PPARGC1A and cardiomyopathy: Cardiac-specific overexpression of PGC-1α during the neonatal stages leads to a dramatic increase in cardiac mitochondrial number and size coincident with upregulation of gene markers associated with mitochondrial biogenesis, whereas in adult mice there is only a modest increase in mitochondrial number, associated with derangements of mitochondrial ultrastructure and development of cardiomyopathy.19 Previously, similar adverse effects following PGC-1α overexpression were also reported for the heart.