The Effects of High-Fat Diet and Flaxseed Oil-Enriched Diet on the Lung Parenchyma of Obese Mice.

Omega-3 (ω3) fatty acids are widely investigated for their anti-inflammatory potential, however, there is little evidence regarding their action in the lung parenchyma in the context of obesity. The objective is to investigate the effects of flaxseed oil (FS), rich in α-linolenic (C18:3 - ω3), on the lungs of obese mice. Mice were fed a high-fat diet (HF) for 8 weeks to induce obesity. Subsequently, a part of these animals received HF containing FS oil for another 8 weeks. The HF consumption induced weight gain and hyperglycemia. The lung parenchyma shows a complete fatty acids profile, compared to the control group (CT). In the lung parenchyma, FS increases the ω3 content and, notwithstanding a reduction in the interleukins (IL) IL1ß and IL18 contents compared to HF. However, FS promoted increased alveolar spaces, followed by MCP1 (Monocytes Chemoattractant Protein-1) positive cell infiltration and a dramatic reduction in the anti-inflammatory cytokine, IL10. Despite reducing the pulmonary inflammatory response, the consumption of a food source of ω3 was associated with alterations in the lipid profile and histoarchitecture of the lung parenchyma, which can lead to the development of pulmonary complications. This study brings an alert against the indiscriminate use of ω3 supplements, warranting caution.

The early impact of diets enriched with saturated and unsaturated fatty acids on intestinal inflammation and tight junctions.

The gut has been suggested as the first organ to be affected by unbalanced diets contributing to the obesogenic process. This study aimed to test a short time-course exposition model to a known pro- or anti-inflammatory enriched fatty diet to understand the early gut alterations. Male mice were exposed to the chow diet (CT), high-fat (HF) diet, or a high-fat diet partially replaced on flaxseed oil (FS), rich in omega-3 (ω3), for 14 days. HF and FS increased the total body weight mass compared with the CT group, but FS reduced the epididymal fat depot compared to HF. The bioinformatics from mice and human databases showed the Zo1-Ocln-Cldn7 tight junctions as the main protein-triad. In the ileum, the HF diet has increased IL1ß transcript and IL1ß, TNFα, and CD11b proteins, but reduced the tight junctions (Zo1, Ocln, and Cld7) compared to the CT group. Despite the FS diet being partially efficient in protecting the ileum against inflammation, the tight junctions were increased, compared to the HF group. The GPR120 and GPR40 receptors were unaffected by diets, but GPR120 was colocalized on the surface of ileum macrophages. The short period of a high-fat diet was enough to start the obesogenic process, ileum inflammation, and reduce the tight junctions. Flaxseed oil did not protect efficiently against dysmetabolism. Still, it increased the tight junctions, even without alteration on inflammatory parameters, suggesting the protection against gut permeability during early obesity development.

Short-chain fatty acids are associated with adiposity, energy and glucose homeostasis among different metabolic phenotypes in the Nutritionists' Health Study.

BACKGROUND AND AIMS: The gut microbiome is associated with obesity, mainly mediated by bacteria-produced short-chain fatty acids (SCFAs). It is unknown how SCFA concentrations are associated with the phenotypes metabolically healthy normal weight (MHNW), metabolically unhealthy normal weight (MUNW), metabolically healthy obese/overweight (MHO), and metabolically unhealthy obese/overweight (MUO). We compared plasma and fecal SCFA concentrations among adult women categorized according to the metabolic phenotypes mentioned above and examined associations between SCFA and adiposity and components of energy and glucose homeostasis. METHODS: This was a cross-sectional study involving 111 participants. Body composition was assessed by DEXA. Energy and glycemic homeostasis were assessed by the standard mixed-meal tolerance test coupled with indirect calorimetry. SCFAs were quantified by gas chromatography and mass spectrometry. RESULTS: Only plasma propionate was increased in the MHNW phenotype compared to the MHO and MUO phenotypes [p < 0.05]. Fecal propionate and butyrate concentrations and plasma propionate concentrations were inversely associated with total and visceral adiposity [p < 0.05]. Fecal and plasma SCFA concentrations were associated with reduced glucose, insulin and HbA1c levels, increased fasting and postprandial GLP-1 levels; and more preserved beta-cell function [p < 0.05]. Fecal and plasma SCFA concentrations were positively correlated with resting energy expenditure and lipid oxidation rate and inversely correlated with the oxidation rate of carbohydrates [p < 0.05]. CONCLUSION: These findings reinforce the concept that fecal and plasma SCFA concentrations are linked to specific components of energy and glucose homeostasis; and body adiposity. However, it was not possible to discriminate the different metabolic phenotypes of adiposity based on the determination of fecal SCFA concentrations.

