In acid sphingomyelinase knock-out mice, which mimic a neurovisceral acid sphingomyelinase deficiency (ASMD) characterized by cellular accumulation of sphingomyelin, the effects of a choline-free diet decreased the activation of liver macrophages and microglia, but it did not significantly alter sphingomyelin levels due to compensatory mechanisms involving methionine metabolism (101). The gene discussed is SMPD1; the disease is hyperinsulinemic hypoglycemia, familial, 4.