The prevalence of fatty liver reaches alarming proportions. Fatty liver increases the risk for insulin resistance, cardiovascular disease, and nonalcoholic steatohepatitis (NASH). Although extensively studied in a preclinical setting, the lack of noninvasive methodologies hampers our understanding of which pathways promote hepatic fat accumulation in humans. Dietary fat retention is one of the pathways that may lead to fatty liver. The low (1.1%) natural abundance (NA) of carbon-13 (13C) allows use of 13C-enriched lipids for in vivo MR studies. Successful implementation of such methodology, however, is challenging due to low sensitivity of 13C-magnetic resonance spectroscopy (13C-MRS). Here, we investigated the use of 1-dimensional gradient enhanced heteronuclear single quantum coherence (ge-HSQC) spectroscopy for the in vivo detection of hepatic 1H-[13C]-lipid signals after a single high-fat meal with 13C-labeled fatty acids in 5 lean and 6 obese subjects. Postprandial retention of orally administered 13C-labeled fatty acids was significant (
Lucas Lindeboom, Robin A. de Graaf, Christine I. Nabuurs, Petronella A. van Ewijk, Matthijs K.C. Hesselink, Joachim E. Wildberger, Patrick Schrauwen, Vera B. Schrauwen-Hinderling
Dermal white adipose tissue (dWAT) was recently recognized for its potential to modify whole body metabolism. Here, we show that dWAT can be quantified using a high-resolution, fat-specific magnetic resonance imaging (MRI) technique. Noninvasive MRI has been used to describe adipocyte depots for many years; the MRI technique we describe uses an advanced fat-specific method to measure the thickness of dWAT, together with the total volume of WAT and the relative activation/fat depletion of brown adipose tissues (BAT). Since skin-embedded adipocytes may provide natural insulation, they provide an important counterpoint to the activation of thermogenic brown and beige adipose tissues, whereby these distinct depots are functionally interrelated and require simultaneous assay. This method was validated using characterized mouse cohorts of a lipodystrophic, dWAT-deficient strain (syndecan-1 KO) and 2 obese models (diet-induced obese mice and genetically obese animals,
Ildiko Kasza, Diego Hernando, Alejandro Roldán-Alzate, Caroline M. Alexander, Scott B. Reeder
Low-grade chronic inflammation is a key etiological phenomenon responsible for the initiation and perpetuation of obesity and diabetes. Novel therapeutic approaches that can specifically target inflammatory pathways are needed to avert this looming epidemic of metabolic disorders. Genetic and chemical inhibition of SH2-containing inositol 5′ phosphatase 1 (SHIP1) has been associated with systemic expansion of immunoregulatory cells that promote a lean-body state; however, SHIP1 function in immunometabolism has never been assessed. This led us to investigate the role of SHIP1 in metabolic disorders during excess caloric intake in mice. Using a small-molecule inhibitor of SHIP1 (SHIPi), here we show that SHIPi treatment in mice significantly reduces body weight and fat content, improves control of blood glucose and insulin sensitivity, and increases energy expenditure, despite continued consumption of a high-fat diet. Additionally, SHIPi reduces age-associated fat in mice. We found that SHIPi treatment reverses diet-associated obesity by attenuating inflammation in the visceral adipose tissue (VAT). SHIPi treatment increases IL-4–producing eosinophils in VAT and consequently increases both alternatively activated macrophages and myeloid-derived suppressor cells. In addition, SHIPi decreases the number of IFN-γ–producing T cells and NK cells in VAT. Thus, SHIPi represents an approach that permits control of obesity and diet-induced metabolic syndrome without apparent toxicity.
Neetu Srivastava, Sonia Iyer, Raki Sudan, Christie Youngs, Robert W. Engelman, Kyle T. Howard, Christopher M. Russo, John D. Chisholm, William G. Kerr
We have previously identified prohibitin (PHB) and annexin A2 (ANX2) as proteins interacting on the surface of vascular endothelial cells in white adipose tissue (WAT) of humans and mice. Here, we demonstrate that ANX2 and PHB also interact in adipocytes. Mice lacking ANX2 have normal WAT vascularization, adipogenesis, and glucose metabolism but display WAT hypotrophy due to reduced fatty acid uptake by WAT endothelium and adipocytes. By using cell culture systems in which ANX2/PHB binding is disrupted either genetically or through treatment with a blocking peptide, we show that fatty acid transport efficiency relies on this protein complex. We also provide evidence that the interaction between ANX2 and PHB mediates fatty acid transport from the endothelium into adipocytes. Moreover, we demonstrate that ANX2 and PHB form a complex with the fatty acid transporter CD36. Finally, we show that the colocalization of PHB and CD36 on adipocyte surface is induced by extracellular fatty acids. Together, our results suggest that an unrecognized biochemical interaction between ANX2 and PHB regulates CD36-mediated fatty acid transport in WAT, thus revealing a new potential pathway for intervention in metabolic diseases.
