Metformin acts in the gut and induces gut-liver crosstalk.

Metformin is the most prescribed drug for DM2, but its site and mechanism of action are still not well established. Here, we investigated the effects of metformin on basolateral intestinal glucose uptake (BIGU), and its consequences on hepatic glucose production (HGP). In diabetic patients and mice, the primary site of metformin action was the gut, increasing BIGU, evaluated through PET-CT. In mice and CaCo2 cells, this increase in BIGU resulted from an increase in GLUT1 and GLUT2, secondary to ATF4 and AMPK. In hyperglycemia, metformin increased the lactate (reducing pH and bicarbonate in portal vein) and acetate production in the gut, modulating liver pyruvate carboxylase, MPC1/2, and FBP1, establishing a gut-liver crosstalk that reduces HGP. In normoglycemia, metformin-induced increases in BIGU is accompanied by hypoglycemia in the portal vein, generating a counter-regulatory mechanism that avoids reductions or even increases HGP. In summary, metformin increases BIGU and through gut-liver crosstalk influences HGP.

Proton Pump Inhibitor Pantoprazole Modulates Intestinal Microbiota and Induces TLR4 Signaling and Fibrosis in Mouse Liver.

Proton pump inhibitors (PPIs) are one of the most prescribed drugs around the world. PPIs induce microbiota modulation such as obesity both in humans and in animal models. However, since PPIs can induce microbiota modulation despite the absence of a high-fat diet or weight gain, it is an interesting model to correlate microbiota modulation with the establishment of non-alcoholic fatty liver disease (NAFLD). We investigated the effect of pantoprazole treatment on TLR4 signaling and liver histology in C57BL/6J mice for 60 days, trying to correlate microbiota modulation with some aspects of liver injury. We performed glucose (GTT) and insulin (ITT) tolerance tests, serum lipopolysaccharide (LPS) dosage, liver histology, liver and intestine extraction for Western blot and qPCR. Fecal microbiota were investigated via metagenomics. Chronic treatment with pantoprazole induced microbiota modulation and impaired ileum barrier integrity, without an association with insulin resistance. Furthermore, increased circulating LPS and increased Toll-like receptor 4 (TLR4) and TGFß downstream signaling may have an important role in the development of the observed liver microvesicular steatosis and fibrosis. Finally, this model of PPI-induced changes in microbiota might be useful to investigate liver microvesicular steatosis and fibrosis.

Retraction notice to "Obesity-Induced Increase in Tumor Necrosis Factor-α Leads to Development of Colon Cancer in Mice" Gastroenterology 2012;143:741-753.e4.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief and Deputy Editor-in-Chief following an investigation into the data that were presented in several figures within the article. A number of images used in this article are believed to be duplicated images. The authors stated that they inadvertently inserted images of the wrong blots in several of the figures, resulting in the duplications; however, they did not address all of the concerns raised. Because the editors were no longer confident in the conclusions of the article based on these incorrect data, a decision was made to retract the paper. All authors have been notified of this decision. The University of Campinas (UNICAMP) in São Paulo, Brazil was contacted regarding these concerns, but to date the journal has received no response.

Helminth infection in mice improves insulin sensitivity via modulation of gut microbiota and fatty acid metabolism.

Intestinal helminths are prevalent in individuals who live in rural areas of developing countries, where obesity, type 2 diabetes, and metabolic syndrome are rare. In the present study, we analyzed the modulation of the gut microbiota in mice infected with the helminth Strongyloides venezuelensis, and fed either a standard rodent chow diet or high-fat diet (HFD). To investigate the effects of the microbiota modulation on the metabolism, we analyzed the expression of tight-junction proteins present in the gut epithelium, inflammatory markers in the serum and tissue and quantified glucose tolerance and insulin sensitivity and resistance. Additionally, the levels of lipids related to inflammation were evaluated in the feces and serum. Our results show that infection with Strongyloides venezuelensis results in a modification of the gut microbiota, most notably by increasing Lactobacillus spp. These modifications in the microbiota alter the host metabolism by increasing the levels of anti-inflammatory cytokines, switching macrophages from a M1 to M2 pattern in the adipose tissue, increasing the expression of tight junction proteins in the intestinal cells (thereby reducing the permeability) and decreasing LPS in the serum. Taken together, these changes correlate with improved insulin signaling and sensitivity, which could also be achieved with HFD mice treated with probiotics. Additionally, helminth infected mice produce higher levels of oleic acid, which participates in anti-inflammatory pathways. These results suggest that modulation of the microbiota by helminth infection or probiotic treatment causes a reduction in subclinical inflammation, which has a positive effect on the glucose metabolism of the host.

