Separation of Intra- and Extramyocellular Lipid Signals in Proton MR Spectra by Determination of Their Magnetic Field Distribution

Steidle, Günter; Machann, Jürgen; Claussen, Claus D.; Schick, Fritz

doi:10.1006/jmre.2001.2481

Cited by 35 publications

(45 citation statements)

References 16 publications

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“…The BMS effect also accounts for the separate resonances from lipid in spherical droplets inside skeletal muscle and outside in elongated, more cylinder-like, adipocytes (2)(3)(4)8). In other words, the situation with DEP in a capillary (cylinder) and sphere assembly is an analog of muscle tissue in which there are lipid droplets inside myocytes and larger, more elongated, lipid bodies in adipocytes between the fibers.…”

Section: Discussionmentioning

confidence: 94%

Magnetic susceptibility: Solutions, emulsions, and cells

Kuchel

Chapman

Bubb

et al. 2003

Concepts Magnetic Resonance

105

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Differences in magnetic susceptibility between various compartments in heterogeneous samples can introduce unanticipated complications to NMR spectra. On the other hand, an understanding of these effects at the level of the underlying physical principles has led to the development of several experimental techniques that provide data on cellular function that are unique to NMR spectroscopy. To illustrate some key features of susceptibility effects we present, among a more general overview, results obtained with red blood cells and a recently described model system involving diethyl phthalate in water. This substance forms a relatively stable emulsion in water and yet it has a significant solubility of ϳ5 mmol L Ϫ1 at room temperature; thus, the NMR spectrum has twice as many resonances as would be expected for a simple solution. What determines the relative intensities of the two families of peaks and can their frequencies be manipulated experimentally in a predictable way? The theory used to interpret the NMR spectra from the model system and cells was first developed in the context of electrostatics nearly a century ago, and yet some of its underlying assumptions now warrant closer scrutiny. While this insight is used in a practical way in this article, the accompanying article deals with the mathematics and physics behind this new analysis.

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Section: Discussionmentioning

confidence: 94%

Magnetic susceptibility: Solutions, emulsions, and cells

Kuchel

Chapman

Bubb

et al. 2003

Concepts Magnetic Resonance

105

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“…The correlation between the magnitude of the IMCL pool, as determined by MRS studies, and insulin resistance, diabetes, and disorders of lipid metabolism has been previously demonstrated (2,3,32,33). Nevertheless, quantification of IMCL and extramyocellular lipid (EMCL) by MRS remains highly problematic (32). The ability to distinguish IMCL from EMCL is based on their different bulk magnetic susceptibility effects due to their geometric arrangements within muscle, which leads to a spectroscopic frequency separation between the two pools; this separation is 0.15 ppm in the soleus and 0.2 ppm in the tibialis muscle and has been validated in vivo (33,34).…”

mentioning

confidence: 86%

“…The ability to distinguish IMCL from EMCL is based on their different bulk magnetic susceptibility effects due to their geometric arrangements within muscle, which leads to a spectroscopic frequency separation between the two pools; this separation is 0.15 ppm in the soleus and 0.2 ppm in the tibialis muscle and has been validated in vivo (33,34). At a clinical field strength of 1.5 T, these values are 9.6 and 12.8 Hz, respectively; at 3 T, the frequency separations are twofold greater (32). This permits the IMCL and EMCL signals to be individually identified in MRS but is not adequate for complete separation.…”

mentioning

confidence: 88%

“…Thus the ability to monitor the IMCL pool and its properties noninvasively by magnetic resonance spectroscopy (MRS) has been an important development (4,28). The correlation between the magnitude of the IMCL pool, as determined by MRS studies, and insulin resistance, diabetes, and disorders of lipid metabolism has been previously demonstrated (2,3,32,33). Nevertheless, quantification of IMCL and extramyocellular lipid (EMCL) by MRS remains highly problematic (32).…”

mentioning

confidence: 99%

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Distinct patterns of fat metabolism in skeletal muscle of normal-weight, overweight, and obese humans

