducted to evaluate the role of fish oil supplementation in pregnancy.

Does Fish Oil Have an Anti-Obesity Effect in Overweight/Obese Adults? A Meta-Analysis of Randomized Controlled Trials

Context

Accumulating evidence has suggested favorable effects of fish oil on weight loss in animal experiments; however, findings remain inconsistent in humans.

Objects

The meta-analysis was performed to investigate the influence of fish oil on some parameters of body composition in overweight/obese adults.

Design

Human randomized, placebo-controlled trials were identified by a systematic search of Embase, PubMed, the Cochrane Library, web of science and reference lists of related reviews and articles. The random-effects model was used to estimate the calculated results.

Results

In total, 21 studies with 30 study arms were included in this analysis. Calculated results of the meta-analysis demonstrated that fish oil had no effect on reducing body weight (overall SMD = -0.07, 95% CI -0.21 to 0.07, P = 0.31) and BMI (overall SMD = -0.09, 95% CI -0.22 to 0.03, P = 0.14) whether alone or combined with life modification intervention in overweight/obese subjects. However, waist circumference was significantly reduced (SMD = -0.23, 95% CI -0.40 to -0.06, P = 0.008) in those with fish oil supplementation combined with life modification intervention. Waist hip ratio (WHR) was significantly reduced (overall SMD = -0.52 95% CI -0.76 to -0.27, P < 0.0005) in fish oil supplemented individuals with or without combination life modification intervention.

Conclusion

Current evidence cannot support an exact anti-obesity role of n-3 polyunsaturated fatty acids (PUFAs) in overweight/obese subjects. However, these subjects may benefit from reducing abdominal fat with fish oil supplementation especially when combined with life modification intervention. Further large-scale and long-term clinical trials are needed to gain definite conclusions.

N-3 Polyunsaturated Fatty Acids and Inflammation in Obesity: Local Effect and Systemic Benefit

Overwhelming consensus emerges among countless evidences that obesity is characterized by a chronic low-grade inflammation in the adipose tissue (AT), which subsequently develops into a systemic inflammatory state contributing to obesity-associated diseases. N-3 Polyunsaturated fatty acids (n-3 PUFA), known as important modulators participating in inflammatory process, turn out to be an effective mitigating strategy dealing with local and systemic inflammation observed in obesity. Some of the effects of n-3 PUFA are brought about by regulation of gene expression through interacting with nuclear receptors and transcription factors; other effects are elicited by modulation of the amount and type of mediator derived from PUFAs. The metabolic effects of n-3 PUFA mainly result from their interactions with several organ systems, not limited to AT. Notably, the attenuation of inflammation in hard-hit AT, in turn, contributes to reducing circulating concentrations of proinflammatory cytokines and detrimental metabolic derivatives, which is beneficial for the function of other involved organs. The present review highlights a bridging mechanism between n-3 PUFA-mediated inflammation relief in AT and systemic benefits.

Omega-3 fatty acids and adipose tissue function in obesity and metabolic syndrome

The n-3 long-chain polyunsaturated fatty acids (n-3 PUFAs) such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) have been reported to improve obesity-associated metabolic disorders including chronic inflammation, insulin resistance and dyslipidaemia. Growing evidence exits about adipose tissue as a target in mediating the beneficial effects of these marine n-3 PUFAs in adverse metabolic syndrome manifestations. Therefore, in this manuscript we focus in reviewing the current knowledge about effects of marine n-3 PUFAs on adipose tissue metabolism and secretory functions. This scope includes n-3 PUFAs actions on adipogenesis, lipogenesis and lipolysis as well as on fatty acid oxidation and mitochondrial biogenesis. The effects of n-3 PUFAs on adipose tissue glucose uptake and insulin signaling are also summarized. Moreover, the roles of peroxisome proliferator-activated receptor γ (PPARγ) and AMPK activation in mediating n-3 PUFAs actions on adipose tissue functions are discussed. Finally, the mechanisms underlying the ability of n-3 PUFAs to prevent and/or ameliorate adipose tissue inflammation are also revised, focusing on the role of n-3 PUFAs-derived specialized proresolving lipid mediators such as resolvins, protectins and maresins.