RETRACTED: Obesity-induced increase in tumor necrosis factor-α leads to development of colon cancer in mice.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editor-in-Chief and Deputy Editor-in-Chief following an investigation into the data that were presented in several figures within the article. A number of images used in this article are believed to be duplicated images. The authors stated that they inadvertently inserted images of the wrong blots in several of the figures, resulting in the duplications; however, they did not address all of the concerns raised. Because the editors were no longer confident in the conclusions of the article based on these incorrect data, a decision was made to retract the paper. All authors have been notified of this decision. The University of Campinas (UNICAMP) in São Paulo, Brazil was contacted regarding these concerns, but to date the journal has received no response.

IL-6 and IL-10 anti-inflammatory activity links exercise to hypothalamic insulin and leptin sensitivity through IKKbeta and ER stress inhibition.

Overnutrition caused by overeating is associated with insulin and leptin resistance through IKKbeta activation and endoplasmic reticulum (ER) stress in the hypothalamus. Here we show that physical exercise suppresses hyperphagia and associated hypothalamic IKKbeta/NF-kappaB activation by a mechanism dependent upon the pro-inflammatory cytokine interleukin (IL)-6. The disruption of hypothalamic-specific IL-6 action blocked the beneficial effects of exercise on the re-balance of food intake and insulin and leptin resistance. This molecular mechanism, mediated by physical activity, involves the anti-inflammatory protein IL-10, a core inhibitor of IKKbeta/NF-kappaB signaling and ER stress. We report that exercise and recombinant IL-6 requires IL-10 expression to suppress hyperphagia-related obesity. Moreover, in contrast to control mice, exercise failed to reverse the pharmacological activation of IKKbeta and ER stress in C3H/HeJ mice deficient in hypothalamic IL-6 and IL-10 signaling. Hence, inflammatory signaling in the hypothalamus links beneficial physiological effects of exercise to the central action of insulin and leptin.

Physical exercise, health, and disease treatment: The role of macrophages.

Subclinical inflammation is linked to comorbidities and risk factors, consolidating the diagnosis of chronic non-communicable diseases, such as insulin resistance, atherosclerosis, hepatic steatosis, and some types of cancer. In this context, the role of macrophages is highlighted as a marker of inflammation as well as for the high power of plasticity of these cells. Macrophages can be activated in a wide range between classical or proinflammatory, named M1, and alternative or anti-inflammatory, also known as M2 polarization. All nuances between M1 and M2 macrophages orchestrate the immune response by secreting different sets of chemokines, while M1 cells promote Th1 response, the M2 macrophages recruit Th2 and Tregs lymphocytes. In turn, physical exercise has been a faithful tool in combating the proinflammatory phenotype of macrophages. This review proposes to investigate the cellular and molecular mechanisms in which physical exercise can help control inflammation and infiltration of macrophages within the non-communicable diseases scope. During obesity progress, proinflammatory macrophages predominate in adipose tissue inflammation, which reduces insulin sensitivity until the development of type 2 diabetes, progression of atherosclerosis, and diagnosis of non-alcoholic fatty liver disease. In this case, physical activity restores the balance between the proinflammatory/anti-inflammatory macrophage ratio, reducing the level of meta-inflammation. In the case of cancer, the tumor microenvironment is compatible with a high level of hypoxia, which contributes to the advancement of the disease. However, exercise increases the level of oxygen supply, favoring macrophage polarization in favor of disease regression.

Effects of a four week detraining period on physical, metabolic, and inflammatory profiles of elderly women who regularly participate in a program of strength training.