Short-term flaxseed oil, rich in omega 3, protects mice against metabolic damage caused by high-fat diet, but not inflammation.

It is known that long-term high-fat diet (HF) feeding drastically affects the adipose tissue, contributing to metabolic disorders. Recently, short-term HF consumption was shown to affect different neuronal signaling pathways. Thus, we aimed to evaluate the inflammatory effects of a short-term HF and whether a diet containing omega-3 fatty acid fats from flaxseed oil (FS) has protective effects. Mice were divided into three groups for 3 d, according to their diets: Control group (CT), HF, or FS for 3 d. Lipid profiles were assessed through mass spectrometry and inflammatory markers by RT-qPCR and Western blotting. After short-term HF, mice increased food intake, body weight, adiposity, and fasting glucose. Increased mRNA content of Ccl2 and Tnf was demonstrated in the HF compared to CT in mesenteric adipose tissue. In the liver, TNFα protein was higher in the HF group than in CT, followed by a decreased polyunsaturated fatty acids tissue incorporation in HF. On the other hand, the consumption of FS reduced food intake and fasting glucose, as well as increased omega-3 fatty acid incorporation in MAT and the liver. However, short-term FS was insufficient to control the early inflammation triggered by HF in MAT and the liver. These data demonstrated that a 3-d HF diet is enough to damage glucose homeostasis and trigger inflammation. In contrast, short-term FS protects against increased food intake and fasting glucose but not inflammation in mice.

EPA/DHA and linseed oil have different effects on liver and adipose tissue in rats fed with a high-fat diet.

The incidence of cardiovascular diseases and metabolic disorders has increased worldwide. Clinical and experimental research has shown that the consumption of ω-3 FAs can be beneficial to metabolism in several ways, as they can act on metabolic pathways. Our objective was to evaluate the effect of treatment with linseed oil, a vegetable oil rich in alpha-linolenic acid, and EPA and DHA in different proportions (3:1 EPA:DHA, and 1:3 EPA:DHA), on the metabolic disorders induced by a high-fat diet (20 % lipids) in rats for 2 weeks, after 18 weeks of consumption of a high-fat diet. In 18 weeks, the high-fat diet increased blood glucose, systolic blood pressure, triglyceride concentration in the liver and adipose tissue, and impaired insulin sensibility without interfering in the weight of the animals. All treatments were effective in reducing the deposition of hepatic type III collagen, the proportion of ω-6/ω-3 in the liver and WAT (white adipose tissue), the proportion of area/number of adipocytes, and the gene expression of the ACC, FAS, and CPT1 enzymes. In addition, treatment with EPA and DHA reduced blood glucose, serum TNF-α concentration, amount of liver fat, degree of microsteatosis and type I collagen deposition in the liver, deposition of type I and III collagen in TA, gene expression of the transcription factor SREBP-1c, and increased hepatic binucleation. EPA in major proportion was more effective in reducing the area of adipocytes, hepatic triglyceride concentration, PPAR-α expression, and WAT fat weight. DHA in a major proportion reduced the concentration of MCP1 in WAT. LO treatment did not have any isolated effects. We concluded that EPA and DHA were more effective in treating metabolic damage than treatment with LO, leading to a more favorable metabolic profile.

Short-term combined training reduces hepatic steatosis and improves hepatic insulin signaling.

Hepatic steatosis is directly associated with hepatic inflammation and insulin resistance, which is correlated with hyperglycemia and type 2 diabetes mellitus (T2DM). Aerobic and strength training have been pointed out as efficient strategies against hepatic steatosis. However, little is known about the effects of the combination of those two protocols on hepatic steatosis. Therefore, this study aimed to evaluate the impact of short-term combined training (STCT) on glucose homeostasis and in the synthesis and oxidation of fat in the liver of obesity-induced mice with hepatic steatosis. Swiss mice were distributed into three groups: control lean (CTL), sedentary obese (OB), and combined training obese (CTO). The CTO group performed the STCT protocol, which consisted of strength and aerobic exercises in the same session. The protocol lasted seven days. The CTO group reduced the glucose levels and fatty liver when compared to the OB group. Interestingly, these results were observed even without reductions in body adiposity. CTO group also showed increased hepatic insulin sensitivity, with lower hepatic glucose production (HGP). STCT reduced the expression of the lipogenic genes Fasn and Scd1 and hepatic inflammation, as well as increased the ACC phosphorylation and the oxidative genes Cpt1a and Ppara, reverting the complications caused by obesity. Since this protocol increased lipid oxidation and reduced hepatic lipogenesis, regardless of body fat mass decrease, it can be considered an effective non-pharmacological strategy for the treatment of hepatic steatosis.

