Fig. 5.

Sequestering intramuscular triacylglycerol into lipid droplets blunts expression of PPAR target genes. Human skeletal myocytes were treated on differentiation day 4 with recombinant adenovirus (5.2 × 10⁸ PFU/cm²) to express either β-galactosidase (β-gal) or mouse perilipin (Plpn1). After 24 h, cells were treated an additional 72 h with 0.1% BSA or 0.1 mM oleate/palmitate (1:1) bound to BSA at a 5:1 ratio, followed by (A) neutral lipid staining with AdipoRed, (B) measurement of glycerol in the culture medium, and (C) gene expression analyses by RT-PCR. (D) On differentiation day 5, human myocytes were pretreated 24 h with 100 µM of the lipase inhibitor diethylumbeliferyl phosphate (DEUP) or the vehicle alone (DMSO), followed by 72 h treatment with 0.1 mM oleate/palmitate (1:1) and measurement of gene expression. (E) Model showing the proposed metabolic interplay between lipid droplets and mitochondria. Data are means ± SE of at least two independent experiments performed in triplicate. Glycerol was normalized to total cellular protein, and gene expression analyses were normalized to 18 s. *P < 0.05 versus β-gal or vehicle control. ^#P < 0.05 versus BSA treatment.