FBXO32 and Endoplasmic Reticulum Stress: As mentioned previously, both the LPS + NAC group and the LPS + 4-PBA group reduced LPS-induced Atrogin-1 and MuRF1 expression, whereas when LPS-induced myotubes were pretreated with NAC and 4-PBA, atrophy protein expression and myotube diameter in the LPS + NAC + 4-PBA group were not statistically different from the LPS + 4-PBA group, which meant that the anti-muscle-atrophy effect of NAC acted partly through ER stress.