Ahmad Salameh, Alexes C. Daquinag, Daniela I. Staquicini, Zhiqiang An, Katherine A. Hajjar, Renata Pasqualini, Wadih Arap, Mikhail G. Kolonin
We have previously reported that obesity attenuates pulmonary inflammation in both patients with acute respiratory distress syndrome (ARDS) and in mouse models of the disease. We hypothesized that obesity-associated hyperleptinemia, and not body mass per se, drives attenuation of the pulmonary inflammatory response and that this effect could also impair the host response to pneumonia. We examined the correlation between circulating leptin levels and risk, severity, and outcome of pneumonia in 2 patient cohorts (NHANES III and ARDSNet-ALVEOLI) and in mouse models of diet-induced obesity and lean hyperleptinemia. Plasma leptin levels in ambulatory subjects (NHANES) correlated positively with annual risk of respiratory infection independent of BMI. In patients with severe pneumonia resulting in ARDS (ARDSNet-ALVEOLI), plasma leptin levels were found to correlate positively with subsequent mortality. In obese mice with pneumonia, plasma leptin levels were associated with pneumonia severity, and in obese mice with sterile lung injury, leptin levels were inversely related to bronchoalveolar lavage neutrophilia, as well as to plasma IL-6 and G-CSF levels. These results were recapitulated in lean mice with experimentally induced hyperleptinemia. Our findings suggest that the association between obesity and elevated risk of pulmonary infection may be driven by hyperleptinemia.
Niki D.J. Ubags, Renee D. Stapleton, Juanita H.J. Vernooy, Elianne Burg, Jenna Bement, Catherine M. Hayes, Sebastian Ventrone, Lennart Zabeau, Jan Tavernier, Matthew E. Poynter, Polly E. Parsons, Anne E. Dixon, Matthew J. Wargo, Benjamin Littenberg, Emiel F.M. Wouters, Benjamin T. Suratt
Obesity is an increasing health problem worldwide, and nonsurgical strategies to treat obesity have remained rather inefficient. We here show that acute loss of TGF-β–activated kinase 1 (TAK1) in adipocytes results in an increased rate of apoptotic adipocyte death and increased numbers of M2 macrophages in white adipose tissue. Mice with adipocyte-specific TAK1 deficiency have reduced adipocyte numbers and are resistant to obesity induced by a high-fat diet or leptin deficiency. In addition, adipocyte-specific TAK1-deficient mice under a high-fat diet showed increased energy expenditure, which was accompanied by enhanced expression of the uncoupling protein UCP1. Interestingly, acute induction of adipocyte-specific TAK1 deficiency in mice already under a high-fat diet was able to stop further weight gain and improved glucose tolerance. Thus, loss of TAK1 in adipocytes reduces the total number of adipocytes, increases browning of white adipose tissue, and may be an attractive strategy to treat obesity, obesity-dependent diabetes, and other associated complications.
Antonia Sassmann-Schweda, Pratibha Singh, Cong Tang, Astrid Wietelmann, Nina Wettschureck, Stefan Offermanns
Despite major advances in early detection and prognosis, chemotherapy resistance is a major hurdle in the battle against breast cancer. Identifying predictive markers and understanding the mechanisms are key steps to overcoming chemoresistance. Methylation-controlled J protein (MCJ, also known as DNAJC15) is a negative regulator of mitochondrial respiration and has been associated with chemotherapeutic drug sensitivity in cancer cell lines. Here we show, in a retrospective study of a large cohort of breast cancer patients, that low MCJ expression in breast tumors predicts high risk of relapse in patients treated with chemotherapy; however, MCJ expression does not correlate with response to endocrine therapy. In a prospective study in breast cancer patients undergoing neoadjuvant therapy, low MCJ expression also correlates with poor clinical response to chemotherapy and decreased disease-free survival. Using MCJ-deficient mice, we demonstrate that lack of MCJ is sufficient to induce mammary tumor chemoresistance in vivo. Thus, loss of expression of this endogenous mitochondrial modulator in breast cancer promotes the development of chemoresistance.