BACKGROUND: Human aging has innumerable health implications, including loss of muscle mass and increased circulating inflammatory markers. Resistance exercise in the elderly can prevent muscle mass loss and improve the inflammatory profile. Conversely, detraining can reverse this picture. Thus, there is a strong need for studies with the elderly population to clarify the real impacts of a training interruption. Therefore, the objective of this study was to analyze the inflammatory profile of resistance trained elderly women after 4 weeks of detraining. METHODS: Seventeen elderly women with regular participation in an exercise program participated in the study. Body mass index (BMI), physical activity level assessments, total cholesterol and its fractions, triglycerides, glycemia and insulin blood levels, IL-1ß, IL-4, IL-6, IL-10, IL-13, TNF-α, IFNγ, and MCP-1 were assessed before and after the detraining protocol. RESULTS: The 4 week detraining period decreased physical fitness without altering body mass and BMI. The short detraining period was able to induce some metabolic disturbances in elderly women who regularly participate in a program of strength training, such as increasing HOMA-IR (0.72 ± 0.14 to 0.81 ± 0.23; p = 0.029), and increasing total blood cholesterol (178.21 ± 23.64 to 220.90 ± 64.98 mg/dL; p = 0.008) and LDL fraction (111.79 ± 21.09 to 155.33 ± 60.95 mg/dL; p = 0.048). No alteration in levels of inflammatory cytokines was observed, however, this detraining period significantly reduced IL-13 (44.84 ± 100.85 to 35.84 ± 78.89 pg/mL; p = 0.031) a Th2 cytokine that induces M2 macrophage polarization. CONCLUSIONS: These data demonstrate that even a short period of detraining is harmful for elderly women who regularly participate in a program of strength training, since it impairs physical performance, insulin sensitivity and cholesterol metabolism.

Head and neck cancer patient-derived xenograft models - A systematic review.

BACKGROUND: Patient-derived xenograft (PDX) involve the direct surgical transfer of fresh human tumor samples to immunodeficient mice. This systematic review aimed to identify publications of head and neck cancer PDX (HNC-PDX) models, describing the main methodological characteristics and outcomes. METHODS: An electronic search was undertaken in four databases, including publications having used HNC-PDX. Data were analyzed descriptively. RESULTS: 63 articles were yielded. The nude mouse was one most commonly animal model used (38.8 %), and squamous cell carcinoma accounted for the majority of HNC-PDX (80.6 %). Tumors were mostly implanted in the flank (86.3 %), and the latency period ranged from 30 to 401 days. The successful rate ranged from 17 % to 100 %. Different drugs and pathways were identified. CONCLUSION: HNC-PDX appears to significantly recapitulate the morphology of the original HNC and represents a valuable method in translational research for the assessment of the in vivo effect of novel therapies for HNC.

Inhibition of hypothalamic Foxo1 expression reduced food intake in diet-induced obesity rats.

Insulin signalling in the hypothalamus plays a role in maintaining body weight. The forkhead transcription factor Foxo1 is an important mediator of insulin signalling in the hypothalamus. Foxo1 stimulates the transcription of the orexigenic neuropeptide Y and Agouti-related protein through the phosphatidylinositol-3-kinase/Akt signalling pathway, but the role of hypothalamic Foxo1 in insulin resistance and obesity remains unclear. Here, we identify that a high-fat diet impaired insulin-induced hypothalamic Foxo1 phosphorylation and degradation, increasing the nuclear Foxo1 activity and hyperphagic response in rats. Thus, we investigated the effects of the intracerebroventricular (i.c.v.) microinfusion of Foxo1-antisense oligonucleotide (Foxo1-ASO) and evaluated the food consumption and weight gain in normal and diet-induced obese (DIO) rats. Three days of Foxo1-ASO microinfusion reduced the hypothalamic Foxo1 expression by about 85%. i.c.v. infusion of Foxo1-ASO reduced the cumulative food intake (21%), body weight change (28%), epididymal fat pad weight (22%) and fasting serum insulin levels (19%) and increased the insulin sensitivity (34%) in DIO but not in control animals. Collectively, these data showed that the Foxo1-ASO treatment blocked the orexigenic effects of Foxo1 and prevented the hyperphagic response in obese rats. Thus, pharmacological manipulation of Foxo1 may be used to prevent or treat obesity.