Short Dietary Intervention with Olive Oil Increases Brown Adipose Tissue Activity in Lean but not Overweight Subjects.

BACKGROUND: The brown adipose tissue (BAT) is a potential target for the treatment of obesity and metabolic disorders. Its activation by cold exposure or adrenergic drugs can increase systemic insulin sensitivity and improve lipid metabolism; however, little is known about the effects of specific dietary components on BAT activity. OBJECTIVES: We asked if a short-term (4 weeks) dietary intervention with olive oil could modify BAT activity in lean and overweight/obese volunteers. DESIGN: This was a 4-week open clinical trial in which all participants underwent a dietary intervention with extra-virgin olive oil supplementation. As the initial intake of olive oil was controlled all the participants were controls of themselves. RESULTS: The intervention resulted in significant increase in blood monounsaturated fatty acid levels, which was accompanied by increased BAT activity in lean but not in overweight/obese volunteers. In the lean group, an increase in leptin was detected after the intervention, and low leptin values at the beginning of the study were predictive of greater BAT activity after intervention. In addition, increase in leptin concentration was associated with increased BAT activity. Three known endogenous mediators of BAT activity, secretin, fibroblast growth factor 21 (FGF21), and 12,13-dihydroxy-9Z-octadecenoic acid (12,13-diHOME) were increased by intervention in lean, whereas only secretin and FGF21 were increased in subjects with excessive weight. CONCLUSION: This study provides clinical evidence for the impact of monounsaturated fatty acids on BAT activity and an advance in the understanding of the beneficial health effects of olive oil.

Strength exercise reduces hepatic pyruvate carboxylase and gluconeogenesis in DIO mice.

Obesity is linked to a reduction in the control of hepatic glucose production, which is the primary mechanism related to fasting hyperglycemia and the development of type 2 diabetes mellitus (T2DM). The main system involved in hepatic gluconeogenesis synthesis is controlled by pyruvate carboxylase (PC), which increases in obesity conditions. Recently, we showed that short-term strength training is an important tool against obesity-induced hyperglycemia. As aerobic exercise can reduce the hepatic PC content of obese animals, we hypothesized that strength exercise can also decrease this gluconeogenic enzyme. Therefore, this study investigated whether the metabolic benefits promoted by short-term strength training are related to changes in hepatic PC content. Swiss mice were divided into three groups: lean control (Ctl), obese sedentary (ObS), and obese short-term strength training (STST). The STST protocol was performed through one session/day for 15 days. The obese exercised animals had reduced hyperglycemia and insulin resistance. These results were related to better control of hepatic glucose production and hepatic insulin sensitivity. Our bioinformatics analysis showed that hepatic PC mRNA levels have positive correlations with glucose levels and adiposity, and negative correlations with locomotor activity and muscle mass. We also found that hepatic mRNA levels are related to lipogenic markers in the liver. Finally, we observed that the obese animals had an increased hepatic PC level; however, STST was efficient in reducing its amount. In conclusion, we provide insights into new biomolecular mechanisms by showing how STST is an efficient tool against obesity-related hyperglycemia and T2DM, even without body weight changes.

Palmitate Is Increased in the Cerebrospinal Fluid of Humans with Obesity and Induces Memory Impairment in Mice via Pro-inflammatory TNF-α.

Obesity has been associated with cognitive decline, atrophy of brain regions related to learning and memory, and higher risk of developing dementia. However, the molecular mechanisms underlying these neurological alterations are still largely unknown. Here, we investigate the effects of palmitate, a saturated fatty acid present at high amounts in fat-rich diets, in the brain. Palmitate is increased in the cerebrospinal fluid (CSF) of overweight and obese patients with amnestic mild cognitive impairment. In mice, intracerebroventricular infusion of palmitate impairs synaptic plasticity and memory. Palmitate induces astroglial and microglial activation in the mouse hippocampus, and its deleterious impact is mediated by microglia-derived tumor necrosis factor alpha (TNF-α) signaling. Our results establish that obesity is associated with increases in CSF palmitate. By defining a pro-inflammatory mechanism by which abnormal levels of palmitate in the brain impair memory, the results further suggest that anti-inflammatory strategies may attenuate memory impairment in obesity.

Microbiota-derived acetate protects against respiratory syncytial virus infection through a GPR43-type 1 interferon response.

