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. 2017 Dec 11;7(1):17338.
doi: 10.1038/s41598-017-17529-1.

Assessment of Lipid and Metabolite Changes in Obese Calf Muscle Using Multi-Echo Echo-planar Correlated Spectroscopic Imaging

Rajakumar Nagarajan  1 , Catherine L Carpenter  2 , Cathy C Lee  3   4 , Navin Michael  5 , Manoj K Sarma  1 , Raissa Souza  1 , Edward Xu  1 , S Sendhil Velan  6   7 , Theodore J Hahn  3   4 , Vay-Liang Go  4 , M Albert Thomas  8
Affiliations

Assessment of Lipid and Metabolite Changes in Obese Calf Muscle Using Multi-Echo Echo-planar Correlated Spectroscopic Imaging

Rajakumar Nagarajan et al. Sci Rep. .

Abstract

Obesity-related conditions including heart disease, stroke, and type 2 diabetes are leading causes of preventable death. Recent evidence suggests that altered myocellular lipid metabolism in obesity may lead to increased insulin resistance (IR) that predisposes to these disorders. To test the hypothesis that muscles rich in type I vs. type II muscle fibers would exhibit similar changes in intramyocellular lipid (IMCL) and extramyocellular lipid (EMCL) content in obesity, we utilized a new four-dimensional multi echo echo-planar correlated spectroscopic imaging technique that allows separate determination of IMCL and EMCL content in individual calf muscles in obese vs. normal healthy human subjects. Calf muscles were scanned in 32 obese and 11 healthy subjects using a 3T MRI/MRS scanner, and IR in the obese subjects was documented by glucose tolerance testing. In obese subjects, elevation of both IMCL and EMCL content was observed in the gastrocnemius and tibialis anterior muscles (with mixed type I and II fiber content), while a significant increase in only IMCL content (+48%, p < 0.001) was observed in the soleus muscle (predominantly type I fibers). These observations indicate unexpected differences in changes in myolipid metabolism in type I vs. type II rich muscle regions in obesity, perhaps related to IR, and warrant further investigation.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1
MRI and 4D ME-EPCOSI voxel placement (a) in a 25 years old obese subject with extracted soleus (b) tibialis anterior (c) and gastrocnemius muscle (d) spectra.
Figure 2
Figure 2
MRI and 4D ME-EPCOSI voxel placement (a) in a 27 years old normal healthy subject with extracted soleus (b) tibialis anterior (c) and gastrocnemius muscle (d) spectra.
Figure 3
Figure 3
IMCL and EMCL creatine ratios of soleus, tibialis anterior and gastrocnemius muscles of obese and normal healthy subjects.
Figure 4
Figure 4
Unsaturation indices of soleus, tibialis anterior and gastrocnemius muscles of obese and normal healthy subjects.
Figure 5
Figure 5
Choline to creatine ratios of soleus, tibialis anterior and gastrocnemius muscles of obese and normal healthy subjects.
Figure 6
Figure 6
Correlations between choline and extramyocellular lipids in the (A) soleus, (B) tibialis anterior. and (C) gastrocnemius muscle regions of obese adults.
See this image and copyright information in PMC

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