Insulin modulation of newly synthesized apolipoproteins B-100 and B-48 in human fetal intestine: gene expression and mRNA editing are not involved.

We investigated insulin's effect on intestinal lipid, transport and, particularly, the biogenesis of apolipoproteins crucial to lipoprotein secretion. Adding insulin (3 mU) to the serum-free medium of cultured jejunal explants from human fetuses (17-20 weeks) reduced triglyceride and chylomicron production and inhibited apo B-48 and apo B-100 secretion. When apo B mRNA was assayed by RT-PCR and its editing by primer extension, no change was detectable following the addition of insulin. HDL lipid content, apo A-1 synthesis and RNA level were unaffected by insulin. Collectively, these results suggest that the insulin-stimulated decline in intestinal chylomicron output may involve apo B co- or post-translational modifications.