The Role of Hepatocyte Growth Factor (HGF) in Insulin Resistance and Diabetes.

In obesity, insulin resistance (IR) and diabetes, there are proteins and hormones that may lead to the discovery of promising biomarkers and treatments for these metabolic disorders. For example, these molecules may impair the insulin signaling pathway or provide protection against IR. Thus, identifying proteins that are upregulated in IR states is relevant to the diagnosis and treatment of the associated disorders. It is becoming clear that hepatocyte growth factor (HGF) is an important component of the pathophysiology of IR, with increased levels in most common IR conditions, including obesity. HGF has a role in the metabolic flux of glucose in different insulin sensitive cell types; plays a key role in ß-cell homeostasis; and is capable of modulating the inflammatory response. In this review, we discuss how, and to what extent HGF contributes to IR and diabetes pathophysiology, as well as its role in cancer which is more prevalent in obesity and diabetes. Based on the current literature and knowledge, it is clear that HGF plays a central role in these metabolic disorders. Thus, HGF levels could be employed as a biomarker for disease status/progression, and HGF/c-Met signaling pathway modulators could effectively regulate IR and treat diabetes.

Insulin Resistance in HIV-Patients: Causes and Consequences.

Here we review how immune activation and insulin resistance contribute to the metabolic alterations observed in HIV-infected patients, and how these alterations increase the risk of developing CVD. The introduction and evolution of antiretroviral drugs over the past 25 years has completely changed the clinical prognosis of HIV-infected patients. The deaths of these individuals are now related to atherosclerotic CVDs, rather than from the viral infection itself. However, HIV infection, cART, and intestinal microbiota are associated with immune activation and insulin resistance, which can lead to the development of a variety of diseases and disorders, especially with regards to CVDs. The increase in LPS and proinflammatory cytokines circulating levels and intracellular mechanisms activate serine kinases, resulting in insulin receptor substrate-1 (IRS-1) serine phosphorylation and consequently a down regulation in insulin signaling. While lifestyle modifications and pharmaceutical interventions can be employed to treat these altered metabolic functions, the mechanisms involved in the development of these chronic complications remain largely unresolved. The elucidation and understanding of these mechanisms will give rise to new classes of drugs that will further improve the quality of life of HIV-infected patients, over the age of 50.

Probiotics modulate gut microbiota and improve insulin sensitivity in DIO mice.

Obesity and type 2 diabetes are characterized by subclinical inflammatory process. Changes in composition or modulation of the gut microbiota may play an important role in the obesity-associated inflammatory process. In the current study, we evaluated the effects of probiotics (Lactobacillus rhamnosus, L. acidophilus and Bifidobacterium bifidumi) on gut microbiota, changes in permeability, and insulin sensitivity and signaling in high-fat diet and control animals. More importantly, we investigated the effects of these gut modulations on hypothalamic control of food intake, and insulin and leptin signaling. Swiss mice were submitted to a high-fat diet (HFD) with probiotics or pair-feeding for 5 weeks. Metagenome analyses were performed on DNA samples from mouse feces. Blood was drawn to determine levels of glucose, insulin, LPS, cytokines and GLP-1. Liver, muscle, ileum and hypothalamus tissue proteins were analyzed by Western blotting and real-time polymerase chain reaction. In addition, liver and adipose tissues were analyzed using histology and immunohistochemistry. The HFD induced huge alterations in gut microbiota accompanied by increased intestinal permeability, LPS translocation and systemic low-grade inflammation, resulting in decreased glucose tolerance and hyperphagic behavior. All these obesity-related features were reversed by changes in the gut microbiota profile induced by probiotics. Probiotics also induced an improvement in hypothalamic insulin and leptin resistance. Our data demonstrate that the intestinal microbiome is a key modulator of inflammatory and metabolic pathways in both peripheral and central tissues. These findings shed light on probiotics as an important tool to prevent and treat patients with obesity and insulin resistance.

