Biochemical Phenomena, Metabolism, and Nutrition Commons^™

Fetal Sex Effects On Maternal Health Can Now Be Tested Via Randomization: A First-In-Class Illustration In Cows On Glucoregulatory Outcomes, Aridany Suarez-Trujillo, Colby J Vorland, Griffin T Nicholls, Daniella E Chusyd, Chelsie Parker, Lilian Golzarri-Arroyo, Sophia Swann, Bethany J Funnell, Kara R Stewart, David B Allison

Children’s Nutrition Research Center Staff Publications

Background: The maternal-offspring relationship, such as whether fetal sex influences maternal health, is essential to explore to advance prenatal and maternal health. While associations exist between fetal sex and maternal health outcomes, it is unclear whether these reflect a causal relationship.

Objective: To demonstrate that fetal sex can be randomly assigned to test the causal effect of fetal sex on maternal outcomes.

Methods: Holstein dairy cows were stratified and randomized using sealed opaque envelopes to be artificially inseminated with either X- or Y-sorted bull semen until 40 cows became pregnant. Monthly body weight measurements were recorded, and an intravenous glucose …

Translational Potential Of Mouse Models Of Human Metabolic Disease, I Sadaf Farooqi, Yong Xu

Children’s Nutrition Research Center Staff Publications

Obesity causes significant morbidity and mortality globally. Research in the last three decades has delivered a step-change in our understanding of the fundamental mechanisms that regulate energy homeostasis, building on foundational discoveries in mouse models of metabolic disease. However, not all findings made in rodents have translated to humans, hampering drug discovery in this field. Here, we review how studies in mice and humans have informed our current framework for understanding energy homeostasis, discuss their challenges and limitations, and offer a perspective on how human studies may play an increasingly important role in the discovery of disease mechanisms and identification …

Mitochondria Regulate Proliferation In Adult Cardiac Myocytes, Gregory B Waypa, Kimberly A Smith, Paul T Mungai, Vincent J Dudley, Kathryn A Helmin, Benjamin D Singer, Clara Bien Peek, Joseph Bass, Lauren Nelson, Sanjiv J Shah, Gaston Ofman, J Andrew Wasserstrom, William A Muller, Alexander V Misharin, G R Scott Budinger, Hiam Abdala-Valencia, Navdeep S Chandel, Danijela Dokic, Elizabeth Bartom, Shuang Zhang, Yuki Tatekoshi, Amir Mahmoodzadeh, Hossein Ardehali, Edward B Thorp, Paul T Schumacker

Faculty, Staff and Student Publications

Newborn mammalian cardiomyocytes quickly transition from a fetal to an adult phenotype that utilizes mitochondrial oxidative phosphorylation but loses mitotic capacity. We tested whether forced reversal of adult cardiomyocytes back to a fetal glycolytic phenotype would restore proliferative capacity. We deleted Uqcrfs1 (mitochondrial Rieske iron-sulfur protein, RISP) in hearts of adult mice. As RISP protein decreased, heart mitochondrial function declined, and glucose utilization increased. Simultaneously, the hearts underwent hyperplastic remodeling during which cardiomyocyte number doubled without cellular hypertrophy. Cellular energy supply was preserved, AMPK activation was absent, and mTOR activation was evident. In ischemic hearts with RISP deletion, new cardiomyocytes …

Glycemia And Gluconeogenesis With Metformin And Liraglutide: A Randomized Trial In Youth-Onset Type 2 Diabetes, Katrina B Dietsche, Sheela N Magge, Sydney A Dixon, Faith S Davis, Andrea Krenek, Aruba Chowdhury, Lilian Mabundo, Michael Stagliano, Amber B Courville, Shanna Yang, Sara Turner, Hongyi Cai, Kannan Kasturi, Arthur S Sherman, Joon Ha, Eileen Shouppe, Mary Walter, Peter J Walter, Kong Y Chen, Robert J Brychta, Cody Peer, Yi Zeng, William Figg, Fran Cogen, D Elizabeth Estrada, Shaji Chacko, Stephanie T Chung

Children’s Nutrition Research Center Staff Publications

OBJECTIVE: Elevated rates of gluconeogenesis are an early pathogenic feature of youth-onset type 2 diabetes (Y-T2D), but targeted first-line therapies are suboptimal, especially in African American (AA) youth. We evaluated glucose-lowering mechanisms of metformin and liraglutide by measuring rates of gluconeogenesis and β-cell function after therapy in AA Y-T2D.