Scallop protein with endogenous high taurine and glycine content prevents high-fat, high-sucrose-induced obesity and improves plasma lipid profile in male C57BL/6J mice

High-protein diets induce alterations in metabolism that may prevent diet-induced obesity. However, little is known as to whether different protein sources consumed at normal levels may affect diet-induced obesity and associated co-morbidities. We fed obesity-prone male C57BL/6J mice high-fat, high-sucrose diets with protein sources of increasing endogenous taurine content, i.e., chicken, cod, crab and scallop, for 6 weeks. The energy intake was lower in crab and scallop-fed mice than in chicken and cod-fed mice, but only scallop-fed mice gained less body and fat mass. Liver mass was reduced in scallop-fed mice, but otherwise no changes in lean body mass were observed between the groups. Feed efficiency and apparent nitrogen digestibility were reduced in scallop-fed mice suggesting alterations in energy utilization and metabolism. Overnight fasted plasma triacylglyceride, non-esterified fatty acids, glycerol and hydroxy-butyrate levels were significantly reduced, indicating reduced lipid mobilization in scallop-fed mice. The plasma HDL-to-total-cholesterol ratio was higher, suggesting increased reverse cholesterol transport or cholesterol clearance in scallop-fed mice in both fasted and non-fasted states. Dietary intake of taurine and glycine correlated negatively with body mass gain and total fat mass, while intake of all other amino acids correlated positively. Furthermore taurine and glycine intake correlated positively with improved plasma lipid profile, i.e., lower levels of plasma lipids and higher HDL-to-total-cholesterol ratio. In conclusion, dietary scallop protein completely prevents high-fat, high-sucrose-induced obesity whilst maintaining lean body mass and improving the plasma lipid profile in male C57BL/6J mice.

The beneficial effects of n-3 polyunsaturated fatty acids on diet induced obesity and impaired glucose control do not require Gpr120

GPR120 (Ffar4) has been postulated to represent an important receptor mediating the improved metabolic profile seen upon ingestion of a diet enriched in polyunsaturated fatty acids (PUFAs). GPR120 is highly expressed in the digestive system, adipose tissue, lung and macrophages and also present in the endocrine pancreas. A new Gpr120 deficient mouse model on pure C57bl/6N background was developed to investigate the importance of the receptor for long-term feeding with a diet enriched with fish oil. Male Gpr120 deficient mice were fed two different high fat diets (HFDs) for 18 weeks. The diets contained lipids that were mainly saturated (SAT) or mainly n-3 polyunsaturated fatty acids (PUFA). Body composition, as well as glucose, lipid and energy metabolism, was studied. As expected, wild type mice fed the PUFA HFD gained less body weight and had lower body fat mass, hepatic lipid levels, plasma cholesterol and insulin levels and better glucose tolerance as compared to those fed the SAT HFD. Gpr120 deficient mice showed a similar improvement on the PUFA HFD as was observed for wild type mice. If anything, the Gpr120 deficient mice responded better to the PUFA HFD as compared to wild type mice with respect to liver fat content, plasma glucose levels and islet morphology. Gpr120 deficient animals were found to have similar energy, glucose and lipid metabolism when fed HFD PUFA compared to wild type mice. Therefore, GPR120 appears to be dispensable for the improved metabolic profile associated with intake of a diet enriched in n-3 PUFA fatty acids.

