The first line of defense against cardiac hypertrophy.

The embryonic phenotype transformation of cardiomyocytes is an important characteristic of pathological cardiac hypertrophy. It includes transcriptional reprogramming of gene expression, a switch from lipid metabolism to carbohydrate metabolism, and a shift from α-myosin heavy chain (MHC) to fetal ß-MHC expression. The embryonic and adult cardiacmyocytes have distinct gene expression profiles. A series of genes that are expressed in embryos are later shut down after birth through the inhibition of endogenous constitutively activated molecules. These genes can be reactivated if these inhibitors are inactivated or down regulated, as occurs under certain pathological conditions. This promotes pathological cardiac hypertrophy. In this review, we list a class of endogenous molecules whose expression is inactivated during cardiac hypertrophy. They play a positive role in inhibition of the occurrence and development of cardiac hypertrophy and constitute the first natural line of defense against pathological cardiac hypertrophy.