METHODS: In this parallel randomized clinical trial, 22 youth with Y-T2D-age 15.3 ± 2.1 years (mean ± SD), 68% female, body mass index (BMI) 40.1 ± 7.9 kg/m2, duration of diagnosis 1.8 ± 1.3 years-were randomized to metformin alone (Met) or metformin + liraglutide (Lira) (Met + Lira) and evaluated before …

Glucose Metabolism In Posterior Cingulate Cortex Has Supplementary Value To Predict The Progression Of Cognitively Unimpaired To Dementia Due To Alzheimer’S Disease: An Exploratory Study Of 18f-Fdg-Pet, Qi Zhang, Chunqiu Fan, Luyao Wang, Taoran Li, Min Wang, Ying Han, Jiehui Jiang, Alzheimer’S Disease Neuroimaging Initiative

Faculty, Staff and Student Publications

Amyloid-β (Aβ) and tau are important biomarkers to predict the progression of cognitively unimpaired (CU) to dementia due to Alzheimer's disease (AD), according to the diagnosis framework from the US National Institute on Aging and the Alzheimer's Association (NIA-AA). However, it is clinically difficult to predict those subjects who were already with Aβ positive (A +) or tau positive (T +). As a typical characteristic of neurodegeneration in the diagnosis framework, the hypometabolism of the posterior cingulate cortex (PCC) has significant clinical value in the early prediction and prevention of AD. In this paper, we proposed the glucose metabolism in …

Tfeb And Tfe3 Control Glucose Homeostasis By Regulating Insulin Gene Expression, Adrien Pasquier, Nunzia Pastore, Luca D'Orsi, Rita Colonna, Alessandra Esposito, Veronica Maffia, Rossella De Cegli, Margherita Mutarelli, Susanna Ambrosio, Gennaro Tufano, Antonio Grimaldi, Marcella Cesana, Davide Cacchiarelli, Nathalie Delalleau, Gennaro Napolitano, Andrea Ballabio

Duncan NRI Faculty and Staff Publications

To fulfill their function, pancreatic beta cells require precise nutrient-sensing mechanisms that control insulin production. Transcription factor EB (TFEB) and its homolog TFE3 have emerged as crucial regulators of the adaptive response of cell metabolism to environmental cues. Here, we show that TFEB and TFE3 regulate beta-cell function and insulin gene expression in response to variations in nutrient availability. We found that nutrient deprivation in beta cells promoted TFEB/TFE3 activation, which resulted in suppression of insulin gene expression. TFEB overexpression was sufficient to inhibit insulin transcription, whereas beta cells depleted of both TFEB and TFE3 failed to suppress insulin gene …

Endogenous Renal Adiponectin Drives Gluconeogenesis Through Enhancing Pyruvate And Fatty Acid Utilization, Toshiharu Onodera, May-Yun Wang, Joseph M Rutkowski, Stanislaw Deja, Shiuhwei Chen, Michael S Balzer, Dae-Seok Kim, Xuenan Sun, Yu A An, Bianca C Field, Charlotte Lee, Ei-Ichi Matsuo, Monika Mizerska, Ina Sanjana, Naoto Fujiwara, Christine M Kusminski, Ruth Gordillo, Laurent Gautron, Denise K Marciano, Ming Chang Hu, Shawn C Burgess, Katalin Susztak, Orson W Moe, Philipp E Scherer

Faculty, Staff and Student Publications

Adiponectin is a secretory protein, primarily produced in adipocytes. However, low but detectable expression of adiponectin can be observed in cell types beyond adipocytes, particularly in kidney tubular cells, but its local renal role is unknown. We assessed the impact of renal adiponectin by utilizing male inducible kidney tubular cell-specific adiponectin overexpression or knockout mice. Kidney-specific adiponectin overexpression induces a doubling of phosphoenolpyruvate carboxylase expression and enhanced pyruvate-mediated glucose production, tricarboxylic acid cycle intermediates and an upregulation of fatty acid oxidation (FAO). Inhibition of FAO reduces the adiponectin-induced enhancement of glucose production, highlighting the role of FAO in the induction …