Severe respiratory syncytial virus (RSV) infection is a major cause of morbidity and mortality in infants <2 years-old. Here we describe that high-fiber diet protects mice from RSV infection. This effect was dependent on intestinal microbiota and production of acetate. Oral administration of acetate mediated interferon-ß (IFN-ß) response by increasing expression of interferon-stimulated genes in the lung. These effects were associated with reduction of viral load and pulmonary inflammation in RSV-infected mice. Type 1 IFN signaling via the IFN-1 receptor (IFNAR) was essential for acetate antiviral activity in pulmonary epithelial cell lines and for the acetate protective effect in RSV-infected mice. Activation of Gpr43 in pulmonary epithelial cells reduced virus-induced cytotoxicity and promoted antiviral effects through IFN-ß response. The effect of acetate on RSV infection was abolished in Gpr43-/- mice. Our findings reveal antiviral effects of acetate involving IFN-ß in lung epithelial cells and engagement of GPR43 and IFNAR.

Acute physical exercise increases APPL1/PI3K signaling in the hypothalamus of lean mice.

Adiponectin is an adipokine that acts in the control of energy homeostasis. The adaptor protein containing the pleckstrin homology domain, phosphotyrosine-binding domain, and leucine zipper motif 1 (APPL1) is a key protein in the adiponectin signaling. The APPL1 mediates a positive effect on the insulin signaling through the interaction with the phosphoinositide 3-kinase (PI3K). Thus, the present study aimed to explore the effects of an acute physical exercise session on the hypothalamic adiponectin signaling. Firstly, using bioinformatics analysis, we found a negative correlation between hypothalamic APPL1 mRNA levels and food consumption in several strains of genetically diverse BXD mice. Also, the mice and the human database revealed a positive correlation between the levels of APPL1 mRNA and PI3K mRNA. At the molecular level, the exercised mice showed increased APPL1 and PI3K (p110) protein contents in the hypothalamus of Swiss mice. Furthermore, the exercise increases co-localization between APPL1 and PI3K p110 predominantly in neurons of the arcuate nucleus of hypothalamus (ARC). Finally, we found an acute exercise session reduced the food intake 5 hr after the end of fasting. In conclusion, our results indicate that physical exercise reduces the food intake and increases some proteins related to adiponectin pathway in the hypothalamus of lean mice.

Short-term strength training reduces gluconeogenesis and NAFLD in obese mice.

Non-alcoholic fatty liver disease (NAFLD) has a positive correlation with obesity, insulin resistance and type 2 diabetes mellitus (T2D). The aerobic training is an important tool in combating NAFLD. However, no studies have demonstrated the molecular effects of short-term strength training on the accumulation of hepatic fat in obese mice. This study aimed to investigate the effects of short-term strength training on the mechanisms of oxidation and lipid synthesis in the liver of obese mice. The short duration protocol was used to avoid changing the amount of adipose tissue. Swiss mice were separated into three groups: lean control (CTL), sedentary obese (OB) and strength training obese (STO). The obese groups were fed a high-fat diet (HFD) and the STO group performed the strength training protocol 1 session/day for 15 days. The short-term strength training reduced hepatic fat accumulation, increasing hepatic insulin sensitivity and controlling hepatic glucose production. The obese animals increased the mRNA of lipogenic genes Fasn and Scd1 and reduced the oxidative genes Cpt1a and Ppara. On the other hand, the STO group presented the opposite results. Finally, the obese animals presented higher levels of lipogenic proteins (ACC and FAS) and proinflammatory cytokines (TNF-α and IL-1ß), but the short-term strength training was efficient in reducing this condition, regardless of body weight loss. In conclusion, there was a reduction of obesity-related hepatic lipogenesis and inflammation after short-term strength training, independent of weight loss, leading to improvements in hepatic insulin sensitivity and glycemic homeostasis in obese mice. Key points: (1) Short-term strength training (STST) reduced fat accumulation and inflammation in the liver; (2) Hepatic insulin sensitivity and HPG control were increased with STST; (3) The content and activity of ACC and content of FAS were reduced with STST; (4) STST improved hepatic fat accumulation and glycemic homeostasis; (5) STST effects were observed independently of body weight change.

Unsaturated fatty acids from flaxseed oil and exercise modulate GPR120 but not GPR40 in the liver of obese mice: a new anti-inflammatory approach.

