Tariq Shah¹, Balaji Krishnamachary¹, Flonne Wildes¹, Yelena Mironchik¹, and Zaver M Bhujwalla^1
1Radiology, Johns Hopkins University, Baltimore, Maryland, United States

The hypoxia inducible factor (HIF) is a master regulator of hypoxia inducible genes several of which facilitate invasion and metastasis. Here, using our MR-compatible cell perfusion assay, we investigated the effect of HIF-1 and HIF-2 silencing on the ability of MDA-MB-231 breast cancer cells to invade and degrade the extracellular matrix (ECM). MDA-MB-231 HIF double knocked down cells showed a significant decrease in invasion and ECM degradation, as well as altered metabolism. These data demonstrate the importance of silencing both HIF-1 and 2; to reduce ECM degradation and invasion in this triple negative aggressive and metastatic breast cancer cell line.

Alexander A Shestov¹, Anthony Mancuso^2,3, Pierre-Gilles Henry¹, Dennis B Leeper⁴, and Jerry D Glickson^2
1CMRR, Radiology, University of Minnesota, Minneapolis, MN, United States, ²Radiology, University of Pennsylvania, Perelman School of Medicine, ³Abramson Comprehensive Cancer Center, ⁴Radiation Oncology, Thomas Jefferson University

The bioreactor techniques are becoming an important tool to study cancer cell metabolism. Modeling of intracellular MRS isotopomer data obtained during perfusion with 13C labeled substrates allows quantitative determination of transport and metabolic parameters and fluxes in vivo/in situ. In this work we develop a 13C metabolic “bonded cumomer” approach to fit data obtained in bioreactor with 13C glucose perfusion and elucidate cancer metabolism bionetwork.

Kavindra Nath¹, David Nelson¹, Andrew Ho¹, Moses Darpolor¹, Stephen Pickup¹, Rong Zhou¹, Daniel Heitjan², Deenis Leeper³, and Jerry Glickson^1
1Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States, ²Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States, ³Radiation Oncology, Thomas Jefferson University, Philadelphia, Pennsylvania, United States

Synopsis: Tumors generally have an acidic extracellular pH (pHe) and a neutral to alkaline intracellular pH (pHi), whereas normal cells generally exhibit neutral intracellular and extracellular environments. Here we demonstrate by 31P MRS that the administration of lonidamine (100 mg/kg, i.p.) reverses the pH gradient of human DB-1 melanoma xenografts in nude mice: pHe going from 7.00 ± 0.04 to 6.80 ± 0.07 (p = 0.085) while pHi goes from 6.90 ± 0.05 to 6.40 ± 0.10 (p < 0.001). Selective tumor acidification makes the tumor much more susceptible to systemic chemotherapy with nitrogen mustards.

Kayvan R. Keshari¹, Victor Sai¹, Kristen Scott¹, John Kurhanewicz¹, Henry F. VanBrocklin¹, and David M. Wilson^1
1Radiology and Biomedical Imaging, University of California, San Francisco (UCSF), San Francisco, CA, United States

We have developed a new in vivo redox sensor, hyperpolarized [1-13C] dehydroascorbate (DHA), the oxidized form of Vitamin C. This probe is rapidly taken into the cell via glucose (GLUT) transporters and then reduced to ascorbate (VitC), to a greater extent in transgenic prostate (TRAMP) tumor than the normal gland. Since [1-13C] DHA has an essentially identical transport mechanism to 2-18F-2-deoxy-D-glucose (FDG), we speculated the two techniques might have significant overlap. DHA-MR and FDG-PET studies were performed in a cohort of TRAMP mice at identical time points revealing similar ability to distinguish between tumor and surrounding benign tissue.

Michael Dodd^1,2, Rosalind Bray¹, Vicky Ball¹, Mark Cole¹, Kieran Clarke¹, and Damian Tyler^1
1Department of Physiology, Anatomy and Genetics, Oxford University, Oxford, OXON, United Kingdom, ²Department of Cardiovascular Medicine, Oxford University, Oxford, OXON, United Kingdom

Peroxisome proliferator-activated receptor-α (PPARα)plays an important role in the regulation of fatty acid oxidation. The PPARα knockout mouse (PPARα-KO) has been developed to investigate the role of PPARα in cardiac metabolism and disease. This work aimed to assess the in vivo metabolic phenotype of PPARα-KO mice using hyperpolarized ¹³C-MRS. During the fed state, PPARα-KO mice had significantly elevated pyruvate dehydrogenase (PDH) flux compared to controls. During fasting there was a similar reduction in PDH flux in both control and PPARα-KO mice, indicating that this alteration is PPARα independent and is a response to increased fatty acid supply and utilization.