Mapping The Metabolic Reprogramming Induced By Sodium-Glucose Cotransporter 2 Inhibition, Aviram Kogot-Levin, Yael Riahi, Ifat Abramovich, Ofri Mosenzon, Bella Agranovich, Liat Kadosh, Rachel Ben-Haroush Schyr, Doron Kleiman, Liad Hinden, Erol Cerasi, Danny Ben-Zvi, Ernesto Bernal-Mizrachi, Joseph Tam, Eyal Gottlieb, Gil Leibowitz

Faculty, Staff and Student Publications

Diabetes is associated with increased risk for kidney disease, heart failure, and mortality. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) prevent these adverse outcomes; however, the mechanisms involved are not clear. We generated a roadmap of the metabolic alterations that occur in different organs in diabetes and in response to SGLT2i. In vivo metabolic labeling with 13C-glucose in normoglycemic and diabetic mice treated with or without dapagliflozin, followed by metabolomics and metabolic flux analyses, showed that, in diabetes, glycolysis and glucose oxidation are impaired in the kidney, liver, and heart. Treatment with dapagliflozin failed to rescue glycolysis. SGLT2 inhibition increased glucose oxidation …

Metabolic Foundations Of Exercise-Induced Cardiac Growth., Kyle Fulghum

Electronic Theses and Dissertations

Regular aerobic exercise promotes physiological cardiac growth, which is an adaptive response thought to enable the heart to meet higher physical demands. Cardiac growth involves coordination of catabolic and anabolic activities to support ATP generation, macromolecule biosynthesis, and myocyte hypertrophy. Although previous studies suggest that exercise-induced reductions in cardiac glycolysis are critical for physiological myocyte hypertrophy, it remains unclear how exercise influences the many interlinked pathways of metabolism that support adaptive remodeling of the heart. In this thesis project, we tested the general hypothesis that aerobic exercise promotes physiological cardiac growth by coordinating myocardial metabolism to promote glucose-supported anabolic pathway …

Haploinsufficiency Of Cyp8b1 Associates With Increased Insulin Sensitivity In Humans, Shiqi Zhong, Raphael Chèvre, David Castaño Mayan, Maria Corlianò, Blake J Cochran, Kai Ping Sem, Theo H Van Dijk, Jianhe Peng, Liang Juin Tan, Siddesh V Hartimath, Boominathan Ramasamy, Peter Cheng, Albert K Groen, Folkert Kuipers, Julian L Goggi, Chester Drum, Rob M Van Dam, Ru San Tan, Kerry-Anne Rye, Michael R Hayden, Ching-Yu Cheng, Shaji Chacko, Jason Flannick, Xueling Sim, Hong Chang Tan, Roshni R Singaraja

Children’s Nutrition Research Center Staff Publications

BACKGROUND

Cytochrome P450 family 8 subfamily B member 1 (CYP8B1) generates 12α-hydroxylated bile acids (BAs) that are associated with insulin resistance in humans.

METHODS

To determine whether reduced CYP8B1 activity improves insulin sensitivity, we sequenced CYP8B1 in individuals without diabetes and identified carriers of complete loss-of-function (CLOF) mutations utilizing functional assays.

RESULTS

Mutation carriers had lower plasma 12α-hydroxylated/non–12α-hydroxylated BA and cholic acid (CA)/chenodeoxycholic acid (CDCA) ratios compared with age-, sex-, and BMI-matched controls. During insulin clamps, hepatic glucose production was suppressed to a similar magnitude by insulin, but glucose infusion rates to maintain euglycemia were higher in mutation carriers, indicating …

French-Fried Potato Consumption And Energy Balance: A Randomized Controlled Trial, Daniel L Smith, Rebecca L Hanson, Stephanie L Dickinson, Xiwei Chen, Amy M Goss, John B Cleek, W Timothy Garvey, David B Allison

Children’s Nutrition Research Center Staff Publications

Background: Epidemiologic observations suggest increased potato consumption correlates with weight gain, adiposity, and diabetes risk, whereas nut consumption is associated with weight control and metabolic health. Randomized controlled trial (RCT) data indicate humans respond to changes in energy intake in single dietary components and compensate for extra energy consumed.

Objectives: We completed an RCT testing whether increased daily potato consumption influences energy balance [specifically, fat mass (FM)] compared with calorie-matched almond consumption.

