Diffusion magnetic resonance monitors intramyocellular lipid droplet size in vivo.
OBJECTIVE
Intramyocellular lipid (IMCL) droplets are dynamic organelles whose morphology reflects their vital roles in lipid synthesis, usage, and storage in muscle energy metabolism. To develop noninvasive means to measure droplet microstructure in vivo, we investigated the molecular diffusion behavior of IMCL with diffusion magnetic resonance spectroscopy.


METHODS
Using extremely large diffusion weighting, we measured the IMCL apparent diffusion coefficients (ADCs) in hindlimb muscle of rodents from normal feeding, 60-h fasting, streptozotocin-induced diabetic, and high-fat-diet-induced obese groups.


RESULTS
IMCL ADCs decreased markedly with diffusion time, confirming the restricted diffusion of lipid molecules within IMCL droplets. IMCL droplet size, determined by transmission electron microscopy, was closely correlated with ADC. IMCL ADC was sensitive to metabolic alterations, decreasing in the 60-h fasting and diabetic groups while increasing in the obese group. These findings indicated that the IMCL droplet size decreased following 60-h fasting and in STZ-induced diabetes but increased in high-fat-diet-induced obesity.


CONCLUSIONS
MR diffusion characterization of IMCL droplet size provides a unique means to examine the intracellular lipid dynamics and metabolic abnormalities in vivo.
Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China.|Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China.
Peng
P
Cao
Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China.|Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China.
Shu-Juan
SJ
Fan
Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China.|Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China.
Anna M
AM
Wang
Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China.|Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China.
Victor B
VB
Xie
Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China.|Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China.
Zhongwei
Z
Qiao
Departments of Pediatrics and Medicine, Columbia University College of Physicians and Surgeons, New York, New York, USA.
Gary M
GM
Brittenham
Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong, China.|Department of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China.
Ed X
EX
Wu
D000465:Algorithms; D000818:Animals; D058948:Cell Tracking / Q000379:methods; D002478:Cells, Cultured; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D066292:Lipid Droplets / Q000737:chemistry* / Q000648:ultrastructure*; D008055:Lipids / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000737:chemistry* / Q000166:cytology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D008055:Lipids
diffusion magnetic resonance spectroscopy; fasting; intracellular lipid; intramyocellular lipid; obesity; streptozotocin-induced diabetes