Metabolism
Abstract
Posttransplantation diabetes mellitus (PTDM) is a common and significant complication related to immunosuppressive agents required to prevent organ or cell transplant rejection. To elucidate the effects of 2 commonly used agents, the calcineurin inhibitor tacrolimus (TAC) and the mTOR inhibitor sirolimus (SIR), on islet function and test whether these effects could be reversed or prevented, we investigated human islets transplanted into immunodeficient mice treated with TAC or SIR at clinically relevant levels. Both TAC and SIR impaired insulin secretion in fasted and/or stimulated conditions. Treatment with TAC or SIR increased amyloid deposition and islet macrophages, disrupted insulin granule formation, and induced broad transcriptional dysregulation related to peptide processing, ion/calcium flux, and the extracellular matrix; however, it did not affect regulation of β cell mass. Interestingly, these β cell abnormalities reversed after withdrawal of drug treatment. Furthermore, cotreatment with a GLP-1 receptor agonist completely prevented TAC-induced β cell dysfunction and partially prevented SIR-induced β cell dysfunction. These results highlight the importance of both calcineurin and mTOR signaling in normal human β cell function in vivo and suggest that modulation of these pathways may prevent or ameliorate PTDM.
Authors
Chunhua Dai, John T. Walker, Alena Shostak, Ana Padgett, Erick Spears, Scott Wisniewski, Greg Poffenberger, Radhika Aramandla, E. Danielle Dean, Nripesh Prasad, Shawn E. Levy, Dale L. Greiner, Leonard D. Shultz, Rita Bottino, Alvin C. Powers
Abstract
The ciliopathies Bardet-Biedl Syndrome and Alström Syndrome are genetically inherited pleiotropic disorders with primary clinical features of hyperphagia and obesity. Methionine aminopeptidase 2 inhibitors (MetAP2i) have been shown in preclinical and clinical studies to reduce food intake, body weight, and adiposity. Here we investigated the effects of MetAP2i administration in a mouse model of ciliopathy produced by conditional deletion of the Thm1 gene in adulthood. Thm1 conditional knock-out (cko) mice show decreased hypothalamic pro-opiomelanocortin expression as well as hyperphagia, obesity, metabolic disease and hepatic steatosis. In obese Thm1 cko mice, two-week administration of MetAP2i reduced daily food intake and reduced body weight 17.1% from baseline (vs. 5% reduction for vehicle). This was accompanied with decreased levels of blood glucose, insulin and leptin. Further, MetAP2i reduced gonadal adipose depots and adipocyte size and improved liver morphology. This is the first report of MetAP2i reducing hyperphagia and body weight, and ameliorating metabolic indices in a mouse model of ciliopathy. These results support further investigation of MetAP2 inhibition as a potential therapeutic strategy for ciliary-mediated forms of obesity.
Authors
Tana S Pottorf, Micaella P. Fagan, Bryan F. Burkey, David J Cho, James E Vath, Pamela V. Tran
Abstract
In humans, chronic glucocorticoid use is associated with side effects like muscle wasting, obesity, and metabolic syndrome. Intermittent steroid dosing has been proposed in Duchenne Muscular Dystrophy patients to mitigate the side effects seen with daily steroid intake. We evaluated biomarkers from Duchenne Muscular Dystrophy patients, finding that, compared with chronic daily steroid use, weekend steroid use was associated with reduced serum insulin, free fatty acids, and branched chain amino acids, as well as reduction in fat mass despite having similar BMIs. We reasoned that intermittent prednisone administration in dystrophic mice would alter muscle epigenomic signatures, and we identified the coordinated action of the glucocorticoid receptor, KLF15 and MEF2C as mediators of a gene expression program driving metabolic reprogramming and enhanced nutrient utilization. Muscle lacking Klf15 failed to respond to intermittent steroids. Furthermore, coadministration of the histone acetyltransferase inhibitor anacardic acid with steroids in mdx mice eliminated steroid-specific epigenetic marks and abrogated the steroid response. Together, these findings indicate that intermittent, repeated exposure to glucocorticoids promotes performance in dystrophic muscle through an epigenetic program that enhances nutrient utilization.