Maria J. Fernández-Cabezudo, Issam Faour, Kenneth Jones, Devin P. Champagne, Mohammed A. Jaloudi, Yassir A. Mohamed, Ghada Bashir, Saeeda Almarzooqi, Alia Albawardi, M. Jawad Hashim, Thomas S. Roberts, Haytham El-Salhat, Hakam El-Taji, Adnan Kassis, Dylan E. O’Sullivan, Brock C. Christensen, James DeGregori, Basel K. al-Ramadi, Mercedes Rincon
IL-1β is a well-established inducer of both insulin resistance and impaired pancreatic islet function. Despite this, findings examining IL-1 receptor deficiency or antagonism in in vivo animal models, as well as in clinical studies of type 2 diabetic (T2D) patients, have led to conflicting results, suggesting that the actions of IL-1β on glycemic control may be pleiotropic in nature. In the present work, we find that the ability of IL-1β to amplify glucose-stimulated insulin secretion from human islets correlates with donor BMI. Islets from obese donors are sensitized to the insulinotropic effects of this cytokine, whereas the stimulatory effects of IL-1β are lost in islets from obese T2D patients, suggesting a role for IL-1 signaling in islet compensation. Indeed, mice deficient in IL-1 receptor type I become glucose intolerant more rapidly than their WT littermates and have impaired secretory responses during the acute stages of inflammatory and metabolic stress induced by LPS and high-fat diet, respectively. IL-1β directly enhances β cell insulin secretion by increasing granule docking and soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) complex formation at the plasma membrane. Together, our study highlights the importance of IL-1β signaling in islet compensation to metabolic and inflammatory stress.
Catherine Hajmrle, Nancy Smith, Aliya F. Spigelman, Xiaoqing Dai, Laura Senior, Austin Bautista, Mourad Ferdaoussi, Patrick E. MacDonald
The capacity of pancreatic β cells to maintain glucose homeostasis during chronic physiologic and immunologic stress is important for cellular and metabolic homeostasis. Insulin receptor substrate 2 (IRS2) is a regulated adapter protein that links the insulin and IGF1 receptors to downstream signaling cascades. Since strategies to maintain or increase IRS2 expression can promote β cell growth, function, and survival, we conducted a screen to find small molecules that can increase IRS2 mRNA in isolated human pancreatic islets. We identified 77 compounds, including 15 that contained a tricyclic core. To establish the efficacy of our approach, one of the tricyclic compounds, trimeprazine tartrate, was investigated in isolated human islets and in mouse models. Trimeprazine is a first-generation antihistamine that acts as a partial agonist against the histamine H1 receptor (H1R) and other GPCRs, some of which are expressed on human islets. Trimeprazine promoted CREB phosphorylation and increased the concentration of IRS2 in islets. IRS2 was required for trimeprazine to increase nuclear Pdx1, islet mass, β cell replication and function, and glucose tolerance in mice. Moreover, trimeprazine synergized with anti-CD3 Abs to reduce the progression of diabetes in NOD mice. Finally, it increased the function of human islet transplants in streptozotocin-induced (STZ-induced) diabetic mice. Thus, trimeprazine, its analogs, or possibly other compounds that increase IRS2 in islets and β cells without adverse systemic effects might provide mechanism-based strategies to prevent the progression of diabetes.
Alexandra Kuznetsova, Yue Yu, Jennifer Hollister-Lock, Lynn Opare-Addo, Aldo Rozzo, Marianna Sadagurski, Lisa Norquay, Jessica E. Reed, Ilham El Khattabi, Susan Bonner-Weir, Gordon C. Weir, Arun Sharma, Morris F. White
Myocardial fuel and energy metabolic derangements contribute to the pathogenesis of heart failure. Recent evidence implicates posttranslational mechanisms in the energy metabolic disturbances that contribute to the pathogenesis of heart failure. We hypothesized that accumulation of metabolite intermediates of fuel oxidation pathways drives posttranslational modifications of mitochondrial proteins during the development of heart failure. Myocardial acetylproteomics demonstrated extensive mitochondrial protein lysine hyperacetylation in the early stages of heart failure in well-defined mouse models and the in end-stage failing human heart. To determine the functional impact of increased mitochondrial protein acetylation, we focused on succinate dehydrogenase A (SDHA), a critical component of both the tricarboxylic acid (TCA) cycle and respiratory complex II. An acetyl-mimetic mutation targeting an SDHA lysine residue shown to be hyperacetylated in the failing human heart reduced catalytic function and reduced complex II–driven respiration. These results identify alterations in mitochondrial acetyl-CoA homeostasis as a potential driver of the development of energy metabolic derangements that contribute to heart failure.
Julie L. Horton, Ola J. Martin, Ling Lai, Nicholas M. Riley, Alicia L. Richards, Rick B. Vega, Teresa C. Leone, David J. Pagliarini, Deborah M. Muoio, Kenneth C. Bedi Jr., Kenneth B. Margulies, Joshua J. Coon, Daniel P. Kelly
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