Distinct patterns of fat metabolism in skeletal muscle of normal-weight, overweight, and obese humans.
The link between body weight, lipid metabolism, and health risks is poorly understood and difficult to study. Magnetic resonance spectroscopy (MRS) permits noninvasive investigation of lipid metabolism. We extended existing two-dimensional MRS techniques to permit quantification of intra- and extramyocellular lipid (IMCL and EMCL, respectively) compartments and their degree of unsaturation in human subjects and correlated these results with body mass index (BMI). Using muscle creatine for normalization, we observed a statistically significant (P < 0.01) increase in the IMCL-to-creatine ratio with BMI (n = 8 subjects per group): 5.9 +/- 1.7 at BMI < 25, 10.9 +/- 1.82 at 25 < BMI < 30, and 13.1 +/- 0.87 at BMI > 30. Similarly, the degree of IMCL unsaturation decreased significantly (P < 0.01) with BMI: 1.51 +/- 0.08 at BMI < 25, 1.30 +/- 0.11 at 25 < BMI < 30, and 0.90 +/- 0.14 at BMI > 30. We conclude that important aspects of lipid metabolism can be evaluated by two-dimensional MRS and propose that degree of unsaturation measured noninvasively may serve as a biomarker for lipid metabolic defects associated with obesity.
Velan
S Sendhil
SS
Center for Advanced Imaging and Radiology, West Virginia Univ., Morgantown, WV 26506, USA. svelan@hsc.wvu.edu
Said
Nicholas
N
Durst
Christopher
C
Frisbee
Stephanie
S
Frisbee
Jefferson
J
Raylman
Raymond R
RR
Thomas
M Albert
MA
Rajendran
Vazhaikkurichi M
VM
Spencer
Richard G
RG
Alway
Stephen E
SE
D000328:Adult; D015992:Body Mass Index; D003401:Creatine / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D006801:Humans; D050356:Lipid Metabolism / Q000502:physiology*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism* / Q000503:physiopathology; D050177:Overweight / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism
D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D014280:Triglycerides; D003401:Creatine