TOF‐SIMS Analysis of Lipid Accumulation in the Skeletal Muscle of ob/ob Mice

Abstract

Skeletal muscle lipid accumulation is associated with several chronic metabolic disorders, including obesity, insulin resistance (IR) and type 2 diabetes. The aim of this study is to evaluate whether static imaging time‐of‐flight‐secondary‐ion mass spectrometry (TOF‐SIMS) equipped with a Bismuth‐cluster ion source can be used for studying skeletal muscle lipid accumulation associated with obesity. Mouse gastrocnemius muscle tissues in 10‐week‐old obese ob/ob (n = 8) and lean wild‐type C57/BL6 (n = 6) mice were analyzed by TOF‐SIMS. Our results showed that signal intensities of fatty acids (FAs) and diacylglycerols (DAGs) were significantly increased in skeletal muscle of the obese ob/ob mice as compared to the lean wild‐type mice. These differences were revealed through a global analytical approach, principal component analysis (PCA) of TOF‐SIMS spectra, and ion‐specific TOF‐SIMS images. Region‐of‐interest (ROI) analysis showed that FA signal intensities within the muscle cell were significantly increased in ob/ob mice. Moreover, analysis of the ratio between different FA peaks revealed changes in monounsaturated FAs (MUFAs) and polyunsaturated FAs (PUFAs), which is in agreement with previous reports on obesity. These changes in FA composition were also reflected in the ratio of different DAGs or phosphatidylcholines (PCs) that contain different FA residues. Imaging TOF‐SIMS together with PCA of TOF‐SIMS spectra is a promising tool for studying skeletal muscle lipid accumulation associated with obesity.

Monolithic graphene oxide sheets with controllable composition

“…A pulsed 25 keV Bi þ primary ion source (average current: 1.0 pA; pulse width: 12.1 ns; and repetition rate 100 mHz) was used over a 500 mm  500 mm area at an operating pressure of B1  10 À 9 mbar. Negative-ion profiles were recorded and analysed; this technique is ideally suited to searching for possible correlations related to the ejected secondary ion polarity of C and O atoms 51 .…”

Visualization of metabolite change in skeletal muscle by contraction using imaging mass spectrometry

“…There are some reports of IMS of skeletal muscles using time-of-flight (TOF)-SIMS. Magnusson et al demonstrated lipid accumulation in the skeletal muscle of leptin-deficient (ob/ob) mice by TOF-SIMS 15) , which revealed changes in the composition of monounsaturated fatty acids (FAs) and polyunsaturated FAs at high resolution. Tahellah et al also used TOF-SIMS in an attempt to visualize lipid distribution of Duchenne muscular dystrophy-affected muscles 16) .…”

Ambient Molecular Analysis of Biological Tissue Using Low-Energy, Femtosecond Laser Vaporization and Nanospray Postionization Mass Spectrometry

“…The low abundance features in the mass region m/z <700 are likely fragments of lipids or metabolites. For example, the peaks at m/z 551.5 and 577.5 have been suggested to arise from diacylglyceride molecules ([M + H − H 2 O] + ) [64,65] but could also be fragments of different classes of phospholipids with acyl chains of 32:0 and 34:1, respectively [66]. The ion at m/z 184.1 corresponds to either free phosphocholine molecules or phosphocholine fragments of PC lipids, which supports the detection of phosphatidylcholine species from the brain by LEMS.…”