Authors
Mattia Quattrocelli, Aaron S. Zelikovich, Zhen Jiang, Clara Bien Peek, Alexis R. Demonbreun, Nancy L. Kuntz, Grant D. Barish, Saptarsi M. Haldar, Joseph Bass, Elizabeth M. McNally
Abstract
Distinct subsets of Tregs reside in nonlymphoid tissues where they mediate unique functions. To interrogate the biology of tissue Tregs in human health and disease, we phenotypically and functionally compared healthy skin Tregs with those in peripheral blood, inflamed psoriatic skin, and metastatic melanoma. The mitochondrial enzyme, arginase 2 (ARG2), was preferentially expressed in Tregs in healthy skin, increased in Tregs in metastatic melanoma, and reduced in Tregs from psoriatic skin. ARG2 enhanced Treg suppressive capacity in vitro and conferred a selective advantage for accumulation in inflamed tissues in vivo. CRISPR-mediated deletion of this gene in primary human Tregs was sufficient to skew away from a tissue Treg transcriptional signature. Notably, the inhibition of ARG2 increased mTOR signaling, whereas the overexpression of this enzyme suppressed it. Taken together, our results suggest that Tregs express ARG2 in human tissues to both regulate inflammation and enhance their metabolic fitness.
Authors
Margaret M. Lowe, Ian Boothby, Sean Clancy, Richard S. Ahn, Wilson Liao, David N. Nguyen, Kathrin Schumann, Alexander Marson, Kelly M. Mahuron, Gillian A. Kingsbury, Zheng Liu, Priscila Munoz Sandoval, Robert Sanchez Rodriguez, Mariela L. Pauli, Keyon Taravati, Sarah T. Arron, Isaac M. Neuhaus, Hobart W. Harris, Esther A. Kim, Uk Sok Shin, Matthew F. Krummel, Adil Daud, Tiffany C. Scharschmidt, Michael D. Rosenblum
Abstract
High-density lipoproteins (HDL) contain hundreds of lipid species and proteins and exert many potentially vasoprotective and anti-diabetogenic activities on cells. To resolve structure-function-disease relationships of HDL we characterized HDL of 51 healthy subjects and 98 patients with diabetes (T2DM), coronary heart disease (CHD), or both for protein and lipid composition as well as functionality in five cell types. The integration of 40 clinical characteristics, 34 NMR features, 182 proteins, 227 lipid species, and 12 functional read-outs by high-dimensional statistical modelling revealed first that CHD and T2DM are associated with different changes of HDL in size distribution, protein and lipid composition as well as function. Second, different cellular functions of HDL are weakly correlated with each other and determined by different structural components. Cholesterol efflux capacity was no proxy of other functions. Third, three novel determinants of HDL function were identified and validated by the use of artificially reconstituted HDL, namely the sphingadienine-based sphingomyelin SM 42:3 and glycosylphosphatidylinositol-phospholipase D1 for the ability of HDL to inhibit starvation induced apoptosis of human aortic endothelial cells and apolipoprotein F for the ability of HDL to promote maximal respiration of brown adipocytes.
Authors
Mathias Cardner, Mustafa Yalcinkaya, Sandra Goetze, Edlira Luca, Miroslav Balaz, Monika Hunjadi, Johannes Hartung, Andrej Shemet, Nicolle Kraenkel, Silvija Radosavljevic, Michaela Keel, Alaa Othman, Gergely Karsai, Thorsten Hornemann, Manfred Claassen, Gerhard Liebisch, Erick Carreira, Andreas Ritsch, Ulf Landmesser, Jan Krützfeldt, Christian Wolfrum, Bernd Wollscheid, Niko Beerenwinkel, Lucia Rohrer, Arnold von Eckardstein
Abstract
Small molecule inhibitors of Dual Specificity, Tyrosine Phosphorylation-Regulated Kinase 1A (DYRK1A), including harmine and others, are able to drive human beta cell regeneration. While DYRK1A is certainly a target of this class, whether it is the only, or the most important target, is uncertain. Here, we employ a combined pharmacologic and genetic approach to refine the potential mitogenic targets of the DYRK1A inhibitor family in human islets. A combination of human beta cell RNAseq, DYRK1A inhibitor kinome screens, pharmacologic inhibitors, and targeted silencing of candidate genes confirms that DYRK1A is a central target. Surprisingly, however, DYRK1B also proves to be an important target: silencing DYRK1A results in an increase in DYRK1B; simultaneous silencing of both DYRK1A and DYRK1B yields greater beta cell proliferation than silencing either individually. Importantly, other potential kinases, such as the CLK and the GSK3 families, are excluded as important harmine targets. Finally, we describe adenoviruses that are able to silence up to seven targets simultaneously. Collectively, we report that inhibition of both DYRK1A and DYRK1B is required for induction of maximal rates of human beta cell proliferation, and provide clarity for future efforts at structure-based drug design for human beta cell regenerative drugs.
