SLC9A1 and heart failure: Many observations postulate that insulin is responsible for the upregulation of the sodium-hydrogen exchanger isoform 1 Sodium/Hydrogen Exchanger Isoform 1 (NHE1) in the heart and Sodium-Hydrogen Exchanger Isoform 3 (NHE3 in the kidneys) which when both overly stimulated cause respectively: cardiac hypertrophy, dysfunction and ensuing heart failure, plus fluid retention and nephropathy [21, 22].