Submitted on April 17, 2008
Revised on June 2, 2008
Accepted on July 28, 2008
Distinct Patterns of Fat Metabolism in Skeletal Muscle of Normal Weight, Overweight, and Obese Humans
S. Sendhil Velan1*, Nicholas Said1, Christopher Durst1, Stephanie J. Frisbee2, Jefferson Frisbee3, Raymond R Raylman1, M. Albert Thomas4, Vazhaikkurichi M Rajendran5, Richard G Spencer6, and Stephen E. Alway2
1 West Virginia University
2 West Virginia University School of Medicine
3 Center for Interdisciplinary Research in Cardiovascular Sciences,West Virginia University School of Medicine
4 University of California, Los Angeles, CA
5 YWest Virginia University
6 Gerontology Research Center, National Institute on Aging, National Institutes of Health
* To whom correspondence should be addressed. E-mail: svelan{at}hsc.wvu.edu.
The link between body weight, lipid metabolism, and health risks is poorly understood and difficult to study. Magnetic resonance spectroscopy (MRS) permits non-invasive investigation of lipid metabolism. We extended existing two-dimensional MRS techniques to permit quantification of intramyocellular (IMCL) and extramyocellular (EMCL) lipid compartments and their degree of unsaturation in human subjects, and correlated these results with BMI. Using muscle creatine (Cr) for normalization, a statistically significant (p < 0.01) increase in IMCL/Cr with BMI (n=8 subjects per group) was observed, with values of 5.9 ± 1.7 (BMI < 25), 10.9 ± 1.82 (25 < BMI< 30) and 13.1± 0.87 (BMI > 30). Similarly, the degree of IMCL unsaturation decreased significantly (p < 0.01) with BMI, with respective values of 1.51 ± 0.08, 1.30 ± 0.11, and 0.90 ± 0.14. We conclude that important aspects of lipid metabolism can be evaluated with 2-dimensional MRS and propose that degree of unsaturation measured noninvasively may serve as a biomarker for lipid metabolic defects associated with obesity.
