Evaluation of Liver Regeneration in Human After Portal Vein Embolization and Partial Hepatectomy Using in Vivo ¹H Decoupled - ³¹P Magnetic Resonance Spectroscopy Imaging
Jing Qi¹, Amita Shukla-Dave, Yuman Fong², Mithat Gönen³, Lawrence H. Schwartz⁴, William M. Jarnagin², Jason A. Koutcher, Kristen L. Zakian^1
1Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY, United States; ²Surgery, Memorial Sloan-Kettering Cancer Center, New York, NY, United States; ³Epidemiology and Biostatistics, Memorial Sloan-Kettering Cancer Center, New York, NY, United States; ⁴Radiology, Memorial Sloan-Kettering Cancer Center, New York, NY, United States

To compare the metabolic feature of hepatic regeneration stimulated by portal vein embolization (PVE) and partial hepatectomy (PH), liver 1H-decoupled 31P-MRSI data acquired from 8 healthy subjects, 6 patients at 48 hours following PVE and 4 patients at 48 hours following PH were analyzed. PH showed similar PME/NTP value as PVE, but significantly higher than control group. PH had significantly elevated PME/PDE, PE/NTP and PE/PC ratios but lower PC/NTP ratio compared to PVE and control subjects. The biochemical difference at 48 hours following PH and PVE indicated that hepatic regeneration process after PVE is not as strong as PH.

In Vivo Hepatic Localized Proton Magnetic Resonance Spectroscopy at 7T in a Glycogen Storage Disease Mouse Model
Nirilanto Ramamonjisoa¹, Hélène Ratiney¹, Fabienne Rajas², Elodie Mutel², Frank Pilleul^1,3, Olivier Beuf¹, Sophie Cavassila^1
1Université de Lyon, CREATIS-LRMN; CNRS UMR 5220; Inserm U630; INSA-Lyon; Université Lyon 1, Villeurbanne, France; ²Inserm U855; Université Lyon1, Faculté de Médecine Laennec, Lyon, France; ³Imagerie Digestive - CHU, Hospices Civils de Lyon, Lyon, France

In vivo 1H magnetic resonance spectroscopy (MRS) was used to evaluate the hepatic steatosis in a mouse model of GSD1a under two different diets, a standard- and a high fat diet. Accumulation of hepatic fat and fat composition within the liver were assessed. The estimated MRS profiles for both groups (Figure 2) showed significant differences for the lipid methyl resonances at 0.9ppm. Both estimated levels of the methylene resonances (1.3ppm) were significantly higher than the estimates obtained for control mice fed on standard diet. Based on MR imaging observations, 90% of the mice fed on high-fat diet exhibited adenomas in the liver while none fed on standard diet. These measurements will give insight into the understanding of the onset and progression of adenomas in a mouse model of GSD1a under different diets

Regional Variability in Triglyceride Composition of Adipose Tissue Measured by ¹H MRS
Gavin Hamilton¹, Michael S. Middleton¹, Takeshi Yokoo¹, Mark Bydder¹, Michael E. Schroeder¹, Claude B. Sirlin^1
1Department of Radiology, University of California, San Diego, San Diego, CA, United States

The multi-peak structure of the fat ¹H MR spectrum allows non-invasive estimation of the triglyceride composition of adipose tissue.  The study compares variability in triglyceride composition of two locations in subcutaneous adipose tissue to the variability seen between subcutaneous and visceral adipose tissue.  We see agreement in triglyceride composition in different locations in subcutaneous adipose tissue, but triglyceride composition of visceral tissue varies compared to that of subcutaneous tissue.

Liver Fat Is More Saturated Than Adipose Fat as Determined by Long TE ¹H-MRS
Jesper Lundbom¹, Antti Hakkarainen¹, Sanni Söderlund², Jukka Westerbacka², Nina Lundbom¹, Marja-Riitta Taskinen^2
1HUS Medical Imaging Centre, University of Helsinki, Helsinki, Finland; ²Department of Medicine, University of Helsinki, Finland

We used long TE 1H-MRS to show that liver fat is more saturated than subcutaneous and intra-abdominal adipose tissue.

In Vivo Identification of a Molecular Marker for Brown Adipose Tissue in NMR Spectra of Large Volumes
Rosa Tamara Branca¹, Warren Sloan Warren^2
1Chemistry, Duke University, Durham, NC, United States; ²Chemistry, Duke University, Durham, NC, United States

A molecular signature of brown adipose tissue is found in the iZQC spectrum of mice. More specifically the iZQC resonance frequency line between methylene protons (-CH2-) at 1.3ppm and water, at cellular length scales, seems to be characteristic of the only BAT tissue. This method is applied in vivo to screen normal and obesity mouse models, and to track the BAT response to adrenergic stimulation and cold exposure.