Methods: A 30-d RCT of 180 adults prescribed calorie-matched (300 kcal/d, n = 60 participants/group) than consumed 1 of the following: 1) almonds (almond group), 2) French fries …

Fibroblast Growth Factor 15/19 Expression, Regulation, And Function: An Overview, Greg Guthrie, Caitlin Vonderohe, Douglas Burrin

Children’s Nutrition Research Center Staff Publications

Since the discovery of fibroblast growth factor (FGF)-19 over 20 years ago, our understanding of the peptide and its role in human biology has moved forward significantly. A member of a superfamily of paracrine growth factors regulating embryonic development, FGF19 is unique in that it is a dietary-responsive endocrine hormone linked with bile acid homeostasis, glucose and lipid metabolism, energy expenditure, and protein synthesis during the fed to fasted state. FGF19 achieves this through targeting multiple tissues and signaling pathways within those tissues. The diverse functional capabilities of FGF19 is due to the unique structural characteristics of the protein and …

Protein Tyrosine Phosphatase Receptor Δ Serves As The Orexigenic Asprosin Receptor, Ila Mishra, Wei Rose Xie, Juan C Bournat, Yang He, Chunmei Wang, Elizabeth Sabath Silva, Hailan Liu, Zhiqiang Ku, Yinghua Chen, Bernadette O Erokwu, Peilin Jia, Zhongming Zhao, Zhiqiang An, Chris A Flask, Yanlin He, Yong Xu, Atul R Chopra

Faculty, Staff and Student Publications

Asprosin is a fasting-induced glucogenic and centrally acting orexigenic hormone. The olfactory receptor Olfr734 is known to be the hepatic receptor for asprosin that mediates its effects on glucose production, but the receptor for asprosin's orexigenic function has been unclear. Here, we have identified protein tyrosine phosphatase receptor δ (Ptprd) as the orexigenic receptor for asprosin. Asprosin functions as a high-affinity Ptprd ligand in hypothalamic AgRP neurons, regulating the activity of this circuit in a cell-autonomous manner. Genetic ablation of Ptprd results in a strong loss of appetite, leanness, and an inability to respond to the orexigenic effects of asprosin. …

Examining 24-Hour Activity And Sleep Behaviors And Related Determinants In Latino Adolescents And Young Adults With Obesity, Erica G Soltero, Neeku Navabi, Kiley B Vander Wyst, Edith Hernandez, Felipe G Castro, Stephanie L Ayers, Jenny Mendez, Gabriel Q Shaibi

Children’s Nutrition Research Center Staff Publications

Background.

Few studies have examined 24-hour activity and sleep behaviors and their contribution to type 2 diabetes (T2D) in Latino adolescents and young adults with obesity.

Aim.

This study included quantitative data on T2D risk and 24-hour activity and sleep behaviors and qualitative data on individual, social, and environmental behavioral determinants.

Method.

A 7 day, 24-hour, wrist-worn accelerometer protocol assessed moderate-to-vigorous physical activity (PA), sedentary behaviors (SB), sleep, and sleep regularity, in adolescents (N = 38; 12–16 years) and young adults (N = 22; 18–22 years). T2D-related outcomes included adiposity (BMI, BF%, waist circumference), fasting, and 2-hour glucose. …

Gabra5 Plays A Sexually Dimorphic Role In Pomc Neuron Activity And Glucose Balance, Zhou Pei, Yang He, Jonathan C Bean, Yongjie Yang, Hailan Liu, Meng Yu, Kaifan Yu, Ilirjana Hyseni, Xing Cai, Hesong Liu, Na Qu, Longlong Tu, Kristine M Conde, Mengjie Wang, Yongxiang Li, Na Yin, Nan Zhang, Junying Han, Camille Hs Potts, Nikolas A Scarcelli, Zili Yan, Pingwen Xu, Qi Wu, Yanlin He, Yong Xu, Chunmei Wang

Children’s Nutrition Research Center Staff Publications

Pro-opiomelanocortin (POMC) neurons are important for the regulation of body weight and glucose balance. The inhibitory tone to POMC neurons is mediated primarily by the GABA receptors. However, the detailed mechanisms and functions of GABA receptors are not well understood. The α5 subunit of GABAA receptor, Gabra5, is reported to regulate feeding, and we found that Gabra5 is highly expressed in POMC neurons. To explore the function of Gabra5 in POMC neurons, we knocked down Gabra5 specifically from mature hypothalamic POMC neurons using the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 strategy. This POMC-specific knock-down of Gabra5 did not affect …

