SLC5A2 and hydrops fetalis: As an example of a metabolomics approach, in the DEFINE-HF (Dapagliflozin Effects on Biomarkers, Symptoms and Functional Status in Patients With HF With Reduced Ejection Fraction) trial, which studied the sodium–glucose cotransporter 2 (SGLT2) inhibitor dapagliflozin in HFrEF, mass spectrometry profiling of 63 plasma metabolites at baseline and after 12 weeks showed increased ketone-related and short-chain acylcarnitine and medium-chain acylcarnitine metabolite clusters defined by principal component analysis [51].