Sphingolipids Modulate the Inflammatory and Functional Response in mdx Mice

Duchenne Muscular Dystrophy (DMD) is characterized by progressive muscle degeneration and a chronic inflammatory response. Sphingolipid metabolites are associated with the generation or perpetuation of low-grade chronic inflammation critical in atherosclerosis, obesity and cancer. Dietary sphingolipids, however, can suppress intestinal inflammation. We hypothesized that dietary sphingomyelin (SM) from bovine milk can modulate the inflammatory signature and improve muscle function in mdx mice, a model of DMD. C57BL10 (WT) and mdx mice were fed AIN 76A diet ± 0.1% SM for 7 weeks starting at age 4 weeks (n=10/group: WT, WT + S, mdx, mdx + S). At ages 5, 7, and 9 weeks, ankle flexor torque was determined in vivo. Mice were euthanized at 11 wks. Serum creatine kinase and extensor digitorum longus (EDL) contractile properties in vitro were determined; Tibialis Anterior (TA) inflammatory markers were profiled by qRT-PCR; TA sections were stained with H&E and immunohistochemistry for p-Akt was performed. At age 9 weeks, in vivo ankle flexor torque at stimulation frequencies 50-150 Hz was greater in mdx+S vs. mdx (P=0.0160) and WT (P<0.0001). At 11 wks, only WT+S EDL stress in vitro was greater than all other groups at 50-150 Hz. The in vitro relative stress-frequency relationship of mdx+S EDL was left shifted from the other treatment groups. Inflammatory genetic markers were increased in mdx+S mice. These data suggest treatment of mdx mice with 0.1% SM improves ankle flexor torque in vivo, causes a left shift of the stress-frequency relationship in vitro, and modulates the inflammatory gene signature.