Alexandre A. S. Teixeira

Palmitoleic Acid (N-7) Attenuates the Immunometabolic Disturbances Caused by a High-Fat Diet Independently of PPARα

Palmitoleic acid (PMA) has anti-inflammatory and antidiabetic activities. Here we tested whether these effects of PMA on glucose homeostasis and liver inflammation, in mice fed with high-fat diet (HFD), are PPAR-α dependent. C57BL6 wild-type (WT) and PPAR-α-knockout (KO) mice fed with a standard diet (SD) or HFD for 12 weeks were treated after the 10th week with oleic acid (OLA, 300 mg/kg of b.w.) or PMA 300 mg/kg of b.w. Steatosis induced by HFD was associated with liver inflammation only in the KO mice, as shown by the increased hepatic levels of IL1-beta, IL-12, and TNF-α; however, the HFD increased the expression of TLR4 and decreased the expression of IL1-Ra in both genotypes. Treatment with palmitoleate markedly attenuated the insulin resistance induced by the HFD, increased glucose uptake and incorporation into muscle in vitro, reduced the serum levels of AST in WT mice, decreased the hepatic levels of IL1-beta and IL-12 in KO mice, reduced the expression of TLR-4 and increased the expression of IL-1Ra in WT mice, and reduced the phosphorylation of NF 𝜅B (p65) in the livers of KO mice. We conclude that palmitoleate attenuates diet-induced insulin resistance, liver inflammation, and damage through mechanisms that do not depend on PPAR-α.

Palmitoleic Acid Improves Metabolic Functions in Fatty Liver by PPARα-Dependent AMPK Activation.

Background: Palmitoleic acid, since described as lipokine, increases glucose uptake by modulation of 5′AMP‐activated protein kinase (AMPK), as well as increasing lipolysis by activation of peroxisome proliferator‐activated receptor‐α (PPARα), in adipose tissue. However, in liver, the effects of palmitoleic acid on glucose metabolism and the role of PPARα remain unknown. Objective: To investigate whether palmitoleic acid improved the hepatic insulin sensitivity of obese mice. Methods: C57BL6 and PPARα knockout (KO) mice were fed for 12 weeks with a standard diet (SD) or high‐fat diet (HF), and in the last 2 weeks were treated with oleic or palmitoleic acid. Results: Palmitoleic acid promoted a faster uptake of glucose in the body, associated with higher insulin concentration; however, even when stimulated with insulin, palmitoleic acid did not modulate the insulin pathway (AKT, IRS). Palmitoleic acid increased the phosphorylation of AMPK, upregulated glucokinase and downregulated SREBP‐1. Regarding AMPK downstream, palmitoleic acid increased the production of FGF‐21 and stimulated the expression of PPARα. Palmitoleic acid treatment did not increase AMPK phosphorylation, modulate glucokinase or increase FGF‐21 in liver of PPARα KO mice. Conclusions: In mice fed with a high‐fat diet, palmitoleic acid supplementation stimulated the uptake of glucose in liver through activation of AMPK and FGF‐21, dependent on PPARα. J. Cell. Physiol. 232: 2168–2177, 2017.

Association between aerobic exercise and rosiglitazone avoided the NAFLD and liver inflammation exacerbated in PPAR-α knockout mice.

Nonalcoholic fatty liver disease (NAFLD) is one of the main liver diseases today, and may progress to steatohepatitis, cirrhosis, and hepatocellular carcinoma. Some studies have shown the beneficial effects of aerobic exercise on reversing NAFLD. To verify whether chronic aerobic exercise improves the insulin resistance, liver inflammation, and steatohepatitis caused by a high fat diet (HF) and whether PPARα is involved in these actions. C57BL6 wild type (WT) and PPAR‐α knockout (KO) mice were fed with a standard diet (SD) or HF during 12 weeks; the HF mice were trained on a treadmill during the last 8 weeks. Serum glucose and insulin tolerances, serum levels of aspartate aminotransferase, hepatic content of triacylglycerol, cytokines, gene expression, and protein expression were evaluated in all animals. Chronic exposure to HF diet increased triacylglycerol accumulation in the liver, leading to NAFLD, increased aminotransferase in the serum, increased peripheral insulin resistance, and higher adiposity index. Exercise reduced all these parameters in both animal genotypes. The liver lipid accumulation was not associated with inflammation; trained KO mice, however, presented a huge inflammatory response that was probably caused by a decrease in PPAR‐γ expression. We conclude that exercise improved the damage caused by a HF independently of PPARα, apparently by a peripheral fatty acid oxidation in the skeletal muscle. We also found that the absence of PPARα together with exercise leads to a decrease in PPAR‐γ and a huge inflammatory response. J. Cell. Physiol. 232: 1008–1019, 2017.

