Although it was reported previously that AMPK activation affects GYS1 expression and glycogen synthesis in tumor cells (25), our data indicate that increased or reduced phosphorylation of AMPK does not result in alteration of intracellular glycogen levels or GYS1 expression in RA FLSs, suggesting a profound cell type-specific interaction of AMPK and glycogen. The gene discussed is GYS1; the disease is rheumatoid arthritis.