Defective regulation of POMC precedes hypothalamic inflammation in diet-induced obesity.

Obesity is the result of a long-term positive energy balance in which caloric intake overrides energy expenditure. This anabolic state results from the defective activity of hypothalamic neurons involved in the sensing and response to adiposity. However, it is currently unknown what the earliest obesity-linked hypothalamic defect is and how it orchestrates the energy imbalance present in obesity. Using an outbred model of diet-induced obesity we show that defective regulation of hypothalamic POMC is the earliest marker distinguishing obesity-prone from obesity-resistant mice. The early inhibition of hypothalamic POMC was sufficient to transform obesity-resistant in obesity-prone mice. In addition, the post-prandial change in the blood level of ß-endorphin, a POMC-derived peptide, correlates with body mass gain in rodents and humans. Taken together, these results suggest that defective regulation of POMC expression, which leads to a change of ß-endorphin levels, is the earliest hypothalamic defect leading to obesity.

Hypothalamic S1P/S1PR1 axis controls energy homeostasis.

Sphingosine 1-phosphate receptor 1 (S1PR1) is a G-protein-coupled receptor for sphingosine-1-phosphate (S1P) that has a role in many physiological and pathophysiological processes. Here we show that the S1P/S1PR1 signalling pathway in hypothalamic neurons regulates energy homeostasis in rodents. We demonstrate that S1PR1 protein is highly enriched in hypothalamic POMC neurons of rats. Intracerebroventricular injections of the bioactive lipid, S1P, reduce food consumption and increase rat energy expenditure through persistent activation of STAT3 and the melanocortin system. Similarly, the selective disruption of hypothalamic S1PR1 increases food intake and reduces the respiratory exchange ratio. We further show that STAT3 controls S1PR1 expression in neurons via a positive feedback mechanism. Interestingly, several models of obesity and cancer anorexia display an imbalance of hypothalamic S1P/S1PR1/STAT3 axis, whereas pharmacological intervention ameliorates these phenotypes. Taken together, our data demonstrate that the neuronal S1P/S1PR1/STAT3 signalling axis plays a critical role in the control of energy homeostasis in rats.

The role of neuronal AMPK as a mediator of nutritional regulation of food intake and energy homeostasis.

Hypothalamic 5'-adenosine monophosphate-activated protein kinase (AMPK) senses intracellular metabolic stress, i.e., an increase in the cellular AMP:ATP ratio, and integrates diverse hormonal and nutritional signals to restore energy balance. Recent evidence suggests that different nutrients can modulate AMPK activity in the hypothalamus, thereby controlling weight gain through a leptin-independent mechanism. Understanding the mechanisms by which nutrients control hypothalamic AMPK activity is crucial to the development of effective nutritional interventions for the treatment of food intake-related disorders, such as anorexia and obesity. This article highlights the current evidence for the intricate relationship between nutrients and hypothalamic AMPK activity.

Acute exercise induces a phenotypic switch in adipose tissue macrophage polarization in diet-induced obese rats.

OBJECTIVE: It has become clear that exercise may be a useful therapy in the insulin resistance treatment, as it has anti-inflammatory effects and improves insulin sensitivity. However, it remains uncertain whether exercise affects the adipocytes or infiltrated macrophages. Thus, the aim was to investigate the effects of acute exercise on the inflammatory status and insulin signaling of the white adipose tissue (WAT) fractions (stromal-vascular fraction [SVF] and adipocytes). DESIGN AND METHODS: The effect of acute swimming exercise was investigated on insulin sensitivity, insulin signaling, inflammatory pathways in the WAT fractions of high-fat fed Wistar rats. Additionally, macrophage infiltration and polarization were analyzed in the WAT. RESULTS: Acute exercise can improve insulin signaling in WAT fractions, along with a phenotypic switch from M1- to M2-macrophages in obese rats, as indicated by a marked increase in macrophage galactose-type C-type lectin 1-positive cells in WAT was observed. Additionally, exercise promoted a reduction in circulating levels of lipopolysaccharide, and toll-like receptor 4 activity along with TNF-alpha, IL-1-beta and MCP-1 mRNA levels in WAT fractions. CONCLUSIONS: These data suggest that acute exercise improves insulin signaling in the WAT, at least in part by inducing macrophage polarization toward the M2-state.