Characterization of Brown Adipose Tissue in Mice with IDEAL Fat-Water MRI
Houchun Harry Hu¹, Daniel Larry Smith, Jr. ², Michael I. Goran³, Tim R. Nagy², Krishna S. Nayak^1
1Electrical Engineering, University of Southern California, Los Angeles, CA, United States; ²Nutrition Sciences, University of Alabama at Birmingham, Birmingham, AL, United States; ³Preventive Medicine, Pediatrics, Physiology & Biophysics, University of Southern California, Los Angeles, CA, United States

The fat fraction from IDEAL-MRI is used to non-invasively characterize brown adipose tissue (BAT) in mice.  We first demonstrate the ability to identify various BAT depots with IDEAL.  We then demonstrate with IDEAL differences in BAT between mice that were housed at 19°C and 25.5°C for three consecutive weeks.  The interscapular BAT fat fractions in the colder animals were (35.2–48.6%), in contrast to the warmer animals (48.4–60.9%), p<0.01.  The two groups exhibited similar gains in body weight, despite a significant 29% greater food intake by the 19°C animals.  These findings support BAT’s involvement in thermogenesis and lipid metabolism.

Pancreatic and Hepatic Fat and Associated Metabolic Complications in Overweight Youth
Catriona A. Syme¹, Greg D. Wells^1,2, Garry Detzler¹, Hai-Ling Margaret Cheng^1,2, Mike D. Noseworthy^3,4, Timo Schirmer⁵, Brian W. McCrindle^2,6, Jill Hamilton, ^2,7
1Physiology & Experimental Medicine, The Hospital for Sick Children, Toronto, ON, Canada; ²University of Toronto, Toronto, ON, Canada; ³Electrical and Computer Engineering, McMaster University, Hamilton, ON, Canada; ⁴Brain-Body Institute, St. Joseph's Healthcare, Hamilton, ON, Canada; ⁵Applied Science Laboratory, GE Healthcare, Munich, Germany; ⁶Cardiology, The Hospital for Sick Children, Toronto, ON, Canada; ⁷Endocrinology, The Hospital for Sick Children, Toronto, ON, Canada

In overweight youth, pancreatic and hepatic fat (PF and HF) were estimated from in- and out-of-phase MRI, and associations with metabolic parameters were assessed. Both showed positive correlations with triglycerides and insulin resistance and secretion. HF did not correlate with liver enzymes, suggesting its early accumulation may influence glucose metabolism before elevation of hepatic transaminases. Lack of associations between intra-abdominal fat or body mass index z-score and these metabolic parameters highlight the importance of fat distribution rather than fat quantity alone. The current study reveals the potential to index simultaneously ectopic fat in two organs important for glucose and lipid metabolism.

Fat Contents of Human Liver, Pancreas and Kidney
Paul E. Sijens¹, Mireille A. Edens¹, Stephan J.L. Bakker¹, Ronald P. Stolk^1
1UMCG, Groningen, Netherlands

Multivoxel MR spectroscopy and a previously validated gradient echo MRI adaptation of Dixon’s two-point technique were used to quantify kidney, liver, and pancreas fat contents in volunteers with diverse body weights, and to assess inter-organ relationships. Respective fat contents of liver, pancreas and kidney were 4.4%, 4.0% and 0.8%. The amount of subcutaneous fat correlated with liver fat content and pancreas fat content (r=0.45 and r=0.44, respectively; P<0.01). Kidney fat content correlated with none of the other parameters, indicating that renal lipid accumulation, unlike the coupled accumulations of fat in liver and pancreas (r=0.43;P<0.01), is not observed in obese subjects.

Use of MRI for Longitudinal in Vivo Phenotyping of Obese Mouse Models Following a Dietary Intervention
Abdel Wahad Bidar¹, Karolina Ploj², Christopher Lelliott², Karin Nelander³, Leonard Storlien², Paul Hockings^1
1DECS Imaging, AstraZeneca R&D, Mölndal, Sweden; ²CVGI, Bioscience, AstraZeneca R&D, Sweden; ³DECS Discovery Statistics, AstraZeneca R&D, Sweden

In preclinical drug discovery, experimental rodent models of obesity are used for the investigation of metabolic disorders. Repeated in vivo measurements of adipose tissue depots and intraorgan fat can provide longitudinal data with greatly reduced usage of experimental animals. The aim of the present study was threefold: (i) validate in vivo MRI/S determinations of brown adipose tissue, total, intra-abdominal and subcutaneous white adipose tissues as well as intrahepatocellular lipids against ex vivo measurement, (ii) address the 3R’s mandate, by presenting a statistical power analysis; (iii) characterize the phenotypic and metabolic switch of the “cafeteria-diet” mouse model during a dietary intervention.

Real-Time Assessment of in Vivo Postprandial Lipid Storage in Rat Liver Using ¹H-[¹³C] MRS
Richard Jonkers¹, Tom Geraedts¹, Luc van Loon², Klaas Nicolay¹, Jeanine Prompers^1
1Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands; ²Department of Human Movement Sciences, Maastricht University Medical Centre+, Maastricht

Insulin resistance and type 2 diabetes are associated with elevated liver lipid content. It remains unknown whether this excessive accumulation of triglycerides is a result of increased lipid uptake or decreased lipid oxidation. In this study, we measured for the first time postprandial lipid storage in rat liver in vivo using localized ¹³C-edited ¹H-observed MRS and ¹³C labeled lipids as tracers. The ¹³C enrichment of the liver lipid pool was 0.9 ± 0.7% at baseline and increased to 4.8 ± 0.9% 5h after ingestion of the tracer, showing that we can assess changes in ¹³C enriched lipid content in vivo.