The first pathway involving insulin receptor substrate 1/ phosphatidylinositol 3-kinase (IRS-1/PIK3) predominantly elicits metabolic responses, while the second pathway via mitogen-activated protein kinase (MAPK) mainly exerts growth promoting effects, contributing to the resultant myocardial hypertrophy and cardiac fibrosis [49]. The gene discussed is PIK3CG; the disease is cardiac hypertrophy.