Palmitoleic acid reduces the inflammation in LPS-stimulated macrophages by inhibition of NFκB, independently of PPARs

Palmitoleic acid (PM, 16:1n‐7) has anti‐inflammatory properties that could be linked to higher expression of PPARα, an inhibitor of NFκB. Macrophages play a major role in the pathogenesis of chronic inflammation, however, the effects of PM on macrophages are underexplored. Thus, we aimed to investigate the effects of PM in activated macrophages as well the role of PPARα. Primary macrophages were isolated from C57BL/6 wild type (WT) and PPARα knockout (KO) mice, cultured under standard conditions and exposed to lipopolysaccharides LPS (2.5 μg/ml) and PM 600 μmol/L conjugated with albumin for 24 hours. The stimulation with LPS increased the production of interleukin (IL)‐6 and IL‐1β while PM decreased the production of IL‐6 in WT macrophages. In KO macrophages, LPS increased the production of tumour necrosis factor (TNF)‐α and IL‐6 and PM decreased the production of TNFα. The expression of inflammatory markers such NFκB and IL1β were increased by LPS and decreased by PM in both WT and KO macrophages. PM reduced the expression of MyD88 and caspase‐1 in KO macrophages, and the expression of TLR4 and HIF‐1α in both WT and KO macrophages, although LPS had no effect. CD86, an inflammatory macrophage marker, was reduced by PM independently of genotype. PM increased PPARγ and reduced PPARβ gene expression in macrophages of both genotypes, and increased ACOX‐1 expression in KO macrophages. In conclusion, PM promotes anti‐inflammatory effects in macrophages exposed to LPS through inhibition of inflammasome pathway, which was independent of PPARα, PPARϒ and AMPK, thus the molecular mechanisms of anti‐inflammatory response caused by PM is still unclear.

Aerobic Exercise Modulates the Free Fatty Acids and Inflammatory Response During Obesity and Cancer Cachexia

White adipose tissue (WAT) is no longer considered a tissue whose main function is the storage of TAG. Since the discovery of leptin in 1994, several studies have elucidated the important role of WAT as an endocrine organ, the source of the adipokines. The low-grade inflammation observed in obese and cancer cachexia patients is explained, at least partially, by the exacerbated release of proinflammatory adipokines. Despite of the recent progress in the characterization of the various adipokines and lipokines produced by WAT, little is known about the mechanisms regulating the secretion of these molecules in different physiological and pathological circumstances. Chronic exercise is a nonpharmacological therapy employed in several chronic diseases and shows an anti-inflammatory effect through the regulation of the cytokine network. In this review, we address the potential mechanisms by which the aerobic physical exercise modulate the production and release of inflammatory adipokines, as well as the inflammation-lipolysis axis in WAT, with special focus in the therapeutic role of exercise in obesity-associated insulin resistance and cancer cachexia.

Effect of an acute moderate‐exercise session on metabolic and inflammatory profile of PPAR‐α knockout mice

Peroxisome proliferator‐activated receptors (PPARs) play a major role in metabolism and inflammatory control. Exercise can modulate PPAR expression in skeletal muscle, adipose tissue, and macrophages. Little is known about the effects of PPAR‐α in metabolic profile and cytokine secretion after acute exercise in macrophages. In this context, the aim of this study was to understand the influence of PPAR‐α on exercise‐mediated immune metabolic parameters in peritoneal macrophages. Mice C57BL/6 (WT) and PPAR‐α knockout (KO) were examined in non‐exercising control (n = 4) or 24 hours after acute moderate exercise (n = 8). Metabolic parameters (glucose, non‐esterified fatty acids, total cholesterol [TC], and triacylglycerol [TG]) were assessed in serum. Cytokine concentrations (IL‐1β, IL‐6, IL‐10, TNF‐α, and MCP‐1) were measured from peritoneal macrophages cultured or not with LPS (2.5 μg/mL) and Rosiglitazone (1 μM). Exercised KO mice exhibited low glucose concentration and higher TC and TG in serum. At baseline, no difference in cytokine production between the genotypes was observed. However, IL‐1β was significantly higher in KO mice after LPS stimulus. IL‐6 and IL‐1β had increased concentrations in KO compared with WT, even after exercise. MCP‐1 was not restored in exercised KO LPS group. Rosiglitazone was not able to reduce proinflammatory cytokine production in KO mice at baseline level or associated with exercise. Acute exercise did not alter mRNA expression in WT mice. Conclusion: PPAR‐α seems to be needed for metabolic glucose homeostasis and anti‐inflammatory effect of acute exercise. Its absence may induce over‐expression of pro‐inflammatory cytokines in LPS stimulus. Moreover, moderate exercise or PPAR‐γ agonist did not reverse this response.

Aerobic exercise, but not metformin, prevents reduction of muscular performance by AMPk activation in mice on doxorubicin chemotherapy: DE LIMA et al.

