By contrast, insufficient energy supply is a major prerequisite of HF,23,24 as demonstrated in rat HF models which have lowered GLUT4 within left ventricular (LV) tissue, compared with wild type; this deficiency exacerbated maladaptive cardiac functional developments in hypertrophic hearts contributing to HF, particularly after exercise.25 This evidence concerns the gene SLC2A4 and hydrops fetalis.