Unraveling biochemical pathways affected by mitochondrial dysfunctions using metabolomic approaches

Mitochondrial dysfunction(s) (MDs) can be defined as alterations in the mitochondria, including mitochondrial uncoupling, mitochondrial depolarization, inhibition of the mitochondrial respiratory chain, mitochondrial network fragmentation, mitochondrial or nuclear DNA mutations and the mitochondrial accumulation of protein aggregates. All these MDs are known to alter the capacity of ATP production and are observed in several pathological states/diseases, including cancer, obesity, muscle and neurological disorders. The induction of MDs can also alter the secretion of several metabolites, reactive oxygen species production and modify several cell-signalling pathways to resolve the mitochondrial dysfunction or ultimately trigger cell death. Many metabolites, such as fatty acids and derived compounds, could be secreted into the blood stream by cells suffering from mitochondrial alterations. In this review, we summarize how a mitochondrial uncoupling can modify metabolites, the signalling pathways and transcription factors involved in this process. We describe how to identify the causes or consequences of mitochondrial dysfunction using metabolomics (liquid and gas chromatography associated with mass spectrometry analysis, NMR spectroscopy) in the obesity and insulin resistance thematic.

Nutraceuticals and regulation of adipocyte life: premises or promises

Obesity is the actual worldwide health threat, that is associated with an increased number of metabolic disorders and diseases. Following the traditional hypothesis stating that in obesity hypertrophic adipocytes trigger the adipose tissue hyperplasia, strategies to treat obesity have increased fat researches of the molecular processes that achieve adipocyte enlargement and formation that finally increase body fat mass. Moreover, a new cell type was recently identified, the "brite" adipocyte that presents a unique gene expression profile of compared to both brown and white adipocytes. Therapies against obesity, targeting these cells and their pathways, would include the induction of lipolysis and apoptosis or the inhibition of differentiation and adipogenesis. However, it should be noted that both the increase of adipocyte size and number take place in association with positive energy balance. According to the adipose tissue expansion hypothesis, adipogenesis could be related with improved metabolic health of obese people, taking back the adipose mass to a traditionally site of lipid storage. Furthermore, new perspectives in fat biology suggest that the conversion of white-to-brown adipocytes and their metabolism could be exploited for the development of therapeutic approaches against obesity-associated diseases and for the regulation of energy balance. Drugs currently available to treat obesity generally have unpleasant side effects. A novel promising approach is the usage of dietary supplements and plant products that could interfere on the life cycle of adipocyte. Here, various dietary bioactive compounds that target different stages of adipocyte life cycle and molecular and metabolic pathways are reviewed.

The Effect of n-3 Fatty Acids on Glucose Homeostasis and Insulin Sensitivity

Type 2 diabetes (T2D) as well as cardiovascular disease (CVD) represent major complications of obesity and associated metabolic disorders (metabolic syndrome). This review focuses on the effects of long-chain n-3 polyunsaturated fatty acids (omega-3) on insulin sensitivity and glucose homeostasis, which are improved by omega-3 in many animal models of metabolic syndrome, but remain frequently unaffected in humans. Here we focus on: (i) mechanistic aspects of omega-3 action, reflecting also our experiments in dietary obese mice; and (ii) recent studies analysing omega-3’s effects in various categories of human subjects. Most animal experiments document beneficial effects of omega-3 on insulin sensitivity and glucose metabolism even under conditions of established obesity and insulin resistance. Besides positive results obtained in both cross-sectional and prospective cohort studies on healthy human populations, also some intervention studies in prediabetic subjects document amelioration of impaired glucose homeostasis by omega-3. However, the use of omega-3 to reduce a risk of new-onset diabetes in prediabetic subjects still remains to be further characterized. The results of a majority of clinical trials performed in T2D patients suggest that omega-3 have none or marginal effects on metabolic control, while effectively reducing hypertriglyceridemia in these patients. Despite most of the recent randomized clinical trials do not support the role of omega-3 in secondary prevention of CVD, this issue remains still controversial. Combined interventions using omega-3 and antidiabetic or hypolipidemic drugs should be further explored and considered for treatment of patients with T2D and other diseases.