Doxorubicin (DOX) is a chemotherapy agent widely used in clinical practice, and it is very efficient in tumor suppression, but the use of DOX is limited by a strong association with the development of severe muscle atrophy and cardiotoxicity effects. Reversion or neutralization of the muscular atrophy can lead to a better prognosis. Recent studies have proposed that the negative effect of DOX on skeletal muscle is linked to its inhibition of AMP‐activated protein kinase (AMPk), a key mediator of cellular metabolism. On the basis of this, our goal was to evaluate if aerobic exercise or metformin treatment, activators of AMPk, would be able to attenuate the deleterious effects on skeletal muscle induced by the DOX treatment. C57BL6 mice received either saline (control) or DOX (2.5 mg/kg body weight) intraperitoneally, twice a week. The animals on DOX were further divided into groups that received adjuvant treatment in the form of moderate aerobic physical exercise (DOX+T) or metformin gavage (300 mg/body weight/day). Body weight, metabolism, distance run, muscle fiber cross‐sectional area (CSA), and protein synthesis and degradation were assessed. We demonstrated that aerobic training, but not metformin, associated with DOX increased the maximal aerobic capacity without changing muscle mass or fiber CSA, rescuing the muscle fatigue observed with DOX treatment alone. This improvement was associated with AMPk activation, thus surpassing the negative effects of DOX on muscle performance and bioenergetics. In conclusion, aerobic exercise increases AMPk activation and improved the skeletal muscle function, reducing the side effects of DOX.

Metformin Mitigates Fibrosis and Glucose Intolerance Induced by Doxorubicin in Subcutaneous Adipose Tissue

Doxorubicin (DX) is a chemotherapeutic drug that is used in clinical practice that promotes deleterious side effects in non-tumor tissues such as adipose tissue. We showed that DX leads to extensive damage in adipose tissue via a disruption in 5′-adenosine monophosphate-activated protein kinase (AMPK) and PPAR-gamma signaling. Thus, we investigated whether co-treatment with the biguanide drug metformin (MET) could prevent the side effects of DX through the activation of AMPK in adipose tissue. The goal of the present study was to verify the effects of DX and adjuvant MET treatment in subcutaneous adipose tissue (SAT) and to determine whether MET could protect against chemotherapy-induced side effects. C57/BL6 mice received DX hydrochloride (2.5 mg/kg) intraperitoneally 2 times per week for 2 weeks (DX), concomitantly or not, with MET administration (300 mg/kg oral daily) (DX + MET). The control group (CTRL) was pair-fed according to the food consumption of the DX group. After euthanasia, adipose tissue fat pads were collected, and SAT was extracted so that adipocytes could be isolated. Glucose uptake was then measured, and histological, gene, and protein analyses were performed. One-way analysis of variance was also performed, and significance was set to 5%. DX reduced retroperitoneal fat mass and epididymal pads and decreased glycemia. In cultured primary subcutaneous adipocytes, mice in the DX group had lower glucose uptake when stimulated with insulin compared with mice in the CTRL group. Adipocytes in the DX group exhibited a reduced area, perimeter, and diameter; decreased adiponectin secretion; and decreased fatty acid synthase gene expression. SAT from MET-treated mice also showed a reduction in collagen deposition. Treatment with MET prevented fibrosis and restored glucose uptake in SAT after insulin stimulation, yet the drug was unable to prevent other side effects of DX such as tissue loss and inflammatory response.

Short treatment of metformin attenuated insulin resistance and hepatic steatosis in obese mice by mechanisms independents of PPAR-alpha

Results Animals submitted to HFD showed higher gain of weight (C57 p<0.001;KO p<0.05), that in C57 was represented by a greater gain of adipose tissue (p<0.001), while the weight of the liver did not change. This diet promotes insulin resistance in C57 and KO, as observed by reduction of glycemia in ITT (p<0.05) and by an increase in GTT (p<0.001). Although no differences in liver weight were observed in KO, these animals showed higher hepatic deposition of triacylglycerols (p<0.01) and more severe steatosis without an increase of pro-inflammatory cytokines levels. After 7 days, both C57 and KO treated with metformin showed an improvement in glucose tolerance in the GTT (p<0.05), and after 10 days metformin reduced the steatosis as evidenced by histology. Controversially, the liver of C57 mice submitted to HFD and treated with metformin showed higher levels of IL1-b (p<0.05), IL-8 and IL-12 (p<0.01). Conclusion The treatment with metformin improves glucose tolerance and decreases steatosis in mice submitted to high fat diet. However, the treatment was not able to reverse the inflammation in C57 mice. The mechanism of metformin is independent of PPAR-alpha.

Palmitoleate attenuates diet induced insulin resistance and hepatic inflammation independently of PPAR-α

Background Previous studies have showed that the lipokine palmitoleic acid (or palmitoleate) reduces diet induced muscle and liver inflammation and insulin resistance [1] and increases adipose tissue lipolysis, the latter through a mechanism that depends on PPAR-a [2]. Here we tested whether palmitoleate protects from the deleterious effects of a high fat diet (HFD) on glucose homeostasis and liver inflammation and whether PPAR-a is involved in these actions.