Velan¹,

Said²,

Durst³

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

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Velan SS, Said N, Durst C, Frisbee S, Frisbee J, Raylman RR, Thomas MA, Rajendran VM, Spencer RG, Alway SE. Distinct patterns of fat metabolism in skeletal muscle of normal-weight, overweight, and obese humans. Am J Physiol Regul Integr Comp Physiol 295: R1060 -R1065, 2008. First published July 30, 2008 doi:10.1152/ajpregu.90367.2008The 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 Ͻ 0.01) increase in the IMCL-to-creatine ratio with BMI (n ϭ 8 subjects per group): 5.9 Ϯ 1.7 at BMI Ͻ 25, 10.9 Ϯ 1.82 at 25 Ͻ BMI Ͻ 30, and 13.1 Ϯ 0.87 at BMI Ͼ 30. Similarly, the degree of IMCL unsaturation decreased significantly (P Ͻ 0.01) with BMI: 1.51 Ϯ 0.08 at BMI Ͻ 25, 1.30 Ϯ 0.11 at 25 Ͻ BMI Ͻ 30, and 0.90 Ϯ 0.14 at BMI Ͼ 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. magnetic resonance spectroscopy; lipid unsaturation; intramyocellular lipid; extramyocellular lipid THE AMOUNT OF BODY FAT is a risk factor for several obesityrelated disorders. Obesity is a known risk factor for the development of insulin resistance and diabetes and is a key component of metabolic syndrome. The causal relationship between increased dyslipidemia and adiposity and impaired glucose homeostasis is unclear, although it is known that lipid oversupply to the organs primarily involved in glucose homeostasis, that is, muscle, liver, and pancreas, leads to impaired insulin function in those tissues (22).Previous studies showed that intramyocellular lipid (IMCL) is increased with obesity and in non-insulin-dependent diabetes mellitus (9,11,15). It has been suggested that increased visceral adiposity and reduced lipid oxidation might contribute to the increase in IMCL (18). Thus the ability to monitor the IMCL pool and its properties noninvasively by magnetic resonance spectroscopy (MRS) has been an important development (4, 28). The correlation between the magnitude of the IMCL pool, as determined by MRS studies, and insulin resistance, diabetes, and disorders of lipid metabolism has been previously demonstrated (2,3,32,33). Nevertheless, quantification of IMCL and extramyocellular lipid (EMCL) by MRS remains highly problematic (32). The ability to distinguish IMCL from EMCL is based on their different bulk magnetic susceptibility effects due to their geometric arrangements within muscle, which leads to a spectroscopic frequency separation between the two pools; this sepa...

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“…Steidle et al (116) suggested an alternative approach allowing the magnetic field distribution (MFD) to be obtained in the lipid containing compartments of a voxel (Fig. 10).…”

Section: Calibration By the Creatine Signalmentioning

confidence: 99%

Role of proton MR for the study of muscle lipid metabolism

et al. 2006

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1 H-MR spectroscopy (MRS) of intramyocellular lipids (IMCL) became particularly important when it was recognized that IMCL levels are related to insulin sensitivity. While this relation is rather complex and depends on the training status of the subjects, various other influences such as exercise and diet also influence IMCL concentrations. This may open insight into many metabolic interactions; however, it also requires careful planning of studies in order to control all these confounding influences. This review summarizes various historical, methodological, and practical aspects of 1 H-MR spectroscopy (MRS) of muscular lipids. That includes a differentiation of bulk magnetic susceptibility effects and residual dipolar coupling that can both be observed in MRS of skeletal muscle, yet affecting different metabolites in a specific way. Fitting of the intra-(IMCL) and extramyocellular (EMCL) signals with complex line shapes and the transformation into absolute concentrations is discussed. Since the determination of IMCL in muscle groups with oblique fiber orientation or in obese subjects is still difficult, potential improvement with high-resolution spectroscopic imaging or at higher field strength is considered. Fat selective imaging is presented as a possible alternative to MRS and the potential of multinuclear MRS is discussed. 1 H-MRS of muscle lipids allows non-invasive and repeated studies of muscle metabolism that lead to highly relevant findings in clinics and patho-physiology.

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Separation of Intra- and Extramyocellular Lipid Signals in Proton MR Spectra by Determination of Their Magnetic Field Distribution

Cited by 35 publications

References 16 publications

Magnetic susceptibility: Solutions, emulsions, and cells

Magnetic susceptibility: Solutions, emulsions, and cells

Distinct patterns of fat metabolism in skeletal muscle of normal-weight, overweight, and obese humans

Role of proton MR for the study of muscle lipid metabolism

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