GPR120 and GPR40 were recently reported as omega-3 (ω3) receptors with anti-inflammatory properties. Physical exercise could increase the expression of these receptors in the liver, improving hepatic metabolism in obesity and type 2 diabetes. Our aim was to investigate GPR120/40 in the liver of lean and obese mice after acute or chronic physical exercise, with or without the supplementation of ω3 rich flaxseed oil (FS), as well as assess the impact of exercise and FS on insulin signaling and inflammation. Mice were fed a high-fat diet (HF) for 4 weeks to induce obesity and subsequently subjected to exercise with or without FS, or FS alone. Insulin signaling, inflammatory markers and GPR120/40 and related cascades were measured. Chronic, but not acute, exercise and FS increased GPR120, but not GPR40, activating ß-arrestin-2 and decreasing the inflammatory response, as well as reducing fat depots in liver and adipose tissue. Exercise or a source of ω3 led to a higher tolerance to fatigue and an increased running distance and speed. The combination of physical exercise and ω3 food sources could provide a new strategy against obesity through the modulation of hepatic GPR120 and an increase in exercise performance.

Short-term high-fat diet modulates several inflammatory, ER stress, and apoptosis markers in the hippocampus of young mice.

The consumption of saturated fatty acids is one of the leading risk factors for Alzheimer's Disease (AD) development. Indeed, the short-term consumption of a high-fat diet (HFD) is related to increased inflammatory signals in the hippocampus; however, the potential molecular mechanisms linking it to AD pathogenesis are not fully elucidated. In our study, we investigated the effects of short-term HFD feeding (within 3, 7 and 10 days) in AD markers and neuroinflammation in the hippocampus of mice. The short period of HFD increased fasting glucose and HOMA-IR. Also, mice fed HFD increased the protein content of ß-Amyloid, pTau, TNFα, IL1ß, pJNK, PTP1B, peIF2α, CHOP, Caspase3, Cleaved-Caspase3 and Alzheimer-related genes (Bax, PS1, PEN2, Aph1b). At 10 days, both neuronal (N2a) and microglial (BV2) cells presented higher expression of inflammatory and apoptotic genes when stimulated with palmitate. These findings suggest that a short period of consumption of a diet rich in saturated fat is associated with activation of inflammatory, ER stress and apoptotic signals in the hippocampus of young mice.

Omega-3 from Flaxseed Oil Protects Obese Mice Against Diabetic Retinopathy Through GPR120 Receptor.

The chronic and low-grade inflammation induced by obesity seem to be the "first hit" to retinopathy associated to diabetes type 2. Herein, we hypothesized that omega-3 fatty acids from flaxseed oil enriched diet disrupt the pro-inflammatory status in the retina, protecting against retinopathy development. For eight weeks under a high-fat diet (HF), several physiological parameters were monitored to follow the metabolic homeostasis disruption. After this period, mice were treated with a HF substituted in part of lard by flaxseed oil (FS) for another eight weeks. Food behavior, weight gain, glucose and insulin sensitivity, electroretinography, RT-qPCR and western blots were carried out. The HF was able to induce a pro-inflammatory background in the retina, changing IL1ß and TNFα. VEGF, a master piece of retinopathy, had early onset increased also induced by HF. The FS-diet was able to decrease inflammation and retinopathy and improved retinal electro stimuli compared to HF group. GPR120 and GPR40 (G Protein-Coupled Receptors 120 and 40), an omega-3 fatty acid receptors, were detected in the retina for the first time. FS-diet modulated the gene expression and protein content of these receptors. Thus, unsaturated fatty acids protect the retina from diabetes type 2 mice model from disease progression.

Physical exercise reduces pyruvate carboxylase (PCB) and contributes to hyperglycemia reduction in obese mice.

The present study evaluated the effects of exercise training on pyruvate carboxylase protein (PCB) levels in hepatic tissue and glucose homeostasis control in obese mice. Swiss mice were distributed into three groups: control mice (CTL), fed a standard rodent chow; diet-induced obesity (DIO), fed an obesity-inducing diet; and a third group, which also received an obesity-inducing diet, but was subjected to an exercise training protocol (DIO + EXE). Protocol training was carried out for 1 h/d, 5 d/wk, for 8 weeks, performed at an intensity of 60% of exhaustion velocity. An insulin tolerance test (ITT) was performed in the last experimental week. Twenty-four hours after the last physical exercise session, the animals were euthanized and the liver was harvested for molecular analysis. Firstly, DIO mice showed increased epididymal fat and serum glucose and these results were accompanied by increased PCB and decreased p-Akt in hepatic tissue. On the other hand, physical exercise was able to increase the performance of the mice and attenuate PCB levels and hyperglycemia in DIO + EXE mice. The above findings show that physical exercise seems to be able to regulate hyperglycemia in obese mice, suggesting the participation of PCB, which was enhanced in the obese condition and attenuated after a treadmill running protocol. This is the first study to be aimed at the role of exercise training in hepatic PCB levels, which may be a novel mechanism that can collaborate to reduce the development of hyperglycemia and type 2 diabetes in DIO mice.