Peder E. Z. Larson¹, Galen D Reed², Adam B Kerr³, John M Pauly³, Robert Bok², Marcus Ferrone², Andrea Harzstark², Sarah J Nelson², John Kurhanewicz², and Daniel B Vigneron^2
1UCSF, San Francisco, California, United States, ²UCSF, ³Stanford University

As part of the first hyperpolarized [1-13C]-pyruvate clinical trial, we developed a specialized dynamic 13C 2D EPSI sequence using short multiband pulses, and applied it in four prostate cancer patients. Time-resolved MR spectroscopic imaging (MRSI) following injection of hyperpolarized [1-13C]-pyruvate can provide valuable and detailed metabolic information, including perfusion, uptake and kinetics. We observed SNRs up to 340 for pyruvate within 15-20 sec after injection, and SNRs up to 17 for lactate within 25-35 sec after injection. The signal lasted for up to 75 sec for pyruvate and 70 sec for lactate.

Zhongwei Qiao^1,2, Peng Cao^1,2, Anna M. Wang^1,2, Victor B. Xie^1,2, Shujuan Fan^1,2, and Ed X. Wu^1,2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China, ²Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China

In this study, we hypothesized that the gradual IMCL storage occurs in skeletal muscle during resting, and such storage at resting state would alter in obesity. Specifically, we investigated the IMCL storage at resting state in obese rats by quantifying the rates of IMCL accumulation using continuous and dynamic 1H-MRS. We demonstrated that dynamic 1H-MRS could quantify the IMCL accumulation at resting state in individual muscles. Our preliminary results revealed that the disorder of lipid metabolism in obesity is associated with not only an increased IMCL content, but also the alterations in the rates of IMCL storage at resting state in both slow-oxidative muscle and fast-oxidative glycolytic muscles.

Peng Cao^1,2, Zhongwei Qiao^1,2, Anna M. Wang^1,2, Shujuan Fan^1,2, Victor B. Xie^1,2, Jian Yang^1,3, and Ed X. Wu^1,2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong SAR, China, ²Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong SAR, China, ³Medical Imaging Center of the First Affiliated Hospital, School of Medicine of Xi'an Jiaotong University, Xi'an, Shanxi Province, China

Biophysical properties of intramyocellular lipid (IMCL) such as droplet size may reflect the balance between droplet synthesis and degradation. In this study, we hypothesized that characterizing the restricted diffusion of IMCL protons could serve as a sensitive marker for monitoring IMCL droplet dynamics during metabolic intervention/abnormality. Our experimental results demonstrated that in vivo IMCL diffusion characteristics are sensitive to metabolic manipulation by fasting. During the 60-hr fasting, IMCL level increased but exhibited more restricted diffusion, largely in agreement with our histological observation of more droplets but of smaller sizes. Such IMCL diffusion characterization may serve as a sensitive marker to probe the IMCL droplet dynamics in vivo.

Ulrich Flögel¹, Sandra Burghoff¹, and Jürgen Schrader^1
1Molecular Cardiology, Heinrich Heine University, Düsseldorf, NRW, Germany

In the present study, we used CD73-deficient mice to characterize the metabolic consequences of impaired extracellular adenosine formation using ¹H MRI and¹H/¹³C MRS for analysis of body fat content and composition as well as hepatic and myocellular lipid distribution. We found that disrupted extracellular adenosine formation due to lack of CD73 leads to an enhanced lipolysis accompanied by accumulation of intramyocellular lipids in skeletal muscle and peripheral insulin resistance. These findings suggest that CD73-derived adenosine is an important modulator of lipolysis and might be critically involved in development of diseases like diabetes mellitus and the metabolic syndrome.

Lidia S Szczepaniak¹, Ruchi Mathur¹, Edward Szczepaniak¹, Nicole Tyer¹, Michael D Nelson¹, Ida Chen¹, Ronald G Victor¹, and Ildiko Lingvay^2
1Cedars-Sinai Medical Center, Los Angeles, California, United States, ²UT Southwestern Medical Center, Dallas, Texas, United States

The exact role of pancreatic fat in the development of human impaired glucose tolerance remains unclear. Basic research using rodent models of type 2 diabetes has identified pancreatic steatosis and lipotoxicity as a leading cause of beta cell dysfunction. We sought to translate these mechanistic studies into the clinical population. Our data suggest that pancreatic steatosis may identify a subset of asymptomatic individuals who are at high risk for development of type 2 diabetes. 1H-MRS and measurement of pancreatic TG content may constitute a new therapeutic target. Our data also highlight a potential need for ethnically appropriate preclinical biomarkers.