Stimulatory effect of human insulin on erythroid progenitors (CFU-E and BFU-E) in human CD34+ separated bone marrow cells and the relationship between insulin and erythropoietin.

Erythropoietin is known to be effective for the treatment of anemia in chronic renal failure, but the efficacy of erythropoietin for anemia in other diseases is not so great. Insulin exerts a growth promoting activity in various kinds of cells. In the present study, the effects of insulin on erythroid progenitors (colony forming units-erythroid, CFU-E; and burst forming units-erythroid, BFU-E) in human bone marrow were examined at various concentrations of recombinant human erythropoietin (rh-Epo) to clarify the relationship between erythropoietin and insulin. Human insulin stimulated the formation of CFU-E and BFU-E in the presence of three concentrations (0.25, 5, and 100 U/ml) of rh-Epo. Stimulatory effects of human insulin on CFU-E and BFU-E were also observed in the nonphagocytic and nonadherent bone marrow fraction (NP-NA fraction) and in the NP-NA and T cell-depleted fraction at each concentration of rh-Epo. Human insulin further stimulated the CFU-E and BFU-E growth in CD34+ separated bone marrow cells. These results indicate that the enhancing effect of human insulin on erythroid progenitors is not mediated through monocytes and macrophages or T cells, suggesting a direct action on erythroid progenitors.