Metformin amplifies chemotherapy-induced AMPK activation and antitumoral growth.

PURPOSE: Metformin is a widely used antidiabetic drug whose anticancer effects, mediated by the activation of AMP-activated protein kinase (AMPK) and reduction of mTOR signaling, have become noteworthy. Chemotherapy produces genotoxic stress and induces p53 activity, which can cross-talk with AMPK/mTOR pathway. Herein, we investigate whether the combination of metformin and paclitaxel has an effect in cancer cell lines. EXPERIMENTAL DESIGN: Human tumors were xenografted into severe combined immunodeficient (SCID) mice and the cancer cell lines were treated with only paclitaxel or only metformin, or a combination of both drugs. Western blotting, flow cytometry, and immunohistochemistry were then used to characterize the effects of the different treatments. RESULTS: The results presented herein show that the addition of metformin to paclitaxel leads to quantitative potentialization of molecular signaling through AMPK and a subsequent potent inhibition of the mTOR signaling pathway. Treatment with metformin and paclitaxel resulted in an increase in the number of cells arrested in the G(2)-M phase of the cell cycle, and decreased the tumor growth and increased apoptosis in tumor-bearing mice, when compared with individual drug treatments. CONCLUSION: We have provided evidence for a convergence of metformin and paclitaxel induced signaling at the level of AMPK. This mechanism shows how different drugs may cooperate to augment antigrowth signals, and suggests that target activation of AMPK by metformin may be a compelling ally in cancer treatment.

Diacerhein improves glucose tolerance and insulin sensitivity in mice on a high-fat diet.

Obesity and type 2 diabetes are characterized by insulin resistance, and the common basis of these events is a chronic and systemic inflammatory process marked by the activation of the c-Jun N-terminal kinase (JNK) and inhibitor-κB kinase (IKKß)/nuclear factor-κB (NFκB) pathways, up-regulated cytokine synthesis, and endoplasmic reticulum dysfunction. The aim of this study was to evaluate the effects of diacerhein administration, an antiinflammatory drug that reduces the levels of inflammatory cytokines, on insulin sensitivity and signaling in diet-induced obese (DIO) mice. Swiss mice were fed with conventional chow (control group) or a high-fat diet (DIO group). Later, DIO mice were randomly subdivided into a new subgroup (DAR) that received 20 mg/kg diacerhein for 10 d. Western blotting was used to quantify the expression and phosphorylation of insulin receptor, insulin receptor substrate 1, and Akt and of inflammatory mediators that modulate insulin signaling in a negative manner (IKKß, JNK, and inducible nitric oxide synthase). We show here, for the first time, that the administration of diacerhein in DIO mice improved endoplasmic reticulum stress, reduced JNK and IKKß phosphorylation, and resulted in a marked improvement in fasting glucose, a decrease in macrophage infiltration in adipose tissue, and a reduced expression and activity of proinflammatory mediators accompanied by an improvement in the insulin signaling mainly in the liver and adipose tissue. Taken together, these results indicate that diacerhein treatment improves insulin sensitivity in obesity, mediated by the reversal of subclinical inflammation, and that this drug may be an alternative therapy for insulin resistance.

Epidemiological and molecular mechanisms aspects linking obesity and cancer.

About 25% of cancer cases globally are due to excess weight and a sedentary lifestyle. These results are alarming, as the world knows a pandemic of obesity and, in consequence, insulin resistance. Obesity may increase risk for various cancers by several mechanisms, including increasing sex and metabolic hormones, and inflammation. Here, we present a review of epidemiological and molecular evidences linking obesity and cancer--particularly colorectal, post-menopausal breast, endometrial, pancreatic, high grade prostate, hepatocellular, gallbladder, kidney and esophageal adenocarcinoma. The expected striking increase in the incidence of cancer in the near future related to obesity turns the knowledge of this field of great impact as it is needed to the development of strategies to prevent and treat this disease.