Divergence exists in the subcellular distribution of intramuscular triglyceride in human skeletal muscle dependent on th
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ORIGINAL PAPER
Divergence exists in the subcellular distribution of intramuscular triglyceride in human skeletal muscle dependent on the choice of lipid dye Juliette A. Strauss1 · Daisy A. Shepherd2,3 · Myfanwy Macey1 · Emily F. P. Jevons1 · Sam O. Shepherd1 Accepted: 27 June 2020 © The Author(s) 2020
Abstract Despite over 50 years of research, a comprehensive understanding of how intramuscular triglyceride (IMTG) is stored in skeletal muscle and its contribution as a fuel during exercise is lacking. Immunohistochemical techniques provide information on IMTG content and lipid droplet (LD) morphology on a fibre type and subcellular-specific basis, and the lipid dye Oil Red O (ORO) is commonly used to achieve this. BODIPY 493/503 (BODIPY) is an alternative lipid dye with lower background staining and narrower emission spectra. Here we provide the first quantitative comparison of BODIPY and ORO for investigating exercise-induced changes in IMTG content and LD morphology on a fibre type and subcellular-specific basis. Estimates of IMTG content were greater when using BODIPY, which was predominantly due to BODIPY detecting a larger number of LDs, compared to ORO. The subcellular distribution of intramuscular lipid was also dependent on the lipid dye used; ORO detects a greater proportion of IMTG in the periphery (5 μm below cell membrane) of the fibre, whereas IMTG content was higher in the central region using BODIPY. In response to 60 min moderate-intensity cycling exercise, IMTG content was reduced in both the peripheral (− 24%) and central region (− 29%) of type I fibres (P type IIx fibres (main effect of fibre type; P
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