Authors
Courtney Ackeifi, Ethan Swartz, Kunal Kumar, Hongtao Liu, Suebsuwong Chalada, Esra Karakose, Donald K. Scott, Adolfo Garcia-Ocaña, Roberto Sanchez, Robert J. DeVita, Andrew F. Stewart, Peng Wang
Abstract
BACKGROUND We hypothesized that obesity-associated hepato-steatosis served as a pathophysiologic chemical depot for fat-soluble vitamins and altered normal physiology. Using α-tocopherol (vitamin E) as a model vitamin, pharmacokinetics and kinetics principles were utilized to determine whether excess liver fat sequestered α-tocopherol in women with obesity-associated hepato-steatosis vs healthy controls. METHODS Custom-synthesized deuterated α-tocopherols (d3- and d6-α-tocopherols) were administered to hospitalized healthy women and women with hepato-steatosis under IND guidelines. Serial samples obtained over 72 hours were analyzed by LC/MS. Fluorescent-labelled α-tocopherol was custom-synthesized for cell studies. RESULTS In healthy subjects, 85% of intravenous d6-α-tocopherol disappeared from the circulation within 20 minutes but reappeared within minutes and peaked at 6-8 hours. d3- and d6-α-Tocopherols localized to lipoproteins. Lipoprotein redistribution occurred only in vivo within 1h, indicating a key role of liver in rapid uptake and re-release into the circulation. Compared to healthy subjects, subjects with hepato-steatosis had similar d6-α-tocopherol entry rates into liver, but reduced initial release rates (p<0.001). Similarly, pharmacokinetics parameters of AUC and Maximum Concentration (Cmax) were reduced (AUC0-8 ,p<0.01;Cmax p<0.02) in hepato-steatosis subjects, indicating reduced hepatic d6-α-tocopherol output. Reduced kinetics and pharmacokinetics parameters (AUC and Cmax) in hepato-steatosis subjects who received 2 mg were mirrored by similar reductions in healthy subjects when comparing 5 and 2 mg doses. In vitro, fluorescent-labelled α-tocopherol localized specifically to lipid in fat-loaded hepatocytes, indicating sequestration. CONCLUSIONS The unique role of the liver in vitamin E physiology is dysregulated by excess liver fat. Obesity-associated hepato-steatosis may produce unrecognized hepatic vitamin E sequestration, which might subsequently drive liver disease. Our findings raise the possibility that hepato-steatosis may similarly alter hepatic physiology of other fat-soluble vitamins.
Authors
Pierre-Christian Violet, Ifechukwude C. Ebenuwa, Yu Wang, Mahtab Niyyati, Sebastian J. Padayatty, Brian Head, Kenneth Wilkins, Stacey Chung, Varsha Thakur, Lynn Ulatowski, Jeffrey Atkinson, Mikel Ghelfi, Sheila Smith, Hongbin Tu, Gerd Bobe, Chia-Ying Liu, David W. Herion, Robert D. Shamburek, Danny Manor, Maret G. Traber, Mark Levine
Abstract
BACKGROUND Insulin resistance results from impaired skeletal muscle glucose transport/phosphorylation, linked to augmented lipid availability. Despite greater intramuscular lipids, athletes are highly insulin sensitive, which could result from higher rates of insulin-stimulated glycogen synthesis or glucose transport/phosphorylation and oxidation. Thus, we examined the time course of muscle glycogen and glucose-6-phosphate concentrations during low and high systemic lipid availability.METHODS Eight endurance-trained and 9 sedentary humans (VO2 peak: 56 ± 2 vs. 33 ± 2 mL/kg/min, P < 0.05) underwent 6-hour hyperinsulinemic-isoglycemic clamp tests with infusions of triglycerides or saline in a randomized crossover design. Glycogen and glucose-6-phosphate concentrations were monitored in vastus lateralis muscles using 13C/31P magnetic resonance spectroscopy.RESULTS Athletes displayed a 25% greater (P < 0.05) insulin-stimulated glucose disposal rate (Rd) than sedentary participants. During Intralipid infusion, insulin sensitivity remained higher in the athletes (ΔRd: 25 ± 3 vs. 17 ± 3 μmol/kg/min, P < 0.05), supported by higher glucose transporter type 4 protein expression than in sedentary humans. Compared to saline infusion, AUC of glucose-6-phosphate remained unchanged during Intralipid infusion in athletes (1.6 ± 0.2 mmol/L vs. 1.4 ± 0.2 [mmol/L] × h, P = n.s.) but tended to decrease by 36% in sedentary humans (1.7 ± 0.4 vs. 1.1 ± 0.1 [mmol/L] × h, P < 0.059). This drop was accompanied by a 72% higher rate of net glycogen synthesis in the athletes upon Intralipid infusion (47 ± 9 vs. 13 ± 3 μmol/kg/min, P < 0.05).CONCLUSION Athletes feature higher skeletal muscle glucose disposal and glycogen synthesis during increased lipid availability, which primarily results from maintained insulin-stimulated glucose transport with increased myocellular glucose-6-phosphate levels for subsequent glycogen synthesis.TRIAL REGISTRATION ClinicalTrials.gov NCT01229059.FUNDING German Federal Ministry of Health (BMG).