Metabolic Flexibility Across The Spectrum Of Glycemic Regulation In Youth, Fida Bacha, Sara Klinepeter Bartz, Maurice Puyau, Anne Adolph, Susan Sharma

Children’s Nutrition Research Center Staff Publications

BACKGROUNDMetabolic flexibility (MF) refers to the relative ability to utilize lipid and carbohydrate substrates and to transition between them. It is not clear whether MF is impaired in obese youth and what the determining factors are.METHODSWe investigated the determinants of MF (increased respiratory exchange ratio [ΔRER] under insulin-stimulated conditions) in pubertal youth (n = 104; 15.6 ± 1.8 years) with obesity across the spectrum of glucose tolerance compared with normal weight (NW) controls, including body composition (fat-free mass [FFM], %body fat), visceral adipose fat (VAT) (MRI), glycemia, and insulin sensitivity (IS) [3-hour hyperinsulinemic-euglycemic clamp with measurement of lipolysis ([2H5] glycerol), …

Estrogen Receptor-Α Expressing Neurons In The Ventrolateral Vmh Regulate Glucose Balance, Yanlin He, Pingwen Xu, Chunmei Wang, Yan Xia, Meng Yu, Yongjie Yang, Kaifan Yu, Xing Cai, Na Qu, Kenji Saito, Julia Wang, Ilirjana Hyseni, Matthew Robertson, Badrajee Piyarathna, Min Gao, Sohaib A Khan, Feng Liu, Rui Chen, Cristian Coarfa, Zhongming Zhao, Qingchun Tong, Zheng Sun, Yong Xu

Children’s Nutrition Research Center Staff Publications

Brain glucose-sensing neurons detect glucose fluctuations and prevent severe hypoglycemia, but mechanisms mediating functions of these glucose-sensing neurons are unclear. Here we report that estrogen receptor-α (ERα)-expressing neurons in the ventrolateral subdivision of the ventromedial hypothalamic nucleus (vlVMH) can sense glucose fluctuations, being glucose-inhibited neurons (GI-ERαvlVMH) or glucose-excited neurons (GE-ERαvlVMH). Hypoglycemia activates GI-ERαvlVMH neurons via the anoctamin 4 channel, and inhibits GE-ERαvlVMH neurons through opening the ATP-sensitive potassium channel. Further, we show that GI-ERαvlVMH neurons preferentially project to the medioposterior arcuate nucleus of the hypothalamus (mpARH) and GE-ERαvlVMH neurons preferentially project to the dorsal Raphe nuclei (DRN). Activation of ERαvlVMH …

Autotaxin-Lpa Signaling Contributes To Obesity-Induced Insulin Resistance In Muscle And Impairs Mitochondrial Metabolism, Kenneth D'Souza, Carine Nzirorera, Andrew M. Cowie, Geena P. Varghese, Purvi Trivedi, Thomas O. Eichmann, Dipsikha Biswas, Mohamed Touaibia, Andrew J. Morris, Vassilis Aidinis, Daniel A. Kane, Thomas Pulinilkunnil, Petra C. Kienesberger

Internal Medicine Faculty Publications

Autotaxin (ATX) is an adipokine that generates the bioactive lipid, lysophosphatidic acid (LPA). ATX-LPA signaling has been implicated in diet-induced obesity and systemic insulin resistance. However, it remains unclear whether the ATX-LPA pathway influences insulin function and energy metabolism in target tissues, particularly skeletal muscle, the major site of insulin-stimulated glucose disposal. The objective of this study was to test whether the ATX-LPA pathway impacts tissue insulin signaling and mitochondrial metabolism in skeletal muscle during obesity. Male mice with heterozygous ATX deficiency (ATX^+/−) were protected from obesity, systemic insulin resistance, and cardiomyocyte dysfunction following high-fat high-sucrose (HFHS) feeding. …

