Fig 1.
The comparison of tibialis anterior (TA) and lumbar muscles.
Representative spectra of TA (a) and lumbar (b) muscles are shown. In both 1a and 1b, scout images (top row) indicate the location of voxels (purple boxes) in both the sagittal and axial view of leg or spinal muscles. Representative spectra (2nd row, raw data) were presented for mice in both normal-control-diet (NCD, left) and high-fat-diet (HFD, right) groups; Raw spectra were analyzed in j-MRUI software to obtain individual fitted component (3rd row, fitted data). The differences between raw data and fitted data in the 4th row (residue); Cr, indicates creatine peak (3.02ppm), and used as reference to measure intramyocellular lipid (IMCL, (1.3ppm) and extramyocellular lipid (EMCL,1.5ppm). (c) The comparison of fat accumulation with and without HFD* Indicates p<0.05. The amount of IMCL/EMCL were recorded as a ratio to Cr-peak, hence it does not associate with an actual unit (y-axis). Representative histology (d) verifies the increases of EMCLs in both TA and lumbar muscles in HFD group. The pale spaces (indicated by “*”) between red stained cell marks the presences of EMCLs, whereas IMCL is not sensitive to the histological staining.
Table 1.
The characteristics of NCD and HCD mice.
Fig 2.
Correlations between anatomically distant fat depots.
(a) EMCL in HFD mice are highly correlated (r = 0.84, p = 0.01) between TA and lumbar muscles (squares). (b) The smaller depot of IMCL is negatively correlated between muscle types in HFD (r = -0.84, p = 0.01). (c) TA IMCL is correlated with the ratio of EMCL to IMCL (EIR) (r = 0.96, p<0.001, and (d) liver ICL (r = 0.77, p = 0.03) fat is correlated with lumbar EIR. Data for control mice are shown in triangles.
Fig 3.
Fiber type analysis of lumbar muscles.
(a) Immunohistochemistry for type I and type II fiber in lumbar muscles. (b) Comparison of fiber type percentage in lumbar muscles between normal-control-diet (NCD) and high-fat-diet (HFD) mice. Type I fiber significantly decreased (p<0.001) and type II fiber significantly increased (p<0.001) in HFD mice (C) Correlation between intramyocellular lipid (IMCL) and percentage of type II fiber in lumbar muscle of HFD mice. IMCL positively correlates to percentage of type II fiber in HFD mice (r = 0.80, p = 0.03).