Short-term treatment with metformin reduces hepatic lipid accumulation but induces liver inflammation in obese mice.

The study aimed to evaluate the metabolic and inflammatory effects of short-term treatments (10 days) with metformin (MET) on the NAFLD caused by a high-fat diet (HFD) in C57BL/6 mice. After the treatment, histological liver slices were obtained, hepatocytes and macrophages were extracted and cultured with phosphate buffered saline, LPS (2.5 µg/mL) and MET (1 µM) for 24 h. Cytokine levels were determined by ELISA. NAFLD caused by the HFD was partially reduced by MET. The lipid accumulation induced by the HFD was not associated with liver inflammation; however, MET seemed to promote pro-inflammatory effects in liver, since it increased hepatic concentration of IL-1ß, TNF-α, IL-6, MCP-1 and IFN-γ. Similarly, MET increased the concentration of IL-1ß, IL-6 in hepatocyte cultures. However, in macrophages culture, MET lowered levels of IL-1ß, IL-6 and TNF-α stimulated by LPS. Overall, MET reduced liver NAFLD but promoted hepatocyte increase in pro-inflammatory cytokines, thus, leading to liver inflammation.

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. © 2016 Wiley Periodicals, Inc.

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. © 2016 Wiley Periodicals, Inc.

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-1ß, 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-1ß was significantly higher in KO mice after LPS stimulus. IL-6 and IL-1ß 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.

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-1ß 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 IL1ß 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 PPARß 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.

Pharmacological Strategies for Insulin Sensitivity in Obesity and Cancer: Thiazolidinediones and Metformin.

BACKGROUND: Chronic diseases, such as obesity and cancer, have high prevalence rates. Both diseases have hyperinsulinemia, hyperglycemia, high levels of IGF-1 and inflammatory cytokines in common. Therefore, these can be considered triggers for cancer development and growth. In addition, low-grade inflammation that modulates the activation of immune cells, cellular metabolism, and production of cytokines and chemokines are common in obesity, cancer, and insulin resistance. Pharmacological strategies are necessary when a change in lifestyle does not improve glycemic homeostasis. In this regard, thiazolidinediones (TZD) possess multiple molecular targets and regulate PPARγ in obesity and cancer related to insulin resistance, while metformin acts through the AMPK pathway. OBJECTIVE: The aim of this study was to review TZD and metformin as pharmacological treatments for insulin resistance associated with obesity and cancer. CONCLUSION: Thiazolidinediones restored adiponectin secretion and leptin sensitivity, reduced lipid droplets in hepatocytes and orexigen peptides in the hypothalamus. In cancer cells, TZD reduced proliferation, production of reactive oxygen species, and inflammation by acting through the mTOR and NFκB pathways. Metformin has similar effects, though these are AMPK-dependent. In addition, both drugs can be efficient against certain side effects caused by chemotherapy.

The Relevance of Thimet Oligopeptidase in the Regulation of Energy Metabolism and Diet-Induced Obesity.

Thimet oligopeptidase (EC 3.4.24.15; EP24.15; THOP1) is a potential therapeutic target, as it plays key biological functions in processing biologically functional peptides. The structural conformation of THOP1 provides a unique restriction regarding substrate size, in that it only hydrolyzes peptides (optimally, those ranging from eight to 12 amino acids) and not proteins. The proteasome activity of hydrolyzing proteins releases a large number of intracellular peptides, providing THOP1 substrates within cells. The present study aimed to investigate the possible function of THOP1 in the development of diet-induced obesity (DIO) and insulin resistance by utilizing a murine model of hyperlipidic DIO with both C57BL6 wild-type (WT) and THOP1 null (THOP1-/-) mice. After 24 weeks of being fed a hyperlipidic diet (HD), THOP1-/- and WT mice ingested similar chow and calories; however, the THOP1-/- mice gained 75% less body weight and showed neither insulin resistance nor non-alcoholic fatty liver steatosis when compared to WT mice. THOP1-/- mice had increased adrenergic-stimulated adipose tissue lipolysis as well as a balanced level of expression of genes and microRNAs associated with energy metabolism, adipogenesis, or inflammation. Altogether, these differences converge to a healthy phenotype of THOP1-/- fed a HD. The molecular mechanism that links THOP1 to energy metabolism is suggested herein to involve intracellular peptides, of which the relative levels were identified to change in the adipose tissue of WT and THOP1-/- mice. Intracellular peptides were observed by molecular modeling to interact with both pre-miR-143 and pre-miR-222, suggesting a possible novel regulatory mechanism for gene expression. Therefore, we successfully demonstrated the previously unanticipated relevance of THOP1 in energy metabolism regulation. It was suggested that intracellular peptides were responsible for mediating the phenotypic differences that are described herein by a yet unknown mechanism of action.

Nutrients, immune system, and exercise: Where will it take us?

The immune system plays a key role in controlling infections, repairing injuries, and restoring homeostasis. Immune cells are bioenergetically expensive during activation, which requires a tightly regulated control of the metabolic pathways, which is mostly regulated by two cellular energy sensors: Adenosine monophosphate-activated protein kinase and mammalian target of rapamycin. The activation and inhibition of this pathways can change cell subtype differentiation. Exercise intensity and duration and nutrient availability (especially glucose and glutamine) tightly regulate immune cell differentiation and function through Adenosine monophosphate-activated protein kinase and mammalian target of rapamycin signaling. Herein, we discuss the innate and adaptive immune-cell metabolism and how they can be affected by exercise and nutrients.

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.