Regulation Of Glucose Homeostasis By The Phlpp1 Phosphatase, Kara L. Larson

Theses and Dissertations--Molecular and Cellular Biochemistry

Type 2 diabetes mellitus is a metabolic disease that affects one in ten people in the United States. It is caused by a combination of genetics and lifestyle factors. Disease progression begins with insulin resistance in peripheral tissues followed by pancreatic beta-cell failure. The mechanisms behind disease progression are not completely understood. PH domain leucine rich repeat protein phosphatase 1 (PHLPP1) is a known regulator of Akt and other members of the AGC kinase family. Akt has been established to play a role in numerous metabolic signaling pathways, including insulin action. It is hypothesized that as a regulator of Akt, …

Offspring And Maternal Health Benefits Of Exercise During Pregnancy, Lindsay G. Carter

Theses and Dissertations--Nutritional Sciences

Maternal lifestyle and nutrient intake during pregnancy can have long-lasting effects on the health of offspring as well as the mother. This dissertation focuses on the impact of maternal exercise during pregnancy on offspring insulin sensitivity and glucose uptake and the maternal effects of exercise during pregnancy.

The first aim of this dissertation was to investigate if exercise prior to and during pregnancy and nursing would improve glucose uptake and insulin sensitivity in mice and rats. In both mice and rats, it was concluded that maternal exercise could enhance whole-body insulin sensitivity and increase glucose uptake into skeletal muscle and …

Metabolic Regulation Of Mtor Activation And Endoplasmic Reticulum Stress In The Heart, Shiraj Sen

Dissertations and Theses (Open Access)

When subjected to increased workload, the heart responds metabolically by increasing its reliance on glucose and structurally by increasing the size of myocytes. Whether changes in metabolism regulate the structural remodeling process is unknown. A likely candidate for a link between metabolism and growth in the heart is the mammalian target of rapamycin (mTOR), which couples energy and nutrient metabolism to cell growth. Recently, sustained mTOR activation has also been implicated in the development of endoplasmic reticulum (ER) stress. We explored possible mechanisms by which acute metabolic changes in the hemodynamically stressed heart regulate mTOR activation, ER stress and cardiac …

Use Of An Animal Model To Explore Prenatal Predictors Of Insulin And Glucose Metabolism In Southwestern Alaskan Yupiit, Julie Jo Kachinski

UNLV Theses, Dissertations, Professional Papers, and Capstones

Compared to other North American indigenous populations, Southwest Alaskan Yupiit exhibit very low rates of type 2 diabetes despite the occurrence of common risk factors. Contemporary Yupiit obtain a substantial portion of their calories from traditional foods, which contain high amounts of omega-3 polyunsaturated fatty acids. Epidemiological and experimental animal research has linked glucose and insulin homeostasis with a diet high in omega-3s. This study used an experimental animal model to explore potential diabetes protective effects (for adult offspring) of prenatal maternal nutrition modeled on traditional locally-obtained Yupiit diets. The results of this study showed that the adult offspring whose …

Role For Akt3/Protein Kinase Bγ In Attainment Of Normal Brain Size, Rachel M. Easton, Han Cho, Kristin Roovers, Diana W. Shineman

Dartmouth Scholarship

Studies of Drosophila and mammals have revealed the importance of insulin signaling through phosphatidylinositol 3-kinase and the serine/threonine kinase Akt/protein kinase B for the regulation of cell, organ, and organismal growth. In mammals, three highly conserved proteins, Akt1, Akt2, and Akt3, comprise the Akt family, of which the first two are required for normal growth and metabolism, respectively. Here we address the function of Akt3. Like Akt1, Akt3 is not required for the maintenance of normal carbohydrate metabolism but is essential for the attainment of normal organ size. However, in contrast to Akt1^−/− mice, which display a …

Translocation Of The Glucose Transporter Glut4 In Cardiac Myocytes Of The Rat., Jan W. Slot, Hans J. Geuze, Sander Gigengack, David E. James, Gustav E. Lienhard

Dartmouth Scholarship

The insulin-regulated glucose transporter GLUT4 was immunolocalized in rat cardiac muscle under conditions of basal and stimulated glucose uptake, achieved by fasting and a combined exercise/insulin stimulus, respectively. In basal myocytes there was very little (less than 1%) GLUT4 in the different domains of the plasma membrane (sarcolemma, intercalated disk, and transverse tubular system). GLUT4 was localized in small tubulo-vesicular elements that occur predominantly near the sarcolemma and the transverse tubular system and in the trans-Golgi region. Upon stimulation approximately 42% of GLUT4 was found in the plasma membrane. Each domain of the plasma membrane contributed equally to this effect. …