Authors
Esther Phielix, Paul Begovatz, Sofiya Gancheva, Alessandra Bierwagen, Esther Kornips, Gert Schaart, Matthijs K. C. Hesselink, Patrick Schrauwen, Michael Roden
Abstract
Intestinally derived glucagon-like peptide-1 (GLP-1), encoded by the preproglucagon (Gcg) gene, is believed to function as an incretin. However, our previous work questioned this dogma and demonstrated that pancreatic peptides rather than intestinal Gcg peptides, including GLP-1, are a primary regulator of glucose homeostasis in normal mice. The objective of these experiments was to determine whether changes in nutrition or alteration of gut hormone secretion by bariatric surgery would result in a larger role for intestinal GLP-1 in the regulation of insulin secretion and glucose homeostasis. Multiple transgenic models, including mouse models with intestine- or pancreas tissue–specific Gcg expression and a whole-body Gcg-null mouse model, were generated to study the role of organ-specific GLP-1 production on glucose homeostasis under dietary-induced obesity and after weight loss from bariatric surgery (vertical sleeve gastrectomy; VSG). Our findings indicated that the intestine is a major source of circulating GLP-1 after various nutrient and surgical stimuli. However, even with the 4-fold increase in intestinally derived GLP-1 with VSG, it is pancreatic peptides, not intestinal Gcg peptides, that are necessary for surgery-induced improvements in glucose homeostasis.
Authors
Ki-Suk Kim, Chelsea R. Hutch, Landon Wood, Irwin J. Magrisso, Randy J. Seeley, Darleen A. Sandoval
Abstract
Previous work has reported the important links between cellular bioenergetics and the development of chronic kidney disease, highlighting the potential for targeting metabolic functions to regulate disease progression. More recently, it has been shown that alterations in fatty acid oxidation (FAO) can have an important impact on the progression of kidney disease. In this work, we demonstrate that loss of miR-33, an important regulator of lipid metabolism, can prevent the repression of FAO in fibrotic kidneys and reduce lipid accumulation. These changes were associated with a dramatic reduction in the extent of fibrosis induced in two different mouse models of kidney disease. These effects were not related to changes in circulating leukocytes, as bone marrow transplant from miR-33 deficient animals did not have a similar impact on disease progression. Most importantly, targeted delivery of miR-33 peptide nucleic acid (PNA) inhibitors to the kidney and other acidic microenvironments was accomplished using pH low insertion peptides (pHLIP) as a carrier. This was effective at both increasing the expression of factors involved in FAO and reducing the development of fibrosis. Together, these findings suggest that miR-33 may be an attractive therapeutic target for the treatment of chronic kidney disease.
Authors
Nathan L. Price, Verónica Miguel, Wen Ding, Abhishek K. Singh, Shipra Malik, Noemi Rotllan, Anna Moshnikova, Jakub Toczek, Caroline Zeiss, Mehran M. Sadeghi, Noemi Arias, Ángel Baldán, Oleg A. Andreev, Diego Rodríguez-Puyol, Raman Bahal, Yana K. Reshetnyak, Yajaira Suárez, Carlos Fernández-Hernando, Santiago Lamas
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