FGF21 and cardiomyopathy: Mutant PNPLA2 and PNPLA8 are causal for neutral lipid storage- or mitochondria-associated cardiomyopathies.66,67 Supplementing palmitate, which compensates for serum deficiency due to FGF21 loss (Fig. 1a), increased HR in both genotypes; however, after 12-h fasting, Fgf21-/- mice showed much less effective recovery during the awakening phase (Fig. 5c, supplementary Fig. 19a), which was consistent with reduced FAO enzymes due to FGF21 deficiency.